Microwave-triggered local high-temperature formation on Ni nanoparticles that enables ultra-fast catalytic pyrolysis of lignocellulose

Focused microwave (MW) heating of Ni/SiO 2 -Al 2 O 3 catalysts achieved “ultra-fast” catalytic pyrolysis of lignocellulose. The MW frequency and the cavity resonator's quality factor effectively accelerated the pyrolysis of bamboo to produce hydrogen more rapidly than conventional heating. In situ XAFS and in situ XRD provided experimental evidence for the formation of locally heated regions on Ni nanoparticles under MW irradiation. In particular, MW irradiation induced rapid Ni nanoparticle sintering at apparent bulk temperatures of 350–400 °C, whereas comparable sintering was not observed under conventional heating even at 1000 °C. These results support the presence of local high-temperature regions on Ni nanoparticles, although the exact local temperature under reaction conditions remains difficult to quantify. We conclude that MW irradiation accelerates the catalytic reforming of biomass by directly coupling MW energy to Ni nanoparticles and generating local hot spots.