(113d) Synthesis of Fine Chemicals in Zeolite Membrane Microreactors

Fine chemicals and pharmaceuticals are high value, seasonal products
that are produced in modest quantities. They are usually customer specific and
have a short shelf life. These characteristics usually place a significant
constraint in their production, such that it is not uncommon to see labour
intensive batch processes being used. This often led to waste generation during
the scale-up from the laboratory to production scale. In addition, the use of
hazardous and often toxic homogeneous catalysts makes the product purification
and waste disposal important issues. Microchemical systems offer a new paradigm
for meeting these challenges. They represent a cheap alternative way for the
production of specialty chemicals and pharmaceuticals by a continuos process,
allowing simpler process optimization, rapid design implementation, better
safety and easier scale-up through replication. This enables rapid product
deployment to the marketplace and thus ensuring a significant competitive edge.

Two types of membrane reactors, the packed-bed membrane reactor
(PBMR) and catalytic membrane reactor (CMR) were successfully miniaturized. Zeolites
were incorporated as catalyst for reaction and membrane for separation. The
membrane microreactors were tested for Knoevenagel condensation reaction
between benzaldehyde and ethyl cyanoacetate to produce ethyl 2-cyano-3 phenylacrylate.
Supra-equilibrium conversion and high product purity were obtained from
selective removal of water during the reaction. Catalytic membrane
reactors often perform better than PBMR, but are more difficult to prepare
since the membrane must exhibit both good catalytic and separation properties. A simple computational model was developed to simulate the reaction
in the multichannel membrane microreactor using kinetic data from batch
reaction, correlated data from membrane separation and published transport
data. The influence of reactor geometry (i.e., channel width and membrane
location), membrane separation and catalyst properties were evaluated and the
results compared well with experimental data. The information provided by the
model suggests several ways of improving the reactor performance.