Selectively converting fructose into furfural by H-beta catalyst is a very interesting catalytic process. However, it is a challenging task to clearly elucidate the roles of framework Al for selective scission of C C and C O bond. Herein, selective elimination of framework Al atoms is realized. Several detailed investigations showed that the framework Al species located in different sites play important role in furfural formation. The framework Al atoms of pristine H-beta mainly occupied at T1, T2, T5, T6 and T7 sites. These Al species at pore mouth can be removed by citric acid, while the treatment of nitric acid mainly eliminated the framework Al atoms from T2 and T7 sites. As for oxalic acid, the Al atoms occupied at T2, T5, T6 and T7 was primarily leached. Upon citric acid and nitric acid treatment afforded the similar yield of furfural, indicating that the formation of furfural could not be governed by these Al species at pore mouth, T2 and T7 sites. However, in the case of oxalic acid treatment, complete removal of the Al species on T2, T5, T6 and T7 sites decreased the yield of furfural. Thus, it is reasonably inferred that these Al atoms populated at T1 sites and intersecting channels is more encouraging for the splitting of C C bond, while the Al species occupied at T5, T6 sites and the larger straight channels is probably more favorable to scission of C O bond.
Aihu Feng,Yang Yu,Le Mi,Yunzhen Cao,Yun Yu,Lixin Song
The non-framework aluminum is inevitably formed in the process of preparing the ultra-stable Y zeolite (USY), which severely blocks the mesopores of USY zeolite. It is necessary to treat the USY with the appropriate acid and/or alkali. In this paper, the USY zeolite is firstly dealuminated with NH 4 HF 2 solution and then desiliconized with NaOH or NH 4 OH solution. The effect and mechanism of NH 4 HF 2 and different alkali treatments on the structural and textural property of USY zeolite are elaborately demonstrated. It is found that the non-framework Al remaining in the mesopores of USY is significantly removed by the NH 4 HF 2 solution. The desiliconization reaction is more likely to start near the mesoporous wall because the Al concentration in here is low and the repulsive force against OH − is weak. The OH − ions from NaOH solution not only etch the framework Si near the inner wall of the mesopores, but also remove the Si on the surface of NH 4 HF 2 -etched USY zeolite. However, the concentration of OH − ions is too low when NH 4 OH is used as the desiliconization agent, the OH − ions just react with silicon around the mesopores. Therefore, the NaOH/NH 4 HF 2 -etched USY contains both some micropores and macropores, and the NH 4 OH/NH 4 HF 2 -etched USY only possesses more mesopores with pore sizes of ～10 nm. In addition, NaOH/NH 4 HF 2 -etched USY exhibits excellent toluene adsorption performance at low pressure stage, while NH 4 OH/NH 4 HF 2 -etched USY has the highest adsorption capacity on toluene at high pressure stage.
Di Deng,Shujun Deng,Dandan He,Zhiheng Wang,Zhipeng Chen,Yi Ji,Guoping Yan,Guangjin Hou,Licheng Liu,Hong He
Ce- or La-doped Cu/SSZ-13 catalysts were prepared by a hydrothermal method and Cu, Ce or La ions were incorporated through stepwise ion exchange. The catalyst activity was measured for the ammonia selective catalytic reduction reaction. The structure and composition of catalyst were characterized by using X-ray diffraction, scanning electron microscopy, inductively coupled plasma mass spectrometry solid-state NMR, NH 3 -TPD techniques, and the active components were examined by XPS and XANES . The results indicate that the Ce and La doping can both completely preserve the SCR activity of Cu/SSZ-13 above 300 °C, but there is also a decrease of activity below 200 °C. On the other hand, Ce doping is beneficial to the formation of framework aluminum , stabilizes molecular sieve framework and Cu active sites of Cu/SSZ-13, thereby improves the catalyst hydrothermal stability. But La doping will decrease the amount of framework aluminum and Cu active sites of Cu/SSZ-13 after hydrothermally aging, even destroy zeolite CHA structure. This is quite harmful to the catalyst hydrothermal stability.
危险品化学品经营许可证（带存储）