PORTABLE AIR POLLUTION DETECTOR
United States Patent 3653840
Method and apparatus for rapidly and accurately testing, in a laboratory or preferably a field location, a sample, preferably a gasoline sample, to determine olefins having up to a predetermined number of carbon atoms therein by first chromatographically separating the olefins having up to one more carbon atom than said predetermined number from the remainder of the olefins, secondly time separating the olefins having up to said predetermined number of carbon atoms from the chromatographically separated stream by switching off the stream after the olefins having a predetermined number of carbon atoms, but before the olefins having one more carbon atom than said predetermined number pass through a detector, and finally detecting the presence of the olefins in the time separated stream by use of a suitable means such as a bromine coulometric titrator.
US Patent References:
Photometric-coulometric bromine number titrator
Miller - April 1962 - 3030280
Hydrocarbon gas chromatography and apparatus
Jenkins - November 1963 - 3111835
Photometric-coulometric bromine number titrator
Miller - April 1962 - 3030280
Hydrocarbon gas chromatography and apparatus
Jenkins - November 1963 - 3111835
Application Number:
04/830612
Publication Date:
04/04/1972
Filing Date:
06/05/1969
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
96/104, 95/86, 73/23.420, 436/161, 422/90, 96/103, 204/405
International Classes:
G01N30/40; G01N33/28; G01N30/46; G01N30/00; G01N33/26; B01K3/00; G01N31/08
Field of Search:
23/230,232C,253 204/195T 55/67,197,386 73/23.1
Other References:
Fisher Bulletin FS-275, (1960). .
Dal Nagare et al., Gas Liquid Chromatography, Interscience Publ., 1962, p. 234.
Primary Examiner:
Wolk, Morris O.
Assistant Examiner:
Reese R. M.
Claims:
I claim
1. A method of detecting the presence of olefins having up to a predetermined number of carbon atoms in a stream comprising olefins and nonolefins comprising the steps of:
2. A method of detecting the presence of olefins having up to five carbon atoms in a stream comprising olefins and nonolefins comprising the steps of:
3. Apparatus comprising, in combination:
4. The apparatus of claim 3 further comprising:
5. The apparatus of claim 4 mounted on a frame structure adapted to be transported by hand, said frame structure being substantially enclosed.
6. The apparatus of claim 3 mounted on a frame structure adapted to be transported by hand.
7. The apparatus of claim 6 wherein said frame structure is substantially enclosed.
8. Apparatus comprising, in combination:
9. The apparatus of claim 8 mounted on a frame structure adapted to be transported by hand.
10. The apparatus of claim 9 wherein said frame structure is substantially enclosed.
11. The apparatus of claim 10 wherein said substantially enclosed frame structure contains handles adapted to provide a hand portable character to said structure.
1. A method of detecting the presence of olefins having up to a predetermined number of carbon atoms in a stream comprising olefins and nonolefins comprising the steps of:
2. A method of detecting the presence of olefins having up to five carbon atoms in a stream comprising olefins and nonolefins comprising the steps of:
3. Apparatus comprising, in combination:
4. The apparatus of claim 3 further comprising:
5. The apparatus of claim 4 mounted on a frame structure adapted to be transported by hand, said frame structure being substantially enclosed.
6. The apparatus of claim 3 mounted on a frame structure adapted to be transported by hand.
7. The apparatus of claim 6 wherein said frame structure is substantially enclosed.
8. Apparatus comprising, in combination:
9. The apparatus of claim 8 mounted on a frame structure adapted to be transported by hand.
10. The apparatus of claim 9 wherein said frame structure is substantially enclosed.
11. The apparatus of claim 10 wherein said substantially enclosed frame structure contains handles adapted to provide a hand portable character to said structure.
Description:
This invention relates to detection of olefins having up to a predetermined number of carbon atoms in a stream containing both olefins and nonolefins.
A method of measuring the concentration of constituents of a fluid stream often involves the use of a chromatographic analyzer. In chromatography, vaporous sample material to be analyzed is introduced into a column containing a selective sorbent or partitioning material. A carrier gas is directed into the column so as to force the sample material therethrough. The selective sorbent, or partitioning material, attempts to hold the constituents of the mixture. This results in the several constituents of the fluid mixture flowing through the column at different rates of speed, depending upon their affinities for the packing material. The column effluent thus consists initially of the carrier gas alone, the individual constituents of the fluid mixture appearing later at spaced time intervals. A conventional method of detecting the presence and concentration of these constituents is to employ a thermal conductivity detector which compares the thermal conductivity of the effluent gas plus carrier gas with the thermal conductivity of the carrier gas directed to the column. The resulting chromatographic peaks produced by the detector are recorded on a chart with each peak representative of a sample constituent.
In recent years great interest has been generated in controlling the production of "smog" and other air pollutants caused by the combustion of hydrocarbons, particularly gasoline in combustion processes, and more particularly gasoline in internal combustion engines of automobiles. Several states have passed legislation directed to the grave problem of air pollution by automobile engines and legislation has been considered at the federal level.
Recent research in the area of air pollution from gasolines has revealed that a large portion of the pollution caused by combustion of gasoline in automobiles results from light olefins, particularly C 5 and lighter olefins, that exist in normal gasolines traveling through the engine uncombusted and exiting to the atmosphere along with the combustion products. Upon entering the atmosphere in a gaseous form lighter olefins exhibit a tendency to combine very readily with various materials in the atmosphere, such as sulfur, oxygen, and halogens and produce air pollutants commonly know as "smog". Generally, air pollution becomes acute when a gasoline contains in excess of 5 per cent by weight olefins of C 5 or lighter based on the weight of the gasoline.
Conventional methods for determination of olefins in a stream take a considerable amount of time, and must be conducted by highly skilled personnel in permanent laboratory installations. Examples of such analytical methods are fluorescent indicator absorption, mass spectrometry, chemical methods (ASTM Method D-875) and conventional chromatography.
In accordance with this invention, a rapid and accurate determination of the quantity of olefins having up to a predetermined number of carbon atoms, particularly C 5 and lighter hydrocarbons, in a stream, and particularly in gasoline, can be conducted by relatively nonskilled personnel in field locations by use of the portable device of this invention. Broadly, the practice of the invention comprises chromatographically separating in a chromatographic column olefins having up to one more carbon atom than a predetermined number of carbon atoms from the remainder of the olefins in a stream that contains both olefins and nonolefins. After the chromatographic separation, then the olefins having up to the predetermined number of carbon atoms are time separated from the olefins having one more carbon atom than the predetermined number in the stream that contains nonolefins and chromatographically separated olefins. This is accomplished by terminating the flow of the chromatographic elute at a time after the olefins having up to a predetermined number of carbon atoms, but before the olefins having one more carbon atom than said predetermined number pass a given point. The stream containing both olefins having up to the predetermined number of carbon atoms and nonolefins is then tested to determine the quantity of olefins present therein, all of which are olefins having up to the predetermined number of carbon atoms. In another embodiment, a restrictor column is operated in series with the chromatographic column to reduce the time necessary for backflushing the chromatographic columns after a test has been run by placing a greater backflushing pressure on the chromatographic column than the pressure used for chromatographic separation.
Accordingly, an object of my invention is to provide an improved chromatographic method of analysis and apparatus therefor.
Another object of my invention is to provide an improved chromatographic method and apparatus wherein said analysis includes a chromatographic column backflushing step.
Another object of my invention is to provide for improved chromatographic analysis of olefins in a stream containing both olefins and nonolefins.
Another object of my invention is to provide a portable apparatus for determining the quantity of olefins having up to a predetermined number of carbon atoms in a stream containing olefins and nonolefins.
Another object of my invention is to provide a portable apparatus for determining the quantity of C 5 and lighter olefins in a gasoline stream.
Another object of my invention is to decrease the time required for olefin determination.
Another object of my invention is to decrease the time necessary for backflushing the chromatographic column after completing a test.
Another object of my invention is to provide olefin determination by relatively unskilled personnel.
Other objects, advantages and features of my invention will be readily apparent to those skilled in the art from the following description, the drawings and the appended claims.
The attached figures represent only one embodiment of the invention as other embodiments will be readily apparent to one skilled in the art. Specifically,
FIG. 1 represents a schematic view of one embodiment of this invention.
FIG. 2 represents the invention in its portable form wherein it has been mounted inside an enclosed structure which is adapted for hand transportation by the installation of handles thereon.
Referring now to the apparatus illustrated in FIG. 1, there is a source of carrier gas 10 and a conduit 15 from said carrier gas to a four-way switching valve means 20 containing valve ports A, B, C and D. In line 15 there is disposed a valve means 25 so as to regulate the pressure of the carrier gas going into the chromatographic system. A restrictor column 30 is connected to valve means 20 and four-way switching valve means 35 containing valve ports A, B and C is connected to column 30. A chromatographic separation column 40 is attached to valve means 35 by conduit 45 containing an injection port 50 wherein the stream to be tested for the existence of olefins is injected into the system. Chromatographic column 40 is connected to valve means 20 via conduit 55 and is further connected by conduit 65 to a means 60 to detect the presence of olefins. Four-way switching valve means 20 and 35 are operably connected to timing means 85 and adapted to switch from a testing position to a backflushing position on response to a given time that was set on timing means 85 elapsing. This operation will be subsequently explained in detail.
Detectors 70 and 75 are disposed in respective conduits 15 and 55. These detectors are adapted to measure a property of the fluid sample mixture directed thereto which property is representative of the composition of the fluid mixture. The detectors can be thermally conductive elements called thermistors which are temperature sensitive resistance elements disposed in the path of fluid flow. The temperature differences between the resistance elements can be measured in detector cell 80 by apparatus including electrical bridge circuits, such as a Wheatstone bridge, and provide response to the temperature difference signals representative of the difference in thermal conductivity in the column of fluid in the carrier gas.
Although thermistors are used as detectors in one embodiment, the detectors can be any other type of apparatus known in the art for measuring the property of a gaseous stream.
Restrictor column 30 is filled with a material that restricts the passage of all components therethrough, thus creating a pressure drop between valve means 20 and 35 through said column 30. According to this invention, the column performs no chromatographic separation and does not function as a chromatographic column. The operation of this column will be described later.
Although this invention is fully applicable to separating from a stream olefins having up to a predetermined number of carbon atoms from a chromatographically separated stream containing olefins having up to one more carbon atom than said predetermined number, in one embodiment C 5 and lighter olefins in gasoline can be separated from a chromatographically separated stream containing C 6 and lighter olefins. In this embodiment, chromatographic column 40 is filled with a material that selectively retards the passage therethrough of olefins having from two to six carbon atoms. A suitable packing material comprises 80-100 mesh Chromasorb-P AW-DMCS coated with Dow-Corning Silicone-200 wherein the silicone comprises 25 percent of the total weight of both materials. Chromasorb-P is a commercially available trade name material sold by Johns Manville Corporation and is crushed fire brick. Dow-Corning Silicone-200 is a commercially available trade name material sold by Dow-Corning Corporation and is a silicone polymer incorporating methyl and phenyl groups. In one embodiment, chromatographic column 40 was 3 feet long and constructed of 1/4-inch O.D. copper tubing. The restrictor column in one embodiment was 4 feet long and was constructed of 1/4-inch O.D. copper tubing filled with 80 to 100 mesh Chromasorb-P.
With reference to FIG. 2 there is noted an enclosed structure 200 incorporating handles 205 and 210. Enclosed structure 200 is specifically adapted in size to be hand transported by one or two men grasping handles 205 and 210. Additionally, there is indicated sample injection port 50, timer 85, and the starter button 215 for the means to detect the presence of olefins 60 which in this particular embodiment is a bromine coulometric titrator. Additionally, there is indicated the timer 220 and the generation current selector 225 associated with the bromine titrator.
Prior to operation the invention can be calibrated to separate olefins having up to five carbon atoms by the following method. Valve means 25 is adjusted to put the design pressure of carrier gas in the system. The sample is then injected by means of a hypodermic syringe or other suitable means into injection port 50 and the time of injection noted. The lighter components which comprise both olefin and nonolefin components begin to elute from column 40 and, subsequently, the olefins of C 2 through C 6 elute from column 40 along with other nonolefinic components. As noted in the drawing, when valve means 20 and 35 are in testing position, the elution products from column 40 move through conduit 55 through ports D and C of valve means 20, through conduit 65 and into detection means 60. The calibration is completed by making various runs and determining the length of time necessary from the injection of the sample material in port 50 to the elapsed time that the last of the C 5 olefins but before any of the C 6 olefins pass port C of valve means 20. After this particular time is determined experimentally, it is noted and will be used in future operation of the machine in actual tests. Obviously, the same method can be used to calibrate the invention to separate other olefins up to a predetermined number of carbon atoms.
In actual operation this predetermined time will be set in timer means 85 and, after the elapsation of the predetermined time, timer means 85 will actuate valve means 20 and 35 to switch from a testing position wherein gas is conducted through ports A and B of valve means 20, through column 30, through ports A and B of valve means 35, through column 40, through ports D and C of valve means 20, and through conduit 65 to olefin detector 60 to a backflushing position wherein carrier gas is conducted through ports A and D of valve means 20 through column 40 and through ports B and C of valve means 35 and to the atmosphere. Thus, after the elapsation of the time known to be associated with the passage of the last of the C 5 olefin through port C of valve means 20, the column is backflushed by action of timer 85 and valve means 20 and 35.
Quite obviously, the maximum elution time is associated with the "heaviest" olefin having the predetermined number of carbon atoms which in the embodiment where olefins having up to five carbon atoms are separated is methyl- 2-butene. Although the time between elution of the last of the C 5 and the first of the C 6 olefins varies with many parameters, in practice up to 20 seconds can elapse, thus time is critical only within a fairly broad range of time.
Thus, according to the operation of the invention, after the invention as been calibrated according to the previously described method actual testing for the presence of C 5 and lighter olefins can be conducted. In this test the carrier gas pressure is set in valve means 25 and carrier gas is caused to flow from source 10 through valve ports A and B of valve means 20, restrictor column 30, valve ports A and B of valve means 35, and through separator column 40. The predetermined time from the calibration method is set in timing means 85 and simultaneously a sample of gasoline is injected into injection port 50. According to the operation of the invention, the carrier gas transports the fluid sample injected into the injection port 50 through chromatographic separation column 40 and through conduit 55, ports D and C of valve means 20, and subsequently through conduit 65 to detector means 60.
According to the operation of chromatographic column 40, both olefin and nonolefin components are simultaneously eluted. Thus, the elution products initially contain nonolefinic components plus lighter olefins and subsequently heavier olefins are eluted along with heavier nonolefinic components. As noted earlier, at the time the sample was injected into injection port 50, timer 85 was set so as to switch valve means 20 and 35 at the end of the period determined by the calibration function. After timer 85 runs down valve means 20 and 35 are switched from the previously described testing position to the previously described backflushing position.
According to this invention, detector means 60 can comprise any means of detecting the presence of olefins and, according to one embodiment of this invention, the only olefins present in said stream containing olefins and nonolefins will be C 5 olefins and lighter. Although many means to detect the presence of olefins can be used, in one embodiment a coulometric bromine titrator was used. This titrator is described in ASTM Method D-1492-60.
Thus, according to the embodiment of the invention where the bromine coulometric titrator is used, after injection of the sample into port 50 but before the first C 2 olefin enters the coulometric titrator starter button 215 in FIG. 2 is depressed. According to ASTM Method D-1492-60 current selector 225 is set according to the estimated bromine index and the estimated sample weight. Depressing starter button 215 actuates the device so that timer 220 records the titration time. The coulometric titrator can be adapted to shut down when the last olefin enters the detector and has been titrated. Thus, according to this embodiment the bromine index is then calculated by knowing the current generation in milliamperes set on current selector 225, the titration time in seconds read off timer 220, and the weight of the sample in grams.
According to another embodiment of this invention, a backflushing function is performed through the use of restrictor column 30 in FIG. 1. According to this feature of the invention, after the C 5 but before the C 6 olefins pass port C of valve means 20 timer 85 actuates four-way switching valves 20 and 35 to the backflushing position so as to conduct carrier gas through ports A and D of valve means 20 through separation column 40 in the opposite direction as during testing, through conduit 45 and through ports B and C of valve means 35. In normal operation of the invention the carrier gas flows through restrictor column 30 and through chromatographic separation column 40, and after the pressure drop across column 30 is known the pressure in valve 25 can be set so as to achieve the design pressure at the inlet of chromatographic column 40. Thus, a first pressure drop occurs through restrictor column 30 and a second pressure drop occurs through chromatographic column 40. Thus, when timer 85 actuates the valves to a backflushing position, the higher pressure on the inlet of restrictor column 30, which is higher than the inlet pressure on chromatographic separation column 40 due to the pressure drop across column 30, is then placed through ports A and D of valve means 20 and through conduit 55 and causes carrier gas to flow in the opposite direction through chromatographic separation column 40, conduit 45, and subsequently through ports B and C of valve means 35 to the atmosphere. Thus, through the use of the additional pressure drop in restrictor column 30 an additional pressure differential is developed through chromatographic column 40 flowing in the opposite direction and used for backflushing the column. This embodiment where the restrictor column is used is an optional feature and it is fully within the scope of this invention to eliminate the restrictor column and merely use the chromatographic column 40, although the chromatographic column 40 can be backflushed much more rapidly according to the practice of the invention where the restrictor column 30 is used.
Thus, this invention is useful for determining the presence of olefins having from two to five carbon atoms in any stream whatsoever and is particularly adapted for determining the quantity of olefins having from two to five carbon atoms and in gasoline streams.
Thus, this invention is broadly applicable to determining the quantity of olefins having up to a predetermined number of carbon atoms in a stream. As noted above, the drawing is merely diagrammatic and is not intended to fully show all component parts of the apparatus which one skilled in the art would routinely design for the operation thereof. Indeed, the showing of an element or piece of equipment does not mean that all such or similar pieces of equipment which may or can be designed by one skilled in the art in possession of the disclosure cannot be utilized as substitution therefor. Likewise, the omission of an element which one skilled in the art may include in an actual unit does not mean that such a piece of equipment is intended to be omitted simply because it does not appear in the drawing. Specifically, as noted restrictor column 30 can be omitted; however, in one embodiment greater backflushing efficiency is obtained by its use. Furthermore, column 40 can be packed with any material that will chromatographically separate olefins having up to one more carbon atom than said predetermined number of carbon atoms. Additionally, the apparatus of this invention can be mounted in various types of enclosed housing for transportation. Suffice to say the drawing is for illustrative purpose only as is the description thereof.
A method of measuring the concentration of constituents of a fluid stream often involves the use of a chromatographic analyzer. In chromatography, vaporous sample material to be analyzed is introduced into a column containing a selective sorbent or partitioning material. A carrier gas is directed into the column so as to force the sample material therethrough. The selective sorbent, or partitioning material, attempts to hold the constituents of the mixture. This results in the several constituents of the fluid mixture flowing through the column at different rates of speed, depending upon their affinities for the packing material. The column effluent thus consists initially of the carrier gas alone, the individual constituents of the fluid mixture appearing later at spaced time intervals. A conventional method of detecting the presence and concentration of these constituents is to employ a thermal conductivity detector which compares the thermal conductivity of the effluent gas plus carrier gas with the thermal conductivity of the carrier gas directed to the column. The resulting chromatographic peaks produced by the detector are recorded on a chart with each peak representative of a sample constituent.
In recent years great interest has been generated in controlling the production of "smog" and other air pollutants caused by the combustion of hydrocarbons, particularly gasoline in combustion processes, and more particularly gasoline in internal combustion engines of automobiles. Several states have passed legislation directed to the grave problem of air pollution by automobile engines and legislation has been considered at the federal level.
Recent research in the area of air pollution from gasolines has revealed that a large portion of the pollution caused by combustion of gasoline in automobiles results from light olefins, particularly C 5 and lighter olefins, that exist in normal gasolines traveling through the engine uncombusted and exiting to the atmosphere along with the combustion products. Upon entering the atmosphere in a gaseous form lighter olefins exhibit a tendency to combine very readily with various materials in the atmosphere, such as sulfur, oxygen, and halogens and produce air pollutants commonly know as "smog". Generally, air pollution becomes acute when a gasoline contains in excess of 5 per cent by weight olefins of C 5 or lighter based on the weight of the gasoline.
Conventional methods for determination of olefins in a stream take a considerable amount of time, and must be conducted by highly skilled personnel in permanent laboratory installations. Examples of such analytical methods are fluorescent indicator absorption, mass spectrometry, chemical methods (ASTM Method D-875) and conventional chromatography.
In accordance with this invention, a rapid and accurate determination of the quantity of olefins having up to a predetermined number of carbon atoms, particularly C 5 and lighter hydrocarbons, in a stream, and particularly in gasoline, can be conducted by relatively nonskilled personnel in field locations by use of the portable device of this invention. Broadly, the practice of the invention comprises chromatographically separating in a chromatographic column olefins having up to one more carbon atom than a predetermined number of carbon atoms from the remainder of the olefins in a stream that contains both olefins and nonolefins. After the chromatographic separation, then the olefins having up to the predetermined number of carbon atoms are time separated from the olefins having one more carbon atom than the predetermined number in the stream that contains nonolefins and chromatographically separated olefins. This is accomplished by terminating the flow of the chromatographic elute at a time after the olefins having up to a predetermined number of carbon atoms, but before the olefins having one more carbon atom than said predetermined number pass a given point. The stream containing both olefins having up to the predetermined number of carbon atoms and nonolefins is then tested to determine the quantity of olefins present therein, all of which are olefins having up to the predetermined number of carbon atoms. In another embodiment, a restrictor column is operated in series with the chromatographic column to reduce the time necessary for backflushing the chromatographic columns after a test has been run by placing a greater backflushing pressure on the chromatographic column than the pressure used for chromatographic separation.
Accordingly, an object of my invention is to provide an improved chromatographic method of analysis and apparatus therefor.
Another object of my invention is to provide an improved chromatographic method and apparatus wherein said analysis includes a chromatographic column backflushing step.
Another object of my invention is to provide for improved chromatographic analysis of olefins in a stream containing both olefins and nonolefins.
Another object of my invention is to provide a portable apparatus for determining the quantity of olefins having up to a predetermined number of carbon atoms in a stream containing olefins and nonolefins.
Another object of my invention is to provide a portable apparatus for determining the quantity of C 5 and lighter olefins in a gasoline stream.
Another object of my invention is to decrease the time required for olefin determination.
Another object of my invention is to decrease the time necessary for backflushing the chromatographic column after completing a test.
Another object of my invention is to provide olefin determination by relatively unskilled personnel.
Other objects, advantages and features of my invention will be readily apparent to those skilled in the art from the following description, the drawings and the appended claims.
The attached figures represent only one embodiment of the invention as other embodiments will be readily apparent to one skilled in the art. Specifically,
FIG. 1 represents a schematic view of one embodiment of this invention.
FIG. 2 represents the invention in its portable form wherein it has been mounted inside an enclosed structure which is adapted for hand transportation by the installation of handles thereon.
Referring now to the apparatus illustrated in FIG. 1, there is a source of carrier gas 10 and a conduit 15 from said carrier gas to a four-way switching valve means 20 containing valve ports A, B, C and D. In line 15 there is disposed a valve means 25 so as to regulate the pressure of the carrier gas going into the chromatographic system. A restrictor column 30 is connected to valve means 20 and four-way switching valve means 35 containing valve ports A, B and C is connected to column 30. A chromatographic separation column 40 is attached to valve means 35 by conduit 45 containing an injection port 50 wherein the stream to be tested for the existence of olefins is injected into the system. Chromatographic column 40 is connected to valve means 20 via conduit 55 and is further connected by conduit 65 to a means 60 to detect the presence of olefins. Four-way switching valve means 20 and 35 are operably connected to timing means 85 and adapted to switch from a testing position to a backflushing position on response to a given time that was set on timing means 85 elapsing. This operation will be subsequently explained in detail.
Detectors 70 and 75 are disposed in respective conduits 15 and 55. These detectors are adapted to measure a property of the fluid sample mixture directed thereto which property is representative of the composition of the fluid mixture. The detectors can be thermally conductive elements called thermistors which are temperature sensitive resistance elements disposed in the path of fluid flow. The temperature differences between the resistance elements can be measured in detector cell 80 by apparatus including electrical bridge circuits, such as a Wheatstone bridge, and provide response to the temperature difference signals representative of the difference in thermal conductivity in the column of fluid in the carrier gas.
Although thermistors are used as detectors in one embodiment, the detectors can be any other type of apparatus known in the art for measuring the property of a gaseous stream.
Restrictor column 30 is filled with a material that restricts the passage of all components therethrough, thus creating a pressure drop between valve means 20 and 35 through said column 30. According to this invention, the column performs no chromatographic separation and does not function as a chromatographic column. The operation of this column will be described later.
Although this invention is fully applicable to separating from a stream olefins having up to a predetermined number of carbon atoms from a chromatographically separated stream containing olefins having up to one more carbon atom than said predetermined number, in one embodiment C 5 and lighter olefins in gasoline can be separated from a chromatographically separated stream containing C 6 and lighter olefins. In this embodiment, chromatographic column 40 is filled with a material that selectively retards the passage therethrough of olefins having from two to six carbon atoms. A suitable packing material comprises 80-100 mesh Chromasorb-P AW-DMCS coated with Dow-Corning Silicone-200 wherein the silicone comprises 25 percent of the total weight of both materials. Chromasorb-P is a commercially available trade name material sold by Johns Manville Corporation and is crushed fire brick. Dow-Corning Silicone-200 is a commercially available trade name material sold by Dow-Corning Corporation and is a silicone polymer incorporating methyl and phenyl groups. In one embodiment, chromatographic column 40 was 3 feet long and constructed of 1/4-inch O.D. copper tubing. The restrictor column in one embodiment was 4 feet long and was constructed of 1/4-inch O.D. copper tubing filled with 80 to 100 mesh Chromasorb-P.
With reference to FIG. 2 there is noted an enclosed structure 200 incorporating handles 205 and 210. Enclosed structure 200 is specifically adapted in size to be hand transported by one or two men grasping handles 205 and 210. Additionally, there is indicated sample injection port 50, timer 85, and the starter button 215 for the means to detect the presence of olefins 60 which in this particular embodiment is a bromine coulometric titrator. Additionally, there is indicated the timer 220 and the generation current selector 225 associated with the bromine titrator.
Prior to operation the invention can be calibrated to separate olefins having up to five carbon atoms by the following method. Valve means 25 is adjusted to put the design pressure of carrier gas in the system. The sample is then injected by means of a hypodermic syringe or other suitable means into injection port 50 and the time of injection noted. The lighter components which comprise both olefin and nonolefin components begin to elute from column 40 and, subsequently, the olefins of C 2 through C 6 elute from column 40 along with other nonolefinic components. As noted in the drawing, when valve means 20 and 35 are in testing position, the elution products from column 40 move through conduit 55 through ports D and C of valve means 20, through conduit 65 and into detection means 60. The calibration is completed by making various runs and determining the length of time necessary from the injection of the sample material in port 50 to the elapsed time that the last of the C 5 olefins but before any of the C 6 olefins pass port C of valve means 20. After this particular time is determined experimentally, it is noted and will be used in future operation of the machine in actual tests. Obviously, the same method can be used to calibrate the invention to separate other olefins up to a predetermined number of carbon atoms.
In actual operation this predetermined time will be set in timer means 85 and, after the elapsation of the predetermined time, timer means 85 will actuate valve means 20 and 35 to switch from a testing position wherein gas is conducted through ports A and B of valve means 20, through column 30, through ports A and B of valve means 35, through column 40, through ports D and C of valve means 20, and through conduit 65 to olefin detector 60 to a backflushing position wherein carrier gas is conducted through ports A and D of valve means 20 through column 40 and through ports B and C of valve means 35 and to the atmosphere. Thus, after the elapsation of the time known to be associated with the passage of the last of the C 5 olefin through port C of valve means 20, the column is backflushed by action of timer 85 and valve means 20 and 35.
Quite obviously, the maximum elution time is associated with the "heaviest" olefin having the predetermined number of carbon atoms which in the embodiment where olefins having up to five carbon atoms are separated is methyl- 2-butene. Although the time between elution of the last of the C 5 and the first of the C 6 olefins varies with many parameters, in practice up to 20 seconds can elapse, thus time is critical only within a fairly broad range of time.
Thus, according to the operation of the invention, after the invention as been calibrated according to the previously described method actual testing for the presence of C 5 and lighter olefins can be conducted. In this test the carrier gas pressure is set in valve means 25 and carrier gas is caused to flow from source 10 through valve ports A and B of valve means 20, restrictor column 30, valve ports A and B of valve means 35, and through separator column 40. The predetermined time from the calibration method is set in timing means 85 and simultaneously a sample of gasoline is injected into injection port 50. According to the operation of the invention, the carrier gas transports the fluid sample injected into the injection port 50 through chromatographic separation column 40 and through conduit 55, ports D and C of valve means 20, and subsequently through conduit 65 to detector means 60.
According to the operation of chromatographic column 40, both olefin and nonolefin components are simultaneously eluted. Thus, the elution products initially contain nonolefinic components plus lighter olefins and subsequently heavier olefins are eluted along with heavier nonolefinic components. As noted earlier, at the time the sample was injected into injection port 50, timer 85 was set so as to switch valve means 20 and 35 at the end of the period determined by the calibration function. After timer 85 runs down valve means 20 and 35 are switched from the previously described testing position to the previously described backflushing position.
According to this invention, detector means 60 can comprise any means of detecting the presence of olefins and, according to one embodiment of this invention, the only olefins present in said stream containing olefins and nonolefins will be C 5 olefins and lighter. Although many means to detect the presence of olefins can be used, in one embodiment a coulometric bromine titrator was used. This titrator is described in ASTM Method D-1492-60.
Thus, according to the embodiment of the invention where the bromine coulometric titrator is used, after injection of the sample into port 50 but before the first C 2 olefin enters the coulometric titrator starter button 215 in FIG. 2 is depressed. According to ASTM Method D-1492-60 current selector 225 is set according to the estimated bromine index and the estimated sample weight. Depressing starter button 215 actuates the device so that timer 220 records the titration time. The coulometric titrator can be adapted to shut down when the last olefin enters the detector and has been titrated. Thus, according to this embodiment the bromine index is then calculated by knowing the current generation in milliamperes set on current selector 225, the titration time in seconds read off timer 220, and the weight of the sample in grams.
According to another embodiment of this invention, a backflushing function is performed through the use of restrictor column 30 in FIG. 1. According to this feature of the invention, after the C 5 but before the C 6 olefins pass port C of valve means 20 timer 85 actuates four-way switching valves 20 and 35 to the backflushing position so as to conduct carrier gas through ports A and D of valve means 20 through separation column 40 in the opposite direction as during testing, through conduit 45 and through ports B and C of valve means 35. In normal operation of the invention the carrier gas flows through restrictor column 30 and through chromatographic separation column 40, and after the pressure drop across column 30 is known the pressure in valve 25 can be set so as to achieve the design pressure at the inlet of chromatographic column 40. Thus, a first pressure drop occurs through restrictor column 30 and a second pressure drop occurs through chromatographic column 40. Thus, when timer 85 actuates the valves to a backflushing position, the higher pressure on the inlet of restrictor column 30, which is higher than the inlet pressure on chromatographic separation column 40 due to the pressure drop across column 30, is then placed through ports A and D of valve means 20 and through conduit 55 and causes carrier gas to flow in the opposite direction through chromatographic separation column 40, conduit 45, and subsequently through ports B and C of valve means 35 to the atmosphere. Thus, through the use of the additional pressure drop in restrictor column 30 an additional pressure differential is developed through chromatographic column 40 flowing in the opposite direction and used for backflushing the column. This embodiment where the restrictor column is used is an optional feature and it is fully within the scope of this invention to eliminate the restrictor column and merely use the chromatographic column 40, although the chromatographic column 40 can be backflushed much more rapidly according to the practice of the invention where the restrictor column 30 is used.
Thus, this invention is useful for determining the presence of olefins having from two to five carbon atoms in any stream whatsoever and is particularly adapted for determining the quantity of olefins having from two to five carbon atoms and in gasoline streams.
Thus, this invention is broadly applicable to determining the quantity of olefins having up to a predetermined number of carbon atoms in a stream. As noted above, the drawing is merely diagrammatic and is not intended to fully show all component parts of the apparatus which one skilled in the art would routinely design for the operation thereof. Indeed, the showing of an element or piece of equipment does not mean that all such or similar pieces of equipment which may or can be designed by one skilled in the art in possession of the disclosure cannot be utilized as substitution therefor. Likewise, the omission of an element which one skilled in the art may include in an actual unit does not mean that such a piece of equipment is intended to be omitted simply because it does not appear in the drawing. Specifically, as noted restrictor column 30 can be omitted; however, in one embodiment greater backflushing efficiency is obtained by its use. Furthermore, column 40 can be packed with any material that will chromatographically separate olefins having up to one more carbon atom than said predetermined number of carbon atoms. Additionally, the apparatus of this invention can be mounted in various types of enclosed housing for transportation. Suffice to say the drawing is for illustrative purpose only as is the description thereof.