Palladium supported on filamentous active carbon as effective catalyst for liquid-phase hydrogenation of 2-butyne-1,4-diol to 2-butene-1,4-diol

Structured palladium catalysts suitable for three-phase reactions have been developed based on woven fabrics of active carbon fibers (ACF) as the catalytic supports. The Pd/ACF were tested in liq.-phase hydrogenation of 2-butyne-1,4-diol showing a selectivity towards 2-butene-1,4-diol up to 97% at conversions up to 80%. Multiple reuse of the catalyst with stable activity/selectivity in a batch reactor was also demonstrated. The reaction kinetics was studied and the main kinetic parameters were obtained. Assuming a Langmuir-Hinshelwood kinetics and a weak hydrogen adsorption a suitable kinetic model was developed consistent with the exptl. data. [on SciFinder (R)]

Solvent-Free Selective Hydrogenation of 2-Butyne-1,4-diol over Structured Palladium Catalyst

Eric Joannet, Lioubov Kiwi, Albert Renken

Hydrogenation of 2-butyne-1,4-diol catalyzed by Pd nanoparticles on activated carbon fibers (ACFs) was studied. The ACF support in the form of woven fabrics provides the basis for structured catalytic fixed beds. In the present study, this catalyst was integrated in the stirrer of an autoclave. Hydrogenations were carried out in pure, solvent-free butynediol at temps. from 352 to 392 K and hydrogen pressures of 1-2 MPa. The results were compared to those obtained for aq. solns. at different pH's and temps. of 293-333 K. High selectivities of >=98% toward 2-butene-1,4-diol at conversions of ?90% were attained in both systems. Turnover frequencies had comparable values at the same temp. The activation energy of 30 kJ/mol was detd. from initial reaction rates. Because this value is identical for the aq. soln. and the solvent-free system, mass-transfer limitations can be excluded for both systems. Concn.-time profiles were quant. predicted assuming the Langmuir-Hinshelwood kinetics with weak hydrogen adsorption. Estd. kinetic parameters allow a coherent interpretation of the exptl. observations. Catalyst reactivation and multiple reuses were demonstrated. [on SciFinder (R)]

American Chemical Society2005

Loop reactor staged with structured fibrous catalytic layers for liquid-phase hydrogenations

Eric Joannet, Lioubov Kiwi, Albert Renken

A novel concept of a recycle loop reactor is developed with structured filamentous catalysts integrated as trays in a staged bubble column. The reactor can be operated in batch or continuous mode. Woven fabrics of activated carbon fibers (ACF) were used as support for the Pd catalyst. The loop reactor was tested in the 2-butyne-1,4-diol hydrogenation showing selectivity up to 97% towards 2-butene-1,4-diol at conversions up to 80%. The reactor behavior was described quant. assuming an ideally mixed reactor and Langmuir-Hinshelwood kinetics with weak hydrogen adsorption. Catalyst reuse was demonstrated in multiple runs over a period of 6 mo with more than 375 h on stream. [on SciFinder (R)]

2004

Kinetics and Mechanism of Formic Acid Decomposition in Aqueous Solution using Ruthenium Pre-catalysts with Hydrophilic Phosphine Ligands

Weijia Gan

Hydrogen holds the potential to be an alternative to replace fossil fuels in the future. The tremendous research effort dedicated to the issue of hydrogen storage has led to considerable advancements in the development of both adsorption materials and chemical storage. Still, for many of these systems the gap between current state of research and industrial application is considerable. When it comes to systems for the reversible storage of hydrogen, the HCOOH/CO2 cycle currently shows the most promises. Its physical-chemical properties make formic acid an ideal system for hydrogen storage. Herein, a series of homogeneous catalytic systems have been developed for hydrogen generation from formic acid in aqueous solution. These catalysts are formed from commercially available RuCl3 with a variety of water-soluble phosphine ligands. These ligands vary in the type, number and position of their hydrophilic substituents. Most of them allow the efficient decomposition of formic acid under mild conditions for a large number of catalytic cycles. Especially a new series of cationic phosphine ligands provide the catalytic systems with high activity. Due to the observed high initial reaction rate of many catalytic systems, mechanistic studies have also been undertaken with important intermediates and a catalytic cycle being proposed. Accordingly, the heterogeneous catalysts have also been developed based on the immobilization of homogeneous ruthenium complexes. The immobilized catalysts also afford hydrogen with high purity and allow easy catalyst separation, overcoming the previous limitations in the use of homogeneous catalysts, particularly for mobile/portable applications. The research undertaken in this thesis is presented in three main parts: (i) the development and optimization of homogeneous catalytic systems; (ii) the development and optimization of heterogeneous/immobilized catalytic systems; (iii) the mechanistic studies on the initial fast catalytic cycle of homogeneous catalysts.

EPFL2012

Kinetics and Mechanism of Formic Acid Decomposition in Aqueous Solution using Ruthenium Pre-catalysts with Hydrophilic Phosphine Ligands

Weijia Gan

EPFL2012