Hydrogenation crotonaldehyde, selective

It is to be mentioned that water-soluble phosphine complexes of rhodium(I), such as [RhCl(TPPMS)3], [RhCl(TPPTS)3], [RhCl(PTA)3], either preformed, or prepared in situ, catalyze the hydrogenation of unsaturated aldehydes at the C=C bond [187, 204, 205]. As an example, at 80 °C and 20 bar H2, in 0.3-3 h cinnamaldehyde and crotonaldehyde were hydrogenated to the corresponding saturated aldehydes with 93 % and 90 % conversion, accompanied with 95.7 % and 95 % selectivity, respectively. Using a water/toluene mixture as reaction medium allowed recycling of the catalyst in the aqueous phase with no loss of activity. 

Unsaturated aliphatic aldehydes were selectively reduced to unsaturated alcohols by specially controlled catalytic hydrogenation. Citral treated with hydrogen over platinum dioxide in the presence of ferrous chloride or sulfate and zinc acetate at room temperature and 3.5 atm was reduced only at the carbonyl group and gave geraniol (3,7-dimethyl-2,6-octadienol) [59], and crotonaldehyde on hydrogenation over 5% osmium on charcoal gave crotyl alcohol [763]. 

Bailie et al. were the first to mention alcohol formation from aldehydes by supported gold-catalyzed selective hydrogenation. The reaction of the formation of crotyl alcohol from crotonaldehyde showed high selectivity (up to 81%) at conversions of 5-10%, with preferential hydrogenation of C=0 rather than the C=C bond [216]. The addition of thiophene promoted this selective hydrogenation. This promotional effect was also observed in similar situations for Cu and Ag, but it was not very common for gold. 

A more common idea assumes chlorine to act in various systems merely as a poison [17,18]. In the case of selective hydrogenation of crotonaldehyde over Pt/ZnO catalyst, it was speculated that Cl" can polarize Zn, increasing the interaction between Zn and C=0 bond, leading to an increase of the selectivity to unsaturated alcohol [19]. 

The selective hydrogenation of an olefinic bond in crotonaldehyde gives n-butyraldehyde in presence of a suitable catalyst n-butyraldehyde reacts with poly (vinyl alcohol) to form poly (vinyl butyral) which is used as an interlayer for safety glass as well as for coating fabrics and for injection-moulding compositions. Butyraldehyde also finds use in making oil-soluble and alcohol-soluble resins. Butyraldehyde is a raw material for the manufacture of butyric acid and butyric anhydride... 

The selective hydrogenation of crotonaldehyde to n-butyraldehyde was studied using Pd/C catalyst. The initial rate of hydrogenation was analysed mainly to assess the importance of various mass transfer effects from which it was found that all the rate data under the conditions of the present work were in the kinetic regime. A Langmuir - Hinshelwood type rate model has been derived and the rate parameters were evaluated by using concentration-time data. The agreement of the predicted results with the experimental data was found to be excellent. 

M Consonni, D Jokic, DYu Murzin, R Touroude. High performances of Pt/ZnO catalysts in selective hydrogenation of crotonaldehyde, Journal of Catalysis 188, 165-175, 1999. 

M Abid, R Touroude. Pt/Ce02 catalysts in selective hydrogenation of crotonaldehyde high performance of chlorine-free caralysts. Catalysis Letters 69, 139-144, 2000. 

M Abid, Thesis, Selective Hydrogenation of Crotonaldehyde, Strasbourg, 2001. 

From these findings, it can be concluded that the structure sensitivity in the selective hydrogenation of a,p unsaturated aldehydes such as crotonaldehyde and cinnamaldehyde largely depends on the steric effect of the bulky substituent on P-carbon of the substrate, but that another interpretation, e.g., an electronic effect, should be proposed for the size effect in the hydrogenation of acrolein. 

Selective Hydrogenation of Crotonaldehyde over Pt Derived Catalysts... 

Formation of butanol as well as small amounts of hydrocarbons (HC) were observed over all samples. Over Pt/SiOj crotylalcohol was not formed in detectable concentrations. The addition of Ni to Pt led to a selectivity of 2%. However, the combination of Pt with Ga and Sn or the use of a partially reducible support like Ti02 led to a significant increase in the rate of crotylalcohol formation (i.e., the selective hydrogenation of the carbonyl bond of crotonaldehyde). The highest selectivity to crotylalcohol was observed for PtGa/SiOj (56%), while it was lower for PVTiOa (46%) and PtSn/SiOa (31%). 

Catalysts for the selective hydrogenation of crotonaldehyde were obtained by controlled pyrolysis of M40[(CO)9Co3CC02]6 (M=Co and Zn) or M 2 (CO)9Co3CCOO 4 (M =Co, Mo, and Cu). The pyrolyses yield high surface area, amorphous solids. These catalysts are active for the hydrogenation of crotonaldehyde to crotyl alcohol. This differs from conventional metal catalysts, which are selective for the double bond hydrogenation. 

Ponec et al. has recently demonstrated that in the selective hydrogenation of crotonaldehyde over Sn-Pt catalysts the selectivity of crotylalcohol increased with time on stream.The observed phenomenon had been ascribed to reaction induced selectivity changes , however the exact origin of these changes was not clarified. 

A heterogeneous catalyst derived from the mixed carboxylates [Mo2 Co3(CO)9CC02 4] selectively hydrogenated crotonaldehyde to crotyl alcohol, in contrast to conventional catalysts selective for the hydrogenation of the C=C double bond. " ... 

Controlled pyrolysis of [Cu2 Co3(CO)9CC02 4] led to a catalytic material of high surface area for the selective hydrogenation of crotonaldehyde to crotyl alcohol. ... 

A class of reactions extensively studied is the selective hydrogenation of a, 13-unsaturated aldehydes, that is of the C=0 bond, to the corresponding unsaturated alcohols, without affecting the C=C double bond. The hydrogenation of crotonaldehyde on Pt/Si02, for example, is a complex reaction involving the following scheme ... 

Touroude and collaborators studied the selective hydrogenation of crotonaldehyde on 5 wt% Pt/Ce02 in the gas phase at atmospheric pressure. " The properties of the catalysts and their catalytic... 

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