NOVELTY - A catalyst bed comprises catalyst layers (L1) and (L2). The catalyst layer (L1) comprises a catalyst (C1) or catalyst precursor (P1), and is catalytically active at 340 degrees C. The catalyst precursor (P1) is activatable at less than 340 degrees C. The catalyst layer (L2) comprises catalyst precursor (P2). The catalyst precursor (P2) comprises nickel in nickel(II) form and is activatable to a catalyst (C2) comprising nickel in nickel(0) form at more than 360 degrees C. The catalyst (C2) has average lateral compression strength after processed at 650 degrees C for 500 hours of 30 N or more.    USE - Catalyst bed is used for reaction system for producing carbon monoxide and hydrogen for producing methane (all claimed).    ADVANTAGE - The catalyst bed has excellent high-temperature stability.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) activation of catalyst precursor (P2) in catalyst bed, which involves applying a flow of synthesis gas to the catalyst layer (L1) at less than 340 degrees C to temperature at which catalyst (C1) is active or the catalyst precursor (P1) is activated under adiabatic conditions, and directing the resulting gas flow onto the catalyst layer (L2);    (2) activation of catalyst (C2) in catalyst bed, which involves applying flow of reaction gas comprising methane and water and optionally nitrogen to catalyst layer (L1) at more than 360 degrees C sufficient for activating the catalyst (C2), and directing the resulting gas flow onto the catalyst layer (L2);    (3) activated catalyst bed;    (4) reaction system, which comprises the catalyst bed or activated catalyst bed in an adiabatic reaction zone, and a preheating zone in upstream. The catalyst layer (L2) is downstream the catalyst layer (L1);    (5) process for providing carbon monoxide and hydrogen, which involves feeding reaction gas comprising methane and water and optionally nitrogen to the preheating zone of the reaction system, heating the reaction gas to more than 360 degrees C sufficient for activating the catalyst (C2), directing the heated reaction gas onto the catalyst layer (L1), and directing resultant gas flow onto the catalyst layer (L2); and    (6) process for providing methane, which involves feeding synthesis gas to the preheating zone of the reaction system, heating the synthesis gas to less than 340 degrees C to temperature at which catalyst (C1) is active or the catalyst precursor (P1) is activated, directing the heated synthesis gas onto the catalyst layer (L1), and directing the resultant gas flow onto the catalyst layer (L2).