KINETICS OF FORMATION OF HCL(G) BY THE REACTION BETWEEN NACL(S) AND SO2, O2, AND H2O(G)

The kinetics of the reaction NaCI(s) + 1/2SO2(g) + 1/4O2(g) + 1/2H2O(g) HCI(g) + V2Na2SO4(s) has been elucidated by laboratory studies at 600 °C (300-900 °C). The rate of reaction, expressed as the amount (moles) of HCI formed per unit of time (and surface), dnHCl/dt, obeys the following rate law: dnHCI/dr = k-pSO2V2-p02 1/2, where k is a specific rate (temperature dependent), and pSo2 and p02 are partial pressures. The rate is practically independent of PH2O Tnis rate law may be explained in terms of a rate-limiting reaction step: SO2(ads, 2∗) + 1/2O2(ads, 2∗) — SO3(ads), between SO2 and O2 molecules adsorbed on two sites (∗) each, on the surface of the NaCI phase. The SO3(ads) then may be assumed to react with adsorbed H2O and with NaCI, probably via the intermediates H2SO4(ads) or NaHSO4, to form the final products HCI and Na2SO4. The magnitude of the specific rate, k, is generally low (reaction rate slow) which may explain the limited rate of HCI formation under recovery furnace conditions. © 1979, American Chemical Society. All rights reserved.