Acetalization of formaldehyde with methanol in batch and continuous reactive distillation columns

Methylal, an important raw material and a solvent, is produced by acetalization of aqueous formaldehyde with methanol. This acetalization reaction 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, reactive 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 distillation column (RDC) using three different types of catalyst packing. The first type of catalyst packing was coarse size macroporous cation-exchange resin Indion 130, which was directly packed along with Raschig rings. The second type of catalyst packing was Indion 130 tied in cloth bags. The third type of catalyst packing used was a silica-supported organic catalyst. Up to 99% conversion of formaldehyde was achieved by reactive distillation. Vapor-liquid equilibrium data for the quaternary system formaldehyde-methanol-methylal-water were experimentally obtained and correlated by the UNIFAC method. On the basis of the experimental results of the single-feed continuous reactive distillation column, 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.