TGA-FT-IR Analysis of Evolution of Oxygenated Organics by Isothermal Low-Temperature Decomposition of Rice Straw Hydrolysis Residue

The study presents a TGA-FT-IR analysis of low-temperature thermochemical transformations of Rice straw hydrolysis residue (RSHR). Isothermal decomposition of RSHR was carried out for 3 h, at decomposition temperatures of 200, 250, 300, and 350 oC. At 200 oC, the rate of mass loss never exceeds %1/min and except for the first five minutes, it is less than %0.5/min. The initial rate of mass loss at 250 oC is %1.6/min which quickly drops to %0.6/min in the first 10 minutes and goes on further decreasing thereafter. At 300 oC, there is a rapid initial mass loss with the initial rate peaking at %8.8/min. At 350 oC, there is an initial burst of volatiles accounting for most of the mass loss with the initial rate of mass loss being %50/min. The residual mass obtained after these runs was 81.5, 38, 24, and 15%, respectively. FT-IR spectra of evolved gases suggest that volatile oxygenated organics along with non-condensable components like CO2, and CO are evolved during low-temperature thermal decomposition of RSHR. Carbonyls – acids, esters, aldehydes, and ketones – are the main functional groups in the volatiles. Strong absorption bands ranging 3400 – 3900 cm-1 indicated the presence of alcohols and phenols as other functional groups. Decomposition residues, the biochar, were demethoxylated and dehydrogenated compared to RSHR but retained their basic lignocellulosic nature.