Use of High-Pressure Impregnation in Preparing Zn-Based Sorbents for Deep Desulfurization of Hot Coal Gas

Abstract

A new preparation method of zinc oxide (ZnO) sorbents for removing H2S from hot coal gas was explored. High-pressure impregnation with semi-coke as the support and zinc nitrate as the active component precursor was used to prepare Zn-based sorbents (HZnSC). The desulfurization activity of the sorbents was studied in a fixed-bed reactor under the simulated coal gas mixture of CO (33 vol%), H2 (39 vol %), H2O (5 vol %), H2S (300 ppmv), and N2 (balance) at 300–550 °C. The results show that the desulfurization activity of the HZnSC sorbents is higher than that of the sorbents prepared using atmospheric pressure impregnation. The surface area of the semi-coke expanded from 16.65 to 272.59 m2/g. Nanoscale ZnO was acquired, and the active component was uniformly dispersed on the support with the high-pressure impregnation method, which afforded H2S removal from hot coal gas. HZn20SC (prepared with 20 wt % zinc nitrate solution) reduced H2S from 300 to less than 0.1 ppmv at 300–550 °C, and its sulfur capacity was 4.5 g of S/100 g of sorbent at 500 °C. It also maintained good heat stability during three desulfurization/regeneration cycles. The findings suggest that semi-coke with a low surface area can be used as a support of sorbents to remove H2S from hot coal gas using high-pressure impregnation.