Preparation Of Cellulose Acetate Through Acetylation Reaction Of Cellulose Under The Catalysis Of Ionic Liquids

Cellulose acetate is prepared through acetylation of cellulose with acetic anhydride, it is usually applied to the cigarete filter material. In this paper, the relevant research about new ionic liquids applied as the catalyst of cellulose acetylation were carried out.Firstly, three ionic liquids N-methylimidazole hydrogen sulfate ([Hmim]HSO4), N-methylpyrrole hydrogen sulfate ([Hnmp] HSO4), 1-methyl-3-sulfonic acid propyl imidazole hydrogen sulfate ([HSO3-pmim]HSO4) were synthesized according to the existing literature methods. The structure of ionic liquids is determined by FTIR and 1H-NMR. UV-Vis spectrophotometer was used to analysis and compare the acid strength of three ionic liquids, [Hmim] HSO4<[Hnmp] HSO4<[HSO3-pmim] HSO4, TG Analysis results showed that the three ionic liquid takes thermal stability, thermal decomposition temperature were 332℃,236℃,307℃, respectively.Ionic liquids [Hnmp] HSO4 and [HSO3-pmim] HSO4 were used as the catalyst of cellulose acetylation. The effect of reaction time, temperature, catalyst concentration, molar ratio of acetic anhydride with cellulose on cellulose acetate substitution degree and intirinsic viscosity was studied. The optimum condition of preparation different substation cellulose acetate with [Hnmp] HSO4:reaction time 3-4 h, temperature 50～60℃, catalyst concentration 12%, n (acetic anhydride):n (cellulose)= 5～8. The optimum condition of preparation different substation cellulose acetate with [HSO3-pmim] HSO4:reaction time 1-2 h, temperature 50℃, catalyst concentration4～8%, n (acetic anhydride):n (cellulose)= 5～8. Thererfore, cellulose acetate of uniformity substitution degree distribution(2.0～3.0) can be prepared under the catalysis of [Hnmp] HSO4 and [HSO3-pmim] HSO4.FTIR, NMR, SEM, XRD and TG were used to analysis the structure, morphology, thermal stability performance of cellulose acetate. [HSO3-pmim] HSO4 takes better catalytic effect than [Hnmp]HSO4, it is possible to replace the concentrated sulfuric acid as the catalyst of cellulose acetylation reaction in the future.