Mordenite modification and utilization as supports for iron catalyst in phenol hydroxylation

The goal of this work was to synthesize mordenite in sodium form (NaMOR) using rice husk silica; modify by leaching with acid, base or both; and use the obtained zeolites as supports for iron (Fe) catalysts in phenol hydroxylation. All MOR zeolites were characterized by X-ray diffraction (XRD), nitrogen adsorption/desorption and the Si/Al ratios were determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The influence of zeolite modification to the phenol hydroxylation was also studied. All modified zeolites still exhibited MOR phase with higher surface area than that of the parent NaMOR. Only the sample leached by acid and base (ABMOR) showed a significant change in adsorption–desorption isotherm from type I to type IV, a characteristic of mesoporous materials. The major forms of Fe (5 wt.%) in all catalysts confirmed by XRD and X-ray Absorption Near Edge Structure (XANES) were Fe2O3. Because mesopores were generated in ABMOR to facilitate diffusion of reactants, the fastest reaction was obtained on Fe/ABMOR catalyst. The conversion was also highest on this catalyst probably because Fe was dispersed on the support with the highest surface area. However, the presence of mesopores did not improve the selectivity and the products observed were catechol and hydroquinone.