The role of pore size on the thermal stability of zeolite supported Cu SCR catalysts

Blakeman, Philip G.; Burkholder, Eric; Chen, Hai-Ying; Collier, Jillian; Fedeyko, Joseph M.; Jobson, Hoi; Rajaram, Raj R.

doi:10.1016/j.cattod.2013.10.047

Cited by 126 publications

(109 citation statements)

References 23 publications

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“…It can be expected that such a process depends on temperature, aging time and Cu loading, where higher aging temperatures, longer aging durations and higher Cu loadings promote more damage. Prior literature is fully in line with this structure damage mechanism [39][40][41]53,61] On the other hand, dealumination alone is apparently much less destructive for this zeolite catalyst.…”

Section: Towards Rational Design Of Cu/ssz-13mentioning

confidence: 60%

“…In contrast, hydrothermal degradation is typically irreversible due to permanent structural changes in the zeolite that result in, for example, loss of Brønsted acid sites and changes to the chemical or physical structure of Cu active centers. This explains why hydrothermal aging effects have been so extensively studied [39][40][41][52][53][54]. Prior studies have suggested that Cu/SSZ-13 durability enhancement can be achieved in a number of ways: (1) composition optimization, that is, choosing optimized Si/Al and Cu/Al ratios [31]; (2) zeolite particle size optimization [55]; (3) new synthesis methods development [30,[56][57][58][59]; and (4) introduction of stability enhancement additives.…”

Section: Towards Rational Design Of Cu/ssz-13mentioning

confidence: 99%

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Recent Progress in Atomic-Level Understanding of Cu/SSZ-13 Selective Catalytic Reduction Catalysts

2018

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Cu/SSZ-13 Selective Catalytic Reduction (SCR) catalysts have been extensively studied for the past five-plus years. New and exciting fundamental and applied science has appeared in the literature quite frequently over this time. In this short review, a few topics specifically focused on a molecular-level understanding of this catalyst are summarized: (1) The nature of the active sites and, in particular, their transformations under varying reaction conditions that include dehydration, the presence of the various SCR reactants and hydrothermal aging; (2) Discussions of standard and fast SCR reaction mechanisms. Considerable progress has been made, especially in the last couple of years, on standard SCR mechanisms. In contrast, mechanisms for fast SCR are much less understood. Possible reaction paths are hypothesized for this latter case to stimulate further investigations; (3) Discussions of rational catalyst design based on new knowledge obtained regarding catalyst stability, overall catalytic performance and mechanistic catalytic chemistry.

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Section: Towards Rational Design Of Cu/ssz-13mentioning

confidence: 60%

Section: Towards Rational Design Of Cu/ssz-13mentioning

confidence: 99%

Recent Progress in Atomic-Level Understanding of Cu/SSZ-13 Selective Catalytic Reduction Catalysts

2018

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“…Fickel et al [15] suggested that the small pore openings in a CHA zeolite restrict migration of the dealumination product Al(OH) 3 , thus slowing down the dealumination process of the zeolite support. Using an in situ XRD technique, Blakeman et al [20] demonstrated that the undesirable Cu-Al interactions were minimized in a small-pore Cu-CHA catalyst, concluding that this was mainly due to pore restriction.…”

Section: Introductionmentioning

confidence: 98%

“…It restricts large hydrocarbons from entering the pores of the catalysts where the SCR reactions take place, minimizing the HC inhibition effect on SCR activity. In contrast, the openings in large-or medium-pore zeolite supports are large enough to allow most hydrocarbons to enter their pores, which can severely inhibit the SCR activity of the catalysts [1,14,20].…”

Section: Introductionmentioning

confidence: 99%

A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts

Chen

Wei

Kollár

et al. 2015

Journal of Catalysis

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126

100

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a b s t r a c tA comparative study was carried out on a small-pore Cu-CHA and a large-pore Cu-BEA zeolite catalyst to understand the lower N 2 O formation on small-pore zeolite supported Cu catalysts in the selective catalytic reduction (SCR) of NOx with NH 3 . On both catalysts, the N 2 O yield increases with an increase in the NO 2 /NOx ratios of the feed gas, suggesting N 2 O formation via the decomposition of NH 4 NO 3 . Temperature-programmed desorption experiments reveal that NH 4 NO 3 is more stable on Cu-CHA than on Cu-BEA. In situ FTIR spectra following stepwise (NO 2 + O 2 ) and ( 15 NO + NH 3 + O 2 ) adsorption and reaction, and product distribution analysis using isotope-labeled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH 4 NO 3 . Furthermore, Cu-CHA is shown to be considerably less active than Cu-BEA in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH 4 NO 3 on Cu-CHA, and (2) the lower activity for this catalyst to catalyze NO oxidation and the subsequent formation of surface nitrates, likely contribute to the higher SCR selectivity with less N 2 O formation on this catalyst as compared to Cu-BEA. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH 4 NO 3 on the catalysts.

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“…Moden et al [85] reported that the active Cu species in Cu-FER catalysts with smaller pore size (0.42 × 0.54 nm) showed higher stability than that in Cu-BETA catalysts with relatively larger pore size (0.66 × 0.67 nm). Using the in situ XRD technique, Blakeman et al [86] confirmed that the small pore structure in Cu-CHA catalysts could prevent the degradation of the zeolite framework structure by Cu species as compared to that in Cu-BETA catalysts, and the undesirable Cu/Al 2 O 3 interaction at high temperatures might play an important role in the catalyst deactivation process. Fickel et al [87] also believed that the higher hydrothermal stability of the Cu-CHA catalyst was related to its small pore structure (0.38 × 0.38 nm).…”

Section: Hydrothermal Stability and Hc Poisoning Resistancementioning

confidence: 91%

Emerging Applications of Environmentally Friendly Zeolites in the Selective Catalytic Reduction of Nitrogen Oxides

Xie

Shi

2016

Green Chemistry and Sustainable Technology

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The catalytic removal of nitrogen oxides (NO x ) from diesel exhaust under oxygen-rich conditions remains a major challenge in the field of environmental catalysis, and the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR), especially over zeolite catalysts, is a well-proven technique for the catalytic deNO x process for diesel vehicles. The comprehensive understanding of the structure-activity relationship of zeolite catalysts in the NH 3 -SCR reaction and the elucidation of the detailed reaction mechanism are very important for the practical use of these catalytic materials. In this chapter, using the environmentally friendly Fe-and Cu-based zeolite catalysts (i.e. Fe-ZSM-5, Cu-ZSM-5, Cu-SSZ-13 and Cu-SAPO-34, etc.) as examples, the influence of preparation methods on NH 3 -SCR performance, the role of metal active sites/surface acid sites, the impact of NO 2 and co-existing pollutants, the hydrothermal stability and also the possible SCR reaction pathways over these materials are discussed in detail, which can provide theoretical and empirical guidance for the redesign and activity improvement of these catalysts in their practical applications.

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The role of pore size on the thermal stability of zeolite supported Cu SCR catalysts

Cited by 126 publications

References 23 publications

Recent Progress in Atomic-Level Understanding of Cu/SSZ-13 Selective Catalytic Reduction Catalysts

Recent Progress in Atomic-Level Understanding of Cu/SSZ-13 Selective Catalytic Reduction Catalysts

A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts

Emerging Applications of Environmentally Friendly Zeolites in the Selective Catalytic Reduction of Nitrogen Oxides

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