An in-situ infrared and XAS study on NO adsorption on Pd/zeolite under complex gas feed

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1 An in-situ infrared and XAS study on NO adsorption on Pd/zeolite under complex gas feed Donna Liu, Loredana Mantorosie, H. Islam, V. Novak, M. Sarwar, H.Y. Chen, J. E. Collier and D. Thompsett

2 Outline Challenges in controlling NOx emission during cold start period Palladium zeolite as passive NOx adsorber Effect of H 2 O on NOx adsorption/release Effect of CO on NOx adsorption/release Effect of SO 2 on NOx adsorption/release Conclusions 2

exceed the limit during the cold start period; Current NOx control technologies, NSR or Urea-SCR function at

3 Challenges in controlling NOx emission during cold start period Reduction of NOx emissions from lean burn diesel engines is essential to meet current and future legislation standards; e.g. SULEV30, Engine-out HC/NOx emissions exceed the limit during the cold start period; Current NOx control technologies, NSR or Urea-SCR function at temperature > ~ 200 C; HC + NOx SULEV30 Therefore, NOx emission control during the cold start period is becoming a significant challenge 3

4 Zeolite supported Pd catalysts exhibit high NO storage capacity & trapping efficiency; Zeolite FW shows a strong impact on storage window Adsorption at 100 C 200ppm NO, 200ppm CO, 500ppm C 10 H 22 (C 1 ), 5%H 2 O, 10%O 2, 5% CO 2 SV 30K/hr 1. H.-Y. Chen et al.; Catal. Lett.; June2016; DOI /s R.Rajaram et al.; US Patent 2015/

5 NO storage is due to NO direct adsorption on isolated Pd 2+ sites NO + NO Pd 2+ NO 3 + NO H.-Y. Chen et al.; Catal. Lett.; June2016; DOI /s

6 Individual gas, such as H 2 O or CO, show influence on NO adsorption on Pd.Z With or without CO, water inhibits NO adsorption at 100 C. With absence of water, CO has no effect on NO adsorption. When water is present, CO improves NO storage. --- NO+O NO+O 2 +H 2 O --- NO+CO+O NO+CO+O 2 +H 2 O (full lines NO; dashed lines NO 2 ) H 2 O CO Test conditions: 1%Pd/CHA Adsorption at 100 C, 100ppm NO, 200ppm CO, 5%H 2 O, 10%O 2. 6

Individual gas, such as H 2 O or CO, show influence on NO adsorption on Pd.Z With or without CO, water inhibits NO adsorption at 100 C. With absence of water, CO has no effect on NO adsorption.

7 Individual gas, such as H 2 O or CO, show influence on NO adsorption on Pd.Z With or without CO, water inhibits NO adsorption at 100 C. With absence of water, CO has no effect on NO adsorption. When water is present, CO improves NO storage. --- NO+O NO+O 2 +H 2 O --- NO+CO+O NO+CO+O 2 +H 2 O (full lines NO; dashed lines NO 2 ) H 2 O CO Test conditions: 1%Pd/CHA Adsorption at 100 C, 100ppm NO, 200ppm CO, 5%H 2 O, 10%O 2. 7

Water inhibits NO adsorption at low temperatures (< = 100C) but enhances NO adsorption as temperature increases above 100C NO+O 2 NO+H 2 O+O 2 --- 80 C --- 100 C --- 120 C --- 150 C --- 80

8 Water inhibits NO adsorption at low temperatures (< = 100C) but enhances NO adsorption as temperature increases above 100C NO+O 2 NO+H 2 O+O C C C C C C C C In the absence of water, less NO stored at higher temperatures. H 2 O inhibits NO storage at low temperatures. As temperature is increased, more NO is stored 8

Water severely inhibits NO adsorption on Brönsted

adsorption on isolated Pd 2+ sites NO, NO +, NO 3-,

suppressing NO + adsorption on Brönsted acid sites as

Pd 0 Pd 2+ In-situ XAS study suggests electronic

9 Water severely inhibits NO adsorption on Brönsted acid sites and surface nitrates, less affects NO adsorption on isolated Pd 2+ sites NO, NO +, NO 3-, NO 2- are present on Pd/CHA; H 2 O is significantly suppressing NO + adsorption on Brönsted acid sites as well as nitrates/nitrites; ---NO+O 2 ---NO+O 2 +H 2 O Pd 0 Pd 2+ In-situ XAS study suggests electronic enrichment on Pd and increase in the number of coordinated species. 9

Water increases the strength of NO adsorption by

10 Water increases the strength of NO adsorption by electronic enrichment on Pd 2+ ion at temperature above 100C At low T, water inhibits some NO adsorption sites; When temperature goes up, water increases the strength of NO adsorption by electronic enrichment on Pd 2+ ions; Presence of H 2 O enhances NO binding energy 10

11 Presence of water delays NO desorption due to stronger binding energy With absence of water, NO x desorbs as soon as the temperature increases; Presence of water delays NO desorption. --- NO+O NO+O 2 +H 2 O --- NO+CO+O NO+CO+O 2 +H 2 O H 2 O Test conditions: 1%Pd/CHA Adsorption at 100 C, 100ppm NO, 200ppm CO, 5%H 2 O, 10%O 2, then ramp up 11

12 Individual gas, such as H 2 O or CO, show influence on NO adsorption on Pd.Z With or without CO, water inhibits NO adsorption at 100 C. With absence of water, CO has no effect on NO adsorption. When water is present, CO improves NO storage. --- NO+O NO+O 2 +H 2 O --- NO+CO+O NO+CO+O 2 +H 2 O (full lines NO; dashed lines NO 2 ) H 2 O CO Test conditions: 1%Pd/CHA Adsorption at 100 C, 100ppm NO, 200ppm CO, 5%H 2 O, 10%O 2. 12

13 NOx (ppm) Increase CO concentration improves NO adsorption ppm NO + 200ppm CO 100ppm NO + 500ppm CO 100ppm NO + 750ppm CO 100ppm NO ppm CO Time (s) Test conditions: 1%Pd/CHA Adsorption at 100 C, 100ppm NO, x ppm CO, 130 ppm C 3 H 6, 5%H 2 O, 10%O 2, 13

14 NOx & CO (ppm) Higher CO concentrations cause earlier NO release ppm NO + 200ppm CO 100ppm NO + 500ppm CO 100ppm NO + 750ppm CO 100ppm NO ppm CO Temp (C) Test conditions: 1%Pd/CHA Adsorption at 100 C, 100ppm NO, x ppm CO, 130 ppm C 3 H 6, 5%H 2 O, 10%O 2, 14

Presence of water and CO enhances NO adsorption.

15 CO, in combination with water, provides electronic enrichment to Pd sites, enhancing NO adsorption Same type of NO adsorbed species are observed in the presence of CO. Presence of water and CO enhances NO adsorption. Pd 0 Pd NO+O NO+O 2 +H 2 O --- NO+CO+O NO+CO+O 2 +H 2 O In-situ XAS shows significant electronic enrichment when both CO and NO are present. More coordination around Pd sites is observed. 15

CO reduces higher Pd oxidation states to +2,

CO co-existence is essential Pd n+ (n=1-4) 2250

FTIR spectra of CO adsorption on Pd/CHA Applied

16 CO reduces higher Pd oxidation states to +2, which is favourable for NO adsorption Water and CO co-existence is essential Pd n+ (n=1-4) Wavenumber (cm -1 ) 2000 FTIR spectra of CO adsorption on Pd/CHA Applied Catalysis B: Environmental Volume 147, 5, 2014,

17 NO storage is due to NO direct adsorption on isolated Pd 2+ sites NO + NO Pd 2+ NO 3 + NO H.-Y. Chen et al.; Catal. Lett.; June2016; DOI /s

18 NOx storage capacity (gno2/l cat.) Sulfur does not affect the NO storage function due to different mechanism 0.8 Sulfur doesn t impacts NO adsorption Initial 0.5 g S/L cat. 1 g S/L cat. 2 g S/L cat. 18

19 NOx (ppm) CO (ppm) Inlet T Sulfur affects CO oxidation activities and delays NOx release to higher temperature Initial 0.5 g S/L 1 g S/L 2 g S/L Initial 0.5 g S/L 1 g S/L 2 g S/L Inlet Temp (C) Test conditions: 1%Pd/CHA Adsorption at 125 C, 200ppm NO, 200ppm CO, 5%H 2 O, 10%O 2, then ramp up Time (s) 19

20 Conclusions Pd.Z exhibits high NO storage at low temperature, which is a key component in dcsc catalysts NO directly adsorbs on isolated Pd 2+ sites Water inhibits some NO adsorption at low T, but enhances NO adsorption as temperature increases CO, in combination with H2O, enhances NO adsorption High CO concentration is detrimental as it lowers NOx release temperature Sulfur doesn t affects NO adsorption function and delays NO release to higher temperature 20

Department of Chemical and Petroleum Engineering Sharif University of Technology, Iran

Tayebeh Hamzehlouyan Department of Chemical and Petroleum Engineering Sharif University of Technology, Iran ETH-Conference on Combustion Generated Nanoparticles June 0, 018 1. Motivation. Experimental