Non-isothermal pyrolysis of pectin: A thermochemical and kinetic approach

• The pyrolytic degradation of the citrus pectin was investigated.
• The pyrolysis decomposition of pectin occurred in at least four main stage.
• Kinetic parameters were calculated by three kinds of model-free kinetics algorithms.
• The kinetic analysis shows the typical behavior of multi-step kinetic processes.
• The direct gasification of char proceeds through autothermic process.

The thermal degradation of pectin was investigated by simultaneous TGA-DSC/FTIR analysis and Hi-Res/modulated-TGA technique under nitrogen atmosphere. Pyrolytic degradation is a complex set of simultaneous and consecutive reactions related to: (i) dehydration at temperatures ≤100 °C; (ii) initial depolymerization by breaking the glycosidic linkages for temperature ≤210 °C, (iii) secondary degradation of the pectin units between 250 and 580 °C, and (iv) direct gasification of char residues at temperatures ≥600 °C. Three model-free-kinetics algorithms, Friedman (F), Kissinger–Akahira–Sunouse (KAS) and modulated TGA (MTGA), were used to predict the pyrolytic cracking kinetics. The results are discussed in terms of activation energy, the most probable mechanisms, and their relationship with the structure.