RESUMEN
Exploring highly efficient and robust non-noble metal catalysts for VOC abatement is crucial but challenging. Mn-based perovskites are a class of redox catalysts with good thermal stability, but their activity in the catalytic combustion of light alkanes is insufficient. In this work, we modulated the Mn-O bond strength in a Mn-based perovskite via defect engineering, over which the catalytic activity of propane combustion was significantly enhanced. It demonstrates that the oxygen vacancy concentration and the Mn-O bond strength can be efficiently modulated by finely tuning the Ni content in SmNixMn1-xO3 perovskite catalysts (SNxM1-x), which in turn can enhance the redox ability and generate more active oxygen species. The SN0.10M0.90 catalyst with the lowest Mn-O bond strength exhibits the lowest apparent activation energy, over which the propane conversion rate increases by 3.6 times compared to that on the SmMnO3 perovskite catalyst (SM). In addition, a SN0.10M0.90/cordierite monolithic catalyst can also exhibit a remarkable catalytic performance and deliver excellent long-term durability (1000 h), indicating broad prospects in industrial applications. Moreover, the promotional effect of Ni substitution was further unveiled by density functional theory (DFT) calculations. This work brings a favorable guidance for the exploration of highly efficient perovskite catalysts for light alkane elimination.
RESUMEN
Fast and comprehensive monitoring of VOCs, required for air quality management in large-scale chemical industrial parks in China, cannot be accomplished by stationary measurements using conventional GC-FID or GC-MS alone due to their low temporal resolutions and limited detectable ranges. Novel direct-inlet mass spectrometry (DI-MS) has been widely applied for real-time monitoring of VOCs. To verify its applicability in industrial settings, high mass-resolution proton-transfer-reaction time-of-flight MS (HMR-PTR-TOFMS), single-photon ionization time-of-flight MS (SPI-TOFMS), together with online GC-FID/MS were simultaneously deployed at the boundary of one of the largest chemical industrial parks in eastern China. Aromatics, acetonitrile, acetic acid, ethyl acetate, aliphatic hydrocarbons, 1,2-dichloroethane, and acetone were detected as the main pollutants. These three instruments detected 12 common species, among which ethyl acetate, toluene, C8-aromatics, and methyl ethyl ketone showed similar time series and levels. Acetone, benzene, chlorobenzene, styrene, and C9-aromatics showed only similar time series. The HMR-PTR-TOFMS uniquely detected 14 species, mainly oxidized VOCs, nitriles, and amines, which greatly helps acknowledge the pollutants in the chemical industrial area. Positive matrix factorization, using the HMR-PTR-TOFMS and GC-FID/MS datasets, was used to identify eight sources. Four of the identified sources were mainly detected by the HMR-PTR-TOFMS, with pollutants mainly comprised of nitriles, amines, carbonyls, and organic acids, most of which were hazardous and/or odorous. These four sources accounted for 41.5% and 33.2% of the total VOCs and ozone formation potential, respectively. The complementary nature of GC-FID/MS and HMR-PTR-TOFMS in VOC source apportionment in industrial settings is of great practical use for advanced VOCs abatement. Thus, the high mass resolution DI-MSs are suggested to be a supplementary measurement for fence-line monitoring. Although with a relatively short period attempt, this study has wide implications for the fence-line stationary observational modes and source apportion methods combining with traditional observations.
