Structured palladium catalysts suitable for three-phase reactions have been developed based on woven fabrics of active carbon ÿbres (ACF) as the catalytic supports. The Pd=ACF were tested in liquid-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%. The catalyst multiple reuse 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 experimental data. ?

Pd nanoparticles (2 nm) stabilized in the micelle core of poly(ethylene oxide)-block-poly-2-vinylpyridine were studied in 2-butyne-1,4-diol partial hydrogenation. Both unsupported micelles (0.6 kg Pd /m 3 ) and supported ones on g-Al 2 O 3 (0.042 wt.% Pd) showed nearly 100% selectivity to 2-butene-1,4-diol up to 94% conversion. The only side product observed was 2-butane-1,4-diol. The catalysis was ascribed to Pd nanoparticles' surface modified by pyridine units of micelles and alkali reaction medium (pH of 13.4). TOFs over the unsupported and supported catalysts were found to be 0.56 and 0.91 s À1 (at 323 K, 0.6 MPa H 2 pressure, solvent 2-propanol/water = 7:3), respectively. Reaction kinetics fit the Langmuir-Hinshelwood model assuming weak hydrogen adsorption. The experiments on the catalyst reuse showed that Pd nanoparticles remain inside the micelle core, but the micelles slightly desorbed (less then 5%) during the catalytic run. #

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 fibres (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 behaviour was described quantitatively 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 months with more than 375 h on stream.

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 temperatures from 352 to 392 K and hydrogen pressures of 1-2 MPa. The results were compared to those obtained for aqueous solutions at different pH's and temperatures of 293-333 K. High selectivities of g98% toward 2-butene-1,4-diol at conversions of e90% were attained in both systems. Turnover frequencies had comparable values at the same temperature. The activation energy of 30 kJ/mol was determined from initial reaction rates. Because this value is identical for the aqueous solution and the solvent-free system, mass-transfer limitations can be excluded for both systems. Concentration-time profiles were quantitatively predicted assuming the Langmuir-Hinshelwood kinetics with weak hydrogen adsorption. Estimated kinetic parameters allow a coherent interpretation of the experimental observations. Catalyst reactivation and multiple reuses were demonstrated.

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