Pd/Al18B4O33: Synthesis and application in the high temperature catalytic combustion of methane

Abstract

ABSTRACT Aluminium borate Al 18 B 4 O 33 has been synthesised from different aluminium and boron precursors: commercial and laboratory made alumina, aluminium sulphate, aluminium nitrate, boric acid, ammonium tetraborate. The Al 18 B 4 O 33 phase was obtained only after calcination at 1100°C as confirmed by X-ray diffraction. Pure Al 18 B 4 O 33 phase with BET surface specific areas ranging between 12 and 27 m 2 /g was obtained by alumina impregnation by ammonium borate or boric acid. On the contrary, the use of aluminium sulphate and boric acid or ammonium tetraborate led to a mixture of Al 18 B 4 O 33 and θ-alumina phases together with boron loss. The former support was used for preparing 2 wt% PdO/Al 18 B 4 O 33 catalyst. Catalytic activity in methane combustion was measured up to 900°C. The Al 18 B 4 O 33 supported PdO catalyst exhibited better activity than PdO/Al 2 O 3 in the whole range of temperature. This was attributed to an interaction of PdO with Al 18 B 4 O 33 .