Research on new DeNOx catalysts for automotive engines

Matsumoto, Shinichi; Yokota, Kenji; Doi, Haruo; Kimura, M.; Sekizawa, Kazuhiko; Kasahara, Senshi

doi:10.1016/0920-5861(94)80097-9

Cited by 113 publications

(38 citation statements)

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“…Copper-containing complex oxides such as Cu/SiNb 3 O 8 [10] and Cu-ZSM5 [11] show good catalytic activity in the decomposition of NO x , and NO x reduction by CO. The incorporation of copper into MCM-41 has been investigated and the catalytic activity of the resulting material studied.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the Structure of MCM‐41 Samples with a High Copper Content

Kong

Zhu

Yang

et al. 2004

Adv Funct Materials

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A series of MCM‐41s with a high copper content were synthesized at room temperature from sodium metasilicate (Na2SiO3) as the silicon source, tetraamminecopper(II) nitrate [Cu(NH3)4(NO3)2] as the copper source and cetyltrimethylammonium bromide (CTABr) as the template. The resulting material was characterized by using the following characterization techniques: X‐ray diffraction (XRD), N2‐adsorption isotherms, high‐resolution transmission electron microscopy (HRTEM), inductively coupled plasma (ICP), temperature‐programmed reduction (H2‐TPR), X‐ray photoelectron spectroscopy (XPS), Fourier‐transform infrared spectroscopy (FTIR), UV‐vis spectroscopy, electron‐spin resonance (ESR) and 29Si magic‐angle sample spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The characterization techniques demonstrated the following: i) the copper atoms are incorporated into the framework of MCM‐41 and ii) the copper species in the samples are in a distorted octahedral coordination environment, with between four and six oxygen atoms in the first coordination sphere. The maximum copper content determined by ICP was 26 wt.‐% in the ordered mesoporous sample with a surface area of 525 m2 g–1 and an average pore diameter of 3.1 nm. The synthesized materials exhibited a high activity for nitrogen monoxide (NO) reduction by carbon monoxide (CO).

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Section: Introductionmentioning

confidence: 99%

Investigation of the Structure of MCM‐41 Samples with a High Copper Content

Kong

Zhu

Yang

et al. 2004

Adv Funct Materials

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“…All three active sites are bonded to the tetrahedral Al 3+ ions in the zeolite and therefore their sum is limited by the number of the latter. By measuring the acidity of Cuexchanged ZSM-5 using NH 3 , other authors have found that beyond a copper loading of 70 % a further increase in copper leads to the continuing rise in Cu + at the expense of H + [13].…”

Section: Resultsmentioning

confidence: 99%

“…The opinions are divided about the state of Brùnsted sites after copper exchange; some consider that their exchange with copper ions is evident and desirable [13], whereas the others claim that copper loading does not influence the number of acid centers [8].…”

Section: Introductionmentioning

confidence: 99%

Acid Sites in HZSM-5 Upon Copper Exchange by FTIR and DSC Using Ammonia

Bošković¹,

Vulic

Kis

et al. 2001

Chem. Eng. Technol.

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The acidity of the parent HZSM‐5 zeolite and Cu‐HZSM‐5 catalyst has been examined by FTIR and DSC using ammonia desorption. Sites of different strength were found in HZSM‐5, desorbing ammonia at a relative temperature difference of about 100 °C. Upon copper exchange a fraction of Brønsted sites were transformed to Lewis sites, but the acid strength of the remaining Brønsted sites was increased. Aside from Lewis sites originating from copper exchange, there might be some additional sites formed from precipitated copper. This could explain the quantity of adsorbed NH3 on Cu‐ZSM‐5 which is higher than theoretically expected. While changing their nature, acid sites of higher strength keep their location, which is manifested by some diffusion effect towards ammonia.

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“…A period of large efforts to understand the properties of this catalytic system followed, but the material was found to be insufficiently stable for automotive applications [3]. The catalytic activity was lost as a result of Cu-ion migration while the zeolite framework remained less affected [3][4][5][6][7][8][9][10][11]. Hence, ways to increase the bonding strength of the Cu-ions to the ZSM-5 framework are of interest to improve stability of Cu-ZSM-5.…”

Section: Introductionmentioning

confidence: 97%