Effect of the polymorphs of cellulose on its pyrolysis kinetic and char yield

- How cellulose polymorphs affect its pyrolysis kinetics and char yield was compared.
- Char yield is in the sequence of cellulose I > cellulose II >amorphous cellulose.
- The additive improves the char yield of cellulose regardless its polymorphs.
- The hydrogen bonding of cellulose possibly affects its pyrolysis pathways.

In this study, we show that the polymorph type of cellulose is an important factor for its pyrolysis behavior. By using TGA, XRD and FTIR, we characterized the pyrolysis kinetics and char yields of amorphous cellulose, cellulose II and cellulose I. All these celluloses with various polymorphs were regenerated from the same source material, microcrystalline cellulose; thus, the lattice difference among these samples was the only factor affecting their thermal pyrolysis. We found that the char yield of cellulose I was the highest among all cellulose polymorphs. With the addition of 5% phosphoric acid, the char yield of cellulose I at 800 °C was as high as 37.4%. The char yield of cellulose I at 800 °C is more than 10% higher than that of cellulose II regardless the addition of additives. This study highlights that the lattice structures of cellulose affects both its thermal pyrolysis kinetics and the char yield. For improving the char yield of cellulose, both structural factors and impregnated additives play independent and important roles.

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