ACETALIZATION OF FORMALDEHYDE WITH METHANOL IN BATCH AND CONTINUOUS REACTIVE DISTILLATION-COLUMNS

Methylal, an important raw material and a solvent, is produced by acet alization of aqueous formaldehyde with methanol. This acetalization re action was carried out in a closed system in the presence of a cation- exchange resin Indion 130 as catalyst and was found to be equilibrium limited. In order to increase the conversion for this reaction, reacti ve distillation was carried. Batch reactive distillation was performed in the presence of the cation-exchange resin Indion 130 as catalyst. Continuous reactive distillation was performed in a reactive distillat ion column (RDC) using three different types of catalyst packing. The first type of catalyst packing was coarse size macroporous cation-exch ange resin Indion 130, which was directly packed along with Raschig ri ngs. The second type of catalyst packing was Indion 130 tied in cloth bags. The third type of catalyst packing used was a silica-supported o rganic catalyst. Up to 99% conversion of formaldehyde was achieved by reactive distillation. Vapor-liquid equilibrium data for the quaternar y system formaldehyde-methanol-methylal-water were experimentally obta ined and correlated by the UNIFAC method. On the basis of the experime ntal results of the single-feed continuous reactive distillation colum n, preliminary modeling has been performed for the calculations of the minimum reflux ratio and the number of reactive equilibrium stages in the column used for synthesis.