The in situ growth of Mg–Al hydrotalcite on spherical alumina and its application as a support of a Pt-based catalyst for isobutane dehydrogenation

Abstract

In this work, Mg–Al hydrotalcite/γ-Al₂O₃ balls with a diameter of about 2.0 mm were prepared by the in situ growth of Mg–Al hydrotalcite on the surface of γ-Al₂O₃ in the presence of Mg²⁺ and urea using surface γ-Al₂O₃ in alumina balls as the aluminum source, and were used as the support precursors of Pt-based catalysts. The results showed that the as-prepared Mg–Al hydrotalcite/Al₂O₃ balls possessed even size, smooth surface, good sphericity, and outstanding crushing strength. The formation of Mg–Al–O mixed oxide nanosheets derived from Mg–Al hydrotalcite on Al₂O₃ balls can significantly increase the specific surface area, decrease the strong acid site amount of alumina and improve the dispersion of Pt particles. As a result, the selectivity of isobutene was increased from about 85% for Pt/Al₂O₃ to 96% for Pt/Mg(Al)O-7/Al₂O₃, and the carbon deposition amount was reduced from about 6.0% for Pt/Al₂O₃ to 2.9% for Pt/Mg(Al)O-7/Al₂O₃ after 4 h reaction, illustrating the important roles of the in situ growth of MgAl-LDH on the surface of γ-Al₂O₃.