Novozym Catalyzed Transesterification of Soybean Oil for

							          NOVOZYM435 -CATALYZED                                                 In batch operation the highest ME yield (92 %) could be obtained
  TRANSESTERIFICATION OF SOYBEAN OIL FOR                                   at methanol/oil molar ratio 4:1. Either higher methanol concentration
  BIODIESEL PRODUCTION IN A SOLVENT-FREE                                   (5:1) or lower methanol concentration (3:1) would decrease ME yield
                                                                           to some degree.
                 MEDIUM
                                                                                 However, it has been demonstrated that during the continuous
                                                                           process, lipase lost its activity dramatically at methanol/oil molar
                Wei Du*, Yuan-yuan Xu, De-hua Liu
                                                                           ratio 4:1 and effect of methanol/oil ratio on enzymatic activity was
                                                                           studied further in continuous batch operation. The optimal molar ratio
 Department of Chemical Engineering, Tsinghua University, Beijing
                                                                           of methanol/oil was 1:1 in continuous batch operation, at which
                      100084, P. R. China
                                                                           lipase remained relatively high activity.

      Biodiesel, generally classified as fatty acid alkyl esters, has      Effect of temperature
                                                                                Effect of temperature on enzymatic transesterification of
become more attractive recently because of its environmental
benefits. Although biodiesel has been successfully produced                soybean oil was examined at the range from 30℃ to 50℃ in batch
chemically at present, there are several associated problems to restrict   operation and high temperature resulted in relatively high ester yield.
its development, such as glycerol recovery and removal of inorganic        However, it has also been found that when temperature is above
salt. The disadvantages caused by chemical catalysts are largely           50℃, enzyme loses its activity dramatically. So in batch process, 40-
prevented by using lipases as the catalysts and enzymatic production       50℃ is optimal for enzymatic biodiesel production.
of biodiesel fuel has drawn considerable attention in recent years.             However, in continuous batch operation, it has been
                                                                           demonstrated that higher temperature resulted in larger loss of lipase
     For large-scale production of biodiesel, the repeated use of          activity and 30℃ is optimal by taking into lipase stability and activity
lipase is one of the major issues. In this paper, effects of some key      into consideration.
issues (such as temperature, alcohol/oil ratio, glycerol removal etc.)          It has been demonstrated that temperature, methanol/oil molar
on the enzymatic reaction during biodiesel production have been            ratio and glycerol have varied effect on lipase-catalyzed
studied and within the optimized conditions, lipase expressed good         transesterification of soybean oil during batch and continuous batch
stability in continuous batch operation in the production of biodiesel.    operation of biodiesel production. Within the optimized conditions,
                                                                           lipase remained high activity after continuous batch operation which
     Effect of temperature, oil/alcohol molar ratio and by-product         demonstrates that enzymatic transesterification of renewable oil is
glycerol were studied during Lipozyme TL IM-catalyzed continuous           very promising for large-scale production of biodiesel.
batch operation when short chain alcohols used as the acyl acceptor.
In non-continuous batch operation, the optimal oil/alcohol ratio and
temperature were 1:4 and 40℃-50℃; however, during the continuous
batch operation, the optimal oil/alcohol ratio and temperature were
1:1 and 30℃ respectively; 95% of enzymatic activity remained after
10 batches when iso-propanol adopted to remove by-product glycerol
during repeated use of the lipase.

Effect of glycerol
      Enzymatic transesterification of renewable oil with short chain
alcohols as acyl acceptor for biodiesel production has been studied
extensively in recent years. However, with these short chain alcohols
as the acyl acceptor, glycerol, as one of the major by-products, has
been demonstrated to have some serious negative effect on enzymatic
activity. During the repeated use, lipase lost its activity dramatically
which mainly due to the negative effect of glycerol.
      Some hydrophilic organic (propanol, iso-propanol, butanol, tert-
butanol) have been tried to remove glycerol during the repeated use
of lipase and iso-propanol has been found to be the most effective for
glycerol removal.
Operational stability with glycerol removal by iso-propanol
      The operational stability of lipase with glycerol removal by iso-
propanol has been studied further in this paper and lipase expressed
good operational stability. There was no observable loss of lipase
activity after 10 batches of continuous operation.
Effect of molar ratio of methanol / oil
      It is well known that excessive short-chain alcohols such as
methanol might inactivate lipase seriously. However, at least three
molar equivalents of methanol are required for the complete
conversion of the oil to its corresponding ME and effect of molar
ratio of oil/methanol has been studied comparatively during batch
and continuous batch operation.




                                      Prepr. Pap.-Am. Chem. Soc., Div. Fuel Chem. 2003, 48(2), 532