US2322025A - Conversion of hydrocarbons - Google Patents

Description

Patented June 15, 1943 CONVERSION OF HYDROCARBONS Vladimir N. Ipatleflf and Arlstid v. Grosse, Chi- 111., assignors to Universal 011 Products Company, Chicago, 111., a corporation of Dela-- ware No Drawing. Application April 3, 1939,

. Serial No. 265,776

4 Claims. (Cl. 260-683) with the practical application of a new type of reaction involving "catalysts in the transfer of combined hydrogen from one type of hydrocarbon to another. The process may involve the interaction of hydrocarbons in synthetic mixtures and is particularly applicable in the case of the hydrocarbon gas mixtures produced incidental to oil cracking operations.

In the cracking of heavy hydrocarbon fractions representing residua and the heavier distillates from petroleum with the primary object of producing maximum yields of low boiling gasoline hydrocarbons there is invariably produced a considerable amount of normally gaseous hydrocaresters and as a basis for the manufacture of halogen derivatives and certain secondary chemical products. However, from the petroleum refiners standpoint greater interest attaches to the reconversion of as much as possible of the gaseous products of straight run distillation and cracking into gasoline, since the average refinery has a superabundance of fuel of all kinds and frequently the fixed gas production is in excess of the total refinery requirements, including steam generation. The marketing of the excess gas as domestic and industrial fuel has been undertaken to some extent but in this case the demand fluctuates with the seasons and the storage and hanwithin the normal range of present day motor bons which at the present time are utilized prin- Hydrogen Butanes Methane Butylenes Ethane Pentanes Ethylene Amylenes Propane Hydrogen sulfide Propylene Inasmuch as the gaseous products of the cracking reaction may at times amount to from 10 to by weight, of the original oil cracked, it is obviously a matter of some importance to make the most efiicient use of the gaseous by-products.

The so-called natural gases produced alone or in conjunction with the production or primary distillation of petroleum comprise the paraflin hydrocarbons indicated in the above table, being substantially devoid of hydrogen and olefins. As will be later developed these gases may also constitute a source of starting material for the present process. The olefinic constituents in cracked hydrocarbon gas mixtures have been employed to some extent as starting material for the manufacture of alcohols by treatment with acids such as sulfuric followed by the hydrolysis of the acid fuels, that is, from about to 400 F., since the dimers and a considerable number of the trimers and the mixed polymers producible from the olefinic constituents of the gases boil within this range. Development work has been divided along the lines of either straight heat treatment or catalytic polymerization. In the former case the yields are inclined to be low and the process requires very careful manipulation so that in general it may be said that the industry is in favor of the catalytic processes when dealing with cracked gas mixtures. These processes have employed numerous catalytic materials including mineral acids such as sulfuric and phosphoric acid alone or with spacing or carrying agents and also certain metallic salts having polymeriz-' ing properties such as, for example, aluminum chloride, zinc chloride, etc. Some attempts have been made to utilize solid contact materials of the nature of fullers earth but without any signal success.

In catalytic polymerization processes the principal efiectsare observed in connection with the olefins containing more than 2 carbon atoms, to wit, propylene, alpha and beta butenes and isobutylene, the readiness with which these polymerize being inverse to the order in which they were just given. In regard to ethylene this compound is so much more difficult to polymerize than the higher gaseous olefins that in most cases it is substantially unaffected under conditions which readily polymerize propylene and the butylenes. If more severe conditions are employed the ethylene tends to polymerize more to form higher boiling polymers than those of gasoline boiling range although in certain instances it is evident that ethylene undergoes some condensation reactions with the other olefins of higher molecular weight. The polymers produced by the combination of gasoline olefin molecules are of high antiknock value and relatively stable and thus are very desirable blending fluids for raising the octane number of straight run gasolines.

In present day gas utilization processes, the paraffins are of the least value since as such they are unreactive and not capable of forming liquids except in small amounts under severe conditions of pyrolysis, which are seldom economical. The conversion of the propanes and the butanes in cracked or natural gases into olefins which are readily polymerizable is an important feature of the present invention, which stands as an improvement in the art of utilizing the gaseous byproducts encountered both in the straight and in the destructive distillation of petroleum.

In one specific embodiment the present invention comprises the production of olefins of more than 2 carbon atoms by reacting the corresponding arafilns with ethylene in the presence of catalysts particularly adapted to accelerating the reactions. 7

The type of reactions with which the present process is concerned is exemplified by the two following equations which show the interaction of ethylene with 3 and 4 carbon atom parafiin hydrocarbons respectively, whereby ethane and 3 and 4 carbon atom olefins are produced.

1. CzHi CaHa CzHo CaHe Catal st Ethylene propane ethane propylene 2. C2H4 CiHio Catalyst ClHa 04H! Ethylene butane ethane butylene We have found that, in the presence of suitable catalysts which will be presently described in detail, it is possible to effect an almost quantitative transfer of hydrogen from\paraiiin to ethylene so that it becomes saturated and in effect its unsaturation is transferred to the compounds of higher molecular weight to yield olefins. The value of such catalyzed reactions is at once apparent in that the resulting olefins are readily polymerized by various types of catalysts to form gasoline boiling range polymers of superior antiknock value and generally stable characteristics. It is further evident that by this type of reaction increased proportions of refinery gases including straight run and cracked gases are made available for the production of gasoline. The ethane produced in the above equations may be dehydrogenated in the presence of the same general types of catalysts suited to the above reactions and reused almost indefinitely so that the process is substantially cyclic and may be operated at a high efiiciency.

The progress of the above equations depends largely upon the preferential afilnity of ethylene for hydrogen in the presence of the preferred catalysts. The types of catalysts which may be employed for furthering and promoting the extent of the above type of reactions are certain of those which have been found to be effective in.

so-called dehydrogenation reactions. In other words, such catalysts have value in promoting the splitting oil of a molecule of hydrogen from a paraflin to produce the corresponding olefin and we have now determined that some of the same materials are particularly 'eifective in transferring hydrogen from parafilns to ethylene, the ethylene acting as an "acceptor" of the released hydrogen, and enabling the reactions to proceed rapidly to equilibrium.

The preferred catalysts in accordance with the present invention consists of alumina (preferably activated) supporting certain alkaline earth metal salts and the oxides of the heavy metals chromium, molybdenum, and vanadium. Alternatively, the chromates and molybdates of beryl1ium, magnesium, calcium, barium, strontium, and zinc may be employed although as a rule the preferred catalyst composites comprise alumina plus oxides of chromium, molybdenum, and vanadium. The materials added to the alumina to increase its catalytic activity are usually less than 25% by weight of the total composites although it is not intended to limit the invention to this particular range of concentration.

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 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.

f Three hydrated oxides of aluminum occur in nature, to wit, hydrargillite or gibbsite having the formula Al203.3HzO, bauxite having the formula A]2O3.2H2O, and diaspore having the formula A.l2O3.HzO. Of these 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 as supports for the preferred catalytic substances. Precipitated trihydrates can also be dehydrated at moderately elevated temperatures readily polymerizable olefins e. g. propene and After the reactions ar completed in any given instance the gas mixture containing the higher molecular weight oleflns may be contacted directly with suitable polymerizing catalysts such as, for example, the so-called solid phosphoric acid catalysts, to remove the olefins and the ethylene necessary for further reaction may be -re'- generated from the residual ethane by dehydrogenating it using the same general types of catalysts employed in the main reactions.

Best results in regard to olefin production are usually obtained when a given paraflin is reacted with its molecular equivalent of ethylene. Howliquid polymers for blending with inferior knock I rating gasolines.

In the case of stabilizer refluxes operated in conjunction with oil cracking plants it is usually good practice to polymerize the 3 and 4 carbon atom olefins by the useof effective catalysts and then add regulated amounts of ethylene to the gas mixture for the conversion of the residual 3 and 4 carbon atom paraflins to their corresponding olefins by reactions of the present character.

The following example is given to illustrate the character of the results obtainable by the use, of the present process although it is not to be looked upon in a limiting sense as regards the scope of the invention, since other data are available. A mixture of ethylene and normal butane w passed at atmospheric pressure and a tempera-- ture of 450 C. over a catalyst comprising aluminum oxide and having deposited thereon about 5% of chromium trioxide. The composition of the inlet and exit gases is given below:

Inlet gas Exit gas Per cent Per cent Ethylene 26 i 2 n-Butane 56 Ethane 0 2o Butylenes 0 2o Hydrogen 0 2 Th analysis indicates that the ethylene was converted to ethane with a relatively high emciency, that there was very little hydrogen actually released as such in the course of the reactions and that practically all the conversion products arising from the n-butane were butylenes. These conditions generally obtain up to equi-molecular mixtures of butane and ethylene, though the efliciency of the desired reaction drops oiT slightly and somewhat larger quantitles of free hydrogen appear. Thus with any given paraflin which is to be converted into an olefin by the present type of reaction, a proportion of ethylene to paraflln would be reached corresponding to maximum efliciency when utilizing a recycling operation so that the unconverted paraflin is returned for further catalytic treatment and dehydrogenation.

The foregoing descriptive section shows at once the novelty and utility of the present invention and the numerical data presented are suflicient for its commercial value. However,

neither section is intended to be unduly limiting.

We claim as our invention:

1. A process which comprises reacting a. paraffin containing more than two carbon atoms with ethylene in the presence of a catalyst eflective in transferring hydrogen from the paraflin to the ethylene, thereby forming ethane and an olefin of more than two carbon atoms, subjecting the admixed ethane and olefin to polymerization to convert the latter to liquid and thereby separate it from the ethane, dehydrogenating the separated ethane and supplying resultant ethylene to the first-mentioned step of the process.

2. The process as defined in claim 1 further characterized in that said catalyst comprises alumina supporting an oxygen-containing comalumina supporting an oxygen-containing compound of vanadium.

VLADIMIR N. IPATIEFF. ARISTID V. GROSSE.