Ethanol steam reforming on Rh: microkinetic analyses on the complex reaction network

• Published in: Catalysis science & technology 2021-11, Vol.11 (21), p.79-717
• Main Authors: Gu, Tangjie, Zhu, Wen, Yang, Bo
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Density functional theory; Ethanol; Hydrogen production; Reforming
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/d1cy01202a

Ethanol steam reforming is one of the most widely used processes for hydrogen production, but the mechanism of the whole reaction pathway from ethanol to CO and CO 2 has not been studied, possibly due to the complex reaction network of this reaction. In this work, we used a method developed recently by our group to determine the preferred reaction pathways under certain conditions from a large network, based on density functional theory (DFT) calculations and microkinetic modeling, and reaction networks with 108 and 110 elementary steps were generated for CO and CO 2 formation, respectively. After the pruning of these networks, we found that at 923-1073 K, the mechanisms of ethanol to CO or CO 2 should be CH 3 CH 2 OH → CH 3 CH 2 O* → CH 3 CHO* → CH 3 CO* → CH 2 CO* → + CO* → CH* + CO* → C* + CO* → COH* + CO* → (2CO* → 2CO or 2CO* + 2O* → 2CO 2 ). Further microkinetic analyses combining the formation of CO and CO 2 showed that CH 3 CH 2 OH → CH 3 CH 2 O + H is the rate determining step of the ethanol steam reforming, and all the coverages of surface species are lower than 0.1 monolayer on Rh(111) at 923-1073 K. We also found that the increase of temperature is beneficial to the production rate of both CO and CO 2 , while only the rate of CO 2 increases with the increase of the H 2 O molar ratio in reactants. Reaction networks were generated for ethanol steam reforming to CO and CO 2 . After the pruning of the networks, the preferred reaction pathways of the CO and CO 2 production on Rh(111) were identified and detailed kinetic information was analyzed.