Catalysis Surveys from Asia最新文献

Iridium nanoparticles were synthesized between graphite layers by thermal treatment of the mixture of iridium chloride (IV) and graphite powder under chlorine atmosphere followed by hydrogen reduction (Ir-GIC). In Ir-GIC samples with 1–6 wt% iridium metal loadings, all iridium nanoparticles with disk-shape (iridium nanodisks) were located between graphite layers; however, iridium nanoparticles on graphite surface were also formed in addition to iridium nanodisks in the Ir-GIC samples with 8 and 10 wt% iridium metal loadings. Iridium nanodisks between graphite layers were highly active for cinnamaldehyde hydrogenation and selective to cinnamyl alcohol compared with the iridium particles on graphite surfaces.

Graphical Abstract

Iridium nanoparticles with disk-shape structure were synthesized between graphite layers by thermal treatment of the mixture of iridium chloride and graphite under chlorine pressure followed by hydrogen reduction.

H-ZSM-5(RH) was synthesized using rice husk without an organic reagent and explored it as a support for Ni in the catalytic cracking of methane (CCM). Detailed investigations of the fresh and used catalysts analysed by using XRD, SEM, TEM, H₂-TPR, DT/TGA and CO pulse chemisorption techniques revealed that the high CCM activity was due to enhanced Ni dispersion and increased Cu-Ni interactions. Among the Ni/H-ZSM-5(RH) and bimetallic (Ni-M/H-ZSM-5(RH) M = Zn, Co, Fe, Cu) catalysts, the Cu-Ni/H-ZSM-5(RH) demonstrated a hydrogen yield of ~ 275 Nm³/mol_Ni which was explained by a high degree of graphitization confirmed by Raman spectroscopic analysis.

Light naphtha (C₅–C₆ alkanes) is commonly used as a feedstock for steam cracking or catalytic cracking to produce ethylene and propylene. This paper summarizes the progress of C₅/C₆ alkanes steam cracking and catalytic cracking, but the key problem of the above method is the high yield of low-value C₁–C₃ alkanes. When C₅/C₆ olefin is used as the feedstock of catalytic cracking, the ethylene and propylene yields are high, while the C₁–C₃ alkanes yield is low. It is of scientific value to dehydrogenate the C₅/C₆ alkanes into the corresponding olefins, and effectively convert the olefins into ethylene and propylene. This paper reviews recent progress of direct catalytic dehydrogenation and oxidative dehydrogenation of C₅/C₆ alkanes, and points out that the key is to develop C₅/C₆ alkanes dehydrogenation catalyst for selective preparation of corresponding mono-olefins. The main issues about how to develop highly selective C₅/C₆ alkanes dehydrogenation catalysts are proposed.

Nanostructured powders xFe/nano-Al₂O₃ with the Fe loading of x = 0.0 – 5.0 wt% were obtained using laser vaporization by CO₂ laser. XRF, XRD, HRTEM, PL and UV–Vis DRS techniques were employed to investigate physicochemical, structural and optical properties of the synthesized nanopowders with the average particle size of 9 nm. Nanopowders xFe/nano-Al₂O₃ as model catalysts were tested in isobutane dehydrogenation reaction. The results obtained were compared with similar data for the xFe/γ_Pb-Al₂O₃ systems synthesized by the conventional sol–gel method. According to XRD and UV–Vis DRS data, in the series of xFe/nano-Al₂O₃ samples a great part of Fe³⁺ ions is in the disordered environment of subsurface layers of Al₂O₃ nanocrystallites, predominantly in the tetrahedral coordination. In distinction to samples of the xFe/γ_Pb-Al₂O₃ series, in the case of nanostructured xFe/nano-Al₂O₃ powders the formation of Fe₂O₃ phase does not occur at any concentrations of iron or conditions of testing. The analysis of the PL spectra of xFe/nano-Al₂O₃ powders also showed the presence of surface sites of Fe³⁺ ions, which were not detected for xFe/γ_Pb-Al₂O₃. Catalytic testing of the xFe/nano-Al₂O₃ series samples in isobutane dehydrogenation revealed the formation of the iron active sites that ensure catalytic activity of the samples. Differences in the catalytic properties of FeO_x/Al₂O₃ samples obtained by the sol–gel method and laser vaporization are related to different states of Fe³⁺ ions. Thus, the xFe/nano-Al₂O₃ nanopowders, in contrast to xFe/γ_Pb-Al₂O₃, contain a large amount of active Fe³⁺ sites. These sites, being involved in the dehydrogenation reaction, are present predominantly on the surface of the nanopowders.

The production of aromatics with fuel properties from either biomass resources or low-cost refinery streams such as C5 is an important industrial interest. However, the strategic design of reliable catalysts with commercial compatibilities remained a challenge. Several investigations were carried out in this direction. This review accordingly presents a comprehensive analysis of the literature on the catalysis-based strategies adopted for aromatization of the feeds. Valorization of furans and allied oxygenates derived from biomass into aromatics was initially covered. The review examined strategies for C5 streams aromatization, co-upgrading of furans with hydrocarbons and methanol and discussed how biomass-derived bio-oils could be valorized into aromatics. In addition to discussion on the influence of catalytic textural, acidity and topological properties, the paper provided substantial updates on the associated reaction mechanisms. A perspective for further investigations in aromatization was also provided.

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.

Graphical abstract