Study On The Preparation, Characterization And Properties Of Nano-Solide Superacid SO₄～(2-)/TiO₂ And SO₄～(2-)/TiO₂-SiO₂ Catalysts

With Green Chemistry being advocated, the brand-new concept of green catalyst has been brought forward recently. Solid superacid has many advantages such as high activity, well selectivity, and no corrosiveness, no pollution, and liability to be separated from the reaction material. It is a green industrial catalyst that is helpful to the recycling and possesses wide prospect of application. Thus, research on solid superacid has drawn more and more attention in industrial catalyst field.The motive of the paper is to combine organically the merits of solid superacid and nanometer materials. Furthermore, some solid superacids have been prepared by nanometer technique, and the researches on its property and application have been carried out systematically. The main contents are as follows.Firstly, by immersing TiO2, which is made with the boiling refluxmethod, into the sulphuric acid, nanometer-sized SO42-TiO2 solid superacid has been prepared. SiO2 supported nanometer SO42-/TiO2-SiO2 solid superacid has been prepared by TiO2-SiO2, which is obtained from SiO2 fabricated with TiO2 using the Sol-Gel technology, modified with sulphuric acid.Secondly, the acid strength, specific surface, size and the feature, the structure of acid center and the content of Sulphur and Titanium have been characterized by IR, XRD, TEM, SEM, BET, EDS,TG-DTA and Hammett indicator. Using the Esterificational Reaction and the Pentane Isomerization Reaction as probes, catalytic activity of these superacids which were prepared by different process conditions such as different concentration of H2SO4, immersing time. heating temperature, heating time , different layer numbers have been researched. The relationship among preparing process parameters, structure and its catalytic activity has been discussed. Also, the mechanism of the Deactivation and Regeneration of the selected catalyst has been investigated.The results show that: both of the solid acids were superacid(Ho<-12.14). The particle size of TiO2 and SO42-TiO2 which was on the surface of SO42-/TiO2-SiO2 is in the range of 10-100 nm. The two series of solid catalysts have high catalytic activity and well selectivity to the Esterificational Reaction and the pentane Isomerization Reaction. Different preparative conditions were required in Esterificational Reaction and Pentane Isomerization Reaction. The acid strength on Esterificational Reaction was widely allowed, but some certain acid strength is limited in Pentane Isomerization Reaction in the lower temperature.By comparison with the two series of solid superacid , we conclude that SiO2 supported nanometer SO42-/TiO2 solid superacid is intensivelyapplied because of its excellent catalytic activity, low concentration of Ti(6.2%~34.8%) and being easy to be segregated, reclaimed and reused for its big size of particles.