The main focus of this project was the extraction of phenolic components from an aqueous stream that is generated during the hydrothermal conversion of lignin to bio-oil. Since water is utilized as a reaction medium in this process, a large amount is used continuously and it has to be recirculated. The water ends up containing high concentrations of phenolic components like guaiacols and catechols that are valuable chemicals for the industry. This fact provides an opportunity to recover the phenolics and add value to the conversion process of lignin. The recovery of the phenolic components from the aqueous phase can be considered a part of the optimization that could give an edge to the process and can make it a sustainable and financially competitive method of fuel and chemicals production.
Within the framework of this master thesis a liquid-liquid extraction experimental setup and a related procedure for the acquisition of liquid-liquid equilibrium (LLE) data were developed. Literature indicated Methyl Isobutyl Ketone (MIBK) as one of the most promising organic solvents for liquid-liquid extraction. The system that was studied in this frame was the ternary system, Water – Guaiacol –MIBK. The equilibrium experiments were performed in separating funnels under temperature regulation and both of the two distinct liquid phases (aqueous and organic) were withdrawn after equilibration for analysis. Gas Chromatography (GC) and Karl Fischer titration (KF) were used for the compositional analysis.
The experimental procedure resulted to be very good for attaining the goal of this master thesis and it presented some very interesting advantages. For example the use of separation funnels gave the opportunity to accurately measure the weight of the two liquid phases. Additionally, the use of KF gave an accurate analytical measurement for the water in the organic phase whereas most of the authors of similar works are using mass balance to calculate it.
Equilibrium data for the ternary system Water – Guaiacol – MIBK were successfully measured experimentally for the temperatures 30 and 55 °C under atmospheric pressure. Using the measured mass fractions, extraction yields, selectivities and distribution coefficients were measured to evaluate the extracting performance of MIBK. The extraction yields for the single stage extraction procedure applied in this work were up to 96%, depending on the relative amount of solvent to the feed (S/F). The values of S/F ranged from 0.05 up to 1 and it was indicated that the optimum value would be between 0.1 and 0.25. In all accounts, the work performed showed that MIBK can effectively be used as an organic solvent for the extraction of guaiacol from water and the experimental procedure that was adopted can very satisfactorily work for the acquisition of experimental LLE data.