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We report the design of a new iron catalyst for the asymmetric transfer hydrogenation of ketones. This type of iron catalyst combines the structural characteristics of the Noyori hydrogenation catalyst (an axially chiral 2,2′-bis(phosphino)-1,1′-binaphthyl fragment and the metal–ligand bifunctional motif) and an ene(amido) group that can activate the iron center. After activation by 8 equivalents of potassium tert-butoxide, (SA,RP,SS)-7a and (SA,RP,SS)-7b are active but nonenantioselective catalysts for the transfer hydrogenation of acetophenone and α,β-unsaturated aldehydes at room temperature in isopropanol. A maximum turnover number of 14480 was observed for (SA,RP,SS)-7a in the reduction of acetophenone. The right combination of the stereochemistry of the axially chiral 2,2′-bis(phosphino)-1,1′-binaphthyl group and the carbon-centered chiral amine-imine moiety in (SA,RP,RR)-7b′ afforded an enantioselective catalyst for the preparation of chiral alcohols with moderate to good yields and a broad functional group tolerance. [ABSTRACT FROM AUTHOR]

The utilization of CO2 to synthesize environmentally benign liquid fuels offers a solution to replacing depleting petroleum resources. Herein, a ternary CuZnZr (CZZ) metal oxide catalyst and a SAPO-34 zeolite were synthesized by co-precipitation and hydrothermal synthesis, respectively. Different metals were impregnated into the latter to obtain MeSAPO-34 (Me = Mn, Zn and Zr). A granule mixture of CZZ and MeSAPO-34 components (CZZ/MeSAPO-34 catalyst) was then effectively utilized in a tandem catalytic process for one-step CO2 hydrogenation to liquefied petroleum gas (LPG). The CZZ/MeSAPO-34 catalysts were characterized by using XRD, H2-TPR, BET, SEM-EDS and NH3-TPD techniques. SEM-EDS and XRD results indicated that an appropriate amount of Zr metal loading induced minimum zeolite framework collapse compared to a similar amount of Mn and Zn, which was more favorable for higher activity. In addition, NH3-TPD results revealed that the acidity of SAPO-34 could be altered after impregnation with different metals in different quantities. Tuning the acid density and strength, together with adjusting the CZZ to MeSAPO-34 weight ratio, had a collectively critical effect on LPG selectivity. An effective hydrogenation microenvironment which favors lower alkane formation (C3–C4) was enhanced after the acidity of the molecular sieve was tuned. LPG selectivity could reach 86% over the CZZ/5% ZrSAPO-34 catalyst at 2 MPa, 350 °C, a W/F ratio of 6, a H2/CO2 ratio of 3 and a weight ratio of 1. [ABSTRACT FROM AUTHOR]

Gamma valerolactone (GVL) is an important chemical feedstock from which several value-added fine chemicals, fuels and fuel additives are manufactured. GVL is the product obtained in the hydrogenation of levulinic acid (LA), which in turn is generally manufactured from several renewable resources such as pentoses and hexoses. The present work deals with the synthesis of SBA-15 and Sn loaded catalysts [x% Sn/Al-SBA-15 (x = Si/Sn = 10, 25, 50, 75 and 100 with Si/Al = 25)] using a hydrothermal in situ method. A variety of both bulk and surface characterization techniques such as XRD, FT-IR, BET, FE-SEM, HR-TEM, XPS, TGA/DTA and UV-DRS were used to characterize the bare and Sn/Al-SBA-15 catalysts. The characterization studies revealed the presence of Sn species well dispersed in the uniform pore channels of Al-SBA-15. All the synthesized catalysts were tested in the liquid-phase catalytic transfer hydrogenation of levulinic acid at atmospheric N2 pressure under mild reaction conditions. Among them, the Sn/Al-SBA-15 (Si/Sn = 25) catalyst showed remarkable conversion of levulinic acid (99%) and very high selectivity towards GVL (100%). The various reaction parameters such as metal loading, reaction temperature, reaction time and catalyst weight were optimized to get the maximum conversion of levulinic acid with high selectivity towards the desired product. The stability and reusability of the best catalysts were also tested up to five cycles and there was not much variation in the catalytic activity in terms of conversion. [ABSTRACT FROM AUTHOR]

In combination with a planetary ball-milling machine, a Ni–Al2O3 catalyst was prepared by a mechanochemical method. The effect of Ni loading on the crystal structure, reduction characteristics, and hydrogenation performance of the Ni–Al2O3 catalyst was investigated. The prepared catalysts were characterized using EDX, XRD, H2-TPR, BET, TEM and NH3-TPD methods. The results of the XRD characterization showed that the peak intensity of the active Ni component increased with an increase in the Ni content. The ratio of the measured Ni content to the theoretical Ni content of the MC25% and MC30% samples exceeded 1.1. As the Ni addition was increased up to 10%, the sample consisted of uniform spherical particles, which could provide more contact surfaces. The medium acid peak temperature shifts towards the high temperature direction as the Ni loading increased from 5% to 20%, and then (>20%) decreased to a lower temperature. The corresponding peak area firstly increased and then decreased, presenting a visual representation of changes in the number of acid centers on the catalyst. Evaluation of the results showed that the MC20% catalyst presented a large specific surface area of 279 m2 g−1, and it showed good hydrogenation performance, with a BYD conversion of 25.0%, BED selectivity of 89.3%, and BED yield of 22.3%. [ABSTRACT FROM AUTHOR]

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) using the η4-(2,3,4,5-tetraphenylcyclopentadienone) ruthenium tricarbonyl precursor of the well-known Shvo catalyst and H2 pressure was established under solvent-free conditions to achieve 100% conversion and 100% selectivity within 5 hours. Kinetic reaction curves were measured in order to deduce the optimal reaction conditions, which were further evaluated by means of density functional theory (DFT) calculations, and compared with catalytic concepts that consume formic acid or isopropyl alcohol as hydrogen donor. Ultimately, this alternative reaction procedure was subjected to a life cycle assessment (LCA) in comparison with the transfer hydrogenation methodologies, in order to verify its contribution towards a practice of environmentally benign chemistry. [ABSTRACT FROM AUTHOR]

A series of Ni-based catalysts, including Ni/SiO2–ZrO2, Ni/HZSM-5, Ni/Al2O3, Ni/SiO2, Ni/AC and Ni/CMK-3, were prepared to produce H2 from the aqueous phase reforming (APR) of methanol. This H2 was then used in the in situ hydrogenation of phenolic compounds for bio-fuel. The effect of different promoters was investigated with the addition of Co, La, Fe and Cu to the Ni/CMK-3 catalyst coupled with analysis using BET, XRD and SEM. The results showed that Ni/SiO2, Ni/AC and Ni/CMK-3 yielded the most hydrogen and they were chosen for further investigation in the in situ hydrogenation of phenol, guaiacol and lignin depolymerization products (LDP). Using these Ni-based catalysts, the APR of methanol provided hydrogen for the hydrogenation of the phenolic compounds. Of the modified Ni/CMK-3 catalysts, La–Ni/CMK-3 exhibited the highest activity for the conversion of phenol (80.88%) with a satisfactory cyclohexanol yield (76.64%) at 240 °C for 4 h without an external H2 source. When using La–Ni/CMK-3, the content of the phenolic compounds in LDP decreased from 75.25% to 25.38% while the content of saturated alcohols increased from 1.34% to 31.19%. It has been shown that it is possible to use the APR of methanol for the hydrogenation of LDP over a series of Ni/CMK-3 catalysts. [ABSTRACT FROM AUTHOR]

The influence of Cu loading on the structural evolution and catalytic behavior in selective hydrogenation of dimethyl oxalate (DMO) by Mg2+ doped nanoscaled Cu–Mg/ZnO catalysts has been investigated. It is found that the accessible Cu0 surface area and ZnO dispersion increased gradually with the Cu loading increasing from 10.0 wt% to 40.0 wt%, and that the Cu and ZnO NP size distribution has a great effect on the chemical interaction between the Cu and ZnO phase, further determining the surface chemical properties of the catalysts. On the other hand, the catalytic behavior of the Cu–Mg/ZnO catalyst in DMO hydrogenation is closely related to the Cu loading introduced into the system. Most of all, the 30Cu–Mg/ZnO catalyst with 30 wt% Cu loading exhibits 100.0% DMO conversion and 98.0% ethylene glycol (EG) yield even under LHSV = 3.5 h−1, superior to those of the other catalysts. This excellent catalytic behavior should be attributed to the strengthened Cu–Zn synergistic effect and suppressed strong surface basic sites, originating from the enhanced Cu–ZnO interface area. Additionally, the correlation between catalytic activity and Cu species distribution suggests that the DMO dissociation on the Cu+ sites generated on the Cu–ZnO interface is the rate-determining step in the presence of enough exposed Cu0 sites over the Cu–Mg/ZnO catalysts. [ABSTRACT FROM AUTHOR]

Carbon aerogels (CA) were applied in the synthesis of Cu/CA catalysts by the impregnation method and the catalysts with boron-doped CA supports were systematically characterized and evaluated in the hydrogenation of dimethyl oxalate (DMO). The Cu/xB–CA catalyst with 25 wt% copper showed 100% DMO conversion and the highest ethylene glycol (EG) or methyl glycolate (MG) selectivity of 70% at 230 °C as well as a lifetime of over 150 h. The characterization results disclosed the reason the performance of the catalysts could be tuned facilely by changing the amount of boron doping, which effectively influenced the interrelation between copper and CA, acidity and alkalinity of catalysts and Cu dispersion. Both the original carbon aerogels and that promoted with little B could provide larger surface areas and high dispersion of the metal. The species, size of copper particles and the ratio of Cu+/(Cu+ + Cu0) could be regulated by boron doping, thus adjusting the type of hydrogenation products. [ABSTRACT FROM AUTHOR]

The catalytic activity of scrap ceramic-cores of automotive catalytic converters (SCATs) was investigated in the continuous-flow hydrogenation of different biomass-derived chemicals. The waste SCAT powders were deeply characterized by ICP-MS, TGA, MP-AES, XRD, N2 physisorption, TPR, HRTEM and EDS before and after utilization as a catalyst. The hydrogenation reactions of isopulegol to menthol, cinnamyl alcohol to hydrocinnamyl alcohol, isoeugenol to dihydroeugenol, vanillin to vanillyl alcohol and benzaldehyde to benzyl alcohol were performed studying the influence of various reaction parameters (temperature, pressure, flow rate and concentration of the starting material) on the final yields. The outstanding performance and stability obtained for the low metal content of waste-derived catalysts can be attributed to the co-presence of different noble metals as well as to the composite structure itself. [ABSTRACT FROM AUTHOR]

Carbon-encapsulated Fe3O4 (Fe3O4@C) catalysts were prepared by a solvothermal method using glucose as the carbon source and their physicochemical properties were characterized via various analytical techniques. Catalytic transfer hydrogenation of furfural over Fe3O4@C catalysts was investigated with isopropanol as the solvent and hydrogen donor. The Fe3O4@C catalysts exhibited high catalytic furfural transfer hydrogenation activity, selectivity of furfuryl alcohol, and high reusability. The mechanism of catalytic transfer hydrogenation of furfural by Fe3O4@C obeys the Meerwein–Ponndorf–Verley reduction on a Lewis acid site (Fe3O4). [ABSTRACT FROM AUTHOR]

Aiming at the preparation of metal catalysts with nanoscale structures, Ni–Cu/Al2O3 nanoparticle catalysts (i.e., Ni&Cu-NP/γ-Al2O3), containing a certain amount of Ni and Cu were prepared for the hydrogenation of acetylene. The highly dispersed and stable Ni&Cu-NP/γ-Al2O3 catalyst with a Ni : Cu atomic ratio of 1 : 1 was obtained from a NiCl2/CuCl2 precursor by a modified co-precipitation method, the average size of which was controlled at 10.0 ± 0.3 nm. Under optimal reaction conditions, approximately 100% conversion and 71% selectivity at 130 °C were achieved using the Ni&Cu-NP/γ-Al2O3 catalyst. The enhanced selectivity was attributed to the formation of nickel–copper alloys, which have been identified by both diffuse reflectance infrared Fourier transform spectroscopy and theoretical calculation results. [ABSTRACT FROM AUTHOR]

Converting CO2 to liquid (C5+) hydrocarbons remains a significant hurdle. Our study shows that CoFe/HZSM-5 boosts C5+ selectivity to 73.4%, up from 59% for Fe/HZSM-5. This study highlights the pivotal roles of zeolite acidity and catalyst proximity in this improvement. These insights pave the way for more effective CO2 utilization. [ABSTRACT FROM AUTHOR]

In this dissertation, silver–palladium (AgPd) bimetallic nanoparticles were synthesized by a green biosynthesis method using Cacumen platycladi leaf extract, which provided both reductive and protective agents. Then the supported AgPd/γ-Al2O3 catalysts were obtained by the sol-immobilization method, and the as-biosynthesized AgPd/γ-Al2O3 catalysts with different particle sizes and compositions were used for 1,3-butadiene hydrogenation. Optimization of the catalyst preparation and selective hydrogenation parameters was performed. Using the catalyst, a 1,3-butadiene conversion of 98.2% and a butene selectivity of 88.1% were achieved. The durability experiment of AgPd/γ-Al2O3 catalysts was carried out for 50 h, and the activity decreased slightly and the selectivity almost remains the same during the 50 h, indicating their remarkable stability. The results of TEM and TG analysis showed that the size of the AgPd nanoparticles was nearly the same before and after the durability experiment, and the existence of residual biomolecules on the catalyst surface helped to prevent agglomeration and modification of the surface properties of the catalyst, which would promote desorption of the product, and then avoid intensifying the level of further hydrogenation. [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]

Semi-hydrogenation of alkynols to alkenols with Pd-based catalysts is of great significance in fine chemical industries. Industrial Lindlar catalysts, employing Pb to modify the Pd nanoparticles for higher selectivity toward alkenols, however, generally suffer from both a severe activity decrease and environment pollution caused by using heavy metal Pb and additives. Therefore, how to overcome the selectivity–activity paradox remains a great challenge in industry. Here, we report a controllable strategy for the synthesis of semi-hydrogenation catalysts, which successfully improves the catalytic performance through selectively poisoning the edge and corner sites of Pd nanoparticles. When the integrity of the crystal face is reserved, both higher activity (∼1340 h−1) and selectivity (∼95% at 99% conversion) are achieved in the semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) in ethanol, an industrially important intermediate product for the synthesis of vitamin E, without adding any toxic additives. What's more, the yield could exceed 98% at 99% conversion under no solvent and organic adsorbate conditions, which had never been achieved before. This work provides a different perspective to design and develop high performance catalysts for semi-hydrogenation of alkenols or even substituted alkynes. [ABSTRACT FROM AUTHOR]

A new type of Pd@mSiO2 composite nanospheres with controlled pore structure, consisting of internal Pd cores and controlled mesoporous silica shells, has been prepared by a facile one-pot method. The thickness and pore size of the shell could be easily tuned by changing the amounts of TEOS and the hydrophobic block length, respectively, during synthesis. In this perspective, the effects of CTAB concentration, pH, and TEOS concentration on the monodisperse sphere morphology of Pd@mSiO2 nanoparticles (NPs) were investigated. In addition, a nucleation mechanism was proposed. Hydrogenation of nitrobenzene to aniline was used as a model reaction to discuss the effect of pore size on the transport rate of the reactants and the product selectivity in metal-catalyzed hydrogenation. The catalysts exhibited a high conversion rate and significantly enhanced stability, leading to a higher recyclability without loss of catalytic activity compared to conventional supported catalysts and commercial catalysts. [ABSTRACT FROM AUTHOR]

A new catalyst was developed for selective hydrogenation of dioctyl phthalate (DOP) to produce the environmentally friendly plasticizer di(2-ethylhexyl)hexahydrophthalate (DEHHP) by incorporating rhodium via chemical fluid deposition into an aluminum-modified mesocellular foam (MCF). The Al-modified MCF containing a Si/Al molar ratio of 5 and 1 wt% Rh achieved 100% conversion of DOP to DEHHP with no side products at 80 °C and 68 atm H2 pressure in one hour reaction time. On the other hand, a 1 wt% Rh/MCF catalyst without any surface modification with Al yielded only 29% conversion. The interaction of Rh with the support became stronger when Al was incorporated onto the MCF support. An effective control of the acidity provided by Al by closely monitoring the Si/Al ratio was key in improving the catalytic activity of the Rh/Al-MCF catalysts. [ABSTRACT FROM AUTHOR]

Developing a highly active, acid-resistant and low-cost catalyst which can perform well in aqueous solution has long been sought for practical and sustainable lignocellulosic biomass transformation. In this work, a series of Ce–P–Co heterogeneous catalysts were prepared by a convenient solvothermal method for catalytic hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL) in water. By comprehensive characterizations and catalytic measurements, the structure of the prepared Ce–P–Co samples was disclosed as (CePO4)m/Co2P composites with a modulated molar ratio (m) of 0.04–0.34. With the introduction of CePO4, the unique hydrogen activation on CePO4 markedly accelerated the reaction, with the GVL yield after 90 min on (CePO4)m/Co2P (45–97%) being much higher than on pure Co2P (26%), together with an attractive TOF of 0.27–0.61 s−1 on (CePO4)m/Co2P (comparable to precious metal catalysts). Further analysis of the kinetic and acidic features indicated a Langmuir–Hinshelwood mechanism, initiated by activation of H2 and LA on CePO4 and Co2P, respectively, followed by a surface reaction of the two activated species as the rate-determining step, as a plausible pathway for producing GVL from LA on (CePO4)m/Co2P. The consistent catalytic performance during recycling tests and the unchanged morphological, bulk and surface structure features of the used catalyst relative to the fresh catalyst confirmed that the (CePO4)m/Co2P structure was robust enough to endure the acidic aqueous environment for efficiently and sustainably converting LA to GVL. The advantages of high catalytic efficiency, stable, acid-resistant structure and low cost marked (CePO4)m/Co2P as a competitive and practical heterogeneous catalyst for sustainable, scaled-up lignocellulosic biomass transformation. [ABSTRACT FROM AUTHOR]

Polystyrene (PS) resin bead supported palladium nanoparticles (Pd NPs@PS resin) were prepared and their catalytic activity for the hydrogenation of olefins was investigated under microwave heating. The hydrogenation of styrene was effectively carried out in EtOH/H2O, in the presence of 0.00035 mmol of the catalyst to afford the corresponding ethylbenzene in high yield within 20 min under microwave heating. The catalyst efficiency measured in terms of turn over number (TON) and turn over frequency (TOF) was found to be 2829 and 8573 (h−1), respectively. The encapsulated palladium nanoparticles were easily recovered by a simple filtration method and reused several times without significant loss in their catalytic activity. Further, the method showed a wide substrate scope under mild reaction conditions, making it a green versatile and highly sustainable protocol. [ABSTRACT FROM AUTHOR]

The mechanism of the ruthenium carboxylate-catalyzed hydrogenation of carboxylic acids was investigated by using density functional theory (DFT) calculations. The novel mechanism including two hydrogenation cycles was proposed for this reaction. The first cycle is the hydrogenation of the carboxylic acid to an aldehyde, while the second cycle is the hydrogenation of the aldehyde to an alcohol. These two catalytic cycles share similar elementary steps, including H2 heterolysis, hydride migration of the carboxylic acid or aldehyde, and catalyst regeneration. In this hydrogenation mechanism, the carboxylic acid is not only a reactant, but also an important proton source. Furthermore, the noncovalent interaction (e.g. hydrogen bonding interaction) between the ligand and carboxylic acid substrate could promote the hydrogenation of the carboxylic acid through stabilizing the transition state of the most energy-demanding step (i.e., hydride migration in the first catalytic cycle). Besides, the strong electron-donating ability of the dppb ligand could also facilitate the hydride migration. [ABSTRACT FROM AUTHOR]

On the way to exploring superior hydrogenation catalysts, Ir-based catalysts with a record catalytic activity (up to 40 h−1) for the hydrogenation of benzoic acid to cyclohexanecarboxylic acid under mild reaction conditions (85 °C, 0.1 MPa H2, in water) have been successfully developed. By excluding various factors, the experimental results showed that the main factor governing the activity discrepancy between the Ir-based catalysts is actually the dispersion stability of the supports (such as N-doped carbon, active carbon, SBA-15 and various metal oxides) in the reaction solution, rather than the interaction between the Ir active component and the supports. Combined with theoretical investigation from first principles, an activity volcano curve considering the competing adsorption between the reactants (H2) and solvent (H2O) for aqueous aromatic ring hydrogenation was presented for the first time. The high activity of Ir can be deduced by the proper discrepancy of dissociation energies or adsorption energies between H2 and H2O on the catalysts. This activity volcano curve provides guidance for further rational design of promising catalysts for benzoic acid or even aromatic ring hydrogenation under true reaction conditions for practical applications. [ABSTRACT FROM AUTHOR]

Cu–ZrO2 catalysts were synthesized by the methanothermal (Me) and oxalate gel precipitation (Og) methods. Detailed characterization of the catalysts synthesized by the Me method shows that these contain only Cu substituted into the tetragonal ZrO2 lattice. For catalysts prepared using the Og method Cu is found not only in the tetragonal ZrO2 lattice but also in the form of CuO particles on the zirconia surface. When these materials were tested for the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) it was found that Me materials show no catalytic activity, whereas GVL was formed using Og catalysts. A reduction treatment of the Og catalysts prior to use resulted in a marked increase in the catalytic activity, however, no activity increase was observed when the Me material was exposed to a similar treatment before testing. Based on these results and characterization data, we conclude that the catalytically active component of Cu–ZrO2 catalysts for the hydrogenation of LA is reduced Cu particles dispersed on the catalyst surface with strong interaction with the Cu incorporated zirconia support, while the role of Cu in the zirconia lattice is to improve the adhesion of these particles and maintain their dispersion. [ABSTRACT FROM AUTHOR]

In Cu/ZnO/Al2O3 catalysts, the Cu–ZnO interface is crucial for the hydrogenation of CO2 to methanol, which is beneficial to H2 adsorption and CO2 activation. In this research, a series of Cu/ZnO/Al2O3 catalysts (named CZA-X-Y, X is the sample number and Y is the sample state) with different Cu–ZnO interface contents were prepared by adjusting the components of zinc-malachite. The CZA-2-R catalyst, which was prepared from zinc-malachite with a zinc substitution amount of 27.13%, had small Cu particle sizes and uniform distribution of Cu and ZnO particles, creating a rich Cu–ZnO interface. As a result, the CZA-2-R catalyst had more catalytic active sites and displayed a good methanol yield of 11.2% as well as a long-term catalytic stability of 120 h. This study proposes a simple and feasible strategy to optimize the commercial Cu/ZnO/Al2O3 catalyst performance from the perspective of Cu–ZnO interface regulation. [ABSTRACT FROM AUTHOR]

Nickel(0) nanoparticles coordinated to NHC ligands bearing N-coordinated cinnamyl moieties were readily prepared by reduction of a [NiCpBr(NHC-cinnamyl)] complex with methyl magnesium bromide. The combination of a strong σ-donor NHC ligand with a π-coordinating appended cinnamyl moiety likely prevents nickel(0) nanoparticle aggregation to larger inactive species, and allows the effective and (Z)-selective semi-hydrogenation of alkynes and ynamides. [ABSTRACT FROM AUTHOR]

Atomically dispersed Pt species supported on Fe2O3 (Pt1/Fe2O3) are successfully constructed by a simple ball milling process. In the selective hydrogenation of cinnamaldehyde (CAL), Pt1/Fe2O3 achieves an excellent cinnamyl alcohol (COL) selectivity of 81.7% at a CAL conversion of 91.2% in pure water medium due to the superior dissociation ability of H2 and preferential adsorption of CAL via C＝O. [ABSTRACT FROM AUTHOR]

The new compounds and potential ligands 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyldiphenlyphosphinite (L1), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyldiethylphosphite (L2), 2-(3,5-di-tert-butyl-1H-pyrazol-1-yl)ethyl-diethylphosphite (L3) and 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyldiethylphosphite (L4) were prepared from the reaction of (3,5-(disubstituted)pyrazol-1H-yl)ethanol and the appropriate phosphine chloride. The phosphinite (L1) and phosphites (L2–L4) and 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L5) were reacted with [Ru(p-cymene)Cl2]2 to afford the ruthenium(ii) complexes [Ru(p-cymene)Cl2(L1)] (1), [Ru(p-cymene)Cl2(L2)] (2), [Ru(p-cymene)Cl2(L3)] (3), [Ru(p-cymene)Cl2(L4)] (4), and [Ru(p-cymene)Cl2(L5)] (5). All ruthenium complexes were characterized by a combination of NMR spectroscopy, elemental analysis and, in selected cases, by single crystal X-ray crystallography. Complexes 1–5 and [Ru(p-cymene)Cl2(L6)] (6) (prepared from 2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L6)) were investigated as catalysts for both transfer and molecular hydrogenation of acetophenone to 1-phenylethanol. At 80 °C the percent conversion of acetophenone in transfer hydrogenation was moderate to high over 10 h (42–87%); for molecular hydrogenation acetophenone, conversions were as high as 98% in 6 h. [ABSTRACT FROM AUTHOR]

The ever-increasing industrial demands for nylon-6 and nylon-66 and the more and more stringent regulations on particulate emission in exhaust gases necessitate the development of an energy-efficient and environment-friendly method for saturation hydrogenation of benzene and its derivatives. However, the hydrogenation of benzene is usually conducted at a high temperature and/or under high H2 pressure, which is energy-consuming and of low environmental safety. Here, we prepared amorphous Ru–B/MIL-53(Al, Cr, and AlCr) catalysts via the wetness impregnation–chemical reduction method, which were comprehensively characterized by a combination of techniques. We found that the Ru–B/MIL-53 catalysts could catalyse the hydrogenation of benzene to cyclohexane under mild reaction conditions of 30 °C and 1.0 MPa of H2 with high efficiency, among which the Ru–B/MIL-53(AlCr) catalyst exhibited the highest turnover frequency (TOF) in terms of benzene of 6.4 s−1. Moreover, this catalyst showed good recyclability and high activities in the hydrogenation of toluene, o-xylene, m-xylene, p-xylene, and mesitylene as well, which shows promise for the application of the Ru–B/MIL-53 catalysts in the industrially important and environmentally desirable hydrogenation reaction of benzene and its derivatives. [ABSTRACT FROM AUTHOR]

Flower-like ruthenium–copper (RuCu) nanodendrites were readily synthesized by RuCl3·xH2O and CuCl with oleylamine as the reducing agent, stabilizer and solvent. The nanodendrites contained various small particles and demonstrated efficient catalytic ability in the hydrogenation of p-nitrophenol as a model reaction. Notably, by adding β-cyclodextrin, the reaction rate can be greatly enhanced. [ABSTRACT FROM AUTHOR]

A series of ruthenium(ii) complexes with three novel PNX-type pincer ligands is reported, in which X denotes a heterocyclic donor group (PNX = Ph2PCH2CH2N(H)CH2-X, X = 2-pyridyl, 2-furanyl, 2-thiophenyl or 2-pyrrolyl). The reaction of [(Ph3P)3RuCl2] with one equivalent of ligand leads to the trans-dichloro complexes [(PNX)RuCl2(PPh3)] (1–4) for all ligands, whereas the complexation of [(Ph3P)3Ru(H)(Cl)(CO)] results in different types of complexes. The variation of the heterocyclic donor group is in line with different binding properties and a labilization of this group. Investigations on the catalytic activity of different types of ruthenium(ii) complexes in hydrogenation and dehydrogenation reactions reveal that more labile bound heterocycle donors result in a decrease of catalytic productivity and activity. [ABSTRACT FROM AUTHOR]

The mimic of hydrogenases has unleashed a myriad of bifunctional catalysts, which are widely used in the catalytic hydrogenation of polar multiple bonds. With respect to ancillary ligands, the bifunctional mechanism is generally considered to proceed via the metal–ligand cooperation transition state. Inspired by the interesting study conducted by Hanson et al. (Chem Commun., 2013, 49, 10151), we present a computational study of a distinctive example, where a CoII-PNP catalyst with an ancillary ligand exhibits efficient transfer hydrogenation through a non-bifunctional mechanism. Both the bifunctional and non-bifunctional mechanisms are discussed. The calculated results, which are based on a full model of the catalyst, suggest that the inner-sphere non-bifunctional mechanism is more favorable (by ∼11 kcal mol−1) than the outer-sphere bifunctional mechanism, which is in agreement with the experimental observations. The origin of this mechanistic preference of the CoII-PNP catalyst can be attributed to its preference for the square planar geometry. A traditional bifunctional mechanism is less plausible for CoII-PNP due to the high distortion energy caused by the change in electronic configuration with the varied ligand field. Considering previous studies that focus on the development of ligands more often, this computational study indicates that the catalytic hydrogenation mechanism is controlled not only by the structure of the ligand but also by the electronic configuration of the metal center. [ABSTRACT FROM AUTHOR]

Metal–ligand cooperativity (MLC) is an established strategy for developing effective hydrogenation and dehydrogenation catalysts. Metal–metal cooperativity (MMC) in bimetallic complexes is not as well understood, and to date has had limited implementation in (de)hydrogenation. Herein we use (de)hydrogenation processes as a platform to examine modes of cooperativity, with a particular focus on catalytic mechanisms. We investigate how lessons learnt from the extensive development of metal–ligand cooperative catalysts can aid the ongoing development of metal–metal cooperative catalysts. [ABSTRACT FROM AUTHOR]

An understanding of the essential roles in adiponitrile hydrogenation is a significant factor in designing promising nickel catalysts. A series of Ni/Al2O3 catalysts have been synthesized by the deposition–precipitation method and used for the selective hydrogenation of adiponitrile. The formation of the Ni compositions and the chemical structures of the catalysts were modulated by the assisting precipitators. Characterization, including XRD, N2 adsorption–desorption, TEM, XPS, H2-TPD and NH3-TPD, were carried out. Smaller particles could be obtained via fast deposition of Ni2+ using NaOH in Ni/Al2O3–OH, or uniform crystal seeds using urea in Ni/Al2O3–U. The use of a strong alkali, and the formation of nickel hydroxide, facilitated the generation of Ni0 with a better H2 activation ability. Meanwhile, a huge number of nickel species in various oxidative states and strong acidity were simultaneously generated in Ni/Al2O3–U, leading easily to the cycloaddition by-products. A kinetics study revealed that adiponitrile hydrogenation is a second-order reaction with respect to adiponitrile. The number of Ni0 active sites and acid sites could be balanced via different precipitation and crystallization methods. The yield of 1,6-hexanediamine reached 75.0% at 90 °C with 20 wt% Ni/Al2O3–OH. [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]

The hydrogenation of carbon dioxide to methanol is perceived as an effective way to mitigate global warming and drive fossil-fuel companies towards sustainable energy sources. In this study, a series of Cu/ZnO–CeO2 catalysts were prepared by a co-precipitation method, and the effect of the CeO2 content on the catalytic performance of the Cu/ZnO–CeO2 catalysts for the hydrogenation of CO2 to CH3OH was analysed. The physicochemical properties of the catalysts were investigated using XRD, H2-TPR, CO2-TPD, BET, XPS, TEM, and DRIFTS. The CZC-3 catalyst (CZC stands for Cu/ZnO–CeO2 catalyst and 3 indicates a 30% CeO2 content) had the best catalytic activity at 280 °C in a 3 MPa CO2/H2 (1/3) atmosphere, exhibiting a CO2 conversion rate of 15.6% and a methanol yield of 10.06%. More dispersed CuO species and oxygen vacancies were detected on the CZC-3 catalyst, leading to good activation of H2 and CO2, respectively. In situ DRIFTS results for the catalysts showed that the hydrogenation of CO2 to methanol over Cu/ZnO–CeO2 catalysts occurs via the formate pathway. The CeO2-rich Cu/ZnO–CeO2 catalyst facilitated the conversion of formate to CH3OH, and the presence of a large number of intermediate species on the surface of the CZC-3 catalyst greatly contributed to its catalytic performance for CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

Sol–gel method was used to prepare Ni12P5/N-doped carbon and amorphous Ni–P–C materials where the dried gel precursors were heated under N2 atmosphere in a tube furnace. By using ethylene diamine tetraacetic acid (EDTA) as the chelating agent, Ni12P5/N-doped carbon catalysts can be obtained when the heating temperatures were 700 °C and 800 °C. The Ni12P5/N-doped carbon nanomaterial heated at 800 °C exhibited high catalytic performance toward the hydrogenation reduction reaction of 4-nitrophenol (4-NP) using NaBH4 as the reducing agent. Pseudo first-order kinetics of the reaction can be observed, where catalytic activity parameters were 450.0 s−1 g−1 and 54.5 s−1 g−1 when the molar ratios of NaBH4 : 4-NP were 1000 : 1 and 100 : 1, respectively. When EDTA was replaced by ethylene glycol, amorphous Ni–P–C materials could be obtained when the heating temperatures were 350 °C, 450 °C, 550 °C, 600 °C and 700 °C. Unexpectedly, all the amorphous materials had desirable catalytic performances toward the hydrogenation of 4-NP. However, the kinetics of the reaction was pseudo zero-order over the amorphous catalysts. Our results provide new insight into the design of useful catalysts toward the hydrogenation reactions of 4-NP via the sol–gel method. [ABSTRACT FROM AUTHOR]

Hydrogenation reactions are an important process in today's chemical industry. Typically, hydrogenation reactions involve the removal of an unsaturated bond in olefins or other polyenes via thermal catalysis using hydrogen. As hydrogenation reactions are often carried out at temperatures up to several hundred degrees, they require significant energy input which typically comes from burning fossil fuels. In order to conserve fossil fuels and reduce CO2 emissions, researchers are now developing photothermal catalysts for hydrogenation reactions, which harness concentrated sunlight to achieve the required reaction temperatures or introduce sunlight into thermal-driven reaction systems to reduce the reaction temperatures. Photothermal catalysts thus need to be able to efficiently absorb sunlight, whilst also being able to drive the desired hydrogenation reaction with high activity and selectivity. In this review, we summarize recent research aimed at the development of photothermal catalysts for CO2/CO hydrogenation and alkene/alkyne/aromatic hydrogenation. Particular emphasis is placed on uncovering the reaction mechanisms at the molecular level, which in turn guides the rational design of photothermal catalysts with better performance. [ABSTRACT FROM AUTHOR]

Fe–Mn/Al2O3 catalysts were prepared via a co-precipitation procedure and used for light olefin production via a CO hydrogenation reaction. The effect of preparation parameters including the precipitation ageing time, pH and temperature on the catalytic performance has been investigated. The ageing time was changed from 60 to 300 min, the precipitation pH was changed from 6.5 to 10.5 and the precipitation temperature was investigated in the range of 40–80 °C. Modeling and optimization processes were performed using response surface methodology (RSM). Polynomial equations for each response were successfully fitted to the experimental data. According to the optimization results the best preparation conditions were found to be aageing time = 160 min, pH = 8.78 and precipitation temperature = 74.16 °C. At these optimized conditions the maximum selectivity toward (C2–C4) light olefins and CO conversion% and minimum selectivity toward methane were achieved. The effect of the preparation parameters was also investigated on the various surface reaction rates. Catalyst characterization was performed using XRD, BET, TGA, DSC and SEM. [ABSTRACT FROM AUTHOR]

Supported Pt catalysts have been extensively investigated for CO2 hydrogenation with methane and CO as the principal products. In this work, a Pt/In2O3 catalyst prepared with decomposition precipitation was tested for CO2 hydrogenation to methanol. The Pt/In2O3 catalyst exhibited a highly improved activity towards CO2 hydrogenation, with methanol selectivity of ca. 100% at temperatures below 225 °C, 74% at 275 °C and 54% at 300 °C, respectively, compared to the pure In2O3 catalyst. This represents the highest methanol selectivity reported on Pt catalysts for CO2 hydrogenation. The stability of the Pt/In2O3 catalyst at elevated temperatures has also been higher than that of the pure In2O3 catalyst, indicated by the methanol formation rate decreasing only to 95% of the initial rate after 5 h in the reaction stream and remaining largely constant thereafter. In contrast, the pure In2O3 catalyst loses 20% of the initial methanol formation rate after 9 h in the reaction stream. The characterization of the catalysts confirms that the Pt nanoparticles are well dispersed on In2O3 with a particle size below 3 nm. The strong metal–support interaction (SMSI) between Pt and In2O3 improves the stability of the catalyst and prevents the over-reduction of In2O3. The synergy between the supported Pt nanoparticles and In2O3 balances the hydrogen activation and the density of the surface oxygen vacancies in In2O3, resulting in the high activity for CO2 hydrogenation and enhanced stability of the Pt/In2O3 catalyst. [ABSTRACT FROM AUTHOR]

γ-Valerolactone (GVL) and 1,4-pentanediol (1,4-PDO) are value-added chemicals that can be produced from levulinic acid/ester via hydrogenation coupled with acid/base-catalyzed reactions. In this study, we demonstrate that the Cu-based catalysts produced via the hydrotalcite precursors with tunable distribution of acidic and basic sites could, according to the requirement of the target products, effectively tune the production of GVL or to 1,4-PDO from levulinic acid/ester. The abundant Brønsted acid sites over the CuAl catalyst suppressed the opening of the ring of GVL, achieving a higher GVL selectivity while inhibiting 1,4-PDO formation. The introduction of Mg species to the catalyst significantly increased the abundance of the basic sites on the surface of the catalyst, which was essential for the selective conversion of GVL to 1,4-PDO via the opening of the ring structure of GVL, the rate-determining step in the conversion from levulinic acid/ester to 1,4-PDO. In addition, the CuMgAl catalyst showed a much superior catalytic stability to the CuMg or CuAl catalyst due to the more stable crystal structure, the more developed porous structure, the higher dispersion of the Cu species and the higher capability to suppress the growth of metallic Cu species under hydrothermal conditions. [ABSTRACT FROM AUTHOR]

This review summarises the most recent advances in Ir–NHC catalysis while revisiting all the classical reactions in which this type of catalyst has proved to be active. The influence of the ligand system and, in particular, the impact of the NHC ligand on the activity and selectivity of the reaction have been analysed, accompanied by an examination of the great variety of catalytic cycles hitherto reported. The reaction mechanisms so far proposed are described and commented on for each individual process. Moreover, some general considerations that attempt to explain the influence of the NHC from a mechanistic viewpoint are presented at the end of the review. The first sections are dedicated to the most widely explored reactions that use Ir–NHCs, i.e., hydrogenation and transfer hydrogenation, for which a general overview that tries to compile all the Ir–NHC catalysts hitherto reported for these processes is provided. The next sections deal with hydrogen borrowing, hydrosilylation, water splitting, dehydrogenation (of alcohols, alkanes, aminoboranes and formic acid), hydrogen isotope exchange (HIE), signal amplification by reversible exchange and C–H bond functionalisation (silylation and borylation). The last section compiles a series of reactions somewhat less explored for Ir–NHC catalysts that include the hydroalkynylation of imines, hydroamination, diboration of olefins, hydrolysis and methanolysis of silanes, arylation of aldehydes with boronic acids, addition of aroyl chlorides to alkynes, visible light driven reactions, isomerisation of alkenes, asymmetric intramolecular allylic amination and reactions that employ heterometallic catalysts containing at least one Ir–NHC unit. [ABSTRACT FROM AUTHOR]

The article discusses a study that examined the recoverable catalyst for hydrogenation and Suzuki reaction of palladium supported on hollow magnetic mesoporous spheres. Topics discussed include the development of a high-performance palladium catalyst by the covalent binding of a Schiff base ligand and high activity in hydrogenation and Suzuki coupling reaction.

Oxidation and hydrogenation catalysis plays a crucial role in the current chemical industry for the production of key chemicals and intermediates. Because of their easy separation and recyclability, supported catalysts are widely used in these two processes. Layered double hydroxides (LDHs) with the advantages of unique structure, composition diversity, high stability, ease of preparation and low cost have shown great potential in the design and synthesis of novel supported catalysts. This review summarizes the recent progress in supported catalysts by using LDHs as supports/precursors for catalytic oxidation and hydrogenation. Particularly, partial hydrogenation of acetylene, hydrogenation of dimethyl terephthalate, methanation, epoxidation of olefins, elimination of NOx and SOx emissions, and selective oxidation of biomass have been chosen as representative reactions in the petrochemical, fine chemicals, environmental protection and clean energy fields to highlight the potential application and the general functionality of LDH-based catalysts in catalytic oxidation and hydrogenation. Finally, we concisely discuss some of the scientific challenges and opportunities of supported catalysts based on LDH materials. [ABSTRACT FROM AUTHOR]