Once a biorefinery is ready to operate, the main processed materials need to be completely evaluated in terms of many different factors, including disposal regulations, technological limitations of installation, the market, and other societal considerations. In biorefinery, glycerol is the main by-product, representing around 10% of biodiesel production. In the last few decades, the large-scale production of biodiesel and glycerol has promoted research on a wide range of strategies in an attempt to valorize this by-product, with its transformation into added value chemicals being the strategy that exhibits the most promising route. Among them, C3 compounds obtained from routes such as hydrogenation, oxidation, esterification, etc. represent an alternative to petroleum-based routes for chemicals such as acrolein, propanediols, or carboxylic acids of interest for the polymer industry. Another widely studied and developed strategy includes processes such as reforming or pyrolysis for energy, clean fuels, and materials such as activated carbon. This review covers recent advances in catalysts used in the most promising strategies considering both chemicals and energy or fuel obtention. Due to the large variety in biorefinery industries, several potential emergent valorization routes are briefly summarized.

The transesterification of rapeseed and castor oil methyl esters with different alcohols (2-ethyl-1-hexanol, 1-heptanol and 4-methyl-2-pentanol) and titanium isopropoxide as a catalyst, to produce biolubricants, was carried out. Parameters such as temperature, alcohol/methyl ester molar ratio, and catalyst concentration were studied to optimize the process. The reaction evolution was monitored with the decrease in FAME concentration by gas chromatography. In general, the reaction was almost complete in two hours, obtaining over 93% conversions. All the variables studied influenced on the reaction yields. Once the optimum conditions for the maximum conversion and minimum costs were selected, a characterization of the biolubricants obtained, along with the study of the influence of the kind of alcohol used, was carried out. The biolubricants had some properties that were better than mineral lubricants (flash points between 222 and 271 °C), needing the use of additives when they do not comply with the standards (low viscosity for rapeseed biolubricant, for instance). There was a clear influence of fatty acids of raw materials (oleic and ricinoleic acids as majority fatty acids in rapeseed and castor oil, respectively) and the structure of the alcohol used on the final features of the biolubricants.

Apart from the evident tragedy that the COVID-19 outbreak has meant regarding both personal and economic costs, the normal functioning of the academic year has been drastically altered at all educational levels. Regarding Spain, the state of alert implemented by the government from mid-March to June has affected traditional face-to-face sessions at universities, as they were forbidden and replaced by online lessons. The aim of this work was to explain our own experience during the COVID-19 outbreak in a chemical engineering laboratory at the University of Extremadura, concerning the university teaching and the final degree project follow-up, whose method of teaching was active and participatory, based on constructivism and focused on the student as the center of the learning process. Thus, the confinement affected both the teachers and students differently, depending on the degree of completion of their main tasks and their previous skills with computing and virtual tools, among other factors. The existence of an operating virtual campus and an online library has made the transition to total e-learning and telework easier for teachers and students.

Biodiesel is gaining more and more importance due to environmental issues. This way, alternative and sustainable crops as new biofuel sources are demanded. Safflower could be a sustainable raw material for biodiesel production, showing one disadvantage (as many biodiesels from vegetable oils), that is, a short oxidative stability. Consequently, the use of antioxidants to increase this parameter is mandatory. The aim of this research work was to assess the effect of two antioxidants (butylated hydroxyanisole, BHA, and tert-butylhydroquinone, TBHQ) on the oxidative stability of safflower biodiesel, which was characterized paying attention to its fatty acid methyl ester profile. For oxidative stability, the Rancimat method was used, whereas for fatty acid profile gas chromatography was selected. For the remaining parameters, the methods were followed according to the UNE-EN 14214 standard. The overall conclusion was that safflower biodiesel could comply with the standard, thanks to the use of antioxidants, with TBHQ being more effective than BHA. On the other hand, the combined use of these antioxidants did not show, especially at low concentrations, a synergic or additive effect, which makes the mixture of these antioxidants unsuitable to improve the oxidative stability.

Biodiesel is an alternative to mineral fuels, with advantages such as biodegradability. However, this makes biodiesel unstable to oxidation. In this way, the use of natural or synthetic antioxidants is necessary. Although many studies have paid attention to the effect of these antioxidants on oxidation stability, not much literature about their effect of them on other properties (before and during storage) was found. The aim of this research study was to characterize biodiesel from corn and sunflower by adding two antioxidants, butylated hydroxyanisole (BHA) and tertbutylhydroquinone (TBHQ), in order to improve its oxidation stability. Moreover, the effect of oxidation on the parameters of biodiesel was studied by using extreme oxidation conditions to accelerate the oxidation process. Both antioxidants improved the oxidation stability of biodiesel, whereas some parameters were altered (viscosity and acid number), which could make this biofuel, if high concentrations of antioxidants are used, unsuitable for commercialization according to standards.Keywords BHA Á TBHQ Á Oxidation stability Á Viscosity Á Thermal analysis Á Fatty acid methyl esters J Am Oil Chem Soc (2020) 97: 201-212.