Fe–Zn–Al layered double hydroxides: synthesis, characterization and CO2-assisted propane oxidative dehydrogenation

Among petrochemical products, propylene is the second most important, with a growing demand that is not met by the steam cracking and fluidized catalytic cracking processes. CO 2 -assisted oxidative dehydrogenation of propane (CO 2 -ODHP) is an alternative route that has the advantage of using a greenhouse gas (CO 2 ) as a raw material and soft oxidant, thereby improving propylene selectivity and supporting carbon capture and utilization strategies. In this study, the importance of precise control of metallic composition in the development of high-performance Zn–Al–Fe catalysts derived from calcined layered double hydroxides (LDH) was highlighted. Trimetallic Zn–Al–Fe LDH were synthesized via pH-controlled coprecipitation with Fe/(Fe + Al) molar ratios of 0.1, 0.5, 0.7 and 0.9, while maintaining (Fe + Al)/(Zn + Fe + Al) at 0.25. Through multi-technique characterization (including XRD, ICP, FTIR–ATR, TGA, Raman spectroscopy, N 2 physisorption, digital colorimetry with chemometric analysis, SEM/TEM, XPS, CO 2 -TPD, NH 3 -TPD and DRIFTS) relationships between iron content and catalytic performance were established. Notably, we introduce digital colorimetry combined with chemometric modeling as a novel, highly accurate tool for predicting precursor composition, matching ICP–OES precision with only two principal components. The optimized catalyst, ZnAlFe10-C (Fe/(Al + Fe) = 0.1), exhibited superior surface characteristics, including balanced acid–base sites. At 590 °C, it achieved 38% propane conversion and a space–time yield of 1.7 mol C 3 H 6 kg cat⁻ 1 h⁻ 1 , reinforcing the potential of this methodology for advanced catalyst design.