Dry reforming of methane using cold plasma reactor for different dielectric materials and modified MgAl2O4 catalysts

Abstract

Dry reforming of methane (DRM) through dielectric barrier discharge (DBD) plasma is one of the promising techniques to convert greenhouse gases (GHGs) such as methane (CH4) and carbon dioxide (CO2) to syngas (H2, CO) and higher hydrocarbons. In this study, Ni-loaded La2O3-MgAl2O4 mix-matrix support lamella-structure catalyst is prepared using modified co-precipitation followed by hydrothermal and wetness incipient impregnation methods. The catalysts are characterised by X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller with N2, H2-temperature-programmed reduction and CO2-temperature-programmed desorption. The spent catalyst is characterised by scanning transmission electron microscopy, energy dispersive X-ray spectroscopy mapping, thermogravimetric analysis and dielectric properties. DRM activity test is carried-out to determine the influence of reactor configuration and dielectric materials on reactant processing and energy efficiency (EE). The reactor configurations include discharge gap, discharge length, volume discharge and catalyst volume are systematically studied to investigate the plasma-catalytic behaviour. The performance and regeneration of the prepared catalysts are tested in a catalytic-DBD reactor which depicts the CH4 and CO2 conversion 84 % and 85.5 %, respectively, while H2 and CO selectivity are 51 % and 49.5 %, respectively (H2/CO=1.01) with EE = 0.13 mmol-kJ-1 for Ni/La2O3-MgAl2O4 catalyst. The optimum process parameters were examined using multiple response surface methodology through a four-factors, five-level central composite design. The optimum values are feed flow rate = 18.8 mL min-1, feed ratio = 1.05, input power = 125.6 W and catalyst loading = 0.6 g. Finally, from the macroscopic kinetics, the apparent activation energies are calculated as 32.6 kJ mol-1and 35.2 kJ mol-1 for CH4 and CO2, respectively. The calculated results fitted-well with the experimental results with ±5 error. The catalytic-DBD reactor exhibits encouraging performance for DRM at larger a scale.