457 / 2018-12-30 18:13:58

Effective Generation of Syngas via Chemical Looping CH4 Conversion and H2O-CO2 Splitting

Chemical looping, redox, syngas

全体主题 > 燃料利用与化学循环技术

Typical methane chemical looping reforming suffers from carbon deposition and low selectivity towards syngas. Moreover, syngas is the only produced in the methane partial oxidation step. An alternative chemical looping redox scheme consisted of partial oxidation of methane and co-splitting of H2O-CO2 has been proposed for the effective and continuous generation of Fischer–Tropsch (F–T)-ready syngas. It provides a thermodynamically optimized redox catalyst by using H2O and CO2 as soft oxidants, guaranteeing a very high selectivity for methane conversion to syngas. The carbon tolerance is greatly enhanced due to H2O or CO2 gasification in re-oxidization step. Experimental studies confirm the redox scheme by using LaFeO3-CeO2 redox catalyst, demonstrating a continuous production of syngas with a H2/CO molar ratio around 2.0 in both methane partial oxidation and co-splitting of H2O-CO2 steps over 30 repeated cycles (CH4 reduction and H2O-CO2 oxidation) at 850 ºC. A syngas selectivity of 95 % in methane partial oxidation and 100 % conversion of CO2 to CO can be achieved. Competing reactions between H2O and CO2 splittings over both of reduced redox catalyst and possible deposited carbon are found to be key factors determining the molar ratio of H2/CO in the oxidation step. The proposed approach can potentially be applied for production of Fischer–Tropsch (F–T)-ready syngas with an increased yield of 33 % without the needs for gas separation when compared to state-of-the-art methane chemical looping reforming processes.