2009 Spring Symposium

 
Gary Haller
Depart­ment of Chem­istry
Yale Uni­ver­si­ty
New Haven, CT

Abstract — Mobil com­po­si­tion of mate­r­i­al No. 41 (MCM-41) was dis­closed in 1992 and short­ly after a research project was ini­ti­at­ed at Yale to use these mate­ri­als to demon­strate a radius of cur­va­ture effect on cat­alyt­ic activ­i­ty. The “radius of cur­va­ture” effect implies a change in the sol­id sur­face ten­sion of the pore wall as the pore diam­e­ter (cur­va­ture) is changed that is expect­ed to change the activity/selectivity of an iso­lat­ed cat­alyt­ic site on the pore wall of the sup­port. An iso­lat­ed site can be formed by iso­mor­phous sub­sti­tu­tion (dur­ing syn­the­sis) of some Si cations by V cations in the MCM-41 sil­i­ca matrix. Sev­er­al labs have report­ed that iso­lat­ed V sites on a sil­i­ca sup­port are prefer­able to dimers, oligomers or poly­mers of van­dia on a sil­i­ca sup­port for the oxi­da­tion of methanol to formalde­hyde. MCM-41 might have an advan­tage rel­a­tive to oth­er sil­i­cas because of its very high sur­face area, >1000 m²/g. Both the air oxi­da­tion of methanol and methane to formalde­hyde have been used as probe reac­tions for cat­alyt­ic char­ac­ter­i­za­tion of V-MCM-41. SBA-15 has a sim­i­lar struc­ture to MCM-41, but larg­er pores and thick­er walls. Iso­mor­phous sub­sti­tu­tion of V dur­ing syn­the­sis is not prac­ti­cal, but well dis­persed V can be pre­pared post-syn­the­sis by graft­ing (reac­tion with sur­face hydrox­yls). The activ­i­ty for methanol oxi­da­tion on V-MCM-41 and V-SBA-15 will be com­pared and dis­cussed.

Speaker’s Biog­ra­phy — Gary L. Haller is the Hen­ry Pren­tiss Bec­ton Pro­fes­sor of Engi­neer­ing and Applied Sci­ence at Yale Uni­ver­si­ty with joint appoint­ments in the Depart­ments of Chem­i­cal Engi­neer­ing and Chem­istry. Pro­fes­sor Haller received a B.S. in math­e­mat­ics and chem­istry from the Uni­ver­si­ty of Nebras­ka at Kear­ney in 1962 and a Ph.D. in phys­i­cal chem­istry from North­west­ern Uni­ver­si­ty in 1966. Fol­low­ing a NATO Post-doc­tor­al Fel­low­ship at Oxford Uni­ver­si­ty, he joined the fac­ul­ty of Yale where he has held a vari­ety of admin­is­tra­tive posts that include Chair of the Depart­ment of Chem­i­cal Engi­neer­ing, Chair of the Coun­cil of Engi­neer­ing, and Deputy Provost for Phys­i­cal Sci­ences and Engi­neer­ing. He was Mas­ter of Jonathan Edwards Col­lege, one of twelve res­i­den­tial col­leges that com­prise Yale Col­lege 1997–2008.

Pro­fes­sor Haller’s research involved the mol­e­c­u­lar under­stand­ing of het­ero­ge­neous cat­a­lysts. His research com­bines the inor­gan­ic chem­istry of cat­a­lyst syn­the­sis, phys­i­cal chem­istry of spec­tro­scop­ic char­ac­ter­i­za­tion of het­ero­ge­neous cat­a­lysts, and the kinet­ics and mech­a­nism of sim­ple organ­ic reac­tions. Cur­rent research is focused on cat­a­lysts for the syn­the­sis of sin­gle walled car­bon nan­otubes and the appli­ca­tion of these car­bon nan­otubes as sup­ports for nov­el cat­alyt­ic reac­tions such as aque­ous phase reform­ing (a route to renew­able ener­gy sources).

2009 Spring Symposium

 
Danielle A. Hans­gen
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Delaware
Newark, DE

Abstract — The ammo­nia decom­po­si­tion reac­tion has recent­ly received increased atten­tion due to the pos­si­bil­i­ty of ammo­nia being used as a hydro­gen stor­age medi­um in a pos­si­ble hydro­gen econ­o­my. We have explored this decom­po­si­tion reac­tion through mul­ti­scale micro­ki­net­ic mod­el­ing for a num­ber of tran­si­tion met­al cat­a­lysts, includ­ing Cu, Pt, Ir, Ru, Pd, Rh, Co, Ni, Fe, W, and Mo, to bet­ter under­stand the reac­tion mech­a­nism. An under­stand­ing of the reac­tion mech­a­nism and elec­tron­ic prop­er­ties of these met­als has giv­en insight into how to tai­lor cat­a­lysts to improve cat­alyt­ic activ­i­ty for this reac­tion.

The mech­a­nism con­sists of 12 ele­men­tary reac­tion steps and 5 sur­face species, name­ly N, H, NH, NH₂, and NH₃. For many of the met­als, a large por­tion of the sur­face is cov­ered by adsor­bates. For these met­als, repul­sive adsor­bate-adsor­bate inter­ac­tions were expect­ed to change the bind­ing ener­gies of the sur­face species, there­by chang­ing the ele­men­tary reac­tion acti­va­tion bar­ri­ers and mod­i­fy­ing the cat­alyt­ic activ­i­ty [1]. Cov­er­age depen­dant atom­ic heats of chemisorp­tion were cal­cu­lat­ed through DFT using the Vien­na Ab-ini­tio Sim­u­la­tion Pack­age (VASP) for the var­i­ous tran­si­tion met­al cat­a­lysts. Cov­er­age depen­dant mol­e­c­u­lar bind­ing ener­gies were cal­cu­lat­ed using a method based on scal­ing rela­tion­ships pub­lished by Abild-Ped­er­son et al. [2] and acti­va­tion bar­ri­ers were cal­cu­lat­ed through the bond-order con­ser­va­tion (BOC) method [3].

Inclu­sion of the inter­ac­tion para­me­ters to the mod­els result­ed in reduced nitro­gen cov­er­ages and a peak shift in the vol­cano curve. The con­ver­sions were plot­ted against the char­ac­ter­is­tic nitro­gen heat of chemisorp­tion for each met­al, which was found to be an ade­quate descrip­tor for this reac­tion. The vol­cano curve of the con­ver­sions cal­cu­lat­ed through the micro­ki­net­ic mod­els are in good agree­ment with exper­i­men­tal data of sin­gle met­al cat­a­lysts by Gan­ley and cowork­ers [4]. The max­i­mum activ­i­ty was found at a nitro­gen heat of chemisorp­tion of approx­i­mate­ly 130 kcal/mol.

A DFT study of nitro­gen bind­ing ener­gies on Pt-3d bimetal­lic sur­faces showed a bind­ing ener­gy of 131 kcal/mol on the Ni-Pt-Pt sur­face, indi­cat­ing that it could be a poten­tial­ly active cat­a­lyst; there­fore sur­face sci­ence exper­i­ments were per­formed to assess the micro­ki­net­ic mod­el and DFT results. The Ni-Pt-Pt sur­face was found to be more active at decom­pos­ing ammo­nia at low tem­per­a­tures and des­orbed nitro­gen at low­er tem­per­a­tures than a Ru(0001) sur­face [5], cur­rent­ly the most active sin­gle met­al cat­a­lyst

Speaker’s Biog­ra­phy — Danielle Hans­gen received her Bachelor’s degree in chem­i­cal engi­neer­ing in 2005 from the Uni­ver­si­ty of Wash­ing­ton. She is cur­rent­ly a third year, PhD can­di­date in chem­i­cal engi­neer­ing at the Uni­ver­si­ty of Delaware. She is advised by Dr. Dion G. Vla­chos and Dr. Jing­guang G. Chen and is work­ing on the ratio­nal design of cat­a­lysts for the ammo­nia decom­po­si­tion reac­tion.

2009 Spring Symposium

 
Dr Christo­pher J. Kiely
Cen­ter for Advanced Mate­ri­als and Nan­otech­nol­o­gy
Lehigh Uni­ver­si­ty
Beth­le­hem, PA

Abstract — Sup­port­ed gold clus­ters and gold-pal­la­di­um nanopar­ti­cles are intense­ly stud­ied mate­ri­als pri­mar­i­ly because of their excit­ing poten­tial appli­ca­tions in catal­y­sis. The recent avail­abil­i­ty of aber­ra­tion cor­rect­ed ana­lyt­i­cal elec­tron micro­scopes is rev­o­lu­tion­iz­ing our abil­i­ty to char­ac­ter­ize the mor­phol­o­gy, crys­tal­log­ra­phy and chem­i­cal com­po­si­tion of such nanoscop­ic vol­umes of mate­ri­als and for the first time are giv­ing us more real­is­tic views of these cat­a­lyst sys­tems. To illus­trate the supe­ri­or imag­ing per­for­mance of this new gen­er­a­tion of elec­tron micro­scopes, we will present a high angle annu­lar dark field (HAADF) imag­ing study of a sys­tem­at­ic set of gold on iron oxide CO oxi­da­tion cat­a­lysts, rang­ing from those with lit­tle or no activ­i­ty, to oth­ers with very high activ­i­ties. Using this approach, com­bined with XPS analy­sis, we will unam­bigu­ous­ly demon­strate that the high cat­alyt­ic activ­i­ty for CO oxi­da­tion derives from the pres­ence of bi-lay­er clus­ters which are ~0.5 nm in diam­e­ter. We will also demon­strate that core-shell struc­tures in sub-5nm Au+Pd, Pd@Au and Au@Pd bimetal­lic nanopar­ti­cles can be direct­ly visu­al­ized using the z-con­trast sen­si­tiv­i­ty of the HAADF imag­ing tech­nique. To illus­trate the chem­i­cal analy­sis capa­bil­i­ties of aber­ra­tion cor­rect­ed ana­lyt­i­cal micro­scopes, we will describe the poten­tial advan­tages of com­bin­ing X-ray Ener­gy Dis­per­sive Spec­troscopy (XEDS) spec­trum imag­ing with mul­ti­vari­ate sta­tis­ti­cal analy­sis (MSA) tech­niques. Through sev­er­al case stud­ies of the Au-Pd bimetal­lic cat­a­lyst sys­tems, we will demon­strate that STEM-XEDS can pro­vide invalu­able high spa­tial res­o­lu­tion com­po­si­tion­al infor­ma­tion on (i) alloy homo­gene­ity and phase seg­re­ga­tion effects with­in indi­vid­ual nanopar­ti­cles, (ii) par­ti­cle size — alloy com­po­si­tion cor­re­la­tions, and (iii) alloy com­po­si­tion changes that can occur as these cat­a­lysts are used.

Speaker’s Biog­ra­phy — Chris Kiely obtained his BSc in Chem­i­cal Physics (1983) and PhD in Microstruc­tur­al Physics (1986) from Bris­tol Uni­ver­si­ty. From 1986–89 he was a vis­it­ing post­doc­tor­al research asso­ciate in the Mate­ri­als Research Lab­o­ra­to­ry at the Uni­ver­si­ty of Illi­nois at Urbana-Cham­paign. He joined the Mate­ri­als Sci­ence and Engi­neer­ing Depart­ment at Liv­er­pool Uni­ver­si­ty as a Lec­tur­er in 1989, where he worked his way through the ranks until even­tu­al­ly being award­ed a Per­son­al Chair in Mate­ri­als Chem­istry in 1999. Kiely joined Lehigh Uni­ver­si­ty (Penn­syl­va­nia, USA) as Pro­fes­sor of Mate­ri­als Sci­ence and Engi­neer­ing in 2002. He is cur­rent­ly the Direc­tor of the Cen­ter of the Nanochar­ac­ter­i­za­tion Lab­o­ra­to­ry at Lehigh Uni­ver­si­ty, which hous­es an array of twelve elec­tron micro­scopes, includ­ing two aber­ra­tion cor­rect­ed instru­ments. He also serves as the Direc­tor of the Lehigh Microscopy Schools. His research exper­tise lies in the appli­ca­tion and devel­op­ment of trans­mis­sion elec­tron microscopy tech­niques for the study of nanoscale fea­tures in mate­ri­als. His areas of inter­est include cat­a­lyst mate­ri­als, nanopar­ti­cle self-assem­bly, car­bona­ceous mate­ri­als, and het­eroepi­tax­i­al inter­face struc­tures. He is also involved in microscopy tech­nique devel­op­ment, and his cur­rent inter­ests include X-Ray Ultra­mi­croscopy (XuM) and aber­ra­tion cor­rect­ed Ana­lyt­i­cal Elec­tron Microscopy (AEM).

2009 Spring Symposium

 
Suljo Lin­ic
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Michi­gan
Ann Arbor, MI

Abstract — The cen­tral objec­tive of our research effort is to employ com­bined experimental/theoretical approach­es to devel­op pre­dic­tive the­o­ries of het­ero­ge­neous catal­y­sis and to apply these the­o­ries to for­mu­late ener­gy-effi­cient, selec­tive, and sta­ble cat­a­lysts. We are moti­vat­ed by a real­iza­tion that recent sci­en­tif­ic advance­ments, main­ly in the area of mol­e­c­u­lar sci­ence, have poten­tial to bring a rev­o­lu­tion­ary trans­for­ma­tion to the field of dis­cov­ery in het­ero­ge­neous cat­a­lysts.

I will present our recent work where we explored poten­tial uti­liza­tion of high­ly uni­form metal­lic nano-struc­tured mate­ri­als as selec­tive het­ero­ge­neous cat­a­lysts. The advan­tage of these mate­ri­als com­pared to con­ven­tion­al cat­alyt­ic mate­ri­als is that their struc­ture can be con­trolled with almost atom­ic pre­ci­sion, and that it is pos­si­ble to syn­the­size high­ly homo­ge­neous struc­tures. We demon­strat­ed some of these advan­tages recent­ly when we showed that well-defined, tai­lored Ag nano-struc­tures are much more selec­tive in het­ero­ge­neous epox­i­da­tion of eth­yl­ene to form eth­yl­ene oxide (EO) (Eth­yl­ene + ½O₂ → EO) than con­ven­tion­al indus­tri­al cat­a­lysts.

We showed using quan­tum chem­i­cal Den­si­ty Func­tion­al The­o­ry (DFT) cal­cu­la­tions, where we stud­ied crit­i­cal ele­men­tary chem­i­cal steps that gov­ern the selec­tiv­i­ty to EO in the process, that the Ag(100) sur­face should be inher­ent­ly more selec­tive than the Ag(111) sur­face. We note that cat­alyt­ic par­ti­cles, syn­the­sized using con­ven­tion­al syn­the­sis pro­ce­dure and cur­rent­ly used in com­mer­cial eth­yl­ene epox­i­da­tion process, are dom­i­nat­ed by the (111) sur­face. To syn­the­size Ag nano-struc­tures which are dom­i­nat­ed with the Ag(100) faces, we employed a syn­the­sis pro­ce­dure which uses organ­ic sta­bi­liz­er mol­e­cules to direct the growth of the nano-struc­ture in a par­tic­u­lar direc­tion and to con­trol the sur­face facets that ter­mi­nate the nano-struc­ture. This syn­thet­ics strat­e­gy allowed us to syn­the­size well-defined and high­ly uni­form Ag nano-wires and nano-cubes which are dom­i­nat­ed by the (100) facet. Sub­se­quent exper­i­ments showed that Ag nano-wires and nano-cube cat­a­lysts can achieve selec­tiv­i­ty to EO, which is, at dif­fer­en­tial con­ver­sion, by ~ 40 % high­er than for con­ven­tion­al Ag cat­a­lysts.

We have also recent­ly start­ed explor­ing these metal­lic nano-struc­tures as pos­si­ble plat­forms for chem­i­cal char­ac­ter­i­za­tion. The fea­tures of these nano-struc­tures that are par­tic­u­lar­ly appeal­ing are: (i) the nanos­truc­tures are well defined on atom­ic lev­el, and their sur­face to vol­ume ratio is fair­ly high, which makes these struc­tures inher­ent­ly bet­ter suit­ed for the stud­ies of sur­face chem­i­cal process­es com­pared to tra­di­tion­al sin­gle crys­tal mod­el sys­tems, which are while very well defined, char­ac­ter­ized by low sur­face to vol­ume ratio. (ii) we can syn­the­size the nanos­truc­tures with high degree of uni­for­mi­ty in size and shape, which rules out pos­si­ble effects due to diver­si­ty in size and shape, i.e. these, (iii) the nanos­truc­tures are effec­tive scat­ter­ers of elec­tro­mag­net­ic radi­a­tion which make them suit­able as plat­forms for a num­ber of chem­i­cal char­ac­ter­i­za­tion tech­niques includ­ing sur­face enhanced Raman (SERS) or IR spec­tro­scopies. We will demon­strate the util­i­ty of the nano-struc­tures for chem­i­cal char­ac­ter­i­za­tion by a way of an exam­ple, where we mon­i­tored in-situ eth­yl­ene epox­i­da­tion.

We will also show that the well-defined metal­lic nano-struc­tures exhib­it inter­est­ing prop­er­ties when exposed to UV and vis­i­ble light. We will show how these char­ac­ter­is­tics can be used to design nov­el pho­to-elec­tro-cat­alyt­ic mate­ri­als and process­es.

Speaker’s Biog­ra­phy — Suljo Linc came to the Unit­ed States from Bosnia under the aus­pices of a Soros Foun­da­tion Fel­low­ship, here he received a BS degree in Physics from West Chester Uni­ver­si­ty (1998) , and a Ph.D. in Chem­i­cal Engi­neer­ing under Pro­fes­sor Mark Barteau (2003) where he inves­ti­gat­ed the the­o­ret­i­cal and exper­i­men­tal aspects of alkene par­tial oxi­da­tion on sil­ver. He accept­ed a post­doc­tor­al posi­tion in Matthias Scheffler’s The­o­ry Group at the Fritz Haber Insti­tute of the Max Planck Soci­ety in Berlin, and in 2004 took a posi­tion in the Depart­ment of Chem­i­cal Engi­neer­ing at the Uni­ver­si­ty of Michi­gan. Suljo has received a num­ber of awards, includ­ing NSF Career Award in 2006, and Young Sci­en­tist Prize from the Coun­cil of the Inter­na­tion­al Asso­ci­a­tion of Catal­y­sis Soci­eties, Paris, France, July 2004. Suljo’s research inter­ests include fuel cells, chi­ral syn­the­sis, car­bon catal­y­sis, catal­y­sis at nano-scales, and the fun­da­men­tals of sur­face activ­i­ty and selec­tiv­i­ty.

2009 Spring Symposium

 
Michael Ward
New York Uni­ver­si­ty
Depart­ment of Chem­istry
New York, NY

Abstract — Guest-free guani­dini­um organomono­sul­fonates (GMS) and their inclu­sion com­pounds dis­play a vari­ety of lamel­lar crys­talline archi­tec­tures dis­tin­guished by dif­fer­ent “up-down” pro­jec­tions of the organomono­sul­fonate residues on either side of a two-dimen­sion­al (2D) hydro­gen-bond­ing net­work of com­ple­men­tary guani­dini­um ions (G) and sul­fonate moi­eties (S), the so-called GS sheet. The GS sheets in the inclu­sion com­pounds behave as “mol­e­c­u­lar jaws” in which organomono­sul­fonate groups pro­ject­ing from oppos­ing sheets clamp down on the guest mol­e­cules, form­ing ordered inter­dig­i­tat­ed arrays of the host organ­ic groups and guests. Guest-free and inclu­sion com­pounds dis­play a vari­ety of archi­tec­tures that reveal the struc­tur­al integri­ty of two-dimen­sion­al GS sheet and the unique abil­i­ty of these hosts to con­form to the steric demands of the organ­ic guests. Cer­tain GMS host-guest com­bi­na­tions prompt for­ma­tion of tubu­lar inclu­sion com­pounds in which the GS sheet curls into cylin­ders with reten­tion of the 2D GS net­work. The cylin­ders assem­ble into hexag­o­nal arrays through inter­dig­i­ta­tion of the organosul­fonate residues that project from their out­er sur­faces, crys­tal­liz­ing in high sym­me­try trig­o­nal or hexag­o­nal space groups. This unique exam­ple of net­work cur­va­ture and struc­tur­al iso­merism between lamel­lar and cylin­dri­cal struc­tures, with reten­tion of supramol­e­c­u­lar con­nec­tiv­i­ty, is rem­i­nis­cent of the phase behav­ior observed in sur­fac­tant microstruc­tures and block copoly­mers. The large num­ber of host-guest com­bi­na­tions explored here per­mits group­ing of the inclu­sion com­pound archi­tec­tures accord­ing to the shape of the guests and the rel­a­tive vol­umes of the organomono­sul­fonate groups, enabling more reli­able struc­ture pre­dic­tion for this class of com­pounds than for mol­e­c­u­lar crys­tals in gen­er­al. More recent results that demon­strate the inclu­sion of laser dyes with con­trolled states of aggre­ga­tion, the intro­duc­tion of mol­e­c­u­lar cap­sules, and unusu­al high sym­me­try struc­tures will be described.

Speaker’s Biog­ra­phy — Michael Ward earned his B.A in Chem­istry from William Pater­son Col­lege of New Jer­sey in 1977, and PhD in Chem­istry from Prince­ton Uni­ver­si­ty in 1981. He cur­rent­ly serves as the Sil­ver Pro­fes­sor and Chair, Depart­ment of Chem­istry, Direc­tor of Mol­e­c­u­lar Design Insti­tute and Direc­tor of Mate­ri­als Research Sci­ence and Engi­neer­ing Cen­ter at New York Uni­ver­si­ty, New York City, NY. He is also Edi­tor of Chem­istry of Mate­ri­als. His research inter­ests include syn­the­sis of mol­e­c­u­lar mate­ri­als and crys­tal engi­neer­ing, phys­i­cal and elec­tron­ic prop­er­ties of mol­e­c­u­lar solids, nucle­ation and growth of organ­ic and pro­tein crys­tals, scan­ning probe microscopy and inter­fa­cial phe­nom­e­na.

2009 Spring Symposium

 
Allen Bur­ton
Chevron Research
Rich­mond, Cal­i­for­nia

Abstract — The zeo­lite com­mu­ni­ty has recent­ly pre­pared a num­ber of new zeo­lite struc­tures byem­ploy­ing diqua­ter­nary ammo­ni­um mol­e­cules as struc­ture direct­ing agents (SDAs). Inpar­tic­u­lar, sev­er­al nov­el mul­ti­di­men­sion­al medi­um-pore zeo­lites have been dis­cov­ered that­pro­vide inter­est­ing com­par­isons with ZSM-5 in their struc­tur­al fea­tures and cat­alyt­ic behaviours.I will first dis­cuss how we have used diqua­ter­nary pyrro­li­dini­um mol­e­cules in flu­o­ride-medi­at­edgels to syn­the­size new zeo­lites like SSZ-74, SSZ-75, and SSZ-83. I will empha­size the struc­turalelu­ci­da­tion and prop­er­ties of SSZ-74, an excep­tion­al zeo­lite that pos­sess­es ordered tetra­he­dral­site vacan­cies. In the sec­ond part of the dis­cus­sion, I will describe how we have pre­pared­di­qua­ter­nary ammo­ni­um mol­e­cules from enam­ine pre­cur­sors. One of these SDA is used topre­pare the nov­el zeo­lite SSZ-82, and sev­er­al of the mol­e­cules are selec­tive for thea­lu­mi­nosil­i­cate and borosil­i­cate ver­sions of the SSZ-26/33 fam­i­ly, which has very few knownS­DA mol­e­cules

Speaker’s Biog­ra­phy — Allen Bur­ton received his BS in Chem­istry at the Uni­ver­si­ty of Mary­land at Col­lege Park, and his PhD in Chem­i­cal Engi­neer­ing from the Uni­ver­si­ty of Delaware under the guid­ance of Prof. Raul Lobo. It was here Allen dis­cov­ered his pas­sion for zeo­lite syn­the­sis, which he con­tin­ued under the post­doc­tor­al guid­ance of Prof Mark Davis at Cal­Tech. In 2001, Allen accept­ed a posi­tion in the research group at Chevron’s Research facil­i­ty in Rich­mond, CA. Despite his admit­ted inep­ti­tude in the game of golf, on week­ends he can some­times be found at the golf range (swear­ing at golf balls and throw­ing his irons).

2009 Spring Symposium

 
Michael Smith
Symyx

Abstract — Not avail­able.