Structural, morphological and textural modifications of ZnO–TiO2 HTGD based sorbents induced by Al2O3 addition, thermal treatment and sulfurizing process

This work is focused on the structural, morphological and textural modifications induced on zinc titanate high temperature desulfurizing sorbents by Al2O3 addition, thermal treatments and sulfurizing processes. ZnO–TiO2–Al2O3 type sorbents were obtained by dry and semi-wet mechanical blending of zinc oxide, titanium oxide and hydrated alumina, drying the intermediate product and by a final calcination at various temperatures. Depending on the initial ZnO:TiO2:Al2O3 molar ratio and final calcination temperatures (400–800 °C), several mixed oxides may be formed: zinc titanates (Zn2TiO4 and Zn2Ti3O8), zinc aluminate (ZnAl2O4) and aluminium titanate (Al2TiO5). The presence of Al2O3 induces structural and textural modifications, causes an improvement in pore structure and an increase in specific surface, alleviating the gas–solid interactions during the desulfurization–regeneration processes. The sulfurization process modifies the structural, morphological and textural characteristics of ZnO–TiO2–Al2O3 sorbents by reducing the zinc titanates and ZnS formation as main phase in the bulk of sorbent.

Graphical abstractThe structural, morphological and textural characteristics of ZnO–TiO2 desulfurizing based sorbents are drastically change by Al2O3 addition, thermal treatment and sulfurizing process. At high temperature, ZnO and TiO2 interact forming zinc titanates, Zn2TiO4 being the main crystalline phase. The presence of Al2O3 induces new crystalline phase formation (ZnAl2O4 and Al2TiO5), determining an important increase of the specific surface, pore volume and main pore dimension.Figure optionsDownload full-size imageDownload as PowerPoint slide