A new process for catalyst-free production of biodiesel using supercritical methyl acetate

TLDR: In this article, the transesterification reaction of triglycerides with methyl acetate can proceed without catalyst under supercritical conditions, generating FAME and triacetin and its effect was investigated on various fuel characteristics.

About: This article is published in Fuel.The article was published on 2009-07-01 and is currently open access. It has received 193 citations till now. The article focuses on the topics: Triacetin & Methyl acetate.

Figures

Fig. 4. Kinematic viscosity (a), pour point (b) and cold filter plugging point (c) of blends of TA in methyl oleate. The shaded area shows a range to satisfy the BDF standard, while the vertical dotted line the TA content in model BDF.

Fig. 5. Effect of TA content over its mixture with methyl oleate on oxidation stability.

Table 1 Comparison of the fuel properties among methyl oleate, Triacetin (TA) and model BDF for established BDF standards

Fig. 3. Arrhenius plots for reaction rate constants on transesterification and esterification by supercritical methyl acetate at 20MPa. Different methods of calculation were adopted for each reactions. For a comparison, the results with methanolin batch-type reaction system are included [13,14]).

Fig. 1. Yields of FAME and BDF (FAME + TA) from rapeseed oil as treated in supercritical methyl acetate at various temperatures in 20MPa (methyl acetate/oil = 42/1 (mol/mol)).

Fig. 6. Process for catalyst-free biodiesel production with supercritical methyl acetate.

Frequently asked questions

Q1. What are the contributions in "A new process for catalyst-free production of biodiesel using supercritical methyl acetate" ?

In this research, therefore, the authors investigated conversion of rapeseed oil to fatty acid methyl esters ( FAME ) and triacetin by processing of supercritical methyl acetate. In order to study the effect of the triacetin addition to FAME, its effect was investigated on various fuel characteristics. Therefore, by defining BDF as a mixture of methyl oleate with triacetin, the authors can obtain an improved yield of 105 % of BDF by the supercritical methyl acetate, in excess of the yield of the conventional process. 

Q2. What products were used for the calibration of the curve of the standard products?

For the calibration of the curve of the standard products, triolein, 1-oleyl-2,3-diacetyl-glycerol, 1,3-dioleyl-2-acetyl-glycerol, methyl oleate, and triacetin were used. 

Q3. What is the methyl acetate used in the BDF process?

The reactants after the removal of the methyl acetate are a mixture of FAME and triacetin and are defined as BDF in this process. 

Q4. What is the effect of the methyl oleate concentration on the flow of the material?

when the methyl oleate concentration is lower in the mixture, the flow of the material is not impeded, if the earlier solidifying layer is less than a certain thickness. 

Q5. How much BDF is recovered from supercritical processing?

If BDF is defined as a mixture of FAME and triacetin, the BDF recovery from supercriticalprocessing of rapeseed oil with methyl acetate is 105 wt% compared with a theoretical maximum of 125 wt%. 

Q6. What is the kinematic viscosity of the BDF?

In a process producing glycerol as a by-product, when there exists glycerol in the BDF or when glycerides are included in reaction intermediates, the glycerides are the main cause of increased kinematic viscosity. 

Q7. What is the kinematic viscosity of a fuel?

The kinematic viscosity, defined as the dynamic viscosity of the material divided by its density, isan index expressing the stickiness of a fuel. 

Q8. How much BDF can be derived from a unit amount of rapeseed?

when the mixture of FAME and triacetin derived in this process is used as BDF, more BDF can be derived from a unit amount of rapeseed oil. 

Q9. how much kinematic viscosity is the oleic acid?

the kinematic viscosity of themodel BDF when the molar ratio of methyl oleate to triacetin is 3:1 (weight ratio of 4:1, which is 20 wt% of triacetin in Fig. 4) is 4.5 mm2/s, well within the viscosity range determined as the Kyoto Standard and EU Standard (3.5–5 mm2/s). 

Q10. Why is the reaction rate constant lower than that of methanol?

This is because the reactivity of methyl acetate with triglycerides is lower than the case with methanol, when BDF is manufactured by non-catalytic trans-esterification,Moreover, in the esterification reaction of oleic acid as described by FA in Fig. 3 with methylacetate at 270°C, the reaction rate constant was kE = 7.0 × 10−5 sec−1, which is lower than that of kE = 2.9 × 10−3 s−1 achieved with methanol at the same temperature [14]. 

Q11. Why is the cold filter plugging point a mutual index?

Because the cold filter plugging point, just like the pour point, is also an index showing the low temperature fluidity of a fuel, in many cases, there is a mutual relationship with the pour point [21]. 

Q12. How much reactivity can be obtained even with processing at 300°C?

In this reaction, over 90 wt% FAME yield can be obtained even with processing at 300°C, showing that the reactivity is better than in the trans-esterification reaction in Fig. 

Q13. What is the effect of the concentration of triacetin on the pour point?

it was concluded that in triacetin mixtures, the concentration of triacetin has almost no effect on the pour point, except at high concentrations where a lowering effect is observed. 

Q14. What is the pour point of a triacetin mixture?

At this point, when the methyl oleate concentration is high, it does not pour even if the triacetinhas not solidified, because the solidified methyl oleate layer is thick. 

Q15. What is the method for producing glycerol from cooking oils?

In one of these methods, the one-step supercritical methanol method (Saka Process), the trans-esterification reaction of TG without catalysts proceeds to produce FAME and glycerol by processing the raw oils and fats using supercritical methanol. 

Q16. How can triacetin be used to improve fuel properties?

by addition of some additives to improve cetane number, negative effect of triacetin on fuel properties can be dissolved. 

Q17. How much FAME can be obtained after 15 min of processing?

In contrast, a relatively high yield of FAME of 76 wt% can be obtained after 15 min of processing at the highest temperature of 380°C, thereafter the rise in yield levels off and maximizes at 86 wt% after 45 min. 

Q18. What is the effect of triacetin on the kinematic viscosity?

In this respect, in a process where triacetin is produced as a by-product, the effect of triacetin is considered to be small on the kinematic viscosity of the mixture.