Basic properties of molybdenum and tungsten nitride catalysts

The basic and related properties of high surface area Mo2N and W2N catalysts were characterized using CO2-temperature programmed desorption (TPD), the decomposition and dehydration of 2-methyl-3-butyn-2-ol (MBOH), and changes in the reaction rates on the addition of CO2, a base site poison. The Mo2N and W2N catalysts were prepared using the temperature programmed reaction method and had surface areas of 135 and 45 m2/g, respectively. The CO2-TPD and MBOH decomposition rates to acetone and acetylene indicated significant densities of base sites. The CO2 poisoning study implicated the involvement of weak sites in MBOH decomposition. The density of base sites and the rate of acetone formation were functions of the reduction temperature. Results for the nitride catalysts were compared to those for MgO and ZnO, known base catalysts. Base sites on the nitrides were of similar strength and density as those on the ZnO catalyst, but were weaker and less dense than those on MgO. Estimated turnover frequencies for the Mo2N and W2N catalysts were (6.0 ± 1.0) × 10−3 and (1.8 ± 0.4) × 10−3 s−1, respectively at 180 °C, and were slightly lower than those for the MgO and ZnO catalysts.