PRODUCTION OF OIL FROM ALGAE AND ITS UPGRADATION USING HETEROGENEOUS CATALYST

Abstract

Algae is considered as 3rd/4th generation feedstock for bio-oil production. It has good potential for bio-oil production since some of the algal species, particularly micro algal species have high growth rate with significantly high lipid content. Out of around 50,000 algal species only few have been exploited. Bio-oil produced from algal biomass basically contains fatty acids and has high viscosity, thus, are not suitable for direct application in combustion engines. Due to this reason upgradation of bio-oil is essential. In the present work native algal biomass collected from Solani River, Roorkee (mainly consisting of Hydrodictyon and Ulotrichalean strains of green alge) has been used. The algal biomass has been found to have ~ 14 % lipid content. Oil from the dried algal biomass has been extracted using hexane as solvent in soxhlet apparatus. Oil was then upgraded to bio-diesel using heterogeneous catalyst to achieve high yield of biodiesel and avoid saponification. Heterogeneous catalysts consisting of various molar ratios of TiO2 and CaO (0.25, 0.5, 1, 2) were prepared using conventional solid state reaction. Mixture with TiO2:CaO molar ratio of 0.25 calcinated at 700oC was found to be the most active. Optimization and modelling of the transesterification reaction was done using Design Expert software version 8.0.7.1 trial. Box-Behnken model using 3 factors (methanol to oil ratio, catalyst doze and reaction time) with 3 levels each was used to fix the experimental conditions. Various levels are methanol to oil ratio (12, 15, 18), catalyst conc. (3, 5, 7 wt. %) and reaction time (6, 8, 10 h). Total 17 reaction conditions were obtained to conduct experiments. The reactions were carried out at boiling temperature of methanol under reflux. The optimized conditions that were obtained by response surface methodology are: methanol to oil ratio 15.68, catalyst concentration 5.12 wt. % and reaction time 8.5h. Further, the catalyst was characterized by using X-Ray diffraction technique, thermo gravimetric analysis method and SEM. The proposed model is suitable to predict the biodiesel yield within the design space with error limit of ±1.5 %. Algal oil and algal biodiesel were analyzed for determining various properties such as viscosity, cloud and pour point, density etc. Properties of bio-diesel matched as those prescribed in IS-15607:2005. GC-MS analysis of bio-diesel was also performed which detected more than 15 compounds ranging from C14 to C29.