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The activity of new guanidine catalysts and optimization of biodiesel production process using response surface methodology

Biodiesel is an alternative fuel that has numerous advantages. It reduces greenhouse gas emissions, it's renewable, biodegradable and non-toxic. It contains no sulfur and can reduce the dependence on fossil fuels. Due to the fact that its production is a catalytic process, there is a constant need for the development of new and better catalysts with the optimization of the process. Current processes are mainly based on NaOH and KOH catalysts needed for the transesterification. However, their application shows a number of obstacles. If the reaction mixture contains a higher amount of water and free fatty acids this leads to the formation of emulsions and the complicated separation of glycerol due to the undesirable side reaction of saponification. In this work application of novel guanidine superbases, is studied. The main advantage of these organic superbases is due to the fact that they don't display difficulties related to the reaction of saponification. The optimization of the rapeseed oil transesterification process was conducted with the most effective guanidine catalyst tested using the design of experiments (DoE) approach. As a result of implementing the response surface methodology (RSM) an empirical mathematical model of the transesterification process was obtained. Three parameters were varied at three levels during the experiments ; the content of the catalyst, the methanol/rapeseed oil molar ratio and the reaction time. We managed to prove that the achievement of an optimal process is possible using 1.75 wt. % of the content of the catalyst, the molar ratio of the methanol/rapeseed oil 6.21:1 coupled with the reaction time of 80 minutes. The optimal conditions for the transesterification process of the rapeseed oil have been confirmed on a larger scale. Thus, the main physico-chemical properties and the properties for the application of the produced biodiesel were determined and according to that, they confirmed a high level of quality on a commercial scale.

guanidine; catalysts; process; optimization; biodiesel

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