# The Effect of SO2 on C3H8 Oxidation over Ru@CoMn2O4 Spinel

## TL;DR

This study shows how sulfur dioxide (SO2) harms the ability of a catalyst to efficiently convert propane, a common industrial gas, into less harmful products.

## Contribution

The study identifies MnSO4 formation as the key mechanism of SO2-induced catalyst deactivation during propane oxidation.

## Key findings

- Exposure to SO2 reduced propane conversion by 30% within two hours.
- SO2 binds to Mn sites, forming MnSO4, which blocks active sites and reduces catalyst performance.
- MnSO4 formation was confirmed via XRD, TEM, and DRIFTS, and correlated with deactivation.

## Abstract

Propane is a typical volatile organic compound (VOC) in coal chemical processing and petroleum refining. However, coexisting SO2 significantly impairs its catalytic oxidative removal, potentially causing catalyst poisoning and deactivation. This study systematically elucidated the inhibitory effects of SO2 on the catalytic oxidation of propane over the Ru@CoMn2O4 catalyst system. Under continuous exposure to 30 ppm SO2, propane conversion plummeted by 30% within two hours. Mechanistic studies revealed that SO2 selectively bound to high-valent Mn sites rather than preferentially interacting with Co sites, leading to the formation of MnSO4 particles. These particles were directly corroborated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. After four hours of exposure to SO2, roughly 11.8 mole percent of manganese in the catalyst was converted into MnSO4. These deposits physically blocked active sites, reduced specific surface area, and disrupted redox cycling. As a result, their combined effects diminished performance progressively, ultimately leading to complete deactivation. Furthermore, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed that SO2 suppressed C=C bond oxidation in propane intermediates, thereby directly limiting conversion efficiency. Combining qualitative and quantitative methods, we characterized SO2-induced poisoning during propane oxidation. This work provides guidelines and strategies for designing anti-sulfur catalysts at the elemental scale for the catalytic combustion of low-carbon alkanes.