Effect of the benzene ring of the dispersant on the rheological characteristics of coal-water slurry: Experiments and theoretical calculations

In this study, low-rank coal-water slurry (LCWS) was prepared using polyoxyethylene dodecylphenol ether (PDPE) and polyoxyethylene lauryl ether (PLE), respectively. A combination of experiments and simulations was used to investigate the pulping properties and microscopic mechanism of the LCWS samples prepared using the two agents, so as to explore the influence of benzene ring on the performance of dispersant. The results of the LCWS preparation experiments revealed that the pulp-forming performance of PDPE exceeded that of PLE. When LCWS concentration is 62%, 64%, and 66%, the apparent viscosity corresponding to PDPE is 247.80, 504.17, and 653.10 mPa·s, and the apparent viscosity corresponding to PLE is 548.10, 1470.61, and 1549.98 mPa·s, respectively. The C1000 (When the apparent viscosity is 1000 mPa·s, the corresponding concentration of LCWS is defined as C1000) values of PDPE and PLE are 67.60% and 62.95%, respectively. In addition to the van der Waals forces and hydrogen bonds between the PDPE and/or PLE molecules and coal, the benzene rings of PDPE present π-π stacking effect with the aromatic rings of coal. That could facilitate and strengthen the adsorption of PDPE on coal, which would be conducive to further improving the dispersion of coal particles. The two dispersants have no significant difference in effect on the pyrolysis of LCWS. The simulation results indicated that the times for PDPE and PLE molecules to reach flat adsorption state on coal are approximately 290 and 565 ps, respectively. The self-diffusion coefficient (D) of the PDPE and PLE on coal is 3.16 × 10−6 and 6.57 × 10−6 m2/s, respectively, and their interaction energies with coal are 785.71 and 648.60 kcal/mol, respectively. The results of the simulation calculations demonstrated that PDPE adsorbed on coal easier than PLE, and its binding is more stable than that of PLE owing to the π-π stacking effect, which is conducive to uniform dispersion of coal in solution. The simulation results confirmed the experimental results.