Cr-Free, Cu Promoted Fe Oxide-Based Catalysts for High-Temperature Water-Gas Shift (HT-WGS) Reaction

Abstract

Ca, Ni, Co, and Ge promoters were examined as potential candidates to substitute for the current toxic Cr in Cu-promoted Fe oxide-based catalysts for the HT-WGS reaction. The Ca and Ni promoters were found to improve catalyst performance relative to promotion with Cr. The HS-LEIS surface analysis data demonstrate that Ca and Ge tend to segregate on the surface, while Ni, Co, and Cr form solid solutions in the Fe3O4 bulk lattice. The corresponding number of catalytic active sites, redox, and WGS activity values of the catalysts were determined with CO-TPR, CO+H2O-TPSR, and SS-WGS studies, respectively. The poorer HT-WGS performances of the Ge and Co promoters are related to the presence of surface Ge and Co that inhibits catalyst redox ability, with the Co also not stabilizing the surface area of the Fe3O4 support. The Ni promoter uniformly disperses the Cu nanoparticles on the catalyst surface and increases the number of FeOx-Cu interfacial redox sites. The Ca promoter on the catalyst surface, however, enhances the activity of the FeOx-Cu interfacial redox sites. The CO+H2O TPSR results reveal that the redox ability of the active sites follows the SS-WGS performance of the catalysts and show the following trend: 3Cu8CaFe > 3Cu8NiFe ≥ 3Cu8CrFe > 3Cu8CoFe >> 3Cu8GeFe. Furthermore, all the catalysts followed a redox-type reaction mechanism for the HT-WGS reaction.

Boosting the performance of Ni/Al2O3 for the reverse water gas shift reaction through formation of CuNi nanoalloys

“…This reaction requires temperatures higher than 700°C in order to activate the thermodynamically stable CO 2 molecule and reach economically feasible conversions 7,12 . However, when the reaction takes place at lower temperatures, methane formation through the Sabatier reaction is favoured due to the exothermic nature of this sidereaction (Equation 2): At a commercial scale, Cu/ZnO/Al 2 O 3 and FeCrCuO x catalysts are employed due to their efficiency [13][14][15] . However, Cu-based catalysts suffer deactivation due to excessive sintering at high reaction temperatures 16,17 .…”

Manipulating Copper Dispersion on Ceria for Enhanced Catalysis: A Nanocrystal‐Based Atom‐Trapping Strategy

“…For the commercial copper‐based catalysts, such as CuCrFeO x , the Cu/FeO x interfaces account for CO activation while H 2 O molecules are activated on the associated oxygen defect sites. [ 46 ] Maximizing the dispersed Cu sites and the associated oxygen defects is desired, while excessive deposition of CuO would block the exposed active sites and consequently decrease the catalytic activities. Given the capability to controllably modulate the copper dispersion on ceria, we applied the atom‐trapped CuO/CeO 2− x samples for WGSR.…”

Modulating the water gas shift reaction via strong interfacial interaction between a defective oxide matrix and exsolved metal nanoparticles

“…The HT-WGSR measurements were conducted at a window temperature from 350 °C to 600 °C (ref. [63][64][65][66] using the experimental setup shown in Fig. 4a.…”