Esterification optimization of cellulose with p-Iodobenzoyl chloride using experimental design method

Abstract

The synthesis and characterization of kraft cellulose p-iodobenzoate is presented in this paper. The ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as a reaction medium for the synthesis of cellulose p-iodobenzoate by homogeneous esterification of dissolved kraft cellulose with p-iodobenzoyl chloride. The degree of substitution (DS) of cellulose ester was calculated from the 1H-NMR spectra. In first time, the chemical structure and properties of the obtained products were characterized by FT-IR and NMR spectroscopy. Cellulose p-Iodobenzoates ester with a DS in the range from about 0.18 to 2.05 were accessible under mild conditions. The DS of cellulose ester increased with the increase of the molar ratio of iodobenzoyl chloride/anhydroglucose unit in cellulose, reaction time, and reaction temperature. In second time, the Response Surface Methodology (RSM) that was based on a Box-Behnken design was used for optimize the esterification of cellulose. The effects of three parameters were investigated: (X1) number of mole of reactant, (X2) reaction temperature, and (X3) reaction time. The Analysis of variance (ANOVA) indicated that linear terms of (X1), (X2), (X3), the quadratic term of (X12) and (X32) have a significant effect (p < 0.10 with a 90% confidence level) on DS of cellulose ester. The fitted model indicated that the optimum reaction conditions to esterification of cellulose were: number of mole 7,49 mol, reaction temperature 100 °C, and 217,50 min for reaction time, respectively. Under these conditions, the numerical estimation of DS was 2,051. This result was experimentally validated obtaining a difference of 2.7% DS of cellulose ester, with respect to simulated values.