Influence of Si/Al ratio of MOR type zeolites for bifunctional catalysts specific to the one-pass synthesis of lower olefins via CO2 hydrogenation

Abstract

Highly efficient CO2 utilization methodologies should be developed to reduce greenhouse gas emissions. Combining methanol synthesis (CO2-to-methanol) catalysts and methanol conversion (methanol-to-olefins) catalysts realizes one-pass hydrocarbon production via CO2 hydrogenation. We focused on ZnO/ZrO2 as metal-oxide-based catalysts for methanol synthesis and MOR zeolites as solid acid catalysts for methanol conversion. These catalysts were physically mixed to produce bifunctional catalysts which work at relatively low pressure (10 bars). Compositions of zeolite catalysts, especially Si/Al ratios, are important since composition influences on properties of zeolites, such as acid density and strength. MOR zeolites with varied Si/Al ratios were tested and found MOR zeolites with Si/Al ratio of 104 showed the best olefin selectivity. The relation between coke formation behavior and acid sites was discussed for explaining catalytic activities. The novel bifunctional catalysts and knowledge of selectivity provide a new methodology for CO2 utilization.