A comparative study on pyrolysis behaviors, product distribution, and kinetics of waste cotton stalk under different organic acidic solutions pretreatment

This study aimed to disclose the effects of different organic acidic solutions' (phenol, guaiacol, citric acid, and acetic acid) pretreatment on the pyrolysis characteristics of waste cotton stalk (CS). Firstly, the organic acidic solutions' pretreatment could effectively improve the physicochemical properties of CS, showing a similar result to inorganic acid pretreatment. The thermogravimetric (TG) analysis indicated that pretreatment was helpful to inhibit the formation of char and enhance the escape of volatile matters. For pyrolysis products, pretreatment promoted a significant increase in the content of anhydrosugars, increasing by 12.48% at most (in Acetic Acid-CS). Besides, pretreatment inhibited the formation of ketones, with a maximum decrease of 11.72% (in Acetic Acid-CS). And the content of nitrogen-containing compounds was also reduced, which made the pyrolysis products more stable and environmentally friendly. The content of C6-C9 compounds was dramatically increased after pretreatment, conducive to upgrading to refined gasoline. Additionally, the apparent activation energy (E-alpha) was calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, and the results indicated that less energy was required for pyrolysis of cotton stalk pretreated with citric acid or acetic acid.