Pilar Olivares-Carrillo

Organosolv extraction of lignin from hydrolyzed almond shells and application of the δ-value theory.

The solubility of lignin from hydrolyzed almond (Prunus amygdalus) shells in different acetone, ethanol and dioxane-water mixtures and conditions (extraction time and temperature) was studied. The concept of the solubility parameter (delta-value) was applied to explain the effect of organic solvent concentration on lignin solubility. The organic solvent-water mixture that led to the highest lignin extraction was composed of a 75% vol. of organic solvent for all the solvent series investigated (acetone, ethanol and dioxane). Moreover, the best lignin extraction conditions were a temperature of 210 degrees C and an extraction time of 40 min for the acetone and ethanol series, and 25 min for the dioxane series. The delta-value of the hydrolyzed almond shell lignin [14.60 (cal/cm(3))(1/2)] and that of the organic solvent-water mixtures was calculated. The experimental delignification capacity of the aqueous organic solvents clearly reflected the proximity of their delta-value to that of lignin. The hydrogen-bonding capacity of the solvent-water mixtures was also taken into account.

A whole biodiesel conversion process combining isolation, cultivation and in situ supercritical methanol transesterification of native microalgae

A coupled process combining microalgae production with direct supercritical biodiesel conversion using a reduced number of operating steps is proposed in this work. Two newly isolated native microalgae strains, identified as Chlorella sp. and Nannochloris sp., were cultivated in both batch and continuous modes. Maximum productivities were achieved during continuous cultures with 318mg/lday and 256mg/lday for Chlorella sp. and Nannochloris sp., respectively. Microalgae were further characterized by determining their photosynthetic performance and nutrient removal efficiency. Biodiesel was produced by catalyst-free in situ supercritical methanol transesterification of wet unwashed algal biomass (75wt.% of moisture). Maximum biodiesel yields of 45.62wt.% and 21.79wt.% were reached for Chlorella sp. and Nannochloris sp., respectively. The analysis of polyunsaturated fatty acids of Chlorella sp. showed a decrease in their proportion when comparing conventional and supercritical transesterification processes (from 37.4% to 13.9%, respectively), thus improving the quality of the biodiesel.