US1994249A - Synthesis of hydrocarbons - Google Patents

Description

atented Mar. 12, 1935 UNITED STATES SYNTHESIS OF HYDROCARBONS Vladimir Ipatieif and Aristid V. Grosse, Chicago, 111., assignors-to Universal Oil Products Company. Chicago, 111., a corporation of Delaware No Drawing. Application August 31, 1932, Serial No. 631,270

2 Claims.

This invention relates to the manufacture of hydrocarbons and refers more particularly to the manufacture of hydrocarbons of a mixed alkylaryl character by the interaction of olefinic hy- 5 drocarbons with aromatic hydrocarbons.

In a more specific sense the invention comprises a process for the manufacture of alkyl derivatives of aromatic hydrocarbons which are of particular value as constituents of motor fuel in that they possess unusually high anti-detonating characteristics. The process of the invention further comprises the use of special catalysts and condi-, tions of operation for the manufacture of these valuable compounds which will be disclosed in the course of the following specification.

The relation between the chemical constitution of gasoline and its anti-knock value is complicated by difilculties encountered in completely analyzing the complex hydrocarbon mixtures which make up commercial motor fuel. In addition, it is not always to be assumed that the anti-knock value'as determined in test engines is an additive property when dealing when mixtures or blends. Investigations have shown the relation of chemical structure and anti-knock value in regard to pure hydrocarbon compounds, particularly cyclic compounds such as naphthenes and aromatics have less knocking tendency than hydrocarbons of open chain structure. The present invention is unique in that a process has been developed for the manufacture of a class of compounds of mixed character which are uniformly of a high anti-knock value.

In one specific embodiment the invention comprises the production of high'anti-knock hydrocarbons of a mixed alkyl-aryl character by interacting olefin hydrocarbon mixtures with aromatic and/or reactive benzenoid hydrocarbons in two stages, the first stage comprising the reaction of olefins of higher molecular weight than ethylene in the presence of sulphuric acid and the second stage comprising the similar reaction of ethylene in the presence of compounds of aluminum halides and aromatic hydrocarbons.

As the process is particularly directed to the efllcient utilization of the oleflns contained in commercial gas mixtures in producing'hydrocarbons of high anti-knock value for use in blending with gasolines inferior in this respect, the following discussion which is given for the purpose of exactly describing the character of the invention will be given in connection with the utilization of gases from oil cracking processes, particularly processes concerned wth the production of high yields of gasoline by cracking the heavier and less valuable portions of petroleum, though the invention is not entirely limited to this field as onthe one hand gas mixtures produced from other hydrocarbon starting materials may be employed and on the other hand any type of aromatic hydrocarbon or hydrocarbon oil mixture that possesses the requisite reactivity with the olefins in the presence of the preferred catalysts.

The following analysis is given as typical of the composition of gases from commercial oil cracking processes though the relative percentages of the compounds vary widely from the figures given depending upon the oils cracked and the conditions under which they are treated.

- Volume Percent Acetylene Ethylene 4.6 Propylene 5.4 i-butene 2.9 1.3 butadiene 4.3

Methane 26.6 Ethane 21.1 Propane 16.3 n-butane 1.5 i-butane 0.8 n-pentane 1.9 i-pentane 1.7 Hydrogen 5.8 Carbon monoxide 0.5 Carbon dioxide 1.5 Nitrogen 4.7

It will be observed that the percentage of unsaturated hydrocarbons in the gas mixture is 17.6% and it may be stated that this figure is fairly representative of the percentage of olefins in gases from commercial cracking processes though under very intensive conditions of cracking the percentage of unsaturated hydrocarbons may run as high as 40 to 50%. Owing to the general utilization of the cracking process for producing gasoline at the present time gases of this character are produced in enormous quantities though as yet but little progress has been made in their eflicient utilization other than as fuel. Ethyl and isopropyl alcohols are manufactured to some extent from ethylene and propylene respectively by, for example, absorption of these oleflns in sulphuric acid of moderate strength and subsequent hydrolysis of the alkyl sulphates under carefully controlled conditions of operation. Ethylene is also converted into ethylenev glycol by chlorination followed by hydrolysis usually under pressure and a few ether derivatives of ethylene glycol are being manufactured. However, the great bulk of such gases is'at present not utilized except as fuel.

In the utilization of gases from commercial cracking processes according to the first step of the present invention they are contacted with aromatic hydrocarbons such as benzol, toluol, the xylols and other .benzol homologs in the presence of sulphuric acid. When conditions of operation are properly controlled, particularly as to strength on of sulphuric acid and temperature of treatment, the tendency toward polymerization of the olefins is minimized and the major portion of the olefins combines directly with the aromatics to form hydrocarbons of a mixed character. The exact role of the sulphuric acid in the reactions of condensation is difficult to determine, but it would appear that intermediate alkyl sulphates are formed from which the alkyl residue splits off to join an aromatic radical, the hydrogen from the aromatic serving to regenerate the sulphuric acid. Insofar as the reactions follow this course, sulphuric acid is not consumed but functions entirely catalytically. However, some loss is apparently unavoidable but owing to the valuable character of the compounds produced as will be developed later in the specification, the consumption of acid is not uneconomical.

The reactions between propylene and benzol in the presence of sulphuric acid at temperatures in the range of 40 to F., may be cited as typical of the reactions involved in the first step of the process. To produce these reactions propylene is passed into a well stirred mixture of benzol and 25-- concentrated sulphuric acid in proper proportions, the main product being monoiso-propyl benzol according to the following reaction:

1 4) a o'i' o o= o a 3 7 Propylene Benzol Mono-iso-propyl benzol There is also produced concurrently a limited yield of di-iso-propyl benzol according to the following equation:

(H2804) ZC HH- C l-Io a 4( a 1)a Propylene Benz'ol Di-iso-propyl benzol the relative production of the two compounds being dependent upon such factors as the relative proportion of the two hydrocarbons employed, the amount and strength of sulphuric acid present and the exact temperature which to some extent controls the rate and course of the reaction.

Similarly condensations between butylenes, amylenes, heptylenes, etc., and benzol or its homologs may be produced with a minimum degree of polymerization occurring between the olefinic hydrocarbons. While the sulphuric acid catalyst employed i the first stage of the process (in a manner and in quantities to be later described) is effective in .causing the interaction of olefins higher than ethylene with benzol and its homologs, it is pracof utilization.

In general such compounds are formed when solutions of such aluminum salts as the chloride AIC13 and the bromide AlBrs are dissolved in aromatic hydrocarbons such as benzol, toluol, xylol, etc., and reaction is brought about by the introduction of halogen acids at ordinary or somewhat elevated temperatures. As a specific example of the manufacture of typical catalyst substances,

the production of compounds of the general formula A12x6.C6HnR6n may be cited, in which X equals a halide and R equals an alkyl residue. A compound included in this class has the formula Al2Cl6.CsHa(C2H5)3, which may thus be looked upon as an addition compound between two molecules of aluminum chloride and one molecule of tri-ethyl benzol. ,While the formula represents the essential composition of the substance as regards its catalytic action, it may be further loosely combined with additional amounts of benzol. To produce compounds of this character anhydrous aluminum halides, particularly the chloride,

are dissolved in suitable solvents such as benzol which also contains an alkylated aromatic in solution. Dry hydrochloric acid gas is then bubbled through the solution and as evidence of a reaction taking place, the solution first becomes turbid and gradually separates a lower layer of orange to brownish colored liquid which is the catalyst desired.

The invention comprises the use of definite individual compounds of the character stated and the use of mixtures of variable composition with the percentage of the different components adjusted to produce optimum effects upon any given reaction or set of reactions. Obviously each particular individual compound or mixture of compounds will exert its own special catalytic infiuence in any given case and not be exactly equivalent to the action of the other substances which may be used alternatively. Catalytic compounds may be produced from aluminum halides and any homolog of benzol or polynuclear hydrocarbons such as naphthalene, anthracene. etc., insofar as their physical properties in regard to melting, boiling and decomposing temperatures may permit.

The types of catalyst preferred for the second step of the process are characterized by a model'- ate and readily controllable activity, in contradistinction to that of many other condensing agents such as, for example, aluminum chloride, zinc chloride, etc., which are more inclined to induce polymerization among the olefins instead of furthering their union with aromatic hydrocarbons to form derivatives of the desired character. Furthermore, they have markedly less tendency to induce combination of halide such as chlorine or bromine with the hydrocarbons undergoing treatment so that no difliculty is experienced from this source.

These catalysts are also effective in causing the condensation of olefins of higher molecular weight than ethylene with aromatics and it is comprised within the scope of the invention to utilize this property in cases where the particular olefin mixture tends to be too easily polymerized or oxidized by sulphuric acid in the first step of the process. In other words, the interaction of the propylenes, butylenes, etc., with aromatics in the presence of sulphuric acid may be stopped short of completion in the first step and finished by catalysts whose use is preferred in the second step.

In conducting the first step of the process, spe-' cial equipment is seldom necessary, the ordinary batch and continuous sulphuric acid treating plants common to petroleum refineries being generally adaptable-to use, if means are provided for maintaining the necessary temperatures. For example, a regulated amount of cooled sulphuric acid of commercial grade may be added to an ordinary cone bottomed agitator (preferably well insulated) a regulated amount of benzol or other aromatic hydrocarbon subsequently added and the mixture agitated either by mechanical means or by circulating pumps. During the agitation or circulation of the benzol and sulphuric acid gases from cracking processes may be passed therethrough at ordinary pressures, the heavier olefinic constituents under these conditions reacting with benzol to form homologs of benzene which are of high anti-knockvalue and suitable for useas blending material to increase the knock rating of inferior or knocking gasolines.

The catalytic compounds employed inthe second step of the process are in general heavy and moderately viscous liquids varying in color from light yellow through red to dark brown and having specific gravities within the approximate range of 1.0 to 1.6 depending upon the particular aluminum halide which they contain and upon the type of aromatic compound chemically combined therewith. Hense they are utilized in a manner quite similar to that employed for the utilization of ordinary sulphuric acid so that the second step may be brought about in a second unit similar to the unit employed in the first step using sulphuric acid, or the two steps may be applied successively in the same treater if the gas mixture from which the heavier olefins have been abstracted is stored and later recycled to insure the absorption of ethylene.

As a typical example of the results obtainable by the operation of the process, the following involving the use of a hydrocarbon gas mixture produced in the cracking of a mixed base charging oil may be cited. This gas contained 6% ethylene and 14% of higher olefins (largely propylene) the other constituents including the ordinary run of paraflinic hydrocarbons from methane to pentane with traces of higher molecular weight paraflins and about 5% free hydrogen.

The gas was caused to react with benzol 1n the presence of 66 B. sulphuric acid, there being present approximately 50 pounds of acid per barrel of benzol. The acid was thoroughly emulsified with the benzol by circulation from and to a batch agitator while the gas mixture was introduced. By the use of cooled oils the temperature was maintained below 100 F., at all times during the treatment. The gas mixture wasintroduced at the rate of approximately 30 cubic feet per hour per barrel of benzol and the treatment was continued until the benzol had increased approximately by volume corresponding to by weight. Treatment was stopped at this point, since the acid had become gradually weakened due to alkyl ester formation and the benzol was sufliciently alkylated.

The acid layer was separated and removed and the synthetic hydrocarbon mixture was given a light acid treatment to remove acid esters which tended to remain dissolved in the hydrocarbon layer. This'acid treatment was followed by further separation of sludge, neutralization with 15% caustic soda and distillation by steam superheated to approximately 340 F., leaving a small residue.

One part of the distillate was mixed with four parts of a gasoline having an octananumber of 50, the octane number being thereby raised to 70, whereas the use of benzol in the same amount increased the octane number only to 60 which indicates that the products obtained from benzol by reaction with the cracked gases have approximately twice the value of benzol. Thus in the first step of the process the olefins in the gas mixture of higher "molecular weight than ethylene were used to produce valuable anti= knock material for blending with gasoline of low knock rating. Accompanying this step the gumforming compounds, usually of a di and tri olefinic character may be removed from both the gas mixture and from the final product so that both are improved.

The acid sludge produced while treating the benzol with the olefinic gases is well adapted to regeneration of the acid by such processes as treatment under pressure with superheated steam, as there is a minimum amount of readily oxidizable tars present and the splitting of the alkyl esters follows for the main part the normal course of hydrolysis. Incidentally, alcohols such as isopropyl alcohol may result in the recovery of the acid and maybe marketed after suitable purification by chemical treatment and subsequent distillation and dehydration.

The residual gases from the first step, containing an increased concentration of ethylene due to absorption of the other olefimic constituents and the polymerization of diand tri-olefins was then contacted with a fresh quantity of benzol in the presence of a catalyst produced by reacting aluminum bromide AlBIa with toluol toform an addition compound of the composition AlBr3-6CvHa, the conditions of operation being generally similar to those of the first step, particularly in respect to the amount of catalytic liquid, (in this step an organo-metallic compound) present. The gas was passed through until the benzol had approximately doubled in weight due to ethylation, the ethylene being practically completely absorbed, 50,000 cubic feet of a residual gas serving for the treatment of 1 barrel of benzol.

After separation of the catalytic layer and redistilling a middle cut was produced having a boiling range of 160 to 210 C. which had double the value of benzol as an anti-knock blending fluid. The total boiling range of the product prior to redistillation was to 220.C., and the portions boiling outside the to 210 range were reserved and mixed with further quantities of benzol in subsequent treatments.

, molecular weight than ethylene, which comprises first subjecting the gaseous mixture in the presence of sulphuric acid to the action of an arcmatic hydrocarbon of the benzene series to condense the higher molecular weight olefins with 60 the aromatic, and subsequently subjecting the thus treated mixture to the action of additional aromatic hydrocarbon of the benzene series in the presence 01 an aluminum halide catalyst to condense the ethylene with the additional aromatic.

2.The process as defined in claim 1- further characterized in that said. catalyst consists oi a complex of aluminum chloride and an aromatic hydrocarbon. I

' VLADIMIR. IPATIEFF'. ARISTID V. GROSSE.