Two catalytic processes have been explored for the preparation of suitable samples for use in 14C measurements on an accelerator mass spectrometer. A heavy hydrocarbon was condensed from C 2H 2 using AlBr 3 as a catalyst. This process had low isotopic fractionation, and the carbon ion beam obtainable was 60-70% that from graphite. In the second process, iron powder was used to produce graphite directly from CO 2 and H 2 at 600 °C. A sample preparation system using this reaction has been built. The carbon product produces exceptionally intense, long-lived ion beams. The process introduces little 14C background, and has no observed memory effects.