In this study, a series of SnO2modified zeolite catalysts (Snx-S-1; x is the weight percentage of Sn) were prepared with SnCl2and a defective Silicalite-1 (S-1) zeolite via facile deposition–precipitation method. It was found that the stannic species modified all-silica zeolite catalysts were active for the intermolecular condensation of ethylenediamine (EDA) to 1, 2-Diazabicyclo [2, 2, 2] octane (TEDA) and piperazine (PIP). The best catalyst Sn6-S-1 (6 wt.% Sn loading) showed 86% EDA conversion and 93% total selectivity to TEDA and PIP. By contrast, the defective S-1 zeolite parent showed only approximately 9% EDA conversion under the same conditions. With the help of catalyst characterization techniques including hydroxyl vibration and pyridine adsorption FT-IR spectroscopy (transmission mode), the enhancement of the catalytic activity of the SnO2modified zeolite catalysts (Snx-S-1) was mainly attributed to the formation of mild Lewis acid sites in the siliceous zeolite. Both the hydroxyl nests of the defective S-1 zeolite and the dispersed SnO2clusters should be the important factors for the formation of mild Lewis acid sites on the modified zeolite. Based on the catalytic performance of the modified zeolite in the conversion of EDA to PIP and TEDA, it is inferred that the mildly acidified defective S-1 zeolite by the SnO2deposition modification might become a very active and durable catalyst for reactions involving strongly alkaline reactants and products.Keywords:defective Silicalite-1;SnO2modification;acidity;condensation of ethylenediamine
Tetracycline poses a major threat to the aquatic environment and human health, and there is an urgent need for a green, efficient and recyclable technological means to remove its negative effects. To address this need, three Fe 3 O 4 @SnO 2 modified wheat straw biochar nanocomposites with different Fe/Sn content ratios (Fe/Sn = 0.5, Fe/Sn = 1, and Fe/Sn = 2) were prepared by pyrolysis. The adsorption and degradation properties and related mechanisms of Fe 3 O 4 @SnO 2 modified wheat straw biochar nanocomposites were investigated by adsorption, degradation and free radical quenching experiments, as well as EPR analysis. The removal of tetracycline by Fe 3 O 4 @SnO 2 modified wheat straw biochar nanocomposites (Fe/Sn = 0.5) at pH 7.0 within 3 h was up to 91.80%, which is in accordance with the quasi-primary kinetic model. Under the interference of inorganic anions and cations, the removal of tetracycline by the composites was not affected by the coexisting ions except Ca 2+ , Mg 2+ , HCO 3 − and CO 3 2− . The composites were able to efficiently remove tetracycline from pharmaceutical wastewater with a removal rate of 82.33%. It was found that the composites could be reused at least five times. FTIR, XPS combined with DFT calculations elucidated the mechanism of tetracycline removal by the composites, with •OH and •O 2 − being the main substances involved in the photodegradation of tetracycline, the incorporation of manganese dioxide quantum dots enhancing the response to visible light, and the incorporation of magnetic nanoparticles resulting in rapid charge transfer and improved spatial separation of photogenerated carriers. The modification measures significantly increased the specific surface area of the biochar and enhanced the adsorption and photocatalytic properties. Based on these studies, the developed nanocomposites provide a new idea for the removal of antibiotics from pharmaceutical wastewater. Graphical
Yun Tian,Zhengyu Wei,Fan Li,Songjie Li,Lixiang Shao,Mengyuan He,Panfei Sun,Yuanyuan Li
Lithium-Sulfur (Li-S) batteries are very competitive in energy storage equipment due to their high theoretical capacity and low cost of raw materials. However, the serious polysulfide "shuttle effect", volume expansion effect and slow conversion reaction kinetics of Li−S batteries during the charge/discharge cycle process still need to be resolved urgently. Herein, we prepared a novel sulfur host of SnO 2 -decorated MoS 2 hollow microspheres (SnO 2 -MoS 2 HMSs). The unique hollow structure provides enough space to accommodate a large amount of sulfur and effectively adapts to its large volume expansion during charge and discharge process. On the other hand, the SnO 2 nanoparticles that attached to the surface of the MoS 2 nanosheets will accelerate the catalysis of MoS 2 and enhance the bonding strength with the polysulfide intermediates through the S−Sn−O chemical bond, which further inhibits the shuttle effect. The newly synthesized SnO 2 -MoS 2 HMSs cathode has achieved excellent electrochemical performance. The initial discharge specific capacity of 1326.4 mAh g −1 was obtained at 0.2 C, and after 100 cycles, the specific capacity of the SnO 2 -MoS 2 HMSs/S cathode only decreased slightly to 1183.8 mAh g −1 , its capacity retention rate reaching as high as 89.2%. We expect the newly synthesized hollow structured MoS 2 with SnO 2 decoration provides a new strategy for the construction of Li-S battery cathode materials.
危险品化学品经营许可证（带存储）