Pt Catalysts For Hydrogenation Research Articles

Engineering acidic and Pt sites on WO3- doped H-mordenite supported Pt catalyst for hydrogenation of γ -valerolactone to methyl tetra hydrofuran

The selective hydrogenation of gamma valerolactone (herein after GVL) into 2-methyl tetra hydrofuran (herein after MTHF) was studied over the different tungsten oxide-loaded Pt-doped H-Mordenite catalysts in a vapour phase continuous flow reactor. These catalysts were characterized by XRD, N2 adsorption-desorption analysis, SEM, TEM, FT-IR, Raman, XPS, TPR, NH3-TPD and pyridine adsorbed FT-IR analysis. XRD analysis result suggests that the tungsten oxide was well dispersed at low tungsten oxide loadings and, the tungsten oxide crystallites were formed at higher tungsten oxide loadings and the crystalline structure related to H-mordenite was retained for all the synthesised samples. The nitrogen adsorption-desorption analysis supported this result well. The TEM analysis confirms nano-sized platinum and tungsten oxide formation at 2Pt/10W-HM samples. The ammonia TPD analysis results suggested that all the samples possess weak and strong acidic sites and the amount and strength of acidic sites varies among the samples. The Pyridine adsorbed FT-IR results suggested that all the sample possesses mainly lewis acidic sites. These catalysts were evaluated for synthesising MTHF from GVL under different reaction conditions. Among the various synthesised catalysts studied, the 2 wt% Pt/10W-HM catalyst was identified as an effective catalyst with the 97 % conversion of GVL and the 98 % selectivity of MTHF. The higher catalytic performance depended on the distribution of surface tungsten oxide species along with the suitable acidic properties of the supported system.

Development of Nickel- and Magnetite-Promoted Carbonized Cellulose Bead-Supported Bimetallic Pd-Pt Catalysts for Hydrogenation of Chlorate Ions in Aqueous Solution.

Cellulose grains were carbonized and applied as catalyst supports for nickel- and magnetite-promoted bimetallic palladium- and platinum-containing catalysts. The bimetallic spherical aggregates of Pd and Pt particles were created to enhance the synergistic effect among the precious metals during catalytic processes. As a first step, the cellulose bead-based supports were impregnated by nitrate salts of nickel and iron and carbonized at 973 K. After this step, the nickel was in an elemental state, while the iron was in a magnetite form in the corresponding supports. Then, Pd and Pt particles were deposited onto the supports and the catalyst surface; precious metal nanoparticles (10–20 nm) were clustered inside spherical aggregated particles 500–600 nm in size. The final bimetallic catalysts (i.e., Pd–Pt/CCB, Pd–Pt/Ni–CCB, and Pd–Pt/Fe3O4–CCB) were tested in hydrogenation of chlorate ions in the aqueous phase. For the nickel-promoted Pd–Pt catalyst, a >99% chlorate conversion was reached after 45 min at 80 °C. In contrast, the magnetite-promoted sample reached an 84.6% chlorate conversion after 3 h. Reuse tests were also carried out with the catalysts, and in the case of Pd–Pt/Ni–CCB after five cycles, the catalytic activity only decreased by ~7% which proves the stability of the system.

Synergism of Pt nanoparticles and iron oxide support for chemoselective hydrogenation of nitroarenes under mild conditions

An efficient and low-cost supported Pt catalyst for hydrogenation of niroarenes was prepared with colloid Pt precursors and α-Fe2O3 as a support. The catalyst with Pt content as low as 0.2 wt% exhibits high activities, chemoselectivities and stability in the hydrogenation of nitrobenzene and a variety of niroarenes. The conversion of nitrobenzene can reach 3170 molconv h−1 molPt−1 under mild conditions (30 °C, 5 bar), which is much higher than that of commercial Pt/C catalyst and many reported catalysts under similar reaction conditions. The spatial separation of the active sites for H2 dissociation and hydrogenation should be responsible for the high chemoselectivity, which decreases the contact possibility between the reducible groups of nitroarenes and Pt nanoparticles. The unique surface properties of α-Fe2O3 play an important role in the reaction process. It provides active sites for hydrogen spillover and reactant adsorption, and ultimately completes the hydrogenation of the nitro group on the catalyst surface.

Catalytically Active Sites of Supported Pt Catalysts for Hydrogenation of Tetralin in the Presence of Dibenzothiophene and Quinoline

The catalytic hydrogenation of aromatic molecules, such as tetralin, on platinum supported on amorphous silica−alumina is significantly reduced by the presence of quinoline and/or dibenzothiophene ...

Combined Experimental and Theoretical Investigation on the Selectivities of Ag, Au, and Pt Catalysts for Hydrogenation of Crotonaldehyde

A parallel study on silver, gold, and platinum catalysts with inert silica support is conducted both experimentally and theoretically for the liquid-phase hydrogenation of crotonaldehyde (Me−CH═CH−CH═O). We find that the silver catalyst exhibits a uniquely high selectivity toward C═O hydrogenation and the selectivity remains constant even at the conversion close to 100%. The gold catalyst, however, shows only a moderate selectivity whereas the platinum catalyst has a rather poor selectivity. Such variation in selectivity is interpreted in terms of the varied adsorption geometries of the crotonaldehyde on different metals. According to our density functional calculations of the chemisorptions of crotonaldehyde on selected M19 (M = Ag, Au, and Pt) model clusters and M(111) surface, the most favored adsorption mode for silver is the C═O oxygen atom being σ-bonded on low-coordinated silver atoms, which results in activation of the C═O bond. In contrast, so-called η4 and di-σC═C modes are preferred on Pt surfa...

MCM-41 Overgrown on Y Composite Zeolite as Support of Pd−Pt Catalyst for Hydrogenation of Polyaromatic Compounds

A composite zoelite Y overgrown with a thin layer of mesoporous MCM-41 was prepared as the support of a sulfur-tolerant catalyst for aromatics reduction in diesel cut. This material is different from the mechanical mixture of the two zeolites in many aspects, that is, the FTIR spectra, appearance of particles, distribution of Si and Al, 29Si MAS NMR spectra, acid strength, and amount of acid sites on the surface. The composite was used as the support of a Pd−Pt catalyst for the hydrogenation of polyaromatic compounds, pyrene and naphthalene. Sulfur tolerance of the catalyst was investigated with naphthalene hydrogenation in the presence of thiophene and 4,6-dimethyldibenzothiophene. It was demonstrated that the introduction of mesopores enhances the activity of pyrene hydrogenation and the sulfur tolerance during naphthalene hydrogenation.

Synthesis and activity of the Pt catalyst supported on CNT

Carbon nanotubes (CNT) were obtained by the decomposition of methane on a Ni catalyst supported on Al 2O 3. After the removal of the catalyst materials from CNT, a CNT-supported Pt catalyst was prepared, and this catalyst was characterized by XRD, XPS, and TEM. Activity of the CNT-supported Pt catalyst for hydrogenation of carbon–carbon double bonds at room temperature under the atmospheric pressure of hydrogen was examined. The CNT-supported Pt catalyst showed higher activity than the commercial Pt catalysts supported on activated carbon.

Role of a co-metal in bimetallic Ni–Pt catalyst for hydrogenation of m-dinitrobenzene to m-phenylenediamine

Bimetallic Ni–Pt catalysts supported on carbon were found to give very high turn over frequency numbers and almost complete selectivity to m-phenylenediamine in m-dinitrobenzene hydrogenation as compared to the monometallic nickel catalysts. The XRD and XPS characterization revealed that most of the nickel remains as Ni 2+ in a monometallic catalyst while, the addition of platinum leads to the stabilization of Ni 0 state, in case of bimetallic catalysts.