Patent ID: 6566559
Filing Date: 2003-05-20
Classification: C07C

Abstract:
A process for the production of an unsaturated ether represented by the formula (1) by pyrolysis of an acetal or ketal represented by the formula(2) wherein R1=H or alkyl with 1-8 C atoms; R2=H, CH3â€”, C2H5â€”, or Clâ€”; R3=alkyl with 1-8 C atoms; R4=H, CH3â€”, C2H5â€”, C3H7â€”, and R1 and R4 may be joined to form a 5-, 6-, or 7-membered ring, comprising: a) in a ketalization reaction, ketalizing, in the presence of an acid catalyst, the corresponding acetal or ketal of the formula (2), which is formed by reacting the corresponding alcohol of the formula (3) R3â€”OHâ€ƒâ€ƒ(3) â€ƒwherein R3 denotes space-holders for the substituents R3 specified above, with an aldehyde or ketone of the formula (4) â€ƒwherein R1, R2 and R3 denote space-holders for the substituents R1, R2 and R3 specified above, to produce a product stream I, and b) combining the product stream I resulting from the ketalization reaction, which includes a mixture of components of the formulae (2), (3), (4) and water, with recycle product stream VI of the ketal or acetal pyrolysis, which includes a ketal or acetal, the desired unsaturated ether of the formula (1) as product, and the alcohol of the formula (3), to form the product stream II, and c) separating water and alcohol from a product stream II and extracting combined organic product streams of product stream II with an aqueous alkaline solution and thereby forming an organic product stream III by this extraction, which includes a mixture of the corresponding ketal or acetal, the desired unsaturated ether as product, and residual amounts of the aldehyde or ketone of the formula (4) and water, and d) distilling product stream III and thereby isolating the desired unsaturated ether product as a product stream V and obtaining a product stream IV as the distillate residue, and e) pyrolyzing said distillation residue which is produced in d), which contains the acetal of the formula (2) and the corresponding carbonyl compound of the formula (4), in a high boiling point organic carboxylic acid at 80Â° C.-300Â° C. to obtain recycle product stream VI, which contains in addition to the desired unsaturated ether also unreacted ketal and/or acetal and the corresponding alcohol, which is recycled to the extraction of c) and is combined with the product stream I from the ketalization.