Fischer Tropsch is typically what people are talking about when they talk about synthetic fuels, and when that is the case, extra heat doesn't help, apart from

Fischer Tropsch is typically what people are talking about when they talk about synthetic fuels, and when that is the case, extra heat doesn't help, apart from starting the reaction. You need enough heat to get it to about 250-300C, but once the reaction has started, you need to aggressively remove heat from the reactor, as the reaction is highly exothermic.