Acetalization reaction of ethanol with butyraldehyde coupled with pervaporation. Semi-batch pervaporation studies and resistance of HybSi® membranes to catalyst impacts

Acetals are seen as important bio-based diesel additives. The production of these compounds from an alcohol and an aldehyde suffers from low conversions due to thermodynamic limitations. These limitations can be overcome through the continuous removal of the by-product water. One of the most promising innovative reaction systems is a membrane reactor equipped with a dehydration membrane. Water selective organic/inorganic HybSi® membranes were used for this purpose. As a representative example the production of 1,1 diethoxy butane from ethanol and butyraldehyde was studied. Permeance data were determined from pervaporation dehydration experiments using non-reacting quaternary mixtures at various temperatures. Membrane reactor experiments show that the conversion of the acetalization reaction can be increased from the thermodynamic value of 40% to 70% at 70 °C and a stoichiometric initial composition. The reactor experiments could be predicted using kinetic data of the reaction and a simple empiric membrane performance relation. The chemical stability of the membrane in the presence of aggressive organic solvents, like butyraldehyde, and its mechanical resistance against the solid catalyst particles of Amberlyst 47 were shown to be satisfactory.