Study On The Catalytic Performance Of Cu/Ti-Pillared Sepiolite And Fe/Ti-Pillared Sepiolite

Sepiolite is a kind of samdwich clay with high ion exchange ability, adsorption and surface area which makes it to be an excellent support for catalyst. But the application is limited by it's pore distribution and thermal unstability. This paper ameliorated the pore distribution and improved the thermal stability and acid amount to adapt to the employment of support by Ti-pillared and acid modification. Many analyzing techniques including BET, XRD, SEM, IR and XPS were employed to characterize the changes of structure and property of sepiolite after Ti-pillaring.The result of XRD and SAXRD indicated the shift of interplanar spacing as follows: the value of d₁₁₀ changed from 1.202nm to 1.18nm after acid modification. For Ti-pillared sepiolite, the value maintained 1.76nm after calcination under 350℃which indicated that the oxidation of titanium enlarged the interplanar spacing. The dispersion of diffraction peak(110) can be observed because the acidity of pillared solution destroyed the order of sepiolite crystal. It could be found that the pillaring eliminated the impurity and dredged the pore by the SEM pattern. From the result of BET, the surface area changed from 55.6 m2·g^-1 to 127.5 m2·g^-1 with the sharp increase of the saturated adsorption after acid modification. The percentage of mesopore increased notably. The total pore volume enhanced from 0.261cm³Â·g ^-1 to 0.525cm³Â·g^-1 and 0.261cm³Â·g^-1 to 0.305 cm³Â·g ^-1 respectively for acid modification and Ti-pillared sepiolite. For the Ti-pillared sepiolite, the surface area argument to 109.8 m²Â·g^-1 and pore diameter of 39.77nm-33.38nm inceased largely. The elevation of surface area and total pore volume were propitious to the adsorption and dispersion of active substance. It was shown that Ti-pillaring increased the thermal stability which improved the capability of support from the spectrogram TG-DTG. TiO₂ were formed after calcinations where produced acid site to advance the catalytic process.This paper used the nature sepiolite to synthesize Ti-pillared sepiolite as the support to prepare both of the Cu-dopped and Fe-dopped Ti-pillared sepiolite for the oxidation of CO and reduction of NOx.A series of Cu dopped sepiolite with various amounts of Cu were prepared by impregnation and ion-exchange method. The factors affecting the catalyst activity were observed including modification of carrier, preparation method, the temperature of pillaring and the loading amount of Cu. It could be concluded as follows:â‘ Na₂CO₃-sepiolite was superior to the NaNO₃-sepiolite during relative low temperature. And there was an improvement in activity for Na₂CO₃-sepiolite which was not existed in the other catalysts which implied that the desorption of CO₃^2- bought active site for the adsorption of reactive gas. Also O- worked as a reducer for the NOx after the decomposition of CO32- which promoted the catalytical process.â‘¡Ti-pillared sepiolite had higher performance than acid sepiolite.â‘¢The Ti-pillared temperature of 40℃had the highest NOx conversion. When the catalyst was applied to the oxidation of CO, the catalyst with high ration of Ti/sepiolite of 30mmol/g and 5% of Cu loading had the highest activity in the experiment.â‘£Cu loading of 7% was proper and the concentration of Cu solution of 0.02 mol·L^-1 had more excellent catalytic activity.The property of Fe-dopped Ti-pillared sepiolite for the reduction of NOx were researched. It can be concluded as follows:â‘ Fe loading of 5% was the best amount for Fe.â‘¡The Fe³⁺ concentration of 0.03mol·L^-1 was more outstanding.When the catalyst was applied to the oxidation of CO, It could be concluded as follows:â‘ Ion-exchange method was superior to impregnation and Ti-pillared sepiolite had higher performance than acid sepiolite.â‘¡The Fe3+ concentration of 0.07mol·L^-1 was more excellent.â‘¢The best loading was also 5%. It could be concluded that Cu dopped sepiolite had higher activity than Fe dopped sepiolite for the reduction of NOx after the comparison.These two catalysises were characterized by XRD, SEM, and XPS. The XRD characterization indicated that the diffraction peak of TiO₂(110) sharpen with the ratio of Ti/sepiolite. The degree of dispersion didn't change after the loading of Cu and the agglutination occurred. Some titanium substance adsorbed on the surface of sepiolite during the pillaring process from the EDS result. It was showed that the surface of sepiolite existed by CuO and Cu₂O for Cu while Fe₂O₃ and Fe₃O₄ for Fe by the spectrogram of XPS. Ti formed TiO₂ on the surface of Cu/Ti-Sep and TiFe was formed in the Fe/Ti-Sep to exert the catalytic activity together.