Heterogeneous Catalytic Hydrogenation of CO2 to Basic Chemicals and Fuels

The ever-increasing level of anthropogenic CO₂ in the atmosphere and its potential in global warming have resulted in worldwide concerns. On the other hand, CO₂ can be utilized as a non-toxic abundant C₁ feedstock in the synthesis of various valuable products. When used in the synthesis of bulk chemicals, CO₂ emission problems can be alleviated. Among reactions, thermochemical reduction of CO₂ with hydrogen to hydrocarbons and oxygenates is of great interest because the products can be used as basic chemical feedstocks in chemical industries and as liquid energy carriers or fuels. The reactions exhibit high kinetic and thermodynamic barriers and thus are equilibrium-limited. Consequently, the product type and composition are governed by operating conditions and the catalyst type employed. Therefore, catalysis has been an active research field in CO₂ utilization. The availability of cost-effective CO₂-capture materials/methods and hydrogen from renewable sources are other important issues for an effective reduction of CO₂ emissions, especially when fuels are considered as the end products. In this chapter, the CO₂ hydrogenation reactions (methanation, water–gas shift, methanol, and dimethyl ether (DME) synthesis, among others) relevant to large-scale industrial operation and thus capable of contributing to the low-carbon economy are studied in detail. The state-of-the-art catalysts and related researches are discussed. Some pilot- and commercial-scale CO₂ utilization process developments are also investigated.