**3. Results and discussion**

#### **3.1 Effect of temperature**

The effect of temperature on percent of FAMEs yields from JCL seeds were investigated. The parameters were fixed at 12 MPa of pressure, 1:40 (w/v) of seeds-to-methanol ratio, 30 min of reaction time and at varying temperatures of 180, 200, 240, 280 and 300 °C. The results of in-situ supercritical methanol on percent of FAMEs yields from JCL seeds at various temperatures are shown in Table 1. For simplification, the data are also plotted in Fig. 2.


1conditions: 12 MPa, 30 min and 1:40 (w/v) seeds-to-methanol ratio.

Table 1. In-situ supercritical methanol transesterification1 results from JCL seeds at various temperatures on percent of FAMEs yield and its contents.

The FAMEs analysis was quantified by Agilent Technologies 6890N with HP-5 5% Phenyl Methyl Siloxane capillary column (30 m by 320 µm by 0.25 mm) and a flame ionization detector. Methyl heptadecanoate (10.0 mg; internal standard) was dissolved in 1 ml hexane to prepare the standard solution. Approximately 100 mg crude methyl ester was dissolved in 1 ml standard solution for GC analysis (Hong, 2009). Approximately 1 µl sample was injected into the GC at an oven temperature of 210 C with Helium as the carrier gas. The GC oven was programmed at 210 C, isothermally for 15 min. the FAMEs content was

The biodiesel was characterized by its density, viscosity, high heating value, cloud and pour

The effect of temperature on percent of FAMEs yields from JCL seeds were investigated. The parameters were fixed at 12 MPa of pressure, 1:40 (w/v) of seeds-to-methanol ratio, 30 min of reaction time and at varying temperatures of 180, 200, 240, 280 and 300 °C. The results of in-situ supercritical methanol on percent of FAMEs yields from JCL seeds at various temperatures are shown in Table 1. For simplification, the data are also plotted in

> **Methyl Oleate**

 63.9 10.3 27.9 22.1 3.6 36.1 76.0 13.4 34.6 23.2 4.8 24.0 90.3 16.2 36.4 31.1 6.6 9.7 97.9 18.1 39.5 33.2 7.1 2.1 90.9 16.3 36.6 31.3 6.7 9.1

Table 1. In-situ supercritical methanol transesterification1 results from JCL seeds at various

**Yields (%)** 

**Methyl Linoleate**  **Methyl** 

**Stearate Others** 

*IS*

*AIS* = peak area of internal standard (methyl heptadecanoate) *CIS* = concentration of the internal standard solution, in mg/ml

*VIS* = volume of the internal standard solution used, ml

points and flash points according to ASTM standards.

**FAMEs Methyl** 

1conditions: 12 MPa, 30 min and 1:40 (w/v) seeds-to-methanol ratio.

temperatures on percent of FAMEs yield and its contents.

**Palmitate** 

*A A C V <sup>C</sup> A m*

100% *IS IS IS*

(1)

**2.3 FAMEs analysis** 

**Where:** 

Fig. 2.

**Temperature (°C)** 

calculated by use of the Equation 1:

*∑A* = total peak area of methyl ester

*m* = mass of the sample, in mg

**3. Results and discussion** 

**3.1 Effect of temperature** 

**2.4 Biodiesel properties** 

Fig. 2. In-situ supercritical methanol transesterification results from JCL seeds at various temperatures on percent of FAMEs yield and its contents.

From Table 1, the results indicate that the percent of FAMEs yields obtained at temperatures of 180 to 300 °C were in the range of 63.9 – 97.9%. The saturated FAMEs content of the seed samples are low, which is between 10.3 – 18.1% for methyl palmitate and 3.6 – 7.1% for methyl stearate. Meanwhile, the content of unsaturated FAMEs, methyl oleate and methyl linoleate are considerably higher at 27.9 – 39.5% and 22.1 – 33.2%, respectively. It should be noted that the critical temperature of methanol is at 240 °C and therefore, the conditions at 180 – 200 °C, 240 and >240 – 300 °C represent subcritical, supercritical and postcritical states of the medium, respectively.

At 180 °C, which is the lowest temperature of investigation, low yields of FAMEs (63.9%) were obtained. This observation might be due to the subcritical state of methanol or the instability of the supercritical state of methanol. It was observed that by increasing the reaction temperature to supercritical conditions had a favorable influence on the yield of ester conversion (Demirbas, 2008). Similar results have been reported by Cao et al., (2005), Madras et al., (2004) and Bunyakiat et al., (2006) on soybean oil, sunflower oil and coconut oil, respectively.

Apparently, by increasing the reaction temperature from 200 to 280 °C, the conversion increases significantly with FAMEs yields increased from 76.0 – 97.9%. The higher conversions observed in the supercritical state can be attributed to the formation of a single phase between alcohol and oil (Madras et al., 2004). Under supercritical conditions, the solubility parameter of alcohol reduces and was close to the solubility parameter of oil (Han et al., 2005). According to Petchmala et al., (2008), the increase in temperature causes the polarity of methanol to decrease, as a result of the breakdown of the hydrogen bonding of methanol, leading to an increased in the solubility of fatty acids in methanol. The complete solubility occurs as the temperature approaches the mixture critical temperature, at which point the reaction mixture became homogeneous and reaction took place rapidly. In addition, higher temperature contributed to the decomposition of cell walls, and as a result crude biodiesel yield was increased (Machmudah et al., 2007).

At 300 °C, the percent of FAMEs (90.9%) yields were slightly decreased. This observation was due to the decomposition of polyunsaturated methyl esters and unreacted triglycerides in postcritical methanol at severe high temperature (Tan et al., 2009). This finding was further supported by Xin et al., (2008) who suggested that the favorable reaction temperature adopted

Production of Biodiesel Via In-Situ Supercritical Methanol Transesterification 235

From Table 2, the results indicated that the percent of FAMEs yields obtained at temperatures of 280 °C and pressures of 6-18 MPa was in the range of 80.6 – 97.9% with maximum yields at 12 MPa. The saturated FAMEs content of the seed samples are low, which is between 13.1 – 18.1% for methyl palmitate and 6.1 – 7.1% for methyl stearate. Meanwhile, the content unsaturated FAMEs, methyl oleate and methyl linoleate are

At the lowest pressure of 6 MPa, FAMEs yields are only 80.6%, but increases to 97.9% when the pressure are increased to 12 MPa. The high FAMEs yields achieved at 12 MPa, which is slightly above the critical pressure of methanol (8.09 MPa), might be due to the increase in

Further, increasing the pressure to 18 MPa, the FAMEs yield decreases slightly to 92.5%. After the pressure increased to a specific level, the increase of pressure does not cause an obvious improvement in the FAME yield (He et al., 2007). This phenomenon might be due to the maximum solubility and/or hydrogen donor ability of the solvent that has been

As the pressure of the system increased, the solubility parameter of the methanol decreased and is close to the solubility parameter of the oil, thus forming a single phase between the alcohol and the oil. Based on these results, it can be seen that the fact that both temperature and pressure play an important role that contributes to high extraction yield, with the later being more prominent. Based on these results, it can be seen that the fact that both temperature and pressure play an important role that contributes to high yield, with the

Table 3 and Fig. 4 shows the effect of reaction time on percent of FAMEs yields from JCL seeds using in-situ supercritical methanol transesterification. The reaction conditions were fixed based on maximum yields at optimized conditions discussed previously, i.e. 280 °C of

> **Methyl Oleate**

Table 3. In-situ supercritical methanol transesterification1 results of JCL seeds at various

From Table 3 and Fig. 4, the results indicated that the percent of FAMEs yields obtained at temperatures of 280 °C, pressures of 12.7 MPa, seeds-to-methanol ratio of 1:40 (w/v) and reaction time of 5 – 35 min was in the range of 88.4 – 97.9% with maximum yields at 30 min.

88.4 15.0 38.5 28.6 6.3 11.6 94.2 16.6 40.5 30.6 6.5 5.2 96.0 17.2 39.6 32.0 7.2 4.0 97.9 18.1 39.5 33.2 7.1 2.1 93.1 16.6 38.8 30.8 6.9 6.9

**Yields (%)** 

**Methyl Linoleate**  **Methyl** 

**Stearate Others** 

considerably higher at 38.6 – 47.1% and 20.4 – 33.2%, respectively.

solvent power of methanol with increasing pressure.

achieved regardless of high pressure employed.

later being more prominent.

**3.3 Effects of reaction time** 

**Reaction time (min)**

temperature and 12.7 MPa of pressure.

**FAMEs Methyl** 

**Palmitate** 

1conditions: 280 °C, 12.7 MPa and 1:40 (w/v) seeds-to-methanol ratio.

reaction times on percent of FAMEs yield and its contents.

in supercritical methanol method should be lower than 300 °C. Reaction temperature at above 380 ºC is insuitable for transesterification reaction because the oil and methyl esters tend to decompose at the highest rate. Furthermore, Kusdiana and Saka's (2001) pointed out that saturated and unsaturated FAMEs undergo side reactions such as thermal decomposition and dehydrogenation reactions at temperature >400 °C and >350 °C, respectively. In these experiments, the temperature used was lower than that of Kusdiana and Saka's work and the side reactions did not occur since the temperature was below 300 °C. Furthermore, at 300 °C, a strong burning smell of the extract was detected. Hence, at this point, there is no reason to further increase the extraction temperature beyond 280 °C.

#### **3.2 Effects of pressure**

The results of in-situ supercritical methanol transesterification on percent of FAMEs yields from JCL seeds at various pressures are shown in Table 2. For simplification, the data are also being plotted and is shown in Fig. 3. The temperature was fixed at 280 °C based on the maximized yield conditions from the previous experiment.


1conditions: 280 °C, 30 min and 1:40 (w/v) seeds-to-methanol ratio.

Table 2. In-situ supercritical methanol transesterification1 results from JCL seeds at various pressures on FAMEs yield and its contents.

Fig. 3. In-situ supercritical methanol transesterification results from JCL seeds at various pressures on FAMEs yield and its contents.

in supercritical methanol method should be lower than 300 °C. Reaction temperature at above 380 ºC is insuitable for transesterification reaction because the oil and methyl esters tend to decompose at the highest rate. Furthermore, Kusdiana and Saka's (2001) pointed out that saturated and unsaturated FAMEs undergo side reactions such as thermal decomposition and dehydrogenation reactions at temperature >400 °C and >350 °C, respectively. In these experiments, the temperature used was lower than that of Kusdiana and Saka's work and the side reactions did not occur since the temperature was below 300 °C. Furthermore, at 300 °C, a strong burning smell of the extract was detected. Hence, at this point, there is no reason to

The results of in-situ supercritical methanol transesterification on percent of FAMEs yields from JCL seeds at various pressures are shown in Table 2. For simplification, the data are also being plotted and is shown in Fig. 3. The temperature was fixed at 280 °C based on the

> **Methyl Oleate**

 80.6 13.1 41.0 20.4 6.1 19.4 95.6 15.7 47.1 26.3 6.5 4.4 97.9 18.1 39.5 33.2 7.1 2.1 93.5 16.0 38.4 32.1 7.0 6.5 92.5 16.0 38.6 31.1 6.8 7.5

Table 2. In-situ supercritical methanol transesterification1 results from JCL seeds at various

**6 8 12 16 18**

**Pressure (MPa) Total FAMEs Methyl palmitate Methyl oleate Methyl linoleate Methyl stearate Others** Fig. 3. In-situ supercritical methanol transesterification results from JCL seeds at various

**Yields (%)**

**Methyl Linoleate** **Methyl** 

**Stearate Others** 

further increase the extraction temperature beyond 280 °C.

maximized yield conditions from the previous experiment.

**FAMEs Methyl** 

1conditions: 280 °C, 30 min and 1:40 (w/v) seeds-to-methanol ratio.

pressures on FAMEs yield and its contents.

pressures on FAMEs yield and its contents.

**Yield (%)**

**Palmitate**

**3.2 Effects of pressure** 

**Pressure (MPa)** 

From Table 2, the results indicated that the percent of FAMEs yields obtained at temperatures of 280 °C and pressures of 6-18 MPa was in the range of 80.6 – 97.9% with maximum yields at 12 MPa. The saturated FAMEs content of the seed samples are low, which is between 13.1 – 18.1% for methyl palmitate and 6.1 – 7.1% for methyl stearate. Meanwhile, the content unsaturated FAMEs, methyl oleate and methyl linoleate are considerably higher at 38.6 – 47.1% and 20.4 – 33.2%, respectively.

At the lowest pressure of 6 MPa, FAMEs yields are only 80.6%, but increases to 97.9% when the pressure are increased to 12 MPa. The high FAMEs yields achieved at 12 MPa, which is slightly above the critical pressure of methanol (8.09 MPa), might be due to the increase in solvent power of methanol with increasing pressure.

Further, increasing the pressure to 18 MPa, the FAMEs yield decreases slightly to 92.5%. After the pressure increased to a specific level, the increase of pressure does not cause an obvious improvement in the FAME yield (He et al., 2007). This phenomenon might be due to the maximum solubility and/or hydrogen donor ability of the solvent that has been achieved regardless of high pressure employed.

As the pressure of the system increased, the solubility parameter of the methanol decreased and is close to the solubility parameter of the oil, thus forming a single phase between the alcohol and the oil. Based on these results, it can be seen that the fact that both temperature and pressure play an important role that contributes to high extraction yield, with the later being more prominent. Based on these results, it can be seen that the fact that both temperature and pressure play an important role that contributes to high yield, with the later being more prominent.

**3.3 Effects of reaction time**  Table 3 and Fig. 4 shows the effect of reaction time on percent of FAMEs yields from JCL seeds using in-situ supercritical methanol transesterification. The reaction conditions were fixed based on maximum yields at optimized conditions discussed previously, i.e. 280 °C of temperature and 12.7 MPa of pressure.


1conditions: 280 °C, 12.7 MPa and 1:40 (w/v) seeds-to-methanol ratio.

Table 3. In-situ supercritical methanol transesterification1 results of JCL seeds at various reaction times on percent of FAMEs yield and its contents.

From Table 3 and Fig. 4, the results indicated that the percent of FAMEs yields obtained at temperatures of 280 °C, pressures of 12.7 MPa, seeds-to-methanol ratio of 1:40 (w/v) and reaction time of 5 – 35 min was in the range of 88.4 – 97.9% with maximum yields at 30 min.

Production of Biodiesel Via In-Situ Supercritical Methanol Transesterification 237

**Methyl Oleate** 

**1:15** 89.0 15.2 37.4 29.8 6.6 11.0 **1:20** 94.4 16.9 38.8 31.6 7.1 5.6 **1:30** 95.9 17.5 38.6 32.3 7.5 4.1 **1:40** 97.9 18.1 39.5 33.2 7.1 2.1 **1:45** 97.0 17.4 40.1 32.3 7.2 3.0

Table 4. In-situ supercritical methanol transesterification1 results of JCL seeds at various

Fig. 5. In-situ supercritical methanol transesterification results of JCL seeds at various seeds-

From Table 4 and Fig. 5, the results indicated that the percent of FAMEs yields obtained at temperatures of 280 °C, pressures of 12.7 MPa, reaction time of 30 min and at various seedsto-methanol ratio (1:15 – 1:45 w/v) was in the range of 89.0 – 97.9%, with maximum yields at 1:40 (w/v). The saturated FAMEs content of the seed samples are low, which is between 15.2 – 18.1% for methyl palmitate and 6.6 – 7.5% for methyl stearate. Meanwhile, the content unsaturated FAMEs, methyl oleate and methyl linoleate are considerably higher at 37.4 –

Obviously, at the lowest seeds-to-methanol ratio of 1:15 (w/v), the percent of FAMEs yields was relatively low (89.0%) and increased with increasing seeds-to-methanol ratio. When the methanol content in the supercritical fluids increased, the percent conversion of methyl ester also increased. The higher methanol content is favorable not only because more molecules of methanol surround the oil molecules but also because it contributes to the lower critical temperature of the mixture. Maximum percent of crude biodiesel and FAMEs yields were

**FAMEs Methyl** 

1 conditions: 280 °C, 12.7 MPa, 30 min reaction time.

**Palmitate** 

seed-to-methanol ratios on percent of FAMEs yield and its contents.

to-methanol ratios on percent of FAMEs yield and FAMEs contents.

39.5% and 29.8 – 33.2%, respectively.

**Yields (%)** 

**Methyl Linoleate**  **Methyl** 

**Stearate Others** 

**Seed-tomethanol ratio (w/v)** 

The saturated FAMEs content of the seed samples are low, which is between 15.0 – 18.1% for methyl palmitate and 6.3 – 7.2% for methyl stearate. Meanwhile, the content unsaturated FAMEs, methyl oleate and methyl linoleate are considerably higher at 38.5 – 39.5% and 28.6 – 33.2%, respectively.

Fig. 4. In-situ supercritical methanol transesterification results from JCL seeds at various reaction times on percent of FAMEs yield and its contents.

From the results, it can be seen that the percent of FAMEs yields were only 88.4% at 5 min of reaction time. According to Saka and Kusdiana (2001), in the common method, the reaction is initially slow because of the two-phase nature of the methanol/oil system, and slows even further because of the polarity problem even with the help of an acid or an alkali catalyst. However, as described in this work, supercritical method can readily solve these problems because of the supercritical temperature and pressure employed. It can be seen that the conversion was increased in the reaction time ranges between 5 and 30 min with the percent of FAMEs yields showed a slight increase in the range of 88.4 – 97.9%.

Further, the results indicated that an extension of the reaction time from 30 to 35 min had leads to a reduction in the FAMEs yield (93.1%). This is because longer reaction time enhanced the hydrolysis of esters (reverse reaction of transesterification), resulted in loss of esters as well as causing more fatty acids to form soap (Eevera et al., 2009). Hence, for this process, there is no reason to prolong the reaction time beyond 30 min. Thus, the reaction time of 30 min can be considered as the economic reaction time by considering the percent of crude biodiesel and FAMEs yields being achieved.

#### **3.4 Effects of seeds-to-methanol ratio**

Table 4 and Fig. 5 shows the effect of seeds-to-methanol ratio on percent of FAMEs yields from JCL seeds using in-situ supercritical methanol transesterification. The reaction conditions were fixed based on maximized yields at optimized conditions discussed previously, i.e. 280 °C of temperature and 12.7 MPa and 30 min of reaction time with varying seeds-to-methanol ratio of 1:20, 1:30 and 1:40 (w/v).


1 conditions: 280 °C, 12.7 MPa, 30 min reaction time.

236 Biodiesel – Feedstocks and Processing Technologies

The saturated FAMEs content of the seed samples are low, which is between 15.0 – 18.1% for methyl palmitate and 6.3 – 7.2% for methyl stearate. Meanwhile, the content unsaturated FAMEs, methyl oleate and methyl linoleate are considerably higher at 38.5 – 39.5% and 28.6

Fig. 4. In-situ supercritical methanol transesterification results from JCL seeds at various

From the results, it can be seen that the percent of FAMEs yields were only 88.4% at 5 min of reaction time. According to Saka and Kusdiana (2001), in the common method, the reaction is initially slow because of the two-phase nature of the methanol/oil system, and slows even further because of the polarity problem even with the help of an acid or an alkali catalyst. However, as described in this work, supercritical method can readily solve these problems because of the supercritical temperature and pressure employed. It can be seen that the conversion was increased in the reaction time ranges between 5 and 30 min with the percent of FAMEs yields showed a slight increase in the range of

Further, the results indicated that an extension of the reaction time from 30 to 35 min had leads to a reduction in the FAMEs yield (93.1%). This is because longer reaction time enhanced the hydrolysis of esters (reverse reaction of transesterification), resulted in loss of esters as well as causing more fatty acids to form soap (Eevera et al., 2009). Hence, for this process, there is no reason to prolong the reaction time beyond 30 min. Thus, the reaction time of 30 min can be considered as the economic reaction time by considering the percent

Table 4 and Fig. 5 shows the effect of seeds-to-methanol ratio on percent of FAMEs yields from JCL seeds using in-situ supercritical methanol transesterification. The reaction conditions were fixed based on maximized yields at optimized conditions discussed previously, i.e. 280 °C of temperature and 12.7 MPa and 30 min of reaction time with

reaction times on percent of FAMEs yield and its contents.

of crude biodiesel and FAMEs yields being achieved.

varying seeds-to-methanol ratio of 1:20, 1:30 and 1:40 (w/v).

**3.4 Effects of seeds-to-methanol ratio** 

– 33.2%, respectively.

88.4 – 97.9%.

Table 4. In-situ supercritical methanol transesterification1 results of JCL seeds at various seed-to-methanol ratios on percent of FAMEs yield and its contents.

Fig. 5. In-situ supercritical methanol transesterification results of JCL seeds at various seedsto-methanol ratios on percent of FAMEs yield and FAMEs contents.

From Table 4 and Fig. 5, the results indicated that the percent of FAMEs yields obtained at temperatures of 280 °C, pressures of 12.7 MPa, reaction time of 30 min and at various seedsto-methanol ratio (1:15 – 1:45 w/v) was in the range of 89.0 – 97.9%, with maximum yields at 1:40 (w/v). The saturated FAMEs content of the seed samples are low, which is between 15.2 – 18.1% for methyl palmitate and 6.6 – 7.5% for methyl stearate. Meanwhile, the content unsaturated FAMEs, methyl oleate and methyl linoleate are considerably higher at 37.4 – 39.5% and 29.8 – 33.2%, respectively.

Obviously, at the lowest seeds-to-methanol ratio of 1:15 (w/v), the percent of FAMEs yields was relatively low (89.0%) and increased with increasing seeds-to-methanol ratio. When the methanol content in the supercritical fluids increased, the percent conversion of methyl ester also increased. The higher methanol content is favorable not only because more molecules of methanol surround the oil molecules but also because it contributes to the lower critical temperature of the mixture. Maximum percent of crude biodiesel and FAMEs yields were

Production of Biodiesel Via In-Situ Supercritical Methanol Transesterification 239

**Peak No. Name Wt%**  1 Methyl Palmitate 18.46 2 Methyl Oleate 40.41 3 Methyl Linoleate 33.91 4 Methyl stearate 7.22

Vegetable oil methyl esters, commonly referred to as ''biodiesel'' are prominent candidates as alternative Diesel fuels. Biodiesel is technically competitive with or offers technical advantages compared to conventional petroleum Diesel fuel. The vegetable oils, as alternative engine fuels, are all extremely viscous with viscosities ranging from 10 to 20 times greater than that of petroleum Diesel fuel (Demirbas, 2003). The purpose of the transesterification process is to lower the viscosity of the oil. In this study, in-situ supercritical methanol transesterification for production of biodiesel from Jatropha curcas L. (JCL) seeds was generate via 1000 ml high-temperature high-pressure batch-wise reactor system in an absence of catalyst. The reaction conditions were conducted at 280 °C of temperature, 12.7 MPa of pressure, 30 min of reaction time and 1:40 of seeds-to-methanol ratio at 450 rpm of stirring rate. Samples of the biodiesel obtained from the in-situ experiment were determined using reference methods published by American Society for Testing and Materials (ASTM) D6751. In order to ensure that it can be used in diesel engine without any modification, the properties of biodiesel produced from this in-situ transesterification reaction was comparable with fuel properties of No. 2 Diesel. Fuel

IS: Internal standard (Methyl heptadecanoate)

**3.5.1 Biodiesel characterization** 

Fig. 6. Total ion current chromatogram of the biodiesel.

Table 5. Names, structure and compositions of *Jatropha curcas* L. FAMEs.

obtained at a 1:40 (w/v) of seeds-to-methanol ratio. This is a significant difference from conventional catalytic reaction for which at least 1 h of reaction time is needed to attain the same yield. In this reaction, an excess of methanol was used in order to shift the equilibrium in the direction of the products (Demirbas, 2007). Kusdiana and Saka (2001) have suggested that higher molar ratios of methanol to oil also result in a more efficient transesterification reaction. The results obtained shows good agreement with previous work, where maximum conversion was obtained for rapeseed oil (Saka and Kusdiana, 2001) at molar ratio of 42:1, for various vegetable oils (Demirbas, 2002; Diasakou et al., 1998; Ma, 1998) and linseed oil (Varma and Madras, 2007) at molar ratio of 41:1 and 40:1, respectively. According to Bunyakiat et al., (2006), when the methanol content in the supercritical fluids increased, the percent of methyl esters conversion also increased.

The higher methanol content is favorable not only because more molecules of methanol surround the oil molecules but also because it contributes to the lower critical temperature of the mixture. It can be seen that an increment in seed-to-methanol ratio can enhance biodiesel yield due to higher contact area between methanol and triglycerides. However, when the ratio is beyond 40, the yield of biodiesel begins to decrease substantially. This might be due to the restriction of the reaction equilibrium and difficulties in separating excessive methanol from methyl esters and glycerol, which subsequently lowered the yield of biodiesel (Tan et al., 2009).

Moreover, it was observed that for high seeds-to-methanol ratio added the set up required longer time for the subsequent separation stage since separation of the FAMEs layer from the organic layer becomes more difficult with the addition of a large amount of methanol. This is due to the fact that methanol, with one polar hydroxyl group, can work as an emulsifier that enhances emulsion. Operating beyond the optimal value, the ester yield would not be increased but will result in additional cost for methanol recovery (Eevera et al., 2009). Therefore, increasing the seeds-to-methanol ratio is another important parameter affecting the FAMEs yield. This report is in line with the results of many investigations based on neat vegetable oils (Freedman et al., 1984; Zhang et al., 2003; Leung et al. 2006, Eevera et al., 2009).

#### **3.5 Biodiesel characterization**

The biodiesel obtained through the one-step supercritical methanol extraction and transesterification in-situ process in this experiment was dark yellow in color. Compositions of samples were analyzed by GC. Figure 6 shows the total ion current chromatogram of the biodiesel. Furthermore, Table 5 shows the names, structure and compositions of *Jatropha curcas* L. FAMEs.

Fig. 6 depicts the gas chromatographic evaluation of the FAMEs produced over the course of reaction. The methyl esters analyzed by GC appear in the retention time of less than 15 min in the chromatograms. The weight percentages were similar for all of the variables condition; temperature, pressure, reaction time and seeds-to-methanol ratio of in-situ transesterification, as suggested by Carrapiso et al., (2000) that transesterification was random. The average saturated FAMEs content of the seed samples are low: 18.1% for methyl palmitate (C17:0) and 7.1% for methyl stearate (C19:0). The average content of the unsaturated FAMEs, methyl oleate (C19:1) and methyl linoleate (C19:2) are considerably higher at 39.5 and 33.2%, respectively which are comparable to the fatty acid composition in crude JCL oil feedstock. Depending on the origin, either oleic or linoleic acid content is higher. In this case, the seed oil belongs to the oleic or linoleic acid group, to which similar to the majority of vegetable oils (Carrapiso et al., 2000).

IS: Internal standard (Methyl heptadecanoate)

obtained at a 1:40 (w/v) of seeds-to-methanol ratio. This is a significant difference from conventional catalytic reaction for which at least 1 h of reaction time is needed to attain the same yield. In this reaction, an excess of methanol was used in order to shift the equilibrium in the direction of the products (Demirbas, 2007). Kusdiana and Saka (2001) have suggested that higher molar ratios of methanol to oil also result in a more efficient transesterification reaction. The results obtained shows good agreement with previous work, where maximum conversion was obtained for rapeseed oil (Saka and Kusdiana, 2001) at molar ratio of 42:1, for various vegetable oils (Demirbas, 2002; Diasakou et al., 1998; Ma, 1998) and linseed oil (Varma and Madras, 2007) at molar ratio of 41:1 and 40:1, respectively. According to Bunyakiat et al., (2006), when the methanol content in the supercritical fluids increased, the

The higher methanol content is favorable not only because more molecules of methanol surround the oil molecules but also because it contributes to the lower critical temperature of the mixture. It can be seen that an increment in seed-to-methanol ratio can enhance biodiesel yield due to higher contact area between methanol and triglycerides. However, when the ratio is beyond 40, the yield of biodiesel begins to decrease substantially. This might be due to the restriction of the reaction equilibrium and difficulties in separating excessive methanol from methyl esters and glycerol, which subsequently lowered the yield

Moreover, it was observed that for high seeds-to-methanol ratio added the set up required longer time for the subsequent separation stage since separation of the FAMEs layer from the organic layer becomes more difficult with the addition of a large amount of methanol. This is due to the fact that methanol, with one polar hydroxyl group, can work as an emulsifier that enhances emulsion. Operating beyond the optimal value, the ester yield would not be increased but will result in additional cost for methanol recovery (Eevera et al., 2009). Therefore, increasing the seeds-to-methanol ratio is another important parameter affecting the FAMEs yield. This report is in line with the results of many investigations based on neat vegetable oils (Freedman et al., 1984; Zhang et al., 2003; Leung et al. 2006, Eevera et al., 2009).

The biodiesel obtained through the one-step supercritical methanol extraction and transesterification in-situ process in this experiment was dark yellow in color. Compositions of samples were analyzed by GC. Figure 6 shows the total ion current chromatogram of the biodiesel. Furthermore, Table 5 shows the names, structure and compositions of *Jatropha* 

Fig. 6 depicts the gas chromatographic evaluation of the FAMEs produced over the course of reaction. The methyl esters analyzed by GC appear in the retention time of less than 15 min in the chromatograms. The weight percentages were similar for all of the variables condition; temperature, pressure, reaction time and seeds-to-methanol ratio of in-situ transesterification, as suggested by Carrapiso et al., (2000) that transesterification was random. The average saturated FAMEs content of the seed samples are low: 18.1% for methyl palmitate (C17:0) and 7.1% for methyl stearate (C19:0). The average content of the unsaturated FAMEs, methyl oleate (C19:1) and methyl linoleate (C19:2) are considerably higher at 39.5 and 33.2%, respectively which are comparable to the fatty acid composition in crude JCL oil feedstock. Depending on the origin, either oleic or linoleic acid content is higher. In this case, the seed oil belongs to the oleic or linoleic acid group, to which similar

percent of methyl esters conversion also increased.

of biodiesel (Tan et al., 2009).

**3.5 Biodiesel characterization** 

to the majority of vegetable oils (Carrapiso et al., 2000).

*curcas* L. FAMEs.

Fig. 6. Total ion current chromatogram of the biodiesel.


Table 5. Names, structure and compositions of *Jatropha curcas* L. FAMEs.

### **3.5.1 Biodiesel characterization**

Vegetable oil methyl esters, commonly referred to as ''biodiesel'' are prominent candidates as alternative Diesel fuels. Biodiesel is technically competitive with or offers technical advantages compared to conventional petroleum Diesel fuel. The vegetable oils, as alternative engine fuels, are all extremely viscous with viscosities ranging from 10 to 20 times greater than that of petroleum Diesel fuel (Demirbas, 2003). The purpose of the transesterification process is to lower the viscosity of the oil. In this study, in-situ supercritical methanol transesterification for production of biodiesel from Jatropha curcas L. (JCL) seeds was generate via 1000 ml high-temperature high-pressure batch-wise reactor system in an absence of catalyst. The reaction conditions were conducted at 280 °C of temperature, 12.7 MPa of pressure, 30 min of reaction time and 1:40 of seeds-to-methanol ratio at 450 rpm of stirring rate. Samples of the biodiesel obtained from the in-situ experiment were determined using reference methods published by American Society for Testing and Materials (ASTM) D6751. In order to ensure that it can be used in diesel engine without any modification, the properties of biodiesel produced from this in-situ transesterification reaction was comparable with fuel properties of No. 2 Diesel. Fuel

Production of Biodiesel Via In-Situ Supercritical Methanol Transesterification 241

respectively) at 280 °C and then decreased with increasing temperature. The loss was caused by thermal decomposition, dehydrogenation and other side reactions. For the effect of pressure, the crude biodiesel and FAMEs yield increased with increasing pressure. Above 12 MPa, no improvement of both yields was observed. The optimum pressure was thus fixed at 12.7 MPa in this experiment. For the effect of reaction time, it can be seen that the conversion was increased in the reaction time ranges between 5 and 30 min, and thereafter reduced as a representative of the equilibrium conversion. The excess reaction time did not promote the conversion but favors the reverse reaction of transesterification which resulted in a reduction in the ester yield. The optimal FAMEs yield was found to be 97.9% in 30 min. For the effect of seeds-to-methanol ratio, the maximum crude biodiesel and FAMEs yields were obtained at a 1:40 of seeds-to-methanol ratio. It can be seen that an increment in seed-tomethanol ratio can enhance biodiesel yield due to higher contact area between methanol and triglycerides. However, when the ratio is beyond 40, the yield of biodiesel begins to

The merit of this method is that this new process just requires a single process, where the normal oil extraction process can be avoided. In addition, because of non-catalytic process, the purification of products after transesterification reaction is much simple, compared to the common method. Therefore, this new process can offer an alternative way to convert the

The authors ackonowledge the scholarship fund provided by Ministry of Science, Technology and Innovative under the National Science Fellowship (NSF), Universiti Teknologi MARA and Fundamental Research Grant Scheme (FRGS grant no: 600-

Ayuso, L. E. G. & Castro M. D. L. (1999). A multivariate study of the performance of a

Berchmans, H. J. & Hirata, S. (2008). Biodiesel production from crude *Jatropha curcas* L. seed

Bunyakiat, K.; Makmee, S.; Sawangkeaw, R. & Ngamprasertsith. (2006). Continous

Cao, W.; Han, H. & Zhang, J. (2005). Preparation of biodiesel from soybean oil using

Cao, X. & Ito, Y. (2003). Supercritical fluid extraction of grape seed oil and subsequent

Carrapiso, A. I. and García, C. (2000). Development in lipid analysis: some new extraction techniques and in situ transesterification. *Lipids*, Vol. 35, pp. 1167–1177.

supercritical methanol and co-solvent. *Fuel*, Vol. 84(4), pp. 347-351.

microwave-assissted Soxhlet extractor for olive seeds. *Analytica Chimica Acta*, Vol.

oil with a high content of free fatty acids. *Bioresource Technology*, Vol. 99, pp. 1716–

production of biodiesel via transesterification from vegetable oils in supercritical

separation of free fatty acids by high-speed counter-current chromatography.

fruits directly to methyl esters by a simpler-shorter production process.

RMI/ST/FRGS 5/3/Fst (2/2009)) for their financial support.

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decrease substantially.

**5. Acknowledgment** 

**6. References** 

1721.

382(3), pp. 309-316.


properties of No. 2 Diesel, JCL biodiesel and ASTM D6751 derived biodiesel standards is shown in Table 6 for comparison.

aDemirbas, (2008); Encinar, (2005); Vyas, (2009)

bGhadge and Rehman, (2005); Vyas, (2009); Sahoo and Das, (2009)

Table 6. Fuel properties of No. 2 Diesel and JCL biodiesel.

The properties of biodiesel produced from this in-situ supercritical methanol transesterification were comparable with fuel properties of commercial No. 2 Diesel. It was found that specific gravity of JCL biodiesel was 0.87 g/cm3 and it falls between the ASTM D6751 ranges. Fuel injection equipment operates on a volume metering system, hence a higher density for biodiesel results in the delivery of a slightly greater mass of fuel (Demirbas, 2005). The kinematic viscosity was 5.27 cSt. Among the general parameters for biodiesel the viscosity of FAMEs can go very high levels and hence it is important to control it within an acceptable level to avoid negative impacts on fuel injector's system performance (Murugesan et al., 2009). The flash point was determined to be at 100 °C. Since biodiesel has a higher flash point than diesel, it is a safer fuel than diesel. Addition of a small quantity of biodiesel with diesel increases the flash point of diesel which can result in improved fire safety for transport purpose (Lu et al., 2009) and it is safer to store biodiesel-diesel blends in comparison to diesel alone (Sahoo et al., 2009). Meanwhile, the pour point was measured to be 0 °C which was slightly higher than that of No. 2 Diesel fuel. This might be due to the presence of wax, which begins to crystallize with the decrease in temperature. This finding was agreed with Vyas et al., (2009) and Raheman and Ghadge, (2007). The problems of higher pour point of JCL biodiesel could be overcome by blending with diesel. The cloud point was reported to be -2.06 °C. The cloud point depends upon the feedstock used and must be taken into consideration if the fuel is to be used in cold environments (Fernando et al., 2007). The calorific value of JCL biodiesel was 39.3 MJ/kg, which was almost 88% of the calorific value of diesel (44.8 MJ/kg). The lower calorific value of JCL is because of the presence of oxygen in the molecular structure, which is confirmed by elemental analysis also. Furthermore, the presence of oxygen in the biodiesel helps for complete combustion of fuel in the engine. These findings were also agreed by Sinha et al., (2008). Therefore, they could be excellent substitutes and blends of No. 2 diesel fuel.
