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

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

Transesterification by Reactive Distillation for Synthesis and Characterization of Biodiesel 313

The biodiesel yield was determined indirectly from the triglyceride as discussed in the materials and methods section. The percentage composition of the triglyceride consumed was assumed to be converted to methyl ester. Therefore, the amount of biodiesel produced was calculated from the difference in composition of triglyceride in the original oil and final

From the experimental investigation done in this research work, the following conclusions

Reactive distillation can be used as a techno economical process for synthesis of biodiesel from vegetable oil by transesterification process. The process proposed here can dramatically improve the economics of current biodiesel synthesis and reduce the number

Using reactive distillation for synthesis of methyl ester has several advantages such as high unit productivity, up to 6–10 times higher than of the current process, lower excess alcohol requirements, reduced capital and operating costs, due to less units and lower energy consumption, Sulfur-free fuel, since solid acids do not leach into the product, no waste streams because no salts are produced. Also there is significant reduction in reaction time as well as in number of equipment units compared to that in conventional batch and

The feasibility of using mixture of two different vegetable oils was tested and it was found that coconut oil and cottonseed oil if mixed in equal proportion and used for transesterification reaction, the methyl esters conversion as high as 95% can be achieved. From the experimental results the optimization of parameters obtained was as follows: Transesterification reaction is affected by methanol to oil molar ratio, catalyst loading, reaction temperature, flow rate of reactant streams, reaction time, mixing intensity. In the present study reaction was carried out using three values of Methanol to oil molar ratios (3:1, 6:1 and 9:1) for individual oils (castor, cottonseed and coconut oil) and KOH catalyst for synthesis of biodiesel the highest ME conversions obtained for castor, cottonseed and coconut oil transesterification were 68%, 72% and 88% respectively. The highest ME conversion was obtained for coconut oil in this case. Whereas by using the heterogeneous catalyst Amberlyst -15, the highest ME conversions obtained for castor, cottonseed and coconut oil transesterification were 89%, 92% and 90% respectively for methanol to oil molar

Also the possibility of using mixed oils was investigated by using three seed oils in 3 different proportions, such as mixed oil 1 (50% castor oil+50% cottonseed oil ), mixed oil 2 (50% castor oil+50% coconut oil ) and mixed oil 3(50% coconut oil+50% cottonseed oil).The highest ME conversion (95%) was obtained for mixed oil 3 at methanol to oil molar ratio of 6:1.Thus the option of using mixed oils is feasible in case of scarcity of one of particular feed stock oil in particular region. Also the application can be further investigated to reduce the cost of production of biodiesel by using cheaper feed stocks in more proportion in mixed oil feed. The flow rate of reactants has an impact on reaction rate of biodiesel production. Out of 5ml/min, 6ml/min and 7ml/min flow rates of reactants to the RD column transesterification reaction. The highest ME conversion (96%) was obtained for cottonseed

**5.2.9 Biodiesel yield** 

biodiesel.

**6. Conclusions** 

of downstream steps.

continuous transesterification processes.

oil at reactants flow rate of 6ml/min.

can be drawn:

ratio of 6:1.


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

Table 19. Effect of reboiler temperature on methyl ester content of the product

Fig. 19. The effect of the reboiler temperature on methyl esters content in product
