改性活性炭对CH_4-CO_2重整制合成气性能的影响

Carbon dioxide reforming of methane over modified activated carbon

使用一系列试剂分别采用浸渍法与浸渍-焙烧法对活性炭进行了表面改性,采用Boehm酸碱滴定法与扫描电镜对活性炭表面基团和形貌进行了测定和表征,研究了改性活性炭对CH_4-CO_2重整制合成气的影响。结果表明:经盐酸、磷酸、过氧乙酸、次氯酸钠改性后活性炭表面呈酸性,催化活性降低;而经氢氧化钠、碳酸钠、碳酸氢钠、硝酸、高锰酸钾溶液改性后活性炭表面为碱性,催化活性提高。改性活性炭的催化活性顺序为:C_2H_4O_3-AC<NaClO-AC<H_3PO_4-AC<HCl-AC<AC<NaHCO_3-AC<Na_2CO_3-AC<NaOH-AC<KMnO_4-AC<HNO_3-AC。硝酸与高锰酸钾改性活性炭催化活性较高,主要是由于经其改性后活性炭表面碱性官能团含量增加,为CH_4-CO_2重整反应提供了活性位;同时经过改性后活性炭发育的孔结构,对CH_4与CO_2分子进行了吸附活化,产生能量较高的过渡态中间体,加快了重整反应速率。

The activated carbon （AC） was modified by impregnation and impregnation-calcination methods using a series of agents to improve its surface property, and the surface functional groups and topography of AC were determined and characterized by Boehm titration and SEM techniques, respectively. The effects of modifying the AC on its catalytic performaces in carbon dioxide reforming of methane were investigated. The resuhs show that the surfaces are acidic for the AC modified by HCl, H3PO4, AcOOH （C2H4O3） and NaClO, respectively, reducing catalytic activity; and the surfaces are alkline for the AC modified by NaOH, Na2CO3, NaHCO3, KMnO4 and HNO3, respectively, enhancing catalytic activity. The catalytic activity of various modified AC is in the following order：C2H4O3-AC 〈 NaCIO-AC 〈 H3PO4-AC 〈 HCl-AC 〈 AC 〈 NaHCO3-AC 〈 Na2CO3-AC 〈 NaOH-AC 〈 KMnO4-AC 〈 HNO3-AC. The high activity of KMnO4-AC and HNO3-AC is attributed to incresed surface basic functional groups and well-developed porous structure.