Multiphase airlift reactors have been widely used for decades in chemical engineering, biochemical fermentation and wastewater treatment. The advantages of theses reactors include simple construction, an absence of moving parts, efficient mixing and mass transfer with low energy consumption per unit volume. The objective of the present work was to study, using of the CFD (computational fluid dynamics) simulations, the hydrodynamics (liquid circulation velocity and on the gas holdup) in an internal loop airlift reactor with air injection between the cylinders. In these simulations the conditions adopted were: dispersed phase (gas) - air; phase continuous (liquid) -water; drag model: Grace and different air superficial velocities (Ug). In the liquid phase, the turbulence can be described using the k-ε model. Through this study, it was possible to obtain useful information about the operation of this equipment to be employed in the enzymatic hydrolysis of sugarcane bagasse.