Dear Jermaine,

Firstly, it is necessary to know if the waste cooking oil has a free fatty acid content lower than 3%. If this is not the case, you must perform an esterification treatment. Then you should check again the free fatty acids content. If these decreased to values below 3% then transesterification can be performed. The problem may be related to the formation of soap. When the oil has a high free fatty acids content in presence of a homogeneous basic catalyst, then the formation of soap may occur.

If you guarantee the above mentioned and the problem continues, then you can try to wash the mixture (biodiesel + glycerol) with a solution of HCL (0.5% volumetric).

Kind regard

use methanol as a solvent and try to separate before it solidifies

kindly use the separating funnel for the separation

I agree with Domínguez that waste cooking oil has high free fatty acid but you still be able to trans-ethylate to ethyl esters. The problem of phase separation can be easily solved from the knowledge of solubility/miscibility of biodiesel-ethanol-glycerol. Ethyl biodiesel and glycerol are immiscible, but ethanol is a very soluble in ethyl biodiesel and it is miscible with glycerol. Thus, if reaction carried out in high molar ratio of of ethanol to oil was used, the excess ethanol will act as the co-solvent for biodiesel and glycerol. A single phase would be formed. If lower ethanol to oil was used, ethanol would be in the glycerol layer and density of the mixture is reduced to possibly close that of biodiesel. In both cases, Domínguez's suggestion was a good advise. Acidify the reaction product with 1 vol. of 0.5 M HCl or any other acids. Solution should be separated into two phases. If you feel that the separation is too slow, added more distilled water and washed till neutral.

You can also see an article, F U E L P R O C E S S I N G T E C H N O L O G Y 8 9 ( 2 0 0 8 ) 1 3 3 0 – 1 3 3 6.

Probably, you have not optimized transesterification process for you oil. The FFA (free fatty acid) of the biodiesel must be lower than 2-3%. If it is more than that then you have to perform acid treatment at first and alkaline treatment then. Now finally after applying optimized conditions, separate layers of glycerol and biodiesel definitely appear. So, take different process parameters, choose their different levels and optimize the parameters at first. I worked on algal biodiesel. Please find my paper if required.

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

I am using corn oil with an %FFA of 12.775. What are some of the optimum conditions (such as the sulphuric acid concentration) I can apply so that I can reduce the %FFA to below 3%?

In addition to the question of free fatty acids, a negative aspect of the use of ethanol in transesterification reactions is that it facilitates the formation of a stable emulsion between glycerol and biodiesel, making the separaion process complicated.

To overcome this problem, we can add an amount of external glycerol to the reaction bag, at the end of the reaction, which promotes the separation of the glycerol by the emulsion breaking effect. However, this procedure generates the addition of one more step in the process.

Some studies aim to use solutions containing ethanol and methanol in different proportions in order to facilitate the separation between glycerol and biodiesel.

Thank you

the reason is in principles of colloid behavior and surface activity of soaps (of fatty acids and of partial glycerides). Look for Co-Sol technology for better results

you can use methanol instead of ethanol .......actually my work is also biodiesel production. what is qualitative and quantitative analysis of your biodiesel.

First of all calculate the acid number, if it is below 4-5, than you can convert your oil into biodiesel with the help of transesterification.

If more than please read this

https://www.sciencedirect.com/science/article/pii/S0306261915008028

For initial assessment of biodiesel production for waste cooking oil you just follow the following condition. However your waste cooking oil FFA does not exceeds 1%, but just confirm the FFA

Most probably due to collidal nature of the waste cooking oil. Different collinary treaments have different impacts on your oil.

I am also working with the production of biodiesel from cooking oil and I'm interested in how the selectivity of biodiesel over that of glycerol can be increased

Using oil with 12.8% FFA and ethanol, The products would be semi-solid at room temperature. No doubt, there was no phase separation.

However, when FFA of the oil is less than 1 but molar ratio is too high, the product will be a single phase too because ethanol is a good solvent for glycerol and biodiesel.

Dear Kanit, what did you observe was due to origin of the fat and not due to reaction conditions, it has nothing, or almost nothing to do with FFA level

Check the %FFA and work with methanol.

Dear Andras, Go back to the post of "Jermaine Omulami added an answer

December 13, 2018

I am using corn oil with an %FFA of 12.775. ..."

Dear Jermaine Omulami,

As per your query, I can infer that you have successfully transesterified the waste cooking oil but failed in separating both biodiesel and glycerol.

This can be explained by the excessive use of alcohol during the transesterification reaction. Both biodiesel and glycerol are soluble in alcohol, and this surplus amount of alcohol is diluting these products and mixing them into a mixture. In that case, try heating the mixture and evaporating the alcohol from it, before decanting the biodiesel-glycerol mixture; then, you have bright chances for getting two separate layers. To avoid this in the future, try using the optimized molar ratio and the exact amount of alcohol (considering extra alcohol during evaporation loss) required for the reaction.

On a quick note, make sure that your reaction is either completed or make sure that the resultant mixture is not soap, as waste cooking oil and alkali-based catalyzed make a good combination for forming soap.

Good luck with your future works.

Regards,

Gokul Raghavendra Srinivasan

Waste cooking oil has a significant amout of FFA ( free fatty acid) which is preffered to react with a base ( NaOH, KOH). In the transesterification many researchers are added base catalyst more popularly KOH and NaOH. Therefore, during the transesterification, a coconsiderable amoimut of soaps are produced through saponification which is dissolved in polar phase of glycerol and thereby reduce the density of glycerol. Reduced density of glycerol intends to mix with biodiesel

Hi

The processing protocols are well explained in the following paper:

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

I hope this helps!

Please go through my paper. This may help you

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

Waste cooking oil has high FFA content. If you want to go for transesterification you have to follow two steps esterification

What should I do when the glycerol is at the top and biodiesel is at the bottom?

Oreoluwa Martins It should not happen as the molecular weight of glycerol is higher. If you get such result, you should find out the conversion rate of your fuel by GC or NMR

Can I get a guide to achieve this?