Dehydration adsorbents deactivate with time due to either pore mouth closure, window blocking, coking and/or hydrothermal decrystallization. These mechanisms of deactivation may be significant under severe hydrothermal conditions and/or in presence of reactive hydrocarbons at elevated temperatures and/or pressures. A mathematical model for predicting the uptake rates for crystal particles partially blocked either due to coking or pore mouth closure has been developed and numerical results, using the orthogonal collocation technique, have been obtained. Concentrated blockage of the crystal surface greatly reduces the mass transfer rate in comparison to uniformly distributed surface blockage.