Catalytic Activity of Oxygen Carriers on the Removal of Tar Byproducts for Biomass Chemical Looping Gasification Application

Journal article, 2023

One of the main advantages of chemical looping gasification (CLG) in comparison to conventional gasification technologies is its potential to enhance in situ tar removal. This is due to the catalytic properties of the oxygen carrier used in the CLG process, which can facilitate tar oxidation, cracking, and reforming reactions under specific operating conditions. Furthermore, this catalytic effect can be harnessed to convert hydrocarbons (C1-C3), thereby increasing syngas production during the process. In this study, the catalytic activity of eight different oxygen carriers (two ores, two wastes, and four synthetic materials) was examined in a batch fluidized bed reactor. The reactions were mainly conducted at three temperatures (850, 900, and 950 °C), utilizing benzene and ethylene as model compounds. The results revealed that the ores and wastes exhibited a low catalytic effect over benzene and ethylene conversion at low temperatures, although this effect was increased with a rising temperature. Conversely, the synthetic materials demonstrated higher catalytic activity in the benzene and ethylene conversion reactions, which also increased with higher temperatures. It should be noted that the Cu/Al oxygen carrier achieved nearly complete conversion of benzene and ethylene at temperatures exceeding 900 °C. Methane production was observed in most of the experiments, indicating its role as an intermediate in the conversion of tar byproducts. Additionally, the Cu/Al oxygen carrier exhibited a promising catalytic performance in methane conversion. These findings highlight the potential of certain synthetic oxygen carriers, such as the Cu/Al oxygen carrier, to serve as effective catalysts for the removal of tar byproducts and light hydrocarbons during CLG processes.