Selective Hydrogenation of Crotonaldehyde Over Cobalt Based Self-Supported Catalysts

1994 ◽  
Vol 368 ◽  
Author(s):  
A. N. Patil ◽  
M. A. Bañares ◽  
X. Lei ◽  
T. P. Fehlner ◽  
E. E. Wolf
Keyword(s):  
Gas Phase ◽  
Supported Catalysts ◽  
Catalyst Activity ◽  
Maximum Yield ◽  
Metal Core ◽  
Molecular Precursors ◽  
Crotyl Alcohol ◽  
Carboxylate Groups ◽  
Heterogenous Catalyst ◽  
Metal Layers

ABSTRACTComplex cobalt-carbonyl ligand based clusters of clusters are used as molecular precursors for self-supported model catalysts. These precursors consist of two metal layers: an outer of the complex Co-carbonyl ligands, and a core of metal (e.g. Co or Zn) carboxylate groups. Partial thermolysis at low temperature (LT) of these materials under hydrogen results in almost completely decarbonylated material with a mainly unchanged carboxylate metal core. Complete pyrolysis at higher temperatures (HT) in hydrogen leads to mixed metal environment. These materials were used as a heterogenous catalyst in the gas phase hydrogenation of crotonaldehyde. The maximum yield of 27 % of desired product crotyl alcohol was observed when HT-CoCo was used as the catalyst at 423 K. The catalyst activity and the crotyl alcohol selectivity remained unchanged over 2 days of operation. The bimetallic ZnCo catalysts showed lower selectivity to crotyl alcohol than the CoCo catalysts.

Regioselective Gas-Phase n-Butane Transfer Dehydrogenation via Silica-Supported Pincer-Iridium Complexes

2020 ◽  
Author(s):  
Boris Sheludko ◽  
Cristina Castro ◽  
Chaitanya Khalap ◽  
Thomas Emge ◽  
Alan Goldman ◽  
...  
Keyword(s):  
Gas Phase ◽  
Active Site ◽  
Lower Cost ◽  
Open Systems ◽  
Iridium Complexes ◽  
Terminal Olefin ◽  
Molecular Precursors ◽  
Sterically Demanding ◽  
Olefin Production ◽  
Steam Cracking

<b>Abstract:</b> The production of olefins via on-purpose dehydrogenation of alkanes allows for a more efficient, selective and lower cost alternative to processes such as steam cracking. Silica-supported pincer-iridium complexes of the form [(≡SiO-<sup>R4</sup>POCOP)Ir(CO)] (<sup>R4</sup>POCOP = κ<sup>3</sup>-C<sub>6</sub>H<sub>3</sub>-2,6-(OPR<sub>2</sub>)<sub>2</sub>) are effective for acceptorless alkane dehydrogenation, and have been shown stable up to 300 °C. However, while solution-phase analogues of such species have demonstrated high regioselectivity for terminal olefin production under transfer dehydrogenation conditions at or below 240 °C, in open systems at 300 °C, regioselectivity under acceptorless dehydrogenation conditions is consistently low. In this work, complexes <a>[(≡SiO-<i><sup>t</sup></i><sup>Bu4</sup>POCOP)Ir(CO)] </a>(<b>1</b>) and [(≡SiO-<i><sup>i</sup></i><sup>Pr4</sup>PCP)Ir(CO)] (<b>2</b>) were synthesized via immobilization of molecular precursors. These complexes were used for gas-phase butane transfer dehydrogenation using increasingly sterically demanding olefins, resulting in observed selectivities of up to 77%. The results indicate that the active site is conserved upon immobilization.

scholarly journals Towards High Efficacy of Pd-Au/C Catalyst for Tetrachloromethane Hydrodechlorination

Chemistry ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 338-359
Author(s):  
Magdalena Bonarowska ◽  
Zbigniew Kaszkur ◽  
Krzysztof Matus ◽  
Alicja Drelinkiewicz ◽  
Tomasz Szumełda ◽  
...  
Keyword(s):  
Microwave Irradiation ◽  
Gas Phase ◽  
Thermal Activation ◽  
Supported Catalysts ◽  
Carbon Support ◽  
Thermal Reduction ◽  
Microwave Oven ◽  
Optimal Conditions ◽  
Catalyst Activation ◽  
Critical Part

We present an efficient strategy for synthesising the PdAu catalysts with a homogeneous PdAu alloy phase for environmentally important hydrodechlorination of tetrachloromethane in the gas phase. The synthesis of carbon-supported catalysts involved two major steps: (i) incorporation of palladium and gold nanoparticles into carbon support and (ii) activation of the catalysts. The critical part of this work was to find the optimal conditions for both steps. Thus, the incorporation of the nanoparticles was carried out in two ways, by impregnation and direct redox reaction method using acetone solutions of metal precursor salts. The activation was performed either by a conventional thermal reduction in hydrogen or flash irradiation in a microwave oven. The homogeneity and structure of the PdAu alloy were found to depend on the catalyst activation method critically. In all cases, we observed better homogeneity for catalysts that were subject to microwave irradiation. Moreover, the flash microwave irradiation of prepared catalysts provided catalysts of better stability and selectivity towards the desired products (hydrocarbons) in the hydrodechlorination of tetrachloromethane as compared to the catalyst obtained by conventional thermal activation in hydrogen.

Laser electrodispersion as a new chlorine-free method for the production of highly effective metal-containing supported catalysts

2012 ◽  
Vol 84 (3) ◽  
pp. 495-508 ◽  
Author(s):  
Ekaterina S. Lokteva ◽  
Anton A. Peristyy ◽  
Natalia E. Kavalerskaya ◽  
Elena V. Golubina ◽  
Lada V. Yashina ◽  
...  
Keyword(s):  
Gas Phase ◽  
High Stability ◽  
Heterogeneous Catalysts ◽  
Supported Catalysts ◽  
Promising Technique ◽  
Wet Impregnation ◽  
Oxide Supports ◽  
Highly Active ◽  
Specific Catalytic Activity ◽  
Free Metal

Laser electrodispersion (LED) of metals is a promising technique for the preparation of heterogeneous catalysts as an alternative to wet impregnation of supports with the corresponding salt solutions. The LED technique can be used to deposit highly active chloride- and nitrate-free metal nanoparticles onto carbon or oxide supports. We report preparation and properties of new Ni-, Pd-, and Au-containing alumina-supported catalysts with low metal loadings (10–3–10–4 % mass) and their comparison with the previously studied carbon (Sibunit) supported systems. The catalysts demonstrate high stability and extremely high specific catalytic activity (by 2–3 orders of magnitude higher than for traditional catalysts) in the gas-phase hydrodechlorination (HDC) of chlorobenzene (CB).

scholarly journals The Effect of Catalyst Support on the Decomposition of Methane to Hydrogen and Carbon

1970 ◽  
Vol 5 (1) ◽  
Author(s):  
Sharif Hussein Sharif Zein Abdul Rahman Mohamed
Keyword(s):  
Supported Catalysts ◽  
Catalyst Activity ◽  
Catalyst Support ◽  
Methane Decomposition ◽  
Filamentous Carbon ◽  
Transmission Electron ◽  
Decomposition Of Methane ◽  
Long Lifetime ◽  
The Relationship ◽  
Ni Supported Catalysts

Decomposition of methane into carbon and hydrogen over Cu/Ni supported catalysts was investigated. The catalytic activities and the lifetimes of the catalysts were studied. Cu/Ni supported on TiO2 showed high activity and long lifetime for the reaction. Transmission electron microscopy (TEM) studies revealed the relationship between the catalyst activity and the formation of the filamentous carbon over the catalyst after methane decomposition. While different types of filamentous carbon formed on the various Cu/Ni supported catalysts, an attractive carbon nanotubes was observed in the Cu/Ni supported on TiO2. Key Words:  Methane decomposition, carbon nanotube, Cu/Ni supported catalysts.

scholarly journals Gas phase synthesis of isopropyl chloride from isopropanol and HCl over alumina and flexible 3-D carbon foam supported catalysts

2017 ◽  
Vol 542 ◽  
pp. 212-225
Author(s):  
Natalia Bukhanko ◽  
Christopher Schwarz ◽  
Ajaikumar Samikannu ◽  
Tung Ngoc Pham ◽  
William Siljebo ◽  
...  
Keyword(s):  
Gas Phase ◽  
Supported Catalysts ◽  
Carbon Foam ◽  
Phase Synthesis ◽  
Gas Phase Synthesis

Technological Aspects of Ethanol Steam Reforming Processors for Molten Carbonate Fuel Cells

2006 ◽  
Author(s):  
S. Freni ◽  
F. Frusteri ◽  
N. Mondello ◽  
V. Chiodo ◽  
S. Siracusano ◽  
...  
Keyword(s):  
Steam Reforming ◽  
Supported Catalysts ◽  
Catalyst Activity ◽  
Supported Catalyst ◽  
Molten Carbonate Fuel Cell ◽  
Water Mixture ◽  
Molten Carbonate ◽  
Carbon Formation ◽  
Molten Carbonate Fuel Cells ◽  
Catalytic Behaviour

Bioethanol, obtained by biomass fermentation, could be an important hydrogen supplier as a renewable source. The availability of active, selective and stable catalyst for bioethanol steam reforming is a key point for the development of processes suitable to this purpose. In this work, the performance of different supported catalysts in the steam reforming of bioethanol at molten carbonate fuel cell (MCFC) operative condition has been focused and a decreasing activity has been related to the formation of carbon. Furthermore catalytic behaviour of a Ni supported catalyst has been tested under reforming condition both distillation industry’s waste and ethanol-water mixture. Results revealed that, superior alcohols (fusel oil) arising from the distillation process influence carbon formation and the presence of oxygen (ATR condition) preserves the catalyst activity which otherwise significantly deactivate mainly due to the carbon formation.

scholarly journals Diamond growth from organic compounds in hydrous fluids deep within the Earth

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Maria Luce Frezzotti
Keyword(s):  
Organic Compounds ◽  
Subduction Zones ◽  
Diamond Growth ◽  
Diamond Surfaces ◽  
Molecular Precursors ◽  
Carbon Saturation ◽  
Carboxylate Groups ◽  
Dissolved Species ◽  
Lithospheric Plates ◽  
The Alps

Abstract At subduction zones, most diamonds form by carbon saturation in hydrous fluids released from lithospheric plates on equilibration with mantle rocks. Although organic molecules are predicted among dissolved species which are the source for carbon in diamonds, their occurrence is not demonstrated in nature, and the physical model for crustal diamond formation is debated. Here, using Raman microspectroscopy, I determine the structure of carbon-based phases inside fluid inclusions in diamond-bearing rocks from the Alps. The results provide direct evidence that diamond surfaces are coated by sp2-, and sp3-bonded amorphous carbon and functional groups of carboxylic acids (e.g., carboxyl, carboxylate, methyl, and methylene), indicating the geosynthesis of organic compounds in deep hydrous fluids. Moreover, this study suggests diamond nucleation via metastable molecular precursors. As a possible scenario, with carbon saturation by reduction of carboxylate groups, I consider tetrahedral H-terminated C groups as templates for the growth of sp3-structured carbon.

On-Particle EDS Analysis of Bimetallic, Carbon-Supported Catalysts

1999 ◽  
Vol 589 ◽  
Author(s):  
Deborah L. Boxall ◽  
Edward A. Kenik ◽  
Charles M. Lukehart
Keyword(s):  
Elemental Analysis ◽  
Energy Dispersive Spectroscopy ◽  
High Spatial Resolution ◽  
Supported Catalysts ◽  
Alloy Nanoparticles ◽  
Single Source ◽  
Volatile Species ◽  
Molecular Precursors ◽  
Eds Analysis ◽  
Compositional Variability

AbstractThermolysis of single-source molecular precursors has been used to prepare carbon-supported Pt1Sn1, Pt1Ru1, and Pt3Mo1 alloy nanoparticles. On-particle, high spatial resolution energy dispersive spectroscopy (HR-EDS) has been used to determine the extent of compositional variability between particles in the nanocomposite. The loss of volatile Ru and Mo oxides during the course of the HR-EDS analysis results in average compositions greatly enriched in Pt. Mathematical correction for loss of these volatile species results in average metal:metal ratios comparable to those measured by bulk elemental analysis.

Gas phase hydrogenation of o-xylene on Ru supported catalysts

1993 ◽  
Vol 49 (2) ◽  
pp. 353-360 ◽  
Author(s):  
M. Viniegra ◽  
N. Martín ◽  
A. López-Gaona ◽  
G. Córdoba
Keyword(s):  
Gas Phase ◽  
Supported Catalysts

Selective gas phase hydrogenation of maleic anhydride over Ni-supported catalysts: Effect of support on the catalytic performance

2012 ◽  
Vol 449 ◽  
pp. 81-87 ◽  
Author(s):  
Silvina A. Regenhardt ◽  
Camilo I. Meyer ◽  
Teresita F. Garetto ◽  
Alberto J. Marchi
Keyword(s):  
Maleic Anhydride ◽  
Gas Phase ◽  
Supported Catalysts ◽  
Catalytic Performance ◽  
Effect Of Support ◽  
Ni Supported Catalysts
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