The availability of inorganic membranes which can withstand high temperatures and
harsh chemical environments has resulted in a wide range of opportunities for the
application of membranes in chemical reactions and separations. In particular, the
combination of membrane separation and catalytic reaction into a single operating
unit is an attractive way to increase conversions, improve yields and more efficient
use of natural resources in many reactions.
In this study, asymmetric alumina hollow fibres with different macrostructures
consisting of finger-like macrovoids and a sponge-like packed pore structure in
varying ratios have been prepared by a combined phase inversion/sintering technique.
The asymmetric membranes in hollow fibre geometry possess superior surface area to
volume ratios with less gas permeation resistance in comparison to commercial
symmetric membranes in tubular and disk configurations. Such asymmetric hollow
fibres are used as substrates onto which a Pd membrane is directly deposited by an
electroless plating (ELP) technique without any pre-treatment of the substrate surface.
A systematic study of the electroless plating of Pd and Ag onto an asymmetric
alumina hollow fibre substrate has been carried out by direct measurement of one of
the gaseous products, i.e. N2, using gas chromatography (GC). In addition, the
influences of the substrate macrostructure on hydrogen permeation through the
Pd/Al2O3 composite membranes have been investigated both experimentally and
theoretically.
Furthermore, a multifunctional Pd/alumina hollow fibre membrane reactor (HFMR)
has been developed and employed for the catalytic dehydrogenation of
methylcyclohexane (MCH) to toluene (TOL). The developed HFMR consists of a thin
and defect-free Pd membrane coated directly onto the outer surface of an asymmetric
alumina hollow fibre substrate. 50 wt% Ni/Al2O3 nano-sized catalysts were directly
impregnated into the substrate. The performance of HFMR has also been compared
with several different reactor configurations.