This work aimed at elucidating the beneficial effect of the solid-phase grinding method on the catalytic performance of K- x Al for catalyzing γ-valerolactone to butene. Research indicated that a part of Al species was successfully introduced into the framework of KIT-6 support without destroying its original ordered mesoporous structure by the solid-phase grinding treatment method. Hence, Lewis and Brønsted acid sites were formed on the surface of the catalyst. By adjusting the amount of Al species, the content of weak acid sites (100-300 °C) on the catalyst surface can reach as much as 0.31 mmol·g −1 . Through the catalytic activity tested, the K-4Al catalyst exhibited optimum catalytic performance. The GVL conversion rate and butene yield can reach 96.2% and 90.1% at 300 °C, respectively. In addition, the K-4Al catalyst also showed satisfactory renewable performance in cycle tests. These findings will provide useful guidelines for further catalyst design for the preparation of butene from γ-valerolactone.
SSZ-13 has been widely used in catalysis and adsorption due to its excellent hydrothermal stability and large specific surface area. It was reported that the long crystallization time was one of the primary challenges limiting its industrial progress. In this paper, we reported a novel solid-state grinding route of synthesizing SSZ-13 zeolite, which was based on interzeolite transformation strategy and promoted by sodium persulfate (Na 2 S 2 O 8 ). The effects of the amount of Na 2 S 2 O 8 and crystallization time on the purity and crystallinity of SSZ-13 zeolite were studied by XRD measurements in detail. The results indicated that the crystallization time could be significantly shortened from 72 to 24 h when the molar ratio of Na 2 S 2 O 8 /SiO 2 was changed from 0 to 0.01, proving that Na 2 S 2 O 8 has the ability of accelerating the crystallization of SSZ-13 as a hydroxyl radical reagent. Three typical SSZ-13 materials and a reference sample were used as the catalysts for methanol-to-olefins reaction (MTO) and their physicochemical properties were analyzed by SEM, N 2 physisorption and NH 3 –TPD techniques. The SEM characterization results showed that the crystal size of SSZ-13 synthesized in the presence of Na 2 S 2 O 8 was larger than that of the one in the absence of it. The NH 3 –TPD results showed that the introduction of Na 2 S 2 O 8 could modulate the acid properties of SSZ-13 zeolites. The MTO tests revealed that the catalytic lifetime of one sample with Na 2 S 2 O 8 promoter (SSZ-13-0.01M-24h) was much longer than that of the other three samples. The observed difference in catalytic stability was mainly attributed to their various concentrations of medium strong acid sites.
Lithium iron phosphate (LiFePO 4 , LFP) is a frequently utilized cathode material for lithium-ion batteries. However, its practical applications are constrained by its relatively low ionic and electronic conductivities. To address this issue, it is possible to utilize highly conductive metallic coatings to enhance the material's electronic conductivity. Herein, LiFePO 4 with Cu composites (LFP/Cu) as cathode was synthesized by a simple solid-state process via one-step grinding in the presence of CuNO 3 and ascorbic acid. The discharge capacity of the LFP/Cu cathode with 0.75 wt% Cu was found to be 160.9 mA h g −1 at 0.1 C, representing a close approximation of its theoretical capacity and a notable enhancement compared to pure LFP (145.9 mA h g −1 ). Furthermore, it demonstrates excellent stability with a capacity retention of 136.5 mA h g −1 after 100 cycles at 2 C, as well as good rate performance. The electrochemical impedance spectra demonstrate that the incorporation of copper results in a further reduction in the resistance of LFP/Cu compared to pure LFP. The incorporation of copper particles into lithium iron phosphate has been shown to enhance its electronic conductivity, thereby further enhancing its electrochemical performance. In this study, we present a facile and cost-effective room-temperature synthesis method for the preparation of LiFePO 4 /Cu composites with improved electrochemical properties. This work provides a promising avenue for the design of cathode materials in lithium-ion batteries.
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