Preparation And Properties Of Nano Sulfated Zirconia

With the increasing consumption of fossil fuels and the increasingly serious environmental pollution,the development of clean and environmentally friendly biomass energy has become a research hotspot in the current society.Biodiesel,as a kind of green,environmental protection,renewable energy,has a strong market potential.At present,biodiesel is mainly prepared from fatty acids or oils through esterification or transesterification process under liquid acid or base catalyst.The main factors hindering the commercialization of biodiesel are the complicated production process and high subsequent processing cost of the product.Therefore,reducing the production cost of biodiesel has become the primary issue in the development of biodiesel.The main methods to reduce the production cost of biodiesel include:（1）improving the use value of low-grade feedstock,（2）developing catalytic materials that are easy to separate and have high activity and can be regenerated.Among many solid acid catalytic materials,sulfated zirconia has attracted extensive attention because of its unique acid properties and good catalytic activity in esterification and transesterification reactions.However,traditional zirconia sulfated materials have some fatal shortcomings,such as low specific surface area,poor catalytic activity and poor stability.Therefore,how to develop a kind of sulfated zirconia material with high catalytic activity and can be reused to solve the problem of its rapid deactivation during esterification or transesterification has become an important and urgent research topic in biodiesel production.Therefore,the preparation method of nanometer sulfated zirconia solid acid has been further studied,and the catalytic material with high activity and high stability has been prepared.It mainly includes the following two aspects:（1）Nano-sulfated zirconia solid acid mesoporous materials with different grain sizes and pore sizes were prepared by adjusting the dosage of triethanolamine and the Solvent heat treatment temperature.（2）Mesoporous sulfated zirconia nanocrystalline solid acid materials with different acid content and catalytic stability were prepared by introducing different contents of tin into the synthesis system.The catalytic activity and reusability of the prepared catalyst were evaluated by transesterification of soybean oil with methanol.In addition,the crystal structure,morphology,element distribution,pore structure,interaction between sulfuric acid and support and chemical binding state of surface elements of catalyst were characterized in detail by XRD,SEM,TEM,element Mapping,N₂ adsorption-desorption,TG,NH₃-TPD,pyridine infrared,FT-IR,XPS and other characterization methods.The following is a summary of the existing findings:（1）With double eight alkyl dimethyl ammonium chloride as the template agent and triethanolamine as the hydrolysis accelerator,was synthesized in the ethanol system composed of nano grain accumulation of zirconia materials,by further sulfating process,was sulfated zirconia materials,and adopt the ester exchange reaction of soybean oil with methanol catalytic property was investigated.The results of the physical properties of the catalytic material show that the catalytic material has a specific surface area of 179 m²/g,a mean pore size of 4.9 nm and a pore volume of 0.29 cm³/g under the optimal conditions.Under the optimal catalyst,soybean oil could be completely converted into biodiesel at 140℃for 5 h,and the conversion rate of soybean oil was higher than 80%in the fifth repeat reaction。（2）By adding tin salt in the synthesis process,the solid nano acid material of tin doped with sulfated zirconia was successfully synthesized.The morphology of the catalyst was investigated by scanning electron microscopy and projection electron microscopy.The results show that the doped Sn material is composed of zirconia grains of about 6 nm.It can be seen that Zr,Sn,O and S are highly dispersed by electron diffraction energy spectrum.The results of transesterification reaction show that the zirconia doped with tin has higher catalytic activity and stability than the zirconia without tin doping.The chemical properties of the materials showed that the content of Bronsted acid and the ratio of Bronsted acid to Lewis acid increased obviously after the introduction of tin,and the introduction of tin on the surface was more conducive to the formation of Bronsted acid.The physical properties of the deactivated catalyst show that the deactivated catalyst is caused by the loss of sulfur species on the surface of the catalyst.