利用笼状的分子筛模型,在B3LYP/6-311++G(d,p)水平下通过对分子筛中各种碱性基团的碱性进行对比来预测硼取代后氨化处理的分子筛的碱性.结果表明,B—NH2基团本身碱性不强,但与质子或路易斯酸作用时,B—NH2基团与周围的Si—OH基团共同参与作用并导致碱性增强.另外,分子筛中含有的Si—NH2基团也可与周围的B—OH共同作用,产生强碱性.因此,硼取代后氨化处理的分子筛是一种优良的碱性材料.
The basicity of boron-substituted zeolite interacted by NH3 was studied by theoretical calculations via density functional theory (DFT) method at the B3 LYP/6-311 + +G (d,p) level. We found that the B-NH2 group itseff didn' t have high basicity. However, when the proton or Lewis acid was adsorbed to it, the coexisting Si-OH group contributed to the basieity by forming a hydrogen bond with B-NH2. Besides, the Si-NH2 group and the coexisting B-OH group cooperatively had rather high basicity. Thus, the boronsubstituted zeolite interacted by NH3, which contains the B-NH2 together with B-OH groups and the Si-NH2 together with B-OH groups, could be a kind of promising basic material.