A heterogeneous chemical reactor analysis and design laboratory: The kinetics of ammonia decomposition

A laboratory module for senior-level reaction engineering/reactor design students is described. Students use low-conversion experimental data to explore and characterize the kinetics of ammonia decomposition over various supported catalysts at atmospheric pressure in a packed-bed reactor. Each student team is assigned one of four catalyst types, a reactor temperature, and a series of feed flow rates and compositions. Aggregate data from all student groups is then summarily analyzed per catalyst type. In each experimental trial, the reactor conversion is determined by a thermal conductivity measurement applied to the feed (reactor bypass) and reactor effluent gases. An analysis of the reaction rate across a range of temperatures and varying feed gas partial pressures allows students to test various reaction mechanisms, to suggest rate-determining steps, and to statistically determine rate law parameters. Students typically use the Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach to derive rate law expressions, and determine rate constants through application of the Arrhenius equation. High student numbers (ca. 140) are accommodated through the availability of four experimental stations — each sharing a common source of feed gas and equipped with independent flow controllers and gas analyzers.