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Supported Pt catalysts play an important role in selective hydrogenation reactions for upgrading bio-derived chemicals, and they are traditionally prepared by methods such as deposition–precipitation (DP), wet impregnation (WI) and chemical reduction (CR) using NaBH4 and H2 under thermal conditions. This study developed a new reduction method to produce supported Pt NPs on nanofibers, in which Ti3AlC2 (a typical MAX phase) and chloroplatinic acid (H2PtCl6) were employed as raw materials, using as-produced H2 as a reducing agent under hydrothermal synthetic conditions. In the selective hydrogenation of furfural to furfuryl alcohol, the newly-developed catalyst of Pt2.0/Ti3AlxC2Ty exhibited high furfural (FUR) conversion (86.3%) and excellent furfuryl alcohol (FA) selectivity (98.1%) under optimized reaction conditions of 600 rpm, 100 °C, 3 h, and 1 MPa H2 in aqueous media. Moreover, these fibrous catalysts exhibited strong reusability and recyclability for five runs without loss of activity and selectivity. [ABSTRACT FROM AUTHOR]

Electrochemical hydrogenation is an environmentally favorable alternative to chemical reduction of indigo because it performs under ambient conditions using water as the donor of hydrogen. The purpose of this work is to fabricate electrocatalysts with high activity and durability for electrocatalytic hydrogenation of indigo. This work compares the performances of a series of Ni based catalysts (Ni, NiMo, NiP and NiMoP) on the substrate of carbon felt (CF) for electrolyzing water. Both the overpotential and Tafel slop are decreased as a function of the components as Ni > NiMo > NiP > NiMoP. Hence, NiMoP/CF shows the excellent performance based on the thermodynamics (η 10 = 239 mV) and kinetics (Tafel slope = 89.7 mV·dec−1) for splitting water. Further, the electrode of NiMoP/CF was used for the electrocatalytic hydrogenation of indigo. The conversion efficiency and Faradic efficiency can be improved as 26.2% and 10.7% respectively. Furthermore, the dyeing behavior of the electrohydrogenated indigo is similar to that of conventional reduction methods. Thus, the present work offers foundational results and paves the way for the design of new catalytic materials for the reduction of vat dyes. [Display omitted] • Electrodeposited NiMoP/CF for HER was explored systematically. • NiMoP/CF shows the better thermodynamics and kinetics of HER. • NiMoP/CF was evaluated as a stable and active electrocatalyst for the ECH of indigo. • NiMoP/CF shows the higher efficiency of conversion and Faraday of ECH of indigo. [ABSTRACT FROM AUTHOR]

Stereoselective hydrogenation of α‐pinene over heterogenous catalysts under solvent‐free conditions is promising for biomass conversion but challenging. Herein, we prepared the Ru‐NiO/Hβ catalysts using chemical reduction and galvanic replacement methods. With the increase of Ni content, the selectivity of cis‐pinane was significantly improved. A high conversion of 100 % and a high cis‐pinane selectivity of 98 % were achieved after 4 h reaction at 80 °C. It has been verified that the addition of Ni can adjust the ratio of Brønsted and Lewis acid, regulate the hydrogen spillover between Ru and support, change the adsorption site of substrate and form steric hindrance effect. All these contribute to the better selectivity of the catalyst. In addition, catalysts presented good stability in the 900 h test. [ABSTRACT FROM AUTHOR]

The synthesis of γ-valerolactone (GVL) from butyl levulinate (BL) hydrogenation over sulfonated activated carbon (SAC) supported SnRuB bifunctional catalysts was studied. These catalysts were characterized by ICP, nitrogen physisorption, XRD, HRTEM, XPS and NH3-TPD techniques. The SnRuB hydrogenation active site and surface acidic site of the SAC support are effectively retained by the co-impregnation followed by a chemical reduction process and display a prominent synergetic effect for BL hydrogenation to GVL. Under the optimal reaction conditions (180 °C, 3 MPa, 800 rpm, 3 h), BL conversion of 99.2% and GVL selectivity of 83.8% were obtained over the optimal 20Sn1RuB/SAC catalyst. The highest total fraction of the C＝O group, lattice oxygen (Oα) and oxygen vacancies (Oβ) and active SnOx species on the surface of the catalyst contribute to the best adsorption and hydrogenation ability for BL conversion to GVL over the 20Sn1RuB/SAC catalyst. The sulfonated carbon-supported SnRuB bifunctional catalyst also showed outstanding recyclability in six runs due to enhanced reduction degree of Snn+ species, and strong interaction between the SnRuB active site and SAC support. In sum, the sulfonated carbon-supported SnRuB bifunctional catalyst with low costs, high activity and good recyclability is a potential candidate for butyl levulinate hydrogenation to GVL. [ABSTRACT FROM AUTHOR]

• Adding Fe to magnetic Ni catalyst improved CO 2 methanation efficiency and selectivity. • Magnetic Ni 8 Fe 2 converted >80% of CO 2 to methane at a low temperature of 150 °C. • Optimal catalyst reduction temperature determined as 200 °C. The power-to-gas (PtG) method has significant potential as a strategy for storing excess renewable energy in the form of synthetic natural gas. PtG involves the hydrogenation of CO 2 to CH 4 from H 2 obtained from renewable energy. In this study, Ni–Fe catalysts with different Ni/Fe ratios were prepared for high-efficiency CO 2 methanation using chemical reduction with an external magnetic field. The Ni–Fe catalysts were characterized by XRD, inductively coupled plasma, and SEM-EDS measurements, and their performance and chemical properties were measured by H 2 temperature programmed reduction experiments. The catalyst with the best performance for CO 2 methanation had a ratio of Ni to Fe of 8/2 (Ni 8 Fe 2). The Ni 8 Fe 2 catalyst could convert over 80% of CO 2 to methane at 150 °C. In addition, the CH 4 selectivity of CO 2 methanation was 95% when the reaction conditions were controlled at H 2 /CO 2 = 4 and GHSV ∼1000 h−1. The low cost and simple preparation of these Ni–Fe catalysts have high potential for future commercialization. [Display omitted] [ABSTRACT FROM AUTHOR]

A low-cost Ni-B alloy catalyst was prepared by chemical reduction method and used for partial hydrogenation of fatty acid methyl esters. The conditions for catalyst preparation, including Ni to B ratio, pH of NaBH4 solution, types and quantity of metal modifiers were optimized. Ni-La-B, prepared by modification of Ni-B with La, showed significantly high catalytic partial hydrogenation activity. The optimum textural properties (small particle size, high specific surface area and well-defined pore structure) and electron enrichment of active Ni sites were the favorable factors for the high hydrogenation activity of Ni-La-B catalyst, which showed reasonable stability in catalyst recycle experiments. [ABSTRACT FROM AUTHOR]

The production of tetrahydrofurfuryl alcohol (THFAL) from biomass-derived furfural (FF) via one-pot hydrogenation is challenging owing to the high hydrogen pressure and temperature requirements of the system. In this study, a hydrothermal method is used to synthesize a series of wrinkled silica (KCC-1) supports having different morphologies and textural properties by modulating the cetylpyridinium bromide hydrate (CPB)/tetraethyl orthosilicate (TEOS) ratio. Subsequently, Pd-supported KCC-1 catalysts are fabricated along with a Pd/SiO 2 catalyst (for comparative studies) via a chemical reduction method. Interestingly, the morphological features of the supports, such as the specific surface area, pore size, and Pd anchoring sites, differed significantly for different CPB/TEOS ratios. Among the synthesized catalysts, Pd/KCC 0.3, with the lowest proportion of Pd nanoparticles deposited on the external porous surface, exhibits the highest catalytic activity, owing to its large specific surface area and moderate pore size. Moreover, it shows the highest FF conversion of 100% and THFAL selectivity of 85% in 6 h at 50 °C under 20 bar H 2. • KCC-1 supports with different morphologies are prepared by tuning CPB/TEOS ratios. • The correlation between the morphological features and the catalytic activity of Pd-based catalysts have been investigated. • Pd/KCC-1 catalsyts show higher selectivity for one-pot hydrogenation of furfural compared to Pd/SiO 2. • Pd/KCC 0.3 catalyst with a large surface area and low fiber density showed the highest selectivity to THFAL. [ABSTRACT FROM AUTHOR]

The influence of the composition of the copper complex and the structure of the ligand on the selectivity of continuous hydrogenation processes of dicyclopentadiene and nitrobenzene, as well as the reductive alkylation of nitrobenzene with isobutanol, up to the production of various reduction products under the same conditions with a selectivity of up to 100%, was discovered. [Display omitted] The reaction of copper(II) acetate with furoic acids (2Hfur / 3Hfur) and imidazole (Im) in methanol resulted in mononuclear complexes [Cu(fur) 2 (Im) 2 (H 2 O)]·L (fur- = 2fur- (1 , 2), 3fur- (3); L = MeCN (1)) whose structures were determined by direct single crystal X-ray analysis. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al 2 O 3 obtained by chemical reduction of 1 , 2 and 3 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of mono- and dihydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD). The catalytic activity tests show a high selectivity (97 %) of the catalyst obtained from an ethanolic solution of complex 1 in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with an excess of hydrogen, whereas the catalyst obtained from an aqueous solution of complex 1 showed 98 % total hydrogenation product (THDCPD) selectivity. The catalysts based on all the complexes 1 – 3 were successfully used in reactions of nitrobenzene (NB) reduction to aniline (AN) and in the reductive alkylation of nitrobenzene with isobutanol (i -BAN) 100 % yields of aniline and N -isobutylaniline were obtained at LHSV 0.16 h−1. [ABSTRACT FROM AUTHOR]

High-throughput (HT) methodology was applied for the synthesis, characterization and catalytic testing of Cu- and Ni-based catalysts for glucose hydrogenation. Design of Experiment (DoE) was used in all steps. The deposition and reduction of both metals was performed using chemical reduction with hydrazine method. In total 36 catalysts were synthetized, characterized and tested in 5 days. The amount of metal deposited on the support was chosen as the discriminative and determining parameter. The catalysts were tested at low temperature in the hydrogenation of glucose to sorbitol. • High-throughput methods allow shortening the time of development of a new catalytic process. • Ni and Cu-supported catalysts can be easily obtained by reduction-precipitation method. • The activity strongly depends on preparation conditions. • The use of Design of Experiments (DoE) permits to minimize the number of experiments and to optimize their interpretation. • Good performances in hydrogenation of glucose to sorbitol were obtained for Cu/SiO 2 and Ni/Al 2 O 3 catalysts. A high-throughput (HT) methodology was applied for the synthesis, characterization and catalytic testing of silica and alumina supported Cu- and Ni-based catalysts for glucose hydrogenation. A design of Experiment (DoE) approach was also used in all steps. The deposition and reduction of both metals was performed using the chemical reduction with hydrazine method. In total, 36 catalysts were synthetized, characterized and tested in 5 days. The amount of metal deposited on the support was chosen as the discriminative and determining parameter. The catalysts were tested at low temperature (130 °C) in the hydrogenation of glucose to sorbitol. The results showed that the chemical reduction-precipitation method could be performed using fully automatized robots. The deposition of the metals strongly depended on the nature of the support, the temperature of the reduction and hydrazine/H 2 O ratio. The maximum metal precipitation occurred at higher temperature (70 °C) and lower N 2 H 4 /H 2 O ratio (0.04 mol/mol) in both cases. The results clearly showed that glucose conversion is higher for the catalysts synthesized at 70 °C compared to the catalysts synthesized at 50 °C, irrespective of the metal precursors, supports and hydrazine/water ratios employed during catalysts syntheses. With a total timespan of around 5 days we showed that HT methods applied to all the steps (synthesis, characterization and testing) can significantly reduce the time needed to develop a new catalytic process. [ABSTRACT FROM AUTHOR]

Understanding photodriven multielectron reaction pathways requires the identification and spectroscopic characterization of intermediates and their excited‐state dynamics, which is very challenging due to their short lifetimes. To the best of our knowledge, this manuscript reports for the first time on in situ spectroelectrochemistry as an alternative approach to study the excited‐state properties of reactive intermediates of photocatalytic cycles. UV/Vis, resonance‐Raman, and transient‐absorption spectroscopy have been employed to characterize the catalytically competent intermediate [(tbbpy)2RuII(tpphz)RhICp*] of [(tbbpy)2Ru(tpphz)Rh(Cp*)Cl]Cl(PF6)2 (Ru(tpphz)RhCp*), a photocatalyst for the hydrogenation of nicotinamide (NAD‐analogue) and proton reduction, generated by electrochemical and chemical reduction. Electronic transitions shifting electron density from the activated catalytic center to the bridging tpphz ligand significantly reduce the catalytic activity upon visible‐light irradiation. [ABSTRACT FROM AUTHOR]

The selective, efficient and sustainable continuous flow hydrogenation of a α,β-unsaturated aldehyde, i.e. cinnamaldehyde, to the corresponding unsaturated alcohol, i.e. cinnamyl alcohol, using a novel catalyst based on Ru-containing scrap waste automotive converters is reported. The catalyst was prepared by recycling and upgrading waste ceramic-cores of scrap automotive catalytic converters as supporting materials. Ruthenium was incorporated into the ceramic structures using a simple, fast and solventless mechanochemically assisted procedure followed by a chemical reduction step. Different catalysts were prepared with varying Ru contents. The materials were characterized by XRD, N2 physisorption, XPS, TEM, HRTEM and SEM/mapping analyses. Compared to Ru supported over most studied silica and alumina supports, the new system displayed an outstanding catalytic performance under continuous-flow conditions in terms of conversion and selectivity and a remarkable stability with time-on-stream, demonstrating a synergistic action between Ru and the waste catalytic converter support. A Ru loading of 10 wt% provided the optimum results, including a cinnamaldehyde conversion of up to 95% with a selectivity to cinnamyl alcohol of 80%. [ABSTRACT FROM AUTHOR]

Two new copper complexes with anions derived from 3-furancarboxylic/ 5-nitro-2-furancarboxylic acid and 4-phenylpyridine were obtained. These catalysts are the first example of copper catalysts for the selective hydrogenation of dicyclopentadiene in flow type reactors. [Display omitted] The reaction of copper(II) acetate with 3-furancarboxylic acid (Hfur) and 5-nitro-2-furancarboxylic acid (Hnfur) with participation of 4-phenylpyridine (phpy) in acetonitrile resulted in mononuclear complexes [Cu(L) 2 (phpy) 2 (H 2 O)]·solv (L = fur (1), nfur (2); solv = phpy (1)) whose structures were determined by direct single crystal X-ray analysis. According to X-ray data, the complexing component in 1 and 2 is in a distorted square-pyramidal environment (CuN 2 O 3); the pyramid base is formed by monodentate-bound oxygen atoms of fur-/nfur- anions and a pair of nitrogen atoms of the phpy moieties, while the water molecule occupies an axial position. It was found for the first time that copper nanoparticles immobilized on the surface of γ-Al 2 O 3 obtained by chemical reduction of 1 and 2 (pre-deposited on the surface from solution) with sodium tetrahydroborate show high selectivity of monohydrogenation of tricyclo[5.2.1.02,6]deca-3,8-diene (dicyclopentadiene, DCPD) to give tricyclo[5.2.1.02,6]dec-4-ene (5,6-dihydrocyclopentadiene, DHDCPD). The catalytic activity tests show high selectivity (up to 100 %) of the catalysts studied in the reaction of partial hydrogenation to DHDCPD under continuous process conditions even at high conversion values (up to 96 %) and with hydrogen present in excess. Thermal behavior of 1 and 2 was studied by simultaneous thermal analysis (STA). [ABSTRACT FROM AUTHOR]

This review focuses on the importance of coupling of catalytic reactions which involves dehydrogenation and hydrogenation simultaneously and the study of catalytic materials that are designed, adopted and/or modified for these reactions. The special features of these reactions are minimization of H utilization and reduction in production cost. Structural and textural properties also play a decisive role in this kind of coupled reactions. This particular review although not comprehensive discusses the significant progress made in the area of coupled reactions and also helps future researchers or engineers to find out the improvements required in areas such as advancements in catalytic material preparation, design of the new reactors and the application of new technologies. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The present work reports up-to-date information regarding the reaction mechanism of the catalytic hydrogenation of nitrates in water media. In the present mechanistic study, an attempt is made, for the first time, to elucidate the crucial role of several catalysts and reaction parameters in the mechanism of the NO-3/H2 reaction. Steady-state isotopic transient kinetic analysis (SSITKA) experiments coupled with ex situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were performed on supported Pd-Cu catalysts for the NO-3/H2 and NO-3/H2/O2 reactions. The latter experiments revealed that the formation and surface coverage of various adsorbed active intermediate N-species on the support or Pd/Cu metal surface is significantly favored in the presence of TiO2 in the support mixture and in the presence of oxygen in the reaction's gaseous feed stream. The differences in the reactivity of these adsorbed N-species, found in the present work, adequately explain the large effect of the chemical composition of the support and the gas feed composition on catalyst behaviour (activity and selectivity). The present study leads to solid mechanistic evidence concerning the presence of a hydrogen spillover process from the metal to the support. Moreover, this study shows that Cu clusters are active sites for the reduction of nitrates to nitrites. [ABSTRACT FROM AUTHOR]

The article offers information on the recent developments in flavin-based catalysis. It informs that flavins can be excited by irradiation with the help of visible light which makes them stronger catalysts for oxidative processes. It also informs that flavins can be used in the reduction of olefins by catalyzing the formation of diimide as flavins show high thermal and chemical stability in the reduction processes.

The article offers information regarding the use of heterogeneous catalysts, such as palladium on carbon for several oxidation and reduction reactions. It discusses the use of DNA-mediated palladium nanoparticles as an efficient catalyst. It also investigates ways of using the waste DNA from discarded industrial salmon milt.

The Noyori transfer hydrogenation of α,β-epoxy and α,β-aziridinyl ynones leads to the corresponding α,β-epoxy or α,β-aziridinyl propargylic alcohols with high reagent-controlled diastereoselectivity. [ABSTRACT FROM AUTHOR]

Abstract: The catalytic asymmetric reduction of ethyl-2-(benzamidomethyl)-3-oxo-phenylpropanoate was realized with high enantiomeric and diastereoisomeric excesses via biotransformation using whole cells of different yeasts and asymmetric hydrogenation with Ru(II) complexes prepared from different chiral diphosphine ligands. With these combined approaches it was possible to prepare both enantiomers of the syn-stereoisomers in almost enantiomerically pure form; one of the enantiomers of the anti-stereoisomer was obtained in high ee with selected yeast while the other enantiomer of the anti was prepared in low ee and de. With three of the four epimers we were able to prepare the corresponding azetidinones. [Copyright &y& Elsevier]

Abstract: The reduction of allyl aryl ethers using sodium borohydride in the presence of a catalytic amount of ruthenium(III) chloride in various aqueous solvent mixtures at 0°C was examined. In aqueous tetrahydrofuran, hydrogenation was the favored pathway (85–100% yield of the corresponding aryl propyl ether); whereas in aqueous N-methylformamide, reductive cleavage predominated (4:1 mixture of phenolic product/aryl propyl ether). In order to gain some insight into the mechanism for this process, 3-octyn-1-ol and trans-2-decen-1-yl acetate were subjected to similar reductive conditions; and both substrates afforded products inconsistent with a single-electron-transfer mechanism. [ABSTRACT FROM AUTHOR]

Abstract: Fructose and invert sugar (fructose/glucose mixture) were hydrogenated over bimetallic amorphous nano-catalysts of CoNiB and polymer polyvinylpyrrolidone (PVP)-stabilized CoNiB (PVP-CoNiB), prepared by chemical reduction, to yield mannitol and sorbitol. The parameters of catalysts and the reaction conditions were discussed. CoNiB and PVP-CoNiB catalysts were much more active than NiB, CoB and Raney nickel in the hydrogenations of fructose and invert sugar. The selectivity of mannitol changed slightly even as the catalysts and the reaction conditions were altered. The highly active catalysts of CoNiB and PVP-CoNiB are promising to replace Raney nickel in the hydrogenations of fructose and invert sugar, although the selectivity of mannitol improved slightly. [Copyright &y& Elsevier]

The organocatalytic transfer hydrogenation reactions of 3-phenyl-2-cyclopentenone with imidazolidinone catalysts are evaluated using the hybrid density functional (B3LYP/6-31G(d)) theory. The origin of the preference for the (E) iminium transition state is determined, and the stereoselectivity of hydride transfer is investigated. [ABSTRACT FROM AUTHOR]

Abstract: A magnetically recoverable Pt(0) catalyst was prepared by in situ H2 reduction of Pt2+ species bound to an amino modified silica-coated magnetic nanoparticles. Compared to ordinary silica (maximum uptake Pt 0.03wt%), the amino-functionalized silica surfaces were loaded with 1.95wt% of metal. The supported Pt(0) nanoparticles exhibit high catalytic activity in the hydrogenation of alkenes and ketones under solventless mild reaction conditions. Partially hydrogenated products could also be isolated. The magnetic property of the catalyst grants a fast and efficient product isolation compared to traditional methods used in heterogeneous systems that generally make use of time- and solvent-consuming procedures. [Copyright &y& Elsevier]

In contrast to its reaction under catalytic hydrogenation, the first instance of an exclusive and chemoselective trans-reduction of the ene part of derivatives of 5,6-dibenzoylbicyclo[2.2.2]oct-5-en-2-one has been reported under moderate photoinduced electron transfer (PET) conditions using triethylamine (TEA). In the absence of TEA, such molecules underwent 1,5-photophenyl migration yielding vinyl ketenes. [ABSTRACT FROM AUTHOR]

A series of NiFeB nanoalloy catalysts were prepared by chemical reduction method using metal acetates as the starting materials, and NaBH4as the reducing agent. The amorphous metal materials, combining the features of amorphous and nanometer materials, have more surface atoms and a higher concentration of coordinately highly unsaturated sites. Sodium borohydride in excess amount was added dropwise into the mixture to ensure full reduction of metal cations. The catalysts were characterized with X-ray diffraction, nitrogen sorption, transmission electron microscopy, and X-ray photoelectron spectroscopy. The hydrogenation of p-chloronitrobenzene was carried out in a batch reactor at 1.2 MPa H2pressure and 323−393 K. The Ni/Fe molar ratios in the starting materials affected the concentration of boron bounded to the nickel and iron metals, resulting in the difference in surface area, electronic structures of the metals, and the catalytic activities of the catalysts. The addition of iron in NiB catalyst could reduce the particle of the nickel metal, suppress the growth of crystalline structure of NiFeB, and help the NiFeB catalyst to maintain its amorphous state. On the basis of the electron transfer between elemental nickel and boron, Ni in NiFeB had more d-band electrons and higher electron density than in NiB; therefore, it also has higher activities of hydrogenation of the nitro group than does NiB. [ABSTRACT FROM AUTHOR]

Cobalt silicate formation reduces the activity of the catalyst in Fischer–Tropsch synthesis (FTS). In this article, the effects of calcination temperature and support surface area on the formation of cobalt silicate are explored. FTS catalysts were prepared by incipient wetness impregnation of cobalt nitrate precursor into various silica supports. Deionized water was used as preparation medium. The properties of catalysts were characterized at different stages using FTIR, XRD and BET techniques. FTIR-ATR analysis of the synthesized catalyst samples before and after 48 h reaction identified cobalt species formed during the impregnation/calcination stage and after the reduction/reaction stage. It was found that in the reduction/reaction stage, metal-support interaction (MSI) added to the formation of irreducible cobalt silicate phase. Co/silica catalysts with lower surface area (300 m2/g) exhibited higher C5+ selectivity which can be attributed to less MSI and higher reducibility and dispersion. The prepared catalysts with different drying and calcination temperatures were also compared. Catalysts dried and calcined at lower temperatures exhibited higher activity and lower cobalt silicate formation. The catalyst sample calcined at 573 K showed the highest CO conversion and the lowest CH4 selectivity. [ABSTRACT FROM AUTHOR]

Uniform Co–B nanoparticles were synthesized for the first time by chemical reduction of cobalt ion with borohydride in an oil-in-water microemulsion system comprising cyclohexane, polyethylene glycol, and water. The particle size was controlled by modulating the cyclohexane content. With the characterization of X-ray diffraction, selective area electronic diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy, the resulting Co–B nanoparticles were identified to be amorphous alloys ranging in size from 6 to 20 nm. During liquid-phase cinnamaldehyde hydrogenation, the as-synthesized Co–B catalyst was extremely active and more selective than the regular Co–B prepared in aqueous solution. Furthermore, this catalyst also was found to be more durable during the hydrogenation process. [Copyright &y& Elsevier]

The gas-phase hydrogenation of ethyne, propyne, and propadiene was investigated over partially reduced Ni–Al mixed oxides derived from takovite, a hydrotalcite-type compound. The unique attributes of the hydrotalcite route leads to more active and selective catalysts compared to conventional Ni/Al2O3 prepared by impregnation. Tuning calcination and reduction conditions of the catalyst precursor is essential to optimize the hydrogenation performance. The best catalyst, calcined and reduced at 773 K, rendered stable propene yields up to ca. 65% and consisted of a Ni(Al)O x solid solution with 55% of the total bulk nickel in reduced form and surface enrichment by aluminum. Sintering of NiO and crystallization of NiAl2O4 at high calcination temperature induce lower activity. The alkyne or diene conversion increases with the percentage of metallic Ni in the samples, while an optimal degree of nickel reduction maximizes the monoalkene selectivity. Below the optimum, oligomer formation is favored and above the optimum, alkane production increases. A similar pattern was found for the H2/HC ratio. The alkene selectivity experiences a dramatic increase in early stages of the reaction, which correlated with the build-up of C-containing species on the catalyst (sub-)surface. These selectivity-enhancing species are formed at specific reaction temperatures, highlighting the relevance of the testing procedure on assessing hydrogenation catalysts. The catalytic performance is strongly influenced by the hydrocarbon substrate. In contrast to propyne and propadiene, ethyne hydrogenation led to a C2H4 yield of only 6%. [Copyright &y& Elsevier]

Solutions of Cp*lrH(rac-TsDPEN) (TsDPEN = H2NCHPhCHPhN(SO2C6H4CH3)-) (1 H(H)) with O2 generate Cp*lr(TsDPEN) (1) and 1 equiv of H2O. Kinetic analysis indicates a third-order rate law (second order in [1H(H)] and first order in [O2]), resulting in an overall rate constant of 0.024 ± 0.013 M-2 s-1. Isotopic labeling revealed that the rate of the reaction of 1 H(H) + O2 was strongly affected by deuteration at the hydride position (kHH2/kDH2 = 6.0 ± 1.3) but insensitive to deuteration of the amine (kHH2/kHD2 = 1.2 ± 0.2); these values are more disparate than for conventional transfer hydrogenation (Casey, C. P.; Johnson, J. B. J. Org. Chem. 2003, 68, 1998-2001). The temperature dependence of the reaction rate indicated ΔH* = 82.2 kJ/mol, ΔS* = 13.2 J/mol·K, and a reaction barrier of 85.0 kJ/mol. A CH2CI2 solution under 0.30 atm of H2 and 0.13 atm of O2 converted to H2O in the presence of 1 and 10 mol % of H(OEt2)2BArF4 (BArF4 = B(C6H3-3,5-(CF3)2)4). The formation of water from H2 was verified by 2H NMR for the reaction of D2 + O2. Solutions of 1 slowly catalyze the oxidation of amyl alcohol to pentanal; using 1 ,4-benzoquinone as a cocatalyst, the conversion was faster. Complex 1 also catalyzes the reaction of O2 with RNH2BH3 (A = H, t-Bu), resulting in the formation of water and H2. The deactivation of the catalyst 1 in its reactions with O2 was traced to degradation of the Cp* ligand to a fulvene derivative. This pathway is not observed in the presence of amine-boranes, which were shown to reduce fulvenes back to Cp*. This work suggests the potential of transfer hydrogenation catalysts in reactions involving O2. [ABSTRACT FROM AUTHOR]

Abstract: PVP-stabilized NiB catalysts were prepared using the chemical reduction method with NaBH4, dissolving the water-soluble polymer of polyvinylpyrrolidone (PVP) in the precursor salt solution as a protective reagent. The PVP-NiB catalysts were characterized and examined for their catalysis on the hydrogenation of furfural, crotonaldehyde and citral. PVP polymer could adsorb on the nano-particles of NiB via a weak coordination bonding and stabilize it; a molecular weight of PVP of about 10,000 was suitable, and the optimal quantity of PVP (PVP/Ni) in the salt solution for preparing catalysts was around 20. The PVP-NiB samples were characterized by XRD as an amorphous structure and by TEM with a particle size distribution in the range of 3–5nm. On catalysis, the PVP-NiB catalyst was significantly more active and slightly more selective than NiB for hydrogenating furfural to furfuryl alcohol and crotonaldehyde to butyraldehyde. A good yield of citronellal, about 90%, could be obtained by reducing citral in cyclohexane at a low reaction temperature of 50°C over the PVP-NiB catalyst. [Copyright &y& Elsevier]

A bimetallic RhNi/Al 2 O 3 catalyst prepared by galvanic replacement (GR) offers enhanced catalytic CO 2 hydrogenation to selectively produce methane. • Galvanic replacement offers a facile route to bimetallic Rh@Ni core–shell catalysts. • Bimetallic Ni@Rh core–shell catalysts offer significant rate enhancements for CO 2 methanation. • Operando IR identifies reactively-formed CO as the key intermediate to CH 4 production. • Surface formate is a catalytic spectator in methanation. CO 2 utilisation as a chemical feedstock could transform fuels production and help mitigate climate change. Direct CO 2 reduction for energy production requires the development of active, stable, and low-cost catalysts selective for methane. A bimetallic Ni@Rh core–shell catalyst prepared by galvanic replacement (GR) exhibits a 3.5-fold rate enhancement for CO 2 methanation relative to an analogue prepared by chemical reduction (CR) and is twice as active as monometallic Rh/Al 2 O 3. Superior performance of RhNi/Al 2 O 3 (GR) is attributed to Rh dispersion as an atomically thin RhO x shell encapsulating Ni nanoparticles, stabilised by a strong Rh-Ni interaction. Operando IR spectroscopy identifies reactively-formed CO from the dissociative chemisorption of CO 2 over Rh as the key intermediate for methane production. Surface formate from the dissociative chemisorption of CO 2 and subsequent hydrogenation (via spillover from Rh sites) over alumina is a catalytic spectator. This mechanistic insight paves the way to high activity nanostructured catalysts for CO 2 methanation. [ABSTRACT FROM AUTHOR]

Abstract: An efficient, easy, cheap, convenient, and safe procedure for the reduction of various alkenes to the corresponding alkanes is developed by using scrap automobile catalyst as an efficient hydrogenation catalyst. This procedure not only gives high yields, but also allows recycling of automobile wastes as a catalyst in organic reactions and is representative of green chemistry. [Copyright &y& Elsevier]

Abstract: Some achiral β-amino alcohols have been shown as efficient ligands for the ruthenium-catalysed asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)imines in isopropanol. The ruthenium complex prepared from [RuCl2(p-cymene)]2 (2.5mol%) and 2-amino-2-methyl-1-propanol (5mol%) leads to α-branched chiral primary amines with very high optical purities (up to 98% ee) by the diastereoselective reduction of the imines followed by removal of the sulfinyl group under mild acidic conditions. Short reaction times (2–3h) were needed to complete the reduction reactions when they were performed at 50°C. [ABSTRACT FROM AUTHOR]

Reduced graphene oxide was used as a catalyst for reduction of nitrobenzene at room temperature. High catalytic activity and stability were exhibited in circular experiments. The catalytic procedure was in situmonitored by NMR and N-phenylhydroxylamine was proved to be the intermediate in this catalytic reaction. [ABSTRACT FROM AUTHOR]

N-Heterocycles form weak adducts with B(C6F5)3that exist in equilibrium with the corresponding FLP; nonetheless, these heterocycles are reduced in the presence of a catalytic amount of the borane B(C6F5)3and H2. [ABSTRACT FROM AUTHOR]

Abstract: Easily accessible in situ catalysts composed of [Ru(cod)(2-methylallyl)2] and N-heterocyclic carbene ligands have been developed for the environmentally benign hydrogenation of various nitriles to give primary amines. Applying optimized conditions in the presence of SIMesBF4 as ligand high catalyst activity of up to 392h−1 is achieved in the hydrogenation of benzonitrile. The general applicability and functional group tolerance of this novel catalyst system are shown in the reduction of ten different nitriles. [Copyright &y& Elsevier]

We investigated the effect of oxide supports on the hydrogenation of furfural over Pd catalysts on various supports (Al2O3, SiO2, TiO2, CeO2, and ZrO2). Pd catalysts (5 wt%) prepared by chemical reduction on various supports. The dispersion and uniformity of Pd were affected by the properties of the support and by the nucleation and growth of Pd. The conversion of furfural was enhanced by greater Pd dispersion. The selectivity for cyclopentanone and tetrahydrofurfuryl alcohol was affected by physicochemical properties of Pd catalyst and reaction parameters. High Pd dispersion and high acidity of the catalyst led to greater C=C hydrogenation, thereby, generating more tetrahydrofurfuryl alcohol. The Pd/TiO2 catalyst showed the highest cyclopentanone yield than other catalysts. The Pd/TiO2 catalyst exhibited the >99% furfural conversion, 55.6% cyclopentanone selectivity, and 55.5% cyclopentanone yield under the optimal conditions; 20 bar of H2, at 170 °C for 4 h with 0.1 g of catalyst. [ABSTRACT FROM AUTHOR]

The selective reduction of a nitro group when other reducible functions are present is a difficult process that often requires stoichiometric amounts of reducing agents or, if H2 is used, the addition of soluble metals. Gold nanoparticles supported on TiO2 or Fe2O3 catalyzed the chemoselective hydrogenation of functionalized nitroarenes with H2 under mild reaction conditions that avoided the accumulation of hydroxylamines and their potential exothermic decomposition. These chemoselective hydrogenation gold catalysts also provide a previously unknown route for the synthesis of the industrially relevant cyclohexanone oxime from 1-nitro-1-cyclohexene. [ABSTRACT FROM AUTHOR]

The article discusses the role of gold catalysts in promoting selective reduction of aromatic nitro compounds to anilines. To produce anilines, aromatic nitro compounds must be reduced in a hydrogenation reaction. In the process, gold particles functions to catalyzed the reduction of various functionalized aromatic nitro compounds without hydroxylamine accumulation and with high chemoselectivity. The discovery of these catalysts furthers the study for the chemoselective catalytic reduction of nitro compounds with hydrogenation-sensitive substituents.

A La-doped Pd-B amorphous catalyst (Pd-La-B) was prepared by chemical reduction of mixed PdCl[sub2] and LACl[sub3] with KBH[sub4]. The La-dopant played a key role in stabilizing the amorphous structure since only the crystalline Pd-B was obtained without the La-dopant. During liquid phase phenol hydrogenation, the as-prepared Pd-La-B exhibited higher activity and better selectivity to cyclohexanone than the undoped Pd-B. [ABSTRACT FROM AUTHOR]

The newly designed complex FAC represents the first example of an NHC-stabilized iron (0) arene complex which efficiently catalyzes the reduction of various amides into amines using Ph2SiH2 as a hydride source. [ABSTRACT FROM AUTHOR]

A new resin-supported peptide is applied as catalyst for the enantioselective reduction of α,β,γ,δ-unsaturated aldehydes of type (I) with Hantzsch dihydropyridine. [ABSTRACT FROM AUTHOR]

Review: 133 refs. [ABSTRACT FROM AUTHOR]