Chromium‐Free Copper Aluminate Spinel Catalyst for Efficient High‐Temperature Water‐Gas Shift Reaction

Abstract A chromium‐free catalyst for the high‐temperature water‐gas shift (HT‐WGS) reaction was developed using copper aluminate spinel synthesized via co‐precipitation. Powder X‐ray diffraction (PXRD) revealed that the material was amorphous when calcined at 500 °C but transformed into a well‐defined crystalline spinel structure at 800 °C. Scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS) confirmed the formation of crystalline spinel morphology, which enhances thermal stability under HT‐WGS conditions. Hydrogen temperature‐programmed reduction (H 2 ‐TPR) showed a shift of the second copper reduction peak to a higher temperature, indicative of the robust nature of the spinel phase. Density functional theory (DFT) calculations further demonstrated that the spinel catalyst exhibits superior CO adsorption and H2O activation compared to its amorphous counterpart, thereby improving WGS activity. The catalyst calcined at 800 °C exhibited activity for both low‐ and high‐temperature WGS reactions; however, after H 2 reduction at 400 °C, it became selectively active for the HT‐WGS reaction. Long‐term stability testing confirmed excellent durability, maintaining an average CO conversion of 53.6% over 120 h at 400 °C, comparable to the 57% achieved by commercial Cr‐containing catalysts. These findings establish copper aluminate spinel as a robust, sustainable, and chromium‐free alternative for industrial HT‐WGS catalysis.