Cobalt supported on zirconia and sulfated zirconia II. Reactivity of adsorbed NOx compounds toward methane

Kantcheva, Margarita; Vakkasoglu, Ahmet S.

doi:10.1016/j.jcat.2004.02.006

Cited by 45 publications

(32 citation statements)

References 19 publications

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“…The band at 1660 cm )1 displays low thermal stability allowing its assignment to adsorbed formic acid. The broad absorption at 1550-1520 cm )1 observed in the spectrum taken at 250°C could be attributed either to bidentate carbonates [the m(C=O) mode] or formate species [the (m as (CO 2 ) mode] [17,[22][23][24][25]. The corresponding concomitant bands should fall in the 1390-1320 cm )1 region.…”

Section: ''Blank Ch 4 '' Experimentsmentioning

confidence: 94%

“…Absorption bands located between 1680 and 1620 cm )1 can be assigned either to the m(C=O) stretching vibration of adsorbed carboxylic acid (most probably formic acid [17,[22][23][24]) or bridged carbonate species [25]. The band at 1660 cm )1 displays low thermal stability allowing its assignment to adsorbed formic acid.…”

Section: ''Blank Ch 4 '' Experimentsmentioning

confidence: 99%

“…The mechanistic schemes proposed involve a reaction between the surface nitrates and the hydrocarbons or their activated fragments leading to the formation of organic nitro compounds in a rate-limiting step. The interaction of methane with NO x complexes strongly adsorbed on catalysts based on anion-modified zirconias has been studied recently by using in situ FT-IR spectroscopy [17][18][19]. It has been concluded that the activation of methane over CoO x /SO 4 2) -ZrO 2 catalysts [17] occurs on cobalt sites and the products of the latter process -formate species -are capable of selectively reducing the surface nitro-nitrato species.…”

Section: Introductionmentioning

confidence: 99%

“…The interaction of methane with NO x complexes strongly adsorbed on catalysts based on anion-modified zirconias has been studied recently by using in situ FT-IR spectroscopy [17][18][19]. It has been concluded that the activation of methane over CoO x /SO 4 2) -ZrO 2 catalysts [17] occurs on cobalt sites and the products of the latter process -formate species -are capable of selectively reducing the surface nitro-nitrato species. Tsyntsarski et al [18] observed that the nitrates coordinated to cobalt ions of an analogous catalytic system react with the methane.…”

Section: Introductionmentioning

confidence: 99%

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FT-IR spectroscopic investigation of the surface reaction of CH4 with NO x species adsorbed on Pd/WO3–ZrO2 catalyst

Kantcheva

Çayırtepe

2007

Catal Lett

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The interaction of methane at various temperatures with NO x species formed by room temperature adsorption of NO + O 2 mixture on tungstated zirconia (18.6 wt.% WO 3 ) and palladium(II)-promoted tungstated zirconia (0.1 wt.% Pd) has been investigated using in situ FT-IR spectroscopy. A mechanism for the reduction of NO over the Pd-promoted tungstated zirconia is proposed, which involves a step consisting of thermal decomposition of the nitromethane to adsorbed NO and formates through the intermediacy of cis-methyl nitrite. The HCOO ) formed acts as a reductant of the adsorbed NO producing nitrogen.

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Section: ''Blank Ch 4 '' Experimentsmentioning

confidence: 94%

Section: ''Blank Ch 4 '' Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

FT-IR spectroscopic investigation of the surface reaction of CH4 with NO x species adsorbed on Pd/WO3–ZrO2 catalyst

Kantcheva

Çayırtepe

2007

Catal Lett

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“…On the other hand, as shown in the results of NH 3 -TPD and IR, the presence of Co 2+ increases the number of strong Lewis acid sites of SZ catalysts. These strong Lewis acid sites may play a very important role for the partial oxidation of CH 4 and the SCR of NO [45]. Co 3 O 4 is also very active for the oxidation of NO [33,56].…”

Section: H 2 -Tpr Characterizationmentioning

confidence: 99%

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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Recent Development in Defects Engineered Photocatalysts: An Overview of the Experimental and Theoretical Strategies

Zafar

et al. 2021

Energy & Environ Materials

119

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Photocatalysis is considered as one of the most appealing advanced technology in solution to the environmental problems and non-renewable energy resources depletion with a variety of applications such as synthesis, industry, water, and environmental remediation. [1][2][3][4][5] Although enormous research has been carried out with impressive advancement in photoactive materials, the process of photocatalysis still suffers from low efficiency and poor stability that is far below the requisites for practical applications. The three main key steps that governs photocatalysis includes light absorption, generation of electron-hole pairs, followed by their migration from the bulk to the surface and initiation of interfacial redox reactions upon their arrival at the active sites. [6,7] In order to boost up the photocatalytic efficiency, various approaches have been adopted such as doping, crystal facet exposure, synthesis parameters, reaction environments, hybridization, dimensions, and morphology tuning of photocatalysts. [8][9][10][11] However, the efficiency of these photocatalysts is still limited by their cost, wide band gap, lower stability and poor charge transfer kinetics. [12] In order to address the aforementioned issues, extensive research has been conducted to increase the surface area, such as nanowires, nanosheets, nanotubes, and other hierarchical nanostructures are developed with abundant active sites for redox reactions. [13][14][15][16][17] Similarly, to enhance charge separation, hetrojunctions were explored utilizing different semiconductors with appreciable band alignment. [18][19][20] Alternatively, effective light absorption with undoubtedly decreased recombination and improved photocatalytic performance through defect engineering have been reported. [21,22] Defects in semiconductors greatly alter carrier concentration and interface reaction affecting the overall process efficiency of a photocatalyst. Thus, defects are the most frequently investigated scenario for tuning the properties of photocatalyst. [23,24] However, defects are detrimental to photocatalysis in regard of the recombination centers and lack detailed explanation in terms of carrier concentration, transfer dynamics, band structure, and interface profiles. [25] The emerging trend of defect engineering still brought the opportunity of deliberately manipulating the photocatalyst properties. Although the influence of defects on photocatalytic performance has been previously elaborated in some reviews, their optimization and intrinsic role in photocatalysis is still elusive. [12,[25][26][27][28] Therefore, some novel strategies based on advanced modeling theoretical and experimental knowledge are of great need to elucidate the role of defects in photocatalysis. Subsequently, it has been suggested that different synthesis strategies offer different mechanisms thus altering the band structure, carrier mobility, and so reactivity (Figure 1). It therefore remains a challenging task to account the relationship between defect chemistry and per...

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Cobalt supported on zirconia and sulfated zirconia II. Reactivity of adsorbed NOx compounds toward methane

Cited by 45 publications

References 19 publications

FT-IR spectroscopic investigation of the surface reaction of CH4 with NO x species adsorbed on Pd/WO3–ZrO2 catalyst

FT-IR spectroscopic investigation of the surface reaction of CH4 with NO x species adsorbed on Pd/WO3–ZrO2 catalyst

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

Recent Development in Defects Engineered Photocatalysts: An Overview of the Experimental and Theoretical Strategies

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