RESUMEN
The ring-rearrangement of 5-hydroxymethylfurfural (HMF) to 3-hydroxymethylcyclopentanone (HCPN) was investigated over Ni catalysts supported on different carbon supports and metallic oxides with different structure and acid-base properties. Their catalytic performance was tested in a batch stirred reactor in aqueous solution at 180 °C and 30â bar of H2. Under these conditions, the HMF hydrogenation proceeds through three possible competitive routes: (i) a non-water path leading to the total hydrogenation product, 2,5-di-hydroxymethyl-tetrahydrofuran (DHMTHF), and two parallel acid-catalyzed water-mediated routes responsible for (ii) ring-opening and (iii) ring-rearrangement reaction products. All catalyst systems primarily produced HCPN, but reaction rates and product distribution were influenced by several variables, some of them intensely analyzed in this work. The most proper conditions resulted to be the presence of the medium/strong Lewis's acidity of a Ni/ZrO2 catalyst (initial TOF=5.99â min-1 and 73 % HCPN selectivity) or the Brønsted acidity originated by an oxidized high surface area graphite, Ni/HSAG-ox (initial TOF=5.92â min-1 and 87 % HCPN selectivity). However, too high density of acidic sites on the catalyst support (Ni/Al2O3) and sulfur impurities from the HMF feedstock led to catalyst deactivation by coke deposition and Ni poisoning, respectively.
RESUMEN
For a series of nanometric ZnO materials, the relationship between their morphological and surface functionalities and their catalytic properties in the selective decomposition of ethanol to yield acetaldehyde was explored. Six ZnO solids were prepared by a microemulsion-precipitation method and the thermal decomposition of different precursors and compared with a commercial sample. All these materials were characterized intensively by XRD and SEM to obtain their morphological specificities. Additionally, surface area determinations and IR spectroscopy were used to detect differences in the surface properties. The density of acid surface sites was determined quantitatively using an isopropanol dehydration test. Based on these characterization studies and on the results of the catalytic tests, it has been established that ZnO basal surfaces seem to be responsible for the production of ethylene as a minor product as well as for secondary reactions that yield acetyl acetate. Furthermore, one specific type of exposed hydroxyl groups appears to govern the surface catalytic properties.
Asunto(s)
Etanol/química , Nanoestructuras/química , Óxido de Zinc/química , Catálisis , Microscopía Electrónica de Rastreo , Nanoestructuras/ultraestructura , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Difracción de Rayos XRESUMEN
Fever is a presenting sign in some patients with acute deep venous thrombosis (DVT), but its influence on outcome has not been thoroughly investigated. RIETE is an ongoing, international, observational registry of consecutive patients with symptomatic, objectively confirmed, acute venous thromboembolism. The aim of the present study was to assess the prevalence of fever in patients with acute DVT, and to compare their outcome during the first month of therapy, according to the presence or absence of fever. As of September 2009, 14,480 patients with symptomatic DVT have been enrolled in RIETE. Of these, 707 (4.9%) had fever at presentation. During the 30-day study period, 448 patients (3.1%) died, 171 (1.2%) developed DVT recurrences, 376 (2.6%) had pulmonary embolism, and 384 (2.6%) had a major bleeding. Patients initially presenting with fever had a higher mortality (5.8% vs. 2.9%; odds ratio: 2.6; 95% CI 1.9-3.5) than those without fever. Among the causes of death, pulmonary embolism (0.7% vs. 0.1%) and infection (1.1% vs. 0.3%) were significantly more common in patients presenting with fever. Multivariate analysis confirmed that DVT patients with fever had an increased mortality (hazard ratio: 2.00; 95% CI 1.44-2.77) irrespectively of the patient's age, body weight, and risk factors for VTE. Fever is not uncommon in patients with DVT, and carries a worse outcome.