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Structure and base properties of calcined hydrotalcites
Author(s) -
Liu HaiChao,
Yang XiYao,
Ran GuoPeng,
Min EnZe,
Liu JianKe,
Ying PinLiang,
Xin Qin,
Li Can
Publication year - 1999
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.19990170403
Subject(s) - calcination , hydrotalcite , chemistry , x ray photoelectron spectroscopy , base (topology) , molar ratio , aluminium , infrared spectroscopy , adsorption , desorption , inorganic chemistry , nuclear chemistry , analytical chemistry (journal) , catalysis , chemical engineering , organic chemistry , mathematical analysis , mathematics , engineering
Five hydrotalcites with Mg/Al molar ratio range of 3–15 were prepared. The structure and basicity of Mg‐Al mixed oxides (Mg(Al)O) transformed from hydrotalcites were investigated by TPD, XPS, XRD, FT‐IR and NMR techniques. The results of elemental analysis and XPS indicate that Al is enriched in the surface regions of Mg(Al)O, and its amount increases with the Mg/Al molar do and the Calcination temperature. 27 Al‐MAS‐NMR results show that Al exists in two chemical environments: tetrahedral aluminium (Al(t)) and octahedral aluminium (Al(o)) in Mg(Al)O. The amount of Al(t) increases with the Mg/Al molar ratio and the calcination temperature. It is assumed that A(t) may be mainly from the surface Al. Temperature‐programmed desorption (IPD) of CO 2 shows that the number of basic sites of Mg(Al)0 samples increases with the Mg/Al molar ratio, and the maximum number of basic sites is obtained for hydrotalcite calcined at 773 K. Infrared spectra of adsorbed CO 2 and B(OCH 3 ) 3 reveal that there are two kinds of basic sites: weak basic OH − sites and strong basic O 2 sites on the Mg(Al)0 samples, the base strength depends on the Mg/Al molar do and calcination temperature.