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基于量子化学ONIOM[B3LYP/6-31G(d,p):UFF]计算方法,研究了β分子筛中Brφnsted酸的落位及其酸性强度.计算采用22T簇模型,得到了不同酸性位的(Al,H)/Si替代能和质子亲和势.研究结果表明,Brφnsted酸最有可能落位在Al(8)-O(11)-Si(4),Al(8)-O(4)-Si(1),Al(7)-O(7)-Si(2)和Al(9)-O(6)-Si(3)位置.根据去质化能的计算,Al(7)-O(7)-Si(2)位置的酸性最强,Al(8)-O(11)-Si(4)的酸性最弱.酸性的强弱顺序为Al(7)-O(7)-Si(2)>Al(9)-O(6)-Si(3)>Al(8)-O(4)-Si(1)>Al(8)-O(11)-Si(4).
Based on the calculation of ONIOM [B3LYP / 6-31G (d, p): UFF], the dislocation and acidity of Brφnsted acid in β molecular sieve were studied.Using the 22T cluster model, , H) / Si, and proton affinities. The results show that Brφnsted acid is most likely to abide by Al (8) -O (11) -Si (4), Al Al (7) -O (7) -Si (2) and Al (9) -O (6) -Si (3) (8) -O (11) -Si (4) has the weakest acidity and the order of acidity is Al (7) -O (7) -Si (2)> Al (9) -O (6) -Si (3)> Al (8) -O (4) -Si (1)> Al (8) -O (11) -Si (4).