**6. Conclusions**

From the experimental investigation done in this research work, the following conclusions can be drawn:

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 of downstream steps.

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 continuous transesterification processes.

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 ratio of 6:1.

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 oil at reactants flow rate of 6ml/min.

Transesterification by Reactive Distillation for Synthesis and Characterization of Biodiesel 315

The castor oil showed yield of biodiesel less than that of cottonseed oil due to its high acid value. High acid value leads to neutralization of part of catalyst present thus producing soaps within the reaction medium which reduce mass transfer during the reaction. Also in basic medium, the hydroxyl group at C-12 of ricinoleic acid is converted into an alcohoxide derivative that can compete with the generation of methoxide species and compromise the conversion reaction. The Coconut oil contains approximately 92.1% saturated fatty acids, 6.2% monounsaturated fatty acids, 1.6% polyunsaturated fatty acids. Different fatty acids in coconut oil range from C6 – C18 carbon atom chains. It contains Lauric acid(over 50%) higher in composition So, it was concluded that cottonseed oil was the most feasible feedstock among the three vegetable oil feed stocks under consideration for this study. The production of biodiesel using transesterification by reactive distillation can be considered as technically as well as economically feasible process and its scale up at

First of all, I wish to express my deepest gratitude to my supervisor Hon'ble, **Dr.V.S.Sapkal**, Vice Chancellor, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur, whose guidance, encouragement, wisdom, motivation, and expectations are indispensable to my

My deepest thanks also go to respected **Dr.R.S.Sapkal**, Head, Department of Chemical Technology, Sant Gadgebaba Amravati University, Amravati, who gave me a lot of helpful ideas, suggestions, and discussions that contribute to the remarkable success achieved in

No thanks are enough to **Dr.N.B.Raut**, Assistant Professor, Faculty of Engineering, Sohar University (Affiliated to Queensland University), Sultanate of Oman, Oman for his valuable

 I would like to thank **Dr.C.V.Rode, Dr.M.G.Sane**, Senior Scientists from NCL, Pune for their technical support and guidance to my research. Thanks go to all the members in my laboratory as well as librarians of NCL, Pune, SGBAU, Amravati, SVIT, Nashik, KKW College of Engineering, Nashik for their help out in literature survey and analytical facilities

I also appreciate all my colleagues and other faculties at SVIT, Nashik, **Prof.R.N.Vaidya**, Brahma Valley College of Engineering, Nashik and **Prof.M.G.Shinde**, MET's Institute Of Engineering, BKC, Nashik for their precious direct and indirect assistance in this research work. I would thank lab assistants and staff of UDCT, Amravati for their kind cooperation during the experimentation phases. A special thanks goes to **Mr.P.R.Wankhade** for his

Finally, I would like to thank my family and friends for their patience, motivation and

Chuaohuymak Pojanalai, Sookkumnerd Terasut, Kinetics of Homogeneous Transesterification Reaction of Palm oil and Methanol, Technology p. 1-6,2005. Demirbas Ayhan, Biodiesel A Realistic Fuel Alternative. Trabzon: Springer-Verlag London

industrial level should be recommended to meet the future energy demand.

achievements and will serve as a continuous inspiration for my future career.

direction, motivation and constant support in accomplishment of my research.

valuable support during the experimentation phases at UDCT, Amravati.

admiration. My success is directly related to their love and strong support.

**7. Acknowledgement** 

this work.

in this research.

**8. References** 

Limited, 2008.

For a practical and economic feasible transesterification process, it is necessary to limit the reaction time at a certain period. Longer reaction time could also permit reversible transesterification reaction to occur, which eventually could reduce the yield of fatty acid alkyl esters. Thus, optimization of reaction time is also necessary. In this study, the reaction time was varied from 4 min, 6min and 8min. It was observed that the highest ME conversion (96%) was obtained for cottonseed oil at 6min reaction time. Whereas for heterogeneous catalyst, reaction times of 0.5,1, 1.5, 3, 3.5 and 4 hrs using catalyst Amberlyst-15 for Methanol to oil molar ratio 6:1, Reaction temperature of 60oC, Catalyst loading of 3wt.% were used and the highest ME conversion (85%) was obtained for cottonseed oil after 1.5 hrs reaction time. There was no significant rise in conversion rate after 1.5 hrs.

The catalyst plays an important role in transesterification reaction. The type and quantity of catalyst usually depend upon the quality of feed stock and method applied for transesterification. Three values of catalyst loadings of 1, 1.5 and 2 wt% KOH were used for Methanol to oil molar ratio 6:1 at 60oC .The highest ME conversion (96%) was observed for coconut oil at 1.5 wt% KOH catalyst loading.

Similarly the second homogeneous catalyst NaOH also resulted in the same conversion for the same experimental conditions. Whereas the heterogeneous catalyst Amberlyst-15 was used in three catalyst loadings of 3, 4.5 and 6 wt% Amberlyst-15 for Methanol to oil molar ratio of 6:1, Reaction temperature of 60oC, Reaction time of 1.5 hrs, the highest ME conversion (90%) was obtained for cottonseed oil at 3wt% Amberlyst-15 catalyst loading.

The transesterification was carried out at reaction temperatures of 55, 60 and 65oC for individual oils-castor, cottonseed and coconut oil and the highest ME conversions obtained for castor, cottonseed and coconut oil transesterification were 92%, 96% and 96% respectively for 60oC temperature using KOH catalyst. For homogeneous catalyst, moderate reaction temperature is enough to commence the reaction whereas for heterogeneous catalyst the operating temperature varies depending upon activation energy and conditions to produce the high yield of methyl esters. For NaOH catalyst the same optimum value of 60 oC temperature was obtained in batch transesterification process with maximum ME conversion of 96%.

The sufficient methanol vapors were generated only with reboiler temperature higher than 90oC. Depending upon the methanol concentrations, therefore, reboiler temperature in the experimental design was 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.

It was found that cottonseed oil resulted into maximum yield of biodiesel. Usually crude cottonseed oil contains palmitic acid (22- 26%), oleic acid (15-20%), linoleic acid (49- 58%) and approximately 10% mixture of arachidic acid, behenic acid and lignoceric acid, as well as about 1% sterculic and malvalic acids. In this study, the used crude cottonseed oil contained 24.60% of palmitic acid, 17.09% of oleic acid, and 50.50% of linoleic acid. Since higher amount of free fatty acids (FFA) (>1% w/w) in the feedstock can directly react with the alkaline catalyst to form soaps, which are subject to form stable emulsions and thus prevent separation of the biodiesel from the glycerol fraction and decrease the yield, it is better to select reactant oils with low FFA content or to remove FFA from the oil to an acceptable level before the reaction. Nevertheless, the FFA (calculated as oleic acid) content of the crude cottonseed oil used in this experiment was only 0.8%, which was in an allowed level for being directly used for reaction with the alkaline catalyst to produce biodiesel.

The castor oil showed yield of biodiesel less than that of cottonseed oil due to its high acid value. High acid value leads to neutralization of part of catalyst present thus producing soaps within the reaction medium which reduce mass transfer during the reaction. Also in basic medium, the hydroxyl group at C-12 of ricinoleic acid is converted into an alcohoxide derivative that can compete with the generation of methoxide species and compromise the conversion reaction. The Coconut oil contains approximately 92.1% saturated fatty acids, 6.2% monounsaturated fatty acids, 1.6% polyunsaturated fatty acids. Different fatty acids in coconut oil range from C6 – C18 carbon atom chains. It contains Lauric acid(over 50%) higher in composition So, it was concluded that cottonseed oil was the most feasible feedstock among the three vegetable oil feed stocks under consideration for this study.

The production of biodiesel using transesterification by reactive distillation can be considered as technically as well as economically feasible process and its scale up at industrial level should be recommended to meet the future energy demand.
