Date: December 10, 2012 

To: Brenda Shine, EPA/OAQPS/SPPD 

From: Jeff Coburn 

Subject: Meeting Minutes for December 4, 2012, Meeting Between the U.S. EPA and 

Representatives from BASF 

On December 4, 2012, representatives of the U.S. Environmental Protection Agency 

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

from BASF to discuss fluid catalytic cracking unit (FCCU) catalyst additives and their impact on 

the formation/degradation of hydrogen cyanide (HCN). 

Attendees 

BASF Representatives 

C.P. Kelkar 

Jason Smith 

U.S. EPA Representatives 

Andrew Bouchard 

Eric Goehl 

Brenda Shine 

Ravi Srivastava 

RTI International (EPA contractor) 

Jeff Coburn 

Kristin Sroka 

Discussion Topics 

BASF representatives provided a brief background on the company. BASF is a large 

diversified chemical company and the largest global catalyst supplier, including a variety of 

automotive and industrial catalysts. BASF’s catalyst division is headquartered in Newark, New 

Jersey. Considering the U.S. refining industry, BASF is the second largest refining catalyst 

supplier behind Grace Davidson; Albemarle and Intercat are the other key refining 

catalyst/catalyst additive suppliers in the U.S. 
2

BASF has several FCCU catalyst additives to help refineries meet emission requirements. 

EnviroSOx is a newly reformulated sulfur oxides (SOx) emission reduction catalyst additive that 

contains a lower content of rare earth materials than previous formulations. COnquer is a new, 

zero rare earth, palladium-based combustion promoter to lower carbon monoxide (CO) emissions 

as well as lower nitrogen oxide (NOx) emissions. CLEANOx® is a proven NOx emission 

reduction additive. EPA representatives noted that it appeared that the palladium-based 

combustion promoters significantly reduced NOx emissions compared to platinum-based 

combustion promoters, but available data did not seem to indicate that straight NOx catalyst 

additives were that effective in further reducing NOx emissions. BASF representatives did note 

that the effectiveness of CLEANOx® is dependent on site-specific parameters, but that 

reductions on the order of 20-30 percent were achievable. 

BASF representatives then provided a summary of the tests they have conducted on 

FCCU catalyst additive impacts on nitrogen compounds, particularly HCN. BASF designed a 

“lambda sweep” lab scale testing apparatus that uses a fixed bed of FCCU catalyst and varies the 

gas phase concentration in order to assess the reaction chemistry as FCCU catalyst goes from 

reductive atmosphere to an oxidative atmosphere (see Attachment 1). A typical experiment 

starts with high CO levels in the sweep gas (reductive atmosphere; lambda (λ) less than 1) then 

gradually increases the oxygen in the sweep gas until there is excess oxygen in the catalyst 

reaction chamber (oxidative atmosphere; λ greater than 1). At stoichiometric amounts of 

oxygen, λ equals 1. The lambda sweep can be performed with various concentrations of water 

(steam), HCN, ammonia (NH3), or nitric oxide (NO) in the sweep gas. All experiments were 

conducted at 704 degrees Celsius (°C) (1,300 degrees Fahrenheit (°F)), a typical complete 

combustion FCCU regenerator operating temperature. Four different catalyst additives were 

tested for each sweep gas scenario: 

1) platinum on alumina oxide (Pt/Al2O3), a traditional platinum-based combustion 

promoter; 

2) palladium on alumina oxide (Pd/Al2O3); 

3) palladium and metal oxide mixture on alumina oxide (Pd/MOx/Al2O3); and 

4) palladium, copper oxide, and metal oxide mixture on alumina oxide 

(Pd/CuO/MOx/Al2O3). 

A series of experiments was performed with different nitrogen species (HCN, NH3 and 

NO) fed to the reactor and the concentration of these nitrogen species were measured leaving the 

reactor. Any nitrogen loss through the reactor was assumed to be converted to nitrogen because 

elemental nitrogen is not detected by the analyzer (which uses Fourier transform infrared 

spectroscopy (FTIR)). In general, steam in the sweep gas reduces the activity of the catalyst. 

HCN is expected to be produced as a result of nitrogen in the coke. When HCN was fed into the 

system as the primary nitrogen species, the metal oxide and copper/metal oxide catalyst 

formulations showed lower HCN outlet concentrations than the platinum or palladium (only) 

catalysts, suggesting that the metal oxides or copper/metal oxide formulations were more 

effective in catalyzing the conversion of HCN to other nitrogen species, which are then more 

easily converted to elemental nitrogen. As such, the newer combustion promoters (which use 
3

metal oxides or copper/metal oxides in addition to palladium) should help to lower HCN 

concentrations compared to traditional platinum-based combustion promoters. The EPA asked if 

they had done similar studies at different temperatures. BASF responded that they had not done 

similar experiments at lower temperature, but they acknowledged that there were often 

temperature variations within the FCCU. 

The experiments with catalyst in the reaction chamber were expected to model the “dense 

phase” of the FCCU regenerator. BASF also ran similar experiments with no catalyst in the 

reaction chamber to simulate the dilute phase of the FCCU regenerator. In these experiments, 

they attempted to simulate coke burn-off. At high CO/CO2 levels, a majority of the HCN in the 

sweep gas remained in the off gas. At lower CO/CO2 ratios (presumably higher oxygen feed), 

the HCN concentrations leaving the reaction (or combustion) chamber were lower than when 

there were high CO/CO2 ratios, but they were still much higher than when there was catalyst in 

the reaction chamber. According to BASF representatives, this suggests that any HCN that exits 

the dense phase and enters the dilute phase in the regenerator has a very good chance of being 

emitted as HCN. 

The EPA representatives thanked the BASF representatives for coming to talk and share 

the results of their testing. The EPA representatives requested a copy of the presentation 

material. BASF representatives said they would review the presentation to make sure there was 

no proprietary information and would send the EPA a copy of the presentation once it is cleared 

by BASF. 
Attachment 1 

Understanding the chemistry of NOx reduction in the FCC regenerator 

by lambda sweep test 

Qi Fu, David M. Stockwell 
Understanding the chemistry of NOx reduction in the FCC regenerator 

by lambda sweep test 

Qi Fu*, David M. Stockwell 

25 Middlesex Essex-Turnpike, Iselin, NJ 08830 (USA)

*qi.fu@basf.com 

Introduction 

NOx emissions from the fluid catalytic cracking units (FCCU) are being limited by 

regulatory agencies to an increasing degree. NOx is formed in the FCCU regenerator, where 

coke is burned off to provide process heat and rejuvenate the catalyst. Typical levels of NOx in 

the flue gas from fluid catalytic cracking regeneration units vary between 50 and 150 ppm, depending upon feed nitrogen content and regenerator conditions. Use of low NOx CO 

oxidation promoter is a simple, cost-effective way in existing FCC units to promote coke combustion and reduce CO and NOx emission, without significant modifications in the

regenerator design or the unit operating conditions. 

In order to develop better low NOx CO promoter, it is essential to understand the 

chemistry of NOx formation in the FCC regenerator. Pathways for conversion of nitrogencontaining species proposed earlier [1-2] include formation of N2 via NO+CO, NO+coke, 

NO+reduced ceria OSC, and NH3-SCR, once NOx is formed, as well as oxidation of HCN and 

NH3. However, during coke-burn experiments, a rather complex reaction network is involved 

which does not lend itself towards dissection of these individual pathways. In this paper, we study the discrete NOx reaction pathways by the lambda sweep test method [3] to learn which 

are most relevant under realistic FCCU conditions for different types of CO oxidation 

promoters. 

Materials and Methods 

Four CO oxidation promoters, Pt/Al2O3, Pd/Al2O3, Pd/CeOx/Al2O3 and 

Pd/CuO/CeOx/Al2O3 were prepared by wet impregnation of appropriate salt solutions on Al2O3

microspheres (95 m

2

•g-1, 0.50 ml g-1 water pore volume), followed by calcination 2 h at 650 

°C. The loading of precious metal is 500 ppm. We have learned FCC catalyst has activity for 

HCN hydrolysis and can improve the selectivity of N

H3 oxidation to N2. To avoid the 

interference of FCC catalyst and overheating of the CO promoters, an inert kaolin microsphere was used both as a control and as a diluent, and this material had been steamed at 816 °C for 4 

hours in 100% steam. CO promoters were tested fresh by blending with this previously steamed material. The performance testing was done using the proprietary lambda sweep test method [3]. Down stream gas analysis was done by FTIR with N2 yield determined by material 

balance. The dose of CO promoter was adjusted to match CO conversion activity, which is 

reported as an overall lean CO2/CO by using the yields of CO2 and CO obtained when the feed 

was λ>1. 

Results and Discussion  It has been found that HCN is the primary nitrogen-containing product formed from FCC coke combustion [3-4]. To understand how HCN and NH3 are converted to NOx/N2, we 

fed HCN, NH3, and NOx individually as well as the various combinations with or without 

steam to probe the pathways of the oxidation of HCN, the hydrolysis of HCN to NH3, the 

selective oxidation of NH3, and the reduction of NO to N2 by 

of the catalysts. The concentration of co-fed gases CO2, CO, S

and exponentially, but the total flow rate of these mixturefluidization and mass transfer constant. We have found that hydrolysis to NH3 so not all HCN is hydrolyzed to NH3, but c

the lean region, NO cannot be reduced by either CO or cok

Addition of CuO reduces NOx yield by improving selectivity o

of CeO2 lowers NOx yield by improving selectivity of NH3 ox

reduction by NH3. 

0%

20%40%60%80%

100%

0.1 

NOx yield, %

Pt/Al2O3 Pd/

Rich 

0%

20%40%60%80%

100%

0.1 

NOx yield, %

Pt/Al2O3 Pd

Rich 

0%

20%40%60%80%

100%

0.1 1 10 100

lambda of feed = 2*[O2]/[CO]

NOx yield, %

Pt/Al2O3 Pd/Al2O3 Pd/CeOx/Al2O3 Pd/CuO/CeOx/Al2O3

Rich Lean

0%

20%40%60%80%

100%

0.1 1 10 100

lambda of Feed = 2*[O2]/[CO]

NOx yield, %

Pt/Al2O3 Pd/Al2O3 Pd/CeOx/Al2O3 Pd/CuO/CeOx/Al2O3

Rich Lean

+ CO

NO

X

N2

HCN

NOx/N2

HCN

Basic site

+ H2O NH3

HCN

NOx/N2

HCN

Basic site

+ H2O NH3

Figure 1 NOx selectivity with various N-species in the feed a) 

only; d) NH3 and NO. 

Significance The often-proposed NO-CO and NO-coke pathways are 

Instead, NOx is reduced by reacting with NH3 via SCR r

hydrolyze HCN to NH3 and/or selectively oxidize NH3 to N2. 

References 1. Zhao, X., Peters, A. W., and Weatherbee, G. W., Ind. En

2. Stevenson, S., Socha, R., and Mathias, M., Ind. Eng. Che

3. Stockwell, D. M., Stud. Surf. Sci. Catal. (Fluid Catalytic 

Ed.), 2007, 166, 79; US Pat. Appl. 2007/0166826 

4. Houser, T. J., Hull, M., Alway, R. M. and Biftu, T., Int. J