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Novel sol-immobilization catalysts for the hydrogenation of levulinic acid and spectroscopic valuation of metal nanoparticles accessibility using probe molecules.

Lari, Giacomo 2014. Novel sol-immobilization catalysts for the hydrogenation of levulinic acid and spectroscopic valuation of metal nanoparticles accessibility using probe molecules. MPhil Thesis, Cardiff University.
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Abstract

Hydrogenation of levulinic acid to gamma-valerolactone has been studied with novel supported-ruthenium catalyst, achieving high conversion and selectivity in mild condition and using water as a green solvent. Sol immobilization has been applied successfully with the aim of increasing the turnover of the hydrogenation reaction per atom of ruthenium. This allows the preparation of supported metal catalysts with lower loading (1 wt.%) in comparison with the established commercial standard (5 wt.%). The study of the influence of the ruthenium precursor has been performed and the results obtained with the best catalyst have been compared with those obtained with different preparation methods. The catalysts were characterized through nitrogen sorption, temperature programmed reduction, CO hemisorption and X-ray diffraction to determine the structure and properties of the support and of the active phase and to make hypotheses regarding the structure-activity relationship. Reusability tests were performed to asses the industrial validity of this system, the result showing that though high performances are achieved with fresh catalysts, deactivation issues have still to be addressed. A deeper investigation of sol-immobilization catalysts and in particular of the role of the capping agent used in the preparation of the metal sol has been performed using titania-supported gold catalysts. The adsorption of carbon monoxide was monitored by the use of infrared and UV-vis spectroscopy on 1 wt.% Au/TiO2 prepared by sol immobilization using polyvinylalcohol and polyvinylpyrrolidone as stabilisers before and after treatments to remove the polymer from the surface. Comparison of spectroscopic results obtained on these catalysts with accessible deposition-precipitation-prepared catalyst allowed finding a relationship between the activity of the catalyst in CO oxidation and the accessibility of the surface. These newly developed tools allow for a easier characterization of the metal surface of supported gold catalysts.

Item Type: Thesis (MPhil)
Status: Unpublished
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Date of First Compliant Deposit: 30 March 2016
Last Modified: 20 Mar 2017 02:30
URI: https://orca.cardiff.ac.uk/id/eprint/71637

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