Metal oxide–zeolite composites in transformation of methanol to hydrocarbons: do iron oxide and nickel oxide matter?

Abstract

The methanol-to-hydrocarbon (MTH) reaction has received considerable attention as utilizing renewable sources of both value-added chemicals and fuels becomes a number one priority for society. Here, for the first time we report the development of hierarchical zeolites (ZSM-5) containing both iron oxide and nickel oxide nanoparticles. By modifying the iron oxide (magnetite, Fe₃O₄) amounts, we are able to control the catalyst activity and the product distribution in the MTH process. At the medium Fe₃O₄ loading, the major fraction is composed of C₉–C₁₁ hydrocarbons (gasoline fraction). At the higher Fe₃O₄ loading, C₁–C₄ hydrocarbons prevail in the reaction mixture, while at the lowest magnetite loading the major component is the C₅–C₈ hydrocarbons. Addition of Ni species to Fe₃O₄–ZSM-5 leads to the formation of mixed Ni oxides (NiO/Ni₂O₃) positioned either on top of or next to Fe₃O₄ nanoparticles. This modification allowed us to significantly improve the catalyst stability due to diminishing coke formation and disordering of the coke formed. The incorporation of Ni oxide species also leads to a higher catalyst activity (up to 9.3 g(methanol)/(g(ZSM-5) × h)) and an improved selectivity (11.3% of the C₅–C₈ hydrocarbons and 23.6% of the C₉–C₁₁ hydrocarbons), making these zeolites highly promising for industrial applications.