Preparation Of Perovskite Typed Mixed Ionic And Electronic Conductor And Advances Of Its Application In Catalytic Pyrolysis Of Lignin

Lignin is the second largest renewable biomass resources, inferior only to cellulose on earth. However, the most part of lignin were burned as a cheap fuel, considered as accumulated waste or poured into the river, which not only led to the serious environmental pollution, but also caused the great waste of resources. Less than 2% were merely used to the production of high value-added products, such as adhesives, anti-rust agent, dye dispersant,diluent, surfactant and so on. So the low degree of lignin efficient utilization is an important problem.In this article, solid state and sol-gel method were used for the preparation of perovskite typed mixed ionic and electronic conductor LaTixFe1-x O3 catalyst, which were characterized by XRD, FTIR and SEM to examine the effect of content, synthetic methods and temperature on the structure and morphology of LaTixFe1-x O3 catalyst. The reaction of catalytic pyrolysis of lignin was carried out on fixed bed reactor to obtain high value-added liquid aromatic products with the bagasse lignin as raw material and LaTi_0.2Fe_0.8O₃ and LaTi_0.2Fe_0.8O₃?Fe₂O₃ prepared by solid state method as catalyst. The activity and recycling of catalyst were investigated through the liquid product yield and the structure and morphology of catalyst after reaction. Liquid product composition was analysed by FTIR and GC-MS.The research results are as follows:（1）Perovskite catalyst LaTi_0.2Fe_0.8O₃ synthesized by solid state and sol-gel method to has good orthogonal perovskite structure. Compared with the sol-gel method, perovskite phase purity of solid state method is lower, which has a mixed La2O3 peak, but it can be used as a follow-up experiment of catalyst preparation method owing to its high yield. Its optimum calcination temperature of catalyst preparation is 1000℃.（2）Thermogravimetric analysis results show that lignin weightlessness mainly occurred in 180-500℃. Considering pyrolysis effeciency and the maximization of liquid product yield, 500℃ is selected for catalytic pyrolysis temperature.（3）In the reaction of catalytic pyrolysis of bagasse lignin on fixed bed reactor with perovskite typed mixed ionic and electronic conductor LaTi_0.2Fe_0.8O₃ as catalyst,LaTi_0.2Fe_0.8O₃ catalyst can effectively provide lattice oxygen for lignin catalytic pyrolysis. 1:1（the ratio of mass）of lignin pyrolysis has higher product yield and better selectivity, and after the reaction LaTi_0.2Fe_0.8O₃ catalyst has good stability. The selectivity of aromatic compounds in the liquid product is up to 41.55%, and its yield is 73.75 mg/g lignin.（4）At the same conditions, that Fe₂O₃?LaTi_0.2Fe_0.8O₃ has better catalytic oxidation performance was found, when pyrolysis of lignin was catalysed by Fe₂O₃, LaTi_0.2Fe_0.8O₃ or Fe₂O₃?LaTi_0.2Fe_0.8O₃. The selectivity of aromatic compounds in the liquid product is as high as 53.89%, and the yield of aromatic compounds is up to 132.03mg/g lignin.（5）After Fe₂O₃·LaTi_0.2Fe_0.8O₃ synthesised by solid state method catalysing lignin pyrolysis, Fe₂O₃ was reduced by lignin, and through the oxidation reaction its crystal phase can remain the orignal crystal phase, which confirms that the composite of catalyst has good stability and reactivity and reach the purpose of recycling. After three times circulation the liquid product yield can still be up to 17.52%.