Highly hydrothermally stable FePO4–SBA-15 synthesized using a novel one-pot hydrothermal method

Abstract

The hydrothermal stability of FePO4–SBA-15 synthesized using a novel one-pot hydrothermal method (OP) was systematically investigated using two methods: treatment with pure steam at 800 °C or with boiling water at 100 °C. The structural changes in the samples were monitored using small angle X-ray diffraction and N2-physisorption methods. It was found that the hydrothermal stabilities of OP samples remained high and showed little difference over the FePO4-doping range 5–40 wt%. These results differ from previous reports that the loading of heterogeneous metal atoms significantly influences the hydrothermal stability of the host ordered mesoporous material. For comparison, the hydrothermal stabilities of FePO4–SBA-15 synthesized using an impregnation method (IMP) and commercially obtained SBA-15 were also studied. The order of the sample hydrothermal stabilities was OP > IMP >> SBA-15. The formed FePO4 protective layers helped to prevent mesostructure degradation during hydrothermal treatment, therefore modified samples showed superior hydrothermal stabilities compared with pure SBA-15. The superior performance of OP samples over IMP samples is mainly attributed to the formation of stable Si–O–Fe bonds and more micropores in OP samples.