Kinetics of Liquid-Phase Condensation of Propylene with Formaldehyde over H-MFI and H-BEA Zeolites
This study investigated the kinetic patterns of the liquid-phase Prins condensation of propylene with formaldehyde in the range of 120-180 degrees C over H-MFI and H-BEA zeolites. The apparent reaction order with respect to formaldehyde was found to vary between 0.1 and 0.2 for H-BEA and to be close to zero for H-MFI. The apparent activation energy for H-MFI and H-BEA was 26.1 +/- 0.6 kJ/mol and 20.0 +/- 4.0 kJ/mol, respectively. Based on these results, the reaction was demonstrated to occur in the intradiffusion or transition region; the calculated Thiele modulus and effectiveness factor further confirmed this fact. The diffusion limitations were partially removed by raising the initial formaldehyde concentration, as indicated by an increase in the apparent order of formaldehyde conversion to 1.0 for H-BEA and to 0.4 in the H-MFI case. To describe the substrate transformations observed, a modernized reaction mechanism was proposed.