Chemical, procedural and economical evaluation of carbon dioxide as feedstock in the chemical industry

The utilisation of CO₂ as feedstock in the chemical industry represents an alternative to the geological storage, which is legally limited and socially debated. Generally, scientific publications about the utilisation of CO₂ in chemical reactions typically address the feasibility of the syntheses without paying attention to the CO₂ reduction potential or the economy in contrast to the conventional process of production. The aim of this doctoral thesis is to identify chemical reactions with CO₂ as feedstock, which have the potential to reduce CO₂ emissions. These reactions are evaluated concerning the industrial realization, CO₂ balance and economy compared to the conventional processes. To achieve this, 123 reactions from the literature were collected and evaluated with the help of selection criteria developed specifically for this application. The criteria consider both, the quantitative potential to reduce CO₂ and possible economical interests in these reactions. Additional to the process of the evaluation of the reactions, a CO₂ reduction potential of 1.33 % of the greenhouse gas emissions within the European Union could be calculated. For the chemicals formic acid, oxalic acid, formaldehyde, methanol, urea and dimethyl ether, which most fully satisfy the selection criteria, a direct comparison of the CO₂ based process with the conventional process is performed. By literature data, process designs, and simulations, it has been shown that the highest reductions of CO₂ emissions can be achieved for methanol with 1.43 kg_CO2/kg_MeOH and dimethyl ether with 2.17 kg_CO2/kg_DME, but only with the assumption that the necessary hydrogen for the CO₂ based reaction is produced by electrolysis operated with renewable energy. Overall, the CO₂ based production processes of methanol and dimethyl ether could reduce 0.059 % of the greenhouse gas emissions of the European Union (EU) if all conventional processes are substituted in the EU. Finally, for the CO₂ based processes of methanol and dimethyl ether it could be shown that the manufacturing costs are 3.3 or 2.9 times higher than for the corresponding conventional processes. The result of this are CO₂ abatement costs of 540 Euro/t_CO2 for the CO₂ based production of methanol and 440 Euro/t_CO2 for dimethyl ether. These abatement costs are respectively 90 and 73 times higher than for the geological storage of CO₂. For the case, that the production costs for the necessary hydrogen decrease from 5.22 to 1.22 or 1.76 Euro/kg_H2 no abatement costs are necessary.