Deactivation of a CoMo catalyst during catalytic hydropyrolysis of biomass. Part II: Characterization of the spent catalysts and char

In this work sulfided CoMo/MgAl2O4 catalysts used in fluid bed catalytic hydropyrolysis for the conversion of biomass to liquid fuels were thoroughly characterized by Raman spectroscopy and scanning (transmission) electron microscopy together with energy dispersive X-ray spectroscopy. Potassium and calcium were transferred from the biomass to the catalyst and the accumulated amounts increased proportionally with the time on stream (TOS) and reached 0.67 and 0.28 wt.% after 16.2 h, respectively, when beech wood was used as biomass feedstock with a feeding rate of approximately 270 g/h beech wood to 50 g of catalyst. The carbon content on the spent catalyst also increased with TOS and was 3.7 wt.% after 3.5 h and 7.2 wt.% after 16.2 h, indicating that the coking rate decreased with time on stream. However, SEM-EDS indicated that the carbon concentration increased more on the surface than in the bulk, thereby increasing the risk of pore blocking. In addition, Raman spectroscopy showed that the initially form...