Steady-state and dynamic-heat regimes on the dry, partially wetted, and completely filled catalyst particles were studied using the model reactions of benzene, alpha-methylstyrene and octene hydrogenation over the several catalysts with different porous structures, apparent catalytic activities, and heat conductivities. A rise in the particle temperature at the external limitation regime was studied and the effective diffusion coefficients of limiting species were determined. The regime of particle preheating, gas temperature, hydrogen saturation of AMS or octene vapors, and the liquid mass flow rate on the top of a catalyst particle were varied. The phase equilibrium between the vapor saturated hydrogen and the partially wetted catalyst particle is found to essentially affect for dynamic runaway of the particle. According to the measured center and surface temperatures of each particle, there are two significantly different steady states in the range of liquid flow rates. A catalyst wetted by liquid and blown off with dry hydrogen provides a temperature hysteresis phenomenon. This phenomenon is characterized by the regime when the catalyst particle is almost liquid filled and its temperature is lower than that of gas. Another high-temperature regime occurs if a catalyst particle is almost dry and its temperature is higher than that of gas. Ignition and extinction dynamics of the catalyst particle were studied under conditions of the combined evaporation and hydrogenation processes. (C) 2003 Elsevier B.V. All rights reserved.