Total oxidation of naphthalene using palladium nanoparticles supported on BETA, ZSM-5, SAPO-5 and alumina powders

A range of catalysts based on Pd nanoparticles supported on inorganic supports such as BETA and ZSM-5 zeolites, a silicoaluminophosphate molecular sieve (SAPO-5) and γ-alumina as a standard support have been tested for the total oxidation of naphthalene (100 ppm, total flow 50 ml/min) showing a conversion to carbon dioxide of 100% between 165 and 180 °C for all the analysed catalysts. From the combined use of zeolites with PVP polymer protected Pd based nanoparticles, enhanced properties have been found for the total abatement of naphthalene in contrast with other kinds of catalysts. A Pd/BETA catalyst has been demonstrated to have excellent activity, with a high degree of stability, as shown by time on line experiments maintaining 100% conversion to CO2 during the 48 h tested.

Abatement of hydrocarbons by acid ZSM-5 and BETA zeolites under cold-start conditions

Simulated cold-start tests have been carried out to evaluate the performance of H-ZSM-5 and H-BETA zeolites as hydrocarbon traps under simulated gasoline car exhaust gases, paying special attention to the effect of water on their behaviour. It is concluded that the hydrothermal treatment of the zeolites in the acidic form contributes to the better performance of these materials as hydrocarbon traps since the stabilization of the zeolites takes place. Moreover, the decrease of the surface acidity of the zeolites results in an increase of the Si/Al ratio, which contributes to the decrease of the water affinity for adsorption sites. Thus, the competition with hydrocarbon molecules in the exhaust for the adsorption sites is reduced which increases their trap efficiency. The stabilized H-ZSM-5 is the zeolite that showed the best performance with a propene offset temperature of 240 °C, which should be high enough for the three-way catalyst to carry out its role as catalytic converter.

CuH-ZSM-5 as Hydrocarbon Trap under Cold Start Conditions

Cold start tests are carried out to evaluate the performance of copper-exchanged zeolites as hydrocarbon traps under simulated gasoline car exhaust gases, paying special attention to the role of copper in the performance of these zeolites. It is concluded that the partial substitution of the protons in the parent H-ZSM-5 zeolite is highly beneficial for hydrocarbon trapping due to the formation of selective adsorption sites with specific affinity for the different exhaust components. However, it is also observed that uncontrolled exchanging process conditions could lead to the presence of CuO nanoparticles in the zeolite surface, which seem to block the pore structure of the zeolite, decreasing the hydrocarbon trap efficiency. Among all the zeolites studied, the results point out that a CuH-ZSM-5 with a partial substitution of extra-framework protons by copper cations and without any detectable surface CuO nanoparticles is the zeolite that showed the best performance under simulated cold start conditions due to both the high stability and the hydrocarbon retaining capacity of this sample during the consecutive cycles.

The role of mesoporosity and Si/Al ratio in the catalytic etherification of glycerol with benzyl alcohol using ZSM-5 zeolites

A comparative study of the influence of three different acid solids as catalysts (conventional zeolites Z15c with Si/Al = 19.5 and Z40c with Si/Al = 48.2, and a hierarchical zeolite Z40c-H with Si/Al = 50.0) for the etherification of glycerol with benzyl alcohol was performed. The catalytic activity and selectivity of these zeolites was elucidated at different catalyst contents. Three different ethers (3-benzyloxy-1,2-propanediol, which is a mono-benzyl-glycerol ether (MBG) and 1,3-dibenzyloxy-2-propanol, which is a di-benzyl-glycerol ether (DBG) and dibenzyl ether (DBz) were identified as the main products. MBG was the major product of the reaction catalyzed by the microporous Z15c zeolite with low Si/Al molar ratio, whereas DBG was formed in higher yield with the use of microporous Z40c and hierarchical Z40c-H zeolites, both of them having a similar high Si/Al molar ratio (≈50). MBG is a value-added product and it is obtained with good yield and selectivity when using the conventional zeolite Z15c as a catalyst. Under the best conditions tested, i.e., 25 mg of catalyst for 8 h at 120 °C, a 62% of conversion was obtained without the need of solvent, with an excellent 84% selectivity toward the MBG and no formation of DBz.

X-Ray Imaging of SAPO-34 Molecular Sieves at the Nanoscale: Influence of Steaming on the Methanol-to-Hydrocarbons Reaction

The effect of a severe steaming treatment on the physicochemical properties and catalytic performance of H-SAPO-34 molecular sieves during the methanol-to-hydrocarbons (MTH) reaction has been investigated with a combination of scanning transmission X-ray microscopy (STXM), catalytic testing, and bulk characterization techniques, including ammonia temperature programmed desorption and 27Al and 29Si magic angle spinning nuclear magnetic resonance. For this purpose, two samples, namely a calcined and a steamed H-SAPO-34 catalyst powder, have been compared. It has been found that calcined H-SAPO-34 displays a high selectivity towards light olefins, yet shows a poor stability as compared to a zeolite H-ZSM-5 catalyst. Moreover, in situ STXM at the carbon K-edge during the MTH reaction allows construction of nanoscale chemical maps of the hydrocarbon species formed within the H-SAPO-34 aggregates as a function of reaction time and steam post-treatment. It was found that there is an initial preferential formation of coke precursor species within the core of the H-SAPO-34 aggregates. For longer times on stream the formation of the coke precursor species is extended to the outer regions, progressively filling the entire H-SAPO-34 catalyst particle. In contrast, the hydrothermally treated H-SAPO-34 showed similar reaction selectivity, but decreased activity and catalyst stability with respect to its calcined counterpart. These variations in MTH performance are related to a faster and more homogeneous formation of coke precursor species filling up the entire steamed H-SAPO-34 catalyst particle. Finally, the chemical imaging capabilities of the STXM method at the Al and Si K-edge are illustrated by visualizing the silicon islands at the nanoscale before and after steaming H-SAPO-34.

Total oxidation of naphthalene at low temperatures using palladium nanoparticles supported on inorganic oxide-coated cordierite honeycomb monoliths

A study on the preparation of thin films of ZSM-5 and BETA zeolites, and a SAPO-5 silicoaluminophosphate, supported on cordierite honeycomb monoliths by in situ synthesis was carried out for their use as catalyst supports. Furthermore γ-Al2O3 was also coated onto a cordierite honeycomb monolith by a dip-coating method for use as a standard support. Structured monolithic catalysts were prepared by impregnation of the aforementioned coated monoliths with polymer-protected Pd nanoparticles. The monolithic catalysts have been tested for the total oxidation of naphthalene (100 ppm, GHSV 1220 h−1). From the combined use of the zeolite with polymer-protected nanoparticles, enhanced catalytic properties have been found for the total abatement of naphthalene. The Pd/MBETA and Pd/MZSM-5 catalytic monoliths have shown excellent activity with a high degree of stability, even after undergoing accelerated ageing experiments.

Investigation of Pd nanoparticles supported on zeolites for hydrogen production from formic acid dehydrogenation

Catalysts based on palladium nanoparticles supported on different zeolites (BETA, ZSM-5 and Y) were prepared and their catalytic performance in formic acid dehydrogenation was studied. The effects of the zeolite structure and porous texture on the catalytic activity were investigated by comparing the behavior of these samples. The results revealed that the samples based on BETA zeolite are promising catalysts for this application.

Optimizing the performance of catalytic traps for hydrocarbon abatement during the cold-start of a gasoline engine

A key target to reduce current hydrocarbon emissions from vehicular exhaust is to improve their abatement under cold-start conditions. Herein, we demonstrate the potential of factorial analysis to design a highly efficient catalytic trap. The impact of the synthesis conditions on the preparation of copper-loaded ZSM-5 is clearly revealed by XRD, N2 sorption, FTIR, NH3-TPD, SEM and TEM. A high concentration of copper nitrate precursor in the synthesis improves the removal of hydrocarbons, providing both strong adsorption sites for hydrocarbon retention at low temperature and copper oxide nanoparticles for full hydrocarbon catalytic combustion at high temperature. The use of copper acetate precursor leads to a more homogeneous dispersion of copper oxide nanoparticles also providing enough catalytic sites for the total oxidation of hydrocarbons released from the adsorption sites, although lower copper loadings are achieved. Thus, synthesis conditions leading to high copper loadings jointly with highly dispersed copper oxide nanoparticles would result in an exceptional catalytic trap able to reach superior hydrocarbon abatement under highly demanding operational conditions.

Variables predictoras de las conductas de autocuidado en las personas con diabetes tipo 2

Objetivo general: - Conocer la prevalencia de déficit de conductas de autocuidado en la población adulta con diabetes tipo 2 (DMT2) del área de salud de Cáceres y determinar los factores o variables asociados a dicho déficit. Objetivos específicos: - Describir el nivel de autocuidado de las personas adultas con DMT2 en relación con la alimentación, ejercicio, cuidado de los pies, control de la glucemia, tratamiento farmacológico, y asistencia a las consultas para su control, a partir de las formas en que expresan el cuidado de su enfermedad. - Determinar si existe asociación entre el nivel de autocuidado y determinadas variables sociodemográficas, de comorbilidad, de información y de zona básica de salud. - Conocer de qué fuentes y de qué forma las personas con DMT2 obtienen la información sobre las conductas de autocuidado. Material y método: Estudio analítico observacional de corte transversal. La población de estudio fueron las personas mayores de 40 años con diagnóstico de DMT2 que acuden a las consultas de enfermería de atención primaria del área de salud de Cáceres para su atención. La muestra estuvo conformada por 260 personas. La obtención de los datos fue a través de la entrevista personal mediante un cuestionario estandarizado elaborado para esta investigación que mide las acciones de autocuidado en cuanto al régimen terapéutico que la enfermedad impone. Resultados: Las características de la muestra fueron similares a las de otros estudios en poblaciones con DMT2. La media de edad fue de 68 años, con predominio de mujeres. Sólo un 15,8% tenían normopeso, la mitad sin estudios, el 80% convive con algún miembro de su familia, más de un tercio son amas de casa y el 42% de los participantes fueron diagnosticados de diabetes hace más de 10 años. El déficit de autocuidado lo presentaron el 49,8% para el cuidado de los pies, el 26,6% para el ejercicio, el23,8% para el control de la glucemia, el 8,1% para la alimentación, el 6,2% para la asistencia a los controles y el 1,2% para el tratamiento farmacológico. El déficit de autocuidado se asoció en la alimentación con el sexo del paciente, el lugar de residencia y el sector profesional. En el ejercicio sólo con la edad, decreciendo el déficit a medida que aumenta la edad de las personas. En el autocuidado de los pies se relacionó con la situación laboral, los antecedentes familiares, haber tenido complicaciones por la diabetes, ser fumador y la edad, siendo los mayores de 70 años los que menos déficit presentaron. En el control de la glucemia el autocuidado se relacionó con la duración de la diabetes, el índice de masa corporal, la información dada por el médico y la información escrita. En la asistencia a las consultas de control se asoció con que el paciente hubiera tenido complicaciones derivadas de su enfermedad. No se observó asociación entre el déficit de autocuidado en el tratamiento farmacológico y ninguna de las variables estudiadas. Para el 98,5% de los participantes, la principal fuente de información sobre los autocuidados de la diabetes fueron los profesionales sanitarios, manifestando el 92,3% que la información sobre los autocuidados recibida de la enfermera es suficiente. Todos habían recibido información individual y ninguno manifestó haber recibido información en grupo. Más de un tercio consideró que la información escrita es insuficiente, así como la información recibida por los familiares. Conclusiones: Las personas con DMT2 presentan déficits de autocuidado, siendo especialmente relevantes en el tratamiento no farmacológico. La prevalencia de déficit de autocuidado se asoció a factores individuales: no modificables por el sistema sanitario como la edad, sexo y situación laboral; modificables como el tabaquismo y el índice de masa corporal. A factores derivados de la enfermedad como el tiempo de evolución de la diabetes y padecer complicaciones. Así mismo, la prevalencia de déficits de autocuidado se asoció a factores del entorno sanitario en cuanto a la información proporcionada por los profesionales, la información escrita recibida por los pacientes y la información facilitada a los familiares. La identificación y comprensión de estos factores facilita diseñar e implementar estrategias adecuando de forma más efectiva el proceso de intervención educativa.