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Catalytic Oxidation of Ethane to Carboxylic Acids in the Liquid Phase at Near Room Temperature at Ambient Pressure

Li, Yuting, Tang, Yu, Nguyen, Luan, Tao, Franklin Feng
ACS sustainable chemistry & engineering 2018 v.7 no.5 pp. 4707-4715
ambient pressure, ambient temperature, aqueous solutions, catalytic activity, chemical industry, energy industry, ethane, feedstocks, formic acid, fuels, hydrogen peroxide, liquids, micropores, oxidation, shale gas
Chemical transformation of shale gas components under mild conditions is ideal for utilizing the shale gas resource to produce high-value intermediates of chemical industries and fuel feedstocks of energy industries. Here we report that single Rh atom sites, Rh₁O₅ anchored in micropores of HZSM-5, can catalyze oxidation of ethane by hydrogen peroxide in aqueous solution to form acetic acid and formic acid at a temperature ≤ 50 °C at a pressure of ethane at 1.5 bar. Conversion of 1.5 bar of ethane to carboxylic acids at 50 °C in a Parr rector reaches 37% within 2 h. Acetic acid and formic acid are formed through two parallel reaction pathways with apparent activation barriers of 32.5 and 35.5 kJ/mol in the temperature range of 50–72 °C, respectively. Turnover rates for forming carboxylic acids are 0.060 acetic acid molecules on each Rh₁O₅ site per second (216 mol of acetic acid per mol Rh per hour) and 0.127 formic acid molecules on each Rh₁O₅ site per second (457 mol of formic acid per mol of Rh per hour) at 50 °C. This study suggests a very promising catalytic process of synthesis of carboxylic acids at near room temperature at ambient pressure.