US2849501A - Process for making chloromesitylene - Google Patents

Description

United States Patent PROCESS FOR MAKING CHLOROIVIESITYLENE Frank H. Bolton, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware N0 Drawing. Application March 18, 1957 Serial N0. 646,545

11 Claims. (Cl. 260-650) This invention concerns a process for making chloromesitylene from mixtures of aromatic hydrocarbons containing nine carbon atoms in the molecule and comprising mesitylene. It relates more particularly to a process for separating from one another aromatic compounds comprising essentially a mixture of ortho-ethyltoluene and mesitylene derived from petroleum stock and pertains especially to the production of monoand dichloromesitylene.

This application is a continuation-in-part of my application Serial No. 573,638, filed March 26, 1956, now abandoned.

It is known that certain petroleum stocks contain substantial proportions of aromatic hydrocarbons which are present as alkylated aromatic compounds in varying degrees of alkylation, e. g. as ethyltoluene, trimethylbenzenes or tetramethylbenzenes. Separation and recovery of these aromatic compounds from one another by fractional distillation is difficult because of their overlapping or closely adjacent boiling points. The separation of ethyltoluenes from trimethylbenzenes, e. g. the separation of ortho-ethyltoluene from mesitylene, is particularly difiicult, and cannot satisfactorily be accomplished by fractional distillation. Recourse to chemical methods for effecting an eflicient separation of such aromatic hydrocarbons from one another has heretofore proved difficult.

It is an object of the invention to provide a process for the separation and recovery of aromatic compounds comprising mesitylene and containing nine carbon atoms in the molecule from one another. Another object is to provide a process for making chloromesitylenes from a mixture of aromatic hydrocarbons containing nine carbon atoms in the molecule and comprising mesitylene. A further object is to provide a process for making chloro mesitylene from a mixture of aromatic hydrocarbons comprising essentially ortho-ethyltoluene and mesitylene. Other related objects may appear from the following description of the invention.

According to the invention a mixture of aromatic hydrocarbons, i. e. alkylated benzenes, containing nine carbon atoms in the molecule and comprising mesitylene can readily be chlorinated under conditions permitting the preferential nuclear chlorination of the mesitylene and the chlorinated mesitylene can thereafter readily be separated from the unchlorinated aromatic hydrocarbons by fractional distillation.

More specifically, the aromatic hydrocarbons obtained by subjecting an aromatic petroleum stock to fractional distillation to obtain a fraction containing substantially only aromatic hydrocarbons having nine carbon atoms in the molecule and comprising essentially a mixture of ortho'ethyltoluene and mesitylene can readily be chlorinated under conditions permitting the preferential nuclear chlorination of the mesitylene, after which the chlorinated mesitylene can readily be separated from the unchlorinated aromatic hydrocarbons, e. g. ortho-ethyltoluene.

The invention provides a process for the production of chloromesitylenes, e. g. monoand dichloromesitylenes, and of separating ortho-ethyltoluene from a mixture of mesitylene and ortho-ethyltoluene.

The process can be applied to any mixture of aromatic hydrocarbons having nine carbon atoms in the molecule and containing mesitylene. In its practical aspects the method is most effective for the production of chloromesitylene from C aromatic hydrocarbon fractions obtained by subjecting an aromatic petroleum stock to fractional distillation to obtain a fraction containing substantially only aromatic hydrocarbons containing nine carbon atoms in the molecule, and preferably a fraction consisting principally of a mixture of ortho-ethyltoluene and mesitylene. For this purpose, the aromatic petroleum fraction usually employed as starting material in the process is a fraction boiling within the range of from to 200 C., preferably from to C., at atmospheric pressure.

The chlorination is carried out in darkness, i. e. in the absence or substantial absence of light at temperatures between 10 and 110 0., preferably from 40 to 100 C., and at atmospheric or substantially atmospheric pressure. It may be mentioned that, within this temperature range of from 10 to 110 C., the chlorination appears to proceed toward the formation of monoand dichloromesitylenes more effectively at temperatures between 40 and 100 C., than at lower temperatures. At the lower temperatures, e. g. at from 10 to 20 C., appreciable amounts of higher chlorinated mesitylenes are produced, apparently by the side chain chlorination of the dichloromesitylene formed in the reaction. For these reasons the chlorination is preferably carried out at temperatures between 40 and 100 (1., although good yields of monochloromesitylene are obtained at reaction temperatures throughout the range of from -10 to 110 C.

The chlorine is usually employed in amount corresponding to from 0.75 to 1.5 grams molecular proportions of the chlorine per gram molecular equivalent proportion of the mesitylene in the aromatic hydrocarbon starting material. The chlorine can be employed in an amount less than the stoichiometric amount required to form monochloromesitylenes, but is preferably employed in amounts of from 1 to 1.2 moles per mole of the mesitylene in the starting material.

The nuclear chlorination can be carried out under the aforesaid reaction conditions in the absence of a halogenation catalyst, or in the presence of a nuclear halogenation catalyst for the reactions. Suitable catalysts are iodine, antimony pentachloride, sulfur, aluminum halides or iron halides, particularly the chlorides and bromides such as ferric chloride, ferric bromide, aluminum bromide or aluminum chloride. The catalyst can be employed in amount corresponding to from 0.01 to 10 percent by weight or more of the mesitylene.

In practice a mixture of aromatic hydrocarbons having nine carbon atoms in the molecule and containing at least 5, suitably from 5 to 50 percent, by weight or more of mesitylene is placed in a reaction vessel, together with a nuclear halogenation catalyst, e. g. ferric chloride .or iron filings. The mixture is stirred and maintained at temperatures between -10 and 110 C. while introducing chlorine into admixture with the liquid in the substantial absence of light in the desired proportions. The chlorine is usually added at a rate not substantially faster than it is consumed in the reaction. Hydrogen chloride is vented from the reaction as it is formed. Upon completion of the chlorination, the resulting material is freed from dissolved hydrogen chloride in usual ways, e. g. by washing with water or with an aqueous solution of sodium hydroxide, and is distilled. The unchlorinated aromatic hydrocarbons are readily separated from the chloromesitylene by distillation. The chlorinated material consists principally of monoand dichloromesitylene, together with higher chlorinated compounds, and the chlorinated compounds can readily be separated from one another by fractional distillation. In mostinstances the chlorination results in a preferential quantitative chlorination of the mesitylene with little, if any, chlorination of the other aromatic hydrocarbons, e. g. 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene or ortho metaor para-ethyltoluenes, containing nine carbon atoms in the molecule which are components of the starting material.

The following examples illustrate ways in which the principle-of the invention has been applied, but are not to be construed as limiting the invention.

EXAMPLE 1 A charge of 1350 grams of an aromatic petroleum fraction boiling at temperatures between 160 and 165 C. atoatmosphere pressure and consisting of 47 percent by weight of mesitylene, 40 percent of ortho-ethyltoluene, 6 percent of meta-ethyltoluene, percent of para-ethyltoluene and 2 percent unidentified, by analysis, was placed in a glass reaction vessel equipped with a reflux. condenser andstirrer. The reaction vessel was painted black to exclude light. A charge of 6.4 grams of iron turnings was added. The mixture was stirred and maintained at temperatures between 48 and 51 C. while introducing 450 grams (6.34 moles) of chlorine into the liquid over a period of about 2 hours. Hydrogen chloride was vented through the reflux condenser. The chlorinated liquid was removed from the reaction vessel and was washed with an aqueous 10 weight percent solution of sodium hydroxide, then with water. The chlorinated liquid was distilled. Table I identifies the fractions. that were obtained from 1490 grams of the reaction mixture.

FractionNo. 1 consisted of 78 percent by weight of ortho-ethyltoluene, 11 percent of meta-ethyltoluene and 11 percent of para-ethyltoluene by analysis. The yield of monochloromesitylene was 74.5 percent based on the mesitylene initially used. The yield of dichloromesitylene was 11.3 percent. The conversion of the mesitylene to chloromesitylenes was quantitative. The recovery of the ethyltoluene was substantially quantitative.

EXAMPLE 2 A charge of 1350grams of an aromatic C hydrocarbon fraction similar to that described in Example 1, together with 10 grams of antimony pentachloride was placed in a darkened glass reaction vessel equipped with a reflux condenser and stirrer. The mixture was stirred and maintained at a temperature of about 0 C. while introducing 374 grams of chlorine into the liquid over a period of about 4 hours. Thereafter the chlorinated liquid was Washed with an aqueous 10 weight percent solution of sodium hydroxide, then with water and was distilled. There were obtained 797 grams of aromatic hydrocarbons (recovered), 15 grams of an intermediate cut, 473 grams of monochloromesitylene and 78 grams of dichloromesitylene. The recovered hydrocarbons consisted of 10 percent by weight of mesitylene, 10 percent of para-ethyltoluene, 10 percent of meta-ethylt'oluene 4 I and 70 percent of ortho-ethyltoluene by analysis. The yield of monochloromesitylene was 59.6 percent based on the mesitylene consumed in the reaction. The yield of dichloromesitylene was 8 percent.

EXAMPLE 3 A charge of 1350 grams of an aromatic C hydrocarbon fraction boiling at temperatures between 144 and 177 C. at atmospheric pressure and obtained by fractionating a petroleum stock was placed in a three liter round bottom glass vessel equipped with a reflux condenser and stirrer. The aromatic hydrocarbon fraction contained 9.9 percent by weight of mesitylene, 8.4 percent of 1,2,3-trimethylbenzene, 30.3 percent of 1,2,4- trirnethylbenzene, 9.9 percent of ortho-ethyltoluene, 16.2 percent of meta-ethyltoluene, 7.1 percent of para-ethyltoluene, 10 percent of n-propylbenzene and 2 percent of non-aromatic, together with trace amounts of lower and higher boiling aromatic hydrocarbons, by analysis. A charge of 6.4 grams of iron turnings was added. The mixture was stirred and maintained at a temperature of 0 C., while introducing 79'grams of chlorine into the liquid over a period of one hour. Thereafter, the liquid was washed with an aqueous 10 weight percent solution of sodium hydroxide, then with water and was distilled. There were obtained 1005 grams of a hydrocarbon fraction boiling at temperatures between 156 and 177 C. at atmospheric pressure, 82 grams of monochloromesitylene boiling at 99103 C. at 25 millimeters absolute pressure and 34 grams of dichloromesitylene. The hydrocarbon fraction contained 3 percent by weight of mestiylene. The yield of monochloromesitylene was 61.5 percent based on the mesitylene consumed in the reaction. The yield of dichloromesitylene was 16.5 percent.

EXAMPLE 4 A charge of 1350 grams of an aromatic hydrocarbon fraction similar -to that described in Example 1 was placed in a black 3-neck glass reaction vessel equipped with a reflux condenser and stirrer. It was stirred and maintained at temperatures between 3 and 1.5 C. while introducing 376 grams of chlorine into the liquid over a period of about 7 hours. The chlorine was added at about the rate it was consumed in the reaction. The liquid material was washed with water to remove the dissolved hydrogen chloride, then was fractionally distilled. Table II gives the fractions that were obtained from 1448 grams of the reaction mixture.

Table II Point, 0.

Pressure. mm.

Hydrocarbons (recovered)-.. 169 170 760 835 Intermediate cut 66. 5401.5 25 18 Monochloromesitylenen 101.5-1025 25 338 d Residue 38 EXAMPLE 5 was added. The mixture was stirred and maintained at temperatures asstated .in the following table while introducing 376 grams (5.28 moles) of chlorine into the liquid over a period of 100 minutes. The chlorinated liquid was cooled, removed from the reaction vessel and was washed with an aqueous 10 weight percent solution of sodium hydroxide, then with water, and dried over anhydrous calcium sulfate. The chlorinated product was distilled. Table III identifies the experiments and gives the proportion of reactants and the reaction temperatures employed. The table also gives the identity and amounts of the products obtained. For purpose of comparison, similar experiments were carried out at chlorination temperatures of 125 C. and at the reflux temperature of the mixture, both of which reaction temperatures are outside the scope of the invention.

The recovered aromatic hydrocarbon fractions from the experiments reported in Table HI above were analyzed to determine their composition. Table IV identifies the experiments and gives the composition of the recovered hydrocarbon fractions.

Table IV Ethyltoluene Mesit- Run No. ylene,

Ortho-, Meta-, Para-, percent percent percent percent The yields of monochloromesitylene and dichloromesitylene obtained in the experiments were as stated in the following Table V, based on the mesitylene consumed in the reaction. The table also gives the temperatures at which the chlorinations were carried out and the amount of residue or material boiling higher than dichloromesitylene obtained in the reactions.

Table V Reac- Chloro- Dichlo- Run No. tion mesitrornesit- Resitemp., ylene, yiene, due, 0. percent percent gms.

EXAMPLE 6 A charge of 1350 grams of an aromatic petroleum fraction similar to that employed in Example was placed in a glass reaction flask painted black and equipped with a reflux condenser and stirrer. The petroleum fraction contained 634 grams (5.28 moles) of mesitylene. A charge of 6.4 grams of iron turnings was added. The mixture was stirred and heated at a temperature of 100 C. while introducing 560 grams (7.9 moles) of chlorine into the liquid over a period of two hours. Thereafter, the chlorinated liquid was cooled, was washed with an aqueous 10 weight percent solution of sodium hydroxide,

then with water, was separated and dried over anhydrous calcium sulfate. There was obtained 1553 grams of crude product. The chlorinated liquid was distilled. Table VI identifies the fractions that were obtained from the distillation.

Table VI Run Boiling Pres- Yield,

N 0. Fraction point, sure, grams 1 Hydrocarbons- -163 760 588 2 Intermediate 66- 98 25 23 3 Monochloromesitylene 98-104 25 626 4 Intermediate cut 104-129 25 14 5 Dichloromesitylene 129-135 25 219 esidm- 71 Loss 26 1 88% monochloromesitylene, 12% ethylchlorotoluene.

Fraction No. 1 consisted'of 83.3 percent by weight of ortho-ethylene, 6.84 percent of meta-ethyltoluene and 9.86 percent of para-ethyltoluene by analysis. The hydrocarbon fraction was free from mesitylene. Fraction 3 was impure and contained 88 percent by weight of monchloromesitylene by analysis. Fraction 5 was substantially pure dichloromesitylene. It crystallized upon cooling. The yield of dichloromesitylene was 22 percent, based on the mesitylene initially used. The yield of monochloromesitylene was 67.4 percent. The conversion of the mesitylene to chloromesitylenes was quantitative.

EXAMPLE 7 A charge of 1350 grams of an aromatic petroleum fraction similar to that employed in Example 5 was placed in a glass reaction vessel painted black and equipped with a reflux condenser and stirrer. A charge of 6.4 grams of iron turnings was added. The mixture was stirred and maintained at a temperature of 0 C. while introducing 281 grams (3.96 moles) of chlorine into the liquid over a period of 2 hours and 40 minutes. The molar ratio of chlorine to mesitylene employed in the reaction was 0.75:1. The chlorinated liquid was washed with an aqueous 10 weight percent solution of sodium hydroxide, then with water and was dried. There were obtained 1474 grams of crude product. The crude product was distilled. Table VII identifies the fractions that were obtained in the distillation.

mesitylene, 60 percent of ortho-ethyltoluene, 5 percent of meta-ethyltoluene and 8 percent of para-ethyltoluene. Fraction No. 3 was monochloromesitylene of high purity. The yield of said product was 67 percent based on the mesitylene consumed in the reaction.

I claim:

1. A process for making monoand dichioromesitylenes which comprises reacting chlorine with a mixture of aromatic hydrocarbons having nine carbon atoms in the molecule and substantially free of unsaturated side chains and boiling at temperatures between 155 and 200 C. at atmospheric pressure and containing at least 5 percent by weight of mesitylene by introducing chlorine into admixture with the liquid aromatic hydrocarbons in amount corresponding to from 0.75 to 1.5 gram molecuof the mixtureto' actinioefrfadiation and at reaction temhydrocarbons. I

2. A process as claimed in claim 1, wherein the chlorination is carried out in the presence of a nuclear halogenation'catalyst.

3. A process-as claimed in claim 2, wherein the nuclear halogenation catalyst is ferridchloride.

4. A processfor makingmonoand dichloromesitylones which comprises reacting-chlorinewith a mixture of aromatic hydrocarbons having ninec'arbon atoms in the molecule and substantially free of unsaturated side chains and boiling attemperatures between 160 and 175 C. at atmospheric pressure and comprised essentially of a mixtureof ortho-ethyltoluene'"and'mesitylene by introducing chlorine into admixture-with ,the liquid-aromatic hydrocarbons at temperatures between--10 and 110 C.

- and in amount-corresponding to from about 0.75 to 1.5 gram molecular proportions-of the-- chlorine per gram molecular proportion of the'mesitylene substantially without exposure of the mixturetoactinic radiation and separating the-chlorinated mesitylene'from the ortho-ethyltoluene.

5.- A process-asclaimed in claim 4,--wherein the chlorination iscarried out in the-presence of a nuclear halogenation catalyst.

6. A process as claimed in claim 5, wherein the nuclear halogenation catalyst is ferric chloride.

' peratures between .10?-.and 110- C. and separating the chlorinated mesitylenes from the unchlorinated aromatic 7.-'A process for making monoand dichloromesitylone which comprises subjecting an aromatic petroleum stock to fractional distillation, separating a fraction boiling at-temperatures between 160 and 175 C. at atmospheric pressure and comprised essentially of a mixture of ortho-ethyltoluene and mesitylene, chlorinating said fraction by introducing'chlorine into the liquid material at temperatures between -10 and 110 C. in amount corresponding to from 0.75 to 1.5 gram molecular proportions of the chlorine per gram molecular proportion of the mesitylene substantially without exposure of the mixture t-o actinic radiation, then fractionating the resulting material and separatingortho-ethyltoluene from the chlorinated material and fractionating the chlorinated material to obtain monochloromesitylene and dichloromesitylene.

8. A process as claimed in claim 7, wherein the chlorination is carried out at temperatures between 40 and C.

9. A process as claimed in claim 8, wherein the chlorination is carried out in the presence of a nuclear halogenation catalyst.

10. A process as claimed in claim 9, wherein the nuclear halogenation catalyst is ferric chloride.

11. A process as claimed in claim 9, wherein the nuclear halogenation catalyst is antimony pentachloride.

No references cited.

UNITED STATES PATENT OFFICE @ERTEHCATE @F CORRECTION Patent Now 2 849 501 August 26, 1958 Frank H Bolton t is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below- Column 6, line 20, for "ortho===etlaylene, read ortho=ethyltoluene, n =0 Signed and sealed this 16th day of December 19580 Attest:

KARL HQ AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents

Claims (1)

1. A PROCESS FOR MAKING MONO- AND DICHLOROMESITYLENES WHICH COMPRISES REACTING CHLORINE WITH A MIXTURE OF AROMATIC HYDROCARBONS HAVING NINE CARBON ATOMS IN THE MOLECULE AND SUBSTANTIALLY FREE OF UNSATURATED SIDE CHAINS AND BOILING AT TEMPERATURES BETWEEN 155* AND 200*C. AT ATMOSPHERIC PRESSURE AND CONTAINING AT LEAST 5 PERCENT BY WEIGHT OF MESITYLENE BY INTRODUCING CHLORINE INTO ADMIXTURE WITH THE LIQUID AROMATIC HYDROCARBONS IN AMOUNT CORRESPONDING TO FROM 0.75 TO 1.5 GRAM MOLECULAR PROPORTION OF THE CHLORINE PER GRAM MOLEUCLAR PROPORTION OF THE MESITYLENE SUBSTANTIALLY WITHOUT EXPOSURE OF THE MIXTURE TO ACTINIC RADIATION AND AT REACTION TEMPERATURES BETWEEN -10* AND 110*C. AND SEPARATING THE CHLORINATED MESITYLENES FROM THE UNCHLORINATED AROMATIC HYDROCARBONS.