US2375021A - Treatment of hydrocarbons - Google Patents

Description

UNITED STATES PATENT OFFICE TREATMENT OF HYDROCARBON S Jacque C. Morrell, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 11]., a

corporation of Delaware No Drawing. Application March 25, 1939, Serial No. 264,206

15 Claims.

This invention relates particularly to the treatment of aliphatic or straight chain hydrocarbons which are either completely saturated, as in the case of the parafiinic hydrocarbons, or straight chain hydrocarbons which may be unsaturated to the extent of their possessing one double bond between carbon atoms, as in the case of the monoolefinic hydrocarbons. The invention is directed primarily to the treatment of aliphatic hydrocarbons having less than 6 carbon atoms in straight chain arrangement, including ethane, ethylene, propane, propylene, butanes, butylenes, pentanes, and amylenes, although it may also be applied to hydrocarbons of more than six carbon atoms. This application is a continuation-inpart of my prior application Serial No. 101,261, filed September 1'7, 1936.

In a more specific sense the invention is concerned with a new and improved type of process for controllably increasing the degree of unsaturation in hydrocarbons of the character mentioned so that, for example, a paramn hydrocarbon may be converted either into its-corresponding mono-oi n or di-olefin or a mono-olefinic hydrocar on may be convertd'i'fito a di-olefin with a practicalmifi'i'mum of undesirable side reactions.

The present process is concerned with the more efficient utilization of aliphatic hydrocarbons of the types mentioned above in that they are convenrted by dehydrogenation into compounds of a more reactimharactenwhich are readily uti- Iizable in the production of polymers and miscellaneous hydrocarbon derivatives useful in the arts.

In the complete utilization of petroleum to form maximum yields of automotive fuel there is a considerable proudction of gaseous parafflnic hydrocarbons which are dissolved in the crude oils as produced and evolved as a light out in the production of straight run gasoline and there are further quantities of similar parafllnic gases produced in connection with the natural gas and natural gasoline industries. These gases are too volatile for direct utilization as motor fuel except in special instances, and at the present time their principal use is as domestic fuel. Owing to their generally unreactive character, it is difficult to transform them into increased yields of motor fuel unless they are converted into their corresponding olefinic counterparts by splitting off a molecule of hydrogen. After this is done the resulting olefins may be polymerized either by heat alone or by heat and catalysts to form gasoline boiling range polymers which are of high antiknock value and eminently suitable as blending fluid for increasing the knock-rating of straight run gasolines which are usually inferior in this respect.

In applying the present invention to the manufacture of mono-olefins from normally gaseous parafllns, the invention is related to processes involving the more complete utilization of the gases produced in connection with the production and refining of petroleum since the oleflnic gases are readily polymerizable by various thermal and catalytic methods to produce liquid polymers having a relatively high octane rating and boiling within the range of gasoline and which may be either utilized as such as hydrogenated to corresponding liquid parafflns. Thus according to the present process the residualwamns remaining after the olefins primarily present in cracked gas mixtures have been polymerized, may be subjected to the treatment to produce additional quantities of polymerizable olefins.

In the process for manufacturing diolefins either from parafiins or mono-olefins according to the present process the invention is related to the synthetic rubber problem in that butadicues and their alkylated derivatives are producible from 4 and 5 carbon atom aliphatic hydrocarbons and these butadienes are polymerizable to form high molecular weight polymers closely resembling natural rubber.

In experimenting with methods and conditions for converting parailln hydrocarbons into oleflns by dehydrogenation, a considerable number of catalytic materials have been tried with greater or lesser effectiveness, since it has been found generally that better results in the matter of yield of olefins without the formation of liquid and gaseous by-products are obtainable by the use of catalysts rather than by the use of heat alone, and furthermore that under proper catalytic influences temperatures, pressures, and time factors are lower, so that less expensive apparatus may be employed and greater capacities insured.

In one specific embodiment the present invention comprises the treatment of parafllnic or mono-olefinic hydrocarbons for the dehydrogenation thereof by subjecting said hydrocarbons at temperatures of the order of 450-700 C, and relatively low pressure to contact with solid granular catalysts consisting essentially of aluminum mixed with or supporting oxides of the elements in the left-hand colfimn of group 4 of the periodic table, which oxides have'ben found to have relatively high catalytic activity in furthering 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 aliphatic hydrocarbons to produce a minimum of undesirable byproducts. Temperatures from approximately 450 to 700 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 atmosphere absolute or lower and times of contact from approximately 0.1 to 6 seconds. In the case of the dehydrogenation of paraffinic hydrocarbons to produce the corresponding mono-olefins, temperatures within the approximate range of 450 to 650 may be employed. atmospheric pressures and times of conact of the order of 0.1 to 10 seconds. When producing di-olefins from mono-olefins, temperatures from 500 to 700 C. are preferred, absolute pessures of approximately 0.25 atmosphere and times of contact of less than 1 second. When it is desired to produce diolefins directly from paramns without a primary stage involving the production and segregation of the mono-olefins, intermediate conditions of operation may be employed which will be more or less fixed by the molecular weight and constituents of the paramn or mixture of parafilns to be subjected to treatment.

In accordance with the present invention, the catalysts which are preferred for selectively dehydrogenating aliphatic 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 ofl 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 catalytic work has been done on a purely empirical basis, though at times certain groups of elements or compounds have been found to be more or less equivalent in accelerating certain types of reaction. For example, the noble metals, platinum and palladium, have been found to be efiective in dehydrogenating reactions, particularly in dehydrogenating naphthenes to form aromatics, but these metals are expensive and easily poisoned by traces of sulfur so that their use is considerably limited in petroleum hydrocarbon reactions.

The present invention is characterized by the use of a particular group of composite catalytic materials which contain aluminum oxide which in itself has some catalytic ability in the dehydrogenating reactions but which is improved greatly in this respect by the addition to or admixture therewith of certain other catalysts (most generally in minor proportions), which comprises the oxides of the elements in the lefthand column of group 4 of the periodic table which includes titanium, zirconium, cerium, hafnium, and thorium.

It is essential to the preparation of these ac- I tive and selective dehydrogenative catalysts that the aluminum oxide used possess certain structural characteristic s permitting the maintenance on its surface and in its pores of a stable deposit of the more active oxide catalysts which is essentially undisturbed under the conditions of operation and when regenerating by burning ofi carbonaceous deposits with air or other oxygen-containing ga mixtures.

The more active compounds which are used in the catalyst composites according to the concepts of the present invention include the oxides of titanium, zirconium, cerium, hafnium, and thorium which constitute a natural group since they are the elements in the lefthand column of group 4 of the periodic table. While the oxides of these elements are effective catalysts in the dehydrogenation reactions, it is not intended to infer that the different oxides of any one element or the correspondingoxides of the difierent elements are exact equivalents in their catalysts activity. Furthermore, some of the elements such as titanium and zirconium are of more common occurrence and more readily obtainable whereas the elements hafnium and thorium are rare and expensive and not frequently used in practice.

Catalyst composites may be prepared by utilizing the soluble compounds of the elements containing a volatile radical in aqueous solutions from which they are absorbed by the prepared alumina or from which they are deposited upon the alumina by evaporation of the solvent, after which the volatile radical is driven off by heat. The invention further comprises the use of catalyst composites made by mixing compounds of the above-mentioned character or prepared oxides with the alumina either in the wet, dry or fused condition. In the following paragraphs some of the compounds of the elements listed above are given which may be used to add the catalytic oxides to the alumina. The known oxides of these elements are also listed.

Titanium Compounds which will ultimately yield titanium catalysts on heating to a proper temperature may be absorbed by stirring them with warm aqueous solutions of soluble titanium compounds, such as for example titanium nitrate having the formula 5TiO2.N2O5.6H2O, which is sufliciently soluble in warm water to render it readily utilizable as a source of titanium oxides, of which the lower oxides are generally the best catalysts. The oxide resulting from the decomposition of such compounds as the nitrate and the hexahydrate is for the most part the dioxide T102. This oxide, however, is reduced by hydrogen, or by the gases and vaporous products resulting from the decomposition of the mono-olefins treated in the first stages of the reactions so that the essential catalyst for the larger portion of the period of service is probably the sesquioxide TizOa.

Zirconium The soluble compounds of zirconium which may be used as primary sources of catalytic oxides in aqueous solution include the slightly solube zirconium ammonium fluoride, the tetrachloride, the fluoride, the iodide and particularly the more soluble selenate and sulfate. The crystalline selenate has the formula Zr (S604) 2.4H2O

and the sulfate which is the more soluble of the two, has the formula Z1(SO4)2.4H2O. As in the 40c, Ln gm; 2 n z, ca-soon CUVlPUUNDS.

case of the other alternative elements the tetrahydroxide of zirconium may be precipitated from a solution of the sulfate or other soluble salt onto the surface and in the pores of an activated alumina carrier by the addition of alkaline carbonate or hydroxide precipitants, after which the zirconium hydroxide is ignited to produce the dioxide. The principal oxide of zirconium is the dioxide and there is little evidence to indicate the existenc of a monoxide since the dioxide is not reducible by hydrogen at moderate temperatures and it has been shown that carbon in the electric furnace reduces the dioxide directly to the metal.

Cerium A properly prepared and activated alumina is ground and sized to produce granules of relatively small mesh of the approximate order of from 4 to and these may be caused to absorb compounds which will ultimately yield oxides of cerium on heating to a proper temperature by stirring them with warm aqueous solutions of soluble cerium compounds, such as for example cerium nitrate having the formula Ce (N03) 3.6H2O

which is sufiiciently soluble in warm water to render it readily utilizable as a source of cerium oxides. Other soluble compounds which may be used to form catalytic deposits containing cerium are the various alkali metal cerous nitrates, such as for example sodium cerous nitrate having the formula 2NaNO3.Ce(NO3)3.H2O. Cerium has a number of oxides including the trioxide CeOa, the dioxide C602, the heptoxide Ce4O'z, and sesquioxide C6203. The dioxide results from the ignition of cerous nitrate, cerous sulfate, cerous carbonate or cerous oxalate and also from the ignition of ceric nitrate, ceric sulfate or ceric hydroxide. Hydrogen reduces the dioxide to the heptoxide, and it is probable that this oxide plus a certain amount of the sesquioxide are the most active dehydrogenating catalysts in the case of cerium,

Hafnium In general the properties of hafnium from a chemical and to some extent a catalytic standpoint are intermediate between those of zirconium and thorium though in most reactions hafnium more closely corresponds to those of zirconium. There is but one known oxide, the dioxide HfOz and this oxide is not readily reducible and probably exists as such when used in minor proportions as a constituent of catalyst composites in hydrocarbon dehydrogenation reactions. Soluble compounds of hafnium include the oxychloride having the formula HfOC12.8H2O and the oxalate which is soluble in an excess of oxalic acid. The mixing of this oxalate solution with alumina and the evaporation of the solution gives a residual material which can be ignited to leave a residue of the dioxide, On account of the rarity of hafnium its compounds are seldom commercially utilizable although the oxide in particular has been found to exert a good catalytic influence in the types of reactions under consideration.

Thorium The element thorium furnishes a number of compounds which can be used as primary sources of catalytic oxides for deposition upon alumina. The following compounds are sumciently soluble in water to enable them to be used in aqueous Qinislws solution to saturate prepared granular alumina particles; the bromide ThBr4, the chloride ThoOl4, the iodide ThI4, and the nitrate Th(NosM which is most conveniently used as the tetrahydrated or dodecahydrated salt. From any of the soluble salts mentioned the tetrahydroxide Th(OH) 4 may be precipitated by the use of alkali carbonates or alkali hydroxides and then ignited to produce the dioxide. The nitrate may be directly ignited, or course, to produce the dioxide.

While the identification of some other oxides of thorium such as the pentatrioxide ThsOs and the monoxide Th0 has been claimed as well as a peroxide having the formula ThzOv, it has been shown that the principal oxide catalyst in operations of the present character is the ordinary dioxide.

Aluminum oxides prepared by careful calcination of certain natural hydroxides and carbonates and by carefully regulated chemical precipitation of aluminum hydroxide followed by calcination are practically always good supporting materials for the preferred dehydrogenating oxides in accordance with the present invention. While some form of alumina may have in themselves some slight dehydrogenating activity, an extensive series of experiments has definitely shown that any inherent catalytic property which different forms of prepared alumina may have made be greatly increased by the addition of oxides of the present character in amounts usually of the order of less than 25% of the total composite of alumina and the oxide.

Aluminum oxide suitable as the base material for the manufacture of catalysts for the process may be obtained from some natural aluminum oxide minerals or ores such as bauxite or carbonates such as dawsonite by proper calcination, prepared by precipitation of aluminum hydroxide from solutions of aluminum sulfate, nitrate, chloride, or different other salts, and dehydration of the precipitate of aluminum hydroxide by heat. 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.

Three hydrated oxides of aluminum occur in nature, to wit, hydrargillate or gibbsite having the formula AI2O3.3H2O, bauxite having the formula Al2O3.2H2O, and diaspore having the formula Al2O3.H2O. Of these three minerals the corresponding oxides from the trihydrated and dihydrated minerals are suitable for the manufacture of alumina for the present type of catalysts and these materials have furnished types of activated alumina which are entirely satisfactory. Precipitated trihydrates can also be dehydrated at moderately elevated temperatures to form satisfactory alumina supports.

It is best practice in the final steps of preparing substantially anhydrous aluminum oxides for use in the catalyst composites to ignite them for some time at temperatures within the approximate range of from 800-900 C. This does not correspond to complete dehydration of the hydrated oxides but gives catalytic materials of good strength and porosity so that they are able to resist for a long period of time the deteriorating effects of the service and regeneration periods to which they are subjected.

While other forms of aluminum oxide may be used, it is of considerable advantage to employ the type of aluminum oxide known as gammaalumina, by which is meant the modification obtained by the dehydration of the mono-hydrate termed bohmite (Al0.0H) or the tri-hydrate Al(OH)a termed hydragillite (or gibbsite, when occurring in nature), at temperatures above 250 C. and preferably of the order of 350-500 C. until a substantial equilibrium is established corresponding to the removal of substantially all of the water and the formation of crystals falling within the regular or cubic classification. Gamma-alumina is characterized by definite 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 diffraction pattern. The gamma-alumina crystallizes in the cubic system with the edge Of the unit cube being about 7.9 Angstrom units.

The most general method for adding the unreactive oxides to the prepared activated alumina, which has a high adsorptive capacity, is to stir the prepared granules of from approximately 4 to 20 mesh into solutions of salts which will yield the desired promoting oxides on ignition under suitable conditions. In some instances the granule 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, washed with water to remove excess solution, and then ignited to produce the desired residual oxide. In cases of certain compounds of relatively low solubility it may be necessary to add the solution in successive portions to the alumina with intermediate heating to drive off solvent in order to get the required quantity of compound deposited upon the surface and in the pores of the alumina. The temperatures used for drying and calcining after the addition of the promoters from solutions will depend entirely upon the individual characteristics of the compound added and no general ranges of temperatures can be given for this step.

In some instances promoters may be deposited from solutions by the addition of precipitants which cause the deposition of dissolved materials upon the alumina granules. As a rule methods of mechanical mixing are not preferable, though in some instances as in the case of hydrated or readily fusible compounds these may be mixed with the proper proportions of alumina and uniformly distributed during the condition of fusing r fiuxing.

Catalyst composites may be made by mixing alumina powders with the preferred oxides, by depositing hydroxides upon alumina powders suspended in solutions of the salts of the preferred metals, by absorbing aqueous acids or nitrates upon alumina powder or by co-precipitation of aluminum hydroxide and metal hydroxides, after which the dried and powdered materials are pelleted in any standard type of machine. Any obvious procedure necessary to obtain a pellet of uniform characteristics may be employed and any minor amount of lubricant may be used which is effective in preventing sticking or abrasion at the parts of the machine used.

In regard to the relative proportions of alumina and promoting oxides it may be stated in general that the latter are generally less than 25% by weight of the total composites, as these percentages usually give the best results from an activity and life standpoint, when considering all economic features. The effect upon the catalytic activity of the alumina caused by varying the percentage of any given oxide or mixture of oxides deposited thereon is not a matter for exact calculation but more one for determination by experiment. Frequently good increases in catalytic eflectlveness are obtainable by the deposition of as low as 1% to 5% of an oxide upon the surface and in the pores of the alumina, though the general average is about 15-20%.

In practicing the dehydrogenation of aliphatic hydrocarbons according to the present process a solid composite catalyst prepared according to the foregoing alternative methods is used as filler in a reaction tube or chamber in the form of particles of graded size or small pellets and the hydrocarbon gas or vapor to be dehydrogenated is passed through the catalyst after being heated to the proper temperature, under a deflnite pressure and for a time of contact adapted to produce the results desired. The catalyst tube may be heated exteriorly if desired to maintain the proper reaction temperature.

As an alternative and frequently preferable method of operation with the present types of catalysts, they may be used as refractory filling material in the form of bricks or special forms or as a coating upon bricks or other forms in furnaces of the'regenerative type which are alternatively blasted and then used as heating means to effect the desired conversion reactions. In such an operation a regenerative chamber may be filled with alternate layers of ordinary noncatalytic refractory forms and layers of catalytic materials. In this method of operation the heat necessary for the dehydrogenation reactions is added during the regenerating period which must be employed in any event to periodically remove carbonaceous deposits from the catalyst surfaces.

It has been found essential to the efficient and selective dehydrogenation of aliphatic hydrocarbons when using the present types of catalysts that the gaseous or vaporized materials be substantially free from water vapor. If appreciable amounts of steam are present, the catalytic activty is adversely aflected so that the active life is shortened, the need for regeneration becomes more frequent and a point is more quickly reached where regeneration is no longer effective. The reasons for this phenomenon are not entirely clear but may possibly be due to a certain degree of hydration of the more active catalytic components of the mixture or the hydration of the aluminum oxide support.

The exit gases from the tube or chamber may be passed through selective absorbents to combine with or absorb the unsaturated hydrocarbons produced. Mono-olefins may be selectively polymerized by suitable catalysts, caused to alkylate other hydrocarbons such as aromatics or treated directly with chemical reagents to produce desirable and commercially valuable derivatives. Di-olefins or di-olefln derivatives may be catalytically condensed or polymerized to form synthetic rubber products as already mentioned. After the olefins have been removed the residual gases may be recycled for further dehydrogenating treatment with or without removal of hydrogen.

Members of the present group of catalysts are selective in removing two hydrogen atoms from aliphatic hydrocarbon molecules to produce the corresponding straight-chain unsaturated products without furthering to any great degree undesirable side reactions, and because of this show an unusually long period of activity in service as will be shown in later examples. When, however, their activity begins to diminish it is readily regenerated by the simple expedient of oxidizing 4.0L), 91. me:

COiviPOUNDS.

with air or other oxidizing gas at a moderately elevated temperature, usually within the range employed in the dehydrogenating reactions. This oxidation effectively removes traces of carbon deposits which contaminate the surface of the particles and decrease their efficiency. It is characteristic of the present types of catalysts that they may be repeatedly regenerated without material loss of porosity or catalyzing efficiency.

The following examples are given to indicate the selective character of the dehydrogenation reactions produced by catalysts comprised within the present group, though they are merely selected from a large number and not given with the intent of unduly limiting the scope of the invention.

Example I The general procedure for manufacturing the catalyst was to dissolve titanium nitrate in cold water and utilize this solution as a means of eventually adding titanium oxides to a carrier. A saturated solution of titanium nitrate in 100 parts of water was prepared and the solution was then added to about 200 parts by weight of activated alumina which had been produced by calcining bauxite at a temperature of about 700 0., followed by grinding and sizing to produce particles of approximately 8-12 mesh. The particles were first dried at 100 C. for about two hours and the temperature was then raised to 350 C. in a period of eight hours. After this calcining treatment the particles were placed in a reaction chamber and the titanium oxides treated in a current of hydrogen at about 500 C. when they were then ready for service.

Using the granular catalyst particles prepared as above described, isobutane was passed through a treating tower containing them as a filler at atmospheric pressure and temperature of from 500-600 C., with a space velocity of from 500 to 800 per hour. At the temperatures employed, the dioxide was partially converted to the sesquioxide. The exit gas at 600 C. and about 4 seconds time of contact consisted of about 33% butylenes, 35% undecomposed i-butane and 33% hydrogen. Thus substantially 50% of the original isobutane was converted into butylenes and hydrogen.

Example II The procedure in the preparation of the catalyst was to dissolve cerous nitrate in water and utilize this solution as a means of adding cerium oxides to a carrier. 25 parts by weight of cerous nitrate was dissolved in about 100 parts by weight of water, and the solution was then added to about 200 parts by weight of activated alumina which had been produced by calcining bauxite at a temperature of about 700 C. followed by grinding and sizing to produce particles of approximately 8-12 mesh. The particles were first dried at 100 C. for about two hours and the temperature was then raised to 350 C. in a period of eight hours. After this calcining treatment the particles were placed in a reaction chamber and the cerium dioxide reduced in a current of hydrogen at about 500 C. to produce principally the oxide C9401 when they were then ready for service.

Pure n-butane was now passed through the catalyst bed at a temperature of 500 C. and atmospheric pressure and the following table summarized the results obtained in two runs wherein different contact times are used.

. 5 garn sh Contact time 3.0 sec. 7.0 sec.

Per Per cent cmt Butylenes 10.0 20. 0

It will be seen from the above data that the lower contact time was not suflicient to dehydrogenate to a practical extent. However, at the contact time of 7.0 seconds dehydrogenation was adequate, and also distinct and selective as shown by the fact that the volume of butylenes equalled the volume of hydrogen, within the accuracy of the analytical data.

After a considerable period of time the catalyst became fouled with carbonaceous deposits but could be readily regenerated to its original efilciency by heating in a stream of air at 500 C.

\ Example III A catalyst was prepared for use in dehydrogenating normal butanes by mixing about 15% by weight of finely divided hafnium dioxide with 4-20 mesh activated alumina particles, adding sufiicient water to make a pasty mix which was afterwards dried to leave the dioxide deposited upon the alumina.

Using the catalyst prepared as described as filler in a treating tower, normal butane was passed through at a temperature of 600 C. and a space velocity of 500 per hour at atmospheric pressure. The exit gas consisted of approximately 30% hydrogen, indicating that about 47 Example IV The catalyst used for dehydrogenating a relatively pure isobutane was prepared by incorporating a moderately saturated solution of thorium nitrate with activated alumina particles of approximately 10-30 mesh size. The concentration of the solution was adjusted so that uniform wetting of the particles was possible without having any appreciable excess of solution. The particles were then carefully dried and ignited at moderately elevated temperatures of the order of 300 C. to convert the nitrate into thorium dioxide.

Using the granular catalyst particles prepared as above described, isobutane was passed through a treating tower containing them as filler at atmospheric pressure and temperatures of from about 575-600 C., with a space velocity of 550 per hour. At the temperatures employed the dioxide was partially converted to the sesquioxide. The exit gase consisted of about 33% butylenes, 33% undecomposed i-butane, and 33% hydrogen. Thus substantially 50% of the original isobutane was converted into butylenes and'hydrogen.

Example V The same catalysts consisting essentially of alumina supporting a minor percentage of titanium dioxide as was used in Example I was employed to dehydrogenate a mixture of n-butenes consisting of approximately equal parts of the alpha and beta compounds. A temperature of approximatley 600 C., a pressure of 0.25 atmosphere, and a contact time of 0.65 second were used. In the products which were condensed by cooling at 80 C., 1,3-butadiene was found to be present in a concentration of about 36%, corresponding to a yield of about 20% based on the materials charged. The identification was made by means of the reaction with maleic anhydride, and further identification was made by the formation of the compound: 1,2,3,4-tetrabromobutane.

Example VI A catalyst was manufactured by precipitating zirconium hydroxide on granular particles of activated alumina by adding the particles to a warm aqueous solution of zirconium sulfate to which a dilute solution of sodium carbonate was added with continual agitation until the zirconium was precipitated. The particles were then filtered from the solution and washed with warm water after which they were ignited to produce a residue of zirconium dioxide on the catalyst granules. The ultimately prepared composite consisted of approximately 86% of alumina and 14% of zirconium dioxide.

Using the catalyst prepared in the above manner an equimolecular mixture of n-butenes was dehydrogenated at a temperature of 600 C., a-

pressure of 0.25 atmosphere, and a contact time of 0.80 second. In the products which were condensed by cooling at 80 C., 1,3-butadiene was found to be present in a concentration of about 34% corresponding to a yield of about 19 percent based on the materials charged. The identification was made by means of the reaction with maleic anhydride, and further identification was made by the formation of the compound 1,23,4- tetrabromobutane.

Example VII The catalyst employed was substantially the same as that used in Example II consisting principally of the cerium heptoxide C6407 deposited upon calcined bauxite particles.

A mixture of unsym-methylethylethylene and trimethylethylene obtained by dehydrogenation of tertiary amyl alcohol was dehydrogenated by passage over the catalyst at a temperature of 610 C., a pressure of 0.25 atmosphere and a contact time of 0.5 second. A once-through yield of 22% of isoprene was obtained, representing a conversion of about 50% of the pentene mixture charged. Isoprene was definitely identified by the preparation of its maleic anhydride addition produce, cis--methyl n tetrahydrophthalic anhydride, M. P. 62.5 C. to 635 C. The production of isoprene indicates concomitant isomerization reactions during the course of the dehydrogenation and shows that there is a tendency for isomeric amylenes to produce important yields of isoprene. The liquid products yielded a rubber-like material by treatment with sodium and other catalysts suitable for this reaction.

Example VIII The same catalyst described in Example III consisting of hafnium oxide on alumina particles was employed to selectively dehydrogenate normally liquid mono-olefins.

A mixture of unsym-methylethylethylene and trimethylethylene obtained by dehydrogenation of tertiary amyl alcohol was dehydrogenated by passage over the catalyst at a temperature of 605 C., a pressure of 0.25 atmosphere and a contact time of 0.65 second. A once-through yield of 24 of isoprene was obtained, representing a conversion of about 51% of the pentane mixture charged. Isoprene was definitely identified by the preparation of its maleic anhydride addition product, cis-5-methylA tetrahydrophthalic anhydride, M. P. 625 C. to 63.5 C. The production of isoprene indicates concomitant isomerization reactions during the course of the dehydrogenation and shows that there is a tendency for isomeric amylenes to produce important yields of isoprene. The liquid products yielded a rubber-like material by treatment with sodium and other catalysts suitable for this reaction.

Example IX The catalyst employed in this case was the same as that already described in connection with the dehydrogenation of butane in Example IV, comprising a small percentage of thorium dioxide supported on alumina.

A mixture of approximately equal parts of alpha and beta butenes was dehydrogenated at a temperature of 610 C., a pressure of 0.25 atmosphere and a contact time of 0.85 second. In the products which were condensed by cooling at C. 1,3-butadiene was found to be present in a concentration of about 35 per cent, corresponding to a yield of about 20 per cent based on the materials charged. The identification was made by means of the reaction with maleic anhydride, and further identification was made by the formation of the compound 1,2,3,4-tetrabromobutane.

I claim as my invention:

1. A process for the dehydrogenation of normally gaseous aliphatic hydrocarbons to produce unsaturated derivatives thereof, which comprises subjecting said aliphatic hydrocarbons at a temperature of the order of 450-700 C., absolute pressure of the order of 0.25 to 'l atmospheres, and time from approximately 0.1 to 10 seconds to contact with a solid granular catalyst comprising essentially aluminum oxide which has a relatively low catalytic activity supporting an oxide which has a relatively high catalytic activity selected from the group consisting of the oxides of titanium, zirconium, cerium, hafnium and thorium.

2. A process for the dehydrogenation of aliphatic hydrocarbons to produce unsaturated derivatives thereof, which comprises subjecting said aliphatic hydrocarbons at a temperature of the order of 450-700 C., absolute pressure of the order of 0.25 to 7 atmospheres, and time from approximately 0.1 to 10 seconds to contact with a solid granular catalyst comprising essentially activated aluminum oxide which has a relatively low catalytic activity supporting an oxide which has a relatively high catalytic activity selected from the group consisting of the oxides of titanium, zirconium, cerium, hafnium, and thorium.

3. A process for the dehydrogenation of paraifin hydrocarbons to produce dioleflns therefrom, which comprises subjecting said paraffin hydrocarbons at a temperature of the order of 500-700 C. subatmospheric pressure and time of the order of 0.01 to 2 seconds to contact with a solid granular catalyst comprising essentially aluminum oxide which has relatively low catalytic activity supporting an oxide which has relatively high catalytic activity selected from the group consisting of the oxides of titanium, zirconium, cerium, hafnium, and thorium.

4. A process for the dehydrogenation of paraflln hydrocarbons to produce dioleflns therefrom, which comprises subjecting said paraffln COMPOUNDS.

hydrocarbons at .a temperature of the order of 500-700 C., subatmospheric pressure and time of the order of 0.01 to 2 seconds to contact with a solid granular catalyst comprising essentially activated aluminum oxide which has relatively low catalytic activity supporting an oxide which has relatively high catalytic activity selected from the group consisting of the oxides of titanium, zirconium, cerium, hafnium, and thorium.

5. A process for the dehydrogenation of paraffin hydrocarbons to produce diolefins therefrom, which comprises subjecting said paraffin hydrocarbons at a temperature of the order of 500-700" C. subatmospheric pressure and time of the order of 0.01 to 2 seconds to contact with a solid granular catalyst comprising essentially a calcined aluminum hydrate of high adsorptive capacity supporting an oxide which has relatively high catalytic activity selected from the group consisting of the oxides of titanium, zirconium, cerium, hafnium, and thorium.

6. A process for the dehydrogenation of aliphatic hydrocarbons to produce unsaturated derivatives thereof, which comprises subjecting said aliphatic hydrocarbons at a temperature of the order of 450-700" C., absolute pressure of the order of 0.25 to '7 atmospheres, and time from approximately 0.1 to 10 seconds to contact with a solid granular catalyst comprising essentially aluminum oxide which has a relatively low catalytic activity supporting titanium oxide which has a relatively high catalytic activity.

7. A process for the dehydrogenation of allphatic hydrocarbons to produce unsaturated derivatives thereof, which comprises subjecting said aliphatic hydrocarbons at a temperature of the order of 450-700" C., absolute pressure of the order of 0.25 to 7 atmospheres, and time from approximately 0.1 to 10 seconds to contact with a solid granular catalyst comprising essentially aluminum oxide which has a relatively low catalytic activity supporting zirconium oxide which has a relatively high catalytic activity.

8. A process for the dehydrogenation of aliphatic hydrocarbons to produce unsaturated derivatives thereof, which comprises subjecting said aliphatic hydrocarbons at a temperature of the order of 450-700" C., absolute pressure of the order of 0.25 to 7 atmospheres, and time from approximately 0.1 to 10 seconds to contact with a solid granular catalyst comprising essentially aluminum oxide which has a relatively low catalytic activity supporting cerium oxide which has relatively high catalytic activity.

9. A process for the dehydrogenation of paraffin hydrocarbons to produce diolefins therefrom, which comprises subjecting said parafiin hydrocarbons at a temperature of the order of 500- secret ric 700 C., subatmospheric pressure and time of the order of 0.01 to 2 seconds to contact with a solid granular catalyst comprising essentially aluminum oxide which has relatively low catalytic activity supporting titanium oxide which has relatively high catalytic activity.

10. A process for the dehydrogenation of paraffin hydrocarbons to produce diolefins therefrom, which comprises subjecting said paraflin hydrocarbons at a temperature of the order of 500- 700 C., subatmospheric pressure and time of the order of 0.01 to 2 seconds contact with a solid granular catalyst comprising essentially aluminum oxide which has relatively low catalytic activity supporting zirconium oxide which has relatively high catalytic activity.

11. A process for the dehydrogenation of paraffin hydrocarbons to produce diolefins therefrom, which comprises subjecting said paramn hydrocarbons at a temperature of the order of 500- 700 C., subatmospheric pressure and time of the order of 0.01 to 2 seconds to contact with a solid granular catalyst comprising essentially aluminum oxide which has relatively low catalytic activity supporting cerium oxide which has relatively high catalytic activity.

12. A process for dehydrogenating aliphatic hydrocarbons which comprises contacting the same under dehydrogenating conditions with an oxide of an element from the left-hand column of group 4 of the periodic table, supported on an activated alumina comprising a calcined aluminum hydrate of high adsorptive capacity.

13. A process for dehydrogenating aliphatic hydrocarbons having less than six carbon atoms in straight chain arrangement which comprises contacting the same under dehydrogenating conditions with an oxide of an element from the left-hand column of group 4 of the periodic table, supported on an activated alumina comprising a calcined aluminum hydrate of high adsorptive capacity.

14. A process for dehydrogenating parafflnic hydrocarbons which comprises contacting the same under dehydrogenating conditions with an oxide of an element from the left-hand column of group 4 of the periodic table, supported on an activated alumina comprising a calcined aluminum hydrate of high adsorptive capacity.

15. A process for converting normally gaseous paraflins to olefins which comprises contacting the paraffins under dehydrogenating conditions with an oxide of an element from'the left-hand column of group 4 of the periodic table, supported on an activated alumina comprising a calcined aluminum hydrate of high adsorptive capacity.

JACQUE C. MORRELL.