GB669074A - Process for the production of unsaturated phenolic compounds - Google Patents

Abstract

Phenols and their ethers having at least one nuclear aliphatic hydrocarbon substituent of 3-28 carbon atoms, the two carbon atoms nearest the aromatic nucleus each bearing at least one hydrogen atom, are cracked in the vapour phase at an elevated temperature to convert the substituent into one with an a : b -double bond. A dehydrogenation catalyst of the kind used for dehydrogenating ethylbenzene (e.g. as in Specification 340,587, [Group III]) is preferably used, the reaction taking place at 400-800 DEG C.; a gaseous diluent such as steam, hydrogen, benzene, nitrogen or carbon dioxide may be present. The pressure may be atmospheric or higher or lower. When no catalyst is used, a solid heat-transfer material is preferably present. The preferred temperature range is 500-700 DEG C. with a contact time of 1-0.01 seconds. Depolymerization and replacement of nuclear carboxyl by hydrogen may occur simultaneously with the cracking, depending on the starting material used. The products may be separated by distillation or fractionation, followed by alkali extraction and selective precipitation with carbon dioxide or a stronger acid. A further fractionation may be carried out as the final step. In the examples: (1) cardanol from cashew nut shell liquid gives m-vinylphenol and non-phenolic bodies; (2) cardanol gives phenol, m-cresol, m-ethylphenol, m-vinylphenol and a higher-boiling residue; (3) cardanyl methyl ether gives m-methoxystyrene, m-vinylphenol and hydrocarbons; (4) p-n-hexylphenol gives p-vinylphenol and hydrocarbons. The process is applicable to alkyl-phenols and their alkyl and aryl ethers, such as those in coal tar and the components or distillates of cashew nut shell liquid including their hydrogenated derivatives. When a phenolic acid such as anacardic acid is used, decarboxylation takes place and the carbon dioxide evolved may function as the whole or part of the inert diluent.ALSO:Dehydrogenation catalysts comprise: (1) granular absorbent alumina on which is deposited 10 per cent by weight of calcium oxide; and (2) granular magnesite carrying 5.3 per cent of sodium vanadate. They are used for the cracking of alkyl-substituted phenols and their ethers to give alkenyl-substituted compounds with fewer carbon atoms.