Catalysts alcohol formation

Alcohols are the most frequently formed products of ester hydrogenolysis. The hydrogenation of esters to alcohols is a reversible reaction with alcohol formation favored at high pressure, ester at low pressure (/). Copper chromite is usually the catalyst of choice. Details for the preparation of this catalyst (/7) and a detailed procedure for hydrogenation of ethyl adipate to hexamethylene glycol (/[Pg.80]

J. E. Bailie, and G. J. Hutchings, Promotion by sulfur of gold catalysts for crotyl alcohol formation from crytonaldehyde hydrogenation, Chem. Commun. 21, 2151-2152 (1999). 

Aldol condensation of acetone is a well-known base-catalyzed reaction, and barium hydroxide is one of the catalysts for this reaction mentioned in textbooks. A family of barium hydroxide samples hydrated to various degress determined by the calcination temperature (473, 573, 873, and 973 K) of the starting commercial Ba(OH)2 8H2O were reported to be active as basic catalysts for acetone aldol condensation (282,286). The reaction was carried out in a batch reactor equipped with a Soxhlet extractor, where the catalyst was placed. The results show that Ba(OH)2 8H2O is less active than any of the other activated Ba(HO)2 samples, and the Ba(OH)2 calcined at 473 K was the most active and selective catalyst for formation of diacetone alcohol, achieving nearly 58% acetone conversion after 8h at 367 K in a batch reactor. When the reaction temperature was increased to 385 K, 78% acetone conversion with 92% selectivity to diacetone alcohol was obtained after 8h. The yield of diacetone alcohol was similar to that described in the literature in applications with commercial barium hydroxide, but this catalyst required longer reaction times (72-120 h) (287). No deactivation of the catalyst was observed in the process, and it could be used at least 9 times without loss of activity. 

The reaction is usually carried out with an acid catalyst. Acetal formation does not proceed to completion because of isolation of single hydroxyl groups between pairs of acetal structures. The two most important acetals are the formal and butyral (R = H and C3H7, respectively). The applications of poly(vinyl alcohol) and its acetals are described in Sec. 3-14c-2. 

Chan and Wilson [52] tried to oxidize methane to methanol by oxygen on TMPcY and TMTPPY (TM= Co, Fe, Ru, Mn) in the temperature range of 548 K to 773 K. Only RuPcY, CoTPPY and MnTPPY are active towards alcohol formation, yields up to 0.5% being claimed (Table 5). All other catalysts give combustion of methane to carbon dioxide and water. In an attempt to repeat these experiments, the present authors only observed CO, CO2 and H2O formation, and rapid autoxidation of the catalyst. 

Calculated adsorption equilibrium constants indicate the Schiffs base is adsorbed more favorably on the catalyst surface than the aldehyde. This observation is consistent with situation kinetics occurring during the initial stage of the hydrogenation. The apparent rate constant shows that the product C formation is much faster than the alcohol formation. 

Advances in higher alcohol synthesis that need to be made include improving productivity and selectivity. Higher spacetime yields are also required which may be achieved by dual catalyst bed reactors, the use of slurry phase synthesis process to increase CO conversion levels, and injection of lower alcohols into the reactant stream to increase the rate of higher alcohol formation.630... 

Fig. 8. Selectivity for ketone and alcohol formation (A) and regioselectivity (B) in the oxidation of n-octane at 5% conversion over FePcY and FePcVPI-5 catalysts. Conditions are those of Fig. 7.

The intrinsic nature of tungsten carbide catalyst in CO-H2 reactions is to form hydrocarbons. This property can be modified by oxidic promoters as for the case of noble metals like Pt or Rh or by the presence of carbon vacancies at the surface. To increase the production of alcohols in the Fischer-Tropsch reaction, the catalyst should be bifunctional, with oxidic and carbidic components as in the case of WC on Ti02. Overcarburization of WC on supports like Si02 or Zr02 where the W-O-metal interaction is weak leads to C/W ratios close to unity and does not result in alcohol formation. 

Four reviews on allylic and vinyl substitution have been published.20-23 The use of pentamethylcyclopentadienylruthenium catalysts for the. S n reactions of allyl substrates has been reviewed.20 The Sn reactions of allyl substrates in the presence of ruthenium catalysts occur primarily at the most substituted position of the allylic group. All the catalysts involve formation of an intermediate where the allyl compound becomes associated with the Ru atom in the catalyst. The regiospecificity (50-98%) depends on the structure of the allylic substrate, the nucleophile, the solvent, the temperature, and the catalyst. These catalysts have also been used for protection of allylic alcohol and amino groups. Some of the reactions are stereospecific. 

In the presence of a base or an acid as a catalyst, alcohols add to aldehydes or ketones with the formation of hemiacetals. You should already be familiar with the corresponding mechanism and its intermediates from your introductory class. Therefore it is sufficient that we briefly review it graphically by means of Figure 9.2. 

Alcohol and aldehyde decarbonylation on Rh(l 11), activation of C-H, C-C, and C-0 bonds, 345-353 Alkane dehydroeyelization with Pt-Sn-alumina catalysts aromatic formation, 120 preparation condition effect, 119... 

The retarding effect of alcohols on the rate of epoxidation manifests itself in the observed autoretardation by the alcohol coproduct.428,434 446,447 The extent of autoretardation is related to the ratio of the equilibrium constants for the formation of catalyst-hydroperoxide and catalyst-alcohol complexes. This ratio will vary with the metal. In metal-catalyzed epoxidations with fe/T-butyl hydroperoxide, autoretardation by tert-butyl alcohol increased in the order W < Mo < Ti < V the rates of Mo- and W-catalyzed epoxidations were only slightly affected. Severe autoretardation by the alcohol coproduct was also observed in vanadium-catalyzed epoxidations.428 434 446 447 The formation of strong catalyst-alcohol complexes explains the better catalytic properties of vanadium compared to molybdenum for the epoxidation of allylic alcohols.429 430 452 On the other hand, molybdenum-catalyzed epoxidations of simple olefins proceed approximately 102 times faster than those catalyzed by vanadium.434 447 Thus, the facile vanadium-catalyzed epoxidation of allyl alcohol with tert-butyl hydroperoxide may involve transfer of an oxygen from coordinated hydroperoxide to the double bond of allyl alcohol which is coordinated to the same metal atom,430 namely,... 

Tautens reported various limitations in rhodium-catalyzed air-alcohol formation. As can be seen in Equation (165), the yield of 280 is only 16%, albeit with 96% ee <2003OL3695>. On the other hand, an identical reaction utilizing Pd(dppp)Cl2 as a catalyst gave 280 in 82% yield but only with 71% ee (dppp = l,3-bis(diphenylphosphino)propane) <2003OL3695>. 

The move from a cobalt- to a rhodium-based process that was seen in methanol carbonylation (Section 4.2.4) is echoed in hydroformylation, thus the late 1960s saw the development of rhodium catalysts here too. Wilkinson and his colleagues found that RhH(CO)(PPh3)2 was an outstanding catalyst as it was very selective to aldehyde products (no alcohol formation, no alkene hydrogenation or isomerization occurred) and that very high n-ji- aldehyde selectivities of 20 1 for a... 

Massie, of UOP, found an influence of C02 on hydroformylation. In the presence of carbon dioxide and a common Co complex catalyst, a decreased alkane formation and an increased alcohol formation were observed [306]. 

Hydrogenations of cyclohexanones in basic media leads to the formation of the more stable, equatorial alcohol, 18, as the primary product (Eqns. 18.18-19). With basic Raney nickel catalysts, the predominance of equatorial alcohol has been shown to arise from the isomerization of the initially produced axial alcohol under hydrogenation conditions. The use of platinum oxide with its alkaline impurity also leads to extensive equatorial alcohol formation unless acetic acid is used as the solvent. This basic impurity was shown to be... 

Pent-l-ene Hexanal (49), 2-methyl-pentanal (23) Co COUPPh), Toluene, 140 C (110/110) 6 20 No comments on alcohol formation, catalyst recoverable (200)... 

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