Ni/(ZSM-5/MCM-41)催化剂的制备及其催化庚烷异构性能

PREPARATION OF Ni/(ZSM-5/MCM-41)CATALYSTS AND THEIR CATALYTIC PERFORMANCE FOR HEPTANE ISOMERIZATION

以ZSM-5为硅源、NaOH为碱源、十六烷基三甲基溴化铵(CTAB)为模板剂,采用水热合成法制备ZSM-5/MCM-41复合分子筛,并浸渍负载金属Ni,制得金属-酸中心双功能催化剂;利用X射线衍射光谱、N_(2)吸附-脱附、氨程序升温脱附和透射电镜等表征手段,考察碱溶条件及Ni负载量对催化剂结构和性能的影响;进而考察催化剂对正庚烷异构化反应的催化性能。结果表明:制备ZSM-5/MCM-41复合分子筛的最佳碱溶条件为NaOH浓度1.5 mol/L、碱溶温度为40℃、碱溶时间30 min;得到的复合分子筛的酸性适宜且具有典型的微孔/介孔复合结构;负载Ni后,金属Ni均匀地分散在复合分子筛表面;使用2%Ni/(ZSM-5/MCM-41)催化正庚烷异构化反应,在反应温度290℃下,正庚烷的转化率达65.44%,异庚烷的选择性达70.59%。

ZSM-5/MCM-41 composite molecular sieves were prepared by hydrothermal method using ZSM-5 as silicon source,NaOH as alkali source and cetyltrimethylammonium bromide(CTAB)as template agent,and the metal-acid center bifunctional catalyst was prepared by impregnating the supported metal Ni.The effects of alkali dissolution conditions and Ni loading on the structure and properties of the catalyst were investigated by means of X-ray diffraction spectroscopy,N_(2) adsorption-desorption,ammonia temperature-programmed desorption,transmission electron microscopy and other characterization methods,then the catalytic performance of catalyst for n-heptane isomerization was evaluated.The results showed that the optimum NaOH concentration,the optimum alkali solution temperature and the optimum alkali solution time were 1.5 mol L,40℃and 30 min respectively,and the obtained composite molecular sieve had a suitable acidity and a typical microporous mesoporous composite structure.After Ni was loaded,Ni was dispersed uniformly on the surface of composite molecular sieve.Using 2%Ni/(ZSM-5/MCM-41)as catalyst,the conversion of n-heptane was 65.44%and the selectivity of iso-heptane was 70.59%at 290℃.