Methane Catalytic Pyrolysis by Microwave and Thermal Heatingover Carbon Nanotube-Supported Catalysts: Productivity, Kinetics,and Energy Efficiency

Methane catalytic pyrolysis, which is the reaction toproduce hydrogen and carbon without emitting CO2, represents anapproach for decarbonization using natural gas as an energy resource.The endothermic pyrolysis reaction was carried out under two heatingscenarios: convective thermal heating and microwave-driven irradiativeheating. The pyrolysis reaction was conducted at 550-600 degrees C overcarbon nanotube (CNT)-supported Ni-Pd and Ni-Cu catalysts. Onboth catalysts, an enhanced methane conversion rate was observedunder microwave irradiation. The enhanced catalytic activity washypothetically caused by the presence of free electrons in the carbonatoms within the CNT that enabled the CNT support to absorbmicrowave energy effectively and to be heated efficiently by microwave.The microwave catalytic pyrolysis has shown improvement in kinetics,where the apparent activation energy dropped from 45.5 kJ/mol underconventional convective heating to 24.8 kJ/mol under microwave irradiation. When the methane conversion rate is increased by37%, the microwave power consumption only changed by 10.8%. The research demonstrated the potential of transforming naturalgas into clean hydrogen and value-added carbon in a more energy-efficient way. Process simulation and techno-economic analysisshowed that potentially hydrogen minimum selling price of about $1/kg H2could be achieved.