The influence of preparation method of char supported metallic Ni catalysts on the catalytic performance for reforming of biomass tar

Abstract

The char-supported nickel catalysts prepared by wet impregnation and precipitation-deposition methods under different nickel loadings and catalytic temperatures for catalytic reforming of rice husk tar were investigated. The influences of preparation methods on the physicochemical properties of catalysts and catalytic activity towards tar conversion and gas yield were studied. The results showed that char-supported metallic Ni catalysts can be directly used without a reduction process because of carbon thermal reaction during calcination. The preparation method had a significant influence on the porosity and Ni dispersion of catalysts. The addition of Ni to char improved the specific surface area from 60 m2 g−1 to 346.8 m2 g−1 because of activation effect of nickel nitrate on char pore structure. The precipitation-deposition method produced higher surface area, smaller Ni nanoparticulates with more corner and step sites, as well as more concentrated size distribution than those of wet impregnation method, leading to higher catalytic activity, in terms of high tar conversion efficiency (83%) and increasing syngas yield. The selectivity to phenols and naphthalene for precipitation-deposited catalysts was strengthened, and the relative content of heavy tars was decreased remarkably. The increasing H2 yield and concentration were indicative of efficient conversion of macromolecular organic matters into small molecules gases. In addition, the precipitation-deposited catalyst exhibited weaker Ni sintering after reaction. The catalytic cracking temperature of 800°C and Ni loading of 10 wt% exhibited the best catalytic effects on gas distribution and tar conversion.