Pt/BaO/Al 2 O 3 catalysts with different BaO loadings prepared from Al 2 O 3 nanorods (Pt/BaO/Al 2 O 3 -nr) and irregular Al 2 O 3 nanoparticles (Pt/BaO/Al 2 O 3 -np) were investigated for NO x storage and reduction (NSR). The Pt/BaO/Al 2 O 3 materials derived from Al 2 O 3 nanorods always exhibited much higher NO x storage capacity (NSC) over the whole temperature range of 100–400°C than the corresponding Pt/BaO/Al 2 O 3 -np samples containing the same BaO loading, giving the maximum NSC value of 966.9 μmol/g cat at 400°C, 1.4 times higher than that of Pt/BaO/Al 2 O 3 -np. Higher catalytic performance of nanorod-supported NSR samples was also observed during lean-rich cyclic conditions (90 sec vs. 5 sec), giving more than 98% NO x conversion at 300–450°C over the Pt/BaO/Al 2 O 3 -nr sample with 15% BaO loading. To reveal this dependence on the shape of the support during the NSR process, a series of characterization techniques including the Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H 2 temperature programmed reduction (H 2 -TPR), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) were also conducted. It was found that intimate contact of Ba–Al and Ba–Pt sites was achieved over the Pt/BaO/Al 2 O 3 surface when using Al 2 O 3 -nr as a support. This strong interaction among the multi-components of Pt/BaO/Al 2 O 3 -nr thus triggered the formation of surface nitrite and nitrate during the lean period, and also accelerated the reverse spillover of ad-NO x species onto the Pt surface, enhancing their reduction and leading to high NSR performance.
A mesoporous LaCoO 3 perovskite oxide (LaCoO 3 -Meso) with three-dimensionally ordered helical interwoven structure was synthesized by a nano-casting method using KIT-6 as the hard template. The obtained LaCoO 3 -Meso with high surface area was tested for its catalytic performance in the NO x storage and reduction (NSR) reaction and compared with a sample synthesized by the conventional sol-gel method. The LaCoO 3 -Meso showed a significant advantage for NO x storage, with a NO x storage capacity 2 times higher than the regular sample. LaCoO 3 -Meso also exhibited improved NSR catalytic performance in the 150–450 °C temperature range, especially within 350–400 °C, where the NO x conversion was raised for 40%. The results of X-ray photoelectron spectroscopy and X-ray absorption fine structure measurements suggested the presence of a high concentration of oxygen defects on the LaCoO 3 -Meso surface. Further results provided by temperature programmed reduction and temperature programmed desorption indicated that the oxygen defects not only increase the amount of trapped NO x , but also improve the low-temperature redox performance of the catalyst. The lower stability of NO x species adsorbed on oxygen defects promotes the NO x release step in the NSR reaction and benefits the regeneration of storage sites.
Yinan Wang,Xuteng Zhao,Ting Chen,Zuwei Zheng,Rijing Zhan,He Lin
Pd/SSZ-13 with different Al distributions were hydrothermally synthesized and utilized as passive NOx adsorbers (PNA). The characterization results indicated that more concentrated Al distribution can not only improve the ion-exchanged level of Pd but also generated more Z 2 Pd 2+ sites at six-member rings. Thus, as revealed by NOx adsorption experiments, samples with more Z 2 Pd 2+ sites showed high NOx storage capacity as well as stronger water resistance. Besides, 84.8 % adsorption capacity of this sample was retained after hydrothermal aging treatment. On the other side, Pd existed as [Pd(OH)] + sites on SSZ-13 with isolated Al as the majority. These sites were vulnerable to H 2 O and less stable. Seriously Pd agglomerated was observed on the aged Pd/SSZ-13 with less paired Al. This study revealed that proper Al distribution on SSZ-13 could significantly improve the performance and stability of the catalyst and provided a new direction for the design of PNA catalysts.
Traditional vanadium-based selective catalytic reduction (SCR) deNO x catalyst can hardly adapt to the gas conditions (much high NO 2 /NO x ratio at lower temperature) of the start-up and low loading periods for a gas turbine . Therefore, a W–Ti-CeO x catalyst with NO x storage and reduction (NSR) function was developed in this work for gas turbine exhaust NO x elimination. The experimental results reveal that W–Ti-CeO x catalyst exhibits high NO 2 adsorption capacity at relatively low temperature while that is quite low for V–W/TiO 2 . The abundant surface Ce 3+ species can be mainly responsible for its high adsorption ability owing to the reaction between NO 2 and Ce 3+ to form nitrate/nitrite species and NO. Meanwhile, the adsorption capacity of W–Ti-CeO x can easily regenerate at medium–high temperature and NH 3 -SCR reaction. Furthermore, W–Ti-CeO x also shows good NH 3 -SCR activity, which can fulfill the deNO x process at high temperature. The addition of W and Ti into ceria can enhance the surface acidity and redox ability, thereby increasing the SCR activity. This work proposes a novel storage-reduction strategy for NO x elimination throughout the operation of gas turbines.
危险品化学品经营许可证（带存储）