Catalytic Activity In Benzene Hydrogenation Research Articles

Effect of ruthenium nickel bimetallic composition on the catalytic performance for benzene hydrogenation to cyclohexane

For bimetallic catalysts, the composition of each metal component has a crucial effect on their catalytic performance. In this work, the Ni/Ni(OH)2/C sample is synthesized at room temperature (RT) by a simple hydrazine hydrate reduction method using carbon black as support, and then Ru–Ni/Ni(OH)2/C is prepared via galvanic replacement reaction based on Ni/Ni(OH)2/C. The Ru–Ni/C catalyst can be obtained when Ru–Ni/Ni(OH)2/C is annealed in N2 at 380°C. The different compositions of Ru–Ni bimetallic catalysts are successfully controlled by adjusting the addition amount of aqueous RuCl3 solution during the galvanic replacement process. The RuxNiy/C catalysts (the subscripts represent atomic ratios) are evaluated by the reaction of the hydrogenation of benzene to cyclohexane and the experimental results reveal a strong correlation between the catalytic activity for benzene hydrogenation and Ru/Ni atomic ratios. The Ru0.56Ni0.44/C catalyst exhibits the highest catalytic performance among the RuxNiy/C catalysts in this work. The characterizations of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), high resolution transmission electron microscope (HRTEM) and EDS-elemental mapping for the Ru0.56Ni0.44/C catalyst demonstrate that the nanostructure of Ru-on-Ni/NiO nanoparticles can improve its catalytic properties.

Preparation of two-dimensional NiO/graphene composite and superior catalytic activity in benzene hydrogenation

Highly dispersed NiO/graphene composite material with the size of about 3–4nm nanoparticles (NPs) and the high specific surface area of 244.2m2g−1 is synthesized by using reduced graphene oxide (RGO) as template. The unique two-dimensional structure of graphene plays a crucial role for keeping the Ni species with a nanosheet structure during the solvothermal process. The prepared NiO/graphene composite exhibits superior catalytic activity in benzene hydrogenation. The enhanced catalytic performance can be attributed to steadily dispersed NiO NPs and the strong interactions between NiO NPs and RGO.

Decoration of Co/Co3O4 nanoparticles with Ru nanoclusters: a new strategy for design of highly active hydrogenation

Ru/Co/Co3O4/C (Ru nanoclusters-on-Co/Co3O4 nanoparticles) shows unexpected catalytic activity for benzene hydrogenation via the synergetic effect of Ru, Co and Co3O4 sites.

A high acid mesoporous USY zeolite prepared by alumination

A high-acidity HUSY zeolite with mesoporous structure was prepared by alumination with a dilute aqueous NaAlO2 solution and characterized by XRD, N2 adsorption, IR framework vibration and 29Si MAS NMR methods. The results indicated the extra-framework aluminum was reinserted into the tetrahedral framework through isomorphic substitution of framework Si (0Al) sites by Al ions, whereas the crystal and micropore structure were unaltered. FTIR spectra of hydroxyl vibrations and pyridine adsorbed on realuminated zeolites showed that the number of Bronsted acid sites and strong Lewis acid sites increased whereas weak Lewis acid sites decreased twice. The mesoporous structure composed of inter-and intra-crystalline pores in the aluminated HUSY increased the external surface area of the zeolite, improving accessibility of molecules to the active sites and enhancing its catalytic ability. The realuminated HUSY zeolite supported with Ru catalyst exhibited a higher catalytic activity for benzene hydrogenation than the parent HUSY zeolite; the reaction rate in comparison to the mesozeolite increased by 5.5 times.

Polyoxomolybdate-Stabilized Ru0 Nanoparticles Deposited on Mesoporous Silica as Catalysts for Aromatic Hydrogenation

We use polyoxometalates as precursors for the preparation of heterogeneous catalysts. In the starting molecular precursor [{Ru(C6Me6)}(2)Mo5O18{Ru(C6Me6)(H2O)}], three ruthenium arene fragments are supported on a formally lacunary Lindqvist-type polyoxomolybdate. This species was introduced by incipient wetness impregnation into the porosity of a SBA-15-type mesoporous silica. The evolution of the system under reducing atmosphere is followed by several methods, such as temperature-programmed reduction (TPR), Raman, and X-ray absorption spectroscopy (XAS). The results indicate that the polyoxometalate structure is retained after grafting on silica and allows the stabilization of Ru(0) nanoparticles after reduction. The resulting system exhibits interesting catalytic activity in benzene hydrogenation.

Layered nanocomposites based on molybdenum disulfide and hydroxy-Al, Cr and CrAl oligocations: Characterization and catalytic activity in benzene hydrogenation to cyclohexane

A series of layered nanocomposites are constructed from MoS 2 layers and hydroxy-Al, Cr and mixed CrAl oligocations with the interlayer expansions of 5.86–8.86 Å. The composites with good crystallinity exhibit good catalytic activity and durability in the hydrogenation reaction of benzene into cyclohexane . Layered nanocomposites were prepared utilizing the exfoliation and restacking properties of Li x MoS 2 under mild conditions and characterized by X-ray powder diffraction, differential scanning calorimetry and BET surface measurements. The intercalated hydroxy-Al, Cr and mixed CrAl oligocations made the MoS 2 host have interlayer expansions of 5.86–8.86 Å. The less steric hindrance and the elevated ratio of rim to edge sites make the as-prepared molybdenum disulfide composites have good catalytic activity in the benzene hydrogenation into cyclohexane. It has been shown that a material with good crystallinity exhibits good durability in the reaction.

Effect of different treatments on Aerosil silica-supported Pd nanoparticles produced by ‘controlled colloidal synthesis’

Pd nanoparticles were prepared by ‘controlled colloidal synthesis’ (CCS) using aerosil silica support. On SiO2, 1–2 nm thick ethanol-rich adsorption layer in ethanol–toluene and ethanol–water mixtures was formed into which Pd(II) ions diffused and were reduced there by ethanol. Using Pd(II)-acetate precursor in an ethanol–toluene mixture (sample G1) and PdCl2 precursor in an ethanol–water mixture (sample G2), palladium particles of 7.0 and 8.8 nm size, respectively, were produced. Effects of treatments in air and hydrogen were studied on the Pd/SiO2 samples. The Pd particles showed a twofold/threefold increase in the catalytic activity in benzene hydrogenation after treatment in air at 573 K. The activity increase cannot be explained by a change in the particle size as indicated by transmission electron microscopy (TEM) and CO chemisorption data. Augmentation of turnover number is interpreted by the removal of carbonaceous residues and by the restructuring of the surface caused by carbon removal followed by PdO/Pd transition in the subsequent hydrogen treatment.

Preparation, Characterization, and Catalytic Activity of Molybdenum Carbide or Nitride Supported on Platinum Clusters Dispersed in EMT Zeolite

Bimetallic Pt–Mo catalysts were prepared by vapor deposition of Mo(CO)6 onto nanometer size platinum particles previously dispersed on EMT zeolite. Subsequent decomposition of the Mo precursor formed a supported molybdenum carbide phase whereas reaction of the precursor with ammonia formed a supported nitride phase. Results from high-resolution transmission electron microscopy and X-ray absorption spectroscopy at the Mo K and Pt LIII edges showed conclusively that highly dispersed particles containing both transition metals were synthesized by the vapor deposition method. Coverage of Pt by Mo suppressed both the total capacity for dihydrogen chemisorption and the catalytic activity for benzene hydrogenation. However, compared to monometallic Mo carbide or nitride clusters supported on EMT zeolite, the bimetallic catalysts were much more active in the catalytic reactions of n-heptane at 623 K. The low thickness of the carbide or nitride phase (about 0.3 nm) allowed for a synergistic influence of the Mo phase on the small areas of exposed Pt and/or a direct activation of the nitride or carbide for catalysis.

Synthesis, characterization and activity of Ru/SiO 2 catalysts prepared by the sol-gel method

The preparation of ruthenium catalysts by the sol-gel method is described. The preparation consists of adding the active metal to a sol which, by hydrolysis and codensation reactions turns into a gel. The catalytic activity for benzene hydrogenation shown by these catalysts is higher than that of catalysts prepared by impregnation of a commercial silica. A superior resistance to catalytic autodeactivation is observed for catalysts prepared by this method.

X‐Ray Photoelectron Spectroscopy of Sulfur Containing Ni/SiO2 Catalysts

AbstractAttempts were made to regenerate two Ni/SiO2 catalysts which were exposed to sulfur‐containing compounds. Attempted regeneration was by oxidation followed by reduction. The amount of sulfur present after these treatments was followed by chemical analysis and X‐ray photoelectron spectroscopy. Oxidation and reduction was successful in removing a large part of the sulfur but catalytic activity for benzene hydrogenation could not be restored. The XPS data indicate that the small amounts of sulfur which remained after treatment in hydrogen were located largely in the bulk rather than at the surface of the nickel particles.

Influence of metal-support interactions on the dispersion, distribution, reducibility and catalytic activity of Ni/SiO 2 catalysts

The influence of metal-support interactions on the dispersion, distribution, reducibility and catalytic activity for benzene hydrogenation of Ni/Si0 2 catalysts, prepared by impregnation or deposition-precipitation, was studied. Weak interact-ions were observed for the former; the latter technique gave rise to strong inter-actions. Nickel contents were from 6–9 wt%. The impregnated precursor featured nickel evenly distributed between the internal (pores) and external surface of the support. Direct reduction did not noticeably change the distribution and a Ni/SiO 2 catalyst formed in which the active phase was finely divided and evenly distributed. Calcination of this precursor caused migration of the nickel to the external surface with the formation there of large crystallites of NiO. The pre-cursor prepared by deposition-precipitation, consisted of nickel hydro-silicate deposited uniquely on the external surface and in the pore mouths. Calcination or reduction of this material did not noticeably change the distribution, but high dispersion was observed in both cases. The stability of catalysts prepared by this technique is discussed in terms of interaction between nickel and silica.

Modification of the catalytic and chemisorptive properties of Pt/SiO2 catalysts by high temperature reduction and restoration by O2−H2 treatments

The reduction of Pt/SiO2 at 1100 K results in a decrease of the quantity of absorbed hydrogen and of the catalytic activity in benzene hydrogenation, ethane hydrogenolysis and neopentane isomerization, which cannot be accounted for by metal sintering. O2 treatment followed by reduction at moderate temperature restores the usual properties of the catalyst. This behavior is similar to that observed on Pt/TiO2 catalysts, the difference lying in the temperature at which the phenomenon appears.

Benzene hydrogenation on platinum-tin bimetallic catalysts

Various catalysts were prepared by impregnating a commercial alumina with solutions containing the complex dichlorobis(trichlorostannato)platinate (II). [Pt Cl2 (SnCl3)2]2−. After reduction, 1–20 fold variations in the catalytic activity in benzene hydrogenation were observed in direct proportion to the stability of the complex in the impregnating solution.