- In this paper, solar photodegradation of caffeine in aqueous solution was studied, this organic compound is the most consumed stimulant around the world. The degradation experiments were carried outdoors in a solar reactor and Evonik-Degussa P25 TiO2 was used as catalyst. The photochemical and photocatalytic effect were tested in aqueous solutions of caffeine. Experimental results indicate that the organic compound is easily degraded over a very short period of time using 0.5g L-1 of catalyst. The kinetic analysis indicates that the initial reaction rate of caffeine is described by the LH-HW model. However, the original compound cannot be mineralized very fast, caffeine is converted to other organic compounds with a longer lifetime before the mineralization, converting caffeine CO2 and water. © 2018 Walter de Gruyter GmbH, Berlin/Boston.