Mechanism study of toluene removal using iron/nickel bimetallic catalysts supported on biochar.

The present study utilized rice husk biomass as a carrier to synthesize rice husk biochar loaded with iron and nickel. Mono-metallic and bimetallic catalysts were prepared for the removal of toluene as the tar model. The efficiency of the catalysts for the removal of toluene was investigated, and finally, the removal mechanisms of mono-metallic and bimetallic catalysts for toluene were revealed. The experimental results showed that the bimetallic-loaded biochar catalysts had excellent toluene removal performance, which was closely related to the ratio of loaded Fe and Ni. Among them, the catalyst DBC-Fe2.5 %-Ni2.5 % (2.5 wt% iron loading and 2.5 wt% nickel loading) obtained through secondary calcination at 700 °C achieved the highest toluene removal efficiency of 92.76 %. The elements of Fe and Ni in the catalyst were uniformly dispersed on the surface and in the pores of the biochar, and the catalyst had a layered structure with good adsorption. Under the interaction of Fe and Ni, the agglomeration and sintering of Ni were reduced, and the surface acidity of the catalyst was increased, the surface acidity was favorable for toluene removal. The iron­nickel catalyst did not form significant alloys when calcined at 400 °C, whereas strong metal interactions occurred at 700 °C, resulting in the formation of Fe0.64Ni0.36 alloy and NiFe2O4 alloy. This NiFe alloy had abundant active sites to enhance the catalytic cracking of toluene and provide lattice oxygen for the reaction. Furthermore, the functional groups on the catalyst surface also had an impact on toluene removal. The catalyst prepared in this paper reduces the cost of tar removal, can be applied to the removal of industrial pollutant tars, reduces the pollution of the environment, and provides theoretical guidance and technical reference for the efficient removal of tar.

Hydrogen-Rich and Clean Fuel Gas Production from Co-pyrolysis of Biomass and Plastic Blends with CaO Additive.

The treatment and disposal of waste biomass and plastics are of great importance to achieve both waste management and resource recycling. In this work, pyrolysis of biomass and plastic blends were investigated to identify the influence of temperature and in situ CaO addition on the production of hydrogen-rich, HCl-free, and low tar content fuel gases. The results show that the increase in temperature and the use of CaO significantly improved both the quantity and quality of the fuel gas and mitigated the formation of tar compounds and HCl. Moreover, H2 yield was significantly improved from 0.30 to 3.68 mmol/g with the increase in temperature from 550 to 850 °C. Also, the use of in situ CaO significantly increased the H2 yield by 28-88%. The H2/CO ratio was also enhanced from 0.35 to 1.50 with the temperature increase and CaO addition. Tar removal efficiency reached approximately 70.09% with the use of CaO at 850 °C. The produced HCl gas could be effectively absorbed by CaO through dechlorination reactions to form CaClOH at a highest mitigation efficiency of 92.37%. The results could be used to develop clean and efficient treatment technologies of waste biomass and plastics.