Empowering catalysis and separation: morphology control of MFI zeolites using organic additives

Abstract

As one of the most successful inorganic materials, MFI zeolite has been widely used in petrochemical and fine chemical industries. However, the presence of only micropores in MFI zeolite creates diffusion barriers and thus precludes its usage in processes involving large substrates. It is highly desirable to mitigate the diffusion pathways in MFI zeolites. One of the efficient methods is the morphology control strategy, which has become a hot topic in the past few decades. In this review, we summarize the progress of MFI zeolite morphology control using specific organic additives as morphology modifiers to enhance the catalytic and separation performance. Organic additives, including urea, amino acids, small organic molecules, and polymers, were categorized based on the MFI zeolites induced by them. The morphologies generated can be classified as nanocrystals, aggregated nanoparticles, nanosheets, intergrown nanosheets, plates, intergrown plates, needles, and bulky prismatic crystals, depending on the specific additives. The formation mechanisms of different morphological MFI zeolites and their properties are also discussed. This review is of great importance for the controllable synthesis of zeolites and rational design of zeolite catalysts.