Pyrolysis of Date Stones Using Natural Activated Kaolin as a Catalyst – Optimization of Variables and Identification of Bio-Oil

Abstract

This research examines the catalytic performance of the catalyst developed from natural kaolin clay as a cheap catalyst for the thermal pyrolysis of date stones (DS). Firstly, the natural kaolin clay was acid-treated, followed by thermal activation at 600 °C for 2h to obtain the activated kaolin catalyst (AKC). Several techniques, like BET surface area, pore volume distribution, XRD, FESEM, and EDX, were utilized to identify the AKC. The BET surface area of the AKC was 119.49 m2/g, while its mean pore diameter amounted to 7.13 nm, indicating its mesoporosity. The catalytic activity of the AKC was examined via the thermal pyrolysis of DS. Effect of pyrolysis temperature (400-500 °C), catalyst loading (2.5-10.0 wt.%), pyrolysis period (30-120 min), and particle size of DS (0.25,0.297,0.4,0.595, and 0.841 mm) on the pyrolysis products yield was investigated. The highest yield of pyrolytic liquid was produced at 425 °C for 1h using 2.5 wt.% of the AKC and 0.40 mm participle size of the feed. At these conditions, the pyrolytic liquid yield amounted to 60.64 %. The analysis of the bio-oil (BO) fraction stripped from the pyrolytic liquid was achieved by FTIR spectroscopy, 1H NMR spectroscopy, and GC-MS analysis, which indicated that the BO fraction was mainly composed of hydrocarbons and oxygenated hydrocarbons. Results from the GC-MS analysis exhibited that hydrocarbons (48.28 %), oxygenates (41.42 %), aromatics (10.44 %), and nitrogenates (2.13 %) were the main components of the BO. Alkenes and n-alkanes were the main constituents of the hydrocarbon part of the BO, while acids were the main component of oxygenates. Non-catalytic thermal cracking of DS at the optimal conditions exhibited a lower pyrolytic liquid yield than the catalytic process. Finally, the fuel properties of the BO produced via catalytic pyrolysis of DS were superior to those measured for that produced by the thermal pyrolysis process.

Keywords

• date stones
• activated kaolin catalyst
• catalytic pyrolysis
• bio-oil
• identification of bo