Catalysis Surveys from Asia最新文献

The use of renewable materials in the epoxidation reaction has gained increasing attention due to the need to reduce reliance on non-renewable resources and minimize environmental impact. To date, there is a paucity of studies on the optimization of process to produce epoxidized oleic acid by auto-catalyst epoxidation using formic acid (by product) as catalyst as it is not fully utilised. The aim of this study is to investigate the effect of hydrogen peroxide concentration, type of oxygen carrier and stirring speed on the auto catalyst epoxidation of oleic acid. In this study, auto-catalyzed epoxidation using formic acid was applied in which formic acid acts as both a reactant and a catalyst to produce oxirane. The maximum selectivity of oleic acid into oxirane was 58% by applying the optimum epoxidation reaction parameters. Based on the Fourier transform infrared (FTIR) spectrum, the absorption peak at 1100 cm⁻¹ indicated the presence of oxirane rings (C–O–C bonds). Lastly, a mathematical model was developed using MATLAB software. In this model, the fourth-order Runge–Kutta method was integrated with genetic algorithm optimization to determine the kinetic model that fit with the experimental data. The kinetic model was validated by the fact that there was good agreement between the simulation and experimental data.

Herein, we report the anchoring of a bis(oxime palladacycle) adduct on magnetic mesoporous silica (Fe₃O₄@SBA-15). Magnetic mesoporous silica was successively treated with (3-aminopropyl) triethoxysilane (APTES), cyanuric chloride (CC), and 4-hydroxyacetophenone oxime-derived palladacycle to give Fe₃O₄@SBA-AP-CC-bis(oxime palladacycle). The obtained nano-catalyst was characterized by FT-IR spectroscopy, CP MAS ¹³C NMR spectroscopy, scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), Brunauer–Emmett–Teller surface area measurement (S_BET) and X-ray diffraction spectroscopy (XRD). X‐Ray photoelectron spectroscopy (XPS) corroborated the (+ 2) oxidation number for palladium. The catalytic potential of Fe₃O₄@SBA-AP-CC-bis(oxime palladacycle) was explored in the Mizoroki–Heck reaction. The effects of different reaction conditions, including the solvent, the base, temperature, and palladium content, were studied in detail. The N-methylpyrrolidone (NMP) solvent, 0.5 mol% of the Pd-catalyst, the NaOAc base, and the reaction temperature of 120 °C, provided the best conditions for the Heck cross-coupling reaction. The catalyst showed a wide substrate scope, including aryl halides (I, Br, Cl) and olefins, in the Mizoroki–Heck reaction, using low catalyst loadings viz., Pd 0.09 mol%. The bis(oxime palladacycle) enjoys easy magnetic separation, stability, and recyclability over five runs.

The present study focused on the modification of zeolite H-BEA via a desilication post-synthetic approach in the presence of a cationic surfactant, dodecyltrimethyl ammonium bromide (DTAB), to synthesise a micro-meso composite of zeolite BEA (mesozeolite BEA). Several techniques were used to characterise the modified zeolite H-BEA catalyst, including scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), ²⁹Si and ²⁷Al magic angle spinning nuclear magnetic resonance (MAS-NMR), high and low angle X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy, N₂ sorption isotherms analysis etc. The synthesised mesozeolite exhibited bimodal porosity (micro and meso) and enhanced catalytic characteristics (surface area, acidity, and thermal strength) as compared to the parent zeolite H-BEA. The catalytic potential of the micro-meso H-BEA catalyst was investigated in the esterification of levulinic acid (LA) to n-butyl levulinate. The Box-Behnken Design (BBD) approach was used to optimise the process parameters for the catalytic reaction. Analysis of variance (ANOVA) was implemented to examine the appropriateness and importance of the quadratic model. The synthesised mesozeolite was found to be a highly efficient catalyst under the optimized reaction conditions, with 99.2% LA conversion, 97% yield, and 97% selectivity of n-butyl levulinate.

Graphical Abstract

Mesozeolite H-BEA catalyzed synthesis of n-butyl levulinate, a value-added chemical

FeC_x catalysts (Fe-CN-Py) were synthesized by co-pyrolyzing the mixture of iron nitrate and a CN source (melamine, bulk g-C₃N₄ (b-C₃N₄), or defective g-C₃N₄ (d-C₃N₄)). The physicochemical properties of Fe-CN-Py catalysts and their activities of CO₂ hydrogenation to light hydrocarbon (C₂-C₆) were analyzed. The results indicated that Fe-d-C₃N₄-(0.3)-Py is the most promising with the highest CO₂ conversion (47.2%), olefin yield (10.8%), and olefin space-time yield (STY = 4.5 µmol olefin/s/g_Fe). The promising activity of Fe-d-C₃N₄-(0.3)-Py was attributed to its high concentration of surface FeC_x. The correlation between surface FeC_x and the STY of hydrocarbons and olefins was established.

The conversion of ethanol and acetaldehyde to 1,3-butadiene has been an emerging process to produce key chemicals. The preparation of highly efficient catalysts and the understanding of reaction mechanism are current research priority. Herein, mesoporous silica framework confining zirconia (Zr-HMS) was prepared and act as catalyst for 1,3-butadiene production from ethanol and acetaldehyde. The prepared catalysts were characterized by Low-angle X-ray powder diffraction, transmission electron microscopy, N₂ physical adsorption-desorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and UV–vis spectra. It has been shown that the Zr-HMS exhibits similar textural properties to supported catalyst (ZrO₂/HMS). However, regardless of their comparable activities, higher 1,3-butadiene selectivity is obtained over Zr–HMS, which can be due to the different active zirconia species in two catalysts. Mesoporous framework confining character of Zr-HMS can achieve uniformly dispersed zirconia species. Further investigation toward the reaction process has presented new viewpoints for formation and consumption of some typical intermediates and byproducts, which will help to understand the reaction mechanism and construct efficient catalysts for conversion of ethanol and acetaldehyde to 1,3-butadiene.

The fabrication of a proficient and durable electrocatalyst for the OER process is the most crucial parameter in the water splitting process. A simple and basic procedure was used in this study to create Cu-substituted ZnMn₂O₄/rGO spinel nanosized composite as an electrode for OER. The morphological and structural investigations indicate that the carbon based spinel successfully bonds, and the addition of copper into rGO results in a substantial change in its electrocatalytic process for the oxygen evolution process. Zn_1−xCu_xMn₂O₄/rGO with x = 0.6 has a minimal overpotential of 150 mV at a current density of 10 mAcm⁻², low onset potential of 1.40 V and a smaller Tafel slope of 31 mV dec⁻¹ than other substitution. The electrocatalyst also exhibits high ECSA (632.5 cm²), R_f (1580), and exceptional stability, all of which improve OER performance. These analysis confirm the enhanced electrocatalytic efficiency of the hybrid material to catalyze OER for energy generation, and other fields.

In this work, we report for the first time, the tungstic acid-catalyzed oxidation of terpene alcohols with hydrogen peroxide. This simple, solid, and commercially available catalyst efficiently promoted the conversion of borneol, geraniol and nerol to camphor and epoxide products, respectively. Effects of main reaction parameters, such as catalyst load, the molar ratio of oxidant to the substrate, time, and reaction temperature were investigated. Conversions and selectivity greater than 90% were achieved using 1.0 mol % of H₂WO₄ after 2 h of reaction at 90 °C. The activation energy was equal to 66 kJmol⁻¹. We propose a reaction mechanism based on the experimental results. This solid catalyst was easily recovered and reused without loss of activity. As far as we know, it is the first time that tungstic acid was used as the catalyst in the oxidation reactions of terpene alcohols.

Graphical Abstract

Chlorine species, widely presented in industrial flue gas such as the waste incineration plants, can poison the catalysts and affect the selective catalytic reduction (SCR) performance. In this work, effects of Cl on the SCR performance of V₂O₅–WO₃/TiO₂ (VW/Ti) catalysts were investigated by NH₄Cl deposition. The results showed that the NO_x conversion efficiency at low reaction temperature (< 300 °C) decreased with the loading of NH₄Cl after calcination. It was found that instead of causing the chlorination of VW/Ti catalyst the NH₄Cl decomposed into volatile Cl species due to the weak V–Cl bonding. Such decomposition reduced significantly the surface non-lattice oxygen species to inhibit NO adsorption and activation, but hardly affected the redox ability and acidity of VW/Ti catalyst. Time–resolved in situ DRIFTs results indicated that NH₃ activation and the SCR process predominated by Eley–Rideal mechanism were not influenced with NH₄Cl impregnation, while the SCR at low temperature following a Langmuir–Hinshelwood path was limited by the decreased and weaker binding sites for NO activation.

Mesoporous silica-alumina spheres were used to create macro- and mesoporous bimodal silica-aluminas. Before removing the surfactant template for mesopores, the silica-alumina spheres were neatly stacked by sedimentation, and the contact points between the spheres were reinforced by silica. The bimodal silica-alumina was used as an acid catalyst for transesterification of triglyceride with methanol. The bimodal catalyst was readily separated from the reaction mixture. It showed the same catalytic activity as the non-sedimented spheres and higher activity than the catalyst prepared by pelletizing the silica-alumina spheres with colloidal silica binders. The bimodal materials were utilized as an adsorbent with an indicator of adsorption amount since the color changed with the amount of toluene that was adsorbed on them.

Nitrogen oxides (NO_x) are major contaminant causing environmental pollution in atmosphere. The most effective method for NO_x removal is ammonia selective catalytic reduction (NH₃-SCR), and catalysts play a crucial role. Cu-based zeolite catalysts are commonly used for the removal of NO_x from diesel engine exhaust, but the complex composition of diesel exhaust and the harsh operating environment of catalysts make zeolite catalysts susceptible to deactivation, thus limiting their practical application. This manuscript focuses on the negative effects of actual working conditions associated with diesel vehicle exhausts and analyses the influence of composition structure that Cu-based zeolite catalysts have on NH₃-SCR reaction, which refers mainly to the effects brought by topology, Si/Al ratio and Cu species. The strategies for developing Cu-based zeolite catalysts are summarized, and the current development bottlenecks such as improving catalytic performance, reducing synthesis cost and enhancing production efficiency are discussed, and the future research directions of Cu-based zeolite are prospected.