Abstract:

In this study, two kinds of biochar were prepared by pyrolysis and carbonization using walnut shell as the starting materials, and then subjected to KOH activation and the sequential Mn-modification to prepare Mn modifying carbon-based denitrification catalyst. The effects of preparation methods of biochar and activation temperature on the physicochemical properties and denitrification performance of the catalysts were investigated by multiple techniques such as physical adsorption. The results showed that compared to the Mn modifying carbonized carbon-based denitrification catalyst, the Mn modifying pyrolytic carbon-based denitrification catalyst possessed larger specific surface area, well-developed pore structure, higher Mn⁴⁺ content, and thus better low-temperature denitrification performance. When the space velocity was 20000h^-1 and the denitrification temperature was 120℃, the denitrification efficiency and N₂ selectivity of the Mn modifying pyrolytic carbon-based catalyst reached 87.2% and 98.1%, respectively, and the denitrification efficiency maintained 85.1% after continuous reaction for 10h. And the denitrification efficiency increased to 95.1% at denitrification temperature of 180℃, much higher than that of the Mn modifying carbonized carbon-based denitrification catalyst (86.4%). The catalysts produced at too high or too low activation temperature showed diminished denitrification performance, and those prepared at activation temperatures of 700℃ and 900℃ had denitrification efficiencies of 80.5% and 87.9% at denitrification temperature of 180℃, respectively. This study provided a new strategy for the high-value utilization of pyrolytic carbon and achieved efficient removal of MnO _x, which was of great significance for the fulfilment of the carbon peak and carbon neutrality goal and environmental protection.

Key words: pyrolytic carbon, MnO _x, selective catalytic reduction, low-temperature denitrification

摘要：

以核桃壳为原料，基于热解和炭化两种制炭方法，耦合KOH活化和锰负载改性制备了炭基载锰低温脱硝催化剂，利用物理吸附等表征方法，并结合实验室催化脱硝反应装置，研究了制炭方法、活化温度等对催化剂理化特性及其脱硝性能的影响。结果表明，与炭化炭基载锰脱硝催化剂相比，热解炭制得的炭基载锰脱硝催化剂具有较大的比表面积、发达的孔隙结构和较高的Mn⁴⁺含量，低温脱硝性能显著。当空速为20000h^-1、脱硝温度为120℃时，热解炭基载锰催化剂脱硝效率和N₂选择性可分别高达87.2%和98.1%，且连续反应10h后，脱硝效率仍能保持85.1%。在脱硝温度为180℃时，热解炭基载锰催化剂脱硝效率提升至95.1%，远高于炭化炭基载锰脱硝催化剂的86.4%。而活化温度过高或过低时均不利于热解炭基载锰催化剂脱硝性能的提升。当活化温度为700℃和900℃时，热解炭基载锰脱硝催化剂在180℃时的脱硝效率仅为80.5%和87.9%。本研究为热解炭的高值利用提供了新的方法，并实现了NO _x 的高效脱除，对“双碳”目标实现和环境保护具有重要意义。

关键词: 热解炭, 氧化锰, 选择性催化还原, 低温脱硝