Pyrolysis of Camellia oleifera Shell at Intermediate Temperatures, and Prediction of Bio-oil Component Levels by Mathematical Modeling

Abstract

Camellia oleifera shell was pyrolysed at 300 to 750 °C to investigate biochar and bio-oil yields under different conditions, and the relationships between pyrolysis temperature and the product yields were established. The thermal decomposition behavior, biochar characteristics, and bio-oil composition were analyzed. The fixed carbon content of C. oleifera shell reached 22.2%, exceeding common biomass materials. Biochar yield decreased from 57.9% to 31.7% as temperature increased from 300 °C to 750 °C, while bio-oil yield increased from 14.4% to 37.1%. The established temperature-dependent yield models demonstrated excellent predictive capability (R²=0.99). Final carbonization levels under heating rates of 5, 10, and 15 °C/min were 35.4%, 29.4%, and 27.2%, respectively. Biochar pore volume increased with pyrolysis temperature, while specific surface area and average pore diameter exhibited an initial rise followed by decline. Specific surface area increased as temperature rose, with predominant pore diameters distributed between 10 and 30 nm. Bio-oil composition analysis revealed acids as predominant components (40.9% to 49.9%), followed by phenols (20.2% to 27.3%), aldehydes (9.2% to 10.2%), ketones (8.4% to 11.8%), esters (3.4% to 3.6%), and alcohols (0.41% to 1.07%). This study provides guidance for optimizing pyrolysis conditions to obtain target products.