氟碳铈精矿矿物学分析及负载锰的NH_(3)-SCR脱硝性能的研究

Mineralogical Analysis of Bastnaesite Concentrate and Denitration Performance of NH_(3)-SCR Loaded with Manganese

利用X射线荧光光谱分析仪(XRF)、扫描电镜(SEM)、矿物特征自动定量分析系统(AMICS)对氟碳铈精矿的元素组成,矿物间连生关系以及粒度分布、表面形貌等进行了分析。结果表明:氟碳铈精矿中的矿物组成复杂,矿物粒度呈细小颗粒状,主要以氟碳铈矿和独居石矿相为主,稀土元素(Ce,La,Nd)也主要赋于二者之中。为了研究氟碳铈精矿的NH_(3)-SCR的脱硝性能,及其作为载体的优势,采用过量浸渍法制备了一系列Mn/氟碳铈精矿催化剂,选用NH_(3)-SCR催化剂的常用载体Al_(2)O_(3)作为对比。通过XRD,BET,NH_(3)(NO)-TPD,H_(2)-TPR,活性测试等实验分析手段对所制备的催化剂进行物理化学性质分析。结果表明:Mn/氟碳铈精矿催化剂表现出最佳的脱硝性能,在150℃条件下NO转化率最高可达85%,这主要归因于Mn可以很好的与氟碳铈精矿相互作用,使得MnO_(3)物种的分散性更好。MnO_(3)物种多以无定形态分布在氟碳铈精矿表面,通过计算催化剂的晶胞常数可得氟碳铈精矿与Mn的结合效果最佳。Mn(NO_(3))_(3)溶液作为前驱体,为催化剂提供了更多的表面酸性位点。Mn^(n+),Ce^(n+)等离子价态的变化释放了更多氧空位有利于氧迁徙,相比于常规载体Al_(2)O_(3),氟碳铈精矿作为载体除了自身有着较多的酸性位点,其内部的稀土元素(Ce,La,Nd)以及部分过渡金属元素等均可以协同所负载的Mn参与氧化循环的反应,有利于催化活性的提高。

X-ray fluorescence spectroscopy(XRF),scanning electron microscope(SEM)and mineral characteristics automatic quantitative analysis system(AMICS)were used to analyze the element composition,mineral continuity relationship,particle size distribution and surface morphology of the fluorocarbon-cerium concentrate.The results showed that:The mineral composition of fluorocarbon-cerium concentrate is complex,and the mineral granularity is fine,mainly fluorocarbon-cerium and monazite facies,and the rare earth elements(Ce,La,Nd)also mainly occur in them.In order to study the denitrification performance of NH_(3)-SCR of cerium fluoride concentrate and its advantages as a carrier,a series of Mn/cerium fluoride concentrate catalysts were prepared by over-impregnation method,and aluminum oxide,a common carrier of NH_(3)-SCR catalyst,was used as a comparison.The physical and chemical properties of the prepared catalyst were analyzed by XRD,BET,NH_(3)(NO)-TPD,H_(2)-TPR,activity test and other experimental analysis methods.The results showed that the Mn/bastnasite concentrate catalyst exhibits the best denitration performance,and the NO conversion rate can reach 85%at 150℃.This is mainly due to the good interaction of Mn with bastnaesite concentrate,which makes the dispersion of Mn Ox species better.Mn Ox species are mostly distributed on the surface of bastnaesite concentrate in amorphous form.The best combination effect of bastnaesite concentrate and Mn can be obtained by calculating the unit cell constant of the catalyst.Manganese nitrate solution as a precursor,provide more surface acid sites for the catalyst.The changes in the plasma valence states of Mn^(n+) and Ce^(n+) release more oxygen vacancies to facilitate oxygen migration.Compared with the conventional carrier Al_(2)O_(3),the cerium fluoride concentrate,as the carrier,has more acidic sites in addition to its own,and the rare earth elements(Ce,La,Nd)and some transition metal elements inside the carrier can participate in the reaction of oxidation cycle in coordination with the loaded Mn,conducive to the improvement of catalytic activity.