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Catalytic ozonation is an efficient method for VOCs abatement at low temperatures, in which the rational design of highly active heterogeneous catalysts constitutes the most significant step. In this study, Al 2 O 3 was first optimized by loading MnO x. And then K was used for modifying MnO x /Al 2 O 3 catalyst, which exhibited 2.4 × 10−3 mol∙g−1∙s−1 oxidation rate for dichloromethane and toluene oxidation with ca. 0.89 ppm ozone detected at 80 °C. That could be directly applied for removing toluene and dichloromethane mixture or coupled with other treatment technologies (such as biological purification). Besides, appropriate K doping could increase the amount of reactive surface oxygen species and the ratio of Mn2+, hence contributing to an enhanced oxidation ability. By contrast, an excess K doping inevitably lowered the activity of active surface oxygen species and interfered with the transformation of Mn3+ to Mn2+, which resulted in a weakened oxidative ability and thus a decreased catalytic activity. Finally, the reaction mechanisms over 0.1 K-MnO x /Al 2 O 3 were tried to be demonstrated that the degradation of toluene mainly followed the pathway of toluene – phenylcarbinol – benzaldehyde – benzoic acid – phenyl group – small-molecule species and/or CO 2 while the route of dichloromethane – methanol – formaldehyde – formic acid – small-molecule species and/or CO 2 explained the catalytic oxidation of dichloromethane. All of these findings may facilitate the design of novel heterogeneous catalysts for VOCs oxidation and progress the development of catalytic ozonation for toluene and dichloromethane abatement. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • K-containing catalyst revealed excellent high-temperature NH 3 -SCR activity. • The hydrothermal stability and resistance to P poisoning increased by K doping. • The presence of K could inhibit the formation of Cu-PO 3 -/PO 4 3- species. • The existence of K could promote the formation of nitrate species on the catalyst. Cu-SSZ-13 (Cu-Z) has been commercialized as an efficient catalyst for NO x removal in mobile sources. However, in practical applications, the catalyst faces problems of poisoning (K and P) and hydrothermal aging. Therefore, in this work, we investigated the effects of K on P poisoning and hydrothermal aging in Al-rich Cu 2 /Z (2 wt% Cu). The presence of 1 wt% K could not only improve the high-temperature activity, which could reach above 99% at 225–600 °C on the K 1 /Cu 2 /Z, but also enhanced the hydrothermal stability and the resistance of P poisoning. Combing with a series of characterizations, K was mainly present in the Brӧnsted acid sites in the CHA cage, which led to the transformation of part of Z-[Cu(OH)]+ to Z 2 -Cu2+, reducing dealumination and the formation of CuO x and CuAl 2 O 4 species during hydrothermal aging. Moreover, the presence of K could inhibit the formation of Cu-PO 3 -/PO 4 3- species by P poisoning of Z-[Cu(OH)]+ species. In-situ DRIFTS results showed that the catalysts followed both E-R and L-H mechanism at 150 ℃. K doping could promote the formation of nitrate species and thus favoring the L-H mechanism, which probably enhanced the NH 3 -SCR activity. [ABSTRACT FROM AUTHOR]

As a typical high-efficient alkane aromatization catalyst, Pt/KL is prone to deactivation due to the sintering growth of Pt on the outer surface of KL and the channel blockage caused by carbon deposition, which is further exacerbated by the one-dimensional channel structure of KL. Therefore, a series of encapsulated catalysts combining the three-dimensional channel structure advantages of S-1 with the role of potassium are prepared and evaluated. It is shown that the encapsulated catalyst KPt@S-1-02 modified by moderate potassium exhibits extremely superior stability and no significant deactivation is observable after n-heptane aromatization for 180 h under harsh conditions. On the one hand, encapsulation structure enables a strong anti-agglomeration ability of Pt and the topological structure of S-1 endows the encapsulation catalysts less susceptible to channel blockage, which has been demonstrated by HAADF-STEM and N 2 -adsorption. On the other hand, characterizations involving NH 3 -TPD, CO-DRIFT and HAADF-STEM verify that the modification by an appropriate amount of K can inhibit acid sites of catalysts and improve Pt dispersion and electron density, thus enhance the stability of catalysts. However, excessive K can serve as weak acid sites, poison of active sites and inhibitor of H 2 adsorption on Pt surface, leading to deactivation of the catalyst. [Display omitted] • Encapsulation catalyst KPt@S-1 modified by potassium can be prepared by one-pot synthesis. • KPt@S-1 modified by moderate potassium exhibits extremely superior stability of alkane aromatization. • Moderate K can act as an inhibitor of acid sites, an electron donor and a dispersion promoter for Pt. • Excessive K can serve as weak acid sites, a poison of Pt active sites and an inhibitor of H 2 adsorption on Pt surface. [ABSTRACT FROM AUTHOR]

Catalytic cracking of butene over potassium modified ZSM-5 catalysts was carried out in a fixed-bed microreactor. By increasing the K loading on the ZSM-5, butene conversion and ethene selectivity decreased almost linearly, while propene selectivity increased first, then passed through a maximum (about 50% selectivity) with the addition of ca. 0.7–1.0% K, and then decreased slowly with further increasing of the K loading. The reaction conditions were 620 °C, WHSV 3.5 h−1, 0.1 MPa 1-butene partial pressure and 1 h of time on stream. Both by potassium modification of the ZSM-5 zeolite and by N2 addition in the butene feed could enhance the selectivity towards propene effectively, but the catalyst stability did not show any improvement. On the other hand, addition of water to the butene feed could not only increase the butene conversion, but also improve the stability of the 0.7%K/ZSM-5 catalyst due to the effective removal of the coke formed, as demonstrated by the TPO spectra. XRD results indicated that the ZSM-5 structure of the 0.07% K/ZSM-5 catalyst was not destroyed even under this serious condition of adding water at 620 °C. [ABSTRACT FROM AUTHOR]