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Oxidative dehydrogenation of ethanol and methanol to the corresponding aldheydes

Summary of the work made

A new class of catalysts has been obtained starting from a silica support rich of hydroxils on the surface. This support is contacted with titanium alkoxide that reacts by grafting on the surface and cover with a thin layer all the silica surface. Then, vanadyl alkoxide is grafted on the titanium oxide. A catalyst, prepared in this way, is very active and selective in the oxidative dehydrogenation of methanol and ethanol to the corresponding aldehydes.



Formaldehyde is currently obtained in industry by gas-phase oxidation of methanol on iron molybdate catalyst. We have studied in detail the kinetics of this reaction [1,2] and concluded that, despite the fact that this process is so popular, it has some important drawbacks. The reaction is highly exothermic and the selectivity is relatively low. The oxidative dehydrogenation (ODH), that is almost athermal, would be more convenient, provided that an active and selective catalyst is is available. We have found such a catalyst, that is a vanadium oxide catalyst prepared by grafting vanadyl alkoxide on a surface of silica opportunely coated with titania [3].

 Acethaldeyde is produced in industry from ethylene with the Wacker process that is a very heavy process, justified in the past, for the very low price of ethylene. Moreover, in this process a large amount of very expensive palladium chloride is necessary. Considering that ethanol is nowadays largely employed as biofuel the possibility exists of using it as raw material for producing acethaldehyde.

In this case there are two different possible routes:

  1. the ethanol dehydrogenation at relatively high temperature on copper chromite (see section devoted to Innovation in the production of ethyl acetate, acetic aldheyde and acetic acid);

  2. Oxidative dehydrogenation in mild conditions of temperature (140-250°C) and pressure (1 atm) on a vanadium oxide catalyst prepared by grafting vanadyl alkoxide on a surface of silica opportunely coated with titania [3], that is, the same catalyst active also in the ODH of methanol to formaldehyde.

The good performances of the mentioned catalyst in both cases is due to method of catalyst preparation [3]. It was well known that vanadium oxide is a very good catalyst promoting ODH in particular of light hydrocarbons like propane, butane, isobutene to obtain the corresponding olefins.In order to obtain a stable catalyst it is necessary to deposit vanadium pentoxide on surface giving place to strong interactions without inhibiting the activity. TiO2 seems the best support, but titania has relatively low specific surface area and vanadium oxide cannot be adequately dispersed. Silica and alumina, that have higher and more stable specific surface area are not suitable for obtaining a good dispersion of vanadium pentoxide. The problem can be solved by opportunely coating a silica support with one or more layers of titania and the grafting vanadyl alkoxide on this surface. This catalyst has shown good performances in the ODH of both the light hydrocarbons [4-7] in a temperature range (400-500°C) and the alcohols methanol [8-10] and ethanol [10-13] (140-250°C).


Literature on oxidative dehydrogenation of ethanol and methanol to the corresponding aldheydes

  1. E. Santacesaria, M. Morbidelli, S. Carrà; "Kinetics of the catalytic oxidation of methanol to formaldehyde". Chemical Engineering Science, 36, 909 (1981).

  2. R. Tesser, M. Di Serio, E. Santacesaria;“Catalytic oxidation of methanol to formaldehyde: an example of kinetics with transport phenomena in a packed-bed reactor”. Catalysis Today 77 (2003) 325-333.

  3. Santacesaria, Elio; Cozzolino, Mariangela; Di Serio, Martino; Tesser, Riccardo. Grafting alkoxides on the surface of oxides. A method for preparing new catalysts and supports. Chimica e l'Industria (Milan, Italy) (2007), 89(10), 112-119.

  4. Santacesaria, E.; Cozzolino, M.; Di Serio, M.; Venezia, A. M.; Tesser, R.;“Vanadium based catalysts prepared by grafting: preparation, properties and performances in the ODH of butane.” Applied Catalysis, A: General (2004), 270(1-2), 177-192.

  5. Cozzolino, M.; Tesser, R.; Di Serio, M.; Santacesaria, E.; “ Oxidative dehydrogenation of n-butane on vanadium-based catalysts prepared by grafting. DGMK” Tagungsbericht (2004), 2004-3 (Proceedings of the DGMK-Conference "C4/C5-Hydrocarbons: Routes to Higher Value-Added Products", (2004), 117-124.

  6. Iannazzo, V.; Neri, G.; Galvagno, S.; Di Serio, M.; Tesser, R.; Santacesaria, E. ;“Oxidative dehydrogenation of isobutane over V2O5-based catalysts prepared by grafting vanadyl alkoxides on TiO2-SiO2 supports” Applied Catalysis, A: General (2003), 246(1), 49-68.

  7. E. Santacesaria, G. Carotenuto, R. Tesser, M. Di Serio; Study of the Performance of Vanadium Based Catalysts Prepared by Grafting in the Oxidative Dehydrogenation of Propane; Catalysis – Innovative Applications in Petrochemistry and Refining; DGMK Conference Proceedings October 4-6, 2011, Dresden, Germany

  8. M. Cozzolino, R. Tesser, M. Di Serio, E.M. Gaigneaux, P. Eloy, E. Santacesaria. “Supported vanadium oxide nanoparticles: effects of preparation method, support and type of precursor on the catalytic performances in the ODH of methanol to formaldehyde.” Studies in Surface Science and Catalysis (2006), 162 (Scientific Bases for Preparation of Heterogeneous Catalysts), 697-704.

  9. Cozzolino, M.; Tesser, R.; Di Serio, M.; D'Onofrio, P.; Santacesaria, E.. Kinetics of the oxidative dehydrogenation (ODH) of methanol to formaldehyde by supported vanadium-based nanocatalysts. Catalysis Today (2007), 128(3-4), 191-200.

  10. Cozzolino, M.; Tesser, R.; Di Serio, M.; Santacesaria, E. “ Methanol and ethanol oxidative dehydrogenation (ODH) to the corresponding aldehydes on vanadium-based catalysts.” DGMK Tagungsbericht (2005), 2005-2 (Proceedings of the DGMK/SCI-Conference "Oxidation and Functionalization: Classical and Alternative Routes and Sources", 2005), 91-98

  11. Santacesaria, E.; Sorrentino, A.; Tesser, R.; Di Serio, M.; Ruggiero, A.;“Oxidative dehydrogenation of ethanol to acetaldehyde on V2O5/TiO2-SiO2 catalysts obtained by grafting vanadium and titanium alkoxides on silica” . Journal of Molecular Catalysis A: Chemical (2003), 204-205 617-627.

  12. Tesser, R.; Maradei, V.; Di Serio, M.; Santacesaria, E. “Kinetics of the Oxidative Dehydrogenation of Ethanol to Acetaldehyde on V2O5/TiO2-SiO2 Catalysts Prepared by Grafting”. Industrial & Engineering Chemistry Research (2004), 43(7), 1623–1633.

  13. D. Sannino, V. Vaiano, P. Ciambelli, G. Carotenuto, M. Di Serio, E. Santacesaria; Enhanced performances of grafted VOx on titania/silica for the selective photocatalytic oxidation of ethanol to acetaldehyde; Catalysis Today 209 (2013) 159–163.