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

Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes

[EN] The increasing environmental concern and promotion of “green processes” are forcing the substitution of traditional acid and base homogeneous catalysts by solid ones. Among these heterogeneous catalysts, zeolites and zeotypes can be considered as real “green” catalysts, due to their benign nature from an environmental point of view. The importance of these inorganic molecular sieves within the field of heterogeneous catalysis relies not only on their microporous structure and the related shape selectivity, but also on the flexibility of their chemical composition. Modification of the zeolite framework composition results in materials with acidic, basic or redox properties, whereas multifunctional catalysts can be obtained by introducing metals by ion exchange or impregnation procedures, that can catalyze hydrogenation–dehydrogenation reactions, and the number of commercial applications of zeolite based catalysts is continuously expanding. In this review we discuss determinant issues for the development of zeolite based catalysts, going from zeolite catalyst preparation up to their industrial application. Concerning the synthesis of microporous materials we present some of the new trends moving into larger pore structures or into organic free synthesis media procedures, thanks to the incorporation of novel organic templates or alternative framework elements, and to the use of high-throughput synthesis methods. Post-synthesis zeolite modification and final catalyst conformation for industrial use are briefly discussed. In a last section we give a thorough overview on the application of zeolites in industrial processes. Some of them are well established mature technologies, such as fluid catalytic cracking, hydrocracking or aromatics alkylation. Although the number of zeolite structures commercially used as heterogeneous catalysts in these fields is limited, the development of new catalysts is a continuous challenge due to the need for processing heavier feeds or for increasing the quality of the products. The application of zeolite based catalysts in the production of chemicals and fine chemicals is an emerging field, and will greatly depend on the discovery of new or known structures by alternative, lower cost, synthesis routes, and the fine tuning of their textural properties. Finally, biomass conversion and selective catalytic reduction for conversion of NOx are two active research fields, highlighting the interest in these potential industrial applications.The authors acknowledge financial support from Ministerio de Ciencia e Innovacion (project Consolider-Ingenio 2010 MULTICAT).Martínez Sánchez, MC.; Corma Canós, A. (2011). Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes. Coordination Chemistry Reviews. 255(13-14):1558-1580. doi:10.1016/j.ccr.2011.03.014S1558158025513-1

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake