Regulation of Dioxins in Combustion Processes Melissa Dettmann CBE 555 March 15, 2010

What are Dioxins? In total, 75 and 135 congeners of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) respectively Only 10 PCDFs and 7 PCDDs are “toxic” Nomenclature: 2,3,7,8-TCDD = 2,3,7,8-Tetrachlorinated dibenzo-p-dioxin

Health effects of dioxins (at levels of μg kg -1 ) Cause a fatal wasting disease in animals (die within 2-6 weeks) Damages to thymus gland (causes changes in cell immunity), liver, kidney, and digestive tract Miscarriage, sterility, birth defects Cancer, most potent cancer promoter known, some evidence of tumor initiation Chloracne (persistent skin eruptions)

Dioxins and the Aryl hydrocarbon (AH) Receptor AH receptor binds to contaminants, stimulates production of cytochrome P-450 enzymes to de- toxify the body 2,3,7,8-TCDD binds extremely tightly to the Ah receptor, causing continuous production of P- 450 enzymes that degrade other chemicals –Intermediates are frequently mutagens Activates genes that regulate the growth and division of cells

Toxicity of dioxins Travis and Nixon (1992), “2,3,7,8-TCDD, the most potent chemical toxin ever evaluated by the EPA” –One millionth of one gram will kill a guinea pig Estimates: –EPA’s virtually safe dose: pg TEQ kg -1 day -1 –WHO’s Tolerable Daily Intake: 10 pg TEQ kg -1 day -1 –Average U.S. daily intake: 1.8 pg TEQ kg -1 day -1 Inclusion of dioxin on 2006 EPA MSAT list dioxins and furans tetrachlorodibenzofuran tetrachlorodibenzo-p-dioxin pentachlorodibenzofuran pentachlorodibenzo-p-dioxin hexachlorodibenzo-p-dioxin hexachlorodibenzofuran heptachlorodibenzofuran heptachlorodibenzo-p-dioxin octachlorodibenzofuran octachlorodibenzo-p-dioxin 1,2,3,4,7,8-hexachlorodibenzofuran 1,2,3,6,7,8-hexachlorodibenzofuran 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin 1,2,3,4,6,7,8-heptachlorodibenzofuran 1,2,3,4,7,8,9-heptachlorodibenzofuran 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin 1,2,3,4,7,8-hexachlorodibenzofuran 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin 1,2,3,7,8,9-hexachlorodibenzo-p-dioxin 1,2,3,7,8,9-hexachlorodibenzofuran 1,2,3,7,8-pentachlorodibenzo-p-dioxin 1,2,3,7,8-pentachlorodibenzofuran 2,3,4,6,7,8-hexachlorodibenzofuran 2,3,4,7,8-pentachlorodibenzofuran 2,3,7,8-tetrachlorodibenzofuran 2,3,7,8-tetrachlorodibenzo-p-dioxin 2,3,4,6,7,8-hexachlorodibenzofuran

Dioxins in the Food Chain

Quantifying the Toxicity Toxic Equivalent Factor (TEF): weighing factors for dioxin compounds

Formation Mechanisms

Role of catalyst in precursor formation

Inventory of Dioxin Emissions- 1985

Inventory of Dioxin Emissions- 1997

Inventory of Dioxin Emissions- 2000

Consideration 1: Regulations for some industries have proven to be effective

Consideration 2: Relatively few methods exist for measuring dioxins from industrial sources Method TO-9A (ambient air) Method 0023A (industrial stacks)

Consideration 3: How to interpret the results of the tests How to handle non-detection? EPA detection limit is 50 pg!!! Pg/bhp-hr vs. pg/m 3

Case study: Diesel Engines Questions: –1. Should dioxins be regulated in diesel engine emissions? –2. What is the effect of a Copper Zeolite SCR have on dioxin formation?

The case against copper Copper has been shown to catalyze PCDD/F formation Studies by Heeb et al. showed that copper “induced intense PCDD/F formation”

Rebuttal PCDD/Fs formation and destruction are equilibrium process –Some studies have actually seen a reduction in PCDD/F emissions in the presence of copper Criticisms of Heeb’s study –Used copper fuel additives, NOT copper zeolite SCR –Unrealistically high levels of chlorine doping = 100 ppm

Why the need for Selective Catalytic Reduction (SCR)? EPA has issued increasingly stringent NOx and PM regulations for diesel engines SCR = aftertreatment component that catalyzes the decomposition of NOx 2010, Tier 4 EPA regulations are “aftertreatment-forcing”

Typical 2010 Architecture 4 NH NO + O 2  4 N H 2 O (1) 4 NH NO + 2 NO 2  4 N H 2 O (2)

Advantages of Copper zeolite

Arguments against PCDD/F Formation in Copper Zeolite SCRs Size-exclusion argument Destructive pathways –Presence of NH 3, SO 2

Dioxin formation conditions: Industrial Incinerators

Dioxin formation conditions: Diesel engine with fuel additives

Dioxin formation conditions: Diesel engine with copper zeolite SCR

Recent Comparisons of TEQ Emissions (linear scale)

Recent Comparisons of TEQ Emissions (logarithmic scale)

References Travis, C. C.; Nixon, A.G. Human exposure to dioxin. The Royal Society of Chemistry EPA. Final rule: Control of hazardous air pollutants from mobile sources. EPA-420-F Harrison, N. Ch. 8: Environmental organic contaminants in food. Food Chemical Safety, Vol. 1. Foods Standards Agency. EPA. An inventory of sources and environmental releases of dioxin-like compounds in the United States for the years 1987, 1995, and , EPA/600/P-03/002F Mayer, A.; Heeb, N.; Czerwinski, J.; Wyser, M. Secondary emissions from catalytic active particle filter systems. SAE, 2003, Stanmore, B.R. The formation of dioxins in combustion systems. Combust. Flame 2004, 136, Altarawneh, M.; Dlugorgorski, B. Z.; Kennedy, E.M.; Mackie, J.C. Mechanisms for formation, chlorination, dechlorination and destruction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Prog. Energy Combust. Sci. 2009, 35, Lomnicki, S.; Dellinger, B. Formation of PCDD/F from the pyrolysis of 2-chlorophenol on the surface of dispersed copper oxide particles. Proc. Combust. Inst. 2002, 29, Lomnicki, S.; Dellinger, B. A Detailed Mechanism of the Surface-Mediated Formation of PCDD/F from the oxidation of 2-chlorophenol on a CuO/Silica Surface. J. Phys. Chem. A. 2003, 107, EPA. Method 0023A: Sampling method for polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofuran emissions from stationary sources Coordinating Research Council. Phase 1 of the Advanced Collaborative Emissions Study, Ura, J. A., Girard, J., Cavataio, G., Montreuil, C., Lambert, C. (2009). Cold start performance and enhanced thermal durability of vanadium SCR catalysts, SAE Paper Heeb, N.V., Ulrich, A., Emmenegger, L., Czerwinski, J., Mayer, A., Wyser, M. (2005). Secondary emissions risk assessment of diesel particulate traps for heavy duty applications, SAE Paper SIAT 2005-ABS-165. EPA (1999). Compendium Method TO-9A: Determination of Polychlorinated, Polybrominated, and Brominated/ Chlorinated Dibenzo-p-Dioxins and Dibenzofurans in Ambient Air. Excerpt from the Comendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air. EPA 1625/R-96/010b. Liu, Z.G., Swor, T.A., Schauer, J.J., Debilzen, J.A., Severance, C.L. (2008). A source dilution sampling system for characterization of engine emissions under transient or steady-state operation, Aerosol Science and Technology 42 (4), pp

EPA Regulations