5 Principle and Processing of Biodiesel Production
139
a significant amount of energy; it is difficult to recycle glycerol; the reaction has
a high alcohol consumption; catalysts must be separated from the resultants, and
the basic wastewater produced must be properly treated; the amount of free fatty
acids and water has a significant impact on the reaction; the process is complicated. Enzyme-catalyzed transesterification overcomes the shortcomings mentioned
above. Particularly, it is convenient to recycle the by-product glycerol. Moreover,
the free fatty acids in waste oils and fats can be sufficiently transformed into methyl
esters. Therefore, biodiesel production by the enzyme catalysis method is drawing more attention. Researches have shown that with catalysis by Ryzopus oryzae
lipase, transesterification of triglycerides and methanol is characterized by a sequential reaction mechanism. Triglycerides and part of the glycerides are hydrolyzed to
produce a certain amount of glycerides and free fatty acids, and then free fatty acids
react with methanol to produce methyl esters. This process is different from a basecatalyzed one. In enzyme-catalyzed reactions, all free fatty acids in vegetable oils can
be transformed into methyl esters. Besides, biodiesel production by enzyme catalysis does not require very strict conditions. Yet, enzymes are expensive. The main
obstacle for enzyme catalysis to be applied in industrial production is the cost factor. Immobilized lipase [26], however, can be recycled and used for reaction, which
lowers the cost. Many researchers outside China are employing immobilized lipase
for transesterification reactions. Furthermore, as enzymes are easily deactivated in
high concentration methanol, a new operational method has been developed. That is,
enzymes are added in a stepwise fashion to avoid deactivation and achieve a higher
conversion rate of methyl esters.
5.2.4 Production Process of Producing Biodiesel
by Transesterification
There are various processes for the industrial production of biodiesel. Their end products have developed into various brands. These include Novamont and Ballestra from
Italy, IFP from France, and Henkel and ATT from Germany. Today, most factories
apply the traditional two-stage transesterification operation–reaction and purification. The most relevant factor in the reaction is the amount of methanol and catalyst. More methanol means higher yield and more difficult separation operation. At
present, most of the factories that are using the two-stage operation have a production
capacity of 500–10,000 t/a. This type of operation requires a smaller investment to
reach a certain output level. However, problems exist in the continuity and security
of the process, which could be solved through modern control technologies [27,
28]. The techniques developed by Henkel have become a widely used process for
biodiesel manufacturers. In this process, the facilities and equipment used are not
exclusive. The distillation operation in the process determines the quality of the diesel
produced. The operating pressure is 0.4–0.5 MPa, and the operating temperature is
70–80 °C. The diesel produced through this process has high quality, light color, and
high purity, and the purity of its by-product glycerol can reach 92% as well. The main
139
a significant amount of energy; it is difficult to recycle glycerol; the reaction has
a high alcohol consumption; catalysts must be separated from the resultants, and
the basic wastewater produced must be properly treated; the amount of free fatty
acids and water has a significant impact on the reaction; the process is complicated. Enzyme-catalyzed transesterification overcomes the shortcomings mentioned
above. Particularly, it is convenient to recycle the by-product glycerol. Moreover,
the free fatty acids in waste oils and fats can be sufficiently transformed into methyl
esters. Therefore, biodiesel production by the enzyme catalysis method is drawing more attention. Researches have shown that with catalysis by Ryzopus oryzae
lipase, transesterification of triglycerides and methanol is characterized by a sequential reaction mechanism. Triglycerides and part of the glycerides are hydrolyzed to
produce a certain amount of glycerides and free fatty acids, and then free fatty acids
react with methanol to produce methyl esters. This process is different from a basecatalyzed one. In enzyme-catalyzed reactions, all free fatty acids in vegetable oils can
be transformed into methyl esters. Besides, biodiesel production by enzyme catalysis does not require very strict conditions. Yet, enzymes are expensive. The main
obstacle for enzyme catalysis to be applied in industrial production is the cost factor. Immobilized lipase [26], however, can be recycled and used for reaction, which
lowers the cost. Many researchers outside China are employing immobilized lipase
for transesterification reactions. Furthermore, as enzymes are easily deactivated in
high concentration methanol, a new operational method has been developed. That is,
enzymes are added in a stepwise fashion to avoid deactivation and achieve a higher
conversion rate of methyl esters.
5.2.4 Production Process of Producing Biodiesel
by Transesterification
There are various processes for the industrial production of biodiesel. Their end products have developed into various brands. These include Novamont and Ballestra from
Italy, IFP from France, and Henkel and ATT from Germany. Today, most factories
apply the traditional two-stage transesterification operation–reaction and purification. The most relevant factor in the reaction is the amount of methanol and catalyst. More methanol means higher yield and more difficult separation operation. At
present, most of the factories that are using the two-stage operation have a production
capacity of 500–10,000 t/a. This type of operation requires a smaller investment to
reach a certain output level. However, problems exist in the continuity and security
of the process, which could be solved through modern control technologies [27,
28]. The techniques developed by Henkel have become a widely used process for
biodiesel manufacturers. In this process, the facilities and equipment used are not
exclusive. The distillation operation in the process determines the quality of the diesel
produced. The operating pressure is 0.4–0.5 MPa, and the operating temperature is
70–80 °C. The diesel produced through this process has high quality, light color, and
high purity, and the purity of its by-product glycerol can reach 92% as well. The main