NAMS 2002 Workshop - ICOM 2008

Inorganic Membranes III – 5
Friday July 18, 11:45 AM-12:15 PM, O’ahu/Waialua
Selective Gas Transfer and Catalytic Processes in Nano-Channels of
Ceramic Catalytic Membranes
V. Teplyakov (Speaker), A.V.Topchiev Institute of Petrochemical Synthesis, RAS, Moscow,
Russia - tepl@ips.ac.ru
M. Tsodikov, A.V.Topchiev Institute of Petrochemical Synthesis, RAS, Moscow, Russia
I. Moiseev, Kurnakov Institute of General and Inorganic Chemistry, RAS, Moscow, Russia
Catalytic processes using of porous ceramics where catalytic coatings on the
microchannel walls are of modern interest for creation of high speed (residence
time is < 10 -3 sec) and compact membrane reactors, especially for C1 reactions.
Catalytic mesoporous inorganic membranes combining selective gas transport
and catalytic activity can be considered as ‘ensemble’ of nanoreactors and be
related to new direction of heterogeneous catalysis. The counter-diffusion
transport in catalyst particles is replaced by unidirectional transport with the
potential of intensified catalysis and increased selectivity.
Mesoporous ceramic membranes with variation of pore size as non-linear
gradient can play an important role for selective mass-transfer control in
membrane catalysis. Based on methanol decomposition and methane
conversion this paper presents the results demonstrating the intensification of
gas phase catalytic processes in nano-channels of ceramic catalytic membranes.
Oxidative condensation of methane was carried out with using tubular ceramic
membranes of "BUM" trademark based on titanium carbide with La- Ce/MgO
catalyst deposited inside the membrane pores. The methanol conversion was
studied using TRUMEM metal-ceramic membranes (TiO2/Stainless steel). For
this reaction a Cr2O3×Al2O3×ZnO catalytic coating formed inside the membrane
channels was prepared. In latter case additionally a mesoporous layer of single
phase oxide P0.03Ti0.97O2±d with a narrow pore size distribution in the range of
2 nm was coated on the top of the catalytic membrane. As a result asymmetric,
three- layer ceramic catalytic membranes with a pore gradient in the range of 2-
3000 nm were prepared.
It was found that such membranes possess "directed permeability" in relation to
H2, He, CO2, O2, CH4, Ar. The dehydration rate of methanol into formaldehyde
and hydrogen directly correlates with selective properties of directed
permeability. Productivity of hydrogen under methanol feeding in direction to
selective layer through large porous one practically in half-order higher then
under contrary direction. Such systems can be considered as membranecatalytic
"diode". Ceramic membranes BUM modified by La-Ce/MgO provide