In this work, a local constrained adaptive output feedback is presented for a class of exothermic tubular reactors models described by a nonlinear partial differential equations. The considered output is the measured temperature in a fixed zone of the reactor to regulate the temperature throughout the reactor to a ball with radius 1 (arbitrarily small) centered at the fixed temperature profile. For a given Measurement zone with length given in terms of the desired profile and lambda and for initial temperature in a fixed domain, it is shown that the tracking error through the reactor tends asymptotically to a ball of arbitrary prescribed radius lambda >0, centered at the given temperature profile. Numerical simulations have been performed to illustrate the performance of the proposed approach. (C) 2016 Elsevier Ltd. All rights reserved.