Role of H₂O in Oxidative Regeneration of ZnS Formed from High-Temperature Desulfurization ZnO Sorbent

Abstract

To develop an easily regenerable zinc oxide high-temperature desulfurization sorbent, the role of H2O in the course of oxidative regeneration of zinc sulfide in the presence of O2 were studied using ZnO without support material as a sorbent. Oxidative regeneration of ZnS in the presence of water vapor was examined using TPR technique and H2 18O. From this study, the following results were obtained: ZnS was converted to SO2 and H2 by H2O in the absence of O2 at high temperature (> ca. 600 °C); in the first step in the oxidative regeneration, ZnS predominantly reacted with H2O more than O2; the SO2 formed from ZnS contained oxygen from H2O. From the experimental results, it was found that the oxidative regeneration of ZnS in the presence of H2O and O2 can be expressed by the following two equations: ZnS + 3H2O ⇔ ZnO + SO2 + 3H2; 3H2 + 3/2O2 ⇒ 3H2O. In the absence of H2O or in the case of very low value of H2O/O2 concentration ratio, the following reaction also occurred: ZnS + 3/2O2 ⇒ ZnO + SO2

Investigation of sulfidation and regeneration of a ZnO-adsorbent used in a biomass tar removal process based on catalytic steam reforming

“…The published results show that when oxygen was present in the regeneration gas, the regeneration was completed at a maximum temperature of 750°C at all tested conditions [21].…”

“…Sasaoka et al [21] sulfided the ZnO-samples in a microreactor at 450°C with a synthetic gas mixture containing 500 ppm V of H 2 S. The regeneration of the samples was carried out in a temperature programmed reaction (TPR) apparatus combined with a quadrupole mass spectrometer. The TPR was heated to 900°C at a rate of 10°C/min.…”

“…The TPR was heated to 900°C at a rate of 10°C/min. According to Sasaoka et al [21], two mechanisms can lead to the regeneration of ZnS. In the first mechanism, shown in Eqs.…”

“…Further, Sasaoka et al [21] reported that at lower temperatures of about 600°C, water reacted mainly with the ZnS. It was suggested that water dissociated on the ZnS-surface according to Eq.…”

“…(9) and reacted with the ZnS in this state via several reaction steps. H 2 O generally accelerates regeneration reactions [21].…”