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This work reported an efficient PdIr/activated carbon (PdIr/AC) catalyst and its application during direct ethane dehydrogenation (EDH) into ethane. The XRD and HADDF-STEM results revealed Pd/Ir nano-particles and atomically dispersed Pd2+and Ir4+species simultaneously. The activity tests demonstrated that Ir species showed higher C2H4selectivity than Pd species and the co-presence of Pd/Ir could further improve the catalytic stability and inhibit carbon deposition over the bimetallic Pd/Ir catalyst. Nevertheless, raising the reaction temperature from 500 °C to 600 °C boosted coking including carbon nanotubes (CNTs) and carbon particles. XPS results of Pd7Ir2/AC-B after Ar or H2pretreatment proved that the active sites are Pd2+/Ir4+species. The simulation results exposed the reaction pathway over Ir4+/Pd2+species, and ethane dehydrogenation was the rate-determining step over the PdIr/AC sample; meanwhile, the synergetic effect between Pd2+and Ir4+increased their TOF (C2H4). Finally, a deactivation mechanism was also proposed to examine the coking over various metal species.

The deactivation mechanism of Cu/SAPO-34 ammonia selective catalytic reduction catalysts (NH3-SCR) by SO2poisoning has been systematically investigated using a range of analytical techniques in order to study the influence on both the zeolitic framework and the active Cu2+ions. The different sulfate samples were obtained by SO2poisoning over Cu/SAPO-34 NH3-SCR catalysts as a function of time and concentration in the feed. The obtained results reveal that the SO2poisoning could seriously decrease NO conversion during the whole temperature range (100–500 °C). The XRF results shows that there is almost no sulfur existing on the SAPO-34 support. The ex situDRIFTS and BET results reveal that SO2poisoning has a less-pronounced effect on its framework structure. The TPR and EPR results demonstrate that SO2poisoning has a significant influence on the coordination environment and the content of the active isolated Cu2+species. The kinetic results demonstrate that the SO2poisoning does not influence the apparent activation energy (Ea) of the NH3-SCR reaction over Cu/SAPO-34 catalysts. The decline of the NH3-SCR activity is due to the reduction of the number of isolated Cu2+ions.

A series of Fe-β catalysts, containing 0.17–0.52 wt% Fe, were prepared by a liquid ion-exchange method to study the influence of various iron species on NH3-SCR activity. A combination of UV-vis and EPR techniques was applied to identify and quantify the iron species. The spectroscopic studies showed that the iron was almost all isolated Fe3+when the Fe content was less than or equal to 0.17 wt%. At higher Fe contents (0.27–0.52 wt% Fe), small oligomers coexisted with isolated Fe3+species. Furthermore, the quantitative analysis indicated that the percentage of tetrahedral Fe3+isolates decreased, while the percentage of octahedral Fe3+isolates increased with incremental iron loading. In situEPR results suggested that isolated Fe3+showed excellent activity for NH3-SCR; moreover, isolated Fe3+sites in distorted tetrahedral (g 6) and octahedral (g 8.8) environments showed better redox abilities than tetrahedral Fe3+(g 4.3). The SCR TOF values proved that isolated Fe3+sites both in tetrahedral and octahedral coordinations were the active sites for the NH3-SCR reaction. In addition, the NH3oxidation TOF results indicated that oligomers were the active sites for NH3oxidation over Fe-β catalysts and the contribution of diverse clustered oligomers was unequal.