Unsupported MoS2 catalysts were prepared for the methanation reaction by varying the pressure and temperature in the hydrothermal reaction by using ammonium tetrathiomolybdate (ATTM). The physical and chemical characteristics of the catalysts were analyzed by using XRD, SEM, TEM, BET, XPS, H-2-TPR, and CO-TPD techniques. The catalyst particles were formed in the bent fringe shape by stacking the (0 0 2) planes, and consisted mostly of MoS2, with some Mo2S5 and MoS3. It was found that the BET surface and active sites such as surface Mo4+ and sulfur vacancies increased with increasing preparation pressure, which could contribute to the improvement of MoS2 catalytic activity. The increase in preparation temperature not only favored the decomposition of ATTM into MoS2, but also lowered the number of active sites accessible for the reaction. Thus, it was suggested that the preparation temperature should be controlled at 350 A degrees C to improve the catalytic activity. [GRAPHICS] .