高表面氧MnOx/类水滑石催化剂常温催化低浓度甲醛的性能

常温催化氧化技术是去除室内低浓度甲醛(HCHO)的一种有效方法，其中过渡金属氧化物锰基催化剂在催化降解方面性能优异，相较于贵金属催化剂，具有成本低、活性高、稳定性良好、应用前景广等优点。采用共沉淀法制备了类水滑石载体和锰基/类水滑石催化剂，将类水滑石与锰基氧化物相结合用于常温催化氧化，克服了锰基氧化物常温条件下因大量吸附水蒸气而导致稳定性降低的缺点，同时研究考察了载体组成、煅烧温度、氧化锰负载量等对催化剂常温催化氧化性能的影响，并通过XRD、SEM、BET、EPR、XPS等技术对催化剂进行了微观表征。结果表明，当类水滑石中n(Mg)∶n(Al)=4∶1，氧化锰负载量 (质量分数) 为40%，煅烧温度为200 ℃时，所述MnO_x/Mg₄Al₁催化剂性能最佳，其48 h甲醛去除率高达98.5%，甲醛质量浓度由1.000 mg·m^-3降至0.015 mg·m⁻³。类水滑石载体表面存有大量羟基基团，有利于吸附低浓度甲醛及中间产物进而利于催化剂催化氧化性能提升。通过XPS分析可知，相较于MnO_x催化剂，MnO_x/Mg₄Al₁催化剂中O_β/(O_α+O_β)相对含量比例由35.7%提升至88.0%，表面氧含量(O_β)大幅提升，其在甲醛常温催化氧化过程中发挥着极其重要作用。本研究结果可为常温催化氧化甲醛提供参考。

Performance of high surface oxygen MnOx/ hydrotalcite-like catalyst for the catalysis of low concentration formaldehyde at ambient temperature

Catalytic oxidation at ambient temperature is an effective method for the removal of low-concentrated formaldehyde (HCHO). The transition metal oxide manganese based catalyst has excellent catalytic degradation performance. Compared with the precious metal catalyst, it has the advantages of low cost, high activity, good stability and wide application prospect. In this study, the hydrotalcite-like and manganese oxides/ hydrotalcite-like catalysts were synthesized by the co-precipitation method. The combination of hydrotalcite-like and manganese oxides for catalytic oxidation of HCHO at ambient temperature overcomed the disadvantage of stability reduction caused by large amount of water vapor adsorption of mangan-based oxides at room temperature. Meanwhile, the effects of carrier composition, calcination temperature and manganese oxides supporting, etc. on the catalytic oxidation at ambient temperature were investigated and characterized by XRD, SEM, BET, EPR and XPS. The results demonstrated that the highest performance of the catalyst was MnOx/Mg4Al1 with n(Mg)∶n(Al)=4∶1, 40 % manganese oxides supporting and calcining at 200 °C. The removal rate of HCHO was up to 98.5% within 48 h, and the concentration was decreased from 1.000 mg·m-3 to 0.015 mg·m-3. The presence of a large number of hydroxyl groups on the surface of the hydrotalcite-like was beneficial to the adsorption of low concentration of HCHO and intermediate by-products, which also improved the oxidation activity of the catalysts. According to XPS analysis, compared to the MnOx catalyst, the Oβ/(Oα+Oβ) ratio of the MnOx/Mg4Al1 was increased from 35.7% to 88.0% and the surface oxygen content (Oβ) also enhanced significantly. The results suggested that the high surface oxygen content played an important role in the catalytic oxidation of HCHO at ambient temperature. This study can provide a reference for the reduction for the catalytic oxidation of HCHO at ambient temperature.