Three different regeneration processes including hydrogen or nitrogen purging and coke-burning treatment were used to restore the Pt-Sn/γ-AlOcatalysts, through which propane dehydrogenation reaction was performed in ...Three different regeneration processes including hydrogen or nitrogen purging and coke-burning treatment were used to restore the Pt-Sn/γ-AlOcatalysts, through which propane dehydrogenation reaction was performed in a consecutive reaction-regeneration mode. It was found that the catalyst using hydrogen regeneration showed the best stability compared with those regenerated by nitrogen purging and coke-burning treatment, suggesting that hydrogen regeneration is an effective approach for maintaining the performance of Pt-Sn/γ-AlOcatalysts in propane dehydrogenation reaction. The effect of different regeneration atmospheres on the metal active center and the coke deposition was investigated by XRD,TEM, N-physisorption, TPO, TG and Raman technologies, and the results revealed that hydrogen or nitrogen regeneration resulted in little impact on the size and structure of metal active center, retaining the effective Pt Sn phase over the catalyst. Moreover, hydrogen regeneration not only removed the low dense components of the coke, but also altered the property of the residual coke through hydrogenation, leading to a higher mobility of coke, and thus a higher accessibility of the metal active centers. Whereas nitrogen regeneration only removed the low dense components of the coke. Although coke-burning regeneration caused a thorough coke removal, the catalyst subjected to repeated redox exhibited poor stability due to metal agglomeration, phase segregation and the resulting large PtSn particle and core-shell structure with a Sn-rich surface.展开更多
In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis（2,4-pentanedionate）- dichlorotin [Sn（acac）2CL2], instead of a silylating agent was used to link the layers at 180 ℃. The obtaine...In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis（2,4-pentanedionate）- dichlorotin [Sn（acac）2CL2], instead of a silylating agent was used to link the layers at 180 ℃. The obtained material, which is designed as Sn-COE-5, shows a shift of the first XRD reflection, which is very similar to that of COK-5 interlayer expanded with dichlorodimethylsilane （DCDMS）, indicating an increase in interlayer distance. X-ray diffraction （XRD）, N2 sorption isotherms, inductively coupled plasma （ICP）, and X-ray photo- electron spectroscopy （XPS） support the incorporation of isolated Sn sites in the sample. In the conversion of glucose to levulinic acid. Sn-COE-5 exhibits much higher activity than COK-5, which is due to the presence of Lewis acidic sites in the Sn-COE-5.展开更多
基金supported by the National Natural Science Foundation of China(nos.21103182,21273049)the Natural Science Foundation of Guangdong Province(no.S2013050014127)Education Department Funding of Guangdong Province(nos.CGZHZD1104,2013CXZDA016).
文摘Three different regeneration processes including hydrogen or nitrogen purging and coke-burning treatment were used to restore the Pt-Sn/γ-AlOcatalysts, through which propane dehydrogenation reaction was performed in a consecutive reaction-regeneration mode. It was found that the catalyst using hydrogen regeneration showed the best stability compared with those regenerated by nitrogen purging and coke-burning treatment, suggesting that hydrogen regeneration is an effective approach for maintaining the performance of Pt-Sn/γ-AlOcatalysts in propane dehydrogenation reaction. The effect of different regeneration atmospheres on the metal active center and the coke deposition was investigated by XRD,TEM, N-physisorption, TPO, TG and Raman technologies, and the results revealed that hydrogen or nitrogen regeneration resulted in little impact on the size and structure of metal active center, retaining the effective Pt Sn phase over the catalyst. Moreover, hydrogen regeneration not only removed the low dense components of the coke, but also altered the property of the residual coke through hydrogenation, leading to a higher mobility of coke, and thus a higher accessibility of the metal active centers. Whereas nitrogen regeneration only removed the low dense components of the coke. Although coke-burning regeneration caused a thorough coke removal, the catalyst subjected to repeated redox exhibited poor stability due to metal agglomeration, phase segregation and the resulting large PtSn particle and core-shell structure with a Sn-rich surface.
基金supported by the National Natural Science Foundation of China (21422306 and 21403192)Zhejiang Provincial Natural Science Foundation of China under grant no. LR15B030001the Fundamental Research Funds for the Central Universities (2015XZZX004-04)
文摘In the interlayer expansion of the layered zeolite precursor COK-5, a Sn, salt, bis（2,4-pentanedionate）- dichlorotin [Sn（acac）2CL2], instead of a silylating agent was used to link the layers at 180 ℃. The obtained material, which is designed as Sn-COE-5, shows a shift of the first XRD reflection, which is very similar to that of COK-5 interlayer expanded with dichlorodimethylsilane （DCDMS）, indicating an increase in interlayer distance. X-ray diffraction （XRD）, N2 sorption isotherms, inductively coupled plasma （ICP）, and X-ray photo- electron spectroscopy （XPS） support the incorporation of isolated Sn sites in the sample. In the conversion of glucose to levulinic acid. Sn-COE-5 exhibits much higher activity than COK-5, which is due to the presence of Lewis acidic sites in the Sn-COE-5.
