- Novel Rate Constants for a Catalytic Hydrogenation Reaction of Propylene Obtained by a Frequency Response Method
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"Reaction rate (or FR) spectra" of a catalytic hydrogenation of propylene over Pt or Rh at 314 K were observed in a cell reactor composed of a proton-conducting membrane.It is shown that a variety of the spectra can be reproduced well by "characteristic functions", K*H(ω) and K*C(ω), which may be derived from a three-stage model composed of five elementary steps: X(g) -->/X(a) -->/X(a) --> propane (X: hydrogen or propylene), where X denotes the gaseous molecule; AX and BX are the first and second intermediate adsorbed species.Seven rate constants concerning these five steps were evaluated by matching K*H(ω) or K*C(ω) to the spectrum; five of them, kPX, k-AX, kAX, k-BX, and kBX, are ordinary rate constants, while the other two, l-BX and lBX, are novel ones.Since all these constants except kPX are independent of the amounts of catalyst, they are characteristic of active sites and can be compared with each other.On the basis of these constants, kinetic details have been discussed; for instance, mean residence times of AX and BX, τAX and τBX, respectively, were determined by (k-AX + kAX)-1 and (k-BX + kBX)-1, resulting in (in second units) τAH ca. 0.3 and τBH ca. 3 for hydrogen and τAC ca. 3 for propylene over Pt, while over Rh they were τAH ca. 1 and τBH ca. 3; τAC ca. 102 and τBC ca. 102.The nondimensional rate constants, l-BX and lBX, were indispensable to reproduce the various FR spectra; l-BH and lBH were positive, whereas l-BC and lBC were negative over both catalysts, which suggests heat effects.
- Yasuda, Yusuke,Iwai, Kayo,Takakura, Kazumi
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- Chemisorption and Surface Reactions in Cooperative Adsorption Systems.
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The kinetics of propylene hydrogenation catalyzed by thermally treated supported platinum catalysts can be described by a Langmuir-Hinshelwood mechanism. The parameter values of the resulting rate equation, however, clearly depend on the coverage of the catalyst surface. Because of the instabilities observed with this reaction, it has to be assumed that lateral interaction of chemisorbed hydrogen and chemisorbed propylene is the main reason for this parameter variation. Using the lattice-gas model and the methods of statistical thermodynamics, straight-forward equations are derived which take into account the influence of this interaction on chemisorption and surface reaction in binary adsystems. The usefulness of these equations for the evaluation of kinetic measurements is demonstrated.
- Hesse
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- Frequency Response Method for the Study of Kinetics of a Heterogeneous Catalytic Reaction of Gases
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A new frequency response method is proposed on the basis of actual data on C3H6 + H2 -> C3H8 over Pt/Al2O3 at 273 K observed under each partial pressure of ca. 10 Pa: the gas space of a continuous-flow reactor was varied sinusoidally, and every partial pressure variation induced was followed by a mass spectrometer.Both amplitude and phase difference of ΔR observed in the angular frequency region from 40 to 60 rad/min were described well by , where Rs and PH(s) denote the overall reaction rate and the partial pressure of H2 at the steady state before the oscillation and is the time derivative of the pressure variation, dΔPH/dt.The "rate constant" n and κ were 0.15 and 7 * 1E-2 min, respectively.The unordinary rate equation involving PH was interpreted by R = ?dμd in terms of the driving force or the free energy drop, μd, and the frequency factor, ?d, at the rate-limiting step; Δ?d/?d = nΔPH/PH(s) and .The newly derived rate constant κ seemed to decrease with increasing temperature.The turnover frequency could be given by n/κ.
- Yasuda, Yusuke
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- Organometallic complexes in supported ionic-liquid phase (SILP) catalysts: A PHIP NMR spectroscopy study
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para-Hydrogen induced polarization (PHIP) NMR spectroscopy emerges as an efficient and robust method for on-line monitoring of gas-phase hydrogenation reactions. Here we report detailed investigations of supported ionic liquid phase (SILP) catalysts in a continuous gas-phase hydrogenation of propene with PHIP NMR spectroscopy. A relocation of the rhodium complex in the thin layer of ionic liquid in the SILP catalyst at the initial stage of the propene hydrogenation is demonstrated. PHIP NMR spectroscopy can provide profound insight into the evolution of SILP catalysts during hydrogenation reactions.
- Gong, Qingxia,Klankermayer, Juergen,Bluemich, Bernhard
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- Reductive dehalogenation of 1,3-dichloropropane by a [Ni(tetramethylcyclam)]Br2-Nafion modified electrode
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Dechlorination reaction of 1,3-dichloropropane, a contaminant solvent, was investigated by electrochemical reduction in aqueous medium using a Ni(tmc)Br2complex, known as effective catalyst in dehalogenation reactions. The catalytic activity of the complex was first investigated by cyclic voltammetry and flow homogeneous redox catalysis using a graphite felt as working electrode. A total degradation of 1,3-dichloropropane was obtained after 5 h of electrolysis with a substrate/catalyst ratio of 2.3. The concentration of chloride ions determined by ion chromatography analysis showed a dechlorination yield of 98%. The complex was then immobilized on the graphite felt electrode in a Nafion film. Flow heterogeneous catalytic reduction of 1,3-dichloropropane was then carried out with the [Ni(tmc)]Br2-modified Nafion electrode. GC analyses underlined the total degradation of the substrate in only 3.5 h with a substrate/catalyst ratio of 100. A dechlorination yield of 80% was obtained, as seen with ion chromatography analyses of chloride ion. Comparison of both homogeneous and heterogeneous reactions highlighted the interest of the [Ni(tmc)]Br2-modified Nafion electrode that led to a higher stability of the catalyst with a turnover number of 180 and a higher current efficiency.
- Fontmorin,He,Floner,Fourcade,Amrane,Geneste
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- In situ x-ray absorption spectroscopy and nonclassical catalytic hydrogenation with an iron(II) catecholate immobilized on a porous organic polymer
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The oxidation state and coordination number of immobilized iron catecholate EtO2Fe(CAT-POP) were determined by X-ray absorption spectroscopy (XAS) under a variety of conditions. We find the as-prepared material to be three-coordinate Fe2+ that readily oxidizes to Fe3+ upon exposure to air but remains three-coordinate. Both the reduced and oxidized Fe(CAT-POP) catalyze olefin hydrogenation in batch and flow reactors. We determined the catalytic rates for both species and also observed by means of XAS that the oxidation state of the iron centers does not change in hydrogen at the reaction temperature. Therefore, we postulate that the mechanism of hydrogenation by Fe(CAT-POP) proceeds through one of several possible nonclassical mechanisms, which are discussed.
- Kraft, Steven J.,Hu, Bo,Zhang, Guanghui,Miller, Jeffrey T.,Hock, Adam S.
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- Selective Catalytic Chemistry at Rhodium(II) Nodes in Bimetallic Metal–Organic Frameworks
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We report the first study of a gas-phase reaction catalyzed by highly dispersed sites at the metal nodes of a crystalline metal–organic framework (MOF). Specifically, CuRhBTC (BTC3?=benzenetricarboxylate) exhibited hydrogenation activity, while other isostructural monometallic and bimetallic MOFs did not. Our multi-technique characterization identifies the oxidation state of Rh in CuRhBTC as +2, which is a Rh oxidation state that has not previously been observed for crystalline MOF metal nodes. These Rh2+ sites are active for the catalytic hydrogenation of propylene to propane at room temperature, and the MOF structure stabilizes the Rh2+ oxidation state under reaction conditions. Density functional theory calculations suggest a mechanism in which hydrogen dissociation and propylene adsorption occur at the Rh2+ sites. The ability to tailor the geometry and ensemble size of the metal nodes in MOFs allows for unprecedented control of the active sites and could lead to significant advances in rational catalyst design.
- Shakya, Deependra M.,Ejegbavwo, Otega A.,Rajeshkumar, Thayalan,Senanayake, Sanjaya D.,Brandt, Amy J.,Farzandh, Sharfa,Acharya, Narayan,Ebrahim, Amani M.,Frenkel, Anatoly I.,Rui, Ning,Tate, Gregory L.,Monnier, John R.,Vogiatzis, Konstantinos D.,Shustova, Natalia B.,Chen, Donna A.
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- REDISPERSION OF COBALT METAL PARTICLES IN Co/TiO2 CATALYST AND ITS EFFECT ON PROPENE HYDROGENATION
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The rate of propene hydrogenation on Co/TiO2 catalyst, prepared by an alkoxide technique, was significantly enhanced when the catalyst was reduced by hydrogen at 700 deg C.However, over the catalyst prepared by an usual impregnation method, the enhancement of the rate was not observed at any reduction temperatures.The effects of reduction temperatures on the rate of propene hydrogenation were elucidated by redispersion of metallic cobalt particles.
- Takasaki, Seiji,Takahashi, Kaoru,Suzuki, Hideo,Sato, Yuzuru,Ueno, Akifumi,Kotera, Toyohashi
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- Kinetic Determination of the Gas-Phase Decarbonylation of Butyraldehyde in the Presence of HCl Catalyst
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The gas-phase kinetics and mechanism of the homogeneous elimination of CO from butyraldehyde in the presence of HCl has been experimentally studied. The reaction is homogeneous and follows the second-order kinetics with the following rate expression: log k1 (s?1 L mol?1) = (13.27 ± 0.36) – (173.2 ± 4.4) kJ mol?1(2.303RT)?1. Experimental data suggested a concerted four-membered cyclic transition state type of mechanism. The first and rate-determining step occurs through a four-membered cyclic transition state to produce propane and formyl chloride. The formyl chloride intermediate rapidly decomposes to CO and HCl gases.
- Julio, Libia L.,Cartaya, Loriett,Maldonado, Alexis,Monascal, Yeljair,Mora, José R.,Cordova, Tania,Chuchani, Gabriel
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- A stable 16-electron iridium(iii) hydride complex grafted on SBA-15: A single-site catalyst for alkene hydrogenation
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The dihydride pincer complex [IrH2(POCOP)] reacts with surface silanols of mesoporous silica (SBA-15) to give the coordinatively unsaturated, yet stable hydridesiloxo Ir(iii) species [IrH(O-SBA-15)(POCOP)]. The silica-grafted complex catalyses the hydrogenation of ethene and propene at low temperature and pressure without prior activation.
- Rimoldi, Martino,Fodor, Daniel,Van Bokhoven, Jeroen A.,Mezzetti, Antonio
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- Direct synthesis of propylene oxide in the liquid phase under mild conditions
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Here, we study the direct synthesis of propylene oxide (PO) on Pd-based catalysts operating under mild conditions (40?°C, 5.5?bar) and in a continuous flow microreactor. We show that the PO yield can be improved by a factor of two, with respect to the values present in literature, by using a Pd–Pt/TS-1 catalyst in excess of oxygen. Moreover, we compare the PO reaction with the hydrogen peroxide (H2O2) synthesis, being H2O2 (or OOH species) the intermediate and rate limiting step of the direct PO formation. We found that the optimal conditions for the PO synthesis are not advantageous for the H2O2 productivity. In this respect, the presence of Pt, which improves the PO selectivity by lowering the hydrogenation of propylene, negatively affects the H2O2 productivity due to an acceleration of its side reactions. This effect is more pronounced for the Pd–Au/TS-1 catalyst, which shows a high performance for H2O2 production. However, the PO formation remains relatively poor due to a very fast hydrogenation of propylene to propane. We conclude that the optimization of the H2O2 synthesis is not sufficient to improve the direct PO formation. Indeed, the hydrogenation of propylene needs also to be considered.
- Kertalli,Schouten,Nijhuis
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- RHODIUM-CATALYSED HYDROGENATION OF ALLENE AS REVEALED BY 14C>PROPYLENE AND 14C>CARBON MONOXIDE TRACER STUDIES
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The low-pressure hydrogenation of allene has been studied over alumina-supported rhodium catalysts.During a series of hydrogenation reactions the activity of the catalyst progressively decreases to a steady-state value and thereafter remains constant.The reaction proceeds in two distinct stages.During the first stage the selectivity for the formation of propylene is ca. 95percent.Hydrogenation of allene+14C>propylene mixtures shows that, in the first stage allene hydrogenation, the yield of propane from the hydrogenation of propylene is relatively small.Direct hydrogenation of adsorbed allene to propane is the major route to formation of the latter, the selectivity being a measure of the relative rates of hydrogenation of allene directly to propylene and propane.Adsorption of 14C>propylene on freshly reduced catalysts occurs in two distinct stages: a non-linear primary region followed by a linear secondary region.No primary region is observed for propylene adsorption on steady-state catalysts or on freshly reduced catalysts in the presence of allene.However, 14C>propylene adsorption and hydrogenation occurs in the presence of allene on the secondary region with both freshly reduced and steady-state catalysts.Adsorption of 14C>carbon monoxide shows that, whilst the decrease in activity of the catalyst to a steady-state constant value corresponds to the progressive build-up of a surface hydrocarbonaceous layer, the combined effects of allene and hydrogen on a carbon monoxide-precovered surface leads to an increase in the capacity of that surface for carbon monoxide adsorption.Treatment of the carbon-monoxide-precovered surface with hydrogen alone does not lead to such an increase.It is suggested that, under the influence of the allene hydrogenation reaction, the surface undergoes some reconstruction.Evidence is presented to show the presence of separate surface site for the hydrogenation of allene to propane and for the hydrogenation of propylene to propane.
- Kuhnen, Nivaldo C.,Thomson, Samuel J.,Webb, Geoffrey
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- Kinetics of Propene Hydrogenation over Platinum and Platinum-Tin Catalysts Supported on Polyamide
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The rate of propene hydrogenation has been measured, in a flow system, over platinum supported on inorganic materials (Al2O3, MgO) and polyamides(Nylon 66 and Nylon 610).The effect of adding tin to Pt/Nylon 66 has also been investigated.The orders of reaction with respect to the reactants have been found to be strongly influenced by the nature of the support used.In particular, higher values of the reaction order with respect to propene have been found on Pt/Nylon samples.The presence of electron-deficient sites is suggested.Addition of Sn causes a drastic decrease in catalytic activity, suggesting Sn enrichment on the surface and/or an electronic interaction between the two metal components.
- Galvagno, Signorino,Staiti, Pietro,Antonucci, Pierluigi,Donato, Andrea,Pietropaolo, Rosario
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- Heterogeneous Parahydrogen Pairwise Addition to Cyclopropane
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Hyperpolarized gases revolutionize functional pulmonary imaging. Hyperpolarized propane is a promising emerging contrast agent for pulmonary MRI. Unlike hyperpolarized noble gases, proton-hyperpolarized propane gas can be imaged using conventional MRI scanners with proton imaging capability. Moreover, it is non-toxic odorless anesthetic. Furthermore, propane hyperpolarization can be accomplished by pairwise addition of parahydrogen to propylene. Here, we demonstrate the feasibility of propane hyperpolarization via hydrogenation of cyclopropane with parahydrogen. 1H propane polarization up to 2.4 % is demonstrated here using 82 % parahydrogen enrichment and heterogeneous Rh/TiO2 hydrogenation catalyst. This level of polarization is several times greater than that obtained with propylene as a precursor under the same conditions despite the fact that direct pairwise addition of parahydrogen to cyclopropane may also lead to formation of propane with NMR-invisible hyperpolarization due to magnetic equivalence of nascent parahydrogen protons in two CH3 groups. NMR-visible hyperpolarized propane demonstrated here can be formed only via a reaction pathway involving cleavage of at least one C–H bond in the reactant molecule. The resulting NMR signal enhancement of hyperpolarized propane was sufficient for 2D gradient echo MRI of ～5.5 mL phantom with 1×1 mm2 spatial resolution and 64×64 imaging matrix despite relatively low chemical conversion of cyclopropane substrate.
- Salnikov, Oleg G.,Kovtunov, Kirill V.,Nikolaou, Panayiotis,Kovtunova, Larisa M.,Bukhtiyarov, Valerii I.,Koptyug, Igor V.,Chekmenev, Eduard Y.
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- Robust In Situ Magnetic Resonance Imaging of Heterogeneous Catalytic Hydrogenation with and without Hyperpolarization
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Magnetic resonance imaging (MRI) is a powerful technique to characterize reactors during operating catalytic processes. However, MRI studies of heterogeneous catalytic reactions are particularly challenging because the low spin density of reacting and product fluids (for gas phase reactions) as well as magnetic field inhomogeneity, caused by the presence of a solid catalyst inside a reactor, exacerbate already low intrinsic sensitivity of this method. While hyperpolarization techniques such as parahydrogen induced polarization (PHIP) can substantially increase the NMR signal intensity, this general strategy to enable MR imaging of working heterogeneous catalysts to date remains underexplored. Here, we present a new type of model catalytic reactors for MRI that allow the characterization of a heterogeneous hydrogenation reaction aided by the PHIP signal enhancement, but also suitable for the imaging of regular non-polarized gases. These catalytic systems permit exploring the complex interplay between chemistry and fluid-dynamics that are typically encountered in practical systems, but mostly absent in simple batch reactors. High stability of the model reactors at catalytic conditions and their fabrication simplicity make this approach compelling for in situ studies of heterogeneous catalytic processes by MRI.
- Kovtunov, Kirill V.,Lebedev, Dmitry,Svyatova, Alexandra,Pokochueva, Ekaterina V.,Prosvirin, Igor P.,Gerasimov, Evgeniy Y.,Bukhtiyarov, Valerii I.,Müller, Christoph R.,Fedorov, Alexey,Koptyug, Igor V.
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- Production of Propane and Other Short-Chain Alkanes by Structure-Based Engineering of Ligand Specificity in Aldehyde-Deformylating Oxygenase
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Biocatalytic propane production: structure-based engineering of aldehyde-deformylating oxygenase improves specificity for short- and medium-chain-length aldehydes and enhances the propane generation in whole-cell biotransformations. This presents new opportunities for developing biocatalytic modules for the production of volatile "drop-in" biofuels.
- Khara, Basile,Menon, Navya,Levy, Colin,Mansell, David,Das, Debasis,Marsh, E. Neil G.,Leys, David,Scrutton, Nigel S.
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- Rhodium catechol containing porous organic polymers: Defined catalysis for single-site and supported nanoparticulate materials
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A single-site, rhodium(I) catecholate containing porous organic polymer was prepared and utilized as an active catalyst for the hydrogenation of olefins in both liquid-phase and gas-phase reactors. Liquid-phase, batch hydrogenation reactions at 50 psi and ambient temperatures result in the formation of rhodium metal nanoparticles supported within the polymer framework. Surprisingly, the Rh(I) complex is catalytically active and stable for propene hydrogenation at ambient temperatures under gas-phase conditions, where reduction of the Rh(I) centers to Rh(0) nanoparticles requires at least 200-250 °C under a flow of hydrogen gas. After high-temperature treatment, the Rh(0) nanoparticles are active arene hydrogenation catalysts that convert toluene to methylcyclohexadiene at a rate of 9.3 × 10-3 mol g-1 h-1 of rhodium metal at room temperature. Conversely, single-site Rh(I) is an active and stable catalyst for the hydrogenation of propylene (but not toluene) under gas-phase conditions at room temperature.
- Kraft, Steven J.,Zhang, Guanghui,Childers, David,Dogan, Fulya,Miller, Jeffrey T.,Nguyen, Sonbinh T.,Hock, Adam S.
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- Tetrahedral Nickel(II) Phosphosilicate Single-Site Selective Propane Dehydrogenation Catalyst
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Silica-supported Ni catalysts usually show poor stability, low selectivity, and short lifetime in high-temperature alkane dehydrogenation reactions owing to the reduction to Ni0 nanoparticles under the reaction conditions. The introduction of a phosphate ligand to silica-supported NiII provided single-site tetrahedral NiII phosphosilicate as a stable and selective propane dehydrogenation catalyst. The NiII?OSi bonds activate the C?H bonds of propane and make the NiII sites catalytically active, whereas the Ni?OP bonds prevent the reduction of NiII to Ni0 under the dehydrogenation conditions and help to achieve high stability and selectivity.
- Zhang, Guanghui,Yang, Ce,Miller, Jeffrey T.
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- Silica-Encapsulated Pt-Sn Intermetallic Nanoparticles: A Robust Catalytic Platform for Parahydrogen-Induced Polarization of Gases and Liquids
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Recently, a facile method for the synthesis of size-monodisperse Pt, Pt3Sn, and PtSn intermetallic nanoparticles (iNPs) that are confined within a thermally robust mesoporous silica (mSiO2) shell was introduced. These nanomaterials offer improved selectivity, activity, and stability for large-scale catalytic applications. Here we present the first study of parahydrogen-induced polarization NMR on these Pt-Sn catalysts. A 3000-fold increase in the pairwise selectivity, relative to the monometallic Pt, was observed using the PtSn@mSiO2 catalyst. The results are explained by the elimination of the three-fold Pt sites on the Pt(111) surface. Furthermore, Pt-Sn iNPs are shown to be a robust catalytic platform for parahydrogen-induced polarization for in vivo magnetic resonance imaging.
- Zhao, Evan W.,Maligal-Ganesh, Raghu,Xiao, Chaoxian,Goh, Tian-Wei,Qi, Zhiyuan,Pei, Yuchen,Hagelin-Weaver, Helena E.,Huang, Wenyu,Bowers, Clifford R.
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- Role of Solid-state Structure in Propene Hydrogenation with Nickel Catalysts
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Various forms of Ni-based catalysts have been prepared by different synthetic procedures, affording ordinary f.c.c.Ni metal, a novel h.c.p.Ni allotrope and amorphous NiB powders.The samples were characterized by physical and chemical methods, including XPS, WAXS and SAXS analysis.These techniques provide detailed descriptions of the degree of oxidation of the metal surface and of the physical state of the bulk.The catalytic performance of each catalyst was tested in propene hydrogenation using a flow reactor under mild conditions.Data of intrinsic catalytic activity and activation energy were obtained and are discussed in relation to the morphology and solid state of the samples studied here.The intrinsic catalytic activity of h.c.p.Ni is much higher that that of f.c.c, suggesting the paramount importance of structural features in determining catalytic activity.
- Carturan, Giovanni,Enzo, Stefano,Ganzeria, Renzo,Lenarda, Maurizio,Zanoni, Roberto
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- Separation of Anti-Phase Signals Due to Parahydrogen Induced Polarization via 2D Nutation NMR Spectroscopy
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The present work introduces a novel method for the selective detection of 1H NMR anti-phase signals caused by the pairwise incorporation of parahydrogen into olefins on noble-metal-containing catalysts. Via a two-dimensional (2D) nutation NMR experiment, the anti-phase signals of hyperpolarized 1H nuclei are separated due to their double nutation frequency compared to that of thermally polarized 1H nuclei. For demonstrating this approach, parahydrogen induced polarization (PHIP) was achieved via the hydrogenation of propene with parahydrogen on platinum-containing silica and investigated by in situ 1H MAS NMR spectroscopy under continuous-flow conditions, that is, the hydrogenation reaction was performed inside the magnet of the NMR spectrometer. The 2D nutation NMR experiment described in the present work is useful for the separation of overlapping anti-phase and in-phase signals due to hyperpolarized and thermally polarized 1H nuclei, respectively, which is important for research in the field of heterogeneous catalysis.
- Obenaus, Utz,Althoff-Ospelt, Gerhard,Lang, Swen,Himmelmann, Robin,Hunger, Michael
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- Ultra-Low Loading Pt/CeO2 Catalysts: Ceria Facet Effect Affords Improved Pairwise Selectivity for Parahydrogen Enhanced NMR Spectroscopy
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Oxide supports with well-defined shapes enable investigations on the effects of surface structure on metal–support interactions and correlations to catalytic activity and selectivity. Here, a modified atomic layer deposition technique was developed to achieve ultra-low loadings (8–16 ppm) of Pt on shaped ceria nanocrystals. Using octahedra and cubes, which expose exclusively (111) and (100) surfaces, respectively, the effect of CeO2 surface facet on Pt-CeO2 interactions under reducing conditions was revealed. Strong electronic interactions result in electron-deficient Pt species on CeO2 (111) after reduction, which increased the stability of the atomically dispersed Pt. This afforded significantly higher NMR signal enhancement in parahydrogen-induced polarization experiments compared with the electron-rich platinum on CeO2 (100), and a factor of two higher pairwise selectivity (6.1 %) in the hydrogenation of propene than any previously reported monometallic heterogeneous Pt catalyst.
- Song, Bochuan,Choi, Diana,Xin, Yan,Bowers, Clifford R.,Hagelin-Weaver, Helena
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- Investigation on the Thermal Cracking and Interaction of Binary Mixture of N-Decane and Cyclohexane
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Abstract: The investigation about the thermal cracking performance and interaction of different components in hydrocarbon fuels is of great significance for optimizing the formulation of high-performance hydrocarbon fuels. In this work, thermal cracking of n-decane, cyclohexane and their binary mixture were studied in a tubular reactor under different temperatures and pressures. The gas and liquid products were analyzed in detail with different gas chromatography. The main gas products of pure n-decane and cyclohexane are similar, and there is a certain difference in the main liquid products. For binary mixture, the overall conversion rate and gas yield are lower than their theoretical value. The cracking conversion rate of n-decane in binary mixture is lower than that in pure n-decane, but the opposite change occurs for cyclohexane, and the effect become more obvious as the increase of the reaction pressure. These experimental phenomena can be explained by bond dissociation energy and free radical reaction mechanism. The pressure affects the free radical reaction path, and high pressure is more conducive to bimolecular hydrogen abstraction reaction, which will lead to different product content. A law of interaction between the n-decane and cyclohexane was observed according to the experimental results. [Figure not available: see fulltext.]
- Chen, Xuejiao,Pang, Weiqiang,Wang, Bo,Zhang, Ziduan,Zhou, Lingxiao,Zhu, Quan
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- Conversion of Phenol and Lignin as Components of Renewable Raw Materials on Pt and Ru-Supported Catalysts
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Hydrogenation of phenol in aqueous solutions on Pt-Ni/SiO2, Pt-Ni-Cr/Al2 O3, Pt/C, and Ru/C catalysts was studied at temperatures of 150–250? C and pressures of 40–80 bar. The possibility of hydrogenation of hydrolysis lignin in an aqueous medium in the presence of a Ru/C catalyst is shown. The conversion of hydrolysis lignin and water-soluble sodium lignosulfonate occurs with the formation of a complex mixture of monomeric products: a number of phenols, products of their catalytic hydrogenation (cyclohexanol and cyclohexanone), and hydrogenolysis products (cyclic and aliphatic C2 –C7 hydrocarbons).
- Bobrova, Nataliia A.,Bogdan, Tatiana V.,Bogdan, Viktor I.,Koklin, Aleksey E.,Mishanin, Igor I.
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- Synergistic effect of Fe and Ga incorporation into ZSM-5 to increase propylene production in the cracking ofn-hexane utilizing a microchannel reactor
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In the present study, the effect of various amounts of Fe and Ga in the catalytic cracking ofn-hexane in a microchannel reactor was investigated using experimental design by the D-optimal method. Nano zeolites incorporated with Fe and Ga metals were synthesized in a fluorine environment to investigate the synergistic effect of the metals on the textural and acidic properties of the catalysts, which ultimately improved the performance of the synthesized catalysts in the efficient production of light olefins, in particular propylene. Three synthesis parameters including the Si/Al, Si/Fe and Si/Ga ratios were considered as the main factors to determine the optimal conditions for obtaining the maximum conversion ofn-hexane, yield of light olefins, and P/E ratio and minimum yield of alkanes as the responses. In sample FeGa-1, the P/E ratio reached 3.97, indicating the significant effect of the substituted metals in improving the desirable routes for propylene production. According to the results of the acidic properties, Fe, Al and Ga increased the number of total acid sites and the strengths of strong and weak acid sites, respectively. In addition, according to the results obtained from sample FeGa-7, the synergistic effect of Fe and Ga increased the number of weak acid sites.
- Halimitabrizi, Parya,Rashidzadeh, Mehdi,Sakha, Mohsen Rostami,Salari, Darush,Soltanali, Saeed
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p. 13833 - 13846
(2021/08/16)
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- Heterogeneous Parahydrogen-Induced Polarization of Diethyl Ether for Magnetic Resonance Imaging Applications
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Magnetic resonance imaging (MRI) with the use of hyperpolarized gases as contrast agents provides valuable information on lungs structure and function. While the technology of 129Xe hyperpolarization for clinical MRI research is well developed, it requires the expensive equipment for production and detection of hyperpolarized 129Xe. Herein we present the 1H hyperpolarization of diethyl ether vapor that can be imaged on any clinical MRI scanner. 1H nuclear spin polarization of up to 1.3 % was achieved using heterogeneous hydrogenation of ethyl vinyl ether with parahydrogen over Rh/TiO2 catalyst. Liquefaction of diethyl ether vapor proceeds with partial preservation of hyperpolarization and prolongs its lifetime by ≈10 times. The proof-of-principle 2D 1H MRI of hyperpolarized diethyl ether was demonstrated with 0.1×1.1 mm2 spatial and 120 ms temporal resolution. The long history of use of diethyl ether for anesthesia is expected to facilitate the clinical translation of the presented approach.
- Salnikov, Oleg G.,Svyatova, Alexandra,Kovtunova, Larisa M.,Chukanov, Nikita V.,Bukhtiyarov, Valerii I.,Kovtunov, Kirill V.,Chekmenev, Eduard Y.,Koptyug, Igor V.
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supporting information
p. 1316 - 1322
(2020/12/14)
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- Photo-Initiated Cobalt-Catalyzed Radical Olefin Hydrogenation
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Outer-sphere radical hydrogenation of olefins proceeds via stepwise hydrogen atom transfer (HAT) from transition metal hydride species to the substrate. Typical catalysts exhibit M?H bonds that are either too weak to efficiently activate H2 or too strong to reduce unactivated olefins. This contribution evaluates an alternative approach, that starts from a square-planar cobalt(II) hydride complex. Photoactivation results in Co?H bond homolysis. The three-coordinate cobalt(I) photoproduct binds H2 to give a dihydrogen complex, which is a strong hydrogen atom donor, enabling the stepwise hydrogenation of both styrenes and unactivated aliphatic olefins with H2 via HAT.
- Sang, Sier,Unruh, Tobias,Demeshko, Serhiy,Domenianni, Luis I.,van Leest, Nicolaas P.,Marquetand, Philipp,Schneck, Felix,Würtele, Christian,de Zwart, Felix J.,de Bruin, Bas,González, Leticia,V?hringer, Peter,Schneider, Sven
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p. 16978 - 16989
(2021/08/09)
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- Transformation synthesis of SSZ-13 zeolite from ZSM-35 zeolite
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Interzeolite conversion as a promising alternative strategy for zeolite synthesis has received extensive attention. It is of great significance to understand the potential rules of conversion between zeolites with different topologies for effective regulation of zeolite synthesis. Hydrothermal conversion of ZSM-35 (FER-type) zeolite containing the mor composite building units into SSZ-13 zeolite (CHA-type) using N,N,N-trimethyl-1-adamantammonium hydroxide (TMAdaOH) as template was performed for the first time. The effects of TMAdaOH/SiO2 ratio, Na2O/SiO2 ratio, the additional starting zeolite and crystallization time on the interzeolite conversion of ZSM-35 into SSZ-13 were investigated. The interzeolite conversion mechanism concerning the synthesis of SSZ-13 from ZSM-35 zeolite was proposed and verified by DFT calculation. The results of DFT calculations suggested that ZSM-35 zeolite with mor composite building unit had the potential to decompose into 6-Membered Rings, and further transform into CHA-type zeolite containing d6r composite building unit. Therefore, zeolites containing mor structure have the potential to be converted into zeolites containing d6r structure.
- Bing, Liancheng,Cong, Wenwen,Han, Dezhi,Li, Kexu,Li, Qiang,Wang, Fang,Wang, Guangjian,Xu, Changyou
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- Pd-Modified ZnO-Au Enabling Alkoxy Intermediates Formation and Dehydrogenation for Photocatalytic Conversion of Methane to Ethylene
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Photocatalysis provides an intriguing approach for the conversion of methane to multicarbon (C2+) compounds under mild conditions; however, with methyl radicals as the sole reaction intermediate, the current C2+ products are dominated by ethane, with a negligible selectivity toward ethylene, which, as a key chemical feedstock, possesses higher added value than ethane. Herein, we report a direct photocatalytic methane-to-ethylene conversion pathway involving the formation and dehydrogenation of alkoxy (i.e., methoxy and ethoxy) intermediates over a Pd-modified ZnO-Au hybrid catalyst. On the basis of various in situ characterizations, it is revealed that the Pd-induced dehydrogenation capability of the catalyst holds the key to turning on the pathway. During the reaction, methane molecules are first dissociated into methoxy on the surface of ZnO under the assistance of Pd. Then these methoxy intermediates are further dehydrogenated and coupled with methyl radical into ethoxy, which can be subsequently converted into ethylene through dehydrogenation. As a result, the optimized ZnO-AuPd hybrid with atomically dispersed Pd sites in the Au lattice achieves a methane conversion of 536.0 μmol g-1 with a C2+ compound selectivity of 96.0% (39.7% C2H4 and 54.9% C2H6 in total produced C2+ compounds) after 8 h of light irradiation. This work provides fresh insight into the methane conversion pathway under mild conditions and highlights the significance of dehydrogenation for enhanced photocatalytic activity and unsaturated hydrocarbon product selectivity.
- Jiang, Wenbin,Low, Jingxiang,Mao, Keke,Duan, Delong,Chen, Shuangming,Liu, Wei,Pao, Chih-Wen,Ma, Jun,Sang, Shuaikang,Shu, Chang,Zhan, Xiaoyi,Qi, Zeming,Zhang, Hui,Liu, Zhi,Wu, Xiaojun,Long, Ran,Song, Li,Xiong, Yujie
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supporting information
p. 269 - 278
(2021/01/12)
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- Enabling Semihydrogenation of Alkynes to Alkenes by Using a Calcium Palladium Complex Hydride
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Selective hydrogenation of alkynes to alkenes requires a catalytic site with suitable electronic properties for modulating the adsorption and conversion of alkyne, alkene as well as dihydrogen. Here, we report a complex palladium hydride, CaPdH2, featured by electron-rich [PdH2]δ- sites that are surrounded by Ca cations that interacts with C2H2 and C2H4 via σ-bonding to Pd and unusual cation-πinteraction with Ca, resulting in a much weaker chemisorption than those of Pd metal catalysts. Concomitantly, the dissociation of H2 and hydrogenation of C2Hx (x = 2-4) species experience significant energy barriers over CaPdH2, which is fundamentally different from those reported Pd-based catalysts. Such a unique catalytic environment enables CaPdH2, the very first complex transition-metal hydride catalyst, to afford a high alkene selectivity for the semihydrogenation of alkynes.
- Chen, Ping,Chen, Ruting,Gao, Wenbo,Guo, Jianping,Guo, Qing,Pei, Qijun,Qin, Chao,Wu, Anan,Xiong, Zhitao,Yan, Hanxue
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supporting information
p. 20891 - 20897
(2021/12/14)
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- Hydrodeoxygenation of C4-C6 sugar alcohols to diols or mono-alcohols with the retention of the carbon chain over a silica-supported tungsten oxide-modified platinum catalyst
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The hydrodeoxygenation of erythritol, xylitol, and sorbitol was investigated over a Pt-WOx/SiO2 (4 wt% Pt, W/Pt = 0.25, molar ratio) catalyst. 1,4-Butanediol can be selectively produced with 51% yield (carbon based) by erythritol hydrodeoxygenation at 413 K, based on the selectivity over this catalyst toward the regioselective removal of the C-O bond in the -O-C-CH2OH structure. Because the catalyst is also active in the hydrodeoxygenation of other polyols to some extent but much less active in that of mono-alcohols, at higher temperature (453 K), mono-alcohols can be produced from sugar alcohols. A good total yield (59%) of pentanols can be obtained from xylitol, which is mainly converted to C2 + C3 products in the literature hydrogenolysis systems. It can be applied to the hydrodeoxygenation of other sugar alcohols to mono-alcohols with high yields as well, such as erythritol to butanols (74%) and sorbitol to hexanols (59%) with very small amounts of C-C bond cleavage products. The active site is suggested to be the Pt-WOx interfacial site, which is supported by the reaction and characterization results (TEM and XAFS). WOx/SiO2 selectively catalyzed the dehydration of xylitol to 1,4-anhydroxylitol, whereas Pt-WOx/SiO2 promoted the transformation of xylitol to pentanols with 1,3,5-pentanetriol as the main intermediate. Pre-calcination of the reused catalyst at 573 K is important to prevent coke formation and to improve the reusability.
- Betchaku, Mii,Cao, Ji,Liu, Lujie,Nakagawa, Yoshinao,Tamura, Masazumi,Tomishige, Keiichi,Yabushita, Mizuho
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p. 5665 - 5679
(2021/08/16)
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- Insight into Carbocation-Induced Noncovalent Interactions in the Methanol-to-Olefins Reaction over ZSM-5 Zeolite by Solid-State NMR Spectroscopy
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Carbocations such as cyclic carbenium ions are important intermediates in the zeolite-catalyzed methanol-to-olefins (MTO) reaction. The MTO reaction propagates through a complex hydrocarbon pool process. Understanding the carbocation-involved hydrocarbon pool reaction on a molecular level still remains challenging. Here we show that electron-deficient cyclopentenyl cations stabilized in ZSM-5 zeolite are able to capture the alkanes, methanol, and olefins produced during MTO reaction via noncovalent interactions. Intermolecular spatial proximities/interactions are identified by using two-dimensional 13C–13C correlation solid-state NMR spectroscopy. Combined NMR experiments and theoretical analysis suggests that in addition to the dispersion and CH/π interactions, the multiple functional groups in the cyclopentenyl cations produce strong attractive force via cation-induced dipole, cation–dipole and cation–π interactions. These carbocation-induced noncovalent interactions modulate the product selectivity of hydrocarbon pool reaction.
- Cai, Wenjin,Chu, Yueying,Deng, Feng,Hu, Min,Li, Shenhui,Qi, Guodong,Wang, Chao,Wang, Qiang,Xu, Jun
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supporting information
p. 26847 - 26854
(2021/11/17)
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- The Hydrodeoxygenation of Glycerol over NiMoSx: Catalyst Stability and Activity at Hydropyrolysis Conditions
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Catalytic activity tests were run to elucidate the chemistry and catalyst stability for the hydrodeoxygenation of glycerol and other aliphatic oxygenates over a NiMoSx/Al2O3 catalyst at different pretreatments at hydropyrolysis conditions in a continuous flow reactor. Reactivity metrics were developed to quantify and compare the reactivity of NiMo for deoxygenation, hydrogenation, and C?C cleavage. Activity experiments showed sulfided NiMo and reduced NiMo catalysts had similar deoxygenation and hydrogenation activity for glycerol HDO at 400 °C and 270 psig H2 with the NiMoSx catalyst showing higher C?C cleavage activity. Without a sulfur co-feed, both the NiMoSx and NiMoOx catalysts lost >40 % deoxygenation activity over 30 h time on stream. With a 2100 ppm H2S co-feed the NiMoSx catalyst showed a 12 times decrease in the deactivation rate for deoxygenation and 6 time decrease in the deactivation rate for hydrogenation. The main products at high conversion were propylene, propane, ethylene, methane, CO, methanol, ethanol, and 1-propanol. At low conversion, the major products were unsaturated allyl alcohol, acrolein, hydroxyacetone, and acetaldehyde. With no H2S co-feed at short contact times, there was a significant amount of carbon loss possibly due to condensation reactions, while at 2100 ppm H2S in the feed, the carbon balance was 102.4 %. Temperature programmed oxidation of the spent NiMoSx catalysts after 30 h of glycerol HDO without an H2S co-feed showed that one of the causes of deactivation was coking.
- Anderson, Anthony D.,Lanci, Michael P.,Buchanan, J. Scott,Dumesic, James A.,Huber, George W.
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p. 425 - 437
(2020/11/30)
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- Coupling conversion of methane with carbon monoxideviacarbonylation over Zn/HZSM-5 catalysts
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Efficient direct transformation of methane into value-added chemicals has great significance for long-term sustainability of fuels and chemicals, but remains a major challenge due to its high inertness. Reported here is that methane can be activated effectivelyviacarbonylation with CO over Zn/HZSM-5 catalysts under mild conditions. The selectivity to aromatics alone reaches 80% among all hydrocarbon products at 823 K, whereas as high as 92% ethane selectivity is achieved at a lower temperature of 673 K.13CO isotope labelling experiments demonstrate that approximately 50% of the carbon atoms in all the products originate from carbon monoxide, whereas another half of the carbons come from methane, indicating that the precursors of hydrocarbon products are acyl compounds and/or acetic acid formed by carbonylation of methane with carbon monoxide. This provides potential for transformation of methane into value-added chemicals under mild reaction conditions.
- Wen, Fuli,Zhang, Jin,Chen, Zhiyang,Zhou, Ziqiao,Liu, Hongchao,Zhu, Wenliang,Liu, Zhongmin
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p. 1358 - 1364
(2021/03/14)
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- Role of Ga3+promoter in the direct synthesis of iso-butanolviasyngas over a K-ZnO/ZnCr2O4catalyst
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The direct synthesis of iso-butanol is an important reaction in syngas (composed of CO and H2) conversion. K-ZnO/ZnCr2O4(K-ZnCr) is a commonly used catalyst. Here, Ga3+is used as an effective promoter to boost the efficiency of the catalyst and retard the production of CO2. X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflection spectroscopy and electron microscopy were used to characterize the structural variations with different amounts of Ga3+, the results showed that the particle size of the catalyst decreases with the addition of Ga3+. The temperature-programmed desorption of NH3and CO2, and diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTs) analysis of the CO adsorption revealed that the acidity and basicity were altered owing to the different forms of Ga3+adoption. X-ray photoelectron spectroscopy and density functional theory (DFT) calculations revealed that the formation of Ga clusters that are coordinated on the exposed surfaces of ZnCr2O4, and undergo a tetra-coordinated Ga3+exchange with one of the Zn in ZnCr2O4(ZG) and ZnGa2O4, probably depends on the amount of Ga added. The structural evolution of the Ga3+promoted K-ZnO/ZnCr2O4catalysts can be described as follows: (i) the main forms are ZG and Ga coordinated ZnCr2O4, in which the amount of Ga3+is below 1.10 wt%; and (ii) the Ga3+containing compound is gradually changed from ZG to ZnGa2O4and the amount of gallium clusters increased when the amount of Ga3+was higher than 1.10 wt%. The catalytic performance evaluation results show that K-Ga1.10ZnCr exhibits the highest space time yield and selectivity of alcohols, in which the three compounds play different roles in syngas conversion: ZG is the main active site that boosts the efficiency of the catalysts, owing to the intensified CO adsorption and decreased activation energy of CHO formation through CO hydrogenation; ZnGa2O4only modifies the surface basicity and acidity on the catalyst, thereby impacting the carbon chain growth after the CO is adsorbed. The effects of Ga coordinated with ZnCr2O4shows little impact on the CO adsorption owing to the weak electron donating effects of Ga.
- Zhang, Tao,Zeng, Chunyang,Wu, Yingquan,Gong, Nana,Yang, Jiaqian,Yang, Guohui,Tsubaki, Noritatsu,Tan, Yisheng
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p. 1077 - 1088
(2021/02/26)
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- Chromium-Based Catalysts and Processes for Converting Alkanes into Higher and Lower Aliphatic Hydrocarbons
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Processes for cracking an alkane reactant to form a lower aliphatic hydrocarbon product and for converting an alkane reactant into a higher aliphatic hydrocarbon product are disclosed, and these processes include a step of contacting the alkane reactant with a supported chromium (II) catalyst. In addition to the formation of various aliphatic hydrocarbons, such as linear alkanes, branched alkanes, 1-alkenes, and internal alkenes, aromatic hydrocarbons and hydrogen also can be produced.
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Paragraph 0081; 0082; 0086; 0104
(2021/03/19)
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- Light-Induced Nonoxidative Coupling of Methane Using Stable Solid Solutions
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Achieving efficient and direct conversion of methane under mild conditions is of great significance for innovations in the chemical industry. However, the efficiency and lifetime of most catalysts remain too far from practical requirements, since it is difficult to break the first C?H bond of methane as well as to suppress the following complete dehydrogenation (or overoxidation) and the resulting carbonaceous deposition (or CO2). Here, we report that wurtzite GaN:ZnO solid solutions exhibit unique and unprecedented photocatalytic performances for the nonoxidative coupling of methane at room temperature, exclusively generating ethane with nearly stoichiometric H2. High conversion rate (>330 μmol g?1 h?1), long-term stability (>70 h), and superior coke-resistance were achieved. At 293 K, the methane conversion exceeds 7 %, comparable to the equilibrium conversion of thermal catalysis at 910 K. Mechanistic studies revealed that the N-ZnGa-ON units and the absence of acid sites on the surface played crucial roles in reactivity and coke resistance, respectively.
- Li, Jiayang,Li, Lu,Mu, Xiaowei,Mu, Xiaoyue,Qian, Yumeng,Wang, Guangming,Zhan, Qingyun
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supporting information
p. 20760 - 20764
(2021/08/13)
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- Synthesis of hierarchical GaZSM-5 zeolites by the HCl treatment method and their catalytic performance in methanol aromatization
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A series of ZSM-5 samples exhibiting isomorphic substitution with Ga and containing both micropores and mesopores were synthesized by a posttreatment method involving different concentrations of hydrochloric acid. Various techniques were used to analyse the posttreatment changes in pores and acidity of GaZSM-5. The effects of pores and acidity on the catalytic lifetime of GaZSM-5 zeolites and on the product distribution for MTA were investigated. Significant amounts of mesopores were introduced by HCl treatment, and the micropore mass transfer rate of the products of the MTA reaction increased as the selectivity for aromatics obviously increased. In addition, skeleton Ga and nonskeletal species were removed simultaneously by HCl treatment, and the strong acid density and weak acid density of GaZSM-5 were decreased significantly. The catalytic lifetimes of the modified samples were obviously extended, and the conversion rate remained at 100% after 30 h at a reaction temperature of 400 °C and a space velocity of 10 h?1. The improvement of catalyst lifetime in the MTA reaction is due to the combination of decreased acidity and increased mesoporosity.
- Han, Zheng,Ma, Fangwei,Ma, Huixia,Wu, Guang,Zhou, Feng
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p. 17108 - 17115
(2021/10/04)
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- Linear Hydrocarbon Chain Growth from a Molecular Diruthenium Carbide Platform
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The formation of linear hydrocarbon chains by sequential coupling of C1units on the metal surface is the central part of the Fischer-Tropsch (F-T) synthesis. Organometallic complexes have provided numerous models of relevant individual C-C coupling events but have failed to reproduce the complete chain lengthening sequence that transforms a linear Cnhydrocarbon chain into its Cn+1homologue in an iterative fashion. In this work, we demonstrate stepwise growth of linear Cnhydrocarbon chains and their conversion to their Cn+1homologues via consecutive addition of CH2units on a molecular diruthenium carbide platform. The chain growth sequence is initiated by the formation of a μ-η1:η1-C═CH2ligand from a C + CH2coupling between the μ-carbido complex [(Cp*Ru)2(η-NPh)(μ-C)] (1; Cp* = η5-C5Me5) and Ph2SCH2. Then, the chain propagates via a general C═CHR + CH2coupling and subsequent hydrogen-assisted isomerization of the resulting allene ligand μ-η1:η3-H2C═C═CHR to a higher vinylidene homologue μ-η1:η1-C═CH(CH2)R. By repeating this reaction sequence, up to C6chains have been synthesized in a stepwise fashion. The key step of this chain homologation sequence is the selective hydrogenation of the μ-η1:η3-allene unit to the corresponding μ-alkylidene ligand. Isotope labeling and computational studies indicate that this transformation proceeds via the hydrogenation of the allene ligand to a terminal alkene form and its isomerization to the μ-alkylidene ligand facilitated by the coordinatively unsaturated diruthenium platform.
- Fujita, Hiroaki,Matsuzaka, Hiroyuki,Ohata, Jun,Takemoto, Shin,Teramoto, Akira
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supporting information
p. 16105 - 16112
(2021/10/01)
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- CO2 hydrogenation to C5+ hydrocarbons over K-promoted Fe/CNT catalyst: Effect of potassium on structure–activity relationship
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Developing efficient catalysts for direct CO2 hydrogenation to fuel hydrocarbons is of great significance for the effective utilization of CO2, and C5+ selectivity is one critical indicator for the process economics. In this work, a series of K-promoted Fe/CNT catalysts were prepared by the co-impregnation method, and their catalytic performance for CO2 hydrogenation was studied in a slurry-bed reactor. As a result, CO2 conversion and C5+ selectivity showed positive correlation with the increase of K/Fe ratio from 0 to 0.3, but further increase of K/Fe ratio above 0.3 slightly affected its. The catalyst with a K/Fe molar ratio of 0.3 achieved the best performance with CO2 conversion of 23.7% and C5+ selectivity of 56%. In addition, the structure–activity relationship of the catalyst was discussed based on various characterization results. K-modified catalysts presented a higher specific surface area and stronger CO2 chemisorption, which helped to improve CO2 conversion and C5+ selectivity. However, excessive potassium loading caused a loss of specific surface area, reduction degree, and graphitization degree of the catalyst, which inhibited the CO2 chemisorption and the formation of C5+ hydrocarbons.
- Dai, Liya,Chen, Yao,Liu, Renjie,Li, Xin,Ullah, Niamat,Li, Zhenhua
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- Rational Manipulation of Stacking Arrangements in Three-Dimensional Zeolites Built from Two-Dimensional Zeolitic Nanosheets
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Unit-cell-thin zeolitic nanosheets have emerged as fascinating materials for catalysis and separation. The controllability of nanosheet stacking is extremely challenging in the chemistry of two-dimensional zeolitic materials. To date, the organization of zeolitic nanosheets in hydrothermal synthesis has been limited by the lack of tunable control over the guest–host interactions between organic structure-directing agents (OSDAs) and zeolitic nanosheets. A direct synthetic methodology is reported that enables systematic manipulation of the aluminosilicate MWW-type nanosheet stacking. Variable control of guest–host interactions is rationally achieved by synergistically altering the charge density of OSDAs and synthetic silica-to-alumina composition. These finely controlled interactions allow successful preparation of a series of three-dimensional (3D) zeolites, with MWW-layer stacking in wide ranges from variably disorder to fully ordered, leading to tunable catalytic activity in the cracking reaction. These results highlight unprecedented opportunities to modulate zeolitic nanosheets arrangement in 3D zeolites whose structure can be tailored for catalysis and separation.
- Chaikittisilp, Watcharop,Han, Lu,Ma, Tianqiong,Okubo, Tatsuya,Shen, Yihan,Sun, Junliang,Wakihara, Toru,Wang, Yong,Xu, Le,Yokoi, Toshiyuki
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supporting information
p. 19934 - 19939
(2020/09/02)
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- Immobilization of an Iridium Pincer Complex in a Microporous Polymer for Application in Room-Temperature Gas Phase Catalysis
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An iridium dihydride pincer complex [IrH2(POCOP)] is immobilized in a hydroxy-functionalized microporous polymer network using the concepts of surface organometallic chemistry. The introduction of this novel, truly innocent support with remote OH-groups enables the formation of isolated active metal sites embedded in a chemically robust and highly inert environment. The catalyst maintained high porosity and without prior activation exhibited efficacy in the gas phase hydrogenation of ethene and propene at room temperature and low pressure. The catalyst can be recycled for at least four times.
- Chaoui, Nicolas,Drie?, Matthias,Epping, Jan Dirk,K?nig, Michaela,Pachfule, Pradip,Rigo, Massimo,Schmidt, Johannes,Teichert, Johannes F.,Thomas, Arne,Tran Ngoc, Trung,Trunk, Matthias,Ye, Meng-Yang
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supporting information
p. 19830 - 19834
(2020/09/02)
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- Effect of Re and Al2O3 Promotion on the Working Stability of Cobalt Catalysts for the Fischer–Tropsch Synthesis
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Abstract: The results of the working stability studies of cobalt catalysts based on SiO2 and Al2O3 promoted with Re and Al2O3 in the synthesis of hydrocarbons from CO and H2 in continuous tests for 200–300 h are presented. The prepared catalysts were characterized by transmission electron spectroscopy, temperature-programmed reduction with hydrogen, temperature-programmed desorption of CO, and X-ray fluorescence spectroscopy and tested at a temperature 200°C, a pressure of 0.1 MPa, and a GHSV of 100 h–1. It was determined that a cobalt–silica catalyst promoted with Al2O3 had the highest activity. It was established that the addition of Al2O3 to a cobalt–silica catalyst increased the conversion of CO and selectivity for C5+ hydrocarbons and inhibited the agglomeration of Co particles under the action of a reaction atmosphere in the Fischer–Tropsch synthesis. It was found that the initial conversion of CO increased by a factor of 2 upon the introduction of 0.1 wt % rhenium into the Co/γ-Al2O3 catalyst; however, the rate of its deactivation increased in this case due to an almost twofold increase in the size of cobalt particles in the course of synthesis after operation for 300 h.
- Denisov, O. D.,Narochniy, G. B.,Papeta, O. P.,Savost’yanov, A. P.,Yakovenko, R. E.,Zubkov, I. N.
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p. 310 - 317
(2020/04/22)
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- Direct synthesis of H2O2 over acid-treated Pd/C catalyst derived from a Pd-Co core-shell structure
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Although a wide range of Pd/C catalysts has been developed for the direct synthesis of H2O2, low H2O2 yields remain a challenging issue. In this study, we propose a novel catalyst design involving the formation of Pd@Co(BO3)2 core-shell nanoparticles (NPs) on an activated carbon support followed by the cobalt borate shell etching with H3PO4. The non-noble metal shell efficiently suppressed unfavorable aggregation of Pd NPs, resulting in the formation of small and monodisperse Pd NPs after stripping the cobalt. The use of H3PO4 was also beneficial to obtain a high H2O2 yield by decreasing the metallic nature of Pd and enabling the acid-treated activated carbon to act as a solid acid support. The features of the acid-treated Pd/C catalyst derived from the Pd@Co(BO3)2 core-shell were superior enough for achieving extremely high activity in the direct synthesis of H2O2. The H2O2 productivity of 5721 mmol-H2O2/g-Pd.h with 88.1% H2O2 selectivity reported herein is one of the best values among Pd/C catalysts developed to date. It was also demonstrated that the cobalt borate shell should be completely removed because cobalt accelerated H2O2 decomposition and hydrogenation.
- Lee, Seungsun,Chung, Young-Min
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p. 270 - 278
(2019/10/02)
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- CO and CO2 methanation over Ni/Al@Al2O3 core–shell catalyst
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Core–shell Al@Al2O3, which was obtained by hydrothermal surface oxidation of Al metal particles, was used as the support in supported Ni catalysts for CO and CO2 methanation. The core–shell micro-structured support (Al@Al2O3) helped develop a highly efficient Ni-based catalyst compared with conventional γ-Al2O3 for these reactions. Moreover, the deposition–precipitation method was shown to outperform the wet impregnation method in the preparation of the active supported Ni catalysts. The catalysts were characterized using various techniques, namely, N2 physisorption, H2 chemisorption, CO2 chemisorption, temperature-programmed reduction with H2, temperature-programmed desorption after CO2 adsorption, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, high-resolution transmission electron microscopy, and in situ diffuse reflectance infrared Fourier transform spectroscopy. Higher Ni dispersion when using Al@Al2O3 as the support and the deposition–precipitation method resulted in better catalytic performance for CO methanation. Furthermore, the higher density of medium basic sites and enhanced CO2 adsorption capacity observed for Ni/Al@Al2O3 helped increase catalytic activity for CO2 methanation.
- Le, Thien An,Kim, Jieun,Kang, Jong Kyu,Park, Eun Duck
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p. 622 - 630
(2019/10/02)
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- CO and CO2 methanation over M (M[dbnd]Mn, Ce, Zr, Mg, K, Zn, or V)-promoted Ni/Al@Al2O3 catalysts
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Effects of metal promoter on CO and CO2 methanation were examined over Ni-M (M = Mn, Ce, Zr, Mg, K, Zn, or V)/Al@Al2O3 catalysts prepared by the co-impregnation method. Ni-M (M = Mn, Ce, or Zr)/γ-Al2O3 catalysts were also investigated for comparison. The prepared catalysts were characterized with a variety of techniques such as N2 physisorption, CO2 chemisorption, H2 chemisorption, temperature-programmed reduction with H2 (H2-TPR), temperature-programmed desorption of CO2 (CO2-TPD), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Among different promoters, Mn, Ce, Mg, V, and Zr are beneficial to enhance both CO and CO2 methanation activity due to the improvement of the Ni dispersion. The Ni-V/Al@Al2O3 catalyst performs the highest CO methanation activity due to the largest Ni sites. However, it is not the best one for CO2 methanation among tested catalysts because of the much decrease in CO2 adsorption capacity. The promotional effect of Mn is the most remarkable for both CO and CO2 methanation. On the other hand, the negative effect of K and Zn was observed on both CO and CO2 methanation by the small number of active Ni sites and the decrease in the amount of basic sites. The CO2 methanation mechanism over Ni-Mn/Al@Al2O3 catalyst is elucidated by the transform route: adsorbed carbonate species – formate species – methane under hydrogenation process.
- Le, Thien An,Kim, Jieun,Kang, Jong Kyu,Park, Eun Duck
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- Co-Ru catalysts with different composite oxide supports for Fischer–Tropsch studies in 3D-printed stainless steel microreactors
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Bimetallic Co-Ru on different mesoporous composite oxides (m-SiO2-Al2O3, m-SiO2-TiO2, m-TiO2-Al2O3) and CoRu-m-SiO2-TiO2 were synthesized by incipient wet-impregnation (IWI) and one-pot (OP) hydrothermal methods, respectively. Bimetallic catalysts were coated in the microchannels of 3D-printed stainless steel (SS) microreactors for Fischer-Tropsch (FT) studies. The physiochemical properties of the catalysts were examined by BET, XRD, SEM, TEM, TPR, TGA-DSC and XPS techniques. The TPR results showed that the method and the composite support had a profound effect on the reducibility of the active sites. All the catalysts resisted deactivation for first 50 h and 10Co5Ru/m-SiO2-TiO2 (IWI) was most stable with ～80 % CO conversion at the end of 60 h. The stability and activity of the catalysts were observed in the order: 10Co5Ru/m-SiO2-TiO2 (IWI) >10Co5Ru/m-SiO2-Al2O3 (IWI) >10Co5Ru/m-Al2O3-TiO2 (IWI) >10Co5Ru-m-SiO2-TiO2 (OP). The TPO and XRD analyses of the spent catalysts confirmed coking as a potential factor but not the only cause of catalyst deactivation over time.
- Abrokwah, R.,Arslan, M.,Bepari, S.,Kuila, D.,Li, Xin,Mohammad, N.
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- Study on the unsteady state oxidative coupling of methane: Effects of oxygen species from O2, surface lattice oxygen, and CO2on the C2+selectivity
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This study examined the effects of oxygen species on the unsteady-state oxidative coupling of methane (OCM) using a lengthy catalyst bed of Na2WO4/Mn/SiO2. The reaction conditions, including the methane-to-oxygen ratio, ratio of feed gas dilution by N2, quantity of catalyst, and feed flow rate were adjusted for the continuous flow fixed bed reaction system. While the O2 gas initiated methyl radical formation from methane, the surface lattice oxygen atoms improved the dehydrogenation of paraffins to olefins without significant activation of methane. The addition of CO2 as a mild oxidizing agent was also tested and slightly improved OCM selectivity with slightly lower methane conversion were observed. This journal is
- Choi, Jae-Wook,Ha, Jeong-Myeong,Lim, Seoyeon,Song, Kwang Ho,Suh, Dong Jin,Yoon, Suji
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p. 35889 - 35897
(2020/10/27)
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- Potassium promoted core-shell-structured FeK@SiO2-GC catalysts used for Fischer-Tropsch synthesis to olefins without further reduction
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Fe-based Fischer-Tropsch synthesis (FTS) catalysts, promoted by graphitic carbon (GC) and potassium, were directly prepared by a novel modified sol-gel method without further reduction. The effects of the GC promoter and K contents on the catalyst structures and FTS performance were systematically studied. The significant improvement of FTS performance was attributed to GC, which acted as a reductant for synthesizing metallic Fe0 from Fe3+ in the chelating complexes, and effectively enhanced the strength of SiO2 channels. Meanwhile, an appropriate amount of K ions promoted CO chemisorption and inhibited H2 chemisorption by affecting the electronic properties of iron, resulting in a lower hydrogenation capacity and a higher olefin selectivity. Transmission electron microscopy and CO-TPD characterization proved that FeK@SiO2-GC catalysts had well-defined core-shell structures and higher CO chemisorption. The FTS results indicated that the introduction of a small amount of GC and K (K/Fe/GC, 1.5/100/100) improved the reduction and dispersion of iron during the calcination process, and significantly enhanced the FTS activity. The CO conversion and C2-C4 olefin selectivity of the catalyst increased rapidly from 21.1% and 23.7% to 53.5% and 41.3% after GC and K promotion. The GC and K promoted Fe-based catalysts prepared by a modified sol-gel method, which omits the complex and high energy consumption reduction process, can be used directly for highly efficient FTS and thus will be more promising in the future.
- Ni, Zhijiang,Zhang, Xuefei,Bai, Jirong,Wang, Zhilei,Li, Xi,Zhang, Yanhu
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- Effect of Promoter Nature on Synthesis Gas Conversion to Alcohols over (K)MeMoS2/Al2O3 Catalysts
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The influence of the promoter nature and of a modifier in (K)(Me)MoS2/Al2O3 (Me=Fe, Co, Ni) catalysts on the conversion and selectivity of products of synthesis gas conversion to alcohols and jnl oxygenates was investigated. Relationships between promoter nature, hydrocarbon chain length and selectivity in the formed alcohols were established. Electronic structure of a promoter atom in an active site (AS) was found to strongly affect selectivity of alcohol formation. Promotion of the S-edge by Fe, Co or Ni suppressed hydrogen activation, which resulted in a lower synthesis gas conversion. Promotion of the M-edge by Fe, Co, or Ni entailed the formation of double vacancies which are active sites of synthesis gas conversion. Potassium affected the oxophilicity of Mo atoms and reduced Co/Ni-promoted MoS AS. It decreased the probability of C?O bond breaking in the adsorbed intermediate and shifted selectivity from the formation of alkyl towards alkoxide fragments over these catalysts.
- Maximov, Vladimir V.,Permyakov, Eugenii A.,Dorokhov, Viktor S.,Wang, Anjie,Kooyman, Patricia J.,Kogan, Victor M.
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p. 1443 - 1452
(2020/02/11)
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- Synthesis of SAPO-34 Zeolite from Laponite and Its Application in the MTO Reaction
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In this work, SAPO-34 zeolite with high catalytic activity was successfully synthesized by hydrothermal method from laponite as the single Si source. Compared with the traditional method of synthesizing zeolites from clay, the laponite after swelling can be directly used in the synthesis process of zeolite. The crystallization behavior of SAPO-34 synthesized from laponite was investigated by XRD, FTIR, N2 adsorption–desorption, SEM-EDX, ICP-MS, and DR-UV/Vis. The process can be summarized as follows: the Si and Mg elements were produced by the depolymerization of laponite, then the primary building units of SAPO-34 zeolite were formed under hydrothermal conditions; finally, the crystal nucleus began to form, and crystallization was triggered. Compared with the conventional SAPO-34 synthesized from TEOS, the SAPO-34 synthesized from laponite exhibited higher selectivity to light olefins and longer lifetime, which can be attributed to the suitable strength of acidity. This work points to a straightforward route to the synthesis of SAPO-34 from laponite.
- Chen, Xueshuai,Jiang, Rongli,Wang, Xingwen,Zhou, Zihan
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supporting information
(2020/06/02)
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- Enhanced Catalytic Performance of Zn-containing HZSM-5 upon Selective Desilication in Ethane Dehydroaromatization Process
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The effect of introducing mesoporosity on the catalytic stability and selectivity of Zn-containing ZSM-5 catalysts was investigated for direct conversion of ethane to high-value aromatics. Voids and mesopores were created in the zeolite (Si/Al=40) by selective desilication (recrystallization) using ammonium hydroxide and cetyltrimethylammonium bromide. Zinc was incorporated in the samples by incipient wetness impregnation to achieve different concentrations of 0.5, 1 and 5 wt %. The samples were characterized by XRD, N2 physisorption, TGA, NH3-TPD, ICP-OES, FTIR, 1H, 27Al and 29Si solid-state MAS NMR. The desilicated samples were compared to their parent analogues for ethane conversion to aromatics such as benzene, toluene and xylenes (BTX). All of the desilicated samples showed an improvement in BTX yield and catalytic stability. Thus, the presence of mesoporosity increases the accessibility to the active sites and facilitates the mass transfer of aromatic compounds, which result in higher performance and catalytic stability of the desilicated ZSM-5 samples containing zinc.
- Goodarzi, Farnoosh,Thumbayil, Rouzana Pulikkal,Enemark-Rasmussen, Kasper,Mielby, Jerrik,Nguyen, Thoa T.M.,Beato, Pablo,Joensen, Finn,Kegn?s, S?ren
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p. 1519 - 1526
(2020/02/11)
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- Revealing the Correlation between Catalytic Selectivity and the Local Coordination Environment of Pt Single Atom
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Single atom catalysts (SACs) have recently attracted great attention in heterogeneous catalysis and have been regarded as ideal models for investigating the strong interaction between metal and support. Despite the huge progress over the past decade, the deep understanding on the structure-performance correlation of SACs at a single atom level still remains to be a great challenge. In this study, we demonstrate that the variation in the coordination number of the Pt single atom can significantly promote the propylene selectivity during propyne semihydrogenation (PSH) for the first time. Specifically, the propylene selectivity greatly increases from 65.4% to 94.1% as the coordination number of Pt-O increases from ～3.4 to ～5, whereas the variation in the coordination number of Pt-O slightly influences the turnover frequency values of SACs. We anticipate that the present work may deepen the understanding on the structure-performance of SACs and also promote the fundamental research in single atom catalysis.
- Cao, Muhan,Chu, Mingyu,Gong, Jin,Li, Youyong,Lin, Haiping,Liu, Fangfang,Liu, Yu,Luo, Jun,Wang, Xuchun,Xu, Yong,Zhang, Qiao
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p. 6865 - 6872
(2020/10/20)
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- Non oxidative and oxidative dehydrogenation of: N -octane using FePO4: Effect of different FePO4phases on the product selectivity
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The activation of n-octane with O2 has been investigated over different phases of FePO4 which were formed under dehydrogenation and oxidative dehydrogenation (ODH) conditions. Catalytic reactions were done with the tridymite-like FePO4 catalyst which showed a high selectivity towards cracked products and carbon oxides. Under dehydrogenation conditions, tridymite phase FePO4 is transformed into the iron pyrophosphate phase (Fe2P2O7). Octenes, aromatics, C8 oxygenates, carbon oxides (COx) and cracked products were present in the product stream. The iron pyrophosphate phase, under oxidative dehydrogenation conditions, showed high selectivity towards cracked products and on regeneration (restoring of the catalytic activity) with molecular oxygen it transformed into the α-phase and quartz type phase. The regenerated catalyst (α-phase and quartz type phase) exhibited a higher selectivity to ODH products when compared to the fresh and deactivated (Fe2P2O7) catalysts. The transformation of both fresh and deactivated catalysts was evident at a temperature of 450 °C. Since the α-phase is the active phase under ODH conditions and transformations between the reduced and α-phase take place reversibly, this could explain the highest selectivity towards octenes within this temperature range. Fresh and regenerated catalysts showed steady state conversions with time under constant conditions, showing that phase transformations were mainly due to varying temperature and oxidative environment. Characterization results show that FePO4 contains fivefold coordinate Fe3+ in the regenerated and fresh catalysts, and this species is believed to be responsible for selective n-octane activation. The surface area, acidity and metal dispersion of the deactivated and regenerated catalyst showed lower values when compared to the fresh catalysts. The results obtained from M?ssbauer spectroscopy showed direct correlation with the XRD data as well as the TPR-TPO results in terms of the phase changes and oxidation state of the calcined, uncalcined, reduced and reoxidised catalyst. This journal is
- Bharuth-Ram, K.,Dasireddy, Venkata D. B. C.,Friedrich, Holger B.,Khan, Faiza B.,Singh, Sooboo
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p. 7591 - 7600
(2020/12/01)
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- Selective Deposition of Cobalt and Copper Oxides on BiVO4 Facets for Enhancement of CO2 Photocatalytic Reduction to Hydrocarbons
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The nanostructure of a semiconductor is a crucial parameter for efficient photocatalytic performance. Hereby, we have synthesized monoclinic bismuth vanadate (BiVO4) crystals with controlled ratio of {010} and {110} facets. The selective deposition of CuOx and CoOx over {010} and {110} facets has been performed using photo-reduction and photo-oxidation methods, respectively. It resulted in a highly efficient charge separation of photogenerated electrons and holes and enhancement of the photocatalytic reduction of CO2 by H2O into hydrocarbons, including CH4, C2H6 and C3H8. The controlled co-catalyst deposition over different semiconductor facets provides a strategy for the synthesis of hydrocarbons from CO2 and H2O by efficient charge separation.
- Yu, Xiang,Ordomsky, Vitaly V.,Khodakov, Andrei Y.
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p. 740 - 749
(2020/01/21)
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- C?C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM-5 Zeolite
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Despite significant progress achieved in Fischer–Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn2+-ion exchanged ZSM-5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO2) at 20 % CO conversion. NMR spectroscopy, X-ray absorption spectroscopy, and X-ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM-5. Quasi-in-situ solid-state NMR, obtained by quenching the reaction in liquid N2, detects C2 species such as acetyl (-COCH3) bonding with an oxygen, ethyl (-CH2CH3) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Br?nsted acid site of the catalyst, respectively. These species could provide insight into C?C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn2+-ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ-13, MCM-22, and ZSM-12) all give ethane predominantly. By contrast, a physical mixture of ZnO-ZSM-5 favors formation of hydrocarbons beyond C3+. These results provide an important guide for tuning the product selectivity in syngas conversion.
- Bao, Xinhe,Chen, Yuxiang,Gong, Ke,Hou, Guangjin,Jiao, Feng,Pan, Xiulian,Si, Rui
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supporting information
p. 6529 - 6534
(2020/03/04)
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- Investigation of metal oxide additives onto Na2WO4-Ti/SiO2 catalysts for oxidative coupling of methane to value-added chemicals
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The oxidative coupling of methane (OCM) is a closely related reaction process involving the transformation of methane (CH4) and O2 mixtures into value-added chemicals such as ethylene and ethane (i.e. C2+). This work presents the effects of metal oxide additives into the Na2WO4-Ti/SiO2 catalyst on the performance of the OCM reaction. Several metal oxide additives—including oxides of Co, Mn, Cu, Fe, Ce, Zn, La, Ni, Zr, Cr, and V—were investigated with the Na2WO4-Ti/SiO2 catalyst. All of the catalysts were prepared using co-impregnation and the catalyst activity test was performed in a plug flow reactor at a reactor temperature range of 600–800 °C and atmospheric pressure. The physicochemical properties of the prepared catalysts relating to their catalytic activity were discussed by using the information of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurements. Na2WO4-Ti/SiO2 added Mn was found to be the most active catalyst, involving shifts of binding energies of W 4f and Ti 2p toward lower binding energies. Moreover, a variety of operating conditions—including reactant- to-nitrogen gas ratio, catalyst mass, reactor temperature, and total feed flow rate—were intensively examined for the OCM reaction using the Na2WO4-Ti-Mn/SiO2 catalyst. The maximum C2+ yield was subsequently discovered at 22.09% with 62.3% C2+ selectivity and 35.43% CH4 conversion. Additionally, the stability of the Na2WO4-Ti-Mn/SiO2 catalyst was also monitored with time on stream for 24 h.
- Sringam, Sarannuch,Kidamorn, Phattaradit,Chukeaw, Thanaphat,Chareonpanich, Metta,Seubsai, Anusorn
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p. 263 - 269
(2020/04/20)
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- Turning Waste into Value: Potassium-Promoted Red Mud as an Effective Catalyst for the Hydrogenation of CO2
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Since 1887, red mud has been an unavoidable waste derived from the production of alumina in the Bayer process. Because of its high alkalinity and metal loading, red mud disposal and storage constitute a significant environmental risk. With worldwide storage capacity reaching its limits and no alternatives to the Bayer Process, the development of methods for the valorization of red mud is a must. In this study, red mud is converted into an efficient catalyst for the valorization of CO2. By simple potassium promotion, 45 % conversion of CO2 with a light olefin (C2–C4) selectivity of 36 % is achieved at 375 °C, 30 bar, and 9600 mL g?1 h?1, matching the performance of some of the best catalysts reported to date.
- Russkikh, Artem,Shterk, Genrikh,Al-Solami, Bandar H.,Fadhel, Bandar A.,Ramirez, Adrian,Gascon, Jorge
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p. 2981 - 2987
(2020/05/04)
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- GAS-PHASE HOMOGENEOUS OXIDATIVE DEHYDROGENATION AND COUPLING OF ORGANIC MOLECULES
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Disclosed are gas-phase ODH and OCP processes for converting alkanes (e.g., C2H6 and C3H8) to alkenes (e.g., C2H4 and C3H6) or oxygenates (e.g., methanol, ethanol, isopropanol, or propylene oxide) or converting alkenes (e.g., ethylene and propene) and oxygenates (e.g., methanol, ethanol, isopropanol or propylene oxide) to longer carbon-chain alkenes or longer carbon-chain alkanes with or without solid catalysts.
- -
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Paragraph 0201
(2020/05/28)
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- PREPARATION METHOD FOR PREPARING A CATALYST BASED ON IRON NANOPARTICLES, COBALT NANOPARTICLES OR ALLOYS THEREOF, THE CATALYST THUS PREPARED AND USE OF THE CATALYST FOR THE SELECTIVE HYDROGENATION OF CARBON DIOXIDE TO ISOBUTANE
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The present invention describes a preparation method for preparing a catalyst made up of a Fe and Co metal alloy in several ratios in the form of nanoparticles embedded in a graphitic carbon matrix. Another object of the invention is also the prepared catalyst which in a surprising manner selectively catalyses the hydrogenation of carbon dioxide into isobutane.
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Page/Page column 15-16; 18-19
(2020/06/19)
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- Hydrogenation of CO2to LPG over CuZnZr/MeSAPO-34 catalysts
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The utilization of CO2to synthesize environmentally benign liquid fuels offers a solution to replacing depleting petroleum resources. Herein, a ternary CuZnZr (CZZ) metal oxide catalyst and a SAPO-34 zeolite were synthesized by co-precipitation and hydrothermal synthesis, respectively. Different metals were impregnated into the latter to obtain MeSAPO-34 (Me = Mn, Zn and Zr). A granule mixture of CZZ and MeSAPO-34 components (CZZ/MeSAPO-34 catalyst) was then effectively utilized in a tandem catalytic process for one-step CO2hydrogenation to liquefied petroleum gas (LPG). The CZZ/MeSAPO-34 catalysts were characterized by using XRD, H2-TPR, BET, SEM-EDS and NH3-TPD techniques. SEM-EDS and XRD results indicated that an appropriate amount of Zr metal loading induced minimum zeolite framework collapse compared to a similar amount of Mn and Zn, which was more favorable for higher activity. In addition, NH3-TPD results revealed that the acidity of SAPO-34 could be altered after impregnation with different metals in different quantities. Tuning the acid density and strength, together with adjusting the CZZ to MeSAPO-34 weight ratio, had a collectively critical effect on LPG selectivity. An effective hydrogenation microenvironment which favors lower alkane formation (C3-C4) was enhanced after the acidity of the molecular sieve was tuned. LPG selectivity could reach 86% over the CZZ/5% ZrSAPO-34 catalyst at 2 MPa, 350 °C, a W/F ratio of 6, a H2/CO2ratio of 3 and a weight ratio of 1.
- Du, Ce,Gapu Chizema, Linet,Hondo, Emmerson,Lu, Chengxue,Lu, Peng,Ma, Qingxiang,Mo, Shuting,Tong, Mingliang,Tsubaki, Noritatsu
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p. 9328 - 9336
(2020/06/17)
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- A Cationic Oligomer as an Organic Template for Direct Synthesis of Aluminosilicate ITH Zeolite
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There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.
- Chen, Wei,Corma, Avelino,De Baerdemaeker, Trees,De Vos, Dirk E.,Dong, Zhuoya,Kolb, Ute,Lei, Chi,Müller, Ulrich,Ma, Yanhang,Marler, Bernd,Martínez, Cristina,Martínez-Triguero, Joaquín,Meng, Xiangju,Parvulescu, Andrei-Nicolae,Wu, Qinming,Xiao, Feng-Shou,Yokoi, Toshiyuki,Zhang, Weiping,Zheng, Anmin
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supporting information
p. 15649 - 15655
(2020/07/04)
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- In situ structural study of manganese and iron oxide promoted rhodium catalysts for oxygenate synthesis
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In situ x-ray diffraction (XRD) and absorption spectroscopy (XAS) was used to characterize the structure and phase composition of a novel Mn and Fe double-promoted Rh-based catalyst for CO hydrogenation to oxygenates. Catalysts with different Mn:Rh molar ratios were prepared by combining Mn and Rh precursors with Fe2O3 powder, which were then calcined in air and reduced under hydrogen. The resulting MnRh/Fe2O3 catalysts are found to be highly selective for ethanol synthesis (～40 %) for CO hydrogenation under mild conditions (～1 bar, 240 °C). Comparison of the reactivity results with quantitative phase information from in situ XRD measurements suggest that reduced metal oxides, MnO and FeOx, and metallic Rh co-exist as active phases to promote oxygenate selectivity. The results of this work also highlight the importance of in situ characterization for extracting meaningful information on the active phases of such complex, ternary catalysts which can vary under reaction conditions.
- Carrillo, Pamela,Senanayake, Sanjaya D.,Shi, Rui,White, Michael G.
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- Ethylene Dehydroaromatization over Ga-ZSM-5 Catalysts: Nature and Role of Gallium Speciation
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Bifunctional catalysis in zeolites possessing both Br?nsted and Lewis acid sites offers unique opportunities to tailor shape selectivity and enhance catalyst performance. Here, we examine the impact of framework and extra-framework gallium species on enriched aromatics production in zeolite ZSM-5. We compare three distinct methods of preparing Ga-ZSM-5 and reveal direct (single step) synthesis leads to optimal catalysts compared to post-synthesis methods. Using a combination of state-of-the-art characterization, catalyst testing, and density functional theory calculations, we show that Ga Lewis acid sites strongly favor aromatization. Our findings also suggest Ga(framework)–Ga(extra-framework) pairings, which can only be achieved in materials prepared by direct synthesis, are the most energetically favorable sites for reaction pathways leading to aromatics. Calculated acid site exchange energies between extra-framework Ga at framework sites comprised of either Al or Ga reveal a site-specific preference for stabilizing Lewis acids, which is qualitatively consistent with experimental measurements. These findings indicate the possibility of tailoring Lewis acid siting by the placement of Ga heteroatoms at distinct tetrahedral sites in the zeolite framework, which can have a marked impact on catalyst performance relative to conventional H-ZSM-5.
- Frenkel, Anatoly I.,Grabow, Lars C.,Liu, Jing,Rimer, Jeffrey D.,Smith, Scott K.,Thirumalai, Hari,Whitmire, Kenton H.,Zhou, Yunwen
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supporting information
p. 19592 - 19601
(2020/09/17)
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- Grubbs Metathesis Enabled by a Light-Driven gem-Hydrogenation of Internal Alkynes
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[(NHC)(cymene)RuCl2] (NHC=N-heterocyclic carbene) complexes instigate a light-driven gem-hydrogenation of internal alkynes with concomitant formation of discrete Grubbs-type ruthenium carbene species. This unorthodox reactivity mode is harnessed in the form of a “hydrogenative metathesis” reaction, which converts an enyne substrate into a cyclic alkene. The intervention of ruthenium carbenes formed in the actual gem-hydrogenation step was proven by the isolation and crystallographic characterization of a rather unusual representative of this series carrying an unconfined alkyl group on a disubstituted carbene center.
- Biberger, Tobias,Fürstner, Alois,Zachmann, Raphael J.
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supporting information
p. 18423 - 18429
(2020/08/25)
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- Synthesis and catalytic performance of zeolite-Y supported on silicon carbide in n-heptane cracking
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In this work, we demonstrate a facile approach for the synthesis of zeolite-Y crystals (size, ca. ～400 nm) supported on silicon carbide (SiC) with the assistance of the cationic template (polydiallyldimethylammonium chloride, PDDA). The polymeric cationic template used to treat SiC particles induces a positive charge on SiC surface which electrostatically attracts negatively charged aluminosilicate seeds and promotes the growth of zeolite (ZY) particles over SiC, thus leading to the formation of stable ZY?SiC supported catalysts. The supported ZY catalysts with different weight ratio of ZY and SiC were synthesized and characterized by various techniques such as XRD, SEM, SEM-EDX, SEM-mapping, TEM, STEM, FT-IR, 27Al MAS NMR and N2 sorption. The characterization of the supported ZY catalysts suggests the uniform growth of ZY particles over SiC together with the creation of hierarchical micro-mesopores assembly. In the catalytic cracking of n-heptane, the catalyst ZY?SiC-50 displayed a remarkable improvement in reaction rate when compared to commercial zeolite-Y (CBV-600) amounting to 3.5 folds enhancement. Interestingly, the light olefins yield is also substantially improved. At WHSV of 8 h?1 and 475 °C, the highest light olefin yield (24–36 %) was achieved over ZY?SiC-50 whereas the reference catalyst, CBV-600 produced lower light olefins yield (7–17 %). Moreover, the supported ZY catalyst exhibited less deactivation rates. This improved performance is attributed to the hierarchical micro-mesopores assembly created by the homogeneous dispersion of zeolite crystals on SiC which offers fast diffusion pathways for the reactants and enhanced accessibility to active sites thus leading to higher observed reaction rates and fast diffusion of products thus minimizing the occurrence of side reactions.
- Alhassan, Saeed M.,Berthod, Mikael,Dabbawala, Aasif A.,Joseph, Tony,Khan, Shaihroz,Mittal, Hemant,Morin, Stephane,Singaravel, Gnana,Vaithilingam, Balasubramanian V.,Wahedi, Yasser Al
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- Isomerization and Selective Hydrogenation of Propyne: Screening of Metal-Organic Frameworks Modified by Atomic Layer Deposition
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Various metal oxide clusters upward of 8 atoms (Cu, Cd, Co, Fe, Ga, Mn, Mo, Ni, Sn, W, Zn, In, and Al) were incorporated into the pores of the metal-organic framework (MOF) NU-1000 via atomic layer deposition (ALD) and tested via high-throughput screening
- Hackler, Ryan A.,Pandharkar, Riddhish,Ferrandon, Magali S.,Kim, In Soo,Vermeulen, Nicolaas A.,Gallington, Leighanne C.,Chapman, Karena W.,Farha, Omar K.,Cramer, Christopher J.,Sauer, Joachim,Gagliardi, Laura,Martinson, Alex B. F.,Delferro, Massimiliano
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p. 20380 - 20389
(2020/11/27)
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- Hydrogenative metathesis of enynes via piano-stool ruthenium carbene complexes formed by alkyne gem-hydrogenation
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The only recently discovered gem-hydrogenation of internal alkynes is a fundamentally new transformation, in which both H atoms of dihydrogen are transferred to the same C atom of a triple bond while the other position transforms into a discrete metal carbene complex. [Cp?RuCl]4 is presently the catalyst of choice: the resulting piano-stool ruthenium carbenes can engage a tethered alkene into either cyclopropanation or metathesis, and a prototypical example of such a reactive intermediate with an olefin ligated to the ruthenium center has been isolated and characterized by X-ray diffraction. It is the substitution pattern of the olefin that determines whether metathesis or cyclopropanation takes place: a systematic survey using alkenes of largely different character in combination with a computational study of the mechanism at the local coupled cluster level of theory allowed the preparative results to be sorted and an intuitive model with predictive power to be proposed. This model links the course of the reaction to the polarization of the double bond as well as to the stability of the secondary carbene complex formed, if metathesis were to take place. The first application of "hydrogenative metathesis"to the total synthesis of sinularones E and F concurred with this interpretation and allowed the proposed structure of these marine natural products to be confirmed. During this synthesis, it was found that gem-hydrogenation also provides opportunities for C-H functionalization. Moreover, silylated alkynes are shown to participate well in hydrogenative metathesis, which opens a new entry into valuable allylsilane building blocks. Crystallographic evidence suggests that the polarized [Ru-Cl] bond of the catalyst interacts with the neighboring R3Si group. Since attractive interligand Cl/R3Si contacts had already previously been invoked to explain the outcome of various ruthenium-catalyzed reactions, including trans-hydrosilylation, the experimental confirmation provided herein has implications beyond the present case.
- Peil, Sebastian,Bistoni, Giovanni,Goddard, Richard,Fürstner, Alois
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supporting information
p. 18541 - 18553
(2020/11/17)
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- Hydrogenation of CO2 on the polymetallic catalysts prepared by self-propagating high-temperature synthesis
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A new class of multifunctional polymetallic catalysts was developed, the precursors of which are complex multicomponent intermetallic compounds prepared by self-propagating high-temperature synthesis. The catalysts based on Co and Ni exhibit high activity in the hydrogenation of CO2 to methane. The maximum yield of methane is observed at 250–350 °C with an almost complete conversion of CO2 and 100% selectivity. Hydrocarbons C1-C4, including unsaturated hydrocarbons (propylene and butadiene), were synthesized on the Co-Fe-La catalyst under a pressure to 2 MPa at 250–350 °C and the ratio CO2: H2 = 1: 1. The new class of catalysts is promising for the development of direct CO2 hydrogenation to heavy (liquid) alkanes and unsaturated hydrocarbons.
- Borshch, V. N.,Demikhova, N. R.,Pugacheva, E. V.,Smirnova, E. M.,Vinokurov, V. A.,Zhuk, S. Ya.
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p. 1697 - 1702
(2020/10/13)
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- Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation
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The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h-1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
- Wu, Wenli,Cui, Enxin,Zhang, Yun,Zhang, Chen,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
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p. 6335 - 6341
(2019/07/04)
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- Unraveling the Homologation Reaction Sequence of the Zeolite-Catalyzed Ethanol-to-Hydrocarbons Process
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Although industrialized, the mechanism for catalytic upgrading of bioethanol over solid-acid catalysts (that is, the ethanol-to-hydrocarbons (ETH) reaction) has not yet been fully resolved. Moreover, mechanistic understanding of the ETH reaction relies heavily on its well-known “sister-reaction” the methanol-to-hydrocarbons (MTH) process. However, the MTH process possesses a C1-entity reactant and cannot, therefore, shed any light on the homologation reaction sequence. The reaction and deactivation mechanism of the zeolite H-ZSM-5-catalyzed ETH process was elucidated using a combination of complementary solid-state NMR and operando UV/Vis diffuse reflectance spectroscopy, coupled with on-line mass spectrometry. This approach establishes the existence of a homologation reaction sequence through analysis of the pattern of the identified reactive and deactivated species. Furthermore, and in contrast to the MTH process, the deficiency of any olefinic-hydrocarbon pool species (that is, the olefin cycle) during the ETH process is also noted.
- Chowdhury, Abhishek Dutta,Lucini Paioni, Alessandra,Whiting, Gareth T.,Fu, Donglong,Baldus, Marc,Weckhuysen, Bert M.
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supporting information
p. 3908 - 3912
(2019/02/20)
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