Loading...
Please wait, while we are loading the content...
Similar Documents
Transformación de biomasa a productos químicos de interés y carburantes mediante descarboxilación cetónica e hidrodesoxigenación
| Content Provider | Semantic Scholar |
|---|---|
| Author | Tomás, Borja Oliver |
| Copyright Year | 2017 |
| Abstract | The purpose of the present thesis was the use and valorisation of biomass platform molecules or their derivatives, applying the principles of sustainable chemistry. The reaction of ketonic decarboxylation of carboxylic acids was studied in the presence of metal oxides. ZrO2 was shown to be an excellent catalyst for the reaction, reasonably stable with time on stream and reusable. The reactivity of different substrates over ZrO2 was investigated with respect to the degree of substitution of the carbon in alpha position. 2-methylbutanoic acid, with one methyl replacing one of the alpha H atoms and, thereby, introducing a steric hindrance, showed slower reaction rates than pentanoic acid with two alpha H?. It was concluded that for 2-methylbutanoic acid reactions occurred preferentially at the edges and the corners of the catalyst. The reactivity of the acids without alpha hydrogen atoms, which cannot not react via the mechanism involving the beta-ketoacid, was studied. There was no reaction under standard conditions, and when the reaction conditions were forced by increasing reaction temperature, pivalic acid was transformed. It was observed that a retro-Koch reaction occurred, in addition to other reactions like hydrogenation, rearrangement and fragmentation. Also in the case of 2,2,5,5-tetramethyladipic acid, the retro-Koch reaction produced two isomers of 2,2,5-trimethylhexenoic acid, which then reacted further to by-products such as a ketone and a lactone. These results further reinforce the proposed mechanism via the beta-ketoacid for carboxylic acids containing at least one alpha hydrogen atom. ZrO2 was used as a catalyst for the production of long chain linear alkanes in the range of waxes, from substances of renewable origin such as vegetable oil and its derivatives. Working under optimized conditions, methyl stearate was converted into waxes with a yield of 60% (72% of this fraction was molecules with 35 carbons). When using sunflower oil as substrate the final yield of the waxes was higher than 40%, but a second hydrodeoxygenation step was required. In the case of the oil, a large number of fragmentations was produced. In part this was due to the insaturations of fatty acids, and probably also to radicals, promoted by the glycerol part. In this thesis, the unique catalytic activity of TiO2, with respect to ZrO2, was evidenced when carboxylic acids were employed as substrates. TiO2 catalyzes the ketone decarboxylation reaction, showing higher yields to the ketone than ZrO2 at low reaction temperatures, between 325 to 350 °C. In addition, TiO2 catalyzes cascade reactions that lead to the production of olefins. It was shown that on the surface of the TiO2, hydrogen transfer occurred between different molecules, and also aldol condensation of ketones, both playing an important role in the formation of the olefins. These reactions were used for the production of a biofuel. With TiO2, the biofuel contains more compounds with higher molecular weight than the biofuel produced with ZrO2 due to the C-C bond formation… |
| Starting Page | 1 |
| Ending Page | 1 |
| Page Count | 1 |
| File Format | PDF HTM / HTML |
| DOI | 10.4995/Thesis/10251/90411 |
| Alternate Webpage(s) | https://riunet.upv.es/bitstream/handle/10251/90411/Oliver%20-%20Transformaci%C3%B3n%20de%20biomasa%20a%20productos%20qu%C3%ADmicos%20de%20inter%C3%A9s%20y%20carburantes%20mediante%20descarb....pdf?isAllowed=y&sequence=1 |
| Alternate Webpage(s) | https://doi.org/10.4995/Thesis%2F10251%2F90411 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
