Reaction Kinetics and Subsequent Rheology of Carboxymethyl Guar Gum Produced from Guar Splits

Carboxymethyl guar gum (CMG) has been widely used in various industrial fields, although its use is especially important in hydraulic fracturing operations because of the high viscosity of its aqueous solutions and the ability to reversibly cross-link the material. However, detailed reaction kinetics for production of carboxymethyl guar has not been previously reported. In this study, we use a two-step environmentally friendly method to produce carboxymethyl guar gum by chemical modification of guar gum (GG) splits. We quantify conversion by NMR spectroscopy and wet chemistry methods and establish a structure and property relationship based on the rheological properties of corresponding CMG products. In addition, borate and zirconium cross-linkers are applied to study the rheological effect of cross-linking on GG and CMG aqueous solutions. Furthermore, we investigate, for the first time, the reaction kinetics of carboxymethylation of guar splits and report a rate equation to quantify the reaction kinetics.