Combustion performances evaluation of bio-oil upgraded via catalytic cracking of coconut oil

Thermal cracking of vegetable oils faces challenges like high acidity. This study employed a two-step process: thermal cracking of coconut oil (yielding oil with acid value > 100 mg KOH/g), followed by gas-phase catalytic cracking using CaO (30 wt%) at 450°C. This upgrading successfully reduced the acid value to 2.8 mg KOH/g, producing Catalytic Cracking Oil (CCO) with a 64.1% liquid yield. CCO was blended with diesel (binary: C10-C30) and diesel/biodiesel (ternary: C5B5-C15B15). Engine tests at 1800 rpm showed blends achieved effective thermal efficiencies (ETEs) nearly identical to diesel at high loads. Under lower loads, binary blends demonstrated lower equivalent specific fuel consumptions (ESFCs) and higher ETEs than ternary blends at equal substitutions. Combustion analysis (50%/100% loads) revealed distinct pre-injection and main injection peaks in heat release rate (HRR), pressure, and temperature. Compared to diesel, blends exhibited lower HRR and pressure peaks during pre-injection but higher HRR peaks during main injection. Overall, the upgraded CCO shows potential as a diesel fuel extender, achieving comparable high-load ETE.