Evaluación de los métodos convencionales de quimisorción para la determinación de superficie de metales soportados altamente dispersos

El objetivo de esta memoria de investigación ha sido tratar de evaluar las técnicas convencionales de quimisorción cuando se aplican a catalizadores metálicos soportados altamente dispersos. Selecciono un método adecuado de preparación de precursores, seguido de una cuidadosa elección de la temperatura de reducción, a fin de preservar la alta dispersión de fase activa. El paso siguiente fue hacer un estudio para comprobar si las técnicas físico-químicas de caracterización habituales eran aplicables, o si los diferentes parámetros que pueden influir en este tipo de sistemas falsearía los datos finales, tratando de esclarecer las discrepancias encontradas en bibliografía. Por ultimo, y como prueba adicional para verificar la bondad o falsedad de los resultados de quimisorción, se utilizaron dos reacciones test cuyos mecanismos estaban afectados por los mismos parámetros que influyen en la quimisorción

Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

Hydrotalcite-like precursors have been synthesized in order to study the influence of lanthanum on the structure and the properties of the precursors, as well as on the catalytic activity and stability of their derived catalyst on biogas reforming. From XRD, and TPO characterization, we confirmed that hydrotalcite-like precursors where obtained. After calcination at 750 ºC, Mg (Ni,Al)O solid solution was detected. High surface areas have been obtained finding the highest surface area on the catalyst without lanthanum. TPR experiments were performed in order to study the reducibility of the catalysts. One reduction peak was found in the catalyst without lanthanum while two peaks were observed in the catalysts with lanthanum. A reduction peak at 900 ºC was observed over the sample without Ni and La. Catalytic tests, at 700 ºC with a feed of CH4:CO2 1:1, were performed after appropriate reduction during 50h. While a decrease on catalytic activity was observed with the addition and the increase of La content, an enhancement in the stability was observed. No sign of deactivation of the catalyst and no carbon deposition were found on the catalysts doped with lanthanum.Financial support from Comunidad de Madrid (DIVERCEL-CM, S2009/ENE-1475) and CDTI (CENIT 2007-1039) is gratefully acknowledged.Peer Reviewe

Biogas reforming on La-promoted NiMgAl catalysts derived from hydrotalcite-like precursors

Hydrotalcite-like precursors have been synthesized in order to study the influence of lanthanum on the structure and the properties of the precursors, as well as on the catalytic activity and stability of their derived catalyst on biogas reforming. From XRD, and TPO characterization, we confirmed that hydrotalcite-like precursors where obtained. After calcination at 750 ºC, Mg (Ni,Al)O solid solution was detected. High surface areas have been obtained finding the highest surface area on the catalyst without lanthanum. TPR experiments were performed in order to study the reducibility of the catalysts. One reduction peak was found in the catalyst without lanthanum while two peaks were observed in the catalysts with lanthanum. A reduction peak at 900 ºC was observed over the sample without Ni and La. Catalytic tests, at 700 ºC with a feed of CH4:CO2 1:1, were performed after appropriate reduction during 50h. While a decrease on catalytic activity was observed with the addition and the increase of La content, an enhancement in the stability was observed. No sign of deactivation of the catalyst and no carbon deposition were found on the catalysts doped with lanthanum.Financial support from Comunidad de Madrid (DIVERCEL-CM, S2009/ENE-1475) and CDTI (CENIT 2007-1039) is gratefully acknowledged.Peer Reviewe

Biogas reforming on La-promoted La-NiMgAl catalysts derived from hydrotalcite-like structure: Influence of calcinations temperature

Hydrotalcite-like compound with general formula [M(II)1-xM(III)x(OH)2]x+(An-x/n) . mH2O, where An- is the compensation anion, has been used as precursor of active catalysts for biogas reforming. This precursor was calcined at six different temperatures between 250 and 750 ºC and the resulting catalysts were tested in order to evaluate the influence of the calcination temperature on the catalytic activity and stability. XRD characterization showed that from 250 ºC the hydrotalcite structure is no longer detected, leading to Mg(Ni,Al)O solid solutions, where no peaks related to lanthanum appear. An increase on the calcination temperature increased the grain size and cell parameter value. 50h-catalytic tests were carried out at 700 ºC, CH4:CO2 molar ratio of 1:1 and a mass/feed alimentation ratio (W/F) of 0.4 mg·min·cm-3. Used catalysts were characterized by temperature programmed oxidation (TPO), scanning electron microscopy (SEM) and Raman spectroscopy in order to obtain information about coke deposition. Catalytic tests highlighted the great influence of calcination temperature over catalytic activity and stability, having found that, as a general trend, calcination temperatures below 750 ºC decrease both the stability and catalytic activity, with the exception of the catalyst calcined at 550 ºC, where a higher activity was achieved but with a comparatively low stability.Financial support from Comunidad de Madrid (DIVERCEL-CM, S2009/ENE-1475) and CDTI (CENIT 2007-1039) is gratefully acknowledged. The authors thank Dr. M.A. Bañares, R. López-Medina and E. M. Mikolajska from Instituto de Catálisis (CSIC) for his help with Raman analysis and their helpful discussions.Peer Reviewe

Discovery of 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-3-hexyl-1H-1,2,4-triazole, a novel in vivo cannabinoid antagonist containing a 1,2,4-triazole motif

A new series of 1,2,4-triazoles have been prepared and the evaluation of their cannabinoid properties have been carried out. Compound 8 showed cannabinoid silent antagonist activity in mouse vas deferens and guinea pig ileum preparations and in vivo assays (cannabinoid tetrad) in mouse. It did not have intrinsic activity in these bioassays, and therefore, it did not behave as a partial agonist or an inverse agonistThis work was supported by Spanish Grant SAF 00-0114-C02. L.H.-F. is recipient of the I3P Fellowship from the C.S.I.C. Laboratorios Dr. Esteve, S.A. is gratefully acknowledged. L.H.-F. thanks the Spanish Society of Therapeutic Chemistry (SEQT) for the Ramon Madroñero Young Researcher Award.Peer reviewe