MgAPO-11分子筛的合成及Pt/MgAPO-11在正十二烷临氢异构化反应中的催化性能

 采用常规水热合成法合成了系列MgAPO-11分子筛,考察了晶化时间、 P/Al投料比和Mg源对MgAPO-11分子筛的物相、酸性以及Pt/MgAPO-11催化正十二烷临氢异构化反应性能的影响. 分别用X射线衍射、 X射线荧光光谱和NH3程序升温脱附测定了样品的晶相、 Mg含量和酸性质. 结果表明,合成条件影响着合成产物的晶相组成、 Mg含量及酸性质,从而影响到Pt/MgAPO-11在正十二烷临氢异构化反应中的催化性能. 反应结果显示, Pt/MgAPO-11催化剂的催化活性与MgAPO-11分子筛的强酸位数目密切相关. 较短的晶化时间、合成凝胶的P/Al摩尔比为1.0以及使用Mg(NO3)2为Mg源有利于提高MgAPO-11的强酸位数目,从而提高Pt/MgAPO-11的催化活性.

Synthesis of MgAPO-11 Molecular Sieves and the Catalytic Performance of Pt/MgAPO-11 for n-Dodecane Hydroisomerization

A series of MgAPO-11 molecular sieves have been synthesized by varying the crystallization time, the P/Al molar ratio, and the Mg source. X-ray diffraction, X-ray fluorescence spectroscopy, and temperature-programmed desorption of NH_3 have been employed to characterize the crystalline phase, the Mg content, and the acidity of MgAPO-11, respectively. The results show that the synthesis conditions have an effect on the crystalline phase, the Mg content, the acidity, and thereby the catalytic performance of Pt/MgAPO-11 in the hydroisomerization of n-dodecane. The reaction data reveal that the activity of Pt/MgAPO-11 is dependent on the amount of strong acid sites of MgAPO-11. Short crystallization time, P/Al molar ratio of 1.0, and Mg(NO_3)_2 as the Mg source favor the increase in the amount of the strong acid sites of MgAPO-11 and hence promote the catalytic activity of Pt/MgAPO-11 for the hydroisomerization of n-dodecane.