At a global level, hydrokinetic power has been considered as a renewable energy source, and it has become an attractive alternative for the rural electrification of non-interconnected areas with the presence of water resources. Aspects such as the low rural electrification rate, the increase in energy demand, the decrease in fossil reserves and the climate change, are some of the factors that have driven the use of this technology for the electricity production. The aim of this work is to give a review of the hydrokinetic energy potential of water resources, the requirements and impacts of the implementation of hydrokinetic technology in different countries, and the current development in the Colombian case. At present, it can be observed that the implementation of this technology in different regions of the world, especially in Colombia, has several challenges and barriers, including gaps in knowledge, information and data, such as well as limitations of water resources and infrastructure, finally, impacting on a low adoption of this technology. On the other hand, publications on studies of implementation and potential of hydrokinetic technology have been increasing over time, indicating that this topic has been gaining interest despite the challenges.

The catalytic activity for dimethyl carbonate formation from carbon dioxide and methanol over mono and bimetallic Cu:Ni supported on activated carbon is presented. Bimetallic catalysts exhibit higher catalytic activity than the monometallic samples, being Cu:Ni-2:1 (molar ratio) the best catalyst; X-Ray diffraction, transmission electron microscopy, and metal dispersion analysis provided insight into the improved activity. In situ FT-IR experiments were conducted to investigate the mechanism of formation of dimethyl carbonate from methanol and carbon dioxide over Cu-Ni:2-1. The kinetics of the direct synthesis of dimethyl carbonate in gas phase over Cu:Ni-2:1 supported on activated carbon catalyst was experimentally investigated at 12 bar and temperatures between 90 °C and 130 °C, varying the partial pressures of CO₂ and methanol. Experimental kinetic data were consistent with a Langmuir–Hinshelwood model that included carbon dioxide and methanol adsorption on catalyst actives sites (Cu, Ni and Cu-Ni), and the reaction of adsorbed CO₂ with methoxi species as the rate determining step. The estimated apparent activation energy was 94.2 kJ mol^-1.

La elevada producción de glicerol, un subproducto de bajo costo proveniente de la industria del biodiésel, ha supuesto una amenaza tanto para el medio ambiente como para la economía. La transformación de glicerol en productos de valor agregado contribuiría positivamente a la economía del biodiésel. En este artículo de revisión se describen las rutas de valorización del glicerol y se presenta la esterificación como una de las más prometedoras para la transformación de glicerol en aditivos para combustibles; igualmente, se describen los resultados más relevantes entre 2010 y 2020 relacionados con las condiciones experimentales (temperatura, relación molar y tiempo de reacción), los catalizadores heterogéneos y la actividad catalítica (en términos de la conversión del glicerol y la selectividad) para la transformación de glicerol en acetinas (monoacetina, diacetina y triacetina). Se espera que esta revisión permita abordar esta técnica de valorización de manera rentable y ambientalmente sostenible.

El efecto combinado de residuos de llantas y microesferas como sustitutos de la materia prima utilizada en la elaboración convencional de concretos fue explorada en este trabajo. Se diseñaron y prepararon mezclas de concreto tradicional, con modificaciones del 15% en masa de los agregados finos con relaciones de residuos de llantas, microesferas de vidrio de 0:1, 1:1, 1:3, 3:1 y 1:0. A partir de las mezclas preparadas se elaboraron especímenes cilíndricos de 150 mm x 300 mm. La evaluación de las propiedades mecánicas y físicas de los especímenes cilíndricos mostró que los materiales con mayor contenido de residuos de llantas presentaron una menor densidad, mientras que los de mayor contenido de microesferas presentaron la mayor resistencia a la compresión; de hecho, las mezclas 0:1 y 1:3 presentaron resistencias a la compresión de 22.4 y 19.1 MPa, respectivamente. Los resultados encontrados muestran que la adición conjunta de microesferas y residuos de llantas presentan un efecto sinérgico combinado entre los dos materiales con potencial uso en la industria de la construcción, en reemplazo de los materiales tradicionales utilizados en la elaboración de concretos, en particular, se espera que el uso de estos materiales se convierta en una alternativa para la utilización de estos residuos, los cuales no cuentan actualmente con un plan de disposición.

In this study, the effect of incorporating hollow glass microspheres (HGM) on the mechanical properties of modified concrete with CR (crumb rubber) was evaluated. Different concrete samples replacing 15% of fine aggregates (total weight of CR + HGM = 15%) were prepared. It was found that the increase in the microsphere content was directly proportional to the slump, compressive strength, and the modulus of elasticity. The increase in the microsphere content was inversely proportional to density. Additionally, we found that in the modified concrete, the width, height and the number of cracks increased as the HGM content increases. The combined sample HGM12.5-CR2.5 (the one with the highest content of microspheres) resulted in concrete with the highest compressive strength of 19.1 MPa, which is 243% stronger than the concrete with only crumb rubber (9.2 MPa). From the XRD results, we were able to detect the presence of different phases formed by hydration during the process of preparing concrete mixtures. The micrographs allowed identifying the fracture in the microspheres during the preparation of the concrete mixtures when they came into contact with the aggregates. The addition of hollow glass microspheres to the mixtures prepared from crumb rubber improved their mechanical properties, and this makes it a potential system that can replace the traditional materials in the production of concrete.