Catalytic Slow Pyrolysis of Corncob Using Rice Husk-Derived Zeolite-A: The Effect of Temperature and Catalyst-to-Biomass Ratio on Pyrolysis Oil Characteristics

Abstract

The depletion of fossil fuel reserves and the growing environmental concerns associated with their use have intensified interest in renewable biofuels. Corncob waste, a lignocellulosic biomass composed of approximately 41% cellulose, 36% hemicellulose, and 6% lignin, represents a promising feedstock for pyrolysis oil production. However, conventional pyrolysis processes typically produce pyrolysis oil with low conversion, low density, and poor stability. This study investigated catalytic pyrolysis in a fixed-bed reactor employing Zeolite-A synthesized from rice husk-derived silica to improve pyrolysis oil quality. Catalytic pyrolysis experiments were conducted at various temperatures (300 °C, 350 °C, and 400 °C) and catalyst-to-biomass ratios (1:0 to 1:20 w/w). The highest pyrolysis oil yield of 34% was achieved at 400 °C without a catalyst (1:0 w/w), indicating that while catalyst presence is not essential for maximizing yield, it plays a crucial role in modifying the physicochemical properties of the oil and accelerating the overall reaction. Oil density ranged from 1.24 to 1.35 g/mL, peaking at 400 °C and 1:15 w/w, reflecting enhanced cracking and polymerization. Viscosity varied from 85.28 to 116.00 mm²/s, increasing with catalyst ratio and influenced by the temperature-dependent cracking and secondary reactions. GC-MS analysis identified hydrocarbons including androstane and spirocyclic compounds, confirming the improvement in fuel quality through catalytic deoxygenation. These findings highlight the potential of Zeolite-A-catalyzed pyrolysis for producing high-quality liquid biofuels.