查看更多>>摘要：In this work, micro-spherical beta-NiOOH/FeMoO4 with multiple active sites was prepared by one-step solvothermal method and its performance in the photo-Fenton system was investigated. The results indicate that highest degradation efficiency of methylene blue (MB) was obtained when the molar ratio of nickel to iron was 1:2.5. In addition, composites were assessed for its degradation performance for MB by adjusting the concentration of H2O2, pH and catalyst dosage. The pseudo-first-order kinetic rate constant of MB degradation in beta-NiOOH/FeMoO4 catalyzed photo-Fenton system was 0.234 min(-1) about 5 folds that of pristine FeMoO4 micro-sphere. The degradation mechanism of MB was deduced by active species quenching experiments and technology of coumarin fluorescent probe. And its degradation pathway was proposed by LC-MS identifying reaction intermediates produced during photo-Fenton catalysis. Recycling tests have confirmed excellent stability of beta-NiOOH/FeMoO4 composite. In conclusion, this study demonstrates the beta-NiOOH/FeMoO4 composite is a promising heterogeneous photo-Fenton catalyst.
查看更多>>摘要：Most of the non-noble metal catalysts used for the Meerwein-Ponndorf-Verley (MPV) reaction of carbonyl compounds rely on the additional alkaline additives during preparation to achieve high efficiency. To solve this problem, in this work, we prepared a novel N-doped carbon supported cobalt catalyst (Co@CN), in which the carriers were derived from the nitrogen-rich organic waste, i.e., oxytetracycline fermentation residue (OFR, obtained from oxytetracycline refining workshop). No additional nitrogen sources were used during preparation. The results showed that inherent nitrogen in OFR could provide N-containing basic sites, and formed Co-N structures via coordinating with cobalt. The Co-N sites together with the coexisting Co-(0) cooperated to catalyze the conversion of ethyl levulinate (EL) to gamma-valerolactone (GVL) by MPV reaction. Co-(0) dominated the activation of H in isopropanol, while Co-N dominated the formation of the six-membered ring transition state.
查看更多>>摘要：The effect of integrating carbon nanotubes (CNTs) into a bi-functional Ni-Zeolite-Y catalyst was studied for the hydrocracking of heptane at 350 and 400 degrees C (total pressure of 5 bar). It was shown that the growth of CNTs on the surface of Ni-Zeolite-Y (Ni-ZY) results in enhanced stability and catalytic activity (conversion increased by 22% at 350 degrees C) compared to the conventional Ni-ZY. A significant increase in the initial transient kinetic rates of CH4 and C2H6 formation was also noticed. The CNT/Ni-ZY also showed reduced coke formation during the reaction as entailed by transient isothermal (400 degrees C) oxidation experiments. The formation of a crystalline NixCy phase on the zeolite surface was observed in the case of CNT/Ni-ZY, potentially responsible for its enhanced catalytic performance. This work demonstrates that the integration of CNTs in hydrocracking catalysts offers new opportunities for enhancing their catalytic activity, selectivity and coking resistance.
查看更多>>摘要：By constructing core-shell ZSM-5@CeO2 support rather than bulk phase for loading copper, the enhanced NH3-SCR performance as well as H2O and SO2 tolerance was achieved. Cu/(ZSM-5@CeO2) catalyst exhibited the superior activity with the lowest T-90 at 215 C, which is due to the interaction between CeO2 shell and copper ions that promotes the redox properties as evidenced by oxygen isotopic exchange technique. The ZSM-5 core provides more acid sites to improve the ammonia adsorption. Thus, the highest activity of Cu/(ZSM-5@CeO2) catalyst can be ascribed to the synergistic effect of redox ability and acidity. The CeO2 shell can react with SO2 preferentially and lead to a high sulfur tolerance. This study provides a strategy for design and the practical applications of NH3-SCR zeolite catalysts.
查看更多>>摘要：A series of amorphous silica-aluminas were hydrothermally synthesized in the presence of tetraethylammonium hydroxide. Their physicochemical properties were well characterized, and particularly, a facile method of preferentially adsorbing bulky 2, 4, 6-collidine followed by adsorbing pyridine for FTIR was innovatively used to quantitively distinguish the Bronsted acid sites in micropores and on external surfaces. All protonic samples were transformed into hydrocracking catalysts by loading with 0.5 wt% platinum; and the relationship between Bronsted acidity of supports and the catalytic performance was studied by hydrocracking of Fischer-Tropsch wax. The results illustrated that the medium strong Bronsted acid sites located on the external surface play important role on the activity. And the lower the strong Bronsted acid density in micropores, the higher the diesel selectivity. Among the catalysts tested, Pt/SA-10 catalyst exhibited high selectivity to diesel (78.7%) at about 48.8% conversion under reaction conditions close to industrial ones.
查看更多>>摘要：_Efficient synthesis of bio-based chemicals from renewable lignocellulosic biomass is of great significance to promote the sustainable development of chemical industry. This work aims to demonstrate that terephthalic acid, a bulk high value chemical in petrochemical industry, can be synthesized using biomass. This novel controllable transformation process was started with the selective catalytic pyrolysis of sawdust biomass to form p-xylene intermediate. The high p-xylene yield of 23.4% was obtained using the Ga2O3/SiO2/HZSM-5 catalyst under the optimized reaction condition. Subsequently, the selective oxidation of the biomass-derived aromatic intermediates to terephthalic acid was realized with the metal oxide catalysts. The highest terephthalic acid yield of 72.8% with the terephthalic acid selectivity of 82.3% was achieved using the CoMn2O4@SiO2@Fe3O4 catalyst. Based on the study of the catalytic conversion of the model compounds and the catalyst characterizations, the reaction pathways and possible reaction mechanism have been proposed.
查看更多>>摘要：ABS T R A C T Cumyl hydroperoxide (CHP) is an important intermediate for the production of phenol/acetone, but suffers from severe reaction conditions and a low yield industrially. Here, an efficient transformation from cumene to CHP was developed. Different solvents were modulated for cumene oxidation catalyzed by NHPI/Co, and reaction network and mechanisms were investigated methodically. Hexafluoroisopropanol (HFIP) markedly promoted the transformation from cumene to CHP compared to other solvents at room temperature. A cumene conversion high up to 64.3% were observed with a selectivity to CHP of 71.7%. The solvent HFIP exhibited a significant pro-motion on cumene oxidation due to its contribution to the enhancement of the concentration of PINO radicals. Moreover, cumyl, cumyl oxyl and methyl radicals were captured by TEMPO and analyzed by HRMS, and the reaction paths and mechanisms from cumene to products were inferred. The preparation method discovered in this work may open an access to the production of CHP.
查看更多>>摘要：In our previous study, an iron-supported silica (Fe/SiO2) catalyst exhibiting excellent activity toward propane dehydrogenation with hydrogen sulfide (H2S) co-feeding was identified. This study investigated the potential application of the Fe/SiO2 catalyst for the dehydrogenation of relatively larger molecules, such as iso-pentane (iso-C-5), n-pentane (n-C5), and n-butane (n-C-4). The reactivity evaluation showed that Fe/SiO2 exhibited a high activity toward iso-C-5 dehydrogenation with H2S co-feeding, producing iso-amylenes, such as 2-methyl-1butene, 2-methyl-2-butene, and isoprene. The total C-5-olefin yield obtained using the Fe/SiO2 catalyst was higher than that obtained using Co/SiO2 and Ni/SiO2 catalysts. When Fe/SiO2 was applied to the dehydrogenation of n-C-4 and n-C-5 with H2S co-feeding, C-4- and C-5-olefins were obtained, respectively, with relatively high selectivities. In particular, the Fe/SiO2-catalyzed n-C-4 dehydrogenation exhibited greater selectivity than iso-C-5 and n-C-5 dehydrogenations; the product of the n-C4 dehydrogenation was stable for 20 h.
查看更多>>摘要：Acceptorless dehydrogenative coupling (ADC) of alcohols and water/hydroxides is an emergent and graceful approach to produce carboxylic acids. Therefore, it is of high demand to develop active and practical catalysts/ catalytic systems for this attractive transformation. Herein, we designed and fabricated a series of cyclometallated N-heterocyclic carbene-Ru (NHC-Ru) complexes via ligand tuning of [Ru-1], the superior complex in our previous work. Gratifyingly, gram-scale synthesis of carboxylic acids was efficiently enabled at an ultralow Ru loading (62.5 ppm) in open air. Moreover, effects of distinct ancillary NHC ligands and other parameters on this catalytic process were thoroughly studied, while further systematic studies were carried out to provide rationales for the activity trend of [Ru-1]-[Ru-7]. Finally, determination of quantitative green metrics illustrated that the present work exhibited superiority over representative literature reports. Hopefully, this study could provide valuable input for researchers who are engaging in metal-catalyzed ADC reactions.
查看更多>>摘要：Upgrading carbon dioxide (CO2) into valuable products is a highly promising strategy of artificial carbon cycle. In this study, a series of in situ reduced CuMgAl layered double hydroxides (R-CuMgAl-LDHs) composites were synthesized, in which Cu nanoparticles were effectively dispersed and anchored on MgAl-LDHs with formation of Cu+ and Cu0 species. The optimized R-Cu1.5Mg1.5Al1-LDH exhibited excellent catalytic performance for the carboxylative cyclization of 2-methyl-3-butyn-2-ol with CO2 (turnover number of 243) under mild conditions. The layered structure of LDH stabilized the active Cu species with high dispersion, enhancing the catalytic efficiency of this carboxylative cyclization reaction. Simultaneously, the dual-activation of both CO2 and propargylic alcohol by Cu0/Cu+ species generated on the surface of LDH contributed significantly to the catalytic efficiency enhancement. Furthermore, R-Cu1.5Mg1.5Al1-LDH catalyzed the reaction of a wide range of terminal or internal propargyl alcohols with CO2, yielding various functionalized alpha-alkylene cyclic carbonates. Finally, a reasonable reaction mechanism was put forward according to the comprehensive analysis.
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Elsevier