Mn-MCM-41介孔分子筛的制备、表征及催化性能研究

Hydrothermal synthesis,characterization and catalytic performance of Mn-MCM-41 mesoporous molecular sieve

以十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,氨水为碱性介质,硝酸锰[Mn(NO_3)_2]为锰源,通过水热合成法制备了Mn-MCM-41介孔分子筛,分别按照同步和异步合成方法合成了硅锰摩尔比为100和50的样品。利用X射线衍射(XRD)、N_2吸附脱附、傅里叶红外(FTIR)、扫描电镜(SEM)、透射电镜(TEM)等对分子筛进行了表征。研究结果表明,随着介孔分子筛载锰量的增加,孔道有序性变差,比表面积和孔道容量减小;同步和异步合成方法对Mn-MCM-41的孔道结构也有影响。以合成的Mn-MCM-41为催化剂,考察不同pH条件下其催化臭氧氧化硝基苯的结果发现,硝基苯降解率及臭氧分解速率均远高于无催化剂时的状态,且随pH呈现规律性变化。

Mn-MCM-41 mesoporous molecular sieves with highly ordered structure are synthesized through hydrothermal synthesis method by using cetyltrimethylammonium bromide（CTAB） as template agent,tetraethyl orthosilicate（TEOS） as silicon source,manganese nitrate（Mn（NO3）2） as manganese source and ammonia as alkaline medium.Mn-MCM-41 samples with molar ratios of Si to Mn being 100 ∶1 and 50 ∶1 respectively are prepared successfully according to synchronous and asynchronous preparing methods,separately. X-ray diffraction（XRD）,N2 adsorptiondesorption,Fourier transform infrared spectroscopy（FTIR）,scanning electron microscope（SEM） and transmission electron microscopy（TEM） are used to characterize the prepared samples. It is observed that with the increase of Mn loading amount in mesoporous molecular sieve,the mesoporous ordering property gets deteriorated and both specific surface area and pore size of Mn-MCM-41 decreases. It is also found that synchronous and asynchronous preparing methods（different dosing sequence of Mn（NO3）2） can result in different mesoporous structure of Mn-MCM-41. The catalytic performance of the prepared Mn-MCM-41 is investigated through catalytic ozonation of nitrobenzene under different pH conditions.It is found both the degradation rate and ozonation decomposition rate of nitrobenzene over MnMCM-41 are far higher than that without presence of catalyst,and change regularly with changes of pH value.