Catalytic Hydrogenation Of Benzene Research Articles

Separation of benzene and cyclohexane azeotrope mixture using 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid using extractive distillation

Most of the cyclohexane used for various industrial applications is largely produced through catalytic hydrogenation of benzene and the separation of cyclohexane from the unreacted benzene is industrially significant. However, it is tough to separate cyclohexane from benzene by conventional distillation processes since these components have close boiling points and form an azeotrope mixture. Currently, extractive distillation is commercially used for the separation of cyclohexane from benzene using conventional solvents (entrainers) such as sulfolane, dimethyl sulfoxide, N-formylmorpholine, and N-methylpyrrolidone. However, separating benzene and cyclohexane with extractive distillation with these solvents makes the process complex and consumes high energy. On the other hand, ionic liquids are considered green and potentially environmentally friendly, hence have been attracting attention in replacing conventional solvents (entrainers) in extractive distillation because of their unique properties. In this work, 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) was used for the separation of cyclohexane from benzene using extractive distillation. The performance of [EMIM][EtSO4] was evaluated by measuring the isothermal vapour-liquid equilibrium (VLE) for benzene, cyclohexane, and [EMIM][EtSO4] ternary mixture at 353.15 K. The isothermal VLE was measured using Head Space Gas Chromatography (HS-GC). Moreover, the VLE data was also predicted using COSMO-RS and compared with the experimental values. The addition of [EMIM][EtSO4] eliminated the azeotrope and increased the relative volatilities of benzene and cyclohexane resulting in their separation. The performance of [EMIM][EtSO4] on the benzene and cyclohexane system was compared with dimethyl sulfoxide. The current ionic liquid shows higher relative volatility compared to dimethyl sulfoxide showing this ionic liquid can be used for the separation of benzene and cyclohexane using extractive distillation.

Separation of the cyclohexane-benzene mixture by the extractive distillation process using ethylene glycol as a solvent

The importance of cyclohexane lies in the fact that it is the main precursor for the production of Nylon 6 and Nylon 6.6, two of the most important synthetic fibers. Cyclohexane (CHX) is produced by catalytic hydrogenation of benzene (BZ), where cyclohexane with benzene is obtained as a product. Since CHX and BZ have close boiling temperatures, and similar molecular structures, their separation by conventional binary distillation is complicated. Thus, ethylene glycol (EG) was selected as a solvent in an extractive distillation (ED) process for the separation of the CHX-BZ mixture in Aspen Plus V9®; where the use of ethylene glycol as a solvent allowed us to obtain cyclohexane and benzene with purities of 99.91 mol%. In addition, compared to the extractive distillation with heat integration (EDHI) process that uses [C5(MIM)2][NTf2]2 + H2O as a mass separation agent; the use of EG as a solvent promotes an energy decrease of 41.14%, a saving of 55.07% in the Total Annual Cost (TAC), and a decrease of 72.38% in CO2 emissions. These outcomes underscore the efficacy of ethylene glycol as a suitable solvent in the purification of the cyclohexane-benzene mixture.

Interfacial Self-Assembly in Halloysite Nanotube Composites.

A self-assembly of clay nanotubes in functional arrays for the production of organized organic/inorganic heterostructures is described. These 50-nm-diameter natural alumosilicate nanotubes are biocompatible. Halloysite allows for 10-20 wt % chemical/drug loading into the inner lumen, and it gives an extended release for days and months (anticorrosion, self-healing, flame-retardant, antifouling, and antibacterial composites). The structured surfaces of the oriented nanotube micropatterns enhance interactions with biological cells, improving their capture and inducing differentiation in stem cells. An encapsulation of the cells with halloysite enables control of their growth and proliferation. This approach was also developed for spill petroleum bioremediation as a synergistic process with Pickering oil emulsification. We produced 2-5-nm-diameter particles (Au, Ag, Pt, Co, Ru, Cu-Ni, Fe3O4, ZrO2, and CdS) selectively inside or outside the aluminosilicate clay nanotubes. The catalytic hydrogenation of benzene and phenol, hydrogen production, impacts of the metal core-shell architecture, the metal particle size, and the seeding density were optimized for high-efficiency processes, exceeding the competitive industrial formulations. These core-shell mesocatalysts are based on a safe and cheap natural clay nanomaterial and may be scaled up for industrial applications.

Hydrogenation of biphenyl and isomeric terphenyls over a Pt-containing catalyst

Catalytic hydrogenation of benzene, biphenyl, and ortho-, metha-, and para-isomers of terphenyl over a 3 wt.% Pt/C at 180 °C and 70 atm was studied. The directions of hydrogenation of each substrate were revealed. Relationships between structures of the substrate and hydrogen consumption rates were found. It was shown that hydrogenation rate decreases on going from benzene to terphenyl and with increasing degree of the substrate hydrogenation. Hydrogenation rate of terphenyl isomers decreases in the following order: p-terphenyl > > m-terphenyl > o-terphenyl.

Benzene and Cyclohexane Separation Using 1-Propanenitrile-3-butylimidazolium Dicyanamide Ionic Liquid

Cyclohexane is mainly produced by catalytic hydrogenation of benzene, and the separation of unreacted benzene is very important process. However, the separation of benzene and cyclohexane mixture is one of the difficult separation processes in petrochemical industry. Presently, extractive distillation is commercially used to separate benzene and cyclohexane using molecular solvents. However, the current process suffers from process complexity and high-energy consumption. In this work, new ionic liquid, 1-propanenitrile-3-butylimidazolium dicyanamide was synthesized and applied for separation benzene and cyclohexane mixture. Some of the thermophysical properties of the ionic liquid were measured. The vapour- liquid equilibrium and relative volatility of the components were determined. The ionic liquid breaks the azeotropic mixture and increased the relative volatility of cyclohexane to benzene.

Substrate-mediated enhanced activity of Ru nanoparticles in catalytic hydrogenation of benzene

The impact of carbon substrate-Ru nanoparticle interactions on benzene and hydrogen adsorption that is directly related to the performance in catalytic hydrogenation of benzene has been investigated by first-principles based calculations. The stability of Ru(13) nanoparticles is enhanced by the defective graphene substrate due to the hybridization between the dsp states of the Ru(13) particle with the sp(2) dangling bonds at the defect sites. The local curvature formed at the interface will also raise the Ru atomic diffusion barrier, and prohibit the particle sintering. The strong interfacial interaction results in the shift of averaged d-band center of the deposited Ru nanoparticle, from -1.41 eV for a freestanding Ru(13) particle, to -1.17 eV for the Ru/Graphene composites, and to -1.54 eV on mesocellular foam carbon. Accordingly, the adsorption energies of benzene are increased from -2.53 eV for the Ru/mesocellular foam carbon composites, to -2.62 eV on freestanding Ru(13) particles, to -2.74 eV on Ru/graphene composites. A similar change in hydrogen adsorption is also observed, and all these can be correlated to the shift of the d-band center of the nanoparticle. Thus, Ru nanoparticles graphene composites are expected to exhibit both high stability and superior catalytic performance in hydrogenation of arenes.

Kinetics of catalytic hydrogenation of benzene using copper nanoparticles as catalysts

The hydrogenation kinetics of benzene was studied using copper nanoparticles as a catalyst. Hydrogenation was carried out under steady-state conditions at different temperatures. The benzene concentration was determined using gas chromatography. The rate constants, activation energies, and conversion degrees were estimated.

ChemInform Abstract: A Novel Synthesis of Cyclohexanol Derivatives (I) by the Catalytic Hydrogenation of Benzene with Acid Additives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Novel Synthesis of Cyclohexanol Derivatives by the Catalytic Hydrogenation of Benzene with Acid Additives

Abstract The hydrogenation of benzene over a platinum group metal in the presence of various strong acids was carried out. Cyclohexanol derivatives (C6H11X, X = OH, OAc, Cl, Br) were found to be produced by the catalytic hydrogenation of benzene with acid additives. The following two sequences of adsorption strength were observed between platinum metals (adsorbent) and additive reagents (adsorbate) : When a weak adsorbate, such as acetic acid or water, was used as an additive reagent, ruthenium, the strongest adsorbent, exhibited the best selectivity. When hydrogen chloride, a strong adsorbate in the sequence (II), was used an additive reagent, palladium or rhodium, moderately strong adsorbent, exhibited excellent selectivity. By the reaction of 2 ml of benzene, 5 ml of 35% HCl and 0.2 g of 5% Pd/SiO2, under 10 atm-G (P atm-G = 1.013(P + 1) × 105 Pa) hydrogen at 100 °C for 20 h, 8.4% of the yield of chlorocyclohexane was obtained at 64.2% of the selectivity (13.1% of the conversion of benzene).

Selectivity to cyclohexene in the gas phase hydrogenation of benzene over ruthenium, as influenced by reaction modifiers: I. Adsorption of the reaction modifiers, water and ε-caprolactam, on ruthenium

Pre-adsorption of water and of ε-caprolactam on the surface of ruthenium influences the selectivity to cyclohexene in the catalytic hydrogenation of benzene. In this article the behaviour of hydrogen-covered ruthenium samples with respect to water and lactam adsorption is studied. At room temperature and up to a water vapour pressure of 1.3 kPa, a clean ruthenium surface is hydrophobic. Due to the presence of chlorine on the surface of many ruthenium samples, hydro-phobicity changes into hydrophylicity. On a chlorine-free surface covered with a monolayer of hydrogen, ε-caprolactam is strongly adsorbed (enthalpy of adsorption approx. -73.5 kJ/mol). Indications are found that ε-caprolactam is hydrogenated over ruthenium to 6-aminohexanal. This compound may easily condense to substituted imines.

ChemInform Abstract: The Role of Support in the Catalytic Hydrogenation of Benzene Over Ruthenium Catalysts.

It is generally agreed that the hydrogenation of benzene over supported noble metal catalysts is a facile reaction which is independent of particle size. Previous benzene hydrogenation studies over supported Ru catalysts have been carried out using relatively noninteractive supports such as alumina and silica. Because of the possibility that more interactive supports such as magnesia or lanthana may modify the catalytic activity of supported Ru catalysts in the hydrogenation of benzene, the authors have extended previous studies to include magnesia, silica-alumina, and graphitic carbon as support materials. 12 references.

The role of support in the catalytic hydrogenation of benzene over ruthenium catalysts

With worldwide petroleum resources dwindling and greenhouse gas emissions rising, it is urgent to find renewable replacements for petroleum-derived products. A biomass-derived chemical with high potential as a platform intermediate, γ-valerolactone (GVL) can be readily synthesized by hydrogenation of levulinic acid (LA), itself a common biomass intermediate, using supported Ru catalysts. To date the literature on many novel biomass conversion processes such as the hydrogenation of LA to GVL has focused more on the process and less on the catalyst.The goal of this work was to derive fundamental synthesis–structure–function relationships of Ru catalysts for LA hydrogenation using carbon- and alumina-supported Ru nanoparticles that have been synthesized in a rational, repeatable, scalable way. We have demonstrated that the method of strong electrostatic adsorption (SEA) yields well-dispersed, homogeneously distributed Ru particles with tight particle size distributions over both types of supports. SEA synthesis of well-dispersed nanoparticles results in higher activity than commercial Ru catalysts with higher Ru loadings. The dramatic, beneficial effect of potassium doping is reported for the first time. The carbon support yields higher inherent activity than alumina. Activity as a function of particle size appears to go through a maximum at about 1.5 nm for both supports and suggests hydrogenation of LA is structure sensitive to Ru particle size. Catalyst deactivation after 24 h occurs to significant extents (8–58%) mainly by nanoparticle sintering, but also by minor amounts of K loss in K-doped samples.

The catalytic hydrogenation of benzene over supported metal catalysts.: III. Gas-phase hydrogenation of benzene over silica-supported Ru-Cu catalysts

A study has been made of the gas-phase hydrogenation of benzene over silica-supported Ru-Cu catalysts in the temperature range from 300 to 400 K and at a total pressure of 130 kPa. Special attention has been given to the catalytic stability and the activity of the catalysts as compared with monometallic supported ruthenium and copper catalysts, described in previous articles. Via a reductive deposition technique, copper was deposited on silica-supported ruthenium catalysts. Two bimetallic catalysts were prepared, one with about 10% of the ruthenium surface covered by copper and one with about 70% copper coverage. The texture of the catalysts was studied by means of mercury penetration, nitrogen physisorption, hydrogen chemisorption and transmission electron microscopy, whereas surface analysis was performed by XPS/AES. At 11% copper coverage a shift in the copper electron binding energy is observed, pointing to a small electron transfer from ruthenium to copper, but at 68% copper coverage this shift has disappeared. Copper deposition on ruthenium increases the lifetime of the catalysts considerably without seriously affecting the activity per ruthenium surface atom. At low copper coverage the reaction kinetics are very similar to the kinetics found with ruthenium, but at high copper coverage the small size of the ruthenium ensembles influences the kinetics considerably.

The catalytic hydrogenation of benzene over supported metal catalysts: I. Gas-phase hydrogenation of benzene over ruthenium-on-silica

A study is reported of the gas-phase hydrogenation of benzene over a ruthenium-on-silica catalyst in the temperature range from 300 to 415 K and at a total pressure of 130 kPa. The texture of the catalyst is studied by TEM, physisorption of nitrogen, chemisorption of hydrogen and by mercury penetration. Surface analysis is performed by XPS/AES. The adsorption enthalpies of the reaction intermediates 1,4-cyclohexadiene and cyclohexene and of cyclohexane on ruthenium are determined. On the basis of the kinetics, a reaction mechanism is proposed in which the rate-determining step shifts from the first hydrogen addition to benzene at low temperatures to the hydrogen addition to cyclohexene at higher temperatures. An approximate diagram is constructed representing the change of the free enthalpy as a function of the extension of the reaction.

The catalytic hydrogenation of benzene over supported metal catalysts.: II. Gas-phase hydrogenation of benzene over copper-on-silica

A study has been made of the kinetics and mechanism of the gas-phase hydrogenation of benzene over a copper-on-silica catalyst in the temperature range from 300 to 450 K and at 130 to 395 kPa total pressure. Attention has been given also to the kinetics of the hydrogenation of the reaction intermediates 1,4-cyclohexadiene and cyclohexene. Two different catalysts were prepared on Shell silica spheres as a support, one according to the Dutch Patent No. 143,139 and the other according to European Patent No. 0006313. Their texture and analytical composition were studied by means of TEM, nitrogen physisorption and capillary condensation, adsorptive decomposition of nitrous oxide, atomic absorption spectrometry and XPS/AES analysis. The catalyst prepared according to European Patent No. 0006313 had a high mechanical strength, a perfect chemical stability and a high sintering resistance. The mean copper particle diameter was 5.5 nm. The other catalyst displayed poor mechanical strength and fragmented during testing. A reaction mechanism is formulated on the analogy of the mechanism proposed for the hydrogenation of benzene over ruthenium [11]. The catalytic activity of copper is compared with that of several other transition metals and presented in the form of modified Tanaka-Tamaru plots.

Synergetic effect of molybdenum dioxide on nickel in the catalytic hydrogenation of benzene

AbstractMolybdenum dioxide is deposited on the form of an aerogel (in the autoclave) on nickel Mond. The catalytic activity for the hydrogenation of benzene into cyclohexane at 100°C depends on the proportion of MoO2 and on the temperature of a pretreatment in hydrogen. When this temperature is 440°C, the catalytic activity exceeds that of pure nickel Mond and exhibits a maximum for about 10% of MoO2. This synergetic effect, which is an exemple of a strong metal‐support interaction (SMSI), is explained by the incorporation into the surface of nickel Mond crystals of molybdenum produced by partial reduction of MoO2, with the formation of an inter‐metallic compound MoNi4.

Facile heterogeneous catalytic hydrogenation of benzene and cyclohexene

Facile heterogeneous catalytic hydrogenation of benzene and cyclohexene

Catalytic hydrogenation of benzene by lamellar compounds C8K and C24K

Graphite–potassium (C8K and C24K) lamellar compounds behave as catalysts, similar to transition-metal catalysts, for the hydrogenation of benzene to cyclohexane in high yields.

Kinetics of the vapour‐phase hydrogenation of benzene over a supported nickel catalyst in a stirred‐vessel reactor

AbstractThe catalytic hydrogenation of benzene was investigated over a supported nickel catalyst in a continuous stirred‐vessel reactor between 260° and 450°F at atmospheric pressure. The effects of temperature, ratio of hydrogen to benzene and total feed rate (or contact time) on the conversion of benzene and yield of cyclohexane were determined.The use of the stirred reactor helped to eliminate mass transfer limitations. The investigation was carried out using surface‐coated catalysts in order to eliminate pore diffusion which might otherwise mask the actual kinetics.Studies of the mixing characteristics of the reactor were carried out under both reacting and non‐reacting conditions, by following conversion as a function of stirrer speed and by a tracer (pulse) technique, respectively.The kinetic data were analysed to determine the most probable model to represent the reaction. The Houghen–Watson type analysis was carried out using non‐linear least squares instead of the usual linear one. The model that satisfactorily correlated the data over the entire temperature range describes the rate‐controlling step as the surface reaction between adsorbed hydrogen and adsorbed benzene, the hydrogen addition being simultaneous. The following Hougen–Watson type equation was proposed: r = ke KH 3KB PH 3PB/(1+KHPH+KBPB+KCPC)4.The constants in this rate equation were expressed as a function of temperature.

Note on the kinetics of the catalytic hydrogenation of benzene on a supported nickel catalyst

Note on the kinetics of the catalytic hydrogenation of benzene on a supported nickel catalyst