Catalysis Surveys from Asia最新文献

Gold nanoparticles supported on hydroxyapatite functions as a very efficient catalyst for the reduction of nitroarenes as well as for the degradation of azo dyes. The reaction takes place in aqueous medium at room temperature, using sodium borohydride as the source of hydrogen. The catalyst was prepared by a deposition–precipitation process using gold (III) chloride trihydrate solution containing hydroxyapatite as the support. The catalyst was thoroughly characterized by a pltehora of analytical techniques viz., TEM, HRTEM, FESEM, powder XRD, EDX and FTIR. The catalyst was then employed after optimization of reaction conditions. No additives or inert atmosphere was required and a very low loading of gold was sufficient enough to promote the reaction. Reaction kinetics studies were performed on the reduction of 4-nitrophenol to 4-aminophenol and a very high apparent rate constant of 1.63 × 10^–2 s⁻¹ was obtained. Reaction kinetics studies have also been demonstrated for the degradation of methyl orange and congo red dyes. Appreciable apparent rate constants namely 8.678 × 10⁻³ and 3.464 × 10⁻³ s⁻¹ were obtained for the degradation of methyl orange and congo red dyes respectively. The catalyst was recoverable by simple centrifugation and can be reused for at least five reaction cycles.

Present study focused on the green nanocomposites synthetization to treat textile wastewater and its reusability for agriculture crops. Punica granatum (leaves and peels) and biomass (almond shells, sugar cane bagasse, eggshells) are used for synthesis of zinc oxide nanocomposites (PGL-ZnO), copper nanocomposites (PGP-Cu) and iron nanocomposites (PGL-Fe). It is characterized by scanning electron microscope, Fourier-transform infrared spectroscopy, X-ray powder diffraction and Brunauer–Emmett–Teller. The highest adsorption efficiency of all synthesized nanocomposites was accomplished at pH 2 which is acidic, 0.01 g dose, 50 mg/L initial dye concentration and 90 min contact time at 40 °C temperature. The highest adsorption proficiency Punica granatum = 18 < Zinc Oxide nanocomposites = 78 < Iron nanocomposites = 65 < Copper nanocomposites = 85 mg/g of all synthesized nanocomposites was obtained. The model Freundlich showed good fitness results which indicate complex nanocomposites nature. The 1st order showed best results on fitness of isotherm on kinetic data and rate constants determined the best fitness of model. The negative value of ΔH^o and ΔS^o of nanocomposites exhibited the exothermic nature and decrease in disorderness of adsorption process for dye exclusion. When values of (Delta {G}^{o}) is positive then the reaction is spontaneous. Desorption of acidic dye from maximum efficient nanocomposites was 99 mg/g using eluent. Hence, it was determined that these nanocomposites serve as the novel, feasible, cost-effective, ecofriendly, and bio recyclability for treating acid dye-containing wastewater.

Graphical Abstract

The loss of catalyst activity over time is a serious challenge in the industry and therefore performing the regeneration process is essential, especially for the catalysts that contain rare and expensive metals with adverse environmental impacts. This work focuses on the recovery of the Pt-based catalysts deactivated in the alkanes’ industrial dehydrogenation process. The Pt re-dispersion process on the catalyst surface was successful in the case of the regenerated catalyst. While fresh catalysts stayed intact when exposed to water during H₂ reduction, the regenerated catalysts were sensitive to hydrogen humidity throughout the reduction period. This could be related to the kinetic inhibiting effect of water molecules due to chlorine stripping. The design of experiments (DOE) technique was applied to statistically evaluate the factors that affect the activity of the regenerated catalysts. The optimum levels for the operating variables such as purity, flow rate, the humidity of hydrogen, as well as temperature and duration of the reduction were found to be 99%, 13 L/h, 20 ppm, 460 °C, and 4 h, respectively. These findings are very important as they are obtained based on realistic conditions, close to those applied in the industrial process. Consequently, this study offers new opportunities for the industrial dehydrogenation of long-chain alkanes from a practical, economic, and environmental point of view.

Two organic–inorganic mesoporous hybrid materials containing iron complexes covalently attached to mesoporous silica MCM-41 have been successfully prepared via post-functionalization modification of MCM-41 (with trifunctional ligand and without the ligand). The catalysts were characterized by Fourier transforms infrared spectra, powder X-ray diffraction, scanning electron microscopy, and N₂ adsorption/desorption. For the composite MCM-41/3,4,5-tri hydroxyphenyl acetic acid/Fe and MCM-41/Fe materials, in the presence of DTAB (dodecyl trimethylammonium bromide), results showed the formation of more stable MCM-41 structure with the higher surface area than in the presence of CTAB (cetyltrimethylammonium bromide) surfactants. The catalysts were tested in the synthesis of 5-substituted 1H-tetrazoles. This catalyst is an efficient catalyst for [3 + 2] cycloaddition with NaN₃ to prepare 5-substituted 1H-tetrazoles. The catalyst was recycled for up to seven cycles without significant loss of activity.

By employing the Knoevenagel–Michael tandem cyclocondensation of malononitrile, aldehydes, and resorcinol, we developed a green method for the radical synthesis of 2-amino-4 H-chromene scaffolds. A photo-induced electron transfer (PET) photocatalyst was employed in an aqueous solution to use visible light as a renewable energy source. This study aims to develop a non-metal dye that is inexpensive and easily accessible. In addition to having speed-saving features and being simple to use, the photochemically catalyzed AYG demonstrates high yields, energy efficiency, and environmental friendliness. This makes it possible to track changes in chemical and environmental variables throughout time. It is amazing that gram-scale cyclization is practical, proving that it has industrial applications.

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.