One-step synthesis of biomass activated char supported copper nanoparticles for catalytic cracking of biomass primary tar

Highlights: • A one-step method was developed to synthesize biomass char supported nanocatalysts. • Synergy of ZnCl₂ as activator and CuCl₂ forming nanoparticles were obtained. • The surface area reached 803.1 m²/g with uniform dispersion of Cu⁰ nanoparticles. • A high tar conversion efficiency of 94.5% was obtained at 800 °C. • The yields of H₂, CH₄ and CO increased significantly after tar catalytic cracking. -- Abstract: Activated char supported copper nanocatalysts were synthesized directly by one-step pyrolysis of CuCl₂ impregnated biomass together with ZnCl₂ as activation agent and applied to the cracking of biomass primary tar in a dual-stage reactor. The characterization of the obtained catalysts using XRD, SEM-EDX, TEM and N₂ adsorption-desorption indicated CuCl₂ can be reduced to Cu⁰ nanoparticles as active sites, and the presence of ZnCl₂ can significantly enlarge the surface area of biomass char to improve the dispersion of copper nanoparticles. A large number of micropores and mesopores were formed during the synthesis process, which also helps to adsorb tar molecules and prolong the reaction time. The prepared nanocatalysts exhibited excellent catalytic activity in the cracking of primary biomass tar as a result of the combining effect of CuCl₂ and ZnCl₂, and a high tar conversion efficiency of 94.5% was obtained using RHC-1.0Cu1·0Zn at 800 °C. The yields of H₂, CH₄, CO and the total gas product increased significantly as a result of the tar reforming reactions using the activated char supported catalysts. GC-MS analysis illustrated that the biomass primary tar was mainly decomposed into oxygenated aromatic compounds and light tar compounds over the biomass char supported copper nanocatalysts.