Non-thermal plasma assisted non-oxidative methane liquefaction for fuel production at near ambient conditions

Abstract

The utilization of natural gas, one of the most important energy sources, has a series of limitations because of its inert characteristics. In this study, the non-thermal plasma assisted non-oxidative methane liquefaction process at near ambient conditions (<100 °C and atmospheric pressure) is reported. As the primary component of natural gas, methane has been successfully transformed into gasoline-range chemicals under mild conditions. The engagement of a mesoporous silica catalyst, SBA-15, can enhance the methane conversion, liquid selectivity, and quality of the collected liquid product. Because of the possible generation of micro-discharge within the mesopores, the methane conversion increased from 38.4% to 43.3% over SBA-15. This catalyst could also greatly mitigate the coke formation, where the coke selectivity decreased from 8.0 C% to 2.6 C%. As the main target of this study, the liquid product with high content of desired iso-paraffins was collected. The loading of the SBA-15 enhanced liquid selectivity (increased from 39.0 C% to 45.8 C%) and the quality of liquid product, where less undesired side-products such as aromatics and olefins (total content decreased from 23.6 C% to 9.6 C% in collected liquid) and more paraffins (elevated from 76.5 C% to 90.4 C%) were collected. The effects of the dielectric constant and acidity of the packing material were also investigated. Several 4-hour long-term experiments were performed to learn the deactivation mechanism. It was proved that deactivation was mainly caused by coke generated between the working electrode and the quartz tube. This study demonstrates a promising process for natural gas utilization at mild conditions.