Abstract:
The capture and hydrogenation of CO
2 into high-value chemicals such as alcohols is one of the important ways to reduce CO
2 emission and achieve carbon resource recycling. In this work, the catalytic performance of Rh/CeO
2 catalyst in the CO
2 hydrogenation was investigated; with the help of various characterization methods including XRD, Raman, H
2-TPR, CO
2-TPD, CO-DRIFTS and XPS, the influence of Rh loading (0.1%–2.0%) on the catalytic activity of Rh/CeO
2 and product selectivity in the CO
2 hydrogenation was revealed. The results indicate that for the hydrogenation of CO
2 at 250 ℃ and 3.0 MPa over the Rh/CeO
2 catalysts, ethanol is the major product at a low Rh loading of 0.1%. With the increase of Rh loading, the conversion of CO
2 increases, but accompanied by a decrease in the selectivity to ethanol; when the Rh loading reaches 2.0%, the main product turns to be methanol. It seems that the difference of various Rh/CeO
2 catalysts with different Rh loadings in the product selectivity for the CO
2 hydrogenation is ascribed to their difference in the structural and electronic properties of Rh; atomically dispersed Rh
+ species favor the stabilization of CO* and its subsequent C–C coupling with CH
3* to form ethanol, whereas metallic Rh clusters facilitate the hydrogenation of CO* to produce methanol.