Direct Production of Lower Olefins from CO₂ Conversion via Bifunctional Catalysis

Abstract

Direct conversion of carbon dioxide (CO2) into lower olefins (C2 =–C4 =), generally referring to ethylene, propylene, and butylene, is highly attractive as a sustainable production route for its great significance in greenhouse gas control and fossil fuel substitution, but such a route always tends to be low in selectivity toward olefins. Here we present a bifunctional catalysis process that offers C2 =–C4 = selectivity as high as 80% and C2–C4 selectivity around 93% at more than 35% CO2 conversion. This is achieved by a bifunctional catalyst composed of indium–zirconium composite oxide and SAPO-34 zeolite, which is responsible for CO2 activation and selective C–C coupling, respectively. We demonstrate that both the precise control of oxygen vacancies on the oxide surface and the integration manner of the components are crucial in the direct production of lower olefins from CO2 hydrogenation. No obvious deactivation is observed over 150 h, indicating a promising potential for industrial application.

A Critical Look at Direct Catalytic Hydrogenation of Carbon Dioxide to Olefins

“…showed that reaction temperatures of around 400 8Cw ere suitablef or synthesizingl ight olefins. [50,51,56,87,93,95] Optimal temperatures differ between studies, but ah igherO /P ratio was obtained upon increasingt he temperature from 200 to 300 8C. [87] Moreover,C O 2 conversion decreases at temperatures ranging from 100 to 450 8C.…”

“…[93,[99][100][101] ZrO 2 is sometimes added as at extural and electronic promoter.I nC O 2 hydrogenation to olefins, addingZ rO 2 increases thes tabilityo ft he catalystb yp reventing sintering. The Cu/ZnO/Al 2 O 3 system currently employed for methanol synthesis from mixed syngas exhibitslimited activity in CO 2 hydrogenation, so it is not ag ood candidate.…”

“…The Cu/ZnO/Al 2 O 3 system currently employed for methanol synthesis from mixed syngas exhibitslimited activity in CO 2 hydrogenation, so it is not ag ood candidate. [98] These new oxygen vacancies can stabilizet he key intermediates,d ecreasing the amount of the side product CO. [93,98] However, the presenceo f > 40 %C Oi nt he product mixture is still ap roblem in this type of reaction. These studies indicate that the oxygen vacancies of In 2 O 3 and Ga 2 O 3 may be the catalytic sites at which CO 2 is activated and hydrogenated to methanol.…”

“…[93] The authors showedt hat the incorporation of Zr into In 2 O 3 created new kinds of vacancies that enhanced the activity,r elativet oI n 2 [98] The composite catalystw ith a4 :1 atomic ratio of In/Zn showedt he highest CO 2 conversion (26.2 %);7 4.5 %l ower olefins were obtained among the hydrocarbons, resulting in aO /P ratio of 3.5. [93] The authors showedt hat the incorporation of Zr into In 2 O 3 created new kinds of vacancies that enhanced the activity,r elativet oI n 2 [98] The composite catalystw ith a4 :1 atomic ratio of In/Zn showedt he highest CO 2 conversion (26.2 %);7 4.5 %l ower olefins were obtained among the hydrocarbons, resulting in aO /P ratio of 3.5.…”

“…[87,93] Individual metal oxidesc an hydrogenate CO 2 to methanol, but they are not activef or methanolc onversion. Experi-mentalw ork shows that the catalystneeds to contain ac ombination of am etal oxide and az eolite/molecular sieve.…”