Preparation Of V-Na₂?TiO?SiO₄ Nanotubes And Study On The Denitration Performance Of V-Ce Catalysts

Natural microporous titanosilicates consist of hexahedral fragments and six-coordinated transition elements?mainly Ti,Nb,Zr,etc.?,which not only have a great similarity with the synthetic zeolite but also with the same minerals containing phosphate cation appear together.These natural materials have a wide range of applications such as ion exchange,adsorption,and catalysis;this is due to the synthesis simplicity,operability,pore structure and adjustable Ti/Si ratio,in addition to other advantages like the unique properties and broad prospects.In the past few years,new multi-functional materials such as molecular sieves,titanium-silicon composite oxide films,titanosilicates and modified titanosilicates have been synthesized and successfully applied in catalysis,ion exchange,and separation processes.Although lots of research works have studied such these materials due to their unique structure,it still needs more investigations because only a few synthetic methods and very few data about their micro-topography and performance are available.Firstly,sol-gel and hydrothermal synthesis have been utilized to study the effects of hydrothermal reaction time,hydrothermal reaction temperature,pH value of precursor solution and preparation method of the precursor on the morphology of Na2?TiO?SiO4.The product phase composition and the phase morphology were characterized by XRD and SEM techniques respectively.The results of SEM showed a clear and uniform Na₂?TiO?SiO₄morphology,where the hydrothermal reaction condition was controlled at 180°C for 30 h.Furthermore,the pH value and the preparation method for the precursor synthesis have a great influence on the phase morphology,thus generate layered,pie-shaped,coin-shaped,hollow double quadrangular pyramidal,multi-walled tubular,solid fusiform and peach-shaped Na₂?TiO?SiO₄ samples were synthesized.BET data declared that the nanotube-like sample possessed very high specific surface area.Secondly,the V_x-Na₂?TiO?SiO₄ nanotubes were prepared by doping different amounts of vanadium on Na₂?TiO?SiO₄ under the same preparation conditions of Na₂?TiO?SiO₄nanotubes.The micro-morphology and the phase structure of V_x-Na₂?TiO?SiO₄ were examined using SEM,TEM,XRD,BET,EDS,XPS,FT-IR,and resonance techniques.The obtained data revealed that the vanadium substituted titanium and incorporated into the lattice structure of Na₂?TiO?SiO₄ successfully when less than 1wt%of vanadium doping was utilized for the modification,and when the vanadium doping amount reached 1wt%,the Vx-Na2?TiO?SiO4 nanotube tube length exhibited more than 800nm,the specific surface area was 316.2m²/g and the amount of the absorbed hydrogen was 0.19%.Finally,Vn/V₁-Na₂?TiO?SiO₄ catalyst was prepared by loading the active component V2O5 to V1-Na2?TiO?SiO4 nanotubes support.Through the NH3-TPD and Py-IR characterization methods,it was found that the B acid content,L acid content and total acid content of Vn/V1-Na2?TiO?SiO4 catalyst increased with the increase of vanadium content.The effect of Ce on the properties of V4/V1-Na2?TiO?SiO4 was investigated by evaluating the SCR catalytic performance of Vn/V₁-Na₂?TiO?SiO₄ catalyst.