Surface-modified cellulose for CO2 hydrate control: molecular insights and sustainable inhibitor design

Abstract

As one of the most abundant natural polymers, cellulose is recognized for its eco-friendly nature and broad applicability. In this study, physical, chemical, and combined physical-chemical treatments were applied to hydrophobic microcrystalline cellulose (MCC) to evaluate its potential use as a CO2 hydrate inhibitor. The cellulose-based inhibitors exhibited excellent biodegradability, and physical treatment was found to reduce the particle size of MCC. Experimental results showed that both non-treated MCC and physically treated cellulose (denoted as HPHC) had an insignificant impact on the hydrate nucleation. In contrast, the chemically treated cellulose (denoted by SMIC) exhibited pronounced CO2 hydrate inhibition by decreasing the hydrate onset temperature by similar to 3.7 K, which was comparable to that of PVCap. The underlying mechanisms responsible for the improved inhibition were investigated through additional experiments and molecular dynamics simulations. The DSC results demonstrated that SMIC showed strengthened interactions between cellulose and surrounding water molecules, which is a major mechanism of hydrate nucleation inhibition. Furthermore, the chemical modification decreased the binding free energy of MCC from -0.37 to -1.95 kJ mol-1, which is associated with the enhanced thermodynamic favourability of cellulose adsorption onto the growing CO2 hydrate surface. The improvement in the adsorption capability contributed to the improved hydrate growth inhibition of cellulose. Our findings deepen the understanding of hydrate inhibition mechanisms, highlight the promise of chemically modified cellulose as a sustainable hydrate inhibitor, and offer a foundation for the rational design of next-generation eco-friendly inhibitors through molecular-level tailoring.