Carbon Supports Regulated the Performances of Copper Catalysts for H₂ Production through Microwave-Initiated Methanol Steam Reforming

To tackle the storage challenges for distributed hydrogen applications, the microwave-initiated methanol steam reforming (MSR) process was deployed to increase the flexibility and energy efficiency of the MSR hydrogen production. As the key, a series of carbon-supported CuZn catalysts were systematically investigated to reveal the impacts of dielectric properties, conductivity, and dispersion on the catalytic performance under microwave irradiation. In addition to the excellent dielectric properties and conductivity exhibited by the carbon supports, the efficient dispersion of active species will dominate the catalytic activity, which was evidenced by the fact that the graphite supported CuZnG-40 is less active than the carbon nanotube supported and well dispersed CuZnCNTs-10, even with CuZnG-40 presenting superior conductivity and dielectric properties. The high specific surface area, tubular structure, and abundant pores of the carbon nanotubes could significantly promote the dispersion of the CuZn active species, forming highly dispersed small CuO particles. The H2-TPR indicated that the reduction temperature of the carbon nanotube supported CuZn can be as low as 175 °C and it is easy to generate highly active Cu0/Cu+ sites. With a 1:1 (molar ratio) CH3OH/H2O feed and a weight hourly space velocity (WHSV) of 3 h-1, the microwave-initiated methanol conversion of the CuZnCNTs-40 reached 90% with a relatively low CO content at 250 °C.