Catalysis Surveys from Asia最新文献

Hydrodeoxygenation (HDO) is a promising way to produce the second generation biodiesel from aliphatic acid based biomass. In this study, Ni_xMo_y@NC bimetallic catalysts with varying molar ratios were prepared using ZIF-8 as a representative MOF precursor. Lauric acid was chosen as the model compound, the catalytic performance of these catalysts with different metal ratios, reaction temperatures, and pressures was investigated. In addition, the reaction of lauric acid, lauric alcohol, and lauric aldehyde at different reaction times were investigated to explore the pathways of lauric acid. The influence of Mo doping on the catalyst structure, reducibility, and electronic properties was investigated through a series of characterizations, including SEM, TEM, XPS, H₂-TPR, and NH₃-TPD. This study revealed that the ZIF-8 support with incorporated Ni and Mo maintained a stable structure. Compared to Ni-based catalysts, the addition of Mo in the bimetallic catalyst can bring the electron transfer between Ni and Mo and increased the active sites and acid sites. An appropriate amount of Mo can lower the reduction temperature and enhance the catalytic activity for hydrogenation and deoxygenation reactions. Based on the catalytic experimental results, it can be observed that liquid alkanes, such as undecane and dodecane, are primarily formed through decarbonylation of lauric aldehyde and hydrodeoxygenation of lauric alcohol. Additionally, under high-temperature conditions, the hydrodeoxygenation reaction is favored over the decarbonylation reaction, promoting the production of dodecane. This indicates that Mo exhibits better activation for the C–OH reaction, leading to these observations. Under repeated use, the catalyst still has good catalytic activity and stability.

Zeolites (Hβ, HZSM-5 and HM), TiO₂ and ZrO₂ supported NiCo alloy catalysts were tested for the hydrodeoxygenation of phenol in aqueous phase. It has been found that the catalyst acidity remarkably influences the catalyst activity and the product distribution. Zeolites supported catalysts give much higher yield of the deoxygenated products (mainly benzene and cyclohexane) than NiCo/TiO₂ and NiCo/ZrO₂, where cyclohexanol and cyclohexanone are dominating. Associated with NH₃-TPD, we suggest that the catalyst acidity promotes the hydrodeoxygenation. Hβ zeolite supported NiCo alloy is more active than others, attributed to its higher metal dispersion and more acid sites. Therein, the Hβ zeolite calcined at 750 ^oC has moderate acidity, and its supported NiCo alloy catalyst (NiCo/HB-750) shows the best performance. Under a suitable reaction condition, the phenol conversion and the total yield of deoxygenated products reaches 96.8% and 94.5% on NiCo/HB-750, respectively.

Natural hematite supported cobalt (Co/Nat-Hem), a new heterogeneous catalyst, was successfully prepared by a simple impregnation technique. Textural, structural, functional groups and morphological aspects of the prepared catalyst were analyzed by BET, XRD, FT-IR, XRF, pH_pzc, SEM-EDX methods. BET analysis shows that the Co/Nat-Hem catalyst has a specific surface area of ​​13.44 m²/g and a pore volume of 0.062 cm³/g. The SEM-EDX method showed that 7.19 wt% of the cobalt species were dispersed on the surface of the prepared catalyst. The catalytic activity of Co/Nat-Hem was evaluated by photo-Fenton oxidation of the dye Cong red (CR). The effect of reaction parameters on CR oxidation efficiency was investigated. Under optimal reaction conditions (1 g/L catalyst concentration, 0.2 mol/L H₂O₂ initial concentration and pH 3), the percentage of CR discoloration reaches 97% after 30 min. The Co/Nat-Hem catalyst achieved a synergistic ratio of 28.5%, which was added to the oxidation rate of the Nat-Hem catalyst. The stability of the Co/Nat-Hem catalyst was demonstrated by the limited activity of leachates in the homogeneous Fenton oxidation of CR. The phytotoxicity of the CR dye was tested during the irrigation of the bean (Vicia faba L.).

In this research, the photocatalytic degradation of methylene blue was investigated using synthesized PdO/CoS nanocomposite under visible light irradiation. The structural and morphological properties were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, Mott–Schottky analysis, and transmission electron microscopy (TEM). The Mott–Schottky analysis confirmed the formation of a p-n heterojunction, and the flat band potential values for the n-type and p-type semiconductors were found to be − 1 and 1.3, respectively. The bandgap of the composite was determined to be 3 eV using Diffuse Reflectance Spectroscopy (DRS). When 0.1 g of the synthesized composite was used for 90 min, it successfully degraded 91% of methylene blue with an initial concentration of 10 ppm. In the Design of Experiments (DOE) approach, the optimum conditions for this research were found to be a catalyst mass of 0.06 g, an initial dye concentration of 8 ppm, and 2% palladium doping at pH 10, resulting in a 92.38% degradation efficiency in 110 min. To model the degradation of methylene blue using the synthesized composite, the Fritz–Schlunder and Koble–Corrigan models achieved the highest correlation coefficients (0.995 and 0.992, respectively) and the lowest error functions (0.024, 0.0008) and (0.032, 0.002), respectively. Additionally, the Langmuir–Hinshelwood and Intra-particle diffusion control kinetic models showed the highest correlation coefficient (98%). In summary, the study demonstrated that the PdO/CoS composite exhibited excellent photocatalytic activity for methylene blue degradation, and the optimized conditions resulted in high degradation efficiency. The proposed kinetic models provided valuable insights into the degradation mechanism of methylene blue using the synthesized composite.

In this work, MoVTeNbO_x catalysts was doped with Cr by using spray drying method. The effect of Cr doping on the crystalline phase, physicochemical properties, and catalytic performance of selective oxidation of propane to acrylic acid of MoVTeNbO_x was investigated. The results showed that the samples as-prepared by spray drying method present unique spherical morphology stacked by rod particles. In addition, Cr doping induced a change in the mesopore structure formed by rod stacking, reducing the pore radius of the catalysts from 5-10 nm to 2-4 nm. Meanwhile, Cr doping dramatically reduced the average particle size of MoVTeNbO_x catalysts, decreasing the rod cross-section diameter of catalysts from 234.21 to 134.96 nm and the rod length from 1.096 μm to 485.71 nm, which significantly increased the amount of (001) active crystalline plane. Moreover, an appropriate amount of Cr doping increased the number of reducible species in the catalyst and reduced its acidity. At the same time, the surface V⁵⁺ content of the catalyst was increased from 35.8% to 72.6%. Cr-doped MoVTeNbO_x with mesoporous structure showed excellent performance in catalyzing selective oxidation of propane to acrylic acid reaction. Among them, S-3 sample (V: Cr = 1:0.015) increased the selectivity and yield to acrylic acid from 67.5% to 84.3% and from 26.4% to 43.2%, respectively, at reaction temperature of 380 °C.

In recently years, the field of organic chemistry has seen a growing interest in the development of environmentally friendly and efficient synthetic methods. In this context, we introduce a new electro-organic approach for the synthesis of methyl cinnamate derivatives through the Heck reaction, carried out under green conditions. The conventional Heck reaction, widely used for synthesizing diverse compounds, suffers from drawbacks like the use of toxic solvents, harsh reaction conditions, and the generation of waste. To address these challenges, we employed an electrochemical method, offering a more sustainable alternative. Our electro-organic process utilized a two-electrode setup with easily available anode and cathode materials. Through the application of an appropriate potential difference, both the aryl halide and olefin substrates were electrochemically activated, leading to the formation of the desired methyl cinnamate derivatives. This innovative approach offers several significant advantages. Firstly, it eliminates the need for toxic catalysts, reducing the environmental impact related to waste disposal. Secondly, the mild reaction conditions allow for the use of a broad range of functional groups, enabling the synthesis of diverse methyl cinnamate derivatives. Moreover, the electrochemical approach demonstrates exceptional selectivity and efficiency, resulting in high product yields. Additionally, the method is easily scalable, making it suitable for large-scale production. The affordability and accessibility of the electrode materials further contribute to the sustainability of the process. In summary, our electro-organic method represents a greener and more efficient strategy for synthesizing methyl cinnamate derivatives via the Heck reaction. It not only addresses the limitations of conventional methods but also aligns with the principles of sustainable chemistry. We expect this novel methodology to find widespread applications in the synthesis of various important compounds, promoting the development of more sustainable chemical processes.

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The visible light-assisted photocatalysis approach allows more sustainable and atom-economical C–H bond arylation processes. The polymer-based photocatalysts are an attractive choice because of their variable design and development feasibility as well as effective catalytic applications. In the present work, by following the basic principles of green chemistry, we have chosen an environmentally friendly and biologically suitable chemical i.e. Erythrosine B as a unit molecule for the generation of photocatalyst EP (C₂₀H₈O₅S₄). The generation of EP has been performed via a one-pot solvothermal reaction of Erythrosine B with sulfur powder. The structural analysis of the EP evidence the generation of an interesting example 2D-polymeric assembly where disulfide (–S–S–) units are acting as linkers and show high thermal stability up to 800 °C (39.9% left as a residue). The low optical band gap of 2.08 eV and electrochemical band gap of 2.09 eV favors its catalytic applicability. The catalytic investigation reveals excellent applicability of EP in C–H arylation (yield 98.5% & selectivity 99%).

This work focuses on the enhancement of removal performance of TiO₂ by the introduction of trace amout of GO composite. Among various synthesis methods, it was found that the GO–doped TiO₂ by microwave-assisted hydrothermal method had the highest performance in the improvement for Cr (VI) treatment. The removal rate of Cr (VI) by TiO₂–GO (0.05%) was 95.96% which is 13.58% higher than that of TiO₂. It can be confirmed that GO was successfully doped on TiO₂ by XRD, XPS, and FT-IR characterizations. In addition, SEM, TEM, N₂ adsorption isotherm, UV–Vis spectra, and photocurrent response elucidate the mechanism of potency enhancement. The addition of trace GO reduces the particle size of TiO₂ and results in the agglomeration phenomenon of TiO₂, so that the specific surface area of TiO₂ becomes larger and the distribution is more uniform, which expands the photoresponse range, and elevating the photoelectron response. Thus, the absorption ability of visible light is greatly improved. The reported method provides a more economical option for treating Cr(VI) wastewater.

To create a potential heterogeneous catalyst for the Domino Knoevenagel cyclo-condensation that produces tetrahydropyran derivatives in aqueous media, amorphous silica derived from rice husk ash (RHA) and cotton ball ash (CBA), were modified with 3-(chloropropyl)triethoxysilane, metformin, and copper acetate. Fourier transform infrared spectroscopy, thermal gravimetric, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray fluorescence, and Brunauer–Emmett–Teller were utilized to characterize the produced catalysts' structure. Based on the characterization results, extracted nano-silica exhibits higher surface area and catalytic activity than commercial nano-silica. These solid acid catalysts demonstrated outstanding catalytic activity for carbonyl group activation to react with malononitrile and 1,3 dicarbonyl compounds to give a high to excellent yield of the desired substances (80–97%). Without losing their catalytic activity and leaching, the catalysts can be recovered, separated by filtration or centrifugation, and reused for several cycles. This research indicates that the desired catalysts are stable and may be effectively exploited in organic synthesis. The high rate of reaction, mild reaction conditions, high product yield, low production cost, availability, and reusability are advantages of these catalysts that make them attractive for organic transformations. A comparison was also made between the catalytic behavior of the prepared natural catalysts and that derived from commercial-grade nano-silica. Based on analyses, the rice husk-derived nano-catalyst is described as a mesoporous catalyst with a higher specific surface area (143 m² g⁻¹) and narrower pore diameter (4.3 nm), showing excellent catalytic activity compared to cotton ball-based nanocatalyst and the catalyst prepared from commercial-grade nano-silica regarding reaction rate and yield.

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This research used rice husks and cotton ball ashes as sources of silica nanoparticles and modified them using metformin and copper acetate. Diverse tetrahydrobenzopyran derivatives were produced with excellent yields in a short reaction time. A comparison was also made between the catalytic behavior of the prepared waste-based nanocatalysts and that derived from commercial-grade nano-silica.

Industrial dyes are the main cause of environmental pollution. The present study consists of the removal of synthetic anionic dye using batch study with photocatalyst using adsorption technology. The adsorbents were prepared using the chemical synthesis method. At pH 5, ZnO₂ shows maximum results in the Reactive Blue dye. At the same time, CuO₂ shows maximum results at pH 2. In contrast, the CdO₂ and PbO₂ nanoparticles presented maximum results at pH 4. The optimum dose for all four kinds of nanoparticles, ZnO₂, CuO₂, PbO₂, and CdO₂, was found to be 0.5 g/50 mL for the elimination of anionic dye at pH 2, 4, and 5. For ZnO₂, CuO₂, PbO₂, and CdO₂ nano photocatalyst, the maximum percentage of dye removal was recorded at 0.05 catalyst dosage. The starting concentration of dye in the series of 25–200 mg/L was measured as optimum for the highest deletion of anionic stain by dissimilar kinds of chosen adsorbents. The maximum adsorption capacity of ZnO₂ (85.69 mg/L), CuO₂ (79.04 mg/L), PbO₂ (64.12 mg/L), and CdO₂ (51.58 mg/L) was obtained at 100, 150 and 75 mg/L dye concentration. The optimum temperature for the highest removal of anionic dyes was detected at 37 °C, and the reduction examined a decline in the adsorption capacity of whole compounds as temperature decreases. It represented the exothermic behavior of all sorption processes intricate in the exclusion of certain anionic dyes. Langmuir biosorption isotherms were given the best fitness on equilibrium biosorption data, whereas the pseudo 2nd order displayed the fitness on adsorption kinetic data. Additionally, data show that the elimination of Reactive Blue dye by adsorption with ZnO₂, CuO₂, PbO₂, and CdO₂ nanoparticles follows second-order kinetics (R² = 0.9855) and Langmuir model (0.9997). Utmost desorption was attained by 0.5 N sodium hydroxide. Fourier Transform Infrared (FTIR) was used to characterize the nanoparticles, which gave information about the functional groups on dyes. So, by using the adsorption technology, maximum dye removal from wastewater was observed, and ZnO₂ showed maximum percentage removal of anionic dye. Reactive Blue is effectively degraded in aqueous solution by photocatalysis with ZnO₂ assistance while being exposed to ultraviolet (UV) radiation.

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