Selective synthesis of para-xylene and light olefins from CO2/H2 in the presence of toluene

Catalytic hydrogenation of CO2 with renewable H-2 into valuable chemicals such as para-xylene and light olefins (C-2(=)-C-4(=)), which are important raw materials for the production of various commodities, is highly attractive. Herein we report that an oxide-zeolite (OXZEO) composite catalyst composed of ZnCrOx-ZSM-5 enables the selective synthesis of para-xylene and light olefins from CO2/H-2 in the presence of toluene. The product selectivities depend strongly on the acidity and location of acid sites of the zeolite function. By modifying ZSM-5 with silica, the external acid sites are shielded, and the pore openings are narrowed, which enhances significantly the formation of para-xylene. By modifying the zeolite with phosphorus, light olefins are co-produced due to the weakened acidity. As a result, the para-xylene fraction in xylene isomers reaches 82.8%, and the light olefin fraction in aliphatic hydrocarbons is as high as 75.8% when CO2 conversion is 20.9% and toluene conversion is 10.6%. Furthermore, the catalyst exhibits a good stability within a 100 h test. This provides a potential route for utilization of centralized greenhouse gas for synthesis of value-added chemicals.

Automated summary

The study reported an oxide-zeolite composite catalyst that enables the selective synthesis of para-xylene and light olefins from CO2 with renewable H-2, leading to higher yields of these valuable compounds. By modifying the zeolite with silica and phosphorus, the product selectivities can be significantly enhanced, providing a potential route for the synthesis of value-added chemicals using centralized greenhouse gas.