Catalytic Activity For Selective Hydrogenation Research Articles

Facile Construction of Alloy‐Metal Oxide Interfaces Boosting the One‐Pot Conversion Of Methyl Levulinate to 1,4‐Pentanediol

AbstractIn this work, a series of N‐doped carbon supported FeCo bimetallic catalysts with plentiful FeCo alloy‐FeO interfaces, which are derived from metal‐organic frameworks (MOFs) ZIF‐67, are designed for the one‐pot direct conversion of methyl levulinate to 1,4‐pentanediol. The FeCo alloy‐FeO interfaces are precisely controlled via tuning the reduction temperatures and Fe/Co ratios. The optimal catalyst gives a high 1,4‐pentanediol yield of 90.5 % along with complete conversion of methyl levulinate. These catalysts are carefully characterized by multiple techniques, such as HRTEM, XRD, XPS, NH3−TPD, and Py−IR. It is found that Co presents in electron deficiency caused by the electron transference from Co to Fe in FeCo alloy, which in turn enhances the heterolysis of H2. In addition, plentiful Lewis acid sites derived from interfacial FeO species favour the re‐adsorption and the ring‐opening reaction of γ‐valerolactone. With the synergy between FeCo alloy and Lewis acid, the FeCo alloy‐FeO interfaces exhibit excellent catalytic activity for selective hydrogenation of methyl levulinate to 1,4‐pentanediol.

Microstructure and catalytic properties of rapidly solidified Al-28.5 at% Fe and Al-28.5 at% Co alloys applied for selective hydrogenation of phenylacetylene

The Al 71.5 Fe 28.5 and Al 71.5 Co 28.5 (at.%) melt-spun alloys were examined in terms of microstructure evolution and catalytic response in the semihydrogenation reaction of phenylacetylene to styrene. In the as-spun state ribbons showed a single-phase composition. The Al 71.5 Co 28.5 alloy contained columnar grains of a metastable decagonal quasicrystal, which transformed into hexagonal Al 5 Co 2 and monoclinic Al 3 Co phases after heat treatment at 900 °C. The Al 71.5 Fe 28.5 ribbon had an ordered orthorhombic Al 5 Fe 2 phase structure in both the as-spun and annealed states. The pulverized ribbons revealed considerable catalytic activity for selective hydrogenation of phenylacetylene to styrene. The best results were achieved for the as-spun quasicrystalline Al 71.5 Co 28.5 alloy, showing a conversion rate of above 80% after 2 h reaction time. The selectivity to styrene was 60% for all catalysts. The tested powders retained their phase composition following liquid reaction therefore the proposed materials can be considered for catalytic use. • The Al5Co2 and Al5Fe2 ribbons were prepare by melt spinning methods • Decagonal quasicrystal in the Al5Co2 transforms into Al 5 Co 2 and Al 3 Co after annealing • Ordered orthorhombic Al 5 Fe 2 phase in both the as-spun and the annealed Al5Fe2 ribbons • Catalytic activity of the powdered ribbons in hydrogenation of phenylacetylene • The conversion rate exceeds 80% after 2 h reaction time for quasicrystalline Al5Co2

Facile fabrication of TiO2 with 3D hierarchical structure and its supported Pd catalysts for high catalytic hydrogenation performance of 4-Nitrophenol to 4-Aminophenol

TiO2 with different morphology as supports can lead to different surface properties and catalytic activities of catalysts. Herein, we reported a novel facile evaporation-induced assisted hydrothermal approach to synthesize three-dimensional hierarchical structure TiO2 assembled from needle flakes by using Brij-35 as the morphology-directing agent. The morphology of the prepared TiO2 from flower-like (TiO2-FT), sea urchin-like (TiO2-SUT), to ball-like (TiO2-BT), as well as the size of needle flakes, were controlled by adjusting the amount of Brij-35. These TiO2 supported palladium catalysts were facilely prepared using a green bio-reductive method with Catalpa Fruit extract as reducing agent, where they showed remarkable catalytic activity in selective hydrogenation of 4-nitrophenol by sodium borohydride. Especially, 1 wt%Pd/TiO2-SUT with sea urchin-like exhibited higher reaction rate constant (1.44 min−1) than 1 wt%Pd/TiO2-FT (1.08 min−1) and 1 wt%Pd/TiO2-BT (0.72 min−1). Furthermore, XRD, N2 adsorption–desorption, SEM, TEM, CO-FTIR, XPS and CO chemisorption measurements were performed to study the effects of different surface morphologies on the surface properties of catalysts. It reveals that the high catalytic performance of 1 wt%Pd/TiO2-SUT can be attributed to its specific hierarchical structure and much higher surface area, improving the uniform dispersion of Pd nanoparticles on the support to expose extra active surface Pd atoms (Pd0 species) over 1 wt%Pd/TiO2-SUT.

Two-Dimensional Pd Nanosheets with Enhanced Catalytic Activity for Selective Hydrogenation of Nitrobenzene to Aniline

Two-dimensional (2D) metallic Pd nanosheets were synthesized by an ion-exchange method using PdCl42– and magnesium- and aluminum-based metallic (LDH) as intercalation ion and host material, respect...

Pd/Mo2N-TiO2 as efficient catalysts for promoted selective hydrogenation of 4-nitrophenol: A green bio-reducing preparation method

The addition of a suitable co-catalyst is an encouraging way to enhance the catalytic performance of Pd based catalyst with low content. Herein, we describe an easy synthesis of Mo2N-TiO2 with well-dispersed Mo2N nanoparticles through one pot evaporation-induced self-assembly and nitridation treatment method. Moreover, a green bio-reductive approach with Catalpa Fruit (CF) extract was adopted to fabricate Pd/Mo2N-TiO2 catalysts for promoting selective hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as model reaction. Among these Pd/Mo2N-TiO2 catalysts, 0.8 wt%Pd/Mo2N-TiO2 exhibits significantly high catalytic activity for selective hydrogenation of various nitrophenols and cinnmaldehyde. Importantly, the catalytic activity of the catalyst prepared by the reduction method of the CF extract is higher than that prepared by the reduction method of NaBH4. A serials of characterization, including XRD, N2 adsorption–desorption, TEM, XPS, CO chemisorption and CO-FTIR etc., was carried out to investigate the influence of the prepared method on the surface Pd species and activity. The high performance can be attributed to the specific nanostructure characteristics of the catalyst and the good synergistic effect between Pd and Mo2N, improving the dispersion of Pd nanoparticles atoms and the exposure of more active Pd atoms (surface Pd0 species) on 0.8 wt%Pd/Mo2N-TiO2 due to the CF extract as reductant.

Microstructure and catalytic activity for selective hydrogenation of phenylacetylene of intermetallic Ni70Ga30, Ni70In30, and Ni70Sn30 melt-spun alloys

The Ni70Ga30, Ni70In30, Ni70Sn30 alloys were manufactured by melt spinning technique. The as melt-spun ribbons showed a multiphase microstructure prone to alteration by heat treatment at 800 °C. The average grain size in the as melt-spun ribbons was circa 3–4 μm and it increased after heat treatment; the increase is tenfold in the case of the Ni70In30 ribbon due to its low homologues temperature. The ribbons show strongly developed <100> fiber texture with high concentration of high angle grain boundaries. Martensite microstructure was found in the Ni70Ga30 ribbon. At room temperature all the studied ribbons were found active for selective hydrogenation of phenylacetylene with conversion rates after 4 h reaction time of around 20%. Further improvement of catalytic activity is expected with surface pretreatment, pulverization and increasing of the reaction temperature. Altogether the as melt spun ribbons present an attractive alternative to cold rolled and annealed ribbons and to nanocrystalline intermetallics for application in a range of chemical reactions.

Template-free one-step synthesis of micro-mesoporous CeO2–ZrO2 mixed oxides with a high surface area for selective hydrogenation

Ceria-zirconia oxide materials with a specific surface area ranging from 160 to 240 m2/g and different meso- and micropores ratio were obtained by a simple deposition-precipitation method with urea (DPU), which allows preparation of ceria-zirconia oxides directly in one-step while avoiding the formation of oxo-hydroxo species and further thermal treatment to obtain oxide phases. Moreover, a microwave-assisted DPU method allowed the decrease of the synthesis time from 24 to 3.5 h. The prepared samples were studied by TG-DTA, BET, N2 adsorption, XRD, SEM, and TEM methods. Pt-containing catalysts based on synthesized oxides have shown a high catalytic activity in selective hydrogenation of benzaldehyde, citral, and cinnamaldehyde at room temperature and atmospheric pressure.

Magnetic Fe3O4@SiO2/Pd and Fe3O4@SiO2/Pd‐M (M=Ag, Cu and Zn) Catalysts for Selective Hydrogenation of Phenylacetylene

AbstractMagnetic core‐shell monometallic Fe3O4@SiO2/Pd and bimetallic Fe3O4@SiO2/Pd−M (M=Ag, Cu and Zn) catalysts with low Pd loading were prepared using a modified Stöber method followed by an ion‐exchange technique, and applied to the selective hydrogenation of phenylacetylene. The structure and magnetism of the catalysts were investigated using N2 physisorption, XRD, FT‐IR, ICP‐OES, H2‐TPR, CO chemisorption, DRIFTS, HRTEM and vibrating sample magnetometer. The characterization results showed that the magnetic catalyst had smaller Pd particle size than the non‐magnetic catalyst; the thinner the silica shell of the magnetic catalyst, the stronger the magnetic intensity and hence the smaller the Pd particle size; the PdM alloy was formed for bimetallic catalysts and geometric and electronic effects occur. By comparing the activity and selectivity of different catalysts, it was found that the catalyst with smaller Pd particle size generally exhibited a higher apparent activity and selectivity to styrene but a lower specific activity, demonstrating the structure‐sensitive catalytic activity for selective hydrogenation of phenylacetylene on the magnetic Pd supported catalysts. In addition, all the bimetallic catalysts displayed higher selectivity but lower activity than the monometallic catalysts as a result of the presence of the PdM alloy. In particular, a Fe3O4@SiO2/Pd−Zn catalyst with the shell thickness of about 80 nm and the Pd and Zn loadings of 0.31 and 1.79 wt%, respectively, showed the best selectivity to styrene, being 86.1 % at above 99.5 % conversion of phenylacetylene. Furthermore, this catalyst maintained its activity and selectivity even after being reused ten times.

Microemulsion-controlled synthesis of one-dimensional Ir nanowires and their catalytic activity in selective hydrogenation of o-chloronitrobenzene.

Ultrathin iridium nanowires have been synthesized using a convenient method mediated by microemulsion via oriented attachment growth for the first time. The interconnected polycrystalline Ir nanowires possess high aspect ratio, small average diameter of 2 nm, and length up to several hundred nanometers. The 1D growth of surfactant-encapsulated primary nanoparticles, which is determined by the inherent crystal growth habit and the specific interactions of nanocrystals with surfactant molecules, accounts for the formation of Ir nanowires. The as-prepared Ir nanowires show high activity and selectivity toward the hydrogenation production of industrially valuable chloroaniline from o-chloronitrobenzene. Theoretical evidence based on DFT calculation indicates that H2 could be dissociated more easily and quickly on Ir(100) surface than on Ir(111), accounting for the higher hydrogenation rate over Ir nanowires exposing both (200) and (111) crystal facets rather than only (111) facet for Ir nanoparticles.

Biodiesel production from hempseed oil using alkaline earth metal oxides supporting copper oxide as bi-functional catalysts for transesterification and selective hydrogenation

Alkaline earth metal oxides supporting copper oxide (Cu/AMO) were used as bi-functional catalysts for transesterification and selective hydrogenation to produce biodiesel from highly unsaturated hempseed oil. Cu/AMO catalysts were characterized by XRD, SEM, N2 adsorption, CO2-TPD, H2-TPR, and XPS to reveal the crystal structure, morphology, texture properties, basicity, reducibility, and surface chemical states. The bi-functional catalysts formed alkaline earth metal cuprates and showed strong basic strengths. Cu/SrO catalyst presented much surface copper species, which were reduced to metallic copper after reactions. The effect of the molar ratio of methanol to oil, copper oxide content, hydrogen pressure, and reaction temperature on the catalytic performance was further investigated. Cu/SrO catalyst showed superior catalytic activity for transesterification and selective hydrogenation. Catalytic activity for transesterification is strongly dependant on basic strength and the amount of basic sites of the bi-functional catalysts. The amount of reduced surface copper species of Cu/SrO catalysts made a large contribution to catalytic activity for selective hydrogenation.

Liquid phase selective hydrogenation of furfural on Raney nickel modified by impregnation of salts of heteropolyacids

In this paper, liquid phase selective hydrogenation of furfural on Raney nickel which has been modified by impregnation of salts (including alkali metals, alkaline earth metals, and transition metals) of heteropolyacids (HPAs) having Keggin type structure was studied. Effects of reaction conditions on catalytic activity and selectivity were examined. It has been found that all Raney nickel catalysts modified with salts of HPAs show higher catalytic activity and selectivity than unmodified Raney nickel catalysts; 12-molybdophosphates give the best results among the modifiers. As far as the effect of competitive cations on catalytic properties is concerned, transition metals are better than both alkali metals and alkaline earth metals. Among the transition metal salts, Cu salt is superb in performance. A Raney nickel catalyst on which 7.1% Cu 3/2PMo 12O 40 has been deposited, under reaction conditions of temperature 353 K, hydrogen pressure 2.0 MPa, amount of catalyst 0.5 g, volume of reactant 10 ml and reaction time 1 h, gave a conversion of furfural and selectivity for furfuryl alcohol of as high as 98.1% and 98.5%, respectively. In this work, the salt of HPA only plays the role of a modifying agent rather than acting as a catalyst. This can be inferred from the experimental evidence that salts of HPAs deposited on active carbon showed no catalytic activity in selective hydrogenation of furfural under similar conditions.

Influence of support and of palladium profile in the pellet on the catalytic activity for selective hydrogenation

The metal profile in the pellets does not affect the catalytic activity of palladium supported catalysts during selective styrene hydrogenation. The support, due to different metal-support interactions, modifies the activity.

Synthesis and catalytic activity in selective hydrogenation of palladium complexes anchored in montmorillonite

Functional groups such as diphenylphosphine, triphenylphosphine, and 4-picoline have been intercalated in montmorillonite, a swelling smectite clay; subsequent complexation with palladium has led to syntheses of various interlamellar montmorillionite-anchored palladium(II) complexes. These montmorillonite ligands and their complexes are characterised by elemental analyses, IR, XRD, and ESCA. Diphenylphosphinomontmorillonite-palladium(II) complex ( 4B(ii), the best catalyst of the series for hydrogenation reactions, hydrogenated alkynes to alkenes and to alkanes selectively, yields are quantitative. The internal double bonds are also hydrogenated, but with decreased rate of activity. Catalyst 4B(ii) has shown consistent activity for a number of recycles in the hydrogenation of styrene, and hex-1-ene. Used catalyst was also tested for hydrogenation activity with various organic reactants. The rate of hydrogen absorption is almost the same as that with fresh catalyst under identical conditions. These data indicate that transient homogeneous complex species formed in the pretreatment remain unchanged during the recycles. Catalyst 4B(ii) hydrogenated mono and disubstitued alkynes and alkenes in ethanol. On the other hand, diphenylphosphinite-montmorillonite-palladium(II) complex ( 2B) selectively hydrogenated monosubstituted alkynes and alkenes only under identical conditions. Catalyst 2B, with its lower initial interlamellar spacings, has induced size selectivity as evidenced in the selective hydrogenation of monosubstituted reactants only, because the preferred perpendicular orientation of the transient reactant-palladium complex formed with monosubstituted olefins in the interlayer spacings of montmorillonite requires a space smaller than that expected for disubstituted ones. Easy adjustment of interlayer spacings by the incorporation of complex moieties of different sizes in the interlayers makes montmorillonite a practical alternative to zeolites for inducing size selectivity.

The Polymer-Protected Pd–Pt Bimetallic Clusters Having Catalytic Activity for Selective Hydrogenation of Diene. Preparation and EXAFS Investigation on the Structure

Abstract The colloidal dispersions of the palladium–platinum bimetallic clusters were prepared by refluxing their salts in water/ethanol in the presence of poly(N-vinyl-2-pyrrolidone) under nitrogen. They work as catalysts for partial hydrogenation of diene. The highest activity was achieved by the bimetallic clusters with the molar ratio of Pd/Pt = 4/1, the EXAFS spectra and the TEM photographs of which strongly suggest the alloy formation with a core structure.