Comparative impact of acidified glycerol pretreatment on the thermal degradation kinetics of crude wheat straw for potential sustainable valorization

The relative impact of acidified glycerol pretreatment on thermal disintegration kinetics and thermodynamic parameters of crude wheat straw (WS) was studied using thermogravimetric analysis coupled with Horowitz-Metzger kinetic method under numerous reaction models. The WS fiber was dissolved in acidified glycerol solution under gentle pretreatment conditions of 90 degrees C for 30 min and was also pretreated by conventional methods including dilute alkaline, acid and hot water to foster a better insight and compare the capability of acidified glycerol for pretreatment of WS fiber. The apparent activation energy values of 27.8-31.8 kJ/mol and 32.3-38.2 kJ/mol were obtained for untreated and glycerol treated WS fibers, whereas the highest values, ranging from 36.2 to 42 kJ/mol, were obtained for alkali treated fiber. The change in enthalpy (Delta H degrees) for untreated WS fiber was within the range of 50.9 to 59.3 kJ/mol. This was enhanced to 59.8-71.6 kJ/mol, 63.6-74.0 kJ/mol and 63.1-74.9 kJ/mol for acidified glycerol, acid and alkali treated WS fibers. Pretreatment with acidified glycerol and alkali reagents increased the Delta G degrees values of WS fiber to 181.2 kJ/mol and 178.6 kJ/mol, in contrast to the value of 167.7 kJ/mol for untreated sample.