CHAPTER 7: Catalysis in Modern Bio-refineries: Towards a New Bio-energy Paradigm1
Published:27 Aug 2020
Today, the conversion of biomass in sub- or super-critical water has been extensively studied to produce liquid fuels or synthesis gas (syngas). Given the extreme conditions of water at high pressure and temperature, along with the complex structure of biomass, the development of such processes remains a challenge. In order to realize the complete decomposition of biomass and a high yield of desired products, such as CH4 and H2, at relatively mild conditions, various catalysts have been synthesized and employed. Different metals (such as Cr, Ni, Zn, Ru and Rh) have been incorporated into various supports, such as mineral compounds of Al2O3, SiO2, TiO2, ZrO2, MgO, Y2O3, CeO2, silica-alumina, zeolites and carbon-based supports (e.g. carbon nanotubes, activated carbon). The stability of various support materials and the function of active metals have been extensively tested to obtain an ideal catalyst support. Therefore, this chapter focuses on the discussion of the catalytic gasification of biomass in supercritical water using heterogeneous catalysts. The stability of the catalyst support, the mechanism of cracking, the methanation and water gas shift reaction of intermediates over catalysts and the deactivation of catalysts in supercritical water are discussed.