Catalytic conversion of high metals feed stocks

Abstract

The conversion of high metals containing feed stock is accomplished in the presence of a low molecular weight carbon-hydrogen fragment contributing material and an acid function crystalline zeolite catalyst to produce gasoline of high quality and yields superior to that obtained heretofore.

Description

BACKGROUND OF THE INVENTION

It is known in the prior art to upgrade hydrogen deficient petroleum oils to more valuable products by thermal and catalytic cracking operations in admixture with a hydrogen donor diluent material. The hydrogen donor diluent is a material, aromatic-naphthenic in nature that has the ability to take up hydrogen in a hydrogenation zone and to readily release hydrogen to a hydrogen deficient oil in a thermal or catalytic cracking operation.

One advantage of a hydrogen donor diluent operation is that it can be relied upon to convert heavy oils or hydrogen deficient oils at relatively high conversions in the presence of catalytic agents with reduced coke formation. Coke as formed during the cracking operation is usually a hydrocarbonaceous material sometimes referred to as a polymer of highly condensed, hydrogen poor hydrocarbons.

A great demand continues for refinery products, particularly gasoline, fuel oils, and gaseous fuels. Because of the shortage of high quality, clean petroleum-type feedstocks, the refiner now must turn to heavier, more hydrogen-deficient, high impurity-containing cracking feedstocks. Included in this category are heavy vacuum gas oils, atmospheric residua, vacuum tower bottoms, and even syncrudes derived from coal, oil shale, and tar sands, and even coal itself.

In some cases, high levels of nitrogen and sulfur constitute a serious problem in such refractory, low-crackability stocks, particularly with reference to down-stream processing and product environmental and pollution limitations. An even more difficult problem is posed by the presence of metallic impurities, nickel, vanadium, iron, etc., preserved through geologic time in heavy petroleum fractions. Such metals, commonly associated with porphyrin rings and asphaltenes in high molecular weight cuts, can cause serious engineering/hardware problems in catalytic cracking. As catalyst is exposed to repeated cycles of reaction/regeneration in a fluid cat cracker (FCC), these metals are adsorbed and tend to build up with time and accumulate on the catalyst. They then cause dehydrogenation-type reactions, resulting in formation of very large amounts of coke, large amounts of H.sub.2 gas, which may put a severe strain on the FCC unit regenerator air blower and wet gas compressor capacity. Further, and very important, their presence is often associated with a serious loss of conversion and gasoline yield.

The present invention is concerned with an improved hydrocarbon conversion operation designed to particularly reduce the hydrogen deficiency as well as the coke forming tendencies of such a catalytic cracking operation.

SUMMARY OF THE INVENTION

The present invention is concerned with providing mobile hydrogen alone or combined with carbon in molecular fragments in a crystalline zeolite hydrocarbon conversion operation in such amounts that the yield of desired hydrocarbon product will be simultaneously increased. In a more particular aspect the present invention is concerned with providing hydrogen contributing materials and/or carbon-hydrogen molecular fragments to a catalytic cracking operation which are lower boiling than a high molecular weight hydrocarbon charged to the cracking operation. In yet another aspect the present invention is concerned with providing the hydrocarbon conversion operation with one or more crystalline zeolite catalytic materials which will promote chemical reactions with mobile hydrogen and/or carbon-hydrogen molecular fragments in addition to promoting catalytic cracking reaction to provide useful products contributing to gasoline boiling range material.

In the present invention large quantities of a "low molecular weight carbon-hydrogen fragment contributing agent or material" and a "high metals content feedstock" are intimately mixed with one another and reacted in the presence of a catalyst with a cracking or acid function such as a crystalline zeolite catalyst comprising an acid function, wherein cracking and additive carbon-hydrogen reactions occur to produce gasoline and other products of (a) quality and (b) yield superior to those formed in the absence of the "low molecular weight carbon-hydrogen fragment contributing material". The cracking and additive reactions may also occur in the presence of a catalyst with a hydrogen activating or hydrogen-transfer function after exposure of the reactant mixture at an elevated temperature to the catalysts herein defined.

A particular advantage of the reaction concepts of this invention is that they occur at low pressures (i.e. at pressures commonly employed in current catalytic cracking operations or slightly higher). It is most preferred that the reactions be performed in fluidized beds (risers, dense beds, etc.), but they can also be practiced in some fixed bed arrangements or moving bed catalytic systems. The reactions described herein may occur in one stage of operation all at the same process conditions, or in a sequence of two or more stages of operation, at the same or different process conditions. Further, the catalyst functions referred to herein may be on the same catalyst particle, or on different catalyst particles such as a mixture of crystalline zeolite catalytic materials.

Some specific advantages derivable from the improved process concept of this invention include improved crackability of heavy feedstocks, increased gasoline yield and/or gasoline quality (including octane and volatility), and fuel oil fractions of improved yield and/or burning quality and lower levels of potentially polluting impurities such as sulfur and nitrogen. The need for costly high pressure hydrotreaters and hydrocrackers using expensive molecular hydrogen rich gas can thus be eliminated, or the severity requirements of the operation greatly decreased, thus saving considerable capital investment and operating costs.

By "low molecular weight carbon-hydrogen contributing material" is meant materials comprising a lesser number of carbon atoms than found in materials within the gasoline boiling range and preferably those materials containing 5 or less carbon atoms that fit into any of the categories of:

a. Hydrogen-rich molecules, i.e. molecules with wt.% H ranging from about 13.0-25.0 wt.%. This may include light paraffins, i.e. CH.sub.4, C.sub.2 H.sub.6, C.sub.3 H.sub.8 and other materials. b. A hydrogen donor molecule, i.e. a molecule whose chemical structure permits or favors intermolecular hydrogen transfer. This includes CH.sub.3 OH, other low boiling alcohols such as ethanol, n-propanol, isopropanol, n-butanol, isobutanol, etc., aliphatic ethers, other oxygen compounds (acetals, aldehydes, ketones) certain sulfur, nitrogen and halogenated compounds. These would include C.sub.2 -C.sub.5 aliphatic mercaptans, disulfides, thioethers, primary, secondary tertiary amines and alkylammonium compounds, and haloalkanes such as methyl chloride etc. c. Reactants that chemically combine to generate hydrogen donors or "active" or "nascent" hydrogen, i.e. carbon monoxide, CO, especially CO + H.sub.2 O, CO + H.sub.2, CO + alcohol, CO + olefin, etc. d. Secondary Reaction Products from materials in categories (a), (b), or (c) above that are hydrogen donors themselves, or transfer hydrogen, or become involved in intermolecular hydrogen transfer in which hydrogen redistribution occurs. This includes olefins, naphthenes, or paraffins. e. Classes of materials which are structurally or chemically equivalent to those of category (d), notably olefins, etc. f. A combination of any or all of the materials in categories (a) through (e). g. Preferred low molecular weight material include methanol and C.sub.2 - C.sub.5 olefins.

By "high molecular weight feedstock" is meant any material that boils higher than a conventional gasoline end boiling point, i.e. about 11-12 C-number or higher. It is especially preferred that "high molecular weight feedstocks" include catalytic cracking feeds or potential feeds therefor such as distillate gas oils, heavy vacuum gas oils, atmospheric resids, syncrudes (from shale oil, tar sands, coal), pulverized coal and combinations thereof.

By catalyst with a "cracking or acid function" is meant an acidic composition, most preferably a solid, such as a zeolitic cracking catalyst and combinations thereof. A preferred composition includes a crystalline zeolite component (or components) intimately dispersed in a matrix. Zeolites ZSM5 and ZSM5 type and mordenite or dealuminized mordenite or TEA mordenite are preferred with or without the presence of the faujasite type zeolite such as REY.

By "high metals stock" is meant any petroleum type stock (i.e. whole crude, distillate gas oil, heavy vacuum gas oil, atmospheric resid, vacuum resid, syncrude from shale oil, tar sands or coal, etc.) which contains > 1-2 ppm of Ni + V, i.e., which contains more of the metals Ni + V than are customarily considered acceptable (in terms of gasoline yield, compressor limitations or air blower capacity) for efficient operation of a typical, existing, commercial FCC unit.

By catalyst with a "hydrogen-activating function" is meant one of several classes of catalysts which aid in the redistribution or transfer of hydrogen, or which are classified as hydrogen dissociation, hydrogen activation, or hydrogenation catalysts. The catalyst with a "hydrogen-activating function" may or may not contain a metal function. Some of the preferred metal functions are Pt, Ni, Fe, Co, Cr, Th, (or other metal function capable of catalyzing the Fischer-Tropsch or water-gas shift reaction), or Re, W, Mo or other metal function capable of catalyzing olefin disproportionation.

The term "hydrogen transfer" is known in the art of catalytic conversion to characterize the ability to transfer hydrogen other than molecular hydrogen from one type of hydrocarbon to another with a catalyst particularly promoting the transfer. This type of chemical reaction is to be contrasted with hydrogenation catalysts or catalyst components capable of attaching hydrogen to an olefin from gaseous molecular hydrogen.

A group of highly active catalysts particularly suitable for use in the practice of the present invention are zeolitic crystalline aluminosilicates of either natural or synthetic origin having an ordered crystal structure. These crystalline zeolite materials are possessed with a high surface area per gram and are microporous. The ordered structure gives rise to a definite pore size of several different forms. For example, the crystalline zeolite may comprise one having an average pore size of about 5A such as Linde 5A or chabasite or it may be an erionite or an offretite type of crystalline zeolite. A crystalline zeolite with a pore size in the range of 8-15-A pore size such as a crystalline zeolite of the "X" or "Y" faujasite type of crystalline material may be used. Mordenite and ZSM-5 type of crystalline aluminosilicates may also be employed. In the process of the present invention it is preferred to use crystalline zeolites having a pore size sufficiently large to afford entry and egress of desired reactant molecules. Thus, the catalyst may be a large pore crystalline zeolite such as an "X" or "Y" faujasite variety or it may be a mixture of large and smaller pore crystalline zeolites. In this regard the mixed crystalline aluminosilicates used in the method of this invention will provide a pore size spread greater than 4 and less than 15 Angstrom units. The small pore zeolite portion of the catalyst may be provided by erionite, offretite, mordenite and ZSM-5 type of crystalline zeolite. Methods of preparing these various crystalline zeolites are the subject of numerous patents now available.

The aluminosilicate active components of the catalyst composite may be varied within relatively wide limits as to the crystalline aluminosilicate employed, cation character, concentration as well as in any added component by precipitation, adsorption and the like. Particularly, important variables of the zeolites employed include the silica-alumina ratio, pore diameter and spatial arrangement of cations.

The crystalline aluminosilicate or crystalline zeolites suitable for use in the present invention may be modified in activity by dilution with a matrix material of significant or little catalytic activity. It may be one providing a synergistic effect as by large molecule cracking, large pore material and act as a coke sink. Catalytically active inorganic oxide matrix material is particularly desired because of its porosity, attrition resistance and stability under the cracking reaction conditions encountered particularly in a fluid catalyst cracking operation. Inorganic oxide gels suitable for this purpose are fully disclosed in U.S. Pat. No. 3,140,253 issued July 7, 1964 and such disclosure is incorporated herein by reference.

The catalytically active inorganic oxide may be combined with a raw or natural clay, a calcined clay, or a clay which has been chemically treated with an acid or an alkali medium or both. The catalyst may also be provided with an amount of iron and/or nickel which materials are known to promote the Fischer-Tropsch reaction. The matrix material is combined with the crystalline aluminosilicate in such proportions that the resulting product contains a minor proportion of up to about 25% by weight of the aluminosilicate material and preferably from about 1% up to about 25 weight percent thereof may be employed in the final composite.

The mobile hydrogen component of the reaction mixture of the present invention may be provided from several different sources, such as the high molecular weight feed and the low molecular weight material, it being preferred to obtain hydrogen moieties from gasiform and vaporous component materials occurring in the operation lower boiling than the hydrocarbon material charged to the cracking operation. Thus, it is proposed to obtain the hydrogen moieties suitable for hydrogen distribution reactions from component and component mixtures selected from the group comprising methanol, dimethylether, CO and water, carbon monoxide and hydrogen, CH.sub.3 SH, CH.sub.3 NH.sub.2, (CH.sub.3).sub.2 NH, (CH.sub.3).sub.3 N, (CH.sub.3).sub.4 N and CH.sub.3 X, where X is a halide such as fluorine, bromine, chlorine and iodine. Of these hydrogen contributing materials it is preferred to use methanol alone or in combination with either CO alone, or CO and water together. On the other hand, it is contemplated combining light olefinic gaseous products found in pyrolysis gas and the products of catalytic cracking such as ethylene, propylene and butylene with the hydrogen contributing material and/or carbon hydrogen contributing material. In any of these combinations, it is preferred that the mobile hydrogen or the carbon-hydrogen fraction be the product of one or more chemical reactions particularly promoted by a relatively small pore crystalline zeolite such as a ZSM-5 type of crystalline zeolite or a small pore mordenite type zeolite. Methanol is a readily available commodity obtained from CO and H.sub.2 synthesis, coal gasification, natural gas conversion, and other known sources.

Current practice for upgrading high molecular weight, hydrogen-deficient, high-impurity refinery stocks generally involves either hydrotreating followed by catalytic cracking, or hydrocracking, both of which involve the use of costly gaseous hydrogen at high pressures (i.e. 500-3000 psig), in expensive, high-pressure process units. Alternately some poor quality stocks are catalytically cracked alone with low quality product being produced which requires extensive upgrading or dilution before becoming saleable. Some of these processes often require expensive gas compressors and complex heat transfer or hydrogen-quenching systems. In addition, although these processes improve conversion and product yields, significant losses in gasoline octane are often incurred, requiring a subsequent reforming step to upgrade gasoline quality.

The current concept employs a fluidized catalyst system at low pressures without the need for high pressure hydrogen gas. Such a system promotes the highly efficient contact of relatively inexpensive hydrogen contributing low molecular weight materials with heavy, refractory molecules in the presence of high-surface area cracking catalyst with or without "hydrogen-activating catalyst functions". Intermolecular hydrogen-transfer interactions and catalytic cracking reactions effected in the presence of fluidized catalyst particles minimize problems due to diffusion/mass transport limitations and/or heat transfer.

The concepts of the present invention make use of relatively cheap, low molecular weight hydrogen contributors readily available in petroleum refineries, such as light gas fractions, light olefins, low boiling liquid streams, etc. It also makes particular use of methanol, a product which is readily available in quantity, either as a transportable product from overseas natural gas conversion processes, or as a product from large scale coal, shale, or tar sand gasification. It also can utilize carbon monoxide (in combination with hydrogen contributors such as water or methanol), which gas is readily available from refinery regeneration flue gas (or other incomplete combustion processes), or from coal, shale or tar sand gasification. Highly efficient recycle or unused hydrogen contributors can also be effected.

A particularly attractive feature of this invention is concerned with converting whole crude hydrocarbon materials. That is, a whole crude may be utilized as the charge with the light end portion thereof constituting a part of the "low molecular weight hydrogen contributor" alone or in combination with added methanol or other hydrogen contributing light materials and the heavier end portion of the whole crude constituting the "high molecular weight feedstock".

It is anticipated that as a result of the processing concepts herein defined, requirements for reforming and alkylation can be greatly reduced, thus saving the petroleum refiner investment and operating cost.

The combination reactions comprising this invention are effective in removing sulfur, oxygen, nitrogen and metal contaminants found in a whole crude or a heavy hydrocarbon portion thereof.

The chemical-conversion operation of this invention is accomplished at temperatures within the range of 400.degree. F. up to about 1200.degree. F. and more usually within the range of 700.degree. F. to about 1100.degree. F. at pressures selected from within the range of below atmospheric up to several hundred pounds but normally less than 100 psig. Preferred conditions include a temperature within the range of about 800.degree. F. to about 1000.degree. F. and pressures within the range of atmospheric to about 100 psig.

In an operation embodying the concepts of this invention using methanol in combination with a gas oil type of hydrocarbon charge stock, a ratio of methanol to hydrocarbon charge passed to the cracking or conversion operation will vary considerably and may be selected from within the range of from about 0.01 to about 5, it being preferred to maintain the ratio within the range of about 0.05 to about 0.30 on a stoichiometric weight basis. However, this may vary depending upon the hydrogen deficiency of the high molecular weight hydrocarbon charge, the amount of sulfur, nitrogen and oxygen in the oil charge, the amount of polycyclic aromatics, the type of catalyst employed, and the level of conversion desired. It is preferred to avoid providing any considerable or significant excess of methanol with the charge because of its tendency to react with itself under some conditions.

In a specific embodiment, this invention includes the catalytic cracking of high boiling residual hydrocarbons in the presence of hydrogen and carbon-hydrogen contributing materials in the presence of crystalline zeolite conversion catalysts particularly performing the chemical reactions of cracking, hydrogen redistribution, olefin cyclization and chemical reaction providing mobile hydrogen in one of several different forms and suitable for completing desired hydrogen transfer reactions. The chemical reactions desired are particularly promoted by a mixture of large and small pore crystalline zeolites in the presence of hydrogen donor materials such as methanol or a mixture of reactants which will form methanol under, for example, Fischer-Tropsch, or other processing conditions. The conditions of cracking may be narrowly confined within the range of 900.degree. F to 1100.degree. F at a hydrocarbon residence time within the range of 0.5 second to about 5 minutes. The catalyst employed is selected from a rare earth exchanged "X" or "Y" faujasite type crystalline zeolite material, a Mordenite or ZSM-5 type crystalline zeolite either component of which is employed alone in an amount within the range of 2 weight percent up to about 15 weight percent dispersed in a suitable matrix material. The faujasite and mordenite crystalline zeolites may be employed alone or in admixture with a ZSM-5 type of crystalline zeolite supported by the same matrix or by a separate silica-clay matrix containing material.

DISCUSSION OF SPECIFIC EMBODIMENTS

EXAMPLE 1

A heavy vacuum gas oil (HVGO) was used as the hydrocarbon feed in the cracking operations of the following examples and provided the following inspections: API gravity (60.degree. F) 20.3; refractive index, 1.5050; average molecular weight 404; weight percent hydrogen, 11.81; weight percent sulfur, 2.69; weight percent total nitrogen, .096; basic nitrogen (p.p.m.), 284; metals; less than 2 p.p.m.; boiling range, 748.degree. F. (10%) - 950.degree. F. (90%). The methanol used with the hydrocarbon feed in comparative runs was C.P. grade methanol.

In run B of Table I presented below, a mixture of methanol (16.5 weight percent based on HVGO) and (HVGO) heavy vacuum gas oil identified above were pumped from separate reservoirs to the inlet of a feed preheater of a 30 ft. bench scale riser FCC unit. The feed materials were intimately mixed in the feed preheater at 790.degree. F and then admitted to the riser inlet, where the hot (1236.degree. F) equilibrium catalyst (15 wt.% REY) (67.5 FAI) (fluid activity index) was admitted and catalytic reaction allowed to occur. The catalyst Fluid Activity Index (FAI) is defined as the conversion obtained to provide a 356.degree. F. 90% ASTM gasoline product processing a Light East Texas Gas Oil (LETGO) at a 2 c/o, 850.degree. F. 6 WHSV for 5 minutes on stream time. Conversion is defined as 100-cycle oil product. The riser reactor inlet and mix temperature were 1000.degree. F., ratio of catalyst to oil (Oil = HVGO + CH.sub.3 OH) by weight was 4.07, catalyst residence time was 4.8 sec., riser inlet pressure was 30 psig, and ratio of catalyst residence time to oil residence time (slip) was 1.26. The riser effluent was passed through a steam stripping chamber, and the gaseous effluent was separated from spent catalyst (1.02 weight percent carbon). The gaseous and liquid products were collected and separated by distillation and analyzed. Data for the operating conditions and mass balance are shown in Table I below.

Table I-A__________________________________________________________________________Heavy Vacuum Gas Oil With/Without MethanolReaction Conditions and Mass Balance15% REY Catalyst__________________________________________________________________________ Run A Run B__________________________________________________________________________OPERATING CONDITIONSReactor Inlet Temp., .degree. F. 1000 1000Oil Temp., .degree. F. 790 790Catalyst Inlet Temp., .degree. F. 1236 1237Catalyst/Oil (Wt/Wt) Ratio.sup.b 3.96 4.07Catalyst Residence Time, Sec. 4.87 4.80Reactor Pressure, Inlet, psig 30 30Carbon, Spent Catalyst, % Wt. .963 1.022Sulfur, Spent Catalyst, % Wt. .0173 .0204Slip Ratio 1.27 1.26Catalyst ##STR1##YIELDS (NLB ON TOTAL FEED)Conversion, % Vol..sup.a 65.23 63.20C.sub.5 + Gasoline, % Vol. 53.53 50.06Total C.sub.4, % Vol. 13.03 9.90Dry Gas, % Wt. 7.36 9.92Coke, % Wt. 4.11 4.82Gaso. Efficiency, % Vol. 82.06 79.2Gasoline R+O, Raw Octane 87.8 89.5H.sub.2 Factor 27 15Recovery, % Wt. 96.83 102.49.sup.cWt. % CH.sub.3 OH, % of Heavy Vacuum Gas Oil -- 16.5Molar ratio, CH.sub.3 OH/HVGO -- .about.2.1__________________________________________________________________________ .sup.a 356.degree. F. at 90 % cut point .sup.b On CH.sub.3 OH + HVGO .sup.c Includes added mass from CH.sub.3 OH reaction.Detailed Mass Balance.sup.a H.sub.2 S, % Wt. .58 .10 H.sub.2, % Wt. .05 .08 C.sub.1, % Wt. .89 3.83 C.sub.2, % Wt. .56 .84 C.sub.2, % Wt. .75 .92 C.sub.3, % Vol. 6.26 5.75 C.sub.3, % Vol. 1.86 1.67 C.sub.4, % Vol. 7.28 6.67i- C.sub.4, % Vol. 4.65 2.53n- C.sub.4, % Vol. 1.10 0.71 C.sub.5, % Vol. 5.54 5.33i- C.sub.5, % Vol. 4.36 2.29n- C.sub.5, % Vol. 0.89 0.58 C.sub.5 + Gaso., % Vol. 53.53 50.06 Cycle Oil, % Vol. 34.77 36.85 Coke, % Wt. 4.11 4.82__________________________________________________________________________ .sup.a Note: Selectivities are based on total products arising from methanol + HVGO reaction. Table I-B______________________________________Gasoline Inspections Run A Run B______________________________________Sp. Grav., 60.degree. F. .7495 .7491API Grav., 60.degree. F. 57.3 57.4Alkylates % Vol. 22.63 18.18C.sub.5 + Gasoline + alkylate, % Vol. 76.16 59.29Outside i-C.sub.4 required, % Vol. 10.65 10.04R+O Octane No., Raw 87.8 89.5Hydrocarbon Types C.sub.5 - Free, vol. %Paraffins 33.1 18.9Olefins 24.1 43.6Naphthenes 12.1 7.2Aromatics 30.2 30.2Distillation, .degree. F. 10% 79 94 50% 222 233 90% 349 363______________________________________

A control run A presented in Table I was made with the identified HVGO alone (no methanol present) in the same manner identified above with Run B. Analysis of the comparative data obtained with the REY catalyst show the following improvements associated with the use of methanol as a "low molecular weight hydrogen donor" when intimately mixed with and cracked with HVGO in a riser fluid catalyst cracking operation.

1. Much higher levels of aromatics + olefins in the gasoline (aromatics and olefins are the major contributors to octane number in gasoline). 2. Higher octane (89.5 R+O with CH.sub.3 OH vs 87.8 R+O without CH.sub.3 OH). 3. lower percent sulfur in fuel oil (4.24 wt.% with CH.sub.3 OH vs 4.45 wt.% without CH.sub.3 OH). 4. higher percent hydrogen in fuel oil (9.18 wt.% with CH.sub.3 OH vs. 8.21 wt.% without CH.sub.3 OH). 5. higher naphthene/aromatic ratios in fuel oil(0.10 with methanol vs. 0.08 without methanol). 6. Higher ratios of Diaromatics/Benzothiophenes (4.55 with CH.sub.3 OH, 3.65 without CH.sub.3 OH); this indicates that increased desulfurization occurs with methanol.

EXAMPLE 2

In this example, the heavy vacuum gas oil identified in Example 1 was cracked with and without the presence of methanol with a catalyst mixture comprising a 2% REY crystalline zeolite in combination with a 10% ZSM-5 crystalline zeolite and supporting matrix (silica-clay). The method of operation was carried out similarly to that identified with respect to Example 1. Table II-A below provides the reaction conditions and mass balance obtained for Runs C (no methanol) and Run D (with methanol). Table II-B provides the gasoline inspection data for runs C and D and Table II-C provides the cycle oil inspection data for these two runs.

Table I-C______________________________________Cycle Oil Inspections Run A Run B______________________________________Sp. Grav., 60.degree. F. .9984 .9746API Grav., 60.degree. F. 10.23 13.69Sulfur, % Wt. 4.45 4.24Hydrogen, % Wt. 8.21 9.18Hydrocarbon Type, Wt.%Paraffins 7.3 8.8Mono-naphthenes 2.3 2.5Poly-naphthenes 4.4 5.9Aromatics 86.1 82.8Naphthene/Aromatic/wt/wt/ratio .078 0.10Distillation, .degree. F. 10% 470 429 50% 695 540 90% 901 794Aromatic Breakdown,Normalized, Wt. -%Mono-aromatics 17.9 26.3Di-aromatics 37.2 37.8Tri-aromatics 10.1 9.1Tetra-aromatics 8.3 5.5Pento-aromatics 1.3 1.1Sulfur CompoundsBenzothiophene 10.2 8.3Dibenzothiophene 10.4 6.2Naphthobenzothiophene 4.6 3.3Other 0.2 2.4Ratio, Diaromatics/Benzothiophene 3.65 4.55______________________________________ Table II-A__________________________________________________________________________Reaction Conditions and Mass Balance__________________________________________________________________________ Run C Run D__________________________________________________________________________OPERATING CONDITIONSReactor Inlet Temp., .degree. F. 900 900Oil Temp., .degree. F. 500 500Catalyst Inlet Temp., .degree. F. 1100 1102Catalyst/Oil (Wt/Wt) Ratio 6.68 6.81.sup.aCatalyst Residence Time, Sec. 4.70 6.11Reactor Pressure, Inlet, psig. 30 30Carbon, Spent Catalyst, % Wt. .285 .342Sulfur, Spent Catalyst, % Wt. .0091 .0006Slip Ratio 1.24 1.24 Catalyst ##STR2## 2% REY +10 % ZSM-5 ##STR3##YIELDS (NLB ON TOTAL FEED)Conversion, % Vol..sup.a 44.16 42.66.sup.bC.sub.5 + Gasoline, % Vol. 33.12 35.15Total C.sub.4, % Vol. 12.04 6.59Dry Gas, % Wt. 5.47 5.29Coke, % Wt. 2.08 2.83Gaso. Efficiency, % Vol. 75.0 82.39Gasoline R+O, Raw Octane No. -- --H.sub.2 Factor 99 25Recovery, % Wt. 94.9 95.10 .sup. a 356.degree. F. at 90% cut point (a) on CH.sub.3 OH + HVGO (b) based on HVGO onlyWt.% CH.sub.3 OH, % of Heavy-72-D-611 Vacuum Gas Oil -- --Molar Ratio, CH.sub.3 OH/HVGO -- .about.2.1Detailed Mass Balance H.sub.2 S, % Wt. .19 .09 H.sub.2, % Wt. .06 .06 C.sub.1, % Wt. .19 1.68 C.sub.2 % Wt. .20 .33 C.sub.2, % Wt. .22 .36 C.sub.3, % Vol. 7.47 4.60 C.sub.3, % Vol. .80 .34 C.sub.4, % Vol. 8.13 5.00i-C.sub.4, % Vol. 3.34 1.13n-C.sub.4, % Vol. .57 .46 C.sub.5, % Vol. 5.82 3.98i-C.sub.5, % Vol. 2.45 1.05n-C.sub.5, % Vol. .51 .23 C.sub.5 + Gaso., % Vol. 33.12 35.15 Cycle Oil, % Vol. 55.84 57.34 Coke, % Wt. 2.08 2.83Gaso./coke(wt/wt) Ratio 12.82 10.14Gaso./gas 4.87 5.43__________________________________________________________________________ Table II-B______________________________________GASOLINE INSPECTIONS Run C Run D______________________________________Sp. Grav., 60.degree. F. .7487 .7620API Grav., 60.degree. F. 57.5 54.2Alkylate, % Vol. 26.05 16.03C.sub.5 + Gaso. + Alky., % Vol. 59.17 51.19Outside i-C.sub.4 Required, % Vol. 14.26 9.69R+0 Octane No., Raw -- --Hydrocarbon Type, C.sub.5 -Free, Vol.%Paraffins 23.6 10.4Olefins 32.4 57.3Naphthenes 18.1 5.9Aromatics 25.7 26.4Distillation, .degree. F. 10% -- -- 50% -- -- 90% -- --______________________________________ Table II-C______________________________________Cycle Oil Inspections Run C Run D______________________________________Sp. Grav., 60.degree. F. .9701 .9580API Gravity, 60.degree. F. 14.4 16.2Sulfur, % Wt. 4.04 3.39Hydrogen, % Wt. 10.13 10.64Hydrocarbon Type, Wt. %Paraffins 15.7 16Mono-naphthenes 6.9 7.8Poly-naphthenes 9.2 10.1Aromatics 68.3 66.2Naphthene/Aromatic (Wt/Wt) Ratio .23 .27Distillation, .degree. F. 10% 536 518 50% 791 756 90% 921 900Aromatic Breakdown, Normalized, Wt.%Mono-aromatics 23.4 34.2Di-aromatics 29.0 32.1Tri-aromatics 11.0 10.0Tetra-aromatics 8.9 5.5Penta-aromatics 1.9 .9Sulfur CompoundsBenzothiophenes 8.7 6.7Dibenzothiophenes 8.3 5.6Naphthobenzothiophenes 5.3 2.0Other 3.8 2.9Ratio, Diaromatics/Benzothiophene 3.33 4.79______________________________________

It will be observed from Table II-A above that the conversion of the heavy gas oil feed with methanol produced significantly higher yields of C.sub.5 + gasoline at a slightly lower conversion level than occurred in the control Run A for comparative purposes. Furthermore, the yield of C.sub.4 's was lower, and the gasoline efficiency was much higher with methanol in the feed. An examination of the mass balance yields shows the methanol operation to be associated with higher gasoline and fuel oil yields at the expense of C.sub.4 and lower boiling hydrocarbons. Also from the gasoline product inspection Table II-B, it is evident that the gasoline product of the methanol operation will be of a higher octane rating than the gasoline product of Run C, because of increased yields of olefins and aromatics. On the other hand, the cycle oil inspection data of Table II-C, shows lower sulfur compounds in the product of Run C (with methanol); a higher hydrogen content, a higher naphthene to aromatic ratio; less polycyclics and higher aromatics and a higher ratio of diaromatics/benzothiophene indicating that hydrogen transfer has occurred thus producing a better fuel.

EXAMPLE 3

In this example, the heavy vacuum gas oil identified in Example 1 was converted in the presence of methylal which is a methyl ether of formaldehyde: (CH.sub.3 O).sub.2 CH.sub.2. The catalyst employed was a mixture comprising 2% REY crystalline zeolite in combination with 10% ZSM-5 type of crystalline zeolite supported by a silica-clay matrix. The method of operation was performed in the same manner identified in Example 1 at the operating conditions provided in Table III below. In the table comparative runs are shown with no promoter Run C and methanol promoter Run D.

Table III-A__________________________________________________________________________Comparison of Reacting HVGO with Methylal and with/withoutMethanol Reaction Conditions and Mass Balance Run C (c) Run E (b) Run D__________________________________________________________________________OPERATING CONDITIONSReactor Inlet Temp., .degree. F. 900 900 900Oil Temp., .degree. F. 500 500 500Catalyst Inlet Temp., .degree. F. 1110 1102 1102Catalyst/Oil (Wt/Wt) Ratio 6.68 6.72 (b) 6.81 (d)Catalyst Residence Time, Sec. 4.70 6.02 6.11Reactor Pressure, Inlet, psig 30 30 30Carbon, Spent Catalyst, % Wt. .285 .601 .342Sulfur, Spent Catalyst, % Wt. .0091 .0145 .0006Slip Ratio 1.24 1.28 1.24Catalyst 2% REY + 10% ZSM-5YIELDS (NLB ON TOTAL FEED) (e)Conversion, % Vol..sup.(a) 44.16 42.14 42.66C.sub.5 + Gasoline, % Vol. 33.12 31.51 35.15Total C.sub.4, % Vol. 12.04 6.46 6.59Dry Gas, % Wt. 5.47 5.78 5.29Coke, % Wt. 2.08 4.90 2.83Gaso. Efficiency, % Vol. 75.0 74.8 82.39Gasoline R+O, Raw Octane No. -- -- --H.sub.2 Factor 99 18 25Recovery, % Wt. 94.9 98.1 95.10Wt. % Promoter % of HVGO 0 16.0 16.0Molar Ratio, Promoter/HVGO 0 0.85 2.1Detailed Mass Balance H.sub.2 S, % Wt. .19 0.1 .09 H.sub.2, % Wt. .06 .05 .06 C.sub.1, % Wt. .19 1.89 1.68 C.sub.2 =, % Wt. .20 .35 .33 C.sub.2, % Wt. .22 .42 .36 C.sub.3 =, % Vol. 7.47 4.04 4.60 C.sub.3, % Vol. .80 1.28 .34 C.sub.4 =, % Vol. 8.13 4.83 5.00 i-C.sub.4, % Vol. 3.34 1.27 1.13n-C.sub.4, % Vol. .57 .36 .46 C.sub.5 =, % Vol. 5.82 3.88 3.98 i-C.sub.5, % Vol. 2.54 1.34 1.05 n-C.sub.5, % Vol. .51 .22 .23 C.sub.5 + Gaso., % Vol. 33.12 31.51 35.15 Cycle Oil, % Vol. 55.84 57.86 57.34 Coke, % Wt. 2.08 4.90 2.83__________________________________________________________________________ (a) 356.degree. F. at 90% cut point. (b) Methylal = methyl ether of formaldehyde (c) Control Run - no promoter (d) On promoter + HVGO (heavy vacuum gas oil) (e) On HVGO feed only. Table III-B______________________________________Gasoline Inspections Run C Run E Run D______________________________________Sp. Grav., 60.degree. F. .7487 .7580 .7620API Grav., 60.degree. F. 57.5 55.18 54.2Alkylate, % Vol. 26.05 14.84 16.03C.sub.5 + Gaso. + Alky., % Vol. 59.17 46.35 51.19Outside i-C.sub.4 Required % Vol. 14.26 8.72 9.69R+O Octane No. Raw -- -- --Hydrocarbon Type, C.sub.5 -Free Vol.%Paraffins 23.6 11.8 10.4Olefins 32.4 49.9 57.3Naphthenes 18.1 6.3 5.9Aromatics 25.7 32.0 26.4Distillation, .degree. F. 10% -- -- -- 50% -- -- -- 90% -- -- --______________________________________ Table III-C______________________________________Cycle Oil Inspections Run C Run E Run D______________________________________Sp. Grav., 60.degree. F. .9701 .9594 .9580API Gravity, 60.degree. F. 14.4 16.0 16.2Sulfur, % Wt. 4.04 3.306 3.39Hydrogen, % Wt. 10.13 10.57 10.64Hydrocarbon Type, Wt.%Paraffins 15.7 15.5 16Mono-naphthenes 6.9 7.6 7.8Poly-naphthenes 9.2 9.7 10.1Aromatics 68.3 67.3 66.2Naphthene/Aromatic (Wt/Wt) Ratio .23 0.26 .27Distillation, .degree. F. 10% 536 523 518 50% 791 749 756 90% 921 903 900Aromatic Breakdown, Normalized,Wt.%Mono-aromatics 23.4 29.2 34.2Di-aromatics 29.0 32.2 32.1Tri-aromatics 11.0 11.1 10.0Tetra-aromatics 8.9 6.0 5.5Penta-aromatics 1.9 1.2 0.9Sulfur CompoundsBenzothiophenes 8.7 6.9 6.7Dibenzothiophenes 8.3 5.6 5.6Naphthobenzothiophenes 5.3 3.1 2.0Other 3.8 4.6 2.9Ratio, Diaromatics/Benzothiophene 3.33 4.67 4.79______________________________________

It will be observed upon examination of the data of Table III that a significant improvement in gasoline quality and cycle oil quality is obtained with either methylal or methanol as a promoter. The gasoline product is shown to have much lower paraffins, much higher olefins and much higher aromatics than obtained by Run C with no promoter. Therefore the gasoline product obtained with the promoter is of a higher octane.

The cycle oil product inspection shows lower sulfur and higher hydrogen in the product of Runs E and D using methylal and methanol as a promoter. In addition there is a higher naphthene/aromatic ratio, lower amounts of the higher molecular weight polyaromatics, more monoaromatics, higher ratio of diaromatics to benzothiophenes - all of which indicate a better quality of fuel oil.

Table 4__________________________________________________________________________Inspections, 650+ Atmospheric ResidDescription Distillation__________________________________________________________________________Physical Properties IBP, .degree. F. 531 Gravity, API, 60.degree. F. 18.8 5 Vol. %, .degree. F. 605 Sp. Gravity, 60.degree. F. .9415 10 Vol. %, .degree. F. 634 Aniline Point, .degree. F. 20 Vol. % .degree. F. -- Bromine Number 30 Vol. %, .degree. F. 713 Pour Point, .degree. F. 40 Vol. %, .degree. F. -- KV, 210.degree. F. cs 50 Vol. %, .degree. F. 790 Carbon Residue, Wt. %, CCR 60 Vol. %, .degree. F. --Carbon Residue, Wt. %, RCR 70 Vol. %, .degree. F. 871 Refractive Index, 70.degree. C. 1.513 80 Vol. %, .degree. F. -- Density, 70.degree. C. .9067 90 Vol. %, .degree. F. 965 Molecular, Wt. (V.P.) 461 95 Vol. %, .degree. F. 999 EP Vol. %, .degree. F. 1041Chemical Analyses Hydrogen, % Wt. 11.48 Sulfur, % Wt. 2.79 Nitrogen, % Wt. .14Metals, ppm Nickel 6.3 Vanadium 2.4Molecular Type, Wt.% Paraffins 18.5 Naphthenes 18.7 Aromatics 62.8__________________________________________________________________________ Table 5__________________________________________________________________________Reaction of light Arab Resid With Cis-2-Buteneand With Methanol Over Zeolite Catalysts__________________________________________________________________________Reaction Conditions H-595 H-596 H-617__________________________________________________________________________Reactor Inlet Temp., .degree. F. 1000 1000 1000Oil Feed Temp., .degree. F. 515 510 790Catalyst Inlet Temp., .degree. F. 1250 1240 1065Catalyst/Oil (wt/wt) Ratio 7.23 7.19 9.30Catalyst Residence Time, Sec. 4.50 4.53 3.85Reactor Inlet Pressure, PSIG 30.0 30 30Mole of Product/Mole Feed (Ex Coke) 4.748 1.345 1.807Oil Partial Pressure, Inlet, psia 25.5 36.1 35.6Tmix, .degree. F. C 1009.5 1024.9 990.3Carbon, Spent Catalyst, % wt. 1.197 1.303 .890Sulfur, Spent Catalyst, % wt. .0511 .0486 .0233Nitrogen, Spent Catalyst, % wt. .013 .013 .0057Slip Ratio 1.23 1.26 1.24Co-Cracking Agent -- CH.sub.3 OH cis-2-ButeneCo-Cracking Agent, Wt.% of Resid -- 25.4 101.0Molar Ratio, Co-Cracking Agent/Resid -- 3.66 8.31 Catalyst ##STR4##__________________________________________________________________________ Table 6__________________________________________________________________________Product Selectivities (Basis: 100g Resid Feed)Run H-595 H-596 H-617__________________________________________________________________________Change In Resid g 100.0 100.0 100.0 Co-reactant g -- (CH.sub.3 OH) : 11.1.sup.(b) cis-2-: 101.0 Total, g 100.0 111.1 C.sub.4 = 201.0Products Out, g C.sub.5 + Gasoline.sup.(a) 43.73 44.33 51.54 Total C.sub.4 10.86 11.00 90.47 Dry Gas 9.73 16.07 20.14 Coke 9.47 12.68 18.11 Cycle Oil.sup.(a) 26.21 27.01 20.74Light Product Breakdown, g H.sub.2 S .19 .26 .28 H.sub.2 .09 .19 .10 C.sub.1 1.37 6.59 2.37 C.sub.2 = .82 1.26 1.77 C.sub.2 .94 1.26 1.55 C.sub.3 = 4.67 5.38 11.74 C.sub.3 1.65 1.60 2.37 C.sub.4 = 5.02 6.57 63.40 i-C.sub.4 4.49 3.56 13.07n-C.sub.4 1.35 .87 14.01 C.sub.5 = 2.95 4.86 8.70 i-C.sub.5 4.60 3.07 7.98 n-C.sub.5 1.00 .69 .96Recovery, wt.% of feed 90.81 92.05.sup.(c) 92.32H.sub.2 -Factor .33 .18 .16Gasoline Efficiency, Apparent.sup. (d) 59.2 60.7 65.0__________________________________________________________________________ .sup.(a) .about.356.degree. F. at 90% ASTM cut point. .sup.(b) Basis is on complete removal of H.sub.2 O from CH.sub.3 OH .sup.(c) Traces only of dimethyl ether found in gaseous products. .sup.(d) Defined as g. gasoline/100 g. oil - g. cycle oil .times. 100. Table 7__________________________________________________________________________Gasoline InspectionsRun H-595 H-596 H-617__________________________________________________________________________Sp. Grav., 60.degree. F. .7513 .7662 .7620API Grav., 60.degree. F. 57.3 53.18 54.20Hydrocarbon Type, C.sub.5 -Free, Vol. %Paraffins 38.2 28.2 35.8Olefins 14.4 19.3 14.1Naphthenes 10.5 8.8 6.8Aromatics 36.8 43.7 43.4 % H 12.88 12.46 12.59 MW 108.44 116.10 106.5Distillation, .degree. F. 10% `98 50% 243 90% 368__________________________________________________________________________ Table 8__________________________________________________________________________Cycle Oil InspectionsRun H-595 H-596 H-617__________________________________________________________________________Sp. Grav., 60.degree. F. 1.0551 1.0370 1.051API Gravity, 60.degree. F. 2.61 4.95 3.25Sulfur, % Wt. 5.24 5.24 --Hydrogen, % Wt. 7.90 8.34 7.35Refractive Index, n.sub.D 70.degree. 1.607 1.598 1.627Hydrocarbon Type, Wt.%Paraffins 5.2 4.8 6.8Mono-naphthenes 1.7 1.6 5.5Poly-naphthenes 4.0 4.1 7.9Aromatics 89.2 89.6 79.8Naphthene/Aromatic (Wt/Wt) Ratio .064 .064 .17Distillation, .degree. F. 10% 478 490 504 50% 633 682 705 90% 892 922 862Aromatic Breakdown, Normalized, Wt.%Mono-aromatics 10.8 15.8 16.6Di-aromatics 44.5 46.6 28.7Tri-aromatics 11.6 9.9 14.6Tetra-aromatics 6.4 5.7 12.1Penta-aromatics 1.3 1.4 4.7Sulfur Compounds Benzothiophenes 12.2 8.6 6.9 Dibenzothiophenes 10.3 6.0 9.6 Naphthobenzothiophenes 2.8 2.2 6.2Other 0.2 0.4 .5Ratio, Diaromatics/Benzothiophene 3.65 5.42 4.16__________________________________________________________________________

The process concept of this invention is particularly supported by the following examples. The examples include the cracking of a raw atmospheric resid (A) in the presence of methanol and (B) in the presence of cis-2-butene in a benchscale riser FCC pilot plant at 1000.degree. F. using an equilibrium fluid zeolite-type catalyst.

The raw atmospheric resid (light Arab origin) briefly identified below showed the inspections provided in Table 4. Methanol was C. P. Grade, Baker.

EXAMPLE 4

Methanol (25.4 wt.% based on resid) and resid above identified were pumped from separate reservoirs to the inlet of the feed preheater of a 30 ft. bench scale riser FCC unit. These materials were intimately mixed in the feed preheater at 510.degree. F, and then admitted to the riser inlet for contact with hot (1240.degree. F.) catalyst (15% REY zeolite, 67.5 FAI) and catalytic reaction allowed to occur. The riser reactor inlet and mix temperature were 1000.degree. F., ratio of catalyst to oil (Oil = resid + CH.sub.3 OH) was 7.2, catalyst residence time was 4.5 sec., riser inlet pressure was 30 psig, and ratio of catalyst residence time to oil residence time (slip) was 1.26. The riser effluent was then passed through a steam stripping chamber, and a gaseous effluent was separated from the spent catalyst containing 1.303 wt.% carbon. The gaseous and liquid products were collected, separated by distillation and analyzed. This run is H-596. Data for the operating conditions and mass balance, gasoline inspections and cycle oil inspections are shown in Tables 5, 6, 7 and 8, respectively, presented above.

A similar (control) run was made with resid only, with no methanol present (H-595). Analyses show the following improvements associated with the use of methanol when intimately mixed with and converted with resid in a riser fluid catalytic cracking unit:

1. Slightly better gasoline yield: .DELTA. = +0.6 wt.% 2. Slightly better gasoline efficiency: .DELTA. = +1.5 wt.% 3. Greatly improved gasoline quality: mass spectrographic "PONA" analysis shows less paraffins, more olefins and more aromatics: ______________________________________ HC Type .DELTA., Vol. %______________________________________ P - 10.0 O + 4.9 N - 1.7 A + 6.9______________________________________

This much more olefinic and aromatic gasoline may be expected to have significantly higher octane (R+O) number.

4. More butenes (.DELTA. = + 1.55), propylene (.DELTA. = + 0.71), and more ethylene (.DELTA. = + 0.44). These higher light olefin yields are useful as potential feed for high octane alkylate manufacture or chemical uses.

5. More H.sub.2 gas (.DELTA. = 0.1 wt.%). This process-generated H.sub.2 -gas can lessen refinery needs for outside H.sub.2 purchase or reduce need for H.sub.2 -plant construction. Excess H.sub.2 can be used in pretreaters, hydrotreaters, etc.

6. Higher hydrogen level in cycle oil (.DELTA. = + 0.44); this higher hydrogen level imparts better burning qualities in fuel applications, or renders the stock more crackable in recycle operations. Also, some small degree of desulfurization has occurred since the ratio of diaromatics/benzothiophene (wt/wt) has increased from 3.65 to 5.42 with use of CH.sub.3 OH.

EXAMPLE 5

Cis-2-Butene (101.0 wt.% based on resid) and the light Arab pumped from separate reservoirs to the inlet of the feed preheater of a 30 ft. bench scale riser FCC unit. The stocks were intimately mixed in the feed preheater at 790.degree. F. and then admitted to the riser inlet, where hot (1065.degree. F.)catalyst (15% REY zeolite, 67.5 FAI) was admitted and catalytic reaction allowed to occur. Riser reactor inlet and mix temperature were 1000.degree. F., ratio of catalyst to oil (oil = resid + butene) was 9.3, catalyst residence time was 3.9 sec., riser inlet pressure was 30 psig, and ratio of catalyst residence time to oil residence time (slip) was 1.24. Riser effluent then passed through a steam stripping chamber, and gaseous effluent was separated from spent catalyst (0.890 wt.% carbon). The gaseous and liquid products were collected, separated by distillation and analyzed. This run is numbered H-617.

Data for the operating conditions and mass balance, gasoline inspections, and cycle oil inspections are also shown in Tables 5, 6, 7 and 8, respectively.

A similar (control) run was made with the light Arab resid only, with no olefin present (H-595). Our analyses show the following improvements associated with the use of very large amounts of cis-2-butene when intimately mixed with and co-cracked with resid in riser FCC unit:

1. Very much better gasoline yield: .DELTA. = +7.81 wt.%, or about 18% higher gasoline yield than without the C.sub.4 -olefin.

2. Much greater (apparent) gasoline efficiency: .DELTA. = + 5.8 wt.%.

3. Significantly improved gasoline quality: Mass spectroscopic "PONA" analysis shows less paraffins and more aromatics; this more hydrogen-deficient gasoline may be expected to have significantly higher octane number:

______________________________________ HC Type .DELTA., Vol. %______________________________________ P - 2.4 O - 0.3 N - 3.7 A + 6.6______________________________________

4. The large amount of butene present in the reaction mix can be recycled to the process again if desired.

5. Very large amounts of isobutane are generated: .DELTA. is + 8.58 wt.%; this can be used as alkylation feed.

6. Substantial amounts of n-butane are generated: .DELTA. = + 12.66 wt.%; this can either be used for RVP control of gasoline or isomerized to iso-C.sub.4 as alkylation feed.

7. Large amounts of propylene (.DELTA. = + 7.07 wt.%), which can be used as alkylation feed, and ethylene (.DELTA. = + 0.95 wt.%), which can be used for alkylation or chemicals.

8. More pentenes: .DELTA. = + 5.75 wt.%. These are a valuable source of octane.

9. More isopentane (.DELTA. = + 3.38 wt.%) and higher iso-C.sub.5 /n-C.sub.5 ratio (8.3 with olefin vs. 4.6) (high octane source).

10. More gaseous H.sub.2 S (.DELTA. = + .09 wt.%); better desulfurization.

11. Higher naphthene/aromatic ratio in cycle oil, and slightly higher diaromatic/benzothiophene ratio.

Having thus generally described the invention and presented specific examples in support thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof except as defined by the following claims.

Claims

1. A method for converting residual hydrocarbons comprising greater than 1 ppm of nickel and vanadium as metal contaminants which comprises,

mixing said metal contaminated residual hydrocarbons with at least 25 wt. percent of low molecular weight carbon hydrogen fragment contributing material of less than 5 carbon atoms and contacting the mixture with a crystalline zeolite cracking catalyst of a pore size opening within the range of 4 to 15 Angstroms under conditions providing a contact mix temperature within the range of 800.degree. F. to 1200.degree. F.,

providing a hydrocarbon residence time in contact with said catalyst within the range of 0.5 to 10 seconds and recovering a product of said conversion operation comprising improved yields of isobutane and aromatic gasoline than obtained in the absence of said carbon hydrogen fragment contributor.

2. The method of claim 1 wherein the catalyst comprises a faujasite crystalline zeolite combined with from about 2 to 15 weight percent of a smaller pore crystalline zeolite.

3. The method of claim 1 wherein the catalyst comprises a mixture of "Y" faujasite and ZSM-5 crystalline zeolite.

4. The method of claim 1 wherein the catalyst comprises mordenite crystalline zeolite.

5. The method of claim 1 wherein the carbonhydrogen fragment contributor is an olefin comprising at least 100 wt. percent of the feed mixture.

6. The method of claim 1 wherein conversion of the residual oil is effected at a temperature within the range of 900 to 1100.degree. F. at a pressure less than 100 psig.