Loop reactors extend the flow-reversal concept to rotating port feeding in a loop-shape system made of N units. To analyze its behavior two limiting models are derived for a system with an infinite number of units: The first one corresponds to an arbitrary switching velocity, whereas the second corresponds to large switching velocities and is essentially a cross-flow model. Both models can admit, with a generic first-order Arrhenius kinetics and typically large Pe and Le numbers, a rotating-pulse solution with peak temperatures that significantly exceeds the increase in adiabatic temperature. Both solutions were corroborated by simulations of finite-N systems that show convergence to the expected asymptotes in realistic system lengths. Rotating pulses emerge over a wide domain of parameters, when the ratio of switching velocity to front propagation velocity is properly tuned around unity, and in a relatively narrow domain of parameters, around the Hopf bifurcation to spatial oscillations, when that ratio is high. Between these two (slow- and fast-switching) behaviors the system exhibits a complex structure of solutions. The asymptotic models enabled us to draw bifurcation diagrams and characterize the properties of emerging solutions. Future studies will apply the loop reactor concept to reversible reactions and endothermic-exothermic reactions. (C) 2004 American institute of Chemical Engineers.