Optimization of two‐dimensional flows with homogeneous and heterogeneously catalyzed gas‐phase reactions

Chemically reacting gaseous flows in catalytic monoliths are numerically investigated to mathematically optimize product yields by the variation of operating conditions and catalyst loading. The fluid dynamics of the single monolith channel is modeled by the two-dimensional boundary layer equations (BLEs), a system of parabolic partial differential equations (PDEs) with highly nonlinear boundary conditions arising from the coupling of surface reactions with the reactive flow field inside the channel. The surface and gas-phase chemical reactions are described by large elementary-step reaction mechanisms. An optimal control problem is formulated with the wall temperature, the catalytic active surface area, and the inlet gas composition and flow parameters as control variables. The newly developed approach and numerical code are applied for the optimization of the oxidative dehydrogenation of ethane to ethylene over platinum at high temperatures and short contact times. The ethylene yield can be significantly increased by choosing the optimal operating conditions. Furthermore, the analysis of the behavior of the reactor at optimized conditions leads to a better understanding of the interaction of physics and chemistry in the catalytic monolith. 2008 American Institute of Chemical Engineers AIChE J, 54: 2432–2440, 2008