The Experts below are selected from a list of 12381 Experts worldwide ranked by ideXlab platform

Walter Leitner - One of the best experts on this subject based on the ideXlab platform.

  • unlocking the potential of supported liquid phase catalysts with supercritical fluids low temperature continuous flow Catalysis with integrated product separation
    Philosophical Transactions of the Royal Society A, 2015
    Co-Authors: Giancarlo Francio, Ulrich Hintermair, Walter Leitner
    Abstract:

    Solution-phase Catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of Homogeneous Catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state Homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with Homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow Homogeneous Catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.

Giancarlo Francio - One of the best experts on this subject based on the ideXlab platform.

  • unlocking the potential of supported liquid phase catalysts with supercritical fluids low temperature continuous flow Catalysis with integrated product separation
    Philosophical Transactions of the Royal Society A, 2015
    Co-Authors: Giancarlo Francio, Ulrich Hintermair, Walter Leitner
    Abstract:

    Solution-phase Catalysis using molecular transition metal complexes is an extremely powerful tool for chemical synthesis and a key technology for sustainable manufacturing. However, as the reaction complexity and thermal sensitivity of the catalytic system increase, engineering challenges associated with product separation and catalyst recovery can override the value of the product. This persistent downstream issue often renders industrial exploitation of Homogeneous Catalysis uneconomical despite impressive batch performance of the catalyst. In this regard, continuous-flow systems that allow steady-state Homogeneous turnover in a stationary liquid phase while at the same time effecting integrated product separation at mild process temperatures represent a particularly attractive scenario. While continuous-flow processing is a standard procedure for large volume manufacturing, capitalizing on its potential in the realm of the molecular complexity of organic synthesis is still an emerging area that requires innovative solutions. Here we highlight some recent developments which have succeeded in realizing such systems by the combination of near- and supercritical fluids with Homogeneous catalysts in supported liquid phases. The cases discussed exemplify how all three levels of continuous-flow Homogeneous Catalysis (catalyst system, separation strategy, process scheme) must be matched to locate viable process conditions.

J T F Keurentjes - One of the best experts on this subject based on the ideXlab platform.

  • membrane reactor for Homogeneous Catalysis in supercritical carbon dioxide
    Journal of Catalysis, 2003
    Co-Authors: Earl Goetheer, Gerard Van Koten, Leo J P Van Den Broeke, Arjan Willem Verkerk, Elwin De Wolf, Berthjan Deelman, J T F Keurentjes
    Abstract:

    A membrane reactor is presented for Homogeneous Catalysis in supercritical carbon dioxide with in situ catalyst separation. This concept offers the advantages of benign high-density gases, i.e., the possibility of achieving a high concentration of gaseous reactants in the same phase as the substrates and catalyst as well as easy catalyst localization by means of a membrane. For the separation of the Homogeneous catalyst from the products an inorganic microporous membrane is used. The concept is demonstrated for the hydrogenation of 1-butene using a fluorous derivative of Wilkinson’s catalyst [RhCl{P–(C 6H4-p-SiMe2CH2CH2C8F17)3}3]. The size of Wilkinson’s catalyst, 2–4 nm, is clearly larger than the pore diameter, 0.5–0.8 nm, of the silica membrane. The membrane will, therefore, retain the catalyst, while the substrates and products diffuse through the membrane. Stable operation and continuous production of n-butane has been achieved at a temperature of 353 K and a pressure of 20 MPa. A turnover number of 1.2× 10 5 has been obtained during 32 h of reaction. The retention of the catalyst was checked using UV–vis spectroscopy and ICP-AAS; no rhodium or phosphorous species were detected at the permeate side of the membrane.

Yasuhiro Ohki - One of the best experts on this subject based on the ideXlab platform.

Terrence J. Collins - One of the best experts on this subject based on the ideXlab platform.

  • Homogeneous Catalysis under ultra dilute conditions taml naclo oxidation of persistent metaldehyde
    Journal of the American Chemical Society, 2017
    Co-Authors: Rakesh Kanda, Matthew A. Denardo, Chakicherla Gayathri, Roberto R. Gil, Liang L Tang, C J Schuler, Terrence J. Collins
    Abstract:

    T.J.C thanks the Heinz Endowments for funding. NMR instrumentation at CMU was partially supported by NSF (CHE-0130903 and CHE-1039870).

  • Homogeneous Catalysis Under Ultradilute Conditions: TAML/NaClO Oxidation of Persistent Metaldehyde
    2016
    Co-Authors: Liang L. Tang, Matthew A. Denardo, Christopher J. Schuler, Matthew R. Mills, Chakicherla Gayathri, Roberto R. Gil, Rakesh Kanda, Terrence J. Collins
    Abstract:

    TAML activators enable Homogeneous oxidation Catalysis where the catalyst and substrate (S) are ultradilute (pM–low μM) and the oxidant is very dilute (high nM–low mM). Water contamination by exceptionally persistent micropollutants (MPs), including metaldehyde (Met), provides an ideal space for determining the characteristics and utilitarian limits of this ultradilute Catalysis. The low MP concentrations decrease throughout Catalysis with S oxidation (kII) and catalyst inactivation (ki) competing for the active catalyst. The percentage of substrate converted (%Cvn) can be increased by discovering methods to increase kII/ki. Here we show that NaClO extends catalyst lifetime to increase the Met turnover number (TON) 3-fold compared with H2O2, highlighting the importance of oxidant choice as a design tool in TAML systems. Met oxidation studies (pH 7, D2O, 0.01 M phosphate, 25 °C) monitored by 1H NMR spectroscopy show benign acetic acid as the only significant product. Analysis of TAML/NaClO treated Met solutions employing successive identical catalyst doses revealed that the processes can be modeled by the recently published relationship between the initial and final [S] (S0 and S∞, respectively), the initial [catalyst] (FeTot) and kII/ki. Consequently, this study establishes that ΔS is proportional to S0 and that the %Cvn is conserved across all catalyst doses in multicatalyst-dose processes because the rate of the kII process depends on [S] while that of the ki process does not. A general tool for determining the FeTot required to effect a desired %Cvn is presented. Examination of the dependence of TON on kII/ki and FeTot at a fixed S0 indicates that for any TAML process employing FeTot < 1 × 10–6 M, small catalyst doses are not more efficient than one large dose