Catalysis Mechanism Study of Potassium Salts on Cellulose Pyrolysis by Using TGA-FTIR Analysis

Abstract

The catalytic effect of three kinds of potassium salts on cellulose pyrolysis kinetics and products was studied on a thermogravimetric analyzer coupled with a Fourier transform infrared spectroscopy. Experimental results showed that potassium salts catalyzed the dehydration and depolymerization reactions in the initial pyrolysis stage, enhanced the release of oxygenated gases, intensively catalyzed the formation of char, and restrained the production of volatiles. Kinetic modeling showed that the presence of potassium ions provided a mechanistic route with lower activation energy, and accelerated the pyrolysis rate. Both KCl and K₂CO₃ restrained the release of levoglucosan, glycoaldehyde and C=O containing compounds, while K₂SO₄ largely promoted the formation of levoglucosan. The presence of KCl and K₂CO₃ might have retarded the unzipping reaction at the terminal units of the cellulose chain, and thus restrained the formation of levoglucosan. K₂SO₄ exhibited different catalytic mechanisms, which uniquely catalyzed the formation of levoglucosan.