The Construction And Controlling Laws Of Active Phases Of Supported Catalysts Based On MoS₂

With air pollution problems getting more serious,the standards of vehicle fuel are increasingly strict in China.This situation requires more studies on hydrodesulfurization catalysts.The activity of present hydrodesulfurization catalysts mainly comes from MoS₂ active phase.And the morphological study is the most direct presentation of MoS₂ structures,and also the base of studies on structure-activity relationship of active phases.To get the controlling laws of active phases under various conditions,this paper prepared catalysts with different Mo precursors?AHM and ATM?,supports,sulfurization conditions?temperature and atmosphere?and loadings.All catalysts were pre-treated by HF and then characterized by HRTEM to explore the micro-morphology of active phases.Results showed that the layer length and stacking number of active phases increased with rising temperature in different atmosphere.When the temperature changed from 300?to600?,average layer length grew 0.3⁰.4 nm and average stacking number increased 0.2⁰.4layers.The force between supports and Mo precursors also influenced layer length and stacking number of active phases.When the force was relatively weak on SiO₂ support,the layer length?2.66 nm?was relatively longer and stacking number?2.92 layers?was bigger,even the distributing range became wider.When the force was relatively weak on Al₂O₃ support,the layer length?2.53 nm?was relatively shorter and stacking number?2.02 layers?was smaller.Under the right conditions?mediate or high temperature,H₂S/H₂?,curved active phases?curving degree of certain active phases<90°?were prepared using nano-supports as hard templates.It was also found that sulfurization conditions and supports made an important impact on the outline of active phases and the outline can change from triangle to hexagon under various conditions.Meanwhile,this research observed orientation behavior of MoS₂active phases on the surface of supports.Precursors,supports and sulfurization temperature affected the orientation behavior.The vetical orientation occurred only when using AHM as precursor,TiO₂ and ZrO₂ as supports in mediate/high temperature.It is worth noting that MoS₂active phases showed random orientation when using ATM as a precursor,TiO₂ and ZrO₂ as supports in the high temperature.According to controlling laws in distinct conditions,the sequence of force between precursors and supports was Al₂O₃?SiO₂>ZrO₂?TiO₂.