ZEOLITE CRYSTALLIZATION PROCESS MODELING AND COMPARISON WITH MICROGRAVITY PLIGHT RESULTS

The study of the transport phenomena during zeolite crystallization ha s indicated that at 1g, gravity-induced secondary nucleation is the on ly possible detrimental effect due to gravitational sedimentation. In this paper experimental results on zeolite growth from the STS-40 and STS-50 mission experiments are compared with our theory for determinin g the conditions where microgravity is beneficial. The theory is consi stent with those experiments. Additionally, zeolites were synthesized in our laboratory using compositions similar to those of the STS-40 an d STS-50 experiments to 1) examine the effect of a nucleation suppress er, triethenolamine, on gravity-induced secondary nucleation, and 2) d evelop a process to synthesize larger zeolites in both 1g and microgra vity. At 1g limitations on the second goal are found. Furthermore, gro wth-in-gel zeolite crystallization in microgravity is modeled. The ove rall porosity of the gel portion is defined as an important space-expe riment parameter, which is a counterpart of the gel-portion shrinkage at 1g. This parameter can be used for zeolite crystallization in micro gravity to determine the time when nutrients should be added to grow m uch larger zeolites in space.