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Home , Hydrogen fluoride

Patented Oct. 18, 1949 2485,237 UNITED STATES PATENT OFFICE 24.85,237 - SYNTHESIS OF ABOMATIC ALDEHYDEs William F. Gresham and Georges E. Tabet, Wi nington, Dell assignors to E. E. du Pont de Nemours & Company, Wilmington, De, a cor poration of Delaware No Drawing. Application August 24, 1946, Serial No. 692,936 14 Claims. (CL 260-599) 2 This invention relates to the synthesis of aro approximately equivalent amount of matic aldehydes and more particularly to a . In a specific embodiment the invention method for the preparation of aromatic alde contemplates the synthesis of p-tolualdehyde by hydes by reaction between aromatic hydrocar subjecting a mixture of toluene and carbon mon bons and in the presence of -3. oxide to the action of a catalyst containing about mixed hydrogen fluoride- cata 0.5 to 1.5 mols of boron fluoride per mol of hy lyst. drogen fluoride at a temperature of -80° to It has been disclosed heretofore (U. S. Patent --50' C. under superatmospheric pressure. 2,135,447) that aromatic aldehydes such as benz One of the surprising features of the present aldehyde can be prepared by reaction between invention is the discovery that at very low tem aromatic and carbon monoxide in peratures the reacticn between carbon monoxide the presence of volatile halides such as hydrogen and the aromatic is very rapid even chloride, hydrogen fluoride, boron fluoride, etc. at pressures which may be as low as about 10 This process for the preparation of aromatic al atmospheres. Higher pressures, i. e. pressures dehydes, however, has not been commercially at 5 up to or greater than about 1000 atmospheres tractive because of the very low yields obtained may be employed if desired. In the synthesis and also because of the tafry nature of the re of p-tolualdehyde, according to the invention, a action product which made it very difficult to pressure of about 30 atmospheres is sufficiently separate pure aromatic aldehyde therefrom. high for excellent yields. The advantages of the It has also been known for many years that 20 invention are realized, however, when the tem carbon monoxide can react with in the perature is maintained within a range consider presence of aluminum chloride to give benzalde ably lower than has heretofore been employed in hyde which, however, could be obtained only in processes for the reaction between carbon mon quantities equivalent to the amount of aluminum oxide and aromatic hydrocarbons in the presence chloride catalyst employed. This process em 25 of either boron trifluoride or hydrogen fluoride ploying aluminum chloride also has been disad catalysts. At the low temperatures employed in vantageous because of the difficulty of separating the practice of the invention neither boron tri or recovering aluminum chloride from the reac fluoride nor hydrogen fluoride, when employed tion mixture thereby obtained. . alone as catalysts, is effective for the synthesis An object of this invention is to provide a 30 of aromatic aldehydes from aromatic hydrocar process for the preparation of aromatic aldehydes bons and carbon monoxide in any substantial from aromatic hydrocarbons and carbon mon yield. oxide in high yield, and under such conditions The hydrocarbons which may be employed in that the catalyst can be readily recovered or sep the practice of the invention include the mono arated from the aromatic aldehyde in the reac 35 cyclic and polycyclic aromatic hydrocarbons such tion product. Other objects of the invention will as benzene, , phenanthrene, diphenyi, appear hereinafter. diaryl methanes, alkyl-substituted aromatic hy The objects of the invention are accomplished drocarbons, such as toluene, ethyl , by subjecting a mixture of aromatic hydrocarbon propyl benzenes, butylbenzenes, hexyl benzenes, and carbon monoxide to the action of a mixed 40 etc. hydrogen fluoride-boron trifluoride catalyst at a It is generally preferred in the practice of the temperature of about -80 C. to --50° C., pref invention to employ a mixed hydrogen fluoride erably -50 to --20 C., under superatmospheric boron trifluoride catalyst which contains approx pressure, whereby a reaction product containing imately equimolal quantities of hydrogen fluoride aromatic aldehyde is obtained. This reaction 45 and boron trifluoride. However, it is by no product can be separated into its constituents means essential that the catalyst contain equiva without difficulty, and both the aromatic alde lent quantities of the said constituents, it being hyde and the recovered catalyst are readily ob Sufficient if both constituents are present, even tainable therefrom. Since the catalyst can be though one is present in relatively minor quan recovered and reused, it is generally preferred 50 tity. The invention is illustrated further by to employ a sufficiently large quantity thereof so means of the following examples: that the reaction may take place at the maximum Eacamaple 1-A mixture containing 0.75 mol of convenient reaction rate. For optimum results toluene, 0.75 mol of hydrogen fluoride and 0.75 this usually requires about 0.5 to 1.5 mols of boron mol of boron trifluoride was cooled in a pressure fluoride per Inol of aromatic hydrocarbon and an 55 resisting vessel at a temperature of -32° to 2,485, 23? 3 4 -12° C. for about 24 minutes with carbon mon verted by oxidation to the corresponding dicar oxide at a pressure of about 210 to 540 pounds boxylic ; for example, p-tolualdehyde is an per square inch. A 40.6% conversion to p-tolu aldehyde (yield, 80%) was obtained. The p excellent source for terephthalic which in tolualdehyde was isolated by distillation after re turn is widely useful in the manufacture of vari 5 Ous resinous materials such as the polyesters. moving the catalyst with several washes. Since many different embodiments may be Eacample 2-A mixture containing two mols of made without departing from the spirit and scope toluene, one mol of hydrogen fluoride and one thereof, it is to be understood that we do not limit mol of boron trifluoride was processed under the Ourselves except as set forth in the following conditions set forth in Example 1. The conver 0. claims. sion to p-tolualdehyde was 28.5% based on the We claim: amount of toluene initially present. 1. The process for the synthesis of aromatic Eacample 3.-A mixture containing 0.5 mol of aldehydes which comprises subjecting a mixture toluene, 0.75 mol of hydrogen fluoride and 0.75 of aromatic hydrocarbon and carbon monoxide mol of boron trifluoride was maintained at a tem to the action of a mixed anhydrous hydrogen perature of -18° to -2° C. for 13 minutes under fluoride-boron trifluoride catalyst at a tempera a carbon monoxide pressure of 75 to 710 atmos ture of about -80 C. to --50° C. under superat pheres. The conversion of toluene to p-tolualde mospheric pressure, and thereafter separating hyde was 80.5% based on the amount of toluene the aromatic aldehyde thus produced from the not reacted, and the yield was 92% of the resulting mixture. theoretical. The p-tolualdehyde was isolated by 20 2. A process for the synthesis of aromatic alde distilling the reaction product after removal of hydes which comprises subjecting a mixture of catalyst by water wash. aromatic hydrocarbon and carbon monoxide to Eacample 4-The following table summarizes the action of a mixed anhydrous hydrogen the data obtained in several experiments in which 25 fluoride-boron trifluoride catalyst at a tempera aromatic hydrocarbons were treated with carbon '' ture of about -80 C. to --50° C. under a pres monoxide in the presence of HFBF's catalyst. sure of about 10 to 1000 atmospheres and there Table-Synthesis of aromatic aldehydes

Mols of Aromatic Hydro- Mols of o Time, Product t

carbon S itsi, Tempo. WIN. benzene------0.75 25-28 26 benzaldehyde------168 Do---- 0.5 1.0 -2 to -7 3 mi-xylene 0.5 1.0 28-40 32 - do------19 Do- 0.5 0 - -38 to -14 3. 2,4-di 65.4 p-xylene.-- 0.5 1.0 -10 to --6 22 -2,5-dimethlybenzaldehyde.------do------80.5O mesitylene ------0.3 ...) 26 to 35 24,6-trimethylbenzaldehyde-- 823 diphenyl------0.25 1.0 -30 to -18 10 p-phenylbenzaldehyde.------825 naphthalene.------0.5 1.0 -30 to --20 0. ornaphthaldehyde------78.8 1 cyclopentane diluent. It is to be understood that any suitable method after separating the aromatic aldehyde produced may be employed for separating the aromatic by the resulting reaction from the ensuing reac aldehyde from the mixed catalyst and the other tion product. constituents of the crude reaction product. One 45 3. A process for the synthesis of aromatic alde- . method which gives satisfactory results is to treat hydes which comprises subjecting a mixture of the crude reaction product with a metal halide, aromatic hydrocarbon and carbon monoxide to whereby the organic constituent is set free and a the action of a catalyst consisting of about equi complex is formed between the metal halide and molal quantities of hydrogen fluoride and boron the inorganic catalyst (cf. U. S. Patent 2,135,458). 5) trifluoride at a temperature of about -80 C. to Another suitable method is to neutralize the cat ... --50° C. under superatmospheric pressure and alyst while maintaining the mixture at sufficient thereafter separating from the resulting mixture ly low temperature to avoid undesirable conden the aromatic aldehyde produced by the ensuing sation reactions, and thereafter to recover the hy reaction. drogen fluoride and boron trifluoride by treating 55 4. A process for the synthesis of p-tolualdehyde the fluoborate Salt thus obtained with sulfuric which comprises subjecting a mixture of toluene acid. If desired, the reaction product may be and carbon monoxide to the action of a catalyst treated with an amount of anhydrous consisting solely of hydrogen fluoride and boron equivalent to the hydrogen fluoride and boron trifluoride at a temperature of about -80 C. to trifluoride present, whereby a mixture containing 80 --50° C. under superatmospheric pressure and fluoborate, which may be admixed thereafter separating p-tolualdehyde from the with , is obtained. Hydrogen resulting mixture. fluoride and boron trifluoride may be recovered 5. A process for the synthesis of p-tolualde from these ammonium Salts by treatment with hyde which comprises subjecting a mixture of . A preferred method for recovery 65 toluene and carbon monoxide to the action of a of the catalyst from the crude reaction product catalyst consisting solely of hydrogen fluoride is to treat the said product with an alkali metal and boron trifluoride at a temperature of about or alkaline earth metal fluoride such as sodium -80° C. to --50° C. under a pressure of about fluoride, , or . In 10 to 1000 atmospheres and thereafter separat this manner the catalyst is very readily separated 70 ing p-tolualdehyde from the resulting mixture. from the aldehyde, and the aldehyde may there 6. A process for the synthesis of p-tolualdehyde after be purified by suitable methods such as low which comprises subjecting a mixture of toluene pressure distillation if desired. - and carbon monoxide to the action of a catalyst The aldehydes obtained in accordance with this consisting of about equimolal quantities of hy invention are widely useful perse or may be con 75 drogen fluoride and boron trifluoride at a tem 2,485,287 5 6 perature of about -80 C. to --50° C. under super to the action of a catalyst consisting solely of atmospheric pressure and thereafter separating hydrogen fluoride and boron trifluoride at a tem p-tolualdehyde from the resulting mixture. perature of about -50 to --20° C. under a pres 7. The process for the synthesis of p-tolualde sure of about 10 to 1000 atmospheres and there hyde which comprises subjecting about 0.5 mol after separating alpha-naphthaldehyde from the of toluene, 0.75 mol of hydrogen fluoride and resulting mixture. 0.75 mol of boron trifluoride to a temperature 13. A process for the synthesis of alpha of about -18° to -2° C. under a pressure of about naphthaldehyde which comprises subjecting a 75 to 710 atmospheres and thereafter separating mixture of naphthalene and carbon monoxide to p-tolualdehyde from the resulting mixture. 10 reaction of a catalyst consisting of about equi 8. A process for the synthesis of benzaldehyde molal quantities of hydrogen fluoride and boron Which comprises subjecting a mixture of benzene trifluoride at a temperature of about -50° to and carbon monoxide to the action of a catalyst -H20° C. under superatmospheric pressure and consisting solely of hydrogen fluoride and boron thereafter separating alpha - naphthaldehyde trifluoride at a temperature of about -80° C. to 5 from the resulting mixture. --50 C. under superatmospheric pressure and 14. A process for the synthesis of p-tolualde thereafter separating benzaldehyde from the re hyde which comprises reacting carbon monoxide Sulting mixture. With toluene at a temperature of about -50 to 9. A process for the Synthesis of benzaldehyde --20° C. under a pressure of about 30 atmospheres Which comprises subjecting benzene and carbon 20 in the presence of a mixed catalyst consisting monoxide to the action of a catalyst consisting Of hydrogen fluoride and boron fluoride, said Solely of hydrogen fluoride and boron trifluoride catalyst containing about 0.5 to 1.5 mols of BF3 at a temperature of about -80° C. to --50° C. per mol of HF, and thereafter separating p-tolu under a pressure of about 10 to 1000 atmospheres aldehyde from the resulting mixture. and thereafter separating benzaldehyde from the WILLIAM E. GRESHAMI. resulting mixture. GEORGES E, TABET. 10. A process for the synthesis of benzaldehyde Which comprises subjecting a mixture of benzene REFERENCES C TED and carbon monoxide to the action of a catalyst The following references are of record in the consisting of about equimolal quantities of hy 30 file of this patent: drogen fluoride and boron trifluoride at a tem perature of about -50 to -20° C. under super UNITED STATES PATENTS atmospheric pressure and thereafter separating Number Name Date benzaldehyde from the resulting mixture. 1885,060 Hoffman et al. ------Oct. 25, 1932 il. A process for the synthesis of alpha 1,933,434 Hoffman et al. ------Oct. 31, 1933 naphthaldehyde which comprises subjecting a 2,158,031 Loder ------May 9, 1939 mixture of naphthalene and carbon monoxide 2,447,565 Chenicek ------Aug. 24, 1948 to the action of a catalyst consisting solely of hydrogen fluoride and boron trifluoride at a tem OTHER REFERENCES perature of about -50° to +20° C. under super 4) , 1940, pages 344-345, 2 pages, Berk atmospheric pressure and thereafter separating man et al. alpha-naphthaldehyde from the resulting mix JacobSon: "Encyclopedia of Chemical Reac ture. tions,” Reinhold Pub. Corp. (1946), citing at page 12. A process for the synthesis of alpha 667, Sowa et al., Jour. Am. Chem. Soc., 57, 454 naphthaldehyde which comprises subjecting a 4 5 (1935), and Davy, New Edin. Phil. J., 17, 246 mixture of naphthalene and carbon monoxide (1812).