【作者】 贾兆昌；

【导师】 庞先勇；

【作者基本信息】 太原理工大学 ， 物理化学， 2007， 硕士

【摘要】 为了不同的目的，特别是吸附特性，需要对分子筛进行改性，目前改性手段很多，得到的产品十分丰富，应用较为复杂仪器的方法进行表征，尽管如此，仍然存在不足，难以全面评估改性结果。气相色谱法以其简便且有一定的准确度，受到重视。然而传统的方法主要应用于分子筛的吸附热力学性质的测定上，对动力学性质应用较少，本文采用气相色谱法系统的测定了O₂、N₂和CO等在自制的不同Ca²⁺交换度、不同活化温度和不同粒度的三个系列的A型分子筛上的吸附热力学参数和扩散系数等吸附动力学参数，并结合分子筛的结构变化阐明原因。主要结论如下：（1）从热力学基本原理出发，根据吸附热力学参数(Δ_adH、Δ_adS、Δ_adG)与调整保留时间的公式，应用气相色谱法测定并计算了气体O₂、N₂和CO在不同钙交换度的A型分子筛中的Δ_adH、Δ_adS和Δ_adG。结果表明：粒度和载气流速对色谱法测定吸附热力学参数没有影响，Ca²⁺交换系列分子筛对O₂、N₂和CO的吸附热随着Ca²⁺交换度的增大而增大，吸附热值在-26～7.8kJ·mol^-1，不同活化脱水温度系列为450℃和650℃的分子筛对O₂、N₂和CO的吸附熵值最大。数据的相关性很好，相关系数在0.999左右。（2）采用反相气相色谱法测定了O₂、N₂和CO在不同钙交换度和不同活化温度系列分子筛的轴向扩散系数和总质量传质阻力等，数据的线性相关性很好。结果表明：钙交换度较小时，由于分子筛内孔径较小，O₂、N₂和CO在分子筛内的总传质阻力较大，随着钙交换度的增加，孔径变大，场强对其影响变为主要因素，钙交换度大的时候总传质阻力也较大。当温度升高时，由于温度变高，分子运动的越快，场强对他的影响变弱，使得O₂、N₂和CO在分子筛内的轴向扩散系数变大，总传质阻力减小。O₂、N₂和CO由于分子直径与分子极性的差别，O₂的轴向扩散系数大于N₂和CO的轴向扩散系数，O₂的总质量传质阻力小于N₂和CO的总质量传质阻力。（3）建立了气相色谱法测定分子筛内扩散系数的方法，采用矩分析法来分解总重量传质阻力项中的各项扩散系数，计算结果为O₂的晶内扩散系数为2.456×10^-9cm²·s^-1，N₂的晶内扩散系数为1.229×10^-9cm²·s^-1，扩散系数的测定值与文献值基本在一数量级。更多还原

【Abstract】 The modification of zeolite is carried on for various purposes, especiallyfor improving the adsorption effect. At present, the means of modification onzeolite are plentiful, and the same as the characterization ways. And even if themost complicated characterization means still have their disadvantages andcannot evaluate the zeolite thoroughly and precisely. Gas chromatography isused in this field for its simplicity and acceptable accuracy. Traditionalcharacterization means on zeolite is focused on their thermodynamic propertiesand have difficulities on determining the dynamic properties. In this paper,parameters of adsorption thermodynamic properties and the diffusion coefficientof adsorption dynamic properties and the parameters of mass transferring aboutO₂, N₂ and CO on three series of zeolite are determined. And the three series ofzeolite are different exchange degree of Ca²⁺, different activation temperatureand different granularity, respectively. Then, the regularity of the determinedparameters is explained depending on the structure of zeolite. The mainconclusions are following:（1） According to the formula about parameters of adsorption thermodynamics (Δ_adH,Δ_adS,Δ_adG) and adjustment retention time, the paramerters ofadsorption thermodynamics about O₂, N₂ and CO on A type of zeolite, whoseexchange degree of Ca²⁺ are different, are determined and calculated by gaschromatography. The results show that: Granularity and the gas velocity have noeffection on parameters of adsorption thermodynamics.the adsorption heat of O₂, N₂ and CO on zeolite increases along with the increase of exchange degree ofCa²⁺, and the adsorption heat ranged from-26 kJ·mol^-1 to-7.8 kJ·mol^-1. Whenthe activation temperatures are 450℃and 650℃, the zeolite have the biggestvalues of adsorption entropies of O₂, N₂ and CO on the zeolite. The relativity ofall data is considerable well, about 0.999.（2） The O₂, N₂ and CO on A type of zeolite with different Ca²⁺ exchangedegree and different activation temperature are determined for the axial diffusioncoefficient, the total mass transfer resistance, et al. The relative coefficient of thedata is well. The results show that: it has small inner pore diameter in zeolitewhen Ca²⁺ exchange degree is low, and total mass transfer resistance value of O₂,N₂ and CO on zeolite is high. Although the inner pore diameter increase with theincrease of Ca²⁺ exchange degree, field intensity in zeolite grew into major facorof affecting total mass transfer resistance when Ca²⁺ exchange degree is high,and total mass transfer resistance value of O₂, N₂ and CO on zeolite is also high.With the increase of adsorption temperature, the axial diffusion coefficient valuebecomes higher and the total mass transfer resistance value becomes lower. Thisis because field intensity in zeolite affects the movement of gas molecule weakerand weaker with the increase of adsorption temperature. Because of thedifference of the molecular diameter and the polarity of O₂, N₂ and CO, the axialdiffusion coefficient value of O₂ is higher than the one of N₂ and CO, and totalmass transfer resistance value of O₂ is lower than the one of N₂ and.CO.（3） A chromatography experimental method for measuring gas diffusivity in5A zeolite is set up. Moment analysis method is used to analyze each diffusioncoefficient of total mass transfer resistance, and the results show that: theintracrystalline diffusion coefficient value of O₂ and N₂ are in the same order ofmagnitude as literature value. They are 2.456×10^-9 cm²·s^-1 and 1.229×10^-9cm²·s^-1, respectively.更多还原