Reactive dissolution of cellulose and pulp through acylation in pyridine

The direct acylation of cellulose and different pulps with various acid chlorides was systematically screened. The syntheses were started in a heterogeneous solid–liquid reaction medium in hot pyridine with aliphatic and aromatic acid chlorides. After a few hours, depending on the reagent used, a homogenous solution was obtained. The obtained cellulose esters usually show a high degree of substitution (DS) and polymerization and are soluble in organic solvents. Esterification of softwood dissolving pulp, hardwood kraft pulp and hardwood kraft pulp-hemicellulose poor were also studied. The results show that almost identical DS were obtained for pulp derivatives compared to esters of microcrystalline cellulose. Thermogravimetric analysis and differential scanning calorimetry of the synthesized materials showed an improved thermal stability and various discrete thermal transitions compared to the original cellulose. The scanning electron microscopy images of derivatives showed a relatively flat and smooth surface with an absence of fibrous structure. The reactive dissolution of cellulose or pulp in pyridine is a straightforward and easy route to obtain long-chain aliphatic and aromatic cellulose esters.