Catalytic coupling of CO2 with epoxide over supported and unsupported amines.

Catalytic coupling of carbon dioxide with epoxide to cyclic carbonate is an important reaction that has recently been receiving renewed interest. This route allows the use of carbon dioxide as a greener chemical feedstock, which challenges the current practices for the synthesis of cyclic carbonates and derivatives. The present study is mainly concerned with catalytic coupling reaction between CO(2) and propylene oxide using organic amine as catalyst. The structural aspects of amines and the effects of their immobilization on solid surfaces on reaction kinetics are particularly studied. It is found that 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) amine maintains high catalytic activity both with and without solid support, but other primary amines, such as p-phenylenediamine give much reduced activity when placed on a solid surface. It is attributed to the absence of surface hydrogen in the supported TBD, prohibiting the catalyst sites from CO(2) poisoning. The coupling of other epoxides, including epichlorohydrin and styrene oxide over the solid supported amine, is also briefly carried out. Reaction mechanisms are proposed to explain the experimental observations.

Engineering preformed cobalt-doped platinum nanocatalysts for ultraselective hydrogenation.

Bimetallic heterostructures are used as industrial catalysts for many important transformations. However, conventional catalysts are primarily prepared in cost-effective manners without much appreciation in metal size control and metal-metal interaction. By employing recent nanotechnology, Pt nanocrystals with tailored sizes can be decorated with Co atoms in a controlled manner in colloid solution as preformed nanocatalysts before they are applied on support materials. Thus, we show that the terminal CO hydrogenation can be achieved in high activity, while the undesirable hydrogenation of the CC group can be totally suppressed in the selective hydrogenation of alpha,beta-unsaturated aldehydes to unsaturated alcohols, when Co decorated Pt nanocrystals within a critical size range are used. This is achieved through blockage of unselective low coordination sites and the optimization in electronic influence of the Pt nanoparticle of appropriate size by the Co decoration. This work clearly demonstrates the advantage in engineering preformed nanoparticles via a bottom-up construction and illustrates that this route of catalyst design may lead to improved catalytic processes.

Colloidal stable silica encapsulated nano-magnetic composite as a novel bio-catalyst carrier.

A colloidal stable silica-encapsulated magnetic nano-composite of a controlled dimension is, for the first time, employed to carry beta-lactamase via chemical linkage on the silica overlayer: activity study reflects that this new type of immobilisation allows site (enzyme) isolation, accessibility as good as free enzyme and recovery & reusability upon application of magnetic separation.