Catalysis Letters最新文献

A dual-enzyme cascade catalytic system (Cu-rGO-Fe₃O₄-GA-CEL-PEI-GOD) was prepared by co-immobilizing cellulase (CEL) and glucose oxidase (GOD) on a nanocomposite (Cu-rGO-Fe₃O₄) to efficiently catalyze the conversion of carboxymethyl cellulose (CMC) to gluconic acid. A layer-by-layer strategy was used by adding polyethyleneimine (PEI) to allow the upper enzyme layer to attach to the lower neighboring layer, increasing the loading capacity of the support. The loading capability of CEL and GOD on Cu-rGO-Fe₃O₄-GA-CEL-PEI-GOD were 55.034 mg g⁻¹ and 12.4 mg g⁻¹, respectively. The specific activity of CEL on Cu-rGO-Fe₃O₄-GA-CEL was 74.3 U·g⁻¹, and that of immobilized CEL after cross-linking PEI was 25.45 U·g⁻¹, which could retain 34.253% of the enzyme activity. The specific activity of GOD on Cu-rGO-Fe₃O₄-GA-CEL-PEI-GOD was 30.9 U·g⁻¹. The carrier Cu-rGO-Fe₃O₄ has peroxidase-like activity, which can timely remove harmful H₂O₂ to the enzyme, thereby improving the yield of gluconic acid and the stability of biocatalysts. The yield of gluconic acid with Cu-rGO-Fe₃O₄-GA-CEL-PEI-GOD reached 96.04% within 2 h, higher than the control systems for comparison. In addition, the Cu-rGO-Fe₃O₄-GA-CEL-PEI-GOD maintained 82.61% of catalytic activity even after undergoing seven cycles of reaction. The dual-enzyme catalytic systems had shallow temperature and pH optima of 40 °C and 4.5. Such a chemoenzymatic cascade system provides a new strategy for the conversion from CMC to gluconic acid in one-step.

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Enzymatic conversion of sodium carboxymethyl cellulose (CMC-Na) to gluconic acid.

Bimetallic synergism can effectively improve the catalytic activity of the catalyst. In this work, different catalysts were synthesized by loading Co and Ce onto copper foam (CF) by impregnation method and applied to the catalytic oxidation of toluene. Catalytic performance of the Co/Ce loaded catalysts was significantly better than the CF. Among these catalysts, Co₁Ce₂/CF catalyst had the best catalytic activity of toluene (T₉₀ = 237 °C), the lowest apparent activation energy (Ea = 35.0 kJ/mol), excellent stability (40 h) and cycle stability (three cycle) at a toluene concentration of 1000 mg/m³ under WHSV = 15,000 mL/(g·h). The good catalytic activity of Co₁Ce₂/CF catalyst is mainly due to a higher proportion of lattice oxygen, Ce⁴⁺ and Co²⁺. Ce⁴⁺ and Co²⁺ can provide more oxygen vacancies for the catalyst. By H₂-TPR and O₂-TPD, it is found that Co₁Ce₂/CF catalyst's effective catalytic activity is probably attributed to its low reduction temperature, ample oxygen storage capacity and low oxygen desorption temperature. In addition, the degradation process of toluene on the catalyst was speculated. The physical and chemical properties of the catalysts were investigated by SEM, EDS, XRD, XPS, BET, H₂-TPR and O₂-TPD. This work provides an effective way for synthesizing Co-Ce bimetallic oxide supported catalysts with great potential in toluene treatment.

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The effect of organic precursors on catalysts was studied and the preparation of catalyst and reaction conditions were optimized. A 91% selectivity of 2,5-dimethylfuran (DMF) from the hydrogenolysis of 5-hydroxymethylfurfural (HMF) was obtained on a Mo monometallic catalyst, in which nitrogen doping played a key role. Density functional theory (DFT) shows that Mo sites with N, O and C coordination have moderate adsorption strength of HMF and H₂ and lower energy barrier of key steps compared with pure molybdenum nitride, molybdenum carbide and molybdenum oxide, which may be conducive to catalytic hydrogenolysis of HMF.

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Abstract

A Z-type AlFeO₃@g-C₃N₄ photocatalyst was successfully prepared via sol-gel and high-temperature polymerization. The morphology, structure, and composition of the catalysts were analyzed by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The photocatalytic performance was evaluated by nitrobenzene degradation experiments and electrochemical station, comparing with single g-C₃N₄ and AlFeO₃. Optimizing AlFeO₃ precursor content in the composite yielded 1.6 and 1.8-fold higher degradation rates than single g-C₃N₄ and AlFeO₃, respectively. Furthermore, in comparison to other ratios of AlFeO₃@g-C₃N₄ composites, AF-CN-100, which exhibited the best degrading performance, had the smallest impedance, the strongest transient photocurrent response strength, and the strongest redox capacity. The heterojunction produced between AlFeO₃ and g-C₃N₄ was a Z-type heterojunction, as revealed by investigations on energy band structure and mechanism. This heterojunction substantially improved the separation efficiency of photogenerated electrons and holes and increased the photocatalytic activity of the composites.

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An efficient C-S cross-dehydrogenative coupling (CDC) has been achieved using rGO/Fe₃O₄-CuO as a robust nanocatalyst in the presence of TBHP and SDS as a surfactant for the thioesterification of cost-effective methylarenes with thiols in water. This heterogeneous Cu catalyst exhibited excellent performance and recyclability in the synthesis of thioesters without the assistance of any directing group.

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Magnetic reduced graphene oxide supported CuO catalyzed cross-dehydrogenative coupling of thiols and alkylbenzenes: Direct access to thioesters.

The immobilized horseradish peroxidase (P1-HRP) was prepared based on the affinity interaction between the phenylborate group in mVBA-b-p (AAm co AN) polymer (P1) and the adjacent dihydroxy group in horseradish peroxidase (HRP). The immobilization conditions of P1-HRP were optimized. Under the conditions of P1 concentration of 20 mg/mL, pH 8, temperature of 50 ℃, and immobilization time of 2 h, the HRP was immobilized to obtain the optimal immobilization amount (84.7 mg/g). The successful preparation of P1-HRP was demonstrated through characterizations such as laser scanning confocal microscopy (LCSM), scanning electron microscope (SEM), dynamic light scattering (DLS) and thermogravimetric analyzer (TGA). P1-HRP exhibited excellent pH stability, thermal stability and storage stability compared to the free horseradish peroxidase. P1-HRP had shown good application value in the degradation of phenol pollutants. After 10 repetitions of phenol degradation, the relative enzyme activity of P1-HRP could still be retained by 55.62%, indicating its good reusability. The optimal conditions for the catalytic degradation of phenol by P1-HRP were optimized. After catalytic degradation of phenol for 60 min under the same conditions, the degradation rate of P1-HRP (92.33%) was higher than that of free horseradish peroxidase (85.32%).

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Ni-W catalysts find extensive application in catalysis; however, the impact of diverse morphologies on their catalytic activity remains a relatively unexplored area. Using hydrothermal/solvothermal synthesis methods, we successfully synthesized Ni-W catalysts with various morphologies, including sheet-like, sphere-like, rod-like, flower-like, and particulate-like structures. Comprehensive investigations into the influence of morphology on the catalytic activity of these Ni-W catalysts were conducted, employing techniques such as SEM, XRD, XPS, TG-DTG, BET, H₂-TPR, and H₂-TPD. Remarkably, the flower-like Ni-W catalyst displayed exceptional catalytic properties in ethylbenzene hydrogenation, exhibiting not only high hydrogenation activity but also superior sulfur resistance. Consequently, the flower-like Ni-W catalyst holds great potential for applications in industrial catalysis.

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Green heterogeneous bifunctional catalyst is sustainable for the production of biodiesel owning to its reusability, eco-friendly, and bifunctionality. In this work, a green heterogeneous bifunctional Zeolite-A/Biochar (Z-A/BC) catalyst was synthesized for the production of biodiesel from waste cooking oil (WCO) through one-pot esterification-transesterification reaction. The functional group, elemental composition, crystallographic structure, and morphology of the synthesized catalyst were characterized using FT-IR, EDX, XRD, and SEM, respectively. Furthermore, the catalytic proficiency of the synthesized catalyst was tested by optimizing methanol to oil ratio, catalyst amount, temperature, and reaction time. The maximum biodiesel yield (86.22%) was achieved at 2.5% wt. of catalyst amount, 10:1 of methanol to oil molar ratio, 70 °C of reaction temperature, and 240 min of reaction time. The synthesized Z-A/BC catalyst showed apparent catalytic efficiency than its parent materials Z-A (69.42%) and BC (74.27%). The recyclability of Z-A/BC catalyst was also found to be 86.22, 82.98, 79.08, 62.87, and 76.84% for 1^st, 2^nd, 3^rd, 4^th, and 5^th cycles, sequentially which is cost effective. Furthermore, the physicochemical properties such as density, ash content, FFA, acid value, saponification value, and kinematic viscosity of the produced biodiesel were analyzed by comparing with standards. These results showed good agreement with ASTM and EN14214 biodiesel standards. Therefore, the produced biodiesel using heterogeneous bifunctional Z-A/BC catalyst from WCO could be used as an alternative engine fuel with/without blending with commercial diesel.

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Fabrication of highly efficient and earth-abundant bifunctional electrocatalyst to accelerate the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical for overall water splitting. In this work, bimetallic Co/Mo oxides modified reduced graphene oxide (rGO) was synthesized using a simple one-pot hydrothermal method, which significantly improved the electrocatalytic activity in both HER and OER. Under the optimal conditions, the double layer capacitance of rGO modified by Co/Mo bimetal is 78.08 mF cm⁻². The overpotential required for HER to reach -10 mA cm⁻² current density is 488 mV, the dynamic Tafel slope is 126 mV dec⁻¹. The overpotential required for OER to reach 10 mA cm⁻² current density is 420 mV, the slope of kinetic Tafel is 169 mV dec⁻¹. This work provides a new prospect for the rational design and fabrication of efficient HER/OER bifunctional electrocatalysts in electrochemical energy device application.

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A sequence of MgO-ZrO₂ mixed oxides with varying their ratios were synthesized by adopting co-precipitation method. These catalysts characteristics were deduced from different spectroscopic methods and used for vapor phase cross-ketonization of pivalic acid with acetic acid to produce pinacolone at atmospheric pressure. The characterization results indicated that at a high ZrO₂ molar ratio, Mg_xZr_1-xO₂-x mixed oxide phase is formed, and it accounted for the presence of strong basic sites. MgO-ZrO₂ mixed oxides ketonization activity is superior to individual oxides and the overall activity mainly depended on their molar ratio, calcination temperature, and presence of mixed oxide phase. The basicity of the MgO-ZrO₂ mixed oxide catalyst is responsible for the high conversion of pivalic acid. The ketonization reaction is carried under different reaction parameters and optimized conditions were established. The catalysts are showed stability during the time on stream analysis.

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