Boosting deep desulfurization of heavy mercaptan using layered intercalated Zn-based hydroxide adsorbents

Abstract

Deep desulfurization of ppm-level secondary heavy mercaptan from hydrotreated FCC gasoline is critical due to the increasingly stringent limits on sulfur content in fuel. Herein, Zn layered hydroxide salts (Zn LHS) adsorbents with high dispersion of Zn bronzes were developed by co-precipitation method and investigated for the reactive adsorptive desulfurization of heavy mercaptan from gasoline. Zn LHS adsorbent intercalated with acetate anions (Zn-Ac-) presents outstanding mercaptan adsorption capacity (336 mg-S/g-Ads.) and selectivity (286.1). Remarkably, the saturated adsorption capacity per mass and per metal site of Zn-Ac- adsorbent were increased by 13 times and 4 times (1.37 mol-S/mol-Zn), respectively, compared to the reported supported Zn hydroxide adsorbent. The appropriate interlayer distances pillared by the intercalated anions inhibit the stacking of host layers and make the active Zn hydroxide sites more accessible for n-C7H16S, thus contributing to the supreme performance. Characterization results implied that the n-C7H16S was mainly intercalated on Zn-Ac- adsorbent by chemical adsorption, while small fraction of n-C7H16S was physically captured. Interestingly, the adsorption rate of n-C7H16S over Zn-Ac- adsorbent can be greatly improved by the introduction of water vapor or expanding the layer spacing. Besides, catalytic reactive regeneration can fully recover the de-mercaptan capacity of spent Zn-Ac- adsorbent. This study aiming to explore Zn-based adsorbent with high Zn-domains exposure for the deep de-mercaptan from gasoline should play an instructive role in the development of excellent desulfurization adsorbents with high adsorption capacity and selectivity.