Low temperature conversion of methanol to higher hydrocarbons and hydrogen using a non-thermal plasma

In recent years, the emission of volatile organic compounds (VOCs) from chemical manufacturing plants, agricultural practises, and indoor sources has attracted public concern, as these emissions have a negative effect on both human health and the environment. VOCs are precursor for the formation of ground level ozone, organic aerosols and photochemical smog. Some of the VOCs are toxic and carcinogenic, while others can cause unpleasant odour that are detrimental to human health. Long-term exposure to VOCs has been linked to a variety of human diseases, including cancer, cardiovascular disease, lung and respiratory diseases. As a result, reducing VOC emissions has become a major concern and a hot research subject around the world. Non-thermal plasma (NTP) is an attractive and emerging technology for removal of odorous volatile organic compounds (VOCs) such as methanol from ambient air. In this study, a dielectric barrier discharge (DBD) reactor has been developed for the conversion of methanol into higher hydrocarbons, hydrogen and other products. The influence of specific input energy (SIE= 1.7 -8.5 kJ/L), methanol concentration (260-350 ppm) and residence time (1.2-3.3 s) on the performance of the plasma DBD reactor has been investigated in pure and humidified nitrogen. The results indicated that the removal efficiency of methanol increased with increasing SIE and residence time. The removal efficiency of methanol decreased with increasing methanol inlet concentration. The humidified nitrogen plasma shows the best performance in terms of removal efficiency and energy efficiency of the decomposition process. The maximum removal efficiency of 96.2% can be achieved at 8.5 kJ/L and a residence time of 3.3 s in humidified nitrogen plasma. Furthermore, water addition at 10% relative humidity improved the conversion of methanol, H2 yield, CO2 and CH4 selectivity. These results reveal that humidified nitrogen plasma provides an alternative approach for improving the performance of DBD reactor for the removal of VOC emissions from ambient air.