Chemically sensitive imaging in heterogeneous catalysis — from microscale to macroscale

2009 Spring Symposium

 
Jochen Lauter­bach
Depart­ment of Chem­i­cal Engi­neer­ing
Uni­ver­si­ty of Delaware
Newark, DE


Abstract — We have been using high-through­put (HT) approach­es based on rapid-scan FTIR hyper­spec­tral imag­ing in the mid-infrared to screen cat­a­lyst for­mu­la­tions for the dis­cov­ery and opti­miza­tion of new and improved mate­ri­als. In com­bi­na­tion with HT meth­ods, we also employ a vari­ety of more tra­di­tion­al spec­tro­scop­ic meth­ods to under­stand the under­ly­ing fun­da­men­tal sci­ence.

Two exam­ples will be used to illus­trate this research approach: de-NOx for auto­mo­tive exhaust after-treat­ment and ammo­nia decom­po­si­tion cat­a­lysts for CO free hydro­gen generation.While HT screen­ing is a macro­scop­ic analy­sis tech­nique, we are also inter­est­ed in observ­ing non-lin­ear phe­nom­e­na on work­ing cat­a­lysts in situ on the microscale using spec­tro­scop­ic imag­ing based on ellip­som­e­try. The col­lec­tive, glob­al behav­iour of a cat­alyt­ic sys­tem depends on the effec­tive com­mu­ni­ca­tion of local reac­tiv­i­ty vari­a­tions to dis­tant points in the sys­tem. One mode of com­mu­ni­ca­tion occurs via par­tial pres­sure fluc­tu­a­tions in the gas-phase above the cat­alyt­i­cal­ly active sur­face. This gas-phase cou­pling mode is con­sid­ered to be most effec­tive under vac­u­um con­di­tions, where the mean free path between mol­e­c­u­lar col­li­sions is large. We take advan­tage of a spa­tial­ly dis­trib­uted sys­tem of iso­lat­ed chem­i­cal oscil­la­tors to inves­ti­gate the details of gas-phase com­mu­ni­ca­tion in the 10–3 Torr range. Char­ac­ter­i­za­tion of local gas-phase vari­a­tions, in con­junc­tion with local kinet­ic activ­i­ty on the sur­face, shows that sur­face/­gas-phase inter­ac­tion might dif­fer from the con­ven­tion­al assump­tion of a gra­di­ent free, mol­e­c­u­lar flow envi­ron­ment near the sur­face. This analy­sis pro­vides a quan­ti­ta­tive esti­mate of the effec­tive gas-phase cou­pling length in a het­ero­ge­neous sys­tem. This cou­pling length was found to be in agree­ment with sur­face imag­ing results which qual­i­ta­tive­ly showed cou­pling between oscil­la­tors.

Speaker’s Biog­ra­phy — Jochen Lauter­bach received his Diplo­ma in Physics at the Uni­ver­si­ty of Bayreuth, Ger­many under Prof. J. Küp­pers and his Doc­tor­ate in Phys­i­cal Chem­istry at the Fritz-Haber Insti­tute of the Max-Planck-Soci­ety, Berlin, Ger­many under Pro­fes­sor G. Ertl. He came to the US in 1994 with a Feodor-Lynen-Fel­low­ship of the Alexan­der von Hum­boldt-Foun­da­tion and per­formed his post-doc­tor­al work at the Uni­ver­si­ty of Cal­i­for­nia at San­ta Bar­bara under Prof. W.H. Wein­berg. He joined the fac­ul­ty at Pur­due in 1996 and, in 2002, moved to the Uni­ver­si­ty of Delaware, where he cur­rent­ly is a Pro­fes­sor in the Chem­i­cal Engi­neer­ing Depart­ment. His research inter­ests include the design of cat­alyt­ic mate­ri­als using high-through­put screen­ing method­olo­gies and in situ spec­tro­scop­ic tech­niques, devel­op­ment of cat­a­lyst syn­the­sis method­olo­gies based on microemul­sions, nano-engi­neered poly­mer films from renew­able feed­stock, and non-lin­ear dynam­ics of chem­i­cal reac­tions, in par­tic­u­lar exter­nal spa­tiotem­po­ral forc­ing. Pro­fes­sor Lauter­bach has pub­lished close to 100 papers/book chap­ters and has giv­en over 150 invit­ed pre­sen­ta­tions.