Reaction kinetics of sodium carboxymethyl cellulose synthesis: Effects of reaction time and temperature on degree of substitution

Chemical Engineering Department, Faculty of Engineering, Universitas Gadjah Mada, Jl. Grafika 2, Yogyakarta 55281, Indonesia

^* Corresponding author: yuni_kusumastuti@ugm.ac.id

Abstract

This study investigated the reaction kinetics of sodium carboxymethyl cellulose (NaCMC) synthesis from a-cellulose to determine the reaction order based on the degree of substitution (DS). As part of the process, an isopropanol-ethanol solvent system combined with 20% NaOH was sequentially alkalized at 30 °C, followed by carboxymethylation occurred for 20-1880 min in a concentration of 25% thricloroacetic acid (TCA) at 45 °C, 55 °C, and 75 °C. DS values are determined via acid-base titration. Fourier-transform infrared spectroscopy (FTIR) confirms the successful incorporation of carboxymethyl groups through characteristic absorption peaks. Results show that both times and temperature significantly influence DS. A longer carboxymethylation process at moderate temperatures increased the substitution efficiency, resulting in a DS of 0.70-1.20, which meets the SNI 3736-1995 standard. Kinetic analysis showed that the reaction followed second-order kinetics with respect to DS, with the rate constant increasing with increasing temperature. These findings provide important parameters for optimizing NaCMC synthesis and highlight its potential in polymer based applications, particularly hydrogels.