Catalyst For Hydrogenation Of Benzene Research Articles

Novel Reaction-Adsorption Method for Preparation of Ru–Zn–La/ZrO2 Catalysts with High Catalytic Performance for Selective Hydrogenation of Benzene

A novel wet-chemistry reaction-adsorption strategy via the facile acid–base interaction under mild conditions is demonstrated to fabricate the state-of-the-art Ru–Zn–La/ZrO2 catalysts for selective hydrogenation of benzene to cyclohexene. The catalyst preparation process is systematically investigated and verified with the combination of various characterization techniques. Preloading of lanthanide salts and alkali treatment after calcination not only favor the introduction of ruthenium and zinc species in the later stages but also help enhance the dispersion of the catalysts. The reaction rate constants (k1 and k2) decrease with the increment of the Zn/Ru molar ratio, and the selectivity at 40% conversion (S40) is positively correlated with the k1/k2 ratio, demonstrating the role of Zn species in retarding the hydrogenation activity of Ru and improvement of the selectivity to cyclohexene. In general, the catalytic behavior is dependent on the particle size of Ru, the La-to-Ru electron transfer effect, the content of Zn species, and the surface hydrophilicity of catalyst. These factors are generated by using different precursors and various predesigned La/Ru molar ratios in the preparation recipe. Moreover, a passivation treatment before the hydrogenation reaction can promote the cyclohexene selectivity of the catalyst Ru–Zn–La/ZrO2 (1.6 La/Ru) to 80.6% at a benzene conversion of 43.7%, which meets the industrial requirement. Notably, the specific activity of the catalyst is as high as 1224 gBZ·gRu–1·h–1, over 10 times higher than the industrial criterion. This work provides new insights into the design of Ru-based catalysts for benzene hydrogenation and other hydrogenation reactions as well.

Preparation of Ruthenium Hollow Spheres as Catalysts for Selective Hydrogenation of Benzene to Cyclohexene

In this paper, a simple and effective method was used to synthesize monodisperse metal Ruthenium nanospheres (Ru-HNSs), and the silicon dioxide (SiO2) nanospheres synthesized by Stober method were used as hard templates. The surface of SiO2 was double modified by γ-aminopropyltriethoxysilane (KH550) and salicylaldehyde, so that Ru3+ grew uniformly on the surface of modified SiO2 and reduced to form a stable and durable layer of Ru metal. Then the hard template SiO2 was corroded by chemical etching to obtain Ru-HNSs hollow spheres. The results show that the diameter of SiO2 microspheres was about 300nm, the wall thickness of Ru-HNSs was about 3nm, and the diameter was about 100nm.

Role of Supports in Ni Nanoparticles Ti-Promoted Composite Catalysts for the Total Hydrogenation of Benzene

Removal of aromatic compounds from fuels due to the strict regulations as well as carcinogenic and detrimental effects on the humans and the environment is one of the main steps in the petrochemical industry. Competitive hydrogenation of benzene in aromatic mixtures not only achieves this goal, but also prevents the significant reduction in the octane number by producing cyclohexane in the fuels. For this purpose, a series of nickel catalysts supported on the Ti-promoted mesoporous-carbon composites have been prepared by the wet impregnation method. Textural and physicochemical properties of catalysts were characterized using FT-IR, N2 adsorption-desorption, XRD, SEM, and EDAX. The activity of the powders was evaluated in the temperature range of 150–210°C. The results confirm that the Ni/Ti-SBA-15 catalyst shows the acceptable selectivity in the test temperature range and the highest activity at 190°C.

HYDROGENATION OF BENZENE IN BATCH REACTOR

In this article is considered hydrogenation of benzene in liquid phase at presence rhodium support catalyst.where as carrieris usedpillar structural montmorillonite obtaining from bentonite clay..The degree of using an internal surface of porous system is depended.of the size particles.Increase the concentration of chromium above 20 mmole per gram of clay does not lead to the further growth of distance. It is probably connected by that in a solution there are not hydrolized forms of chromium chloride which do not influence formation pillar structures. Modifying montmorillonite minerals containing in bentonite clay gives to them heat resistance. The specific surface of samples(containing 15-30 mmole Cr3+) were defined after heat treatment at 180°C are 240-260 m2 /g and increasing the temperature up to 500-560°C decreases this value insignificant to 220-240 м2 /г, accordingly. Not modified bentonite clay lost their porosity at 140°C, and a specific surface made 20 m2 /g. Besides reaction of hydro-dehydrogenation of cyclic hydrocarbons a huge interest are represented in hydrogen technology. Everyone mole of benzene and its derivatives attaching of three and more quantities of hydrogen, and are unique objects at storages and transportation of hydrogen. Thereby, necessity to develop of catalysts of hydro-dehyrogenation also follows under rather soft conditions. developed rhodium support catalyst for hydrogenation of benzene and defined the factor of efficiency using the internal surface of porosity systems. Presence of water in hydrogenated system leads to phasic course of restoration of benzene on a surface of the catalyst with formation cyclohexane and cyclohexene. The received experimental results expand a circle of data in the field of hydrodearomatization motor fuels, especially transformations of aromatic hydrocarbons cycloalkans

Role of ZnNb2O6 in ZnO-promoted amorphous-Nb2O5 supported Ru catalyst for the partial hydrogenation of benzene

Ruthenium catalysts supported on zinc-promoted amorphous-niobium mixed oxides were prepared, characterized, and studied in the additive-free partial hydrogenation of benzene reaction. The amorphous matrix of Nb2O5 was responsible for a highly active Ru/Nb2O5 catalyst, although less selective than those containing zinc. The ZnO-containing supports were prepared by wet impregnation technique, followed by incipient wetness of ruthenium chloride salt. The catalysts were characterized by textural analysis, X-ray fluorescence, X-ray diffraction, H2 chemisorption, temperature-programmed reduction (TPR), Scanning electron microscopy, H2 temperature-programmed desorption, and X-ray photoelectron spectroscopy (XPS) of the calcined-reduced samples. Chlorine retention was observed on zinc-containing samples. An unexpected ZnNb2O6 oxide phase, ascribed to a selectivity increase with less activity loss, was obtained for the supports at lower temperatures than those related on the literature. A very complex electronic environment of Ru- and Zn-containing species interactions was observed by TPR. The presence of surface-reduced (Ru0) and partially reduced (Ruδ+) Ru species observed by XPS justified well, respectively, the activity and selectivity achieved with every catalyst. The addition of water as a solvent resulted in very constant yield to cyclohexene, as expected, despite activity diminution due to low solubility of the reactants.

Ru/TiO2 catalyst for selective hydrogenation of benzene: Effect of surface hydroxyl groups and spillover hydrogen

Three Ru/TiO2 catalysts were prepared via an impregnation-chemical reduction method by supporting Ru on three different TiO2 supports, namely TiO2-A (anatase), TiO2-R (rutile) and TiO2-A-750 (annealing TiO2-A at 750 °C). The amount of surface hydroxyl groups in the TiO2 supports and Ru/TiO2 catalysts is evaluated by the FTIR technique, which is found to be affected by crystal and textural property of TiO2. It is found that, for the Ru/TiO2 catalyst, the presence of more spillover hydrogen, and more hydroxyl groups that lead to stronger surface hydrophilicity and lower benzene diffusion rate, thereby improve its catalytic activity and selectivity towards selective hydrogenation of benzene. For the Ru/TiO2-A catalyst, it has much more spillover hydrogen and hydroxyl groups than the other two, hence showing the best catalytic activity (TOF of 0.8 s−1) and cyclohexene selectivity (66%) at a benzene conversion of 50%.

Using modeling to select catalyst dilution methods for mass transfer intensification in lab gas–liquid fixed-bed reactors

Heterogeneous catalyst testing methodology at the lab scale must provide intrinsic kinetics data for reactor design purposes as well as the intrinsic activity ranking during catalyst screening in the field of refining and petrochemistry. The significant downscaling of the past century coupled with the increasingly active catalytic formulations may introduce considerable momentum, mass and heat effects in experiments at small scale. Catalyst dilution has emerged as one versatile and robust way to reduce the impact of momentum and heat effects on heterogeneous catalyst testing. This paper presents a methodology based on global phenomena and catalyst dilution modeling to assess and optimize reactor loading techniques for specific problems. More particularly, the aim is to provide catalysts developers and kinetics experts with concrete guidelines for intensifying gas-liquid mass transfer in lab gas–liquid fixed-bed reactors through catalyst dilution. The methodology is applied to the kinetics determination of the oil residue Hydrodemetallation (HDM) and to the screening of catalysts for benzene hydrogenation. Layered dilution, consisting on the split of the catalyst in two beds separated by an intermediate bed containing an inert material of the same size as the catalyst, poorly improves gas–liquid mass transfer. Uniform dilution, based on the direct mixture of catalyst and inert material of the same size, significantly enhances gas–liquid mass transfer as the reactant local consumption per reactor unit volume is strongly reduced. Combinations of both abovementioned dilution techniques can be used with fast and/or high stoichiometric factor chemical systems operated at conversions higher than 70%. A new criterion is proposed to calculate the minimum dilution factor to guarantee negligible gas–liquid mass transfer limitations as a function of conversion, external mass transfer and global pseudo second-order kinetics.

Surface investigation by X-ray photoelectron spectroscopy of Ru-Zn catalysts for the partial hydrogenation of benzene

Partial hydrogenation of benzene with ruthenium-supported catalysts is an interesting alternative route to produce cyclohexene, an intermediate in the production of nylon 6.6 and other fine chemicals. In this work, ruthenium chloride solution was added to xZnO/Al2O3 by wetness impregnation. The supports were derived from hydrotalcite compounds and tested on the partial hydrogenation of benzene. The catalyst with 10 wt.% of ZnO (Ru10ZnAl) presented the best catalytic performance reaching total conversion in 40 min of the reaction, and a maximum yield of 35% using pure benzene (without water, salts or other additives). The samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), X-ray diffraction (XRD), temperature programmed reduction (TPR) and H2 Chemisorption. Metallic and partially reduced ruthenium surface species were identified on the surface of the Ru10ZnAl catalyst and the electronic vicinity of Ru is proposed to be responsible for promoting the cyclohexene desorption, revealing a synergistic effect. In this sense, the electronic surroundings modification of surface zinc species with ruthenium species, followed by reduction, was evidenced by using the Modified Auger Parameter (MAP). These species played an important role in the reaction.

Родий және родий-алтын отырылғызган катализаторлардың бензолмен толуолды гидрлеу реакциясындағы белсендiлiгi мен селективтiгi

Аморфты алюмосликат тасымалдағышына (ASA) және титан қос тотығына(рутил, TiO 2 ) отырғызылған родий және родий-алтын катализаторлары екi түрлi әдiспендайындалды: сiңiру және коллоидтық әдiс. Катализаторлар индуктивтi байланысқан плазмаоптикалық эмиссиялық спектрометр (ICP-OES), трансмиссиялық электронды микроскопия(ТЕМ) және рентгендiк дифракция (XRD) әдiстерiмен сипатталды. Дайындалғанкатализаторлардың белсендiлiгi мен селективтiлiгi бензолды және толуолды гидрлеуреакциясы арқылы сыналды. Гидрлеу 4 МПа қысым мен 80 0 С температурада жүргiзiлдi.Нәтижесiнде, сiңiру әдiсiмен дайындалған биметалды Rh-Au/ASA катализаторы бензолдыгидрлеу реакциясында, ал, коллоидтық әдiспен дайындалған осы катализатор толуолдыгидрлеу реакциясында жоғарырақ белсендiлiк көрсеттi. Бұл нәтиже басқа ароматтықосылыстар арасындағы бензолды селективтi гидрлейтiн катализатор алуға мүмкiндiк бередiдеп есептеймiз. Алтынның қосылуы родий катализаторының белсендiлiгiн айтарлықтайжоғарылата алмайтындығы, тиiмдi тасымалдағыш алюмосликат екендiгi, сондай-ақ, бензолмен толуолды гидрлеудiң өнiмдерi тек циклогексан және метил-циклогексан екенi анықталды.

Rhodium nanoparticles supported on covalent triazine-based frameworks as re-usable catalyst for benzene hydrogenation and hydrogen evolution reaction

Rh@CTF-1 nanomaterial is a highly active (TOF ∼ 31 000 h−1) heterogeneous catalyst for the efficient hydrogenation of benzene under mild and solvent-free conditions.

Nanostructured Ruthenium Catalysts in Hydrogenation of Aromatic Compounds

Ru-containing catalysts based on aluminosilicate halloysite nanotubes (HNTs) are synthesized by preliminary functionalization of the support surface by aminopropyltriethoxysilane (APTES) followed by the microwave-assisted deposition of ruthenium to provide the intercalation of metal nanoparticles into the inner space of nanotubes. The composition and structure of the synthesized catalysts are studied by X-ray fluorescent analysis, low-temperature nitrogen adsorption/desorption, transmission electron microscopy, and hydrogen temperature-programmed reduction. The activity of the catalysts in benzene hydrogenation at a temperature of 80°С and a hydrogen pressure of 3 MPa both in the hydrocarbon medium and in the two-phase system with water is studied. It is shown that, in the presence of water, the hydrogenating activity of the catalyst based on modified halloysite nanotubes is considerably higher than that of the sample prepared using the initial halloysite as a support.

Effect of the Crystallographic Phase of Ruthenium Nanosponges on Arene and Substituted‐Arene Hydrogenation Activity

AbstractIdentifying crystal structure sensitivity of a catalyst for a particular reaction is an important issue in heterogeneous catalysis. In this context, the activity of different phases of ruthenium catalysts for benzene hydrogenation has not yet been investigated. The synthesis of hcp and fcc phases of ruthenium nanosponges by chemical reduction method has been described. Reduction of ruthenium chloride using ammonia borane (AB) and tert‐butylamine borane (TBAB) as reducing agents gave ruthenium nanosponge in its hcp phase. On the other hand, reduction using sodium borohydride (SB) afforded ruthenium nanosponge in its fcc phase. The as prepared hcp ruthenium nanosponge was found to be catalytically more active compared to the as prepared fcc ruthenium nanosponge for hydrogenation of benzene. The hcp ruthenium nanosponge was found to be thermally stable and recyclable over several cycles. This self‐supported hcp ruthenium nanosponge shows excellent catalytic activity towards hydrogenation of various substituted benzenes. Moreover, the ruthenium nanosponge catalyst was found to bring about selective hydrogenation of aromatic cores of phenols and aryl ethers to the respective alicyclic products without hydrogenolysis of the C−O bond.

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.

Development of Heterogeneous Ni-Ni Complex/HPA-RNi Catalyst for Hydrogenation of Benzene

Development of Heterogeneous Ni-Ni Complex/HPA-RNi Catalyst for Hydrogenation of Benzene

Ru–B nanoparticles on metal–organic frameworks as excellent catalysts for hydrogenation of benzene to cyclohexane under mild reaction conditions

Ru–B/MIL-53(AlCr) affords an exceptionally high turnover frequency (TOF) of 6.4 s−1for hydrogenation of benzene to cyclohexane under mild reaction conditions.

Performance of Ru/La2O3–ZnO Catalyst for the Selective Hydrogenation of Benzene to Cyclohexene

Cyclohexene is an important intermediate product for a highly efficient and greener formation of major end products like adipic acid, nylon 6, and nylon 6.6. By using a complex tetra-phase system (g/l/l/s) including hydrogen (g), water (l), an organic phase, i.e., benzene (l), and a supported ruthenium catalyst (s) it is possible to get the desired intermediate cyclohexene based on benzene. We prepared an oxide-supported ruthenium catalyst that was applied together with minimal amounts of the additive NaDCA (sodium dicyanamide) in a batch and continuous apparatus for the selective benzene hydrogenation. We compared these two processes and reached by an optimization of the reaction parameters in continuous process selectivities up to 50% at conversions of 36%. This corresponds to cyclohexene yields of 18% over a period of 100 h. Finally, the catalyst was characterized using X-ray diffraction (XRD), transmission electron spectroscopy (TEM), inductively coupled plasma optical emission spectrometry (ICP-OES), and laser scattering to understand the performance of the catalyst and the effect of the small deactivation.

Synthesis of ruthenium@graphene nanomaterials in propylene carbonate as re-usable catalysts for the solvent-free hydrogenation of benzene

Ruthenium nanoparticles (Ru-NPs) can be deposited on thermally reduced graphite oxide (TRGO) in propylene carbonate (PC). Propylene carbonate is a biodegradable and non-toxic solvent. Synthesis of Ru-NPs and deposition on TRGO were achieved by decomposition of ruthenium dodecacarbonyl, Ru3(CO)12, by microwave irradiation. Ru@graphene nanomaterials were identified and characterized by high resolution transmission electron microscopy (TEM, HR-TEM), energy-dispersive X-ray diffraction (EDX), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and powder X-ray diffraction (PXRD) with a small diameter and size distribution of 7±4nm Ru-NPs on TRGO. These Ru@graphene nanomaterials are active catalysts for the solvent-free hydrogenation of benzene to cyclohexane under mild conditions (100 °C, 10 bar) with activities of 34,000(molcyclohexane)⋅(molRu)−1⋅h−1 and over 90% conversion in at least ten consecutive runs.

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.

Ru-Zn catalysts for selective hydrogenation of benzene using coprecipitation in low alkalinity

Several unsupported Ru-Zn catalysts were successfully prepared using the coprecipitation method under low alkaline conditions, and their catalytic performance was evaluated for the selective liquid-phase hydrogenation of benzene. The effect of the amount of ZnCl2 added to the coprecipitation solution on the physical and catalytic properties of the Ru-Zn catalysts was studied whilst keeping the amount of the NaOH precipitant constant. The properties of the resulting catalysts were characterized by N2 adsorption, X-ray diffraction, and temperature-programmed reduction. The effects of the stirring rate and the amount of ZnSO4 additive on the catalytic properties of the Ru-Zn catalysts were investigated using the optimal Zn content. The recyclability of the optimal Ru-Zn catalyst was also explored. The results revealed that the optimal Zn content for the Ru-Zn catalysts was 16.7 wt%, and the selectivity for cyclohexene could reach up to 80% (yield > 45%) when the benzene conversion was 57% in an aqueous solution of ZnSO4 (0.45 mol/L) under the optimal reaction conditions (i.e., hastelloy reactor, 1200 r/min, 150 °C and 5 MPa of H2 pressure). The presence of ZnO crystals in the Ru catalysts was found to be critical to obtaining high selectivity for cyclohexene (>80%). The Ru-Zn catalysts prepared under the low alkaline conditions also showed good stability, which indicates that they could potentially be used for industrial application.

Partial Hydrogenation of Benzene to Cyclohexene over Ru-Zn/MCM-41

Ru-Zn/MCM-41 catalysts for the partial hydrogenation of benzene with differing Zn contents were prepared by the incipient-wetness impregnation method. The evaluation results indicate that Zn simultaneously depresses the catalysts activity and cyclohexene selectivity. This can be attributed to the change in the amount of the different hydrogenation sites affected by Zn. The weak hydrogenation sites can promote benzene conversion, and the strong hydrogenation sites, a novel kind of hydrogenation site found on the surface of the catalysts under the influence of Zn, are beneficial for cyclohexene hydrogenation.