The four cyclic glycerol acetal isomers can be readily produced via the acid-catalyzed reaction of glycerol with acetaldehyde or a related acetal species. In the presence of the acid catalyst used in acetal formation, the isomers interconvert to form an equilibrated mixture that contains similar quantities of the four products. Vacuum distillation can separate the four acetals into their purified forms, with the cis-5-hydroxy-2-methyl-1,3-dioxane (1) as the most volatile. When the distillation is carried out in the presence of an acid catalyst to promote interconversion, 1 is obtained as a nearly pure distillate stream. This is further adapted to a continuous reactive distillation which produced 90–96% 1. Thus a novel process is presented to convert glycerol to the desired acetal (1), which can be further converted to products such as 1,3-propanediol and dihydroxyacetone.