Preparation and performance of TS-1/SiO2 egg-shell catalysts

A monolayer of zeolite nanoparticles was deposited uniformly on SiO2 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/SiO2 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/SiO2 catalyst beads were shown to be resistant to attrition and were easier to separate and recover from reaction.

Graphical abstractA TS-1/SiO2 egg-shell catalyst with excellent adhesion properties was prepared by a new seeding and synthesis procedure. The egg-shell TS-1/SiO2 catalyst exhibited high turnover number and good selectivity to phenylacetaldehyde compared to powder catalysts in styrene oxidation. TS-1/SiO2 beads were robust and easy to recover and regenerate compared to TS-1 catalyst powders.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A robust TS-1/SiO2 egg-shell catalyst was successfully prepared. ► TS-1/SiO2 catalyst beads gave high turnover number and good selectivity. ► TS-1/SiO2 beads were easy to recover and regenerate compared to powder. ► Catalyst lost was less a problem for the TS-1 egg-shell catalyst than powder.