No abstract

In this research, the reforming of simulated natural gas containing a high CO 2 content under AC non-thermal gliding arc discharge with partial oxidation was conducted at ambient temperature and atmospheric pressure, with specific regards to the concept of the direct utilization of natural gas. This work aimed at investigating the effects of applied voltage and input frequency, as well as the effect of adding oxygen on the reaction performance and discharge stability in the reforming of the simulated natural gas having a CH 4 :C 2 H 6 :C 3 H 8 :CO 2 molar ratio of 70:5:5:20. The results showed marked increases in both CH 4 conversion and product yield with increasing applied voltage and decreasing input frequency. The selectivities for H 2 , C 2 H 6 , C 2 H 4 , C 4 H 10 , and CO were observed to be enhanced at a higher applied voltage and at a lower frequency, whereas the selectivity for C 2 H 2 showed an opposite trend. The use of oxygen was found to provide a great enhancement of the plasma reforming of the simulated natural gas. For the combined plasma and partial oxidation in the reforming of CO 2 -containing natural gas, air was found to be superior to pure oxygen in terms of reactant conversions, product selectivities, and specific energy consumption. The optimum conditions were found to be a hydrocarbons-tooxygen feed molar ratio of 2/1 using air as an oxygen source, an applied voltage of 17.5 kV, and a frequency of 300 Hz, in providing the highest CH 4 conversion and synthesis gas selectivity, as well as extremely low specific energy consumption. The energy consumption was as low as 2.73 9 10 -18 W s (17.02 eV) per molecule of converted reactant and 2.49 9 10 -18 W s (16.60 eV) per molecule of produced hydrogen.

The objective of the present work was to study the reforming of simulated natural gas via the nonthermal plasma process with the focus on the production of hydrogen and higher hydrocarbons. The reforming of simulated natural gas was conducted in an alternating current (AC) gliding arc reactor under ambient conditions. The feed composition of the simulated natural gas contained a CH 4 :C 2 H 6 :C 3 H 8 :CO 2 molar ratio of 70:5:5:20. To investigate the effects of all gaseous hydrocarbons and CO 2 present in the natural gas, the plasma reactor was operated with different feed compositions: pure CH 4 , CH 4 /He, CH 4 /C 2 H 6 /He, CH 4 /C 2 H 6 /C 3 H 8 /He and CH 4 /C 2 H 6 /C 3 H 8 /CO 2 . The results showed that the addition of gas components to the feed strongly influenced the reaction performance and the plasma stability. In comparisons among all the studied feed systems, both hydrogen and C 2 hydrocarbon yields were found to depend on the feed gas composition in the following order: CH 4 /C 2 H 6 /C 3 H 8 /CO 2 > CH 4 /C 2 H 6 /C 3 H 8 /He > CH 4 /C 2 H 6 /He > CH 4 /He > CH 4 . The maximum yields of hydrogen and C 2 products of approximately 35% and 42%, respectively, were achieved in the CH 4 /C 2 H 6 /C 3 H 8 /CO 2 feed system. In terms of energy consumption for producing hydrogen, the feed system of the CH 4 /C 2 H 6 / C 3 H 8 /CO 2 mixture required the lowest input energy, in the range of 3.58 · 10 À18 -4.14 · 10 À18 W s (22.35-25.82 eV) per molecule of produced hydrogen.

In this work, a mini-gliding arc discharge reactor was employed for the reforming of methane under ambient temperature and pressure operation. Acetylene and hydrogen were produced dominantly with high selectivities of *70-90 and *75%, respectively. The results showed that both methane conversion and product selectivities depended strongly on various operating parameters, including feed methane concentration, feed flow rate, electrode gap distance, residence time, and the presence of a reforming catalyst (as a function of catalyst distance). The Ni catalyst-loaded porous alumina-silica plate was used to study the catalytic effect on the process performance at various residence times. A considerable enhancement of methane conversion and product yields was achieved in the combined plasma-catalytic system, particularly at a longer residence time. The catalyst distance, or packing position of catalyst plate, was also found to be an important factor affecting the process performance of the combined plasma-catalytic methane reforming. The closer catalyst distance led to the greater methane conversion because of the greater possibility of adsorption-desorption interactions of excited gaseous species on the catalyst surface to enhance subsequent reactions.