Process for preparing acetals and ketals with the aid of multistage pervaporation or vapor permeation

摘要

An acetal or a ketal are prepared by reacting a carbonyl compound and an alcohol in the presence of an acid catalyst and water. Water and alcohol are removed from the reaction mixture in an at least two-stage pervaporation or vapor permeation process using a plurality of membranes. Additional alcohol is fed into a retentate stream of at least one of the two stages. At least one of the plurality of membranes in the two-stage pervaporation or vapor permeation process is different from the other membranes in terms of selectivity behavior in the removal of water and alcohol.