1 3,267,165 United States Patent 0 Ce Patented August 16, 1966

1 2 that the addition of polyphosphoric acid to 3,267,165 has the effect of lowering the freezing point of the mix PREPARATION OF MESITYLENE BY DEHYDRO CONDENSATION 0F ture and improving the viscosity index, thus enabling the Robert C. Kimble, Charanjit Rai, and John B. Brann use of the acid in reaction involving lower temperatures warth, Crystal Lake, 11]., assignors, by mesne assign necessary to prevent charting, e.g., in dehydrocondensa ments, to Union Oil Company of California, Los An tion reactions, as illustrated by the synthesis of mesitylene geles, Cali?, a corporation of California from acetone. The freezing point of concentrated sul No Drawing. Filed Dec. 19, 1963, Ser. No. 331,928 furic acid (0° to 10° C.) presents a lower limit of operat 8 Claims. (Cl. 260-668) ing temperatures and such temperatures sometimes allow 10 considerable side reactions to take place. At best, the This invention relates to a method of preparing mesity prior art yields of mesitylene from acetone are only about lene and more particularly to a new catalyst composition 16%. In accordance with this invention, ‘the use of poly comprising concentrated sulfuric acid and about 1 to 5 0% phosphoric acid .with sulfuric acid produces yields of by weight of polyphosphoric acid for the condensation 17.5% and higher. Furthermore, charring is prevented of acetone to mesitylene. The reaction may be repre 15 and the total reaction time is reduced. sented as follows: Accordingly it becomes a primary object of this inven on: on. tion to provide a method of synthesizing mesitylene vfrom (i=0 on; ‘ acetone using sulfuric acid containing a small amount, up to about 50%, of polyphosphoric as the catalyst. Another object of this invention is to provide a method Hio/ %h\ Elsi; m for synthesizing rnesitylene ‘from acetone using catalytic 0 o ona crn-V-orr, amounts of sulfuric acid containing a su?icient ‘amount (Ii-on, of polyphosphoric acid to allow the reaction to proceed CH; without charring. 25 3 moles acetone rnesitylene Another object of this invention is to provide a method This illustrates one of the rare syntheses of an aromatic for synthesizing mesitylene from acetone using a catalyst ‘from aliphatic starting materials. Mesity~ consisting essentially of concentrated sulfuric acid and lene is useful in many organic syntheses. It is an aro about 1 to 50% by weight of polyphosplioric acid. matic compound having free ortho and para positions Another object of this invention is to provide a method and as such is useful in diazo coupling reactions with for synthesizing mesitylene from acetone using a catalyst phenols and amines. One is the coupling of mesitylene consisting essentially of concentrated sulfuric acid and with diazotized picramide: about 2 to 30% by weight of polyphosphoric acid.

N0: CH: Another .object . of .this invention is to provide. a method I Hm 35 for synthesizing mesitylene from acetone using a catalyst [O,N__ NENBOJI- + OH: consisting essentially of concentrated sulfuric acid and —— I——— about 10% by weight of polyphosphoric: acid. NO; OH; These and other objects of this invention will become N01 0H3 apparent or be described as the speci?cation proceeds. l 40 In order to demonstrate the invention, a series of tests O?N-©_N=N—/ CH5 were conducted to show the ‘freezing point and viscosity I index effects of adding polyphosphoric acid (PPA) to N01 sulfuric acid (H2504). The results of these tests are 2,4,G-trinitrobenzeneazotnesitylone Shown in Table I_

TABLE I

Freezing Viscosities (SUS) at- n _ Composition Point 1 \/ lscosity (° C.) ndex 2 70° )3‘ 100° F. 130° F. 210° F.

987 H so. ______-1 —7 68.6 51. 0 42. 6 33. 5 9s satin pQercent msoi, 2\v.pcrcent PPA. 68.3 50.9 42.6 33.5 100 93 w. percent H1804, 5 w. percent PPA, 68. 4 51.1 42. 8 (33. 7 110 78 w. percent H2804, 20 w. percent PPA 74. 6 54. 7 45.1 234. 9 152 58 w. percent H2804, 40 w. percent PPA 121 76.1 56. 7 d8. 8 112 100% PPA ______1,815 718 335 86.9 120

l Freezing points were determined in the manner of ASTM pour points. = Viscosity indices were determined from 100° F. and 210° F. viscosities.

Mesitylene can be easily oxidized to trimesic acid, use From these results it is readily seen that amounts of ful in resin preparation and the like. Other uses of me PPA up to about 50 w. percent in concentrated H2804 sitylene are known to those skilled in the art. results in lowered freezing point and improved viscosity In accordance with this invention it has been found index. ‘ 3,267,165 3 4 In order to compare the catalytic effect of the combina conversion of acetone to mesitylene which require low tion catalyst of this invention, two experiments were con temperatures to avoid charring. ducted to compare the instant process with the prior art. No particular precautions need be taken in carrying out In experiment A the results reported by Adams and Huf the process of this invention, aside from those that one -feed, Org. syntheses, I, 341, Second Ed. (1956) are re skilled in the art is aware of using acetone-acid mixtures. produced. The reaction is conducted at a temperature of about TABLE II Procedure \ A B 0

Acid ______90 v. percent H2SO4-10 v percent PPA. Cone. H2504. Temp. ______—13° to —10° C ______-—13° to -—10° C. Acid addition time. 35 min ______. _ 35 min. Mixing after acid addition.___ 2 hours ______2 hours. Allowed to react at room temp .... ._ 6-24 hours ______0 hours ______0 hours. Steam distillation ______. _ Steam distillation ______. _ Steam distillation. Product isolation """""""""" ' ‘ Fractional distillation _ _ _. . gractional distillation. . . . Fractional distillation. Mesitylene yield ______. _ Averages 51 g_ - ___ 5 g ______43.3 g. Percent of theoretical yicld_ __ 16.3% ______17.5%. . 13.8% Minimum total reaction time ______. 9% hours ...... __ 2% hours_____ . 2% hours.

In experiment B the use of 90 vol. percent sulfuric acid —l0° C. to —50° C., e.g., the acid addition temperature containing 10 vol. percent PPA is shown to produce a 20 is about —l0° C. to about -50° C. The acid composi greater yield at lower temperatures and shorter reaction tion is concentrated sulfuric acid containing about 1% time. Furthermore, there was no problem of the viscosity by wt. to 50% by wt. of polyphosphoric acid. The mix of the catalyst mixture and the handling of reaction B ing time will vary with the temperature chosen for the was facilitated. In experiment C the Adams and Hutfeed reaction. In general the mixing time is essentially the Experiment (A) is duplicated at the temperatures of this time required to slowly heat the mixture from the acid invention, i.e., at —13" to 10° C. instead of 0° to 10° C. addition temperature to the steam distillation tempera This shows the superiority of the combination catalyst ture. Between about 200 to 800 parts of acetone can be of this invention as compared with concentrated sulfuric used with 400 parts of acid catalyst. Preferably the acid at ~13° to —10° C. It is apparent from the data weight or part ratio of acetone to acid catalyst is about that the yield of mesitylene using concentrated sulfuric 1/ l. 1 acid at —10° to ~13" C. is even lower than the yield at In order to illustrate a speci?c procedure the ‘following 0° to 10° C. and that even higher yield obtained by is given: Adams and Huffeed was lower than the yield obtained Into a 2-liter, 3-necked ?ask equipped with mechanical with the combination catalyst of this invention at the stirrer and thermometer was charged 460 g. of acetone. lower reaction temperature. The acetone was cooled to -—10° C. and a mixture of 41 In carrying out the process of this invention, concen cc. of polyphosphoric acid and 375 cc. of concentrated trated sulfuric acid is used having a concentration of sulfuric (95.7%) acid was slowly added with stirring over about 90% to 98%. The polyphosphoric acid (PPA) a period of 35 minutes. Temperature was maintained at ‘used in accordance with this invention is an equilibrium —l0° to ~15“ C. After addition of acid was completed mixture of ortho-, pyro, and polymeric phosphoric acids. the mixture was slowly heated to steam distillation tem The composition is expressed in terms of P205. The perature. The ?ask meanwhile was equipped with a present commercially available product, as used to dem steam inlet tube extending to the bottom of the ?ask and onstrate this invention, contains 82-84 percent phos a water cooled condenser attached in a downward posi phorus pentoxide, as such containing a mixture of ortho tion for distillation. The mixture was distilled with steam (5%), pyro (20%), tripoly (16%), tetrapoly (16%), stripping. The crude product, collected over a one-hour penta (13%), hexapoly (9% ), heptapoly (6%), octapoly period was water washed. Mesitylene was obtained by (4%), monopoly (4%) and hypolyphosphoric acids fractional distillation at 87° to 92° C. at 100 mm. pres ( 1%) at the 85% level, and 66% hypolyphosphoric sure in 55 g. yield. This is 17.5 percent of the theoretical acids with 2-6% of each of the ortho to monopoly acids yield. at the 86% level. PPA containing 72-89.9% P205 can 50 7 Because of both the physical and catalytic effect of be prepared by dehydration of commercial 85% phos PPA on sulfuric acid as demonstrated herein, this inven phoric acid by heating, addition of the proper amount of tion and the H2SO4—PPA mixtures described have other water to P205 and the application of heat to establish uses wherein one or both such properties are utilized. equilibrium or by the reaction of P205 with 35% phos Sulfuric acid is widely used in chemical technology, as a phoric acid. catalyst, selective solvent, condensation agent, reactantt, By the most recent analytical methods, it has been etc. To control many processes using sulfuric acid, it is established that commercially available PPA with 82 frequently necessary to operate at low temperatures. It 89.4% P205 contains about 10% tripoly-, 10—12% pyro-, is also advantageous to operate at low temperatures with 12% tetr-apolyphosphoric acid, the remainder being ortho, out derogation of the catalytic action of the sulfuric some cyclic phosphoric acids and other polyphosphoric 60 acid. Examples of these other sulfuric acid processes that acids. Accordingly the term Polyphosphoric acid, as ‘used are necessarily operated at low temperatures are: the syn in this speci?cation and claims is intended to mean and thesis of thiophenol from -sulfonyl chloride, the include any condensed phosphoric acid containing about synthesis of nitrourea from urea nitrate, the separation 72% P205 to about 90% P205 and preferably about 82 to of aromatic and unsaturated from satu 89.4% P205. Polyphosphoric acid is an extremely vis 65 rated hydrocarbons and some sulfonation reactions. cous, colorless, hygroscopic liquid having a speci?c gravity Accordingly, this invention is applicable to any re of 2.060 at room temperature (20° C.). It is a rigid action employing sulfuric acid wherein lower tempera glass when cold and conveniently ?uid at 60° C. tures are necessary, as to avoid charring, or wherein a ' The catalytic mixture of this invention is prepared by combination of lower temperatures and the catalytic effect mixing H2SO4 and PPA in any order so as to incorporate of the combination of H2504 and PPA can be used. 1 to 50% of PPA with the H2804. This mixture is ?uid The embodiments of the invention in which an exclu and readily used in conventional apparatus to carry out sive property or privilege is claimed are de?ned as ‘fol the reaction of this invention. lows: The process is carried out by using the known tech 1. The process of preparing mesitylene which com ‘niques for dehydro-condensation reactions involving the prises subjecting acetone to dehydrocondensation in the 3,267,165 5 6 presence of sulfuric acid containing at least about 1% by said polyphosphoric acid contains about 82 to 89.4% weight of polyphosphoric acid. phosphorus pentoxide. 2. The process in accordance with claim 1 in which 7. The process in accordance with claim 5 in which said sulfuric acid contains about 1% to 50% by Weight about one part of acetone is reacted with about one part of polyphosphoric acid and said polyphosphoric acid con of said sulfuric acid-polyphosphoric acid mixture. tains about 72 to 90% by wt. of P205. 8. The process in accordance with claim 5 in which 3. The process in accordance with claim 1 in which the the time of the reaction is essentially the time required to reaction is conducted at a temperature of about —10° slowly heat the mixture from the acid addition tempera~ to —50° C. ture to steam distillation temperature, and said mesity 4. Process in accordance with claim 1 in which the 10 lene is recovered by steam distillation. sulfuric acid has a concentration of about 90% to 98%. References Cited by the Examiner 5. The process of preparing mesitylene which consists in subjecting acetone to dehydrocondensation in the UNITED STATES PATENTS presence of sulfuric acid containing about 10% by 2,431,754 12/1947 Ipaticff et ‘a1 ______260——668 15 volume of polyphosphoric acid, said polyphosphoric acid 3,201,485 8/1965 Kovach ______.__ 260—668 containing about 72 to 90% by weight of phosphorus pentoxide. DELBERT E. GANTZ, Primary Examiner. 6. The process in accordance with claim 5 in which C. R. DAVIS, Assistant Examiner.