cleers passive nox adsorber (pna)
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CLEERS Passive NOx Adsorber (PNA)
JÁNOS SZANYI, KONSTANTIN KHIVANTSEV, FENG GAO, LIBOR KOVARIK,JAMIE HOLLADAY, DONGHAI MEI, YONG WANG
PACIFIC NORTHWEST NATIONAL LABORATORY
JUNE 12, 2019ACE118
This presentation does not contain any proprietary, confidential, or otherwise restricted information
Overview
Timeline
► Status: On-going core R&D
Budget
► FY18 funding – $400K
Barriers and Technical Targets
► Emission controls contribute to durability, cost and fuel penalties
■ Low-temp performance is now of particular concern
► Improvements limited by:
■ Available modeling tools
■ Chemistry fundamentals
■ Knowledge of material behavior
► Effective dissemination of information
Partners
► Oak Ridge National Lab: synergies in evaluating both practical and model materials
► BASF: focus on addressing industrially relevant issues
2
Relevance
Increasing the efficiency of internal combustion engines is a
technologically-proven and cost-effective approach to dramatically
improving the fuel economy of the nation's fleet of vehicles in the
near- to mid-term, with the corresponding benefits of reducing our
dependence on foreign oil and reducing carbon emissions.
The overarching emissions goal is the U.S. EPA Tier 3 Bin 30
emission standard.
Compliance with exhaust emission regulations will be mandated and
requires aftertreatment technologies integrated with the engine
combustion approaches.
Achieve greater than 90% conversion of criteria pollutants (NOx, CO,
HCs) at 150°C for the full useful life of the vehicle (defined as the
longer of 150,000 miles or 15 years).
Require the research and development of new and novel material
combinations that will enable lower temperature catalytic
performance, increased selectivity to inert species, and optimal
storage of pollutant and reductant species.
Aligns wit the 2017 CLEERS Industry Priorities Survey.
3
Relevance (and Goals)
“CLEERS is a R&D focus project of the Diesel Cross-Cut Team. The overall objective is to promote development of improved computational tools for simulating realistic full-system performance of lean-burn engines and the associated emissions control systems.”
VT program goals are achieved through these project objectives:
■ interact with technical community to identify relevant technological gaps
■ understand fundamental underlying mechanisms and material behavior
■ develop analytical and modeling tools, methodologies, and best practices
■ apply knowledge and tools to advance technologies leading to reducing vehicle emissions while improving efficiency
Specific work tasks in support of the objectives are arrived at through:
■ focus group industrial monthly teleconferences, diesel cross-cut meetings
■ yearly workshops and surveys
■ ongoing discussions on program priorities with the VT office
CLEERS PNNL Subprogram Goal
Working closely with our National Lab partners, the CLEERS industrial/academic team and in coordination with our CRADA portfolio, PNNL will…
…provide the practical & scientific understanding and analytical base, e.g., molecular level understanding of active sites, required to enable the development of efficient, commercially viable emissions control solutions and accurate modeling tools for ultra high efficiency vehicles.
4
Milestones
Milestones:Achieve atomic dispersion of Pd by optimizing the preparation method and quantifying the dispersion of Pd species.
Provide molecular level understanding of the nature of active sites under practical conditions, e.g., CO, NOx, H2O, HCs
Identify the major cause of PNA material degradation associated with hydrothermal aging, cycling, and sulfur poisoning
Demonstrate >95% NOx adsorption within 3mins at 100°C and release at >200°C (go/no-go decision)
5
3/31/2019 √
7/30/2019 on track
9/30/2019 on track
9/30/2019 √
Approach
“Science to Solutions”► Build on our strong base in fundamental
sciences to reveal fundamental aspects of the chemistry and catalytic materials in PNA:
■ Institute for Integrated Catalysis (IIC)
■ Environmental Molecular Sciences Laboratory (EMSL)
■ Synchrotron Facilities
► Work closely with our partners and sponsors
■ ORNL (coordination of CLEERS Workshop, synergy in PNA, etc.)
■ BASF (addressing the issues of most importance to industries)
6
Flow reactors
E-TEM
NMR
FTIR/XANES/XRD
NOx Adsorption and Release Depend on Zeolite Structure and Pd is Under-utilized
Pd/Zeolite materials are active
for PNA.
Pd/BEA and Pd/SSZ-13 are the
focus of studies - more active
than Pd/MFI, BEA and SSSZ-13
are also the most stable ones for
commercial use.
Pd-SSZ-13 has the appropriate
release temperature
Effectiveness expressed as
NO/Pd, Pd is underutilized and
thus not used with maximum
efficiency if <1.
Pd utilization efficiency is far from
ideal in Pd/Zeolite materials
prepared by the traditional IWI
method.
0 20 40 60
0
25
50
75
100
125
150
175
200
225
250
500 °C
100 °C
430 - 490°C400°C
310°C250°C230°C
NO
x c
oncentr
ation, ppm
Time, minutes
200°C
Si/Al ratio~12 NO/Pd ratio
1 wt%Pd H-SSZ-13 IWI 0.43
1 wt% Pd H-ZSM-5 IWI 0.3
1 wt% Pd H-BEA IWI 0.52
200 ppm NOx (185 ppm NO and 15 ppm NO2), 14%
O2, balanced with N2 at a flow rate of 300 sccm
7
Modified IWI preparation provides
high performance PNA (Pd/Zeolite)
materials.
At Si/Al=6, atomic Pd dispersion is
achieved at up to 2 wt% metal
loading.
Complete NOx removal for ~3 min at
2 wt% Pd loading.
At Pd loadings >2 wt%, Pd utilization
efficiency decreases with metal
loading.10 20 30 40 50 60 70
0
100
200
300
400
NO
x c
oncentr
ation, ppm
Time, minutes
1 wt% Pd/SSZ-13 Si/Al=6
1.9 wt% Pd/SSZ-13 Si/Al=6
500 oC
100 oC
Pd wt% (Si/Al 6)
1 1.9 3 5
NO/Pd: 1 1 0.9 0.6
Storage (mg/g) 2.8 5.4 7.6 8.4
200 ppm NOx (185 ppm NO and 15 ppm NO2), 14% O2, 3%
H2O, 200ppm CO balanced with N2 at a flow rate of 300 sccm
Preparation Route, Si/Al Ratio and Form of Zeolite are
Critical: Achieving ~8 mg NOx/g-catalyst Storage at NO/Pd
of 0.9 with 3 wt% Pd/(NH4)-SSZ-13 (Si/Al=6)
K.Khivantsev et. al., Angewandte Chemie, Int.Ed.,2018, DOI: 10.1002/anie.201809343 8
Atomically Dispersed Pd, e.g., 1wt%Pd/SSZ-13
Shows Better Hydrothermal Stability
HTA reduces NOx storage efficiency and affects the release temperature.
HTA reduces or removes the high-temperature NO2 desorption stage.
Less than 10 to 20% performance lost for Pd/SSZ-13 (1-3 wt%Pd, Si/Al=6) with atomically
dispersed Pd.
Hydrothermal aging conditions: 750 C in flowing air containing 10% water vapor for 16 hours.
0 10 20 30 40 50 60 70
50
100
150
200
250
NO
x c
on
cen
trati
on
/ p
pm
Time/ min
Fresh
Hydrothermally Aged
1 wt% Pd/SSZ-13
(Si/Al=12)1 wt% Pd/SSZ-13
Si/Al = 12
0 10 20 30 40 50 60 70
50
100
150
200
250
NO
x c
on
ce
ntr
ati
on
/ p
pm
Time/ min
Fresh
Hydrothermally Aged
1 wt% Pd/SSZ-13
(Si/Al=6)
Si/Al = 6
1 wt% Pd/SSZ-13
0 10 20 30 40 50 60 70
80
100
120
140
160
180
200
Fresh
Hydrothermally Aged
NO
x c
on
ce
ntr
ati
on
/ p
pm
Time/ min
1 wt% Pd/SSZ-13
(Si/Al=30)
Si/Al = 30
1 wt% Pd/SSZ-13
20 nm 20 nm 100 nm
9
Hydrothermal Aging Leads to Dealumination
of SSZ-13 and Negligible Sulfur Effect on 1wt% Pd/SSZ-13
After HTA, a large number of Al3+penta ions form on both materials (Si/Al=6 and 12), and the Al3+
tetra27Al
NMR signal broadens, possible due to the significant changes in the environment around these ions.
Removal of framework Al ions (key in stabilizing isolated Pd ions) leads to the formation of PdO particles.
Only minor performance degradation after SO2 poisoning under the conditions studied.
27Al NMR
1 wt% Pd/SSZ-13Si/Al 6 12 30NO/Pd: 1 0.87 0.31NO/Pd-SO2: 1 0.80 0.3
(The samples were treated using standard protocol:
5 ppm SO2 in SO2/10%O2/N2 mix for 5 hours at 300 °C)
-7.00E-01
-5.00E-01
-3.00E-01
-1.00E-01
1.00E-01
3.00E-01
5.00E-01
7.00E-01
1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4
2.01
3.07
3.43
Pair Distribution Functionof 1 wt% fresh and HTA Pd/SSZ-13 Si/Al=12
10
Pd/BEA with Large Crystalline Size Shows
Promising Hydrothermal Stability (1 wt% Pd/BEA)
► Large BEA crystallites: higher NOx storage capacity
► Low T NOx release related to large number of crystal defects in nano BEA
► Decreased amount of total NOx uptake
► HTA increases defect density, thus decreases high T and increases low T NOx release
► No change in total NOx uptake
► Increased defect density results in low T NOx release
K.Khivantsev et. al., Appl.Catal. A, 2019, 569, 181-189
0 20 40 60 80
0
50
100
150
200
250
NO
x c
once
ntr
atio
n,
pp
m
Time, minutes
NanoBEA
Large BEA crystal
20 40 60 80
20
40
60
80
100
120
140
160
180
200
220
240
NO
x c
oncentr
ation, ppm
Time, minutes
----- Fresh
----- Aged
20 40 60 80
25
50
75
100
125
150
175
200
225
250
NO
x c
oncentr
ation, ppm
Time, minutes
--- 1wt% Pd/Large BEA Fresh
--- 1wt% Pd/Large BEA Aged
Fresh nano vs large BEA Fresh vs aged nano BEA Fresh vs aged large BEA
11
Same NOx Chemistry on 1 wt% Pd/BEA (Si/Al=12) as SSZ-13 Except the Presence of High Temperature NOx Release
Two different mononitrosyl Pd(II)-NO formed upon NO adsorption
At higher NO pressures unstable Pd(II)(NO)2 complexes form
NO+O2 leads to formation of NO+ ions, Pd-NO complexes and N2O3
CO promotes NO uptake by forming Pd(II)(NO)(CO) complexes
Provides accurate description of Pd sites for detailed kinetic modeling
1900 1875 1850 1825
0.00
0.02
0.04 1845
Absorb
ance, a.u
.
Wavenumbers, cm-1
1886
1925 1900 1875 1850 1825 1800 1775
0.000
0.005
0.010
0.015
0.020
0.025
0.030 1845
Ab
sorb
an
ce,
a.u
.
Wavenumbers, cm-1
1886
2200 2100 2000 1900 1800 1700 1600
0.0
0.1
1570
Absorb
ance, a.u
.
Wavenumbers, cm-1
2138
1950
Pd(NO)2
NO NO+O2 CO after NO
Low PNO
high PNO
dinitrosyl
mononitrosyl
NO+
2150 2100 2050 2000 1950 1900 1850 1800 1750
0.00
0.02
0.04
0.06
1791
Absorb
ance, a.u
.
Wavenumbers, cm-1
2145
CO…..Pd2+……NO
K.Khivantsev et. al., Appl.Catal. A, 2019, 569, 181-189
12
Accomplishments – Responses to
Previous Years Reviewers’ Comments
Nearly all the comments from the reviewers last year were very supportive and complimentary.Some comments/recommendations included:
1. It would be better to stick to two or three topics maximum as opposed to the four chosen here.
2. examine the effects of other exhaust species on the performance of the Pd/SSZ-13 PNA catalyst, including hydrocarbons, H2, CO2, H2O, and sulfur dioxide.
3. corresponding anti-deactivation mechanism and approach should be studied with considerable urgency.
4. how much PNNL really collaborates with ORNL on coordination of CLEERS as it seems to be solely ORNL.
5. including an increased range of industrial partnersPNNL response:
1. Focuses on PNA in FY20192. Study the effects of SO2, and C2
=
3. Understand the mechanism and evaluating mitigating approaches of crystalline beta zeolite.
4. Assist ORNL in organizing CLEERS workshop, including organizing and leading the panel discussion, monthly teleconf calls.
5. BASF as new partner13
Collaborators/Coordination
DOE Advanced Engine Crosscut Team (this group is the primary sponsor and overseer of all activities)
CLEERS Focus Groups
USCAR/USDRIVE ACEC team
21CTP partners
Oak Ridge National Lab: Melanie Debusk, Jim Parks, Josh Pihl, Vitaly Prikhodko, Todd Toops
BASF: Saeed Alerasool, Pascaline Tran, Xinyi Wei, Jeff Hoke
Cummins: Krishna Kamasamudram
Sofia University, Bulgaria: Hristiyan A. Aleksandrov and Georgi N.Vayssilov
University of Kansas: Franklin Tao
Acknowledgements
DOE EERE Vehicle Technologies Program: Gurpreet Singh and Ken Howden.
Collaboration and Coordination with Other Institutions
14
Long-term cyclic stability including NOx storage capacity and release temperature.
Performances under extreme conditions including temperatures, hydrothermal aging, exhaust gas compositions such as reducing conditions (high CO content) and presence of olefins.
Interference with other catalysts such as DOC.
Remaining Challenges and Barriers
15
Any proposed future work is subject to change based on funding levels
► Evaluate PNA performances under highly reducing conditions such as high CO concentration, understand the underlying mechanisms of PNA materials degradation, e.g., possible Pd sintering, and provide guidance in mitigating the issue.
► Modification of zeolites to minimize the defect sites to improve hydrothermal stability.
► Further study the poisons of PNA materials by sulfur and HC.
► Understand the potential interference and interactions with DOC etc.
Proposed Future Work
16
Summary
► Achieved atomic Pd dispersion with modified preparation method and selection of right form of zeolites.
► Provided more accurate descriptions of Pd sites under practical conditions for simulations under CLEERS.
► Negligible sulfur effect was observed with Pd/SSZ-13.
► Understood the degradation issues under hydrothermal aging.
► Identified large crystalline BEA is a potential candidate with improved hydrothermal stability.
17
Technical Backup Slides
May 9, 2019 18
JÁNOS SZANYI, KONSTANTIN KHIVANTSEV, FENG GAO, LIBOR KOVARIK JAMIE HOLLADAY, DONGHAI MEI, YONG WANG
Pacific Northwest National Laboratory
Si
/Al=
6
Si/A
l=1
2
Si/A
l=3
0
Si/Al 6 12 30NO/Pd: 1 0.87 0.31Storage (mg/g) 2.8 2.4 0.9
Effect of Si/Al ratio on PNA performance: 1 wt% Pd/SSZ-13 prepared by IWI with NH4-SSZ-13
Progressive agglomerations of Pd as Si/Al ratio
increases
PdO is not active for PNA
Atomically dispersed Pd is the true PNA active
species
In 1 wt% Pd/SSZ-13 with Si/Al=6 potentially all
Pd is atomically dispersed and this sample
utilizes each Pd atom for PNA storage
Hydrophilicity decreases with increasing Si/Al
ratio
19
EXAFS of 0.1 and 1 wt% Pd/SSZ-13 (Si/Al = 6)
Both 0.1 and 1 wt% Pd show no Pd-Pd contributions
Pd is atomically dispersed, Pd1O(3-4) site
K.Khivantsev et. al., Angewandte Chemie, Int.Ed.,2018, DOI: 10.1002/anie.201809343
20
Pd(II) ions are super electrophilic in SSZ-13
Moisture
Dehydrated
Non-classical dicarbonyl complex form on Pd/SSZ-13
Unprecedented 2.3 eV shift in the XPS spectra of Pd(II) upon dehydration proves superelecrophilic nature of Pd ions in zeolite:
ion-pair/charge-transfer complex with framework O atoms
Atomically dispersed 1 wt% Pd/SSZ-13 (Si/Al=6)
K.Khivantsev et. al., submitted
21
1 wt% Pd/SSZ-13
22
He ion microscopy
1.0
0.5
In
ten
sity (
a.u
.)
403530252015105
2q (°)
BEA15OH
BEA230
BEA110
BEA50
BEA26
BEA16
In contrast to OH- medium no intercrystalline mesoporosity
XRD shows well resolved and narrow peaks indicating high degree of
order and no amorphous background.
Two different sizes for BEA crystals with similar Si/Al
13 & 15: nanoBEA and large, defect-free, more
hydrophobic BEA produced using fluoride
23
Large BEA crystals are less defective and more hydrothermally stable
HTA of 1 wt% Pd/nanoBEA induces a lot of dealumination
HTA of 1 wt% Pd/large BEA induces less structural degradation
Due to this, Pd on large BEA shows much better hydrothermal stability compared with Pd supported on regular nanosized BEA crystals
Enhanced HTA stability of large BEA crystallites:
MAS Solid-state 27Al NMR for BEA fresh and aged
samples
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