活性炭负载金催化分解空气中低浓度臭氧

采用等体积浸渍法制备了以煤质活性炭为载体的负载金催化剂,并运用N2吸附-脱附法和X射线光电子能谱对样品进行了表征.考察了该催化剂催化分解低浓度臭氧的活性,并研究了载体预处理方法和催化剂后处理方法对催化剂活性的影响.在常温,相对湿度为60%,臭氧浓度为45 mg/m3,空速为60 000 h-1的条件下,1.6 g活性炭经HNO3和NaBH4处理后负载金再经H2还原后的催化剂在反应最初的16 h内臭氧去除率稳定在100%,反应100 h后对臭氧的去除率仍在97%以上.表征结果表明,NaBH4还原处理使得活性炭比表面积、孔体积及石墨碳含量增加,含氧官能团下降,从而提高了催化剂的活性.载金后,催化剂比表面积和孔体积进一步增大,但石墨碳含量下降,C-O和COO-等含氧官能团增加.经臭氧氧化后,催化剂的比表面积和孔体积减小,石墨碳含量下降,C-O,COO-和C=O等含氧官能团增加,而金的粒径和价态并未改变,表明活性炭在金催化下被臭氧氧化.

Decomposition of Low- Level Ozone in Air over Activated Carbon-Supported Gold Catalyst

Activated carbon-supported gold catalysts were prepared by the incipient wetness method and characterized by N2 adsorption and X-ray photoelectron spectroscopy.The catalyst activity for the decomposition of low-level ozone was evaluated,and the effects of pretreatment of activated carbon and post-treatment methods were investigated.Pretreatment of the activated carbon with dilute nitric acid and NaBH4 reduction could improve activity for ozone decomposition.The catalytic activity tests were conducted with feed gas of 45 mg/m3 ozone in air and relative humidity 60% at room temperature.The contact time was controlled at 0.06 s.The ozone removal ratio was maintained at 100% in the beginning 1?000 min when the support was pretreated with HNO3 and NaBH4 and the catalyst was reduced with H2.Then it slowly dropped off to 97% in the following 5?000 min.After pretreatment of the support by NaBH4,the specific surface area,pore volume,and elemental C fraction increased,but oxygen-containing groups decreased.This might be responsible for the improvement of catalytic activity.After gold was supported on the activated carbon,the catalyst surface area and pore volume further increased.However,the graphitic carbon fraction decreased while C-O and COO-groups increased.After reaction with ozone,the surface area and pore volume of samples as well as graphitic C content decreased,while the amount of C-O,COO-,and C=O groups increased.This indicated that activated carbon was catalyzed by gold to react with ozone and thereby ozone was decomposed.