Process to reduce the temperature of a hydrogen and carbon monoxide containing gas and heat exchanger for use in said process

A process to reduce the formation of coke and to reduce the temperature of a hydrogen and carbon monoxide containing gas obtained from the partial oxidation of a hydrocarbon feedstock by contacting the gas with a metal alloy surface having a lower temperature than the temperature of the gas, wherein the metal alloy surface comprises between 0 and 20 wt % iron, between 1 and 5 wt % aluminium, between 0 and 5 wt % silicon, more than 30 wt % chromium and at least 35 wt % nickel, wherein said alloy metal surface is maintained at a lower temperature than the temperature of the gas by making use of coolant water, and whereby coke formation on the metal alloy surface is minimized.