Synthesis of metal oxide-hierarchical ZSM-5 (CO3O4/ZSM-5 and Fe2O3/ZSM-5) as catalysts for partial oxidation of biomethane to methanol

Abstract

This study presents a partial oxidation of biomethane from anaerobic organic waste of cow dung (83.7 % of methane and 16.3 % of oxygen) to methanol using modified cobalt and iron metal oxide-hierarchical ZSM-5 catalysts. Hierarchical ZSM-5 was synthesized using double template methods with tetrapropylammonium hydroxide (TPAOH) and dimethyl diallyl ammonium chloride acrylamide copolymer (PDDAM) as the first and secondary templates, respectively. The as-synthesized ZSM-5 materials were characterized with Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), and the results show the similarities of physicochemical properties with standard ZSM-5 materials. The hierarchical ZSM-5 was then modified with cobalt or iron oxides through impregnation with incipient wetness. The results of XPS analysis show that the impregnated cobalt and iron metal oxide are Co3O4 and Fe2O3, respectively. While the AAS analysis indicates that the metal content in Co3O4/ZSM-5 and Fe2O3/ZSM-5 are 2.1 % (Co) and 2.4 % (Fe), respectively. The partial oxidation of bio-methane to methanol was carried out in an atmospheric fixed batch reactor, c.a. 200 mL, with biomethane to N2 ratio of 0,2:2 (in bar). The results of application using biomethane show the hierarchical Fe2O3/ZSM-5 catalyst has higher methanol yield (17.61 %), compared to the yield by using hierarchical Co3O4/ZSM-5 (10.99 %). In addition, no side product is detected after reaction. Thus, it can be concluded that Fe2O3 is more active than Co3O4 as catalyst and biomethane can be utilized as source in this partial oxidation reaction.