Photo catalytic reduction of benzophenone on TiO2: Effect of preparation method and reaction conditions

International Nuclear Information System (INIS)

Albiter E, E.; Valenzuela Z, M. A.; Alfaro H, S.; Flores V, S. O.; Rios B, O.; Gonzalez A, V. J.; Cordova R, I.

2010-01-01

The photo catalytic reduction of benzophenone was studied focussing on improving the yield to benzhydrol. TiO 2 was synthesized by means of a hydrothermal technique. TiO 2 (Degussa TiO 2 -P25) was used as a reference. Catalysts were characterized by X-ray diffraction and nitrogen physisorption. The photo catalytic reduction was carried out in a batch reactor at 25 C under nitrogen atmosphere, acetonitrile as solvent and isopropanol as electron donor. A 200 W Xe-Hg lamp (λ= 360 nm) was employed as irradiation source. The chemical composition of the reaction system was determined by HPLC. Structural and textural properties of the synthesized TiO 2 depended on the type of acid used during sol formation step. Using HCl, a higher specific surface area and narrower pore size distribution of TiO 2 was obtained in comparison with acetic acid. As expected, the photochemical reduction of benzophenone yielded benzopinacol as main product, whereas, benzhydrol is only produced in presence of TiO 2 (i.e. photo catalytic route). In general, the hydrothermally synthesized catalysts were less active and with a lower yield to benzhydrol. The optimal reaction conditions to highest values of benzhydrol yield (70-80%) were found at 2 g/L (catalyst loading) and 0.5 m M of initial concentration of benzophenone, using commercial TiO 2 -P25. (Author)

Photo catalytic reduction of benzophenone on TiO{sub 2}: Effect of preparation method and reaction conditions

Energy Technology Data Exchange (ETDEWEB)

Albiter E, E.; Valenzuela Z, M. A.; Alfaro H, S.; Flores V, S. O.; Rios B, O.; Gonzalez A, V. J.; Cordova R, I., E-mail: mavalenz@ipn.m [IPN, Escuela Superior de Ingenieria Quimica e Industrias Extractivas, Laboratorio de Catalisis y Materiales, Zacatenco, 07738 Mexico D. F. (Mexico)

2010-07-01

The photo catalytic reduction of benzophenone was studied focussing on improving the yield to benzhydrol. TiO{sub 2} was synthesized by means of a hydrothermal technique. TiO{sub 2} (Degussa TiO{sub 2}-P25) was used as a reference. Catalysts were characterized by X-ray diffraction and nitrogen physisorption. The photo catalytic reduction was carried out in a batch reactor at 25 C under nitrogen atmosphere, acetonitrile as solvent and isopropanol as electron donor. A 200 W Xe-Hg lamp ({lambda}= 360 nm) was employed as irradiation source. The chemical composition of the reaction system was determined by HPLC. Structural and textural properties of the synthesized TiO{sub 2} depended on the type of acid used during sol formation step. Using HCl, a higher specific surface area and narrower pore size distribution of TiO{sub 2} was obtained in comparison with acetic acid. As expected, the photochemical reduction of benzophenone yielded benzopinacol as main product, whereas, benzhydrol is only produced in presence of TiO{sub 2} (i.e. photo catalytic route). In general, the hydrothermally synthesized catalysts were less active and with a lower yield to benzhydrol. The optimal reaction conditions to highest values of benzhydrol yield (70-80%) were found at 2 g/L (catalyst loading) and 0.5 m M of initial concentration of benzophenone, using commercial TiO{sub 2}-P25. (Author)

Action of Mercaptan and Disulfide in Hydrogen Atom Exchange Reactions; Action des Thioalcools et des Disulfures dans les Reactions d'Echange d'Atomes d'Hydrogene; Vozdejstvie merkaptanov i disul'fidov v reaktsiyakh obmena atoma vodoroda; Accion de los Mercaptanos y Disulfuros en las Reacciones de Intercambio del Hidrogeno Atomico

Energy Technology Data Exchange (ETDEWEB)

Cohen, S. G. [Brandeis University Waltham, MA (United States)

1965-10-15

transfer reactions. The photoreduction of benzophenone in an ether is also inhibited by the sulfur compounds, by hydrogen atom transfer reactions. A mechanism exists in this system (unlike the ketone-alcohol systems) by which the sulfur compounds may be consumed irreversibly. This leads to an induction period, instead of to permanent retardation, about 15 quanta being negated by each molecule of sulfur compound. (author) [French] Des reactions induites par des radicaux libres, par photochimie et par des rayonnements de haute energie, peuvent etre catalysees ou inhibees par des reactions rapides d'echange d'atomes d'hydrogene des thioalcools et des disulfures. Les decarbonylations d'aldehydes, induites par des radicaux libres, amorcees par la lumiere et sensibilisees par la benzophenone,sont catalysees par les thioalcools. La reaction en chaftie de transfert d'atomes d'hydrogene, R' + RCH = O -> RH + RC = O est acceleree par une suite analogue de transferts d'atomes d'hydrogene mettant en jeu le compose soufre: R' + C{sub 6}H{sub 5}CH{sub 2}SH -> RH + C{sub 6}H{sub 5}CH{sub 2}S'; C{sub 6}H{sub 5}CH{sub 2}S + RCH = 0 -> C{sub 6}H{sub 5}CH{sub 2}SH + RC = 0. La photoreduction de la benzophenone en propanol-2 aboutit a un benzopinacol par une reaction qui n'est pas en chaine et se fait par l'intermediaire des radicaux (C{sub 6}H{sub 5}){sub 2}C-OH and (CH{sub 3}){sub 2}COH. . La reaction est retardee et inhibee par les thioalcools et les disulfures qui retransforment les radicaux en produits de depart par reactions rapides de transfert d'atomes d'hydrogene et retrouvent eux-memes leurs etats de valence primitifs, chaque molecule du compose soufre annulant les effets chimiques de nombreux quanta: (C{sub 6}H{sub 5}){sub 2}C-OH + AS' -> (C{sub 6}H{sub 5}){sub 2}C = O + ASH; (CH{sub 3}){sub 2}C-OH + ASH -> (CH{sub 3}){sub 2}C = 0 + AS'. On trouve la preuve de ce mecanisme dans l'equilibrage du thioalcool ou disulfure initialement present, dans la racemisation de l