Abstract: The present invention generally relates to gasification processes using high-temperature steam. In one aspect, steam at relatively high temperatures (e.g., at a temperature of at least about 1500° F.) is reacted with a carbon-containing fuel. The carbon-containing fuel may be reacted to produce a carbonaceous intermediate, which may then be reacted to produce a hydrocarbon. The hydrocarbon may then be purified, further reacted, or the like. In some cases, the carbonaceous intermediate may be reacted in a different reactor than the reactor involving reaction of the carbon-containing fuel with the steam. In addition, in some embodiments, H2 may be produced in reaction systems of the invention, which may be separated and purified, used to produce heat, reacted to produce a hydrocarbon, or the like. In some embodiments, the steam used in this reaction system may be heated to relatively high temperatures using a ceramic heat exchanger, such as those described in U.S. Pat. No. 4,029,465.