[2008年05月04日]

 

 

  我组范峰滔等人关于“原位紫外拉曼光谱研究X型分子筛合成机理”的工作发表在 Chemistry - A European Journal Published Online: Apr 21 2008上。分子筛作为催化、吸附和离子交换材料已经在石油加工、石油化工、煤化工、精细化工和环境等领域中得到重要的应用。近些年来,分子筛材料的应用范围又扩展到了新型组装材料,生物芯片、生物传感器等各个方面。但目前许多分子筛的合成更多地是依据经验,因而分子筛生成过程与晶化机理的研究对分子筛的合成研究具有重要的科学意义。本研究利用紫外拉曼光谱结合专门为高温高压水热体系设计的原位拉曼光谱池首次实现了水热条件下分子筛结构的原位监测,通过跟踪X型分子筛的合成过程,考察了合成过程当中液相和固相组分的变化。在合成过程中,液相中存在大量的单态硅物种,这些单态硅物种在反应中富集到固相表面,与固相物种结合并参与了分子筛的合成。初始凝胶的固相含有大量的硅铝四员环物种,通过拉曼谱峰的演变结合DFT理论计算认为:这些四员环以及含有支链的四员环物种之间相互连接形成四六员环的结构单元从而搭建出X型分子筛骨架结构。

AbstractThe hydrothermal synthesis of Zeolite X was studied by in situ UV Raman spectroscopy for the first time. An in situ Raman cell was specially fabricated for investigating the species derived in both solid and liquid phase under high pressure at temperatures up to 250 . Under hydrothermal synthesis condition, it was observed that the liquid phase is dominated by monomer silicate species, which are loosely bonded to the gel phase and involve in zeolite framework formation, and amorphous aluminosilicate species composed of predominately four-membered rings are formed in the solid phase in the early stage of nucleation. The characteristic Raman bands of four-membered rings species were also calculated with DFT. It is proposed that four-membered rings formed at initial nucleation interconnect with each other via six-membered rings to form the zeolite X framework.

Keywordshydrothermal synthesis • Raman spectroscopy • reaction mechanisms • UV spectroscopy • zeolites