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.