The diffusion coefficients of DEB and EVB into a synthesized and a commercial catalyst pellet were determined by numerical integration of the Stewart-Johanson equation at the reaction condition. The continuity equation was solved by the orthogonal collocation method. DVB was prepared by a commercial catalyst. The production rate and effectiveness factor were determined experimentally and compared with the predicted value. It was seen that the diffusion into the catalyst pellet is strongly limiting the process of DVB production.