Phase Equilibria of Pyrolysis Oil Components and Distillation of Pyrolysis Oil Containing Styrene

Abstract

This thesis focuses on vapor-liquid and liquid-liquid-(liquid) equilibrium measurements of a few selected model components of pyrolysis oil and their mixtures. The vapor-liquid equilibrium of phenol – dodecane/hexadecane systems was measured at temperatures 523 – 573 K. Similarly, the vapor-liquid equilibrium of styrene – toluene/alpha-methylstyrene systems was measured at lower pressure range of 20 – 40 kPa. In this study, the phenol – dodecane system showed azeotropic behavior at the temperature range of 393 – 573 K. The ideal behavior of styrene – toluene/alpha-methylstyrene systems was observed at the pressure range of 20 – 40 kPa as the calculated activity coefficients were very close to unity. The applied thermodynamic models Peng-Robinson (PR), Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) and Non-Random Two-Liquid–Redlich-Kwong (NRTL-RK) correlated very well with the experimental data. The model parameters were also regressed from the experimental data.

The liquid-liquid equilibrium of binary and ternary systems of water – phenol – dodecane/hexadecane were measured with the analytical and the cloud point detection methods at 298 – 353 K. The two and three liquid phases were studied for the ternary systems. The Non-Random Two-Liquid (NRTL) activity coefficient model described the phase behavior very well. The results from the three-liquid phase decanter model were comparable with the experimental three-liquid phase data.

Further, the purification of polystyrene pyrolysis oil to a pure styrene monomer was carried out by employing a batch distillation unit at 99 mbar condenser pressure. It was important to perform the batch distillations at lower pressures to minimize the risk of polymerization in the distillation column. Five batches of distillate fractions were obtained. The purity of the styrene monomer in the distillate fraction was 99.94 wt.%. This grade of styrene monomer was suitable for further polymerization and subsequent production of latex or other polymers. The experimental distillation and the proposed continuous distillation model show a possibility of scale-up of the process where styrene monomer can be obtained with a high purity.