Print

Patel, Rahul S.

Chemistry

2010

MS

In recent years, tremendous progress has been made in the field of catalysis. Catalysis is mainly of two types; homogeneous and heterogeneous. In homogeneous catalysis, the catalyst is soluble in the reaction medium and mayor may not be isolated at the end of the reaction. This is the chief disadvantage of homogeneous catalysis. A heterogeneous catalyst on the other hand is insoluble in the reaction medium and can be simply filtered off after the reaction is over and reused. The insolubility of the heterogeneous catalyst comes either being high molecular weight or supported on thermally stable, benign porous or non porous solids such as silica, polymers or cellulose. Many transition metal based catalysts find wide applications in industry today. They are used as catalysts for many important synthetic reactions. Of all the transition metals, vanadiwn based catalysts are extremely useful. Vanadiwn and vanadium based catalysts are known to catalyze many reactions in particular oxidations in presence of peroxide oxidants.
Mesoporous silica materials are very popular as supports for immobilizing catalysts to make them heterogeneous. They provide higher surface area and pore size and the reactants are able to diffuse easily into the pores where they come into contact with the catalysts and are cop-verted into products.
Acid Prepared Mesoporous Silica (APMS) was synthesized and two oxo vanadium complexes of pyridine-2,4,6-tricarboxylic acid (PYTCA) and 3-[N', N"--Bis-3-(salicylidenamino)ethyltriamine, "Salten" were covalently immobilized on its surface. APMS has a very high surface area, tunable pore size and thermal stability, making it an ideal support for heterogenizing catalyst systems. It is also synthesized in less than two hours. The complexes were characterized by FTIR, UVvisible spectroscopy (UV-Vis.), diffused reflectance spectroscopy (DR-UV-vis.), electron paramagnetic resonance spectroscopy (EPR), and nitrogen physisorption. The catalysts were studied for their activity towards room temperature oxidation of mustard gas analogue (2chloroethyl) ethyl sulfide (CEES) in various solvents.
Mustard gas (HD) is a toxic chemical warfare agent, whose safe disposal is of particular interest to the army. Most common methods of disposal include incineration which often leads to incomplete combustion products or green house gases such as SOx, CO and CO₂. Also large quantities of mustard gas are stored in underground drums across various sites in the country. If mustard leaks out of these drums, it could remain in soil for months without degrading. Also in case of a chemical or biological attack, the importance of minimizing number of casualties in the shortest possible time is of paramount importance. Thus detoxification of the affected areas quickly is extremely important.