No abstract

The steam reforming reaction of hydrocarbons and organic fuels, in general, is followed by a two-stage reaction of water gas shift, which allows increasing the hydrogen yield and a final purification step for CO removal to use hydrogen in an ammonia plant or a PEM fuel cell. This paper is focused on the CO Preferential Oxidation, CO PROX (or CO selective oxidation in excess hydrogen) reaction, considered as the simplest and cost effective process to achieve the less than 10 ppm CO. The objective of this paper is to review the performances of noble metals (Pt, Ru, Rh, Pd), gold and transition metal oxides catalysts in this reaction. Although the results reported are largely influenced by the experimental conditions (reactant flow composition, mass of catalyst, duration of experiment …) a comparison of advantages and drawbacks for each type of catalysts is proposed in terms of activity and selectivity as well as of CO 2 and H 2 O influences. A special attention will be paid to copper-doped ceria catalysts which appear to be very active and selective in a range of temperatures appropriate for fuel cell application. The performances, the stability and the low cost of these formulations compared to noble metal-based catalysts make them very attractive for an industrial application.

Supported noble-metal catalysts (Ru, Pd or Pt) and the corresponding Re-promoted catalysts exhibit a high activity for the hydrogenation of biobased carboxylic acids. Levulinic acid and succinic acid are converted into the lactones or the diols depending on the nature of the catalyst and the reaction conditions. The highest selectivity to 1,4-pentanediol of 82 % is achieved at 140 °C in the presence of the 1.9 % Ru-3.6 % Re/C catalyst.

No abstract

This paperisd edicated to Dr.D anielDuprez and Dr.Pierre Gallezotw ith whom we have sharedm any discussions about supported (bi)metallic catalysts.Supporting information for this articleisa vailable on the WWW under http://dx.

BIOVERT+BKL:CPIA series of 2 wt % Pd/TiO2 monometallic catalysts were prepared by varying some parameters, such as the nature of the precursor salt, the titania support, and the preparation method. The structural and textural properties of the catalytic systems were fully characterized by several physical and chemical techniques (inductively coupled plasma optical emission spectrometry, N-2 physisorption, H-2 chemisorption, transmission.electron microscopy coupled with energy dispersive X-ray spectroscopy, powder X-ray diffraction, temperature programmed reduction, X-ray photoelectron spectroscopy, and gas phase reaction of cyclohexane dehydrogenation). The catalytic performances were further estimated for the hydrogenation of an aqueous solution of succinic acid (SUC) performed in a batch reactor at 160 degrees C and under 150 bar total pressure. The results showed that all the Pd catalysts are very Selective to produce gamma-butyrolactone, the first hydrogenated product. However, the rate of succinic acid conversion is a function of both the Pd dispersion and the preparation method. The deposition-precipitation method allows one to obtain the highest performing 2 wt % Pd/TiO2 samples during SUC hydrogenation in terms of activity and stability

No abstract

A kinetic study of ethanol steam-reforming reaction on Rh catalyst supported over a spinel structure (MgAl 2 O 4 / Al 2 O 3 ) was carried out. From the analysis of products distribution, the following four reactions were proposed as the reaction scheme:water-gas shift reaction, and methane steam-reforming reaction. When the initial rate method was applied, it was demonstrated that in the rate-determining step (RDS) two active sites of the same type are involved. With use of our experimental results and data obtained from the literature, a sequence of 14 elementary steps were proposed, in agreement with the reaction scheme. Taking into account both the reaction mechanism and the occurrence of two active sites in the RDS, four different kinetic expressions can be formulated in which the RDS is (1) dissociative adsorption of ethanol, (2) dehydrogenation of ethoxide, (3) C-C bond scission, or (4) reaction between two adsorbed species. Finally, when discrimination models were applied, it was verified that the mechanism that fits experimental data is that in which the RDS is the surface reaction.