Kinetic and thermodynamic comparative study of quince bio-waste slow pyrolysis before and after sustainable recovery of pectin compounds

Abstract

This work aims to study and compare the kinetic and thermodynamic behavior of pyrolysis of quince waste (QW) and pectin-free quince waste (PFQW) after extraction. The pectin extraction with acid treatment had a yield of 3.2 ± 0.1 % (dry basis, db). Pyrolysis experiments were conducted in a macro-TG reactor at three heating rates (5, 10, and 15 °C/min) and temperatures in the range 27–900 °C under a nitrogen atmosphere. A better fit of the experimental data was achieved by modeling the reactions by a multi-step mechanism considering three different parallel reactions for thermal decomposition of hemicelluloses, cellulose, and lignin. The results indicated that the Flynn-Wall-Ozawa (FWO) method provided the best R2, MSE, and AAD values. The resulting values of the thermodynamic activation parameters ΔH, ΔG, and ΔS were 53.28–89.36 kJ/mol, 114.54–155.01 kJ/mol, and −0.17–(−0.04) kJ/(mol K) for pyrolysis of QW, and 29.97–90.68 kJ/mol, 99.42–158.86 kJ/mol, and −0.23 – (−0.01) kJ/(mol K) for PFQW. According to bioenergy indicators, PFQW presented good characteristics as a biofuel feedstock due to its high energy density values. The kinetic and thermodynamic parameters indicated greater reactivity of PFQW to pyrolysis compared to QW, showing that in addition to obtaining a product with added value, such as pectin, the extraction process generates a solid residue that is easier to treat under a thermochemical platform. The novelty of the paper focuses on the influence of the pretreatment of quince bio-waste (by extracting pectin compounds) on reactivity to pyrolysis, providing valuable kinetic and thermodynamic information.