Sol−Gel Auto-Combustion Synthesis of Zinc Ferrite for Moderate Temperature Desulfurization

Abstract

Zinc ferrite as a desulfurization sorbent with an average crystallite size of about 36 nm was synthesized by a sol−gel auto-combustion method. The precursor for the sorbent was a gel obtained from metal nitrates and citric acid by a sol process. The nitrate−citrate gel exhibits a self-propagating combustion behavior, and after combustion, it can transform into a nanosized spinel structured zinc ferrite directly. The prepared sorbent has a larger specific surface area and higher reactivity when compared with the sorbent achieved by a solid mixing method, and it could efficiently reduce the H2S concentration from 6000 ppm to less than 2 ppm at a moderate temperature range. The sulfur capacity at 400 °C reaches about 38.5 g of sulfur/100 g of sorbent, which corresponds to 96.4% of the theoretical value. The temperature programmed oxidation test for the sulfided sorbent shows that the most sulfur is desorbed before 500 °C. XRD results confirm that the sulfided sample after exposure to a 5% O2/N2 gas mixture a...