Structure and reactivity of ZSM-5 supported oxalate ligand functionalized nano-Fe catalyst for low temperature direct methane conversion to methanol

The feasibility of low temperature direct methane conversion to methanol (DMCM) over ferrioxalate supported on ZSM-5 catalyst (FeOx/ZSM-5) was investigated in this study. FeOx/ZSM-5 was synthesized via functionalization of Fe with oxalate ligand and employed to generate hydroxyl radicals (HO center dot) from hydrogen peroxide (HP) in a Fenton-like process to activate the methane C-H bond scission to form methoxyl radical which in turn reacted with water to form methanol. The Fourier transformed infrared (FTIR) spectroscopy result showed the presence of v(a)(C=O) from the oxalate anion (C2O4-) at 1655 cm(-1) and v(3) asymmetry stretch from CO32- at 1343 cm(-1). The presence of Fe in the catalyst was elucidated by the energy dispersive X-ray, X-ray diffraction patterns and X-ray photoelectron spectroscopy (XPS). Furthermore, the XPS results showed that Fe2+/Fe3+ ratio in FeOx/ZSM-5 was 4.29. The effect of operating conditions showed that while FeOx/ZSM-5 loading and reaction time followed a simple power function (y = a . x(n)), the effect of HP dosage followed exponential function (y = a . e(x)), which signifies that the latter is more significant. The used-FeOx/ZSM-5 characterization result showed that virtually all the Fe2+ have been oxidized to Fe3+ after 15 min of reaction time. This novel result is promising for further research towards commercial low temperature DMCM. (C) 2016 Elsevier Ltd. All rights reserved.