Atanassova, Paolina (Albuquerque, NM, US)
Shen, Jian-ping (Albuquerque, NM, US)
Napolitano, Paul (Albuquerque, NM, US)
Brewster, James (Rio Rancho, NM, US)
Plaque It!
Sponsored by: Flash of Genius |
2. A method as recited in claim 1, wherein said converting step comprises steam reforming of said carbon-based fuel.
3. A method as recited in claim 1, wherein said converting step is selected from the group consisting of autothermal reforming, partial oxidation and catalytic partial oxidation of said carbon-based fuel.
4. A method as recited in claim 1, further comprising the step of contacting said H2-rich gas with a water-gas shift catalyst.
5. A method as recited in claim 1, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 50 times.
6. A method as recited in claim 1, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 100 times.
7. A method as recited in claim 1, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 500 times.
8. A method as recited in claim 1, wherein said absorbent material retains at least about 70 mol. % of said theoretical capacity after said repeating step.
9. A method as recited in claim 1, wherein said absorbent material retains at least about 90 mol. % of said theoretical capacity after said repeating step.
10. A method as recited in claim 1, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 200 times and wherein said absorbent material retains at least about 10 mol. % of said theoretical absorption capacity after said repeating step.
11. A method as recited in claim 1, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 200 times and wherein said absorbent material retains at least about 25 mol. % of said theoretical absorption capacity after said repeating step.
12. A method as recited in claim 1, wherein said repeating step comprises repeating steps (a), (b), (c) and (d) at least 200 times and wherein said absorbent material retains at least about 50 mol. % of said theoretical absorption capacity after said repeating step.
13. A method as recited in claim 1, wherein said absorbent material comprises at least one metal oxide selected from the group consisting of Group IA and Group IIA metal oxides.
14. A method as recited in claim 1, wherein said absorbent material comprises a calcium-containing compound.
15. A method as recited in claim 1, wherein said absorbent material comprises CaO.
16. A method as recited in claim 1, wherein said absorbent material comprises CaO:MgO.
17. A method as recited in claim 1, wherein said absorbent material comprises CaO and from about 1 wt. % to about 40 wt. % Al2O3.
18. A method as recited in claim 1, wherein said contacting step occurs at a temperature of not greater than about 800° C.
19. A method as recited in claim 1, wherein said carbon-based fuel is a hydrocarbon-based fuel.
20. A method as recited in claim 1, wherein said carbon-based fuel is a gaseous fuel.
21. A method as recited in claim 1, wherein said carbon-based fuel comprises methane.
22. A method as recited in claim 1, wherein said carbon-based fuel comprises a liquid fuel.
23. A method as recited in claim 1, wherein said carbon-based fuel comprises a liquid fuel selected from the group consisting of diesel fuel, JP-8 aviation fuel, kerosene, ethanol and gasoline.
24. A method as recited in claim 1, wherein said H2-rich gas comprises at least about 95 mol. % H2 after each said repeating steps.
25. A method as recited in claim 1, wherein said regenerating step comprises heating said absorbent material to a temperature of at least about 700° C.
26. A method as recited in claim 1, wherein said absorbent material is pelletized.
27. A method as recited in claim 1, wherein said absorbent material is coated on a support structure.
28. A method as recited in claim 1, wherein said absorbent material has substantially spherical morphology
29. A method for the conversion of a carbon-based fuel to a H2-rich product gas, comprising the steps of: (a) providing a carbon-based fuel; (b) converting said carbon-based fuel to an intermediate gas product by contacting said carbon-based fuel with at least a first conversion catalyst; (c) contacting said intermediate gas product with an absorbent material to absorb CO2 and form a H2-rich gas, said absorbent material having an theoretical absorption capacity for CO2; (d) extracting said H2-rich gas from said contacting step; 1-0 (e) regenerating said absorbent; and (f) repeating said steps (a), (b), (c), (d) and (e) at least 10 times, wherein said total mass of absorbent material retains at least about 10 grams CO2 per 100 grams unreacted absorbent after each of said repeating steps.
30. A method as recited in claim 29, wherein said absorbent material retains at least 20 grams CO2 per 100 grams unreacted absorbent after each of said repeating steps.
31. A method as recited in claim 29, wherein said absorbent material retains at least 30 grams CO2 per 100 grams unreacted absorbent after each of said repeating steps.
32. A method as recited in claim 29, wherein said absorbent material retains at least 40 grams CO2 per 100 grams unreacted absorbent after each of said repeating steps.
33. A method as recited in claim 29, wherein said absorbent material retains at least 50 grams CO2 per 100 grams unreacted absorbent after each of said repeating steps.
34. A method as recited in claim 29, wherein said absorbent material is pelletized.
35. A method as recited in claim 29, wherein said converting step comprises steam reforming of said carbon-based fuel.
36. A method as recited in claim 29, wherein said converting step is selected from the group consisting of autothermal reforming, partial oxidation and catalytic partial oxidation of said carbon-based fuel.
37. A method as recited in claim 29, further comprising the step of contacting said H2-rich gas with a water-gas shift catalyst.
38. A method as recited in claim 29, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 50 times.
39. A method as recited in claim 29, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 100 times.
40. A method as recited in claim 29, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 500 times.
41. A method as recited in claim 29, wherein said absorbent retains at least about 70 mol. % of said theoretical absorption capacity after said repeating step.
42. A method as recited in claim 29, wherein said absorbent retains at least about 90 mol. % of said theoretical absorption capacity after said repeating step.
43. A method as recited in claim 29, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 200 times and wherein said absorbent material retains at least about 10 mol. % of said theoretical absorption capacity after said repeating step.
44. A method as recited in claim 29, wherein said repeating step comprises repeating steps (a), (b), (c), (d) and (e) at least 200 times and wherein said absorbent material retains at least about 25 mol. % of said theoretical absorption capacity after said repeating step.
45. A method as recited in claim 29, wherein said repeating step comprises repeating steps (a), (b), (c) and (d) at least 200 times and wherein said absorbent material retains at least about 50 mol. % of said theoretical absorption capacity after said repeating step.
46. A method as recited in claim 29, wherein said absorbent material comprises at least one metal-oxide selected from the group consisting of Group IA and Group IIA metal oxides.
47. A method as recited in claim 29, wherein said absorbent material comprises a calcium-containing compound.
48. A method as recited in claim 29, wherein said absorbent material comprises CaO.
49. A method as recited in claim 29, wherein said absorbent material comprises CaO:MgO.
50. A method as recited in claim 29, wherein said absorbent material comprises CaO and from about 1 wt. % to about 40 wt. % Al2O3.
51. A method as recited in claim 29, wherein said contacting step occurs at a temperature of not greater than about 800° C.
52. A method as recited in claim 29, wherein said carbon-based fuel is a hydrocarbon-based fuel.
53. A method as recited in claim 29, wherein said carbon-based fuel is a gaseous fuel.
54. A method as recited in claim 29, wherein said carbon-based fuel comprises methane.
55. A method as recited in claim 29, wherein said carbon-based fuel is a liquid fuel.
56. A method as recited in claim 29, wherein said carbon-based fuel comprises a liquid selected from the group consisting of diesel fuel, JP-8 aviation fuel, kerosene, ethanol and gasoline.
57. A method as recited in claim 29, wherein said H2-rich gas comprises at least about 95 mol. % H2 after said repeating step.
58. A method as recited in claim 29, wherein said regenerating step comprises heating said absorbent material to a temperature of at least about 700° C.
59. A method as recited in claim 29, wherein said absorbent material is pelletized.
60. A method as recited in claim 29, wherein said absorbent material is coated on a support structure.
61. A method as recited in claim 29, wherein said absorbent material has substantially spherical morphology.
62. A method for the conversion of a carbon-based fuel to a H2-rich gas, comprising the steps of: (a) providing a carbon-based fuel and steam; (b) converting said carbon-based fuel and said steam to an intermediate gas product by contacting with at least a first conversion catalyst; (c) contacting said intermediate gas product with an absorbent material to absorb CO2 and form an H2-rich gas, said absorbent material having a theoretical absorption capacity and wherein at least said absorbent material is pelletized; (d) extracting said H2-rich gas from said contacting step; (e) regenerating said absorbent; and (f) repeating said steps (a), (b), (c), (d) and (e) at least 50 times, wherein said absorbent material retains at least about 20 mol. % of its theoretical CO2 absorption capacity after each of said repeating steps.
63. A method as recited in claim 62, wherein said absorbent material retains at least about 40 mol. % of said theoretical CO2 absorption capacity after each of said repeating steps.
64. A method as recited in claim 62, wherein said absorbent material retains at least about 60 mol. % of said theoretical CO2 absorption capacity after each of said repeating steps.
65. A method as recited in claim 62, wherein said absorbent material retains at least about 90 mol. % of said theoretical CO2 absorption capacity after each of said repeating steps.
66. A method as recited in claim 62, wherein said absorbent material retains at least 10 grams CO2 per 100 grams unreacted absorbent material after each of said repeating steps.
67. A method as recited in claim 62, wherein said absorbent material retains at least 20 grams CO2 per 100 grams unreacted absorbent material after each of said repeating steps.
68. A method as recited in claim 62, wherein said absorbent material retains at least 30 grams CO2 per 100 grams unreacted absorbent material after each of said repeating steps.
69. A method as recited in claim 62, wherein said absorbent material retains at least 40 grams CO2 per 100 grams unreacted absorbent material after each of said repeating steps.
70. A method as recited in claim 62, wherein said absorbent material is regenerated at least about 100 times and wherein said absorbent material retains at least about 20 mol. % of said theoretical CO2 absorption capacity.
71. A method as recited in claim 62, wherein said absorbent material has substantially spherical morphology
72. A method as recited in claim 62, wherein said first conversion catalyst is a steam reforming catalyst.
73. A method as recited in claim 62, further comprising the step of contacting said H2-rich product gas with a water-gas shift catalyst.
74. A method as recited in claim 62, wherein said absorbent material comprises at least one metal oxide selected from the group consisting of Group IA and Group IIA metal oxides.
75. A method as recited in claim 62, wherein said absorbent material comprises a calcium-containing compound.
76. A method as recited in claim 62, wherein said absorbent material comprises CaO.
77. A method as recited in claim 62, wherein said absorbent material comprises CaO and from about 1 wt. % to about 40 wt. % Al2O3.
78. A method as recited in claim 62, wherein said absorbent comprises CaO and a metal oxide selected from the group consisting of Al2O3 and MgO.
79. A method as recited in claim 62, wherein said first conversion catalyst comprises a metal selected from the group consisting of Rh, Ni, Ru, Pt, and Pd.
80. A method as recited in claim 62, wherein said contacting step occurs at a temperature of not greater than about 800° C.
81. A method as recited in claim 62, wherein said regenerating step comprises heating said absorbent material to a temperature of at least about 700° C.
82. A method as recited in claim 62, wherein said conversion catalyst is pelletized with said absorbent material.
83. A method as recited in claim 62, wherein said H2-rich product gas comprises at least about 95 mol. % H2.
84. A method for absorption enhanced reforming of a carbon-based fuel, comprising the steps of: (a) providing a carbon-based fuel; (b) contacting said carbon-based fuel with at least a first conversion catalyst to catalyze the formation of an intermediate gas product; (c) contacting said intermediate gas product with a pelletized absorbent compound having a first bulk density, wherein said pelletized absorbent is converted to a carbonized absorbent having a second bulk density; and (d) regenerating said carbonized absorbent to form a regenerated absorbent having a third bulk density, wherein said third bulk density is greater than said first bulk density.
85. A method as recited in claim 84, wherein said third bulk density is up to about 140% of said first bulk density.
86. A method as recited in claim 84, wherein said regenerating step comprises heating said carbonized absorbent to a temperature of at least about 700° C.
87. A method as recited in claim 84, wherein said carbon-based fuel is a hydrocarbon-based fuel.
88. A method as recited in claim 84, wherein said carbon-based fuel is gaseous fuel.
89. A method as recited in claim 84, wherein said carbon-based fuel comprises methane.
90. A method as recited in claim 84, wherein said carbon-based fuel is a liquid fuel.
91. A method as recited in claim 84, wherein said carbon-based fuel is selected from the group consisting of gasoline, kerosene, jet fuel, bio-oil from carbon.
92. A method as recited in claim 84, further comprising the step of providing steam with said carbon-based fuel.
93. A method as recited in claim 84, further comprising the step of providing steam, or an oxygen-containing gas with said carbon-based fuel.
94. A method as recited in claim 84, wherein said absorbent compound comprises a calcium-containing compound.
95. A method as recited in claim 84, wherein said absorbent compound comprises CaO.
96. A method as recited in claim 84, wherein said absorbent compound comprises CaO:MgO.
97. A method as recited in claim 84, wherein said absorbent has substantially spherical morphology.
98. A method as recited in claim 84, wherein said regenerating step comprises heating said absorbent compound to a temperature of at least about 700° C.
99. A steam-reforming catalyst, comprising: (a) a particulate support structure; and (b) a metal dispersed on said support structure, wherein said reforming catalyst achieves at least about 90% of the theoretical thermodynamic conversion of methane to hydrogen at a temperature of 600° C., a H2O:C ratio of 3:1 and a gas hour space velocity (GHSV) of 5000 hour−1 in the absence of an absorbent for CO2.
100. A reforming catalyst as recited in claim 99, wherein said catalyst achieves at least about 95% of the theoretical thermodynamic conversion.
101. A reforming catalyst as recited in claim 99, wherein said catalyst achieves at least about 90% of the theoretical thermodynamic conversion of methane to hydrogen at a temperature of 600° C., a H2O:C ratio of 3:1 and a gas hour space velocity (GHSV) of 10000 hour−1 in the absence of an absorbent for CO2.
102. A reforming catalyst as recited in claim 99, wherein said catalyst achieves at least about 90% of the theoretical thermodynamic conversion of methane to hydrogen at a temperature of 600° C., a H2O:C ratio of 3:1 and a gas hour space velocity (GHSV) of 12500 hour−1 in the absence of an absorbent for CO2.
103. A reforming catalyst as recited in claim 99, wherein said support is selected from the group consisting of the metal oxides of aluminum, cerium, zirconium, lanthanum, silicon, magnesium, zinc and combinations thereof.
104. A reforming catalyst as recited in claim 99, wherein said dispersed metal is selected from the group consisting of Rh, Ni, Ru, Pt, Pd and alloys thereof.
105. A reforming catalyst as recited in claim 99, wherein said dispersed metal comprises Rh.
106. A reforming catalyst as recited in claim 99, wherein said reforming catalyst comprises from about 0.1 wt. % to about 1 wt. % of said metal.
107. A reforming catalyst as recited in claim 99, wherein said support structure comprises Al2O3 and said dispersed metal comprises Rh.
108. A reforming catalyst as recited in claim 99, wherein said reforming catalyst is pelletized.
109. A reforming catalyst as recited in claim 99, wherein said reforming catalyst is coated on a support.
110. A reforming catalyst as recited in claim 99, wherein said reforming catalyst has substantially spherical morphology.
111. A particulate composite material, said particulates comprising: (a) an absorbent phase adapted to absorb CO2; and (b) a catalyst phase selected from the group consisting of a reforming catalyst phase and a water-gas shift catalyst phase.
112. A particulate composite material as recited in claim 111, wherein said absorbent phase comprises a calcium compound.
113. A particulate composite material as recited in claim 111, wherein the mass ratio of said absorbent phase to said catalyst phase is greater than 1:1.
114. A particulate composite material as recited in claim 111, wherein the mass ratio of said absorbent phase to said catalyst phase is from about 20:1 to about 3:1.
115. A particulate composite material as recited in claim 111, wherein the mass ratio of said absorbent phase to said catalyst phase is from about 9:1 to about 5:1.
116. A particulate composite as recited in claim 111, wherein said catalyst phase comprises a supported metal.
117. A particulate composite material as recited in claim 111, wherein said catalyst phase comprises a reforming catalyst.
118. A particulate composite material as recited in claim 111, wherein said catalyst is a reforming catalyst comprising a metal selected from Rh, Ni, Ru, Pt, Pd, and alloys thereof dispersed on a support phase selected from the group consisting of metal oxides of aluminum, cerium, zirconium, lanthanum, silicon, magnesium, zinc and combinations thereof.
119. A particulate composite material as recited in claim 111, wherein said catalyst phase comprises a water-gas shift catalyst.
120. A particulate composite material as recited in claim 111, wherein said catalyst is a water-gas shift catalyst comprising a metal dispersed on a support phase, said metal being selected from the group consisting of Fe, Co, Cu and Cr.
121. A particulate composite material as recited in claim 111, wherein said particulate composite material is pelletized.
122. A particulate composite material as recited in claim 111, wherein said particulate composite material is coated on a support structure.
123. A particulate composite material as recited in claim 111, wherein said absorbent phase includes an absorbent compound having a reaction fraction of at least about 70 mol. %.
124. A particulate composite material as recited in claim 111, wherein said absorbent material has a reaction fraction of at least about 70 mol. % after 100 cycles.
125. A particulate composite material as recited in claim 111, wherein said absorbent phase comprises a reversible absorbent.
126. A particulate composite material as recited in claim 111, wherein said absorbent phase comprises an absorbent compound that retains at least about 40 mol. % of the theoretical CO2 absorption capacity of the absorbent compound after at least about 10 cycles.
127. A particulate composite material as recited in claim 111, wherein the said absorbent phase comprises an absorbent compound that retains at least about 60 mol. % of the theoretical CO2 absorption capacity of the absorbent compound after at least about 10 cycles.
128. A particulate composite material as recited in claim 111, wherein said absorbent phase comprises an absorbent compound retains at least about 90 mol. % of the theoretical CO2 absorption capacity of the absorbent compound after at least about 10 cycles.
129. A particulate composite material as recited in claim 111, wherein said absorbent phase retains at least 10 grams CO2 per 100 grams unreacted absorbent after 10 cycles.
130. A particulate composite material as recited in claim 111, wherein said absorbent retains at least 20 grams CO2 per 100 grams unreacted absorbent after 10 cycles.
131. A particulate composite material as recited in claim 111, wherein said absorbent retains at least 30 grams CO2 per 100 grams unreacted absorbent after 10 cycles.
132. A particulate composite material as recited in claim 111, wherein said absorbent retains at least 40 grams CO2 per 100 grams unreacted absorbent after 10 cycles.
133. A particulate composite material as recited in claim 111, wherein said absorbent retains at least 50 grams CO2 per 100 grams unreacted absorbent after 10 cycles.
134. A particulate composite material as recited in claim 111, wherein said particulate composite has substantially spherical morphology.
135. A method for the fabrication of supported reforming catalyst particles, comprising the steps of: (a) forming a precursor solution comprising a metal precursor and an alumina precursor; (b) atomizing said precursor solution to form precursor droplets; (c) heating said precursor droplets to convert at least said metal precursor to metal-containing clusters dispersed on said alumina.
136. A method as recited in claim 135, wherein said metal precursor comprises a precursor to a metal selected from the group consisting of Rh, Ni, Ru, Pt, Pd and alloys thereof.
137. A method as recited in claim 135, wherein said metal precursor comprises a precursor to Rh.
138. A method as recited in claim 135, wherein said alumina precursor comprises particulate alumina.
139. A method as recited in claim 135, wherein said alumina precursor comprises particulate boehmite alumina.
140. A method as recited in claim 135, wherein said alumina precursor comprises particulate alumina having an average particle size of not greater than about 100 nm.
141. A method as recited in claim 135, wherein said catalyst particles have an average particle size (d50) of from about 1 μm to about 30 μm.
142. A method as recited in claim 135, wherein said catalyst particles have a surface area of at least about 150 m2/g.
143. A method as recited in claim 135, wherein said catalyst particles are aggregate particles comprising aggregated primary support particles, said primary support particles having an average size of from about 10 nanometers to about 100 nanometers.
144. A method as recited in claim 135, wherein said heating step comprises heating said precursor droplets to a temperature of at least about 500° C.
145. A method as recited in claim 135, wherein said catalyst particles comprise from about 0.1 wt. % to about 5 wt. % of said metal-containing clusters.
146. A method as recited in claim 135, wherein said heating step is carried out in a spray dryer.
147. A method as recited in claim 135, further comprising the step of heating said particles to a temperature of at least about 500° C.
148. A method as recited in claim 135, wherein said reforming particles have substantially spherical morphology.
149. A method for the fabrication of composite particles including an absorbent phase and a catalyst phase comprising the steps of: (a) forming a precursor solution, said precursor solution comprising: (i) a liquid; (ii) a precursor to an absorbent phase; and (iii) a precursor to a catalyst phase; (b) atomizing said precursor solution to form precursor droplets; and (c) heating said precursor droplets to remove said liquid and form composite particles.
150. A method as recited in claim 149, wherein said heating step comprises a first heating step to react said active absorbent precursor to an intermediate precursor compound and a second heating step to convert said intermediate precursor compound to said absorbent material.
151. A method as recited in claim 150, wherein said second heating step is at a temperature that is higher than said first heating step.
152. A method as recited in claim 149, wherein said heating step comprises heating said precursor mixture to form said absorbent material in a single step.
153. A method as recited in claim 149, wherein said absorbent phase precursor is selected from the group consisting of calcium oxalate, calcium nitrate, calcium acetate, calcium lactate and calcium hydroxide.
154. A method as recited in claim 149, wherein said absorbent phase precursor comprises calcium nitrate.
155. A method as recited in claim 149, wherein said precursor solution further comprises a porosity enhancing agent.
156. A method as recited in claim 149, wherein said catalyst phase precursor comprises a precursor to a metal selected from the group consisting of Rh, Ni, Ru, Pt, Pd and alloys thereof.
157. A method as recited in claim 149, wherein said catalyst phase precursor comprises a precursor to Rh.
158. A method as recited in claim 149, wherein said catalyst phase precursor comprises particulate alumina.
159. A method as recited in claim 149, wherein said composite particles have an average particle size (d50) of from about 1 μm to about 30 μm.
160. A method as recited in claim 149, wherein said heating step comprises heating said precursor droplets to a temperature of at least about 200° C.
161. A method as recited in claim 149, wherein said heating step is carried out in a spray dryer.
162. A method as recited in claim 149, wherein said composite particles have substantially spherical morphology.
163. A method for the fabrication of composite particles including an absorbent phase and a catalyst phase, comprising the steps of: (a) forming a particulate suspension, said particulate suspension comprising: (i) a liquid; (ii) a first particulate phase comprising an absorbent phase or an intermediate precursor to an absorbent phase; and (iii) a second particulate phase comprising a catalyst phase; (b) atomizing said particulate suspension to form suspension droplets; and (c) heating said suspension droplets to remove said liquid and form composite particles.
164. A method as recited in claim 163, wherein said heating step comprises a first heating step to react said active absorbent precursor to an intermediate precursor compound and a second heating step to convert said intermediate precursor compound to said absorbent material.
165. A method as recited in claim 163, wherein said second heating step is at a temperature that is higher than said first heating step.
166. A method as recited in claim 163, wherein said heating step comprises heating said precursor mixture to form said absorbent material in a single step.
167. A method as recited in claim 163, wherein said absorbent phase precursor is selected from the group consisting of calcium oxalate, calcium nitrate, calcium acetate, calcium lactate and calcium hydroxide.
168. A method as recited in claim 163, wherein said absorbent phase precursor comprises calcium nitrate.
169. A method as recited in claim 163, wherein said precursor solution further comprises a porosity enhancing agent.
170. A method as recited in claim 163, wherein said catalyst phase precursor comprises a precursor to a metal selected from the group consisting of Rh, Ni, Ru, Pt, Pd and alloys thereof.
171. A method as recited in claim 163, wherein said catalyst phase precursor comprises a precursor to Rh.
172. A method as recited in claim 163, wherein said catalyst phase precursor comprises particulate alumina.
173. A method as recited in claim 163, wherein said composite particles have an average particle size (d50) of from about 1 μm to about 30 μm.
174. A method as recited in claim 163, wherein said heating step comprises heating said precursor droplets to a temperature of at least about 200° C.
175. A method as recited in claim 163, wherein said heating step is carried out in a spray dryer.
176. A method as recited in claim 163, wherein said composite particles have substantially spherical morphology.
177. A method as recited in claim 163, wherein said first particulate phase has substantially spherical morphology.
178. A method as recited in claim 163, wherein said second particulate phase has substantially spherical morphology.
179. A pellet adapted for absorption enhanced reforming of a carbon-based fuel, said pellet comprising: (a) a particulate absorbent material; and (b) a particulate catalyst material.
180. A pellet as recited in claim 179, wherein said absorbent material comprises a calcium-containing compound.
181. A pellet as recited in claim 179, wherein said absorbent comprises CaO.
182. A pellet as recited in claim 179, wherein said catalyst is a reforming catalyst comprising a metal selected from the group consisting of Rh, Ni, Ru, Pt, Pd and alloys thereof dispersed on a support phase.
183. A pellet as recited in claim 179, wherein the mass ratio of said absorbent material to said catalyst material is at least about 1:1.
184. A pellet as recited in claim 179, wherein the mass ratio of said absorbent material to said catalyst material is from about 20:1 to about 3:1.
185. A pellet as recited in claim 179, wherein the mass ratio of said absorbent material to said catalyst material is from about 9:1 to about 5:1.
186. A pellet as recited in claim 179, wherein said pellet further comprises a binder.
187. A pellet as recited in claim 186, wherein said binder comprises aluminum oxide.
188. A pellet as recited in claim 179, wherein said particulate absorbent material comprises an active absorbent phase and an inert metal oxide phase.
189. A pellet as recited in claim 179, wherein said particulate absorbent material has substantially spherical morphology.
190. A pellet as recited in claim 179, wherein said particulate catalyst material has substantially spherical morphology.
191. A pellet adapted for absorption enhanced reforming of a carbon-based fuel, said pellet comprising composite particulates including an absorbent phase adapted to absorb CO2 and a catalyst phase selected from the group consisting of a reforming catalyst and a water-gas shift catalyst.
192. A pellet as recited in claim 191, wherein said absorbent phase comprises a calcium-containing compound.
193. A pellet as recited in claim 191, wherein said absorbent phase comprises CaO.
194. A pellet as recited in claim 191, wherein said catalyst phase is a steam-methane reforming catalyst.
195. A pellet as recited in claim 191, wherein said catalyst phase is a reforming catalyst comprising a metal selected from the group consisting of Rh, Ni, Ru, Pt, Pd and alloys thereof dispersed on a support phase.
196. A pellet as recited in claim 191, wherein the mass ratio of said absorbent phase to said catalyst phase is at least about 1:1.
197. A pellet as recited in claim 191, wherein the mass ratio of said absorbent phase to said catalyst phase is from about 20:1 to about 3:1.
198. A pellet as recited in claim 191, wherein the mass ratio of said absorbent phase to said catalyst phase is from about 9:1 to about 5:1.
199. A pellet as recited in claim 191, wherein said pellet has a crush strength of at least about 1 N/mm.
200. A pellet as recited in claim 191, wherein said pellet further comprises a binder.
201. A pellet as recited in claim 191, wherein said absorbent phase has substantially spherical morphology.
202. A pellet as recited in claim 191, wherein said catalyst phase has substantially spherical morphology.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. Provisional Patent Application Serial No. ______ by Hampden-Smith et al., entitled CARBON DIOXIDE ABSORBENT MATERIALS AND METHODS FOR MAKING SAME, and filed on Nov. 26, 2003, the disclosure of which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to particulate materials that are useful for fuel reformers, such as catalyst materials for hydrogen production from carbon-based fuels and absorbent materials for the removal of acid gases such as CO 2 and H 2 S from gas streams. The particulate materials can be produced by spray processing of precursors to form a powder batch. The present invention is also directed to fuel reformers incorporating the particulate materials and methods for using the materials. The present invention is also directed to the combination of a highly reversible, high-capacity CO 2 absorbent with steam reforming and/or water gas shift catalysts to achieve single step conversion of hydrocarbon fuels to hydrogen with a high conversion efficiency.
2. Description of the Related Art
Hydrogen (H 2 ) is an important material in the chemical, petroleum and energy industries. In the chemical and petroleum industries, hydrogen is used for the manufacture of ammonia (NH 4 ) and methanol (CH 3 OH), and is used in a variety of petroleum hydrotreating processes. A growing demand for hydrogen is forecast in the future, particularly for petroleum refining of heavy, high-sulfur crude oil. Hydrogen is also an environmentally clean energy source for the generation of electric power and space heating, and a substantial increase in hydrogen demand is expected in the near future.
Steam reforming, including steam-methane reforming (SMR), partial oxidation (POX) and autothermal reforming (ATR) are the major processes for hydrogen production from fossil-based fuels such as natural gas, and are expected to remain processes of choice for the next several decades. These fuel-processing technologies involve multiple steps and severe operating conditions. For example, SMR involves the endothermic reaction of methane (e.g., natural gas) with water to form H 2 and carbon monoxide (CO). The primary reformer operates at a temperature of approximately 800° C. to 850° C. and about 20 atm of pressure, and large quantities of supplemental fuel must be burned to supply the energy necessary to maintain the reformer temperature. Further, the reforming step is followed by at least one water gas shift (WGS) reactor to increase the H 2 content and reduce the CO content. This is followed by CO cleanup using selective oxidation, hydrogen membrane separation, pressure swing absorption or methanation. The reactions that occur during SMR of methane (CH 4 ), the major component of natural gas, are illustrated by Equations 1 to 4:
| Reforming | CH 4 + H 2 O → 3H 2 + CO | (1) | |
| Shift | CO + H 2 O → H 2 + CO 2 | (2) | |
| Cleanup | CO + O 2 → CO 2 | (3) | |
| or CO + 3H 2 → CH 4 + H 2 O | (4) | ||
Another commercially available method for the production of hydrogen from hydrocarbons is partial oxidation (POX). According to this method, CH 4 or a similar hydrocarbon feed stock is oxidized to produce CO and H 2 in accordance with the reaction illustrated by Equation 5:
CH 4 +½O 2 →2H 2 +CO (5)
This reaction is exothermic and therefore no heat is required. A typical POX system includes a POX reactor, followed by a shift reactor and a H 2 purification step. A POX reactor is more compact than a steam reformer since no additional heat must be added. The efficiency of the POX reactor is relatively high, however, POX systems are typically less energy efficient than SMR because of the utilization of higher temperatures and the problem of heat recovery.
Auto thermal reforming (ATR) combines some of the features of SMR and POX. In ATR, a hydrocarbon feed such as CH 4 is reacted with both steam and air to produce an H 2 -rich gas. Both the SMR and POX reactions take place (Equations 1 and 5). With the correct mixture of input fuel, air and steam, the POX reaction supplies all the heat needed to drive the catalytic SMR reaction. However, as with SMR and POX systems, a WGS reactor and a H 2 purification stage are required to remove carbon oxides.
Fuel cells provide electricity through chemical oxidation-reduction reactions and have tremendous advantages over other types of power generation devices in terms of energy efficiency and environmental compatibility. For low temperature applications, the most promising type of fuel cell is the proton exchange membrane (PEM) fuel cell, which employs H 2 as a fuel in the anode and O 2 as an oxidant in the cathode. However, the cost of constructing the distribution infrastructure to safely transport pure H 2 gas over large distances presents an economic barrier to the exploitation of fuel cells, particularly for the transportation sector. Therefore, distributed production by smaller reforming systems that convert hydrocarbons to H 2 gas is a more viable option for the near future. However, conventional fuel-processing technologies for H 2 production from hydrocarbons are unsatisfactory for providing H 2 to PEM fuel cells due to low reforming efficiencies resulting from the multiple steps that are required and the severe operating conditions that are required, as is discussed above. Further, the reformate typically has a low H 2 content (45 to 50 mol. % on a dry basis) and a high CO and CO 2 content. The reformate can also include other gases, such as N 2 , depending on the reforming method.
The low H 2 content in the reformate reduces the fuel cell performance and requires that greater amounts of expensive Pt and PtRu catalysts and membrane materials be utilized for reasonable system efficiency as compared to fuel cells operating on pure H 2 . The high levels of CO 2 in the reformate also cause two additional problems. The CO 2 converts to CO in the PEM stack due to the reverse water gas shift reaction (reverse of Equation 2) and the CO can poison the catalyst. Also, the acidic nature of CO 2 and water solutions promotes a number of reactions that can reduce the useful lifetime of the PEM stacks by greater than 50%.
The deficiencies of conventional fuel reforming processes can be overcome to a certain extent by following the WGS step with amine scrubbing, hydrogen membrane separation and/or pressure swing adsorption (PSA). With amine scrubbing it is often necessary to further reduce the concentration of carbon oxides to trace levels by methanation. PSA requires operation at a significant pressure, which lowers system efficiency and produces a tail gas containing 25% to 30% of the H 2 produced during column blowdown and purge. While the energy content of the tail gas can be recovered and used in the reforming process it is often the case that the energy content of the combined fuel cell anode tail gas and the purification tail gas is greater than the energy required by the reforming process.
A variety of approaches have been explored to develop a fuel processing technology that uses simple chemical processes, has low energy consumption and generates high purity H 2 . These include the application of reaction-separation membranes and the application of absorption materials. One promising approach is absorption enhanced reforming (AER). AER combines a SMR catalyst and a CO 2 absorbent (e.g., CaO) in a single reactor so that reforming, shift, and CO 2 absorption occur simultaneously.
| CO 2 absorption | CaO + CO 2 → CaCO 3 | (6) | |
| Overall | CaO + CH 4 + 2H 2 O → 4H 2 + CaCO 3 | (7) | |
Many potential benefits over conventional reforming have been demonstrated using AER. These include: (i) reforming at a significantly lower temperature (about 600° C.), while achieving an increased conversion of CH 4 to H 2 ; (ii) lower capital cost as compared to conventional SMR; (iii) producing H 2 at feed gas pressure (200 to 400 psig) and at relatively high purity (>95%) directly from the reactor; (iv) reducing or even eliminating downstream purification steps; (v) minimizing side reactions and increasing catalyst lifetime; (vi) reducing the excess steam used in conventional reforming, particularly when treating heavy fuels; and (vii) effective fixing of CO 2 .
It should be noted that various terminology has been used in the literature to describe the reaction of CO 2 and a solid material such as CaO. Among the terms used are adsorption, absorption, sorption and fixing of CO 2 . In general, none of these terms precisely describes this complex process, which starts with adsorption of the CO 2 onto the surface of a solid, followed by a chemical conversion of the solid and expansion of this process into the bulk of the solid. Therefore, the terms adsorption, absorption and fixing (to describe the process), and adsorbent and absorbent (to describe the solid material) are used interchangeably within the present specification.
The use of AER for H 2 production for use in a fuel cell has been disclosed in U.S. Patent Application Publication No. 20020155329 by Stevens. More recently, the benefits of this approach for hydrogen production from solid fuels such as biomass and coal have also been demonstrated by S. Lin et al. ( Fuel 2002, 81, 2079).
There are a variety of CO 2 absorption materials available for AER. Reaction-based CO 2 absorption materials such as CaO-based absorbents are preferred because these types of materials typically have much higher equilibrium capacities than other absorbents. For example, under ideal conditions methylethanolamine captures 6 g/100 g (grams of CO 2 per 100 gram of material), silica gel absorbs 1.32 g/100 g, and activated carbon absorbs 8.8 g/100 g. Materials used for PSA such as K 2 CO 3 /Hydrotalcite can only remove a small portion of CO 2 , about 1.98 g/100 g. In contrast, CaO can capture 78.57 g/100 g. Even assuming only a 50 wt. % capacity over repeated cycles, the value of 39.3 g/100 g for AER is 5 to 10 times higher than the above absorbents.
The conversion of hydrocarbons in the presence of steam and a CO 2 absorbent can be traced back to as early as 1868. Recently some results for hydrogen production using this concept have been reported by: D. P. Harrison et al, Chemical Engineering Science 1999, 54, 3543; V. K. Ravi et al., Proceeding of the 2002 U.S. DOE Hydrogen Program Review NREL/CP610-32405; M. Spectht et al., Hydrogen Energy Progress XIII, Z. Q. Mao, T. N. Veriroglu (Eds.), 2000, 1203; and J. R. Hufton et al., Proceedings of the 1995 U.S DOE Hydrogen Program Review, 1995, 1, 815. The CO 2 absorbents typically used for AER have poor reactivity, low CO 2 capacity, and poor recyclability. The key to successfully commercialize AER methods is to develop an absorbent with high activity and capacity, and particularly with high recyclability to maintain sufficient activity and capacity over numerous carbonation and decarbonation cycles.
The absorbent materials have other applications in addition to AER. The increasing use of fossil fuels to meet energy needs has led to higher CO 2 emissions into the atmosphere and CO 2 emissions from direct combustion of fossil fuels account for one-half of the greenhouse effect that causes global warming. It is therefore necessary to develop cost-effective CO 2 management schemes to curb CO 2 emissions. Many CO 2 management schemes consist of three parts: separation, transportation, and sequestration. The capture of CO 2 accounts for about 75% of the total cost of CO 2 management, and imposes a severe energy requirement on fossil fuel-based power plants, reducing their net electricity output by as much as 37%. The costs associated with current CO 2 separation technologies necessitate the development of economical alternative.
Integrated gasification combined cycle (IGCC) power generation systems hold great promise for producing electric power efficiently and economically. Instead of direct combustion, coal is gasified by means of enriched air, O 2 , and/or H 2 O to obtain a concentrated coal gas. After cleanup, the coal gas is used to fire a gas turbine. The hot exhaust from the gas turbine is passed to a boiler to generate steam, which is then used to drive a steam turbine.
Coal includes sulfur as an impurity, which upon gasification typically enters the coal gas stream as hydrogen sulfide (H 2 S). It has been common practice to cool the gas below 77° C. to remove H 2 S by wet scrubbing. However, this practice reduces the overall efficiency of the power generation plant significantly. Hot gas cleanup methods capable of operating at temperatures close to the gasifier outlet temperature, which may range from 725° C. to 1325° C., would increase the overall energy conversion efficiency. While various absorbents have been proposed for desulfurizing hot coal gas, few are effective at such high temperatures.
It is known that zinc-based materials such as zinc oxide (ZnO) are highly effective for removing H 2 S, but their use is limited to temperatures below 650° C. At higher temperatures, calcium-based absorbents are promising because the reaction of CaO with H 2 S is both thermodynamically and kinetically favorable. The reactions are illustrated by Equations 8 to 11.
| Absorption | CaO + H 2 S → CaS + H 2 O | (8) | |
| Oxidation | CaS + 2O 2 → CaSO 4 | (9) | |
| Reduction | CaSO 4 + CO → CaO + CO 2 + SO 2 | (10) | |
| CaSO 4 + H 2 → CaO + H 2 O + SO 2 | (11) | ||
It has been proven experimentally and thermodynamically by van der Ham et al. (Ind. Eng. Chem. Res., 1996, 35, 1487) that the H 2 S content of gas produced by an air- and steam-blown coal gasifier operating under typical conditions can be reduced to 20 ppmv by employing CaO in highly reducing conditions at a temperature higher than 800° C. Regeneration can be accomplished at a temperature above the absorption temperature by employing a cyclic oxidation and reduction process, as is disclosed by S. B. Jagtap et al., Energy Fuels, 1996, 10, 821 and in U.S. Pat. No. 6,083,862 by Wheelock.
Natural CaO-based absorbents such as limestone and dolomite are plentiful and inexpensive, but they are soft and friable and do not stand up well to handling and recycle use. To improve the recyclability, some work has been focused on the pelletizing of limestone by using different binders. See, for example, U.S. Pat. No. 4,316,813 by Voss et al. Some work also focused on the modification of natural materials such as dolomite to tailor the physicochemical properties of the material. The synthesis of a CaO-based absorbent through boiling of CaO into Ca(OH) 2 or the carbonation of calcium salt solution such as calcium nitrate or Ca(OH) 2 into calcium carbonate, then decomposition of the carbonate into CaO has been disclosed by L. S. Fan et al., Ind. Eng. Chem. Res., 1999, 38, 2283. Others have disclosed the preparation of CaO-based materials by aerogel methods.
The foregoing methods generally result in limited control over the composition and microstructure of the powders. The morphology and surface properties such as surface area, pore volume and pore size are among the characteristics that have a critical impact on the performance of the absorbent. This is due to the nature of the reactions that occur. First, carbonation takes place on the external and internal surfaces of CaO-based absorbent, which forms a carbonate layer. Then, the chemical reaction advances with the diffusion of CO 2 through the carbonate layer into the unreacted core CaO active sites. Therefore, higher reactivity and faster kinetics can be expected for small particle size CaO due to the higher surface to bulk ratio of the absorbent species. A more porous structure will also lead to higher reactivity and recyclability, and a lower decarbonation temperature due to the easier CO 2 diffusion into or out of the outer carbonate layer.
It would be advantageous to provide a method for producing absorbent powders that would enable control over the powder characteristics such as particle size, surface area and pore structure as well as the versatility to accommodate compositions which are either difficult or impossible to produce using existing production methods. It would be particularly advantageous if such powders could be produced in large quantities on a substantially continuous basis. Further value can be derived from these powders if they can be incorporated into structures that can be integrated into reactor beds that enable a suitable combination of high space velocity and high absorption capacity while retaining their performance characteristics. Such structures include coatings, such as wash coatings on highly porous monoliths, pellets that have pore structures that retain the performance of the powders and also coatings or impregnation of the powder particles into other structures such as metals, metal oxides, textiles or cloths, which may provide beneficial heat transfer characteristics.
SUMMARY OF THE INVENTION
According to one embodiment of the present invention, a method for the conversion of a carbon-based fuel to a hydrogen-rich product gas is provided. The method includes the steps of providing a carbon-based fuel, converting the carbon-based fuel to an intermediate gas product by contacting the fuel with at least a first conversion catalyst, contacting the intermediate gas product with an absorbent material to absorb CO 2 and form a hydrogen-rich gas, extracting the hydrogen-rich gas from the contacting step and regenerating the absorbent. The foregoing steps are repeated at least ten times wherein the absorbent material retains at least about 50 mol. % of its theoretical absorption capacity after each of the repeating steps.
According to another embodiment, a method for the conversion of a carbon-based fuel to a hydrogen-rich product gas is provided. The method includes providing a carbon-based fuel, converting the carbon-based fuel to an intermediate gas product by contacting the fuel with at least a first conversion catalyst, contacting the intermediate gas product with an absorbent material to absorb CO 2 and form a hydrogen-rich gas, extracting the hydrogen-rich gas from the contacting step and regenerating the absorbent. The foregoing steps can be repeated at least ten times wherein the total mass of the absorbent material retains at least about 10 grams CO 2 per 100 grams of unreacted absorbent after each cycle.
According to yet another embodiment, a method for the conversion of a carbon-based fuel to a hydrogen-rich product gas is provided. The method includes the steps of providing a carbon-based fuel and steam, converting the fuel and steam to an intermediate gas product by contacting the fuel and steam with at least a first conversion catalyst, contacting the intermediate gas product with an absorbent material to absorb CO 2 and form a hydrogen-rich gas, extracting the hydrogen-rich gas from the contacting step and regenerating the absorbent. At least the absorbent material is a pelletized form and the foregoing steps can be repeated at least 50 times wherein the absorbent material retains at least about 20 mol. % of its theoretical CO 2 absorption capacity after each cycles.
According to another embodiment, a method for absorption enhanced reforming of a carbon-based fuel is provided. The method includes providing a carbon-based fuel, contacting the fuel with at least a first conversion catalyst to catalyze the formation of hydrogen and with a pelletized absorbent compound having a first bulk density, wherein the pelletized absorbent is converted to a carbonized absorbent having a second bulk density and regenerating the carbonized absorbent to form a regenerated absorbent having a third bulk density, wherein the third bulk density is greater than the first bulk density.
According to another embodiment of the present invention, an absorbent material for the absorption of CO 2 is provided which includes an absorbent compound and a metal oxide, wherein the absorbent material has a surface area of at least about 5 m 2 /g.
According to another embodiment of the present invention, a CO 2 absorbent material is provided including particulates of a calcium-containing compound selectively doped with at least about 0.1 at. % of an additional element selected from the monovalent and divalent and polyvalent metals, the particulates having a surface area of at least 5 m 2 /g.
According to another embodiment of the present invention, a steam-reforming catalyst is provided. The steam-reforming catalyst includes a particulate support structure and a metal dispersed on the support structure wherein the reforming catalyst achieves at least about 90% of the theoretical thermodynamic conversion of methane to hydrogen at a temperature of 600° C., a H 2 O:C ratio of 3:1 and a gas hour space velocity (GHSV) of 5000 hour −1 in the absence of an absorbent for CO 2 .
According to another embodiment of the present invention, a particulate composite material is provided which includes an absorbent phase adopted to absorb CO 2 and a catalyst phase selected from the group consisting of a reforming catalyst phase and a water-gas shift catalyst phase.
According to another embodiment of the present invention, a method for the fabrication of a particulate calcium oxide-containing absorbent material is provided. The method includes the steps of providing a precursor solution including at least a first precursor to a calcium oxide-containing compound, atomizing the precursor solution to form precursor droplets and heating the precursor droplets to form a particulate calcium oxide-containing compound.
According to another embodiment of the present invention, a method for the fabrication of a calcium oxide-containing absorbent material is provided. The method includes the steps of providing a precursor solution including at least a first precursor to an intermediate calcium compound, atomizing the precursor solution to form precursor droplets, heating the precursor droplets to form a particulate intermediate calcium compound, the calcium compound having a theoretical density that is less than the theoretical density of calcium oxide, and converting the intermediate calcium compound to a calcium oxide-containing absorbent material.
According to another embodiment of the present invention, a method for the fabrication of an absorbent material including an absorbent phase and a metal oxide is provided. The method includes providing a precursor solution including at least a first precursor to an absorbent compound and a solvent. A particulate metal oxide is mixed with the precursor solution and the solvent is removed from the precursor mixture. The precursor mixture is heated to at least partially react the active absorbent compound precursor and form the absorbent material.
According to another embodiment of the present invention, a method for the fabrication of supported reforming catalyst particles is provided. The method includes forming a precursor solution including a metal precursor and an alumina precursor, atomizing the precursor solution to form precursor droplets and heating the precursor droplets to convert at least the metal precursor to metal-containing clusters dispersed on the alumina.
According to another embodiment of the present invention, a method for the fabrication of composite particles including an absorbent phase and a catalyst phase is provided. The method includes the steps of forming a precursor solution including a liquid, a precursor to an absorbent phase and a precursor to a catalyst phase. The precursor solution is atomized to form precursor droplets and the precursor droplets are heated to remove liquid from the droplets and form composite particles.
According to another embodiment of the present invention, a method for the fabrication of composite particles including an absorbent phase and a catalyst phase is provided. The method includes forming a particulate suspension, where the particulate suspension includes a liquid, a first particulate phase comprising an absorbent phase or an intermediate precursor to an absorbent phase and a second particulate phase comprising a catalyst phase. The particulate suspension is atomized to form suspension droplets and the droplets are heated to remove liquid from the droplets and form composite particles.
According to another embodiment of the present invention, a pellet is provided that includes at least about 5 wt. % of a particulate intermediate compound to an absorbent compound, wherein the particulate intermediate compound has a theoretical density that is not greater than the theoretical density of the absorbent compound and wherein the particulates are substantially spherical.
According to another embodiment of the present invention, a pellet for the absorption of CO 2 is provided. The pellet includes composite particulates of a calcium compound and from about 1 wt. % to about 40 wt. % of a metal oxide selected from the group consisting of aluminum oxides and titanium oxides, wherein the particulates are substantially spherical.
According to another embodiment of the present invention, a pellet adapted for the absorption enhanced reforming of a carbon-based fuel is provided. The pellet includes a particulate absorbent material and a particulate catalyst material.
According to yet another embodiment of the present invention, a pellet adapted for the absorption enhanced reforming of a carbon-based fuel is provided. The pellet includes composite particulates including an absorbent phase adapted to absorb CO 2 and a catalyst phase selected from the group consisting of a reforming catalyst and a water-gas shift catalyst.
These and other embodiments of the present invention are described in more detail herein below.
DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically illustrates a spray pyrolysis method for the fabrication of particles according to an embodiment of the present invention.
FIG. 2 schematically illustrates a spray conversion method for the fabrication of particles according to an embodiment of the present invention.
FIG. 3 schematically illustrates a post-processing method for the fabrication of particles according to an embodiment of the present invention.
FIG. 4 illustrates the calculated equilibrium gas composition for steam reforming of methane in the presence of a CO 2 absorbent such as CaO.
FIG. 5 illustrates the calculated equilibrium gas composition for steam reforming of methane without a CO 2 absorbent.
FIG. 6 illustrates a process of the absorption of a contaminant from a gas stream with a regenerating step.
FIG. 7 illustrates the aggregate particle morphology of a particulate absorbent material according to an embodiment of the present invention.
FIG. 8 illustrates the aggregate particle morphology of a particulate absorbent material according to an embodiment of the present invention.
FIG. 9 illustrates the aggregate particle morphology of a supported absorbent material according to an embodiment of the present invention.
FIG. 10 illustrates the aggregate particle morphology of an absorbent material according to an embodiment of the present invention.
FIG. 11 illustrates the structure of a supported composite particle including a water gas shift catalyst and reforming catalyst according to an embodiment of the present invention.
FIG. 12 illustrates the structure of a composite absorbent/catalyst particle according to an embodiment of the present invention.
FIG. 13 illustrates the particle size distribution of absorbent powders according to the present invention compared to the prior art.
FIG. 14 illustrates the BET surface area of absorbent powders according to the present invention compared to the prior art.
FIG. 15 illustrates the pore volume of absorbent powders according to the present invention compared to the prior art.
FIG. 16 illustrates the carbonation and decarbonation kinetics of a commercial CaO powder according to the prior art.
FIG. 17 illustrates the absorption capacity of a commercial CaO absorbent powder over 26 cycles.
FIG. 18 illustrates the particle size distribution of a commercial CaO absorbent powder before and after 27 cycles.
FIG. 19 illustrates the pore volume, BET surface area and average pore size of a commercial CaO absorbent powder before and after 27 cycles.
FIG. 20 illustrates the absorption capacity in terms of CaO reaction fraction of CaO-based absorbents over multiple cycles according to the present invention compared to the prior art.
FIG. 21 illustrates the carbonation and decarbonation kinetics of CaO-based absorbents according to the present invention compared to the prior art.
FIG. 22 illustrates the particle size distribution of absorbent powders according to the present invention.
FIG. 23 illustrates the pore volume, BET surface area and average pore diameter for absorbent powders according to the present invention.
FIG. 24 illustrates the absorption capacity in terms of CaO reaction fraction of absorbent powders according to the present invention over multiple cycles.
FIGS. 25 ( a ) and 25 ( b ) illustrate SEM photomicrographs of a commercial CaO powder before and after 27 cycles.
FIGS. 26 ( a ) and 26 ( b ) illustrate SEM photomicrographs of an absorbent powder according to the present invention before and after 12 cycles.
FIGS. 27 ( a ) and 27 ( b ) illustrate SEM photomicrographs of an absorbent powder according to the present invention before and after 12 cycles.
FIG. 28 illustrates the particle size distribution of absorbent powders according to the present invention before and after 12 cycles.
FIG. 29 illustrates the absorption capacity in terms of CaO reaction fraction of absorbent powders according to the present invention over 12 cycles.
FIG. 30 illustrates the carbonation and decarbonation kinetics of several absorbent powders according to the present invention.
FIG. 31 illustrates the carbonation and decarbonation kinetics of a composite absorbent powder according to the present invention.
FIG. 32 illustrates the adsorption capacity over 12 cycles for 2 absorbent materials according to the present invention.
FIG. 33 illustrates the carbonation and decarbonation kinetics of several absorbent powders according to the present invention.
FIG. 34 illustrates the particle size distribution of absorbent powders according to the present invention before and after 12 cycles.
FIG. 35 illustrates the pore volume, BET surface area and average pore diameter of absorbent powders according to the present invention before and after 12 regeneration cycles.
FIG. 36 illustrates the methane conversion over steam reforming catalysts according to the present invention compared to a prior art catalyst.
FIG. 37 illustrates the methane conversion over steam reforming catalysts according to the present invention compared to a prior art catalyst.
FIG. 38 illustrates the methane conversion over steam reforming catalysts according to the present invention compared to a prior art catalyst.
FIG. 39 illustrates the methane conversion over steam reforming catalysts according to the present invention compared to a prior art catalyst.
FIG. 40 illustrates the absorption capacity in terms of CaO reaction fraction of multi-functional composite powders according to the present invention.
FIG. 41 illustrates the carbonation and decarbonation kinetics of multi-functional composite powders according to the present invention.
FIG. 42 illustrates the absorption capacity over 92 cycles in terms of CaO reaction fraction of a multi-functional composite powder according to the present invention.
FIG. 43 illustrates the absorption capacity over 92 cycles of a multi-functional composite powder according to the present invention.
FIG. 44 illustrates the carbonation and decarbonation kinetics for a multi-functional composite powder according to the present invention.
FIG. 45 illustrates the absorption capacity in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention.
FIG. 46 illustrates the absorption capacity of pelletized absorbent powders according to the present invention.
FIG. 47 illustrates the carbonation and decarbonation kinetics of pelletized absorbent powders according to the present invention.
FIG. 48 illustrates the absorption capacity in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention over 116 cycles.
FIG. 49 illustrates the absorption capacity of pelletized absorbent powders according to the present invention over 116 cycles.
FIG. 50 illustrates the absorption capacity in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention over multiple cycles.
FIG. 51 illustrates the absorption capacity of pelletized absorbent powders according to the present invention over multiple cycles.
FIG. 52 illustrates the absorption capacity in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention over multiple cycles.
FIG. 53 illustrates the absorption capacity of pelletized absorbent powders according to the present invention over multiple cycles.
FIG. 54 illustrates the absorption capacity in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention over multiple cycles.
FIG. 55 illustrates the absorption capacity over 66 cycles of pelletized absorbent powders according to the present invention.
FIG. 56 illustrates the absorption capacity over 66 cycles in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention.
FIG. 57 illustrates the absorption capacity over 66 cycles of pelletized absorbent powders according to the present invention.
FIG. 58 illustrates the absorption capacity over 66 cycles in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention over multiple cycles.
FIG. 59 illustrates the absorption capacity over 66 cycles of pelletized absorbent powders according to the present invention.
FIG. 60 illustrates the absorption capacity over 64 cycles in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention.
FIG. 61 illustrates the absorption capacity over 64 cycles of pelletized absorbent powders according to the present invention.
FIG. 62 illustrates the absorption capacity over 64 cycles in terms of CaO reaction fraction of pelletized absorbent powders according to the present invention.
FIG. 63 illustrates the conversion efficiency of a composite absorbent/catalyst material according to an embodiment of the present invention.
FIG. 64 illustrates the conversion efficiency of a composite absorbent/catalyst material according to an embodiment of the present invention.
DESCRIPTION OF THE INVENTION
The present invention is directed to improved materials and methods for making materials that are particularly useful in absorption-enhanced reforming (AER) processes for the production of a hydrogen-rich gas from carbon-based fuels such as hydrocarbons. The materials can include, but are not limited to, CaO-based materials for CO 2 absorption and supported Rh/Al 2 O 3 for steam reforming and water-gas shift catalysts.
Overview of Spray Processing
The materials of the present invention are preferably fabricated by spray drying, spray conversion or spray pyrolysis methods, which are collectively referred to herein as spray processing. The spray processing methods of the present invention are capable of producing a wide variety of materials and microstructures. The major attribute of this approach is the ability to fabricate compositions and microstructures that cannot be fabricated by other powder manufacturing methods, combined with the ability to economically produce high volumes of material. The flexibility to fabricate unique combinations of compositions and microstructures comes from the fact that spray processing combines aspects of both liquid phase and solid state processing.
Spray processing generally includes the steps of providing a precursor composition, typically in a flowable liquid form. The precursor composition typically includes at least a precursor to the absorbent or catalytic material, which are collectively referred to herein as an active material. In the case of supported active materials, the precursor composition can also include a precursor to or a suspension of the support phase. The precursor composition is atomized to form a suspension of liquid precursor droplets and the liquid is removed from the liquid precursor droplets, such as by heating, to form the powder. Typically, at least one component of the liquid precursor is chemically converted into a desired component of the powder.
CaO is a preferred absorbent material according to one embodiment of the present invention. Spray processing precursors for CaO can be selected from calcium metal salts such as calcium nitrate Ca(NO 3 ) 2 , calcium oxalate, calcium acetate and calcium hydroxide, with calcium nitrate being particularly preferred for some applications. It is often desirable to form the CaO with a high level of porosity or crystallinity and therefore it may be advantageous to include a morphology enhancing agent in the precursor composition to enhance the porosity or crystallinity of the powder. Morphology enhancing agents can be selected from lactic acid, glycine, alcohols, ammonium nitrate, polymers and carbohydrazide. The amount of porosity or crystallinity enhancing agent in the precursor composition can be varied from about 5 vol. % to about 40 vol. %.
Other materials can be included in the absorbent materials according to the present invention, as is discussed in more detail below. Included among these are aluminum oxides, magnesium oxides, silicon oxides, titanium oxides and mixtures of two or more oxides. Precursors for such materials can include nitrate salts such as aluminum nitrate or magnesium nitrate as well as others. In addition, the material can include other metals such as iron, magnesium, zinc and copper. Precursors for these metals can be selected from the metal nitrates, sulfates, carbonates, acetates, oxalates, hydroxides and metal oxide nanoparticles, including fumed metal oxides.
Preferred steam reforming catalysts include rhodium (Rh) metal dispersed on a support such as alumina (Al 2 O 3 ). Accordingly, the Rh precursor can preferably be selected from rhodium acetate Rh(OAc) 3 and rhodium nitrate Rh(NO 3 ) 3 . The active metal species can also include metals such as nickel (Ni), platinum (Pt) and palladium (Pd) and precursors for these metals can be selected from nitrates, ammines, hydroxides, chlorides and the like.
The spray processing methods can combine the drying of the precursors and the conversion to the active material in one step, where both the removal of the solvent and the conversion of a precursor occur essentially simultaneously. This method is referred to as spray pyrolysis, and is schematically illustrated in FIG. 1. In another embodiment, the spray processing method achieves the drying of the precursors and a partial conversion of the precursors to an intermediate compound. This method is schematically illustrated in FIG. 2. The complete conversion to the active material and/or the crystallization of the material can occur in a second step, such as the step that is schematically illustrated in FIG. 3. This second step is referred to herein as post-processing. Thus, spray drying or spray conversion is followed by conventional heating or calcination, e.g., a method illustrated in FIG. 2 followed by a method such as that illustrated in FIG. 3. By varying reaction time, temperature and type of precursors, the spray processing methods can produce powder morphologies and active material structures that yield improved performance.
When the active material phase is dispersed on an inert support in the form of active material clusters, the precursor composition can include particulates that form the inert support phase. According to the present invention, such particulates can include particulate carbon or particulate aluminum oxide, such as particulate boehmite.
Preferably, the supported active material phase is formed while the precursor to the active material phase is in intimate contact with the surface of the support phase particles and the active material precursor is rapidly reacted on the surface of the support phase particles. The reaction and formation of the supported active material preferably occurs over a very short period of time such that the growth of large active material clusters is limited. Preferably, the active material precursor is exposed to the elevated reaction temperature to form the active material for not more than about 600 seconds, more preferably not more than about 100 seconds and even more preferably not more than about 10 seconds. The means by which the active material precursor is reacted is discussed in detail below.
Preferably, the spray processing methods are capable of simultaneously forming a spherical particle structure. The spherical particles form as a result of the formation and drying of the precursor droplets during spray processing.
Spray processing methods for the production of the active materials can be grouped by reference to several different attributes of the apparatus used to carry out the method. These attributes include: the main gas flow direction (vertical or horizontal); the type of atomizer (submerged ultrasonic, ultrasonic nozzle, two-fluid nozzle, single nozzle pressurized fluid); the type of gas flow (e.g., laminar with no mixing, turbulent with no mixing, co-current of droplets and hot gas, countercurrent of droplets and gas or mixed flow); the type of heating (e.g., hot wall system, hot gas introduction, combined hot gas and hot wall, plasma or flame); and the type of powder collection system (e.g., cyclone, bag house, electrostatic or settling).
For example, absorbent and catalytic powders of the present invention can be prepared by starting with an aqueous-based precursor liquid consisting of a dissolved metal salt. The processing temperature of the precursor droplets can be controlled so the metal salt precursor decomposes to form the active material or a solid precursor to the active material.
The first step in the process is the evaporation of the solvent (typically water) as the droplet is heated resulting in a particle of dried solids and/or metal salts. A number of methods to deliver heat to the particle are possible: horizontal hot-wall tubular reactors, spray dryer and vertical tubular reactors can be used, as well as plasma, flame and laser reactors. As the particles experience either higher temperature or longer time at a specific temperature, the metal precursor decomposes. Preferably, the time that the droplets/particles experience a given temperature can be controlled and therefore the degree of porosity, crystallinity, the microstructure and other properties can also be controlled.
The atomization technique for generating the precursor droplets has a significant influence over the characteristics of the final active material powder, such as the particle surface area, porosity, size, the spread of the particle size distribution (PSD), as well as the production rate of the powder. In extreme cases, some techniques cannot atomize fluids with even moderate particle loadings or high viscosities. Several methods exist for the atomization of precursor compositions, including those that contain suspended particulates. These methods include but are not limited to: ultrasonic transducers (usually at a frequency of 1-3 MHz); ultrasonic nozzles (usually at a frequency of 10-150 KHz); rotary atomizers; two-fluid nozzles; and pressure atomizers.
Ultrasonic transducers are generally submerged in a liquid and the ultrasonic energy produces atomized droplets on the surface of the liquid. Two basic ultrasonic transducer disc configurations, planar and point source can be used. Deeper fluid levels can be atomized using a point source configuration since the energy is focused at a point that is some distance above the surface of the transducer. The scale-up of submerged ultrasonic transducers can be accomplished by placing a large number of ultrasonic transducers in an array. Such a system is illustrated in U.S. Pat. No. 6,338,809 by Hampden-Smith et al., the disclosure of which is incorporated herein by reference in its entirety.
Scale-up of nozzle systems can be accomplished by either selecting a nozzle with a larger capacity or by increasing the number of nozzles used in parallel. Typically, the droplets produced by nozzles are larger than those produced by ultrasonic transducers. Particle size is also dependent on the gas flow rate. For a fixed liquid flow rate, an increased airflow decreases the average droplet size and a decreased airflow increases the average droplet size. It is difficult to change droplet size without varying the liquid or airflow rates. However, two-fluid nozzles have the ability to process larger volumes of liquid per unit time than ultrasonic transducers.
Ultrasonic spray nozzles also use high frequency energy fo atomize a fluid. Ultrasonic spray nozzles have some advantages over single or two-fluid nozzles such as the low velocity of the spray leaving the nozzle and lack of associated gas flow. The nozzles are available with various orifice sizes and orifice diameters that allow the system to be scaled for the desired production capacity. In general, higher frequency nozzles are physically smaller, produce smaller droplets, and have a lower flow capacity than nozzles that operate at lower frequencies. A drawback of ultrasonic nozzle systems is that scaling up the process by increasing the nozzle size increases the average particle size. If a particular particle size is required, then the maximum production rate per nozzle is set. If the desired production rate exceeds the maximum production rate of the nozzle, additional nozzles or additional production units are required to achieve the desired production rate.
The shape of the atomizing surface determines the shape and spread of the spray pattern. Conical, microspray and flat atomizing surface shapes are available. The conical atomizing surface provides the greatest atomizing capability and has a large spray envelope. The flat atomizing surface provides almost as much flow as the conical surface but limits the overall diameter of the spray. The microspray atomizing surface is for very low flow rates where narrow spray patterns are needed. These nozzles are preferred for configurations where minimal gas flow is required in association with the droplets.
Particulate suspensions in the precursor solution (e.g., for the production of a supported active material) may present several problems with respect to atomization. For example, submerged ultrasonic atomizers re-circulate the suspension through the generation chamber and the suspension concentrates over time. Further, some fraction of the liquid atomizes without carrying the suspended particulates. Other problems encountered when using submerged ultrasonic transducers is that the transducer discs can become coated with the particles and or precursor over time. Further, the generation rate of particulate suspensions can be very low using submerged ultrasonic transducer discs. This is due in part to energy being absorbed or reflected by the suspended particles.
For spray drying, the aerosol can be generated using three basic methods. These methods differ in the type of energy used to break the liquid masses into small droplets. Rotary atomizers (utilization of centrifugal energy) make use of spinning liquid droplets off of a rotating wheel or disc. Rotary atomizers are useful for co-current production of droplets in the range of 20 μm to 150 μm in diameter. Pressure nozzles (utilization of pressure energy) generate droplets by passing a fluid under high pressure through an orifice. These can be used for both co-current and mixed-flow reactor configurations and typically produce droplets in the range of 50 μm to 300 μm. Multiple fluid nozzles such as a two-fluid nozzle (utilization of kinetic energy) produce droplets by passing a relatively slow moving fluid through an orifice while shearing the fluid stream with a relatively fast moving gas stream. As with pressure nozzles, multiple fluid nozzles can be used with both co-current and mixed-flow spray dryer configurations. This type of nozzle can typically produce droplets in the size range of 5 μm to 200 μm.
For example, two-fluid nozzles are used to produce aerosol sprays in many commercial applications, typically in conjunction with spray drying processes. In a two-fluid nozzle, a low-velocity liquid stream encounters a high-velocity gas stream that generates high shear forces to accomplish atomization of the liquid. A direct result of this interaction is that the droplet size characteristics of the aerosol are dependent on the relative mass flow rates of the liquid precursor and nozzle gas stream. The velocity of the droplets as they leave the generation zone can be quite large which may lead to unacceptable losses due to impaction. The aerosol also leaves the nozzle in a characteristic pattern, typically a flat fan, and this may require that the dimensions of the reactor be sufficiently large to prevent unwanted losses on the walls of the system.
Thus, numerous atomization techniques for spray processing are possible for the production of active material powders and different versions are preferred for different feed streams and products.
The atomized precursor composition must be heated to remove solvents and react precursor components. For example, a horizontal, tubular hot-wall reactor can be used to heat a gas stream to a desired temperature. Energy is delivered to the system by maintaining a fixed boundary temperature at the wall of the reactor and the maximum temperature of the gas is the wall temperature. Heat transfer within a hot wall reactor occurs through the bulk of the gas. Buoyant forces that occur naturally in horizontal hot wall reactors aid this transfer. The mixing also helps to improve the radial homogeneity of the gas stream. Passive or active mixing of the gas can also increase the heat transfer rate. The maximum temperature and the heating rate can be controlled independent of the inlet stream with small changes in residence time. The heating rate of the inlet stream can also be controlled using a multi-zone furnace.
The use of a horizontal hot-wall reactor according to the present invention is generally preferred to produce particles with a size of not greater than about 5 μm. Above about 5 μm, settling of particles can cause significant material losses. One disadvantage of such reactors is the poor ability to atomize particulates when using submerged ultrasonics for atomization.
Alternatively, the horizontal hot-wall reactor can be used with a two-fluid nozzle to atomize the droplets. This approach is preferred for precursor feed streams containing higher levels of particulate materials, such as a particulate support precursor. A horizontal hot-wall reactor can also be used with ultrasonic nozzle atomization techniques. This allows atomization of precursor containing particulates, however the large droplet size leads to losses of materials on reactor walls and other surfaces making this an expensive method for powder production.
While horizontal hot-wall reactors are specifically useful for some particle morphologies and compositions according to the present invention, particularly for the spray pyrolysis method illustrated in FIG. 1, spray processing systems in the configuration of a spray dryer are the preferred production method for large quantities of absorbent and catalytic powders in accordance with some applications of the present invention. Such spray processing systems are particularly useful for the method schematically illustrated in FIG. 2.
Spray drying is a process wherein powders are produced by atomizing a precursor to produce droplets and evaporating the liquid to produce a dry aerosol, wherein thermal decomposition of one or more precursors may take place to produce the powder. The residence time in the spray dryer is the average time the process gas spends in the drying vessel as calculated by the vessel volume divided by the process gas flow using the outlet gas conditions. The peak excursion temperature (i.e., the reaction temperature) in the spray dryer is the maximum temperature of a particle, averaged throughout its diameter, while the particle is being processed and/or dried. The droplets are heated by supplying a pre-heated carrier gas.
Three types of spray dryer systems are useful for the spray drying of the active material powders according to the present invention. An open system is useful for spray drying of powders using air as an aerosol carrier gas and an aqueous feed solution as a precursor. A closed system is useful for spray drying of powders using an aerosol carrier gas other than air. A closed system is also useful when using a non-aqueous or a semi-non-aqueous solution as a precursor. A semi-closed system, including a self-inertizing system, is useful for spray drying of powders that require an inert atmosphere and/or precursors that are potentially flammable.
Two spray dryer designs are particularly useful for the production of the active material powders of the present invention. A co-current spray dryer is useful for the production of materials that are sensitive to high temperature excursions (e.g., greater than about 350° C.) or that require a rotary atomizer to generate the aerosol. Mixed-flow spray dryers are useful for producing materials that require relatively high temperature excursions (e.g., greater than about 350° C.) or require turbulent mixing forces.
In a co-current spray dryer, the hot gas is introduced at the top of the unit where the droplets are generated with any of the atomization techniques mentioned above. The maximum temperature that a droplet/particle is exposed to in a co-current spray dryer is the temperature of the outlet. Typically, the outlet temperature is limited to about 200° C., although some designs allow for higher temperatures. In addition, since the particles experience the lowest temperature in the beginning of the time-temperature curve and the highest temperature at the end, the possibility of precursor surface diffusion and agglomeration is high.
A preferred spray processing system is based on a mixed-flow spray dryer. A mixed-flow spray dryer introduces the hot gas at the top of the unit and the precursor droplets are generated near the bottom and are directed upwardly. The droplets/particles are forced towards the top of the unit then fall and flow back down with the gas, increasing the residence time in the spray dryer. The temperature the particles experience is also higher as compared to a co-current spray dryer. This is important, as most spray dryers are not capable of reaching the higher temperatures that are required for the conversion of some precursor salts.
For mixed flow spray dryers the reaction temperatures can be high enough for the decomposition of metal precursors such as Rh precursors (e.g., between 250° C. and 350° C.) useful for preparation of reforming catalysts such as a Rh/Al 2 O 3 supported catalyst. The highest temperature in these spray dryers is the inlet temperature (e.g., 600° C. and higher), and the outlet temperature can be as low as 90° C. Therefore, the particles reach the highest temperature for a relatively short time, which advantageously reduces precursor migration or surface diffusion. This spike of high temperature quickly converts the precursor and is followed by a mild quench since the spray dryer temperature quickly decreases after the maximum temperature is achieved. The spike-like temperature profile is advantageous for the generation of highly dispersed metal or metal oxide active material clusters on the surface of a support phase.
The range of useful residence times for producing the active material powders depends on the spray dryer design type, atmosphere used, nozzle configuration, feed liquid inlet temperature and the residual moisture content. In general, residence times for the production of the active material powders can range from 5 seconds up to 5 minutes. According to one embodiment, the residence time is from about 15 seconds to about 45 seconds.
The range of inlet temperatures for producing the active material powders depends on the spray dryer design type, atmosphere used, nozzle configuration, feed liquid, and energy required to perform drying and/or decomposition functions.
In general, the outlet temperature of the spray dryer determines the residual moisture content of the powder. For the production of the absorbent and catalytic powders according to the present invention, the range of useful outlet temperatures depends on the spray dryer design type, atmosphere used, nozzle configuration, feed liquid, inlet temperature, and residual moisture content. For example, a useful outlet temperature according to one embodiment of the present invention ranges from about 200° C. to about 350° C.
Other equipment that is desirable for producing the active material powders using a spray dryer includes a heater for the gas and a collection system. Either direct heating or indirect heating, including burning fuel, heating electrically, liquid-phase heating or steam heating, can accomplish heating of the gas. The most useful type of heating for the production of the powders processed with an inlet temperature greater than 350° C. is direct fuel burning.
Many collection methods are useful for collecting powders produced on a spray dryer. These methods include, but are not limited to those using cyclone, bag/cartridge filter, electrostatic precipitator, and various wet collection techniques.
The powders may also need to be post-processed by conventional calcination methods to convert them into another chemical composition prior to pelletization. For example, it may be advantageous to convert a metal oxalate with a particular structure into a metal carbonate and/or further to a metal oxide through a thermal post-processing step (FIG. 3). Likewise, it may be advantageous to convert a metal carbonate to a metal oxide while retaining the beneficial attributes of the pore structure. The post process ideally needs to be carried out under conditions that are not detrimental to the structure and performance of the material. Where the post processing is a thermally-induced transformation