US2409695A - Method for improving aviation fuels - Google Patents

Description

Oct. 22, 1946.

Y K. C; LAUGHLIN METHOD FOR IMPROVING AVIATION FUELS 2 sheets-sheet 1 Filed Jan.V 30, .1943

NINMN Oct. 22, 1946. v K. c.`LAuGHl.|N 2,409,695

METHD FOR IMPHOVING AVIATION FUELS Filed' Jan.I 3o, 1943 2 sneetsshee 2 MMV Patented Oct. 22, 1946 METHOD non IMPRovING AVIATION FUELS Kenneth C. Laughlin, Baton Rouge, La., assigner to Standard Oil Development Company, a corporation of Delaware Application January 30, 1943, Serial No. 474,077

Claims. (C1. 260-668) The present invention relates to the process of producing aromatics, in particular toluene, by aromatization of straight chain and/or cycloparalins in the presence of a catalyst. More particularly, the present invention is concerned with a two-stage operation in which a naphtha fraction of a crude petroleum oil (which may be admixed with some cracked naphtha) is successively treated in a two-stage operation to produce maximum quantities of the desiredv aromatic (usually toluene), the process being characterized by the Ause of a different catalyst in the two stages, i. e.,

lyst adapted to aromatize straight chain paraiiins and olens. y

Other aspects of my invention include carrying out the reforming and/or aromatization of paraffins in the presence of added hydrogen to suppress carbon deposition on the catalyst, to superimpose pressure on the reaction zones eX- ceeding atmospheric, to recover aromatics from stage to convert the non-benzenoid hydrocarbons paraflins and olefins .by means of a solvent having a greater solvent power for aromatics than for other hydrocarbons, and to employ `other eX- pedients tending to promote eniciency, economy and good yields of pure products, all of which will appear more fully hereinafter in the detailed description of my invention which follows:

It is a matter of record, broadly, to produce aromatics from hydrocarbon oil including petroleum oil. It is also knownto reform i. e., to treat at'elevated temperatures, say 850 to 950 F., in the presence of a dehydrogenation catalyst, a petroleum naphtha withthe result that some aromatics are formed. It is old to operate such a process under pressures up to 1000 atmospheres and in the presence of added hydrogen. A

My invention resides in specc improvements in the process of treating naphthas `to form aromatics, the principal novelty residing in the multi-stage process I employ, coupled with the use of a catalyst most eilective in a particular present to aromatics.

For a better understanding of my invention reference is made to the accompanying drawings showing a flow plan indicating a preferred modication of my invention.

Referring to the drawings, I represents a naphtha feed line through which a`200 to 250 F. cut of light naphtha containing naphthenes in substantial quantity was charged to the system. The naphtha was mixed with hydrogen from line 2, thence discharged into a iired coil 3, thence withdrawn through line 6 and forced through a reactor I0 containing a molybdenum oxidealumina catalyst. The flow of hydrocarbons was downwardly through the catalyst which was in the form of pills having a diameter of about 3/8 of an inch and a length of about of an inch, the catalyst being supported on a false bottom T in the formY of a screen or other perforate member. The catalyst composition will be given hereinafter.

The products of the reaction in I0 were withdrawn through line I4 and thence discharged into a fractionator I5, A cycle stock was withdrawn through line I6 and this product, boiling above 250 F., was returned to feed inlet I for further processing, However, provision was made to bleed off aportion of this oil periodically through drawoff pipe I9 asit becomes too inactive or refractory for further conversion.

Overhead from fractionator I5, through line II, the light ends and hydrogen were removed,

passed into a hydrogen separator 20 where a split between hydrogen and hydrocarbons was effected, the hydrogen recycling through line 25 to hydrogen feed line 2, while the hydrocarbons were withdrawn through pipe 30 carrying a pressure release valve 3|. These hydrocarbons boil up to about 200 F. and may be utilized in any convenient manner such as a blending agent for automotive fuel of high octane number, dehydrogenated to form synthetic rubber intermediates, isomerized to form paralns capable of alkylating olens, etc.

A fraction boiling lfrom 200 to 250 F., viz., the crude toluene out, was withdrawn from fractionator I5 through line 35 and solvent treated in tower 40. Preferably, I employ a phenolic solvent in liquefied state, which solvent such as ordinary phenol heated say `from 250 to 300 F. was discharged into solvent treater 40 through feed pipe 42 where it flowed downwardly in countercurrent flow to the ascending crude toluene vapors, dissolved toluene out of the latter to form an extract phase which was withdrawn through pipe 48 and discharged into a solvent stripper 10 where the toluene Was stripped by heating or other means from the solvent, the latter being returned to solvent treater 40 through pipe 12. The toluene was recovered from stripper 'lil through pipe 16, and to remove olens which may be present, the toluene was treated with a polymerizing clay or an acid such as sulfuric acid, in 18, thence passed through line 80 into distillation tower 82 from which the polymers were removed through pipe 84, while the purified toluene was recovered through line 85, condensed in cooling coil 8l' and thence collected in storage drum 90.

Referring back to solvent treater 40, the raffinate phase in which the paraflins were concen- CFI trated was recovered through pipe 45, thence Y passed into a stripper 50 from which the hydrocarbons were stripped of solvent, as by heating, the solvent recycling through pipe 5l to solvent feed line 42. The stripped raffinate was withdrawn through line 55, heated in furnace 58 and thence charged to the top of reactor 59 through which it flowed downwardly through catalyst C consisting of alumina and chromia, the catalyst being supported on perforate tray T, and being in pilled form, preferably, as catalyst M in reactor I0.

Reaction products were withdrawn through line 65 and charged into the stream I4 entering fractionator I5y where the crude toluene formed in 59 was fractionated and thereafter puried with the toluene formed in reactor l0 in a manner previously described.

Having generally described my invention, I shall now set forth a specific example giving additional details as to a preferred method of operating. In reactor l0, the catalyst consisted, in a particular run, of molybdenum oxide on Activated Alumina, the proportions being by weight 12 parts of molybdenum oxide and 88 parts of Activated Alumina, the molybdenum oxide being uniformly distributed throughout the body of the catalyst mass. A temperature of about 910 F. and a pressure of about 225 lbs. per square inch were maintained in this reactor. The oil was fed to the reactor at a rate of about 0.65 volume of oil per volume of catalyst per hour on a cold oil basis. Hydrogen equivalent to about 2500 cubic feet per barrel of oil wasalso admitted to reactor I 0. The reactor was operated for four hours, whereupon the flow of oil and hydrogen was discontinued in order to regenerate the catalyst. The aromatics formed corresponded to 35 volume per cent of the feed. The toluene yield amounted to of the total feed.

With respect to the reaction in reactor 59, the non-aromatic rafnate boiling in the range of 200 to 250 F. and amounting to about 25 volume per cent of the original feed was fed to reactor 59. In reactor 59, the catalyst was a chromiaalumina catalyst containing 40% chromia and 60% of alumina, preferably promoted by the inclusion of less than 1% of a mixture of K2O and CeO, say more or less of each oxide, based on 100 parts by weight of the chromia and alumina. Here it will be noted that no hydrogen or other gas was mixed with the feed and that a temperature of about 395 F. was maintained within the reactor which operated at about atmospheric pressure. The feed rate was 1 volume of cil per volume of catalyst per hour on a cold oil basis. This reactor may be operated for three 4 to six hours before regeneration is necessary. The product withdrawn through line 60 corresponded to 27 volume per cent of the feed to the reactor, and 20% of the feed was converted to toluene. It will be understood that the above conditions are purely illustrative and do not impose any limitation on my invention.

For example, good results are obtainable in reactor |0 by operating under the following conditions:

Temperature 850 F. to 1100 F.

Pressure -1000 lbs, per sq. in. (gauge) Feed rate 0.5-2 volumes of oil per Volume of catalyst per hr. Hydrogen 100G-4000 cu. ft. hydrogen per barrel of oil Catalyst The amount of molybdenum oxide may vary from 5-12% of the total catalyst, the balance being Activated Alumina Conditions in reactor 59: In this reactor good results are obtained by operating at balance being alumina.

It is possible to increase the ultimate yield in reactor 59 by recycling the product in 6D remaining after removal of the toluene, by solvent extraction, for example; thus, by recycling it is possible to convert up to 77 of the feed going to reactor 59 to toluene. For simplification, many common expedients such as recycling, regeneration of the catalyst, and other known expedients have been eliminated, since it is believed that the invention is thus better described. Thus, for example, the catalyst need not have the form of pills of the size indicated previously, but may be in the form of larger or smaller lumps, granules, extruded shapes, and the like, or it may be in the form of a powder suspended in the vapors during the conversion in the reaction zones. Also, it is deemed obvious that in order to provide overall continuity of operation two or more reactors Il! and 59 may be employed, so that while one is undergoing regeneration, another may be in the onstream operation.

To recapitulate, my present invention relates vto improvements in the art of producing aromatics, particularly toluene, from petroleum oil and in its essence it involves hydroforming a naphtha cut containing at least 40 volume per cent naphthenes such as methylcyclohexane in the presence of a molybdenum oxide-alumina catalyst, whereby the naphthenes present are converted to aromatics including toluene, whereupon the products are treated to separate an acyclic hydrocarbon fraction boiling within the range of from 20G-250 F., and this fraction is treated with a catalyst under aromatizing conditions to form additional quantities of toluene, the catalyst in this second stage being chromia on alumina. I have found that by thus operating, I may secure increased yields of toluene, for example, from a given feed stock.

Also, catalysts other than molybdenum oxide may be used in the first zone. These include sulphides of nickel and tungsten (mixture) or oxides of the II to the VI groups of the periodic system. Instead of using alumina, I may use magnesia, or

troleum oil which comprises charging a naphtha fraction containing naphthenes to a reaction zone Where it contacts a molybdenum oxide-alumina catalyst at temperatures within the range of from 850 F. to 11G0 F., simultaneously adding hydrogen to the heated oil in the reaction zone, maintaining a superatmospheric pressure on the reactants in the reaction zone, permitting the reactants to remain in the reaction zone for a sufficient period of time to effect the desired con- Version, withdrawing the reaction products, fractionating the latter to recover an aromatic-containing fraction, subjecting the latter fraction to solvent extraction whereby a solvent extract phase and a raffinate phase are formed, separating the phases, recovering aromatics from the extract phase, subjecting the rainate phase to a further treatment in a second reaction zone at temperatures Within the range of from 850-1050" F. in the presence of a promoted chromia-alumina catalyst for a sufficient period of time to effect the desired conversion, and recovering from said second reaction zone a further quantity of aromatics.

2. The method set forth in claim 1 in which the catalyst in the rst reaction zone contains from A542% of molybdenum oxide, and the catalyst in the second reaction zone contains from l0-40% `of chromia.

3. The method set forth in claim 1 in which the crude reaction products from both zones are fractionated and thereafter puried to recover toluene in a common system.

4. The method of increasing the aromaticity of a petroleum naphtha which comprises charging the feed naphtha to a rst reaction zone where it contacts a molybdenum oxide-alumina catalyst Y at temperatures within the range of from about 350-1100 F., simultaneously charging a hydrogen-containing gas to the reaction Zone, maintaining a pressure within the reaction zone of at least about 100 pounds per square inch, permitting the reactants to remain in the reaction zone for a suicient period of time to effect the desired conversion, withdrawing the reaction products containing aromatics and paraflins, subjecting the said products to a further treatment in a second reaction zone maintained at a temperature within the range of from about 850- 1050 F. in the presence of a promoted chromiaalumina catalyst, maintaining a pressure in the said second reaction zone substantially` lower than that in the rst reaction zone, permitting the reactants to remain in the reaction Zone for a sufcient period of time to convert paraiiins into aromatics and recovering from said second reaction Zone a quantity of naphtha substantially enriched in aromatic hydrocarbons.

5. The process set forth in claim 4 in which the pressure in the first reaction zone is about 225 pounds per square inch and in the second Zone is about atmospheric.

KENNETH C. LAUGHLIN.

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