The gas-phase alkylation of m-cresol with methanol was studied at 523 K on Al-MCM-41 and zeolites ZnY, HBEA, HZSM5 and HMCM22. The acidity was determined by ammonia TPD and FTIR of adsorbed pyridine. On acid sites of moderate strength (Al-MCM-41), initially the O-alkylation rate was higher than the C-alkylation rate. In contrast, formation of dimethylphenols by C-alkylation was highly favored on ZnY and HMCM22 which have both strong acidity although different nature; Lewis (ZnY) and Brønsted and Lewis (HMCM22). High selectivity of 2,5-DMP was observed on HZSM5, probably due to diffusional constraint. All catalysts, except Al-MCM-41, showed deactivation by coke formation.

In this paper, glycerol esterification with acetic acid (AA) was studied on several solid acid catalysts: AlO, Al-MCM-41, HPA/SiO, HBEA, Amberlyst 15 and Amberlyst 36 with the aim of determining the reaction conditions and the nature of the surface acid sites required to produce selectively triacetylglycerol (triacetin). The acidity of the catalysts (nature, density and strength of acid sites) was characterized by temperature-programmed desorption of NH and FTIR of adsorbed pyridine. AlO (Lewis acidity) did not show any activity in the reaction. In contrast, highest activity and selectivity to the triacetylated product (triacetin) were obtained on catalysts with Brønsted acidity: Amberlyst 15 and Amberlyst 36. The effect of temperature and molar ratio of AA to glycerol was studied, and the results showed that both parameters have a significant impact on the production of the desired product. Glycerol conversion rate and selectivity to triacetin increased when temperature or AA to glycerol molar ratio were increased, reaching a triacetin yield on Amberlyst 36 of 44% at 393 K and AA to glycerol molar ratio of 6. Deactivation and reusability of Amberlyst 36 were evaluated by performing consecutive catalytic tests. The presence of some irreversible deactivation due to sulfur loss was observed. In addition, the feasibility of using crude glycerol from biodiesel production as reactant was also investigated. Conversion of crude pretreated glycerol yielded values of triacetin and diacetin similar to those obtained with the commercial pure glycerol although at a lower rate.

This work describes theoretical and experimental studies on glycerol esterification to obtain acetins focusing on the obtained isomers. The reaction of glycerol with acetic acid was carried out on Amberlyst 36 wet. Density functional theory calculations on the level of M06-2X functional and 6-311+G(d,p) basis set are carried out and the most stable structures of the reactants and products are located by considering a large number of conformers. The thermodynamics is discussed in terms of the calculated reaction Gibbs free energy. The AIM theory was used to characterize reactants and products. The glycerol esterification with acetic acid is found to be thermodynamically favored, with exothermal property. These agree well with experiments and allow us to explain the relative selectivity of products.

La formación de los futuros ingenieros desde un enfoque por competencias es un tema ya instalado desde hace décadas. Si bien existe una profusa bibliografía, son pocos los casos en los que se describe de manera exhaustiva el modo en que se pone en práctica el modelo. En este trabajo se describe el proceso de implementación del desarrollo de competencias articuladas con el desarrollo de capacidades y habilidades desde etapas tempranas del Plan de Estudios de la carrera de Ingeniería Química de la Universidad Nacional del Chaco Austral