Desarrollo de catalizadores híbridos CuZnOAl2O3/zeolita para el proceso de síntesis directa de DME

El plan de investigación se centra en el estudio y diseño de catalizadores híbridos para el proceso de síntesis directa de dimetil éter (DME) a partir de gas de síntesis, también conocido en la literatura como "Syngas-To-DME o STD process" [1]. Para llevar a cabo el proceso de síntesis directa de DME se emplean catalizadores híbridos constituidos por mezclas físicas del componente de síntesis de metanol (catalizador basado en Cu) y el componente ácido que lleva a cabo la deshidratación de metanol para dar lugar al DME (zeolita) [1]. De manera general, las labores en las que se centra el plan de investigación persiguen lograr un mayor entendimiento de las propiedades del catalizador híbrido que determinan su comportamiento en el proceso de síntesis directa de DME (STD), prestando especial atención al componente zeolítico con el cual están asociadas la mayoría de controversias en la literatura científica.García Trenco, A. (2013). Desarrollo de catalizadores híbridos CuZnOAl2O3/zeolita para el proceso de síntesis directa de DME [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34781TESI

Direct synthesis of DME from syngas on hybrid CuZnAl/ZSM-5 catalysts: New insights into the role of zeolite acidity

[EN] A commercial HZSM-5 zeolite (Si/Al = 16) was submitted to mild acid treatment and partial exchange of H+ by Na+ and Co2+ cations in order to produce samples with different amounts and strengths of Brensted and Lewis acid sites. The acid properties of the zeolites were determined by both FTIR of adsorbed pyridine and NH3-TPD. Then, hybrid catalysts comprising a CuO/ZnO/Al2O3 (CZA) methanol synthesis catalyst and the original and treated zeolites were prepared in order to analyze the impact of the zeolite acidity in the efficiency of the hybrids for the direct syngas-to-DME process. Independent methanol dehydration experiments on the bare zeolites and syngas-to-DME runs under methanol dehydration-controlled conditions were performed using hybrids with low zeolite concentration (CZA:zeolite mass ratio of 10:1) prepared by mixing the pre-pelletized CZA and zeolite components. The results revealed that both strong Bronsted and EFAL-related strong Lewis acid sites are the likely zeolite active sites for methanol dehydration at the typical syngas-to-DME temperature of 260 degrees C. Interestingly, we have found that different conclusions regarding the effect of zeolite acidity may be reached depending on the specific method used for preparing the hybrid catalysts when the overall syngas-to-DME process becomes controlled by the methanol synthesis rate on the Cu-based catalyst (i.e. using hybrids with a CZA:zeolite mass ratio of 2:1, that is, with an "excess" of acid sites). Thus, for hybrids prepared by mixing the pre-pelletized components, the same CO conversion and product selectivity (with values approaching those predicted by the thermodynamic equilibrium at the studied conditions) with no signs of deactivation during at least 50h on stream was attained irrespective of the zeolite acidity. By contrast, significant differences in catalyst stability were found for hybrids prepared by grinding the component powders prior to pelletizing. This fact points towards the occurrence of detrimental interactions between the CZA and zeolite components during the grinding preparation stage. The kind and extent of such detrimental interactions are tightly related to the properties (i.e. acidity, chemical composition) of the ZSM-5 zeolite. (C) 2011 Elsevier B.V. All rights reserved.Financial support by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of Spain through the Project CTQ2010- 17988/PPQ is gratefully acknowledged. A. García-Trenco thanks the Ministerio de Ciencia e Innovación (MICINN) of Spain for a predoctoral (FPI) scholarship.García Trenco, A.; Martinez Feliu, A. (2012). Direct synthesis of DME from syngas on hybrid CuZnAl/ZSM-5 catalysts: New insights into the role of zeolite acidity. Applied Catalysis A General. 411:170-179. https://doi.org/10.1016/j.apcata.2011.10.036S17017941

The impact of zeolite pore structure on the catalytic behavior of CuZnAl/zeolite hybrid catalysts for the direct DME synthesis

[EN] In this work, the influence of the pore structure of 10-ring zeolites used as the methanol dehydration func-tion in CuZnAl(CZA)/zeolite hybrid catalysts was studied for the direct dimethyl ether (DME) synthesis. Tothis purpose, six different 10-ring H-zeolites (ZSM-5, FER, IM-5, TNU-9, MCM-22, ITQ-2) with alike bulkSi/Al ratios (in the 9 14 range) were employed. Additionally, the effect of crystallite size (for ZSM-5) andselective surface dealumination by treatment with oxalic acid (for MCM-22) was also investigated. Whilethe initial activity of the zeolites for methanol dehydration was driven by the concentration of strongBrønsted acid sites, the extent of decay was dictated by the pore structure, which determined the amountand nature of the formed carbon species. When evaluated for direct DME synthesis under methanolsynthesis-controlled conditions, all CZA/zeolite hybrid catalysts (prepared by grinding, CZA:zeolite massratio of 2:1) experienced a decline of CO conversion (and DME yield) with time-on-stream (TOS) due toa gradual loss of the methanol synthesis activity of the Cu-based component. Interestingly, the stabilitywith TOS was the lowest for the hybrid catalysts comprising zeolites with large external surface areas(Sext) such as ITQ-2 and MCM-22. Moreover, for zeolites with similar Sext, the deactivation extent of thehybrid catalysts increased with the concentration of surface Al species (from XPS) in the zeolite. Thus,the delaminated ITQ-2 zeolite (Si/Alsurf= 10.6, Sext= 324 m2/g) produced the less stable hybrid while thatcomprising zeolite TNU-9 (Si/Alsurf= 17.9, Sext= 12 m2/g) displayed the highest stability during the syngas-to-DME experiments. These results suggest that the deterioration of the methanol synthesis activity ofthe CZA catalyst in the hybrid catalysts prepared by grinding is produced by detrimental interactionsbetween zeolitic Al species and Cu sites at the surface-contact between zeolite and CZA particleFinancial support by the Comision Interministerial de Ciencia y Tecnologia (CICYT) of Spain through the Project CTQ2010-17988/PPQ is gratefully acknowledged. A. Garcia-Trenco thanks the Ministerio de Economia y Competitividad (former Ministerio de Ciencia e Innovacion) of Spain for a predoctoral (FPI) scholarship.García Trenco, A.; Valencia Valencia, S.; Martinez Feliu, A. (2013). The impact of zeolite pore structure on the catalytic behavior of CuZnAl/zeolite hybrid catalysts for the direct DME synthesis. Applied Catalysis A General. 468:102-111. doi:10.1016/j.apcata.2013.08.038S10211146

Situación del Dietista-Nutricionista en el Sistema Nacional de Salud Español: Documento de posicionamiento del Grupo de Especialización en Nutrición Clínica y Dietética de la Academia Española de Nutrición y Dietética

In Spain, the 44/2003 law on health professions, considers the Dietitian-Nutritionist (DN) a health professional since 2003. This regulation with the force of law qualifies this professional as the reference health expert in the dietetic-nutritional treatment. However, so far, the presence of this collective in the Spanish public health field has been limited, despite multiple studies that support the cost-benefit of these professionals within the National Health System (SNS). In improvement visas, the first stance statement on the incorporation of the DN collective within the Spanish SNS was made in 2009. Now, after a decade, it is necessary to assess the degree regarding the incorporation of the collective, so the specialization Group in Clinical Nutrition and Dietetics of the Spanish Academy of Nutrition and Dietetics issues this position paper to update the situation of the DN within the SNS.En España, la Ley 44/2003 de Ordenación de las Profesiones Sanitarias considera al Dietista-Nutricionista (DN) un profesional sanitario desde el año 2003. Esta norma con rango de ley habilita a este profesional como el experto sanitario de referencia en el tratamiento dietético-nutricional. Sin embargo, hasta ahora la presencia de este colectivo en el ámbito sanitario público español ha sido limitada, a pesar de los múltiples estudios que avalan la intervención coste-beneficio de este profesional en el Sistema Nacional de Salud (SNS). En visos de mejora, en el año 2009 se realizó la primera declaración de postura sobre la incorporación del colectivo de DN al SNS español. Ahora, transcurrida una década, se hace necesario valorar el grado de incorporación del colectivo, por lo que el Grupo de Especialización en Nutrición Clínica y Dietética de la Academia Española de Nutrición y Dietética emite este documento de posicionamiento para actualizar la situación del DN en el SNS

Estudio de la acidez en catalizadores bifuncionales para la síntesis directa de DME

Catalizadores bifuncionales basados en Cu/Zn/Al203 y la zeolita HZSM-5 fueron evaluados en el proceso de síntesis directa de DME a partir de gas de síntesis (STD) con el fin de determinar la influencia del número, fortaleza y tipo de centros ácidos. El catalizador que contiene la zeolita HZSM-5 (Si/Al=40) exhibe la mayor acitvidad.García Trenco, A. (2009). Estudio de la acidez en catalizadores bifuncionales para la síntesis directa de DME. http://hdl.handle.net/10251/14532Archivo delegad

A simple an efficient approach to confine Cu/ZnO methanol synthesis catalysts in the ordered mesoporous SBA-15 silica

The ammonia-driving deposition-precipitation (ADP) method has been applied with the purpose of confining active Cu/ZnO methanol synthesis phases inside the pores of the ordered mesoporous SBA-15 silica. Thus, a series of CuZnx/SBA-15 catalysts with total (Cu + Zn) metal loading of 35 wt% and Cu/Zn mass ratios (x) of 0.5, 1, 2, 4, and 6, as well as a Zn-free Cu/SBA-15 sample, have been prepared. Additionally, a CuZn2/SBA-15 sample (Cu + Zn = 35 wt%, Cu/Zn = 2) prepared by impregnation and a coprecipitated Cu-ZnO-Al2O3 (CZA) catalyst have been prepared as reference. The materials have been characterized by ICP-OES, N2 physisorption, XRD, in situ H2-XRD, TEM, H2-TPR, and N2O chemisorption, and their methanol synthesis activities determined, after in situ H2 reduction, under realistic conditions (533 K, 4.0 MPa, syngas: 66%/30%CO/4%CO2). Copper NPs in CuZnx/SBA-15 (ADP) catalysts with Cu/Zn mass ratios up to 2 were effectively confined within the SBA-15 pores (dCu 2-XRD experiments. A. Garcia-Trenco thanks the Ministerio de Economia y Competitividad (former Ministerio de Ciencia e Innovacion) of Spain for a predoctoral (FPI) scholarship.García Trenco, A.; Martinez Feliu, A. (2013). A simple an efficient approach to confine Cu/ZnO methanol synthesis catalysts in the ordered mesoporous SBA-15 silica. Catalysis Today. 215:152-161. https://doi.org/10.1016/j.cattod.2013.03.005S15216121

The influence of zeolite surface-aluminum species on the deactivationof CuZnAl/zeolite hybrid catalysts for the direct DME synthesis

[EN] The influence of the nature and amount of zeolite-surface Al species on the deactivation behavior ofbifunctional CZA/zeolite hybrid catalysts during the direct DME synthesis (260◦C, 4.0 MPa) from syn-gas (66% H2, 30% CO, 4% CO2) has been studied. To this aim, a series of delaminated ITQ-2 zeolites hasbeen prepared by acid treatment and steaming of an Al-ITQ-2 (Si/Al = 12) sample as well as by impreg-nation of an all-silica Si-ITQ-2 sample with Al(NO3)3(aq.) and calcination, and used as the methanoldehydration function of the hybrids. When prepared by grinding, all the hybrid catalysts experienced aloss of activity with time during the syngas-to-DME reaction under conditions where the synthesis ofmethanol on the copper catalyst (CZA) controlled the overall DME synthesis rate. The decay was neitherrelated to changes in the properties of the Cu species (dispersion, Cu0surface area) nor to depositionof carbon species on the metallic function (as ascertained by TPO) but to a particular mode of deacti-vation of the CZA catalyst due to adverse interactions between the copper component and the zeolite.Interestingly, the extent of the deactivation was seen to increase linearly with a parameter ˇ, arbitrarilydefined as ˇ = Sext× [Al/(Si + Al)]surf× %EFAL/100, where Sextis the external surface area of the zeolite,[Al/(Si + Al)]surfis the relative Al surface concentration (from XPS), and %EFAL is the percentage of penta-and hexacoordinated extraframework Al species with respect to the total Al detected by27Al MAS NMR.The correlation suggests that EFAL species located at the surface contact between the CZA and zeoliteparticles were primarily responsible for this particular mode of deactivation of the copper catalyst. Wehypothesize that EFAL species could migrate to the CZA catalyst during DME synthesis through a water-assisted mechanism, modifying the interaction between Cu and ZnOxat the Cu ZnOxinterface where theactive copper sites are likely locatedFinancial support by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of Spain through the Project CTQ2010-17988/PPQ is gratefully acknowledged. A. García-Trenco thanks the Ministerio de Economía y Competitividad (former Ministerio de Ciencia e Innovación) of Spain for a predoctoral (FPI) scholarship.García Trenco, A.; Martinez Feliu, A. (2014). The influence of zeolite surface-aluminum species on the deactivationof CuZnAl/zeolite hybrid catalysts for the direct DME synthesis. Catalysis Today. 227:144-153. https://doi.org/10.1016/j.cattod.2013.09.051S14415322