A kinetic study has been made into the hydrogenation of 3-methyl-1-pentyn-3-ol over palladium on silica catalysts. This reaction already proceeds at very high rates under mild reaction conditions and, therefore, mass-transfer inside the catalyst particle inevitably influences the reaction progress, making the determination of the reaction kinetics difficult. To be able to determine the reaction mechanism and the kinetic parameters, a model has been drawn up in which both mass-transfer and kinetics are modeled simultaneously. This model is able to accurately describe the reaction progress. The model can also be used to explain the effect of commonly used reaction modifiers like quinoline on the reaction. Quinoline can be added to increase the selectivity to the desired alkene intermediate. From the calculations it is shown that the primary function of this type of modifier is to decrease the reaction rate. The lower reaction rate and thereby relatively smaller mass-transfer resistance in the catalyst is most likely a primary cause for the increased selectivity when a reaction modifier is used.