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Study on Preparation and Catalytic Properties of Baotou Rare Earth Catalyst

Author: LiYanFeng
Tutor: HaoMaoRong；LiMei；LiuZhaoGang；HuYanHong
School: Inner Mongolia University of Science and Technology
Course: Iron and steel metallurgy
Keywords: Baotou rare-earth catalyst kinetics study doping modified DFT
CLC: O643.36
Type: Master's thesis
Year: 2009
Downloads: 37
Quote: 0
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Abstract


In this paper, Baotou rare earth mineral catalyst was prepared by precipitation method. It doped Y, Dy, Tb and Mn for modification the catalyst of property. The catalyst property was characterized by X-ray diffraction, laser particle size analyzer, specific surface area, scanning electron microscopy and transmission electron microscopy. Catalytic mechanism was calculated by DFT methods.Preparation of the optimum conditions was concluded by measuring specific surface area of catalyst to study the concentration of the precipitant, the concentration of rare earth nitrate, reaction temperature and stirring speed. The DTA / TG were used to study the catalyst precursor of the thermal decomposition kinetic analysis. The results showed thermal decomposition reaction in line with the D3 model, the activation energy is 62.939 kJ·mol-1, pre-exponential factor A = 1.184×103s-1, kinetic equation: dα/ dt = 1.776×103exp [-62.939×103 / （RT）]·（1-α）2/3[1 - （1-α）1/3]-1.Crystal structure of Baotou rare earth catalyst is cubic crystal system, fluorite structure by measuring X-ray diffraction. Morphology of non-doped catalyst is a large number of particles within the distribution of the gap. But, when the calcination temperature increased, the internal gap disappears and particle size has increased and specific surface area decreased. Doped Y, Dy, and Tb sample have small particle size, large specific surface area, H2-TPR reduction temperature shifted to lower temperature, and anti-aging properties of high temperature better than non-doped sample.But the Mn-doped sample is not good at anti-aging properties of high temperature and can not improve the catalytic properties of catalyst obviously.We are based on plane wave expansion of the first principles pseudopotential method to study the before and after doping of rare-earth catalyst electronic structure. The results show that the Zr-doped high-energy band in the emergence of a large number of Zr 3d and O 2p contributions to the free carrier electronics, an increase of Ce ions of the probability of price change. At the same time, the calculation of the doped Y, Dy, Tb and Mn in LaCePrZrO of the electronic structure found that doping Y, Dy and Tb will take more active system of internal electronics, an increase of solid solution of Ce3+ and Ce4+ between the probability of price change, which will increase the solid solution in the mobility of oxygen ions to improve the catalytic environment, and improve the catalytic properties and catalytic activity, but Mn-doped system has reduced the mobility of oxygen ions, the restore performance improvement is not very good.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst
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