Linear Driving Force Approximations as Predictive Models for Reactive Sorption

Herein, the utilization of linear driving-force approximations as predictive models for hydrogen sulfide removal on a commercial copper-based sorbent is assessed. Sorption experiments are carried out in a fixed-bed reactor at different flow conditions, temperatures, total pressures, and inlet hydrogen sulfide concentrations. For large pellet sizes (>= 800 mu m), quasi-chemical linear driving-force approximations, that are first order in both bulk gas-phase concentration and solid-phase capacity, effectively model contaminant breakthrough curves. Experimentally determined rate parameters (10.7 +/- 0.7 s(-1) and 6.5 +/- 0.5 s(-1) for 800 and 1000 mu m-sized particles, respectively) reflect those determined from pore diffusion within pellets. For small pellet sizes (<= 212 mu m), linear driving-force approximations, that are zero order in bulk gas-phase concentration but first order in solid-phase capacity, model contaminant breakthrough curves; and rate parameters reflect reaction and diffusion at reactive interfaces rather than bulk or pore diffusion. These studies demonstrate that linear driving-force approximations can model experimentally determined trace hydrogen sulfide removal parameters. Alternatively, under conditions where bulk and/or pore diffusions are limiting, the rate parameters can be calculated from known engineering theories (e.g., the Chapman-Enskog relation or the Wilke-Chang correlation).