Investigation of interactions of nickel with pyrolytic products in pyrolysis of poplar with nickel acetate via furnace or microwave heating

Abstract

Metal/biochar is an important catalyst with feature of easy recovering of metal via combustion of biochar carrier. During preparation of metal/biochar, interaction of metal with biochar affects evolution of pyrolytic products and dispersion of metal. Heating mode could influence interaction of metal with pyrolytic products. This was investigated by pyrolysis of sawdust loaded with nickel acetate at 400 or 600 °C with furnace and microwave heating, respectively. The results showed that cracking of biochar and volatiles was effectively promoted with Ni, generating more gases while reducing aliphatic organics and heavy phenolics in bio-oil. The enhanced cracking facilitated aromatization in microwave heating, forming biochar of higher thermostability and gases with more hydrogen. However, the furnace heating at 600 °C formed Ni/biochar of more developed pores than from microwave heating (409.1 versus 385.0 m2g−1). Microwave heating could induce merging of micropores on biochar, resulting in migration and aggregation of Ni. This led to lower capability for chemical adsorption of hydrogen and dispersion of nickel, further leading to inferior activity of Ni/biochar from microwave heating for hydrogenation of vanillin or furfural. The in-situ IR characterization of the pyrolysis showed the furnace heating reserved more oxygen-containing organics and aliphatic structures, promoting dispersion of nickel.