Biodiesel is emerging as an alternative fuel with several advantages over the common petroleum based fuels. In its production, however, variables such as raw material, catalyst, and co-solvent are an issue worth exploring because of the impact they have on final biodiesel properties. Therefore, this work aims to establish the effect of the aforesaid variables on methyl ester content, viscosity, acidity, and water content of biodiesel produced from castor oil. In this context, the methanolysis of castor oil has been conducted at 60 °C in a batch reactor, and the effect of three alkaline catalysts (CH3ONa, NaOH, and KOH) and a co-solvent (hexane) has been established. It is concluded that sodium methoxide leads to considerably higher methyl ester content than the other essayed catalysts. Besides, when utilizing a co-solvent the methyl ester content increases up to a very close value (95.5%) to that established by the EN14214 norm (>96.5%). This has been ascribed to a significant improvement on oil−methanol contact.
The process of carbon dioxide (CO2) reduction to value-added chemicals is being extensively studied worldwide. The main purpose is to decrease emissions to the environment that are associated with global warming, as well as the creation of renewable and sustainable energy sources. In the aforementioned process, the absorption of CO2 is of paramount importance as well as the reactor where the CO2 conversion takes place. In this context, the objective of this chapter is to present and analyze the results of the CO2 absorption in alkaline solutions in capillary reactors. A hydrodynamic study is included in order to establish the operational window of liquid and gas velocities in order to achieve the Taylor flow regime. All experiments were conducted in a capillary reactor (dc = 3 mm). The studied variables were temperature, NaOH concentration (0-0.75 M) and capillary length (300 and 100 mm). It was found that the volumetric mass transfer coefficient of the absorption of CO2 in water increases when the temperature decreases, while the CO2 absorption in NaOH solutions increases directly with temperature. By means of the Ha number, it was concluded that the mass transfer controlled the absorption process when using alkaline solutions.
The continuous combustion of non-renewable fossil fuels and the depletion of the natural resources from which they come and, consequently, the continuous increase of carbon dioxide (CO2) emissions into the atmosphere are intensifying the search for the conversion of carbon dioxide to fuels and value-added chemicals, with the main objective of reducing emissions and creating renewable and sustainable energy sources. In this sense, there is a lot of interest in the photocatalytic reduction of CO2 with H2O, mainly using solar energy, which is a renewable source with a continuous and easily available light supply. Recent progress in this area has focused on the development of promising photocatalysts, primarily based on TiO2. In this context, this article analyzes: (i) the role of CO2 in the treatment of problems related to energy and global warming, (ii) the fundamental knowledge of the photocatalytic reduction of CO2, (iii) the role of the catalysts of copper-doped TiO2 in the photocatalytic transformation CO2; as well as (iv) emerging and crucial opportunities for future research employing Cu-TiO2 photocatalysts; mentioning the most up-to-date relevant references.
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