Luis García

Phenol alkylation with methanol: effect of sodium content and ammonia selective poisoning of an HY zeolite

Sodium exchange and ammonia selective poisoning of the acid sites of an HY zeolite (Si/Al=20) were carried out and their effects on the catalytic properties for the alkylation of phenol with methanol (200‡C, 1 atm and N2/reactants molar ratio of 4) were evaluated. Results show that the reaction is highly sensitive to the number and strength of the acid sites of the catalyst. A decrease in the number of acid sites by sodium exchange of the protons or by ammonia selective poisoning produces important changes in the selectivity of the reaction. In fact, a high increase in the anisole/cresol ratio is observed as the percentage of exchanged sodium in the zeolite increases, while the ammonia selective poisoning shows that at low desorption temperatures (⩽250‡C) only anisole is formed while at higher desorption temperatures both anisole and cresols were observed. These results show that anisole formation requires sites with lower acid strength compared to those necessary for cresol formation.

Acetone transformation into methyl isobutyl ketone over Pt/HMFI catalysts. IV. Effect of density and strength of the acidic sites

Acetone transformation into methyl isobutyl ketone (MIBK) was studied using a fixed-bed dynamic reactor at 160°C, 1 atm pressure and acetone/H2 molar ratio=3. The reaction was carried out over Pt/HMFI bifunctional catalysts, with 0.30 wt% of platinum which was supported over three aluminosilicates (Si/Al ratio=40, 95 and 160) and a borosilicate (Si/B ratio=44) with similar dispersion. The results show that catalytic properties depend greatly on density and strength of the acidic sites of the catalysts. Moreover, the limiting step of the MIBK synthesis reaction (aldolization of two acetone molecules) is carried out over the acidic sites of the aluminosilicates, but not over those of the borosilicate, which considerably affects reaction selectivity.

Synthesis of methyl isobutyl ketone using Pt–H[Al]ZSM5 bifunctional catalysts. III. Effect of the nPt/nA parameter on the xPt–H[Al]ZSM5(y) catalysts

Synthesis of 4-methyl-2-pentanone, better known as methyl isobutyl ketone (MIBK), from propanone (Ac) was studied in a fixed-bed and a flow reactor at 160 °C, 1 atm and an H2/Ac molar ratio equal to 0.33, using Pt-H[Al]ZSM5 bifunctional catalysts with variable platinum percentage and Si/Al ratio. The results show that initial total activity to all measured products at t = 0, per acidic site (Ao/nA), residual activity (Ar = A265/A0, ratio of activity after 265 min of stream and the initial total activity to all measured products at t = 0) and initial formation rate of each product per acidic site (Ro/nA) largely depend on the relationship between the number of hydro-dehydrogenating metallic sites and the number of theoretical acidic sites (nPt/nA) present in the catalysts used.

Palladium-based catalysts for the synthesis of alcohols

Abstract The present work intends to illustrate the effects of precursor and support composition on the structure and performance of Pd-based catalysts for the synthesis of methanol and higher oxygenated compounds. The power of the XRD technique and the reaction itself, as characterisation tools, was evidenced. The hydrogenation of carbon monoxide has been studied over palladium supported on ZnO, Zr(OH) 4 and ZrO 2 using PdCl 2 and Pd(NO 3 ) 2 as salt precursors. Catalysts were characterised by XRD and Raman spectroscopy. The results show that activity and selectivity are strongly dependent on the salt precursor and on the acid–basic properties of the support. As seen from the CH 3 OH/DME ratio, the order of acidity of the supports is: Zr(OH) 4 >ZrO 2 >ZnO independently of the salt precursor used. The Pd(NO 3 ) 2 /ZnO catalyst shown the highest methanol selectivity which was related to the presence of large particles of a PdZn alloy. A double bifunctionality on the catalysts for the production of higher oxygenated seems evident. On the one hand, an acid–base bifunctionality of the support seems to be needed for the formation, stabilisation, chain growth and further reactivity of intermediates such as formate, as well as for the dissociative adsorption of CO, and on the other hand, a metal-support bifunctionality, where the palladium metal particles would play the role of hydrogenating the intermediates and possibly adsorb non-dissociatively the CO.

Acetone Transformation over PtCu/H[Al]ZSM5 Catalysts. Effect of Copper Content

A series of bifunctional bimetallic PtCu/H[Al]ZSM5-type catalysts was prepared and acetone transformation was carried out over them at 160 °C, 1 atm, acetone/hydrogen molar ratio=3, and WHSV (weight of reactant injected per weight of catalyst per hour) ranging between 9.4 and 38 h−1. According to the results, as copper atomic fraction (X(Cu)) increases in the bimetallic catalyst, propane formation rate decreases and methyl isobutyl ketone (MIBK) formation rate increases until X(Cu) equals 0.40. These results suggest that active metallic centers for the olefin double bond hydrogenation in the α-β unsaturated ketone, which leads to the MIBK formation, do not appear to be those hydrogenating the acetone carbonyl double bond to form propane. When X(Cu)>0.40, MIBK formation rate considerably decreases, meaning that practically all platinum metallic centers have been passivated for those copper atomic fractions over the PtCu/H[Al]ZSM5-type catalyst. Therefore, catalysts begin to act only by means of the acid function, and as a result a logical increase in the mesityl oxide (MO) concentration occurs, a substance that is formed by means of an acid catalysis.

Determinación de parámetros físicos aplicables en el escalamiento de la síntesis de zeolita NaA, a partir de geles aluminosilicatos

Among the different technologies with important implications today in such areas as education, health and business, videostreaming is highlighted. This considering how this technology facilitates the access to multimedia content remotely, live or offline. The goal of this paper is to propose a test environment for the support of the video streaming service, using open source tools. Moreover, this work proposes, as part of the environment, a stress measurement tool (Hermes), which allows obtaining the response times to establish multiple RTSP connections to streaming servers. The methodology used in this work is divided into four phases: analysis of technologies and tools, configuration of the video streaming environment, design and implementation of Hermes, and finally tests. This methodology allowed the construction of the test environment and its evaluation, through the stress measurement tool Hermes. Finally, in this work we demonstrate how the proposed environment becomes a reference point for different application environments that require the implementation of a video streaming service.Se aplico la mecanica de solidos hiperelasticos al estudio del comportamiento del tubo arterial, ya que es un medio consolidado en la comprension de fenomenos de interes para los profesionales de la medicina y de la ingenieria biomedica. En el caso del organo en cuestion, su estudio se realizo mediante el modelado como un recipiente cilindrico de pared gruesa, donde la funcion de energia empleada permitio considerar aspectos microestructurales como la anisotropia y la dispersion de fibras de colageno. En el problema de equilibrio estatico en el que se implementa esta caracterizacion se representaron las capas media y adventicia de la pared arterial. La solucion expedita del problema de valores en la frontera resultante es posible gracias a la asuncion de un patron de deformacion de simetria axial. Se encontro que el factor de dispersion de fibras y los demas parametros adimensionales del mismo orden de magnitud tienen el rol dominante en la rigidez radial del tubo arterial. Los resultados se presentan utilizando grupos adimensionales, lo cual facilita la interpretacion rapida del efecto de los numerosos parametros que emergen

Determination of physical parameters applicable for scale-up of NaA zeolite synthesis from aluminosilicate gels

Among the different technologies with important implications today in such areas as education, health and business, videostreaming is highlighted. This considering how this technology facilitates the access to multimedia content remotely, live or offline. The goal of this paper is to propose a test environment for the support of the video streaming service, using open source tools. Moreover, this work proposes, as part of the environment, a stress measurement tool (Hermes), which allows obtaining the response times to establish multiple RTSP connections to streaming servers. The methodology used in this work is divided into four phases: analysis of technologies and tools, configuration of the video streaming environment, design and implementation of Hermes, and finally tests. This methodology allowed the construction of the test environment and its evaluation, through the stress measurement tool Hermes. Finally, in this work we demonstrate how the proposed environment becomes a reference point for different application environments that require the implementation of a video streaming service.Se aplico la mecanica de solidos hiperelasticos al estudio del comportamiento del tubo arterial, ya que es un medio consolidado en la comprension de fenomenos de interes para los profesionales de la medicina y de la ingenieria biomedica. En el caso del organo en cuestion, su estudio se realizo mediante el modelado como un recipiente cilindrico de pared gruesa, donde la funcion de energia empleada permitio considerar aspectos microestructurales como la anisotropia y la dispersion de fibras de colageno. En el problema de equilibrio estatico en el que se implementa esta caracterizacion se representaron las capas media y adventicia de la pared arterial. La solucion expedita del problema de valores en la frontera resultante es posible gracias a la asuncion de un patron de deformacion de simetria axial. Se encontro que el factor de dispersion de fibras y los demas parametros adimensionales del mismo orden de magnitud tienen el rol dominante en la rigidez radial del tubo arterial. Los resultados se presentan utilizando grupos adimensionales, lo cual facilita la interpretacion rapida del efecto de los numerosos parametros que emergen