US3202725A - Production of xylene - Google Patents

Description

Aug. 24, E5 w. LoRz ETAL PRODUCTION OF XYLENE Filed June 2, 1961 United States VPatent O 3,202,725 PRODUCTEGN OF XYLENE Waldemar Lorz, Yeadon, George Alexander Mills,

Swarthmore, and Harold Shalit, Drexel Hill, Pa., as-

signors to Air Products and Chemicals, Inc., a corporation of Delaware Filed June 2,1961, Ser. No.`114,522 3 Claims. (Cl. 260--67`3.5)

The present invention relates to dehydrocyclization of C8 acyclic hydrocarbons and is more particularly concerned with the production of xylene from C8 acyclic hydrocarbons with special emphasis on the selective production of p-xylene.

The production of aromatic hydrocarbons by dehydrocyclization of appropriate C6 and higher hydrocarbons is described in prior patents and other technical literature. Itis also known to aromatize selected C8 aliphatic hydrocarbons to produce xylenes. Thus, from n-octane there is obtained a mixture of all three isomers of xylene accompanied by ethyl benzene, which mixture predominates in o-xylene. Among the catalysts recommended for use in these dehydrocyclization processes there is chromium oxide, with or without minor quantities of other metal oxides, supported on gamma alumina.

For selective production of the desired p-xylene isomer by dehy-drocycl'ization -of acyclic C8 hydrocarbons, with only very small quantities of the other xylene isomers in .the reaction product, it is proposed by F. G. Herington and E. K. Rideal [Proc Roy. Soc. (London) A184, p. 434 (1955)] to -utilize 2,2,4-trimethylpentane :as starting material. Similar processes are described in U.S. Patents 2,785,209 and 2,785,210 wherein the suggested initial charge is iso-octane (2,2,4-trimethylpentane) or di-isofbutylene (2,4,t4-trirnethylpentenes), or mixtures of these. These patents describe various catalysts for this process, with lindicated preference :for catalyst comprising to 40% (preferably about y12%) chromium oxide on Igamma. yalumina `and containing also minor lamounts of potassium -oxide and cerium oxide. While the aromatics produced in the liquid reaction product reported by these patents may contain as high as 9598% p-xylene, the total conversion of the charge starting with isooctane does not exceed about 30% and up to about 36% in the case of the mixed trimethylpentene charge; the yield of p-xylene based on charge being at most less than about 12%.

It has now been found, in accordance with the present invention, that selective conversion of C8 acyclic (parafnic or oleiinic) hydrocarbons can be obtained at high conversion levels by using specially prepared catalyst comprising 15% to 25% chromiuml oxide (Cr203) on an alumina base composed essentially of eta alumina. By the use of such catalyst in the conversion of isooctane, up to 85% or more of the charge can be converted, with pxylene yields amounting to about 35% to 45% by weight of vthe charge.

The advantages of the invention can be further enhanced in accordance with another aspect thereof, by adding to the C8 charge C4 hydrocarbons which are simultaneously dehydrogenated. In this manner, not only is there the advantage of economically converting readily available and relatively inexpensive C4 parailins to xylenes, but in addition more eiective temperature control is achieved inasmuch as the presence of the C4 hydrocarbons has a dampening effect on the cyclic temperature swing otherwise encountered in the dehydrocyclization of the C8 hydrocarbon feed under adiabatic operation, wherein periodic burning of the coke deposited in the catalyst during the on-stream, period supplies at least part of the heat'utilized in the succeeding endothermic hydrocarbon conversion operation. The design of an operative process for beneficial utilization of this feature to augment production of desired C8 aromatics is illustrated in the accompanying drawing by way of a schematic flow diagram.

Referring now to the embodiment illustrated in the drawing, there is charged to the dehydrogenation reactor system 10 a fresh feed 11 composed essentially of isobutane and recycle streams 12 and 13 containing di-isobutylenes and previously unconverted isobutane. The dehydrogenation effluent from reactor 10 is sent to a liash drum or other liquid-vapor separator system 14 wherein hydrogen and low molecular weight gases (to or through C3) are separated as overhead, while the unvaporized products are withdrawn as liquid in line 15.

The liquid products are sent to a debutanizer 16 preferably in the form. of a fractionating column operated so as to separate out an overhead vapor fraction, withdrawn through line 17, consisting essentially of C3 and C., hydrocarbons; the unvaporized higher boiling materials are discharged through line 18. The overhead gases from the vapor separator 14 are sent to an absorber 19, after being compressed to about 50 to 200 pounds per square inch. Absorption is effected by means of an aromatic hydrocarbon oil introduced into an upper portion of the absorber through line 20, whereby unabsorbed hydrogen and low molecular weight gases (through C2), which are not absorbed, are withdrawn overhead in line 21, while the rich oil containing absorbed higher molecular weight hydrocarbons is sent by line 22 to stripper 23, operated to separate as overhead the C3 and C4 hydrocarbons from the absorber oil, the lean oil being returned to the absorber 19 through line 20. Thus, the stripper 23 may be operated under conditions to discharge as vapor overhead hydrocarbon materials boiling substantially above the initial boiling point of the absorber oil. In the typical situation, 'aromatic absorber oils of a boiling range from about F. to about 400 F. can be conveniently employed.

The overhead streams from debutanizer 16 and stripper 23, predominating in C3 and C4 hydrocarbons, are sent by lines 17 and 24, respectively, to a depropanizer 25, operated to separate out an overhead fraction, discharged through line 26, composed essentially of C3 hydrocarbons rich in propylene, while the unvaporized bottoms, composed essentially of isobutane and isobutene, are sent through line 27 to polymerization (dimerization) in any suitable reactor 28.

Any suitable kno-wn process for dimerization of the isobutenes may be employed in reactor 2S. For example, the hydrocarbon stream introduced through line 27 may be passed over a xed bed of silica alumina catalyst at moderate temperatures and pressures and high space rates. Typical operations involve temperatures of 300 to 400 F., pressures of 300 to 800 pounds per square inch and liquid hourly space rates of .about 3 to l0. Other known dimerization processes employ either phosphoric acid catalyst or sulfuric acid catalyst at moderate temperatures designed to obtain high yields of desired dimers rich in 2,2,4-trimethyl pentene, and avoiding severity which may tend to promote excessive production of dimethyl hexenes or 2,3,4- and 2,2,3-trimethyl pentenes. The total polymerization product rich in 2,4,4-trimethyl pentene-l and 2,4,4-trimethy1 pentene-Z, together with some triisobutylenes in the product, is recycled to the dehydrogenation reaction system 10 by means of line 12 as already indicated.

The bottoms fraction from the debutanizer 16 Vconsists essentially of C7| hydrocarbons rich in aromatics. These are fractionated in column 29 to separate out as overhead vapors hydrocarbons boiling up to about 222 F. or

slightly above, but short of the boiling point of toluene (about 230 R). The overhead fraction, which is compo-sed chiefly of unconverted diisobutylene together with a some higher liquid polymer, is recycled by line 13 to the dehydrogenation reactor as already indicated, The buttoms fraction from column 29 is sent by line 31 to fractionating column 32 wherein toluene and lower boiling hydrocarbons are withdrawn as vapor overhead in line 33, thereby recovering at 34 the C8 aromatic hydrocarbons, which will contain 95% or higher p-xylene, the remainder being almost entirely isomers thereof.

For the combined dehydrogenation operation carried out in reactor 10, wherein the fresh charge is composed essentially of fresh isobutane which is dehydrogenated to isobutylene while recycled dimer is simultaneously converted to xylene, preferred operating conditions include temperatures in the range of 1000 to 1100 F., and low pressures ranging from about 5 inches or mercury absolute to atmospheric (30 in. Hg). Space rates may be in the range of 0.5 to 2 volumes per hour.

When the dehydrocyclization process is operated, with iso-octane or diisobutylene as fresh charge, for production of an aromatics product consisting essentially of p-xylene, somewhat lower operating severity can be employed; thus temperatures in .the range of about 950 to 1050 F. can be utilized, preferably in the range of 975 to 1025 F. for best overall results from the standpoint of achieving high conversion levels without excessive production of coke and light hydrocarbon gases. While atmospheric or even slightly elevated pressure can be used, it is advantageous even here to operate at subatmospheric pressure so as to favor 1'C4 olens rather than parains in the by-products. The isobutane and iso C4 olens produced in this process can be recovered and separated, if desired, or these can be directly recycled 'as such, joining the fresh C3 charge fed to dehydrocyclization. The presence of recycled isobutylene may serve to suppress splitting of the C8 feed to some extent, and in addition thereto some part of the z'C4 parains and olefins may be directly converted to xylene by a gas reversion type mechanism taking place in the dehydrocyclization reactor, as illustrated by the reactions:

Operating at the indicated pressure, the feed rate of the C8 hydrocarbon may lie in the range of 0.2 to 2.0 volumes per hour per volume of catalyst (Ll-ISV) and is preferably selected so that at the temperature and pressure employed at least 50% and preferably greater conversion of the C8 charge is obtained. If the iC4 hydrocarbons are recycled-as parans, olens or mixtures of these-the same temperatures and pressure in general may be employed as when fresh C8 feed only is used, but the total hydrocarbon space rate should be accordingly adjusted to obtain operating severity consistent with a minimum of 50% conversion of C8 hydrocarbons.

As indicated above, an important feature of the invention is the particular catalyst used. Eta alumina, which constitutes the whole or major part of the support or carrier for the active catalytic component, can be produced by heating beta alumina trihydrate (Bayerite) at temperature in the range of about 600-1400" F. Alumina beta trihydrate can be obtained by various methods known to the art; one such method involves the hydrolysis of aluminum alcoholate with ammonium hydroxide. Other methods involve the controlled aging of aluminum hydroxide gels. Beta alumina trihydrate in substantially pure form (97-{-%) is now available commercially; also available are marketed mixtures of hydrated alumina contining 75% or more beta alumina trihydrate in association with alpha trihydrate (Gibbsite) or with alpha monohydrate (boehmite) or sometimes with both of these. Calcination (dehydration) of the alpha trihydrate leads to the production of typical gamma form of alumina, heretofore known to the art, as activated alumina. In calcining alumina hydrate mixtures containing beta trihydrate with these alpha hydrates, there is obtained a corresponding calcined product comprising eta and gamma forms of alumina. The catalysts used in the practice of the present invention are prepared by impregnation of a dehydrated alumina base obtained from hydrated alumina containing at least 60% Iand preferably in excess of 75 beta trihydrate. The dehydrated alumina product is subjected to further heat treatment to adjust the surface area to the range of about 100 to 300 square meters per gram and then impregnated with chromic acid or other decomposable soluble chromium compound to incorporate 15 to 25% Cr2O3 by weight of the finished catalyst, after which the impregnated product is dried and calcined. The calcined chrome-alumina catalyst has a surface area of about 50-150 square meters per gram.

The preferred catalysts used in practice of the invention are those which contain at least 0.6% and preferably 0.8 to 1.5% by weight alkali metal ion calculated at Na2O; ie., the corresponding potassium compound used in the same molecular proportions would entail the weight range of at least 0.9% K2O, preferably 1.2 to 2.3% KZO by weight of the catalyst. Commercial hydrated alumina compositions composed of or predominating in beta trihydrate vary in alkali metal content from about less than 0.1% NazO to generally about 0.6% NaZO. To incorporate additional alkali metal ion there may be admixed with the aqueous paste of the alumina hydrate employed in formation of granules or pellets, sodium bentonite or sodium hydroxide in an amount sucient to provide the desired alkali metal content in the finished catalyst. On the other hand, the sodium or other alkali metal may be incorporated in the pelleted material by inclusion in the solution employed for chrome impregnation. Thus, the desired amount of Na2O may be furnished by adding a small amount of sodium chromate to the chromic acid or the chromic acid solution may be partly neutralized by sodium hydroxide. The presence of the indicated amount of alkali metal in the catalyst is believed to enhance the selectivity of the catalyst for dehydrocyclization operations while reducing the degree of acid-catalyzed side reactions including isomerization, polymerization, and carbon-carbon scission.

EXAMPLE I The preferred catalyst employed in practice of the invention is prepared in the manner described below:

Commercial alumina beta trihydrate (96-{-% bayerite) was thoroughly admixed by mulling with aqueous nitric acid employing 0.09 part nitric acid (1.42 S.G.) and 0.108 water by weight of the alumina trihydrate. The acid mix after standing overnight was extruded through a die plate and the strands cut to form 2.4 mm. pellets. The pellets were dried at 240 F. and dehydrated iu air at about G-900 F. (surface area=367 m.2/g.). The dehydrated pellets were then subjected to surface area adjustment by steaming (100% H2O) for 2 hours at 900 F. (surface area=170190 m.2/g.).

The area-adjusted pellets were impregnated by soaking in a chromic acid solution, employing 1 liter of the solution for each kilogram of pellets. The chromic acid solution was prepared by dissolving Cr03 in water to form a solution of 1.420 specific gravity (6D/60 F.) containing about 550 grams CrO3 per liter of solution, in which there was also dissolved solid sodium hydroxide furnishing 41.8 grams NaOH per liter. After 2 hours soaking, the excess liquid was decanted from the pellets. The drained pellets were dried in air at 250 F., then heat treated for 4 hours at 1400 F., in an atmosphere of 20% steam and 80% air. The finished pellets analyzed 1.09% NazO by weight.

The catalyst pellets had the following approximate composition:

EXAMPLE 1I Table 1 ISOOCTANE RUNS Run No 1 2 3 4 5 6 950 1 000 1, 000 1, 000 1, 000 1, 000 0.25 0 25 1.0 1.0 1. 5 0.5 l 3 3 Products Wt. percent chg.

(no loss basis): a

77. 4 63. 3 86. 9 79. 4 65. 8 69. 1 22. 4 36. 4 11. 4 18. 7 3l. 7 28. 6 0.2 0.3 1.7 1.9 2.5 2.3 Conversion,

chg.x 35; 7 75. 2 53. 9 69. 1 83. 7 81. 7 Sellec., wt. percent chg 34 38. 5 71 64.7 53. 1 56.1 Yleld/pass, wt. percent .chg 12. 2 28. 9V 38. 3 44. 7 44. 4V 45. 8 Liquid anal., wt. perl f cent:

lsopctane 77. 4 28. 36 26. 1 17. 4 18. 6 Diisobutylene.. 5. 7 10.0 17. 1 12. 9 7. 3 7. 9 p-Xylene 15. 7 45. 7 43. 7 56. 3 67. 6 66. [J Gas Analysis, wt. percent:

Hydrogen 4. 7 5. 4 20. 5 14. 3 8.8 9. 4 Isobutane. 60. 8 63.8 44. 7 48. 4 45. 2 49. 2 lTotal butenes 16. 7 19. 5 17. 7 24. 4 23. 0 23. 3

1 Conversion is based on and diisobutylene.

2 Utilization of at least a portion of the butenes as recycle material after suitable processing as by dimerization will increase the selectivity products in the effluent other than isooctane value.

Table 2 DIISOBUTYLENE RUNS Run No 7 8 9 10 Oper. Cond.:

Temp 1, 000 1, 000 1, 000 1, 000

Hz/oil mol 3 1. 5 Products, wt. percent chg. (no loss basis):

Liquid 60 66. 7 61. 3 66. 7

Gas 35. 6 32. 9 87.3 31. 3

Coke 4. 4 0. 8 1. 4 2. 0 Conversion, wt. percent chg.- 94 92. 4 92 89. 4 Selectivlty, wt. percent chg 35. 7 41 37. 2 45. 7 Yield/pass, wt. percent chg 33. 6 37 9 34. 2 40. 9 Liquid anal., wt. percent:

Diisobutylene 11. 3 11. 4 13. 1 15.9

p-Xylene 56 56. 8 55. 9 61.2 Gas analysis, wt.

Hydrogen- 0. 5 1. 6 1. 6 4. 7

Isobutane 76. 2 73. 4 64. 1 50. 8

Total buteues 14. 9 11. 8 22. 7 29. 8

It will be seen from the foregoing tables that under conditions of suliicient severity to obtain 50% or greater conversion of the charge, once-through yields of -45% p-xylene are obtained by weight of charge. Moreover, the aromatics fraction in the liquid effluent is of high purity in p-xylene and relatively free of the other C8 aromatic isomers. The isooctane and diisobutylene in the liquid product can, of course,` be recycled to dehydrocyclization for conversion to additional p-xylene. Considering such recycle operation, the highest ultimate yields would be obtainedunder conditions of Runs 3 and 4, carried out at a severity level giving about 50-70% per pass conversion of C8 charge. At higher conversion level, there is a corresponding loss in selectivity. The addition of hydrogen appears to lower the once-through yield to some extent, but on the other hand may tend to reduce the quantity of coke deposited.

' EXAMPLE n1 A series of runs were made over catalyst similar to that of the previous example at the conditions given below to determine the effect of varying the ratio of isobutane/di- 6 isobutylen'e in' the feed. The results are table below:

reported in the T able 3 Run N0 1 2 3 4 5 6 Temp., F 1, 050 l, 050 1, 050 1, 100 1, 100 1, 100 Pressure, mm. Hg 400 400 400 400 120 120 Space rate (GHSV l) 200 300 400 400 800 400 Isobutane to DIB mol ratio 0.9 1. 9 2.8 2. 8 6. 4 2. 8

Data Based On: Isobutane and YDIB-Isobutylene and pXylene Wt. percent chg.:

Conversion 74. 2 66. 7 62. 4 74. 8 44. 3 60. 7 Selectivity 80. 3 85. 8 83. 3 77. 3 79. 9 76. 9 Yield/pass 59. 6 57 52 57. 8 35. 4 46. 7

Data Based On: Isobutane pXylene Wt. percent chg.:

Conversion 37. 8 26. 7 Y 23. 9 29. 4 16. 8 25. 4 selectivity- 61. 6 64. 4 56. 6 42. 2 47 44. 9

Yield/pass... 23. 3 17. 2 13. 5 12. 4 7. 9 11.4

1 GHSV=Volume vapor per hour per volume catalyst.

From these runs it appears that desired product 'balance is obtained at isobutane/DIB rnol ratios of 2 to 3; approximate equilibrium conditions `are`obtained when the mol ratio of isobutane/isobutylene in the charge lies in the range of 2 to 4. i

`In the illustrated embodiment of the invention diisobutylene is recycled to the reactor in which dehydrogenation of isobutane isalso eiected. If desired, alternatively, separate reactors may be provided, respectively, for dehydrogenation of the isobutane and Vfor cyclization of the diisobutylene, wherein the latter may be operated at somewhat lower severity including lower temperature and higher pressure approaching atmospheric. In such operation, any isobutylene that is not polymerized at Z8 would Obviously many modifications and variations of the invention as hereinbefore set forth may be made Without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

What is claimed is:

1. The method for production of p-xylene which comprises: feeding to a catalytic dehydrogenation zone mixed hydrocarbon streams, including at least one recycled products stream comprising diisobutylene, and isoC4 hydrocarbons comprising isobutane, the ratio of isoC4 hydrocarbons to diisobutylene ibeing within the range from about 2:1 to about 3:1; contacting said mixed hydrocarbon streams in said dehydrogenation zone with chromealumina catalyst comprising 15 to 25% chromium oxide, determined as CrZOB, and alkali metal in an amount equivalentto at least 0.6% by weight Na20 on alumina carrier, said catalyst having been obtained by dehydratng beta alumina trihydrate to produce sorptive alumina having a large surface area, lowering the surface area to within the range from to 300 m.2/ g. by treatment with hot steam, impregnating the surface reduced alumina, and heating the impregnated eta alumina, said contacting being effected at a temperature in the range of 1000 to 1100 F. and pressure in the range of 5-30 inches Hg absolute, and at a space rate correlated therewith to obtain at least 50% conversion of C8 hydrocarbons in the charge with resulting production of products including p-xylene and isobutylene; separatingfrom the resulting products hydrogen and hydrocarbons up to C3; further separating from the reaction products isoC., hydrocarbons to provide an aromatic residual fraction; subjecting said separated isoC4 hydrocarbons to dimerization in a separate reaction zone to obtain diisobutylene; admixing the obtained diisobutylene with the fresh isobutane charged aromatic residual fraction a Xylene cut highly concentrated in p-xylene.

2. The method producing a hydrocarbon product of high p-Xylene content which comprises feeding to a dehydrogenation zone a hydrocarbon mixture of isobutane and diisobutylene under conditions effecting simultaneous cyclization of said diisobutylene and dehydrogenation of said isobutane, said condi-tions including contact of said hydrocarbon mixture to obtain at least 50% conversion of C8 hydrocarbons and the contacting of said hydrocarbon mixture with catalyst prepared by dehydrating an alumina hydrate composition containing at least 60% beta trihydrate, adjusting the surface areaby treatment with hot steam to a surface area in the range of 100 to 300 m.2/ g., impregnating the surface reduced alumina, and heating the impregnated alumina to prepare a chromia on eta alumina comprising 15 to 25% Cr203, and said conditions including temperature in the range of 1000 to 1100 F., and at a pressure in the range of from about 5 inches of mercury absolute pressure to about 30 inches of mercury absolute pressure.

3. The method for preparation of p- Xylene which cornprises the following steps:

l (a) feeding to a catalytic dehydrogenation zone a fresh hydrocarbon chargeconsisting essentially of isobutane,

(b) feeding to said dehydrogenation zone diisobutylene, v (c) dehydrogenating said fresh hydrocarbon charge in the presence of said diisobutylene to produce isobutylene therefrom while converting part of said diisobutylene to Xylene, said dehydrogenation zone being at temperature inthe range of 1000 to 1100" F.

and at subatmospheric pressure within the range fromv about 5 inches of mercury absolute to about 30 inches of mercury absolute and containing a bed of l catalyst comprising 15 to 25% Cr2O3 on an alumina base comprising eta alumina, said base having been obtained by dehydration of a hydrated alumina consisting essentially of beta alumina trihydrate,

(d) withdrawing the reaction products from said dehydrogenation zone and removingrtherefrom hydrogen and light hydrocarbons through C3 leaving a,

(e) removing from said C4| hydrocarbon product a fraction concentrated in iC4 hydrocarbons, including isobutylene, leaving an aromatics-containing hydrocarbon fraction,

(f) separating unconverted diisobutylene from said aromatics-containing fraction and recycling said diisobutylene to said dehydrogenation zone,

g) further fractionating the aromatics-containing fraction, after removal of diisobutylene therefrom, to separate out toluene and lower boiling hydrocarbons, thereby recovering a C8 aromatic fraction concentrated in p-xylene,

(h) polymerizing the isobutylene from step (e) to produce additional diisobutylene, and

' (i) feeding the polymerization product from step (h) to the dehydrogenation zone.

References Cited by the Examiner UNITED STATES PATENTS 2,734,022 2/56 Kimberlin et al. 208-136 2,785,209 3/ 57 Schmetterling et al. 260-673.5 2,785,210 3/57 Schmetterling et al. 260-673.5 2,796,326 6/57 Kimberlinet al. 20S-138 XR 2,863,826 12/58 Holcomb et al. 260-673.5 XR 2,941,016 6/ 60 Schmetterling et al. 260-673.5 2,962,536 11/60 Pitts 260-673.5 2,985,693 5/61 Probst et al. 260673.5 3,064,062 11/62 Lorz et al. 260-683.3

ALPHONSO D. SULLIVAN, Primary Examiner.

MILTON STERMAN, Examiner.

Claims (1)

1. THE METHOD FOR PRODUCTION OF P-XYLENE WHICH COMPRISES: FEEDING TO A CATALYTIC DEHYDROGENATION ZONE MIXED HYDROCARBON STREAMS, INCLUDING AT LEAST ONE RECYCLED PRODUCTS STREAM COMPRISING DIISOBUTYLENE, AND ISOC4 HYDROCARBONS COMPRISING ISOBUTANE, THE RATIO OF ISOC4 HYDROCARBONS TO DIISOBUTYLENE BEING WITHIN THE RANGE FROM ABOUT 2:1 TO ABOUT 3:1; CONTACTING SAID MIXED HYDROCARBON STREAMS IN SAID DEHYDROGENATION ZONE WITH CHROMEALUMINA CATALYST COMPRISING 15 TO 25% CHROMIUM OXIDE, DETERMINED AS CR2/3, AND ALKALI METAL IN AN AMOUNT EQUIVALENT TO AT LEAST 0.6% BY WEIGHT NA2O ON ALUMINA CARRIER, SAID CATALYST HAVING BEEN OBTAINED BY DEHYDRATING BETA ALUMINA TRIHYDRATE TO PRODUCE SORPTIVE ALUMINA HAVING A LARGE SURFACE AREA, LOWERING THE SURFACE AREA TO WITHIN THE RANGE FROM 100 TO 300 AM.2/G. BY TREATMENT WITH HOT STEAM, IMPREGNATING THE SURFACE REDUCED ALUMINA, AND HEATING THE IMPREGNATED ETA ALUMINA, SAID CONTACTING BEING EFFECTED AT A TEMPERATURE IN THE RANGE OF 1000 TO 1100*F. AND PRESSURE IN THE RANGE OF 5-30 INCHES HG ABSOLUTE, AND AT A SPACE RATE CORRELATED THEREWITH TO OBTAIN AT LEAST 50, CONVERSION OF C8 HYDROCARBONS IN THE CHARGE WITH RESULTING PRODUCTION OF PRODUCTS INCLUDING

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