This paper reports an experimental investigation into the desulphurisation of a spent tyre pyrolysis oil and its distillate using a combined catalytic oxidative and selective adsorption method. The oxidative desulphurisation (ODS) experiments were carried out in a batch reactor using H2O2formic acid as oxidant. The effect of reaction temperature, time, and oil to H2O2-formic acid ratio on the percentage of sulphur removal was studied. The oil samples after ODS were treated using Al2O3 as an adsorbent in a batch reactor at 25 °C and atmospheric pressure. The oil samples were analysed using ICP-OES for sulphur content, GC-MS and GC-SCD for chemical compositions and sulphur species. The ODS successfully converted the sulphur compounds to sulphoxides and sulphones but only exhibited moderate sulphur removal efficiency because sulphoxides and sulphones were dissolved in the oil and cannot be easily extracted by water. Al2O3 was effective in adsorbing sulphoxides and sulphones. A maximum of 81% and 84% sulphur removal were achieved for the raw pyrolysis oil and distillate, respectively, using combined ODS and Al2O3 adsorption.After three desulphurisation cycles, the sulphur adsorption capacity of Al2O3 decreased from 0.31 to 0.22 mg S g -1 Al2O3, still exhibiting high sulphur removal ability.
The activation of a spent tyre pyrolysis char using CO2 and steam was experimentally investigated, focusing on the pore development of the char during activation. The pyrolysis char, produced in an industrial scale retort process, was ground and sieved to a particle size fraction <150 μm, and activated in a fixed bed reactor under CO2 and steam, respectively. The effect of temperature (750 to 1050 °C), reaction time (0.5 to 4 h for steam activation, 1 to 6 h for CO2 activation) and activation agent concentration (33.3 to 66.7 vol% of CO2 or steam in N2) on the carbon conversion and reaction rate was measured. The activated chars were characterised for the BET surface area, pore volume and average pore size of the activated chars using N2 adsorption and morphology using SEM. Higher temperature and activation agent concentration, and longer reaction time led to higher carbon conversion. As the carbon conversion increased, the BET surface area initially increased linearly and then decreased, reaching a maximum surface area of 666.6 m 2 g -1 (0.60 conversion) for steam and 434.5 m 2 g -1 (0.52 conversion) for CO2. Micropores were created in the early stage of activation, increasing first until carbon conversion reaching ca.0.30. Steam-activated chars showed higher BET surface areas than CO2-activated chars at the same carbon conversion. Steam was found to generate both greater microporosity and mesoporosity than CO2.
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