Catalyst design to direct high-octane gasoline fuel properties for improved engine efficiency

The paraffin-to-olefin (P/O) ratio in gasoline fuel is a critical metric affecting fuel properties and engine efficiency. In the conversion of dimethyl ether (DME) to high-octane hydrocarbons over BEA zeolite catalysts, the P/O ratio can be controlled through catalyst design. Here, we report bimetallic catalysts that balance the net hydrogenation and dehydrogenation activity during DME homologation. The Cu-Zn/BEA catalyst exhibited greater relative dehydrogenation activity attributed to higher ionic site density, resulting in a lower P/O ratio (6.6) versus the benchmark Cu/BEA (9.4). The Cu-Ni/BEA catalyst exhibited increased hydrogenation due to reduced Ni species, resulting in a higher P/O ratio (19). The product fuel properties were estimated with an efficiency merit function and compared against finished gasolines and a typical alkylate blendstock. Merit values for the hydrocarbon product from all three BEA catalysts exceeded those of the comparison fuels (0-5.3), with the product from Cu-Zn/BEA exhibiting the highest merit value (9.7).

Automated summary

The study introduces bimetallic catalysts to control the paraffin-to-olefin ratio in the conversion of dimethyl ether to high-octane hydrocarbons. The Cu-Zn/BEA catalyst showed higher dehydrogenation activity, resulting in a lower P/O ratio, while the Cu-Ni/BEA catalyst exhibited increased hydrogenation activity, leading to a higher P/O ratio. The product from Cu-Zn/BEA had the highest efficiency merit value among the three BEA catalysts compared to finished gasolines and alkylate blendstock.