Abstract: A start-up method for a methanation process wherein a plurality of catalyst beds are used. The method comprises heating a first catalyst bed to a suitable temperature and thereafter charging a synthesis gas in mixture with an inert diluent to the first catalyst bed. The product stream from the first catalyst bed contains an excess of hydrogen and is passed to a second catalyst bed thereby heating the second catalyst bed. At least a portion of the product stream from the first catalyst bed is recycled to form the inert diluent used with the synthesis gas stream passed to the first catalyst bed.