US2767230A - Alkylation process - Google Patents

Description

United States Patent ALKYLATION PROCESS Herbert C. Brown, West Lafayette, and Willard S. Higley, Hammond, Ind., assignors to Standard Oil Company,

Chicago, 11]., a corporation of Indiana a This invention relates to a process for the alkylation of alkylatable aromatic compounds with alkylating agents containing at least three carbon atoms in the alkylating group in the presence of catalytic proportions of phosphorus pentafiuoride.

One object of this invention is to provide novel catalysts for the alkylation of alkylatable aromatic compounds with alkylating agents containing at least three carbon atoms in the entering (alkylating) group. Another object is to provide a process for the alkylation of aromatic hydrocarbons having at least one alkylatable nuclear carbon atom with an alkylating agent containing at least three carbons in the alkylating group in the presence of PFs or a material furnishing PFs under the alkylation reaction conditions. An additional object is to provide a process for the alkylation of aromatic hydrocarbons having at least one alkylatable nuclear carbon atom with a monoolefinic hydrocarbon containing at least three carbon atoms per molecule in the presence of PF5. A further object is to provide a process for the selective alkylation of alkylatable aromatic hydrocarbons with a terminal vinyl olefin containing at least three carbon atoms per molecule in the presence of ethylene. These and other objects of our invention will become apparent fiom the ensuing description thereof.

We have discovered that PFs, or materials which furnish PF5, in the alkylation zone under the conditions of the alkylation reaction, such as benzenediazonium hexafluorophosphate, function as catalysts for the alkylation of alkylatable aromatic compounds with olefinic hydrocarbons or other alkylating agents containing at least three carbon atoms per molecule. Since the alkylation process of this invention is broadly applicable to a large variety of aromatic compounds and alkylating reagents containing at least three carbon atoms in the alkylating group, the preferred reaction conditions cannot be indicated for each possible instance of the application of this invention; these are, however, readily determinable by simple small-scale routine experimentation.

The alkylation process of the present invention may be practiced with a variety of aromatic compounds such as alkylatable aromatic hydrocarbons or alkylatable derivatives of aromatic hydrocarbons, for example, substitution products such as halogen-, hydroxy, alkoxy-, or other substitution derivatives of aromatic hydrocarbons. Specific examples which are supplied for purposes of illustration but not as limitations include monocyclic aromatic hydrocarbons containing at least one alkylatable nuclear carbon atom, for. example, benzene, toluene, the isomeric xylenes, ethylbenzene, n-propylbenzene, isopropylbenzene, the ethyl toluenes, the ethyl xylenes, pseudocumene, hemimellitene, sec-butylbenzene, tbutylbenzene, isodurene, diethylbenzenes, prehnitene, isoamylbenzene or the like. Examples of dicyclic aromatic hydrocarbons containing an alkylatable nuclear carbon atom comprise tetralin, naphthalene; alkyl naphthalenes, such as l-methylnaphthalene, 2-methylnaphthalene, l-isopro- Patented Oct. 16, 1956 pylnaphthalene, 2-ethylnaphthalene, 2,6-dimethylnaphthalene, isopropylnaphthalene, and the like; diphenyl, alkyl-substituted diphenyls; indene, alkylindenes, dihydroindenes and the like. The alkylation process of this invention may also be applied to tricyclic aromatic hydrocarbons such as anthracene, alkyl anthracenes, phenanthrene and even to alkylatable aromatic hydrocarbons containing more than three rings. Examples of alkylatable aromatic compounds (which may be considered as derivatives of aromatic hydrocarbons) include various phenolic compounds, such as phenol, pyrocatechol, resorcinol, hydroquinone, pyrogallol; phenolic ethers such as phenetole, anisole, phenyl t-butyl ether and the like. Also included are halogenated aromatic hydrocarbons suchas' chlorobenzene, dichlorobenzenes, bromobenzene, fiuoro-. benzene, iodobenzene, 2-chloronaphthalene, orthochlorotoluene, parachlorotoluene, etc.

The alkylating reagent employed in our process is an olefinic hydrocarbon containing at least three carbon atoms per molecule, or a functional equivalent thereof under the alkylation reaction conditions in the presence of PFs catalyst. By the term olefin-acting compound as used herein, we intend to define olefins and compounds which function like olefins under the reaction conditions, i. e. they react with the aromatic compounds to substitute therein a group containing at least three carbon atoms. By way of example, we may employ as alkylating agents various monoolefinic hydrocarbons and mixtures thereof, specifically propylene, l-butene, Z-butene, isobutylene, l-pentene, 2-pentene, B-methylbutene, 2- methylbutene, various hexenes, heptenes, octenes, l-dodecene; mixtures of isomeric dodecenes derived from the polymerization of isobutylenes or isobutylene-n-butenes, or from propylene; cyclic monoolefinic hydrocarbons such as cyclopentene, various alkyl cyclopentenes, cyclohexene, alkyl cyclohexenes such as l-methyl cyclohexene, 4- methyl cyclohexene or the like; aromatic olefins such as styrene, alpha-methylstyrene, vinyl toluenes, chlorostyrenes and the like; (2,2,l)-bicycloheptene and alkyl derivatives thereof, particularly the 4-alkyl(2,2,l)-bicycloheptenes, and the like. Especially desirable are olefins containing a terminal vinyl group, CH2.

We may also employ polyolefinic hydrocarbons containing at least three carbon atoms per molecule as alkylating reagents, particularly the diolefinic hydrocarbons. Examples of conjugated diolefinic hydrocarbons which we may employ include 1,3-butadiene, isoprene, 2,3- dimethyl-l,3-butadiene, piperylene, 4-methyl-1,3-pentadiene, 1,3-cyclohexadiene and the like. Examples of nonconjugated diolefinic hydrocarbons which we may employ include 1,5-hexadiene, dipentene and related terpenic hydrocarbons, and the like.

Olefin-acting compounds which we may employ as alkylating agents include various halohydrocarbons, alcohols, ethers, alkyl sulfates or the like containing at least three carbon atoms in the alkylating group. We may employ such halohydrocarbons as alkyl and cycloalkyl halides, especially chlorides or bromides, e. g., isopropyl chloride, n-propyl bromide, t-butylchloride, t-butyl fluoride, isopropyl fluoride, diisobutylene hydrochloride, cyclohexyl chloride, cyclohexyl fluoride, t-methylcyclopentyl chloride, benzyl chloride, 2,4-dichlorobenzyl chloride, bis(chloromethyl)benzenes, allyl chloride, methallyl chloride, 2,3-dichloro-2,3-dimethylbutane, 3-methyl-l,3- dichlorobutane and the like.

Examples of alcohols which may be employed in this invention include isopropyl, n-propyl, isobutyl, t-butyl, t-amyl, benzyl, cyclohexyl, t-methylcyclopentyl and t-octyl alcohols such as dimethylneopentyl carbinol. Various olefin-acting ethers may be employed as alkylating re- Example 1 -A- mixture of toluene and propylene in the molar ratio of 1.1 to 1 was rocked inan autoclavewith 9P5 in the concentration of one 'mol perceng based on propylene,

. at 25C. for 4.5 hours and then allowed to stand an a'dditional 'l hours. In detail; the following procedure was-used. The autoclave was evacuated -a'nd 68 gp'of toluene: was introduced, following which l 69 cc. F1 5 gas was charged-from a calibrated mercury displacement bulbiz Propyle'ne was then pressured into the autoclave at roomtemperature in'the initial quantity of 28 gf The initialtpressure wasabout 200p s. i. g.-' Upon completion of the reaction, the excess pressure in vthe'autoc'lave was-bled olf;and 88.1 g. of a liquid product of slightly reddish color-was removed therefrom, washedwithwater and dried with anhydrous calcium chloride. Upon' comtemperatures ranging upward from 170 C., and its re- 'fractive' index (hi- Wa's 134902.

7 In the following table are recorded examples illustrating the alkylation of benzene by the appropriate alcohols to produce isopropylated, cyclohexylated and t-butylated V V In some of the ex: 7 amples benzenediazonium hexafluorophosphate was egg benzenes in the presence. of PFs.

ployed as catalyst." Reaction was efiected by placing 2.5 mols of benzene and 0.5 molof the alcohol in an Erlenmeyer flask. The: resultant solution was. cooled in ,an

ice hath and approximately one-half mol' of phosphorus pentatluoride was bubbled into the' solution, causing it to becom'ebrown'l: iThefiask was then .placed'onpa steam? plate and the reaction. mixture was refluxed for 2 hours]: The reaction mixture was then allowed-to cool to roorn temperature. It separateddnto' two liquid layers, via. an upper organic'layer and a lower aqueous layer, the

- latterbeing separated. and discarded. The. orgariiclayn was washed twice with 50 ml. portions of 10% aqueous NaOH and twice WithS'O ml; portions of distilled water, following which it was driedfor aboutlZhours with calcium chloride and then distilled from sodium. When benzenediazonium hexafluorophosphate was employed, it

pletio'nofsthe reaction, the product contained 47.2 weight The following'data'were obtained.

TABLE 1 Benzene alkylation .CaHsR CsHlR: .Total :Time Percent 7 Ex. Alcohol ",(Hrs) Catalyst Yield, Yield,. of.

Mols Percfent Mols Percfent Theory 0 0 T e ry. eo y 6 rI N2PFLN .093 19 .066 26 45' 2 PM .100 20 .042 17 '37 6 do v 2' tNzPFh" .-069 14 .061 24 .38 Cyclohexyl. 2 'PF5 .198 40 1037 15 55 '8 .410. i 2' N2PF6- .1 62 32. .058 23 .55

cent of alkylate containing 16 carbon atoms per-molecule; The cymenes yield was 21.7% of theoretical and 'the diisopropyltoluene yield was 20% of. theoretical.

' -Example 2 7 Into a B-necked flask fitted with a reflux-condenser were placed 200 g. oft-butylbenzene and 35 glof Z-pentene. T he flask was also provided with a thermometer and a'PFs inlet tube extendingbelow the liquid level. The mixture was heated to reflux-and PFa' gas-was slowly introduced from a calibrated mercury displacement 'bulb. @ver a 48 hour period the pot temperature increased fromfiifi" C. to 197 C. A total-of--6'l2cfibfPFs; gas Wasadded. .The solution turned dark and opaque: Product was cooled, 'water-wasned and .dr'iedz'over calcium chloride. The product weighed2l'd5 'g. Distillalation yi eIdedl-ZA g." ofmate'rial beiling 216243 :CL, n 1.4828; The yield of the mon'o'alkylate, based on Z-pentene, is 12.7% of theoretical Y i 'urpris'ingly, we'have found: that anhydrousy..liquid hydrogen fluoride exerts an :ifrhibitin g ietrect =in.;-.a;lkyla- .In the above table, R represents the alkyl or;,cycloalkyl group whichwas'substituted in the benzeneQnucleustviz.

7 In order todeterrnine the p'ositionlof thealk-yl, groups in the diallcylated benzenes,.-oxidation"of theside chains to well-known benzene derivativeswas usedf' The iso:

. meriophthalic acids or theirniethyl esters diiferwidely tion, particularly in the alkylation of toluene :by proin melting pointsh Two and fivertenths grains of .diisc-- propyl lbeuzene were r-iflixed with300 ,ml. of 5 N nitric acid fori18 hours. .A 77% yield of phthalic. acidwas obtained; After recrystallization from hot; water .and drying, the acid fsublirned without. melting above '300 f indicatingterephthalic acid This acid..was' heated with absolute methanol'in 'the presence of lqrydrogen clilor'-ide. On cooling, a mass of White. crystals separated in the form'pf thin plates 'Ihe-crystalsmelted at 1412;, in:

dicatingthe dimethylrester ofterephthalic acidgThere was noindication'ofjs'ophthalic ester; A-separate-sample of the acid "was'atested- -f or orthophthalie acid by conver} sion to fluorescein (S. P. Mulliken, The Identification of Pure Organic Compounds, vol. I, pp. 84-5). The test indicated the presence of the ortho isomer but in very small quantity. The strongest test was given by the phthalic acid derived from the diisopropyl compound. The structures of the di-t-butyl and dicyclohexyl compounds were determined by oxidation with chromic acid, and 86% and 72% of terephthalic acid was obtained.

This was identified as before.

In Table 3 are presented data obtained in examples of the alkylation of benzene with isopropyl alcohol, characterized chiefly by the employment of relatively small proportions of PFs, based on the alcohol, as compared izvith the examples of Table 1. The alkylations of Table 3 were carried out in glass apparatus at atmospheric pressure, employing PFs gas derived from the thermal deco position of benzene-diazonium hexafluorophosphate i an autoclave at 120l25 C. The PF5 and nitrogen gases which were formed were bubbled through the reaction mixture contained in a flask cooled in an ice bath. Upon absorption of PR; in the reaction mixture it changed from colorless to a canary yellow color and two liquid layers formed. The reaction mixture was refluxed thereafter for one hour. The reaction mixture Was then cooled to room temperature, the lower aqueous layer was discarded and the upper hydrocarbon layer was washed twice with aqueous sodium hydroxide and then with water. The hydrocarbon products were then dried over anhydrous calcium chloride and distilled from sodium.

TABLE 3 6 the 1,2,4-isomer. The tetraisopropylbenzene of Example 10 was found to melt at 117.5 to 118.5 C., indicating the l,2,4,5-isorner.

In Table 4 are presented data obtained in examples in which PF5 gas was employed as a catalyst under pressure with isopropanol, isopropyl chloride and propylene for the alkylation of benzene and toluene. In these examples the PF5 was free of nitrogen,

The procedure employed in performing Example 15 is described in detail since it is typical of the procedure employed in the other examples of Table 4. The reactor was a 250 cc. stainless steel autoclave provided with a magnetically-actuated stirrup-type stirrer (a commercial Magne-Dash reactor). It was pressure-tested with nitrogen, then evacuated and 78 g. of reagent grade benzene and 20 g. of isopropanol were introduced. The autoclave was then heated to 150 C. and PFs from a weighed sausage bomb was added over a 2.5 hour period, more being added as the pressure dropped. A total of 19 g. of PFs was added and the maximum pressure was 500 p. s. i. g. at 150 C. Stirring of the reaction mixture was stopped after 2.5 hours and the autoclave was allowed to cool. The autoclave was opened and the product was transferred to a separatory funnel. The lower aqueous layer was separated and discarded. The upper hydrocarbon layer was Washed twice with 50 cc, each of aque ous 10% NaOH solution and twice with water. The hydrocarbon product was dried over calcium chloride and, weighed 71.2 g. The product was distilled from Alkylation of aromatic hydrocarbons with isopropanol using PFs gas Molar Reaction Alkylate, Percent Theor. Yield Total Ex. Me] Ratio, Ratio, Period, Alkylate,

Aromatic/Alcohol Pf5/A1Clh0l Hrs. Percent CaH5R COH4R: CuHaRa C HzR4 Theory (CaHo) 5/1 0. 6 35. 7 17. 3 12. 2 l5. 6 80. 8 (CaHa) 3/1 0. 52 5 31. 8 l 17. 3 12. 7 30. 9 92. 7 (CuHu) 2/1 0. 59 8 25. 5 14. 5 b 53 93.0 (05111) 1/1 0. 59 2 24. 2 18. 5 12. 2 35. 8 90. 7 (Cumene) 5/1 0. 45 2 I 25. 4 19. 2 15. 1 59. 7 (Toluene) 5/1 0. 45 2 48. 0 15. O 18. 0 81. 0

I Largely para-diisopropylbenzene. b Based on triisopropylbenzene. Ortho:meta:para=2:1:1.

Examples 9 to 12 show that decreasing the ratio of sodium using a 3-foot high, %-inch diameter Stedman benzene to alcohol has little elfect on the yield of diisopacked still. Distillation of products gave:

propylbenzene. The yield of monoisopropylbenzene is reduced as the ratio is decreased and higher yields of Grams Presslge, the polyalkylated benzenes are attained. Alkylation of g toluene and cumene with isopropanol in Examples 13 and 14, respectively, gave higher Yields of the dialkyliftfifilfiarsaun'ai: :3 i213 i ifrIIIIIIIII Z2333 benzene products. Diisopropylbpgzeneun 60.8 T triisopropylbenzene of Example 10 Was f01 1nd t0 gg if flgfff lffi fi Z; i{ f boil at C. at 20 mm. Hg, 11 1.4910, indicating TABLE 4 Alkylatz'on of aromatics under pressure using PF5 gas Alkylate, Percent Theor. Molar Ratio, Aromatic/Alkylating MolarRatio, Temp., Press, Reaction Ex. Agent PF5/Alkylat- O. p. s. 1. g. Penod,

ing Agent Hrs. G0H5R O6H4R2 Poly- Total alkylate (CnHs) 3/1 (Isopropanol) 0. 45 500 2. 5 45. s 18.9 n 15. 6 so. 3 (C6Hfl)3/1(ISOPTOP3HOD 0.5 24 350 24.0 71.4 21.5 92.9 (CrHa)3/1(Isopr0pylchlon e) 0.59 142 525 3.0 50.0 29.0 =14.7 03.1 (Toluene) 5/1 (Propene) 0.05 24 200 1.0 s 40.0 d 49.3 89.3

H Based on tetraisopropylbenzene. b Largely para-.

B 60% orthu; 20% meta; 20% para. 6 Based on diisopropyltoluene.

that a much higher yield of isopropylbenzene was ob .tained at room temperature and a'r'elatively long reaction period than at the conditions of'high temperatureand relatively short reaction period.

. Substitution of .isopropyl chloride for isopropyl alcoholin the 'alkylation of benzene in an autoclave at elevated temperature and. pressure gave higher yields; of mono and diisopropylbenzenes as: shown by Example 17; This reaction may. be eifected with much smalleramounts of PF but it was carried out with this much PF-s to compare it with alkylations using alcohols. position was preferred in,dialkylation, possibly because of steric as well as electronicefiects.

.In Example 18 the alkylation of toluene with propylene proceeded at room temperature (and 200 p. s. i. g.) using only a small amount of PFs. the steric' effect of'a methyl group in the aromatic feed stock is much smaller than that'of an isopropyl' group since the predominant dialkylbenzene was the ortho isomer. 7 V

In the alkylation of benzene by isopropanol in the presence of 0.5 to 1" mol of benzenediazonium hexafiuorophosphate per mol of isopropanol, the formation of substantial yields of diphenyl, amounting to about onethird of the theoretical maximum, was noted in some instances. Apparently, decomposition of the hexafluorophosphate in the presence of benzene and PFs occurs to form nitrogen, HF and diphenyl.

Chemical and physical tests we'reusecl to determine the isomer distribution of the diisopropylbenzene s of Examples 10, 13 and 17. These were'oxidized withl SN 'nitric acid for 16-18 hours at reflux temperature. Oxidation yields of 75 to 82% were obtained. .'The phthalic :acids sublimed above 300 C.- Only a faint test for 'orthophthalic acidwas obtained by means of the fluoi rescein test. The acids were converted to the dirnethyl ester by reaction with absolute methanol and anhydrous HCl during one hour at reflux temperature. 'White plates of the dimethyl ester were obtained which melted at 139440 C. indicating the para isomer, dimethyl terephthalate. Thus the'strueture of the original hydro- .carbon was predominantly para-diisopropylbenzene.

Although the specificexamples illustrate certain facets of our invention, it will be understood that it is more broadly applicable. The alkylation may be conducted at temperatures between about C. and about 150 C., the most desirable temperature or. temperaturerangeemployed in any specific instance beingreadily determined by simple small-scale experiment. The pressure "can likewise be broadly varied as well as the molar ratios of the reactants and of catalyst to the reactants. The-re action can be carried out in the presence of-inert-solvents or reaction media, usually in the presence of non-reactive Example 18 indicates that tion,products (resulting from the introduction of. more than onealkyl group in the aromatic 'compoundcmployed as charging stock): arewnot desired, the'ipolyalkylation products formedin the reaction may be recycled, in*continuousprocesses, orrnay; be charged in proportions up to about the equilibrium proportion in batch. .a'lkylation procedures. The usual :equipment-and operating methods I which are known in the alkylation artand in related arts of effecting chemical reactions and processes may be employed for the purposes of our invention: and especially forits adaptation to large scale usage.

Having. thus described our invention, what we claim is: f 3 1. Anqalkylationv process-which comprises contacting;

aniaromatic-compound having at leastonefialkylatablet nuclear carbon atom with an olefin-acting compound cointaining at least three carbon atoms in .the. alkylatigng group withPFs under alkylation reactiontconditionsfia The para 2. The process of claim lwherein said: aromatic coh pound is" an aromatic-hydrocarbon.

3. An alkylation process which :comprises contacting an aromatic hydrocarbonih'aving at, least .one alkylatable nuclear carbon'atom with a monoolefinic hydrocarbon containingat least three' carbon.atomsper molecule and WithPFs underalkylation reaction. conditions. a

Y 4. The process of claim 3 wherein'saidmonoolefinic hydrocarbon contains azterminal vinyl group.

5. The process of -claim 3 wherein said aromatic hydrocarbon is benzene andsaid'monoolefinic hydrocarbon is propylene.

6. The process of claim 3 wherein said aromatic hydrocarbon is toluene and said monoolefinic hydrocarbon is propylene. V e

. .7.. The process ,of claim 3 wherein-said aromatic hy drocarbon is cumene and said monoolefinic hydrocarbon is propylene V V H 8. The process of claim 3 wherein said aromatic hydrocarbon: is t-butylbenzeneand saidmonoolefinic hydro- .carbon is isobutylene hydrocarbons such as liquid paraffins and/or cyclo" per part by weight of the aromatic compound employed 7 as a .feed stock. Inthoseinstances in which polyalkylw a k tm q s s .wh s 9 P i wad an aromatic hydrocarbon having at least one alkylatable nuclear. carbon atom with an alcohol having at least three carbOn-atomsper molecule and-with P-Fs under alkylation reaction conditions; j W 1;; i V

10;:alkylation process which comprisescontacting an' aromatic hydrocarbonhavingat least one alkylatable nuclear carbon atom with a hal'ohydrocarbon: having at least three carbon atoms per molecule [andwith PFsunder alkylation reaction conditions.

-11.. Analkylation process which comprises reacting a secondary aleohol'containing' at leastlthree carbon' atoms per moleculeand at least an equimolarproportion of an aromatic compound having at least one alkylatable nuclear carbon atom WithPFs in a proportion of at least about 30 mol percent,based onsaid alcohol, at-a ternperature suflicient' to efiect' 'alkylation.

References Cited in the file of this patent UNITED STATES PATENTS 1,933,434 Hofmann et a1. Oct. 31, 1933 2,430,660 Axe Nov. 11, 1947 2,584,102 Mavity- Feb. 5. 1952 2,683,763 Lien et: al. 2 July 13 1954 2,683,764 Lien et al. Julyl3j1954

Claims (1)

1. AN ALKYLATION PROCESS WHICH COMPRISES CONTACTING AN AROMATIC COMPOUND HAVING AT LEAST ONE ALKYLATABLE NUCLEAR CARBON ATOM WITH AN OLEFIN-ACTING COMPOUND CONTAINING AT LEAST THREE CARBON ATOMS IN THE ALKYLATING GROUP WITH PF6 UNDER ALKYLATION REACTION CONDITIONS.