Conversion of Propanal Over HZSM-5 with Mesopores

ZSM-5, a typical microporous zeolite, plays an important role in the oil refining industry due to its unique acidic properties and 3-D pore structure. However, there can be difficulties in diffusional transport of both reactants and products inside the micropores leading to lower activity and rapid deactivation. Desilication of ZSM-5 using alkaline solutions with varied basicity, temperature, and treatment time was carried out to generate materials with varying amounts of mesopores with controlled pore size and pore volume. These modified materials have been studied for conversion of propanal and found to have extended catalyst lifetimes compared with the parent, along with changes in product distribution. The samples were characterized by TPD of isopropylamine, nitrogen adsorption/desorption, SEM/EDX, XRD, and dynamic pulses of n-butane to study changes in catalyst structure. Slightly desilicated samples were found to improve the yield for aromatics while severely desilicated samples were found to reduce aromatics yield to alkanes and alkenes, when compared to the parent zeolite. Furthermore, all desilicated samples were found to be more tolerant to coke than the parent zeolite.