US2479120A - Production of relatively straight chain alkyl aromatic hydrocarbons - Google Patents

Description

Patented Aug. 16,1949

PRODUCTION OF CHAIN ALKYL BONS RELATIVELY s'rnucn'r AROMATIC monocu- Warren W. Johnstone, Riverside-Alt, asslgnor to Universal Oil Products Company, Chicago,

a corporation of Delaware No Drawing. Application November 29, 1946, Serial No. 713,071

6 Claims.

The present invention relates to a process for the production of a specific type of alkyl aromatic hydrocarbon having a molecular structure and containing a particular type of alkyl substituent which renders said aromatic alkylate especially useful for the production of detergents therefrom, said detergents being characterized as the alkali metal sulfonate salts of the alkyl aromatic hydrocarbon produced by the process of this invention. More specifically, the invention concerns an improvement in said process for producing alkyl aromatic hydrocarbons, which comprises subjecting an olefinic charging stock of specific composition utilized in the preparation of said aromatic alkylate to a particular pretreatment prior to the alkylation reaction in which the alkylate is formed.

The type of detergent, for the production of which the present alkyl aromatic hydrocarbon product is utilized as starting material, maybe represented by the following structural formula:

n Rr produced by a process involving the alkylation of a benzenoid aromatic hydrocarbon containing the radicals R and R." selected from the group consisting of hydrogen, methyl, and ethyl radicals with an olefinic hydrocarbon fraction containing olefins having from about 9 to about 18 carbon atoms per molecule to form the alkylate represented as an alkyl aryl hydrocarbon containing the substituents R, R" and R, in which R represents the group introduced'by the alkylation reaction. The alkylate product is thereafter separated into a fraction containing the desired alkylate which upon sulfonation introduces the sulfonic acid radical on the aromatic nucleus. The resultant alkyl aryl sulfonic acid when neutralized with an alkali base, the metallic anion thereof reprcsentedby M in the above formula, forms the alkyl aromatic sulfonate salt comprising the detergent product herein referred to. It is one object of the present invention to provide a process for the production of an alkyl aromatic hydrocarbon containing no more than 2 I one alkyl group of fromabout 9 to about 18 carbon atoms of a relatively nombranched chain structure and containing in addition no more than two other alkyl groups of more than two carbon atoms per alkyl group.

Another object of this invention is to provide a 7 process for removing tertiary and other highly branched chain olefins as well as polyolefins from a hydrocarbon fraction containing desirable monoolefins of from about Cato about C a chain length per molecule, and thereafter alkylating a benzenoid hydrocarbon with said treated olefinic fraction to form an alkylate product particularly useful as starting material for the production of detergents by subsequent sulfonation and neutralization. Still another object of the invention is to remove undesirable components normally present in olefinic fractions of from about C9 to a C18 chain length utilized in alkylating an aromatic hydrocarbon for the ultimate production of detergents.

One embodiment of the present invention relates to a process for the production of an alkyl aromatic hydrocarbon, the alkyl group of which is of relatively straight chain configuration containing from about 9 to about. 18 carbon atoms which comprises in combination the steps ;of treating an olefinic hydrocarbon fraction boiling from about 150 to about 225 C. with sulfuric acid of from about to about concentration to remove from said fraction highly branched chain olefins and polyolefins, separating an acid phase from a hydrocarbon phase and alkylating an aromatic hydrocarbon with said hydrocarbon phase.

In a more specific embodiment of my invention, the present process comprises treating an olefinic hydrocarbon fraction boiling from about to about 225 C. with sulfuric acid of from about 85 to about 100% concentration in an amount thereof within the range of from about 2 to about 25 pounds of acid per barrel of olefinic hydrocarbon fraction, removing an acid phase from a hydrocarbon phase, and subsequently alkylating a benzenoid hydrocarbon with said hydrocarbon phase to form an alkyl aromatic hydrocarbon utilizable as charging stock for the roduction of detergents.

Other specific embodiments of the process comprising this invention relate to operating condiable in the alkylation stage, and to other factors affecting the production of the present alkyl aromatic product,.which factors will hereinafter be referred to in greater detail.

I have found in an attempt to improve the quality and effectiveness of alkyl aromatic sulfonate detergents that the product is markedly affected by the character and particularly the molecular composition and structure of the alkyl aromatic hydrocarbon portion of the product. Detergents of optimum quality, for example, are formed when one, but no more than one, of said alkyl substituents is a hydrocarbon radical of relatively straight chain configuration corresponding in chain length to at least a nonyl radical but of no greater chain length than an octadecyl radical. It is further shown that detergents of the above indicated type progressively decrease in quality as the number of alkyl substituents attached to the benzenoid nucleus, other than said long chain alkyl group, is increased beyond two Realizing the optimum properties and constitution desired of the above alkyl aromatic sulfonate type of detergents, various attempts at commercial production of the alkyl aromatic hydrocarbon portion of these detergents have been undertaken. Heretofore, however, the production of the above desired type of detergent alkylates has often eecaanpanied by high operating and material costs occasioned by the unavoidable, simultaneous production of a large proportion of alkyl aromatic hydrocarbons containing shorter chain alkyl groups than the product desired. The formation of the latter undesirable alkylates necessarily involves the corresponding consumption of the relatively costly aromatic reactant and when the product contains a large proportion of alkyl aromatic hydrocarbons unsuitable for conversion into detergents, material costs become excessive. The formation of the latter alkylates undesirable for the production of detergents therefrom, is occasioned by the fact that certain components normally present in the CaC1s olefinic hydrocarbon alkylating fraction depolymerize into shorter chain olefins under the alkylating conditions usually employed. The latter short chain olefins alkylate the aromatic hydrocarbon as readily and .in some cases more rapidly than the desired long chain olefins, thereby producing alkylates containing one or more short chain alkyl groups which when sulfonated and neutralized do not yield the preferred and more efllcient type of detergent described above. In an investigation of the factors influencing the formation of alkylates containing short chain alkyl groups, I have found that the highly branched chain olefinic components of the alkylating charge and especially the olefins containing tertiary carbon atoms are particularly subject to cracking reactions in the presence of an alkylation catalyst. It is also true that where polyolefinic components (especially diolefins) are present in the alkylating charge, these hydrocarbons enter the catalyst phase, polymerize, and effectively dilute the alkylation catalyst as well as reducing its activity by removing a portion of the catalyst in the form of a catalyst-hydrocarbon complex. Furthermore, even when the undesirable branched 4 chain olefins do not crack during the alkylation reaction, the alkylates formed thereby do not contain the preferred straight chain alkyl groups. By means of the present invention whereby the oleflnic alkylating charge is pretreated prior to the alkylationreaction with sulfuric acid to remove not only the highly branched chain olefins but polyoleilns as well, it has been found that the undesired components are selectively removed from the alkylating charge and the alkylates formed in the alkylation reaction are of the preferred type which yield superior detergents.

It is the principal feature of this invention, therefore, to provide a process for selectively removing the undesired. olefins from the alkylating charge.

Olefins containing from about 9 to about 18 carbon atoms per molecule which are utilizable in the process herein described may be obtained from any suitable source. Such olefins are most .conveniently derived from the olefinic fractions of thermally cracked petroleum products boiling from about to about 300 C. and preferably those boiling in the range of from about 180 to about 225 C. (commonly referred to as a pressure distillate fraction). Another source of olefins utilizable as charging stocks herein, which in some cases is the preferred olefinic charging stock, are the polymers produced by the catalytic or thermal polymerization of short chain olefins, preferably those containing from 2 to 4 carbon atoms per molecule. Both of the above common sources of long chain olefins utilizable as alkylating charge herein, besides containing the desired olefins of straight chain structure, also contain olefins having one or more secondary or tertiary carbon atoms and other olefins having more than one double bond per molecule which readily crack or depolymerize at relatively mild temperature conditions, especially when such olefins are subsequently contacted with an alkylation catalyst at conditions normally tending to catalyze the cracking of said olefins as a side reaction of the principal alkylation reaction. As a result of these side reactions or the production of the cracked short chain olefinic hydrocarbons, the formation of undesired alkylate is increased causing a simultaneous increase in the consumption of the aromatic hydrocarbon starting material and, further, an increase in the amount of alkylation catalyst converted to spent catalyst sludge by virtue of the formation of an olefinic hydrocarbon-catalyst addition complex comprising the sludge. The formation of the catalytically in active sludge necessitates frequent addition of fresh catalyst to the alkylation reactor and/or frequent regeneration of the catalyst to remove the contaminating hydrocarbons contained in the sludge. It thus becomes desirable to remove those highly branched chain olefins and polyolefins contained in the alkylating charging stock not only from the standpoint of effecting an economy in the consumption of the aromatic reactant and of the alkylation catalyst, but also for the purpose of producing a more selective alkylate from which superior detergents can be prepared.

According to the operation of the present invention, the olefinic hydrocarbon fraction utilized as the alkylating charge, whether obtained from the polymerization product of short chain olefins or separated as an olefinic fraction Of a cracked petroleum distillate is treated with sulfuric acid to selectively remove therefrom the hereinabove named undesirable components of the alkylating charge.

The method of treatment herein provided consists in intimately contacting the olefinic alkylating charge with sulfuric acid of from about 85 to about 100% concentration ata temperature sufficient to react with the secondary, tertiary, and polyolefinic components only, leaving substantially unaffected the desired straight chain mono-olefins. It is usually sufficient to efiect the operation at temperatures below about 100 C. and preferably at temperatures below about 40 C., and above about 20 C. although the temperature factor is also mutually dependent upon other conditions, such as the concentration of acid, the period of contact between the alkylating charge and acid. and the degree of mixing the hydrocarbon and sulfuric acid phases. Although it is generally necessary to utilize from about 2 to about 25 pounds of acid of the above concentration per barrel of olefinic alkylating harge treated (each barrel representing 42 U. S. gallons), the latter factor is most advantageously determined by the gradual addition of the acid reactant to a given quantity of the hydrocarbon fraction and continuing the addition of the acid until the maleic anhydride value determined on the effluent treated product has been reduced to a low predetermined value indicating substantially complete removal of diolefins from the efiluent. In a process of the present nature, the total effect of which is dependent upon several variables, it is necessary to correlate the various operating conditions to correspond to the particular charging stock utilized and said correlation is best determined by trial. The treatment is generally completed after a period of contact which may range from several seconds to 2 or more hours depending upon the concentration of treating acid, the amount of undesirable olefins in the charge, etc. The mixture is preferably stirred vigorously during the treatment to effect intimate contact of the reactants. Following the specified treating period, an acidic phase is separated from the remaining olefinic hydrocarbon phase and, if desired, the hydrocarbon phase may be given several water washing treatments and dried to prepare the hydrocarbons for the alkylation stage of the present process.

A convenient and readily available source of acid for treating the olefinic charge is the spent sulfuric acid recovered from other treating or conversion processes in which sulfuric acid is employed as reagent or catalyst. Thus, the sulfuric acid phase of an alkylation reaction in which the acid is utilized .as catalyst may be used as the treating acid in the present process. This source of acid is especially applicable where the concentrated acid is used for alkylating the aromatic reactant in the production of detergent alkylates.

It is to be emphasized that although the process is particularly applicable to the production of alkyl aromatic hydrocarbons for detergent manufacture, the process may also be employed for the production of any alkyl aromatic hydrocarbons utilizing the charging stocks herein specified and from which process it is ultimately desired to manufacture a product containing predominantly long chain alkyl aromatic hydrocarbons free of polyalkylates containing a multiplicity of short chain alkyl groups.

Of the aromatic hydrocarbons utilizable herein for the production of the present alkyl aromatic hydrocarbon product by alkylation thereof with the aforementioned olefinic hydrocarbon fraction, I prefer to utilize a benzenoid aromatic hydrocarbon containing no more than 2 alkyl substituents, especially when said product is to be utilized for the production of detergents by subsequent sulfonation thereof. Preferably, neither of said alkyl substituents are of greater chain length than the ethyl radical and more desirable still are methyl radicals. Thus, benzene, toluene, xylene, methylethyl benzene and diethyl benzene comprise aromatic hydrocarbons of the above preferred type and of this group it is preferred to utilize benzene and toluene for the production of detergents having the highest degree of detersive action. When alkyl aromatic hydrocarbons are desired for purposes other than detergent production, it is also within the scope of the present invention to utilize other benzenoid as Well as polycyclic aromatic hydrocarbons as the reactant to be alkylated. Thus, any alkylatable aromatic hydrocarbon containing a nuclearly substitutable hydrogen atom may be utilized in the alkylation reaction, including such compounds as the triand tetra-aikyl benzenoid hydrocarbons, as for example, mesitylene, 1,2,3- trimethyl benzene, etc. or the polycyclic aromatic hydrocarbons such as naphthalene, etc. and its alkylatable alkyl derivatives.

In the alkylation stage of the present process, the aromatic reactant and treated olefinic alkylating charge may be introduced simultaneously or in admixture with each other into the alkylation reactor containing the desired alkylation catalyst or alternatively the aromatic hydrocarbon may be contacted with the alkylation catalyst followed by the addition of the olefinic alkylating charge thereto. The molecular proportion of aromatic hydrocarbon and treated olefinic fraction introduced into the alkylation reactor is generally maintained above an equimolecular ratio, preferably from about 2 to 1 to about 30 to 1 or even higher to minimize polyalkylation of the aromatic reactant. Any suitable alkylation catalyst may be utilized to effect the condensation of the olefinic and aromatic hydrocarbons among which may be mentioned: (1) sulfuric acid of from about to about 100% or higher concentration, said higher concentration containing free sulfur trioxide up to about 15% of the latter component, (2) substantially anhydrous hydrogen fluoride, generally not containing more than about 10% water, (3) anhydrous aluminum chloride or aluminum bromide, preferably in the presence of the corresponding hydrogen halide, (4) boron trifiuoride, with or without addition thereto of hydrogen fluoride, (5) a sulfonic acid of either alkane or aromatic derivation, (6) a phosphoric acid, preferably pyrophosphoric acid, which is desirably deposited on a separating or spacing material such as alumina or a siliceous material such as hydrated silica, kieselguhr, kaolin, etc. and (7) hydrogen chloride, usually in the anhydrous condition. The preferred alkylation catalyst of my invention comprises hydrogen fluoride of from about to about concentration or sulfuric acid of about 95% concentration, the order of preference being in the order named.

When utilizing the above specified ratio of aromatic reactant to alkylating olefinic hydrocarbons, said hydrocarbons are maintained in the alkylation reactor in contact with the alkylation catalyst for a reaction period which may vary from about 5 to about 80 minutes, the particular time of-reaction depending upon the relative case of alkylating the selected charge stocks. The temperature maintained in the alkylation reactor in the presence of the above preferred alkylating catalyst is within the range of from about 30 to about 100 C. (preferably from about to about 50 0.). Superatmospheric pressures, sufficient to maintain the catalyst and hydrocarbons in liquid phase are preferably maintained during the alkylation reaction, although pressures in excess of 100 atmospheres are usually not required. The process conditions vary with the particular charging stock and with the particular catalyst utilized to effect alkylation, but the conditions necessary to fix these variables are well known to those skilled in the art of alkylating hydrocarbons so that they may be readily determined when the above variables are known.

Following the alkylation reaction, the products formed thereby may be separated by fractionating the desired alkyl aromatic hydrocarbon product from other hydrocarbons introduced into the alkylation zone. The excess aromatic reactant, usually the lowest boiling fraction, may be separated and recycled to the alkylation reactor. Although the present process is characterized by the production of minimum amounts of short chain alkyl aromatic hydrocarbons, a small amount of these will ordinarily be formed in spite of the precautions taken to avoid their .formation and these are separable from the product of the alkylation reaction as an intermediate fraction. The desired alkyl aromatic product, boiling from about 260 to about 345 C. when toluene is the aromatic selected for alkylation, is separated as a bottoms fraction upon fractionally distillating the total alkylation product at vatmospheric pressure. In order to separate a purified product boiling within a particular temperature range, the bottoms fraction is ordinarily subjected to vacuum distillation and the desired fraction separated from the distillate. The following examples are introduced for the purpose of further illustrating the process herein described for producing alkyl aromatic hydrocarbons containing a single long chain alkyl group of relatively non-branched structure containing from about 9 to about 18 carbon atoms per group. The conditions specified therein however, should not be construed as limiting the generally broad scope of this invention in strict accordance thereto.

A pressure distillate fraction boiling from about 170 to about 220 C. containing olefins of from about C9 to about C15 chain length recovered from the thermally cracked products of a Trinidad gas oil fraction was utilized in the following examples to alkylate toluene for the ultimate production of detergents from the toluene alkylate. The fraction herein utilized, typical of pressure distillate fractions, contained approximately'28% by weight of unsaturates, predominantly of olefinic character. In Example I below, the pressure distillate alkylating charge was utilized as received, Without pretreatment with the sulfuric acid extractant herein provided prior to the alkylation reaction, while in Example II, the pressure distillate alkylating charge derivedfrom the same source was subjected to an acid treatment with sulfuric acid prior to the alkylation stage; yields are included in each example to indicate conclusively the advantage of acid pretreatment. r

EXAMPLE I 7.5 pounds (3.5 liters) of hydrogen fluoride was added to a turboreactor and cooled to about 4 C. at a pressure of about 100 pounds per square inch gage. 2680 cc. (25.2 mols) of toluene were pumped into the reactor followed by 1 liter (1.5 mols) of the above indicated pressure distillate fraction. The latter fraction was introduced into the mixture of hydrogen fluoride and toluene over a period of 30 minutes as the mixture was Table I Yield, lbs. 1 315 Identity g g agg range' no charged 50-125 Toluene (Recovered) 2, 016 125-190 Olefins plus aromatics ll. 1

190475 Olefins plus short chain 289 alkyl aromatics.

275-325 lkyl e 288 275-345 .--do 1 450 1 Total alkylate utillzable in detergent manufacture.

EXAMPLE II A portion of the same pressure distillate fraction utilized in Example I as the alkylating charge, was given an acid pretreatment by means of the following procedure: 1708 cc. of the indicated pressure distillate fraction was rapidly stirred with 25.5 cc. of sulfuric acid (corresponding to 10 pounds of acid per barrel of pressure distillate) added thereto at 25 C. The two phases were stirred for an additional 10 minutes and then allowed to settle into separate layers, the acid layer being drawn off from the hy drocarbon layer and hydrolyzed by the addition thereto of an equal volume of water. Hydrolysis caused the separation of 30 cc. of a viscous oil having properties different from the pressure distillate from which it was separated. The volume,

of the hydrocarbon phase separated in the settler from the acid was 1645 cc., representing a loss of 63 cc. of the pressure distillate to the sulfuric acid extractant. The recovered, treated olefins were utilized as alkylating charge in the following alkylation reaction.

8.34 pounds (3.78 liters) of hydrogen fluoride was added to a turboreacto'r and cooled to about 2 C. at a pressure of pounds per square inch gage. 2343 cc. of toluene (22.2 mols) was pumped into the reactor followed by the addition of 1068 cc. (1.6 mols of olefins) thereto of the acid treated pressure distillate fraction prepared as indicated above. The latter pressure distillate was introduced into'the stirred mixture of toluene and hydrogen fluoride over a period of 23 minutes, the temperature being maintained at about 2 C. Stirring was continued for 5.7 hours and the mixture was then allowed to settle, an upper hydrocarbon layer separating from a lower acid layer on standing. The hydrocarbon layer was defiuorinated and fractionally distilled, the following Table II indicating the yields and properties of the hydrocarbons recovered.

1 Where the pounds of olelin charged is calculated on the basis of the pressure distillate containing approximately 28% olefins.

' otal alkylate utilizable in detergent manufacture.

A comparison of the results of Example I and Example II indicate that an increase in the alkylate yield utilizable from 0.53 pound of alkylate per pound of olefin charge to 0.77 is'obtained when utilizing an acid treated pressure distillate from which undesirable olefins and polyoleflns are removed as the alkylating charge.

I claim as my invention:

1. A process for the production of an alkyl aromatic hydrocarbon, the alkyl group of which contains from about 9 to about 18 carbon atoms of relatively straight chain configuration which comprises in combination the steps: treating an olefinic hydrocarbon fraction boiling from about 150 to about 225 C. with sulfuric acid of from about 85 to about 100% concentration to remove therefrom highly branched chain olefins and polyolefins, separating acid from hydrocarbons and alkylating an aromatic hydrocarbon with the sulfuric acid treated olefinic hydrocarbon fraction.

2. A process for producing an alkylated benzenoid hydrocarbon having the structural formula wherein R is a relatively straight chain alkyl for detergentproduction of radical containing from about 9 to about 18 carbon atoms and R and R" are selected from the group consisting of hydrogen, methyl and ethyl radicals, said process comprising in comblnatlon the steps: treating an olefinic hydrocarbon fraction boiling from about 150 to about 225 C. with sulfuric acid of from about to about concentration to remove therefrom 10 highly branched chain oleflns and polyolefins. separating an acid phase from a hydrocarbon phase and contacting said acid treated olefinic fraction at alkylating conditions with a benzenoid hydrocarbon corresponding in structure to wherein R and R" are as indicated for said above alkylated benzenoid hydrocarbon.

3. The process of claim 1 further characterized in that the olefinic alkylating charge is contacted with the sulfuric acid treating agent at a temperature below about 100 C.

4. The process of claim 1 further characterized in that the olefinic alkylating charge is contacted with the sulfuric acid treating agent at a temperature below about 40 C. and above about -20 C.

5. The process of claim 1 further characterized in that the olefinic alkylating charge is contacted with from about 2 to about 25 pounds of said sulfuric acid per barrel of olefinic alkylating charge.

6. The process which comprises treating an olefinic alkylating charge containing olefins having from about 9 to about 18 carbon atoms per molecule with sulfuric acid of from about 85 to about 100% concentration at a temperature below about 100 C., separating a predominantly acid phase from the olefinic hydrocarbon phase, contacting said hydrocarbon phase with a benzenoid hydrocarbon at alkylating conditions in the presence of an alkylation catalyst, separating from the resulting reaction products an alkylate fraction containing an alkyl aromatic hydrocarbon having a relatively straight chain alkyl group of from about 9 to about 18 carbon atoms per group utillzable in the production of detergents.

- WARREN W. JOHNSTONE.

REFERENCES orrEn The following references are of record in the flle of this patent: I

UNITED STATES PATENTS Number Name Date 2,007,160 Engs et al. July 9, 1935 2,232,117 Kyrides Feb. 18, 1941