A series of CeO2–WO3/TiO2–SiO2 catalysts were prepared for SCR of NOx with NH3, and the effect of WO3 and SiO2 doping on the activity and stability of the catalysts were discussed.
Poly(N-isopropylacrylamide) (PNIPAM) microgels have a number of potential biomedical applications, especially being considered as next-generation drug delivery systems. So far, nm-sized PNIPAM microgels have been commonly prepared in lab-scale experiments. In this work, nm-size controllable and monodisperse PNIPAM-based microgels were synthesized for the first time by surfactant-free precipitation polymerization using a high-gravity rotating packed bed reactor (RPB). The microgel size could be synergistically controlled by adjusting the amount of cross-linker and initiator in an RPB. Compared with the conventional stirred tank reactor, the RPB synthesis procedure could obtain a higher yield within 2 h of the reaction time. The higee level exhibited significant influence on the microgel size. Depending on the variation of the higee level, the particle size was tailored from 129 to 325 nm, and the hydrodynamic diameter was tailored from 217.7 to 805.4 nm without the usage of surfactants. In addition, different comonomers were introduced to regulate the lower critical solution temperature (LCST), achieve multiresponsiveness, and control microgel size. The in vitro DOX-loaded release demonstrated that PNIPAM-based microgels dramatically contributed to the sustained release of drugs.
Cu-SSZ-13 has been generally considered as the predominant commercial selective catalytic reduction (SCR) catalyst in the NH3-SCR reaction because of its superior activity and durability. However, in real applications, SCR catalysts readily undergo hydrothermal aging and sulfur poisoning. In this work, the deactivation and regeneration of a commercial Cu-SSZ-13 catalyst was investigated for SO2 exposures during hydrothermal aging and the effect of different regeneration temperatures was compared. By using XRD, SEM, H2-temperature programmed reduction (TPR), X–ray photoelectron spectra (XPS) and NH3-temperature programmed desorption (TPD) analysis, it was found that SO2 poisoning influenced the chabazite (CHA) structure even if regeneration cannot restore its original structure, the redox ability and ammonia storage performance also influenced by sulfation and the regeneration process. Moreover, the extent of a decrease in redox ability was more severe than acidity, suggesting that the amount of isolated Cu2+ and Cu+ reduction was responsible for irreversible deactivation over the Cu-SSZ-13 catalyst. Combined with the analysis of Ea values and pre-exponential factor of the SCR reaction, a more likely explanation for the irreversible deactivation was that active sites were lost mostly in sulfated and regenerated process sites.
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