IR spectroscopic studies of the acidic properties of the mesoporous molecular sieve MCM-41
IR spectroscopic studies of the acidic properties of the mesoporous molecular sieve MCM-41
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介孔分子筛MCM-41酸性特性的红外光谱研究
DOI：
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发表时间：
1996
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通讯作者：
J. Klinowski
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作者：
J. Wȩglarski;J. Datka;Heyong He;J. Klinowski
采用红外光谱法测定了介孔分子筛MCM-41中质子形式的Bronsted-和lewis -酸位点的浓度、酸强度和热稳定性与Al含量的关系。并与相同元素组成的沸石H+-ZSM-5进行了比较。纯硅质[Si]- mcm -41和H+-[Si， Al]- mcm -41中羟基的光谱在3740 cm-1处有一个单波段，归属于Si - oh基团，与Al含量无关。氨或吡啶的吸附从铵离子和吡啶离子中产生带。H+-[Si， Al]- mcm -41中Bronsted-和lewis -酸位点的浓度均低于四配位铝的浓度。H+-MCM-41沸石中的Bronsted位点比H+-ZSM-5沸石中的Bronsted位点更容易发生去羟基化，且随Al含量的增加而增强。H+-MCM-41分子筛中Bronsted位点的酸强度与Al含量无关，且远低于H+-ZSM-5分子筛。
The concentration, acid strength and thermal stability of the Bronsted- and Lewis-acid sites in the proton form of the mesoporous molecular sieve MCM-41 were monitored by IR spectroscopy as function of the Al content. The results were compared with those for zeolite H+-ZSM-5 with the same elemental composition. The spectra of hydroxy groups in purely siliceous [Si]-MCM-41 and H+-[Si, Al]-MCM-41 contain a single band at 3740 cm–1, assigned to the Si—OH groups, and are independent of the Al content. Sorption of ammonia or pyridine generates bands from the ammonium and pyridinium ions. The concentrations of both Bronsted- and Lewis-acid sites in H+-[Si, Al]-MCM-41 are lower than the concentration of four-coordinate aluminium. The Bronsted sites in H+-MCM-41 are more prone to dehydroxylation than those in zeolite H+-ZSM-5, and the effect increases with the Al content. The acid strength of the Bronsted sites in H+-MCM-41 is independent of the Al content and much lower than in zeolite H+-ZSM-5.