煤基活性炭上K-Cu-Fe混合物的催化活化造孔及机理

Preparation of Meso-Porous Activated Carbon by Catalytic Activation of Commercial Coal-Based Activated Carbon

采用浸渍法将混合催化剂KNO31%、Fe(NO3)347%、Cu(NO3)252%负载在经HF脱灰处理的商品活性炭(5F)上,并采用水蒸气二次活化的方法制备了改性活性炭(5F-AC-cat),商品活性炭和5F样同条件活化作为对比,所得活性炭分别记作M-AC和5F-AC.测定了M-AC、5F-AC及5F-AC-cat的碘值、亚甲蓝值和孔径分布;借助XRD、SEM和EDX等手段分析了5F-AC-cat上催化剂的形态、形貌和分布情况,探讨了混合催化剂的催化造孔机理.结果表明,相同活化条件下,M-AC、5F-AC及5F-AC-cat的烧失率相近,碘值相近;5F-AC-cat的亚甲蓝值分别高于5F-AC和M-AC的亚甲蓝值20,mg/g、31,mg/g;孔径分布结果显示负载混合催化剂后活性炭3.5～4.0,nm的孔明显增加;证实了混合催化剂的催化造中孔能力.结合SEM和EDX结果发现,有催化气化造孔作用的活性成分主要是Cu和Fe,而且Cu的比例高达90%以上;值得注意的是,Cu、Fe催化剂只要和煤中其他无机矿物质结合就会失去催化造孔性能;K主要是以和灰分相结合的状态存在.含Cu、Fe催化剂的催化造孔机理为氧传递机理.

K-Fe-Cu nitrates were loaded on the HF treated commercial activated carbon sample （5F）by impregnation method, and then the modified activated carbon （5F-AC-cat）was prepared by further steam activation from 5F. As comparison, the commercial activated carbon （AC）and 5F were further steam activated separately under the same activation condition, and the prepared activated carbon samples were denoted as M-AC and 5F-AC respectively. The adsorption performance of all activated carbon samples, including 5F-AC-cat, 5F-AC and M-AC was characterized by determining the Iodine number and methylene blue value. The configuration, morphology and distribution of cata- lysts on 5F-AC-cat were investigated with the help of XRD, SEM and EDX, and the mechanism of mesoporous pore formation by catalytic activation was discussed in detail. Results show that the bum-off ratio and Iodine number of samples are similar in the cases of 5F-AC-cat, 5F-AC and M-AC. The methylene blue of 5F-AC-cat is 20 mg/g higher than that of 5F-AC and 31 mg/g higher than that of M-AC. It is obvious that the loaded K-Fe-Cu catalysts en- hance the formation ofmeso-pores in 5F-AC-cat. The information provided by XRD, SEM and EDX analyses reveals that the active components which accelerate the carbon gasification reaction are Cu and Fe, and the proportion of Cu is higher than 90%. Besides, once the Fe-Cu catalyst is combined with the minerals in the coal, no ＂pore＂ appears around the catalyst particles, and no particle migration phenomenon is observed by SEM; meanwhile, K mainly exists in the form of compounds with silicate in the coal and shows no catalytic activity. The catalytic mechanism ot Fe and Cu can be explained by oxygen transport process.