Biodiesel Production from Reactive Distillation Process: a Comparative Study between Experimental Results and Simulation

Biodiesel is a fuel made from vegetable oils, animal fats and microbial oil (algae, bacteria and fungi). The raw materials are converted to biodiesel through a chemical reaction involving alcohol and catalyst. The purpose of the present work is to present an efficient process using reactive distillation columns applied to biodiesel production. Reactive distillation is the simultaneous implementation of reaction and separation within a single unit of column. Nowadays, it is appropriated called “Intensified Process”. This combined operation is especially suited for the chemical reaction limited by equilibrium constraints, since one or more of the products of the reaction are continuously separated from the reactants. This work presents the biodiesel production from soy oil oil and bioethanol by reactive distillation. The RD process was carried out in a semi-batch system. The RD column used in this process was a packed column filled with glass rings and equipped with water condenser, temperature controller and reflux controller. The system design was based on the relative volatilities of the raw materials and products. A simulation of the reactive distillation process was carried out in Aspen Plus. Different variables affect the conventional biodiesel production process such as: catalyst concentration, reaction temperature, level of agitation, ethanol:soy oil oil molar ratio, reaction time, and raw material type. In this study, the experimental design was used to optimize the following process variables: the catalyst concentration (from 0.5 %wt to 1.5%wt), and the ethanol:soy oil oil molar ratio (from 3:1 to 9:1). The reactive column reflux rate was 83 ml/min, and the reaction time was 6 minutes. The difference between the boiling temperature of ethanol and the product mixture, ethyl esters and glycerol, is so large that the separation of the alcohol from the product mixture became easy. The use of reactive distillation process to biodiesel production leads to a more efficient process than the conventional transesterification one. The results showed many advantages of the integration process as compared with the conventional biodiesel production such: decrease of the ethanol excess, decrease of the reaction time, and decrease of the equipment units. The best ester conversion was 98.18%wt with 0.65%wt of sodium hydroxide, ethanol:soy oil oil molar ratio of 8:1 and reaction time of 6 minutes. The process simulation results are in agreement with the experimental ones.