DESIGN OF A REACTIVE DISTILLATION COLUMN FOR GLYCEROL ETHER PRODUCTION

Abstract

Biodiesel, an important alternative energy, is generally produced from a transesterification reaction of vegetable oils and alcohol. This reaction always generates crude glycerol as by-product. As a result, the utilization of crude glycerol to produce higher value-added products can increase the competitive potential of biodiesel producers. In this research, the production of di and tri tert-butyl ether of glycerol (known as glycerol ether) from etherification of glycerol and tert-butyl alcohol is studied. Due to the nature of the reversible etherification reaction, a reactive distillation in which chemical reaction and separation can occur at the same time in single unit is considered to improve the glycerol ether production. Furthermore, since methanol is always present in crude glycerol, it is considered to be used for the production of dimethyl ether, a promising alternative fuel to replace diesel fuel and liquefied petroleum gas. This study is divided into three parts. In the first part, the effects of key design and operating parameters of the reactive distillation on the performance of glycerol ether production are studied. The results show that the use of the reactive distillation can increase the conversion of glycerol to glycerol ether into 99%. Based on a total annual cost analysis, the optimal configuration of reactive distillation column consists of 2 rectifying stages, 8 reactive stages and 1 stripping stages. In the second part, the application of a reactive distillation to the dimethyl ether production is investigated and the analysis of a total annual cost is used to design the reactive distillation column. The simulation results show that the reactive distillation can increase the conversion of methanol in crude glycerol to dimethyl ether into 99% and the optimal configuration of the reactive distillation column consists of 2 rectifying stages, 8 reactive stages and 2 stripping stages. As a separation of tert-butyl alcohol and water, which forms a azeotrope mixture is a difficult task, in the final part of the study, the use of a extractive distillation using different solvents, which are hexyl acetate, 2-heptanone and 3-octanone, for recovery of tert-butyl alcohol in the production process of glycerol ether is studied and compared in terms of the total annual cost and potential environmental impact as criteria. The results show that hexyl acetate is the most appropriate solvent.