This report described the experiments that used plasma reaction between plasma source gases and brown coal (Yallourn). The properties of the products were influenced by changes of the experimental conditions. The reaction experiments were carried out with 2.45GHz microwave plasma by using hydrogen, helium and argon systems. Ratios of coal conversion (Xc) were as follows;Xc (H2) was 33.2%, (He) was 13.7%, and Xc (Ar) was 24.8% at reaction time 1 minute. No practical difference was detected after 3 minutes. Yields of benzene soluble oily fractions (Yoil) were as follows; Yoil (H2) was 6.0%, Yoil (He) was 3.4% and Yoil (Ar) was 8.7% at 1 minute, while at 3 minutes Yoil (H2) was 4.9%, Yoil (He) was 4.1% and You (Ar) was 7.7%. In addition at 1 minute, no difference of molecular weight distribution measured by MALDI-TOFMS spectra and GC was observed, while the polymerization of oily products under argon or hydrogen system was occurred after 3 minutes. Yields of gaseous components (Ygas) were as follows; Ygas (H2) was 27.2%, Ygas (He) was 10.3% and Ygas (Ar) was 16.0% at 1 minute, while Y, (H2) was 48.1%, Ygas (He) was 50.9% and Ygas (Ar) was 46.6% at 3 minutes. Typical patterns of time change in molar fraction of gaseous components by GC were shown on each plasma source gas.
