**5.2.4 Effect of catalyst loading on methyl esters conversion**

306 Biodiesel – Feedstocks and Processing Technologies

The feed stream flow rates for the test run were chosen carefully in order to avoid any column flooding problem. The flow rate, which is inversely related to retention time, is used as an experimental factor to interpret the reaction conversion with the liquid retention time. The flow rate achieved in the experimental runs varied from 5 to 7 mL/min. The retention time varied from about 4 to 8 min. These values may not be the actual reaction time because of some reaction that takes place in the reboiler. Since the concentrations of methanol and catalyst were very small in the liquid phase of the reboiler, it was not possible to determine the actual retention time of reactants and catalyst in the reboiler. The effect of flow rate was mainly on the production of methyl ester of the reactor. The % weight of methyl ester decreased while the flow rate increased since the retention time is less. For the RD operation of setup in this study, the feed flow rate should not be higher 6mL/min in order to avoid flooding in column and this rate

> Methyl esters Conversion (%), Cottonseed oil

4 92 95 89 6 94 96 93 8 94 96 93 Molar ratio of Methanol to Oil = 6:1, Catalyst (KOH) = 1% (by wt. of oil), Flow rate = 6ml/min,

> 0 2 4 6 8 10 12 14 **Reaction Time, min.**

Methyl esters Conversion (%), Coconut oil

> Castor oil Cottonsee oil Coconut oil

were considered as optimum range of operation.

Reaction Time (min.)

Temperature = 60oC

80

Optimum Reaction time = 6min.

85

90

**Methylester conversion(%**

95

100

**5.2.3 Effect of reaction time on methyl ester conversion** 

Methyl esters Conversion (%) , Castor oil

Table 12. Effect of Reaction time on methyl ester conversion

Fig. 12. Effect of reaction time on methyl ester conversion

The type of catalyst and the amount of catalyst has a great impact on formation of biodiesel. The adequate catalyst loading is necessary to obtain the maximum conversion of triglycerides to methyl esters. In the above experimentation, different types of catalysts with different catalyst loadings were utilized for transesterification reaction and their effects were studied. In the course of the tests, it is observed that addition of excess amount of catalyst, give rise to the formation of an emulsion, which has increased the viscosity and led to the formation of gel.


a. Effect of catalyst (KOH) loading on methyl ester conversion

Methanol to oil molar ratio = 6, Temperature =60oC, Catalyst loadings used for experimentation = 1% , 1.5% and 2% KOH by wt of oil

Table 13. Effect of catalysts loadings on methyl ester conversion

Fig. 13. Effect of catalyst (KOH) loading on Methyl ester Conversion

b. Effect of catalyst(NaOH) loading on methyl ester conversion

Transesterification by Reactive Distillation for Synthesis and Characterization of Biodiesel 309

Castor oil Cottonseed oil Coconut oil

Methyl esters Conversion (%), Coconut oil

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 **Catalyst loading(wt%)**

Fig. 15. Effect of catalyst (Amberlyst-15) loading on Methyl ester Conversion

atmospheric pressure and a 6:1 methanol-to-oil initial molar ratio.

Methyl esters Conversion (%), Castor oil

It can be observed that there was no rise in ME conversion when catalyst loading was increased from 3 to 6 wt%. The highest conversion was achieved at catalyst loading of

**5.2.5 Effect of reaction time on methyl ester conversion using amberlyst -15 catalyst**  Amberlyst-15 a solid acid catalysts been studied for transesterification for production of methyl esters. However, mild reaction conditions are necessary to avoid degradation of the catalyst. At a relatively low temperature (60 °C), the conversion of castor, cottonseed and coconut oil was reported to be only between 2% to 5%, when carrying out the reaction at

0.5 60 65 55 1 76 79 74 1.5 80 85 82 3 72 80 76 3.5 65 62 60 4 56 50 52 Methanol to oil molar ratio= 6, Reaction temperature =60oC, Catalyst loading=3wt.% Amberlyst-15 Table 16. Effect of Reaction time on Methyl ester Conversion using Amberlyst -15 Catalyst During the initial 30 minutes reaction time the percent conversion was less. But as the reaction time progressed the conversion of triglycerides to methyl esters was increased till further one hour. After 1.5 hrs of reaction time, there was no significant rise in conversion. But the ME conversion decreased after 1.5 hrs. So, 1.5 hrs is obtained as the optimum

Methyl esters Conversion (%), Cottonseed oil

0

Optimum catalyst loading = 3wt%

20

40

**Methylesters conversion(%)**

3 wt%.

Reaction Time(hrs)

reaction time for this study.

60

80

100


Methanol to oil molar ratio= 6, Temperature =60oC, Catalyst loadings used for experimentation = 0.5%, 1%, 1.5% and 2% NaOH

Table 14. Effect of Catalyst (NaOH) loadings on Methyl ester Conversion

Fig. 14. Effect of catalyst (NaOH) loading on Methyl ester Conversion

It can be seen that the conversion of triglyceride to methyl ester increased as the catalyst loading increased from 0.5 to 1 wt.%. However, with the increase of the catalyst loading from 1% to 2 wt.%, the conversion of triglyceride to methyl ester decreased. Since the conversions of triglycerides to methyl esters did not change significantly for the catalyst loadings from 1wt.%, the optimum catalyst loading for this reaction was 1wt.%.

c. Effect of catalyst (Amberlyst-15) loading on Methyl ester Conversion


Methanol to oil molar ratio= 6, Reaction temperature =60oC, Reaction time = 1.5 hrs

Table 15. Effect of catalyst (Amberlyst-15) loading on Methyl ester Conversion

#### Optimum catalyst loading = 3wt%

308 Biodiesel – Feedstocks and Processing Technologies

0.5 72 89 94 1 80 80 95 1.5 78 91 96 2 60 91 97 Methanol to oil molar ratio= 6, Temperature =60oC, Catalyst loadings used for experimentation = 0.5%,

Methyl esters Conversion (%), Cottonseed oil

Methyl esters Conversion (%), Coconut oil

Castor oil Cottonseed oil Coconut oil

Methyl esters Conversion (%), Coconut oil

Methyl esters Conversion (%), Castor oil

Table 14. Effect of Catalyst (NaOH) loadings on Methyl ester Conversion

0 0.5 1 1.5 2 2.5 **Catalyst , NaOH(wt%)**

loadings from 1wt.%, the optimum catalyst loading for this reaction was 1wt.%. c. Effect of catalyst (Amberlyst-15) loading on Methyl ester Conversion

It can be seen that the conversion of triglyceride to methyl ester increased as the catalyst loading increased from 0.5 to 1 wt.%. However, with the increase of the catalyst loading from 1% to 2 wt.%, the conversion of triglyceride to methyl ester decreased. Since the conversions of triglycerides to methyl esters did not change significantly for the catalyst

> 3 89 90 88 4.5 77 80 76 6 56 65 60

Methyl esters Conversion (%), Cottonseed oil

Fig. 14. Effect of catalyst (NaOH) loading on Methyl ester Conversion

Methyl esters Conversion (%), Castor oil

Methanol to oil molar ratio= 6, Reaction temperature =60oC, Reaction time = 1.5 hrs Table 15. Effect of catalyst (Amberlyst-15) loading on Methyl ester Conversion

NaOH Catalyst loading (wt.%)

1%, 1.5% and 2% NaOH

Amberlyst-15 Catalyst loading (wt.%)

**Methylester conversion(%)**

Fig. 15. Effect of catalyst (Amberlyst-15) loading on Methyl ester Conversion

It can be observed that there was no rise in ME conversion when catalyst loading was increased from 3 to 6 wt%. The highest conversion was achieved at catalyst loading of 3 wt%.

#### **5.2.5 Effect of reaction time on methyl ester conversion using amberlyst -15 catalyst**

Amberlyst-15 a solid acid catalysts been studied for transesterification for production of methyl esters. However, mild reaction conditions are necessary to avoid degradation of the catalyst. At a relatively low temperature (60 °C), the conversion of castor, cottonseed and coconut oil was reported to be only between 2% to 5%, when carrying out the reaction at atmospheric pressure and a 6:1 methanol-to-oil initial molar ratio.


Methanol to oil molar ratio= 6, Reaction temperature =60oC, Catalyst loading=3wt.% Amberlyst-15

Table 16. Effect of Reaction time on Methyl ester Conversion using Amberlyst -15 Catalyst

During the initial 30 minutes reaction time the percent conversion was less. But as the reaction time progressed the conversion of triglycerides to methyl esters was increased till further one hour. After 1.5 hrs of reaction time, there was no significant rise in conversion. But the ME conversion decreased after 1.5 hrs. So, 1.5 hrs is obtained as the optimum reaction time for this study.

Transesterification by Reactive Distillation for Synthesis and Characterization of Biodiesel 311

55 89 84 90 60 92 96 96 65 94 97 96

Molar ratio of Methanol to Oil = 6:1, Catalyst (KOH) = 1% (by wt. of oil), Flow rate = 6ml/min,

54 56 58 60 62 64 66 **Reaction Temperature(Degrees Celcius)**

**5.2.8 Effect of reboiler temperature on methyl ester content of the product** 

the rates of soap formation increase more rapidly than that of transesterification.

The effect of temperature on methyl ester conversion was studied by transesterification at different temperature i.e. 55 oC, 60 oC and 65 oC. It was observed that the conversion increased with increase in temperature from 55 oC to 60 oC . But there was no significant rise in conversion after 60 oC upto 65 oC. So, the optimum value of temperature for this

The function of reboiler is to vaporize the residual methanol present in the liquid reaching the bottom of the column. At steady state, the boiling-up rate of methanol is determined by the heat load on the reboiler, heat transfer efficiency and the amount of methanol in the reboiler. Methanol boils at 64.7oC, however, according to the experiments, sufficient methanol vapors were generated only with reboiler temperature higher than 90oC. Depending upon the methanol concentrations, therefore, reboiler temperature in the experimental design varied from 80oC to 120oC in order to produce smooth and consistent methanol vapor flow rates. It was found that the lower reboiler temperatures are favorable for better reactor performance. A possible reason is that with higher operating temperatures,

Fig. 18. Effect of Temperature on Methyl ester conversion (%)

transesterification reaction was considered as 60 oC.

Methyl esters Conversion (%), Cottonseed oil

Methyl esters Conversion (%), Coconut oil

> Castor oil Cottonseed oil Coconut oil

**5.2.7 Evaluation of column operating conditions** 

Temperature (oC)

reaction time =6min

Optimum reaction Temperature = 60oC

**Methylester conversion(%)**

**Effect of reaction temperature on methyl ester conversion** 

Methyl esters Conversion (%), Castor oil

Table 18. Effect of reaction temperature on methyl ester conversion

Optimum reaction time =1.5 hours

Fig. 16. Effect of reaction time on Methyl ester Conversion using Amberlyst -15 Catalyst

#### **5.2.6 Effect of methanol to oil molar ratio on methyl ester conversion using Amberlyst-15 catalyst**


Reaction time = 1.5 hrs, Reaction temperature =60oC, Catalyst loading=3wt. % Amberlyst-15

Table 17. Effect of methanol to oil molar ratio on Methyl ester conversion using Amberlyst-15 catalyst

Optimum methanol to oil molar ratio = 6:1

Fig. 17. Effect of methanol to oil molar ratio on methyl ester conversion using Amberlyst-15 catalyst

It can be observed that there was no rise in ME conversion when methanol to oil molar ratio was increased from 6:1 to 12:1 .The highest conversion was achieved at methanol to oil molar ratio of 6:1.So, it is considered as optimum methanol to oil molar ratio.
