Effect of alumina incorporation on the sulfur tolerance of the dual-catalyst aftertreatment system for reduction of nitrogen oxides under lean conditions

Sreshtha Sinha Majumdar; Anne Marie Alexander; Preshit Gawade; Gokhan Celik; Umit S. Ozkan

doi:10.1016/j.cattod.2018.01.027

Effect of alumina incorporation on the sulfur tolerance of the dual-catalyst aftertreatment system for reduction of nitrogen oxides under lean conditions

Sreshtha Sinha Majumdar, Anne Marie Alexander, Preshit Gawade, Gokhan Celik, Umit S. Ozkan

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

Presence of sulfur or sulfur additives in natural gas lead to the formation of sulfur dioxide in the exhaust stream of natural gas-fired lean-burn engines. The sulfur tolerance and hydrothermal stability of the dual-catalyst aftertreatment system comprising a reduction catalyst (palladium supported on sulfated zirconia- Pd/SZ) and an oxidation catalyst (cobalt oxide supported on ceria- CoO_x/CeO₂) for NO_x reduction under lean-burn conditions has been tested under simulated engine exhaust conditions. Alumina-incorporated Pd/SZ (Pd/SZ(Alumina)) reduction catalyst as part of the dual catalyst bed demonstrated superior sulfur tolerance in the presence of 5 ppm SO₂ in the feed. The ratio of the reduction to oxidation catalyst was also seen to affect the hydrothermal stability under wet conditions with SO₂ in the reaction medium. The effect of hydrocarbon and water concentration in the reaction mixture on the sulfur tolerance of the dual-catalyst bed was studied. Increasing the reaction temperature from 450 °C to 500 °C demonstrated very stable NO_x conversion and improved CH₄ conversions when the dual-catalyst bed was kept on-stream for 40 h⁻¹. X-ray photoelectron spectroscopy on samples poisoned with SO₂ ex-situ revealed the deposition of surface sulfates on the Pd/SZ catalyst samples and a combination of sulfates and sulfites on the CoO_x/CeO₂ on treatment with SO₂. The presence of alumina in the Pd/SZ sample protects the support from SO₂ poisoning as the oxidation state of the zirconia support remained largely unchanged on poisoning while in the CoO_x/CeO₂ sample, sulfur poisoning likely affects the cerium redox cycle (Ce³⁺-Ce⁴⁺). ²⁷Al magic angle spinning nuclear magnetic resonance (MAS NMR) revealed redistribution of the octahedral and tetrahedral Al-O coordination on SO₂ poisoning. Due to association with deposited sulfates on the catalyst, shielding effect on the Al nuclei resulted in an increased octahedral Al-O coordination in the poisoned sample.

Original language	English
Pages (from-to)	204-213
Number of pages	10
Journal	Catalysis Today
Volume	320
DOIs	https://doi.org/10.1016/j.cattod.2018.01.027
State	Published - Jan 15 2019
Externally published	Yes

Funding

The financial support provided by the US Department of Energy and Caterpillar Inc . is gratefully acknowledged. The authors thank Dr. Ronald Silver of Caterpillar Inc. for his valuable feedback. The authors would also like to Dr. Elizabeth Hommel and Dr. Philippe Nadaud for assistance with acquiring the XPS and NMR spectra respectively. The financial support provided by the US Department of Energy and Caterpillar Inc. is gratefully acknowledged. The authors thank Dr. Ronald Silver of Caterpillar Inc. for his valuable feedback. The authors would also like to Dr. Elizabeth Hommel and Dr. Philippe Nadaud for assistance with acquiring the XPS and NMR spectra respectively.

Funders	Funder number
US Department of Energy and Caterpillar Inc
US Department of Energy and Caterpillar Inc.
spectra

Keywords

Al MAS NMR
Lean-burn
NO reduction
SO tolerance
XPS

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1016/j.cattod.2018.01.027

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title = "Effect of alumina incorporation on the sulfur tolerance of the dual-catalyst aftertreatment system for reduction of nitrogen oxides under lean conditions",

abstract = "Presence of sulfur or sulfur additives in natural gas lead to the formation of sulfur dioxide in the exhaust stream of natural gas-fired lean-burn engines. The sulfur tolerance and hydrothermal stability of the dual-catalyst aftertreatment system comprising a reduction catalyst (palladium supported on sulfated zirconia- Pd/SZ) and an oxidation catalyst (cobalt oxide supported on ceria- CoOx/CeO2) for NOx reduction under lean-burn conditions has been tested under simulated engine exhaust conditions. Alumina-incorporated Pd/SZ (Pd/SZ(Alumina)) reduction catalyst as part of the dual catalyst bed demonstrated superior sulfur tolerance in the presence of 5 ppm SO2 in the feed. The ratio of the reduction to oxidation catalyst was also seen to affect the hydrothermal stability under wet conditions with SO2 in the reaction medium. The effect of hydrocarbon and water concentration in the reaction mixture on the sulfur tolerance of the dual-catalyst bed was studied. Increasing the reaction temperature from 450 °C to 500 °C demonstrated very stable NOx conversion and improved CH4 conversions when the dual-catalyst bed was kept on-stream for 40 h−1. X-ray photoelectron spectroscopy on samples poisoned with SO2 ex-situ revealed the deposition of surface sulfates on the Pd/SZ catalyst samples and a combination of sulfates and sulfites on the CoOx/CeO2 on treatment with SO2. The presence of alumina in the Pd/SZ sample protects the support from SO2 poisoning as the oxidation state of the zirconia support remained largely unchanged on poisoning while in the CoOx/CeO2 sample, sulfur poisoning likely affects the cerium redox cycle (Ce3+-Ce4+). 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) revealed redistribution of the octahedral and tetrahedral Al-O coordination on SO2 poisoning. Due to association with deposited sulfates on the catalyst, shielding effect on the Al nuclei resulted in an increased octahedral Al-O coordination in the poisoned sample.",

keywords = "Al MAS NMR, Lean-burn, NO reduction, SO tolerance, XPS",

author = "{Sinha Majumdar}, Sreshtha and Alexander, {Anne Marie} and Preshit Gawade and Gokhan Celik and Ozkan, {Umit S.}",

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T1 - Effect of alumina incorporation on the sulfur tolerance of the dual-catalyst aftertreatment system for reduction of nitrogen oxides under lean conditions

AU - Sinha Majumdar, Sreshtha

AU - Alexander, Anne Marie

AU - Gawade, Preshit

AU - Celik, Gokhan

AU - Ozkan, Umit S.

PY - 2019/1/15

Y1 - 2019/1/15

N2 - Presence of sulfur or sulfur additives in natural gas lead to the formation of sulfur dioxide in the exhaust stream of natural gas-fired lean-burn engines. The sulfur tolerance and hydrothermal stability of the dual-catalyst aftertreatment system comprising a reduction catalyst (palladium supported on sulfated zirconia- Pd/SZ) and an oxidation catalyst (cobalt oxide supported on ceria- CoOx/CeO2) for NOx reduction under lean-burn conditions has been tested under simulated engine exhaust conditions. Alumina-incorporated Pd/SZ (Pd/SZ(Alumina)) reduction catalyst as part of the dual catalyst bed demonstrated superior sulfur tolerance in the presence of 5 ppm SO2 in the feed. The ratio of the reduction to oxidation catalyst was also seen to affect the hydrothermal stability under wet conditions with SO2 in the reaction medium. The effect of hydrocarbon and water concentration in the reaction mixture on the sulfur tolerance of the dual-catalyst bed was studied. Increasing the reaction temperature from 450 °C to 500 °C demonstrated very stable NOx conversion and improved CH4 conversions when the dual-catalyst bed was kept on-stream for 40 h−1. X-ray photoelectron spectroscopy on samples poisoned with SO2 ex-situ revealed the deposition of surface sulfates on the Pd/SZ catalyst samples and a combination of sulfates and sulfites on the CoOx/CeO2 on treatment with SO2. The presence of alumina in the Pd/SZ sample protects the support from SO2 poisoning as the oxidation state of the zirconia support remained largely unchanged on poisoning while in the CoOx/CeO2 sample, sulfur poisoning likely affects the cerium redox cycle (Ce3+-Ce4+). 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) revealed redistribution of the octahedral and tetrahedral Al-O coordination on SO2 poisoning. Due to association with deposited sulfates on the catalyst, shielding effect on the Al nuclei resulted in an increased octahedral Al-O coordination in the poisoned sample.

AB - Presence of sulfur or sulfur additives in natural gas lead to the formation of sulfur dioxide in the exhaust stream of natural gas-fired lean-burn engines. The sulfur tolerance and hydrothermal stability of the dual-catalyst aftertreatment system comprising a reduction catalyst (palladium supported on sulfated zirconia- Pd/SZ) and an oxidation catalyst (cobalt oxide supported on ceria- CoOx/CeO2) for NOx reduction under lean-burn conditions has been tested under simulated engine exhaust conditions. Alumina-incorporated Pd/SZ (Pd/SZ(Alumina)) reduction catalyst as part of the dual catalyst bed demonstrated superior sulfur tolerance in the presence of 5 ppm SO2 in the feed. The ratio of the reduction to oxidation catalyst was also seen to affect the hydrothermal stability under wet conditions with SO2 in the reaction medium. The effect of hydrocarbon and water concentration in the reaction mixture on the sulfur tolerance of the dual-catalyst bed was studied. Increasing the reaction temperature from 450 °C to 500 °C demonstrated very stable NOx conversion and improved CH4 conversions when the dual-catalyst bed was kept on-stream for 40 h−1. X-ray photoelectron spectroscopy on samples poisoned with SO2 ex-situ revealed the deposition of surface sulfates on the Pd/SZ catalyst samples and a combination of sulfates and sulfites on the CoOx/CeO2 on treatment with SO2. The presence of alumina in the Pd/SZ sample protects the support from SO2 poisoning as the oxidation state of the zirconia support remained largely unchanged on poisoning while in the CoOx/CeO2 sample, sulfur poisoning likely affects the cerium redox cycle (Ce3+-Ce4+). 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) revealed redistribution of the octahedral and tetrahedral Al-O coordination on SO2 poisoning. Due to association with deposited sulfates on the catalyst, shielding effect on the Al nuclei resulted in an increased octahedral Al-O coordination in the poisoned sample.

KW - Al MAS NMR

KW - Lean-burn

KW - NO reduction

KW - SO tolerance

KW - XPS

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VL - 320

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JO - Catalysis Today

JF - Catalysis Today

ER -

Effect of alumina incorporation on the sulfur tolerance of the dual-catalyst aftertreatment system for reduction of nitrogen oxides under lean conditions

Abstract

Funding

Keywords

UN SDGs

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