Coupling hydropyrolysis and vapor-phase catalytic hydrotreatment to produce biomethane from pine sawdust.

This study investigated hydropyrolysis and subsequent vapor-phase hydrotreatment over a NiAlO catalyst to produce biomethane (CH) from pine sawdust. The non-catalytic pressurized hydropyrolysis generated tar, CO, and CO as the primary products. However, using a NiAlO catalyst in the second-stage reactor significantly increased the formation of CH and reduced CO and CO in gas products. The catalyst also fully converted tar intermediates to produce CH, resulting in a maximum carbon yield of 77.7% with 97.8% selectivity. The temperature plays a crucial role in CH generation, with both its yield and selectivity showing a positive correlation with the reaction temperature. Increasing the reaction pressure from 0.2 to 1.2 MPa notably inhibited the production of CH, leading to a shift towards cycloalkanes due to a competitive reaction. This tandem approach shows great potential as an innovative technique for producing alternative fuels from biomass wastes.