Alkali-promoted cobalt-molybdenum sulfide is a potential catalyst for the conversion of syngas into higher alcohols. This work is an investigation of how the feed composition influences the behavior of the sulfide catalyst. In a sulfur-free syngas the production of higher alcohols is observed to be optimal with an equimolar mixture of CO and H-2 in the feed, while the methanol production benefits from an increasing hydrogen content in the feed. The influence of NH3 and H2O in the syngas feed has also been investigated. Ammonia (741 ppmv) in the feed is observed to cause a general and largely reversible deactivation of the catalyst. Operation with elevated water levels in the syngas feed (4.7-13.4 mol %) is observed to cause a deactivation of the catalyst, and it is especially the chain growth that is affected.