Modeling the thermal DENO x process in flow reactors. Surface effects and Nitrous Oxide formation

Abstract

We have investigated the impact of surface reactions such as NH 3 decomposition and radical adsorption on quartz flow reactor data for Thermal DeNOx using a model that accounts for surface chemistry as well as molecular transport. Our calculations support experimental observations that surface effects are not important for experiments carried out in low surface to volume quartz reactors. The reaction mechanism for Thermal DeNOx has been revised in order to reflect recent experimental results. Among the important changes are a smaller chain branching ratio for the NH 2 + NO reaction and a shorter NNH lifetime than previously used in modeling. The revised mechanism has been tested against a range of experimental flow reactor data for Thermal DeNOx with reasonable results. The formation of N 2 O in Thermal DeNOx has been modelled and calculations show good agreement with experimental data. The important reactions in formation and destruction of N 2 O have been identified. Our calculations indicate that N 2 O is formed primarily from the reaction between NH and NO, even though the NH 2 + NO 2 reaction possibly contributes at lower temperatures. At higher temperatures N 2 O concentrations are limited by thermal dissociation of N 2 O and by reaction with radicals, primarily OH. © 1994 John Wiley & Sons, Inc.