Selective catalytic reduction of nitric oxide by hydrocarbons

Amiridis, Michael D.; Zhang, Tiejun; Farrauto, Robert J.

doi:10.1016/0926-3373(96)00031-8

Cited by 294 publications

(137 citation statements)

References 93 publications

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“…A promoting effect was also observed in NO x reduction with propene by the addition of small amounts of palladium to In/TiO 2 -ZrO 2 [18]. Similarly, a small amount of Pd added to Ag-MOR promotes the SCR of NO x when oxygenates are used as reductants [4]. Fig.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

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Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Córdoba

Flytzani‐Stephanopoulos

Correa

2001

Applied Catalysis B: Environmental

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The selective catalytic reduction (SCR) of NO x by dodecane in excess oxygen-containing gas mixtures was studied on Ce and/or Pd-loaded HMOR. Under dry conditions the best fresh bimetallic catalyst, 6.2 wt.% Ce-0.08 wt.% Pd-HMOR, displayed a maximum of about 70% NO x conversion to N 2 at 350 • C and GHSV = 30,000 h −1 , while either Ce-HMOR or Pd-HMOR exhibited low activity for the SCR reaction. The presence of both Ce and Pd in the zeolite was crucial for high deNO x activity. The dodecane concentration is very important for the reaction. The catalyst is not active in the absence of the reducing agent and inhibition of NO x reduction is observed at dodecane concentrations higher than 440-500 ppm. The presence of 40 ppm SO 2 in the gas feed suppresses the reaction. However, the coexistence of 15% H 2 O and 40 ppm SO 2 has no appreciable effect on the catalyst activity. Enhanced activity and a broader temperature window was observed in the NO 2 + dodecane + O 2 reaction in the presence of 15% H 2 O and 100 ppm SO 2 . In this reaction mixture, the catalyst was capable of retaining a stable NO 2 conversion to N 2 for a period of ten days. Characterization by XPS and UV-VIS-diffuse reflectance spectra (UV-VIS-DRS) of selected fresh and aged catalyst samples indicates that Pd exists mainly as Pd 2+ cations in Ce-Pd-HMOR. Cerium is mostly present as CeO 2 on the surface of the zeolite particles. However, part of the cerium in 6Ce-Pd-HMOR, exists as stable Ce 3+ species.

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Section: Catalyst Characterizationmentioning

confidence: 99%

“…Over the last several years, many different lean SCR catalysts have been studied including zeolites and metal oxides [4]. Low durability under hydrothermal conditions, low SO x resistance, or a narrow temperature window are the main drawbacks found for practical application.…”

Section: Introductionmentioning

confidence: 99%

Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Córdoba

Flytzani‐Stephanopoulos

Correa

2001

Applied Catalysis B: Environmental

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“…Moreover, large amounts of water vapor inhibit the catalyst's action, promoting the migration of Al +3 out of the zeolite structure and leading to a loss of the activity of the Cu ions attached to the Al sites. 8 Platinum SCR catalysts are very active at low temperatures, and are thermally stable and resistant to SO 2 . Obuchi and co-workers 9 studied the SCR reaction in the presence of propylene with Pt, Ir, Pd, Rh and Ru metals based on -alumina, obtaining the best results with the metals Pt, Rh and Ru, with NO conversions of over 50%.…”

Section: Introductionmentioning

confidence: 99%

Selective reduction of NOx by propylene over silver catalyst under oxidative conditions

Cónsul

Thiele

Baibich

et al. 2004

J. Braz. Chem. Soc.

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Neste trabalho foram estudados catalisadores Ag/Al 2 O 3 e Ag/Al 2 O 3 /Corderita, preparados por um método de impregnação convencional, na reação de redução de NO utilizando propeno como agente redutor. Os catalisadores foram caracterizados por redução a temperatura programada (RTP), quimissorção de oxigênio e área superficial, pelo método BET. A atividade catalítica foi determinada utilizando uma mistura reacional contendo 100 ppm de NO, 250 ppm de C 3 H 6 e 2% de oxigênio e uma velocidade espacial de 100000 h -1 . Os produtos da reação foram estudados por FTIR. Os resultados dos testes catalíticos mostraram 56% de conversão de NO para o catalisador 2,22%Ag/ Al 2 O 3 a 723 K. Os catalisadores de cordierita apresentaram um comportamento semelhante, mas a temperatura de máxima conversão de NO deslocou-se para temperaturas menores.In this study, a Ag/Al 2 O 3 and Ag/Al 2 O 3 /Cordierite catalyst was prepared by a conventional impregnation method and NOx reduction investigated using propylene as a reducing agent. The catalysts were characterized by Temperature Programmed Reduction (TPR), oxygen chemisorption and surface area, using the standard BET method. The catalytic activities were measured under the same reaction conditions, i.e., 100 ppm NO, 250 ppm C 3 H 6 , 2% of oxygen and 100000 h -1 space velocity. The reaction products were analyzed by FTIR. The results of the catalytic activity obtained for the 2.22%Ag/Al 2 O 3 catalyst showed 56% NO conversion at 723 K. The catalysts based on Cordierite presented an analogous behavior, but the temperature of maximum NO conversion was lower (620 K).Keywords: NOx reduction, silver/alumina catalyst, propylene, Cordierite IntroductionThe generation of NOx effluents from stationary and mobile sources poses an important environmental problem. [1][2][3][4] Gas effluent control in internal combustion engines, whose air/gasoline ratio is stoichiometric, can be achieved by using the so-called "three way catalysts" (TWC) typically containing Pt and Rh as the active metals. On the other hand, lean-burn engines, such as diesel engines and stationary sources for industrial use, operate with excess oxygen to ensure complete combustion. In these cases, TWCs are ineffective for NO elimination, for which reason selective catalytic reduction (SCR) is used. A typical commercial SCR catalyst uses V 2 O 5 -WO 3 -TiO 2 as the metal system and NH 3 as the reducing agent. This catalyst involves problems relating to the transport and storage of NH 3 and to vanadium toxicity. 5 In their studies of several catalysts prepared from zeolites substituted with H + , Na + , K + , Mg 2+ , Ca 2+ , Cr 3+ , Fe 3+ , Co 3+ , Ni 2+ , Cu 2+ , Zn 2+ and Ag, Iwamoto et al. 6,7 found that Cu-ZSM5 provided better NO reduction activity when hydrocarbons were used as reductants. However, this catalyst has a low thermal stability 6 and deactivates in the presence of water vapor and SO 2 . Moreover, large amounts of water vapor inhibit the catalyst's action, promoting the migration of Al +3 out of the zeolite struct...

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“…8,10,11 However, few studies on SCR on Rh supported catalysts have been reported and the mechanism for NO reduction on Rh catalysts is still unclear. 2,7,12 .…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9] Platinum, iridium, palladium, rhodium and ruthenium supported on Al 2 O 3 , TiO 2 , SiO 2 , ZrO 2 , and ZSM-5 have been studied. [3][4][5][6][7][8] More recently, MCM-41 as a support and ion-exchanged MCM-41 have been studied in our laboratory 9 for the SCR reaction.…”

Section: Introductionmentioning

confidence: 99%

Pillared Clays as Superior Catalysts for Selective Catalytic Reduction of Nitric Oxide

Yang¹,

Long²

1999

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In the last annual reports, we reported Cu-exchanged pillared clays as superior selective catalytic reduction (SCR) catalysts. During the past year we explored the possibilities with MCM-41, a new class of molecular sieve. In this report, Rh exchanged Al-MCM-41 is studied for the SCR of NO by C 3 H 6 in the presence of excess oxygen. It shows a high activity in converting NO to N 2 and N 2 O at low temperatures.

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Selective catalytic reduction of nitric oxide by hydrocarbons

Cited by 294 publications

References 93 publications

Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Selective reduction of NOx by propylene over silver catalyst under oxidative conditions

Pillared Clays as Superior Catalysts for Selective Catalytic Reduction of Nitric Oxide

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