Behavior of silver-thorium phosphate AgTh2(PO4)3 in butan-2-ol conversion Original Research Article

Catalytic conversion of butan-2-ol was studied over silver-thorium phosphate AgTh2(PO4)3. Its selectivity was found to be mainly oriented towards the oxide hydrogenation reaction when oxygen was added to the reaction mixture. This activity was interpreted as reflecting the Ag+ ions mobility in the conduction tunnels of the phosphate framework. Under reaction conditions, butan-2-ol reduces the silver cations. The ensuing crystallites, in presence of O2 form Agxsingle bondOy species which are active in the production of methyl ethyl ketone. Concurrently, the Ag+ ions are replaced by protons released by the alcohol, without any detectable modification of the structure. The influence of their acidity on the dehydration reaction was very limited. Similar results were achieved by using hydrogen as agent for Ag+ reduction. Physical techniques were used to characterize the phosphate before and after the catalytic tests and to support this results: (i) XRD, XPS, TEM and EDX-STEM showed the formation of silver crystallites with an average size of 10 nm, well dispersed on the sample; (ii) UV-visible spectroscopy confirmed the nucleation of the silver particles; (iii) 1H NMR MAS established that new protons bonded to [PO4] groups appear in the sample.