非金属氮掺杂活性炭催化剂制备及其催化CH4-CO2重整反应

采用硝酸和尿素联合对活性炭进行改性，制备了富含氮元素的氮掺杂活性炭，考察了孔结构、氮含量和氮种类（吡啶氮、吡咯氮和石墨氮）对CH₄-CO₂重整反应催化性能的影响。采用BET、SEM、EA、FTIR、XPS、CO₂-TPD和TG表征手段对反应前后催化剂的物理化学性质进行了表征，对引入活性炭表面的含氮官能团的种类及其在重整过程中所起的作用进行了分析。相比于未改性的原活性炭，硝酸和尿素同时改性制备的氮掺杂活性炭（AC-U.NA）引入了更多的羟基官能团和含氮官能团。特别是通过两者共同改性后，所制备的氮掺杂活性炭引入的吡啶氮官能团比例明显提高，为CH₄-CO₂重整反应提供了更多的活性位点，初始CH₄和CO₂转化率达到55.94%和66.46%。同时经过两者联合改性后，所制备的AC-U.NA材料表面具有极性，不仅有利于酸性CO₂分子的吸附和活化，而且有利于CO₂消碳反应，减少了积炭的生成，对所制备的非金属重整催化剂的活性和抗积炭性具有重要的意义。

Preparation of metal-free nitrogen-doped activated carbon as catalysts for carbon dioxide reforming of methane

Nitrogen-doped activated carbon was prepared by modifying activated carbon with nitric acid and urea. The effects of pore structure, nitrogen content and nitrogen species (pyridine nitrogen, pyrrole nitrogen and quaternary nitrogen) on the catalytic performance of CO₂ reforming of CH₄ were investigated. The physicochemical properties of the catalysts before and after the reaction were characterized by BET, SEM, EA, FTIR, XPS, CO₂-TPD and TG. The types of the nitrogen-containing functional groups introduced on the surface of activated carbon and their roles in the reforming process were analyzed. Compared with the unmodified activated carbon, the nitrogen-doped activated carbon (AC-U.NA) simultaneously introduced more hydroxyl and nitrogen-containing functional groups. Especially, the content of pyridine nitrogen functional groups in AC-U.NA was significantly increased, which provided more active sites for CO₂ reforming of CH₄. The initial conversion of CH₄ and CO₂ was 55.94% and 66.46%, respectively. At the same time, the prepared AC-U.NA surface had polarity, which was conducive not only to the adsorption and activation of the acidic CO₂ molecules, but also to the carbon elimination reaction of CO₂, and hence reduced the carbon deposition, which is of great significance to the activity and anti-carbon deposition of the prepared metal-free reforming catalyst.