An efficient solvent-free catalyst system for hydrosilylation of aldehydes and ketones was developed based on iron pre-catalyst Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH. The reactions were tolerant of many functional groups and the corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the reaction products. The reaction is likely catalyzed by an in situ generated pincer ligated iron hydride complex.
Graphic AbstractNi–Mo2C and Ni–WC were evaluated in dry reforming of methane employing different CH4/CO2 ratios. Ni–Mo2C remained active under an excess of CH4, but deactivation occurred under an excess of CO2. Ni–WC was resistant to excess of CO2 but showed carbon deposition under excess of CH4.
Graphic AbstractThis work addresses the reduction of NOx by H2 under O2-rich conditions using Al2O3/SiO2-supported Pt catalysts with different loads of WOx promotor. The samples were thoroughly characterised by N2 physisorption, temperature-programmed desorption of CO, scanning electron microscopy, X-ray diffraction, laser raman spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance infrared fourier transform spectroscopy with probe molecule CO. The catalytic studies of the samples without WOx showed pronounced NOx conversion below 200 °C, whereas highest efficiency was related to small Pt particles. The introduction of WOx provided increasing deNOx activity as well as N2 selectivity. This promoting effect was referred to an additional reaction path at the Pt-WOx/Al2O3/SiO2 interface, whereas an electronic activation of Pt by strong metal support interaction was excluded.
Graphic AbstractIn order to further improve the catalytic activity and stability of heterogeneous acid catalysts, a polystyrene microspheres modified sulfonic acid-based catalyst (PS-SO3H) was prepared. PS-SO3H was characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscope, transmission electron microscope, N2 adsorption–desorption, and X-ray photoelectron spectroscopy. Catalytic efficiency was determined using the reaction of furfuryl alcoholysis to ethyl levulinate (EL). The obtained results showed that PS-SO3H had excellent catalytic performance, with EL yield of 94.7%. In addition, PS-SO3H was easily separated from the reaction system and recycled multiple times without significant reduction in activity. High catalytic activity stemmed from the effect of Brønsted acid sites and appropriate structural properties.
Graphical AbstractThis work proposed a new path to synthesize Ni-phyllosilicate through the reaction of nickel hydroxide and silica sol on the surface of Ni-foam to form the monolithic Ni-phyllosilicate/Ni-foam catalyst. Ni-phyllosilicate could reprint the morphology of nickel hydroxid and firmly anchor on the framework of Ni-foam, which obtained fine Ni particles of 2.8 nm after reduction in H2 at 650 °C, resulting in high catalytic activity for CO2 methanation. In addition, the Ni-phyllosilicate/Ni-foam catalyst showed high long-term stability in a 100 h-lifetime test owing to the combined effects of surface confinement of Ni-phyllosilicate, firm anchoring between Ni-phyllosilicate and Ni-foam, as well as the high heat transfer property of Ni-foam.
Graphical AbstractIn this work, density functional theory is used to study the mechanism of propane dehydrogenation over non-metallic C3N catalyst. The structure, electrostatic potential and density of state of C3N are introduced, as well as the adsorption of reactants on catalyst is studied. The propane dehydrogenation reaction is divided into the first dehydrogenation and the second dehydrogenation (deep dehydrogenation). We explore the possible dehydrogenation pathways in two-step dehydrogenation. The rate control step of the first dehydrogenation is the removal of methylene hydrogen atom from propane, and its energy barrier is 47.79 kcal/mol, which reflected the catalytic activity of the catalyst. The rate control step of deep dehydrogenation is the process of removing the first hydrogen atom of the product propylene to produce the by-product. The energy barrier is 72.80 kcal/mol, which is much larger than that of the first step of dehydrogenation, reflecting the excellent selectivity of the catalyst.
Graphic AbstractBeta-zeolite supported ruthenium catalysts for reductive amination of 5-hydroxymethyl-2-furaldehyde (HMF) with an aqueous solution of ammonia (NH3 aq.) and molecular hydrogen (H2) are examined to synthesize the corresponding primary amine of 5-aminomethyl-2-furylmethanol (FAA). Various SiO2/Al2O3 (Si/2Al) ratios of the beta-zeolite support were used to prepare the Ru-based catalysts. It was observed that the Si/2Al ratio was contributed to the catalytic activity, and the Si/2Al?=?150 of beta-zeolite was found to be the most active for Ru catalyzed reductive amination of HMF, affording ca. 70% yield. Characterization techniques were taken to analysis the factors that influence the reactivity of catalysts, and which revealed that not only the ruthenium nanoparticle size but also the ratio of RuO2 against metallic Ru species were crucial factors for the reactivity of reductive amination of HMF to FAA.
Graphical AbstractThe statistical selectivity models were developed for four different Fischer–Tropsch synthesis product range, including methane (CH4), light olefins (C2=C4), light paraffins (C2–C4), and long-chain hydrocarbons (C5+), based on the experimental data obtained over thirteen γ-Al2O3 supported cobalt-based catalysts with different cobalt particle and pore sizes. The input variables consist of cobalt metal particle size and catalyst pore size. The cubic and quadratic polynomial equations were fitted to the experimental data, however, the mathematical models were subjected to model reduction for the enhancement of model adequacy, which was investigated through ANOVA. The multi-objective optimization revealed that the maximum C5+?selectivity (84.150%) could be achieved at the cobalt particle size and pore sizes of 14.764 and 23.129 nm, respectively, while keeping the selectivity to other hydrocarbon products minimum.
Graphic AbstractMicro-mesoporous aluminosilicates based on ZSM-5 zeolite, obtained by a dual template method, as well as in the presence of a dual-functional template (i.e. a Gemini-type surfactant), were tested in the oxidation of furfural with hydrogen peroxide. Even substantial changes in acidity and porosity of the catalysts result in minor variations of selectivity towards the desired products. Application of the synthesized zeolite-based materials in the oxidation of furfural with hydrogen peroxide leads to formation of 2(5H)-furanone (yield up to 28.5%) and succinic acid (up to 19.5%) as the main C4 reaction products. The kinetic model developed previously to treat the results for oxidation of furfural over sulfated zirconia was able to describe the data also for micro-mesoporous aluminosilicates.
Graphical Abstract0D/2D Pt-C3N4/CdS heterojunction photocatalyst were fabricated with CdS quantum dots interspersed on g-C3N4 nanosheets via successive ionic layer absorption process. The obtained Pt-C3N4/CdS Z-scheme heterojunction with Pt cocatalyst deposited on g-C3N4 nanosheets exhibited H2 production rate of 35.3 mmol g?1 h?1, which is 3.1 times higher than that of Pt-CdS/C3N4. The enhanced photocatalytic activity are attributed to the Z-scheme charge carrier transfer mechanism with stronger redox ability. The photocatalytic mechanism of the CdS/g-C3N4 composite is investigated and demonstrated in this work. It may provide unique insights to design 0D/2D Z-scheme heterojunction photocatalyst systems using a facile method for highly efficient H2 production.
Graphic AbstractSchematic illustration of charge transfer modulated by the metal cocatalyst selective deposition on heterojunction-type II (a) and direct Z-Scheme mechanisms (b) over the C3N4/CdS heterostructure composites under visible light irradiation.
The magic number clusters Au102(p-MBA)44 and Au144(p-MBA)60 were synthesized and tested for their ability to catalyze the reduction of 4-nitrophenol. Kinetic and thermodynamic analyses demonstrate that both clusters are effective catalysts with activation energies less than 10 kJ/mol and turnover frequencies approaching 103 h–1 per surface gold atom.
Graphic AbstractLignocellulosic biofuels are the most promising sustainable fuels for supplementing shrinking fossil resources. In this work, acid-modified vermiculite (AVM)-supported Pd–Ni bimetallic catalyst (Pd–Ni/AVM) was investigated for the hydrodeoxygenation of bio-oil and its model compounds to assess its reactivity. Pd–Ni/AVM was found to efficiently hydrodeoxygenate the investigated model compound (phenol). The phenol conversion reached 94% at 0.5% of Ni loading and temperatures beyond 513 K. Using these parameters, the phenolic hydroxyl group was removed, and the C?=?C bonds were saturated. This catalyst was also efficient in the hydrodeoxygenation of bio-oil. H2-TPR experiments elucidated the synergistic effects between the active component and the carrier, which were considered the main reason for the catalytic activity. Strong influences of the Ni loading and temperature on the hydrogenation of phenol were also observed when the Pd loading was fixed at 1 wt%.
Graphic AbstractAchieving the removal of the toxic nitric oxide (NO) gas efficiently and cheaply has always been a challenge. Herein, we systematically investigate the reduction mechanisms of NO on the surface of the Fe–PCs (PCs?=?phthalocyanines) using density functional theory calculations. The isolated iron atom not only plays the role of an adsorption and activation site for the NO molecule but also works as an electron transfer medium in the whole reaction process. The results indicate that the catalytic reduction of NO to N2 takes place through a continuous two-step pathway. The first step involves the reduction of NO to N2O through a competitive Langmuir–Hinshelwood and Eley–Rideal mechanisms with the energy barrier of 1.19 eV and 0.60 eV, respectively. The second step involves the reduction of N2O to N2 with an energy barrier of 0.91 eV. These reaction pathways are favorable thermodynamically, thus the Fe–PCs catalyst is a promising candidate for the abatement of NO gases.
Graphic AbstractCo3?xMnxO4 is a bimetal oxide with excellent electrochemical activity in alkaline solution, has been regarded as a promising alternative in the field of ion-air batteries and proton exchange membrane fuel cell (PEMFC). Herein, we report a simple solvothermal-calcination method to fabricate Co3?xMnxO4 with tunable external Co3+/Co2+ and Mn3+/Mn2+ ratio. The tunable ratio of element valence in the bimetal results in a higher exposure of active center for oxygen redox reaction (ORR), and thus lead to a better ORR activity, which was confirmed by X-ray photoelectron spectroscopy characterizations and electrochemical measurements. Specially, Co1.8Mn1.2O4 with a Co3+/Co2+ ratio of 2.08 showed an overpotential of 0.37 V at benchmark ORR current density of 3 mA/cm2 in 0.1 M KOH, which is lower than that of pure oxide (Mn3O4 0.53 V and Co3O4 0.56 V). In addition, the as prepared Co1.8Mn1.2O4 exhibited a positive half-wave potential (0.83 V vs RHE) due to their more active sites, promotes charge transfer, adsorption and desorption of oxygen species. This work provides a strategy for the design and fabrication of earth-abundant, low-cost electrocatalysts for PEMFC in practical applications.
Graphic AbstractCo3?xMnxO4 was fabricated by tuning external Co3+/Co2+ and Mn3+/Mn2+ ratio, and the activity initially shows a positive correlation with the ration of Co3+/Co2+ in Co3?xMnxO4.
CuO–CeO2 (Cu–Ce) catalyst with a CuO/CeO2 mass ratio of 1 prepared by a sol–gel method is used in the CO catalytic oxidation reaction in the actual industrial sulfur-containing atmosphere. At a reaction temperature of 200 °C, the catalyst exhibits quite different stability under sulfur-containing and sulfur-free conditions. When 30 ppm SO2 was added to the feed gas, the Cu–Ce catalyst had an initial CO conversion rate of 100%, gradually decreasing after 26 h, and this catalyst completely deactivated at about 50 h. However, the CO conversion rate of the catalyst under sulfur-free conditions could be nearly maintained at 100% within the measured time range (60 h). The results of IR, Raman, and XPS characterizations proved that the accumulation of cerium sulfate on the Cu–Ce catalyst would cover the active sites of the catalyst, eventually leading to the complete deactivation of the catalyst, which provides favorable evidence for the actual industrial anti-sulfur application.
Graphical AbstractMethyl-2-(1-methyl-2′-amino-ethane)amino-1-cyclopentenedithiocarbo-xylate was supported on the modified Fe3O4 MNPs. Afterwards, Pd(OAc)2 was immobilized on the modified MNPs and, then, the nanoparticles were analyzed using FT-IR, XRD, EDS, ICP-OSE, SEM, TGA and VSM spectroscopy. The catalytic efficiency of the prepared heterogeneous Pd-NPs was successfully examined in “Heck cross coupling reaction”, involving the reaction of butyl acrylate with various aryl halides in water. The advantages of this strategy include, easy recovery and efficient reusability of the expensive Pd-NPs, obtaining high yields of the butyl cinnamate cross-coupled products, short reaction times, and being performed in water for a wide range of substrates.
Graphical AbstractA novel HcdMeen-Pd(0) complex was synthesized on the surface of modified Fe3O4 MNPs and fully characterized by FT-IR, XRD, EDS, ICP-OSE, SEM, TGA and VSM spectroscopy analysis. The obtained complex was then used for Chemo And Homoselective Heck C–C cross-coupling synthesis of butyl cinnamates with in water as green solvent.
The reaction network of oxidative carbonylation of methanol (CH3OH) over CuY catalyst prepared by solid-state ion exchange of HY zeolite with CuCl was enriched by combination of in-situ diffuse reflectance infrared fourier transform spectroscopy and mass spectrometric. Based on the proposed mechanism of dimethyl carbonate formation on CuY in literature, this study mainly focused on the origin of the O atom in methoxyl and the reaction pathway for by-products formation. The interaction of the catalyst with different reactants and reactant mixtures (CH3OH, CH318OH, HCHO, O2, CH3OH/HCHO and CH318OH/CO/O2) was studied in detail. It was found that in the presence of CuOx or oxygen, methoxide species are generated by breaking of the O–H bond. Reaction of methoxide species with oxygen leads to the formation of formaldehyde (HCHO), followed by the generation of formate species through consecutive oxidation of HCHO.
Graphic AbstractThe present work aims to investigate the effect adding Ag, Co, Ni, Cd and Pt to copper on ethanol dehydrogenation. The catalysts synthesized by deposition–precipitation method were characterized using various physicochemical methods such as N2 adsorption–desorption, TPR, SEM–EDX, XRD, XPS and TGA–DSC-MS. Catalytic evaluation results revealed that the predominant product of the reaction was acetaldehyde. Monometallic copper or mixed with Cd, Ag or Co show good catalytic performances. Adding nickel to copper improves the process conversion but reduces acetaldehyde selectivity, giving rise to methane in produced hydrogen. Pt-Cu/SiO2 catalyst guides the reaction towards diethyl ether. Time on stream tests performed during 12 h at 260 °C, showed that adding Cd to Cu enhances its stability by over 30% of conversion, this is explained by the reduction of copper crystallites sintering, which makes Cd-Cu/SiO2 a promising catalyst for the production of acetaldehyde by ethanol dehydrogenation.
Graphic AbstractSolid base metal oxide catalysts such as MgO offer utility in a wide variety of syntheses from pharmaceuticals to fuels. The (111) facet of MgO shows enhanced, unique properties relative to the other facets. Carbon coatings have emerged as a promising modification to impart metal oxide catalyst stability. Here, we report the synthesis, characterization, and catalytic properties of commercial MgO, MgO(111), and carbon coated derivatives thereof for 2-pentanone condensation. The dimer and trimer products of this reaction can be used as precursors for biofuels upon oxygen removal and thus have relevance in environmental sustainability. MgO(111) maintained impressive selectivity towards the dimer product after carbon coating, whereas the other catalysts experienced a decrease in conversion and selectivity as a consequence of the carbon coating. Our findings highlight the catalytic efficacy of MgO(111), provide insight into carbon coating for catalyst stability, and pave the way for continued mechanistic investigations.
Graphical AbstractVanadium(IV) oxido complex of 1-Phenyl-1,3-butanedione [VIVO(bzac)2] (1) was prepared, characterized, and heterogenized onto APTMS modified graphene oxide, as well as imidazole modified polystyrene beads. Graphene oxide supported complex GO-APTMS-[VIVO(bzac)2] (2) and polymer anchored complex PS-im-[VIVO(bzac)2] (3) were used for the oxidative bromination of a number of small organic molecules and oxidation of a series of thioethers. Both 2 and 3 evolve as excellent heterogeneous catalysts. The nature of solid support does not impact substrate conversion (%) during the oxidative bromination of salicylaldehyde, phenol, or styrene, whereas it influences the substrate conversion (%) as well as the product selectivity (%) during the oxidation of thioethers.
Graphic Abstract