Reaction Pathways over ZnZrO₂‑Based Catalysts and Catalytic Sorbents

Area of Science:

• Chemical Engineering
• Catalysis
• Process Intensification

Background:

• Traditional CO2 conversion involves separate capture and hydrogenation steps.
• Process intensification aims to combine steps for efficiency.
• Reactive capture and conversion (RCC) offers a novel approach by integrating these processes.

Purpose of the Study:

• Investigate reaction pathways under RCC conditions for CO2 to methanol conversion.
• Compare RCC pathways with traditional steady-state (SS) processes.
• Understand the role of catalytic sorbent (CS) in RCC.

Main Methods:

• Fixed-bed kinetic measurements.
• In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS).
• Steady-state isotopic transient kinetic analysis-DRIFTS (SSITKA-DRIFTS).

Main Results:

• Under SS, ZnZrO2 produced methanol via HCOO* and CH3O* intermediates.
• CO formation was linked to CO2 dissociation at oxygen vacancies.
• Catalytic sorbent (CS) facilitated hydrogenation of monodentate carbonate species (m-CO3^2-) to methanol.
• RCC revealed two competing pathways for m-CO3^2-: direct hydrogenation to methane or migration to ZnZrO2 for methanol synthesis.

Conclusions:

• RCC enables unique carbonate hydrogenation routes absent in SS conditions.
• Product distribution in RCC is governed by competition between direct hydrogenation and migration pathways.
• Reaction pathways and rates differ significantly between RCC and SS operations.