Sol-gel derived mixed metal oxide sorbents for high temperature gas desulfurization

High temperature gas desulfurization (HTGD) is the main process for hydrogen sulphide removal from hot gases. Currently leading regenerable desulfurization sorbents are based on ZnO–TiO2 system. This work presents structural and textural modifications of ZnO–TiO2 based sorbents by Al2O3 addition in order to ensure high temperature mechanical support. Sorbents with composition Zn(2-x)Al2xTi(1-x)O4 (x = 0, 0.25, 0.5, 0.75, 1) were prepared by sol-gel process followed by thermal treatment. Nanocrystalline powders were produced at moderate sintering conditions (500 °C, 2 h). Depending on the initial ZnO:TiO2:Al2O3 molar ratio, zincite (ZnO), brookite (TiO2) as well as gahnite (ZnAl2O4) solid solution were formed. Al2O3 induced textural modifications, rising specific surface area from 34 to 90 m2g-1. The sorbent sulphidation performance was tested using newly developed procedure comprising batch sulphidation process. Sorbent with composition Zn1.75Al0.5Ti0.75O4 was found to possess the highest sulphidation reactivity, i.e. sulphur removal efficiency.