Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for NH 3 -SCR (II): The impact of copper loading

Tang, Jiaojiao; Xu, Ming; Yu, Tie; Ma, Haile; Shen, Meiqing; Wang, Jun

doi:10.1016/j.ces.2017.04.053

Cited by 42 publications

(16 citation statements)

References 27 publications

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“…The decrease of Cu 2+ contents in Cu-SAPO-17-8.0%-0.11 (Table 1) results in its lower activity in the low-temperature region. Compared with Cu-SAPO-17-8.0%-0.22, the activity of Cu-SAPO-17-8.0%-0.43 decreases in the high-temperature region, which might be attributed to the decrease of its crystallinity framework (Table S6) and a higher Cu content [40]. As mentioned earlier, the HT and LT hydrothermal stabilities of NH3-SCR catalysts are important to practical applications.…”

Section: Catalytic Performance In Nh3-scr Reactionmentioning

confidence: 84%

Cu-SAPO-17: A novel catalyst for selective catalytic reduction of NO

Liu

Cao

Yan

et al. 2020

Chinese Journal of Catalysis

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Section: Catalytic Performance In Nh3-scr Reactionmentioning

confidence: 84%

Cu-SAPO-17: A novel catalyst for selective catalytic reduction of NO

Liu

Cao

Yan

et al. 2020

Chinese Journal of Catalysis

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“…The improved activities after HT hydrothermal aging might be attributed to the redistribution of active species, which will be discussed in the following paragraph. [ 18,19 ] Although the fresh activity of Cu‐SAPO‐42‐BAEA‐6.6% is remarkable, it declines after HT hydrothermal aging, which might be attributed to the degradation of framework crystallinity (Figure S14, Supporting Information). Considering both fresh activities and the ones after HT hydrothermal aging comprehensively, it is notable that Cu‐SAPO‐42‐BAEA‐4.7% and Cu‐SAPO‐42‐BAEA‐6.0% display better activities than the others.…”

Section: Resultsmentioning

confidence: 99%

Rational Design of a Novel Catalyst Cu‐SAPO‐42 for NH₃‐SCR Reaction

Yan

Cao

et al. 2020

Small

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vehicles have become stricter. At present, selective catalytic reduction of NO x with ammonia (NH 3-SCR) has been regarded as the most efficient technology to facilitate the NO x reduction in oxygen-rich exhaust released from diesel engines. [1-4] Metal-exchanged conventional aluminosilicate zeolites or silicoaluminophosphates (SAPO) molecular sieves (MSs) have been extensively investigated for catalyzing this reaction. Zeolites or SAPO MSs are a class of crystalline microporous materials with well-defined cavities or channels of molecular size. TO 4 tetrahedra (T = Al, Si, P, etc.) are considered as basic building units (BBUs). Until now, distinct 252 threedimensional (3D) zeolitic frameworks constructed by BBUs have been approved by IZA-structure committee. [5] They can be categorized into small pore (delimited by 8 T), medium pore (10 T), large pore (12 T), and extra-large pore (>12 T) MSs. Thereinto, small pore MSs, especially aluminosilicate SSZ-13 and SAPO-34 with the identical CHA framework, have been regarded as the efficient catalysts for the NH 3-SCR reaction due to their high NO x conversion and N 2 selectivity. [3] Although Cu-SSZ-13 catalyst has been commercialized, its thermal durability after the high-temperature (HT) hydrothermal aging, arising from the regeneration process of diesel particulate filter (DPF), can be further improved. Moreover, Cu-SAPO-34 catalyst has some disputes on the low-temperature (LT) hydrothermal stability. Therefore, it stimulates the interest of researchers to explore other novel zeolite frameworks with small pore openings. Recently, Hong et al. have reported a Cu exchanged LTA-type high-silica (3D 8 × 8 × 8-ring channel system) zeolite which has the better activity and durability than Cu-SSZ-13 after HT hydrothermal aging. [6,7] However, the expensive organic structure-directing agents (OSDAs) and the presence of the toxic fluoride used in its recipe might inhibit its further utilization as an NH 3-SCR catalyst. It is of interest to note that SAPO-42 with the LTA topology might be a potential catalyst for the NH 3-SCR reaction. The initial synthesis of SAPO-42 templated by TMA + and Na + was reported in 1984. [8,9] Strictly speaking, it is not an exact SAPO since only a few portions of phosphor are incorporated into the framework. After that, several works reported the synthesis of SAPO-42 by using complex OSDAs in the fluoride system or the ionothermal synthesis. [10-13] For example, Corma's Cu-exchanged LTA-type aluminosilicate catalyst has been considered as an efficient catalyst for the selective catalytic reduction of NO x with ammonia (NH 3-SCR). However, expensive organic structure-directing agents (OSDAs) and the corrosive fluoride medium are inevitably used to synthesize LTA-type molecular sieve (high-silica LTA-type aluminosilicate and its analogue LTAtype silicoaluminophosphate SAPO-42). Herein, a series of cheap and commercialized OSDAs, which are successfully applied for the targeted synthesis of SAPO-42 in the fluoride-free system, are identified by a nove...

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“…It can be concluded that the decrease of BET surface area was due to the declined structure integrity of Cu/SSZ-13. Notably, the diffraction peak centered at 21.63 • assigned to SiO 2 or NaSiO 3 crystalline appeared on Na-Cu-1.0 and Na-Cu-1.5 [11,18], which also suggests that the CHA structure was no longer intact. The intensity of this new peak became more intense with an increased Na amount.…”

Section: Samples' Namementioning

confidence: 99%

The Role of Impregnated Sodium Ions in Cu/SSZ-13 NH3-SCR Catalysts

Wang

et al. 2018

Catalysts

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To reveal the role of impregnated sodium (Na) ions in Cu/SSZ-13 catalysts, Cu/SSZ-13 catalysts with four Na-loading contents were prepared using an incipient wetness impregnation method and hydrothermally treated at 600 • C for 16 h. The physicochemical property and selective catalytic reduction (SCR) activity of these catalysts were studied to probe the deactivation mechanism. The impregnated Na exists as Na + on catalysts and results in the loss of both Brönsted acid sites and Cu 2+ ions. Moreover, the high loading of Na ions destroy the framework structure of Cu/SSZ-13 and forms new phases (SiO 2 /NaSiO 3 and amorphous species) when Na loading was higher than 1.0 mmol/g. The decreased Cu 2+ ions finally transformed into Cu x O, CuO, and CuAlO x species. The inferior SCR activity of Na impregnated catalysts was mainly due to the reduced contents of Cu 2+ ions at kinetic temperature region. The reduction in the amount of acid sites and Cu 2+ ions, as well as copper oxide species (Cu x O and CuO) formation, led to low SCR performance at high temperature. Our study also revealed that the existing problem of the Na ions' effect should be well-considered, especially at high hydrothermal aging when diesel particulate filter (DPF) is applied in upstream of the SCR applications.Catalysts 2018, 8, 593 2 of 15 (>0.5%) mainly due to the decreased amount of isolated Cu 2+ formed CuO x clusters. Wang et al. [10] further found that alkali decreased the number of Brönsted acid sites and NH 3 coverage, and would decrease the SCR reaction rate. In our previous study [11], the different contents of Na impact on Cu/SAPO-34 were also studied. Except for the decrease of active sites and acidity, the results also showed the framework of Cu/SAPO-34 damaged and CuAlO x species formed at a high content of sodium (>0.8%), and all these factors hindered the SCR activity.In recent years, some studies have also considered the Na ions' effect on Cu/SSZ-13 catalysts, but most of them focused on co-cation Na ions. Gao et al. [12] investigated the effects of co-cation Na on Cu/SSZ-13 catalyst. They found ≈1.78% Na promoted SCR performance at low temperatures and helped to improve the hydrothermal stability of Cu/SSZ-13 because Na ions modified the redox of active sites and protected the framework of CHA structure. Zhao et al. [13] found a high amount of co-cation Na ions decreased the hydrothermal stability of Al-rich Cu/SSZ-13 at 750 • C for 5 h because the excess amount of Na ions weakened the interaction between Cu ions and the zeolitic framework and formed Cu x O species. Xie et al. [14] found one-pot-synthesized Cu/SSZ-13 with higher co-cation Na contents showed poorer hydrothermal stability at 750 • C for 16 h, which was attributed to Cu species with poor stability and CHA structure deterioration. Even though some achievements have been made on co-cation Na, the conclusion could not be applied in real-world applications because co-cation Na ions have already existed before Cu exchange and could not represent the deposition of Na in the ...

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Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for NH 3 -SCR (II): The impact of copper loading

Cited by 42 publications

References 27 publications

Cu-SAPO-17: A novel catalyst for selective catalytic reduction of NO

Cu-SAPO-17: A novel catalyst for selective catalytic reduction of NO

Rational Design of a Novel Catalyst Cu‐SAPO‐42 for NH₃‐SCR Reaction

The Role of Impregnated Sodium Ions in Cu/SSZ-13 NH3-SCR Catalysts

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Catalytic deactivation mechanism research over Cu/SAPO-34 catalysts for NH 3 -SCR (II): The impact of copper loading

Cited by 42 publications

References 27 publications

Cu-SAPO-17: A novel catalyst for selective catalytic reduction of NO

Cu-SAPO-17: A novel catalyst for selective catalytic reduction of NO

Rational Design of a Novel Catalyst Cu‐SAPO‐42 for NH3‐SCR Reaction

The Role of Impregnated Sodium Ions in Cu/SSZ-13 NH3-SCR Catalysts

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Rational Design of a Novel Catalyst Cu‐SAPO‐42 for NH₃‐SCR Reaction