Hierarchical zeolites as catalysts for biodiesel production from Nannochloropsis microalga oil

Abstract

Oleaginous microalgae are potential sources for biodiesel production as they accumulate high levels of lipids (>20%) and they do not compete with food production. The lipid extraction from Nannochloropsis gaditana was studied using three procedures (sonication, microwaves and magnetic stirring under reflux) with different extraction solvents (methanol, chloroform/methanol and hexane). The extraction with methanol and magnetic stirring under reflux gave the highest cell disruption and therefore, the highest lipid extraction. The extracted lipids were characterized to determine the fatty acid profile.On the other hand, microalga lipids were tested as a feedstock in the biodiesel production using hierarchical zeolites as heterogeneous catalysts, to overcome the disadvantages of homogeneous catalysts currently used in the industrial plants. Hierarchical Beta zeolite showed a significant activity in the microalga oil reaction with methanol, because it presented a secondary porosity in the range micro-mesopores maintaining the acid properties of the Beta zeolite. In this sense, the diffusion restrictions to the mass transfer of large lipids into zeolite framework were reduced, improving the accessibility of microalga oil to the h-Beta acid sites.