CA1168647A

CA1168647A - Catalytic oxycracking of polynuclear aromatic hydrocarbons

Info

Publication number: CA1168647A
Application number: CA000389317A
Authority: CA
Inventors: Derk T. A. Huibers; Robert Barclay, Jr.; Rajni C. Shah
Original assignee: HRI Inc
Current assignee: HRI Inc
Priority date: 1981-03-16
Filing date: 1981-11-03
Publication date: 1984-06-05
Also published as: ZA823804B; DE3141645A1; AU8068382A; JPS57159727A; GB2094827B; GB2132107A; GB8401168D0; GB2094827A

Abstract

ABSTRACT
Feedstocks of fused polynuclear aromatic hydrocarbons, such as phenanthrene, anthracene, fluorene, and mixtures thereof, are converted to fluorenone and biphenyl products by a catalytic oxycracking step using oxygen-containing gas and steam. Reaction conditions used are 700-1250°F temperature and 5-50 psia pressure. The process can utilize either a single oxycracking zone containing a bifunctional catalyst, or two reaction zones connected in series each containing a single functional catalyst. If desired, the intermediate products of fluorenone and biphenyl can be thermally hydro-cracked to produce additional benzene. Raw hydrocarbon feed materials having a normal boiling range of 500-900°F can be treated by hydrodealkylation to provide the fused polynuclear aromatic feedstock to the catalytic oxycracking step. Also, intermediate products from the oxycracking step are preferably hydrocracked in the same hydrodealkylation step to produce benzene product. The catalyst composition which is utilized comprises a mixture of at least one Group IIB metal oxide and an oxide of molybdenum or vanadium deposited on a .gamma.-alumina support.

Description

CAT~LYTIC OXYCRACKING
OF POLYNUCLEAR AROMATIC HYDROCARBONS

BACKGROUND OF THE INVENTION

Field of the Invention This invention relates to a process for converting fused polynuclear aromatic hydrocarbons or heavy oils containing such aromatic materials either to monocyclic aromatic hydro-carbons such as benzene, or to nonfused bicyclic aromatic compounds such as fluorenone and biphenyl, which are con-verted to benzene. More particularly, this invention is directed to a process for cleaving the center ring of tri-cyclic aromatics by catalytic oxidation and steam cracking to produce monocyclic aromatic hydrocarbon products such as benzene.

Descri tion of the Prior Art P

High-boiling hydrocarbon fractions derived from fossil fuel sources, such as coal and petroleum, normally contain substantial quantities of fused polycyclic aromatic hydrocarbons, such as phenanthrene, anthracene, and the l~ke and their alkylated -derivatives. Although these compounds are valuable when purified, the costs and difficulty of purifying them by extraction are usually prohibitive. For this reason, many investigat~rs have sought to convert such polycyclic aromatic materials to monocyclic hydrocarbons, such as benzene, by thermal hydrocracking. Some of these prior art processes have been reviewed in ~.S. Patent 4,13~,452 to Beuther et al. Ben2ene yields from such .' ' 1 .

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feedstocks are usually low because only saturated rings are cracked. Hydrogenation usually begins with a terminal ring and degrades the rings successively, as shown by Penninger et al, American Chemical Society Symposium Series, Vol. 32, pp.
444-456 (published 1976). As a result, hydrogen consumption is undesirably high. If a center ring becomes hydrogenated, it usually undergoes dehydrogenation rather than cracking as reported by Wiser et al, Ind Eng. Chem Prod. Res. Develop., 9, 350 (1~70). Conventional catalytic hydrocracking, as described by Langlois et al, Advances in Chemistry Series, Vol. 97, pp. 62-64 (1970), also yields predominan~ly bicyclic products.

The use of an oxidative process to make polycyclic aro-matic hydrocarbons susceptible to thermal hydrocracking has also been proposed. Sakai et al, U. S. Patent 4,097,541, describes thermal hydrodecarbonylation of products, such as 9, 10-anthraquinone, and 9,10~phenanthrenequinone to biphenyl and benzene by reaction with hydrogen at a temperature of from about 932 to about 1652F at atmospheric pressure and in the absence of a catalyst. Sakai also described the production of monocyclic aromatics in 38~ yield by treatment of a fraction containin~ naphthalene or more polycyclic aro-matic hydrocarbons of a residual oil from a naphtha steam cracker with atmospheric oxygen at 150C followed by reaction with hydrogen. However, it was shown by Larsen et al, Ind. Eng. Chem., 34, 183 (1942), that oxidation of phe-nanthrene under similar conditions is extremely slow and gives no carbonyl compounds, so that the monocyclic aromatics observed by Sakai et al, were probably formed by some route not involving oxidation of phenanthrene. Oxidation of phenanthrene to 9,10 phenanthrenequinone requires much more severe conditions as shown by Morotskii et al. Morotskii et al, Chemical Abstracts, 67, 81982~ (1967) and 68, 68776 S
(1968), described the oxidation of phenanthrene over a V2Os/K2SO4/SiO2 catalyst. Therefore, it is most likely that Sakai in this experiment did not oxidize any aromatic rings, but rather formed benzene from thermal hydrocracking of naphthalene.

'Daly, in U. S. Patent 4,234,749, described a two-step process by which anthracene, in either pure form or present in mixtures of polynuclear aromatic hydrocarbons with normal boiling points between about 338 and 716F, is oxidized with molecular oxygen in the presence of a cerium salt catalyst, and the product anthraquinone is then thermally cracked at temperature of about 797 to 1400F to form benzene.
Similarly, Robinson et al, U. S. Patent 3,855,252, taught that anthracene can be selectively oxidized to anthraquinone in the presence of phenanthrene in synthetic blends or in middle distillates from coal tar. This demonstrates that anthracene is oxidized considerably faster than phenanthrene.

In most practical feedstocks derived from either coal or petroleum sources, phenanthrene and substituted phenanthrenes are present in significantly higher concentrations than anthracenes and other polycyclic c,ompounds~ In an oxidation process for conversion of the three-ring fraction of such feedstocks to benzene or precursors of benzene, it is desirable to effect controlled center-ring oxidation of phe-nanthrenes as well as of anthracenes.

We have discovered that in the presence of suitable catalysts, polycyclic aromatic hydrocarbons such as phe-nanthrene and mixtures of phenanthrene with anthracene react I:~.6~

with oxygen and steam in ~he vapor phase to form fluorenone and biphenyl. It is known from the work of Richter - U.S~
Patent 3,210,432 and others that these intermediate compounds can be converted to benzene by thermal hydrocracking. By combining oxidative steam cracking and thermal hydrodealkyation, a process has been devised to convert 3-ring and 4-ring aromatics into benzene in à high yield.
These oxycracking and thermal hydrocracking steps used in combination provide an advantageous and novel method for the conversion of trinuclear aromatics to provide monocyclic aromatic hydrocarbon products such as benzene in high yields.

S~MMARY OF INVENTION

A primary object of the present invention is to provide a process for converting fused tricyclic aromatic hydrocarbon feedstock, such as phenanthrene, anthracene, fluorene and mixtures thereof to fluorenone and biphenyl products by catalytic reaction in the vapor phase with a molecular oxygen-containing gas and with steam. The fluorenone and biphenyl intermediate materials produced in the oxycracking step are then thermally hydrocracked to produce benzene product. The term "oxycracking" is used herein to denote the basic process of this invention, because the center ring of a fused polycyclic molecule can be both oxidized and cracked in a single operation. Such fused trinuclear aromatic feed materials to the oxycracking step can be provided by the hydrodealkylation of heavy hydrocarbon materials. The thermal hydrocracking of fluorenone and biphenyl intermediates from the oxycracking step to produce benzene can be performed in a separate thermal hydrocracking step;
however, such thermal hydrocracking is advantageously and preferably performed in the same hydrodealkylation reaction step used to produce the intermediate materials.

While we do not wish to be bound by any particular theoretical explanation, we believe that the following sequence of reaction steps is involved when the feedstock is phenanthrene:

~ + - ~2 ~~~~~~~ ~ + ~2~ +C

Phenanthrene Fluorlnone J, + H20 siphenyl i~

Another object of the invention is to provide novel bifunctional catalysts having activity for both the oxidation and cracking reaction steps referred to above. Such catalysts utilize two or more selected metal oxides deposited on an acidic support such as alumina or silica alumina. Other objects of the invention will become apparent from the description which follows.

DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic flow diagram of a process for hydrodealkylation of polynuclear aromatic feedstocks, followed by catalytic oxycracking the residue 7 then by a thermal hydxocracking step to produce benzene.

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Figure 2 is a flow diagram of the process utiliæing two catalytic oxycracking steps and additional fractional distillation steps.

DETAILED DESCRIPTION OF THE INVENTION

Feedstocks Hydrocarbon feedstocks containing fused polynuclear aro-matic molecules and which are suitable for reaction in the basic oxycracking step of this invention include phenanthrene, anthracene, fluorene, their alkyl derivatives as further defined below, and techn,ical mixtures comprising these substances. Because aliphatic side chains are subject to oxidation with the undesired formation of carboxylic acids, such side chains should be present in technical feedstocks to an average extent ,of not more than about one side chain per two trinuclear aromatic molecules. The feedstock composition can be estimated in various ways, for example, by means of nuclear magnetic resonance. By way of illustration, a mixture of 2 moles phenanthrene, 1 mole of methylphenanthrene and 1 mole of ethylphenanthrene has an aromatic proton/aliphatic proton ratio of about 83/17 and an aromatic carbon/aliphatic carbon ratio of about 95/S. The side chains, if present, should be substantially free of unsaturation.

Hydrocarbon raw materials containing trinuclear aromatic hydrocarbons and which can be treated to provide feedstocks suitable for the oxycracking reaction step include the anthracene oil fraction from coke oven tar, heavy distillate oilc from coal liquefaction processes, and products of petroleum origin such as pyrolysis tars obtai,ned as by-G

products from steam crackers used to make light olefins,coker gas oils, fluid catalytic cracker decant oils, etc.
Other raw hydrocarbon sources include tar sand bitumens and shale oils. While the normal boiling points of the most useful raw material feedstock fractions can vary depending on the size and number of aliphatic side chains present, in general the boiling points will be within a broad range of about 500-900F, and preferably 600-800F. Raw materials which contain aliphatic groups in concentrations higher than those defined above should be dealkylated before they are used as feedstocks for the oxycracking reaction step of this invention. The most preferred hydrocarbon feedstocks to the oxycracking step are substantially free of aliphatic side chains.

If the feedstock contains substantial amounts of sulfur in compounds such as dibenzothiophene, these feeds could be hydrodesulfurized prior to hydrodealkylation. It is also possible to let the benzothiophene pass through the hydro-dealkylation step for cracking in the oxycracking reactor.

~odes of Operation According to the present invention, trinuclear aromatic compounds such as phena~threne are reacted catalytically with molecular oxygen and steam in the vapor phase to produce fluorenone and biphenyl as principal products. The oxycracking process step can be operated in either of two basic modes. In one mode or embodiment, a single catalytic reaction zone is used containing a single bifunctional oxycracking catalyst. The catalysts may be used in fixed beds, although fluidized catalyst beds can be used to advan-. 6~ cl V~

tage in order to dis-sipate the exothermie heat of reaction.
In the other mode of operation, the reactants pass suc-eessively through two catalytic reaction zones; the first zone for oxidation reaction, and the second zone for steam eracking reaction. Each reaction zone may be operated with a different catalyst and at different temperatures and space veloeities.

The steam eracking step can be effected at temperatures of about 700~1100F, at spaee velocities of about 0.2-40 millimoles of hydrocarbon per hour per gram of catalyst, and at water to hydroearbon molar ratios of at least about 5/1.
The proeess is operated at 5-50 psia pressure and is preferably operated at about atmospheric pressure.

Catalysts useful for the vapor phase oxidation of tri-eyelic aromatic hydroearbons include cobal~ or nickel molybdate, and oxides of vanadium, molybdenum, titanium, tin, antimony, bismuth, ehromium, manganese, iron, cobalt and niekel.

Bifunetional catalysts having activity for both the oxi-dation reaction and the steam eracking reaction typically eontain two or more metal oxides. In general, these metal oxides are seleeted for their activity in the separate reac-tion steps as disclosed above, and may advantageously be deposited on aeidic support materials such as alumina or siliea-alumina. Particularly useful are catalysts comprising eadmium or zinc oxide or mixtures thereof, and V2O5 or MoO3 or mixtures thereof, both on a ~-alumina support.
Teehniques for the preparation of such catalysts are generally known to khose skilled in the art. Thus, the support material may be impregnated with an aqueous solution of Cd(NO3)2 or 2n(N3)2 ~fter drying and calcining to decompose the metal nitrates, these operations may be repeated with a solution of NH4Vo3 or ammonium heptamolybdate. Alternatively, the metal oxides may be deposited on the support in the reverse order or simultaneously. Aluminas with relatively large pores, such as greater than about 50 Angstrom units, are preferred in order to permit the polycyclic hydrocarbon molecules ~o dif-fuse to and away from the reaction sites.

The molar ratio of oxygen to hydrocarbon feed may range from about 1/1 to about 30/1. Air is the preferred oxygen-containing gas, but mixtures o oxygen and nitrogen containing more or less oxygen than is normally present in air may also be used.

The molar ratio of steam to hydrocarbon in the oxycracking step is not critical, but in general will be at least about S/l. Reaction temperatures of about 800 to 1250F are suitable, and space velocities range from about 0.2 to 40 millimoles of hydrocarbon per hour per gram of catalyst. Pressures substantially atmospheric are preferred.

It will be apparent to those skilled in the art that these operational variables may be combined in a variety of ways. For example, space velocities should typically be increased when reaction temperatures are increased. Also, while it is desirable to effect a high conversion of tri-nuclear hydrocarbons to biphenyl in a single pass, the pro-cess may be operated continuously with separation of the biphenyl product by distillation or partial condensation and recycle of the fluorenone and tricyclic hydrocarbons to the oxycracking reactor.

DESCRIPTION OF PRE~ERRED EMBODIMENT
.

As shown by Figure 1, a polynuclear aromatic hydrocarbon feedstock at 10 having a normal boiling range of 500-900F is introduced with hydrogen 12 into hydrodealkylation reactor 14 where the feed material is hydrodealkylated with the hydrogen to substantially remove alkyl side chains. Useful hydrodealkylation reaction conditions are within the range of 1000-1500F temperature and 500-1200 psi hydrogen partial pressu.re. It is important that excess hydrogen be maintained in the reaction to prevent coking by having a relatively high hydrogen circulation rate relative to feed rate of at least about 5/1, and preferably exceeding~about 6/1. A hydrocarbon gas stream is withdrawn at 18 and stream 2:0 containing a hydrocarbon mixture is passed to successive fractional distillation steps 2Z and 28 f or removal of benzene at 21 and naphthalene at 21. A stream 29 containing biphenyl and fluorene can be recycled to hydrodealkylation reactor 14 for further reaction.

After fractionation steps at 22 and 28 to remove lighter fractions, the resulting heavy liquid residue stream 30 con-taining mainly phenanthrene is heated, vaporized and passed to catalyst-containlng oxycracking reactor 32, along with oxygen at 34 and steam at 35. ~ A desirable catalyst is CdO/MoO3 on ~ -alumina. Oxycracking reaction conditions used are 800-1200F temperature and 5-50 psia pressure. An effluent gas containing CO2 and some SO2 is withdrawn at 33 and the liquid biphenyl-containing product is withdrawn at 36.

If the product stream 36 contains substantial amounts of fluorenone and phenanthrene, these mate.rials can be separated , .

from the liquid product by a distillation step at 40. The resulting . :. biphenyl product withdrawn as stream 41 can be passed to a separate thermal hydrocracking reactor (not shown) for reaction to produce benzene product.
Useful hydrocracking reaction conditions are within the range of about 1000-1500F temperature and 500-1200 psi hydrogen pressure. Hydrogen circulation rate relative to feed rate to the hydrocracking reactor should be at least about 4/1 and preferably exceeding 5/1 flow ratio to prevent coking. However, stream 41 containing mainly biphenyl is advantageously and preferably returned to hydrodealkylation step at 14 for reactionO Bottoms stream 42 containing increased phenanthrene and fluorenone is recycled to the oxycracking reactor 32 for further reaction to increase the yield of fluorenone and biphenyl products.

It is pointed out that the hydrodealkylation reactor 14 used to prepare feedstock for the oxycracking reaction step 32 can also be used for splitting biphenyl, and even :for splitting fluorenone, if these materials are substantially free of phenanthrene. However, if the fluorenone contains relatively large percentages of phenanthrene, it is pre-ferable to recycle it back to the oxycracking reactor for further cracking.

As an alternative embodiment, the oxycracking reaction may be carried out in two steps as generally shown in Figure

2. This embodiment is similar to Figure 1 except an addi-.
tional fractional distillation step is provided at 24 to remove toluene and xylene at 25 for recycle with stream 29 to hydrodealkylation reactor 14. Also, the heated phenanthrene feed at 50 is passed with air at 52 and optional steam at 53 to first. catalytic reactor 54, which is maintained at reaction cond-itions within the range of 800-1250F
temperature and 5-50 psia pressure. An effluent gas con-taining CO2 and some SO2 is withdrawn at 51. The remaining material is passed with additional steam 56 to a second catalytic reactor 58, which is maintained at reaction con-ditions within the range o~ 700-1100F and 5-45 psia. If desired, the resulting fluorenone and biphenyl products can be passed to a separate thermal hydrocracking reactor for producing benzene. Similarly as in the Figure l.embodiment, residue stream 60 containing fluorenone and phenanthrene is cooled at 62 by stream 63 to remove water at 61 and then passed to fractional distillation step 64. Overhead stream containing fluorenone and biphenyl is returned to the hydrodealkylation reactor 14, and ~ bottoms stream 66 is recycled to the first oxycracking reaction step 54 for ~urther reaction to increase the yield of fluorenone and biphenyl product.

The present invention is further illustrated by the following examples, which are illustrative only and should not be construed as limiting the scope of the invention~

In preparation of a CdO/MoO3/A12O3 catalyst, the catalyst support used was a ~-alumina extrudate, 4.7 mm long x 1.6 mm diameter, having surface area 96 m2/g, pore volume 0.537 cc/g, and minimum pore diameter about 64 Angstroms. The support (81.0g) was impregnated with a solution containing 14.49 g of Cd(NO3)2~4 E12O and ~5 cc of water. After drying at 220F and calcining at 920F, the catalyst weight was 83.4 g. Of this catalyst material, about 67.2 g was impregnated with a solution of 6.9 9 of (NH4)6Mo7024~4H20 in 65 cc of water. The final weight after drying and calcining as above was 74.6 9. This final prepared catalyst sample contained about 6.4 W ~ CdO and 7.7 W ~ MoO3.

A catalyst sample of CdO/V205/A1203/ catalyst was pre-pared similarly to Example 1 from ~1203 (71.2 g), Cd(NO3)2.4 H20 (25.46 g) and NH4VO3 Go.965 g). The resulting catalyst contained about 12.8 W % CdO and 0.9 W ~ V205.

Oxycracking reactions of phenanthrene over CdO/MoO3/A1203 catalyst were carried out using experimental apparatus fabricated from stainless steel pipe and tubing.
Liquid water and compressed air were mixed together and passed through a heated tube in which the water was vaporized. The resulting air-steam mixture was passed through a reservoir containing molten feed material comprising about 90~ phenanthrene, 8% anthracene, and 2 other materials. The resulting vapor mixture was passed through a preheater then into the reactor. The reactor volume was about 30 cc and contained about 25 cc of catalyst comprising CdO/MoO3 on alumina support prepared as described in Example 1. The reactor was heated uniformly by an electrically heated fluidized sand bath. The vapors exiting the reactor were condensed, and the organic product was separated from water, weighed, and analyzed. Samples of the uncondensed gases were collected periodically for analysis.

~ '7 The water feed rate was measured directly; air flow rate was estimated from flo~rmeter readings. The dry product weight was used to estimate phenanthrene feed rate. Reactor tem-peratures were measured by thermocouples. Typical results from this run are tabulated in Table 1 below:
.

,~
Air flow rate (assumed atmospheric pressure), mole/hr ~ 0.308 Water flow rate, cc/hr 171 Reactor temperature, F 1040 Reactor pressure, psig 0 Solid organic products collected, gm/hr 1.31 Solid Product Analysis, W ~
Phenanthrene 67.2 Fluorenone 25.9 Biphenyl 8.4 Off Gases Composition, V %
Carbon Dioxide 11.04 Carbon Monoxide 2.03 Oxygen 5~86 Phenanthrene evaporation rate, mole/hr 0.0128 O2/PN mole ratio 4.97 H2O/PN mole ratio 740 Space Velocity, total gases at reactor temperature, sec~l Space Velocity, millimoles phenanthrene per gram of catalyst per hour 0.5 Phenanthrene going to respective products, M ~
Phenanthrene (unreacted) 52.6 Fluorenone 20.0 Biphenyl 7.6 CO by combustion 1.5 C2 by combustion 18.3 Additional oxycracking runs were made with the same 90%
phenanthrene feed using CdO/MoO3/A12O3 catalyst. Results are shown in Table 2 below:

~ tB8~7 OXYCRACKING PHENANTHRENE WITH CdO/MoO3/A1203 CATALYST
_ Run No. 9C lOB lOC 12C

Feedstream Flow Rates Air, moles, hr. 0.31 0.30 0.30 0.30 Water, cc/hr. 157 159 156 150 Reaction Temp., F 1040 1110 1180 11~5 Solid Product Yield, g/hr. 8~6 -1.6 1.9 4.2 Solid Product Composition, W ~
Phenanthrene 78 68 69 80 Fluorenone 4.2 18 10 5.9 Biphenyl 1.8 11.5 9.3 3.2 It is noted that using feed stream of 90 W %
phenanthrene, significant amounts of the desired fluorenone and biphenyl products were produced at reaction temperature within the range of 1040-1185F, with the remainder of the solid products being 68-80 W ~ phenanthrene.

.

Further oxycracking runs were made using 90~ phenanthrene feedstock with other catalysts comprising CdO/V2Os on alumina and nickel molybdate. The results of these experiments are shown in Table 3.

OXYCRACKING PHENANTHRENE WITH OTHER CATALYSTS

Run No. 6C 8~ 14A

Catalyst(a) V V N
Feedstream Flow Rates Air, moles, hr. 0~85 0.850.475 Water, cc/hr. 138 145 107 Reaction Temp., F(b) 1240 825 930 Solid Product Yield, g/hr. 1.3 2.2 3.2 Solid Product Composition, W ~
Phenanthrene 81 66 74 Fluorenone 8.3 20 9.4 Biphenyl 3.1 3.1 1.8 (a)V indicates CdO/V2OS/Al2O3 catalyst N indicates nickel molybdate (H-Coal catalyst) (b)Exothermic reactions Similarly as for Example 4, 90 W % phenanthrene feed w~s successfuly oxycracked using different catalysts to produce significant amounts of fluorenone and biphenyl products. It was observed that the oxycrac~ing reaction with the catalyst containing vanadium was more exothermic than with the other catalysts. Anthracene, naphthalene and one or more uniden-tified compounds were observed in some of the solid products.

Losses of hydrocarbon values due to combustion occurred to some extent.

' ' ' This example describes the oxycracking reaction as used in a commercial-scale, fixed-bed~type reactor. The mole ratio used for phenanthrene/oxygen/water is l/6/17.

A mixture of air (140 standard cubic feed per second) and steam (13,750 pounds per hour) is preheated to about 600F.

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Phenanthrene feedstock (8000 pounds per hour) is heated to about 400F and pumped into an evaporator, in which it is vaporized by contact with .the warmer steam-air mixture. The resulting vapor stream is fed to the reactor, which comprises an array of about 10,000 tubes, each 1 inch diameter and containing about 1.2 liters of catalyst. The catalyst con-sists of cadmium and molybdenum oxides supported on alumina having about 0.060-inch-diameter particle size as extrudates.
The catalyst-filled tubes are cooled by a fused salt mixture and maximum temperature is maintained in the range of 1000-1100F. The molten salt mixture is circulated through heat exchangers in which process steam is generated.

The gases leaving the oxycracking reactor are partially cooled by a heat exchange step to about 180F. The conden-sable aromatic products are separatèd from the water and gases, and the resuIting condensed organic products are fed into a fractional distillation unit for separation into a biphenyl stream taken overhead and a bottoms stream consisting essentially of fluorenone and phenanthrene. The biphenyl overhead stream is passed to a thermal hydrocracking unit, while the distillation bottoms product of mainly phenanthrene and fluorenone is recycled to the oxycracking reactor for further reaction to increase the product yi.eld.

The mixture of water vapor and gases is further cooled to about 85F to effect condensation of biphenyl and most of the water; the composition of the resulting vent gase.s is shown in Table 4. An approximate material balance for the feed and product streams to the oxycracking step is also provided below in Table 4.

MATERIAL BALANCE FOR OXYCRAC~ING REACTION

Feed Reaction Streams, Products, Stack Gases ~ Lb/Hr Lb/HrComposition, V
Phenanthrene 8000 320 Water 13753 14748 4.1 Oxygen 8629 1622 3;6 Nitrogen 30202 30202 77.0 Fluorenone - 243 ~iphenyl - 4776 0.001 2 - 7345 11.9 CO - 1329 3~4 Total 60584 60584 100.0 Although this invention has been described in terms of the accompanying drawings and preferred embodiments, it will be appreciated by those skilled in the art that many modifi-cations and adaptations of the basic process are possible within the spirit and scope of the invention, which is defined solely by the following claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for producing-fluorenone and biphenyl products from a polynuclear hydrocarbon feedstock selected from the group consisting of phenanthrene, anthracene, fluorene and technical mixtures thereof, which comprises:
(a) heating and vaporizing said hydrocarbon feedstock;
(b) passing a mixture of the vaporized feedstock with a molecular oxygen-containing gas and steam through at least one catalytic reaction zone at a temperature within the range of 700-1250°F, said at least one catalytic reaction zone containing-a catalyst comprising a mixture of at least one Group IIB metal oxide and an oxide of molybdenum or vanadium deposited on a .gamma.-alumina support; and (c) withdrawing fluorenone and biphenyl products.

2. The process of Claim 1, wherein the oxygen-containing gas is air and the molar ratio of oxygen to hydrocarbon is from about 1/1 to 30/1.

3. The process of Claim 1, wherein the reaction temperature is within the range of 800-1200°F and pressure is between about 5 and 50 psia.

4. The process of Claim 1, wherein the number of catalytic reaction zones is one and said zone contains a bifunctional oxycracking catalyst.

5. The process of Claim 4, wherein the oxygen-containing gas is air, the reaction pressure is 5-50 psia, the molar ratio of oxygen to hydrocarbon feedstock is from about 1/1 to about 30/1, the molar ratio of steam to hydrocarbon feedstock is at least about 5/1, the reaction temperature is about 900 to 1200°F, and the space velocity of hydrocarbon feedstock is about 0.2 to 40 millimoles per hour per gram of catalyst.

6. The process of Claim 1, wherein the hydrocarbon feedstock is phenanthrene which is substantially free of aliphatic side chains.

7. The process of Claim 1, wherein said hydrocarbon feedstocks are obtained from raw materials having normal boiling points in the range of about 500°F to about 900°F, and are selected from the group consisting of the anthracene oil fraction from coke oven tar, heavy distillate oils from coal liqufaction, and products of petroleum origin comprising pyrolysis tars, coker gas oils, fluid catalytic cracker decant oils, tar sand, bitumen, shale oils, and the like by a hydrodealkylation reaction prior to the oxycracking reaction step.

8. The process of Claim 7, wherein at least one step of fractional distillation is used between the hydrodealkylation reaction and oxycrackinq reaction steps to remove light fractions of benzene and naphthalene.

9. The process of Claim 1, wherein the number of catalytic reaction zones is two, the oxygen-containing gas is injected into the first zone, and steam is injected between the two reaction zones.

10. The process of Claim 1, wherein the fluorenone and biphenyl products are further thermally hydrocracked to produce benzene product.

11. The process of Claim 10, wherein the thermal hydrocracking step is provided hy a hydrodealkylation step preceding the oxycracking step.

12. A process for producing fluorenone and biphenyl products from a polynuclear aromatic hydrocarbon feedstock selected from the group consisting of phenanthrene, anthracene, fluorene and technical mixtures thereof together with their alkyl derivatives, in which the average number of side chains is not more than about one per two molecules of feedstock, which comprises:
(a) heating and vaporizing the feedstock;
(b) passing a mixture of vaporized feedstock with a molecular oxygen-containing gas and steam through at least one catalytic reaction zone at a temperature of 800-1100°F, said at least one catalytic reaction zone containing a catalyst comprising at least one Group IIB metal oxide and an oxide of molybdenum or vanadium deposited on a .gamma.-alumina support;
(c) withdrawing the fluorenone and biphenyl products;
and (d) further thermally hydrocracking the fluorenone and biphenyl intermediate products at temperature of 1000 to 1500°F to produce benzene product.

13. A catalyst material comprising a mixture of at least one Group IIB metal oxide comprising between l and 15 W % and an oxide of molybdenum or vanadium deposited on a .gamma.-alumina support.

14. The catalyst material of Claim 13, wherein the catalyst contains CdO/MoO3/Al2O3.