The present work demonstrates, for the first time, the development of a computationally efficient closed-loop system with a model predictive controller (MPC) where a computational fluid dynamics (CFD) process model is utilized to represent the process behavior. Specifically, we present the development of a MPC and its implementation within the CFD model of a steam methane reforming reactor, which has been developed and validated in our previous work, to create the CFD-based closed-loop system. Initially, we develop an MPC algorithm using a linear approximation of the dynamics based on the CFD data, and implement it within the CFD simulation as a user-defined function. The MPC accounts for the physical limitations (maximum allowable operating temperature of the outer reforming tube wall) of the reactor as a constraint. We demonstrate the application of the developed MPC within the CFD simulations for a set-point change under the influence of a tube-side feed disturbance. The CFD model determines an optimal outer reforming tube wall temperature trajectory to track the set-point, and the results of the simulation are compared with those resulting from a CFD-based closed-loop simulation under proportional-integral (PI) control.