Last time I did 7 reactions and I got 2 layers (after removing the methanol), but now I run the same Cat and there is only one layer.
**note:- I took my oil ( waste cooking oil from my friend he says he has done the pretreatment ) now I also have done the pretreatment but only got one layer. I did the same as my friend had done ( heating for 3hr at 120C after filtering the oil)
my catalyst is soiled acid catalyst.
Any advice?
thank you very much
maybe there is something that can interfare with the reaction. Take care that all is pure and clean.
thanks for your replay
every thing clean and dry
but I dont know why its happen like that
water is the main interfere in waste cooking oil and try to pre-treated your catalyst in ethanol before reacting to oil for some time 15-30 min in room temperature and control your reac tion that may not remove your methanol
Waste cooking oil contains some water so before start your experiment you have to remove water by evaporation. One more thing the oil/acyl acceptor /catalyst molar ratio is very important factor which determine the biodiesel formation. so you have fix exact molar ration for the experiment. one more thing you may try with alkali catalyst so you can get results within a hour. all the best
better to evaporate the water, and Surendhiran suggested alkali catalyst which is not suitable for waste cooking oil because producing soap due to water content in oil, if he want to use alkali catalyst then do two step reaction,1st esterification with acids and then use alkali catalysts in the 2nd step.
You should be sure that all is dry. The waste cooking oil normally contain a lot of water, and you had to dry the oil. Personally, I don't recommend heat the oil, because this generate more free fatty acids and more water. I prefer use desiccants like sodium sulfate and washing with ethanol. After that you remove the desiccant and ethanol you should do the reaction immediately.
Definitely there isn't a complete transesterification, because has not been formed glycerin. The waste cooking oil has a high level of water and free fatty acids which seriously affects the transesterificarion reaction. I suggest doing pretreatment of esterification to reduce free fatty acids and then perform the transesterification with a minumum ratio of Alcohol:oil ; 6: 1.
If you did seven reactions, obtaining two layers at the end of each reaction; and now you made two reactions without expected results: Then the problem should be in found in the experimental methodology that you make. Assuming that you are complying properly with the methodology, the only variable that you're not controlling is the oil that you use as feedstock. It is very important to know the water content and free fatty acids present in used oil, because they are the main factors affecting the reactions (esterification / transesterification). It is likely that in the last two experiments, oil quality is very different from the oil you used it in the first experiments. Check out these factors, measuring its content. Good luck.
The quality of your waste cooking oil could be different. Also, may be while you were heating, triglycerides were converted to other compounds, such as ketons. In such case, you will not get glycerol... i may also suggest you to check the fatty acid profile of your oil before transesterification.
It might be possible that the glycerol layer has dissolved into the methanol . Even if not so , check your methanol layer through distillation . The only correct way to find the conversion , is to find how much of glycerol is formed , and i believe glycerol will dissolve into the alcohol that you use .
For the transterification reaction you must take into account the physical-chemical characterization of the initial raw material, specifically the acidity index. If this value is bigger than 3%, a pretreatment (esterification reaction) is necessary to decrease the free fatty acid content. In this reaction an acid catalyst is employed. In the transesterification reaction, a basic catalyst is used, because employing an acid catalysts the extraction times would be extremely long and the temperature and pressure too high. Then I recommend that you measure the acid number, and that this value will define the next steps. In the reaction it is important to define the oil-alcohol ratio and the reaction temperature.
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