Influence of the reactant concentration in selective hydrogenation of 1,3-butadiene over supported gold catalysts under alkene rich conditions: A consideration of reaction mechanism

Abstract

This article is about the reaction of selective hydrogenation of 1,3-butadiene performed in an excess of alkenes (propene/butadiene ratio = 100) over supported gold catalysts, so as to mimic the conditions of purification of light alkenes (C4 cuts) from the presence of impurities (highly unsaturated compounds, 1-3%). Gold was found highly selective (close to 100%, no propane or butane formation) for the hydrogenation of butadiene to butenes at 100% conversion of butadiene. The influence of the concentrations of the various reactants, i.e. hydrogen, butadiene and propene, on the rates of butadiene and propene hydrogenation was investigated, and the apparent reaction orders were deduced from the dependence of rate on partial pressure in the gas phase. The reason for the high selectivity of gold catalysts is that the reaction of hydrogenation of alkenes occurs at much higher temperature (0.1% conversion at 300°C) than that of selective hydrogenation of butadiene (100% at T <170°C).

High performance of carbon nanotubes confining gold nanoparticles for selective hydrogenation of 1,3-butadiene and cinnamaldehyde

“…o and Au/CNTs-m catalysts. It should be pointed out that the outstanding feature of high selectivity for butenes was earlier observed for hydrogenation of BD over oxide-supported gold catalysts [26,39,43,45,53]. The reason for the high selectivity could be due to the weak activation/dissociation of molecular H 2 and adsorption of monobutenes on gold catalyst.…”

“…In the case of gold catalysts, Buchanan and Webb [52] deduced on the basis of the result of first order in hydrogen and zero order in BD that step 1 of dissociative adsorption of H 2 was the rate-determining step over Au/Al 2 O 3 catalyst for hydrogenation of BD. Hugon et al [53] reported recently that the reaction order was 0.7 with respect to H 2 and 0.2 with respect to BD over Au/Al 2 O 3 catalyst for the selective hydrogenation of BD in propene-rich atmosphere. Although no kinetic data including reaction order and apparent activation energy were addressed, H 2 dissociation was presumed to be the rate-determining step over oxidesupported gold catalysts on the basis of the reaction results of hydrogenation of BD and crotonaldehyde [43,54].…”

“…The reaction order with respect to H 2 is 0.5, while the reaction order with respect to hydrocarbons is dependent on the adsorption sites of RH. In a similar calculation of the overall reaction rate, however, h RH was regarded as the number of adsorption sites and the 0 reaction order with respect to hydrocarbons was reported [53].…”

Hydrogenation by gold catalysts: an unexpected discovery and a current assessment

“…Completely selective hydrogenation of ethyne and other alkynes on Au catalysts has frequently been observed, rates being faster than for those of alkenes [20][21][22], unlike the situation with metals of groups 8 to 10 [19]; detailed kinetic and mechanistic studies are however quite rare [22]. In particular, it is not clear whether high selectivity arises from surfaces partly covered with 'carbonaceous residues', as is thought to be the case with Pd catalysts [23], but probably not, as high selectivity is shown from the start [22].…”

A review of the use of gold catalysts in selective hydrogenation reactions Lynsey McEwana

“…To this effect, Hugon and co-workers (47,65) investigated the selective hydrogenation of 1,3-butadiene in propene by gold supported on zirconia, ceria, alumina and titania. In contrast to the results of Zhang et al (63,64) the Au 3+ species was inactive and only became active once reduced to Au 0 under the reactant stream.…”