Identification of Active Sites in Gold-Catalyzed Hydrogenation of Acrolein

Abstract

The active sites of supported gold catalysts, favoring the adsorption of C=O groups of acrolein and subsequent reaction to allyl alcohol, have been identified as edges of gold nanoparticles. After our recent finding that this reaction preferentially occurs on single crystalline particles rather than multiply twinned ones, this paper reports on a new approach to distinguish different features of the gold particle morphology. Elucidation of the active site issue cannot be simply done by varying the size of gold particles, since the effects of faceting and multiply twinned particles may interfere. Therefore, modification of the gold particle surface by indium has been used to vary the active site characteristics of a suitable catalyst, and a selective decoration of gold particle faces has been observed, leaving edges free. This is in contradiction to theoretical predictions, suggesting a preferred occupation of the low-coordinated edges of the gold particles. On the bimetallic catalyst, the desired allyl alcohol is the main product (selectivity 63%; temperature 593 K, total pressure p(total) = 2 MPa). From the experimentally proven correlation between surface structure and catalytic behavior, the edges of single crystalline gold particles have been identified as active sites for the preferred C=O hydrogenation.

Theoretical Studies of Acrolein Hydrogenation to Propenol and Propanal on Au₃ and Au₅

“…These facts indicate that the selectivity of acrolein hydrogenation has close relationship with cluster size, which is consistent with the experiments observation that the activity and selectivity to the desired unsaturated alcohol depends on particle size and increases with increasing particle size [17,[23][24].…”

“…[14][15][16][17] Experimental studies substantiated the crucial role of Au as an active component in the selective hydrogenation. But the periodic density functional calculation of our group showed that acrolein is very weakly adsorbed on the clean regular Au(111) or the flat Au(110) surface [18].…”

Molecular surface chemistry by metal single crystals and nanoparticles from vacuum to high pressure

“…That is, if there are several thermodynamically stable products, only one desired product is formed [44][45][46] . We have investigated some typical multipath reaction selectivities: benzene and cyclohexene hydrogenation.…”

Nickel Based Catalysts for Selective Hydrogenation of Cinnamaldehyde- Influence of Support Phases

“…1 Formation of COL by a preferential hydrogenation of the C=O group is not favoured, because the hydrogenation of C=C double bond, leading to the formation of HCAL, is thermodynamically favoured by 35 kJ mol -1 and the kinetics of hydrogenation also favours this route. 2 Conventionally, hydrogenation of C=O bond in CAL is achieved by reduction with various hydride donors, such as LiAlH4 and NaBH4. [3][4][5] Development of non-noble metal catalysts with high activity and selectivity towards COL remains a challenge.…”