The monolith honeycomb substrate forms the basis of essentially all of the catalytic converters used in mobile (transportation related) applications.Depending on the application, various catalytic washcoats are applied to the monolith substrate.Converters have been developed for oxidation of carbon monoxide and hydrocarbons, and for the reduction of oxides of nitrogen.More recently, considerable interest has been seen in the development of catalytic converters for natural gas fuelled engines.The development of a catalytic converter for a lean burn engine presents a challenge, owing to the relative inactivity of methane, which in turn results from its inherent stability.As a result, higher temperatures are typically required than for other hydrocarbons.