Selective Hydrogenation of Crotonaldehyde

With respect to the reaction rate, tin-modified catalysts evidence a marked increase, as compared to the monometallic catalyst. The reaction rate follows the sequence PtSn-OM PtSn-BM PtSn-OM Pt/Si02. Table 6.7 shows values of the overall reaction rate, SAL and UOL formation rates (estimated between 0 and 10% conversion) and the selectivities to SAL, UOL and SOL at 5 and 80% conversion. The effect produced by the addition of tin is clearly shown by the following data the Pt/Si02 system gives an Suol value near 10% for all conversion 

Catalyst r (jimol ) ruoL( imols gM, ) rsAL(M-mols gris) 

It is very interesting to analyze the results shown in Table 6.7 concerning the formation rates of hydrogenation products of the C=0 (UOL) and C=C (SAL) bonds. The presence of tin notably increases the UOL formation rate for the three 

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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 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. 

Selective Hydrogenation of Crotonaldehyde over Pt Derived Catalysts... 

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. 

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. ... 

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... 

It is noteworthy that even a separate treatment of the initial data on branched reactions (1) and (2) (hydrogenation of crotonaldehyde to butyr-aldehyde and to crotyl alcohol) results in practically the same values of the adsorption coefficient of crotonaldehyde (17 and 19 atm-1)- This indicates that the adsorbed form of crotonaldehyde is the same in both reactions. From the kinetic viewpoint it means that the ratio of the initial rates of both branched reactions of crotonaldehyde is constant, as follows from Eq. (31) simplified for the initial rate, and that the selectivity of the formation of butyraldehyde and crotyl alcohol is therefore independent of the initial partial pressure of crotonaldehyde. This may be the consequence of a very similar chemical nature of both reaction branches. 

A major improvement in the selectivity towards crotyl alcohol by the hydrogenation of crotonaldehyde has been attained by Margitfalvi et al. [91] through the modificahon of Pt/Si02 by Sn addition via SnEfi, which was then reduced at 573 K. For Sn/Pb = 1.2, both the overall activity of the catalyst and its selectivity towards the formahon of crotyl alcohol were strongly increased. On this bimetallic catalyst, the selechvity of the formation of crotyl alcohol was over 70%. 

Table 6.7 Hydrogenation of crotonaldehyde formation rate of SAL (rsAL) and UOL (ruor) (estimated between conversion 0 and 10%), overall reaction rate (ro) and selectivities to SAL,...

Nagase et al. studied the hydrogenation of crotonaldehyde over a Ag-Mn catalyst supported on A1203-5A1P04 in hexane at 5 MPa H2.68 The high activity and selectivity to crotyl alcohol was obtained over Ag-Mn catalysts with >1.5 Mn/Ag atom ratio at 180°C (72.0% selectivity at 98% conversion, compared to 43.2% selectivity at 84.3% conversion over the catalyst without Mn). 

In vapor-phase hydrogenation of crotonaldehyde over Rh-Sn-Si02 catalysts, the selectivity to trans- and cA-crotyl alcohol increased strongly with the tin content, reaching 62-69% for the trans compound with the Sn/(Sn+Rh) atomic ratio higher than 40%.83... 

Type II selectivity involves the differentiation between two parallel reactions in which different products are formed by separate paths from the same starting material.33 This type of selectivity is encountered in the hydrogenation of crotonaldehyde to either butyraldehyde or 2 buten-l-ol (Eqn. 5.8). When both reactions are of the same kinetic order changes in mass transport will influence them both to the same extent and there will be no effect on reaction selectivity. When the reactions are of different kinetic orders, that one with the higher order will be more affected by mass transport limitation. 

While a nickel boride catalyst preferentially saturates the carbon-carbon double bond of a,p-unsaturated aldehydes, the cobalt borides have a tendency to favor carbonyl group hydrogenation. Cinnamaldehyde was hydrogenated to cinnamoyl alcohol in 97% selectivity at 50% conversion and 86% selectivity at 74% conversion over a P-2 cobalt boride (Eqn. 12.7).5 With a P-2W cobalt boride the unsaturated alcohol was produced in 97% selectivity at 73% conversion. The presence of the aromatic ring enhances selectivity in this reaction since the hydrogenation of crotonaldehyde to 2-buten-l-ol occurred with only about a 25% selectivity at under 20% conversion over either catalyst (Eqn. 12.8).54... 

While some vapor phase hydrogenations of unsaturated aldehydes have shown good initial selectivities, in most cases the reaction selectivity decreases significantly with prolonged reaction time. The vapor phase hydrogenation of crotonaldehyde over a Pt/Ti02 catalyst in the SMSI state, however, showed reasonable selectivities that remained relatively constant over the entire time of the reaction. 0°... 

Activity and selectivity of monometallic Ag catalysts can be controlled by the preparation conditions leading to micro- and meso- to macroporous catalysts which are active and selective in the hydrogenation of crotonaldehyde. In Ag catalysts modified by a second metal, bimetallic sites exhibiting surface polarity and Ag particles in close contact with a partially reduced early transition metal or a rare earth element, or Ag species stabilized and incorporated in these oxides were concluded to be the active species in the working state of these catalysts. Simultaneous introduction of both metals during the sol-gel process under optimized hydrolyzing conditions could further increase the metal-promoter interaction and lead to well-tailored new hydrogenation catalysts. 

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... 

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