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Dry reforming of CH4(DRM) using a plasma-enabled catalytic process is an appealing approach for reducing greenhouse gas emissions while producing fuels and chemicals. However, this is a complex process that is influenced by both catalysts and discharge plasmas, and low energy efficiency remains a challenge for this technology. Here, we developed a water-cooled dielectric barrier discharge (DBD) reactor for plasma DRM reactions over supported catalysts (Ni/γ-Al2O3, Ag/γ-Al2O3and Pt/γ-Al2O3) prepared via plasma-modified impregnation. Results show that metal loading on γ-Al2O3enhanced the basic nature of the catalysts and promoted the formation of discharge channels and reactive species. The maximum conversion of CO2(21.4 %) and CH4(27.6 %) was obtained when using Ag/γ-Al2O3. The basic nature of the catalytic materials dominated CO2conversion, whereas the properties of the catalyst and discharge plasma determined CH4conversion. The highest selectivity of hydrogen (∼34.5 %) and carbon-containing gas products (∼81.0 %) were attained when using the noble metal catalysts (Ag/γ-Al2O3and Pt/γ-Al2O3), while the highest total selectivity of liquid products (14.1 %) was achieved in the presence of Ni/γ-Al2O3. Compared with γ-Al2O3, the supported catalysts demonstrated higher stability, especially for Ag/γ-Al2O3and Pt/γ-Al2O3, which also provided higher energy efficiency for gas conversion and product formation.

Non-thermal plasma reforming of CH4with CO2into value-added fuels and chemicals is very promising but challenging due to the low energy efficiency of the reforming process. One of the most important factors influencing energy efficiency is plasma power supply, and nanosecond pulsed power sources are gaining increasing interest in enhancing the energy efficiency of plasma chemical processes. Here, we investigate plasma-assisted CH4reforming with CO2using a nanosecond pulsed dielectric barrier discharge (DBD) plasma. Both electrical characteristics and reaction performance were investigated under different operating parameters, including applied voltage, gas flow rate, CH4/CO2molar ratio, and discharge length. Increasing applied voltage (from 20 to 28kV) and discharge length (from 6 to 14cm) enhanced the total gas conversion by 53.2% and 41.2%, respectively, but decreased the energy efficiency by 30.6% and 14.3%, respectively. The highest energy efficiency (12.4%) was obtained at an applied voltage of 20kV, a total flow rate of 50ml/min, a CH4/CO2molar ratio of 1:1 and a discharge length of 10cm, while the highest total gas conversion of 30.3% was achieved at a higher applied voltage of 26kV and a lower total gas flow rate of 25ml/min. An artificial neural network (ANN) model was developed to predict the plasma reforming process, and to investigate the relative contributions of key operating parameters to the reaction performance of this process. The results of the ANN model indicate that the CH4/CO2molar ratio and total flow rate affect the gas conversion most significantly, while the CH4/CO2molar ratio plays a dominant role in determining the product selectivity and energy efficiency.

•CO2reforming of CH4was performed in DBDs with different dielectric layers.•More intensified filamentary microdischarges were displayed in DBD-SD.•DBD-SD exhibited higher reactant conversion and liquid product selectivity.•Higher gas product selectivity and stable carbon balance were achieved in DBD-DD.•Higher energy efficiency for plasma reforming process was obtained in DBD-SD.