Abstract：
Nowadays, it is still a challenge to prepared high efficiency and low cost formaldehyde (HCHO) removal catalysts in order to tackle the long-living indoor air pollution. Herein, δ-MnO2 is successfully synthesized by a facile ozonation strategy, where Mn2+ is oxidized by ozone (O3) bubble in an alkaline solution. It presents one of the best catalytic properties with a low 100% conversion temperature of 85°C for 50 ppm of HCHO under a GHSV of 48,000 mL/(g·hr). As a comparison, more than 6 times far longer oxidation time is needed if O3 is replaced by O2. Characterizations show that ozonation process generates a different intermediate of tetragonal β-HMnO2, which would favor the quick transformation into the final product δ-MnO2, as compared with the relatively more thermodynamically stable monoclinic γ-HMnO2 in the O2 process. Finally, HCHO is found to be decomposed into CO2 via formate, dioxymethylene and carbonate species as identified by room temperature in-situ diffuse reflectance infrared fourier transform spectroscopy. All these results show great potency of this facile ozonation routine for the highly active δ-MnO2 synthesis in order to remove the HCHO contamination.
摘要：
如今,制备高效低成本的甲醛（HCHO）去除催化剂以解决长期存在的室内空气污染仍然是一个挑战。在这里，通过简单的臭氧化策略成功合成了δ-MnO2，其中Mn2+在碱性溶液中被臭氧(O3)气泡氧化。在48,000mL/（g·hr）的GHSV下，对于50ppm的HCHO，它表现出最佳的催化性能之一，其100％的转化率低，为85°C。作为比较,如果O3被O2取代，则需要6倍以上的氧化时间。表征表明，与O2过程中热力学相对更稳定的单斜晶γ-HMnO2相比，臭氧化过程会产生不同的四方β-HMnO2中间体，这将有利于快速转化为最终产物δ-MnO2。最后,发现HCHO通过甲酸盐分解为CO2，通过室温原位漫反射红外傅里叶变换光谱鉴定的二甲醛和碳酸酯物种。所有这些结果表明，这种简单的臭氧化程序对于高活性的δ-MnO2合成以去除HCHO污染物具有很大的效力。
