椰壳活性炭氧化后负载硅基复合氧化物低温脱硝催化剂的研究

Research of Silicon-based Composite Oxides Supported on Oxided Cocount Shell Active Carbon as Denitration Catalyst at Low Temperature

椰壳活性炭经硝酸氧化处理后做载体,采用浸渍法负载含SiO_2的复合氧化物,用做低温脱硝催化剂.在锰氧化物中添加Ti O2,可以提高催化剂的抗硫性能,但低温脱硝活性降低.然而在锰氧化物中添加SiO_2,不仅提高了催化剂的抗硫性能,而且也提高了脱硝活性.TEM结果表明加入SiO_2可以有效的减小复合氧化物晶粒尺寸,更提高了其在载体上的分散度.NH_3-TPD结果显示加入SiO_2后催化剂表面酸性显著增强.XPS分析发现加入SiO_2还增大了催化剂表面Mn^(4+)的相对含量.此外,经硝酸氧化处理过的椰壳活性炭,表面含氧基团增加,从而也大大提高了对NH_3及NO的吸附容量.在相同脱硝条件下,与原料活性炭负载的催化剂比较,硝酸氧化处理后的活性炭负载的催化剂具有更高的脱硝效率.

The cocount shell active carbon（ AC） was pretreated with nitric acid,and supported the SiO_2 containing composite oxides by impregnation for denitration at low temperature. The introduction of Ti O2 in manganese oxide enhanced the resistance of catalyst to SO2,but decreased the denitration activity at low temperature. Comparatively,addition of SiO_2 in the oxides improved not only the resistance of catalyst to SO2 but also their denitration activity. TEM images indicated that SiO_2 might effectively reduce the crystal size of the composite oxides and improve the dispersion on the carrier surface. NH_3-TPD results showed that the surface acidity of catalysts was improved remarkably after the addition of SiO_2. Moreover,XPS results revealed that the relative content of Mn^（4＋） in the oxides was increased as well. In addition,pretreating with nitric acid greatly increased the contents of the oxygen-containing groups on the AC surface,which would benefit the adsorption of NH_3 and NO. Under the same denitration conditions,the oxided AC supported oxides exhibited higher denitration activities compared to those of the raw AC supported ones.