Feasibility assessment of recycling waste aluminum dross as a basic catalyst for biomass pyrolysis to produce hydrogen-rich gas

Abstract

Waste aluminum dross (AD) was used as a substrate on which active constituents were loaded after different activating treatments. A hydrothermal method was applied to synthesize the carbon-aluminum-based composite catalysts (C-ACC), whose pore structures, surface characteristics, and thermal stability were analyzed with the methods of XRF, SEM, and BET. Then, the feasibility of using recycled aluminum dross to catalyze biomass (bits of poplar wood, BPw) pyrolysis to produce hydrogen-rich gas was thoroughly evaluated. The results showed that aluminum dross exhibited significantly enhanced stability after the activating treatments and obtained a relatively large specific surface area and pore volume, presenting similar pore structure characteristics to aluminum oxides (Al2O3). Aluminum dross can be used as an excellent catalyst carrier. Carbon-aluminum-based composite material has a well-developed pore structure. Its specific surface area, average pore size, and pore volume are 118 m2/g, 10.3 nm, and 0.43 cm3/g, respectively, and its heat conductivity coefficient is 0.22 W/m · K. With a combination of advantages of activated carbon and Al2O3, the properties of iron-loaded carbon-aluminum composite catalysts are superior to those of active constituents and carrier materials. With these catalysts, a relatively high gas yield (43.77%) and a relatively small amount of char deposition (19.79%) have been achieved during the process of catalyzing BPw pyrolysis, with the H2 yield significantly increased to 64.24mL/g-biomass. So, it provides a new idea for oriented catalyzation of biomass pyrolysis to produce hydrogen-rich gas. Using aluminum dross as a catalyst carrier or a substitute for some part of the carrier can significantly improve the quality of hydrogen-rich gas. A new method of using aluminum dross to obtain catalysts for producing cheap biomass fuel through a pretreatment process has been put forward.