【作者】 范翠云；

【导师】 王道；

【作者基本信息】 北京工业大学 ， 环境科学， 2007， 硕士

【摘要】 摘要本研究以改性后的天然海泡石作载体,Cu为活性组分,制备Cu/Sep催化剂,考察其催化氧化CO和选择催化还原NOx的性能,及稀土元素La、Sm、Ce和Pr的负载种类、负载量、制备方法、制备条件等对Cu/Sep催化剂性能的影响。分别使用气相色谱和氮氧化物分析仪对催化剂进行活性评价,另外运用XRD、SEM、BET、XPS和TGA等方法对制备的催化剂进行表征,探讨稀土元素对Cu/Sep催化剂性能的影响。实验结果表明:以酸改性后的海泡石为载体负载活性组分Cu制备的催化剂在180℃左右能将浓度为2.94%的CO完全转化为CO2;分别在Cu/Sep上负载0.5～5%的La、Sm、Ce、Pr稀土助剂后,催化剂对CO催化氧化的活性有一定的影响,但影响并不明显。Cu/Sep对NOx有一定的选择催化还原效果,在310℃左右,NOx的最高转化率为17%左右。Cu/Sep用于NOx选择催化还原时,添加稀土元素作助剂,是十分必要的,在Cu/Sep上添加1%～5%的稀土助剂后,催化活性有明显提高,NOx的最高转化率能提高20%～50%。其中以加入Ce相对最好,其负载量2%相对最佳;采用混合稀土时,以同时加入Ce和La为好,其负载顺序为先负载Ce后负载La,负载量Ce:La为5:1时能使NOx的最高转化率达到28%。与用CO作还原剂相比,以C3H6为还原剂时Cu/Sep催化剂的活性温度相对较低,活性温度能降低约90℃,同时NOx的转化率相对较高,转化率能提高50%左右,因此,在本实验条件下,Cu/Sep用于NOx选择催化还原时, C3H6是较为适宜的还原剂。XRD分析表明,稀土助剂负载在Cu/Sep上,稀土的存在形态分别为La₂O₃、Sm₂O₃、CeO₂和PrO2;BET结果显示,使用盐酸和硝酸改性,对海泡石载体的比表面积和孔径分布影响不大;SEM结果显示负载稀土后的Cu/Sep上粒状物团聚现象明显减少,分散也较均匀,表明稀土对活性组分在Cu/Sep上起到了良好的分散作用;XPS的分析结果表明,Cu/Sep中添加稀土元素Ce后,Cu_2p3电子结合能明显降低,说明添加稀土后能导致表面还原态Cu物种增加,使得催化剂反应活性增强。本研究对于丰富催化NOx和CO的研究提供新的素材,也为Cu/Sep类催化剂添加稀土助剂研究能提供技术借鉴。更多还原

【Abstract】 Natural sepiolite was modified by acid and used as the support. Then active promoters copper was loaded. The performance of Cu/Sep catalyst for catalytic oxidation of CO and catalytic reduction of NOx was studied. And influence of adding rare earth element La、Sm、Ce and Pr on activity of the catalyst also was studied. The catalytic activity for CO oxidation was evaluated by gas chromatogram and Oxides of Nitrogen Analyzer evaluated the catalytic activity for NOx reduction. XRD、BET、SEM and XRD were applied to characterize the catalysts.The experiment results show that after sepiolite was modified by hydrochloric acid and nitric acid respectively, Cu/Sep could make the conversion of CO reach 100% at about 180℃. The addition of 0.5%⁵% rare earth elements La、Sm、Ce and Pr to Cu/Sep catalysts had no obvious influence on the reaction of CO oxidation.Cu/Sep had a certain active for NOx reduction. The highest conversion of NOx was 17% in about 310℃. It is necessary to add rare earth elements on Cu/Sep for NOx reduction. The addition of 1%⁵% rare earth elements to Cu/Sep catalysts could improve the reaction of NOx reduction obviously. The highest conversion of NOx could improve from 20% to 50%. The 2% loading of Ce was propriety on Cu/Sep. When Ce and La were impregnated orderly and their proportion was 5:1 on catalysts, Cu/Sep could make the highest conversion of NOx reach 28%. When C3H6 was used reducer, Cu/Sep had lower active temperature and higher active for NOx reduction. The active temperature could decrease about 90℃and the conversion of NOx could improve 50%. So C3H6 was the appropriate reducer for NOx reduction in the experiments.From XRD、BET、SEM and XPS results, it was found that the oxidized form of rare earths was La₂O₃、Sm₂O₃、CeO₂ and PrO₂ on the Cu/Sep. The special surface area and pore distribution of sepiolite had no large difference between different acid modification methods. Large particles dispersed more equably in the SEM pictures of Re-Cu/Sep than in that of Cu/Sep. This showed that rare earth was a good dispersant to activity components. After the rare earth element Ce was added into Cu/Sep, the binding energy of Cu2p3 decreased from 934.1ev to 933.0ev. It showed that reductive Cu species increased in the surface of Cu/Sep and the catalytic activity of Cu/Sep could improve.This study were not only enriching the material of catalyst for NOx reduction and CO oxidation but also providing a reference to the technology of adding rare earth as the promoter into Cu/Sep catalysts.更多还原