US3855114A - Process for pretreating mixed hydrocarbon dealkylation stock - Google Patents

Abstract

A hydrocarbon liquid stream is conditioned for hydrodealkylation by first fractionating the stream to obtain a heart-cut containing aromatics, and substituted aromatics and paraffinic hydrocarbons of similar boiling points. The heart-cut is then contacted in the presence of a suitable catalyst with a gas comprising a mixture of hydrogen and carbon dioxide, hydrogen and carbon monoxide. The resultant product is fractionated into a hydrodealkylation feed stream low in those paraffinic hydrocarbons which crack and consume hydrogen during the hydrodealkylation of alkyl-substituted aromatics and rich in compound having a molecular weight greater than napthalene.

Description

Elite States Patent [191 Green et al.

451 Dec. 17,1974

[54] PROCESS FOR PRETREATING MIXED 2,774,801 12/1956 Coonradt et a1. 260/672 R HYDROCARBON DEALKYLATION S O 2,958,643 11/1960 Friedman 3,197,524 7/1965 Backlund 260/672 R [75] Inventors: William S. Green, Columbus; John Newman Ashland both of Primary Examinerl-lerbert Levine 73] Assignee: Ashland Oil, Inc., Ashland, Ky. Attorney, Agent, or Firm-Van D. Harrison, Jr. [22] Filed: Apr. 27, 1973 211 App]. No.: 355,089 [57] ABSTRACT Rdated Application Data A hydrocarbon liquid stream is conditioned for hydro- [63] Continuation an of s r N '63 845 J l 19 dealkylation by first fractionating the stream to obtain 1971 abando'ne: e u y a heart-cut containing aromatics, and substituted aro matics and paraffinic hydrocarbons of similar boiling [52] us Cl 208/121 208/59 208/] 12 points. The heart-cut is then contacted in the presence 36 268/123 560/672 of a suitable catalyst with a gas comprising a mixture [51] Int Cl i 11/04 C10g 13/04 of hydrogen and carbon dioxide, hydrogen and carbon [58] Fieid 260/672 2O8/59 123 monoxide. The resultant product is fractionated into a 208/121 1 hydrodealkylation feed stream low in those paraffinic hydrocarbons which crack and consume hydrogen [56] References Cited during the hydrodealkylation of alkyl-substituted aromatics and rich in compound having a molecular UNITED STATES PATENTS weight greater than napthalene. 2,653,176 9/1953 Beckberger 260/672 R 2,734,929 2/1956 Doumani 260/672 R 4 Claims, 1 Drawing Figure LIGHT GASOLINE 36-7. 16 -S GASOLINE l *2 FUEL OIL 25 34 CRACKED PRODUCT 20 2e 38 FROM Fcc UNIT 7 Y K J CYCLE HEART on. cm

SLURRY OIL l za PITCH FRACTION H2 co on CO2 PROCESS FOR PRETREATING MIXED I-IYDROCARBON DEALKYLATION STOCK CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of our copending application Ser. No. 163,845 filed July 19, 1971 now abandoned.

NATURE OF THE INVENTION The present invention relates to a method for preconditioning or pretreating a liquid hydrocarbon stream which subsequently is to be the feedstock for hydrodealkylation and relates also to the hydrocarbon product so preconditioned or pretreated.

PRIOR ART In the prior art, it has been well known to obtain mononuclear and polynuclear aromatic hydrocarbons from various sources. One such source of aromatics is a coal tar fraction. The coal tar fraction contains some aromatics which are unsubstituted and, therefore, useful as such, and substituted aromatics having substituent groups, such as methyl and ethyl groups. It is also known that the alkyl substituted aromatics may be dealkylated to improve the product yield. Other sources of aromatics, in addition to coal tar distillates, include tar sands, shale oil, bone oils, wood tar and other naturally occurring materials. Still another source of aromatics are the various products resulting from processes for refining liquid petroleum oil. Since liquid petroleum oils are basically made up of the same components as tar sands, shale oils and the like, except for relative quantities of components and the form of crude products, large amounts of aromatics occur in petroleum oils, depending upon their origin, and as a result large amounts of impure aromatics and aromatic precursors are obtained as products of various processes for refining petroleum oil to produce the usual ultimate product gasoline. Most refinery streams containing substantial amounts of aromatics are, of course, impure streams and the aromatics must be separated from paraffinic, naphthenic and other types of hydrocarbons. One method of making this separation involves the use of aromatic selective solvents such as furfural and the like. Such selective solvents, however, also separate alkylated aromatics, which were previously referred to as aromatic precursors. As is the case with coal tar distillate fractions, the alkylated aromatics in petroleum oil streams include both mononuclear and polynuclear alkyl substituent materials. In addition, the substituent groups include one or more methyl groups, ethyl groups and the like. Accordingly, in order to produce aromatics in commercial yields it is necessary to convert the alkylated aromatics to unsubstituted products. This conversion is generally carried out by dealkylating the substituted aromatics generally by what is known as a hydrodealkylation operation. In such hydrodealkylation methods the feedstock is treated at high temperatures with hydrogen or hydrogenproducing compounds in the presence of a catalyst in order to selectively split off the alkyl group or groups. This process is especially well suited for the dealkylation of mononuclear and binuclear aromatics. Such hydrodealkylation operations may be carried out at temperatures between 800 and l,500F. Higher yields can generally be obtained by operating at or near the upper temperature limits. These upper temperature limits are also advantageous when operating on comparatively high boiling feedstock materials. The major difficulty, however, in all hydrodealkylation processes, even at low temperatures, is in the formation of carbon and coke during the reaction. The carbon and coke formation is considered to result, at least in part, from the cracking of paraffinic hydrocarbons present in the hydrocarbon stream being subjected to hydrodealkylation. Because some of the paraffinic hydrocarbons have boiling points in the same range as those of the alkyl substituted aromatics to be treated in a hydrodealkylation process, fractionation of mixtures of aromatics, alkyl-substituted aromatics and paraffinic hydrocarbons will remove only those paraffins of lower boiling point ranges. The formation of tar and coke in the hydrodealkylation process results in a rapid plugging and deactivation of the catalyst and the frequent necessity of shutting down the operation to clear the catalyst and regenerator. This frequent and time-consuming shut down, clean up, and regeneration obviously results in an expensive and a highly inefficient overall operation.

The presence of paraffins in hydrocarbon mixtures being subjected to hydrodealkylation also contributes to the excessive consumption of hydrogen gas required in the process. A number of years ago hydrogen gas was a refinery byproduct in excess supply and its cost was not a major factor in the cost of hydrodealkylating. Now, however, the need for hydrogen gas in other refining processes such as sulfur removal and isomerization has increased the demand for hydrogen to such an extent that often it must be specifically manufactured from natural gas for refining uses. During the hydrodealkylation of hydrocarbon mixtures the extreme conditions prevailing result in excessive cracking of the paraffinic hydrocarbons. The cracked hydrocarbons in turn, because they contain reactive carbon atoms, react with hydrogen gas present in the hydrodealkylation process. Consequently the excessive cracking of paraffin hydrocarbons in the hydrodealkylation process results in excessive consumption of hydrogen gas.

OBJECT OF THE INVENTION It is, therefore, an object of the present invention to provide a method for pretreating a hydrodealkylation feedstock. Another object of the present invention is to provide an improved technique for the preparation of a hydrodealkylation feedstock from high boiling catalytic cracking products. Yet another object of the present invention is to provide an improved technique for the preparation of a hydrodealkylation feedstock from a catalytically cracked slurry oil, a catalytically cracked cycle oil and mixtures thereof.

Still another object of this invention is to provide a method whereby a feedstock to be hydrodealkylated may be preconditioned or pretreated so that excessive quantities of hydrogen will not be consumed during the hydrodealkylation process by reaction of cracked paraffins with hydrogen gas present.

Still another object of this invention is to provide a method whereby the paraffins present in a mixture of paraffins, aromatics, and alkyl substituted aromatics, all of which have similar boiling points, may be mildly cracked and hydrogenated to paraffins having boiling points lower than the associated aromatics and alkyl substituted aromatics.

SUMMARY OF THE INVENTION Briefly stated, our invention comprises a method whereby a hydrocarbon stream containing paraffins, aromatic, and substituted aromatic compounds is fractionated to provide a heart-cut fraction containing a concentration of aromatic, substituted aromatic compounds and substantial amounts of paraffins which is then contacted with a gas mixture of carbon oxide gases and hydrogen-containing gases over a suitable hydrocracking catalyst. In still another embodiment carbon dioxide alone is contacted with the heart-cut fraction over a suitable catalyst.

BRIEF DESCRIPTION OF THE DRAWING The accompanying Drawing is a flow sheet depicting our invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Our invention is applicable to any hydrocarbon product of petroleum or coal tar origin containing significant amounts of paraffins together with aromatics, specifically mononuclear and polynuclear aromatic compounds having substituent alkyl groups and particularly the higher boiling mononuclear and polynuclear materials.

One source of mixtures of these materials is product streams from the cracking of petroleum hydrocarbons. Such cracking yields large amounts of mixtures of aromatics, alkyl substituted aromatics and paraffins. While such mixtures may be utilized in motor fuels and other products as such, greater demand for these products exist in the pure chemical field where highly purified materials are desired for use as solvents and chemical intermediates. By way of specific example, product streams obtained by fractionating the liquid product of a fluid catalytic cracking process, produce feedstocks which benefit most significantly by the use of the present treatment.

Referring now to the drawing, a cracked product from a fluid catalytic cracking unit is fed to fractionator 10 through line 12. In fractionator 10, the fluid catalytic cracking product is separated into a light gasoline fraction which is discharged through line 14, a gasoline product discharged through line 16 and a No. 2 fuel oil product discharged through line 18. These three materials, of course, have direct uses in industry and further reference thereto is unnecessary. In addition to the above, the remaining or bottoms of the fractionating operation is split into what is called a cycle oil normally having a boiling point of about 400 to 700F and a higher boiling slurry oil normally having a boiling range of about 650 to l,000F. The cycle oil is discharged from fractionator 10 through line 20 and the slurry oil through line 22. Both of these materials are rich in alkyl aromatics and by the same token because of their high boiling point also contain substantial amounts of paraffins. Preferably, the slurry oil is clarified as by settling, distillation, or other means after it leaves fractionator l and before it is treated further. However, this conventional operation is not shown so that the drawing will not be unduly complicated.

The slurry oil and/or the cycle oil are fed to fractionator 21 where either (or a mixture of the two) is fractionated to provide a heart-cut fraction boiling between about 400 to 575F. Preferably, a fraction boiling between 400 and 515F. is used. The heart-cut fraction so obtained contains quantities of aromatics and alkyl substituted aromatics, but although free of the lowerboiling point paraffins and naphthenes, this fraction still contains paraffins having boiling points of or near the boiling point of the desired aromatics. From fractionator 21, the heavier fraction or higher boiling pitch fraction is discharged through line 23 and the overhead fraction is discharged through line 24. The heart-cut fraction after leaving fractionator 21 and before entering line 26 can, if desired, be desulfurized by known techniques. This desulfurization is a conventional and well-known process to those skilled in the art and for this reason is not specifically illustrated in the drawing.

In line 26 the heart-cut fraction is mixed with hydrogen and a carbon oxide gas (or with carbon dioxide alone) and is then passed to reactor 25 by way of line 26. Hydrogen is injected into line 26 through line 28 and at the same time, a carbon oxide gas, either carbon dioxide or carbon monoxide, is injected into line 26 through line 30. In still another alternative, carbon dioxide alone is injected into line 26 by means of line 30, that is, no hydrogen is added to the system from an extraneous source. A mixture of hydrogen, carbon oxide gas and heart-cut fractions, or alternatively carbon dioxide and heart-cut fraction flows through line 27 into reactor 25.

The reactor 25 may be any conventional apparatus adapted for contacting gases and liquids in the presence of a solid catalyst. For example, fixed, circulating and fluid bed contactors having single or multiple beds may be employed. Such contactors may be operated according to various modes such as batch, cyclical or continuous. In a continuous operation, the heart-cut liquid is contacted countercurrently or concurrently with gases introduced into the reactor in the presence of the solid catalyst. Heat may be supplied by suitable preheating of the catalyst or by internal or external heating of the reactor itself and/or by preheating the feed fluids. Contact time and heat supplied may be regulated by suitably adjusting the flow rate of catalyst and feed materials. In a cyclic operation, a plurality of stationary beds of catalysts are ordinarily employed wherein some of the units may be maintained on stream at all times while others are undergoing regeneration or cleaning. Heat ordinarily is supplied externally or by internal heating elements and the operation may be conducted at atmospheric pressure or above. In accordance with the preferred embodiment of the invention, a fixed bed reactor unit is employed. Fresh or regenerated catalyst is held stationary in the reactor and the feed is passed downwardly through the bed under pressure on a continuous basis. If coke or carbon build up in the bed, the pressure drop across the bed increases. When the pressure drop and carbon content of the bed reach levels which are either inconvenient or impossible to work with, the bed is no longer usable and the reactor is shut down. Then the catalyst is either regenerated in the reactor or is removed and replaced with fresh catalyst. Under the mild operating temperatures the paraffinic hydrocarbons present are only mildly cracked and hydrogenated to a point where their boiling points are substantially lower than the boiling points of the aromatics and alkyl substituted aromatics present. Because the mild operating temperatures used minimize the production of carbon in the catalyst bed, only infrequent shut downs on account of carbon formation in the catalyst bed are necessitated and do not constitute a serious interruption of production.

In operation of the reactor or treating unit 25, temperatures of between about 500 to 1,150F. can be employed although about 900 to 1,100F. is preferred. A weight-hourly space velocity between about 0.25 and 2.5 can be employed, although about 0.8 to 1.5 is preferred. The pressure utilized may also vary over a wide range from about 250 to 2,000 psi. However, the preferred operating pressure is between about 400 and 1,000 psi. The hydrogen to feedstock mol. ratio may range from about 1 to 50 but is'preferably from about 2.5 to 25. correspondingly, the carbon oxide to feedstock mol. ratio may range from about 0.1 to 50 but is preferably from about 0.25 to 25.

As for the catalyst used in reactor 25, it has been found that a catalyst having nickel oxide as an active ingredient is best suited for use where the hydrocarbon stream is to be contacted with a mixture of carbon oxide and hydrogen, or carbon dioxide by itself. A catalyst meeting this description is one manufactured by the American Cyanamid Company under the trade name of AERO I-IDS-3 and AERO HDS-BA. These are extruded nickel-molybdena catalysts on an alumina base and have typical propertles shown in Table I.

TABLE I COMPOSITION (WT. AERO l-IDS-3 AERO I-IDS-3A NiO 3.2 3.2 MoO 15.1 15.1 Na O 0.02 0.02 Fe 0.04 0.04 80.. 0.3 0.3 SiO 0.1 0.1 Loss on ignition 1.4 1.4

PHYSICAL PROPERTIES Apparent bulk density (lbs/ft) 40 40 Comgacted bulk density (lbs/ 43 43 Average diameter (in) 0.13 0.07 Average length (in) 0.22 0.18 Average crush strength (lbs) l7 15 Loss on abrasion (wt%) 0.4 0.4 Pore volume 0.6 0.6 Surface area (m fg) 180 180 Through No. 7 mesh (wt%) 0.2 0.2 Through No. 14 mesh (wt%) *ACI'IVITY sulfur removal at SLHSV 93 94 at IOLHSV 82 84 nitro en removal at L SV 70 75 at IOLHSV 50 55 Standard conditions 01' 705F., 750 psig. 2500 scf/bbl H, rate. Texas gas oil of 33.5AP| and 1.2 wt. '1 sulfur. LHSV liquid hourly space velocity, or volume of l'eed/hrJvolume of catalyst LI-ISV liquid hourly space velocity, or volume of feed/hr./volume of catalyst Another suitable catalyst is a cobalt-molybdenum catalyst. A typical cobalt-molybdenum catalyst is marketed under the trade name Nalco 471 by the Nalco Chemical Company. Another suitable catalyst is marketed by Harshaw Chemical Company under the trade name ZN-0308T. This catalyst comprises zinc chromite and has a typical composition of 74% zinc oxide and 22 to 23% chrome oxide.

After passage through reactor 25 the feedstock is passed through line 32 to fractionator 34. In fractionator 34 any high boiling condensed and polymerized paraffins present are separated, but more importantly the newly formed cracked and hydrogenated paraffins now having substantially reduced boiling points are removed. The overhead fraction is discharged through line 36 and the higher boiling materials, those boiling above about 550F. are discharged through line 40. The principal and desired fraction containing most of the monoor polycyclic material boiling from about 400 to 550F. or more desirably between about 425 and 500F. is removed through line 38. This is the hydrodealkylation feedstock now depleted in paraffin content which is then subjected to conventional hydrodealkylation treatment. The step of hydrodealkylation does not form a part of our invention and is a process well known to those skilled in the art. Accordingly, it is not discussed further here. Hydrodealkylation is described in a number of patents, for example US. Pat. No. 3,075,022.

The following examples illustrate the outstanding results which have been obtained in accordance with our invention.

EXAMPLE 1 A light cycle oil from a fluid catalytic cracking unit was fractionated to provide a heart-cut having a boiling point range of 400 to 515F. Seven separate portions of this fraction were contacted with a nickel molybdenum catalyst and a cobalt molybdenum catalyst as shown in Table II in the presence of carbon dioxide and hydrogen injected at the flow rate shown in Table II. Other conditions of contact are also shown in Table II. As shown in Table II, the percentage of material having a molecular weight less than that of the alkyl naphtha lene was increased from 2.8 in the feedstock to between 26 and 42%. The amount of material having a molecular weight greater than that of methyl naphthalene was substantially decreased.

The data in Table II shows that feedstock to the hydrodealkylation process can be preconditioned or pretreated successfully in a mixed hydrogen-carbon dioxide atmosphere. Either the Nalco 471 or l-IDS-3A catalyst will achieve the pretreatment level desired.

TABLE II TREATMENT OF UIOI-IC IN A CO -H (25%COJ75%H ATMOSPHERE Test 48-5-1 48-5-2 48-7-1 48-7-2 48-1 1-1 48-1 1-2 48-51-] Catal st HDS-3A l-IDS-3A l-IDS-3A EDS-3A N-471 N-471 HDS3A Feed l-"(ate of Heart-cut light cycle oil (Wl-ISV) 1 1 1 1 1.1 1 0.9 Gas Rate In (SCF/l-I) 1.9 1.9 1.9 1.9 1.65 1.65 1.20 Gas Rate Out (SCF/l-I) 1.67 1.65 1.68 1.73 1.42 1.66 0.79 Pressure (PSIG) 400 400 400 400 400 1000 1000 Avera e Bed Tem (F.) 933 983 1033 1084 983 984 985 LiquicFYield (Wt. 11) 89.5 71.3 70.2 67.7 82.7 75.3 79.1

TABLE II Continued TREATMENT OF LCOHC IN A CO -H (25%CO /75%H ATMOSPHERE Test 48-5-1 48-5-2 48-7-1 48-7-2 48-1 l-l 48-1 1-2 48-51-1 Weight Per Cent Product Analysis Feed Molecular wt. less than naphthalene 2.8 26.1 33.3 34.4 31.3 29.5 42.0 37.2 Naphthalene 1.4 5.6 6.9 8.0 5.2 5.9 10.4 8.0 Molecular wt. between na hthalene & meth naphthalene 4.7 6.0 5.5 4.8 9.6 3.4 5.8 4.6 Methyl aphthulcnc 18.7 20.1 21.5 21.6 18.3 26.6 20.9 209 Molecular wt. greater than naphthalene 72.0 42.2 g 32.8 31.2 35.6 34.6 20.9 29.3

EXAMPLE 2 EXAMPLE 3 Additional samples of light cycle oil having the same boiling point range as that of Example 1 was contacted with nickel molybdenum and zinc chromite catalysts and a synthesis or water gas comprising: two-thirds hydrogen gas and one-third carbon monoxide gas. The amount of material converted into the lighter than naphthalene range was again substantially increased to Additional samples of the heart-cut fraction of Example l were contacted in a pure carbon dioxide atmo- 20 sphere with nickel molybdenum and zinc chromite catalysts as shown in Table IV. Again the percentage of material having a molecular weight less than the alkyl naphthalenes was substantially increased.

While specific examples have been given herein and percentages of from about 22 to about 36%. The result 25 specific illustrations set forth, it is to be recognized that of these series is shown in Table 111.

these recitals are made only in an effort to teach those TABLE 111 TREATMENT OF LCOHC IN A SYNTllESlS GAS ATMOSPHERE Test 21-195-1 21-195-2 48-3-1 44-41-1 44-41-2 44-41-3 Catal st HUS-3A HDS-3A HDS-3A Zn-0308T Zn-0308T Zn-0308T Feed ate (WHSV) 0.99 1.01 0.97 0.96 0.99 0.86

Gas Rate ln (SCF/H) 1.9 1.9 1.9 4.1 4.1 4.1

Gas Rate Out (SCF/H) 1.66 1.83 1.30 3.38 3.60 2.33

Pressure (PSlG) 400 400 Average Bed Temp. (F.) 984 1035 1084 985 1035 1078 Li uld Yield Product Analysis Weight Per Cent Molecular wt less than naphthalene 36.2 35.1 32.5 22.0 23.4 30.3

Naphthalene 6.8 7.3 5.3 4.2 4.7 4.2

Molecular wt.

between naphthalene and methyl naphthalene 5.0 4.8 3.6 4.9 4.5 4.7

Methyl naph. 19.7 20.5 20.4 19.7 19.8 185 Molecular wt.

heavier than methyl naph. 32.7 32.3 38.3 49.2 47.5 42.3

TABLE IV PARTlAL DEALKYLATION OF LCOHC IN A CO ATMOSPHERE Test 21-191-1 21-191-2 4435-1 4437-1 4437-2 Catalyst HDS-3A HDS-3A Zn-0308 ZN-0308 Zn-0308 Feed Rate (WHSV) 1.0 1.0 1.01 1.01 0.99 Gas Rate 1n (SCF/l-l) 1.9 1.9 4.1 4.1 4.1 Gas Rate Out (SCF/l-l) 1.93 1.76 4.03 4.15 4.45 Pressure (PSlG) 600 400 400 400 400 Avera e Bed Tmp. (F.) 983 983 1036 983 1034 1083 Liqui Yield (Wt. 89.2 65.2 97.2 89.2 78.4

Product Analysis Feed Weight Percent Molecular wt. less than naphthalene 2.8 18.4 28.1 9.2 17.0 26 1 Naphthalene 1.4 2.3 2.8 1.1 1.6 2 1 TABLE lV-Continued PARTIAL DEALKYLATION OF bCOHC IN A CO ATMOSPl-lERE Test 21-191-1 21-191-2 44-35-1 44-37-1 44-37-2 Molecular wei t between naph alene & methyl naphthalene 4.7 5.4 4.2 6.3 5.5 3.0 Methyl naphthalene 18.7 17.1 17.2 17.4 17.0 18.4 Molecular weight greater than methyl naphthalene 72.4 56.8 47.7 66.0 7 13,9 50.4

skilled in the art a preferred operation in accordance on alumina, and Zinc chromite; and with the present invention. Accordingly, it is to be unb f ti ti h li id r duct obtained from (a) derstood that the present invention is to be limited only i t a f ti b ili g between about 400F. and

by the appended claims.

What we claim is:

1. A process for preparing a hydrocarbon mixture containing paraffinic, aromatic and alkyl substituted aromatic hydrocarbons for subsequent hydrodealkylation, said mixture having a boiling point of between about 400F. and about 550F. comprising:

a. contacting said hydrocarbonmixture with a gas consisting of carbon dioxide in the absence of hydrogen added from sources extraneous to said process and in the presence of a catalyst selected from the group consisting of nickel oxide and molybdena about 550F., thereby providing a suitable hydrodealkylation feedstock.

2. The process of claim 1 wherein said catalyst of (a) consists essentially of zinc chromite.

3. The process of claim 1 wherein said catalyst comprises nickel oxide and molybdena on alumina.

4. The process of claim 1 wherein said hydrocarbon mixture having a boiling point of between about 400F. and about 550F. is a fraction of a cycle oil having a boiling point of about 400F. to about 1,000F.

Claims (4)

1. A PROCESS FOR PREPARING A HYDROCARBON MIXTURE CONTAINING PARAFFINIC, AROMATIC AND ALKYL SUBSTITUTED AROMATIC HYDROCARBONS FOR SUBSEQUENT HYDRODEALKYLATION, SAID MIXTURE HAVING A BOILING POINT OF BETWEEN 400*F. AND ABOUT 550*F. COMPRISING: A. CONTACTING SAID HYDROCARBON MIXTURE WITH A GAS CONSISTING OF ACCARBON DIOXIDE IN THE ABSENCE OF HYDROGEN ADDED FROM SOURCES EXTRANEOUS TO SAID PROCESS AND IN THE PRESENCE OF A CATALYST SELECTED FROM THE GROUP CONSISTING OF NICKEL OXIDE AND MOLYBDENA ON ALUMINA, AND ZINC CHROMITE; AND B. FRACTIONATING THE LIQUID PRODUCT OBTAINED FROM (A) INTO A FRACTION BOILING BETWEEN ABOUT 400*F. AND ABOUT 550*F., THEREBY PROVIDING A SUITABLE HYDRODEALKYLATION FEEDSTOCK.

2. The process of claim 1 wherein said catalyst of (a) consists essentially of zinc chromite.

3. The process of claim 1 wherein said catalyst comprises nickel oxide and molybdena on alumina.

4. The process of claim 1 wherein said hydrocarbon mixture having a boiling point of between about 400*F. and about 550*F. is a fraction of a cycle oil having a boiling point of about 400*F. to about 1,000*F.

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