Patent GB-559957-A (GB)
Title: Production of acrylic acids, heterocyclic acrylic acids, aryl alkenes and heterocyclic alkenes
IPC: C07D307/36
Filed: 1942-09-09
Abstract: 559,957. Acrylic acid derivatives. DU PONT DE NEMOURS & CO., E. I. Sept. 9, 1942, No. 12707. Convention date, Sept. 9, 1941. [Class 2 (iii)] Aryl acrylic acids, aryl alkenes, heterocyclic acrylic acids and heterocyclic alkenes are produced by passing a mixture of an aryl or a heterocyclic aldehyde with at least an equimolecular weight of acetic acid or a carboxylic acid containing an active methylene group or a compound which on hydrolysis yields such an acid over a catalyst consisting of an oxide, hydroxide, carbonate or carboxylic acid salt of an alkali or an alkaline earth at a temperature between 200‹ C. and 500‹ C. The catalyst is preferably employed supported on a carrier such as silica gel, active carbon, pumice, alundum, alumina, or fuller's earth. The preferred conditions are a temperature range of 325‹ C. and 450‹ C. and a space velocity of 50 to 200 volumes of gaseous reactants per unit volume of catalyst per hour. An inert diluent which may either be an inert carrier gas or an organic solvent may be present. Carboxylic acids mentioned include straight chain acids such as acetic, propionic, butyric, caproic, and lauric acids, branched chain acids such as isovaleric and isocaproic acids, dibasic acids such as malonic, succinic or adipic acids, cyclic carboxylic acids such as phenylacetic, furylacetic and hydrocinnamic acids, unsaturated carboxylic acids such as crotonic, sorbic, #-ethyl acrylic, tiglic, vinylacetic, #10 : 11- undecylenic and oleic acids. In place of the acids themselves, their nitriles, anhydrides, esters, amides or acid halides may be used. The definition of carboxylic acids which contain an active methylene group is for the purpose of the present invention a carboxylic acid which contains a methylene group joined directly to the carboxyl group or which contains a methylene group joined by a single bond to a chain carbon sharing a plural bond with another carbon which is in turn directly attached to the carboxyl group. Aldehydes mentioned include benzaldehyde, the tolualdehydes, furfural and the substituted furfurals such as 8-methyl-2 furaldehyde and 3:5-dimethyl-2- furaldehyde, naphthaldehydes and substituted naphthaldehydes, and the aldehydo derivative of pyridine and pyrrnole. In examples (1) a mixture of furfural and glacial acetic acid is passed in the vapour phase at 350‹ C. through a tube containing potassium acetate on silica gel catalyst. The product is 2-vinyl furane which is purified by steam distillation. (2) As in example (1) using crotonic acid instead of acetic acid to form 1-(alpha furyl)-1:3-butadiene. (3) As in example (1) using as the catalyst barium oxide on silica gel. The same product is obtained. (4) Furfural and acetic anhydride are passed over a sodium acetate on silica gel catalyst at 270‹ C. Steam distillation of the product yields 2-vinyl furane and on cooling the residual liquid from the steam distillation furylacrylic acid separates out. (5) A mixture of furfural and acetonitrile is passed over a sodium carbonate on silica gel catalyst at 320‹ C. to produce furylacrylonitrile. (6) A mixture of benzaldehyde and glacial acetic acid is passed over a potassium acetate on silica gel catalyst at 395‹ C. to form styrene.