HCl will not work, because of concentration, but sulfuric yes, but basically you can use any acid, including solids for esterification and any base for transesterification

Waste cooking oil has high contents of free fatty acids.

From my previous experience it can be assumed that increased free fatty acid content in feed stock is the root cause of malfunctioning of the process. Because increased free fatty acid will react with base catalyst and will produce soap. This will impede phase separation in sedimentation column and will malfunction of the biodeisel-glycerol phase separator. In addition less catalyst will be available to influence the transesterification and biodeisel yield will be lower.

Solution to this problem: First, analyze the feed stock’s quality parameters (triglycerides contents, free fatty acid contents (acid value), saponification value etc.). If free acid contents are > 0.7% (weight/weight), then pre conditioning of the feed stock is required. This can be done by esterification of the free fatty acid by acid (H2SO4) catalyzed esterification process followed by base catalyzed (KOH) transesterification process.

Hope, this information will help.

Best Regards,

/Shahidul

Yes you can go for two step treatment i.e. Acid treatment followed by alkali treatment

These papers may help you

Article Production of biodiesel from unused algal biomass in Punjab, India

https://www.researchgate.net/publication/322023788_Fuel_properties_and_emission_characteristics_of_biodiesel_produced_from_unused_algae_grown_in_India

Article Optimization of safflower oil transesterification using the ...

Generally, waste cooking oil has a high FFA (free fatty acid) level, which will be reacted with a base catalyst and undergo saponification reaction. As a result, numerous studies have highlighted the advantages of converting FFA to FAME (fatty acid methyl ester) in the presence of acid catalysts. However, acid esterification is necessary if the acid value of waste cooking oil less than 2 mg KOH /g. A catalyst is a substance that accelerates or decreases the temperature or pressure required to initiate a chemical reaction without being consumed in the process. As a result, the catalyst encouraged the formation of a surface for the reactant to react by participating in the reaction mechanism. The active species, rather than the complete complex, has a greater role in this phenomenon. The active species in an alkaline catalyst for transesterification is the methoxide ion (-CH3O), whereas in an acid catalyst for esterification, the active species is the hydrogen ion (H+). theoretically, any acid could be employed for acid esterification and any base can be employed could be a base catalyst for transesterification since strong base react with methanol and produce alkaline metal methoxide which is acted as an active species for transesterification.

just to finish what Viraj wrote, but the reaction partners and the catalyst must come into intimate contact and this might be hindered by phase transfer difficulties!

Yes, mass transfer resistance is critical in transesterification reactions due to the immiscibility of the reactants. To minimize mass transfer resistance, either the reaction operation should be optimized or a co-solvent should be introduced at the start of the reaction. Co-solvent addition is a viable solution. Kindly refer if you are interested in the influence of co-solvents on transesterification.

Article Production of Biodiesel Using Acetone as a Co- Solvent

please refer this article

Article Catalysts for Biodiesel Production: A Review

Hi

The calculation and processing protocols are well explained in the following paper:

https://doi.org/10.1007/s12161-021-02203-0

I hope this helps!

Hi

The calculation and processing protocols are well explained in the following paper:

https://doi.org/10.1007/s12161-021-02203-0

I hope this helps!

yes. you can use sulfuric for acid esterification.