“Síntesis de valiosas cetonas a,b-insaturadas sobre catalizadores basados en MgO promovido con Li”

VERÓNICA K. DÍEZ; ISAAC BARCAROLO; CARLOS R. APESTEGUÍA; JUANA I. DI COSIMO

Foz do Iguazú, Brasil

Congreso; 13° Congreso Brasilero de Catálisis y 3° Congreso de Catálisis del Mercosur; 2005

Se estudió a 353 K la condensación de citral con acetona en fase líquida para producir pseudoiononas (PS) sobre catalizadores de MgO promovido con Li+. Los catalizadores Li/MgO-x con diferentes contenidos de Li+ se prepararon por impregnación de MgO. Las propiedades texturales de los mismos se determinaron por fisisorción de N2 a 77 K. La densidad y naturaleza de los sitios básicos superficiales se investigaron por desorción a temperatura programada de CO2 preadsorbido y por espectroscopía infrarroja utilizando CO2 como molécula sonda. La caracterización estructural de los sólidos se realizó por difracción de rayos X. La adición de Li+ al MgO aumentó tanto la densidad superficial de los sitios básicos OH- y O2-, como la velocidad de formación de PS respecto del MgO puro. Relacionando los datos de actividad catalítica con la naturaleza, fuerza y densidad de los sitios activos básicos, se concluyó que la formación de PS se llevaría a cabo preferencialmente sobre grupos OH- superficiales formados durante la calcinación del catalizador o en el transcurso de la reacción a partir de aniones O2- superficiales. The liquid-phase aldol condensation of citral with acetone to produce pseudoionones (PS) was studied at 353 K on Lipromoted MgO. Li/MgO catalysts with different amounts of Li+ were prepared by impregnation of MgO. Catalyst textural properties were determined by N2 physisorption at 77 K. The density and nature of surface basic sites were investigated by temperature programmed desorption of preadsorbed CO2 and by infrared spectroscopy using CO2 as a probe molecule. The structural characterization of the solids was carried out by X-ray diffraction. The Li+ addition to MgO increased both the surface density of OH- and O2- basic sites and the PS formation rate as compared to pure MgO. By relating the activity for PS synthesis with the nature, strength and density of active basic sites, we concluded that the formation of PS would take place preferentially on surface OH- groups formed during catalyst calcination or in situ, during reaction from O2- anions. The liquid-phase aldol condensation of citral with acetone to produce pseudoionones (PS) was studied at 353 K on Lipromoted MgO. Li/MgO catalysts with different amounts of Li+ were prepared by impregnation of MgO. Catalyst textural properties were determined by N2 physisorption at 77 K. The density and nature of surface basic sites were investigated by temperature programmed desorption of preadsorbed CO2 and by infrared spectroscopy using CO2 as a probe molecule. The structural characterization of the solids was carried out by X-ray diffraction. The Li+ addition to MgO increased both the surface density of OH- and O2- basic sites and the PS formation rate as compared to pure MgO. By relating the activity for PS synthesis with the nature, strength and density of active basic sites, we concluded that the formation of PS would take place preferentially on surface OH- groups formed during catalyst calcination or in situ, during reaction from O2- anions. +. Los catalizadores Li/MgO-x con diferentes contenidos de Li+ se prepararon por impregnación de MgO. Las propiedades texturales de los mismos se determinaron por fisisorción de N2 a 77 K. La densidad y naturaleza de los sitios básicos superficiales se investigaron por desorción a temperatura programada de CO2 preadsorbido y por espectroscopía infrarroja utilizando CO2 como molécula sonda. La caracterización estructural de los sólidos se realizó por difracción de rayos X. La adición de Li+ al MgO aumentó tanto la densidad superficial de los sitios básicos OH- y O2-, como la velocidad de formación de PS respecto del MgO puro. Relacionando los datos de actividad catalítica con la naturaleza, fuerza y densidad de los sitios activos básicos, se concluyó que la formación de PS se llevaría a cabo preferencialmente sobre grupos OH- superficiales formados durante la calcinación del catalizador o en el transcurso de la reacción a partir de aniones O2- superficiales. The liquid-phase aldol condensation of citral with acetone to produce pseudoionones (PS) was studied at 353 K on Lipromoted MgO. Li/MgO catalysts with different amounts of Li+ were prepared by impregnation of MgO. Catalyst textural properties were determined by N2 physisorption at 77 K. The density and nature of surface basic sites were investigated by temperature programmed desorption of preadsorbed CO2 and by infrared spectroscopy using CO2 as a probe molecule. The structural characterization of the solids was carried out by X-ray diffraction. The Li+ addition to MgO increased both the surface density of OH- and O2- basic sites and the PS formation rate as compared to pure MgO. By relating the activity for PS synthesis with the nature, strength and density of active basic sites, we concluded that the formation of PS would take place preferentially on surface OH- groups formed during catalyst calcination or in situ, during reaction from O2- anions.+ were prepared by impregnation of MgO. Catalyst textural properties were determined by N2 physisorption at 77 K. The density and nature of surface basic sites were investigated by temperature programmed desorption of preadsorbed CO2 and by infrared spectroscopy using CO2 as a probe molecule. The structural characterization of the solids was carried out by X-ray diffraction. The Li+ addition to MgO increased both the surface density of OH- and O2- basic sites and the PS formation rate as compared to pure MgO. By relating the activity for PS synthesis with the nature, strength and density of active basic sites, we concluded that the formation of PS would take place preferentially on surface OH- groups formed during catalyst calcination or in situ, during reaction from O2- anions.