Abstract
Typically, the products from waste tyre pyrolysis consist of (i) gas fraction (18 – 23 %wt ), (ii) liquid fraction (41 – 49 %wt), and (iii) char fraction (38 – 40 %wt). The liquid amount is considered the highest among those obtained from waste tyre pyrolysis. The improvements of tyre-derived oils (liquid fraction) could be accomplished by increasing mono-aromatics as a result of the reductions in di-aromatics and poly- aromatics through hydrogenation and the conversion of terpenes through aromatization. A basic catalystthat has potassium as a cation such as potassium tert-butoxide (K+(CH3)3CO-)) can provide hydrogenation and aromatization. KL zeolite is a representative of a solid basic catalyst. It has a pore diameter 0.71 Åand 1-dimensional pore structure. Moreover, the 1-dimensional pore structure can align the incoming molecules parallel on the surface of KL, resulting in high yields of hydrogenated products. Two- Dimensional Gas Chromatography coupled with Time-of-Flight Mass Spectrometry (GC × GC / TOF-MS) that can separate and identify the chemicals that have same retention time and boiling points due to overlapped mass spectra was employed for better identification of components in tyre-derived oils. The objective of this research was thus to observe the changes the hydrocarbon species upon the use of a KL catalyst. The GC × GC / TOF-MS was used to investigate hydrocarbon species in the maltenes (liquid fraction without asphaltene) from the non-catalyst and KL batches. The liquid products were categorized into saturated hydrocarbons (SATs), olefins (OLEs), terpenes (TERs), mono-aromatics (MAHs), di- aromatics (DAHs), poly-aromatics (PAHs), and polar-aromatics (PPAHs), including sulphur compounds. The pyrolysis experiments were performed in a bench-scaled autoclave reactor from room temperature to 500 °C (for the pyrolysis zone) and 350 °C (for the catalytic zone) with the heating rate of 10 °C/min. As aresult, KL was found to increase the MAHs from 20.1 to 26.8 %wt (mostly, 2-ethyltetralin) and decrease DAHs form 13.31 to 6.37 %wt (mostly, 2-ethylnaphthalene), and TERs from 4.06 to 2.56 %wt (mostly, d- limonene and 3-carene). The sulphur compounds in tyre-derived oils were found to be thiophenes, phenylthiophenes, benzothiophenes, methylbenzothiophenes, dibenzothiophenes, and napthols.
