低温等离子体改性Mn-CeO_x催化剂强化甲硫醚催化氧化性能的机理

Mechanism of Catalytic O_xidation Enhancement of Dimethyl Dulfides Over the Mn-CeO_x Catalyst Modified by Nonthermal Plasma

为研究低温等离子改性催化剂的机理,利用介质阻挡放电产生低温等离子体改性Mn–CeO_x催化剂,并研究了不同放电功率和处理时间对催化剂物理结构及化学特性的影响。选取恶臭气体甲硫醚作为污染物对改性后的催化剂进行活性测试。结果发现,经过等离子体改性的催化剂活性提高,改性效果与放电功率和处理时间相关。同时选取催化剂进行XRD、BET、H_2–TPR和XPS表征测试,结果发现,等离子体改性后的催化剂比表面积增加,孔径增大;放电功率和放电时间都会对催化剂的表面物理结构、化学特性活性产生较大影响;表面活性氧以及Mn4+和Ce^(3+)含量增加,Mn和Ce相互作用增强。其中,Mn–Ce–20 W–60 min催化剂比表面积为66.92 m^2/g,孔容为0.172 cm^3/g,远大于未经处理的Mn–Ce催化剂,且具有较高的Mn4+和Ce^(3+)含量,与其他条件处理的催化剂相比,在催化氧化甲硫醚过程中催化活性最高。

In order to study the mechanism of nonthermal plasma(NTP) for modifying the catalyst, we applied nonthermal plasma to modify the Mn-CeOx catalyst in different modification conditions such as discharge power and treatment time for the oxidation of dimethyl sulfides(DMS), and studied the effects of discharge power and treatment time on the physical structure and chemical properties of the catalyst. And DMS was chosen as the pollutant in catalytic oxidation activity tests. The results showed that the catalytic activity increased after the nonthermal plasma treatment, and the modification effect was related to the discharge power and treatment time. To elucidate the plasma modification effect, XRD, BET, H2-TPR, and XPS techniques were used for catalyst characterization, and it was found that the structural and morphological properties of the NTP-modified catalysts changed with higher surface areas and microspore volume. Both discharge power and treatment time had great influences on the surface physical structure and chemical properties of catalysts. The relative concentration of manganese and cerium ions in different valence on catalyst surface and oxidation states of surface species over catalysts also varied. High surface areas and microspore volume, high concentration of chemisorbed oxygen, Mn4+ and Ce3+, and the efficient synergetic catalytic effect between manganese ions and cerium ions played an important role in the higher activity of NTP-modified catalysts. The Mn-Ce-20 W-60 min catalyst possessed the highest BET surface area and pore volume of about 66.92 m2/g and 0.172 cm3/g, and showed the highest concentrations of chemisorbed oxygen Oα, Mn4+ and Ce3+ on the catalyst surface. Compared with other catalysts, the Mn-Ce-20 W-60 min catalyst showed the best catalytic activity for DMS oxidation.