(534h) Red Mud Catalyst for Tar-Free Syngas Production for Higher Value Applications

Coal is one of the major sources of fossil fuels used for power generation in the USA, but it also has negative environmental impact and greenhouse gas emissions. Coal gasification is an alternative to mitigate pollutant emissions. Syngas produced by coal gasification can be used for electricity generation, chemical feedstocks, or production of synthetic natural gas. Red mud or red sludge is a by-product of the Bayer process has catalytic properties that could be used for coal gasification. Attention has been paid to the application of red mud as a catalyst or adsorbent in several published investigations. In this work, sub-bituminous coal was catalytically gasified at atmospheric pressure in a bubbling fluidized bed reactor at 700, 800, and 900 °C on red mud. Three types of fluidizing medium were investigated: N₂, CO₂, and Steam. It was observed that gasification of coal on red mud under nitrogen improved with increase in temperature. Steam in combination with red mud promoted water-gas shift reaction (WGSR). Thus, using steam medium at 900 °C, the hydrogen concentration was tripled compared to the standard gasification under nitrogen. The steam gasification of coal on red mud also destroyed tar and produced a very clean aqueous residue. Gasification in carbon dioxide medium suppressed the overall gas yield, but the combination of carbon dioxide with steam dramatically increased the syngas production. Because the gas produced using red mud in steam atmosphere is very clean, the syngas could find application in chemical synthesis such as hydrocarbons, methanol, and dimethyl ether.