EXHIBITS TO DECLARATION OF STANLEY ROTH, PH.D. UNDER 37 C.F.R. § 1.132
`
`Contents lists available at ScienceDirect
`
`journal of Catalysis
`
`journal homepage: www.elsevier.com/locate/jcat
`
`Priority Communication
`Excellent activity and selectivity of Cu-SSZ-13 in the selective catalytic reduction
`of NOx with NH3
`]a Hun Kwak, Russell G. Tonkyn, Do Heui Kim, Janos Szanyi, Charles H.F. Peden*
`
`Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, Richland, WA 99354, United States
`
`ARTICLE INFO
`
`A B S T R A C T
`
`Superior activity and selectivity of a Cu ion-exchanged SSZ-13 zeolite in the selective catalytic reduction
`(SCR) of NOx with NH 3 were observed, in comparison with Cu-beta and Cu-ZSM-5 zeolites. Cu-SSZ-13 was
`not only more active in the NOx SCR reaction over the entire temperature range studied (up to 550 °C),
`but also more selective toward nitrogen formation, resulting in significantly lower amounts of NOx by(cid:173)
`products (i.e., N02 and N20) than the other two zeolites. In addition, Cu-SSZ-13 demonstrated the highest
`activity and N2 formation selectivity in the oxidation of NH 3 . The results of this study strongly suggest
`that Cu-SSZ-13 is a promising candidate as a catalyst for NOx SCR with great potential in after-treatment
`systems for either mobile or stationary sources.
`
`© 2010 Elsevier Inc. All rights reserved.
`
`Article history:
`Received 15 June 2010
`Revised 30 July 2010
`Accepted 30 July 2010
`Available online 15 September 2010
`
`Keywords:
`Cu-SSZ-13
`Zeolites
`Ammonia SCR
`N2 selectivity
`
`1. Introduction
`
`The abatement of environmentally harmful NOx compounds
`(NO, N0 2 , and N2 0) emitted from mobile or stationary power
`sources remains a challenging task for the catalysis community.
`In particular, conventional three-way catalysts used in the exhaust
`after treatment technologies of internal combustion engines prove
`ineffective when the engine is operated under highly oxidizing
`conditions (to achieve better fuel efficiency). The problem is daunt(cid:173)
`ing, since reduction chemistry (NOx to N2 ) has to be carried out un(cid:173)
`der highly oxidizing conditions. Several approaches have been
`proposed for lean-NOx abatement, each of them with its own spe(cid:173)
`cific sets of problems. The two technologies that seem to have clear
`advantages among the processes proposed are the selective cata(cid:173)
`lytic reduction either with hydrocarbons (HC-SCR) or with ammo(cid:173)
`nia (NHrSCR), and lean-NOx traps (LNT). For the NHrSCR
`technology, transition metal (in particular Fe and Cu) ion-ex(cid:173)
`changed zeolite catalysts have shown high activity and N2
`selectivity.
`The most extensive studies have been carried out on Cu2+ ion(cid:173)
`exchanged ZSM-5 (Cu-ZSM-5) zeolites, first shown to exhibit high
`NO decomposition rates and NOx SCR activities in the 1980s i .l --7].
`More recently, Cu2
`+ -exchanged beta zeolite (Cu-beta) has been
`shown to have excellent activity in the SCR of NOx with NH 3 , and
`metal-exchanged beta zeolites are generally found to have greater
`hydrothermal stability than similar ZSM-5 catalysts [8]. In the very
`recent patent literature, Cu2 + ion-exchanged SSZ-13 ( Cu-SSZ-13)
`
`* Corresponding author_ Fax: + 1 509 3 76 283 7.
`E-mail address: chuckpeden@pnLgov (CH_f_ Peden).
`
`0021-9517 /$ - see front matter© 2010 Elsevier Inc All rights reserved.
`doi:10.101 G/j .jcdt.2010.07.031
`
`has been reported to exhibit NOx conversions of 90-100% over a
`wide temperature range in the NHrSCR process, and its activity
`exceeded 80% even after extensive high-temperature hydrother(cid:173)
`mal aging [9]. The SSZ-13 zeolite has chabazite (CHA) structure
`with a relatively small pore radius (~3.8 A) in an eight-membered
`ring [10]. The enhanced thermal stability of the Cu-SSZ-13 catalyst
`has been attributed to the location of copper ions within the cage;
`i.e., just outside the six-membered rings of the zeolite framework,
`as evidenced by XRD analysis I 11 ]. Although, high catalytic activity
`has been reported in the patent literature for the Cu-SSZ-13 cata(cid:173)
`lyst under a specific set of reaction conditions, no comparisons
`have been made with other, widely studied NHrSCR catalysts
`(i.e., Cu-ZSM-5 and Cu-beta) under the same reaction conditions.
`Here, we report on the performance of a Cu-SSZ-13 catalyst in
`the SCR of NOx with NH3 , particularly focusing on the activity
`and N2 selectivity in comparison with those of Cu-beta and Cu(cid:173)
`ZSM-5. We also compare the NH 3 oxidation activities/selectivities
`of these catalysts under highly oxidizing conditions. Our results
`confirm that the activity and selectivity of the Cu-SSZ-13 catalyst
`for both NOx SCR with NH 3 and NH3 oxidation are superior to those
`of both Cu-beta and Cu-ZSM-5.
`
`2. Experimental
`
`The SSZ-13 zeolite was synthesized using the methods recently
`published by Fickel and Lobo [11 I. reported to give a material with
`a Si/Al2 ratio of~ 12. The structure-directing agent used in the syn(cid:173)
`thesis, N,N,N-trimethyl-1-adamantanamine iodide, was synthe(cid:173)
`sized using the procedure reported by Zones [ 10]. After synthesis,
`
`Exhibit 2014.001
`
`

`
`188
`
`j.H. Kwak et al./joumal of Catalysis 275 (2010) 187-190
`
`EXHIBITS TO DECLARATION OF STANLEY ROTH, PH.D. UNDER 37 C.F.R. § 1.132
`
`the SSZ-13 was calcined at 550 °C for 5 h in air before ion exchange
`in order to remove the zeolite framework structure-directing
`agent. Copper ions were exchanged into the zeolite in an aqueous
`ion-exchange process, using 0.1 M Cu(N03 )2 solutions; solution
`volumes were such that they contained twice the amount of Cu2+
`needed for complete ion exchange. After ion exchange over 1 day
`at room temperature, the catalysts were filtered, thoroughly
`washed with distilled water, and dried overnight at 100 °C. To
`ensure complete ion exchange, this process was carried out a sec(cid:173)
`ond time with an aqueous solution of Cu2+ of the same initial con(cid:173)
`centration. The dried catalysts were pre-calcined at 500 °C in
`laboratory air for 2 h before reaction tests. The CHA structure in
`Cu-SSZ-13 was confirmed with XRD measurement.
`For comparison purposes, Cu2+-exchanged ZSM-5 and beta zeo(cid:173)
`lites were prepared from commercially available zeolites (ZSM-5
`(CBV-3024, Si/Ah= 30) and beta (CP-814(, Si/Ah= 38), both from
`Zeolyst International Co.), using the same ion-exchange and calci(cid:173)
`nation procedures applied to the preparation of the Cu-SSZ-13
`sample, except for varying the Cu2+ concentration of the solution
`to match the Si/Al2 ratios of the particular zeolite.
`The NOx SCR activities were measured in a flow-through pow(cid:173)
`der reactor system using gas mixtures containing 350 ppm NO,
`350 ppm NH3 , 14% 0 2, and 2% H20 with a balance of N2. The total
`flow rate was held at 300 seem over the 120-130 mg catalyst pow(cid:173)
`
`der samples (SV ~ 30,000 h- 1 ). The temperature was varied from
`550 to 160 °C in approximately 50 °C steps, as measured by a small
`type K thermocouple inserted directly into the center of the cata(cid:173)
`lyst powder bed. The NH 3 oxidation reaction was carried out under
`similar reaction conditions in the absence of NO in the gas mixture.
`The reactant and product gas mixtures (NO, N02, N20, and NH3 )
`were analyzed using FTIR spectroscopy (Nicolet Magma 760 with
`OMNIC Series software) in a heated, 2-m path-length gas cell.
`Our reported NOx conversions (%) are defined as {NOiniet - (NO+
`N02 + 2 * NzO)outlet/NOinietl * 100.
`
`3. Results and discussion
`
`NOx conversions as a function of reaction temperatures be(cid:173)
`tween 150 and 550 °C are shown in fig. 1 over the three Cu-zeo(cid:173)
`lites studied. Both Cu-ZSM-5 and Cu-SSZ-13 catalysts exhibit
`maximum conversion (>95%) at temperatures somewhat above
`
`80
`
`~
`5 60
`'iii
`~
`8 40
`~ z
`
`250 °C, while the maximum conversion over Cu-beta in the same
`temperature range is slightly lower (90%). Note that the Cu-SSZ-
`13 catalyst maintains its high conversion (>90%) up to 500 °C,
`while the NOx conversion of Cu-ZSM-5 begins to decline above
`300 °C. Even at 550 °C, the highest temperature of this study, Cu(cid:173)
`SSZ-13 exhibits a respectably high conversion of 83%. The order
`of activity of these catalysts in the high-temperature region
`(350-550 °C) is as follows: Cu-SSZ-13 > Cu-ZSM-5 >Cu-beta.
`In addition to NOx conversion, significant differences in product
`selectivity were observed for the three zeolite catalysts studied.
`Fig. 2 displays the amounts of by-products N02 (a) and N20 (b)
`formed in the SCR reaction. At reaction temperatures above
`300 °C, Cu-ZSM-5 and Cu-beta produce significant amounts of
`N02, and at 500 °C the amounts of N02 produced over these two
`catalysts are 30 and 25 ppm, respectively, much higher than the
`<10 ppm measured over the Cu-SSZ-13. N20 formation profiles as
`a function of reaction temperature, shown in Fig. 2b, also exhibit
`large differences among the three Cu ion-exchanged zeolite cata(cid:173)
`lysts. The N20 level over the Cu-SSZ-13 is very low ( <5 ppm) over
`the entire temperature range studied, while the Cu-beta catalyst
`shows a double maxima in N20 concentrations at low and high
`
`a 4o-r-~~~~~~~~~~~~~~~
`Cu-Z5M-5 ~
`()
`i~s.s--,b~·~a
`Z\~ ... ~$:~ .. ,l~~ t:J
`
`'E 30
`D. .e
`c
`0
`-~ 20
`E ...
`.2
`0 z 10
`
`600
`
`500
`400
`300
`200
`Reaction temperature (0 C)
`b 40~----------~
`Cu-Z5M-5 ~
`~).~---b~t:..~ ()
`{;_~.,ss.s.-:-· 1~~ L:1
`
`30
`
`-
`E
`D. .e
`c
`0 -:g 20
`E ...
`.2
`q.
`z 10
`
`20
`
`8 Cu-ZSM-5
`t:~~ .. ·b~3ta
`•"'>
`\.,.}
`f""~
`~).~ .. §~~~ ,.. '3_~$
`~ ..... ,,,,.,:.
`O+-~.-----.-~""T""~-r---,~---.-~-.-~,----.~-1
`200
`300
`400
`500
`600
`100
`Reaction temperature (°C)
`
`Fig. 1. NOx conversion profiles for Cu-SSZ-13 (squares), Cu-beta (circles), and Cu(cid:173)
`ZSM-5 (triangles) at various temperatures in a gas mixture containing 350 ppm NO,
`350 ppm NH3 , 14% o,. and 2% H20 with a balance of N2•
`
`O+---,.--~~~~.-----.-~-.-~.-----.-~-r---t
`400
`100
`300
`200
`500
`600
`Reaction temperature {°C)
`
`Fig. 2. N0 2 (a) and N20 (b) formation profiles during NH3 SCR on Cu-SSZ-13
`(squares), Cu-beta (circles), and Cu-ZSM-5 (triangles) at various temperatures in a
`gas mixture containing 350 ppm NO, 350 ppm NH3 , 14% o,. and 2% H20 with a
`balance of N2.
`
`Exhibit 2014.002
`
`

`
`EXHIBITS TO DECLARATION OF STANLEY ROTH, PH.D. UNDER 37 C.F.R. § 1.132
`
`j.H. Kwak et al./joumal of Catalysis 275 (2010) 187-190
`
`189
`
`a 100
`
`80
`
`~
`'iii .. cu
`c 60
`0
`> c
`0 40
`u ...
`::c z
`
`zo
`
`fl. Cu-ZSM-5
`
`0
`100
`
`600
`
`400
`200
`500
`300
`Reaction temperature (0 C)
`b 60,....-~~~~~~~~~~~~--,
`Cu-ZSM-5 fl.
`E' 1:1.
`..!?; 50
`c
`0
`~ 40
`
`E .. .E
`
`0 30
`
`
`O{
`
`20
`
`~
`~ 10
`0 z
`
`O+---,~~Vi-..r-~~~~~~~~~~---1
`100
`200
`300
`400
`500
`600
`Reaction temperature (°C)
`
`Fig. 3. (a) NH3 conversion profiles and (b) NOx product distributions during the NH3
`oxidation reaction on Cu-SSZ-13 (squares), Cu-beta (circles), and Cu-ZSM-5
`(triangles) at various temperatures in a gas mixture containing 350 ppm NH3 ,
`14% 0 2 , and 2% H20 with a balance of N2.
`
`4. Conclusions
`
`Under the same reaction conditions for NOx SCR with NH 3 ,
`formation
`Cu-SSZ-13 demonstrates superior activity and N2
`selectivity in comparison with Cu-beta and Cu-ZSM-5 zeolites.
`We find that Cu-SSZ-13 is more active for N Ox conversion over
`the entire temperature range studied (160-550 °C). Moreover,
`the Cu-SSZ-13 is also more selective toward the formation of
`N2 , producing lower amounts of undesired by-products such
`as N0 2 and N20. Our results also demonstrate that Cu-SSZ-13
`has superior performance for NH 3 oxidation (lower light-off
`temperature) than Cu-beta and Cu-ZSM-5 zeolites, while also
`producing significantly lower amounts of (over-oxidized) NOx
`species. These results suggest that Cu-SSZ-13 is an excellent
`candidate catalyst for use in practical NH 3 SCR of NOx and/or
`NH3 oxidation applications (the after-treatment systems of var(cid:173)
`ious mobile or stationary sources). Detailed mechanistic studies
`are currently under way in our laboratory to understand the
`origin of the different activities and selectivities observed for
`these three catalysts in both the NOx SCR and NH 3 oxidation
`reactions.
`
`temperatures; i.e., 27 ppm at 200 °C and 24 ppm at 450 °C, respec(cid:173)
`tively. The Cu-ZSM-5 catalyst produced a similar N20 formation
`profile to Cu-beta, but the amounts of N20 formed were much
`smaller. These N2 0 formation profiles are likely related to the reac(cid:173)
`tion mechanisms of the NOx reduction reactions. For example, our
`results demonstrate that reaction intermediates (e.g., NOx-NH3 ad(cid:173)
`sorbed complexes) on Cu-SSZ-13 take a more selective reaction
`route toward the production of N2 than do the complexes on the
`Cu-beta and Cu-ZSM-5 catalysts.
`The differences in activity and selectivity of the three zeolites
`studied may be related to fundamental differences in the known
`structures of these zeolites, i.e., the pore sizes and locations of
`the copper ions. The order of high-temperature NH 3 SCR reactivity
`discussed earlier is the inverse of the order in pore size, i.e., SSZ-13
`having the smallest pores ( ~4 A, 8-membered ring) being the most
`active, ZSM-5 with medium size pore opening (~5.5 A, 10-mem(cid:173)
`bered ring) having medium activity, and beta with the largest
`pores (~7 A and ~s.s A, 12-membered ring) having the lowest
`activity and N2 selectivity. For these three catalysts, the smaller
`size pores seem to be preferred for the desirable reaction path(cid:173)
`ways; however, detailed mechanistic studies need to be conducted
`to substantiate the correlation between pore size and activity/
`selectivity. In summary, both the activity and selectivity of NOx
`SCR with NH 3 for Cu-SSZ-13 are superior to those of Cu-ZSM-5
`and Cu-beta over the entire temperature range studied (up to
`550 °C).
`The differences observed in the ammonia SCR reactivities and
`N2 formation selectivities for the three catalysts studied may also
`be related (at least in part) to their abilities to oxidize ammonia.
`Therefore, we performed NH 3 oxidation reactions over the three
`different Cu-zeolite catalysts in the absence of NO and the results
`are presented in Fig. 3. Ammonia conversions (Fig. 3a) reveal that
`the light-off temperature for NH3 oxidation is the lowest for Cu(cid:173)
`SSZ-13, indicating its superior intrinsic NH3 oxidation ability. For
`this catalyst, the NH3 oxidation reaction lights off at around
`200 °C and reaches a conversion level of more than 90% at
`~300 °C. The NH 3 conversion profiles for Cu-beta and Cu-ZSM-5
`are shifted to higher temperatures by ~so and ~ 100 °C, respec(cid:173)
`tively, relative to that of Cu-SSZ-13.
`The concentrations of NOx (NO+ N02 + N2 0) in the reaction
`effluent, which are regarded as by-products during NH3 oxida(cid:173)
`tion to N2 , are plotted in Fig. 3b. The Cu-beta catalyst produced
`relatively higher levels of these by-products, with a maximum of
`about 55 ppm at 350 °C, while the Cu-ZSM-5 catalyst produced
`significant amounts of by-products at 550 °C. The relative lack
`of NOx formation during ammonia oxidation on the Cu-SSZ-13
`catalyst implies that most of the NH3 is converted to N2 over
`a wide temperature range for this catalyst. The near absence
`of further oxidization to N20, NO, or N0 2 , as was the case for
`the Cu-beta and Cu-ZSM-5 catalysts, suggests again that the
`environment within the Cu-SSZ-13 catalyst may provide opti(cid:173)
`mum conditions for selective conversion of reaction intermedi(cid:173)
`ates to Nz.
`According to the results of previous studies, noble metal cata(cid:173)
`lysts, including Pt [12], have been found to be very active in
`ammonia oxidation, but rather non-selective to N2 formation,
`while transition metal oxides such as Mn02 and CuO 113] have
`higher N2 selectivity, but require significantly higher tempera(cid:173)
`tures. Cu-SSZ-13, on the other hand, can meet the two important
`requirements: excellent NH3 oxidation activity and N2 selectivity
`over a wide temperature range. Thus, for example, the use of Cu(cid:173)
`SSZ-13 as an NH 3 oxidation catalyst at the downstream end of a
`NOx SCR with NH3 unit might provide flexibility for controlling
`the dose of urea introduced before the SCR catalyst, since any ex(cid:173)
`cess of NH 3 can perhaps be removed more easily over the catalyst
`bed.
`
`Exhibit 2014.003
`
`

`
`EXHIBITS TO DECLARATION OF STANLEY ROTH, PH.D. UNDER 37 C.F.R. § 1.132
`
`190
`
`j.H. Kwak et al./joumal of Catalysis 275 (2010) 187-190
`
`Acknowledgments
`
`Financial support was provided by the US Department of Energy
`(DOE), Office of FreedomCar and Vehicle Technologies. Portions of
`this work were performed in the Environmental Molecular
`Sciences Laboratory (EMSL) at Pacific Northwest National Labora(cid:173)
`tory (PNNL). The EMSL is a national scientific user facility and sup(cid:173)
`ported by the US DOE, Office of Biological and Environmental
`Research. PNNL is a multi-program national laboratory operated
`for the US Department of Energy by Batte lie Memorial Institute un(cid:173)
`der Contract DE-AC06-76RLO 1830.
`
`References
`
`[1] M. Iwamoto, H. Furukawa, Y. Mine, F. Uemura, S. Mikuriya, S. Kagawa, j. Chem.
`Soc. Chem. Commun. (1986) 1272.
`
`[2] M. Iwamoto, H. Yahiro, Y. Torikai, T. Yoshioka, N. Mizuno, Chem. Lett. 19 (1990)
`1967.
`[3] j.Y. Yan, G.D. Lei, W.M.H. Sachtler, H.H. Kung, J. Cata!. 161 (1996) 43.
`[4] R.Q. Long, R.T. Yang, j. Am. Chem. Soc. 121 (1999) 5595.
`[5] A. Grossale, I. Nova, E. Tronconi, D. Chatterjee, M. Weibel, j. Cata!. 256 (2008)
`312.
`[6] K. Rahkamaa-Tolonen, T. Maunula, M. Lomma, M. Huuhtanen, R.L. Keiski, Cata!.
`Today 100 (2005) 217.
`[7] T. Komatsu, M. Nunokawa, LS. Moon, T. Takahara, S. Namba, T. Yashima, j.
`Cata!. 148 (1994) 427.
`[8] S. Brandenberger, 0. Krocher, A. Tissler, R. Althoff, Cata!. Rev. - Sci. Eng. 50
`(2008) 492.
`[9] I. Bull, W.-M. Xue, P. Burk, R.S. Boorse, W.M. jaglowski, G.S. Koermer, A. Moini,
`j.A. Patchett, J.C. Dettling, M.T. Caudle, US Patent 7,610,662, 2009.
`[10] S.I. Zones, US Patent 4,544,538, 1985.
`[11] D.W. Fickel, R.F. Lobo,]. Phys. Chem. C 114(2010)1633.
`[12] j.J. Ostermaier, j.R. Katzer, W.H. Manogue, j. Cata!. 41 (1976) 277.
`[13] A. Wollner, F. Lange, H. Schmelz, H. Knozinger, Appl. Cata!. A 94 (1993)
`181.
`
`Exhibit 2014.004