Reducibility of Cobalt Supported on SBA-15 and Zirconia for Fischer-Tropsch Synthesis

2011 Spring Symposium

Kevin Bakhmut­sky1, Noah Wieder1, Thomas Bal­das­sare2, Michael A. Smith2 and Ray­mond J. Gorte1
1Depart­ment of Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing
Uni­ver­si­ty of Penn­syl­va­nia
2Depart­ment of Chem­i­cal Engi­neer­ing
Vil­lano­va Uni­ver­si­ty

Abstract — High demand for petro­le­um and the ris­ing costs of the crude oil feed­stock have spurred a great deal of inter­est in the con­ver­sion of nat­ur­al gas into liq­uid fuels via the gas-to-liq­uids (GTL) process. As a key step in the process, the Fis­ch­er-Trop­sch syn­the­sis (FTS) con­verts syn­gas (CO and H2) to pro­duce hydro­car­bons. Cobalt cat­a­lysts are pref­er­en­tial­ly used in the low tem­per­a­ture Fis­ch­er-Trop­sch syn­the­sis because of their high activ­i­ty, paraf­fin selec­tiv­i­ty and rel­a­tive resis­tance to oxi­da­tion [1,2]. How­ev­er, stud­ies have shown that dis­persed cobalt on cat­a­lyst sup­ports tends to deac­ti­vate into sta­ble cobalt (II) oxide or irre­ducible cobalt sup­port mixed com­pounds [3–5]. This decrease of active cobalt met­al sites has pri­mar­i­ly been attrib­uted to oxi­da­tion by water. Ther­mo­dy­nam­ic data for bulk cobalt sug­gests oth­er­wise, as oxi­da­tion of cobalt at FTS oper­at­ing con­di­tions would not be expect­ed. Coulo­met­ric titra­tion was used to exam­ine redox char­ac­ter­is­tics of cobalt sup­port­ed on meso­porous sil­i­ca and zir­co­nia. Exper­i­men­tal data of cobalt con­strained by pore size in a meso­porous sil­i­ca sup­port sug­gests that oxi­da­tion ener­get­ics of Co nanopar­ti­cles are near­ly iden­ti­cal to those of bulk par­ti­cles [6]. How­ev­er, ther­mo­dy­nam­ic mea­sure­ments of cobalt sup­port­ed on zir­co­nia revealed that low cobalt load­ing sam­ples do appear to under­go par­tial oxi­da­tion at FTS con­di­tions, unlike bulk cobalt and high­er cobalt load­ing sam­ples. Fur­ther exper­i­ments have sug­gest­ed that the appar­ent dis­tinc­tion in redox prop­er­ties is like­ly due to sup­port inter­ac­tions of cobalt oxide with the zir­co­nia rather than an inher­ent dif­fer­ence in ther­mo­dy­nam­ics of bulk and dis­persed cobalt.

Speaker’s Biog­ra­phy – Kevin Bakhmut­sky com­plet­ed his under­grad­u­ate stud­ies at the Johns Hop­kins Uni­ver­si­ty, obtain­ing a B.S. in Chem­i­cal Engi­neer­ing in 2007. Kevin has since worked on his doc­tor­al research at the Uni­ver­si­ty of Penn­syl­va­nia and is present­ly in his fourth year of study as a mem­ber of Dr. Ray­mond J. Gorte’s research group. Kevin’s the­sis research focus­es on catal­y­sis and reac­tion engi­neer­ing, with an empha­sis on a ther­mo­dy­nam­ic approach to met­al-sup­port inter­ac­tions.