Synthesis, spectroscopic and catalytic properties of cobalt and copper ions in aluminophosphates with chabasite-like structure. Studies of the NO reactivity

A combined spectroscopic and catalytic study of the NO reactivity on microporous cobalt-aluminophosphates, copper-aluminophosphates and copper-silicoaluminophosphates with chabasite-related structure, CoAPO-18, CoAPO-34, CuAPO-34 and CuAPSO-34 is reported. CoAPO-18 catalyst was synthesised using N,N-diiso-propylethylamine (DIPE), whereas CoAPO-34, CuAPO-34 and CuAPSO-34 were prepared using morpholine as structure directing template. NO and CO adsorption on both oxidised and reduced catalysts was monitored by FTIR spectroscopy. These studies revealed that Co²⁺/Co³⁺ and Cu⁺/Cu²⁺ redox couples, which should be the locus of the catalytic activity, are present respectively in the cobalt- and copper-containing catalysts. Catalytic tests of both NO oxidation to NO₂ by oxygen and NO reduction by CO were performed. CoAPO-34 catalysts showed exceptionally high performances in the NO oxidation, which were superior of the well-known Cu-ZSM-5, and a very poor activity in the NO reduction. A different behaviour was found for CuAPO-34 catalysts which, beside a good activity in the NO oxidation to NO₂, showed a very high activity in the NO reduction by CO when oxygen was absent in the reaction feed.