Stability studies on undoped and doped Mg<Subscript>2</Subscript>TiO<Subscript>4</Subscript>, obtained by the polymeric precursor method.

A series of AlMCM-41 molecular sieves were synthesized starting from a hydrogel keeping the following molar composition: 1CTMABr:4.58SiO<Subscript>2</Subscript>:(0.437+<Emphasis Type=”Italic”>X</Emphasis>)Na<Subscript>2</Subscript>O:<Emphasis Type=”Italic”>X</Emphasis>Al<Subscript>2</Subscript>O<Subscript>3</Subscript>:200H<Subscript>2</Subscript>O. Tetramethylammonium silicate (TMAS) was used as silicon source and cethyltrimethylammonium bromide (CTMABr) was used as structure template. The obtained materials were characterized by nitrogen adsorption, XRD and TG/DTG. Acid properties were determined by pyridine thermodesorption. Model-free and Flynn-Wall kinetic models were used in order to correlate the total acidity with the apparent activation energy of pyridine desorption. [ABSTRACT FROM AUTHOR]