A facile and effective post-treatment route has been systematically applied for the preparation of hierarchical zeolites SAPO-18 using oxalic acid or sodium citrate etching solution. The influence of acidic or alkaline post-treatment on the relative crystallinity, morphology, chemical composition, pore characteristics, and acidity of a series of zeolites SAPO-18 was investigated by X-ray diffraction, scanning and transmission electron microscopy, X-ray fluorescence spectroscopy, nitrogen adsorption–desorption, temperature-programmed desorption of ammonia, and solid-state magic angle spinning nuclear magnetic resonance spectroscopy experiments. Post-treatment led to an increase in mesoporosity by widening the micropores, but a decrease in the acid strength of zeolite SAPO-18 samples. The effects of mesoporosity and acidity on the catalytic cracking performance of zeolite SAPO-18 samples were studied. The hierarchical zeolite SAPO-18 sample post-treated by alkaline sodium citrate solution with suitable concentration exhibited better catalytic conversion and improved light olefin selectivity in cracking of 1-butene.
Fe, Mn co-supported SAPO-18 zeolite was synthesized via ion-exchange method and exhibited high performance in catalytic degradation of methyl orange (MO). The bimetallic Fe-Mn/SAPO-18 catalyst showed almost 100% MO (50 mg/L) removal within 20 min, which was superior to the MO degradation efficiency over monometallic Fe or Mn catalysts. The hydroxyl group (OH ) generated in the photo-Fenton catalysis was determined by fluorescence probe and the corresponding reaction mechanism was explored. We proposed that the light and synergistic effect of bimetal promote the conversion of metal ion valence, thereby enhancing the generation of the active species and the degradation efficiency of MO. Furthermore, the influences of some essential factors on MO degradation rate were investigated. The results indicated that the pH of the solution plays an important role in Fenton degradation of MO. 100% MO degradation is achieved within 10 min when the initial pH is set at 2–3 under UV for Fe-Mn/SAPO-18. Moreover, it also shows good performance under neutral conditions, thus exhibits considerable activity at expanded pH range. And the concentrations of H 2 O 2 and MO solution and the dosage of catalysts can influence the degradation rate of dyes. This work not only made significant progress on the development of high-performance catalysts for the degradation of MO, but also provided a direction for the study of organic contaminant degradation.
Xiaoyun Li,Rui Xu,Qingling Liu,Min Liang,Jiaxin Yang,Shuangchun Lu,Guangbi Li,Lefu Lu,Chuanling Si
A one-step process was proposed for valorization of corn stover into furfural and levulinic acid catalyzed by SAPO-18 zeolites. With the aim to produce furfural and levulinic acid, the Brønsted to Lewis acid site ratios of SAPO-18 were modified. The influence of reaction temperature, time and the ratios of Brønsted to Lewis acid site on the valorization of corn stover were investigated. At the fixed catalyst concentration of 20 g/L, a furfural yield of 95.1% was observed at 205 °C for 40 min using SAPO-18 with Brønsted to Lewis acid site ratio of 0.11, and a levulinic acid yield of 70.2% achieved at 190 °C for 80 min using SAPO-18 with Brønsted to Lewis acid site ratio of 0.17. The Brønsted to Lewis acid site ratios of SAPO-18 were adjusted by altering the framework Si/Al ratio of SAPO-18. The SAPO-18 with lower Brønsted to Lewis acid site ratios showed higher activity for furfural production from corn stover and that with higher ratios exhibit superior catalytic effect for levulinic acid formation. The kinetic models considering the effect of Brønsted to Lewis acid site ratios agreed with the experiment values well, which provided detailed insights on the conversion of hemicellulose and cellulose fraction of corn stover into furfural and levulinic acid.
The reduction of NO x emission during the cold start period of diesel vehicles requires special attention in accordance with the emission regulations. In this work, the direct incorporation of cerium and copper in SAPO-18 catalyst with AEI type framework structure (CuCe-SAPO-18) resulting in a substantial enhancement of the performance in the low-temperature NH 3 -SCR reaction (<200 ℃). A small amount of cerium (0.13–0.31 wt%) broadened the reaction temperature range of use and increased the hydrothermal stability of the catalyst considerably. The cerium species was introduced in the ion-exchange sites of Cu-SAPO-18 in the form of Ce 3+ ions even with high loading (3.15 wt%). The Ce 3+ ions were found to affect the distribution of silicon and aluminum atom coordination ( 29 Si NMR, 27 Al MAS NMR) in the AEI-type skeleton structure leading to an increase of both the amount of active Cu 2+ species and the acidity of the CuCe-SAPO-18 catalysts that are beneficial for the NH 3 -SCR reaction.
危险品化学品经营许可证（带存储）