Ciapetta Award Lecture: Novel Zeolite Catalysts for Diesel Emission Applications

Meeting Program — January 2017

Ahmad Moini
Ahmad Moi­ni
BASF Cor­po­ra­tion


Abstract — Auto­mo­tive exhaust con­di­tions present unique chal­lenges for the design of effec­tive cat­a­lysts. In addi­tion to the need for cat­alyt­ic activ­i­ty over a wide tem­per­a­ture range, the cat­a­lyst must show dura­bil­i­ty towards extreme hydrother­mal aging con­di­tions. The use of zeolitic mate­ri­als under such con­di­tions is espe­cial­ly chal­leng­ing due to the vul­ner­a­bil­i­ty of zeo­lites to steam aging. The BASF dis­cov­ery of the Cu-CHA cat­a­lyst for selec­tive cat­alyt­ic reduc­tion (SCR) of NOx demon­strat­ed an effec­tive bal­ance between favor­able active sites and zeo­lite frame­work dura­bil­i­ty. It also paved the way for the imple­men­ta­tion of urea SCR as the key approach for NOx reduc­tion in diesel vehi­cles. This pre­sen­ta­tion will high­light the devel­op­ment of Cu-CHA as the lead­ing tech­nol­o­gy for diesel emis­sion appli­ca­tions. Spe­cif­ic focus will be placed on the syn­the­sis and struc­tur­al fea­tures of the zeo­lite. In addi­tion, there will be a dis­cus­sion of spe­cif­ic char­ac­ter­i­za­tion and mod­el­ing approach­es focus­ing on the unique attrib­ut­es of the met­al active sites and the inter­ac­tion of these met­al species with the zeo­lite frame­work.

Biog­ra­phy — Dr. Ahmad Moi­ni is a Research Fel­low at BASF Cor­po­ra­tion in Iselin, NJ. He obtained his Ph.D. in Chem­istry from Texas A&M Uni­ver­si­ty, and held a post­doc­tor­al appoint­ment at Michi­gan State Uni­ver­si­ty. Dr. Moi­ni start­ed his career at Mobil Research & Devel­op­ment Cor­po­ra­tion (now Exxon­Mo­bil), where he con­duct­ed research on micro­p­orous mate­ri­als. With a focus on explorato­ry zeo­lite syn­the­sis, he stud­ied the mech­a­nism of zeo­lite crys­tal­liza­tion and the role of spe­cif­ic class­es of organ­ic direct­ing agents in the for­ma­tion of var­i­ous zeo­lite frame­works. He joined Engel­hard Cor­po­ra­tion (now BASF) in 1996. Since then, his pri­ma­ry research inter­ests have been in the area of mate­ri­als syn­the­sis, direct­ed at a range of cat­alyt­ic and func­tion­al appli­ca­tions. He applied high through­put meth­ods for the syn­the­sis and eval­u­a­tion of cat­alyt­ic mate­ri­als, and used these tools for the devel­op­ment of new prod­ucts. A sig­nif­i­cant part of his work has been direct­ed towards cat­a­lysts for envi­ron­men­tal appli­ca­tions. These efforts, in col­lab­o­ra­tion with the extend­ed BASF team, led to the dis­cov­ery and devel­op­ment of Cu-CHA cat­a­lyst for selec­tive cat­alyt­ic reduc­tion (SCR) of NOx from diesel vehi­cles. He holds 48 US patents relat­ing to var­i­ous aspects of mate­ri­als and cat­a­lyst devel­op­ment.

Unraveling Catalytic Mechanisms and Kinetics: Lessons from Electrical Networks

Meeting Program — November 2016

Ravindra Datta
Pro­fes­sor Ravin­dra Dat­ta
Pro­fes­sor in the Depart­ment of Chem­i­cal Engi­neer­ing,
Fuel Cell Cen­ter,
Worch­ester Poly­tech­nic Insti­tute


Abstract — Cat­alyt­ic reac­tion net­works, in gen­er­al, com­prise of mul­ti­ple steps and path­ways. While one can now read­i­ly pre­dict kinet­ics of these mol­e­c­u­lar steps from first prin­ci­ples, there is not yet avail­able a com­pre­hen­sive frame­work for: 1) visu­al­iz­ing and ana­lyz­ing these reac­tion net­works in their full com­plex­i­ty; and 2) unequiv­o­cal­ly iden­ti­fy­ing the ger­mane steps and path­ways.

Thus, we have devel­oped an approach called the “Reac­tion Route (RR) Graph” approach, which allows: 1) direct enu­mer­a­tion of all the path­ways as walks on the RR Graph; 2) ther­mo­dy­nam­ic con­sis­tence of step kinet­ics; 3) elu­ci­da­tion of dom­i­nant path­ways that con­tribute mate­ri­al­ly to the over­all flux; 4) iden­ti­fi­ca­tion of bot­tle­neck steps in each of these path­ways; and 5) devel­op­ment of explic­it rate laws based on the elec­tri­cal anal­o­gy.

The elec­tri­cal net­work anal­o­gy is based on two aspects of RR Graphs, name­ly: 1) qua­si-steady state (QSS) mass bal­ance of inter­me­di­ate species, the equiv­a­lent of the Kirchhoff’s Cur­rent Law (KCL) of elec­tri­cal cir­cuits; and 2) Hess’s law, or ther­mo­dy­nam­ic con­sis­tence, the equiv­a­lent of the Kirchhoff’s Poten­tial Law (KPL), which makes RR Graphs pre­cise­ly equiv­a­lent to elec­tri­cal net­works. Fur­ther, we define the step resis­tance in terms of step kinet­ics to make the anal­o­gy com­plete. The approach is described with the help of the water-gas shift exam­ple.

Biog­ra­phy — Ravi Dat­ta is Pro­fes­sor of Chem­i­cal Engi­neer­ing and Direc­tor of WPI Fuel Cell Cen­ter. He obtained his Ph.D. degree from the Uni­ver­si­ty of Cal­i­for­nia, San­ta Bar­bara, in 1981. From then until 1998, he was a Pro­fes­sor of Chem­i­cal Engi­neer­ing at the Uni­ver­si­ty of Iowa, when he moved to WPI, and served as Chem­i­cal Engi­neer­ing Depart­ment Head until 2005. Ravi’s research is focused on cat­alyt­ic and elec­tro­cat­alyt­ic reac­tion engi­neer­ing of Clean Ener­gy, includ­ing, fuel cells, hydro­gen, renew­able fuels, nov­el cat­a­lysts, and cat­alyt­ic reac­tion net­works. He is a coau­thor of 150 papers and 8 patents, and has been a men­tor to 25 doc­tor­al stu­dents.

Development of heterogeneous catalysts for the production of biomass-derived chemicals by selective C-O hydrogenolysis and deoxydehydration

Meeting Program — October 2016

Keiichi Tomishige
Kei­ichi Tomishige
Pro­fes­sor in the School of Engi­neer­ing,
Tohoku Uni­ver­si­ty


Keiichi Tomishige

Abstract — Chem­i­cal com­po­si­tion of the feed­stock from bio­mass and bio­mass-based build­ing blocks has much high­er oxy­gen con­tents than that from crude oil. It has been known that the tar­get prod­ucts such as monomers for the poly­mer syn­the­sis have com­par­a­tive­ly low­er oxy­gen con­tent, and the method­ol­o­gy for the decrease of the oxy­gen con­tent is more and more impor­tant. One of effec­tive meth­ods is the uti­liza­tion of the hydrogenol­y­sis of C-O bonds in the sub­strates. For exam­ple, C3-C6 sug­ar alco­hols (glyc­erol, ery­thri­tol, xyl­i­tol, and sor­bitol) are also regard­ed as promis­ing build­ing blocks in the bio­mass refin­ery. If the selec­tive hydrogenol­y­sis of the tar­get C-O bond among var­i­ous kinds of the C-O bonds is pos­si­ble, valu­able chem­i­cals such as diols, mono-ols, alka­nes can be pro­duced from bio­mass in high yield. ReOx-mod­i­fied Ir met­al cat­a­lyst (Ir-ReOx) is report­ed to be effec­tive to the selec­tive hydrogenol­y­sis of poly­ols and cyclic ethers in water sol­vent. Ir-ReOx/SiO2 cat­alyzes the hydrogenol­y­sis of glyc­erol to 1,3-propanediol. The hydrogenol­y­sis of ery­thri­tol over the cat­a­lyst pro­duces 1,4- and 1,3-butanediols. The selec­tive hydrogenol­y­sis of tetrahy­dro­fur­furyl alco­hol to 1,5-pentanediol also pro­ceeds using Ir-ReOx/SiO2. In addi­tion, the com­bi­na­tion of Ir-ReOx/SiO2 with H-ZSM-5 gives n-alka­nes and hexa­nols from cel­lu­lose, sug­ars, and sug­ar alco­hols in high yield with the total C-O hydrogenol­y­sis and with­out C-C bond dis­so­ci­a­tion and skele­tal iso­mer­iza­tion. Anoth­er inter­est­ing cat­a­lyst is ReOx-Pd/CeO2. The cat­a­lyst showed excel­lent per­for­mance for simul­ta­ne­ous hydrodeoxy­gena­tion of vic­i­nal OH groups in var­i­ous sub­strates. High yield (>99%), turnover fre­quen­cy, and turnover num­ber were obtained in the reac­tion of 1,4-anhydroerythritol to tetrahy­dro­fu­ran. This cat­a­lyst is also applic­a­ble to the con­ver­sion of sug­ar alco­hols mono-alco­hols and diols are obtained in high yields from sub­strates with even and odd num­bers of OH groups, respec­tive­ly. In addi­tion, ReOx-Au/CeO2 cat­alyzed the con­ver­sion of glyc­erol and ery­thri­tol to allyl alco­hol and 1,3-butadiene in high yield (91% and 81%), respec­tive­ly.

Biog­ra­phy — Kei­ichi Tomishige received his B.S., M.S. and Ph.D. from Grad­u­ate School of Sci­ence, Depart­ment of Chem­istry, The Uni­ver­si­ty of Tokyo with Prof. Y. Iwa­sawa. Dur­ing his Ph.D. course in 1994, he moved to Grad­u­ate School of Engi­neer­ing, The Uni­ver­si­ty of Tokyo as a research asso­ciate and worked with Prof. K. Fuji­mo­to. In 1998, he became a lec­tur­er, and then he moved to Insti­tute of Mate­ri­als Sci­ence, Uni­ver­si­ty of Tsuku­ba as a lec­tur­er in 2001. Since 2004 he has been an asso­ciate pro­fes­sor, Grad­u­ate School of Pure and Applied Sci­ences, Uni­ver­si­ty of Tsuku­ba. Since 2010, he is a pro­fes­sor, School of Engi­neer­ing, Tohoku Uni­ver­si­ty.
His research inter­ests are the devel­op­ment of het­ero­ge­neous cat­a­lysts for

  1. pro­duc­tion of bio­mass-derived chem­i­cals
  2. direct syn­the­sis of organ­ic car­bon­ates from CO2 and alco­hols
  3. steam reform­ing of bio­mass tar
  4. syn­gas pro­duc­tion by nat­ur­al gas reform­ing

He is Asso­ciate Edi­tor of Fuel Pro­cess­ing Tech­nol­o­gy (2014/2-), Edi­to­r­i­al board of Applied Catal­y­sis A:General (2009/4-), Edi­to­r­i­al advi­so­ry board of ACS Catal­y­sis (2013/11-), Inter­na­tion­al Advi­so­ry Board of Chem­SusChem (2015/1-) and Advi­so­ry Board of Green Chemistry(2016/8-).

In Silico Prediction of Materials for Energy Applications

Meeting Program — September 2016

Dion Vlachos
Dion Vla­chos
Eliz­a­beth Inez Kel­ley Pro­fes­sor of Chem­i­cal
& Bio­mol­e­c­u­lar Engi­neer­ing and Pro­fes­sor of Physics,
Uni­ver­si­ty of Delaware

Abstract — In this talk, the need for new mate­ri­als in var­i­ous ener­gy domains will be dis­cussed. Mul­ti­scale sim­u­la­tion will then briefly be intro­duced as an enabling tech­nol­o­gy to address diverse engi­neer­ing top­ics. A spe­cif­ic appli­ca­tion of mul­ti­scale sim­u­la­tion is the pre­dic­tion of macro­scop­ic behav­ior from first prin­ci­ples. A more impact­ful avenue of research is how one could use mul­ti­scale mod­el­ing in reverse engi­neer­ing for pre­dict­ing new mate­ri­als for pro­duc­tion of ener­gy and chem­i­cals and ener­gy stor­age. We will demon­strate how descrip­tor-based mod­el­ing can enable such a search of nov­el mate­ri­als with emer­gent behav­ior and assess this frame­work with exper­i­ments. An out­stand­ing ques­tion is how reli­able and robust are mod­el pre­dic­tions in com­par­ing to data and our quest for search­ing new mate­ri­als. We will demon­strate this method­ol­o­gy for the spe­cif­ic exam­ple of ammo­nia decom­po­si­tion for hydro­gen pro­duc­tion for fuel cells and briefly touch upon renew­able chem­i­cals and fuels from lig­no­cel­lu­losic bio­mass.
Biog­ra­phy — Dion­i­sios (Dion) G. Vla­chos is the Eliz­a­beth Inez Kel­ley Pro­fes­sor of Chem­i­cal & Bio­mol­e­c­u­lar Engi­neer­ing and Pro­fes­sor of Physics at the Uni­ver­si­ty of Delaware and the Direc­tor of the Catal­y­sis Cen­ter for Ener­gy Inno­va­tion (CCEI), an Ener­gy Fron­tier Research Cen­ter (EFRC) fund­ed by the Depart­ment of Ener­gy (DOE). He obtained a five-year diplo­ma in Chem­i­cal Engi­neer­ing from the Nation­al Tech­ni­cal Uni­ver­si­ty of Athens, Greece in 1987, his M.S. and Ph.D. from the Uni­ver­si­ty of Min­neso­ta in 1990 and 1992 respec­tive­ly, and spent a post­doc­tor­al year at the Army High Per­for­mance Com­put­ing Research Cen­ter in Min­neso­ta. After that, Dr. Vla­chos joined the Uni­ver­si­ty of Mass­a­chu­setts as an assis­tant pro­fes­sor, was pro­mot­ed to an asso­ciate pro­fes­sor in 1998 and joined the Uni­ver­si­ty of Delaware in 2000. He was a vis­it­ing fel­low at Prince­ton Uni­ver­si­ty in the spring of 2000, a vis­it­ing fac­ul­ty mem­ber at Thomas Jef­fer­son Uni­ver­si­ty and Hos­pi­tal in the spring of 2007 and the George Pierce Dis­tin­guished Pro­fes­sor of Chem­i­cal Engi­neer­ing and Mate­ri­als Sci­ence at the Uni­ver­si­ty of Min­neso­ta in the fall of 2007.

Pro­fes­sor Vla­chos is the recip­i­ent of the R. H. Wil­helm Award in Chem­i­cal Reac­tion Engi­neer­ing from AIChE and is an AAAS Fel­low. He also received a NSF Career Award and an Office of Naval Research Young Inves­ti­ga­tor Award. He is a mem­ber of AIChE, ACS, the Com­bus­tion Insti­tute, MRS, the North Amer­i­can Catal­y­sis Soci­ety (NACS) and the Soci­ety for Indus­tri­al and Applied Math­e­mat­ics (SIAM).

Dr. Vla­chos’ main research thrust is mul­ti­scale mod­el­ing and sim­u­la­tion along with their appli­ca­tion to catal­y­sis, crys­tal growth, portable micro­chem­i­cal devices for pow­er gen­er­a­tion, pro­duc­tion of renew­able fuels and chem­i­cals, cat­a­lyst infor­mat­ics, detailed and reduced kinet­ic mod­el devel­op­ment and process inten­si­fi­ca­tion. He is the cor­re­spond­ing author of more than 340 ref­er­eed pub­li­ca­tions with near­ly 10,000 cita­tions and has giv­en over 200 ple­nary lec­tures, keynote lec­tures and oth­er invit­ed talks. Pro­fes­sor Vla­chos has served as an exec­u­tive edi­tor of the Chem­i­cal Engi­neer­ing Sci­ence jour­nal and also served or cur­rent­ly serves on the edi­to­r­i­al advi­so­ry board of ACS Catal­y­sis, Reac­tion Chem­istry & Engi­neer­ing, Indus­tri­al and Engi­neer­ing Chem­istry Research, Applied Catal­y­sis A: Gen­er­al, Pro­ceed­ings of the Com­bus­tion Insti­tute, the Open Ener­gy and Fuels Jour­nal, the Jour­nal of Nano Ener­gy and Pow­er Research and the Jour­nal of Chem­i­cal Engi­neer­ing & Process Tech­nol­o­gy.

Insight into Supported Metal Catalyst Stability by Quantifying Thermodynamic Interactions at the Solid-liquid Interface

Meeting Program — April 2016

Robert Rioux
Robert Rioux
Friedrich G. Helf­ferich Asso­ciate Pro­fes­sor of Chem­i­cal Engi­neer­ing
Penn­syl­va­nia State Uni­ver­si­ty

Abstract — Indus­tri­al appli­ca­tions of sup­port­ed late tran­si­tion met­al cat­a­lysts demand eco­nom­ic and scal­able syn­the­sis of these cat­a­lysts and cur­rent syn­thet­ic meth­ods lack pre­ci­sion in terms of size, shape and com­po­si­tion­al con­trol. More­over, sup­port­ed met­al cat­a­lysts suf­fer from poor sta­bil­i­ty, man­i­fest­ed in the form of sin­ter­ing (i.e., par­ti­cle growth) dur­ing reac­tion. The prop­er selec­tion of the oxide sup­port is of great impor­tance to ensure high dis­per­sion, activ­i­ty and selec­tiv­i­ty of the nanopar­ti­cles. The abil­i­ty of these sup­ports to enhance the dis­per­sion of the active met­al on their sur­face and con­trol their mor­phol­o­gy and sin­ter­ing kinet­ics is fun­da­men­tal­ly relat­ed to the nature and strength of the metal–metal oxide inter­ac­tion at the time of adsorp­tion. In this work, we have uti­lized isother­mal titra­tion calorime­try (ITC), a tech­nique capa­ble of quan­ti­fy­ing the ther­mo­dy­nam­ic descrip­tion (ΔG, ΔH, ΔS, n (sto­i­chiom­e­try)) of tran­si­tion met­al asso­ci­a­tion with a sup­port mate­r­i­al in a sin­gle exper­i­ment. After pro­vid­ing a brief intro­duc­tion to ITC and meth­ods of cat­a­lyst syn­the­sis, we will dis­cuss our results to quan­ti­fy the elec­tro­sta­t­ic inter­ac­tions between sol­vat­ed tran­si­tion met­al ions and charged ampho­teric met­al oxide sur­face. With­in this inter­ac­tion-type, we have stud­ied both refrac­to­ry and reducible met­al oxides. With a reducible met­al oxide, ceria, we demon­strate a poten­tial­ly new mech­a­nism of adsorp­tion, which may describe the suc­cess­ful sta­bi­liza­tion of noble met­als enabling main­te­nance of small sized nanopar­ti­cles com­pared to oth­er oxide sup­ports. In addi­tion to ITC, bulk uptake stud­ies have aid­ed in quan­ti­fy­ing the amount of met­al pre­cur­sor adsorbed on the sup­port sur­face and equi­lib­ri­um isotherms describe the uptake behav­ior and may pro­vide insight for pre­dict­ing long term sta­bil­i­ty of the nanopar­ti­cles. In the sec­ond half of the talk, we dis­cuss the adsorp­tion of tran­si­tion met­al oxide and hydrox­ide nanopar­ti­cles in the gal­leries of of Nb-based per­ovskites. ITC was used to quan­ti­ta­tive­ly rank the strength of adsorp­tion between the met­al nanopar­ti­cle and their propen­si­ty to sin­ter, as assessed by in-situ, high-tem­per­a­ture trans­mis­sion elec­tron microscopy. In both exam­ples, we will empha­size this ini­tial inter­ac­tion at the sol­id-liq­uid inter­face is impor­tant and con­veys a his­to­ry effect to the cat­a­lyst that is evi­dent dur­ing post-pro­cess­ing (dry­ing, cal­ci­na­tion and reduc­tion). The esti­mat­ed ther­mo­dy­nam­ic para­me­ters are expect­ed to quan­ti­fy the type of bond­ing at the inter­face, shed light on the bind­ing mech­a­nism and the growth and sin­ter­ing kinet­ics of sup­port­ed cat­a­lysts.
Biog­ra­phy — Robert (Rob) M Rioux is the Friedrich G. Helf­ferich Asso­ciate Pro­fes­sor of Chem­i­cal Engi­neer­ing at the Penn­syl­va­nia State Uni­ver­si­ty. Pri­or to join­ing the Penn­syl­va­nia State Uni­ver­si­ty in 2008, he was a Nation­al Insti­tutes of Health Post­doc­tor­al Fel­low at Har­vard Uni­ver­si­ty in the Depart­ment of Chem­istry and Chem­i­cal Biol­o­gy work­ing with Pro­fes­sor George White­sides. He received his Ph.D. in phys­i­cal chem­istry from the Uni­ver­si­ty of Cal­i­for­nia, Berke­ley in 2006 work­ing for Pro­fes­sor Gabor Somor­jai. He holds a B.S. and M.S. degree in chem­i­cal engi­neer­ing from Worces­ter Poly­tech­nic Insti­tute and the Penn­syl­va­nia State Uni­ver­si­ty, respec­tive­ly. Since join­ing the Penn. State fac­ul­ty, he has received a num­ber of awards, includ­ing a DARPA Young Fac­ul­ty Award, an Air Force Office of Sci­en­tif­ic Research Young Inves­ti­ga­tor Pro­gram Award, a NSF CAREER Award and a 3M Non-Tenured Fac­ul­ty Award. Research in his lab­o­ra­to­ry is cur­rent­ly spon­sored by NSF, DOE-BES, DARPA, AFOSR, AFRL, ACS-PRF and indus­try. His group’s cur­rent research focus is on the devel­op­ment of spa­tial­ly- and tem­po­ral­ly-resolved spec­tro­scop­ic tech­niques for imag­ing cat­alyt­ic chem­istry, sin­gle mol­e­cule meth­ods to under­stand sin­gle molecule/particle cat­alyt­ic kinet­ics and dynam­ics, elu­ci­dat­ing reac­tion mech­a­nisms in nanoscale sys­tems, includ­ing cat­a­lyst syn­the­sis, devel­op­ment of solu­tion calori­met­ric tech­niques to under­stand cat­alyt­ic process­es at the sol­id-liq­uid inter­face and the devel­op­ment of base-met­al cat­a­lysts for chemos­e­lec­tive chem­i­cal trans­for­ma­tions, includ­ing bio­mass to chem­i­cals con­ver­sion.

Identification of Active Sites for Methyl Lactate Dehydration on Faujasites

Meeting Program — March 2016

Bingjun Xu
Bingjun Xu
Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing
Uni­ver­si­ty of Delaware

Abstract — The dwin­dling reserve of crude oil and surge in nat­ur­al gas pro­duc­tion is rapid­ly chang­ing the mix of the car­bon source pool for the pro­duc­tion of fuels and chem­i­cal feed­stocks, and in turn cre­at­ing short­ages of sev­er­al key com­mod­i­ty chem­i­cals, e.g., propy­lene and buta­di­ene. The short­age of cer­tain com­mod­i­ty chem­i­cals, such as propy­lene, dri­ves up their prices, which in turn rais­es the cost of the down­stream chem­i­cals, such as acrylic acid. In this regard, lig­no­cel­lu­losic bio­mass derived feed­stocks, e.g., lac­tic acid and its esters, can poten­tial­ly bridge the gap. Cur­rent­ly, the com­mer­cial fer­men­ta­tion process using bio­mass-derived sug­ars can achieve a lac­tic acid (or its esters) yield of up to 90%. The absence of effi­cient and selec­tive cat­a­lyst for lac­tic acid dehy­dra­tion is the main miss­ing link in the pro­duc­tion of renew­able acrylic acid. The pri­ma­ry road­block for the ratio­nal design of cat­a­lysts for lac­tic acid dehy­dra­tion is the lack of the mech­a­nis­tic under­stand­ing of the nature of active sites and mech­a­nis­tic steps lead­ing to the selec­tive removal of the α-hydrox­yl group by dehy­dra­tion. Through kinet­ic and in-situ spec­tro­scop­ic inves­ti­ga­tions, we iden­ti­fy the dehy­dra­tion reac­tion pro­ceeds through dis­so­cia­tive adsorp­tion, acid-medi­at­ed dehy­dra­tion, and asso­cia­tive des­orp­tion steps. These mech­a­nis­tic insights will guide the design of selec­tive cat­a­lysts for this reac­tion.
Biog­ra­phy — Bingjun Xu is cur­rent­ly an Assis­tant Pro­fes­sor in the Depart­ment of Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing at Uni­ver­si­ty of Delaware. Dr. Xu received his Ph.D. in Phys­i­cal Chem­istry, advised by Prof. Friend, from Har­vard Uni­ver­si­ty in 2011. His the­sis estab­lished a mech­a­nis­tic frame­work for oxida­tive cou­pling reac­tions on Au sur­face through sur­face sci­ence stud­ies. Dr. Xu worked with Prof. Davis at Cal­tech on the devel­op­ment of a low tem­per­a­ture, man­ganese oxide based ther­mo­chem­i­cal cycle for water split­ting. Upon fin­ish­ing his post­doc, he joined Uni­ver­si­ty of Delaware in the fall of 2013. The cur­rent research inter­est of the Xu lab spans het­ero­ge­neous catal­y­sis, elec­tro­catal­y­sis and in-situ spec­troscopy.

Activation and Self-Initiation in the Phillips Ethylene Polymerization Catalyst

Meeting Program — February 2016

Susannah Scott
Susan­nah Scott
Dun­can and Suzanne Mel­lichamp Chair in Sus­tain­able Catal­y­sis
Chem­i­cal Engi­neer­ing and Chem­istry & Bio­chem­istry
Uni­ver­si­ty of Cal­i­for­nia, San­ta Bar­bara

Abstract — The mech­a­nism of spon­ta­neous acti­va­tion of the Phillips (Cr/SiO2) eth­yl­ene poly­mer­iza­tion cat­a­lyst in the absence of an alky­lat­ing co-cat­a­lyst is one of the longest-stand­ing prob­lems in het­ero­ge­neous catal­y­sis. Exper­i­men­tal and com­pu­ta­tion­al evi­dence has long point­ed to organochromium(III) active sites, and the prepa­ra­tion of graft­ed (SiO)2CrCH(SiMe3)2 sites by the reac­tion of Cr[CH(SiMe3)2]3 with par­tial­ly dehy­drox­y­lat­ed sil­i­ca sup­ports this con­clu­sion. How­ev­er, a plau­si­ble mech­a­nism for their for­ma­tion from the inter­ac­tion of chro­mate and eth­yl­ene alone remains to be found. A key issue is the incom­men­su­rate nature of the required redox reac­tions, since Cr(VI) must be reduced by an odd num­ber of elec­trons (three), while only closed-shell organ­ic oxi­da­tion prod­ucts are detect­ed. For the CO-reduced cat­a­lyst, Cr K-edge XANES, EPR and UV-vis spec­tro­scopies are con­sis­tent with ini­tial step-wise reduc­tion of Cr(VI) in two-elec­tron steps, first to Cr(IV), and ulti­mate­ly to Cr(II). Accord­ing to Cr K-edge EXAFS and UV-vis spec­troscopy, the Cr(II) sites have a coor­di­na­tion num­ber high­er than two, most like­ly through inter­ac­tion with neigh­bor­ing silox­ane oxy­gens. After removal of adsorbed CO, the Cr(II) sites react with eth­yl­ene in an over­all one-elec­tron redox reac­tion to gen­er­ate organochromium(III) sites and organ­ic rad­i­cals.
Biog­ra­phy — Scott received her B.Sc. in Chem­istry from the Uni­ver­si­ty of Alber­ta (Cana­da) in 1987, and her Ph.D. in Inor­gan­ic Chem­istry from Iowa State Uni­ver­si­ty in 1991, where she worked with J. Espen­son and A. Bakac on the acti­va­tion of O2 and organ­ic oxi­da­tion mech­a­nisms. She was a NATO Post­doc­tor­al Fel­low with Jean-Marie Bas­set at the Insti­tut de recherch­es sur la catal­yse (CNRS) in Lyon, France, before join­ing the fac­ul­ty of the Uni­ver­si­ty of Ottawa (Cana­da) in 1994 as an Assis­tant Pro­fes­sor of Chem­istry. She held an NSERC Women’s Fac­ul­ty Award, a Cot­trell Schol­ar Award, a Union Car­bide Inno­va­tion Award and was named a Cana­da Research Chair in 2001. She moved to the Uni­ver­si­ty of Cal­i­for­nia, San­ta Bar­bara in 2003, where she is cur­rent­ly holds the Dun­can and Suzanne Mel­lichamp Chair in Sus­tain­able Catal­y­sis, with joint fac­ul­ty appoint­ments in both Chem­i­cal Engi­neer­ing and Chem­istry & Bio­chem­istry. She directs the NSF-spon­sored Part­ner­ship for Inter­na­tion­al Research and Edu­ca­tion in Elec­tron Chem­istry and Catal­y­sis at Inter­faces, a col­lab­o­ra­tive research pro­gram involv­ing UCSB and sev­er­al promi­nent catal­y­sis research groups in Chi­na. Her research inter­ests include sur­face organometal­lic chem­istry, olefin poly­mer­iza­tion, nano­ma­te­ri­als, bio­mass con­ver­sion, envi­ron­men­tal catal­y­sis and the devel­op­ment of new kinet­ic and spec­tro­scop­ic meth­ods to probe reac­tion mech­a­nisms at sur­faces. In 2013, Scott became an Asso­ciate Edi­tor for the jour­nal ACS Catal­y­sis.