Acidity and basicity of hydrotalcite derived mixed Mg–Al oxides studied by test reaction of MBOH conversion and temperature programmed desorption of NH3 and CO2

Mg-Al hydrotalcites intercalated with five different interlayer anions--CO{sub 3}{sup 2-}, SO{sub 4}{sup 2-}, Cl{sup -}, HPO{sub 4}{sup 2-} or terephthalate--were synthesized by either the coprecipitation or ion-exchange method. The structure of the as-synthesized samples and the presence of intended anions in the interlayer gallery of hydrotalcites were determined by X-ray diffraction and FTIR spectroscopy. On calcination at 600 deg. C the materials were transformed into mixed metal oxides. The kind of the counterbalancing anions present in the parent hydrotalcite influences strongly textural parameters of the obtained Mg-Al oxides. Both temperature-programmed desorption of NH{sub 3} and CO{sub 2}, and test reaction of 2-methyl-3-butyn-2-ol (MBOH) conversion were used to determine the acidity and basicity of the samples. The hydrotalcite derived mixed Mg-Al oxides showed the presence of Broensted and Lewis acid and base sites. However, the strong basic character of the solids caused that acetone and acetylene were observed as the major products of MBOH conversion.