Conversion of cotton byproducts to mixed cellulose esters

Cotton byproducts, such as cotton burr and cottonseed hull, can be used as low-cost feedstock for the production of specialty chemicals. The conversion of these cellulosic byproducts into mixed cellulose esters, e.g., cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB), was studied. Instead of using the conventional process for preparing these materials, which uses the appropriate anhydrides, sulfuric or perchloric acid, and methylene chloride as solvent, an iodine-promoted process was used that requires no chlorinated solvent in the reaction mixture. Product ester ratios and degrees of substitution were determined by 1H NMR spectroscopy. At the conditions studied, acetic anhydride was only slightly more reactive than propionic anhydride in the formation of CAP, but acetic anhydride was noticeably more reactive than butyric anhydride in the formation of CAB.