Hydrogen oxidation catalysed by X zeolite containing transition metal ions

Abstract

The catalytic activity of X zeolite for the oxidation of 1% H₂/air in a flow system was augmented by the exchange of 20% of the Na⁺ for transition metal ions. The kinetics were first order in H₂ pressure, and from the temperature required to maintain k₁= 2.0 × 10¹³ molecules g^–1 s^–1 Pa^–1 the activity sequence is: Pd,HX Cu,HX > Fe,HX > Ni,HX > Cr,HX > Zn,HX > Mn,HX > Co,HX > HX.

The activity of Cu,HX increased with increasing Cu²⁺ content but was insensitive to the proton content. Close similarities in the kinetics and energetics for catalysis on Cu,HX, CuX, CuX, CuO on SiO₂/Al₂O₃ and for published work on Cu,HY, support Cu–O–Cu bridges as the centres of activity. Temperature programmed reduction measurements suggest that the ease of interaction of H₂ with such bridges controls the pattern of catalytic activity.