Cr 2 O 3 has been recognized as a key oxide component in bifunctional catalysts to produce bridging intermediate, e.g., methanol, from syngas. By combining density functional theory calculations and microkinetic modeling, we computationally studied the surface structures and catalytic activities of bare Cr 2 O 3 (001) and (012) surfaces, and two reduced (012) surfaces covered with dissociative hydrogens or oxygen vacancies. The reduction of (001) surface is much more difficult than that of (012) surface. The stepwise or the concerted reaction pathways were explored for the syngas to methanol conversion, and the hydrogenation of CO or CHO is identified as rate-determining step. Microkinetic modeling reveals that (001) surface is inactive for the reaction, and the rates of both reduced (012) surfaces (25−28 s −1 ) are about five times higher than bare (012) surface (4.3 s −1 ) at 673 K. These theoretical results highlight the importance of surface reducibility on the reaction and may provide some implications on the design of individual component in bifunctional catalysis. 

https://doi.org/10.1063/1674-0068/cjcp2204066

Insights into syngas to methanol conversion on Cr2O3 oxide from first-principles-based microkinetic simulations

Structure Sensitivity of Ethanol Steam Reforming over the Rh Catalyst: Reaction Kinetics and Deactivation Mechanisms

Highly textured zinc aluminate: Nd, Ce films over sapphire for NIR emitting applications

The dominating hydrocarbon pool species (HCPs) in zeolites for methanol-to-olefin (MTO) conversion have been the subject of intense debate for decades due to the diversity of structures and the complexity of reaction networks. We performed microkinetic simulations in a three-site model to study the MTO conversion in industrially relevant H-SAPO-34 zeolite under a wide range of operating conditions. The energetics of 229 and 342 elementary reaction steps were employed, respectively, in the aromatic-based and olefin-based cycles. The dynamic distribution and evolution of the retained aromatic or olefinic HCPs and the origin of olefin products were revealed with respect to reaction conditions. We corroborate that the olefin-based cycle dominates the MTO conversion in H-SAPO-34 under most reaction conditions, and the contribution of the aromatic-based cycle increase with increasing temperature, decreasing pressure, and/or decreasing water partial pressure. The paring route, dedicated highly to propene formation, prevails in the aromatic-based cycle; the side chain route, favoring exclusively ethene formation, only prevails at extremely lower temperatures, higher pressures, and higher water contents. The inherent activity of each aromatic HCP via the paring cycle increases, while its population retained in H-SAPO-34 usually decreases, with the methylation degree remarkably from tetramethylbenzene to hexamethylbenzene. The contents of higher methylbenzenes increase with decreasing water partial pressure, leading to the enhanced contribution of the aromatic-based cycle. The olefin-based cycle contributes to the formation of both ethene and other olefins, and the product distribution is drastically sensitive to reaction conditions. Ethene predominantly comes from the cracking of C5 and C6 species, and propene comes from C5 to C7 species. The olefin-based cycle shifts from the interconversion of C2–C7 olefins toward C2–C5 ones with increasing temperature and water partial pressure to enhance ethene formation. Under industrially relevant conditions, the conversion rate of methanol via the olefin-based cycle is 40-fold greater than that via the aromatic-based cycle (6.6 vs 0.15 s–1), and the former agrees unexpectedly with the experimental value in low-silica AlPO-34 (7.0 s–1). This work thus solves the puzzle of dominating HCPs as a function of reaction conditions in H-SAPO-34 and provides mechanistic insights into the kinetic behaviors, which are the basis for the optimization of the MTO catalyst and process. 

Microkinetic Simulations of Methanol-to-Olefin Conversion in H-SAPO-34: Dynamic Distribution and Evolution of the Hydrocarbon Pool and Implications for Catalytic Performance

Effect of P modification on the structure and catalytic performance of Ti-MWW zeolite

First-principles-based microkinetic simulations of syngas to methanol conversion on ZnAl2O4 spinel oxide

First-principles microkinetic simulations revealing the scaling relations and structure sensitivity of CO2 hydrogenation to C1 & C2 oxygenates on Pd surfaces

Jun Ke

Papers

First-principles-based microkinetic simulations of syngas to methanol conversion on ZnAl2O4 spinel oxide

First-principles microkinetic simulations revealing the scaling relations and structure sensitivity of CO2 hydrogenation to C1 & C2 oxygenates on Pd surfaces