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

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.