Active Centers of Catalysts for Higher Alcohol Synthesis from Syngas: A Review

The gradual depletion of oil resources and the necessity to reduce greenhouse gas emissions portray a concerning image of our contemporary security of liquid transportation fuels in the event of a global crisis. Despite a vast amount of natural gas resources that we have and the huge economic incentive, the conversion of gas to liquid fuels or chemicals is still very limited because of the high technological complexity and capital cost for facilities. However, with the anticipated depletion of liquid petroleum and the soaring price of crude oil, the conversion of natural gas to liquid feedstock or fuels will become more and more important. Higher alcohols are important feedstocks for the chemical and pharmaceutical industries and have wide applications as potential fuel additives or hydrogen carriers for fuel cells for clean energy delivery. There is a long-standing interest in the synthesis of higher alcohols from syngas, an important Fischer–Tropsch technology for natural gas conversion. The purpose of this review is to provide readers with an extensive account of catalytic synthesis of higher alcohols from syngas using various catalysts reviewed from a unique perspective: clarification of the active centers and reaction pathways. In light of the different sources providing the active centers, three major classes of catalysts in terms of monometallic, bimetallic, and trimetallic/multimetallic catalysts are systematically reviewed, and their respective performances are carefully compared. Finally, future works proposed to improve the catalyst design are described.