Monolithic reactors are in many cases an attractive alternative to conventional multi-phase reactors. Advantages are the low-pressure drop, the absence of a need for a catalyst separation, and the large geometrical surface area. The main disadvantage is, however, the lack of practical experience with monolithic reactors. A pilot-scale study has been carried out to overcome this disadvantage and to evaluate the performance of a monolithic reactor. The results of this study have demonstrated that a higher productivity or a higher selectivity can be obtained, when a monolithic reactor is used instead of a trickle-bed reactor.