Catalytic aspects of high temperature methanation

Methanation for SNG production is complex because the high concentrations of CO and CO/sub 2/ involved result in large potential temperature increases. This may cause sintering of the catalyst or for some cases a potential for carbon formation. One solution is to include a recycle stream of product gas as a diluent which involves a loss of energy in the recycle operation. An economic process should allow minimum recycle but, for an adiabatic process, this is equivalent to a large temperature increase. Another solution is to carry out the methanation in a cooled reactor in which the heat of reaction is transferred from the reaction zone into a cooling medium, e.g. boiling water. For adiabatic and for cooled reactors as well, in order to meet these process requirements, the catalyst should be active and stable both at high and low temperatures. The paper summarizes catalyst studies of important phenomena to be controlled in the development and use of an industrial catalyst meeting these requirements. The use of a nickel catalyst for methanation is limited to a minimum operating temperature because of the risk of carbonyl formation and deactivation, and to a maximum operating temperature because of sintering and in certainmore » cases the risk of carbon formation. Between these temperature limits, the activity and stability of the catalyst determines the optimum layout of the methanation process. The Topsoee MCR-2X catalyst allows operation in the temperature range 250/sup 0/C to well above 700/sup 0/C.« less