MoS2 is a potential catalyst for the conversion of synthesis gas obtained from different carbon-containing feedstock into methane, hydrocarbons and alcohols. We performed a combined density functional theory and microkinetics simulation study of all relevant reaction pathways of CO and H2 into methane, ethylene, ethane, formaldehyde, methanol, carbon dioxide and water at the bare and partially sulfided Mo-edge of MoS2(1 0 0). Reaction barriers were substantially lower for the 25% sulfur-covered Mo-edge in comparison to the bare Mo-edge. H-assisted CO dissociation is preferred over direct CO dissociation for both surfaces. Microkinetics simulations predict a negligible methanation rate for the bare Mo-edge, which contradicts experiment. The discrepancy stems from oxygen poisoning of the surface. Oxygen removal barriers are substantially lowered at a sulfur coverage of 25%. The resulting CO conversion rate and product distribution are in good agreement with reported experimental data. These simulations show how density functional theory combined with microkinetics simulations can predict performance of catalytic surface used in complex chemical reactions.