Catalysis Surveys from Asia最新文献

Traditional catalysts with one core and one shell structure have few active sites and shell structure parameters are difficult to be regulated. In order to solve these two problems, it is presented herein a multi-Pd-core and porous carbon shell catalyst mPd@HCS, where multiple Pd nuclei provide more active sites for the reaction, the shell structure parameters are tuned by the adjustment of shell thickness, and the influence of shell thickness on the performance of H₂O₂ direct synthesis was mainly investigated. The results showed that the selectivity and yield of H₂O₂ changed volcanically with the increase of carbon crust thickness because of the compromise between reactants diffusion and product degradation, and the selectivity (87%) and productivity (1938 mmol g_Pd⁻¹ h⁻¹) of the sample with middle shell thickness (10.18 nm) were the highest.

The catalytic properties and applications of Fenton and Fenton-like catalysts based on graphitic carbon nitride (g-C₃N₄) are reviewed. Compared with semiconductor photocatalytic, the synergistic system of photocatalysis and Fenton-like oxidation has a stronger ability to degrade organic wastewater, but there are still some shortcomings, such as high recombination rate of photogenerated carriers and serious agglomeration of metals on the catalyst surface, and its catalytic performance still needs to be further improved. The development of heterogeneous photo-Fenton-like catalysts based on g-C₃N₄ and their Fenton-like mechanism will be the focus of future research.

The over-consumption of petroleum fuel due to the progressive increase in population, transportation, industrialization, modernization as well as improvement in the lifestyle of the society leads to the fast declining of non-renewable resources. Therefore, it is important to discover low cost, environmentally friendly and sustainable surrogates of petroleum fuels. In this regard, biodiesel production is one of the gorgeous solutions for the research community. Contrary to the benefits, the high cost of the biodiesel is the main disadvantage, greatly reliant on the feedstock. In this sense, wild olive oil was explored for the first time as a suitable and novel feedstock for biodiesel technology development. The fatty acid composition was identified by GC–MS analysis whereas various physiochemical properties were determined by ASTM and EN methods. Furthermore, this review paper conveys a detailed overview of biodiesel production technologies, various generation feedstocks and types of catalyst along with their plausible mechanism.

Highly dispersed Au nanoparticles supported on Ni–Al mixed metal oxides (Au/NiAl-MMO) were prepared by a facile method, which is significantly efficient for the aerobic oxidation of ethyl lactate using authentic air as the oxidant, achieving 72.6% ethyl lactate conversion and 88.3% selectivity to ethyl pyruvate at 240 °C in a continuous fixed-bed reactor. The catalyst retained its catalytic performance during a long-term stability test. Characterization and experimental studies on the kinetic dependence sequence of the reactants and elementary reaction steps confirmed that the Au/NiAl-MMO catalyst followed the Mars–van Krevelen mechanism, with the activation of O₂ as the elementary step. The quasi in situ X-ray photoelectron spectroscopy spectra demonstrated that the active sites in the Au/NiAl-MMO catalyst were Au nanoparticles. This work may provide a novel technique for developing more efficient supported metal catalysts for the aerobic oxidation of ethyl lactate using authentic air as the oxidant.

Graphical abstract

Highly dispersed Au nanoparticle catalyst was facilely prepared for the efficient catalytic oxidation of ethyl lactate with authentic air.

2-(2-Pyridyl)benzimidazole (PyBzIm) was supported onto magnetic mesoporous silica, Fe₃O₄@SiO₂@SBA-15 via the click chemistry. The supported ligand was treated with Na₂PdCl₄ in methanol to afford Fe₃O₄@SiO₂@SBA-PyBzIm-Pd(II) as a magnetically retrievable supported catalyst. The catalyst was fully characterized by conventional methods. X-ray photoelectron spectroscopy (XPS) studies confirmed some C = N nitrogen atoms interact with palladium in the + 2 oxidation state. The prepared catalyst was found to catalyze the aerobic oxidation of benzyl alcohols and benzaldehydes to the corresponding benzoic acids, and excellent conversions were obtained. The magnetic catalyst showed a very low metal leaching (3.9%) in the first run. Fe₃O₄@SiO₂@SBA-PyBzIm-Pd(II) was then treated with aqueous NaBH₄ to give Fe₃O₄@SBA-PyBzIm-Pd(0). The obtained catalyst was found to catalyze the transfer hydrogenation of nitroarenes to the corresponding anilines in the presence of hydrazine, and excellent yields were obtained. The prepared catalysts present an excellent recycling efficiency over seven consecutive runs without significant loss of catalyst reactivity.

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Although nanostructures based on noble metal alloys are widely used in the anode catalysts of direct ethanol fuel cells, their commercialization remains a remarkable challenge due to their high cost and poor durability. We describe the successful synthesis of trimetallic PtTiMg alloy nanoparticles with adjustable composition using a simple one-step three-target magnetron co-sputtering method. Various physical characterization and electrochemical methods were used to investigate the structure/composition and electrochemical properties of the obtained PtTiMg alloy catalysts toward ethanol oxidation reaction (EOR). The PtTiMg alloy catalyst demonstrated excellent electrocatalytic activity and high durability when the Mg content was 2.76%, (after 3000 cycles, retained 91% of its electrochemical surface area). Furthermore, the electrochemically active surface area and peak current density of the PtTiMg alloy catalyst are 1.5 and 0.8 times higher than those of the commercial pure Pt catalyst, respectively. Furthermore, the long-term strong acid immersion test demonstrated that the PtTiMg alloy catalysts retain high electrocatalytic activity in harsh environments, demonstrating the potential application of the obtained PtTiMg alloy catalysts for EOR.

Biodiesel is one of the renewable energy (RE) sources that has received much interest due to its promising properties. Recently, the use of coconut oil as biodiesel has caught the attention of many researchers. As a result, this paper presents a comprehensive overview of the current catalysts used to produce coconut oil biodiesel via the transesterification method.

Graphical Abstract

Zinc molybdate (ZnMoO₄), a layer perovskite material, has the advantages of high stability, excellent optical and charge properties. However, its high band gap and high electron–hole recombination efficiency limit its application in the photocatalytic reduction field like hydrogen production. In this study, we used CdS as a co-catalyst and successfully prepared CdS/ZnMoO₄ composite photocatalysts with different loadings. The hydrogen evolution rate of CdS/ZnMoO₄ reached 530.2 µmol h⁻¹ g⁻¹, which was approximately 11 and 100 times more than rates of pure CdS and ZnMoO₄ under the same conditions, respectively. It is the presence of CdS that contributed to this improved performance, which acted as an electron acceptor to separate electrons and holes. Besides, a reasonable mechanism was provided based on photoelectrochemical characterizations. CdS loading greatly improved the hydrogen evolution performance of ZnMoO₄ under visible light, providing a direction to improving the performance of perovskite based photocatalysts.

An environment-friendly selective catalytic reduction (SCR) catalyst with high catalytic activity and strong anti-poisoning performance at low temperature is strongly needed to achieve the wide application of low temperature NH₃-SCR technology. Selection of appropriate carrier is one of the most important measures to improve catalytic activity as well as anti-poisoning capability of SCR catalyst. Manganese oxide-cerium oxide supported on traditional titanium dioxide (denoted as MnCe/TiO₂) and titanate nanotubes (denoted as MnCe/TiNTs) were prepared by impregnation method and their catalytic activities towards NH₃-SCR of NO were evaluated in flue gas with or without SO₂ & H₂O. The results indicate that TiNTs with optimum morphology and microstructure can be obtained when P25 TiO₂ is hydrothermally treated at 130 °C for 24 h. Supporting MnO_x–CeO₂ composite on TiNTs not only enhances the catalytic activity at low temperature, but also improves N₂ selectivity and widens active temperature window of catalyst. The main reason is the large specific surface area as well as the unique hollow tubular structure of TiNTs facilitates high dispersion of catalytic active components on the inner and outer walls of TiNTs, which enriches surface acid sites and surface reactive oxygen species to fulfill low temperature SCR reaction cycle. Moreover, TiNTs significantly enhances the SO₂ & H₂O tolerance of catalyst, for the competitive adsorption between SO₂, H₂O and reactants is alleviated and the deposition of ammonium sulphate or ammonium bisulphate becomes more difficult on MnCe/TiNTs catalyst. Besides, the confinement effect of TiNTs makes partial toxicants be trapped inside the tubular channel of TiNTs. So that protects the active components, which are distributed on the out wall of TiNTs, from being poisoned.

The catalytic performances and mechanism differences of model catalysts Cu–SSZ-13 and Fe–SSZ-13 with similar metal content and Si/Al ratio were compared. In the NH₃-SCR reaction, Cu–SSZ-13 had a good NO conversion at low temperature, broad active temperature windows and better hydrothermal stability. Fe–SSZ-13 showed better high-temperature NO conversion rate and better resistance to sulfur poisoning, but poorer low-temperature NH₃-SCR activity. NH₃-TPD verified the content difference of L-NH₃ and B-NH₃ of Cu- and Fe–SSZ-13. UV–Vis DRS, EPR, H₂-TPR indicated the active species of Cu- and Fe–SSZ-13. Results showed that Cu–SSZ-13 only had one type active species of Cu²⁺, Fe–SSZ-13 had Fe³⁺ species that acted as active centers at low temperature and reactivity oligomeric Fe species at high temperature. The diffuse reflection infrared Fourier transform spectrum (DRIFTS) results showed that the reactions of Cu–SSZ-13 and Fe–SSZ-13 at low temperature both followed the Eley–Rideal (E–R) mechanism and the Langmuir–Hinshelwood (L–H) mechanism. Cu–SSZ-13 could perform the catalytic process well under both mechanisms, but when Fe–SSZ-13 followed the E–R mechanism, there were many B-NH₃ species, which was not conducive to the reaction. When following the L–H mechanism, the speed of NO₃⁻ participating in the reaction was slow due to ammonia inhibition, resulting in poor low-temperature activity.