Combined TPD and FTIR studies of Co/ZrO<sub>2</sub> catalysts: determination of the cobalt dispersion

Hadjiivanov, Konstantin; Panayotov, D.; Avreyska, V.; Tsyntsarski, Boyko; Klissurski, D.; Marinova, Ts.

doi:10.1002/sia.1259

Cited by 5 publications

(7 citation statements)

References 12 publications

(14 reference statements)

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“…These bands are due to nitrosyl complexes on cobalt cations [64][65][66][67][68]. In agreement with literature data [64][65][66][67][68], the bands at 1875 and 1795 cm -1 can be assigned to Co(II)-(NO)2 type dinitrosyls. The weak band at 1620 cm -1 present in the FT-IR spectrum for Co(PS)SiBEA (Fig.…”

Section: Ft-ir Of Nh3 or No Adsorbed On Co(ps)sibea Co(imp)albea Andsupporting

confidence: 90%

“…For Co(IMP)AlBEA and Co(IE)AlBEA, additional IR band at 1930 cm -1 is observed ( Fig. 6), which can be attributed to linear Co n+ -NO mononitrosyls [67]. In this case the possible oxidation state of cobalt ions is 3+ since, as a rule, Co(II)-NO compounds absorb at lower frequencies than Co(III)-NO ( Fig.…”

Section: Ft-ir Of Nh3 or No Adsorbed On Co(ps)sibea Co(imp)albea Andmentioning

confidence: 92%

“…6), indicates the presence of small amount of bridged NO (NO2) species [69]. FT-IR spectra recorded for the Co(IMP)AlBEA and Co(IE)AlBEA samples, exhibit bands at 1895, 1815 and 1620 cm -1 , which can be assigned to Co(II)-(NO)2 type dinitrosyls (1895, 1815 cm -1 ) and bridged NO species (1620 cm -1 ) [66][67][68][69], respectively. For Co(IMP)AlBEA and Co(IE)AlBEA, additional IR band at 1930 cm -1 is observed ( Fig.…”

Section: Ft-ir Of Nh3 or No Adsorbed On Co(ps)sibea Co(imp)albea Andmentioning

confidence: 99%

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Experimental evidence of NO SCR mechanism in the presence of the BEA zeolite with framework and extra-framework cobalt species

Boroń

Chmielarz

Gil

et al. 2016

Applied Catalysis B: Environmental

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Highlights  Co introduced in Beta supports effectively activates NH3 for reaction with NO. The highest reactivity of ammonia in SCR of NO found for Co(IE)BEA catalyst. During SCR of NO ammonia and NO compete for the same adsorption sites. SCR of NO process involves the reaction of chemisorbed NH3 with NO from gas phase. AbstractTemperature-programmed desorption (TPD), temperature-programmed surface reaction (TPSR) and stop flow-TPD techniques as well as FT-IR spectroscopy of pre-adsorbed NH3 and NO are applied to characterize active sites present in Co-containing BEA zeolites. Cobalt is introduced into BEA zeolite by different methods: (i) two-step postsynthesis -PS, (ii) conventional wet impregnation -Imp and (iii) ion exchange -IE. The obtained catalysts are 3 labelled as Co(PS)SiBEA (postsynthesis), Co(IMP)AlBEA (wet impregnation) and Co(IE)AlBEA (ion exchange). All the obtained catalysts are found to be active in the process of selective catalytic reduction (SCR) of NO with ammonia. The catalytic activity depends on the method used for cobalt introduction and thus on cobalt centres speciation. The reactivity of NH3 and NO adsorbed on Co(IMP)AlBEA and Co(IE)AlBEA is higher than that measured for the Co(PS)SiBEA catalysts. The temperature-programmed studies and FT-IR with NO and/or NH3 adsorption for the Co-containing samples show that during SCR reaction NO and NH3 molecules compete for the same adsorption sites. The main reaction pathways of the DeNOx process performed in the presence of Co(IMP)AlBEA and Co(IE)AlBEA involves the reaction between chemisorbed ammonia and NO from gas phase, according to the Eley-Riedel mechanism.experimental studies focused on mechanistic issues and reaction pathways, the SCR mechanism on the Co-BEA zeolite catalysts is still the subject of the debate.In this study, the Co-containing BEA zeolite catalysts were prepared by different methods: two-step postsynthesis, wet impregnation and conventional ion exchange. The obtained samples exhibited high activity and selectivity in SCR NO with NH3. Thus, the studies of the reaction mechanism for this series of the catalysts were undertaken to determine the role of cobalt species type on catalytic performance of the catalysts. Experimental Catalysts preparationThree series of Co-containing zeolites were prepared by two-step postsynthesis (PS), conventional wet impregnation (IMP) and ion exchange (IE) procedures.Co(PS)SiBEA zeolite (with Co loading of 1.0 wt %) was prepared by two-step postsynthesis procedure reported earlier [6][7][8][9]. In the first step, 2 g of HAlBEA zeolite, obtained by calcination of tetraethyl-ammonium BEA (TEABEA) zeolite at 823 K for 15 h provided by RIPP (China) was treated with 13 mol L -1 HNO3 solution under stirring (353 K, 4 h) to remove aluminium from the zeolite structure. In the second step, 2 g of resulting SiBEA obtained after filtration were dispersed in aqueous solutions (pH = 2.8) containing 1.7 • 10 -3 mol L -1 of Co(NO3)2 · 6H2O and stirred at room temperature for 24 h. Then, the obtained su...

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Section: Ft-ir Of Nh3 or No Adsorbed On Co(ps)sibea Co(imp)albea Andsupporting

confidence: 90%

Section: Ft-ir Of Nh3 or No Adsorbed On Co(ps)sibea Co(imp)albea Andmentioning

confidence: 92%

Section: Ft-ir Of Nh3 or No Adsorbed On Co(ps)sibea Co(imp)albea Andmentioning

confidence: 99%

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Experimental evidence of NO SCR mechanism in the presence of the BEA zeolite with framework and extra-framework cobalt species

Boroń

Chmielarz

Gil

et al. 2016

Applied Catalysis B: Environmental

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“…12 that the NO-TPD profile of a 4 wt% Co/SZ catalyst contains two peaks. According to the literature [60], the first peak at low temperature can be attributed to the NO desorption from Zr 4+ -NO and Co 2+ (NO) 2 ; the second peak at high temperature can be assigned to the NO desorption from the Co n+ -NO (n = 2, 3) species. Furthermore, it is found that the NO-TPD profile of our 4 wt% Co/SZ seems very similar to that obtained by Hadjiivanov et al [60] on their highly dispersed Co/SZ sample (relative Co dispersion is 1.00), which reflects the high Co dispersion in our 4 wt% Co/SZ catalyst in another way.…”

Section: No-tpd Characterizationmentioning

confidence: 94%

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

2004

Journal of Catalysis

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In this work, the structural and surface properties of Co-loaded sulfated zirconia (SZ) catalysts were studied by X-ray diffraction (XRD), N 2 adsorption, NH 3 -TPD, FT-IR spectroscopy, H 2 -TPR, UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and NO-TPD. NH 3 -TPD and FT-IR spectra results of the catalysts showed that the sulfation process of the support resulted in the generation of strong Brønsted and Lewis acid sites, which is essential for the SCR of NO with methane. On the other hand, the N 2 adsorption, H 2 -TPR, UV/vis DRS, and XPS of the catalysts demonstrated that the presence of the SO 4 2− species promoted the dispersion of the Co species and prevented the formation of Co 3 O 4 . Such an increased dispersion of Co species suppressed the combustion reaction of CH 4 by O 2 and increased the selectivity toward NO reduction. The NO-TPD proved that the loading of Co increased the adsorption of NO over SZ catalysts, which is another reason for the promoting effect of Co.  2004 Elsevier Inc. All rights reserved.

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Section: No-tpd Characterizationmentioning

confidence: 98%

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

Wang

Zheng

et al. 2004

Journal of Catalysis

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Combined TPD and FTIR studies of Co/ZrO₂ catalysts: determination of the cobalt dispersion

Cited by 5 publications

References 12 publications

Experimental evidence of NO SCR mechanism in the presence of the BEA zeolite with framework and extra-framework cobalt species

Experimental evidence of NO SCR mechanism in the presence of the BEA zeolite with framework and extra-framework cobalt species

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

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Combined TPD and FTIR studies of Co/ZrO2 catalysts: determination of the cobalt dispersion

Cited by 5 publications

References 12 publications

Experimental evidence of NO SCR mechanism in the presence of the BEA zeolite with framework and extra-framework cobalt species

Experimental evidence of NO SCR mechanism in the presence of the BEA zeolite with framework and extra-framework cobalt species

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

Probing into the catalytic nature of Co/sulfated zirconia for selective reduction of NO with methane

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Combined TPD and FTIR studies of Co/ZrO₂ catalysts: determination of the cobalt dispersion