Direct Conversion of Syngas to Light Olefins over a ZnCrOx + H-SSZ-13 Bifunctional Catalyst

In recent years, bifunctional catalysts for the syngas-to-olefins (STO) reaction via the oxide-zeolite (OX-ZEO) strategy has been intensively investigated. However, the bifunctional catalyst containing H-SSZ-13 with a 100% H+-exchanging degree for the STO reaction has not been developed because of the high selectivity to paraffin. Here, we report a ZnCrOx + H-SSZ-13 bifunctional catalyst, which contains the submicron H-SSZ-13 with adequate acidic strength. Light olefins in hydrocarbon reached 70.8% at a CO conversion of 20.9% over the ZnCrOx + H-SSZ-13(23S) bifunctional catalyst at 653 K, 1.0 MPa, and GHSV = 6000 mL.g(-1).h(-1) after 800 min of STO reaction. The effect of CO and H-2 on the C-C coupling was discussed by carrying out the methanol-to-olefins (MTO) reaction under a similar atmosphere as that of the STO reaction. H-2 and CO should play a more dominant role than the conventional hydrogen transfer reaction on the undesired high selectivity of paraffins. These findings provide new insight into the design of the bifunctional catalyst for the STO process via the OX-ZEO strategy.

Automated summary

A ZnCrOx + H-SSZ-13 bifunctional catalyst has been developed with adequate acidic strength, leading to a high percentage of light olefins in hydrocarbons during the STO reaction. The role of H2 and CO in affecting the selectivity towards paraffins was found to be more dominant than traditional hydrogen transfer reactions.