Promising Directions in Chemical Processing of Methane from Coal Industry. Part 2. Development of Catalysts

Abstract

For the creation of new highly active and stable catalysts for the complete processing of coal methane, different methods for designing catalytic systems are being applied, including the use of the effects of mutual strengthening of the action of metals and modifying the composition of the supports. Different chemical synthesis approaches were considered for obtaining supported Ni nanoparticles with controllable compositions and sizes. For the citrate sol-gel method, it was found that with an increase in the citric acid/metals molar ratio from 0 to 1, the textural characteristics (specific surface area: 76→100 m²/g) of Сe_0.2Ni_0.8O_1.2/Al₂O₃ catalysts, dispersion (average particle size: 10→5 nm) and reducibility (temperature of maximum H₂ consumption: 580→530 °C) of the Ni-containing species improved. For calcined in air at 500 °C catalysts it was shown that Ni²⁺ cations stabilized in NiO or in the Ce-Ni-O solid solution. The proportion of the latter was maximum at a citric acid/metal molar ratio equal to 0.25, which was chosen as the optimal value in the investigated range of 0.25–1.0. An increase in the calcination temperature from 500 to 900 °C contributes to the stabilization of Ni²⁺ in the Al-Ni-O solid solution, which leads to a slight deterioration in the textural properties of the samples and a significant difficulty in their reducibility. After reductive activation at 800 °C of Сe_0.2Ni_0.8O_1.2/Al₂O₃ samples, catalytically active metal Nio nanoparticles of ~7 nm in size were formed for effective reforming of coal industry methane into synthesis gas.