Enhanced Methanol to Olefin Catalysis by Physical Mixtures of SAPO-34 Molecular Sieve and MgO

Abstract

Reaction rates, product distributions, and catalyst deactivation are reported for SAPO-34, MgO, MoO3, and physical blends of these materials in fixed-bed reactors. Methanol is converted to small olefins (C2 and C3 primarily) over SAPO-34. A small fraction of the methanol oligomerizes further, forming coke that deactivates the catalyst. Methanol is dehydrogenated to CO and H2 over MgO catalysts. Methanol is oxidized to CO2 over MoO3 catalysts. Physically blending SAPO-34 with MgO or MoO3 reduces the reaction selectivity for the methanol to olefins (MTO) reaction. Physical mixing of SAPO-34 and MgO favorably extends the catalyst lifetimes by reducing the rate of coke formation on SAPO-34. This is explained by opening up parallel reaction pathways involving oxygenated reaction intermediates. In contrast, SAPO-34 deactivation is more rapid when SAPO-34 is physically blended with MoO3. MgO by itself shows almost no catalytic activity for methanol. However, when MgO is sandwiched between layers of SAPO-34, the ...