DEER CONFERENCE 2011 Weiyong Tang , Xiwen Huang, and Sanath Kumar BASF Corporation, Iselin, NJ DEER Conference 2011, Detroit, MI Tuesday, October 04, 2011 

# Sulfur Effect and Performance Recovery of a DOC + CSF + Cu

- Zeolite SCR SystemDEER CONFERENCE 2011 

# Outline

 Introduction  Zeolite

- based SCR behavior

– Performance

– Sulfation issue: literature  Reactor experiments to simulate transient behavior  Accelerated low temperature sulfation behavior  Sulfation effects and mechanism  Desulfation methods  SummaryDEER CONFERENCE 2011 

# Recent developments have led to Cu - zeolite SCR catalysts with remarkably improved low temperature activity and high thermal stability

SAE 2008

- 01

- 1025: Enhanced Durability of a Cu/Zeolite Based SCR Catalyst. Giovanni Cavataio, et alDEER CONFERENCE 2011 

# On the other hand, Cu - zeolite SCR also provides benefit over V/Ti SCR for applications with “cold” exhaust that never see high temperatures Temperature window of one HDD engine platform and SCR NOx conversion

0 10 20 30 40 50 60 70 80 90 100

200 225 250 275 300 325 350 375 400 

### SCR in temperature ( o 

### C)Time above temperatureand deNOx Cu - SCR V - SCR



### Average cycle Coldest cycleDEER CONFERENCE 2011 

# Zeolite SCR sulfation issue: literature

 Several recent presentations have highlighted effects of sulfur compounds on zeolite

- based SCR performance  “The Effects of SO 2 

## and SO 3 

## Poisoning on Cu/Zeolite SCR Catalysts”. Christine Lambert, et al: SAE 2009

- 01

- 0898  “Investigation of Sulfur Deactivation on Cu/Zeolite SCR Catalysts in Diesel Application”. 

# Yisun Cheng, et al: 2009 DEER Conference  “The Effects of Sulfur Poisoning and Desulfation Temperature on the NOx Conversion of LNT+SCR Systems for Diesel Applications”. Joe Theis, et al: SAE 2010

- 01

- 0300  Past experience from Euro IV applications has shown V/Ti SCR to be insensitive to sulfation, although overall NOx conversion may be lower than zeolite

- based SCRDEER CONFERENCE 2011 

# Background and motivation

 Background:

– Systems with active regeneration used in low sulfur environments have shown stable, sustained performance to end

- of

- useful life*

– Some systems running under high sulfur conditions and/or extended low temperature operation have shown performance loss  Motivation:

– Better understanding of degradation mechanism

– Generate system

- level performance features with realistic SCR

- inlet SO 2 

## /SO 3 

## and NO 2 

## /NO x 

## in a DOC + CSF + Cu

- SCR system

– Determination of conditions for system performance recovery

* The New Challenge

- Heavy Duty Diesel Engine Emission Control. Sanath V Kumar; SIAT 2011 Keynote PresentationDEER CONFERENCE 2011 

# Laboratory study of sulfation effect at system level

 D iesel S ystem S imulator (DSS)  System level study  Capable of simulating various transient cycles

– By matching temperature, space velocity and compositions from engine experiments  Catalyst size  DOC: 1.5"x3"  CSF: 1.5"x6"  SCR: 1.5"x6" SO 2

MS

FTIRCu-SCRCSF 1.5 ” x6 ”

1.5 ” x6 ” 

### NH 3DOC 1.5 ” x3 ” FID

FID 

## DSS setupDEER CONFERENCE 2011 

# Engine HDFTP data “derated” to simulate cold engine operation

Transient temperature and space velocity profiles in the first four cycles (200 - 300 C SCR inlet ~55,000 h - 1 

### peak SCR SV)

0 20 40 60 80 100 125 150 175 200 225 250 275 300 325 350

DOC-in temp. SCR-in tempTemperature (°C)



### Run Time (min) Temperatures in the first 4 FTP cycles of D3C3S6_061209_3 sulfation runs



### 0 20 40 60 80 0 10000 20000 30000 40000 50000 60000 70000 SCR SVSpace Velocity(hr-1)



### Run Time (min) High SO 2 in feed to simulate extended sulfur exposure on engine:

• ~1.0 g/L sulfur exposure = 100 h on engine (using ULSD fuel)

• ~12.5 g/L sulfur exposure on reactor ≅ 1250 h on engine (~35 PPM SO 2 for 12 h in reactor)DEER CONFERENCE 2011 

# System deactivation after accelerated sulfur exposure at low temperature

Sulfur (SO 2 

### ) breakthrough after different components

0 2 4 6 8 10 12 14 0 10 20 30 40 50 60 70 80 90 100SO2overall consumption (%)

System sulfur exposure (g/L_SCR) Loss after DOC Loss after CSF Loss after SCR 

## System response to 12h continuous derated HDFTP cycles under 35 ppm SO 2 

## in feed conditions

Approx. 1300 h on engine Multiple derated FTP runs (200 - 300 C SCR in, NSR=1, 35ppm SO 2 in feed)

0 2 4 6 8 10 12 14 0 10 20 30 40 50 60 70 80 90 100Conversion (%)or NO2/NOx (x100%)



### System sulfur exposure (g/L_SCR) 

### CSF/O NO 2 

### /NOx Cycle deNOxDEER CONFERENCE 2011 

# After sulfur exposure, Cu - zeolite SCR became sensitive to NO 2 

# /NOx ratio , especially for T < 250 C

80 82 84 86 88 90 92 94 96 98 100 0 50 100 150 200 250 300 0.00 0.25 0.50 0.75 1.00SCR Out NOx(ppm)



## Run Time (min) Temperature

NO xSCR in NO2/NOxDEER CONFERENCE 2011 

# Sulfur concentration gradients in Cu - SCR after 13 g/L_SCR sulfur exposure

Front to rear Washcoat surface to substrate

Washcoat sulfur profile via EPMA Sulfate content via ICP wet analysis 

## 1.5”x6”

0.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0Weight (%)



### Distance (um) Front core Middle core Rear core 0 5000 10000 15000 20000 25000 30000 35000 40000Component Oxide Mass (ppm) 

### washcoatDEER CONFERENCE 2011 

# TGA/DTA - MS of sulfated sample shows two major sulfation modes

‘ Low - T ’ sulfate

‘ High - T ’ sulfate 13 g/L sufated TEX - 0088

13 g/L sufated TEX - 0088 Absence of NH 3 during sulfation (NH 4 ) 2 SO 4 control CuSO 4 control 

## Sulfur release and weight loss (a)

(b)

(c)

(d) Sulfated Cu - SCR

CuSO 4



### (NH 4 

### ) 2 

### SO 4



### Sulfated Cu - SCR (w/o NH 3 

### )DEER CONFERENCE 2011 50 55 60 65 70 75 80 85 90 95 100Cycle NOx conversion (%) Set #1, NSR=1.5 @ deS (NSR=1.0 for 450°C deS) Set #2, NSR=1.0 @ deS Set #3, NSR=0.0 @ deS 

# NOx conversion recovery is incremental with temperature

NOx conversion (Baseline: ~95%, all evaluated at NSR=1.0)  Parametric study for desulfation effectiveness  NSR (NH 3 

### /NOx) = 0.0, 1.0, 1.5  Durations = 0.5, 1.0 hr  Temperature = 375, 400, 450, 500, 600 C (SCR in)

375C - 1h

deSOx 400C - 1h deSOx 450C - 0.5h deSOxDEER CONFERENCE 2011 

# Full performance recovered at 500 C deSOx ... and does not further degrade during multiple sulfation - desulfation cycles

0 10 20 30 40 50 60 70 80 90 100

0 5 10 15 20 25 30 

### System sulfur exposure (g/L_SCR)deNOx and CSF out NO2/Nox (x100%)


### deSOx@ 500 C NOx conversion
CSF out NO 2 /NOx SO 2 NH 3 DOC CSF Cu - SCR SO 2 NH 3 DOC CSF Cu - SCR 

### NO 2 

### /NOx ratio and NOx conversion after sulfation and desulfation SO 2

7 g/L_SCR sulfationDEER CONFERENCE 2011 

# DOC/CSF generated fairly repeatable HDFTP NO 2 

# /NOx profile in post - deSOx evaluations

0.00 0.25 0.50 0.75 1.00 2SCR in NO2/NOx

160 162 164 166 168 170 172 174 176 178 180 0.00 0.25 0.50 0.75 1.00 2SCR in NO2/NOx 

## After 1 st 

## Sulfation

- deSOx

After 3 rd 

## Sulfation

- deSOxDEER CONFERENCE 2011 

# SCR - out NOx slip values were very similar after 500 C deSOx

Baseline After 7 g/L sulfation (SOx) After 1st SOx-deSOx After 2nd SOx-deSOx After 3rd SOx-deSOx After 4th SOx-deSOx

160 165 170 175 180 0 15 30 45 60 75 90 105 120 135 150SCR out NOx Slip(ppm)



### Run Time (min) D5C5S15 SCR out NOx in the last cycle of different test stagesDEER CONFERENCE 2011 

# Summary

 Zeolite

- based SCRs provide high thermal stability and durability in active regeneration systems with periodic high temperature exposures  Literature reveals all zeolite

- based SCRs are susceptible to sulfation under low temperature SO 3 

### exposure  This study has shown that Cu

- Zeolite SCR degrades after severe sulfur exposure under extended low temperature conditions  Two major sulfation modes are most likely involved

– Formation of (NH 4 

### ) 2 

### SO 4 

### or (NH 4 

### )HSO 4



### – Formation of CuSO 4 

###  System performance can be recovered  Temperature is the most important factor determining desulfation efficiency  The system recovered most but not all of its performance after 450 C desulfation  Upon 500 C desulfation, NOx conversion efficiency was fully restored and sustained in multiple sulfation

- desulfation experimentsDEER CONFERENCE 2011 

# Thank You!