Continuous Flow Synthesis of a ZSM-5 Film in Capillary Microchannel for Efficient Production of Solketal.

This work presented the microfluidic preparation of zeolite film in a capillary microchannel with different length-to-diameter ratios. In the quartz capillary with an inner diameter of 0.53 and 0.32 mm, Zeolite Socony Mobil-5 (ZSM-5) film was prepared by a continuous flow hydrothermal method. Considering the chemically inert surface of quartz capillary and the difficulty of preparing uniform and continuous zeolite film by conventional static synthesis, the ZSM-5 seed layer was precoated as active sites to induce film growth. The parameters of length-to-diameter ratio, seed coating, feed flow rate, and synthesis time were investigated. It revealed that the crystallinity of the ZSM-5 film was significantly affected by the capillary length-to-diameter ratio and seed coating in this flow system. The film morphology and thickness could be precisely controlled by adjusting the feed flow rate and synthesis time. This hydrogen form of the ZSM-5 (HZSM-5) film capillary microreactor was applied in the ketalization reaction of glycerol with acetone to produce solketal. The single-pass yield of solketal could reach ∼30% under mild conditions. This work provided a convenient stratagem of preparing zeolite catalytic coating or other support coatings in closed microchannels with a high length-to-diameter ratio and the potential application in valuable transformation of biomass glycerol.