I've conducted numerous Transesterification experiments aimed at producing biodiesel, particularly focusing on the utilization of used cooking oil. Before these experiments, I ensured to assess the Free Fatty Acid (FFA) content and esterify the oil if necessary. Throughout the experimentation process, I explored various oils, catalysts, reaction durations, and oil to methanol molar ratios. Interestingly, while employing heterogeneous catalysts, I consistently encountered a lack of biodiesel-glycerol separation, with the exception of using KOH as a homogeneous catalyst. However, when adopting simple ratios like 1:3 (1 part oil to 3 parts methanol), a distinct separation of biodiesel and glycerol occurred. Could someone kindly clarify this observation? Additionally, I'd appreciate details on the volume of oil and methanol utilized in these experiments.
Different literature shows different result of molar ratio. Numbers of parameters for optimum yield such as molar ratio, catalyst concentration, reaction duration reaction temperature etc.The trend in biodiesel yield with increase in methanol-to-oil ratio is found to be consistent with suggesting that molar ratio of methanol-to-oil has significant effect on biodiesel yield. Increasing methanol to oil molar ratio increased the yield of biodiesel production. Oil to methanol molar ratio of 1:1 gave the optimum yield of biodiesel among them. Approximately 100 pounds of oil or fat is reacted with 10 pounds of short-chain alcohol (usually methanol) in the presence of a catalyst (usually sodium hydroxide [NaOH] or potassium hydroxide [KOH]) to produce 100 pounds of biodiesel and 10 Pounds of glycerol.
https://www.researchgate.net/figure/The-effect-of-oil-to-methanol-molar-ratio-on-biodiesel-production-Bars-indicate-mean_fig1_236236249#:~:text=The%20results%20show%20that%20increasing,oil%20to%20methanol%20molar%20ratio.
https://www.researchgate.net/publication/321758415_EFFECT_OF_ALCOHOL_RATIO_AND_REACTION_TEMERATURE_ON_THE_BIODIESEL_PRODUCTION_FROM_USED_COOKING_OIL
https://www.researchgate.net/figure/Biodiesel-yield-at-methanol-to-oil-ratio-31-at-different-reaction-times_fig3_323044104
Prem Baboo Firstly thank you for the response and yes sir what you said is absolutely right. The paper you referred to uses KOH/NaOH, which are homogeneous catalysts. As you rightly mentioned, using molar ratios for oil to methanol works with homogeneous catalysts. However, when it comes to heterogeneous catalysts, molar ratios DO NOT work.
conversion has a main control on separability, would you have low, but reversible conversion mono- and di-glycerides do act as surface active agents. From that point onward separation is controlled by colloid principles. But working on strict "equal" molar ratios is difficult to get to final level of achievable conversion level
@Andras Kovacs
Thank you for the explanation sir. However, even when we use methanol in excess with adjusted molar ratios, we still do not achieve the desired separation. So according to my
understanding and the numerous experiments conducted with heterogeneous catalysts to produce biodiesel from used cooking oil, it is evident that the molar ratios (oil to methanol) do not yield biodiesel under standard conditions. Could you provide any further insights on the same?
starting from used cooking oil the situation is more complicated, but still dependent on colloid characteristics, especially of phosphatides and oxidation products. The only way is to conduct targeted experiments, with unit operational skills.