The kinetic study of fruit processing waste pyrolysis for efficient production of platform chemicals

Abstract

This paper considers possible uses of fruit-based waste for the production of valuable chemicals and biofuel precursors through recycling by thermochemical conversion. Slow pyrolysis of goji berry mesocarp as sugar-riched feedstock was investigated using simultaneous thermal analysis measurements in non-isothermal conditions. This work announced that pyrolysis of goji berry mesocarp represents a promising route to obtaining an important key platform chemical - 5- hydroxymethylfurfural (5-HMF). To establish the process mechanism, two kinetic approaches were used for kinetic parameters determination: first, Friedman’s and Vyazovkin’s model-free (inverse) methods supported by numerical optimization of the process, and second, the modelbased (direct) method. Model-free results showed a complex evolution of activation energy with conversion, indicating a multi-step mechanism. It was found that autocatalytic dehydration of fructose (in the presence of Lewis acids) is responsible for the production of 5-HMF at a low heating rate (5.0 K/min) with a maximum 5-HMF theoretical yield of 63.20 %. Higher heating rates (10.0 K/min and 15.0 K/min) trigger the fructose autogenesis behavior which opens the transferability channel to glucose (substrate) engagement for 5-HMF theoretical high yield production. It was revealed that differences between kinetic parameters are a consequence of the change in the mechanism of glycosidic bond cleavage. The validity of the proposed reaction mechanism scheme and accuracy of kinetic parameters was confirmed by modulated dynamic predictions.