Date: October 12, 2012 

To: Brenda Shine, EPA/OAQPS/SPPD 

From: Jeff Coburn 

Subject: Meeting Minutes for October 10, 2012, Meeting Between the U.S. EPA and 

Representatives from Johnson Matthey 

Introduction 

On October 10, 2012, representatives of the U.S. Environmental Protection Agency 

(EPA) and their contractor (RTI International) participated in a meeting with representatives 

from Johnson Matthey, a specialty chemical company. Representatives were present from 

Tracerco and Intercat, both of which are in Johnson Matthey’s Process Technologies Division. 

The names and affiliations of the participants are included in Attachment 1. The major 

discussion points are provided below. 

Tracerco 

The representative from Tracerco provided a brief presentation about the types of 

services and studies that Tracerco performs; a copy of the presentation is included as 

Attachment 2 to this memorandum. Tracerco uses low level radioactive tracers to diagnose 

process operations. The technologies can be used to assess flow rates, diagnose distillation 

column issues, and identify leaks, blockages and other issues without disrupting normal 

processing. For example, the technology can be used to identify sources of flare gas flow in flare 

header systems using pulse injection of radioactive material and measuring the time it takes to 

travel across different points within the flare header system. 

Intercat 

Intercat specializes in catalysts for the fluid catalytic cracking unit (FCCU). 

Representatives from Intercat presented their recent work to better understand hydrogen cyanide 

(HCN) formation and emissions from the FCCU as well as the relationship between HCN and 

nitrogen oxide (NOX) emissions from the FCCU. A copy of the presentation is included as 

Attachment 3 to this memorandum. Key points discussed during the presentation are 

summarized below. 

 Most NOX emissions from a complete combustion FCCU are fuel NOX. That is, they are 

formed from nitrogen deposited in the coke. Complete and partial combustion FCCU are 

not operated at temperatures that would generate thermal NOX. Most (85-90 percent) of 

NOX is NO, with 8-12 percent N2O and little NO2. 
2

 Platinum (Pt) combustion additives generally favor NOX formation; NOX emissions are 

generally about 3 times higher than an FCCU with no combustion promoter. Pt 

combustion promoters were originally used to reduce afterburning of carbon monoxide 

(CO) and the resulting high temperatures in the dilute and exhaust gas sections of the 

regenerator. In the dense section of the regenerator, the catalyst acts as a heat sink so CO 

combustion does not create the same high temperature perturbations as are caused when 

CO burns in the dilute and exhaust gas sections of the regenerator. 

 Non-Pt combustion promoters generally use palladium (Pd) and favor the conversion of 

fuel nitrogen (in the coke) to nitrogen (N2) rather than NOX. Non-Pt combustion 

promoters do increase NOX emissions relative to no combustion promoter, but by only 

about 30 percent (compared to a factor of 3 for Pt combustion promoters). 

 Partial burn FCCU do not use combustion promoters; the lack of oxygen in the 

regenerator prevents afterburning until the CO boiler. “Deeper” partial burn is marked by 

higher levels of CO (and HCN) in the regenerator exhaust; the higher CO levels in the 

exhaust lead to higher combustion temperatures in and higher NOX emissions from the 

CO boiler. The increase in NOX emissions relative to complete combustion units is due 

primarily to the generation of thermal NOX generation; CO boilers operate at higher 

temperatures than the regenerator and these temperatures are high enough to generate 

NOX from N2 in the inlet air. At the elevated temperatures in the CO boiler, all of the 

HCN in the regenerator exhaust is expected to be converted to NOX. As such, partial 

burn FCCU are not expected to be significant HCN emission sources. 

 Intercat did a series of temperature ramping experiments with coked FCCU catalyst. 

These experiments showed that: 

o With no combustion promoters, HCN formation appears to have two mechanisms of 

formation as seen by two distinct peaks, one at about 570 °C and one at about 715 °C. 

o Pt combustion promoters do not appear to significantly reduce the low temperature 

formation of HCN, but they greatly reduce the higher temperature formation of HCN 

(i.e., no significant secondary peak at higher temperatures). 

o Non-Pt combustion promoters appear to reduce both the low temperature formation 

of HCN (smaller peak between 550 to 650 °C) and the higher temperature formation 

of HCN (no significant secondary peak at higher temperatures, similar to Pt catalyst 

combustion promoters). 

 From these temperature ramping experiments, Intercat concluded that HCN emissions 

should be lower with combustion promoters than without, and that non-Pt combustion 

promoters should yield lower HCN emissions than Pt combustion promoters. Therefore, 

the use of non-Pt combustion promoters cannot be the primary cause for the “discovery” 

of high HCN emissions. All of the complete combustion FCCU recently tested used nonPt catalyst promoters; therefore, the wide range in measured HCN concentrations 

suggests that other factors, such as regenerator design and nitrogen content of the coke, 

may play an important role in HCN emissions. 

 Although theoretical, the Intercat representatives hypothesized that spent catalyst return 

design may play a critical role in HCN emissions. The catalyst is generally returned at 

520 °C. If the catalyst is returned in the dilute phase or near the top of the dense phase 
3

(or perhaps too near the air inlets where the temperature is cooler), the initial catalyst 

combustion may occur at temperatures below 600 °C, where HCN formation is favored. 

The HCN formed may then exit the regenerator without experiencing the higher 

temperatures where HCN may be converted to NOX or N2 (either because the vapors are 

generated in or near the dilute phase or in large air bubbles that “burp” through the dense 

phase of the regenerator). Thus, the regenerator design modifications made to lower NOX

emissions may have had the unintended consequence of increasing HCN emissions. 
Attachment 1 

Participants in October 10, 2012, EPA/Johnson Matthey Meeting 

Industry Representatives 

Guido Aru, Intercat 

Bart de Graaf, Intercat 

Paul Diddams, Intercat 

Dave Ferguson, Tracerco 

U.S. EPA Representatives 

Andrew Bouchard 

Eric Goehl 

Brenda Shine 

RTI International (EPA contractor) 

Jeff Coburn 

Kristin Sroka 
Attachment 2 

Presentation Slides 

Tracerco - Delivering Diagnostic Services and Measurement Solutions Worldwide 
Delivering diagnostic services and measurement solutions worl

www.tracerco.com Tel: 281 291 7769

Presented by Dave Ferguson
July 2010 TruTec Scanning S

28 Office Locations Strategically Placed

Worldwide For Rapid Response

North American

Headquarters

PASADENA, TEXAS

Corporate Headquarters

BILLINGHAM, UNITED KINGDOM
July 2010 TruTec Scanning S

TRACERCO Diagnostics

Safety

• Tracerco is Licensed by State and Federal

Agencies and inspected once a year by

appropriate agencies

• Tracerco is responsible for the Transport,

Use, and Disposal of any radioactive

material we bring onto your site

• Plant does NOT inform EPA, State, or

Federal Agencies about testing

• Similar to radiographers, Tracerco will barricade an area aroun

the injection point, but only about 15 feet in radius

• There is no danger to plant personnel working around process

equipment, as long as they stay out of the barricaded area

• Our radiation sources are about 1000 times smaller than

radiography sources.
July 2010 TruTec Scanning S

TRU-SCAN® Procedure

I=Ioe

-
July 2010 TruTec Scanning S

Tru-Grid Scan Procedure

Packed Bed

I=Ioe

-
July 2010 TruTec Scanning S

TRACERCO DiagnosticsFlow

Study - Flare Flow Measurement
July 2010 TruTec Scanning S

TRACERCO DiagnosticsFlow

Study

CO

Boiler

FCC

Regen

Air

Flue Gas

Detectors Injection Point
July 2010 TruTec Scanning S

TRACERCO DiagnosticsFlow

Study

Unit 1

Unit 2 Unit 4

Unit 5

Unit 6

Unit 3 Unit 7

D-1

D-2 D-4

D-5 D-3

D-6

D-7

D-8

D-9

Identify Leak Origination

Flow

Meter

Injection

• Measure where flow rate inc

• Repeat steps in Unit sub-hea

• Pinpoint leaking PSV

• Eliminate Units that do not

contribute
July 2010 TruTec Scanning S

TRACERCO DiagnosticsFlow Study

– Relief Valve Leakage

• Once it is determined

which unit(s) are

contributing to the flare

flow, each PSV, block or

relief valves can be

individually tested to

determine which are

leaking

• Tracer flow (or lack thereof)

is used to determine which

pressure relief devices are

leaking and by how much
July 2010 TruTec Scanning S

Flow

Measurement

Residenc

Time

Distribution

Studies

Leak Testing

TRACERCO DiagnosticsTM
July 2010 TruTec Scanning S

Any Questions?
Attachment 3 

Presentation Slides 

FCC Regenerator Nitrogen Chemistry 
FCC Regenerator Nitrogen Chemistry

Bart de Graaf

Guido Aru

Paul Diddams
FCC Regenerator N Chemistry

• Where does NOx come from in Full Burn 

regenerators?

• What’s different about Partial burn regenerators ?

• Afterburn and CO Promotor Effects

• NOx Control Additives

• Cyanide in the FCC

• Preliminary Conclusions
Nitrogen Balance – Full Burn FCC

N in Feed

40% Feed N

in Coke

RX

REGENERATOR

C + O2 = CO2 + xs O2

Regen Air

N in Products

10% NH3/HCN

2% Gasoline

15% LCO

33% Bottoms

Typical Coke:

H in Coke 5 - 8%

S in Coke 0 - 2%

N in Coke 0 - 2%
NOx Formation – Full Burn

N in Feed

40% Feed N

in Coke

RX

REGENERATOR

Regen Air

N in Products

10% NH3/HCN

2% Gasoline

15% LCO

33% Bottoms

NOx in 

Flue Gas

N in Coke

N2 NOx

HCN / NH3

NOx comes from FEED Nitrogen (not combustion air)
NOx Formation – Full Burn

NOx formation in Full Burn regenerators is generally increased by:

 high flue gas excess oxygen levels

 poor coke / air mixing (regen. design)

 use of Pt based CO promotors

 use of Sb passivator often increases NOx

What factors affect NOx formation?
N-Balance in the FCC Regen

N in Coke converts primarily to N2 or NOx depending 

strongly on the absence or type of CO Promotor used

Example: Full Burn 

FCC Regenerator 

Nitrogen Balance:

In the absence of Pt-COP

most of the N in coke is 

converted to N2rather 

than NOx

No-COP Pt-COP COP NP

N in Coke 

(wt%) 1.16 1.17 1.17

Total N in FG 

(ppmw)

478 492 498

NOx

(ppmw)

112 388 145

wt% N in 

Coke to NOx 24 79 29

Balance:

wt% N in 

Coke to N2

(plus very small 

amounts of NH3

and HCN)

76 21 71
NOx Reduction – CO-Promotion

Why do we use CO promotors?

 

CO promotors are used to reduce afterburning in the dilute phase

CO + 1⁄2 O2  CO2 - reaction releases heat

There is insufficient catalyst in the dilute phase to absorb the heat

CO Promotors move this reaction into the dense phase where the 

heat of reaction is absorbed by the high heat capacity of the catalyst

Pt-based CO promotors have 

been used for many years and 

are very effective at controlling 

afterburn...

... BUT, they also lead to 

increased NOx emissions

Non-Pt promotors do the same job 

with much lower NOx formation
NOx Reduction – COP-NP

FCC REGENERATOR

N2

N in Coke HCN / NH3

Non-Pt Promotors decrease NOx by elimination of Pt

NOx formation is 

promoted by Pt NOx

How do non-Pt promotors decrease NOx?
NOx Reduction – COP-NP

CO promotors (Pt, non-Pt)

– CO oxidation effect is short-lived

NOx formation on Pt COP deactivates very slowly in FCC 

– only be eliminated by change-out of inventory

Immediate Stable

NOx Formation

Commercial FCCU 

Transition from 

Pt COP to COP NP

NOx drops by 70%

Pt COP

COP-NP additions begin

CO oxidation activity

deactivates rapidly

NOx ppm
NOx Reduction – Full Burn Units

Non-Pt promotors are generally very efficient in Full Burn regenerators

NOx levels can generally be decreased to 10-20 ppm in the flue gas

COP-NP has a Pt-equivalent level of 375 ppm for CO promotion 

NOx reduction is generally favored by:

 good spent catalyst / air mixing

 lower flue gas excess O2

 elimination of Pt and Sb usage

Continuous addition via a dedicated addition system ensures most

flexible and economic usage of additive

How far can NOx be lowered using Non-Pt Additives?
Partial Burn Regenerators

What is different about Partial Burn?

RX

REGENERATOR

Regen Air

CO BOILER

COB Air

C + O2 = CO2

C + 1⁄2O2 = CO

CO + 1⁄2O2 = CO2

CO2

CO

Steam

CO + 1⁄2O2 = CO2

CO2

xs O2
Partial Burn Regenerators

What is different about Partial Burn?

RX

REGENERATOR

Regen Air

CO BOILER

COB Air

NOx (1)

HCN (2)

Steam

HCN + O2  NOx

NOx (1)

NOx (2)

NOx (3)

N in Coke

HCN / NH3

NOx + N2

also, thermal 

NOx (3) from 

COB air
NOx Formation – Partial Burn

NOx formation in Partial Burn - without COP
NOx Formation – Partial Burn

What is different about NOx Reduction Partial Burn?

At high %CO in flue gas the level of NOx exiting the regen. decreases 

markedly, but this is more than made up by an increase in emissions 

of reduced N species such as HCN !

HCN from the regenerator readily forms NOx in the CO boiler

Further NOx is formed in the CO boiler via thermal oxidation of 

nitrogen (thermal NOx) – especially with older COB designs that do 

not have advanced features to maintain low peak flame temperatures

For additives to be effective they must decrease levels of the reduced 

N species leaving the regenerator... 

Where COP’s are used, substitution to non-Pt promotors is helpful
NOx Formation – Partial Burn

What are the best conditions to minimize NOx?

CO% Xs. O2 %

In Full burn – increasing excess O2 increases NOx

In Partial Burn – increasing CO increases overall NOx

There is a “sweet-spot” at minimum excess O2 or minimum CO
NOx Formation – 2-Stage Regen

What is different about 2-Stage Regenerators?

RG 1: Partial Burn

RG1 Air

RG2: Full Burn

RG2 Air

N in Coke 

  NOx (1) + HCN

NOx (1) 

HCN(2)

to COB

Coked

Catalyst

Clean

Catalyst

Partially

Regen

Catalyst

NOx (2)

to COB

Residual N in Coke 

  NOx (2)
NOx Formation – 2-Stage Regen

What is different about 2-Stage Regenerators?

Two-Stage Regenerators are essentially a combination of Partial and 

Full Burn (note: some 2-Stage regenerators operate in Partial Burn in both stages)

NOx Reduction additives work better in Full Burn, for additives to be 

effective in Partial Burn stages they must decrease levels of the 

reduced N species leaving the regenerator... 

Where COP’s are used, substitution to non-Pt promotors is helpful
Cyanide in the FCC

How much of the “intermediate” Cyanide leaves the regenerator?

N Chemistry in the regenerator is complex:

Most of the N in Coke initially burns to form Cyanide, a minor 

portion forms Ammonia

Cyanide is reactive and readily converts to NOx, NH3 and N2

NOx may also be converted to N2 via reaction with CO or coke

A small amount of Cyanide survives (up to 150 ppm) and exits with 

the flue gas

N2

N in Coke HCN / NH3

NOx N2
Cyanide in the FCC w/o Additive

HCN is formed at a low temperatures 

but is thermally unstable, above ca. 

650°C it is converted to other N 

species

N2O is formed at similar temperatures 

to NO, however N2O is also thermally 

unstable, above ca. 650°C (this may 

be an intermediate for conversion of 

NO to N2)

NH3levels are very low, but some 

ammonia may be reacting with SOx 

forming ammonium sulphate thereby 

preventing it’s detection – we are still 

evaluating this possibility

TPO Procedure

2 g sample (spent catalyst w or w/o 1 wt% additive)

Heat up to 730°C in 2%O2/N2 (total 50cc/min) from room temperature at 

15°C/min, and hold at 730°C for 30min

Gas species monitored by an MKS multi-gas analyzer: 

H2O CO CO2 COS CS2 H2S SO2 SO3 HCN HNCO HNO2 N2O NH3 HNO3 NO NO2

propane propylene ethane ethylene formaldehyde formic acid
HCN and NOx w/ w/o Additives

NOx is higher in the presence of Pt-COP or COP-NP : Pt > Pd > none

HCN is lower when either Pt-COP or COP-NP is added : none > Pt > Pd

w/ COP-NP

lowest HCN

w/ Pt-COP

highest NO

No Additive

lowest NO

highest HCN

A low temperature NO peak is 

also present with both Pt-COP 

and COP-NP : conversion of 

some of the HCN to NO

CO/CO2 NO HCN N2O Total N

Vol Ratio (V%) (V%) (V%) Rel V%

No additive 0.52 43 13 0.25 56

w/ Pt-COP 0.30 92 8 - 100

w/ COP-NP 0.34 67 6 - 74
CO Promotors Decrease Cyanide

How much of the “intermediate” Cyanide leaves the regenerator?

Cyanide is fully converted 

via reaction with O2 at 

temp’s above ca. 650 degC

Use of Pt-COP or non-Pt 

CO Promotor (COP-NP) 

facilitates conversion of 

cyanide (lower temperature 

required for cyanide conv.)

COP-NP is more effective 

than Pt-COP (lower temp.) 

Residual cyanide levels depend on several factors, importantly: local 

O2 and CO concentrations (mixing) and areas of low temperature 

(e.g. spent catalyst return)
New Additives...

Aim: decrease HCN and NOx

HCN

COP-NP = 46I > 105F

NO

COP-NP > 105F > 46I

Cyanide and NOx levels are not 

simply trading-off...

...they are independently variable by 

controlling selectivity to N2

COP NP

46I

105F

COP NP

46I

105F
Promising Leads...
Cyanide in the FCC

Conclusions regarding Cyanide

N in Coke forms Cyanide at low temperatures (e.g. spent cat return)

Cyanide is thermally unstable and converted to NOx and N2

Pt-COP and COP-NP (Pd) increase Cyanide conversion (Pd > Pt)

Pt favours Cyanide conversion to NOx

Pd favours Cyanide conversion to N2

Residual HCN emissions depends on factors limiting it’s conversion...
Conclusion

• NOx chemistry is complex, involving many N-species

– Pt favours pathways that form NOx

– Pd favours pathways that convert N-species to N2

– Both Pt and Pd decrease HCN

• Aging in the FCC Regenerator affects CO Promotors differently:

– Rapid Loss of CO oxidation

– Aging of Pt does not decrease NOx !

– Aging of Pd has little impact on NOx

• HCN is especially formed at fronts in the regenerator 

– Higher Coke, Lower Temperatures – spent cat. distribution

– Mixing effects are very important

• Replace Pt-COP’s with COP-NP to decrease NOx w/o HCN penalty
Mechanistic

Considerations

Appendix
Thousands of reactions involved...

Homogeneous Formation of NO and N2O from the Oxidation of HCN and NH3 at 600–1000°C V. J. 

WARGADALAM, 2000

The radicals could be replaced by the adsorbed species 

in heterogeneous reactions... 
One proposed elementary pathway for 

HCN + O2 on Pt/Al2O3

Catalytic oxidation of HCN over a 0.5% Pt/Al2O3 catalyst, Zhao et al. 2006
Comparison of Pd/Pt for HCN 

oxidation/hydrolysis

“Hydrolysis and oxidation of gaseous HCN over heterogeneous catalysts”, Krocher and Elsener 2009

HCN HCN

NH3

NOx

N2

O2, H2O

O2, H2O, NO Pt>Pd

Pt is a stronger oxidizing catalyst; hydrolysis is more favorable on Pd; a significant 

portion of N2 is from the reaction b/w NH3 and NOx on Pd.

Pt>Pd
Pathway for NO + CO

1. CO + * ↔ CO*

2. NO + * ↔ NO*

3. NO* + *  N* + O* rate limiting step

4. N* + N* N2 + 2*

5a. N* + NO*  N2O + 2*

5b. N* + NO  N2O + *

5c. NO* + NO*  N2O + O*

6. CO + O*  CO2 + *

The reduction of NO is enhanced when the catalyst surface is partially reduced 

-- e.g. Cu(II) ions act as NO adsorption sites while Cu(I) ions act as recipients of 

the O atoms produced through the dissociation

Catalytic removal of NO, Parvulescu et al. 1998
Unique adsorption of NO on Pd/Al2O3

In situ Raman spectra during CO + NO on 

Pd(pre-reduced/Al2O3

300oC

200oC

100oC

50oC

Cooling down

Characteristic of the formation of PdO; the accumulation 

of chemisorbed O atoms could lead to a shift of rate 

limiting step

In situ IR spectra during CO + NO on Pd(prereduced)/Al2O3

An overview of kinetic and spectroscopic investigations on three-way catalysts: mechanistic aspects of the

CO+NO and CO+N2O reactions, Granger et al. 2005
Comparison of Pt/Pd for CO oxidation 

and NO reduction by CO (contd.)

An overview of kinetic and spectroscopic investigations on three-way catalysts: mechanistic aspects of the

CO+NO and CO+N2O reactions, Granger et al. 2005

λ: the equilibrium adsorption constant

CO + NO

N2

N2O
Over anatase-supported metal oxides

Selective catalytic oxidation of NH3

imide (NH2) as common 

intermediate in SCO and SCR; 

(Amores, Escribano et al. 1997)