US 2918509 A
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Dec. 22, 1959 E. MILLER ETAL 2,918,509
PROCESS AND CATALYST FOR THE ISOMERIZATION OF HYDROCARBONS AND LIGHTER uouoas wouovaa LIGHT NAPHTHA FEED INVENTORS ELMER L. MILLER BY HILLIS o. FOLKINS ATTORNE E. L. MILLER ETAL Dec. 22, 1959 PROCESS AND CATALYST FOR THE ISOMERIZATION 0F HYDROCARBONS Filed Oct. 31, 1957 2 Sheets-Sheet 2 R mm N Q k R m M m m L F mwm mmhIQJ W R 0. wmzsrmmr mwZ xmI mZ OPmz m& IkIm Z QZ 1 MS 02 #63 o a w m Y W U I\ I" .w .w 3 1 G S H S H m 3 S aw w um o w w m m um m um L N w 4 E Q mm M c a a a. w m N T n N u. 4 MN H H W U R H u. u n u a 3 3 3 H H H H a I! I! M024, ATTORNEY United States Patent PROCESS AND CATALYST FOR THE ISOMERIZA- TION 0F HYDROCARBONS Elmer L. Miller, Cary, and Hillis 0. Folkins, Crystal Lake, 11]., assignors to The Pure Oil Company, Chicago, 111., a corporation of Ohio Application October 31, 1957, Serial No. 693,727 10 Claims. (Cl. 260-48355) This invention relates to the catalytic hydroisomerization of isomerizable hydrocarbons having 4 to 7 carbon atoms per molecule. It is more specifically concerned with improving the octane rating of petroleum hydrocarbon feed stocks consisting predominately of normal hexane and/or normal pentane hydrocarbons.
According to this invention, it has been found that the hydroisomerization of hydrocarbon feed stocks consisting predominately of isomerizable aliphatic and alicyclic hydrocarbons having 4 to 7 carbon atoms per molecule can be efiiciently carried out by processing the feed stocks at a temperature within the range of about 600 to 800 F., in the absence of appreciable hydrocracking, a pressure within the range of 100 to 1000 p.s.i.g., and a hydrogen/hydrocarbon mol ratio within the range of about 0.5 to 5 in the presence of a composite catalyst consisting essentially of a major portion of a refractory, oxide support composited to evince hydrocarbon cracking activity and acidic properties copromoted with small amounts of a combination of metallic nickel and a noble metal of the Group VIII series, e.g., platinum, palladium, rhodium, iridium, etc.
In integrated petroleum refining operations for the production of high-octane-number gasolines, in order to obtain maximum effectiveness, one of the unit processes :selected must be for the processing of feed stocks con- .sisting predominately of the lower-molecular-weight, normally liquid, aliphatic and alicyclic hydrocarbons containing 4 to 7 carbon atoms per molecule. Substantial quantities of these feed stocks are available to warrant the separate processing of these materials. Although octane number improvement can be obtained by treating these feed stocks in a dehydrogenation process to produce -olefins, it is more desirable from an octane-yield relation- .ship to utilize isomerization processes for effecting the octane number improvement in these compositions. Furthermore, the isomerization product has an increased moltor octane number and improved road performance, and is a stable product which augments the stability of the blended, finished gasoline.
Because of the importance of isomerization as a unit process in an integrated refining scheme for the production of high-octane-number gasolines, a number of commerical isomerization processes have been developed which utilize solid catalysts. The use of such catalysts eliminate plant corrosion problems and the accompanying high maintenance cost which are attendant upon the use of catalysts of the Friedel-Crafts type. The effectiveness of platinum-promoted catalyst composites such as platinum-halogen-alumina, platinum-silica-alumina, etc., in hydroforrning operations, wherein isomerization is included as one of the concomitant reactions, has prompted the utilization of these same catalysts in isomerization processes. These catalysts, however, require high, operating temperatures which are disadvantageous because isomerization is an equilibrium reaction, the efficiency of which decreases with an increase in the processing, temperature. As a result, at the high temperatures em- Patented Dec. 22, 1 959 2 ployed, the equilibrium product contains substantial quantities of loW-octane-number paraflins which were not isomerized during the course of the reaction. In addition, it has been reported thatas the equilibrium conversion is approached, the gas loss increases very sharply. Further disadvantages resulting from the use of hightemperature processing conditions are higher fuel cost for carrying out the reaction, and added expense for fabricating process vessels to withstand the combination of high pressures and high temperatures required" for this type of isomerization. A catalyst, however, has been found which permits the isomerization reaction to be carried out at lower operating temperatures and thus avoids the disadvantages accompanying high-temperature isomerization using platinum catalysts.
It is, therefore, the primary objective of this invention to provide a hydroisomerization process for the isomerization of hydrocarbon feed stocks consisting predominately of low-molecular-weight, isomerizable, hydrocarbons having 4 to 7 carbon atoms per molecule, carried out at temperatures not in excess of about 800 F, in the substantial absence of hydrocracking. It is another object of this invention to provide a relatively low-temperature process for improving the octane number of petroleumderived, feedstocks consisting essentially of C -C normal paraflinic hydrocarbons. It is an additional object of this invention to process low-boiling, normally liquid, petroleum fractions in a hydroisomerization process employing a solid, noncorrosive catalyst utilizing relatively low temperatures which permit the substantial production of branched chain, isomerization products with a minimum loss to gaseous products consisting of butanes and lower-molecular-Weight hydrocarbons.
These and other objects will become more apparent from the following detailed description of this invention.
Figures 1 and 2 are illustrative processing schemes employing the process of this invention.
As catalysts for use in isomerization processes employed in the upgrading of mixtures of saturated aliphatic and/or alicyclic light hydrocarbons such as straight-run, petroleum, naphtha distillates to provide high-octanenumbcr gasoline blending agents, it has been found that composites of hydrocarbon cracking catalysts and various hydrogenation catalysts are highly active and selective (see isomerization of Saturated Hydrocarbons in the Presence of Hydrogenation-Cracking Catalysts, Ciapetta et a1., Industrial and Engineering Chemistry, (l) 147, et seq.). Specific catalysts are prepared by incorporating a small amount of an hydrogenation agent in a refractory, mixed oxides base, composited to evince acidic properties and hydrocarbon cracking activity. Although a variety of suitable hydrogenation agents have been employed, the use of metallic nickel as the hydrogenation agent in the preparation of illustrative isomerization catalysts has provided examples. These catalysts, al.- though active, possess poor selectivity. According to this invention, however, it has been found that the selectivity of nickel-promoted, refractory, acidic oxide, composite isomerization catalysts containing preferably about l5% Wt. nickel, based on total catalyst, can be enhanced by incorporating small amounts of a Group VIII noble metal, in proportions, viz., preferably 0.010.05% by weight, based on total catalyst, which by themselves would only manifest a small amount of promotional effect. The total promotional effect which is more than additive is obtained by incorporating into a selected, solid, refractory, acidic support, metallic nickel in the range of about 1 to 5% by weight and a metallic Group VIII noble metal in amounts within the range of about 0.01 to 0.10% by wt. In general, the amount of nickel employed will be the major portion of the copromoter with the total amount of co-promoting contotal catalyst.
In the preparation of catalyst compositions employed in-the processof this invention, varieties of techniques have been devised and are described in the prior art. Toincorporate the metallic nickel in the selected refractory mixed oxides base, the support is impregnated with asolution of a soluble nickel salt, such as the sulfate, acetate, chloride, nitrate, or complex nickel ammonium compound. Another well-known technique involves the use of the molten salt for impregnating the acidic oxide carrier. The metallic nickel is then produced by reducing the nickel compound with a reducing gas such as hydrogen, carbon monoxide, hydrocarbons, etc. Another technique involves the admixing ofa solution of a nickel salt with the acidic. oxide carrier. A nickel hydroxide or carbonate is then-precipitated to effect the impregnation of the acidic oxide carrier. The resultant admixture is then filtered and the impregnated acidic oxide support washed free of soluble salts and dried, after which the metallic nickel is produced by the reduction of the hydroxide or carbonate. In certain instances itmay be preferred to initially convert the impregnated nickel compound to the oxide by heating it in a suitable oxidizing atmosphere prior to reduction to metallic nickel. An illustrative technique employing the oxidizing step involves impregnating acidic oxide base with a complex nickel ammonium salt solution, and thereafter contacting the impregnated acidic oxide carrier with carbon dioxide to produce the carbonate. The impregnated carrier is then dried and calcined at a temperature at which the carbonate will decompose to form the oxide, after which the oxide is subjected to reduction to form the metallic catalysts. It is essential in preparing catalysts of this nature, wherein an ammonium compound is employed in the catalyst preparation to utilize reducing conditions of-time and temperature sufficient to effect the substantially complete removal of ammonium ions from the catalysts in order to avoi adversely affecting catalyst activity. I
The small amount of Group VIII noble metal is incorporated in the acidic oxide support in accordance with conventional prior art techniques, such as by impregnation of the support with a solution of the selected Group VIII noble metal salt such as the chloride or nitrate, or with a solution of a mixed Group VIII metal salt such as ammonium chloropalladite. Thereafter the impregnated support is dried at about 200-250 F. and reduced in a hydrogen atmosphere at an elevated temperature. The incorporation of the promoter combination can be effected either simultaneously or sequentially. In the latter instance, either the metallic nickel or the metallic noble metal can be initially introduced into the refractory acidic oxide support.
Prior to impregnating the activated acidic oxide support, it is preferred, that this component of the catalyst composition be dried at an elevated temperature within the range of about 250400 F. The impregnated mass is then dried for at least about 4 hours at a temperature within the range of about 225 350 F. The green catalysts are then pelleted and activated by contacting the dried catalyst mass with a reducing gaseous stream, such as hydrogen, at an elevated temperature for a time sufficient to effect the reduction of the nickel compound and the Group VIII noble metal impregnants to the metallic state. This reduction can generally be carried out by heating the catalyst mass to a temperature between 750975 F. in the presence of hydrogen for a period of at least about 2 hours. In this reducing step about 200)-5000 s.c.f.h. of hydrogen per barrel of catalyst is. use
The refractory mixed oxides base can be any suitable composition which,.when composited, evinces acidic propcities and hydrocarboncracking activity. Conventionai solid hydrocarbon cracking catalysts such as composites of silica-alumina, silica-zirconia, silica-titania, silicaboria, alumina-zirconia, alumina-beryllia, alumina-boria, silica-chromia, boria-titania, silica-alumina-zirconia, silicaalumina-beryllia, acid-treated clays, and other similar oxide compositions are preferred. It is preferred, however, to employ silica-alumina hydrocarbon cracking catalysts for use as supports in the preparation of the isomerization catalysts employed in this invention. Hydrocarbon cracking catalysts which have a silica content within the range of about 50-95% by Weight, and preferably -90%. by wt., and alumnia contents within the range of about 505%, and preferably 25-10%, are preferred. The silica-alumina support can be obtained commercially or can be prepared by admixing separately prepared portions of silica-gel and alumina gel, or in the alternative, by conventional coprecipitation techniques. It is also possible that a catalyst can be prepared for the instant invention by contacting silicagel particles with a solution of an aluminum saltand a nickel salt, and a salt of a Group VIII noble metal, in the desired concentration. After drying the mixture, it is heated for a sufficient time to effect the decomposition of the salt. Thereafter the nickel and Group VIII noble metal salts are reduced to the metallic state by treatment with hydrogen at elevated temperatures.
The process of this invention is especially adaptable for effecting the isomerization of feed stocks consisting predominately of normal pentane and/or normal hexane to produce an octane improvement by promoting the molecular rearrangement of these hydrocarbons, or mix tures containing these hydrocarbons, such as light petroleum fractions having an ASTM boiling range of F.-200 F.
To illustrate the instant invention, a catalyst consist ing essentially of 3.0% nickel and 0.01% palladium, incorporated on a silica-alumina cracking catalystwas prepared as follows: 89.2 grams of ni(NO .6H O were dissolved in 1350 milliliters of distilled water at about room temperature. An acidified, aqueous solution of palladium chloride was prepared by dissolving 1.0 gram of palladium chloride dihydrate in 250 ml. of1.0 normal hydrochloric acid. A silica-alumina hydrocarbon cracking catalyst-having the following characteristics was used:
A1 0 "weight percent 24.4 Na O do 0.02 50., do e 0.02 Fe do 0.25 SiO do 75.3 Surfacearea m. /g 440 Pore volume ml./g 0.71. Particle density g./ml 0.88
The catalyst particles were spheroidal, as produced for use in a fluidized system. To the nickel nitrate solution was added 582 grams of support, accompanied with vigorous mixing, thereby producing a slurry. Then 500 milliliters of 0.85 M ammonium carbonate solution was admixed with the slurry and the resulting admixture was stirred for about 15 minutes, filtered, and the wet catalyst cake dried at 230 F. for 16 hours. The amount of ammonium carbonate employed in this preparation corresponded to about 39% excess of the theoretical amount needed to form NiCO Two hundred grams of the dried, nickel-containing support were then impregnated by adding 200 milliliters of an aqueous solution containing l0rnilliliters of the palladium chloride stock solution, an amount sufficient to satisfy thead sorptive capacity of the support. a
The impregnated support was dried at about 230 F. for 16 hours. The dried masswas pelleted into /s-inch by As-inch pellets and activated by heating to 975 F. in hydrogen for a period of 5 hours, followed by continued treatment with hydrogen at 975 F. for 16 hours.
In order to insure a complete removal of the undesirable anions from the catalyst composition, which might deleteriously affect their activity, the reduced active catalyst was purged with nitrogen and cooled to 750 F. Thereafter the catalyst was oxidized with air for 1 hour and allowed to cool to room temperature to facilitate handling. The catalyst was then placed in a reactor and heated to 975 F. in hydrogen. Thereafter the catalyst was treated with 8 to 4- s.c.f.h. of hydrogen at 975 F. for 8 to 16 hours after which it was cooled to 725 F. Following this, the reactor was pressurized to reaction pressure with hydrogen, and the hydrocarbon feed stock charged under the desired conditions. The eifectiveness of the above catalyst composition as an isomerization catalyst was compared with other nickel catalysts and palladium catalysts prepared according to conventional catalyst preparation techniques. The results of this investigation are shown in Table I, in which is set forth comparative data demonstrating the superiority of the composite co-promoted, metallic nickel-Group VIII noble metal-silica-alumina composite over other catalysts which contain the respective co-promoters as the single promoting constituent. In addition, the advantage of a catalyst composition co-promoted with nickel and rhodium is also shown.
Table II Total Hr/HC Feed Description Tempera- Pressure, Mol LVHSV ture, F. p.s.i.g. Ratio 80% n-hexane20% cyclohexane 725 645 3. 2 2:8 60% n-pentane% nhexane10% eyclohexane 725 700 2 2 An admixture consisting n-pentane- 30% n-hexane 10 cyclohexane diluted with 5% n-heptane 725 700 2 2 In the isomerization process of this invention a variety of processing schemes are available. In Figure 1 is shown a simple scheme which utilizes a feed preparation and product recovery system employing a minimum number of process towers. A light, straight-run naphtha having an ASTM boiling range of about 100-180 F. is introduced into de-isohexanizer 10 via line '11. The residue consisting essentially of n-hexane and heavier hydrocarbons is sent through line 12 to reactor 13 for isomerization. The isohexanes and lighter hydrocarbons are re- Table I Catalyst Composition:
Promoter, Wt. Percent 0 3 0 Ni 0 01 Pd 3.0 Ni+0. 01 Pd 0 01 Rh 3. 0 N1+0.01 Rh pp r Wt. Percent 75 Si0225Al203 Run Conditions:
Temp., F 723 725 Pressure, p. 500 500 2.85 3.0 H2/HO mol rati 1. 01 1.0 Feed, Wt. Percent:
i-Os 1. 3 1. 6 n-Cs 96. 3 96.3 Cyelopentane. 2.0 1. 8 i- 5- 0.4 0.3 Product, Wt. Percent:
C4 and lighter 3. 0 0.1 2. 0 1-1 5.1 4.2 39. 3 42.6 89. 9 93. 3 56. 2 53. 8 1. 6 2. 2 1.9 2.1 0.4 0.2 0.6 0.4 6. 6 2.3 41. 6 44.1 3.9 2. 2 39.1 42. 6 59 91 97 94 96.5
1 Based on catalyst composition. 1 Based on support.
From these data it is evident that increases in catalyst efficiency, not apparent from the respective properties of each of the promoting agents, is obtained employing the co-promoted catalysts of this invention.
In carrying out the process of this invention employing the co-promoted, acidic oxide, hydrocracking catalyst composite of this invention, isomerization of saturated hydrocarbons having 4-7 carbon atoms per mole cule is effected employing the following conditions:
Temperature, F. Range Preferred Range 700-800 725800 680-775 700-760 650-740 675-725 600-725 625-700 Pressure, 100-1, 000 350-750 Liquid hourly v0 0. 5-10 1-4 Hz/hydrocarbon mol ratio 0. 5-5 1. 5-4. 5
moved from de-isohexanizer 10 and transferred by means of line 14 to depentam'zer 15 where the isohexanes and heavier hydrocarbons are separated and removed from the system via line 16 to storage. The overhead from depentanizer 15 which consists essentially of normal and isopentane, is sent to C -splitter 18 through line 19. Isopentane is recovered in the fractionator overhead and is sent to storage or transferred to gasoline blending facilities (not shown) through line 20, and the residue consisting predominantly of normal pentane is transferred by means of line 21 to a point of confluence wth line 12, wherein it is sent to reactor 13 for processing. The reaction eflluent is initially treated in stabilizer 22 to separate the butane-and-lighter products. The butaneand-heavier fraction is then processed in de-isohexanizer 10 as described above.
It is also apparent that numerous combinations of reactors and fractionators are possible for carrying out the isomerization process of this invention for the processing of light hydrocarbon feed stocks. For example, an alternative processing scheme is shown in Figure 2. The process of this invention finds application in combination with other conventional, unit-refining processes, such as reforming, or with split-stream techniques employing a plurality of reactors, to separately process feed stocks under'isomerization conditions selected to obtain maximum efiiciency with respect to the feed stock being processed. The various feed components can be processed jointly or singly, and on a once-through or recycle basis. In applications of this nature, the debutanized, light,
straight-run gasoline is deheptanized, either in existing equipment, such as a catalytic reformer feed preparation unit, or in new equipment. The C -C fraction is then split, and the C s, including debutanized C reactor effiuent, are split to produce an isopentane product and a normal pentane reactor feed. The degree of fractionation determines the product octane number, since normal pentane is recycled to extinction.
In the alternative, the C fraction. can beemployed in gasoline blending, or can be isomerized by one of two methods. Hexane fractions high in normal hexane content can be improved considerably by direct single-pass isomerization. Further improvement in octane number is possible by first splitting the isofrom the normal hexane, and then isomerizing the normal hexane fraction. Further octane improvement is possible by recycling normal hexane to extinction. This, however, would require an extra fractionation step to prevent an excessive build-up of methyl cyclopentane in the recycle stream.
An alternate method for processing normal pentane and the total hexane fraction in a single reactor involves de heptanizing a debutanized feed stock. The deheptanized feed is deisopentanized, and the resultant stream passed through the reaction system. The debutanized reactor efiluent then is fractionated to produce an isomerized hexane fraction, and a pentane recycle stream which passes to the deisopentanizer. In this alternate processing, reaction conditions are determined by the more reactive hexanes, resulting in a lower conversion per pass of normal pentane. The greater fractionation cost must be balanced by the decreased reactor section costs, since only one reaction section is required.
The relative quantities of pentanes and hexanes, as well as the isoto-normal-hexane ratio determine which processing method is most economical.
To obtain maximum efiiciency, auxiliary equipment is employed for pretreating the feed stock and the hydrogen utilized in the isomerization process. In order to insure long catalyst life, it is necessary to employ a hydrocarbon feed stock which is substantially free from sulfur or sulfur-containing compounds. Accordingly, a pretreater or guard case should be installed in the feed line to effect the removal of the sulfur compounds from the feed. Preferably, the pretreatment should be effected by a catalytic, vapor phase, desulfurization process in the presence of clay, bauxite, cobalt molybdate, or other suitable catalysts for effecting the desulfurization of the feed stock in the presence of hydrogen. A variety of desulfurization methods based upon the decomposition of the sulfur compounds at elevated temperatures in the vapor phase are briefly described by Kalichevsky, Petroleum Refiner, vol. (4) at page 117, et seq. It is also preferred that the hydrogen employed as a processing aid in the hydroisomerization process be substantially free of water, 0 CO, H 8, and related compounds, including those which react under hydroisomerization conditions to form the above. Although it is preferred that the hydrogen be free of these impurities, trace amounts of these substances not in excess of about 2 parts per million can be tolerated.
Although the foregoing invention is illustrated by a number of illustrative embodiments, it is apparent to those skilled in the art that these are non-limiting examples and that other modifications can be made without departing from the invention defined in the appended claims.
What is claimed is:
1. An isomerization catalyst consisting essentially of a refractory mixed oxides catalyst composited to evince acidic properties and hydrocarbon cracking activity and 8 co-promoted with 1-5% by weight of metallic nickel, and 0.01-0.10% of a Group VIII nobel metal, based on total catalyst composition.
2. A catalyst composition in accordance with claim 1 in which. said refractory mixed oxides catalyst is silicaalumina.
3. A catalyst composition in accordance with claim 2 in which said silica-alumina catalyst has a silica content within the range of about 50-95% by weight, based on said silica-alumina catalyst, and alumina content within the range of about 505%, based on said silica-alumina composition.
,4. An isomerization catalyst consisting essentially of a silica-alumina catalyst composited to evince acidic properties and hydrocarbon cracking activity and containing by weight of silica and 25% by weight of alumina, based on said silica-alumina catalyst, and copromoted with 3.0% by weight of metallic nickel, based on said isomerization catalyst composition and 0.01% palladium based on said isomerization catalyst composition.
5. An isomerization catalyst consisting essentially of a silica-alumina catalyst composited to evince acidic properties and hydrocarbon cracking activity and containing 75% by weight of silica and 25% by weight of alumina, based on said silica-alumina catalyst, and copromoted with 3.0% by weight of metallic nickel, based on said isomerization catalyst composition and 0.01% rhodium based on said isomerization catalyst composition.
6. An isomerization process which comprises contacting an isomerizable saturated hydrocarbon having 47 carbon atoms per molecule at a temperature within the range of about 600 to 800 F., a pressure within the range of about to 1000 p.s.i.a., liquid volume hourly space velocity of 1'-4, and a hydrogen/hydrocarbon mol ratio within the range of about 0.5 to 5, in the presence of a catalyst consisting essentially of a refractory, mixed oxides catalyst composited to evince acidic properties and hydrocarbon cracking activity and co-promoted with 15% Wt. of metallic nickel and 0.01-0.1% wt. of a Group VIII noble metal.
7. An isomerization process in accordance with claim 6 in which said refractory oxide catalyst is silica-alumina.
8. An isomerization process in accordance with claim 7 in which said silica-alumina catalyst has a silica content within the range of about 5095% by weight, based on said silica-alumina catalyst, and alumina content within the range of about 505%, based on said silica-alumina composition.
9. An isomerization process in accordance with claim 8 in which said catalyst consists of a silica-alumina cracking catalyst containing 75% silica and 25% alumina and copromoted with 3.0% nickel and 0.01% palladium.
10. An isomerization process in accordance with claim 8 in which said catalyst consists of a silica-alumina cracking catalyst containing 75 silica and 25 alumina and copromoted with 3.0% nickel and 0.01% rhodium.
References Cited in the file of this patent UNITED STATES PATENTS 1,266,782 Ellis May 21, 1918 1,426,517 Sulzberger Aug. 22, 1922 1,925,820 Reyerson Sept. 5, 1933 2,550,531 Ciapetta Apr. 24, 1951 2,666,756 Boyd et al. Jan. 19, 1954 2,698,829 Haensel Ian. 4, 1955 2,781,323 Hunter Feb. 12, 1957 FOREIGN PATENTS 487,392 Canada Oct. 21, 1952