Kinetics Study Of Homogeneous Cellulose Acylation In An Ionic Liquid And Its Reuse And Recycle

With the non-renewable resource becoming more and more exhausted, cellulose has attracted much attention for its plentiful and renewable. Recently cellulose derivatives are more and more popular. For example, cellulose esters are one of the most important cellulose derivatives, which have wide application in our daily life. However, the derivatization of cellulose is very challenging due to its complex inter and inner hydrogen bond and super-molecular structure. Ionic liquid as a novel green and environmentally friendly solvent, have attracted much interest of the researchers for its excellent properties, such as thermal stability, lower melting point, negligible vapor, especially good solubility for cellulose, which provide a new way for cellulose functionalization, and thus increase the efficiency of cellulose derivatization.The homogeneous cellulose esterification is successful in lab, to provide the basis for large scale production, as well as better control of conditions and increase the derivatization rate, using ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as reaction media, cellulose as raw material, the kinetics of homogeneous acylation of cellulose in ionic liquid was studied in this paper. The effect of initial cellulose hydroxyl concentration from 0.21 to 0.85 mol·L^-1 and temperatures from 353 K to 373 K on the acylation rate were measured. Results showed that the acylation rate increases with increasing initial cellulose hydroxyl concentration and reaction temperatures. The reaction kinetic equations were determined based on the experimental data. The reaction order for both acylation by acetic anhydride and by mixture of butyric anhydride and acetic anhydride is first-order, and their apparent activation energies are 19.03kJ·mol^-1 and 20.04kJ·mol^-1 respectively.At last, the recycle and reuse of ionic liquid in the homogeneous cellulose acylation is studied in order to resolve the problem of high cost of IL in the large scale production of cellulose esters. The conventional vacuum distillation and molecular distillation were used to recycle the IL; the effects of the operating parameters, including evaporating temperature, operating pressure, feeding flow rate on the purity of IL were studied. According to andorthogonal experiment data, the optimum conditions of recycling on ILs were obtained. Results showed that the purity of the recycled ILs can reach up to as high as 99.5%, and the product prepared in both fresh and recycled IL is consistent with each other.