Yoshimune Wataru, Kato Satoru, Harada Masashi
Toyota Central R&D Labs., Inc., 41-1 Yokomichi, Nagakute 480-1192 Aichi, Japan.
ACS Appl Mater Interfaces. 2022 Apr 20;14(15):17396-17404. doi: 10.1021/acsami.2c01594. Epub 2022 Apr 7.
Porous media as catalyst supports are key to developing automotive exhaust purification systems. In particular, the water content of these porous media is attracting research attention because catalyst supports containing condensed water vapor at the early stage of cold start require a longer warm-up period. In this regard, water isotherms and evaporation in porous AlO were investigated in this study using in situ small-angle neutron scattering (SANS) experiments. Unlike conventional evaluation methods, such as weighing and X-ray tomography, SANS distinguishes water in the primary and secondary pores using a contrast-matching method. Time-resolved measurements showed that water started to evaporate from the secondary pores in tens of seconds and subsequently from the primary pores in a hundred seconds. Exhaustive experiments conducted using nine alumina-based samples revealed that the drying rate depended on the secondary pore size of the porous AlO. The proposed approach can enable the evaluation of controlling factors to additionally optimize the performance of automotive exhaust gas catalysts, especially during cold start.
多孔介质作为催化剂载体是开发汽车尾气净化系统的关键。特别是，这些多孔介质的含水量备受研究关注，因为在冷启动初期含有凝结水蒸气的催化剂载体需要更长的预热时间。在这方面，本研究使用原位小角中子散射（SANS）实验研究了多孔AlO中的水等温线和蒸发情况。与传统评估方法（如称重和X射线断层扫描）不同，SANS使用对比匹配方法区分一次孔和二次孔中的水。时间分辨测量表明，水在几十秒内开始从二次孔蒸发，随后在一百秒内从一次孔蒸发。使用九个氧化铝基样品进行的详尽实验表明，干燥速率取决于多孔AlO的二次孔径。所提出的方法能够评估控制因素，以进一步优化汽车尾气催化剂的性能，尤其是在冷启动期间。
