Preparation and performance of TS-1/SiO 2 egg-shell catalysts

Abstract

A monolayer of zeolite nanoparticles was deposited uniformly on SiO 2 beads’ surface by a new seeding method based on the combined use of organic linker and dip-coating procedure. The seeds were transformed into a well-intergrown TS-1 zeolite film and characterizations by SEM and XRD indicated that the film has a preferred (0 1 1) orientation. EDXS, XPS and UV–vis spectroscopies confirmed the successful preparation of egg-shell TS-1/SiO 2 catalysts. Thin shell catalysts (i.e., <11 μm) were more active for styrene oxidation. Conversion reaction rate of 8.9 mmol g −1 h −1 and turnover frequency of 28 h −1 were obtained with aromatic aldehydes (i.e., benzaldehyde and phenyl acetaldehyde) being the main products. Greater mass transfer resistance made thick shell catalysts less efficient with lower specific conversion rate of 6.9 mmol g −1 h −1 and turnover frequency of 25 h −1. Also, the extra-framework titanium resulting from the longer synthesis led to poorer selectivity. Egg-shell TS-1/SiO 2 catalyst beads were shown to be resistant to attrition and were easier to separate and recover from reaction.