US2319452A - Treatment of cyclic hydrocarbons - Google Patents

Description

Patented May 18, 1943 Aristld V. Grosse and William J. Mattox, Chicago,

Ill., assignors to Universal Oil Products Oomj pany, Chicago, 111., a corporation of Delaware N Drawing.

8 Claims.

This invention relates particularly to-the treatment of cyclic hydrocarbons which are characterized by partial or complete saturation of the ring and relates therefore to such hydrocarbons as cyclo-hexane' and its alkylated derivatives, and also cyclo-hexene and cyclo-hexa-diene and their corresponding alkyl derivatives. While the process of the invention to be disclosed is Application February 24, 1939, Serial No. 258,289

more particularly applicable to the treatment of naphthene hydrocarbons of 6 carbon atoms in the ring, there will be some effect on the hydrocarbons of 5, 7, and higher carbon-atoms, particularly when these have a tendency to isomerize under the conditions of treatment, to the corresponding 6 carbon-atom ring compounds.

In one aspect of the invention it may be directed to the production of more highly unsaturated compounds from cyclo-hexane, cyclo-hexene, and cyclo-hexa-diene to the extent of producing benzol from thesecompoundsor alkylated benzols fromtheir alkyl derivatives and in another aspect, it is related to the treatment of mixtures of naphthenes such as those present in naphthenic gasolines' or similar compounds present in cracked gasolines although there would generally be a relatively low percentage of the completely unsaturated ring compounds in cracked gasolines. Thevalue of the, process in the treatment of pure compounds is to produce more highly reactive-hydrocarbons in the case of gasolines to produce compounds of higher antiknock value. The process to be disclosed may be operated so as to selectively effect dehydrogenation of ring hydrocarbons without essential change in structure. or any undesirably large amounts of side reactions. In one specific embodiment the present invention comprises the treatment of naphthenic hydrocarbons for the dehydrogenation'thereof by subjecting said hydrocarbons at elevated temperatures and substantially atmospheric or subatmospheric pressures to contact with solid granular catalysts comprising major proportions by weight of carrying materials of relatively low catalytic activity supporting minor proportions by weight of compounds of the elements in the lefthand column of group V of the periodic table, and preferably the oxides thereof which have straight dehydrogenation reactions.

The present invention is characterized by the use of particular catalytic materials and suitable combinations of temperature, pressure, and time of contact to control the character and extent of the dehydrogenation of naphthenic hydrocarbons to produce high yields of desired products and a minimum of undesirable byproducts. Temperatures from approximately 400 to 650 C. may be employed, pressures from moderately superatmospheric of the order of 50 to 100 lbs. per square inch down to those of the order of 0.25 atmospheres absolute and times of contact from approximately 0.1 to seconds. Obviously'the interrelated conditions of temperature, pressure,

catalyst activity, and time of contact will be varied with difierent compounds or mixtures of compounds undergoing treatment and with the extent of dehydrogenation desired. For example, to produce benzene from cyclo-hexane may require more severe conditions in these interrelated factors than in the production of benzene from cyclo-hexa-diene, which is already partly dehydrogenated. Variables will also be introduced whenealkyl derivatives of the ring compounds are trea d.

In the present instance, the catalysts which are preferred for selectively dehydrogenating naphthenic hydrocarbons have been evolved as the result of a large amount of investigation with catalysts having a dehydrogenating action upon various types of hydrocarbons, such as, for example, those which are encountered in the fractions produced in the distillation and/or pyrolysis of petroleum and other naturally occurring hydrocarbon oil mixtures. The criterion of an acceptable dehydrogenating catalyst is that it shall split of! hydrogen without inducing either scission of the bonds between carbon atoms or carbon separation.

It should be emphasized that in the field of catalysts there have been very few rules evolved which would enable the prediction of what materials will catalyze a given reaction. Most of the t catalytic work has been done on a purely empirical basis, though at times certain groups of 'elements or compounds have been found to be metals, platinum, and palladium, have been found relatively high catalytic activity in furthering to be effective in dehydrogenating reactions, particularly in dehydrogenating naphthenes to form aromatics, but these metals are expensive and easily poisoned by tracesof sulfur so that their use is considerably limited in petroleum hydrociflc catalytic ability in the dehydrogenating reactions but which are improved greatly in this respect by the addition of certain promoters or secondary catalysts in minor proportions, which comprise in the present instance the compounds and preferably the oxides of the element in the lefthand column of group V of the periodic table columbium A properly prepared carrier may be ground and sized to produce granules of relatively small including vanadium, columbium, and tantalum.

The base supporting materials for these compounds are preferably of a rugged and refractory character capable of withstanding the severe use to which the catalysts are put in regard to temperature during service and in regeneration by means of air or other oxidizing gas mixtures after they have become fouled with carbonaceous deposits after a period of service. As examples of materials which may be employed in granular form as supports for the preferred catalytic substances may be mentioned the following:

Magnesium oxide Kieselguhr Aluminum oxide Crushed silica Bauxite Crushed firebrick Bentonite clays Glauconite (greensand) Montmorillonite clays The active compounds or promoters which are used in the catalyst composites according to the concepts of the present invention constitute a natural group since they are the elements in the lefthand column of group V of the periodic table. While the compounds and particularly the oxides of these elements are effective catalysts in the dehydrogenation reactions, it is not intended to infer that the different compounds of any one element or the corresponding compounds of difierent elements are exact equivalents in their catalytic activity.

In general practically all 03. the compounds of the preferred elements will have some catalytic activity in dehydrogenating naphthenic hydrocarbons though as a rule the oxides and particularly the lower oxides are the best catalysts. Catalyst composites may be prepared by utilizing the soluble compounds of the elements in aqueous solutions from which they are absorbed by prepared granular carriers or from which they are deposited upon the carriers by evaporation of the solvent. The invention further comprises the use of catalyst composites made by mechan-= ically mixing relatively insoluble compounds with carriers either in the wet or the dry condition. In the following paragraphs some of the compounds of the elements listed above are given which are soluble in water and which may be used to add catalytic material to carriers.

Vanadium Catalysts comprising 2 to 20 per cent by weight of the lower oxides of vanadium such as the sesquioxide V20: and the tetroxide V204. may be used. Some of the monoxide VO may be present in some instances. The oxides mentioned are particularly emcient as catalysts for the present types of reactions but the invention is not limited to their use but may employ other compounds of vanadium. Thus solutions of the ammonium and the alkali metal vanadates may be employed to add vanadium compounds to the carriers and also the soluble vanadyl sulfates and the vanadium nitrate and carbonate. The alkaline earth vanadates may be mixed mechanically and also the halides of vanadium. The oxides per se or those produced by reduction or decomposition of other vanadium compounds are preferred.

mesh of the approximate order of from 4 to 20 and these caused to absorb compounds which will ultimately yield compounds of columbium on heating to a proper temperature by stirring them with warm aqueous solutions of soluble columbium compounds, such as for example the mixed fluoride of columbium and potassium already mentioned having the formula CbOF2.2KF.H2O, which is sufiiciently soluble in water to render it utilizable as a source of columbium catalyst. Other soluble compounds which may be used to form catalytic deposits containing columbium are the various alkali metal columbates. Still other compounds of columbic acids, including salts of the alkaline earth and heavy metals, may be distributed upon the carriers by mechanical mixing either in the wet or the dry condition. As a,

rule the lower oxides are the best catalysts. The oxide resulting from the decomposition of such compounds as the pentahydroxide is for the most part the pentoxide CbaOs. This oxide, however, is reduced to a definite extent by hydrogen or by the gases and vaporous products resulting from the decomposition of the hydrocarbons treated in the first stages of the process, so that the essential catalysts for the larger portion of the period of service are evidently the lower oxides Cb02, Chaos, and CbO.

' Wntalum Compounds of tantalum, such as for example, the pentoxide TazOs and the tetroxide T3204, and possibly the sesquioxide TazOa. which result from the reduction of the pentoxide are particularly eflicient as catalysts for the present types of reactions but the invention is not limited to their use but may employ any of the catalytically active compounds of tantalum. Tantalum fluoride and the double fluoride of tantalum and potassium having the formula TaKzFv are soluble in water and may be conveniently used in aqueous solution as ultimate sources of the oxides which result from the ignition of the precipitated hydroxide to form the pentoxide and the partial reduction of this oxide by hydrogen or the gases and vapors in contact with the catalyst in the normal operation of the process. The tantalum pentahydroxide may be precipitated from a solution of'the double fluoride by the use of ammonium or alkali metal hydroxides or carbonates as precipitants, the hydrate being later ignited to form the pentoxide, which may undergo some reductionas already stated.

Aluminum oxide, a particularly good support for use in the manufacture of catalysts for the process may be obtained from natural aluminum oxide minerals or ores such as bauxite or carbonates such as Dawsonite by proper calcination, or it may be prepared by precipitation of aluminum hydrate from solutions of aluminum sulfate or different alums, and dehydration of the precipitate of aluminum hydroxide by heat, and usually it is desirable and advantageous to further treat it with air or other gases, or by other means to activate it prior to use.

Two hydrated oxides of aluminum occur in nature, to wit, bauxite having the formula AlzOaZHzO and Diaspore Al2O3.HzO. In both of these oxides iron sesqui-oxide may partially replace the alumina. These two minerals or corresponding oxides produced from precipitated alubase compounds whose 'mlmnnhydroxidearesdaptablefor themanufactureofthepresenttypeofcatalystsandinscme instanceshavegiventhebestresultsofanyofthe use is at presentcontemplated. The mineral Dawsonitc havin the formula NnsAKCOshBAKOH): is another mineral which may be usedas a source of. aluminum oxide.

It is insaluminum oxide as a base catalyst to ignite for sometime at temperatures within the same approximate range as those employed in the process,to-wit,from400to850'C. Thisprobably goodpraeticeinthefinalstepsofprepardoes not correspondpto complete dehydration of 1 the-hydroxides but apparently gives a material of goodstrength and porosity so that it is able to resist for a long period of'time the deteriorat- Qingefiects of the service and regeneration periods towhichitis'subiected. Inthecdsedf thee] which may serve as base catalytic materials-for promoters, the better materials are those which have been acid-treated to render them more. siliceous. These may be pelleted or formed in any manner before or after the addition of the promotercatalyst since ordinarily they have a high percentage of fines. The additionof certain of the promoters, however, exerts a binding influence so that the formed materials or fluxing. 7

In regardto-the relative proportions of carrim and catalysts it may be stated in general thatthelatteraregenerallylessthanmmoiper cent ofthe The effect upon the catalytic'activiiw of the base catalysts caused tics'oithecompoundaddedandnogeneral ranges oftemperaturecanbe'givenforthisstep.

Insomeinstance'sproinotersmaybedeposited from 80111110!! by the addition 01 precipitant:

which cause the deposition oi precipitates upon the catalyst granules. As, a'rule methods of mechanical mixing are not preferable, though in someinstancesinthecaseofhydratedorreadily fusible compoimdsthesemaybemixedwiththe properproportions of base catalyst-sand uniformly distributed during the condition of fusing him the percentsgeof any given compound or mixture of compounds deposited thereon is not .a matter for exact calculation but more one for determination by experiment. Frequently good increases in catalyticeifectiveness are obtainable by'the deposition of sslowas2% to 8% of a promotlng compound upon the surface and in the V poresof the base catalyst.

Iii-operating theprocess the general procedure is to-vaporise hydrocarbons or mixtures of maybe employed without fear of structural de terioration inservice. I

It is particularly advantageous to'employ the typeof aluminum oxide known as gammaalumina, by which is meant the modification obtained by the dehydration of the monohydrate termed bohmite (AIQOH) or the tri-hydrate AMOH); termed hydrargillite or glbbsite, when occurring in nature. It is characterized by de'flnite crystallographic properties and can be readily distinguished from the large number of other modifications of alumina, such 'as alpha, beta, epsilon, zeta, etc., by its X-ray difraction pattern. The'gamma-alumina crystallizes in the cubic system with the edge of the unit cube being about 7.9 Angstrom units.

Our investigations have also definitely demonstrated that the catalytic emciency of such substance as alumina, magnesium oxide, and clays which may have some catalytic potency in themselves is greatly improved by the presence of compounds of the preferred elements in relatively minor amounts, usually of the order of less than mol per cent of the carrier.

The most general method for adding the promoting materials is to stir the prepared granules of from approximately 4 to 20 mesh into solutions of salts which will yield the desired promoting compounds on ignition under suitable conditions. -In some instances the granules may be merely stirred in slightly warm solutions of salts until the dissolved compounds have been retained on the particles by absorption or occlusion, after which the particles are separated from the excess solvent by settling or filtration, and

' then ignited to produce the desired residual promoter. In cases of certain compounds of relatively low solubility it may be necessary to add drocarbons and after heating the vapors to a suitable temperature within the ranges previously specified to pass them through stationary masses of granular catalytic material in vertical cylindrical treating columns or banks of catalystner depending upon their composition. Yieldsmay obviously be increased by recycling unconverted materials, although this is not specifically characteristic of the present invention.

The following examples are given to indicate the character of the results obtainable by the use of the process but not with the intention-of correspondingly limiting its proper scope.

Example I The catalyst used consisted of activated alu mina granules of approximately 10-20 mesh supporting about 15% by weight of vanadium oxide.

The preparation was made by using the principles outlined in the foregoing specification.

Cycle-hexane vapors were passed over the bed of the solution in successive portions to the adsorbent base catalyst with intermediate heating to drive off solvent in order to get the required quantity of promoter deposited upon the surface .and in the poresof the base catalyst. The temperatures used for drying and calcining after the addition of the promoters from solutions will depend entirely upon the individual characteris-.

catalyst granules at a temperature of 525 C. at substantially atmospheric pressure at a rate corresponding to approximately 12 seconds contact time. In a once-through operation, a 25% yield of benzene was obtained and by recycling, an ultimate yield of was possible. Tests for olefins in the products could be obtained, but there was no indication of isomerization reactions.

Example II A catalyst comprising about 12% of columbium oxidessupported upona prepared granular silica was used to dehydrogenate methyl-cyclo-hexane, using a temperature of'530" C. and various times of contact. In the following table, the rate of Toluene pro- (uniaettime, seconds auction We claim as our invention:

1. A process for the dehydrogenation of naphthene hydrocarbons which comprises subjecting the vapors of said hydrocarbons to contactunder dehydrogenating conditions with gamma alumina supporting a compound or a metal selected from those in the lefthand column of group V of the periodic table consisting of vanadium, columbium, and tantalum.

2. A process for the dehydrogenation of naphthene hydrocarbons which comprises subjecting the vapors of said hydrocarbons at a temperature within the approximate range of 400+6f50 C. to contact with gamma alumina supporting a compound of a metal selected from those in the lefthand column of group V of the periodic table consisting of vanadium, columbium, and tantalum. I

3. A process for the dehydrogenation of naphthene hydrocarbons which comprises subjecting the vapors of said hydrocarbons at a temperature within the approximate range of 400-650 C.-under a pressure of from atmospheric to 100 lbs. per square inch to contact with gamma alumina supporting a compound of a metal selected from those in the lefthand column of group V or the per hour/100 g.

catalyst consisting oi' vanadium, columbium, and tantaium.

,5. A process forv the dehydrogenation of naphthene, hydrocarbons which comprises subjecting the vapors or said hydrocarbons at a temperature within the approximate range of 400-650 0. un-

der a pressure of from atmospheric to 100 lbs.

per square inch for a time of 0.01-80 seconds to contact with gamma alumina supporting a minor amount, of the order of less than 20% by weight.

or a compound 01' a metal selected those in the lefthand column of group V or the periodic table consisting oi. vanadium, columbium, and tantalum.

6. A process for the dehydrogenation of naphthene hydrocarbons which comprises subjecting the vapors 01' said hydrocarbons at a temperature within the approximate range 01400-650 0. under a pressure of from atmospheric to 100- lbs. per. square inch for a time'of 0.01-80 seconds to contact with gamma alumina supporting a minor amount, of the order of less than 20% by weight, of vanadium oxide.

7. A process for the dehydrogenation of methyl-cyclo-hexane to produce toluene therefrom which comprises subjecting the vapors of said methyl-cyclo-hexane to contact under dehydrogenating conditions with gamma alumina supporting a compound of a metal selected from those in the lefthand column of group V or the periodic table consisting of vanadium, colum- I periodic table consisting of vanadium, colum- I per square inch for a time of 0.01-60 seconds to as bium, and tantalum.

8. A process for the dehydrogenation of cyclohexane which comprises subjecting the vapors o! the cyclo-hexane to contact under dehydrogenating conditions with gamma alumina supporting a compound or a metal selected from those in the lefthand column 01' group V of the periodic table consisting of vanadium, columbium, and tantalum.

ARISTID V. GROSSE. WILLIAM J. MA'I'IOX.