Thermodynamic and kinetic effect of biodegradable polymers on carbondioxide hydrates

In this work, the effect of biodegradable polymers, i.e. pectin (PC), sodium-carboxymethyl cellulose (Na-CMC), tapioca starch (TS) and dextran (DX) on thermodynamics and kinetics of CO2 hydrates are evaluated on sapphire hydrate reactor. The CO2 hydrate liquid vapour equilibrium (HLWVE) data is evaluated in the presence of biopolymers (1.5 wt%) using isochoric T-cycle method at temperature and pressure ranging from 278.7 to 283.0 K and 23 to 4.3 MPa respectively. The effect of biopolymers on HLWVE curve is reported by measuring average increment temperature (AT). The constant cooling method is used to evaluate the kinetics of CO2 hydrates at 4.3 MPa in the presence of biopolymers (0.12-1.5 wt%) at 274.15 K and 277.15 K. The inhibition effect of biopolymers on the kinetics of CO2 hydrate is reported by measuring induction time, hydrate formation rate and amount of gas consumed. The kinetic inhibition strength of biopolymers is compared with poly-N-vinylpyrrolidone (PVP) and with two non-commercial inhibitors, i.e. glycine and tetra-methyl ammonium chloride (TMACI) through relative inhibition strength (RIS). Results reveal that DX shows maximum increment temperature of 0.36 K. While PC and Na-CMC delayed CO2 hydrate nucleation for 423 and 181 min respectively. Additionally, biodegradation study on biopolymers indicates that, compared to PVP, biopolymers are easily biodegradable and show potential for gas hydrate offshore applications. (C) 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.