摘要
通过水热法合成介孔分子筛MCM-41,采用等体积浸渍法制备了Mn负载MCM-41分子筛催化剂(Mn/MCM-41)。采用小角X射线粉末衍射(XRD)、N2吸附-脱附等温线及透射电镜(TEM)等对催化剂的成分结构进行了表征。结果表明,Mn/MCM-41保持了纯硅MCM-41有序的介孔结构,锰元素以锰氧化物形式存在,比表面达到852 m2/g。在草酸初始质量浓度为20 mg/L、O3投加量为100 mg/h、反应60 min、1%负载量、反应温度为35℃时,催化剂的加入显著改善了草酸的去除率,达到92.8%,是单独O3氧化的5.9倍。
In this paper,we have prepared Mn loaded mesoporous MCM-41 known as Mn / MCM-41 to be used as the heterogeneous catalysts for ozonating the oxalic acid with the methods of hydrothermal as well as dipping,respectively. As a result,the catalysts we have prepared have been verified and characterized by using the low-angle X-ray powder diffractor（ XRD） and transmission of the electronic microscopy（ TEM）,indicating the surface area,the pore size and the wall thickness of the catalysts have been worked out with the BET equation and BJH method via the nitrogen absorption technique. We have also made an investigation of the ozonation of oxalic acid in the aqueous solution by changing the concentration of Mn and the testing temperature.The small angle XRD patterns of MCM-41 and Mn / MCM-41 show three distinct Bragg diffraction peaks,that is,100,110,and200,indicating that the Mn / MCM-41 has been formed in a highly ordered manner of the two-dimensional hexagonal meso-struc-tures. In the same way,the N2 adsorption isotherms of MCM-41 and Mn / MCM-41 tend to exhibit a Type-IV shape,which is characteristic of a typical mesoporous substance. What is more,the pore structure of MCM-41 almost tends to remain intact before and after the Mn loadings with a large surface area being of 852 m2/ g.At the same time,the pore size distribution of the samples tends to reveal that there has been formed a uniform pore with the size of 2-3 nm. Furthermore,the loading of Mn on MCM-41 may result in the reduction of its surface area,the pore diameter and the pore volume,too,which may be attributed to the presence of Mn species in the channels. The TEM images prove that the mining species of Mn tends to disperse uniformly at the interior surface of MCM-41 channel,which implies that the surface active sites of the catalyst turn to be increasing with Mn content on MCM-41 owner. The overloaded Mn species help to eventually enhance the steric hindrance and decrease the catalyst＇s surface area,which turns to depress its catalytic activity. Furthermore,the oxalic acid removal efficiency can be found significantly rising with the rise of temperature from 5 ℃ to 35 ℃. Under the chosen condition（ 100 mg / h ozone dose,20 mg / L oxalic acid solution,1. 2 g catalyst dosage,35 ℃ and 1% Mn）,a high mineralization efficiency（ 92. 8%） can be gained in the Mn/MCM-41 /O3 process during a period of 60 min,to a 5. 9 times higher than the O3 alone. Thus,it can be seen that Mn / MCM-41 / O3 process helps to obviously improve the oxalic acid removal efficiency due to the generation of hydroxyl radical（ HO·）,the presence of which may have significantly improved its mineralization efficiency. Thus Mn / MCM-41 has been proved to be a highly promising catalyst.
出处
《安全与环境学报》
CAS
CSCD
北大核心
2015年第4期256-260,共5页
Journal of Safety and Environment
关键词
环境工程学
非均相臭氧催化
降解
草酸
催化剂
environmental engineering
heterogeneous catalytic ozonation
degradation
oxalic acid
catalyst
