Highly active Ir‐La‐S/AC catalyst was successfully prepared by co‐impregnation of an activated carbon（AC） carrier with a sulfuric acid solution of Ir and La species and compared with a tradition‐ally prepared Ir...Highly active Ir‐La‐S/AC catalyst was successfully prepared by co‐impregnation of an activated carbon（AC） carrier with a sulfuric acid solution of Ir and La species and compared with a tradition‐ally prepared Ir‐La/AC catalyst. High angle annular dark‐field‐scanning transmission electron mi‐croscopy（HAADF‐STEM） measurement results show that most of the Ir species on Ir‐La‐S/AC exist as single atomic sites, while those on Ir‐La/AC exist as nanoparticles with an average diameter of 1.5 nm. Evaluation of Ir‐La‐S/AC as a catalyst for heterogeneous carbonylation of methanol to acetyl gave a maximum TOF （turn‐over‐frequency） of 2760 h^–1, which was distinctly higher than that achieved by the Ir‐La/AC catalyst（approximately 1000 h^-1）. Temperature‐programmed desorption of ammonia（NH3‐TPD） result shows that the addition of sulfuric acid during the preparation pro‐cedure results in significantly more acidic sites on Ir‐La‐S/AC than those on Ir‐La/AC, which plays a key role in the enhancement of CO insertion as the rate‐determining step. Tempera‐ture‐programmed reduction（TPR） and in situ X‐ray photoelectron spectroscopy reveal that Ir spe‐cies are more reducible, and that more Ir^＋ might be formed by activation of Ir‐La‐S/AC than those on the Ir‐La/AC catalyst, which is thought to be beneficial for reductive elimination of AcI from Ir^3＋ species as an essential step for CH3I regeneration and acetyl formation.展开更多
A flux equation of diffusion for bi-disperse porous catalyst pellets was proposed by modifying the previously developed model equation over fractal trajectories. The proposed fractal model equation considered the same...A flux equation of diffusion for bi-disperse porous catalyst pellets was proposed by modifying the previously developed model equation over fractal trajectories. The proposed fractal model equation considered the same tortuous degree for both micro-and macro-pores. The experimental data of diffusion over a bi-disperse Ni/gamma-alumina pellet were obtained with a standard Wicke-Kallenbach diffusion cell for both carbon monoxide- ethylene and carbon dioxide-ethylene binary mixtures. The fitting between experimental results and the fractal model equation leads to a fractal dimension of 1.11. The prediction of diffusion flux over the bi-disperse Ni/gamma- alumina pellet by the proposed fractal model equation is much better than the traditional tortuosity-based model equation by comparison with the measured flux through the pellet.展开更多
基金supported by the National Key R&D Program of China (2017YFB0602203)~~
文摘Highly active Ir‐La‐S/AC catalyst was successfully prepared by co‐impregnation of an activated carbon（AC） carrier with a sulfuric acid solution of Ir and La species and compared with a tradition‐ally prepared Ir‐La/AC catalyst. High angle annular dark‐field‐scanning transmission electron mi‐croscopy（HAADF‐STEM） measurement results show that most of the Ir species on Ir‐La‐S/AC exist as single atomic sites, while those on Ir‐La/AC exist as nanoparticles with an average diameter of 1.5 nm. Evaluation of Ir‐La‐S/AC as a catalyst for heterogeneous carbonylation of methanol to acetyl gave a maximum TOF （turn‐over‐frequency） of 2760 h^–1, which was distinctly higher than that achieved by the Ir‐La/AC catalyst（approximately 1000 h^-1）. Temperature‐programmed desorption of ammonia（NH3‐TPD） result shows that the addition of sulfuric acid during the preparation pro‐cedure results in significantly more acidic sites on Ir‐La‐S/AC than those on Ir‐La/AC, which plays a key role in the enhancement of CO insertion as the rate‐determining step. Tempera‐ture‐programmed reduction（TPR） and in situ X‐ray photoelectron spectroscopy reveal that Ir spe‐cies are more reducible, and that more Ir^＋ might be formed by activation of Ir‐La‐S/AC than those on the Ir‐La/AC catalyst, which is thought to be beneficial for reductive elimination of AcI from Ir^3＋ species as an essential step for CH3I regeneration and acetyl formation.
基金Supported by the National Natural Science Foundation of China (No. 50228203 and No. 20476076)
文摘A flux equation of diffusion for bi-disperse porous catalyst pellets was proposed by modifying the previously developed model equation over fractal trajectories. The proposed fractal model equation considered the same tortuous degree for both micro-and macro-pores. The experimental data of diffusion over a bi-disperse Ni/gamma-alumina pellet were obtained with a standard Wicke-Kallenbach diffusion cell for both carbon monoxide- ethylene and carbon dioxide-ethylene binary mixtures. The fitting between experimental results and the fractal model equation leads to a fractal dimension of 1.11. The prediction of diffusion flux over the bi-disperse Ni/gamma- alumina pellet by the proposed fractal model equation is much better than the traditional tortuosity-based model equation by comparison with the measured flux through the pellet.
