Peroxide oxidation of n-octane over Na-Fe-silicalite-1 and H-Fe-Silicalite-1 catalysts

Abstract

The synthesis of the catalysts Na-Fe-silicalite-1(34), H-Fe-silicalite-1(34) and Na-Fe-silicalite-1(68) has been achieved by using the sol-gel method to incorporate the Fe as a T-atom in the zeolite framework (the values in brackets refer to Si/Fe molar ratios). Techniques that include FT-IR, XRD, SEM, TEM, ICP-OES, XRF, BET, TPR and TPD were used to characterize the catalysts. The XRD results show that only the ZSM-5 phase was present in all the synthesized catalysts. In addition, the TPR data showed a single peak assignable to Fe(III) species at 809.3, 806.5, and 777.9°C for Na-Fe-silicalite-1(34), H-Fe-silicalite-1(34) and Na-Fe-silicalite-1(68) respectively. The oxidation of octane over Na-Fe-silicalite-1(34) using H2O2 as an oxidant showed a direct dependence of conversion on temperature such that conversions of 9.6, 16.1 and 18% were recorded at 40, 60 and 80°C respectively. However, an inverse relationship was observed for the selectivity to terminal products (1-octanol and octanal). Selectivities of 30, 25 and 24% were recorded at 40, 60 and 80°C respectively. The H-Fe-silicalite-1(34) and Na-Fe-silicalite-1(68) catalysts were further tested at 80°C with the results showing that the H-Fe-silicalite-1(34) attained a terminal product selectivity of 26% at 19.8% conversion, while Na-Fe-silicalite-1(68) showed 27% selectivity to terminal products at 13.7% conversion. Only linear C8 products were observed under the conducted reaction conditions.