Upgrading Bio-Oil Properties from Date Stones by Co-Pyrolysis with Waste Tires Rubber in a Fixed-Bed Reactor

This study examined the co-pyrolysis of an equivalent blend of date stones (DS) and waste tires (WT). Co-pyrolysis of the DSWT blend was performed in a batch reactor under an inert atmosphere. Operating conditions, including pyrolysis temperature (400–600 °C), pyrolysis period (30–150 min), feed particle size (20–60 mesh), and heating rate (10–30 °C/min), were optimized to ensure maximum liquid fuel yield. Under the typical conditions of pyrolysis (500 °C, 1 h, 20/°C heating rate, and 1.12 mm particle size), the highest yield of liquid fuel was 64.10%, while the yield of pyrolytic liquid from the separate pyrolysis of DS and WT under the same conditions was 49.20 and 51.55%, respectively. Gas chromatography/mass spectrometry (GC/MS), ultimate analysis, and proton nuclear magnetic resonance spectroscopy (1H NMR) were employed to identify the liquid fuel. The GC–MS showed that aromatics (mono- and poly-aromatics, 32.11%) and D-limonene derivatives (30.97%) were the major components of the liquid fuel. Unsaturated hydrocarbons (13.25%), S-containing compounds (8.10%), oxygenated hydrocarbons (11.06%), and saturated hydrocarbons (3.20%) were also present in the fuel. The percentage of O-compounds in the liquid oil obtained from the co-pyrolysis was much less than that observed in the liquid oil obtained from DS pyrolysis, suggesting that the co-pyrolysis of DS and synthetic wastes like WT could be a potential method of upgrading the crude bio-oil produced from the pyrolysis of DS. The co-pyrolysis of DS and WT upgraded the properties of the fuel produced by decreasing its O-compound content.