沸石
分子
布朗斯特德-洛瑞酸碱理论
化学
吸附
路易斯酸
ZSM-5型
固态核磁共振
核磁共振谱数据库
分子筛
无机化学
物理化学
催化作用
谱线
有机化学
核磁共振
物理
天文
作者
Carlos Bornes,Dušan Stošić,Carlos F. G. C. Geraldes,Svetlana Mintova,João Rocha,Luís Mafra
标识
DOI:10.1002/chem.202201795
摘要
The identification of acid and nonacid species at the external surface of zeolites remains a major challenge, in contrast to the extensively-studied internal acid sites. Here, it is shown that the synthesis of zeolite ZSM-5 samples with distinct particle sizes, combined with solid-state NMR and computational studies of trimethylphosphine oxide (TMPO) adsorption, provides insight into the chemical species on the external surface of the zeolite crystals. 1 H-31 P HETCOR NMR spectra of TMPO-loaded zeolites exhibit a broad correlation peak at δP ∼35-55 ppm and δH ∼5-12 ppm assigned to external SiOH species. Pore-mouth Brønsted acid sites exhibit 31 P and 1 H NMR resonances and adsorption energies close to those reported for internal acid sites interacting with TMPO. The presence of an external tricoordinate Al-Lewis site interacting strongly with TMPO is suggested, resulting in 31 P resonances that overlap with the peaks usually ascribed to the interaction of TMPO with Brønsted sites.
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