Preparation And Performance Of Zeolites And Zeolite Membranes In Microreactors

Microreactors are the key equipment of micro-chemical technology. It's well-known that the large surface area-to-volume ratio can be obtained in microreactors, and the reduction of characteristic dimensions can enhance heat and mass transfer rates on per unit area of microreactors compared to conventional reactors. The research shows that the conversion and selectivity of reaction are promoted in microreactor. Microreactors which provides a new research concept and technology choice have huge application potential and research value.Zeolites, with the supercages and channels of defined sizes, are important catalysts in many chemical and petrochemical processes because of their high specificity in adsorption and catalysis. Recent years, zeolites are considerable interest in incorporating in microsystem and strong candidates for membrane separation and catalysis.In this paper, the NaA zeolite particles were introduced onto the surface of the stainless steel multi-channel plate via electrophoretic deposition (EPD) to form densely packed seed layers which can serve as good seeds for zeolite membrane growth. After hydrothermal treatment, a continuous and uniform NaA membrane was obtained. The result shows that the permeate flux 0.159 kg/m~2 h and the separation factor 302. The prepared NaY zeolite particles are uniformly and compactly coated on the NaA membrane of microchannel, and the NaA/NaY composite zeolite membrane were synthesized by sencondary hydrothermal treatment. The catalysis performance of Cs-exchanged NaY zeolite membranes was promoted.The separation performance of the NaA membrane and NaA/NaY zeolite membrane was test by pervaporation. The optimal reaction conditions were choosed for pervaporation throngh a series of researchs. Experiments also show that the permeate flux through the multi-channel membrane plate is larger than that of the tubular zeolite membrane because the rapid mass and heat transfer rates are obtained in microsystem. The catalysis performance of the membrane was tested and compared with that of a microreactor and batch reaction for the Knoevenagel condension reaction of benzaldehyde and ethyl cyanoacetate to produce water and ethyl 2-cyano-3-phenylacrylate. The highest yield obtained from the conventional reactor is 79%, and the higher yields were obtained at the microreactor, but the best performance belongs to the membrane microreacto which product yield achieve 93% The stabilized,catalyst coated multi-channel membrane plate was monitored for 12 h under reaction condition. The conversion of reaction is constant throughout the experiment.