Abstract:

Under the urgent need to reduce the energy consumption of industrial thermal dehydration processes, this work reports a new strategy for low-energy dehydration of hydrated calcium chloride coupled with low-temperature water-gas shift (WGS) reaction based on the basic principle of reaction coupling. Using industrial-garde hydrated calcium chloride as raw material, water with certain chemical reactivity in hydrated calcium chloride was directly used as a reactant in the water-gas shift reaction. The experimental results showed that the residual crystallized water number was reduced to 0.38 via this coupling process at 413 K for 2 h, while there is 0.37 via the tradition way at 413 K for 3 h. In this way, a type Ⅰ industrial anhydrous calcium chloride product (CaCl₂·0.38H₂O) was prepared by coupling catalytic dehydration with the treatment time shortened by 1/3, indicating that the coupled catalytic dehydration strategy is conducive to saving energy consumption. In situ FTIR and CO-TPD-MS experiments showed that CO can be chemically or quasi-chemically adsorbed on the surface of hydrated calcium chloride samples, and MS analysis detected CO₂ and H₂ in the dehydration products, indicating that coupled catalytic dehydration indeed occurred. Furthermore, SEM, BET and MIP showed that the anhydrous CaCl₂ prepared by coupling WGS reaction dehydration has abundant pore structures, which are formed during coupling WGS reaction dehydration from the surface. The results of the water vapor adsorption test showed that the pore structure is beneficial to increasing the contact area with water, so that it showed a faster water absorption rate than commercial anhydrous calcium chloride. The low-energy consuming coupled catalytic dehydration strategy reported in this work is expected to show universality for the dehydration of more materials.

Key words: water-gas shift reaction, autocatalysis, calcium chloride, hydrate, carbon monoxide

摘要：

在降低工业热脱水工艺能耗的迫切需求下，基于反应耦合基本原理，报道了一种低温水煤气变换反应耦合水合氯化钙低能耗脱水的新策略。以工业水合氯化钙为原料，将其中具有一定化学反应活性的结晶水作为反应物与CO耦合反应，在413 K下即可制备得到符合国家标准（GB/T 26520—2021）要求的Ⅰ型工业无水氯化钙产品（CaCl₂·0.38H₂O），较在N₂条件下获得同等结晶水含量产品的处理时间缩短了1/3，说明耦合催化脱水策略在降低过程能耗方面具有优势。原位FTIR和CO-TPD-MS实验研究表明，CO可化学吸附或准化学吸附于水合氯化钙样品表面，结合MS分析在脱水产物中检测到CO₂和H₂，说明发生了一定程度的耦合催化脱水。进一步，对所得无水氯化钙样品进行SEM、压汞测试及水蒸气吸附测试，结果表明，与CO耦合反应使得无水CaCl₂样品形成了较为丰富的孔结构，在作为干燥剂使用时有利于增加与水的接触面积，从而使其表现出比商用无水氯化钙更快的吸水速率。本工作报道的低能耗耦合催化脱水策略有望拓展至更多材料的脱水环节。

关键词: 水煤气变换反应, 自催化, 氯化钙, 水合物, 一氧化碳