Niobium-based heterogeneous catalysts synthesised in supercritical carbon dioxide for selective olefin epoxidation

Collina, Irene (2022) Niobium-based heterogeneous catalysts synthesised in supercritical carbon dioxide for selective olefin epoxidation. [Laurea magistrale], Università di Bologna, Corso di Studio in Chimica industriale [LM-DM270], Documento ad accesso riservato.
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Abstract

In this work, two different protocols for the synthesis of Nb2O5-SiO2 with a sol-gel route in which supercritical carbon dioxide was used as solvent have been developed. The tailored design of the reactor allowed the reactants to come into contact only when supercritical CO2 is present, and the high-throughput experimentation scCO2 unit allowed the screening of synthetic parameters, that led to a Nb2O5 incorporation into the silica matrix of 2.5 wt%. N2-physisorption revealed high surface areas and the presence of meso- and micropores. XRD allowed to demonstrate the amorphous character of these materials. SEM-EDX proved the excellent dispersion of Nb2O5 into the silica matrix. These materials were tested in the epoxidation of cyclooctene with hydrogen peroxide, which is considered an environmentally friendly oxidant. The catalysts were virtually inactive in an organic, polar, aprotic solvent (1,4-dioxane). However, the most active scCO2 Nb2O5-SiO2 catalyst achieved a cyclooctene conversion of 44% with a selectivity of 88% towards the epoxide when tested in ethanol. Catalytic tests on cyclohexene revealed the presence of the epoxide, which is remarkable, considering that this substrate is easily oxidised to the diol. The behaviour in protic and aprotic solvents is compared to that of TS-1.

Abstract
Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Collina, Irene
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Indirizzo
CHIMICA INDUSTRIALE
Ordinamento Cds
DM270
Parole chiave
olefin epoxidation hydrogen peroxide heterogeneous catalysis niobium oxide sol-gel supercritical CO2
Data di discussione della Tesi
20 Ottobre 2022
URI

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