The gas volume concentrations of the

The simplification of tar components is attributed to two reasons. One is the catalytic cracking process and catalytic reforming process as listed in (3), (4), (5), (6) and (7). The other is the cracking of heavy compounds at higher temperatures with the addition of Ni/RHC and Fe/RHC catalysts in microwave pyrolysis (Xie et al., 2014). It is noteworthy that small hydrocarbon VCH 222 and radicals could recombine as usual to form macromolecular compounds at high reaction temperature (Baldwin et al., 2012). Whereas, the addition of rice husk char and rice husk char-supported metallic catalysts has the effect on restraining the formation of macromolecular organics by polymerization. It can be seen that rice husk char used as catalyst support could enhance the surface area of catalysts, and its developed porous structure contributes to the adsorption of macromolecular organic compounds in tar. Furthermore, the high specific surface area of rice husk char possessing microporous and mesoporous structures extends the residence time of tar cracking, thereby enhances the tar reforming performance to a community succession certain extent. The macromolecular tars adsorbed on the active sites of char particles were catalytically reformed to CO and H2 when contacted with metal active component (Shen and Yoshikawa, 2014). The metallic forms of Ni and Fe were considered to be the most active catalytic phase for tar reforming (Torres et al., 2007).