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Catalytic activity of TiO2, 2%Re–TiO2 and 10%Re–TiO2 in the conversion of carbohydrates into levulinic acid under autoclave conditions was evaluated. These materials were prepared by aerogel method, for the first time to the best of our knowledge, and characterized by XPS, SEM-EDX, DRIFTS, DR UV-vis, Raman, N2 adsorption/desorption isotherms, TGA and XRD. Further, the surface acidity was probed by NH3-TPD and pyridine-FT-IR where it was observed that increasing the amount of rhenium doped into TiO2 led to an increase in the total number of acid sites (Lewis + Brønsted) but with an overall lower strength. The presence of both Brønsted and Lewis acid sites led to the hypothesis that these materials may be well suited for conversion of carbohydrates into levulinic acid. Indeed a levulinic acid yield of 57% was reached over 10%Re–TiO2 for a low mass ratio catalyst to glucose (1 : 5). Moreover, the 10%Re–TiO2 catalyst was reused in the conversion of glucose for four catalytic cycles without a significant loss of the catalytic activity.

An effective biogenic approach is proposed to synthesize size-tunable CuO nanostructures using seed shell extract of Sapindus mukorossi plant to use as efficient catalysts for conjugate addition of amines to acrylonitrile under ambient conditions.

Selective hydrogenation plays an important role in the chemical industry and has a wide range of applications, including the production of fine chemicals and petrochemicals, pharmaceutical synthesis, healthcare product development, and the synthesis of agrochemicals. Pd-based catalysts have been widely applied for selective hydrogenation due to their unique electronic structure and ability to adsorb and activate hydrogen and unsaturated substrates. However, the exclusive and comprehensive summarization of the size, composition, and surface and interface effect of metal Pd on the performance for selective hydrogenation is still lacking. In this perspective, the research progress on selective hydrogenation using Pd-based catalysts is summarized. The strategies for improving the catalytic hydrogenation performance over Pd-based catalysts are investigated. Specifically, the effects of the size, composition, and surface and interfacial structure of Pd-based catalysts, which could influence the dissociation mode of hydrogen, the adsorption, and the reaction mode of the catalytic substrate, on the performance have been systemically reviewed. Then, the progress on Pd-based catalysts for selective hydrogenation of unsaturated alkynes, aldehydes, ketones, and nitroaromatic hydrocarbons is revealed based on the fundamental principles of selective hydrogenation. Finally, perspectives on the further development of strategies for chemical selective hydrogenation are provided. It is hoped that this perspective would provide an instructive guideline for constructing efficient heterogeneous Pd-based catalysts for various selective hydrogenation reactions. ispartof: ACS OMEGA vol:7 issue:1 pages:17-31 ispartof: location:United States status: published

Aim: The current work aims to enhance catalytic performance of gold nanoparticle– carbon nanotube (Au-CNT) composites towards the reduction of p-nitrophenol. Background: The synthesis of Au-CNTs has received extensive attention because of their high stability and catalytic efficiency, particularly as a heterogeneous catalyst in the reduction of pnitrophenol (p-NP) to p-aminophenol (p-AP) However, most of the Au-CNT preparation processes reported in the literatures are time-consuming or require expensive instrumentation. In the present work, Au-CNT catalysts were synthesized via a straightforward, low-cost deposition– precipitation (DP) method. Objective: Evaluate the effect of pH and aging time on catalytic activity of Au-CNTs catalyst. Methods: The Au-CNT nanocomposite catalysts were synthesized using a simple deposition– precipitation method and characterized by Brunauer–Emmett–Teller analysis, fourier transform infrared spectroscopy, atomic absorption spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, and transmission electron microscopy. Results: The particle size and the loading of Au nanoparticles on the CNTs can be easily controlled by varying the pH and aging time during the synthesis process. The nanocomposite catalysts exhibited excellent catalytic activity for the reduction of p-nitrophenol to p-aminophenol in the presence of excess sodium borohydride (NaBH4). The highest rate constant (k) achieved based on the pseudo-first-order kinetic model was 1.2 × 10-3 s-1. Conclusion: This study offers a simple and cost-effective route to synthesize Au-CNT catalysts with high stability and catalytic efficiency for large-scale application.

In this research, a novel CuFe catalyst was fabricated using a simple, single-step electrodeposition method on a traditional Cu electrode. CuFe films from various electrodeposition baths with different Cu and Fe ratios were prepared by chronopotentiometry and characterised by X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray analysis (EDX), and Pb underpotential deposition (Pb-UPD). The Cu electrode coated with CuFe8020 (from electrodeposition bath containing 80% Cu and 20% Fe) showed the highest reduction current among the film produced. The Cu electrode coated with CuFe8020 exhibited three times higher nitrate reduction efficiency and less undesired products like NO2− và NH4+ than the traditional Cu.

Sodium citrate as a highly efficient catalyst is developed for the synthesis of functionalized 2-amino-3-cyano-4H-pyrans and pyran-annulated heterocycles. This method involves a one-pot three-component reaction of aromatic aldehydes, malononitrile and 1,3-dicarbonyl compounds with EtOH: H2O (1:1 v/v) as solvent under room temperature. This protocol presents several advantages such as shorter reaction time, utilization of eco-friendly solvents, operational simplicity, mild reaction conditions, and maximum product yield. Moreover, the use of sodium citrate as an easily available, cheap and benign catalyst plays a pivotal role from a green perspective, considering its high recyclability and easy recovery. Therefore, this present methodology offers numerous possibilities in terms of large-scale industrial syntheses or application to numerous organic conversions. Furthermore, theoretical studies on the mechanistic pathway of the formation of product 4aa were also carried out to determine the catalytic role of sodium citrate on the feasibility of the reaction with DFT method, using B3LYP functional.

3-Methyl-1-sulfonic acid imidazolium trichlorido copper (II) {[Msim]CuCl3} was prepared and used as a new catalyst for the preparation of 5-amino-1H-pyrazole-4-carbonitriles. In this reaction, the pyrazole ring was formed by an anomeric and vinylogous anomeric effect in the structure of the product.

A novel method for the synthesis of four-component pyrano[2,3-c]phenazin-15-yl) methanone derivatives has been developed via condensation/Knoevenagel/Michael in the presence of Fe3O4@ZnO-SO3H as a ...

Ammonia (NH3) is considered an attractive candidate as a clean, highly efficient energy carrier. The electrocatalytic nitrogen reduction reaction (NRR) can reduce energy input and carbon footprint; therefore, rational design of effective electrocatalysts is essential for achieving high-efficiency electrocatalytic NH3 synthesis. Herein, we report that the enzymatic mechanism is the more favourable pathway for NRR, due to lower limiting potential (−0.44 V), lower free energy (only 0.02 eV) of the first hydrogenation step (*N–N to *NH–N), and more electron transfer from Fe2B2 to the reaction species. In addition, both vacancies and dopants can be helpful in reducing the reaction energy barrier of the potential-determining step. Therefore, we have demonstrated that Fe2B2 is a potential new candidate for effective NRR and highlighted its potential for applications in electrocatalytic NH3 synthesis.

Conversion of CO2 into chemicals is a promising strategy for CO2 utilization, but its intricate transformation pathways and insufficient product selectivity still pose challenges. Exploiting new catalysts for tuning product selectivity in CO2 hydrogenation is important to improve the viability of this technology, where reverse water-gas shift (RWGS) and methanation as competitive reactions play key roles in controlling product selectivity in CO2 hydrogenation. So far, a series of metal-based catalysts with adjustable strong metal–support interactions, metal surface structure, and local environment of active sites have been developed, significantly tuning the product selectivity in CO2 hydrogenation. Herein, we describe the recent advances in the fundamental understanding of the two reactions in CO2 hydrogenation, in terms of emerging new catalysts which regulate the catalytic structure and switch reaction pathways, where the strong metal–support interactions, metal surface structure, and local environment of the active sites are particularly discussed. They are expected to enable efficient catalyst design for minimizing the deep hydrogenation and controlling the reaction towards the RWGS reaction. Finally, the potential utilization of these strategies for improving the performance of industrial catalysts is examined., A series of metal oxide, phosphate, alloy, and carbide-based catalysts for selective CO2 hydrogenation are summarized, showing their abilities to switch CO2 methanation to RWGS.

Polyoxometalates (POMs), large oxoanions of the group 5 and 6 elements, attract attention due to their use as oxidation-stable catalysts and ligands. Different from the well-known V, Mo, and W POMs, the group V POMs of Ta assemble and are stable only in highly alkaline solution rather than acidic solution. In this paper, we successfully synthesized and structurally characterized two unprecedented peroxotantalum-containing clusters, KNa2[HSe2(TaO2)6(OH)4(H2O)2O13]·15H2O (1) and Cs2K1.5Na1.5[Se4(TaO2)6 (OH)3O18]·17H2O (2), which comprises a 6-peroxo-6-tantalum core stabilized by two and four selenite centers, respectively. The simple, one-pot synthesis of 1 and 2 involving addition of sodium selenite into the acidified hexatantalate aqueous solution in the presence of hydrogen peroxide could represent a general procedure for incorporating heteroatoms into peroxo-polyoxotantalate species, thus opening new possibilities for this emergent branch of polyoxotantalate chemistry. Moreover, the catalytic properties of these two compounds were investigated using succinic anhydride and phenylamine as the model substrate, and compound 2 presents excellent catalytic activity in the amidation reactions of anhydrides and amines.

Utilizing the abundant biogas resources in an efficient and sustainable way helps to mitigate the energy and environmental problems. CH4 oxy-CO2 reforming reaction is a promising technic and an efficient catalyst for the reaction is in great demand. In this work, Ru was incorporated into monometallic Co/MgO-Al2O3 aerogel catalyst via supercritical drying process combined with sol–gel method and a series of Co-Ru bimetallic aerogel catalyst with different Ru contents was synthesized. Catalytic performance screening for the catalysts indicated that combination of Ru and Co significantly raised the activity of monometallic catalysts, e.g., the activity of Co15-Ru0.2 (Co content: 15 wt.%, Ru content: 0.2 wt.%) was 64.7% and 63.9% higher than those of the monometallic Co15 and Ru0.5 catalysts, respectively. The results also indicated that Co/Ru ratio had a great influence on the catalytic activity: Co15-Ru0.2 > Co15-Ru0.1 ≈ Co15-Ru0.5 > Co15-Ru0.05 > Ru0.5 > Co15. XRD, BET, H2-TPR, XPS, TEM, TG/DSC, and FESEM analyses were performed, disclosing that the reducibility and active metal particle size of the catalysts can be manipulated by the Co/Ru ratio due to the transportation of bulk Co2+ to the surface. The Co15-Ru0.2 catalyst had a mean active metal particle size below 10 nm and medium reducibility, resulting in a high activity and stable performance.

Background: Acetylation of protic nucleophiles is used to protect these functional groups. Most of the methods described in the literature use solvents, one or more equivalent of toxic bases or expensive and toxic catalysts. Therefore, new methodologies, above all, greener and more economical procedures, are still in demand. Objective: An eco-efficient method was developed for the acetylation of alcohols, phenols, thiols, amines, and carbohydrates, using acetic anhydride and a catalytic amount of the environmentally benign and inexpensive FeCl3.6H2O, under solvent-free conditions. Methods: Acetylation of a variety of protic nucleophiles was performed using 0.2 mol % of FeCl3.6H2O as the catalyst, and 1.2 equivalent of Ac2O as the acetylating agent at room temperature and under solvent-free conditions. Results: This procedure appears to be highly efficient and promoted rapid and quantitative acetylation under simple and minimum manipulation. Chromatography or recrystallization was generally not necessary for the purification of products. Conclusion: This eco-friendly protocol appears to be potentially universally applicable in organic design to protect protic nucleophiles and isscalable for industrial fields.

In this study, the Co-based catalyst was prepared by cobalt immobilization on the surface of functionalized silica-coated magnetic NPs (Fe3O4@SiO2-CT-Co) as a magnetically core–shell nanocatalyst and characterized by FT-IR, TGA, XRD, VSM, SEM, TEM, EDX, EDX mapping, and ICP techniques and appraised in the Suzuki–Miyaura cross-coupling reaction under mild reaction conditions. The results displayed the superparamagnetic behavior of the Fe3O4 NPs core encapsulated by SiO2 shell, and the size of the particles was estimated about 30 nm. Compared with the previously reported catalysts, the engineered Fe3O4@SiO2-CT-Co catalyst provided perfect catalytic performance for the Suzuki–Miyaura cross-coupling reaction in water as a green solvent and it was much cheaper in the comparison with the traditional Pd-based catalysts. Importantly, the durability of magnetic nanocatalyst was studied and observed that it is stable under the reaction conditions and could be easily reused for at least six successive cycles without any significant decrease in its catalytic activity.

Indium compounds are versatile and efficient materials for catalysis in chemical science, especially in organic synthesis. Amongst indium compounds, indium bromide (InBr3) is widely employed in man...

Finding a highly efficient catalyst for proton exchange membrane fuel cells is still the subject of extensive research. This article describes heterostructured Pd/Ti/Pd bimetallic thin films prepared using a strain-release technology as electrocatalysts for fuel cells. With their particular structure, these materials exhibit intriguing electrocatalytic activity toward the oxidation of both methanol and formic acid, yielding current densities of 0.17 and 0.56 A mg-1Pd, much superior to that of the commercial Pd black catalyst. Moreover, the Pd/Ti/Pd thin films display a low onset oxidation potential and extremely high current retention in both acidic and alkaline media. The carbon monoxide poisoning resistance is also significantly enhanced, thus contributing to ultrahigh stability in the long-term electrocatalytic processes. Their encouraging performance implies that such composites could be potential materials for energy conversion in the fuel cell field.

Millimeter-sized porous carbon spheres (MPCS) with both controllable interior architecture and high mechanical strength are highly desired for practical applications, but there is no efficient method to synthesize these materials. Here, we report a strategy to fabricate millimeter-sized porous carbon spheres by harnessing the liquid marble phenomenon. This strategy enables us to obtain a series of MPCS with tunable interior architectures, such as honeycombed MPCS, foam-like MPCS, cavity-containing MPCS and hollow MPCS, which add new members to carbon microsphere family. Crucially, the mechanical strength of MPCS reaches as high as 14.6 N, favoring its practical applications. Moreover, our protocol allows for nitrogen element and metal to be in situ incorporated within the body of MPCS, leading to an efficient catalyst for levulinic acid (LA) hydrogenation or benzene hydrogenation. Impressively, turnover numbers (TONs) of 113000 in the LA hydrogenation and 480 h of continuous benzene hydrogenation with TONs of 116000 are achieved, which highlights the potential in engineering applications of these novel microspheres.

Hydrolytic dehydrogenation of Ammonia-borane (NH3BH3, abbreviation AB) has attracted much attention due to its high hydrogen content and stability. Therefore, the design and construction of low cost and high performance catalysts for AB hydrolysis are of great significance. In this work, a series of RhCu/CoOx alloy catalysts were prepared by a in-situ reduction method. The catalytic activity of hydrolytic dehydrogenation of AB was optimized by regulating the molar ratio of Rh to Cu in the RhCu/CoOx catalysts. The results verify that Rh1Cu2/CoOx has the best catalytic activity for hydrolytic dehydrogenation of AB, and the corresponding hydrolysis reaction type was first order. The turnover frequency (TOF) reached 670.95 mol H 2 mol cat − 1 min−1, and the apparent activation energy (Ea) was 28.86 kJ mol−1, showing excellent catalytic performance for hydrolytic dehydrogenation of AB.

The La0.6Ca0.4Fe0.7Ni0.3O2.9 perovskite was synthesized using a modified ultrasonic spray pyrolysis technique with sorbitol as the fuel and ozone as the oxidizer, resulting in chemically homogeneou...

A cobalt-catalyzed oxidative [4+2] annulation of benz­amides with dihydrofuran was developed for the expeditious synthesis of tetrahydrofuro[2,3-c]isoquinolinones. Commercially available and inexpensive Co(OAc)2·4H2O was used as an efficient catalyst. Various functional groups were tolerated, affording the desired products in good yields with excellent regioselectivity and good diastereoselectivity under mild conditions.

Background Silver orthophosphate (Ag3PO4) has received enormous attention over the past few years for its higher visible light photocatalytic performance as well as for various organic pollutants degradation in aqueous media. Therefore, considerable efforts have been made to the synthesis of Ag3PO4 with high catalytic efficiency, long lifetime, and using low-cost inorganic precursors. Results This article describes our efforts to develop a novel approach to synthesize of nanostructured silver phosphate (Ag3PO4) using phosphate rock as alternative and natural source of PO43− precursor ions. The catalytic experimental studies showed that the nanostructured Ag3PO4 exhibited excellent catalytic activity for reduction of p-nitrophenol in the presence of NaBH4 at room temperature. Furthermore, the antibacterial studies revealed that the obtained Ag3PO4 possess significant effect against E. Coli and S. Aureus bacteria. Conclusion The obtained results make the nanostructured Ag3PO4 prepared from natural phosphate as a highly promising candidate to be used as efficient catalyst and antibacterial agent. Graphic Abstract

Ag–TiO2 nanocomposite as an efficient catalyst was synthesized and characterized by AFM analysis. This nanocomposite acts as a heterogeneous and recyclable catalyst for the room temperature synthesis of 1,2,4,5-tetrasubstituted imidazoles from aldehydes, benzil, ammonium acetate and several anilines or aliphatic amines via one-pot four-component condensation reaction in H2O as a green solvent. Ag–TiO2 nanocomposite was simply recovered by filtration and was reused up to three times.