2008 Spring Symposium

 
Charles H.F. Peden, Ja Hun Kwak, Jian Zhi Hu, Do Heui Kim, and János Szanyi
Insti­tute for Inter­fa­cial Catal­y­sis
Pacif­ic North­west Nation­al Lab­o­ra­to­ry
Rich­land, Wash­ing­ton 99352, USA

Abstract — γ-alu­mi­na, one of the metastable ‘tran­si­tion’ alu­mi­na struc­tur­al poly­morphs, is an impor­tant cat­alyt­ic mate­r­i­al both as an active phase and as a sup­port for oth­er cat­alyt­i­cal­ly active phas­es. As such, the bulk and sur­face struc­ture of γ-alu­mi­na, and its for­ma­tion and ther­mal sta­bil­i­ty con­tin­ue to be the sub­ject of a con­sid­er­able amount of research. How­ev­er, due to the low crys­tallini­ty and very fine par­ti­cle size of γ-alu­mi­na, it is very dif­fi­cult to apply well-estab­lished ana­lyt­i­cal tech­niques for deter­min­ing its sur­face struc­tures.

Of par­tic­u­lar impor­tance for under­stand­ing the cat­alyt­ic prop­er­ties of γ-alu­mi­na, relat­ing its sur­face struc­ture to the ori­gin of Lewis acid­i­ty has been of con­sid­er­able inter­est and has been stud­ied by sol­id state NMR and FTIR spec­tro­scopies, and most recent­ly by the­o­ret­i­cal cal­cu­la­tions. In this pre­sen­ta­tion, we report the first use of very high field (21.1T) NMR to iden­ti­fy and quan­ti­fy sur­face Al species thought to be respon­si­ble for impart­ing Lewis acid­i­ty to the γ-Al₂O₃ sur­face. In par­tic­u­lar, a peak in the NMR spec­trum at ~23 ppm with rel­a­tive­ly low inten­si­ty, can be assigned to 5-coor­di­nat­ed Al³⁺ ions, and can be clear­ly dis­tin­guished from the two oth­er peaks rep­re­sent­ing Al³⁺ ions in tetra-, and octa­he­dral coor­di­na­tion sites. Spin-lat­tice ²⁷Al relax­ation time mea­sure­ments clear­ly show that these pen­ta-coor­di­nat­ed Al³⁺ sites are locat­ed on the sur­face of the γ-alu­mi­na sup­port. Fur­ther­more, we report the first obser­va­tion of pref­er­en­tial anchor­ing of an impreg­nat­ed cat­alyt­ic phase onto these pen­ta­co­or­di­nat­ed Al³⁺ sites by not­ing that BaO and Pt depo­si­tion onto this γ-alu­mi­na sam­ple results in the loss of inten­si­ty of the 23 ppm peak lin­ear­ly pro­por­tion­al to the amount of cat­alyt­ic phase deposit­ed. Final­ly, our recent results also sug­gest an impor­tant role for these sites in deter­min­ing the ther­mal sta­bil­i­ty of the γ-Al₂O₃ phase dur­ing high tem­per­a­ture cal­ci­na­tion.

Speaker’s Biog­ra­phy — Dr. Peden is Inter­im Direc­tor of the Insti­tute for Inter­fa­cial Catal­y­sis at Pacif­ic North­west Nation­al Lab­o­ra­to­ry (PNNL). He is also a Lab­o­ra­to­ry Fel­low and man­ages 8 sci­en­tif­ic staff with­in the Chem­i­cal Sci­ences Divi­sion at PNNL. Dr. Peden’s main research inter­ests are in the sur­face and inter­fa­cial chem­istry of inor­gan­ic solids; in par­tic­u­lar, the het­ero­ge­neous cat­alyt­ic chem­istry of met­als and oxides (reac­tion mech­a­nisms, mate­ri­als).

2008 Spring Symposium

 
Ray­mond J. Gorte
Chem­i­cal & Bio­mol­e­c­u­lar Engi­neer­ing
Uni­ver­si­ty of Penn­syl­va­nia
Philadel­phia, PA

Abstract — Elec­trodes are being devel­oped for Sol­id Oxide Elec­trolyz­ers (SOE), espe­cial­lythose that could be used for Nat­ur­al-Gas Assist­ed Steam Elec­trol­y­sis (NGASE). NGASErequires elec­trodes that exhib­it sta­ble per­for­mance in dry methane, with lowover­po­ten­tials, and allow oper­a­tion at high tem­per­a­tures. A vari­ety of nov­el air and fuel­elec­trodes have been devel­oped and test­ed for SOE and NGASE devices.

In all cas­es, the­elec­trodes are made by addi­tion of the active, elec­trode com­po­nents into porous yttri­asta­bi­lizedzir­co­nia (YSZ) lay­ers that had been pre-sin­tered with the YSZ elec­trolyte. Air­elec­trodes based on Sr-doped LaFeO₃ (LSF) have been shown to exhib­it supe­ri­or­per­for­mance to more tra­di­tion­al LSM-based elec­trodes but can deac­ti­vate after long time­sor high tem­per­a­tures, appar­ent­ly due to sin­ter­ing of the LSF. Cu-based elec­trodes were­found to exhib­it poor ther­mal sta­bil­i­ty above 1073 K due to sin­ter­ing of Cu, but Cu-Coelec­trodes pre­pared by Co elec­trode­po­si­tion onto the Cu com­pos­ite had sig­nif­i­cant­ly­im­proved per­for­mance. It was shown that a Cu mono­lay­er forms at the Co sur­face after­heat­ing in H2 due to free-ener­gy con­sid­er­a­tions, so that the Cu-Co elec­trodes exhib­it thether­mal sta­bil­i­ty of Co and the chem­i­cal sta­bil­i­ty of Cu. Final­ly, a nov­el, all-ceram­ic­elec­trode was devel­oped for use in fuel envi­ron­ments. The ceram­ic elec­trode con­sists of athin func­tion­al lay­er opti­mized for cat­alyt­ic activ­i­ty with a thick­er con­duc­tion lay­er.

Speaker’s Biog­ra­phy — Dr. Gorte is the Rus­sell Pearce and Eliz­a­beth Crim­i­an Heuer Pro­fes­so­rof Chem­i­cal & Bio­mol­e­c­u­lar Engi­neer­ing, with a sec­ondary appoint­ment in Mate­ri­als­S­cience & Engi­neer­ing, at Uni­ver­si­ty of Penn­syl­va­nia. His cur­rent research inter­ests arein ceria-based cat­a­lysts and sol­id-oxide fuel cells.

2008 Spring Symposium

 
Andy Walk­er
HDD Glob­al Tech­nol­o­gy Direc­tor
John­son Matthey
Wayne, PA

Abstract — The role and require­ments of Diesel emis­sion con­trol sys­tems have changed­sub­stan­tial­ly since the intro­duc­tion of the ear­ly Diesel Oxi­da­tion Cat­a­lysts (DOC) tocon­trol car­bon monox­ide (CO) and hydro­car­bon (HC) emis­sions from light duty Die­selve­hi­cles. Since then, emis­sions leg­is­la­tion has tight­ened sig­nif­i­cant­ly around the world,driving the devel­op­ment and imple­men­ta­tion of com­plex sys­tems to con­trol emis­sions ofPar­tic­u­late Mat­ter (PM) and nitro­gen oxides (NOx), as well as CO and HC. This­p­re­sen­ta­tion pro­vides an overview of the sys­tems cur­rent­ly being used to meet today∍sDiesel leg­is­la­tion, and looks ahead to the cat­a­lyst sys­tems that will be used to meet­fu­ture, incom­ing reg­u­la­tions.

An overview will be giv­en of the require­ments and capa­bil­i­ties of the cur­rent­DOC plus Diesel Par­tic­u­late Fil­ter (DPF) sys­tems being used to con­trol CO, HC and PMe­mis­sions with very high effi­cien­cy. The chal­lenges that these sys­tems face, and the­ways in which these chal­lenges have been over­come will be out­lined. The futuredi­rec­tion of this tech­nol­o­gy will be dis­cussed.

Some of the main chal­lenges cur­rent­ly fac­ing the catalyst/engine com­mu­ni­tyre­late to the con­trol of NOx emis­sions from Diesel engines. Reduc­ing NOx (to nitrogen)under the high­ly oxi­diz­ing con­di­tions preva­lent in the Diesel exhaust is extreme­ly­chal­leng­ing, but two approach­es have already been suc­cess­ful­ly intro­duced into largescale series pro­duc­tion.

NOx Adsor­ber Cat­a­lysts (NAC) oper­ate by stor­ing NOx under oxi­diz­ing­con­di­tions, and then reduc­ing this NOx dur­ing the peri­od­ic, short-term reduc­ing eventscre­at­ed by run­ning the engine under fuel-rich con­di­tions. An overview of the oper­at­ing­prin­ci­ples, capa­bil­i­ties and future chal­lenges in the NAC area will be giv­en.

Selec­tive Cat­alyt­ic Reduc­tion (SCR) sys­tems oper­ate by using ammo­nia to react­s­e­lec­tive­ly with the NOx under oxi­diz­ing con­di­tions. SCR sys­tems are already in use onheavy duty Diesel vehi­cles in Europe, and are start­ing to be intro­duced into the NorthAmer­i­can mar­ket. The per­for­mance capa­bil­i­ties and future chal­lenges fac­ing SCR­cat­a­lyst tech­nol­o­gy will be dis­cussed. Some alter­na­tive NOx con­trol approach­es are alsobe­ing con­sid­ered, and a brief overview of the most promis­ing will be giv­en.

The increas­ing­ly strin­gent leg­is­la­tion requires simul­ta­ne­ous very high con­ver­sion­sof all four reg­u­lat­ed pol­lu­tants. This can be achieved by com­bin­ing DPF and NOx­con­trol sys­tems. The con­fig­u­ra­tions being used to pro­vide the nec­es­sary emis­sion­scon­trol are pre­sent­ed, and the future direc­tion of Diesel emis­sion con­trol will be dis­cussed.

Speaker’s Biog­ra­phy — Dr. Walk­er is Heavy Duty diesel Glob­al Tech­nol­o­gy Direc­tor at John­son Matthey, Emis­sion Con­trol Tech­nolo­gies. He is lead­ing the devel­op­ment of JM prod­ucts for the glob­al on-road and non-road HDD mar­kets.

2008 Spring Symposium

 
Mosha Zhao¹, D. Li², J. Gar­ra², D. A. Bon­nell², J. M. Vohs^1
1Depart­ment of Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing
²Depart­ment of Mate­ri­als Sci­ence and Engi­neer­ing
Uni­ver­si­ty of Penn­syl­va­nia
Philadel­phia, PA 19104

Abstract — The abil­i­ty to manip­u­late the ori­en­ta­tion of the dipoles in fer­ro­elec­tric ceram­ic­sh­olds promise as a method to tai­lor the sur­face reac­tiv­i­ty of these mate­ri­als for speci­f­i­cap­pli­ca­tions. While over the last 50 years mul­ti­ple stud­ies have sug­gest­ed that the ori­en­ta­tionof fer­ro­elec­tric domains may affect the ener­get­ics of adsorp­tion on fer­ro­elec­tric oxides,definitive evi­dence is still lack­ing. In this talk we will present the first unam­bigu­ousob­ser­va­tions of dif­fer­ences in the ener­get­ics of adsorp­tion on fer­ro­elec­tric domains forad­sorp­tion of methanol and ethanol on bar­i­um titanate. Domain-depen­dent stick­ing­co­ef­fi­cients are observed and indi­cate that the fer­ro­elec­tric ori­en­ta­tion alters the strength ofthe inter­ac­tion of adsorbed species with the sur­face. Addi­tion­al­ly, in ethanol TPD thedes­orp­tion peak shapes and the rel­a­tive prod­uct yields were found to be polar­iza­tion­de­pen­dent sug­gest­ing that fer­ro­elec­tric polar­iza­tion may also affect the intrin­sic reac­tiv­i­ty­of the sur­face.

Speaker’s Biog­ra­phy — Mosha Zhao is cur­rent­ly a PhD can­di­date of chem­i­cal and bio­mol­e­c­u­larengi­neer­ing in School of Engi­neer­ing and Applied Sci­ence (SEAS), Uni­ver­si­ty ofPenn­syl­va­nia. She is cur­rent­ly study­ing the fer­ro­elec­tric polar­iza­tion on sur­face reac­tion­ad­vised by Dr. John Vohs. She is the win­ner of the Catal­y­sis Club of Philadel­phia 2007student poster com­pe­ti­tion.

2008 Spring Symposium

 
Harold H. Kung
Chem­i­cal and Bio­log­i­cal Engi­neer­ing Depart­ment
North­west­ern Uni­ver­si­ty, Evanston
IL 60208–3120, USA

Abstract — In nature, enzymes func­tion effec­tive­ly under mild con­di­tions of near neu­tral pHand room tem­per­a­ture using com­mon organ­ic func­tion­al groups such as amines,hydroxyls, and car­boxylic acids, which, when used out­side the enzyme environment,exhibit activ­i­ties many orders of mag­ni­tude low­er. It is under­stood that the enzymepro­tein pro­vides an envi­ron­ment that is con­ducive to coop­er­a­tive effect among the group­sand hydropho­bic­i­ty at the active cen­ter. In con­trast, catal­y­sis in abi­ot­ic sys­tems sel­do­mu­ti­lized such func­tions, espe­cial­ly het­ero­ge­neous catal­y­sis. Instead, they rely on harshre­ac­tion con­di­tions of ele­vat­ed tem­per­a­tures and pres­sures, and/or strong acids and bases,with the con­se­quence of sac­ri­fic­ing selec­tiv­i­ty. Recent­ly, advances in cat­a­lyst syn­the­sistech­niques make it increas­ing­ly pos­si­ble to design and syn­the­size abi­ot­ic sys­tems that­pos­sess mul­ti­ple func­tion­al­i­ties to achieve coop­er­a­tive catal­y­sis.

Exam­ples include­co­op­er­a­tive acid-base catal­y­sis in which a Lewis acid and a basic func­tion are anchore­don a sil­i­ca sur­face, includ­ing SBA-15 and coor­di­nat­ed met­al ions on the periph­ery of aden­drimer. We have inves­ti­gat­ed using nanocage struc­tures to exam­ine the effect ofen­vi­ron­ment and dis­cov­ered evi­dence of the “pKa shift” effect of amines groups insid­e­the cage, pri­mar­i­ly due to elec­tro­sta­t­ic repul­sion. These and oth­er exam­ples will bedis­cussed.

Speaker’s Biog­ra­phy — Dr. Kung is Pro­fes­sor at the Depart­ment of Chem­i­cal and Bio­log­i­calEngi­neer­ing, and Direc­tor of the Cen­ter for Ener­gy Effi­cient Trans­porta­tion atNorth­west­ern Uni­ver­si­ty. His research goal is to search for and devel­op the under­ly­ing­chem­i­cal and engi­neer­ing prin­ci­ples gov­ern­ing catal­y­sis, espe­cial­ly regard­ing activ­i­ty and­prod­uct selec­tiv­i­ty, and to make use of such knowl­edge to design nov­el and effi­cient­cat­a­lysts and process­es.

2008 Spring Symposium

 
Luis Boll­mann, Joshua L. Ratts, W. Damion Williams, Jorge Pazmino,Jeffrey T. Miller1, W. Nicholas Del­gass, Fabio H. Ribeiro
School of Chem­i­cal Engi­neer­ing
Pur­due Uni­ver­si­ty
480 Sta­di­um Mall Dri­ve
West Lafayette, IN 47907–2100

¹BP Research Cen­ter
E-1F, 150 W.Warrenville Rd.
Naperville, IL 60563

Abstract — We are attempt­ing to syn­the­size a cat­a­lyst for the WGS reac­tion that has the high­turnover rate (TOR) of the Cu-based sys­tem and the capa­bil­i­ty typ­i­cal of noble met­al­sys­tems to recov­er from oper­a­tional upsets. The kinet­ic mea­sure­ments were car­ried out­at 300 °C, 1 bar, 6.8% CO, 22% H₂O, 8.5% CO₂, 37.3% H₂, and bal­ance Argon. As aref­er­ence, the TOR for a Cu based cat­a­lyst at these con­di­tions was about 2 s^-1. Wes­t­ud­ied cat­a­lysts based on Pd and Pt. For Pt on alu­mi­na, par­ti­cle size (2–15 nm) caused­no change in the TOR, which was about 1 s^-1 for Pt on CeO₂, TiO₂, and ZrO₂ supports,implying that these sup­ports do not influ­ence the reac­tiv­i­ty.

How­ev­er, cat­a­lysts sup­port­e­don sil­i­ca and alu­mi­na showed a TOR about 10 times low­er than those on these three­sup­ports. The addi­tion of, for exam­ple, Mo, Fe, and Zn to Pd and Pt cat­a­lysts on alu­mi­nasig­nif­i­cant­ly increased the rate (up to a fac­tor of 100), but only up to the rate on the non­in­ter­act­ing­sup­ports. The rates of Pd and Pt cat­a­lysts sup­port­ed on the non-inter­act­ing­sup­ports CeO₂, TiO₂, and ZrO₂ could not be fur­ther increased by any of these additives.For a series of Pd-Zn cat­a­lysts rang­ing from 2 to 19 wt% Zn on Al₂O₃, it was observed byEX­AFS and DRIFTS of CO that Pd alloyed with Zn, and that the alloy exhib­it­ed anin­creased TOR of up to 20 times as com­pared to Pd on Al₂O₃. The pres­ence of zin­ca­lu­mi­nate was also observed. The addi­tion of 2 wt% Zn to Pd cat­a­lysts sup­port­ed onTiO₂, CeO₂ and ZrO₂ did not enhance the WGS rate, although alloy­ing was ver­i­fied byEX­AFS and DRIFTS of CO. The TORs of Pd on these three sup­ports were as high as theTOR on the best PdZn on alu­mi­na. One expla­na­tion of the results is that Zn forms ana­lu­mi­nate and pre­vents a dele­te­ri­ous inter­ac­tion between Pd and alu­mi­na. Zinc is thus­not a true pro­mot­er for WGS, although it decreased the unde­sir­able metha­na­tion reac­tion­to below detec­tion lim­its. While we have found ways to mit­i­gate the dele­te­ri­ous effect­sof alu­mi­na and sil­i­ca on the WGS rate, we have not yet found a pro­mot­er that will­increase the TOR sig­nif­i­cant­ly for Pd or Pt on non-inter­act­ing sup­ports.

Speaker’s BioBiog­ra­phy — Dr. Ribeiro is Pro­fes­sor at the School of Chem­i­cal Engi­neer­ing, Pur­due­U­ni­ver­si­ty. His research inter­est is in kinet­ics of het­ero­ge­neous cat­alyt­ic processes.Before start­ing on acad­e­mia, Dr. Ribeiro has worked in indus­try and in research using­mod­el cat­a­lysts and sur­face sci­ence tech­niques.

2008 Spring Symposium

 
Chun­shan Song
Direc­tor, EMS Ener­gy Insti­tute and Pro­fes­sor of Fuel Sci­ence
Depart­ment of Ener­gy and Min­er­al Engi­neer­ing
The Penn­syl­va­nia State Uni­ver­si­ty
209 Aca­d­e­m­ic Projects Build­ing
Uni­ver­si­ty Park, PA 16802, USA
Tel: 814–863-4466
csong@​psu.​edu

Abstract — This lec­ture will begin with an overview of ener­gy-relat­ed cap­ture, sequestration,conversion, and uti­liza­tion of car­bon diox­ide (CO₂) [C.S. Song, Catal. Today, 115 (2006)2–32]. Car­bon cap­ture and seques­tra­tion (CCS) is con­sid­ered as one of the key options for mit­i­gat­ing the emis­sions of CO₂ from ener­gy sys­tems. Accord­ing to stud­ies by U.S. Depart­ment of Ener­gy, CO₂ cap­ture by cur­rent com­mer­cial tech­nol­o­gy using aque­ous solu­tions of liq­uid alka­nolamines is ener­gy inten­sive and con­tributes to as much as two thirds of the total cost for CO₂ seques­tra­tion. We have pro­posed a new design con­cept of “mol­e­c­u­lar bas­ket sor­bent (MBS)” as a nov­el approach to CO₂ cap­ture and sep­a­ra­tion using selec­tive sol­id sor­bent [X. Xu et al., Micro­p­or. Meso­por. Materi., 62 (2003) 29–45]. CO₂ “mol­e­c­u­lar bas­ket” is nano-porous, CO₂-selec­tive high-capac­i­ty sor­bent for adsorp­tion sep­a­ra­tion of CO₂ from var­i­ous gas mix­tures.

We have explored a num­ber of new MBS for­mu­la­tions. An exam­ple of the MBS-CO₂ is a nano-porous com­pos­ite of poly­eth­yl­eneimine and a meso­porous moec­u­lar sieve MCM-41. PEI-MCM-41 type sor­bents have been found to be effec­tive for remov­ing CO₂ from flue gas and oth­er gas streams with high capac­i­ty and selec­tiv­i­ty at 20–100 °C under atmos­pher­ic pres­sure. The CO₂ adsorp­tion capac­i­ty and CO₂ sep­a­ra­tion selec­tiv­i­ty of MCM-41 were great­ly improved by load­ing PEI into its nano-sized pore chan­nels (about 3 nm), which made the result­ing sor­bent oper­at­ing like a “mol­e­c­u­lar bas­ket” for CO₂ (MBS-CO₂). The influ­ence of mois­ture con­cen­tra­tions in the sim­u­lat­ed flue gas on the CO₂ adsorp­tion sep­a­ra­tion per­for­mance was also exam­ined. CO₂ adsorp­tion capac­i­ty of the MCM-41-PEI adsor­bent for the sim­u­lat­ed moist flue gas was high­er than that for the sim­u­lat­ed dry flue gas. The cap­tured CO₂ can be eas­i­ly and com­plete­ly recov­ered by using a purge gas or a vac­u­um sys­tem at 75–100 °C. The mul­ti-cycle exper­i­ments have shown that the MBS-CO₂sor­bents have very good regen­er­a­bil­i­ty and sta­bil­i­ty [C. S. Song et al., Stud. Surf, Sci.Catal., 153 (2004) 411–416]. With the MBS, CO₂ cap­ture from flue gas can be con­duct­ed in a sol­vent-free and com­pact sol­id sor­bent sys­tem more ener­gy effi­cient­ly, eco­nom­i­cal­ly and envi­ron­men­tal­ly friend­ly. The MBS-CO₂ con­cept has also been found applic­a­ble to cap­ture and sep­a­ra­tion of hydro­gen sul­fide H₂S in gas mix­tures [X.Wang et al., Green Chem­istry, 9 (2007) 695–702]. Results of ana­lyt­i­cal char­ac­ter­i­za­tion of MBS will also bedis­cussed to shed light on why and how these nov­el sor­bents work under real­is­tic con­di­tions.

Speaker’s Biog­ra­phy — Dr. Chun­shan Song is a Pro­fes­sor of Fuel Sci­ence and the Direc­tor of the EMS Ener­gy Insti­tute at the Penn­syl­va­nia State Uni­ver­si­ty. His research inter­ests include catal­y­sis and adsorp­tion for fuel pro­cess­ing, adsorp­tion desul­fu­r­iza­tion of fuels and reform­ing of hydro­car­bons and bio­fu­els for fuel cells, shape-selec­tive catal­y­sis for chem­i­cals, CO₂ cap­ture and uti­liza­tion, heavy oil upgrad­ing, and con­ver­sion of coal and bio­mass to liq­uid fuels and chem­i­cals.