(476bn) Monodispersed Pd-Nanoparticles for Selective Hydrogenation | AIChE

(476bn) Monodispersed Pd-Nanoparticles for Selective Hydrogenation


Kiwi-Minsker, L. - Presenter, Ecole Polytechnique Fédérale de Lausanne
Semagina, N. - Presenter, École Polytechnique Fédérale de Lausanne
Renken, A. - Presenter, École Polytechnique Fédérale de Lausanne

hydrogenation is one of the key processes for manufacturing pharmaceuticals,
vitamins and fine chemicals. The performance of the hydrogenation process and
product distribution is influenced by the catalyst activity and selectivity,
which in turn is strongly dependent on the metal particles morphology and their
size. The main problem in studying the size effects in catalytic hydrogenations
is that the particle size should be varied keeping all other parameters
constant. Moreover, the interaction of chemical kinetics with mass & heat
transfer should be avoided. This can be achieved by the appropriate design of the
reactor used.


One approach to overcome
these problems is the use of monodispersed nanoparticles of different size, but
prepared in the same manner. Herein, we report a new method of the preparation
of Pd-cluster with a narrow size distribution via reversed
micro-emulsion of water in isooctane, followed by nanoparticles extraction from
microemulsion and their redispersion directly in the hydrogenating substrate.
Size of Pd-clusters is mainly governed by a water-to-surfactant ratio and was
between 6 and 13 nm. It is important to note that no studies on the size-effect
in hydrogenation of acetylenic alcohols were performed up-to-now for the
particle size above 7.5 nm. Usually, it is considered that the
structure-sensitive reactions do not reveal size dependence above 5 nm owing to
the small contribution of the atoms with low coordination numbers on the
nanoparticle surface in this range.


As a test
reaction, hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol
(MBE) was chosen. The product MBE is an important intermediate in the synthesis
of vitamins A and E and perfumes. The reaction is also interesting for basic
catalysis because of several by-products formation. This allows elucidating an
influence of cluster size on product distribution besides controlling the
selectivity towards the target MBE. Kinetics of MBY hydrogenation was studied
and simulated based on Langmuir-Hinschelwood model. The Pd-clusters were
characterized by high-resolution transmission electron microscopy, an
energy-dispersive X-ray (EDX) and XRD methods.


In addition to
the use of Pd-cluster per se, they were deposited on active carbon
fibres in the form of woven fabrics. This allows understanding an influence of
the support on the catalytic performance of Pd°-nanoparticles and to suggest an
alternative reactor design based on structured catalytic bed. The results will
be presented in detail.