The partial oxidation of methanol to formaldehyde is highly exothermic and reactors are operated with a hot spot in the range of 100 degrees C above the desired operating temperature, which can affect selectivity considerably and can also reduce the catalyst life. Nitrogen-diluted air is a common feed gas but by replacing the nitrogen for a gas with a substantially higher heat capacity, the heat evolution may be more efficiently controlled. In this work, we have studied the potential of propane as a substitute for nitrogen. According to a simple reactor model using current commercial conditions as a "base" case, substituting propane for nitrogen could increase productivity by as much as 50%. Furthermore, propane would be safer to use because the gas mixture would be further away from the flammable region versus current operation. (c) 2007 Elsevier Ltd. All rights reserved.