The Study Of Nano-sized Tungsten Carbide Catalyst

The presence of carbon in tungsten carbide modifies the electronic surface properties of tungsten in such a way that they resemble those of platinum. Tungsten carbide has been assumed as a new catalyst that can be substituted for Pt and Ru because of its catalytic activities in some organic reactions. Results of research reported that tungsten carbide powders showed catalytic activities in hydrogenation, dehydrogenation and isomerization of hydrocarbons, oxidization of hydrogen at low temperature and oxidization of Hydrazine. So, tungsten carbide has been universally studied as a new promising platinum-like catalyst. In this research, catalytic activity of nano-sized tungsten carbide waspreliminarily studied through hydrogenation of benzene.Nano-sized tungsten carbide has huge surface area and can provide a large number of active centers (situ) for catalytic reaction. Preparation of nano-sized tungsten carbide powder with great surface area is meaningful to its catalytic activity. In this research , Embedment - Direct Reduction Carburization Process was selected to Synthesize Tungsten Carbide, which synthesized the WC powder by 4 hours' heat preservation at 1300 ℃. In order to control the grain size of WC powders, planetary high-energy ball milling machine was applied in pretreatment of WO3 and C mixture and aftertreatment of WC powders. SEM showed that both pretreatment and aftertreatment contributed to reducing the grain size of WC powders. The effects of WO₃/C(wt), synthesis temperature and heat-preservation time to tungsten carbide synthesis and the effects of pretreatment and aftertreatment to the size of produced tungsten carbide were discussed.The catalytic activity of tungsten carbide was studied through hydrogenation of benzene. The reaction occurred in a flow reaction equipment with atmospheric pressure. Tungsten carbide powders were dispersed by short-cut glass fibre and situated in reaction equipment. Benzene was heated to its evaporation temperature(80.1 ℃ ) and evaporated. Its vapor was carried into reaction equipment by hydrogen.The product of reaction was also carried out by hydrogen and collected after condensation in liquid. The collected liquid was characterized by infrared spectra. There is no group of -CH2- in benzene molecular. On the contrary, the products of benzene hydrogenation are constituted of group of -CH2-. So, the catalytic activity of tungsten carbide can be estimated through examining the characteristic absorption peak of -CH2- in curve of infrared spectra.The intensity of characteristic absorption peak of -CH2- of product with tungsten carbide catalyzing was stronger those without tungsten carbide when the reaction occurred in a certain temperature. In a certain range of temperature, it increased with reaction temperature increasing. This change would disappear when the reaction temperature continue increasing because of the further dehydrogenation of benzene hydrogenation product. It means that the catalytic activity of tungsten carbide in hydrogenation of benzene increases with reaction temperature increasing.The catalytic mechanism of tungsten carbide was demonstrated.