Unsupported MoS 2 and bifunctional MoS 2 -amorphous silica-alumina (ASA) catalysts, active for hydrogenation and hydrocracking reactions, were obtained by in situ thermal decomposition of molybdenum octoate in the presence of a sulfur source at temperatures between 300 and 400 °C. Unsupported MoS 2 was formed at temperatures as low as 300 °C with yields higher than 76%. Increasing temperature increased the degree of sulfidation but also increased particle dimensions and, consequently, decreased the MoS 2 dispersion. The presence of ASA reduced MoS 2 particle dimensions compared to the unsupported MoS 2 , while the effect on sulfidation degree was dependent on temperature. High temperature (400 °C) was required to achieve high MoS 2 yield due to interactions with the support at lower temperatures. The catalytic activity of the unsupported MoS 2 showed that, as a result of the opposing effects of temperature on the MoS 2 dispersion and MoS 2 sulfidation degree, the activity toward hydrogenation of phenanthrene, reported on a per edge site basis, was not affected by morphological and structural differences. The bifunctional MoS 2 -ASA catalyst at 400 °C promoted cracking, isomerization, and ring-opening reactions due to the moderate Brønsted acidity of the ASA and changed the product distribution favorably when compared to the unsupported MoS 2 .

To achieve maximum yield from bifunctional catalysts in slurry-phase hydrocracking of heavy oil, an appropriate balance between the acidic and hydrogenating functions of the catalyst is required. In this study, the bifunctional behavior of MoS2-amorphous silica–alumina (ASA) catalysts was investigated by varying the number of Brønsted acid sites (ηH+) and MoS2 edge sites (ηMo) associated with ASA and MoS2, respectively. Using a model feed consisting of phenanthrene and decalin, we report evidence of bifunctional catalysis for MoS2-ASA catalysts with ηH+/ηMo ratios between 3.1 and 15.5. Deviations from bifunctional behavior were also observed: at a low ηH+/ηMo ratio (0.39), phenanthrene hydrogenation was preferred, whereas at the highest ηH+/ηMo ratio (30.9), acid-catalyzed reactions dominated and promoted coke formation that resulted in catalyst deactivation. Considering that the in situ formation of MoS2 blocked some acid sites on the ASA, we introduced a new parameter that quantified the number of Brønsted acid sites available in the reactor system (ηH+ c). We show that the total product yield correlated with ηH+ c and that the maximum yield occurred for the catalyst with the highest ηH+ c.

MoS2-amorphous silica-alumina (MoS2-ASA) bifunctional catalysts for slurry-phase hydroconversion of the model reactants phenanthrene and decalin were prepared using three distinct methodologies. The MoS2-ASA catalysts were prepared by (i) a mechanical mixture of MoS2 (prepared separately) and ASA, which were mixed directly in the reactor for the hydroconversion test (MM catalyst); (ii) in situ sulfidation of the molybdenum precursor in the presence of the ASA, both dispersed in the phenanthrene-decalin reaction mixture (IS catalysts); and (iii) impregnation of molybdenum octoate onto ASA, followed by thermal treatment to chemically link the Mo precursor to the ASA surface followed by sulfidation prior to the catalytic test (IMP catalyst). Among the three preparation methods, the MoS2-ASA catalysts prepared in situ (IS) had the highest MoS2 dispersion and degree of sulfidation and yielded the highest hydrogenating activity at the lowest Mo catalyst content (2.9Mo-ASA). Although the MoS2 blocked Brønsted acid sites decreasing the ASA acidity, especially in IS and IMP catalysts, at the low Mo concentrations required with the IS methodology, most of the acidity was retained. In addition, in the case of IS catalysts, MoS2 particles were also found dispersed in the slurry feed independently of the ASA. Consequently, the IS catalyst retained the advantages of the unsupported MoS2 with the additional functionality of the acid component of the bifunctional catalyst; hence, conversion was promoted due to both hydrogenation and hydrocracking reactions. These observations suggested that the bifunctional MoS2-ASA catalysts prepared in situ promotes hydrocracking reactions at lower temperatures reducing the severity of reaction conditions and limiting coke formation in slurry-phase hydroconversion.

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Introducción La dificultad en la identificación morfológica de las hembras de varias especies del subgénero Nyssorhynchus ha sido documentada y se debe a la similitud morfológica interespecie, variación intraespecífica y la existencia de especies crípticas. Por ello, se han utilizado pruebas moleculares como la PCR-RFLP-ITS2, que permiten confirmar la identidad de las especies presentes en regiones endémicas. obJetivo Confirmar la identificación de mosquitos del género Anopheles recolectados en Juan José, Puerto Libertador, Córdoba, como aporte a un inventario de especies en la localidad. Materiales y métodos De 2.070 hembras de Anopheles identificados por caracteres morfológicos, 513 (24,8%) se confirmaron molecularmente mediante una PCR-RFLP-ITS2. Resultados Las especies identificadas por morfología presentes en Juan José fueron: Anopheles (Nyssorhynchus) nuneztovari s.l. Gabaldon (97,44%), Anopheles (Nys.) darlingi Root (0,77%) y Anopheles (Nys.) oswaldoi s.l. Peryassu (0,10%); el resto de especímenes (1,69%) se definieron como pertenecientes a una de las especies del grupo Oswaldoi. La confirmación molecular permitió determinar la presencia de sólo dos especies entre los especímenes analizados, 99,23% A. (Nys.) nuneztovari s.l. y 0,77% A. (Nys.) darlingi. Conclusión Las dos especies de Anopheles encontradas en Juan José, durante el muestreo, son consideradas vectores primarios en Colombia; esta información es importante para dirigir los esfuerzos de control vectorial. Adicionalmente, los resultados reiteran previos reportes sobre la dificultad en la identificación morfológica de A. nuneztovari s.l. y la importancia de utilizar pruebas moleculares en su confirmación de especie.