Study on the thermal decomposition characteristics of different carbohydrates by TG-FTIR-GC/MS

Abstract

Thermal decomposition of carbohydrates plays a critical role in various technological fields, including biomass energy conversion, thermal food processing, and the synthesis of functional carbon materials. This study investigated the thermal decomposition of carbohydrates at a high heating rate in both inert (N₂) and oxidative (air) atmospheres. The analysis was performed using thermogravimetric analysis (TGA) coupled with Fourier-transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC/MS). This approach enables the simultaneous detection of small-molecule gases and organic volatiles. Each carbohydrate exhibited the same number of pyrolysis stages in both N₂ and air. The temperature corresponding to the maximum mass loss rate observed in air was consistently lower than or equal to that in N₂. The presence of oxygen promoted pyrolysis reactions, resulting in minimal residual carbon in air. Infrared absorption peaks indicated that the main pyrolysis products of carbohydrates appeared at 400 °C. CO₂ was the dominant gaseous product in both atmospheres, with significantly higher yields in air. Other major small-molecule gases evolved included H₂O, CO, and CH₄. GC/MS analysis identified furans, aldehydes, and ketones as the major organic volatiles, with minor amounts of acids, esters, dehydrated carbohydrates, benzene, phenol, and crotonaldehyde. While furfural was the dominant product in N₂, both furfural and 5-hydroxymethyl furfural were identified as the primary products in air. This research investigated the thermal decomposition behavior and characterized the pyrolysis products from carbohydrates at a high heating rate.