Title:
Manufacture of motor fuel
United States Patent 2397085


Abstract:
This invention relates to the production of gasoline hydrocarbons of high anti-knock value from isoparaflins and oleflns. The invention relates particularly to an improved process for the production of high octane gasoline in which a hydrofluoric acid alkylation process, involving the step...



Inventors:
Boedeker, Edward R.
Oblad, Alex G.
Application Number:
US60004245A
Publication Date:
03/26/1946
Filing Date:
06/18/1945
Assignee:
SOCONY VACUUM OIL CO INC
Primary Class:
Other Classes:
208/64, 502/38, 585/331, 585/703, 585/713, 585/738, 585/822
International Classes:
C10G50/00
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Description:

This invention relates to the production of gasoline hydrocarbons of high anti-knock value from isoparaflins and oleflns. The invention relates particularly to an improved process for the production of high octane gasoline in which a hydrofluoric acid alkylation process, involving the step of defluorinating the alkylate product hydrocarbons by means of a solid defluorinating agent, is combined with an isomerization process for the conversion of terminal bond oleflns to non-ter- I minal bond olefins.

It is well known that motor fuel of high octane quality may be obtained by the alkylation of low boiling isoparamns, such as isobutane, with low boiling oleflns, such as the butenes, to produce saturated hydrocarbons within the gasoline boiling range. In commercial practice the feed stocks ordinarily employed for the production of alkylate gasoline comprise butane-butene mixtures which contain all the butane and butene isomers, viz., normal butane, isobutane, isobutylene, butene-1 and butene-2, these isomers being present in varying, though significant quantities. Such feed stocks are commonly employed for the reason that they are readily available in large quantities, and because they produce alkylate hydrocarbons having highly desirable octane ratings and volatility characteristics.

It has recently been discovered, as disclosed and claimed in a copending application of Joe E.

Penick and Urban H. Wagner, Serial No. 532,794, filed April 26, 1944, that the yields and octane numbers of the product hydrocarbons obtained by the hydrofluoric acid alkylation of butane-butene mixtures may be markedly increased by decreasing the proportion of butene-1 in the feed mixture prior to alkylation. As proposed in that application, a particularly suitable method of accomplishing this decrease in the proportion of butene-1, especially from the viewpoint of economical utilization of the olefin components of the feed stock, is to subject the feed stock to isomerization, so as to convert the butene-1 contained therein to butene-2.

It is the primary object of the present invention to provide an improved method for the manufacture of high octane motor fuel in which the advantageous step of isomerizing the terminal bond oleflns contained in commonly utilized alkylation charge stocks is combined with a hydrofluoric acid alkylation process in a novel and economical manner.

Other and further objects of our invention will appear from the following description thereof.

In conventional hydrofluoric acid alkylation processes for the production of high octane gasoline, an important and necessary step is the treatment of the product hydrocarbons for the removal therefrom of small amounts of fluorine compounds, such as organic fluorides and hydrogen fluoride, which remain In the product hydrocarbons after the usual settling and fractionating treatments for the removal of hydrofluoric acid and excess reactants. This "defluorination" of the alkylate product hydrocarbons is ordinarily carried out by passing the hydrocarbon product stream in contact, under proper conditions, with a solid, porous, adsorbent material known to be catalytically active for hydrohalogenation and dehydrohalogenation reactions, such as dehydrated bauxite, Activated Alumina, alumina gel, or the like. When utilized for this purpose, these materials gradually become inactive for the efficient removal of the fluorides, and it is necessary that they be either discarded and replaced by fresh materials, or reactivated. However, reactivation of the spent catalyst is costly, and it has been found to be more economical to utilize bauxite until its activity becomes too low and then discard it rather than to utilize the more effective, but more costly, synthetic materials, such as Activated Alumina.

We have found that these contact materials, after they have been used as defluorination agents, are highly effcient catalysts for the isomerization of terminal bond oleflns to non-terminal bond olefins. And we have found that when such materials are used as isomerization catalysts, such use tends to assist their reactivation, so that they may be more readily and less expensively reactivated as defluorination agents, since the isomerization reaction produces a deposit of carbon on the contact material which is readily oxidized in the regeneration treatment. This oxidation reaction, being highly exothermic, facilitates the attainment of the relatively high temperatures required for the removal of the adsorbed fluorides from the contact bed in the regeneration treatment.

In accordance with the present invention, a process for the manufacture of high octane gasoline hydrocarbons is proposed, which includes an alkylation step, a defluorination step and an isomerization step, in which process the contact materials are used, in one stage, for the defluorination of alkylate product hydrocarbons, and, in another stage, for the isomerization of terminal bond oleflns contained in alkylation charge stocks, after which they are regenerated for fur5 ther use in the process. In this way, the cost of SS897,0865 continually replacing the defluorination contact material, rom time to time, as heretofore required, is avoided and two processing steps, vz., defluorinatin and isomerzatmon, are accomplished by the use of a single contact material.

In accordance with the preferred manner of carrying out our process, separate contact beds are provided, and the steps of defluorinating the alkylate product hydrocarbons and Isomerizing the charge stock comprising terminal bond 10 oleflns are effected simultaneously in the different beds, the beds being alternated with respect to the different steps at regulated Intervals in the course of the process. Since a required step in our process is the reactivation of the contact bed after the Isomerization step of the process has been completed, we prefer to utilze three such beds, in order that the Isomerizing and defuorinating steps may be effected concurrently with the regeneration step.

The regeneration step of our process requires that the contact bed, after completion of the Isomerization step, be purged of an volatile hydrocarbon material and then subjected to a treatment with a hot oxidizing gas mixture at a terperature of from about 9000 F. to about 1100' F. for several hours to remove, by combustion, the carbonaceous material deposited on the contact agent, particularly in the course of the Isomerizaton cycle. The contact bed is then cooled down to defluorinatlon temperature for use in the next process cycle.

The operating conditions required for carrying out the defluorination step of our process are already well known. Thus, the alkylate product hydrocarbons may be effectively defluorinated by contacting them with materials, such as alumina gel or dehydrated bauxite, preferably the former, at a variety of flow rates, at temperatures ranging from as low as 50° F. to as high as 700° F.

The operation may be effected in either the liquid or vapor state, suitably high pressures being employed, where liquid phase operation is used, to substantially suppress vaporization of the hydrocarbons.

The Isomerization step of the process may be conducted over a relatively wide range of space velocities at temperatures of from about 300* F. to about 700* F. in the liquid or vapor phase, suitably high pressure being employed, where the 50 Isomerization is effected in the liquid phase, to maintain the hydrocarbons liquid at the particular temperature employed, The principle of our invention is applicable to any ydrofluoricacidalkylationprocesswhereit s desirable to isomerize terminal bond oleflns, such as butene-1, pentene-1, 3 methyl butene-1 or the like, contained in the alkylation feed stock to the corresponding non-terminal bond oleflns. The specific conditions to be employed for the defluorination and isomerization steps, such as the temperatures and the space velocities will, of course, vary depending upon the particular contact material employed and the flow requirements of the alkylaton process to which the invention is applied, In order that our invention may be better understood, reference is made to attached drawing which diagrammacally ustrates a suitable form of apparatus for carrying out the process of our invention.

In the drawing there are shown three contactors A, B, and C, containing beds of contact material such as Activated Alumina, dehydrated bauxite or alumina gel. preferably the latter.

When the process is in operation, one of the contactors will be on stream for the isomerization of the alkylation feed stock containing tIrminal bond oleflns, another will be operating as a defluorinating zone for the alkylate hydrocarbon products, while the third will be undergoing regeneration for further use as a defluorination zone.

Assuming contactor A to be on stream for Isomerization, a feed stock comprising terminal bond olefins enters the process system by way .of line I provided with a control valve 2, and is directed, by operation of control valves 3 and 4, in lines I and 5 to the contactor A. Suitable conditions for the operation of contactor A when isomerizing a butane-butene mixture, having a total butenes content of 46 weight per cent and 18 weight per cent of butene-1, are the use of space velocities of from about 5 to about 25 liquid volumes of butane-butene feed per volume of alumina gel contact material per hour, at temperatures ranging from about 500° F. to about 700° F.

Under these conditions the butene-1 content of the feed stock mixture will be substantially completely isomerized, i. e., to an equilibrium mixture of butene-1 and butene-2.

At the same time, contactor B will be on stream for defluorination of high octane alkylate hydrocarbons produced in the process as hereinafter described. The alkylate product hydrocarbon stream is withdrawn from preheater S, wherein it Is heated to a temperature suitable for the defluorination treatment, through line 12 and is directed by operation of control valves 8, 9, 10 and II, in lines 12 and 13, to contactor B. The use of temperatures of from about 200 to about 3500 F. and liquid space velocities of from about 3.5 to about 18 volumes of hydrocarbon per volume of alumina gel contact material per hour are effective for the defluorination of the hydrocarbon stream in contactor B.

During the period that contactors A and B are on stream, for isomerization and defluorination respectively, contactor C may be subjected to regeneration treatment comprising a steam purge, followed by a blast with hot oxidizing gases, such as an air-flue gas mixture, followed by a second steam purge to remove any oxygen containing gases, the contact bed thus being reconditioned for further use in the defluorination treatment.

During the period that the contactors A, B, and C are subjected successively and alternately to the defluorinatlon, isomerization and regeneration treatment, as described above, the material flow in the remainder of the system is as follows: From contactor A, isomerized feed stock is withdrawn in line 14, whence it is directed, by the operation of control valve 15, in lines 14 and 16 to a cooler 17, wherein it is suitably cooled prior to use in the alkylation step of the process.

The feed stock is withdrawn from the cooler in line 18 which discharges it into line 19, whence it enters alkylation zone 20. In line 19 the isomerized feed is joined by supplemental isobutane feed being admitted to the process in this line through valve 21, and recycle isobutane entering this line from line 22.

Hydrofluoric acid catalyst in the liquid state enters the process system from line 25 through valve 26 and is carried to alkylation zone 20 by way of lines 25 and 27. The alkylation zone 20 may comprise any suitable form of alkylation vessel, capable of effecting the required intimate 7 contacting of the catalyst with the reactant material, for example a conventional reaction loop, or a Stratco contactor, suitable means being provided for maintaining the proper alkylating conditions of temperature, the pressure being sufficient to maintain the reaction mixture in the liquid state.

From the alkylator, the reaction mixture is withdrawn in line 28, whence it is discharged into separator 30, wherein it is stratified to form an upper hydrocarbon layer and a lower acid cata- 1C lyst layer. From the separator, the lower acid catalyst layer is withdrawn in line 31 and returned, by way of lines 31 and 27, to the alkylation zone. The used acid catalyst may be withdrawn from the process for regeneration as de- 1 sired through line 32, by operation of valve 33.

The upper hydrocarbon layer formed in separator 30 is withdrawn therefrom in line 35 whence it enters at the top of hydrofluoric acid stripping tower 36. From the stripping tower 2' the main portion of the hydrofluoric acid content of the hydrocarbon charge is stripped off and withdrawn overhead in line 37 together with a small amount of light end fractions of the charge. This overhead hydrofluoric acid stream 2 is returned to the separator 38, by way of lines 31 and 28.

The stripped hydrocarbon product mixture is withdrawn from the bottom of tower 36 in line 38 wherein it is directed to debutanizing fractionator 40. From the debutanizer unreacted isobutane is removed overhead in line 4, and sent to condenser 42, wherein it Is condensed before being returned to alkylation zone 28 by way of lines 22 and 1I. Normal butane is withdrawn h from tower 48 by way of line 43 and removed from the process system, although it may be isomerized and returned to the alkylation zone, desired.

The debutanized alkylate products are withdrawn from tower 48 in line 45 and sent to accumulator 46, from which they are withdrawn in line 41 ,and conducted to preheater 6, wherein they are heated to defluorination temperature.

The heated product stream is withdrawn from preheater' in line 12 and directed, as already described above, by- way of lines 12 and 13 to contactor B. It will be understood that preheater 6 may be replaced by a cooler, or It may simply be omitted as in instances where the temperature employed in the defluorination contactor is relatively close to the temperature of the alkylate products effluent from the accumulator 46. The defluorinated product stream is withdrawn from contactor B in line 48 and is directed, by operation of control valve 49, to line 50, wherein it is conducted to fractionating tower 51. In tower 51 the alkylate products are separated into desired alkylate product of high octane boiling range and heavy alkylate. The heavy alkylate fraction is withdrawn from the bottom of the tower in line 52, while the desired high octane alkylate product is withdrawn overhead in line 53.

We have found that an operating cycle of about 30 hours for the isomerizatlon and defluorination treatments may be employed before regeneration of the alumina gel contact bed Is necessary.

Since it is generally desirable that the Isomerization process be carried out at a higher temperature level than is employed in the defluorination operation, the flow of hydrocarbons through the defluorination contactor should be discontinued a sufcient period of time before the contactor Is to be utilized for Isomerization to permit the contact bed to be brought up to the proper temperature level. The defluorination operation is, therefore, started in the contactor containing freshly regenerated contact material before the isomerization stage of the process is changed over to a new contactor. It is generally advisable to allow from two to five hours, depending upon the size of the contact bed and the heat transfer Sprovisions made, for the heating of the contact bed to the isomerization temperature level.

For the sakq of simplicity and clarity, in the foregoing description of our invention and in the drawing, various details have been omitted, inc luding, for example, flow lines for the conduction of the regeneration gases to and from the different contactors, as well as conventional heaters, pumps, valves, flow control means, etc., the use of which is well understood by those familiar 0 with the art.

From the foregoing description of our invention it will be appreciated that several noteworthy advantages are obtainable by its use. Thus, provision is made for the economical regeneration of the contact material utilized for the defluorination of the alkylate hydrocarbon products thereby avoiding the expense of frequent replacement of this material, as heretofore required.

Further, by our process it is economically fea0 sible to utilize the more costly, but more efficient synthetic contact materials, such as alumina gel, -for the defluorination treatment rather than the less active contact agents, since the contact materials are regenerated by our process rather than discarded upon deactivation. Also, the activity of the contact catalyst for the isomerization treatment of the olefin charge stock is enhanced by its prior use as a defluorination agent in accordance with our process. Finally, improve10 ments in the yield and quality of the alkylate product hydroutrocarbons are obtained by our process.

While in describing our invention we have indicated that we prefer to use three contact beds, w it will be apparent to those skilled in the art that the manner of operating our process may be modified to permit use of a greater or lesser number of such beds. For example, only one contact bed is required for operation of our procM0 ess where an adequate reserve of isomerized feed stock is maintained, so that operation of the alkylation process may be carried on while the contact bed in use for defluorinating the product hydrocarbons, and where means are provided for 55 temporarily storing untreated alkylate products, while the contact bed is on stream for the isomerization of the olefin feed stock.

Other modifications of our invention, not specifically described herein, may be made by those 60 skilled in the art without departing from the spirit and scope of our invention, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim: 65 1. A process of producing high octane motor fuel from isoparafflns and a charge stock containing terminal bond olefins which comprises the steps of: (1) passing said charge stock over a contact bed comprising a solid, porous, metal 70 oxide material known to be catalytically active for hydrohalogenation and dehydrohalogenation reactions, said bed having been treated in a manner hereinafter defined, under olefin Isomerizing conditions, to isomerize said terminal bond oleIf fins, (2) subjecting the contact bed from step 1 to an oxidation-regeneration treatment by means of hot oxidizing gases to condition it for further use in the process, (3) alkylating the isomerized charge stock obtained in step 1 with said isoparafflns in the presence of hydrofluoric acid catalyst to produce a mixture comprising high octane alkylate hydrocarbons, (4) separating the main portion of said acid catalyst from said alkylate product hydrocarbons, (5) passing the product hydrocarbons from step 4 over the regenerated con- I tact bed from step 2, under defluorinating conditions, to remove therefrom substantially all residual hydrofluoric acid not removed in step 4 and substantially all other fluoride compounds formed in step 3, (6) utilizing the contact bed 1 from step 5 as the contact bed in step 1 of the process, and (7) fractionating the defluorinated product hydrocarbons from step 5 to separate the, desired high octane motor fuel therefrom.

2. A process for the production of high octane 2 motor fuel from isoparafflns and a charge stock containing terminal bond olefins which comprises the steps of: (1) Passing said charge stock over a contact bed comprising active alumina gel catalyst treated in a manner hereinafter defined, 2w under olefln isomerizing conditions, to isomerize said terminal bond oleflns, (2) subjecting the contact bed from step 1 to an oxidation-regeneration treatment by means of hot oxidizing gases to condition it for further use in the process, (3) alkylating the isomerized charge stock obtained in step 1 with said isoparaffins in the presence of hydrofluoric acid catalyst to produce a mixture comprising high octane alkylate hydrocarbons, (4) separating the main portion of said acid cat- -3 alyst from said alkylate product hydrocarbons, (5) passing the product hydrocarbons from step 4 over the regenerated contact bed from step 2, under defluorinating conditions, to remove therefrom substantially all residual hydrofluoric acid not removed in step 4 and substantially all other fluoride compounds formed in step 3, (6) utilizing the contact bed from step 5 as the contact bed in step 1 of the process, and (7) fractionating the defluorinated product hydrocarbons from step 5 to separate the desired high octane motor fuel therefrom.

3. The method of conducting a continuous process for the manufacture of high octane motor fuel in a reaction system comprising an alkylation zone and a defluorination-isomerizatton zone, said defluorination-isomerization zone comprising a series of solid alumina gel contact beds which process comprises: (1) reacting isobutane with an olefln feed stock rich in butene-2 and obtained in a manner hereinafter defined in the presence of hydrofluoric acid catalyst in said alkylation zone, (2) withdrawing a product mixture comprising high octane alkylate hydrocarbons from said alkylation zone, (3) separating said 00 mixture into an acid phase and a hydrocarbon products phase, (4) treating said hydrocarbon products phase to remove fluorine containing substances therefrom by passing said phase through one of the aforementioned alumina gel contact beds, (5) treating an olefin feed stock, rich in butene-1, to isomerization, by passing said stock through another of said alumina gel contact beds which has been previously utilized as the contact bed in step 4 of the process whereby the butene-1 content of said olefin feed stock is converted to butene-2, (6) using the isomerized feed stock from step 5 as the butene-2 rich feed stock in step 1 of the process, (7) alternately and successively utilizing each of the alumina gel contact 7T beds in said defluorination-Isomerization zoe to defluorinate said alkylate product hydrocarbons and to isomerze said olefin feed stock, and (8) fractionating the defluorinated alkylate product h hydrocarbons from step 4 to obtain the desired high octane motor fuel.

4. A process for the production of high octane motor fuel from isobutane and a butane-butene fraction containing significant amounts of buo tene-1 which comprises: (1) passing said butanebutene fraction over a bed of active alumina gel catalyst treated in a manner hereinafter defined, under olefin isomerizing conditions, to convert the butene-1 in said fraction to an isomer thereof, (2) reacting the isomerized butane-butene fraction from step 1 with said isobutane, under alkylating conditions, in the presence of hydrofluore acid catalyst to produce a mixture comprising high octane alkylate hydrocarbons, (3) separat0 ing the main portion of the hydrofluoric add catalyst from the alkylate hydrocarbons obtained in step 2, (4) contacting said alkylate hydrocarbons with a bed of alumina gel catalyst, under defluorinating conditions, to remove therefrom sub5 stantially all residual hydrofluoric acd not removed in step 3 and substantially all other floride compounds formed in step 2, (5) utilizing the bed of alumina gel from step 4 as the catalyst bed in step 1, (6) utilizing the bed of alumina gel from o step 1 as the catalyst bed in step 4 after an intermediate oxidation-regeneration treatment and (7) fractionating the defluorinated alkylate hydrocarbons from step 4 to separate the desired high octane motor fuel therefrom.

S5. In a process for the production of alkylate motor fuel hydrocarbons from isoparafns and a charge stock containing terminal bond olefns comprising subjecting the charge stock to olefln Isomn~rization conditions over an olefin IsomerizaStion catalyst, alkylating said isomerized charge stock with said isoparaffins in the presence of hydrofluoric acid catalyst, separating the main portion of said acid catalyst from the alkylate product mixture derived from said alkylation step, Ssubjecting said product mixture to defluorination treatment by contacting said mixture with a solid adsorbent material to remove minor quantities of hydrofluoric acid and also organic fluorides therefrom, the improvement which comprises utilizing the contact material from the defluorination treatment of the process as the effective catalyst for the isomerization of said charge stock. 6. In a process for the manufacture of high octane gasoline from isoparafns and a charge stock containing 1-oleflns comprising subjecting said charge stock to isomerization to convert said 1-oleflns to 2-olefins, alkylating said isomerized charge stock with said Isoparafins in the presence of hydrofluoric acid catalyst, separating the main portion of said catalyst from the alkylate product mixture, subjecting said product mixture to a defluorination treatment by contacting said mixture with a bed of solid adsorbent contact material to--substantially completely remove hydrofluorlde and organic fluorides therefrom, the improvement comprising providing a plurality of separate adsorbent contact beds, effecting the defluorination step of the process in one of said beds, effecting the isomerization step of-the process by passing the charge stock to be isomerized in contact with another of said beds which has previously been used for the defluorination step. regenerating another of said beds for further use in the defluorination step of the process, and Intermittently switching the defluorination, Isomerization and regeneration steps of the process, successively, from one of said contact beds to the other.

7. In a process for the manufacture of high octane gasoline from isoparaflins and a charge stock containing 1-olefins comprising subjecting said charge stock to isomerization to convert said 1-oleflns to 2-olefins, alkylating said isomerized charge stock with said isoparaffns in the presence of hydrofluoric acid catalyst, separating the main portion of said catalyst from the alkylate product mixture, subjecting said product mixture to a defluorination treatment by contacting said mixture with a bed of solid adsorbent contact material to substantially completely remove hydrogen fluoride and organic fluorides therefrom, the improvement comprising providing a plurality of separate adsorbent contact beds comprising alumina gel, effecting the defluorination step of the process in one of said beds, effecting the isomerization step of the process by passing the charge stock to be isomerized in contact with another of said beds which has previously been used for the * defluorination step, regenerating another of said beds for further use in the defluorination step of the process, and intermittently switching the defluorination, isomerization and regeneration steps of the process, successively, from one of said contact beds to the other.

8. The process of claim 5 wherein said contact material is dehydrated bauxite.

9. The process of claim 5 wherein said contact material Is Activated Alumina.

10. The process of claim 5 wherein said contact material is alumina gel.

EDWARD R. BOEDEKER.

ALEX 0. OBLAD.