The influence of silicon on the catalytic properties of Cu/SAPO-34 for NOx reduction by ammonia-SCR

Wang, Jun; Yu, Tie; Wang, Xinquan; Qi, Gongshin; Xue, Jinbo; Shen, Meiqing; Wei, Li

doi:10.1016/j.apcatb.2012.08.016

Cited by 241 publications

(122 citation statements)

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“…The asymmetric shape of the temperature-programmed desorption (TPD) profile indicates that there may be another, lower peak centred at around 250 °C. Such a peak has indeed been observed when adsorbing at temperatures lower than the 150 °C used here [20,33,34]. It has been assigned to desorption from either weak Brønsted sites or weak Lewis sites.…”

Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 84%

“…It has been assigned to desorption from either weak Brønsted sites or weak Lewis sites. The trend of total desorbed NH3 in function of copper loading is increasing overall, but should be interpreted qualitatively, due to the fact that the catalysts stem from different parent batches, which may impact on the structure and the Si content of the SAPO-34 (see Table S1), and thus on the amounts adsorbed [33]. Furthermore, the interpretation of ammonia storage trends is made difficult by the fact that the number of Brønsted acid sites in zeolites decreases with the incorporation of copper, as Lewis acid sites are formed instead [20,37].…”

Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 99%

“…Given that the Si content of this sample is much larger, at 1.75 mmol Si/g cat , it is likely that H/SAPO-34 contains silicon islands [33,35,36]. The high-temperature desorption peak centred on average at about 340 • C can be attributed to strongly-bound NH 3 molecules adsorbed on both strong Brønsted sites and new Lewis acid sites generated by the incorporation of copper [33,34]. The asymmetric shape of the temperature-programmed desorption (TPD) profile indicates that there may be another, lower peak centred at around 250 • C. Such a peak has indeed been observed when adsorbing at temperatures lower than the 150 • C used here [20,33,34].…”

Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 99%

“…The desorption profiles are shown in Figure 3. Ammonia molecules physisorbed onto weak Brønsted and Lewis acid sites and desorbed during the purge at 150 °C (not shown here) [20,33,34]. Integration of the signal for H/SAPO-34, yields a storage capacity of 0.59 mmol NH3/gcat.…”

Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 99%

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Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

et al. 2017

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Abstract:We developed a procedure for aqueous ion exchange to obtain different Cu loadings of Cu/SAPO-34 (between 0 and 2.6 wt %). The catalysts were washcoated on monoliths and characterised with respect to their activity and selectivity under standard selective catalytic reduction (SCR), fast SCR, NH 3 oxidation and NO oxidation reactions. They were further characterised using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), H 2 -temperature programmed reduction (H 2 -TPR), ultraviolet (UV)-vis spectroscopy and NH 3 adsorption. As expected, activity of all reactions increased with copper loading, due to increased number of active sites. However, the N 2 O formation during standard and fast SCR yielded interesting mechanistic information. We observed that N 2 O formation at low temperature increased with copper loading for the standard SCR reaction, while it decreased for fast SCR. The low-temperature N 2 O formation during fast SCR thus occurs predominantly over Brønsted sites. Species responsible for N 2 O formation during standard SCR, on the other hand, are formed on the copper sites. We further found that the fast SCR reaction occurs to a significant extent even over the H/SAPO-34 form. The Brønsted sites in SAPO-34 are thus active for the fast SCR reaction.

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Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 84%

Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 99%

Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 99%

Section: Characterisation By Nh3 Adsorptionmentioning

confidence: 99%

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Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

et al. 2017

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“…According to literature, [12] the peaks located at lower temperatures (250-270ºC) represent the reduction of isolated Cu 2+ , [13] the peaks centered at 350-370 represent the reduction of bulk CuO to Cu 0 , [14] and finally, the higher temperature peaks can be assigned to the reduction of Cu + to Cu 0 .…”

Section: 34-catalytic Active Sites Characterizationmentioning

confidence: 99%

Synthesis, characterization and reactivity of high hydrothermally stable Cu-SAPO-34 materials prepared by “one-pot” processes

Martínez-Franco

Moliner

Concepción

et al. 2014

Journal of Catalysis

105

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ElsevierMartinez Franco, R.; Moliner Marin, M.; Concepción Heydorn, P.; Thogersen, JR.; Corma Canós, A. (2014). Synthesis, characterization and reactivity of high hydrothermally stable Cu-SAPO-34 materials prepared by one-pot processes. Journal of AbstractA Cu-SAPO-34 material with very high activity for selective catalytic reduction (SCR) of NOx and hydrothermal stability has been synthesized following a sequential rationalized design. By using specific combinations of organic structure directing agents (OSDAs) and gel compositions in a "one-pot" method, it was possible to control Cu occupancy, framework Si distribution, and to maximize the yield of solids. The amount of Cu 2+ is maximized and remains stable even after steaming at 750ºC for 13 hours. Highlights-A rationalized methodology has allowed the one-pot synthesis of Cu-SAPO-34zeotypes.-An optimized Cu-SAPO-34 shows high activity and hydrothermal stability for SCR-NOx.-Cu 2+ species remain in the optimized Cu-SAPO-34 even after severe ageing. KeywordsOne-pot synthesis, silicoaluminophosphate, SAPO-34, selective catalytic reduction (SCR), nitrogen oxides (NOx) 4 1.-IntroductionThe design of an attractive heterogeneous catalyst for a relevant chemical process,involves the synthesis of materials with high activity, selectivity, and stability.Moreover, if the catalyst is mean to be used industrially, the synthesis procedure should be economically competitive. In many cases, the combination of innovative work together with accumulated knowledge allows to achieve new synthesis that not only improves the physico-chemical properties of the catalysts but can meet the economical targets.In the last years, the synthesis of small pore zeolites with large cavities containing extra-framework cationic metals, such as Cu 2+, has received much attention thanks to their excellent activity and stability for the selective catalytic reduction (SCR) of NOx.[1]Traditionally, copper species are introduced in small pore zeolites by post-synthesis cationic exchange-impregnation methods.[ 1 ,2] However, the distribution of Cu within the zeolitic crystals following these procedures can be limited by diffusion of the Cu due to the presence of small pores (openings  3.5 Å), being the metal preferentially located close to the external surface. [3] To avoid this, different "one-pot" synthesis methods introducing organo-copper complexes in the synthesis gel have been recently described.[4] These direct procedures permit better metal dispersion within zeolitic crystals, and also allow reducing the overall synthesis steps required to achieve the final Cu-zeolite catalyst.[5] Diverse Cu-complexes and synthesis conditions have been reported in the last years to direct the "one-pot" preparation of different small pore chabazite (CHA) polymorphs, as Cu-SSZ-13, [4a,6] and Cu-SAPO-34. [4b,7] In a previous report, we have described the direct preparation of Cu-SAPO-34 using a combination of diethylamine (DEA) and Cu-tetraethylenepentamine (Cu-TEPA) as organic structure directing agents (...

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NH₃ Oxidation Mechanism over Cu/SAPO‐34 Catalysts Prepared by Different Methods

Wang

Huang

et al. 2014

ChemCatChem

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NH3 oxidation mechanism and its inhibition effect on the selective catalytic reduction of NOx by NH3 (NH3–SCR) reaction over two series of Cu/SAPO‐34 catalysts were studied. It was found that the different NO conversions were induced by the diverse NH3 oxidation degree. X‐ray diffraction, scanning electron microscopy, H2 temperature‐programmed reduction (H2–TPR), and CO diffuse reflectance infrared Fourier transform spectroscopy (CO–DRIFTS) analyses were conducted to estimate the Cu species distribution. The TPR results showed that the CuO species was dominant in impregnated Cu/SAPO‐34 samples, and the ion‐exchanged Cu/SAPO‐34 samples contained more isolated Cu2+ species. Furthermore, H2–TPR, electron paramagnetic resonance, and CO–DRIFTS analyses were utilized to quantify the CuO, Cu2+, and Cu+ species. The results together with the kinetic results revealed the CuO is the active site for NH3 oxidation, and the NH3 oxidation over Cu/SAPO‐34 sample consists two steps: (a) NO production; (b) further NO consumption by adsorbed NH3 species on Cu2+ sites. Finally, the inhibition of NH3 oxidation on NH3–SCR activity was explained and the NO conversion at high temperature was related to the Cu2+/CuO ratio in Cu/SAPO‐34 sample.

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The influence of silicon on the catalytic properties of Cu/SAPO-34 for NOx reduction by ammonia-SCR

Cited by 241 publications

References 50 publications

Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

Synthesis, characterization and reactivity of high hydrothermally stable Cu-SAPO-34 materials prepared by “one-pot” processes

NH₃ Oxidation Mechanism over Cu/SAPO‐34 Catalysts Prepared by Different Methods

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The influence of silicon on the catalytic properties of Cu/SAPO-34 for NOx reduction by ammonia-SCR

Cited by 241 publications

References 50 publications

Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

Impact of Copper Loading on NH3-Selective Catalytic Reduction, Oxidation Reactions and N2O Formation over Cu/SAPO-34

Synthesis, characterization and reactivity of high hydrothermally stable Cu-SAPO-34 materials prepared by “one-pot” processes

NH3 Oxidation Mechanism over Cu/SAPO‐34 Catalysts Prepared by Different Methods

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NH₃ Oxidation Mechanism over Cu/SAPO‐34 Catalysts Prepared by Different Methods