Synthesis and Properties of Lanthanide Incorporated Mesoporous Molecular Sieves.
Nanostructured lanthanum and cerium incorporated MCM-41 molecular sieves were synthesized via a hydrothermal method using cethyltrimethylammonium bromide as template and trimethylammonim hydroxide as mineralizer. Characterization of these materials by X-ray diffraction and nitrogen adsorption indicates that the resulting materials possess an MCM-41-like mesoporous structure. Atomic absorption and infrared spectroscopy studies revealed the presence of La and Ce in these materials. Their BET surface areas were ca. 590 and 700 m(2)/g for La- and CeMCM-41, respectively, whereas the average mesopore diameters were in the range between 3.0 and 3.5 nm. Total acidity determined by n-butylamine adsorption showed that the samples possess from weak to strong acid sites, the strengths of which are much higher for CeMCM-41 than for LaMCM-41. Adsorption energy distributions evaluated from low pressure adsorption isotherms indicate that the amount of surface hydroxyls is also higher for the cerium containing materials. Copyright 1999 Academic Press.
Araujo
AS
Department of Chemistry, Kent State University, Kent, Ohio, 44242
Jaroniec
M