Gemma Vicente

Application of the factorial design of experiments and response surface methodology to optimize biodiesel production

The production of fatty acid methyl esters, to be used as a diesel substitute (biodiesel), has been studied. The reaction of refined sunflower oil and methanol was carried out over different types (acid and basic, homogeneous and heterogeneous) of catalysts. The catalyst that led to largest conversions was sodium hydroxide. No methyl esters were detected when zirconium-based catalysts and an immobilized lipase were used. The process of biodiesel production was optimized by application of the factorial design and response surface methodology. Temperature and catalyst concentration were found to have a positive influence on conversion, concentration effect being larger than temperature effect. A second-order model was obtained to predict conversions as a function of temperature and catalyst concentration. Optimum conditions for the production of methyl esters were found to be mild temperatures (20‐50°C) and large catalyst concentrations (1.3%).

Acetalisation of bio-glycerol with acetone to produce solketal over sulfonic mesostructured silicas

Sulfonic acid-functionalized mesostructured silicas have demonstrated excellent catalytic behaviour in the acetalisation of glycerol with acetone to yield 2,2-dimethyl-1,3-dioxolane-4-methanol, also known as solketal. This molecule constitutes an excellent compound for the formulation of gasoline, diesel and biodiesel fuels. The activity achieved with arenesulfonic acid-functionalized silica is comparable to that displayed by Amberlyst-15. Optimal production of solketal over arenesulfonic acid mesostructured silica has been established for a reaction system consisting of three consecutive 2-step batches (30 min under reflux and an evaporation step under vacuum), and using a 6/1 acetone/glycerol molar ratio. The use of lower grades of glycerol, such as technical (purity of 91.6 wt%) and crude (85.8 wt%) glycerol, has also provided high conversions of glycerol over sulfonic acid-modified heterogeneous catalysts (84% and 81%, respectively). For refined and technical glycerol the catalysts have been reused, without any regeneration treatment, up to three times, keeping the high initial activity. However, the high sodium content in crude glycerol deactivates the sulfonic acid sites by cation exchange. This deactivation is readily reversed by simple acidification of the catalyst after reaction.

Etherification of biodiesel-derived glycerol with ethanol for fuel formulation over sulfonic modified catalysts.

The present study is focused on the etherification of biodiesel-derived glycerol with anhydrous ethanol over arenesulfonic acid-functionalized mesostructured silicas to produce ethyl ethers of glycerol that can be used as gasoline or diesel fuel biocomponents. Within the studied range, the best conditions to maximize glycerol conversion and yield towards ethyl-glycerols are: T=200 °C, ethanol/glycerol molar ratio=15/1, and catalyst loading=19 wt%. Under these reaction conditions, 74% glycerol conversion and 42% yield to ethyl ethers have been achieved after 4 h of reaction but with a significant presence of glycerol by-products. In contrast, lower reaction temperatures (T=160 °C) and moderate catalyst loading (14 wt%) in presence of a high ethanol concentration (ethanol/glycerol molar ratio=15/1) are necessary to avoid the formation of glycerol by-products and maximize ethyl-glycerols selectivity. Interestingly, a close catalytic performance to that achieved using high purity glycerol has been obtained with low-grade water-containing glycerol.

Biodiesel from microbial oil.

Abstract: Fatty acid methyl esters (biodiesel) are usually obtained from plant oils. Oleaginous microorganisms present an alternative to plant oils because they can accumulate high levels of lipids and do not require arable land. In particular, heterotrophic microorganisms (bacteria, fungi and yeasts) can be grown on waste or low-grade biomass as a carbon and energy source. After biomass production, biodiesel can be produced by transformation of extracted microbial lipids or direct transformation of dry microbial biomass. Direct transformation of lipids into FAMEs gives cost savings and increases lipid extraction. Careful characterization of the lipid composition of each microbial candidate should be carried out before it can be adopted since biodiesel fuel as an alternative needs to comply with existing standards. Genetic engineering and biorefinery-based production strategies can reduce costs by increasing lipid accumulation of microorganisms.