Fe改性MoNi/γ⁃Al_(2)O_(3)催化剂的制备与表征

Preparation and Characterization of Iron Modified MoNi/γ⁃Al_(2)O_(3) Catalysts

以大孔纳米氧化铝为载体、铁为助剂,对以Mo、Ni为活性中心的加氢催化剂进行改性,采用二次纳米自组装方法分别制备Fe⁃Mo⁃Ni和Fe⁃Ni催化剂。结果表明,经Fe改性的MNF⁃70C与NF⁃70C催化剂均为双峰孔结构,较大最可几孔径分别为50.0、40.0 nm,较小最可几孔径均为5.5 nm左右。在络合剂和助剂Fe的作用下,MNF⁃70C催化剂中Fe与Mo、Ni在大孔氧化铝内外表面以金属键的形式形成大量纳米自组装体,分散更加均匀,具有更多适合加氢反应的孔道。同时,MNF⁃70C和NF⁃70C催化剂的孔径分布在6.0~60.0 nm的比例分别达到78.05%和72.80%,这说明结构型助剂Fe的加入改善了活性金属的分散性,从而有效改善催化剂的孔径分布。CO吸附、H_(2)⁃TPR、TEM和XPS的表征分析结果进一步表明,经Fe改性的催化剂对CO的吸附均以线式吸附,其还原温度较低,且均已纳米粒子的形式均匀分散,具有更多的催化活性中心,而Fe改性的MNF⁃70C催化剂活性中心较多,说明此类催化剂具有较好的加氢催化活性。由于Fe元素廉价,助剂的加入可提高加氢后油品的质量或者降低催化剂活性金属的用量,从而降低合成催化剂的成本,适合工业应用重油加氢催化剂的开发。

The hydrogenation catalysts with Mo and Ni as active centers were modified with macroporous nano⁃alumina as carrier and iron as auxiliary agent,and Fe⁃Mo⁃Ni and Fe⁃Ni catalysts were prepared by secondary nano⁃self⁃assembly method respectively.The experimental results show that the iron modified catalysts MNF⁃70C and NF⁃70C have bimodal pore structure,the larger most probable pore diameter is 50.0 nm and 40.0 nm respectively,and the smaller most probable pore diameter is 5.5 nm.It can be seen that under the action of complexing agent and promoter Fe,Fe,Mo and Ni in MNF⁃70C catalyst form a large number of nano self⁃assemblies in the form of metal bonds on the inner and outer surfaces of macroporous alumina,which are more evenly dispersed and have more pores suitable for hydrogenation reaction.The pore size distribution of MNF⁃70C and NF⁃70C catalysts in the range of 6.0~60.0 nm reached 78.05%and 72.80%respectively.It shows that the addition of structural assistant iron improves the dispersion of active metals,so as to effectively improve the pore size distribution of the catalyst.The characterization analysis of CO adsorption,H_(2)⁃TPR TEM and XPS further shows that the Fe modified catalyst has linear adsorption for CO,its reduction temperature is low,and it has been evenly dispersed in the form of nanoparticles,with more catalytic active centers,indicating that this kind of catalyst has better hydrogenation catalytic activity.Because Fe is cheap,the addition of additives can improve the quality of the oil after hydrogenation or reduce the amount of catalyst active metal,so as to reduce the cost of synthetic catalyst,which is suitable for the development of heavy oil hydrogenation catalyst for industrial application.