Conditions for the joint conversion of CO2 and syngas in the direct synthesis of light olefins using In2O3−ZrO2/SAPO-34 catalyst

Abstract

The conditions for promoting the joint conversion of CO2 and syngas in the direct synthesis of light olefins have been studied. In addition, given the relevance for the viability of the process, the stability of the In2O3−ZrO2/SAPO-34 (InZr/S34) catalyst has also been pursued. The CO+CO2 (COx) hydrogenation experimental runs were conducted in a packed bed isothermal reactor under the following conditions: 375−425 °C; 20−40 bar; space time, 1.25−20 gcatalyst h molC −1; H2/(COx) ratio in the feed, 1−3; CO2/(COx) ratio in the feed, 0.5; time on stream (TOS), up to 24 h. Analyzing the reaction indices (CO2 and COx conversions, yield and selectivity of olefins and paraffins, and stability), the following have been established as suitable conditions: 400 °C, 30 bar, 5−10 gcat h molC −1, CO2/COx = 0.5, and H2/COx = 3. Under these conditions, the catalyst is stable (after an initial period of deactivation by coke), and olefin yield and selectivity surpass 4 and 70%, respectively, with light paraffins as byproducts. Produced olefin yields follow propylene > ethylene > butenes. The conditions of the process (low pressure and low H2/COx ratio) may facilitate the integration of sustainable H2 production with PEM electrolyzers and the covalorization of CO2 and syngas obtained from biomass.