Some reactions of cyclohexene with hydrogen and deuterium on evaporated gold films

Abstract

The reactions of cyclohexene with hydrogen or deuterium on gold films have been investigated using a mass spectrometer to analyze the products. Reactions of oyclohexene and hydrogen between 196 and 342°C yielded cyclohexane and benzene, the proportion of the latter increasing with temperature. Activation energies for the reactions were determined and the kinetics which showed some complex features were examined at 246°C. A simple exchange reaction occurred with cyclohexene and deuterium in the range 150-240" and small amounts of cyclohexanes, initially mainly cyclohexane-t& were produced.The mechanisms of the reactions are discussed in terms of an approximate energy level diagram for the various reaction paths. Gold appears to be a relatively effective catalyst for the dehydrogenation of cyclohexene but a poor catalyst for hydrogenation of the olefm chiefly because the frequency factor of the addition reaction is low.The catalytic properties of gold have not been investigated in nearly as great detail as have those of the transition metals. The decomposition of formic acid * present address :

Hydrogenation of aromatics over Au-Pd/SiO2-Al2O3 catalysts; support acidity effect

“…Silica-, titania-and alumina-supported Au particles of 1-6 nm size, prepared by various synthetic routes were studied by Claus group in selective hydrogenation of acrolein, crotoaldehyde and 1,3-butadiene [24]. The very previous study on the reaction of cyclohexane with hydrogen on gold films [27] and gold powder [28] demonstrated that simultaneous dehydrogenation and hydrogenation of cyclohexane might occur.…”

“…The use of Au in hydrogenation reactions has been investigated relatively recently [22][23][24][25][26][27][28][29][30][31][32][33]. This is because gold with a completely filled Au d-band has a limited ability to dissociate H 2 molecules [22].…”

The use of titania- and iron oxide-supported gold catalysts for the hydrogenation of propyne

“…Gold catalysts have been reported to hydrogenate a range of olefins, such as ethene [8], propene [9,10], pent-1-ene [11], cyclohexene [12,13], 1,3-butadiene [14,15], ethyne [16,17], propyne [18], but-2-yne [19], phenylacetylene [20] and aromatic compounds such as toluene and naphthalene [21]. Moreover, early work on gold films examined the hydrogenation of acetone to iso-propanol [22], although more recently, supported gold catalysts were reported to be inactive for the same reaction [23].…”

Hydrogenation over gold catalysts: The interaction of gold with hydrogen

“…Gold catalyzes various hydrogenation reactions such as the hydrogenation of alkenes (3)(4)(5)(6)(7)(8)(9)(10)(11)(12), alkadiens (13)(14)(15)(16)(17)(18) alkynes (13,(19)(20)(21)(22)(23)(24)(25), , -unsaturated carbonyl compounds and nitro compounds (47)(48)(49)(50)(51)(52)(53). In contrast to traditional hydrogenation catalysts such as platinum, palladium or ruthenium, which require modification, it often shows remarkable selectivities when multiple functional groups are present.…”