Investigation of the reaction kinetics of 3-chloro-2-hydroxypropyl-N,N,N-trimethylammonium chloride (CHPTAC) with cellulose fibres

In the reaction system consisting of 3-chloro-2-hydroxypropyl-N,N,N-trimethylammonium chloride (CHPTAC), sodium hydroxide, cellulose and H₂O, it is widely accepted that the low reaction yield is the result of fast alkaline hydrolysis of CHPTAC. Some inconsistencies remain unexplained by rapid hydrolysis alone, indicating the need to understand the role of the cellulose-NaOH interaction to advance beyond the current state of the art. This raises two key questions: is NaOH uptake on cellulose decisive for cationisation yield, and is all epoxide consumed by end of the cationisation? Investigations into the reactions rates were conducted in the absence and the presence of cellulose fibres by applying a novel ion-exchange high-performance liquid chromatography method and nitrogen analysis to quantify both reactant in solution and product formation. It was found that hydrolysis rates are slower in the presence of the fibre, which was attributed to sorption of reactants, particularly sodium hydroxide, onto the fibre. The bonding of CHPTAC to cellulose shows initially high reaction rates but approaches a plateau, even though 40% of the cationisation agent is still available in solution. This phenomenon is attributed to the consumption of "active" (deprotonated) cellulose sites, highlighting the need for improved understanding of the cellulose-NaOH interaction, and its influence on derivatisation reactions.