Formaldehyde production from methanol over silver catalyst is a fast, exothermic process where dilution is used to control heat release. These properties are indicators of Process Intensification potential. The process is run adiabatically and produces hydrogen (currently left in the tail gas, which is burnt). To investigate the possibility of using a combination of heat exchange and a lower concentration of oxygen in the feed stream to increase hydrogen selectivity while maintaining the required formaldehyde yield, a complete reaction mechanism is necessary. This book combines a review of existing literature on the mechanism of formaldehyde production over silver with an extensive experimental investigation and microkinetic modelling to give a clearer picture of the reaction mechanism. It then outlines the pathways and reaction species that require further investigation. This information should be useful for students and researchers looking at reactions over silver catalyst.