Investigation of the ketonization reaction of renewable acids and esters

Ketonization is a promising reaction for the upgrading of bio oils produced from biomass and it is used for the preparation of highly valuable asymmetrical ketones such as di-hydrocalchone (HC) and acetyl furan (Ac-Fur). But, they are produced in the liquid-phase with poorly sustainable processes, e.g. Friedel-Crafts acylations (Ac-Fur) and tandem acylation/alkylation (HC) with homogeneous Lewis acid catalysts or oxidations with organic peroxides and excess MnO2 (HC) or H2O2 and inorganic homogeneous catalysts. The development of an alternative gas-phase process to produce HC and Et-Fur by means of cross-ketonization is highly desirable because it would avoid the issues of traditional methods. Moreover, most reactants required for the ketonization process could be prepared from renewable resources. This thesis was dedicated to the study of the cross-ketonization between ethyl benzoate (EB) and ethyl-3-phenylpropionate (EPP) and between ethyl acetate (EtOAc) and ethyl-2-furoate (Et-Fur) to synthetize HC and 2-Ac-Fur respectively. Ketonization of EPP with EB was carried out over different metal oxides (namely ZrO2, La2O3, CeO2) and it was found that ZrO2 was the best catalyst, probably due to its amphoteric properties. Over this material, the formation of HC was maximized by a large excess of EB (EB/EPP= 9) and by a high reaction temperature (350 °C); the effect of water co-feeding was also evaluated in the attempt of maximize HC yield by hydrolyzing EB in situ and producing the more reactive BA, but it was found that instead water reduces catalyst activity. Similar conclusions were drawn investigating the ketonization of Et-Fur with EtOAc over ZrO2. In conclusion, HC was obtained with 80% selectivity at 77% EPP conversion at 350 °C, with 1 second and with a EB/EPP molar ratio = 9, while Ac-Fur was obtained with 82% selectivity at 82% Et-Fur conversion in the same conditions but with a lower EtOAc/Et-Fur molar ratio of 4.