The replacement of conventional packed beds of catalyst pellets with novel 'high conductivity' honeycomb catalysts in industrial externally cooled multitubular fixed-bed reactors for exothermic gas/solid processes offers potential advantages besides reduced pressure drops. Near-isothermal operation could result in safer reaction operation, better catalyst thermal stability, improved selectivities, higher throughputs. and more economical reactors with larger tubes. We report herein an experimental and theoretical investigation of this concept.