Benzene Hydrogenation Activity Research Articles

A novel Ni-Co alloy catalyst derived from spinel

In this work, five Ni-Co alloy catalysts (NiCo2-N, NiCo2-200, NiCo2-350, NiCo2-500, NiCo2-700) were prepared by the reduction of precursors, which came from different calcination temperatures. The catalyst characterization suggested that all these catalysts had different alloy structures. No calcination or calcination temperatures lower than 200 °C would generate Ni-Co alloy prone to collapse. However, catalysts would possess solid structures when these precursors were calcinated at 350, 500, or 700 °C. Moreover, the calcination temperature significantly affected the surface Ni/Co compositions on these catalysts and the H2 adsorption and activation capabilities of these Ni-Co alloy catalysts. Finally, when using benzene hydrogenation as a probe reaction, the catalyst activities were evaluated, and it’s observed that NiCo2-350 catalyst, not only having a uniform Ni-Co alloy structure but pore structure on the surface of spherical particles, demonstrated the highest activity for benzene hydrogenation.

Benzene hydrogenation activities of Ni catalyst supported on N- and B-doped carbons

A catalyst support can improve the catalytic activity of metal catalysts, and this phenomenon is well known as the support effect. The effective use of this support effect is considered important for improving catalytic activity. However, the factors affecting this phenomenon are complex. It is, therefore, important to understand the interaction between the support and metal catalyst as well as the surface characteristics of the support for elucidating this phenomenon. Carbon is a useful support material because of its high chemical and thermal stability and electroconductivity. Moreover, its surface properties can be controlled by doping the carbon structure with heteroatoms. In this study, the catalytic activity of metal particles supported on heteroatom-doped carbon materials was evaluated to investigate the support effect of the doped carbon. The catalytic activity of carbon-supported Ni particles in benzene hydrogenation was improved by introducing N and B into the carbon support. In particular, Ni supported on N-doped carbon showed a two-fold improvement in activity compared to that supported on undoped carbon. A compensation effect was confirmed for the catalytic activity of Ni particles. The results suggest that the introduction of heteroatoms into the carbon support changed the adsorption energy of the reactant on Ni, thereby improving the Ni catalytic activity.

Effect of the ruthenium deposition method on the nanostructured catalyst activity in the deep hydrogenation of benzene

Ru-containing catalysts supported on halloysite aluminosilicate nanotubes (HNTs) were prepared by incipient wetness impregnation, vacuum impregnation, and impregnation under the microwave irradiation methods. Composition and structure of the catalysts were determined by X-ray fluorescence (XRF), thermo-programmed reduction (TPR-H2), and transmission electron microscopy (TEM). Textural characteristics were detected by low-temperature nitrogen adsorption—desorption. The activity of the catalysts was investigated in benzene hydrogenation at 80°?, a hydrogen pressure of 3.0 MPa, and a molar ratio of benzene to Ru of 2000. It was found that Ru nanoparticles prepared by vacuum impregnation are deposited mainly into the internal cavity of aluminosilicate nanotubes, while in samples obtained by wetness impregnation the active phase is formed predominantly on the external surface of halloysite. The catalyst prepared by impregnation under microwave irradiation is characterized by a high Ru content, its uniformly distributed metal particles are located mainly on the external surface of HNT, and it demonstrated the superior activity in hydrogenation of benzene to cyclohexane.

Characterization and competitive benzene hydrogenation activity of nickel supported on SBA-15/LxOy (L = Zn, Ti, W) composites in an aromatic mixture

SBA-15/metal oxide composites were prepared by the mixing-calcination method and the nickel phase was impregnated by the wet impregnation method. The textural and structural properties of catalysts were characterized with scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray fluorescence, UV–visible diffuse reflectance spectra, and nitrogen adsorption–desorption analysis. Ni/composite materials were used for competitive hydrogenation of benzene in the range of 403–463 K and ambient pressure. It is found that the reaction kinetics follows the pseudo-first-order kinetic for hydrogen. Activity data demonstrated that the highest activity and the best selectivity were obtained for Ni/SBA-15/TiO2 (> 93%) at 403 K, and nickel supported over SBA-15/W2O (> 73%) at 403 K.

Study on sulfur-tolerant benzene hydrogenation catalyst based on Pt-encapsulated sodalite zeolite

The sulfur resistance, activity in benzene hydrogenation and hydrogen spillover of the Pt-encapsulated sodalite zeolite Pt/SOD-M have been investigated. The prepared of Pt/SOD-M zeolite catalyst by directly hydrothermal synthesis in the presence of Pt(NH3)4Cl2 metal precursor and subsequently performing ion exchange with aqueous nitrate solution. The characterization of framework structure, pore textural properties and the acidity of the obtained Pt/SOD-M by XRD, N2 adsorption–desorption and NH3-TPD, respectively. The hydrogen spillover of Pt/SOD-M before and after poisoning of H2S and its hybrid samples were examined by H2-TPD. Catalytic hydrogenation activity was measured by benzene hydrogenation. The results indicated that there is no catalytic hydrogenation activity for Pt/SOD-Na and Pt/SOD-K alone, whereas Pt/SOD-H and Pt/SOD ion exchanged with Mg2+, Ca2+ and Ba2+ show appreciable activity. Notably, alone Pt/SOD-H and Pt/SOD ion exchanged with Mg2+, Ca2+ and Ba2+ still show excellent catalytic benzene hydrogenation activity after poisoning of H2S. It was demonstrated that Pt/SOD-H, Pt/SOD-Mg, Pt/SOD-Ca and Pt/SOD-Ba not only can resist sulfur-poisoning, but also exhibit superior catalytic hydrogenation performance without mixing with spillover hydrogen receptor.

Acidity in Titania–Alumina Mixed Metal Oxides

Titania–alumina mixed oxides were prepared with varying titania content. The catalysts contained sulfate which was introduced via titanyl sulfate used as precursor during the synthesis. Samples were characterized by IR spectroscopy of adsorbed pyridine to determine Lewis and Bronsted acidity. At titania loadings below about 5 wt% no protonation of pyridine was detected by IR spectroscopy. However, 2-methyl-2-pentene isomerization indicated an increase in medium strength acidity in these samples relative to pure alumina and titania as inferred from an increased methyl shift activity. IR spectroscopy revealed the generation of fourfold coordinated Ti4+ sites and mildly acidic Ti–OH groups that may be responsible for the enhanced olefin isomerization reactivity of the mixed oxides. Addition of small amounts of titania also increased the concentration of the type Ia Al–OH group on the alumina surface characterized by an IR band at 3771 cm−1. At titania loadings of about 8 wt% and above Bronsted acidity was generated by sulfate groups as detected by the protonation of pyridine. Deposition of 0.3 wt% Pt on the titania–alumina mixed oxides generated finely dispersed Pt as measured by H2 chemisorption and TEM. The benzene hydrogenation activity on the Pt–TiO2–Al2O3 catalysts showed a maximum for the sample containing about 1 wt% titania and correlated with the relative abundance of the type Ia Al–OH groups on the alumina surface.

Effect of palladium precursor and preparation method on the catalytic performance of Pd/SiO2 catalysts for benzene hydrogenation

ABSTRACTSupported Pd catalysts on silica were prepared by different synthesis methods using Pd(Ac)2 and PdCl2 as salts precursors. The obtained materials were characterized by X-Ray Diffraction (XRD), H2 chemisorption, and temperature programmed desorption of hydrogen (H2-TPD). The catalytic performances of these catalysts have been evaluated in the hydrogenation of benzene. The obtained results show that metal dispersion and catalytic activity are strongly dependent on the salts precursor and the method of preparation of the catalyst. The catalysts prepared by hydrazine reduction exhibit higher activity in benzene hydrogenation than that by the polyol reduction method. Moreover, the catalyst prepared with palladium acetate showed higher catalytic activity than those prepared with palladium chloride. The superior catalytic performance of this catalyst in the hydrogenation of benzene was ascribed to a significantly better dispersion of Pd particles on the silica support.

Effect of oxidative pre-treatment on hydrogen spillover for a Ni/SiO2 catalyst

The chemisorption and hydrogenating properties of Ni/SiO2 catalysts prepared by the hydrazine method then calcined at 400°C with various times were investigated. Metal dispersion and activity in benzene hydrogenation increased with increasing calcination time whereas desorbed amounts of hydrogen significantly decreased. Dilution of a calcined sample by the support led to a sharp increase of both hydrogen storage by the support and catalytic activity. Metal dispersion and hydrogen storage capacity influenced the reaction mechanisms of hydrogenation of benzene which, therefore, is believed to occur on the metal phase or/and on the support by the hydrogen spillover mechanism. The metal active phase would be composed of an ensemble of metallic and oxidized nickel species.

The effect of copper on benzene hydrogenation to cyclohexane over Ni/Al2O3 catalyst

The effect of a copper modifier on physicochemical properties of coprecipitated precursors and final Ni–Cu/Al2O3 catalysts for benzene to cyclohexane hydrogenation was investigated. Based on the studies of physicochemical properties, the influence of copper on the catalytic activity and selectivity of Ni–Cu/Al2O3 systems was discussed. The addition of copper resulted in a decrease of the specific and nickel surface area, improvement of the selectivity and a slight decrease of the benzene hydrogenation activity compared to the reference catalyst. A decrease of methylcyclopentane and methylcyclohexane by-products formation on the surface of Ni–Cu/Al2O3 catalyst containing 10–17wt% CuO by, respectively, 70% and 10% was observed. The results reveal a distinct, beneficial effect of the Ni/Al2O3 modification by copper on the catalyst selectivity. However, this effect depends on temperature and is limited to ca. 20wt% CuO, above this content the activity was found to decrease considerably.

Crystal transformation synthesis, hydrogenation activity and sulfur-tolerant performance of Pt particles encapsulated in sodalite

Noble metals are widely used as hydrogenation catalysts for refining and modifying fuel oil. However, their stability is still a problem. Thus, crystal transformation method was used here to encapsulate platinum (Pt) particles in sodalite through two steps. First, the sample was crystallized at 100°C for 12 h. Then, it was further crystallized at 120°C for 144 h, 130°C for 96 h, 140°C for 60 h, 150°C for 42 h, or 160°C for 30 h. The resultant solid (designated as Pt/SOD) shows high activity and excellent sulfur-tolerant performance in benzene hydrogenation. The crystalline phases were identified by X-ray diffraction technique. The hydrogen spillover effect of Pt/SOD and the spillover hydrogen acceptability of HZSM-5 were investigated with H2-TPD.

Synthesis of Supported Ultrafine Non-noble Subnanometer-Scale Metal Particles Derived from Metal-Organic Frameworks as Highly Efficient Heterogeneous Catalysts.

The properties of supported non-noble metal particles with a size of less than 1 nm are unknown because their synthesis is a challenge. A strategy has now been created to immobilize ultrafine non-noble metal particles on supports using metal-organic frameworks (MOFs) as metal precursors. Ni/SiO2 and Co/SiO2 catalysts were synthesized with an average metal particle size of 0.9 nm. The metal nanoparticles were immobilized uniformly on the support with a metal loading of about 20 wt%. Interestingly, the ultrafine non-noble metal particles exhibited very high activity for liquid-phase hydrogenation of benzene to cyclohexane even at 80 °C, while Ni/SiO2 with larger Ni particles fabricated by a conventional method was not active under the same conditions.

Iridium@graphene composite nanomaterials synthesized in ionic liquid as re-usable catalysts for solvent-free hydrogenation of benzene and cyclohexene

Synthesis of stable hybrid iridium@graphene nanomaterials in the ionic liquid (IL) 1-butyl-3-methyl-imidazolium tetrafluoroborate ([BMIm][BF4] through microwave irradiation (MWI) or electron-beam (e-beam) irradiation (IBA Rhodotron accelerator) induced decomposition of Ir4(CO)12 in the presence of graphene provides an easy method for the generation of small iridium nanoparticles with size distributions of 1.0 ± 0.4 and 2.7 ± 0.7 nm by MWI reactions with 90 and 60 min decomposition time, respectively, and of 3.6 ± 1.0 nm for e-beam irradiation synthesis. Graphene was derived by thermal reduction of graphite oxide (TRGO). Powder X-ray diffraction (PXRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDX) showed the formation of Ir nanoparticles which are evenly distributed on the TRGO sheets. Ir@TRGO proved to be a highly active (∼10000 mol cyclohexane x(mol Ir)−1x h−1 for benzene hydrogenation) and selective heterogeneous catalyst for the industrially relevant hydrogenation of benzene or cyclohexene to cyclohexane under mild conditions (100 °C, 10 bar H2) with quantitative conversion. The catalyst could be re-used over 10 consecutive hydrogenation reactions with similar activities. A brief correlation between activity and particle size points to an optimal diameter or surface regime for the catalytic activity with iridium particles of 3.6 ± 1.0 nm on TRGO giving here the highest activity in benzene hydrogenation.

Partial hydrogenation of benzene to cyclohexene over Ru/γ-Al2O3 nanocatalyst via w/o microemulsion using boric acid and ethanolamine additives

Ru/γ-Al2O3 nanocatalyst was synthesized by water-in-oil reverse microemulsion technique and characterized by TEM, SEM–EDX, XRD, N2 adsorption–desorption, and H2 chemisorption. The surface area and active sites (S M) of 3 wt% Ru/γ-Al2O3 was obtained around 217.6 m2/g and 45.70 m2/gcat, respectively. The catalyst performance of Ru/γ-Al2O3 was assessed in the selective hydrogenation benzene to cyclohexene in the presence of boric acid (BA) and ethanolamine (EA) additives. The effect of such specific additives alone and in combination on the activity and selectivity of benzene hydrogenation was systematically investigated. Ru catalyst displayed pre-eminent performance at 0.5 mmol ratio of BA to EA exhibiting the highest selectivity (40 %) and yield (16 %) of the intermediate product, cyclohexene at 40 % of benzene conversion.

Benzene selectivity in competitive arene hydrogenation: effects of single-site catalyst···acidic oxide surface binding geometry.

Organozirconium complexes are chemisorbed on Brønsted acidic sulfated ZrO2 (ZrS), sulfated Al2O3 (AlS), and ZrO2-WO3 (ZrW). Under mild conditions (25 °C, 1 atm H2), the supported Cp*ZrMe3, Cp*ZrBz3, and Cp*ZrPh3 catalysts are very active for benzene hydrogenation with activities declining with decreasing acidity, ZrS ≫ AlS ≈ ZrW, arguing that more Brønsted acidic oxides (those having weaker corresponding conjugate bases) yield stronger surface organometallic electrophiles and for this reason have higher benzene hydrogenation activity. Benzene selective hydrogenation, a potential approach for carcinogenic benzene removal from gasoline, is probed using benzene/toluene mixtures, and selectivities for benzene hydrogenation vary with catalyst as ZrBz3(+)/ZrS(-), 83% > Cp*ZrMe2(+)/ZrS(-), 80% > Cp*ZrBz2(+)/ZrS(-), 67% > Cp*ZrPh2(+)/ZrS(-), 57%. For Cp*ZrBz2(+)/ZrS(-), which displays the highest benzene hydrogenation activity with moderate selectivity in benzene/toluene mixtures. Other benzene/arene mixtures are examined, and benzene selectivities vary with arene as mesitylene, 99%, > ethylbenzene, 86% > toluene, 67%. Structural and computational studies by solid-state NMR spectroscopy, XAS, and periodic DFT methods applied to supported Cp*ZrMe3 and Cp*ZrBz3 indicate that larger Zr···surface distances are present in more sterically encumbered Cp*ZrBz2(+)/AlS(-) vs Cp*ZrMe2(+)/AlS(-). The combined XAS, solid state NMR, and DFT data argue that the bulky catalyst benzyl groups expand the "cationic" metal center-anionic sulfated oxide surface distances, and this separation/weakened ion-pairing enables the activation/insertion of more sterically encumbered arenes and influences hydrogenation rates and selectivity patterns.

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.

Revisiting hydrogen spillover in Pt/LTA: Effects of physical diluents having different acid site distributions

Historically, Pt/LTA (e.g., Pt/NaA) has often been used as a model catalyst for studying the catalytic functions of hydrogen spillover (H spillover). Notably, none of the works reported appreciable catalytic activities for Pt/LTA alone, while markedly enhanced activities were reported after physical dilution with some acidic oxides. It was often speculated without experimental evidence that activated hydrogen generated from Pt/LTA can migrate to the diluents surface (“inter-particular” H spillover) where organic reactants can react with spilt-over hydrogen. In this work, we carefully studied benzene hydrogenation activities of Pt/NaA and its decationized form (Pt/HA), before and after the physical dilution with various metal oxides possessing different Lewis and Brønsted acidity. The originally negligible activity of Pt/NaA increased significantly after mixing with various acidic oxides. The physical dilutions, however, resulted in a significant alteration of Pt/NaA structure due to solid-state H+ exchange, which made the catalytic interpretation vague. In contrast, Pt/HA structure did not change after the dilutions, and thus could be used as an ideal catalytic model system for studying inter-particular H spillover. The catalytic results showed that Al-rich metal oxides with abundant Lewis acid sites are effective for enhancing the catalytic activity.

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.

Relationship Between Metal Dispersion, Hydrogen Desorption, and Activity for Benzene Hydrogenation Over Pd/SiO2 Catalysts

A series of Pd/SiO2 catalysts with Pd loadings from 1–10 wt% were prepared by aqueous hydrazine reduction. They were characterized by XRD, TEM, EDX, H2 chemisorption, and H2-TPD. The catalytic performances were evaluated in benzene hydrogenation in the temperature range 100–250°C. The metal dispersion (mean particle size 6.8–28.4 nm) and hydrogen reservoir increase with decreasing metal content. The catalytic activity of the Pd/SiO2 catalysts was found influenced by the reaction temperature and metal dispersion. The activity increases with metal dispersion. This might be ascribed to the Pd sites, which increase with the increase of the metal dispersion.

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.