Liquid Phase Hydrogenation Of Benzene Research Articles

Catalytic Properties of a Novel Raney-Nickel Foam in the Hydrogenation of Benzene

The catalytic properties of a novel Raney-Nickel mold were investigated in the liquid-phase hydrogenation of benzene and compared to commercially available Raney-Nickel. The novel Raney-Nickel catalyst showed similar activity as the commercial catalyst but facile product/catalyst separation. Furthermore, the novel Raney-Nickel catalyst is recyclable without loss in activity unlike the commercial nickel sponge.

The influence of transition metal ions on the catalytic performance of Ru particles during the liquid phase hydrogenation of benzene to cyclohexene

The influence of some transition metal ions including Fe2+, Ni2+, Cr3+, Mn2+, Zn2+, Cd2+ on the catalytic performance of Ru particles during the liquid phase partial hydrogenation of benzene to cyclohexene was investigated in a titanium autoclave and a stainless steel autoclave. The Ru particles were prepared by the precipitation method. The catalysts were characterized using XRD, BET surface area measurement and XPS. The structure configurations and formation enthalpies of the hydrated metal ions, the complexes of the metal ions with benzene and cyclohexene as well as the complexes of hydrated metal ions with benzene and cyclohexene were optimized and evaluated using quantum chemical calculation methods. It was found that the poisoning effect of the transition metal ions on the catalytic activity of Ru particles only partially obeys the “Maxted rule”. The enhancing effect of the transition metal ions on the cyclohexene selectivity is associated with both the interaction of the metal ions with the active sites on Ru surface and with the tendency of metal ions to form hydrated complexes. In the stainless steel autoclave, the Fe2+, Ni2+ and Cr3+ resulted from the corrosion of the stainless steel have a synergetic effect with Zn2+, leading to a higher selectivity to cyclohexene.

Hydrophilicity Modification of MCM-41 With Zirconia and Supported Ruthenium-Lanthanum for Benzene Hydrogenation to Cyclohexene

Zirconia modified mesoporous molecular sieve MCM-41 supports were prepared by hydrothermal synthesis method, in situ synthesis method and precipitation method. Ruthenium and lanthanum supported on MCM-41 and zirconia modified MCM-41 catalysts were prepared via two solvents impregnation method. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption, and water/benzene static adsorptions techniques. It has been found that Ru-La supported on MCM-41 modified with zirconia by hydrothermal synthesis method (Ru-La/ZrO2-MCM-41-HS) leads to the biggest increase of the hydrophilicity. Ru-La/ZrO2-MCM-41-HS catalyst with the highest hydrophilicity shows the best performance in liquid phase hydrogenation of benzene to cyclohexene.

Effect of alcohols as additives on the performance of a nano-sized Ru–Zn(2.8%) catalyst for selective hydrogenation of benzene to cyclohexene

In liquid phase hydrogenation of benzene, Ru–Zn(2.8%) catalyst (Ru–Zn catalyst with the Zn mass percentage of 2.8%) exhibited the excellent selectivity to cyclohexene for the nano-size effect and the chemisorbed ZnSO4·3(ZnOH)2⋅7H2O salt formed by the promoter ZnO reacting with ZnSO4. It is found that the cyclohexene yield of Ru–Zn(2.8%) catalyst generally increased with the molecular weight of PEG (Polyethylene glycol) in the presence of ZnSO4. PEG-10000 (Polyethylene glycol with the molecular weight of 10,000) as an additive made Ru–Zn(2.8%) catalyst give the highest cyclohexene yield of 62.3% in presence of ZnSO4 for the following two reasons. Firstly, the addition of PEG-10000 in presence of ZnSO4 could make more Zn2+ chemisorbed on the surface of the catalyst. The Zn2+ ions chemisorbed could be beneficial for stabilizing the formed cyclohexene, accelerating the desorption and hindering the re-adsorption of cyclohexene on the surface of the catalyst. Secondly, the PEG-10000 added might form two molecular hydrogen bonds in eight-numbered rings with the cyclohexene in the liquid phase, which could stabilize the cyclohexene in the liquid phase and hinder the re-adsorption. 2g of this catalyst with 0.2g PEG-10000 as an additive pretreated in presence of ZnSO4 gave a selectivity to cyclohexene of 78.6% and the best cyclohexene yield of 64.5% at the benzene conversion of 82.0% at 15min. Moreover, this catalyst had an excellent stability since ZrO2 and PEG-10000 could effectively inhibit the agglomeration of Ru–Zn(2.8%) catalyst.

Partial hydrogenation of benzene catalyzed by Pt/N‐n‐propyl chitosan hybrid membrane

AbstractThe partial hydrogenation of benzene by a Pt nano‐cluster/N‐n‐propyl chitosan hybrid membrane was investigated in this article. Monodispersed Pt nano‐clusters were prepared by the reduction of H2PtCl6 with ethylene glycol under microwave conditions. TEM, FTIR, XRD, 1H‐NMR, and XPS were used to characterize the structure of Pt nano‐particles, N‐n‐propyl chitosan and Pt/N‐n‐propyl chitosan hybrid membrane, respectively. Experimental results showed that Pt/N‐n‐propyl chitosan hybrid membrane catalyst gave a high selectivity for cyclohexene of 85.2% in the liquid phase hydrogenation of benzene, while the selectivity of cyclohexene was only 58.2% over the Pt/chitosan hybrid membrane catalyst. It was worth noting that there was no cyclohexene in the product when the catalyst was only Pt nano‐particles without chitosan hybrid membrane. So the chitosan or modified‐chitosan membranes played an important role in the controlling to the hydrogenation of benzene, and the relationship of the swelling degree and the catalytic activity was discussed in detail. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Selective hydrogenation of benzene to cyclohexene on Ru-based catalysts promoted with Mn and Zn

Abstract Ru-based catalysts promoted with Mn and Zn were prepared by a co-precipitation method. In liquid-phase hydrogenation of benzene, the Ru-Mn-Zn catalysts exhibited superior catalytic performance to the catalysts promoted with Zn or Mn alone. The optimum Mn/Zn molar ratio was determined to be 0.3. With the addition of 0.5 g NaOH, the Ru-Mn-Zn-0.3 catalyst, which was reduced at 150 °C, afforded a cyclohexene selectivity of 81.1% at a benzene conversion of 60.2% at 5 min and a maximum cyclohexene yield of 59.9% at 20 min. Based on characterizations, the excellent performance of Ru-Mn-Zn catalyst was ascribed to the suitable pore structure, the appropriate reducibility and the homogenous chemical environment of the catalyst.

Discrimination of the roles of CdSO 4 and ZnSO 4 in liquid phase hydrogenation of benzene to cyclohexene

CdSO 4 and ZnSO 4 as co-modifiers of RuLa/SBA-15 lead to improved catalysts for the partial hydrogenation of benzene to cyclohexene. Based on the experimental results and theoretical calculations, it is shown that CdSO 4 acts as surface modification, suppressing more the adsorption of cyclohexene than that of benzene, while the function of ZnSO 4 is mainly the stabilization of cyclohexene in the liquid phase, accelerating the desorption as well as hindering the re-adsorption of cyclohexene.

Carbon nanofibers supported nickel catalyst for liquid phase hydrogenation of benzene with high activity and selectivity

Carbon nanofibers (CNFs) prepared by catalytic decomposition of ethylene are used as support for nickel. The CNF support displays a mean diameter of 50–60 nm, lengths up to several tens of micrometers, as highlighted by TEM. The nickel particles have a size distribution from 10 to 20 nm of diameter. This novel Ni/CNFs catalyst displays good catalytic properties in liquid phase hydrogenation of benzene at a reaction temperature of around 180 °C.

Fabrication of a Pt Nano-cluster/Photosensitive Polyimide Hybrid Membrane Reactor and Its Partial Hydrogenation of Benzene

Abstract The partial hydrogenation of benzene by a Pt nano-cluster/photosensitive polyimide (Pt/PSPI) hybrid membrane was investigated. Monodisperse Pt nano-clusters were obtained by microwave-assisted reduction of H 2 PtCl 6 with ethylene glycol. Transmission electron microscopy showed that the average diameter of the Pt nanoparticles was 3.7 nm. The Pt/PSPI hybrid catalyst gave a high selectivity for cyclohexene of 72.4% in the liquid phase hydrogenation of benzene.

Kinetics of liquid-phase benzene hydrogenation on Rh/C

Liquid-phase hydrogenation of benzene was studied over Rh catalyst supported on a carbon carrier sibunit between 13 and 100°C and in a hydrogen pressure range of 20–100 bar. Kinetic data were obtained under mass transfer-free conditions. Similar to gas-phase hydrogenation activity, a maximum with temperature was observed. A kinetic model consistent with thermodynamics was applied for numerical parameter estimation. Good correspondence between the experimental and calculated data was achieved.

Ce-promoted Ru/SBA-15 catalysts prepared by a “two solvents” impregnation method for selective hydrogenation of benzene to cyclohexene

Abstract Ce-promoted Ru/SBA-15 catalysts were prepared by a “two solvents” impregnation method. In liquid-phase hydrogenation of benzene, the Ce-promoted Ru/SBA-15 catalysts exhibited superior catalytic performance to the un-promoted catalyst. The optimum bulk Ce/Ru molar ratio was determined to be 0.25, at which a cyclohexene yield of 53.8% was obtained. Based on characterizations, the beneficial effect of the Ce promoter on the selectivity to cyclohexene was ascribed to the enhancement of the hydrophilicity of the catalyst and to the electron transfer between the Ce(III) species and metallic Ru.

Ru/SBA-15 catalysts for partial hydrogenation of benzene to cyclohexene: Tuning the Ru crystallite size by Ba

Ru–Ba/SBA-15 catalysts with different Ba/Ru molar ratios were prepared by the ‘two solvents’ method, which can readily introduce the active components into the channels of SBA-15. Characterizations revealed that the crystallite size of Ru was tuned smoothly from 3.6 to 7.5 nm by increasing the Ba/Ru ratio from 0.1 to 1.0. In liquid phase hydrogenation of benzene, the maximum yield of cyclohexene was obtained on the Ru–Ba/SBA-15 catalyst with Ru crystallite size of 5.6 nm, which is interpreted as the presence of the highest population of the active sites favorable for the production of cyclohexene on such Ru crystallites.

Palladium cluster filled in inner of carbon nanotubes and their catalytic properties in liquid phase benzene hydrogenation

This is the first report indicating the Pd clusters filled in multi-walled carbon nanotubes (MWNT) as catalyst applied in liquid phase benzene hydrogenation. The treatment of MWNT, filling of metals, the effects of the filling amount of palladium, evaluation of catalytic property, and the comparison with various conventional supports were investigated. The experiment results indicated that the Pd clusters filled in the inner of carbon nanotubes exhibited higher activity than other supports such as Y zeolite and activated carbon. According to various characterizations, the relationship between catalytic activity and the structure of the carrier was briefly discussed.

Partial liquid-phase hydrogenation of benzene to cylohexene on SiO2-immobilized lanthanide (Eu and Yb) catalysts

SiO2-immobilized Eu and Yb catalysts (≡Si–O–Ln–NH2) obtained by the reaction of surface hydroxyl groups on SiO2 with lanthanide metals dissolved in liquid ammonia are active for the partial liquid-phase hydrogenation of benzene to cyclohexene when the reaction was carried out at 423–483 K with hydrogen pressures of 1–5 MPa. Interestingly, only divalent amides are catalytically effective for the partial hydrogenation of benzene.

Liquid phase benzene hydrogenation to cyclohexane over modified Ni–P amorphous catalysts

Four kinds of Ni–P amorphous catalysts, ultrafine Ni–P, Ni–P/SiO 2, Ni–W–P/SiO 2 and Raney Ni–P, were prepared by either the rapid quenching technique, following the alkali leaching, or the chemical reduction with NaH 2PO 2. During the liquid phase hydrogenation of benzene, all these catalysts exhibited higher TOF values than Raney Ni catalyst, owing to their unique amorphous structure. Except for the ultrafine Ni–P, which had extremely low surface active area, all the other Ni–P catalysts also exhibited higher activity per gram Ni than Raney Ni. The crystallization of the Ni–P amorphous catalysts at high temperature caused a considerable decrease in their activities. According to various characterizations, the relationship between catalytic activity and the structure of the as-prepared Ni–P catalysts was briefly discussed.

Liquid phase hydrogenation of benzene to cyclohexene on ruthenium catalysts supported on zinc oxide‐based binary oxides

AbstractA series of binary oxide‐supported ruthenium catalysts with zinc oxide as a component of the support was prepared. Zinc oxide was a major component of the support, the other component was lanthanum oxide, zirconium oxide, chromium oxide, barium oxide, gallium oxide, strontium oxide, calcium oxide or magnesium oxide. Liquid phase hydrogenation of benzene to cyclohexene was studied on these catalysts in a stirred tank reactor at a hydrogen pressure of 2.5–6.0 MPa and 448 K. The reaction was operated in a kinetic‐controlled regime. In order to have high selectivity to cyclohexene, a large amount of water should be present. In addition, the reaction medium should be an alkaline solution. The yield of cyclohexene was in the order: Ru/Ga2O3–ZnO > Ru/La2O3–ZnO > Ru/Cr2O3–ZnO > Ru/ZrO2–ZnO > Ru/MgO–ZnO = Ru/CaO–ZnO = Ru/SrO–ZnO = Ru/BaO–ZnO.Ru/Ga2O3–ZnO demonstrated the highest selectivity and yield of cyclohexene. A model of the low solubilities of reactants in the water film surrounding the catalyst can explain the reaction behavior of the catalyst.© 2001 Society of Chemical Industry

Amorphous Ni-B/γ-Al 2O 3 catalyst prepared in a modified drying approach and its excellent activity in benzene hydrogenation

A two-step dying approach was proposed for the preparation of supported amorphous Ni-B/γ-Al 2O 3 catalyst. After wetness impregnation of NiCl 2 aqueous solution, the catalyst precursor was dried at 343 K first, followed by drying at 383 K before KBH 4 reduction (denoted as Ni-B/γ-Al 2O 3 (LT)). For comparison, the precursor was directly dried at 383 K and reduced by KBH 4 (denoted as Ni-B/γ-Al 2O 3 (HT)). Liquid phase hydrogenation of benzene to cyclohexane was employed as the probe reaction. While X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS) and turnover frequency (TOF) revealed no considerable electronic or structural difference between the active components of these two catalysts, scanning electron micrography (SEM), H 2 chemisorption and XPS intensity analysis demonstrated the higher dispersion of active component in the Ni-B/γ-Al 2O 3 catalyst prepared by the two-step drying approach, which can account for the superior catalytic performance of Ni-B/γ-Al 2O 3 (LT) to Ni-B/γ-Al 2O 3 (HT) in benzene hydrogenation.

Ultrafine Ni–Co–W–B amorphous alloys and their activities in benzene hydrogenation to cyclohexane

Quaternary Ni–Co–W–B amorphous alloys were prepared by chemical reduction of the aqueous solution of nickel and cobalt salts and sodium tungstate with potassium borohydride. The catalytic activities of the as-prepared materials were measured through liquid phase hydrogenation of benzene under moderate pressure. In comparison with Ni–Co–B, the as-prepared Ni–Co–W–B amorphous alloys showed superior activity, attributable to the promoting effect of tungsten on the microstructure of the alloys as revealed by XPS, XRD and DSC measurements.

Analysis of a Two-Phase Perfectly Mixed Reactor under the Condition of a Phase Equilibrium

A mathematical model is formulated for a gas–liquid perfectly mixed flow reactor under the condition that the two-phase flow at the reactor outlet is at thermodynamic equilibrium. The phase equilibrium is calculated using the Redlich–Kwong–Soave equation of state. The set of nonlinear algebraic equations of the model is numerically solved by the efficient algorithm of the homotopy method. The steady-state modes of reactor operation are analyzed for liquid-phase benzene hydrogenation. It is shown that, under isothermal isobaric conditions, there can be a multiplicity of steady-state solutions, which is, on the one hand, due to the nonlinearity of the kinetic law and, on the other, due to the deviation of the properties of the reaction mixture from the properties of an ideal system. The stability of the steady-state solutions is analyzed, and the causes of the multiplicity and instability are explained.

The liquid phase hydrogenation of benzene and substituted alkylbenzenes over a nickel catalyst in a semi-batch reactor

The liquid phase hydrogenation kinetics of benzene, toluene, ethylbenzene and cumene was studied in a three-phase semibatch reactor at pressures of 20–40 bar and at temperatures of 95–140°C. The experimental kinetics was described with a rate equation based on rapid adsorption and desorption steps and slow consecutive hydrogen steps. A pseudo-homogeneous model neglecting the diffusion resistances in the catalyst particles was able to phenomenologically describe the observed kinetics, but numerical simulations showed that there exist significant concentration gradients in the particles. Therefore a complete dynamic heterogeneous model was developed for the reactor and the catalyst particles including the reaction-diffusion process. The kinetic parameters were re-determined using the heterogeneous reactiondiffusion model. The model enables the investigation of the reaction-diffusion effects and the dynamics of the catalyst particles.