查看更多>>摘要：Achieving efficient metal-free synthesis of 2,5-diformylfuran and 2,5-furandicarboxylic acid is always a challenge. In this manuscript, the selective oxidation of 5-hydroxymethylfurfural was achieved by using TEMPO system in t-BuOH solvent with the suitable acid promoters. And t-BuOH was considered to be a suitable solvent due to its excellent stability, oxidation promotion and solubility for intermediates. Remarkably, 90% and 83% yield of DFF and FDCA can be obtained with acetic acid and phosphoric acid, respectively. Additionally, the role of acid additives was discussed in detail and the hydration degree of aldehyde intermediates was considered to be key to controlling the selectivity of this reaction. The isolated yield of 2,5-diformylfuran and 2,5-furandicarboxylic acid were 82% and 78% through the scale-up oxidation, respectively. This approach may be a promising alternative to traditional oxidations for the synthesis of carboxylic acids.
查看更多>>摘要：Epoxide ring-opening is a key reaction in organic chemistry. We have previously shown that B(C6F5)(3), a strongly Lewis acidic arylborane, exhibited high rates and unusual selectivities for catalyzing the ring-opening of aliphatic epoxides with alcohols. Here we compare catalysts of the form B(C6H5_XFX)(3 )(x = 5, 4, 3, and 0) and determine that moderately Lewis acidic arylboranes have higher regioselectivity, but slower rates in this reaction. At high temperatures, these arylboranes can also hydrolyze into inactive species. However, deactivation is suppressed in the presence of co-catalytic amounts of 1,2-propanediol, and DFT calculations suggest a role for arylborane-H2O-diol complexes. Thermal stabilization and regioselectivity enhancement by diol are both more pronounced for B (C6F5)(3) than for less Lewis acidic B(C6HF4)(3) and B(C6H2F3)3 catalysts. These results further demonstrate the catalytic relevance of H-bound networks of arylboranes and diols and enable their use at higher temperatures and greatly increased rates.
查看更多>>摘要：A CrFeO mixed oxide with an FeCr2O4 spinel structure was treated with sulfuric acid and tested for catalytic combustion of dichloromethane (DCM). The acid-treated catalysts (denoted as CrFeO-4S and CrFeO-9S) were more active than the pristine one, with the CrFeO-9S giving a 2-fold higher rate at 240 degrees C (35.7 versus 17.8 mu mol m(- 2) h(-1)). More importantly, the acid treatment greatly enhanced the catalyst stability in long term reaction. Various characterizations revealed that the acid treatment improved the redox property and surface acidity of the CrFeO oxide, which accounted for the enhance activity. Meanwhile, the acid treatment removed weakly coordinated Cr species on the catalyst surface and thus avoided the Cr leakage during the reaction, which was responsible for the excellent stability. Moreover, kinetics and spectroscopic results revealed that the surface sulfate evolved a new reaction path to the formation of formaldehyde intermediate, which could be further oxidized to COx.
查看更多>>摘要：Catalytic transfer hydrogenation (CTH) recently attracts significant attention in biorefinery due to the free of using high-pressure fossil-derived H-2 that potentially reduce the equipment cost. Herein, up to 20 kinds of metal oxide-nitrogen-doped carbon (MOx-N-C) hybrid catalysts are prepared via a hydrothermal method followed by heat treatment under argon, and the successful preparation of such hybrid catalyst is confirmed by various means. Al is found to be the best element to construct such hybrid catalyst towards CTH, giving 96.6% yield of furfuryl alcohol at 99.3% furfural conversion at 120 degrees C for 6 h. By combining various characterization techniques, the deactivation and regeneration of AlOx-N-C catalyst is attributed to the change in specific surface area, pore volume, and the number of oxygen vacancies. The excellent catalytic performance of AlOx-N-C catalysts provides a broader prospect for its utilization in other biomass conversions as catalysts or active supports.
Su, FabingZeng, FanchaoZhu, YongxiaJin, Baofang...
10页
查看更多>>摘要：Multi-component promoters may efficiently improve the catalytic performance of the primary Cu-based catalysts in the Rochow-Muller reaction, but this approach is not well explored, and the roles of the promoters are not very clear. Herein, we report the ZrO2-supported CuO catalyst (CuO/ZrO2) modified with a co-promoter of ZnO, Sn, and CuP prepared by a simple dry ball-milling method. The co-promoter could significantly increase the amount of surface adsorbed oxygen and improve the reducing ability of catalysts, facilitating the formation of the active Cu3Si phase and further advancing dimethyldichlorosilane ((CH3)(2)SiCl2, M2) selectivity and Si conversion in the Rochow-Muller reaction. Compared to the state-of-the-art commercial catalyst, these CuO/ZrO2 catalysts with the co-promoters all showed enhanced catalytic activity. Especially, the CuO/ZrO2 catalyst with the co-existence of ZnO, Sn, and CuP promoters achieved the highest M2 selectivity and Si conversion, attributed to its most abundant surface adsorption oxygen and the strongest reducibility. This work opens up a new avenue to improve the catalytic activity of Cu-based catalysts for the Rochow-Muller reaction.
查看更多>>摘要：Adjusting the catalytic degradation route of nitrogen-containing VOCs (NVOCs) is still a challenge as both the oxidation and reduction reactions are simultaneously involved. Herein, a series of hierarchical Cu-Mn/ZSM-5 materials with different pore structures and surface acidities were prepared via an impregnation method and adopted for catalytic n-butylamine destruction. Experimental results show that the CuMn/Z-2 sample has the highest activity and N2 selectivity, over which n-butylamine can be totally decomposed at 280 degrees C with N2 selectivity over 82%. The superior catalytic performance of CuMn/Z-2 is owing to its developed porosity (accelerating the oxidation process and inhibiting organic byproducts formation) and weak acidity (slight adsorption of NH3 and preventing the formation of N2O). In situ DRIFTS reveal that the catalytic destruction of nbutylamine over Cu-Mn/ZSM-5 obeys two parallel pathways of n-butylamine adsorbed on acidic sites with C-N cleavage and n-butylamine adsorbed on metal sites and oxidized to amide before alcohol.
查看更多>>摘要：Graphitic carbon nitride (g-C3N4, CN) has been applied to degrade a variety of pollutants. However, two major defects, the low utilization of light energy and the high recombination of photogenerated electron and hole (e(-)-h(+)) pairs, need to be improved. In this study, a LED-light-driven photocatalyst, carbon dots decorated graphitic carbon nitride (CNC), was successfully prepared by simple thermal polymerization. Due to the remarkable up-conversion photoluminescence properties and superior charge transport capability of CDs, CNC had higher e(-)-h(+) separation efficiency and broader visible light response. In this experiment, a combined process of CNC and persulfate (CNC/PS) was used for tetracycline (TC) degradation. High-efficient photocatalytic degradation rate of 81.9% was obtained in the CNC/PS system. Moreover, the mechanism analysis indicated that the reaction be-tween PS and photogenerated e(-) effectively promoted the separation of electrons-holes pairs, thereby enhancing the formation of dominant active radicals center dot O-2(-) and holes for TC degradation.
NSTL
Elsevier