Green synthesis

Xiongfu Zhang
School of Chem. Eng., Dalian Univeristy of Technology

*Guohui Yang
School of Chem. Eng., Dalian Univeristy of Technology

*King Lun Yeung
Department of Chemical Engineering, the Hong Kong University of Science and Technology, Hong Kong

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     Last modified: January 12, 2006

Abstract
Microreactors exist numerous practical advantanges including safety, easy modulation and numbering-up for industrial production, compared with traditional batch-scale reactors. Microreactors have found large application in chemicals processes with large heat evolution and on-demand production of toxic and hazardous chemicals and are expected to make a revolutionary change in chemical engineering and technology. Zeolite catalysis is moving further into the area of the synthesis of fine chemicals. Zeolite-based microreactors formed by incoporating zeolites as catalysts or separation membranes in the microreactor can allow integration of zeolite catalysis and microreactor and realize the green synthesis of many fine chemicals. Reactions conducted in zeolite-based microreactors can have better selectivity and higher product yield. This means better reactant utilization and less waste generation leading to green chemical synthesis. This work investigates the preparation of zeolite NaA microreactor using a green method of assembling a zeolite layer on stainless steel microchannels.
Nanozeolite NaA particles with ~100nm as seeds were successfully introduced onto the microchannels of the microreactor via linker reagent. A closely packed seed layer was formed by self-assembly of nanozeolite crystals on the microchannels using ethanol as solvent instead of toluene. Then a continuous zeolite NaA layer was grown by subsequent hydrothermal treatment. Thus, the procedure is simple, safe and green. The coverage degree strongly depends on the type of linker reagents. The mechanism of self-assembly of nanozeolite crystals via linker reagent is predicted. The characterization results of SEM, XRD and reaction indicate that the seed layer is densely packed and NaA membrane intergrows well on the seeded microchannels. This method is simpler and green and can be suitable for synthesizing various types of zeolite-based microreactors by modifying seed types.