Obtenção de carbeto de tungstênio suportado em carvão ativado e dopado com níquel para fins catalíticos

Abstract

The obtainment of catalysts based on tungsten carbide-WC doped with nickel-N and supported on activated carbon (WC-Ni/AC), using the gas-solid reaction method in a fixed bed reactor, was studied through a 2³ factorial experimental planning, with the objective of evaluating the influence of the synthesis parameters and the Ni concentration in the specific surface area. Ammonium Paratungstate Tetrahydrate (APT) was used as a W source, mixed with nickel nitrate and impregnated with activated carbon. The WC-Ni powders were synthesized through a gas-solid reaction, in proportions of 49%w. WC-1%w. Ni/AC, 48%w. WC-2%wt. Ni/AC, 47%w. WC-3%w. Ni/AC, by carboreduction of the mixture of hydrated ammonium paratungstate (APT) with nickel nitrate at low temperature (750°C to 850ºC) and in short reaction times (60 min to 120 min). The specific surface area was studied through an experimental design, based on the results obtained by BET. The materials obtained were characterized using the techniques of XRD (crystallite size), BET and SEM. With its characterization, it was possible to understand the relationship between its structural properties and its specific surface area, aiming its application in heterogeneous catalysis. It was possible to produce nanostructured WC-Ni/AC powders in the desired proportions, with average crystallite size ranging from 16.2 nm to 47.7 nm and specific surface area ranging from 257.9 m²/g to 343.5 m²/g. The results shown through the statistical analysis, found that the temperature alone is the factor that most influences the increase in the size of the specific surface area of the WC-Ni/AC. The factors temperature, isotherm and Ni concentration combined have a small influence on the increase in surface area. The other combinations, temperature and isotherm, concentration, and isotherm, had no evident influence.