(532aj) Surface Compositional and Chemistry Tuning of Ni-Zn Catalyst for Low-Temperature Dry Reforming of Methane.

Dry reforming of methane (DRM) utilizes two of the most potent greenhouse gases (CO₂ and CH₄) to produce syngas (CO and H₂), a feedstock for downstream chemical and fuels production. However, the reaction is endothermic and plagued by coking under 800℃ process temperature. The development of low-temperature DRM will enable integration of DRM with downstream exothermic processes like Fischer-Tropsch (FT) and DME synthesis. DRM at low temperature (300-500℃) thermodynamically favors CH₄ decomposition, Boudouard reaction, and CO hydrogenation excessively. This leads to severe deposition of coke due to the low H/C feed ratio.

Intermetallic nanoparticles (iNPs) composed of ordered crystal structure and well-defined atomic arrangement from transition metals provide the design space for surface chemistry in different heterogeneous catalysis applications. In this study, a low-cost iNPs (Nickel and Zinc) catalyst was investigated for low-temperature DRM. The effect of the catalyst well-defined and tailored surface composition on CH₄ decomposition, surface carbon oxygenation chemistry and mechanism were investigated using varying in-situ spectroscopy methods coupled with Steady-state Isotopic Transient Kinetic analyses.

The stability and coke resistance of Ni₃Zn catalyst was demonstrated by 160-hour time on stream study at 450℃, in which CO₂ and CH₄ conversion and H₂/CO remained constant. Post-study TPO also confirmed the absence or negligible coke formation. HS-LEIS and in-situ CO DRIFTS show varying surface composition and structure. Keeping the bulk phase of the catalyst the same (as observed from TPR and XRD), systemically modifying the surface of the catalyst leads to changes in reactivity to DRM while retaining its coke resistivity. Isotopically labeled ¹³CH₄ and ¹³CO₂ in multiple SSTIKA experiments show shorter CO₂ residence time with increasing zinc content and carbon atom crossover from reactant CH₄ to product CO₂. This study shows that Ni-Zn catalysts have potential for achieving efficient low temperature dry reforming of methane.