Optimization of process parameters on the extrusion of honeycomb shaped monolith of H-ZSM-5 zeolite

摘要

The optimization of the process parameters for the preparation of H-ZSM-5 zeolite monolith structure by direct extrusion technique is reported. This preparation method avoids the difficulties associated with the anchoring the crystalline zeolite material to the monolithic support or with the uniform synthesis of zeolite along the whole monolith, and shows the advantage that the active phase is uniformly distributed throughout the monolith and reduces the number of steps necessary for the preparation: paste preparation, extrusion, drying and firing. Colloidal silica was used as a permanent binder and methylcellulose as a temporary binder. It was found the best paste composition (zeolite, binders and water) to assure best Theological properties must show stabilized drive torque around 10 N m in wet kneading. Extrusion through high quality designed nozzle (123 cells/in.~2) resulted optimal at conditions of room temperature and the highest extrusion-rate without formation of surface defects (40 rpm). Drying of the green monoliths at heating rates lower than 0.15° Cmin~(-1) in the initial stages prevents from the migration of the binder and led to a uniform shrinkage avoiding formation of fractures or deformities. Resulted monoliths showed high activity in the oxidation of chlorinated volatile organic compounds.