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Site poisoning is a powerful method to unravel the nature of active sites or reaction intermediates. The nature of the intermediates involved in the hydrogenation of CO was unraveled by poisoning alumina-supported cobalt catalysts with various concentrations of tin. The rate of formation of the main reaction products (methane and propylene) was found to be proportional to the concentration of multi-bonded CO, likely located in hollow sites. The specific rate of decomposition of these species was sufficient to account for the formation of the main products. These hollow-CO are proposed to be main reaction intermediates in the hydrogenation of CO under the reaction conditions used here, while linear CO are mostly spectators. [ABSTRACT FROM AUTHOR]

Abstract: The hydrogenation of nitrates in aqueous solution has been studied using Pd–Cu catalysts deposited in mesoporous ceramic membranes operated in a flow-through catalytic membrane reactor. The effect of the top-layer pore size (5, 10 or 25nm) on the catalytic activity was explored. The activity increased with trans-membrane flow rate for the three membranes, although moderately with the 25nm pore membrane. At a similar flow rate, the activity increased when the pore size decreased. Concentration polarization of nitrates was evidenced by ultrafiltration experiments with bare membranes, and was enhanced when the pore size decreased. Concentration polarization appeared effective in improving the catalytic activity, due to a local increase in nitrate concentration in the catalytic top-layer of the membranes. [ABSTRACT FROM AUTHOR]

The catalytic conversion of linoleic acid in ethanol/water mixtures (1:1 vol. ratio) was explored in a batch reactor using a Pt/C catalyst. Linoleic acid was converted into heptadecane with high yields (>80%) after 6 h at 350 °C under autogenous pressure. The reaction proceeded through consecutive steps: linoleic acid → stearic acid → ethyl stearate → heptadecane. Hydrogen was generated in-situ by oxidation of ethanol into acetaldehyde. A moderate sintering of platinum was evidenced after hydrothermal reaction. A reaction network based on products distribution and kinetic studies was proposed. It was found that the hydrogenation route proceeds via the free acids whereas the hydrogenation of the ethyl esters was negligible. The formation of heptadecane, on the other hand, proceeded via ethyl stearate and not via stearic acid. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 doped with Nb or Mg synthesized by hydrolysis of metal alkoxides. [•] Mg–TiO2 is basic, pure TiO2 is amphoteric, Nb–TiO2 is acidic. [•] Pd–Cu/(Mg or Nb)–TiO2 active catalysts for NO3 − hydrogenation. [•] Activity moderately influenced by support acid–base properties. [•] NH4 + selectivity unaffected by support acid–base properties. [ABSTRACT FROM AUTHOR]