Provided is a process for the preparation of glutaraldehyde. The process comprises reacting an alkoxydihydropyran with water in the presence of an acidic catalyst. The alcohol by-product distilled from the reaction mixture is subjected to a heterogeneous catalyst that is located external to the distillation column used for distilling the alcohol, thereby increasing glutaraldehyde yield and decreasing the level of alkoxydihydropyran contamination in the alcohol.