US2471922A - Production of aromatic derivatives - Google Patents

Description

Patented May 31 19 49 PRODUCTION OF William N. Axe,

AROMATIC DERIVATIVES Bartlecville, Okla, assignor to Phillips Petroleum Company, a corporation of pelaware No Drawing. Application June 22, 1944,- Serial No. 541,663

1 This invention relates to derivatives of aromatic compounds. In one modification it relates to alkenyl derivatives of aromatic compounds. In

another modification it relates to normal alkyl derivatives of aromatic compounds. As specific modifications it relates to the .alkenylation of aromatic hydrocarbons and to the production of normal alkyl derivatives of aromatic hydrocarbons. This application is a continuation-in-part of my copending application Serial No. 433,191, filed March 3, 1942, now Patent 2,412,595, granted December 17, 1946. Normal alkenyl aromatic compounds and normal alkyl aromatic compounds are valuable in- ;ermediate compounds both in their own rights ind as intermediates in organic syntheses. They nay. be used for the production of normal ali- Jhatic derivatives of such compounds as aminoienzenes, aminonaphthalenes, phenols, naph- .hols, aminophenols, aminonaphthols, quinoines, and the like. These materials can be used If the preparation of oxidation inhibitors, pharnaceuticals, dyestuifs, and explosives. The deelopment of the full potentialities of normal aliphatic derivatives of such compounds has been irecluded by the absence of suitable sources of uch compounds. Thus, when .olefins are used to .lkylate aromatic compounds the normal alkyl lerivative is produced only in the caseof ethylne and with other olefins it is impossible to pro- [uce a normal alkyl derivative by catalytic alklation. Synthetic methods for the production f normal alkyl derivatives have been limited ieretofore to reactions of the Wurtz-Fittig type 1 which aromatic halides have been condensed, 1 the presence of ametal such as sodium, with ormal alkyl halides. The best yields reported )1 such reactions have not exceeded about 30 er cent of the theoretical yield and more often ctual yields are from about to per cent f the theoretical yields. Other disadvantages of ich synthesis operations include the use of large uantities of metals such as sodium with appreable attendant hazards, the employment of exensive intermediate compounds, the necessity of aecial solvents, and the relatively diiiicult prouction of normal alkyl halides.

An object of this invention is to produce norial aliphatic derivatives of aromatic compounds. Another object of this invention is to produce armal alkyl derivatives of aromatic compounds. A further object of this invention is to produce Jrmal alkenyl derivatives of aromatic com- Minds.

A still further object of this invention is to 6 Claims. (Cl. 260-671) 2 react low-boiling aromatic hydrocarbons with low-boiling normal 1,3-dioleflns to produce normal monoalkenyl derivatives of said aromatic hydrocarbons.

Still another object of this invention is to-produce normal butyl benzene.

Further objects and advantages of my invention will become apparent to one skilled in the art from the accompanying disclosure and discussion.

I have now found that aromatic compounds, including aromatic hydrocarbons, phenols, naphthols, and aromatic halides, can be reacted with normal 1,3-diolefins to produce alkenyl derivatives of said aromatic compounds. I have further found that such alkenyl derivatives include normal monoalkenyl derivatives which can be successfully subjected to nondestructive hydrogenation to produce the corresponding normal alkyl derivatives. I have further discovered that such derivatives can be produced in extremely high yields and can be recovered in substantial quantities in a condition of high purity. v As the arcmatic reactant of my process I prefer to use benzene, naphthalene, simple alkyl derivatives of these hydrocarbons such as toluene, ethylbenzene, xylenes, and the like, phenol, naphthols, and simple alkyl derivatives of these materials, and aromatic halides such as phenyl chloride, phenyl bromide, one of the naphthyl chlorides, and the like, although other alkenylatable aromatic compounds are not to be excluded from the broad concept of my invention. As the diolefin reactant I prefer to use a low-boiling normal 1,3-dio1efin such as 1,3-butadiene, 1,3-pentacliene, 1,3-hexadiene, and the like. Although'it is a primary object of my invention to produc normal aliphatic derivatives by the use of normal 1,3.-diolefins, it is to be understood that alkyl derivatives of normal 1,3-diolefins, such as 5-methyl- 1,3-hexadiene and 6-methyl-1,3-heptadiene, to

produce aromatic derivatives such as l-ph enyl- 5-methyl hexylene and 1-phenyl-6-methyl heptylene, and the like, are not to be excluded from the broad concepts of my invention.

Broad features of this process may be more readily understood by considering a typical pro cedure. A blend of butadiene in benzene, in which the benzene is present in substantial molar excess, serves as theprimary feed stock. The blend is charged to a reaction zone at moderate temperatures and pressures where it is intimate- 1y commingled with a liquid complex compound of boron fluoride such as one of those to be hereinafter described. The eflluent is preferably con- 3 tinuously removed from the reaction zone and after mechanical separation of the catalyst phase, the hydrocarbon stream is washed free of dissolved boron fluoride and the excess benzene is recovered by fractional distillation. The debenzenizcd product is further fractionally distilled to separate a main product (normal butenyl benzene, or phenyl butene) boiling at about 365 to about 370 F., and a higherboiling kettle product. The main product fraction may be hydrogenated over a conventional hydrogenation catalyst such as Raney nickel, platinum or any of the more rugged industrial hydrogenation catalysts to yield n-butylbenzene, which ordinarily requires no further purification.

I have found that efflcient catalysts for such alkenylation reactions can be prepared by substantially saturating with a boron trihalide an oxygen-containing acid of phosphorus. ferred boron trihalide is boron trifiuoride although I do not intend to exclude other boron trihalides, particularly boron trichloride and boron tribromide which are low-boiling materials. Oxygencontaining acids. of phosphorus which I may use in making such complex catalysts include the various phosphoric and phosphorous acids, including thiophosphoric acid. Of these, however, I prefer to use ordinary orthophosphoric acid, which is generally readily obtained in a concentrated form containing between about 85* to about 100 per cent HsPOi, with the remainder being water. The complex catalyst for the alkenylation reaction is preferably prepared by adding the boron trihalide to the acid, or to a suitable aqueous solution thereof, until the acid has become substantially completely saturated with the boron trihalide. The resulting reaction is exothermic and the rate of addition of boron trihalide should be controlled, together with a cooling of the reacting mixture, to avoid reaction temperatures above about 200 F. This catalystpreparation reaction may be conducted, if desired, under pressure, particularly when using boron trifluoride or boron trichloride. Saturation of the acid of phosphoruswill be noted by lack of additional reaction upon addition of boron trihalide. The exact mechanism of the addition reaction and the formulae of the compounds formed in the preparation of the catalyst have not been determined with certainty, but it has been fairly well'established that two reactions occur. One reaction is the formation of a complex between the boron trihalide and the oxygen-containing acid of phosphorus, and the other reaction is the formation of a complex between the boron trihalide and any water which may be present. When a state of saturation has been effected each of these complexes contains approximately equal molecular proportions of the boron trihalide and the water or acid of phosphorus. For example, when preparing a complex catalyst from boron trifluoridle and orthophosphoric acid containing 85 per cent of the acid, the amount of boron trifluoride absorbed corresponds to the formation of a BF3'H3PO4 addition compound plus sufficient boron trifluoride to form a mono-hydrate with the water which was initially present. As previously stated I prefer to use orthophosphoric acid and for most applications a moderately concentrated to concentrated acid (1. e., from about 70 per cent to about 100 perv cent HaPOa.) is preferred, since dilute solutions require excessive quantities of boron fluoride to produce an active catalyst. A material which results from the addition of orthothe continued A prephosphoric acid to a boron trifluoride hydrate has been found to be relatively inactive as ation of a slight excess of the original oxygen-containing acid of phosphorus to an active complex catalyst results in a material having properties similar to that of a partially spent catalyst. 0n the other hand addition of a boron trihalide hydrate to an active complex catalyst does not materially impair its activity. From this evidence it may be deduced that decomposition of the acid complex is the primary reaction eifecting the activity of the catalyst, and this complex is therefore believed to be the essential ingredient of a complex catalyst.

Many of the catalysts are liquid materials at the usual reaction, temperatures and have viscosities sufliciently low that intimate mixing, during the alkenylation reaction, with the reacting mixture can be effected without too great dimculty. Thus the complex resulting from saturating concentrated orthophosphoric acid with boron trifluoride is normally a, liquid material which shows no tendency to solidify at temperatures as low as F. These materials can be employed as such, preferably with intimate mixing with the reaction mixture. If it is desired to use such a catalyst in the solid form it may be used in admixture with porous granular catalyst supports such as activated charcoal, activated alumina, activated bauxite, and the like, although when using boron trifluoride-containing complexes it'is preferable not to use a granular material containing appreciable amount: 0f silica.

In the alkenylation step the reaction appear: to be primarily monoalkenylation to form monoalkenyl derivatives of the aromatic compound It also appears that secondary reactions taki place to certain extents, including cyclizatior and/or polymerization of the resulting monoalkenyl derivatives. This conclusion is based or the observation that the aromatic compound re acted is molecularly equivalent to the diolefin re acted. Ii extensive polyalkenylation occurred, t1 form dior tri-alkeny1 aromatic derivatives, th amount of aromatic hydrocarbon reaction WOllll be substantially less than the molecular equiva lent of the diolefin, while if the monoalkenyl de rivative entered into reaction with the aromati hydrocarbon, to form the corresponding di-sub stituted paraflin hydrocarbon, the amount 0 aromatic hydrocarbon reacted would be substan tially greater than a molecular equivalent of th diolefin. No appreciable polymerization of th diolefin is believed to take place under preferre conditions of operation, a conclusion deduce from a consideration of the relativeamounts c reactants which undergo reaction and from th characteristics of such high-boiling product Such results contrast with the results obtaine when catalysts such as sulfuric acid are use with the same reactants. Thus, when benzen and 1,3-butadiene are reacted in the presence c not is 'diphenylbutane and that no phenylbutene is produced.

In order to favor thedesired primary reaction I preler to use moderate reaction temperatures, relatively shortreaction periods, and relatively high molar ratios of aromatic compound to dioleiin reactant. The reaction may be satisfactorily and conveniently conducted at a temperature between about (3 and about 150 F., with a temperature between about 80 to 90 and about 110 to 120 F. being preferred. Temperatures above 150, F., or below 75 F., are not to be excluded, however. The average reaction time may be between a few minutes and a few hours, with satisfactory results being obtained with a reaction time between about 5 and about 20 minutes. The molar ratio of aromatic compounds to dioleiln in the feed to a continuous reaction step may be between about 2:1 and about :1 with satisfactory operation generally being obtained with a ratio between about 4:1 and about 6:1. Intimate mixing of the reaction mixture, accompanied by recirculation, will generally result in higher eflective ratios in the reaction zone. In some instances it is desirable to use moderate superatmospheric pressures, particularly with the lower boiling reactants, but generally the pres- .sure need not be appreciably above that which will insure that the reactants are present in liquid phase and to insure that the catalyst is adequately saturated with the boron trihalide. As previously stated, it is preferred that the reacting mixture and the catalyst be intimately admixed. This may be accomplished by eflicient stirring mechanism, by continuously recirculating in a closed cycle a substantial amount of the reaction mixture comprising reactants, products and catalyst, by pumping such a reaction mixture through a long tube coil at a rate such that conditions of turbulent flow exist, or by other means well known to those skilled in the art of hydrocarbon alkylations. vIt is preferred that the rethat this material may be readily converted to the normal alltyl derivative by nondestructive hydrogenation. This hydrogenation will most oiten be conducted'in a manner such that the alkenyl group is saturated by hydrogen. However, it will be appreciated that, particularly when aromatic hydrocarbons are reacted in accordance with my invention, not only may normal alkyl derivatives thereof be produced by such a nondestructive hydrogenation, but the hydrogenation may be extended to include partial or complete saturation of the aromatic nucleus. Thus, it is possible to react a benzene with a low-boiling 1,3-diolefin to produce a normal alkenyl derivative of said benzene, and subsequently to hydrogenate this product, in one or more steps, to produce a normal alkyl derivative or a corresponding normal alkyl cyclohexane. Lixewise, a naphthalene may be converted to normal alkenyl derivative, and this product may subsequently be hydrogenated, in.

one or more steps, to produce a normal alkyl derivative, a normalalkyl tetralin, or a normal alkyl decalin. For such hydrogenations any suitable known nondestructive hydrogenation catalyst may be employed which is capable of effecting saturation of the alkenyl group without saturation of the aromatic nucleus or without reaction of any other reactive group in the alkenyl compound. So-called Raney nickel has been found desirable in accomplishing this result when the hydrogenation is conducted at moderate temperates and pressures. More drastic hydrogenation conditions will be necessary in order to produce the more saturated products just discussed.

Thus, in the selective hydrogenation of the olefinic linkage, the rate of absorption of hydrogen may amount to about 1 mol per hour at pressures -of 20 to 50 pounds per square inch and temperffi atures ranging from about 75 F. to about 150 F.

action mixture contain at least about 5 per cent by volume of the catalyst and that the amount of catalyst present should not exceed that which will permit a continuous phase of reacting materials when tne reaction mixture is intimately admixed. Thus it is desired that the catalyst phase not be the continuous phase when a liquid catalyst is used. Inert materials may be present during the reaction, such as relatively nonreactive im urities normally accompanying the reactants,

added low-boiling parafiin hydrocarbons such as a parafllnic naphtha fraction, or the like.

When Lit-butadiene is the diolefin reactant the monoalkenyl product is substantially completely the normal alkenyl derivative. With diolefin reactants containing a higher number of carbon atoms per molecule such high yields of the normal derivative will often not be obtained but it will still be possibleto obtain quite substantial yields of the normal. alkenyl derivative. In any case a fraction containing, or comprising essentially, the desired normal alkenyl derivative may be readily separated from the reaction eiliuents, gener lly by passing the eiiiuents to a settling chamber wherein the catalyst separates from a liquid phase containing unreacted charge stock and reaction products, and separating from this liquid phase, as by fractional distillation, a fraction of any desired purity.

As will be appreciated the normal alkenyl derivative may, in many instances, be a desired product of the process. However, I have found Nuclear hydrogenation can be efiected with the same catalyst at pressures of about500 to 5000 pounds per square inch and at temperatures of about 250 to 350 F.

The following examples illustrate my invention further. However, it is to be understood that specific limitations expressed in such examples are not to be used to restrict my invention unduly.

Example I Two mols of butadiene vapor were passed at a moderate flow rate into a mixture of four mols of benzene and 50 ml. of BF3H3PO4 catalyst at to 88 F. The benzene-alkylate solution yielded over 80 per cent of phenylbutenes boiling between 355 and 365 F. No butadiene polymers were identified in the products.

' Example I! Preparation of' n-butylbenzene was effected by a continuous alkenylation procedure followed by batchwise hydrogenation of the n-butenylbenzene. A'hydrocarbon blend having a benzenebutadiene mol ratio of 3:1 was charged to a 1500 ml. reaction vessel containing ml. of boron fluoride-phosphoric acid catalyst the total alkenylate under 12 mm. pressure gave a,50"per cent yield of butenylbenzene boiling at 157 to 159 F. The product fraction from the preliminary distillation was refractionated at atmospheric pressure to yield a fraction equivalent to approximately 90 per cent of the charge, with a boilin'grange of 365 to 367 F. and having a reiractive index, N 1.5115. Hydrogenation of this latter product .over Raney nickel catalyst resulted in a hydrocarbon having a completely saturated side chain distilling at 361 F. and having a refractive index, N 1.4889. The physical, constants of the reduced material are in close agreement with the best literature values for n-butylbenzene.

Example III Operating under conditions similar to those given in Example 11, toluene may be reacted with piperylene (1,3-pentadiene) to produce npentenyltoluene. In this instance, the tolueneiree product is subjected to a, preliminary fractionation under mm. pressure to eiiect a rough separation of higher-boiling products from the pentenyltoluene. Final purification involves fractional distillation at atmospheric pressure to give a product boiling at about 430 to 440 F. amounting to about 60 per cent of the total alkenylate. Analytical data and oxidation reactions indicate this material to be essentially 1- (p-tolyl) -2-pentene. genation results in quantitative reductions to 1-methyl-4-n-pentylbenzene having substantially the same boiling range as the original alkenyl derivative.

Although I have described my invention in considerable detail, with the inclusion of certain specific embodiments, it is not intended that the scope or the invention be limited unduly by such details. I

I claim:

1. A process for the production of phenyl butene, which comprises reacting benzene and 1,3-butadiene at a temperature in the range of about 80 to about 120 F'., and with a substantial molar excess of benzene, in the presence of a catalyst comprising a liquid addition compound of boron fluoride and phosphoric acid resulting from reacting boron fluoride and orthophosphoric acid. I

2. A process for the production of an alkenyl aromatic compound, which comprises reacting an alkenylatable aromatic hydrocarbon with a- 1,3-butadiene at 'a reaction temperature between about 80 F. and about 120 F., and with a substantial molar excess of said aromatic hydrocarbon, in the presence of a catalyst comprising a liquid addition compound of boron fluoride and phosphoric acid resulting from reacting boron fluoride and ortho-phosphoric acid.

3. A procssfor the production of a normal alkenyl aromatic hydrocarbon, which comprises reacting an aromatic hydrocarbon with a normal 1,3-diolefln at a reaction temperature be- Nondestructive hydrotween about and about F. and under a pressure suflicient to maintain the reactants in the liquid phase, said aromatic hydrocarbon and said diolefin being in a molar ratio of about 2:1 to 10:1 of aromatic hydrocarbon to diolefln, in the presence of a catalystcomprising a liquid complex resulting from reacting at least a molecular equivalent of boron trifluoride with orthophosphoric acid, and maintaining a reaction time between about 5 and about 10 minutes.

4. The process of claim 3 in which said aromatic hydrocarbon is benzene and said diolefln is 1,3-butadiene and said alkenyl aromatic hydrocarbon is butenyl benzene.

5. A process for the production of a normal aliphatic derivative of an aromatic compound, which comprises reacting an alkenylatable aromatic compound with a normal 1,3-diolefln at a reaction temperature not greater than about 150 F. and under a pressure suflicientto maintain the reactants substantially in liquid phase, with a molal excess of said aromatic compound, in the presence of a catalyst comprising a complex resulting from saturating orthophosphoric acid with boron trifluoride, and recovering from effiuents of said reaction a hydrocarbon fraction comprising an alkenyl derivative of said aromatic compound so produced.

6. A process for the production of an aliphatic derivative of an aromatic compound, which comprises reacting an alkenylatable aromatic compound with an open chain 1,3-diolefin at a reaction temperature not greater than about 150 F. and under a pressure sufficient to maintain the reactants substantiallyin liquid phase, with a molal excess of said aromatic compound, in the presence of a catalyst comprising a complex resulting from saturating an oxygen-containing acid of phosphorus with a boron trihalide, and recovering from efliuents of said reaction a hydrocarbon fraction comprising an alkenyl derivative of said aromatic compound so produced.

. WILLIAM N. AXE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS France Nov. 28,4929