固相转晶合成含硼CF-2沸石过程中甲胺分子的状态变化

以¹³C MAS NMR与TG-DTG为主要手段,研究了多孔玻璃粉于蒸汽相中转变为含硼CF-2沸石过程中模板剂甲胺分子的状态变化.结果表明甲胺分子经历了三种状态变化:在反应初期,甲胺分子与多孔玻璃表面羟基形成弱相互作用;随着反应进行,一部分弱相互作用的甲胺分子转变为强相互作用的甲胺分子;强相互作用的甲胺分子与硅羟基、铝羟基、硼羟基共同形成CF-2沸石晶核,晶核长大成晶体,甲胺分子进入沸石孔道内,此时存在与多孔玻璃粉表面羟基弱相互作用、强相互作用以及处于沸石孔道内的三种甲胺分子.随着结晶度进一步升高,多孔玻璃表面弱相互作用与强相互作用的甲胺分子依次逐渐消失,最终全部进入CF-2沸石孔道内.孔道内有自由状态和质子化的甲胺分子.SEM照片从形貌上直观地表征了多孔玻璃向CF-2沸石的转变过程.

State Changes of Methylamine Molecules in Synthetic Process of Boron-containing CF-2 Zeolite by Solid-phase Transformation

The state changes of methylamine molecules in synthesis process of boron-containing CF-2 zeolite transformed from porous glass granules in a vapor phase of methylamine and water were studied using 13C MAS NMR and TG-DTG techniques. The results show that the methylamine molecules go through three states during the entire process of reaction. At the early stage of reaction, methylamine molecules weakly interact with the hydroxyls on the surfaces of porous glass. With the progress of reaction, part of them change to strongly interacting ones, resulting in co-existence of weakly and strongly interacting methylamine molecules. Then the strongly interacting methylamine molecules together with Si-OH, Al-OH, B-OH form nuclei, which grow up to form CF-2 zeolite crystals. The methylamine molecules gradually enter into the zeolite channels. At this stage, there are three kinds of methylamine, i.e., weakly and strongly interacting ones in porous glass, and molecules in zeolite channels. With further reaction, the weakly and strongly interacting methylamine molecules successively disappear. Finally, there are only free and protonated molecules located in the channels of CF-2 zeolite. SEM images support the transformation process from porous glass granules to boron-containing CF-2 zeolite in morphology.