An experimental study of oxidative desulphurisation of a spent tyre pyrolysis oil and its distillate using H2O2 and formic acid

This paper reports an experimental investigation into the oxidative desulphurisation of a spent tyre pyrolysis oil and its distillate in H2O2-formic acid system. The raw pyrolysis oil was produced from an industrial scale retort process. The raw pyrolysis oil was distilled using a packed-bed distillation column to obtain the fraction with boiling points from 105 degreesC to 210 degreesC as solvent (solvent fraction). The oxidative desulphurisation experiments were carried out and the effect of reaction temperatures (50 - 80 degreesC), time (10 - 240 min), and oil to H2O2-formic acid ratio (up to 1:4 v/v) on the percentage of sulphur removal was studied. The ratio of H2O2 to formic acid was fixed at 1:1 v/v. The desulphurised samples were washed with DI water before subsequent analysis. The raw pyrolysis oil and solvent fraction before and after oxidative desulphurisation were analysed using ICP-OES for sulphur content, GC-MS and GC-SCD for chemical compositions and sulphur species. The results showed that the percentage of sulphur removal increased with increasing the temperature, time, and amount of oxidant. The H2O2-formic acid system exhibited high sulphur removal efficiency, with 40 wt% sulphur removal for raw pyrolysis oil and 66 wt% for solvent fraction. However, it was also found that unsaturated hydrocarbons in the raw pyrolysis oil and solvent fraction compete with sulphur-containing compounds for the H2O2-formic acid via the epoxidation reaction, reducing sulphur removal percentage and changing the compositions of the treated pyrolysis oil and solvent fraction.