The sulfonation process is usually applied either using H2SO4 acid solutions or SO3 vapors. The result is the creation of –SO3H groups onto the microalgae surface. These groups are highly important for the activity of the catalyst. They exhibit high Bronsted acidity and they are ideal for lipids with high concentration of acids like cook waste oils. The conversion achieved is usually high, as high as 95%, while the yield in fatty acid methyl esters (FAME) is lower and in the best cases, about 80%. In most cases, the catalyst is a strong base like NaOH or KOH. The strong base is dissolved in methanol and the catalyst is working homogeneous.

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For analysis point of view, trans-esterification using acid catalyst is advisable to have all the fatty acid conversion to FAME(including Free fatty acid, FFA) even though it requires more time & electricity.

If you are looking at large scale, base catalyst will help you to prepare FAME with minimum time and less energy. If your oil have high FFA, you will have to process your oil for FFA removal prior to transesterification using base catalyst to minimize the product loss.

Hi

For transesterification decision you have to check the free vfa (volatile fatty acids) of your biomass sludge. If the vfa is high you have to use the acidic route. If the vfa is low you can proceed by alcaline route.

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Thank you very much Mr Asad Ali , Dr Rathod and Mr Servio for your answers.

Best regards