Z. Shan et al., Optimization of the preparation of binderless ZSM-5 coatings on stainless steel monoliths by in situ hydrothermal synthesis, MICROP M M, 34(1), 2000, pp. 81-91
Metal monoliths containing binderless zeolitic coatings are interesting str
uctured catalyst packings that combine attractive hydrodynamical properties
, such as a low pressure drop, with special chemical properties, such as a
high catalyst effectiveness and a high reaction selectivity. It was attempt
ed to find an optimized recipe for in situ hydrothermal synthesis of a bind
erless ZSM-5 coating on stainless steel monoliths with a volume of about 11
. Using synthesis mixtures with a typical molar composition of 60 SiO2:Al2O
3:4 (TPA)(2)O:4000 H2O, homogeneous zeolitic coatings with an Si/Al ratio o
f 34 and with coverages of up to 25 g(ZSM-5)/m(packing surface)(2) were obt
ained in a single synthesis run of 24 h at 150 to 170 degrees C. The covera
ge increased proportionally with the number of synthesis runs that a packin
g was subjected to. An effective zeolite density of ca. 200 kg(ZSM-5)/m(pac
king)(3) was obtained in a sequence of four runs. Neither the state of the
silicon source (TEOS or colloidal silica) nor the curvature of the support
surface (monoliths constructed from foil or 35 mu m wire gauze) had a signi
ficant effect on these figures. By contrast, agitating the synthesis mixtur
e during synthesis proved to be essential to obtain the high coverage value
s mentioned. (C) 2000 Elsevier Science B.V. All rights reserved.