Syngas is converted into alcohols using microbial or chemical catalysts. Syngas fermentation research using micro-organisms such as strains of Clostridium ljungdahli, Clostridium autoethanogenum, Clostridium carboxidivorans, Clostridium ragsdalei and Alkalibaculum bachi yielded ethanol, butanolisopropanol and acetic acid. Recent advances in the syngas fermentation include developing new strains of microorganisms, improved reactor design and optimized conditions such as temperature, pH, buffer presence and media to increase yield and reduce the cost for production of alcohols (Kundiyana et al. 2010, 2011a, b; Maddipati et al. 2011; Liu et al. 2012).

Chemical catalysts have also been used to convert syngas into mixed alcohols. The process takes places at high pressure and low temperature in presence of catalysts with the function of hydrogenation, C-O bond breaking and CO insertion. Catalysts based on both noble and non-noble metals have been used for synthesis of mixed alcohols. Noble metal based catalysts containing Rh, Ru or Re and supported on oxides such as SiO2 and Al2O3 have high alcohol selectivity but are not economical for commercial applications. Major non-noble metal based catalysts for mixed-alcohol synthesis contain MoS2, Cu-Co, Cu-Zn-Al and Zn-Cr-K (Fang et al. 2009). Recent advances in mixed alcohols production using chemical catalysts include synthesis and development of new catalysts, optimization of reaction conditions to increase yield and reduce cost of alcohols production. However, the alcohol synthesis process still suffers from low yield and poor selectivity of the desired alcohol product (Subramani and Gangwal 2008). Syngas is also considered building block for many chemicals, such as aldehydes and acetic acid, produced through catalytic and microbial conversions. Hydrogen can also be separated from syngas for producing ammonia or refining hydrocarbon fuels.