Two types of niobium-containing silica catalysts, (i) in-framework mixed oxide, obtained by co-precipitation type synthesis, and (ii) grafted niobium sites on silica supports, obtained via post-synthesis deposition from niobocene dichloride, were prepared. Both solids were tested in a series of five repeated batch-wise liquid-phase epoxidation tests of limonene with 50% aqueous hydrogen peroxide. Nb/SiO2 prepared by co-precipitation synthesis kept fully its epoxidation activity during the first two recycles, with a gradual decrease in activity in the following runs. Conversely, Nb/SiO2 prepared by deposition suffered from a more marked loss of activity since the first reuses. Most of the isolated Nb sites were maintained and no large Nb2O5 domains were formed during the recovery and regeneration tests. The distribution, geometry and coordination state of the Nb sites was therefore preserved, especially for the Nb/SiO2 sample prepared via co-precipitation. The presence of small Nb2O5 domains, even formed during repeated recycles, was not detrimental for the epoxidation reaction and, in general, Nb(V) sites inserted in a silica matrix proved to be a rather robust epoxidation catalyst for alkenes in the presence of aqueous hydrogen peroxide.

The stability of niobium-silica catalysts in repeated liquid-phase epoxidation tests : an evaluation of in-framework and grafted mixed oxides / C. Tiozzo, C. Palumbo, C. Bisio, F. Carniato, A. Gervasini, P. Carniti, M. Guidotti. - In: INORGANICA CHIMICA ACTA. - ISSN 0020-1693. - 431(2015), pp. 190-196. [10.1016/J.ICA.2015.01.048]

The stability of niobium-silica catalysts in repeated liquid-phase epoxidation tests : an evaluation of in-framework and grafted mixed oxides

A. Gervasini;P. Carniti;
2015

Abstract

Two types of niobium-containing silica catalysts, (i) in-framework mixed oxide, obtained by co-precipitation type synthesis, and (ii) grafted niobium sites on silica supports, obtained via post-synthesis deposition from niobocene dichloride, were prepared. Both solids were tested in a series of five repeated batch-wise liquid-phase epoxidation tests of limonene with 50% aqueous hydrogen peroxide. Nb/SiO2 prepared by co-precipitation synthesis kept fully its epoxidation activity during the first two recycles, with a gradual decrease in activity in the following runs. Conversely, Nb/SiO2 prepared by deposition suffered from a more marked loss of activity since the first reuses. Most of the isolated Nb sites were maintained and no large Nb2O5 domains were formed during the recovery and regeneration tests. The distribution, geometry and coordination state of the Nb sites was therefore preserved, especially for the Nb/SiO2 sample prepared via co-precipitation. The presence of small Nb2O5 domains, even formed during repeated recycles, was not detrimental for the epoxidation reaction and, in general, Nb(V) sites inserted in a silica matrix proved to be a rather robust epoxidation catalyst for alkenes in the presence of aqueous hydrogen peroxide.
Alkene epoxidation; Heterogeneous catalysis; Hydrogen peroxide; Mesoporous silica; Niobium
Settore CHIM/02 - Chimica Fisica
2015
Article (author)
File in questo prodotto:
File Dimensione Formato  
1-s2.0-S0020169315000845-main.pdf

accesso riservato

Tipologia: Publisher's version/PDF
Dimensione 891.78 kB
Formato Adobe PDF
891.78 kB Adobe PDF   Visualizza/Apri   Richiedi una copia
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/346962
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 22
  • ???jsp.display-item.citation.isi??? 22
social impact