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本文提出“壳层钝化”模型,对 K-V 催化剂上 SO_2氧化反应“表现活化能”在低温下急剧增加的现象进行了数学描述。作者认为,低温下催化剂活性组分熔盐所析出的固相无活性化合物斑驳相问地分布于熔盐表面附近,对液相扩散的影响相当于液相表面存在厚度为ωδ的饨化壳层,大大增加了气相反应物的液相扩散阻力,致使催化剂低温活性急剧下降.用一维模型处理,建立了包含钝化因子ω的低温反应速度表达式.在400—500℃的温区,0.2—0.9的 SO_2转化率范围内,测定了排除内、外扩散影响的小颗粒催化剂样品上的氧化反应速度,并用“壳层钝化”模型同速度数据进行了关联。
In this paper, a “shell passivation” model is proposed to describe the phenomenon that the “activation energy” of SO 2 oxidation on K-V catalyst increases sharply at low temperature. The authors believe that the solid active compound precipitated from molten salt of catalyst active component at low temperature distributes around the surface of molten salt unevenly and has the same effect on the liquid phase diffusion as the existence of the evanescent shell with thickness δδ , Greatly increased the liquid phase diffusion resistance of the gas phase reactant, resulting in a sharp decline in the activity of the catalyst at low temperature.Using the one-dimensional model, the expression of the low temperature reaction rate including the passivation factor ω was established. In the temperature range of 400-500 ℃, 0.2 -0.9 SO_2 conversion rate, the oxidation reaction rate on the small particle catalyst samples excluding the influence of internal and external diffusion was measured and was related to the velocity data by the “shell passivation” model.