Mechanistic insights into the pyrolysis of pine resin sludge based on experiments and ReaxFF-MD simulation: High-value bio-oil production, nitrogen conversion, kinetics and environmental risk assessment

Forestry and agro-industrial waste conversion into high-value chemicals and fuels is considered one of the hottest ongoing research and industrial topics toward sustainable development. As one of the forestry and agroindustrial waste, pine resin sludge (PRS) with amino acids, pine resin residues and their derivatives such as abietic acid and 4-Epidehydroabietal, have ecological toxicity and require environmentally friendly treatment. Herein, a thermal process of PRS that generates high-value biofuels while reducing environmental pollution was reported. The results of the experiment and simulation reveal that the N of bio-oil is the major evolution direction of N, and the nitrogenous gas product is mainly NH3, a useful synthesis gas. ReaxFF-MD simulations elucidated the migration and conversion mechanism of nitrogen in amino acids. The main products of amino acid pyrolysis are 3-oxo-2-Propenenitrile, 2,4-Cyclopentadien-1-ylidenemethanone and 4R)-4-amino-5,5-dihydroxypentanoic acid. PRS's thermal weightlessness was divided into three phases, and the average activation under nonisothermal conditions was calculated at 78.17, 85.68, 206.42 kJ/mol (thermal decomposition) and final 117.78, 149.31, 195.54 kJ/mol (thermal oxidation). Thermal decomposition and oxidation process followed Avrami-Erofeev model (n=2), three-dimensional diffusion model (n=3) and mampel power (n=1). PY-GC/MS analysis shows that pyrolysis at different temperatures recovered mainly 4-Epidehydroabietal (37.15-89.67 %) for potential use as the biosynthesis of dehydrofolate. The bio-oil from PRS pyrolysis shows an excellent yield (31.43 %) and a high calorific value (37.21 MJ/kg), which is comparable to biodiesel. This work focused on offering an appealing and instructive guide for the logical treatment of sludge from pine resin production.