LA FOTOCATALISI ETEROGENEA UTILIZZATA COME METODO PER LE SINTESI ORGANICHE SELETTIVE IN CONDIZIONI SPERIMENTALI BLANDE

2014

Nel corso di questi tre anni di Dottorato di Ricerca in “Tecnologie per la Sostenibilità ed il Risanamento Ambientale”, XXIV ciclo, presso il laboratorio di ricerca di fotocatalisi eterogenea “Schiavello-Grillone”, sono stati sviluppati processi innovativi per la produzione selettiva di specie organiche ad alto valore aggiunto, seguendo i principi della Chimica Verde; in particolare sono state studiate reazioni di ossidazione parziale di composti aromatici. La metodologia prevalentemente utilizzata è stata la fotocatalisi eterogenea mediante l’utilizzo del biossido di Titanio policristallino (TiO2) come fotocatalizzatore, utilizzato sospeso in soluzione acquosa o immobilizzato su supporti r…

Ferulic Acid Oxidation Through Visible Light Induced TiO2 Photocatalysis

2012

Synthesis of vanillin in water by TiO2 photocatalysis

2012

Abstract The photoproduction of vanillin is studied in aqueous medium starting from trans-ferulic acid, isoeugenol, eugenol or vanillyl alcohol by using both commercial and home prepared TiO2 samples as photocatalysts and batch Pyrex photoreactors. The photo-oxidation at room temperature of these compounds produces vanillin with a selectivity ranging from 1.4 to 21 mol% with respect to the converted substrate. An investigation on the intermediates was performed in the case of trans-ferulic acid; for this substrate the most important intermediates were homovanillic acid, vanillyl mandelic acid, trans-caffeic acid, formic acid, acetic acid, and oxalic acid. The carbon mass balance, including …

Hydroxilation of benzoic acid and phenol in the presence of TiO2 photocatalysts: selectivity and kinetics

2011

Visible-light-induced oxidation of trans-ferulic acid by TiO2 photocatalysis

2012

Abstract The oxidation of trans-ferulic acid (C10H10O4) in aqueous TiO2 dispersion occurs via the formation of a charge-transfer complex on the TiO2 surface that is able to absorb visible light (λ ⩾ 400 nm). The main product is CO2, whereas secondary oxidation products are organic species such as vanillin, caffeic acid, homovanillic acid, and vanillylmandelic acid. Oxidation through the formation of a charge-transfer complex occurs only in the presence of specific TiO2 samples. Experiments in the absence of oxygen, in the presence of bromate ions and by using a phosphate-modified TiO2, have been carried out for investigating the reaction mechanism. In order to study the interaction between …

Sintesi di Vanillina tramite Reazione di Ossidazione Fotocatalitica con TiO2 in Fase Acquosa

2011

Preparation, thermal analysis and photoactivity of TiO2 samples

2012

Visible Light Induced Oxidation of Ferulic Acid by TiO2 Photocatalysis

2012

Oxidation of ferulic acid (C10H10O4) in aqueous medium occurs by using both commercial and home prepared TiO2 samples under visible light irradiation. Among the oxidation products vanillin was found with a selectivity ranging from 1 to 2% with respect to the converted substrate. By considering that TiO2 is unable to absorb visible light and ferulic acid does not react in the absence of TiO2, the observed photoactivity may be explained by the formation of a charge-transfer complex between ferulic acid and TiO2, being the complex able to absorb visible light. Among all the tested semiconductor oxides, only Merck anatase TiO2 does not perform the oxidation of ferulic acid under visible light i…

Selective oxidation of phenol and benzoic acid in water via home-prepared TiO2 photocatalysts: Distribution of hydroxylation products

2012

Abstract The hydroxylation of phenol (a substrate containing an electron donor group) and of benzoic acid (a substrate containing an electron withdrawing group) has been carried out by the photocatalytic method in aqueous suspensions containing commercial or home prepared TiO2 samples. The aim of the work was to study the distribution of hydroxylation products when different photocatalysts were used and to correlate the selectivity to some physico-chemical features of the powders. The samples were characterized by X-ray diffraction, thermogravimetry, determination of crystalline phase percentage, specific surface area and zero charge point. The photoreactivity results indicate that the prod…