Low molecular weight hydrocarbon synthesis from carbon dioxide (CO2) gas via non-thermal plasma process

Abstract

Low molecular weight hydrocarbons such as methane and ethane are considered to be a crucial potential alternative energy sources owing to the high magnitude of heating. They are employed as fuel gas feedstocks in many industries which mainly hosting the combustion process. In this study, we aimed to produce such low molecular weight hydrocarbons via the methanation process through the assisting of plasma technology at low temperature. In the methanation reaction, one equivalent mole of carbon dioxide (CO₂) reacted with two moles of hydrogen gas (H₂). The feedstock gas in this work was 30 vol. % CO₂ diluted in inert argon gas, flowing through a DI water saturator at 10 ml/min. The saturated H₂O/CO₂ was activated by non-thermal plasma beam. The electricity potential (E), an energy source generated plasma beam, was varied from 3 to 20 kV. To characterize the qualitative and quantitative output gas, on-line Gas-Chromatography instrument (GC) was connected with the reactor line. The experimental result showed plasma discharge gap related to the diameter of reactor was the key parameter to enhance high CO₂ conversion rate. The highest CO₂ conversion percentage yielded 7 % using the reactor of 7.5 mm in diameter. According to the electrical potential in range of 3 – 20 kV, the CO₂ dissociation was not found significantly different. The concentration and yield percentage of methane (CH₄) were approximately 2.12x10^-7 ppm and 0.08%, respectively. Such low quantity of CH₄ production was detected, it might be due to either a consequence reaction of methane cracking or hydrocarbon polymerization to produce higher molecule of hydrocarbon (C2-C5). The selectivity of C2-C5 production was further reported.