CHARACTERIZATION AND N-HEPTANE CRACKING ISOMERIZATION CATALYSIS OF TUNGSTEN OXYNITRIDES ON EMT ZEOLITE/

Catalysts made of two tungsten precursors (one of them containing phos phorus) impregnated on EMT zeolite were nitridated in flowing pure amm onia and passivated by O-2 (1 vol%) in an Ar stream leading to tungste n oxynitrides/EMT (W2N/EMT) and phosphotungsten oxynitrides/EMT (PW2N/ EMT). The catalysts were examined by X-ray diffraction, NMR spectrosco py, transmission electron microscopy and energy dispersive X-ray spect roscopy. The materials were tested for the cracking/isomerization of n -heptane at atmospheric pressure and 623 K. Cracking (C-3 + C-4) was t he major (about 90%) n-heptane reaction for all the catalysts. The inf luence of EMT supercages upon selectivity was observed. The yield of n -haptane isomers was significantly enhanced for W2N/EMT and principall y for PW2N/EMT showing a higher hydrogenation function.