engleski

Application of deep eutectic solvents and water for biodiesel purification on a microscale

Purification of crude biodiesel is mandatory for the fuel to meet the strict international standard specifications for biodiesel (the American standard ASTM D 6751 and the European standard EN 14214). Conventional technologies used for biodiesel separation such as sedimentation, decantation and filtration, and for biodiesel purification such as water washing, acid washing and washing with ether and absorbents have proven to be inefficient, time and energy consumptive, and less cost effective. Besides that, most of them generate large quantities of water that must be properly disposed and represents a great economic and environmental burden. Additionally, conventional biodiesel separation and purification processes result in a significant loss of biodiesel during production. Due to all that new pathways for biodiesel separation and purification are developed. One of new methods for biodiesel purification is combination of advantages of deep eutectic solvents (DES’s) and microseparation systems. DES’s are interesting because they resemble various unique characteristics such as low volatility, non-flammability, non-toxicity and they can be prepared easily. Microseparators are promising process solution due to numerous well known advantages - a high surface to volume ratio, faster diffusion dominated transport, enhanced heat transfer and consequently reduced energy demands, good process control, high throughput, and usage of minimal (microlitres) reagent volumes etc. In this study application of microseparator was explored for biodiesel purification (glycerol extraction) using different DES’s based on choline chloride and ethylene glycol with presence or absence of water. Four different microseparators (all tubular but with different channel diameter) were tested and compared. Obtained results were compared with results obtained in experiments performed in microseparators where water was used as extraction medium. In experiments where extraction was performed using DES, extraction efficiency of 99.98% was achieved meaning that amount of glycerol that remained corresponds to ASTM D 6751 and EN 14214 standards. In the second experiment where water was used as extraction medium, extraction efficiency was determined to be 99.19%. To achieve equal extraction efficiency, experiments with water where performed in three microseparators connected in to series e.g. equal efficiency was achieved with three fold larger volume of water and using more complex experimental set-up. Additionally, mathematical model was developed and used for additional optimization of process conditions necessary to produce biodiesel with less than 0.02 w/w of glycerol.

deep eutectic solvents, biodiesel, microseparator, purifcation

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