H. Zhang et al., ZEOLITE CRYSTALLIZATION PROCESS MODELING AND COMPARISON WITH MICROGRAVITY PLIGHT RESULTS, Journal of spacecraft and rockets, 32(1), 1995, pp. 110-116
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.