From Fed-batch to Continuous Enzymatic Biodiesel Production

In this this paper, we use mechanistic modelling to guide the development of acontinuous enzymatic process that is performed as a fed-batch operation. In this workwe use the enzymatic biodiesel process as a case study. A mechanistic model developedin our previous work was used to determine the reactor operating conditions for adesired conversion.

However, in using a detailed mechanistic model, given the largenumber of parameters and few experimental data points, the parameters were found notidentifiable. The model is then only applicable within the limited operating range for which the model was validated. We hypothesize that fitting this model to fed-batch and continuous stirred tank reactor (CSTR) data together will enable us to use the model for determination of residence times to reach a specified conversion in a CSTR.

With this approach, the model fits the experimental data for the five measured components (triglycerides, diglycerides, monoglycerides, free fatty acid and fatty acid methyl esters(biodiesel)) much better than using fed-batch data alone given the smaller residuals. We also observe a reduction in the correlation between the parameters.The model was then used to predict that 5 reactors are required (with a combined residence time of 30 hours) to reach a final biodiesel concentration within 2 % of the95.6 mass % achieved in a fed-batch operation, for 24 hours.