Insights into synergistic oxidation mechanism of Hg0 and chlorobenzene over MnCo2O4 microsphere with oxygen vacancy and acidic site.

The simultaneous control of Hg0 and chlorinated organics has become the frontier of environmental engineering but still lacks the understanding of synergistic oxidation mechanism. Herein, we designed a Mn-Co catalyst with abundant oxygen vacancies and acidities, which delivered more than 90 % oxidation performance of Hg0 within 100-325 °C and achieved 90 % conversion of chlorobenzene at 220 °C. A synergistic effect was observed in the oxidation of Hg0 and chlorobenzene. Experimental and computational results revealed that Lewis acid over Mn site weakened C-Cl bands of chlorobenzene by electronic traction. The strong interaction between adsorbed mercury and Cl further promoted dechlorination process to generate HgCl2 gas, while accelerating the nucleophilic substitution of Brønsted acid attacking the benzene ring over Co site, consequently triggering synergistic oxidation of Hg0 and chlorobenzene. Oxygen vacancies enhanced the initial adsorption of Hg0 and chlorobenzene. Meanwhile, the interfacial charge-transfer from Hg-d to Cl-p orbitals alleviated deactivation of Lewis acid and slowed down the consumption of Brønsted acid, which accelerated the conversion of intermediates to CO2/H2O and promoted deep oxidation of chlorobenzene. This work provides a unique insight into the promotion of the synergistic oxidation of Hg0 and chlorobenzene and is expected to guide the industrial applications.

Enhanced hydrogen production from catalytic biomass gasification with in-situ CO2 capture.

In order to cope with the global energy crisis and environmental pollution problems, there are urgent needs for clean energy such as biomass-derived hydrogen. CaO is effective to promote hydrogen production from biomass gasification due to its high capacity of in-situ CO2 capture. In this work, a two-stage fixed bed reactor was used to produce hydrogen by catalytic conversion of biomass with and without in-situ CO2 capture. In addition, three Ni loadings (5 wt%, 10 wt%, and 20 wt%) supported by Al2O3 and sol-gel CaO have been prepared and tested. The BET analysis shows the surface area of the catalysts increases first and then decreases with the increase of Ni loading. Results from high-resolution transmission electron microscopy (HRTEM) images reveals that NiO particles are well distributed over the porous CaO. The X-ray diffraction (XRD) analysis indicates the NiO nanocrystalline size is increased with increasing Ni loading on Ni/Al2O3, and the most homogeneous dispersion was shown by 10 wt% Ni/CaO. Around 666 mgCO2/gCaO of CO2 adsorption capacity and 850 min stability were obtained using the sol-gel CaO sorbent. Compared to the reference Ni/Al2O3 catalysts, the resistance of carbon deposition on the Ni/CaO results in a lower coke deposition, which is attributed to the basicity of the catalysts. In addition, the increase of loading promotes the decomposition of biomass-derived oxygenated compounds. Much more hydrogen is obtained using the Ni/CaO catalysts compared with Ni/Al2O3 due to in-situ CO2 capture. However, the sintering and particle agglomeration using the 20 wt% Ni-catalyst might be responsible for the reduction of hydrogen production. The highest H2 concentration of 19.32 vol% at 424 °C was obtained when the 10 wt% Ni/CaO catalyst was used.

Emission control strategies of hazardous trace elements from coal-fired power plants in China.

China's energy dependents on coal due to the abundance and low cost of coal. Coal provides a secure and stable energy source in China. Over-dependence on coal results in the emission of Hazardous Trace Elements (HTEs) including selenium (Se), mercury (Hg), lead (Pb), arsenic (As), etc., from Coal-Fired Power Plants (CFPPs), which are the major toxic air pollutants causing widespread concern. For this reason, it is essential to provide a succinct analysis of the main HTEs emission control techniques while concurrently identifying the research prospects framework and specifying future research directions. The study herein reviews various techniques applied in China for the selected HTEs emission control, including the technical, institutional, policy, and regulatory aspects. The specific areas covered in this study include health effects, future coal production and consumption, the current situation of HTEs in Chinese coal, the chemistry of selected HTEs, control techniques, policies, and action plans safeguarding the emission control. The review emphasizes the fact that China must establish and promote efficient and clean ways to utilize coal in order to realize sustainable development. The principal conclusion is that cleaning coal technologies and fuel substitution should be great potential HTEs control technologies in China. Future research should focus on the simultaneous removal of HTEs, PM, SOx, and NOx in the complex flue gas.