Gold catalysts supported on ZrO2 and ZrO2-SiO2 were prepared by incipient impregnation and depositionprecipitation with urea (DPU) with 1 % of nominal gold loading. The solids were characterized by X-ray diffraction analysis (XRD), N2-physisorption and temperature programmed reduction (TPR). Catalytic activities were investigated in cinnamaldehyde hydrogenation. The selectivity towards the desired product was influenced by the crystalline or amorphous phase support and method of gold deposition

Se prepararon catalizadores de oro soportados en ZrO2 and ZrO2-SiO2 por impregnación incipiente (Imp.I.) y depositación-precipitación con urea (DPU) con una carga nominal del metal del 1 %. Los sólidos fueron caracterizados por difracción de rayos X (DRX), fisisorción de nitrógeno y reducción a temperatura programada (TPR). La actividad catalítica fue evaluada en la hidrogenación de cinamaldehído. La selectividad hacia el producto deseado es influenciada por la fase cristalina o amorfa del soporte y el método de deposición del oro

The m-dinitrobenzene hydrogenation to m-phenylenediamine in liquid phase was studied with platinum supported on SiO2, TiO2, Al2O3 and Nb2O5 catalysts. Incipient impregnation method was used to prepare the catalysts with 1wt% of Pt. The effect of the support and the reduction temperature (473 K or 773 K) were analyzed. The materials were characterized by X-ray diffraction (XRD), nitrogen physisorption (77 K), hydrogen chemisorption (298 K), transmission electron microscopy (TEM), temperature programmed reduction (H2-TPR) and temperature programmed desorption of ammonia (NH3-TPD). The results showed that Pt/ TiO2 (HT) catalyst had a higher yield (60%) toward m- phenylenediamine and conversion level (98.2%) of m-dinitrobenzene. This behavior can be attributed to the reduction of PtO crystallites to metallic Pt, small particle size and the strong metal-support interaction due to the migration of TiO species on the Pt crystallites.

Titania-supported Ir catalysts were used in the hydrogenation of furfural. Reactions were carried out in a stirred batch type reactor at 0.62MPa and 363K using a 0.10M solution of furfural in a 1:1 mixture n-heptane -ethanol as solvent. Catalysts containing 2 wt% of Ir were reduced in H2 flow at different temperatures in the range 473-773K. The catalysts were characterized by H2 chemisorption, TEM, TPR, TPD of NH3 and XPS. Conversion of furfural is higher at lower reduction temperatures, but leads to byproducts whereas reduction at higher temperatures shows selectivity to furfuryl alcohol close to 100%.

Se evaluó el comportamiento de diferentes catalizadores de Ir, en la hidrogenación de aldehídos a,b-insaturados, acroleína y crotonaldehído, para la obtención de sus alcoholes insaturados alcohol alílico y crotílico respectivamente, cuya utilidad en la industria de la química fina es de amplio reconocimiento. Los aldehídos objeto de esta investigación representan un alto riesgo ambiental, por lo que la investigación presentada en este trabajo resulta de gran importancia en ese campo. En general los resultados obtenidos muestran que factores como temperatura de reducción y contenido de TiO2 en los catalizadores son determinantes en el comportamiento catalítico; análisis de caracterización permitieron establecer que en los catalizadores reducidos a alta temperatura se presenta el efecto de interacción fuerte metal soporte, conocido por su símbolo SMSI, lo que favorece la conversión, actividad inicial y TOF. De igual manera los catalizadores evaluados son altamente selectivos hacia los alcoholes insaturados que representan los productos de interés en este estudio.

The behavior of different Ir catalysts in the hydrogenation of a,b-unsaturated acrolein and crotonaldehyde aldehydes has been evaluated to obtain their allyl and crotyl unsaturated alcohols respectively; their products are used in fine chemicals industry. The present work is of great importance in this field because of the unsaturated aldehydes studied having high environmental risk besides the great academic contribution. The results show that factors such as reduction temperature and TiO2 content are critical in the catalytic behavior, through the analysis of characterization was established that the catalysts reduced at high temperature shows the Strong Metal Support Interaction effect (SMSI), which favors conversion percentage, initial activity and TOF. The analyzed catalysts were highly selective towards the unsaturated alcohols.

Se estudió la hidrogenación de crotonaldehído en fase líquida, sobre catalizadores Ir/TiO2-SiO2; este aldehído es altamente contaminante y proviene de fuentes tan diversas como humo de tabaco, gases de escape de motores de gasolina o diesel y humo de combustión de madera [1]. El objetivo principal de esta investigación fue la obtención del alcohol insaturado (crotil alcohol). A partir de los estudios realizados logró demostrarse que un aumento en el contenido de TiO2, lo mismo que la reducción de los catalizadores a altas temperaturas favorece parámetros como selectividad hacia el producto de interés, actividad catalítica y en general se logró mejorar de manera notable los niveles de conversión. El comportamiento observado se atribuyó principalmente a la fuerte influencia del efecto SMSI (Strong Metal Support Interaction), presente a altas temperaturas en óxidos parcialmente reducibles.

Liquid phase crotonaldehyde hydrogenation over Ir/TiO2-SiO2 catalysts was studied; this aldehyde is highly pollutant comes from cigarette smoke, exhaust from gasoline and diesel engines and the burning of wood [1]. The main objective of this research was unsaturated alcohol (crotyl alcohol) obtention. This study showed that an increase in TiO2 content and high temperature reduction in catalysts produce high selectivity to crotyl alcohol, high activity, and an increase in conversion levels. This behavior is due to SMSI (Strong Metal Support Interaction) effect, at high temperatures in partially reducible oxides.

Se estudió la hidrogenación enantio selectiva de 4-metoxiacetofenona sobre catalizadores de Pt/TiO2 reducidos a 773K y modificados con cinconidina (CD). Los catalizadores se caracterizaron por fisiadsorción de N2, quimiadsorción de H2, DRX y XPS. Las transformaciones se llevaron a cabo en un reactor tipo STR a distintas concentraciones de cinconidina (CD) con el propósito de evaluar la incidencia de algunos parámetros de reacción como el orden de adición del modificador y la presión de hidrógeno. Se demostró que a bajas concentraciones de CD es posible obtener excesos enantioméricos cercanos al 30%. Se encontró que la estructura de la molécula puede afectar el comportamiento observado.

The enantioselective hydrogenation of 4-methoxyacetophenone over Pt/TiO2 catalyst reduced to 773 K in the presence of cinchonidine (CD) was studied. The catalysts were characterized by N2 physisorption, H2 chemisorption, XRD and XPS. The reactions were carried out in a STR reactor at various concentrations of CD. The effect of several reaction parameters was investigated, such as the addition order of the modifier and hydrogen pressure. Lower concentrations of CD can produce an enantiomeric excess near to 30%. The structure of the molecule can influence the behavior observed.

Neste trabalho, foi estudada a hidrogenação enantioselective do 4-metoxiaceto-fenona em catalisadores Pt/TiO2 reduzidos a 773 K e modificados com cinconidina (CD). Os sólidos foram caracterizados por adsorção de nitrogênio a 77K, quimisorção de hidrogênio a temperatura ambiente, DRX, TEM e XPS. As reações foram realizadas em um reator STR a diferentes concentrações de CD. Alem de isso o efeito de vários parâmetros de reação foi estudado, como ordem de adição do modificador e pressão do hidrogênio. Baixas concentrações do CD podem produzir excesso enantiomêricos próximos aos 30%. A estrutura da molécula pode influenciar o comportamento obtido.

Se estudió la cinética de hidrogenación de furfural sobre el catalizador Ir/Nb2O5 que presenta el efecto SMSI (Fuerte interacción metal soporte). Se examinaron el efecto de diferentes parámetros de reacción como concentración inicial en el rango de 0,025 a 0,1 M, presión parcial en el rango de 0,48 MPa a 0,98 Mpa, temperatura de 353 a 393 K y peso del catalizador de 0,1 a 0,4 g. Se encontró una alta selectividad hacía el alcohol insaturado, (alcohol furfurílico), que es el producto más importante de esta reacción. Solventes alcohólicos producen trazas de acetales, especialmente de 2,6 dietil-acetal. Las velocidades iniciales de la hidrogenación de furfural con respecto al estudio de la presión y concentración se incrementaron linealmente con la masa del catalizador, lo que demuestra la ausencia de fenómenos de transporte. La cinética de la reacción se representó con un modelo Langmuir-Hinshelwood (LH) con un solo tipo de sitio activo. La adición de un átomo de hidrógeno sobre la molécula orgánica demostró ser la etapa determinante de la reacción, ajustándose a los datos experimentales.

Kinetics of furfural hydrogenation over Ir/Nb2O5 catalyst with SMSI effect (Strong Metal Support Interaction) was studied. The effect of different parameters such as initial concentration (0,025 to 0,1 M), H2 pressure partial (0,48 to 0,98 MPa), temperature (353 to 393 K) and catalyst loading (0,1 to 0,4 g) were examined. A high selectivity towards unsaturated alcohol (furfuryl alcohol) using this catalyst was demonstrated. The effect of solvent also was studied. The alcoholic solvents produces acetals traces, especially 2,6-diethyl-acetal. The initial rates of furfural hydrogenation increased linearly with the catalyst loading, indicating absence of mass transfer effects. The reaction kinetics was represented by a Langmuir-Hinshelwood model (LH). A single site Langmuir-Hinshelwood type model suggesting the addition of a hydrogen atom on the organic molecules as the rate determining step provided the best fit of the experimental data.

The citronellal hydrogenation was studied on Ir/Nb(2)0(5)-Si0(2) catalysts. Aseries of catalysts was synthesized with different niobia contents (Ir/Nl 1.10%; Ir/N2 2.54%; Ir/N3 3.25%; Ir/N4 5.30%wt%) using the wet impregnation method. These catalysts were reduced in hydrogen atmosphere at low or high temperatures. 473K (LTR) or 773K respectively. Their structural and surface properties were investigated by XRD, TEM, XPS, DTP, FTIR, H2 chemisorption at 298 K and surface specific area by using the BET method. The X ray diffraction studies revealed only the peaks due to niobia, mainly in those with higher niobia loading. No diffraction lines due to Ir were observed due to its lower content and/or to its high dispersion. The catalytic tests in the hydrogenation of citronellal were carried out in a batch reactor operated at 6.2 bar of H2 and 343 K. All catalysts showed higher selectivity to isopulegol and to their products due to the cyclization of the citronellal molecule.

En este trabajo se estudió la hidrogenación selectiva de citronelal sobre sistemas de Ir/TiO2, Ir/SiO2, e Ir soportado en óxidos mixtos (Ir/TiO2-SiO2) reducidos a 473 y 773 K. Se analizó el efecto de la adición de TiO2 al soporte y de las temperaturas de reducción de los catalizadores para evaluar el posible efecto de especies TiOx parcialmente reducidas, sobre la actividad y selectividad de la reacción. Los sólidos resultantes se caracterizaron por quimisorción de hidrógeno a temperatura ambiente, adsorción de nitrógeno a 77 K, DRX, TEM y XPS. Los resultados indican que los catalizadores reducidos a alta temperatura (HT: 773 K) favorecen la producción del alcohol insaturado debido al efecto de interacción fuerte metal-soporte conocido como SMSI. Los catalizadores reducidos a baja temperatura (LT: 473 K) llevan a la ciclización del anillo produciendo isopulegol. Estos catalizadores mostraron una alta actividad y una menor selectividad hacia el alcohol insaturado.

Catalytic hydrogenation of citronellal over Ir/TiO2, Ir/SiO2, and Ir supported on mixed oxides (Ir/TiO2/SiO2) reduced at 473 y 773 K was studied. The effects of the partially reducible support species, the reduction temperatures (473 K or 773 K) and the successive TiO2 addition were analyzed. The catalysts were characterized by H2 chemisorption at room temperature, N2 adsorption at 77 K, XRD, TEM and XPS. The results showed that the high temperature reduction treatment (HT: 773 K) favored the production of the unsaturated alcohol, which can be explained in terms of the so-called strong metalsupport interaction (SMSI) effect. Catalysts reduced at low temperature (LT: 473 K) mainly led to a cyclization reaction producing isopulegol. These catalysts showed high activity but low selectivity to the unsaturated alcohol.

Nesse trabalho, foi estudada a hidrogenação seletiva do citronelal em catalisadores Ir/TiO2, Ir/SiO2 e Ir suportado em óxidos mistos (Ir/TiO2-SiO2) reduzidos a 473 e 773 K. Foi analisado o efeito da adição da TiO2 no suporte e das temperaturas de redução dos catalisadores para evaliar o possível efeito das espécies TiOx parcialmente reduzidas, sobre a atividade e seletividade da reação. Os sólidos resultantes foram caracterizados por quimisorção de hidrogênio a temperatura ambiente, adsorção de nitrogênio a 77 K, DRX, TEM e XPS. Os resultados indican que os catalisadores reduzidos a alta temperatura (HT: 773 K) favorecem a produção do álcool insaturado pelo efeito da interação forte metal-suporte conhecido como SMSI. Os catalisadores reduzidos a baixa temperatura (LT: 473 K) conduzen para a ciclização do anel produzindo isopulegol. Esses catalisadores mostraram uma alta atividade e uma baixa seletividade para álcool insaturado.