Electromagnetic and heat transfer analysis is used to determine possibility of selective heating of nanometer-sized, metallic catalyst particles attached to a ceramic support through microwave irradiation. This analysis is incorporated into a macroscopic heat transfer model of a packed and fluidized catalyst bed heated by a microwave field to predict thermal effects associated with selective heating of the catalyst sites. The model shows a dependence on particle size and microwave frequency on the selective heating of the catalyst sites. The macroscopic thermal effects are shown to be small for a typical experiment. However, changing the support material and catalyst particle size are shown to distinguish the thermal effects associated with selective heating of the metallic catalysts.