Insight into the effect of gel drying temperature on the structure and desulfurization performance of ZnO/SiO2 adsorbents

Abstract

A series of ZnO/SiO2 adsorbents were prepared by a sol–gel method using tetraethyl orthosilicate, ethylene glycol (EG) and nitrates as precursors. The effect of gel drying temperature on the structure and desulfurization performance of the adsorbents were investigated in detail. It is found that the low drying temperature led to a weak interaction among EG, Si−OH/H2O and the nitrates in the gel system, which caused the oxidation of EG by NO3− and formed zinc glyoxylate complex during the gel calcination process, whereas this oxidation process also occurred at a high drying temperature during the gel drying process. The formed zinc glyoxylate complex promoted the generation of monodentate carbonate on the surface of ZnO, which resulted in the inferior desulfurization performance of adsorbents despite they have smaller ZnO nanoparticles. The gel dried at 120 °C formed the hydrogen bonds between EG and Si−OH/H2O and a strong interaction between zinc oxo-clusters and NO3− was also found in the gel system, which avoided the oxidation of EG by NO3− during the preparation process and the ZnO nanoparticles with sizes of 6 nm were formed by a combustion method. The adsorbent affords a highest sulfur capacity of 104.9 mg∙g–1 in this case. In addition, the gel drying temperature has a significant influence on the textural properties of the adsorbents except their surface area.