This paper focuses on the application of a nonlinear model predictive control (MPC) method to coal-based integrated gasification combined cycle (IGCC) plants with water gas shift membrane reactors (WGS-MR) for pre-combustion capture of CO2. A systems-level nonlinear model of the integrated IGCC-MR process is introduced. The simulation results for a steady-state design used as a starting point for the control studies are presented. For such studies, a centralized nonlinear MPC strategy using a collocation-based algorithm is formulated to control power generation according to the demand. This strategy is successfully implemented to address scenarios that consider power load transitions (setpoint tracking) and variability in coal/slurry feed composition (disturbance rejection). The closed-loop simulation results show that power control is attained without violating process constraints related to target specifications and regulations imposed in stream temperatures and purities, including the carbon capture goal of 90% recommended by the U.S. Department of Energy (DOE).