Multi-functional Catalysts and Reactors for Lean NOx Reduction

2011 Spring Symposium

Mike Harold
Depart­ment of Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing
Uni­ver­si­ty of Hous­ton

Abstract — Cat­alyt­ic tech­nolo­gies are crit­i­cal to reduc­ing NOx and par­tic­u­late soot from diesel exhaust. In this talk an overview will be pro­vid­ed of efforts span­ning exper­i­men­tal stud­ies of NOx stor­age and reduc­tion and selec­tive cat­alyt­ic reduc­tion, mod­el­ing of mono­lith reac­tors, and dynamome­ter test­ing of fuels and aftertreat­ment tech­nolo­gies. The effec­tive­ness and spa­tio-tem­po­ral fea­tures of the “lean NOx trap” (LNT) will be described based on our com­bined exper­i­men­tal and mod­el­ing stud­ies. Our recent work focused on the gen­er­a­tion and reac­tiv­i­ty of NH3 has sig­nif­i­cance in NSR/SCR appli­ca­tions. Exper­i­ments in both bench-scale and Tem­po­ral Analy­sis of Prod­ucts (TAP) reac­tors reveal a com­plex cou­pling between the stor­age chem­istry and trans­port process­es. Mea­sure­ments of the con­cen­tra­tion fronts show that a major route to N2 for­ma­tion is via NH3. Sys­tem­at­ic vari­a­tion of the Pt dis­per­sion results in a sig­nif­i­cant vari­a­tion in stor­age and reduc­tion activ­i­ty as well as the prod­uct dis­tri­b­u­tion. Iso­topic TAP exper­i­ments reveal the exis­tence of gra­di­ents in the stored NOx in the vicin­i­ty of the Pt crys­tal­lites. The trans­port of the stored NOx can lim­it the regen­er­a­tion rate under some con­di­tions. Glob­al kinet­ic and micro­ki­net­ic mod­els are devel­oped that pre­dict most of the obser­va­tions and direct ongo­ing design and opti­miza­tion efforts. Stud­ies of selec­tive cat­alyt­ic reduc­tion of NOx with NH3 on Fe- and Cu-based zeo­lite coat­ed mono­liths will be also be high­light­ed described. Steady-state kinet­ics exper­i­ments reveal sev­er­al com­pet­ing reac­tions. The NOx con­ver­sion is shown to be a non­lin­ear func­tion of the NO: NO2 feed ratio and is under­mined by the com­pet­ing reac­tions of NH3 and NO oxi­da­tion. Trans­port lim­i­ta­tions become prob­lem­at­ic when NO2 is present.

Speaker’s Biog­ra­phy — Mike Harold is the M.D. Ander­son Pro­fes­sor of Chem­i­cal & Bio­mol­e­c­u­lar Engi­neer­ing at the Uni­ver­si­ty of Hous­ton. He received his B.S. in Chem­i­cal Engi­neer­ing from Penn State in 1980 and his PhD in Chem­i­cal Engi­neer­ing from the Uni­ver­si­ty of Hous­ton in 1985. Mike joined the fac­ul­ty of the Chem­i­cal Engi­neer­ing Depart­ment at the Uni­ver­si­ty of Mass­a­chu­setts at Amherst, where he became Asso­ciate Pro­fes­sor in 1991. In 1993 Mike joined DuPont Com­pa­ny where he held sev­er­al research and super­vi­so­ry posi­tions. In 1999 Mike was appoint­ed Research Man­ag­er of the Chem­i­cal Process Fun­da­men­tals Group in the Cen­tral Research Depart­ment of the DuPont Com­pa­ny. Mike returned to acad­e­mia as the Dow Chair of the UH Depart­ment of Chem­i­cal Engi­neer­ing, which lat­er became the Depart­ment of Chem­i­cal and Bio­mol­e­c­u­lar Engi­neer­ing. He served this post until fall 2008.