Center for Excellence in Regional Atmospheric Environment, Key Laboratory of Urban Pollutant Conversion, Chinese Academy of Sciences, Institute of Urban Environment, Xiamen 361021, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Center for Excellence in Regional Atmospheric Environment, Key Laboratory of Urban Pollutant Conversion, Chinese Academy of Sciences, Institute of Urban Environment, Xiamen 361021, China; Zhejiang Key Laboratory of Urban Environmental Processes and Pollution Control, Chinese Academy of Sciences, Ningbo Urban Environment Observation and Research Station-NUEORS, Ningbo 315800, China.
J Environ Sci (China). 2023 Mar;125:811-822. doi: 10.1016/j.jes.2022.02.025. Epub 2022 Feb 27.
The complete catalytic oxidation of formaldehyde (HCHO) to CO and HO at room temperature is a green route for indoor HCHO removal. Zeolite is an excellent carrier material for HCHO oxidation due to its large surface area, intricate pores and high adsorption capacity. However, the zeolite-supported noble metal catalysts have currently shown relatively low activity especially at room temperature. In this work, we present a facile acid treatment strategy for zeolite catalysts to improve the hydroxyl concentration and further enhance their catalytic activity for HCHO oxidation. Activity tests illustrated that HCHO could be completely oxidized to CO and HO at a nearly 100% conversion rate with a weight hourly space velocity (WHSV) of 150,000 mL/(g∙hr) at 25°C, when the support of Pd/USY catalysts was pretreated by hydrochloric acid with a concentration of 0.20 mol/L. The characterization results revealed that the active hydroxyl groups originated from the dealumination in the acid treatment play a key role in the HCHO oxidation reaction. The deduced reaction mechanism suggests that bridging hydroxyl groups may oxidize HCHO to dioxymethylene (DOM) species and terminal hydroxyl groups are responsible for the transformation of DOM groups to formate (HCOO) species.
室温下完全催化氧化甲醛（HCHO）为 CO 和 HO 是室内 HCHO 去除的绿色途径。由于沸石具有较大的比表面积、复杂的孔道和较高的吸附能力，因此是 HCHO 氧化的优良载体材料。然而，负载贵金属的沸石催化剂目前表现出相对较低的活性，特别是在室温下。在这项工作中，我们提出了一种简便的酸处理策略来改善沸石催化剂的羟基浓度，从而进一步提高其 HCHO 氧化催化活性。活性测试表明，当 Pd/USY 催化剂的载体用浓度为 0.20 mol/L 的盐酸预处理时，在 25°C 下，WHSV 为 150,000 mL/(g·hr)时，HCHO 可以几乎 100%的转化率完全氧化为 CO 和 HO。表征结果表明，酸处理中脱铝产生的活性羟基基团在 HCHO 氧化反应中起关键作用。推断的反应机理表明，桥连羟基基团可能将 HCHO 氧化为二氧亚甲基（DOM）物种，而末端羟基基团负责将 DOM 基团转化为甲酸盐（HCOO）物种。
