Chenyao Bi,Zhuangzhuang Zhang,Daizong Han,Chengan Wang,Jianbo Zhang,Ming Sun,Qingqing Hao,Huiyong Chen,Xiaoxun Ma
Quality improvement of pyrolysis tar with yield increasing of high value-added components is highly desired for coal utilization. Herein, Ga-impregnated mesoporous ZSM-5 (Ga/MZ5) directed by organosilane surfactant of [3-(trimethoxysilyl) propyl] octadecyldimethylammonium chloride (TPOAC) is used as a catalyst for the catalytic upgrading of coal pyrolysis volatiles. Effective regulation by reduction and reduction/reoxidation promotes a secondary dispersion of gallium species from external surface deposition to micropore permeation. The comprehensive evaluation of catalytic upgrading performance indicates that the designedly regulated gallium species (mainly Ga + , GaH 2 + and GaO + ), feasible balance of Brønsted and Lewis active sites and mesopore diffusion superiority effectively contribute the yield increasing of both light-fraction ( M LF / M Tar ) and target products of BTEXN (benzene, toluene, ethylbenzene, xylene and naphthalene). The optimal catalyst of Ga/MZ5_R/O exhibited the highest value of M LF / M Tar (88 %) and highest yield of BTEXN (31.84 mg.g −1 ), which are 173 and 589 % higher than non-catalytic single pyrolysis and 133 and 280 % higher than those over the conventional Ga-impregnated ZSM-5 (Ga/Z5). Moreover, the possible reaction networks towards high value-added products of BTEXN based on the positive conversion of polycyclic aromatic hydrocarbons (PAHs), phenols, and other oxygen-containing compounds (abbreviated as PPO) is further proposed.
Chengcheng Yan,Long Lin,Dunfeng Gao,Guoxiong Wang,Xinhe Bao
The electrochemical CO2 reduction reaction (CO2RR) powered by renewable electricity has emerged as a promising approach to alleviate global warming and energy depletion simultaneously. Notably, efficient catalysts containing Earth-abundant elements to achieve high CO2RR performance are in great demand for future applications. Herein, carbon-supported gallia gel nanoparticles were synthesized by precipitating gallium nitrate on carbon black in an ethanolic ammonia solution. Nano-sized gallia nanoparticles uniformly dispersed on the carbon support achieved a maximum CO faradaic efficiency of 77.0% at −0.71 V vs. the reversible hydrogen electrode (RHE) in CO2-saturated 0.1 M KHCO3 solution, showing a dramatic improvement compared to a bulk Ga electrode with only 24.2% CO faradaic efficiency at −0.80 V vs. RHE. X-ray photoelectron spectroscopy measurements revealed that surface Ga3+ species were reduced to metallic Ga when subjected to a negative potential during the CO2RR, indicative of the formation of oxide-derived active gallium sites. Control experiments further highlighted the necessity of close coalescence between the nano-sized gallia particles and the conductive carbon support. The present study underscores the feasibility of improving the CO2RR performance of Ga-related materials through nanostructuring of oxide-derived gallium catalysts.
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