|Publication number||US3206525 A|
|Publication date||Sep 14, 1965|
|Filing date||Oct 26, 1960|
|Priority date||Oct 26, 1960|
|Publication number||US 3206525 A, US 3206525A, US-A-3206525, US3206525 A, US3206525A|
|Inventors||Mooi John, Carl D Keith, Glenn O Michaels|
|Original Assignee||Sinclair Refining Co|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (17), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Glenn 0. Michaels, Park Forest,
United States Patent 3,206,525 PROCESS FOR ISOMERIZING PARAFFINIC HYDROCARBONS and John Mooi, Homewood, 11]., and Carl D. Keith, Summit, N.J., assignors to Sinclair Refining Company No Drawing. Filed Oct. 26, 1960, Ser. No. 65,014 10 Claims. (Cl. 260683.66)
This application is a continuation-in-part of applica tion Serial No. 851,526, filed November 9, 1959, and now abandoned.
The invention relates to the isomerization of n-paraffinic hydrocarbons to obtain good yields of branched chain aliphatic structures and is particularly concerned With the catalytic isomerization of n-paraflinic hydrocarbons employing a hydrocarbon conversion catalyst consisting essentially of a noble metal, an activity enhancing compound and alumina. The branched chain aliphatic structures, e.g. isomeric structures of n-parafiins, are particularly useful in providing gasoline components of high octane rating.
In recent years automobile manufacturers have steadily increased the compression ratios of their spark ignition engines as a means of obtaining more power and greater efficiency. As the compression ratios of the engines increase, the hydrocarbon fuel employed must be of higher octane rating to provide efficient knock-free operation notwithstanding that fuel octane rating can be increased through the addition of tetraethyl lead, and other undesirable aspects of engine operation, for instance pre-ignition, can be overcome by the use of other additive components. Thus, the problem remains for petroleum refiners to produce higher octane base hydrocarbon fuels under economically feasible conditions.
These refiners now have installed a substantial number of units for reforming straight run petroleum fractions in the presence of free hydrogen and over a platinum metal-alumina catalyst to obtain relatively high octane products. Primarily these products, frequently called reformates, are blended with other gasoline components such as thermal and catalytically cracked gasolines, alkylates, etc., and additives such as tetraethyl lead in obtaining present-day motor fuels. The reforming operation has a number of disadvantages. First, as the octane ratings of the blended engine fuels rise, the octane quality of the reformate must also increase if the blends be otherwise unaltered. This increase results in a substantial reduction in yield particularly in obtaining reformates having octanes (RON neat) of the order of 10 to 95 or above. When the severity of the operation is increased, the platinum metal-containing catalyst becomes fouled more often with carbonaceous deposits which requires more frequent regenerations or replacements. The platinum metal-alumina catalysts are relatively expensive, and either replacement or withdrawal from use during regeneration materially increases the cost of providing a given volume of reformate. These and other factors affecting the yield-octane number-cost relationship make it desirable for the refiner to consider various ways in which high octane hydrocarbon fuel components can be obtained by employing processing methods other than the platinum metal-alumina catalyst reforming operation.
One method now under consideration by petroleum refiners for obtaining stocks of higher octane value involves the isomerization of C or C to C n-paraflinic hydrocarbons, that is, n-butane, n-pentane, n-hexane, nheptane, n-octane, n-nonane and their mixtures with each other and with other hydrocarbons in the same approximate boiling range. In general, as the side chain branching of these n-paraffins increases, their octane ratings rise. In the process of the present invention we have found Patented Sept. 14, 1965 catalysts which are useful in the isomerization of the C to C n-paraflins in the presence of free hydrogen to afford highly satisfactory yields of isomer products. These catalysts are characterized by being sufficiently active to allow the use of relatively lower isomerization temperatures and provide for advantageous isomerization equilibrium conditions.
The catalyst used in the process of the present invention includes catalytically effective amounts of a noble or platinum group metal and activity enhancing or promoting amounts of a component selected from the group consisting of H SiF NH BF and Ni(BF supported on an alumina base. The catalyst generally contains about 0.01 to 2 weight percent, preferably 0.1 to 1 weight percent, of one or more of the platinum metals of Group VIII, such as platinum, palladium, or rhodium. The small amount of noble metal may be present in the metallic form or as a sulfide, oxide or other combined form. The metal may interact with other constituents of the catalysts, but if during use the noble metal be present in metallic form then it is preferred that it be so finely divided that it is not detectable by X-ray diffraction means, i.e. that it exists as crystals of less than 50 Angstrom units size. Of the noble metals platinum, palladium and rhodium are preferred.
The activity enhancing component is surface dispersible on the support. It is employed in amounts sufiicient to enhance the life of the alumina support and such amounts are, therefore, preferably added in direct proportion to the area of the support. For instance, the amount of the activity enhancing component will depend upon the specified promoting component employed. Generally, however, the activity enhancing component will be employed in a molar ratio to the alumina of about 0.001 to 03:1 and preferably from about 0.02 to 0.1:1. When the activity enhancing component contains boron and fluorine, the molar ratio of the fluorine to boron will generally be from about 2 to 6:1. The weight percent of the fluorine in the catalyst will generally be from about 0.1 to 15% and preferably from about 1.5 or 3 to 6 or 7.5 weight percent.
The noble metal and activity enhancing component constituents of the catalyst are supported on an absorptive alumina base of the activated or calcined type. The base is usually the major component of the catalyst, generally constituting at least about weight percent on the basis of the catalyst, preferably at least about to The catalyst base is an activated or gamma-alumina such as those derived by calcination of amorphous hydrous alumina, alumina monohydrate, alumina trihydrate or their mixtures. The catalyst base precursor most advantageously is a mixture predominating in, or containing a major proportion of, for instance about 65 to weight percent, one or more of the alumina trihydrates bayerite I, bayerite II (randomite) or gibbsite, and about 5 to 35 weight percent of alumina monohydrate (boehmite), amorphous hydrous alumina or their mixture. The alumina base can contain small amounts of other solid oxides such as silica, magnesia, natural or activated clays (such as kaolinite, montmorillonite, halloysite, etc), titania, zirconia, etc., or their mixtures. Although the components of the catalyst can vary as stated, a preferred catalyst contains platinum and the activity enhancing component deposited on activated alumina.
The isomerization reaction conditions used in the method of the present invention include a temperature suflicient to maintain the n-paraffin feed in the vapor phase under the pressure employed. Generally, this temperature will be from about 500 to 800 F., preferably about 600 to 700 F. or 750 F., while the pressure will be superatmospheric for instance ranging from about 50 to 1500 p.s.i.g., preferably about 200 to 1000 p.s.i.g. The catalyst can be used as a fixed, moving or fluidized bed or in any other convenient type of handling system. The fixed bed system seems most advantageous at this time and the space velocity will in most cases be from about 0.25 to 8:1, preferably about 0.75 to 4:1, weight of n-paraffin per weight of catalyst per hour (WI-ISV).
Free or molecular hydrogen must be present in our reaction system and the hydrogen to n-paraffin molar ratio will usually be from about 0.01 to 2011 or more, preferably about 2 to 10:1. Conveniently, the hydrogen concentration is maintained by recycling hydrogen-rich gases from the reaction zone.
As previously stated the preferred catalyst base material is an activated or gamma-alumina made by calcining a precursor predominating in alumina trihydrate. An alumina of this type is disclosed in US. Patent No. 2,838,444. The alumina base is derived from a precursor alumina hydrate composition containing about 65 to 95 weight percent of one or more of the alumina trihydrate forms gibbsite, bayerite I and bayerite II (randomite) as defined by X-ray diffraction analysis. The substantial balance of the hydrate is amorphous hydrous or monohydrate alumina. Trihydrates are present as well defined crystallites, that is they are crystalline in form when examined by X-ray diffraction means. The crystallite size of the precursor alumina trihydrate is relatively large and usually is in the 100 to 1000 Angstrom unit range. The calcined alumina has a large portion of its pore volume in the pore size range of about 100 to 1000 Angstrom units generally having about 0.1 to about 0.5 and preferably about 0.15 to about 0.3 cc./g. of pore volume in this range. As described in the patent the calcined catalyst base can be characterized by large surface area ranging from about 350 to about 550 or more square meters/gram when in the virgin state as determined, for example, by the BET adsorption technique. A low area catalyst base prepared by treating the predominantly trihydrate base precursor is described in U.S. Patent No. 2,838,445. This base when in the virgin state has substantially no pores of radius less than about 10 Angstrom units and the surface area of the catalyst base is less than about 350 square meters/ gram and most advantageously is in the range of about 150 to 300 square meters/gram.
The platinum group metal component of the catalyst can be added to the alumina base by known procedures. For instance, the platinum metal component can be deposited on a calcined or activated alumina, but it is preferred to add the platinum metal component to the alumina hydrate precursor. Thus, platinum can be added through reaction of a halogen platinum acid, for instance, fiuoro-, chloro-, bromoor iodo-platinic acid, and hydrogen sulfide in an aqueous slurry of the alumina hydrate. The hydrogen sulfide can be employed as a gas or an aqueous solution. Alternatively, the platinum component can be provided by mixing an aqueous platinum sulfide sol with the alumina hydrate. This sol can be made by reaction in an aqueous medium of a halogen platinic acid with hydrogen sulfide. The alumina hydrate containing the platinum metal can be dried and calcined usually at a temperature from about 750 to 1300 F. or more to provide the activated or gammaalumina modifications. The activity enhancing component can be added to the catalyst in any stage of its preparation. It may be incorporated in the support, either before or after the addition of the Group VIII metal. It will usually be applied by impregnation from solution (water, organic or inorganic solvents) or from a gas phase. It is frequently added to the catalyst after it has been formed by tabletting or extrusion and calcined. After the activity enhancing component is added in this procedure the catalyst can be recalcined.
Even though our catalyst can be employed directly in the isomerization system, it can be pretreated with free or molecular hydrogen. For instance, the catalyst can be heated at temp ratures from about 800 to 900 F. in
a slowly flowing stream of hydrogen for a period of time (e.g. 1 to 3 hours) sufiicient to activate the catalyst.
The catalyst employed in the process of the present invention can be regenerated employing conventional procedures, for instance by subjecting it to an oxygencontaining gas at temperatures sufficient to burn off carbon deposited on the catalyst during the conversion of petroleum hydrocarbon feedstock. This oxygen-containing gas, e.g. an oxygen-nitrogen mixture, can contain about 0.01 weight percent to 5 weight percent oxygen but preferably contains about 0.5 to 1.5 weight percent oxygen and is introduced at a flow rate such that the maximum temperature at the site of combustion is below about 1000 F.
The paraffinic feed material employed in our process is generally a C to C n-paraflinic-containing cut derived from crude petroleum hydrocarbons, as by distillation, reforming and extraction processes. The feed can be a blend of n-pentane and n-hexane usually containing about 25 percent or more of n-hexane and preferably a predominant amount of n-hexane.
The following specific examples will serve to illustrate our invention but they are not to be considered limiting.
Example I PREPARATION OF NOBLE METAL ALUMINA CATALYST A noble metal alumina composition of the kind described in US. Patent No. 2,838,444 can be employed in preparing the catalyst used in the process of our invention. The composition of this patent can be made as follows. Pure aluminum metal is dissolved in pure hydrochloric acid, and the resulting solution is mixed with deionized water to form an aqueous aluminum chloride solution and an alumina gel is prepared equivalent to approximately 65 grams of A1 0 per liter. A separate deionized water solution of NH OH is prepared containing approximately 65 grams of ammonia per liter. These two reagents in approximate volume ratio of 1:1 are intimately mixed as a flowing stream at a pH of 8.0. The flowing stream is passed to a stoneware container and an alumina hydrate is visible. The precipitated hydrate is filtered from the mother liquid and washed to 0.2% chloride by successive filtrations and reslurryings in deionized water until the desired chloride concentration is reached. In each reslurrying ammonia is added to give a pH of about 9. The washed hydrate is covered with water in a container and aged at about F. until it is approximately 70% trihydrate, the remaining being substantially of the amorphous or monohydrate forms. The total hydrate composition is comprised of 42% bayerite, 18% randomite, 11% gibbsite, 20% boehmite, and 9% amorphous as determined by X-ray difiraction analysis. The aged hydrate is mixed with deionized water in a rubber lined container to provide a slurry of about 7 weight percent A1 0 at a pH of about 8.0. A chloroplatinic acid solution in deionized water (0.102 gram platinum per milliliter) is stirred into the slurry and the slurry is then contacted with a deionized water solution which has been saturated with H 5 at 78 F. to precipitate the platinum. The pH of the slurry is adjusted to 6.0 to 6.5 by ammonium hydroxide addition and the solids of the slurry are dried on a horizontal drum drier to give a powder of generally less than 20 mesh. The drum drier powder is mixed in a planetary type dough beater with sufiicient deionized water to indicate Q5 weight percent water on a Central Scientific Company Infra-red Moisture Meter containing a watt bulb, Cat. No. 26675. The resulting mixture is forced through a die plate having holes in diameter bolted to a 3%" Welding Engineers screw extruder. The resulting strands .are broken to particles of length varying generally between about A to 1".
The particles are dried at 230 F. and calcined by heatlng to 925 F. in a flow of nitrogen gas followed by a flow of -air while the composition is maintained at a temperature in the range of 865 F. to 920 F. The composition thus produced analyzes about 0.6 weight percent of platinum which is in sufliciently divided form so as to exhibit by X-ray diffraction studies the substantial absence of crystallites or crystals of size larger than 50 Angstrom units. After the calcination the composition has an area (BET method) within the range from about 350 to 550 square meters/gram.
Example II PREPARATION OF NOBLE METAL-NHgBF4ALUMINA. CATALYST A platinum-alumina composition prepared essentially as described above in Example I, except that air was used for the complete calcination procedure, and containing about 0.6% platinum was employed in preparing the noble metalNH BF alumina catalyst by the following procedure. 209 grams of the calcined platinumalumina composition were placed in a 1-liter 3-neck flask. The flask was connected through one neck to the house vacuum line and through another with a short length of Tygon tubing to a buret. The third neck was stoppered. The flask was evacuated and pumped with house vacuum for minutes. 12.05 grams (General Chemical technical grade ammonium fiuoborate) were dissolved in DI water to make 170 ml. of solution which were poured into the buret. The solution was allowed to flow slowly into the flask while vacuum was still applied and the catalyst was shaken vigorously. When all the solution had been admitted, the vacuum was broken. The catalyst was transferred to a 6 crystallizing dish and dried in the forced air drying oven at 250 F. The catalyst was stirred occasionally while it was drying. The oven dry catalyst was placed in a cool muifle furnace, brought to 1000 F. and held at that temperature for 2 hours. The catalyst was then removed from the furnace and cooled in a desiccator. The catalyst analyzed 5.31% volatile matter (1000 C.), 0.57% B, and 3.71% F.
Example III PREPARATION OF NOBLE METAIFH SIFG ALUMINA CATALYST A platinum-alumina composition prepared essentially as described above in Example I, except that air was used for the complete calcination procedure, and containing about 0.6% platinum was employed in preparing the noble metalH SiF alumina catalyst by the following procedure. 209 grams of calcined platinum-alumina composition were placed in a 1 liter 3-neck flask. The flask was connected through one neck to house vacuum line and through another with a short length of Tygon tubingto a buret. The third neck was stoppered. The flask was pumped with house vacuum for 10 minutes. The H SiF was diluted with DI water to make 170 ml. which were poured into the buret. The solution was allowed to flow slowly into the flask while vacuum was still applied and the catalyst was shaken vigorously. When all the solution had been admitted, vacuum was broken. The catalyst was transferred to a 6" crystallizing dish and dried in the forced air drying oven at 250 F. The catalyst was stirred occasionally while it was drying. The oven dry catalyst was placed in a cool rnuflle furnace, brought to 1000 F., and held at that temperature for 2 hours. The catalyst was then removed from the furnace and cooled in a desiccator. The catalyst analyzed 4.85 percent volatile matter (1100 C.) and 2.7 percent F.
Example IV BREPAIGAT'IO-N OF vN O BlLE MET AL-Ni(B F4)2 ALUMINA CATALYST A platinum-alumina composition prepared essentially as described above in Example I except that air was used 6 for the complete calcination procedure, and containing about 0.6% platinum was employed in. preparing the noble metal-Ni(BF -alumina catalyst by the following procedure (Prep. 805-3211).
209 grams of the platinum-alumina composition were weighed into a S-neck, 1 liter round bottom flask. One neck of the flask was stoppered, one neck attached to the closed stop-cock of a buret, and the third neck attached to a vacuum line. Ten minutes were allowed for removal of air from the flask and the catalyst. A solution of 16.7 g. of Ni(NO -6H O and 12.05 g. of NH4BF dissolved in deionized water to make 170 ml. was then admitted through the buret. The flask and contents were shaken vigorously while the solution was being added. The catalyst was transferred to a 6" crystallizing dish and placed in a forced-air drying oven, set at 250 F., for about 16 hours. The oven-dried catalyst was placed in a sagger and heated in a muflie furnace 2 hours at 1000 F. The catalyst was cooled in a desiccator. Sample No. 500- K7030 Analysis: 1.49% Ni, 0.57% B, 3.02% F.
Example V The isomerization process of the present invention is illustrated by Runs A, B, and C (illustrated below in Table I employing platinum as the Group VIH metal). A catalyst prepared essentially as described above in Example II was employed in Run A, a catalyst prepared essentially as described above in Example III was employed in Run B and a catalyst prepared essentially as described above in Example IV was employed in Run C. All runs were conducted under the conditions specified in the table which also shows the results of these runs.
TABLE I Run A B 0 Sample N o 5004,02 1 500-7, 038 500-7, 030 alyst percent 5. 31 4. F, percent 3.71 2. 70 B, percent... 0. 57 Isomerization activity:
Conditions Feedstock 650 680 650 300 300 300 3 2. 9 3 112/116 mol ratio 3/1 3/1 3/1 Product 1 Pt-NH BF -alumina.
2 Pt-H SiF -alumina.
The following data indicates that a platinum-alumina composition, prepared essentially as described above in Example I except that air was used for the complete calcination procedure, containing promoter components in a combination of F and Sior BF provides better results in the isomerization of n-pentane than the results provided by using any of these components alone. The results are based upon the isomerization of n-pentane to isopentane under conditions, unless otherwise specified, including a temperature of 600 F., a pressure of 300 p.s.i.g., a hydrogen to hydrocarbon mole ratio of 3/1 and 1.5 WHSV. The data sets forth the particular promoter component employed with the platinum-alumina composition and the results when a particular component is employed. The relative activity is based upon a 0.6% platinum-alumina3.23% boria catalyst (Cat. No. 480279) as a reference standard and was calculated using the following formula in which K represents the reaction rate constants:
7 Selectivity and conversion were calculated according to the formulae: Selectivity to LCFWX 100 Total conversion Total conversionzl-mole percent n-C remaining in the product 7. The method of claim 5 in which the noble metal is platinum and is about 0.1 to 2% of the catalyst.
8. The method of claim 5 in which the activated alumina is derived by calcination of an alumina hydrate precursor consisting essentially of about 65 to 95% of alumina trihydrate and about 5 to 35% of a member selected from the group consisting of amorphous hydrous Data Promoter Total Selectivity, Relative Catalyst No. conversion, mole activity mole percent percent 4 Analysis Component percent 2.70% F, 0.6% SiO (est.) HQSIFB 1 61. 6 1 93. 465 0.20% '0 Si 02 7,030 1.5% Ni, 0.57% B, 3.02% F N1(BF4) 4 58.1 4 98.2 520 480-279. 3.23 0 B B1 3 27.9 100 100 1 Evaluated at 680 F., 3 WHSV.
2 Excessive demethanation at 650 F. 3 Reference Catalyst: No. 480279.
4 Evaluated at 650 F., 3 WHSV.
What is claimed:
1. In a method of isomerizing a C -C n-paraflinic containing hydrocarbon feed, the step comprising contacting said feed in the vapor phase with a catalyst at a temperature of about 500 to 750 F., superatmospheric pressure, and in the presence of free hydrogen, said catalyst consisting essentially of about 0.1 to 2% of a platinum group noble metal and NH BF on an activated alumina, said component being present in an amount effective to enhance the activity of the catalyst.
2. The method of claim 1 in which the temperature is from about 600700 F. and the n-paraffin is n-pentane.
3. The method of claim 1 in which the noble metal is platinum and is about 0.1 to 2% of the catalyst.
4. The method of claim 1 in which the activated alumina is derived by calcination of an alumina hydrate precursor consisting essentially of about 65 to 95% of alumina trihydrate and about 5 to 35% of a member selected from the group consisting of amorphous hydrous alumina, alumina monohydrate and their mixture and the activated alumina has an area of about 350 to 550 square meters per gram.
5. In a method of isomerizing a C to C n-paraffinic containing hydrocarbon feed, the step comprising contacting said feed in the vapor phase with a catalyst at a temperature of about 500 to 750 F., superatmospheric pressure, and in the presence of free hydrogen, said catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and Ni(BF on an activated alumina, said component being present in an amount effective to enhance the activity of the catalyst.
6. The method of claim 5 in which the temperature is from about 600 to 700 F. and the n-paraifin is n-pentane.
alumina, alumina monohydrate and their mixture and the activated alumina has an area of about 350 to 550 square meters per gram.
9. In a method of isomerizing a C to C n-paraffinic containing hydrocarbon feed, the step comprising contacting said feed in the vapor phase with a catalyst at a temperature of about 500 to 750 F., superatmospheric pressure, and in the presence of free hydrogen, said catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and NH BF on an activated alumina, said NH BF being present in a molar ratio with respect to said alumina of from about 0.001 to 0.311.
10. In a method of isomerizing a C to C n-parafiinic containing hydrocarbon feed, the step comprising contacting said feed in the vapor phase with a catalyst at a temperature of about 500 to 750 F., superatmospheric pressure, and in the presence of free hydrogen, said catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and Ni(BF on an activated alumina, said Ni(BF being present in a molar ratio with respect to said alumina of from about 0.001 to 0.3 1.
References Cited by the Examiner UNITED STATES PATENTS 2,483,130 9/49 Garrison 25244l 2,838,444 6/58 Teter et al. 252-441 2,852,472 9/58 Barrett 208-139 X 2,935,545 5/60 Block et al 260683.66 2,951,889 9/60 Geerts et al 260-683.66 2,999,074 9/61 Bloch et al. 252441 X ALPHONSO D. SULLIVAN, Primary Examiner.
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|U.S. Classification||585/740, 502/203, 585/749|