Major research areas include selective reduction and oxidation catalysis, hydrocarbon reforming, asymmetric catalysis and gas absorption studies. Current projects in these areas are detailed below.
Selective reduction:Cinnamyl alcohol is an important fragrance used in the perfumery industry. Preparation of the unsaturated alcohol by the selective reduction of cinnamaldehyde is difficult as the C=C tends to be preferentially hydrogenated. High selectivity to cinnamyl alcohol has been achieved in the liquid phase hydrogenation of cinnamaldehyde (in collaboration with Professor Webb) using supported copper catalysts. More recently, in collaboration with Dr. Cross, supported Pd2X4 (PMe3)2 and Pd2X4 (PEt3)2 complexes (X = Cl,Br,or I) have been prepared and used as catalysts in the liquid phase hydrogenation of cinnamaldehyde. Selectivity was found to be critically dependent on both the phosphine and the halogen used. Bimetallics and related ligands are now under investigation.
Selective oxidation:Butenes are valuable feedstocks for the production of a wide range of organic products used in the fine chemicals industry. Traditionally, they have been prepared by the thermal cracking of C4 alkanes, but this gives a complex mixture of products that are difficult to separate. We have developed a route that is very selective to butenes by the oxidative dehydrogenation of butane using supported WO3 catalysts. Novel routes to high surface area catalysts are now being pursued using sol-gel technology. Hydrocarbon reforming: In collaboration with Professor Webb and Dr. Fryer bimetallic supported Pt/Re, Pt/Sn and Pt/Ge catalysts have been synthesised and investigated by TEM both before and after being subjected to reforming conditions. Selectivity to aromatics was found to be critically dependent on both the composition of the bimetallic and the order of addition of metal salts to the support in the preparation of the catalyst precursor.
Asymmetric catalysis:The use of heterogeneous catalysts in asymmetric catalysis removes the need for the time-consuming and costly separation procedures associated with the use of homogeneous catalysts for these reactions. In collaboration with Drs. Cross and Peacock, a series of novel chiral ligands have been synthesised and attached to transition metals which are known oxidation catalysts. They are currently being intercalated in clays and will be used to promote enantioselectivity in the asymmetric oxidation of prochiral sulphides to sulphoxides.
Gas absorption studies:Many industrially important hydrocarbon feedstocks are contaminated with 0.2-4.0 % sulphur. These sulphur contaminants are ultimately released into the atmosphere in the form of sulphur oxides which contribute to acid rain. There is therefore a need to remove sulphur contaminants down to ppm levels. In collaboration with Drs.Campbell and Baird, high surface area pure and doped transition metal oxides have been prepared which are efficient at gas desulphurisation even at room temperature. These oxides were prepared by decomposition of mixed metal basic carbonates by precipitation routes. Mechanistic studies of these systems are being carried out using spectroscopic and radiotracer techniques.