负载型Cu基结构催化剂的制备及其含氰废气净化性能研究

Preparation of Supported Cu-based Catalysts and Catalytic Purification of Acrylonitrile and HCN

目的调整Cu基结构催化剂浸渍液的组分,研究其对丙烯腈、氰化氢含氰组分净化效率的影响。方法通过表面改性的方法,在常见的分子筛和氧化物表面负载不同种类与含量的助剂,得到结构催化剂,并且利用X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、透射电子显微镜(TEM)、比表面积分析仪、催化剂颗粒强度仪,对催化剂的微观形貌、结构特性和机械强度等进行系统表征。利用氢气程序升温还原(H2-TPR)和氨气程序升温脱附(NH3-TPD),对催化剂表面物种的氧化还原性和酸性进行研究。结果通过筛选发现,添加Fe和Ce助剂得到的结构催化剂,在含氰废气净化过程中表现出优异的催化性能和稳定性。各浸渍组分均匀分布在所用的载体表面,经ICP分析测得催化剂中各负载组分的含量为4.5%Cu+1.1%Ce+1.2%Fe(均为质量分数)。利用该方法得到的催化剂比表面积高,孔道结构丰富,表面物种分布均匀且径向强度超过100 N/cm。含丙烯腈和氢氰酸的废气经过催化剂处理后,高效转化为无害的CO2、H2O和N2。废气中丙烯腈含量小于0.5 mg/m^3,氰化氢小于1.9 mg/m^3,氮氧化物小于100 mg/m^3,均低于国家排放标准的限值,且经过2500h连续反应,未发现明显失活现象。另外,催化剂同时具有较好的丙烷催化燃烧去除性能和水热稳定性,450℃下300 h内丙烷的去除率保持在85%以上。结论开发了一种简捷的方法对常见载体(分子筛、氧化物)进行表面改性处理,调控催化剂表面物种的化学性质。通过浸渍过程赋予其高效净化含氰废气的性能,同时催化剂具有优异的活性、稳定性和机械强度,存在良好的工业化应用前景。

The work aims to adjust the components in the impregnation solution of Cu-based catalysts, and investigate their influence on the purification efficiency of acrylonitrile(AN) and HCN. Through appropriate surface modification method, various catalysts were prepared by supporting different kinds and contents of additives on the surface of the commonly seen support(zeolite and oxide). The morphological and structural properties as well as the mechanical strength of the catalysts werecharacterized by X-ray Diffraction(XRD), Electron Microscope(EM), Energy Dispersive Spectrometer(EDS), surface area analysis and catalyst strength test methods. Moreover, the redox property and surface acidity of the catalysts were researched by H2-TPR and NH3-TPD method, respectively. Specifically, the Ce and Fe-modified catalyst showed excellent catalytic activity and stability in the purification of AN and HCN. Impregnated components were well distributed on the surface of the supports. Through ICP analysis, the support components of the catalyst contained 4.5%Cu+1.1%Ce+1.2%Fe(mass fraction). All catalysts obtained through the method exhibited high surface area, abundant pore structure with radial mechanical strength exceeding 100 N/cm. The acrylonitrile(AN) and HCN in the exhaust gas were converted into harmless CO2, H2 O and N2 effectively after catalytic treatment and the concentrations of AN, HCN and NOx were below national standard(0.5 mg/m^3, 1.9 mg/m^3, 100 mg/m^3, respectively). Moreover, no obvious deactivation was found after 2500 h of continuous reaction. The catalyst also demonstrated good hydrothermal stability and catalytic activity in C3 H8 catalytic combustion reaction, with the C3 H8 purification efficiency above 85% for 300 h at 450 ℃. A facile method has been developed to modify the surface of some commonly seen materials(zeolite and oxide) used in catalysis by adjusting the chemical properties of the supported components. The impregnation of active components endow the materials with effective purification properties of AN and HCN. The catalysts have excellent catalytic activity, stability and mechanical strength, which exhibits good prospects in industrial application.