(232e) CO2 Utilization in the Production of Ethylene Oxide
AIChE Annual Meeting
2017 Annual Meeting
Topical Conference: Advances in Fossil Energy R&D
Novel Approaches to CO2 Utilization
Monday, October 30, 2017 - 4:43pm to 5:05pm
The chemical methodology by which ethylene oxide is currently produced is the partial oxidation of ethylene using oxygen (this process is called epoxidation). A silver-based catalyst is used, and either air or preferably oxygen is the oxidant. Ethylene epoxidation is performed at lower temperatures (220 to 280°C) compared with other selective oxidation processes and at high pressure (10 to 30 bar).1
The Captured CO2 Catalyst for the Production of Ethylene oxide (C3-PEO), a technology being developed at RTI International, aims at producing ethylene oxideâa high-value chemicalâwhile consuming CO2âa greenhouse gas. This technology is based on novel catalysts utilizing the following key discoveries:
Abstraction of oxygen from CO2 using the reduced mixed-metal oxide catalysts
Transfer of the abstracted oxygen from CO2 to react with hydrocarbons to form desired products
Operation at temperatures which make these catalysts commercially practical to produce ethylene oxide
Our proposed process uses a cofeed reactor as shown in Figure 1. The proposed ethylene oxide process will have a concentrated CO byproduct stream, which could be used for the manufacture of many products such as methanol, dimethyl ether, acetic acid, acetic anhydride, vinyl acetate, styrene, terephthalic acid, formic acid, n-butanol, 2-methylpropanal, acrylic acids, neopentylacids, propanoic acid, dimethyl formamide, and Fischer-Tropsch hydrocarbons.2 Therefore, the two marketable product streams from the proposed process are ethylene oxide and CO, which are both valuable intermediates for the petrochemical industry.
Figure 1. Conceptual schematic of the transport reactor process used in this process.
RTI has improved on its previous catalyst formulations for CO2 utilization3 and developed families of catalysts which can both remove oxygen from CO2 and transfer the oxygen to ethylene to make ethylene oxide. The catalyst families are based on metal oxide phases which were found to be similar to iron in terms of reacting with CO2, but are more selective than iron for ethylene epoxidation. Improvements on the production of ethylene oxide have been made by the use of promoters, probing the catalyst support to identify a correlation with support acidity, and observing the impact of surface area on dispersion. Ethylene oxide has been produced at small scale in the fixed-bed catalyst test reactor in both a continuous cofeed and a transport mode of operation. However, a cofeed system was found to be optimal and studied for scale-up of the technology.
Life cycle analysis has shown that the process avoids more than 2.8 kg of CO2 per kg of ethylene oxide produced. Techno-economic analysis results show that the process can produce an IRR above 15%, and sensitivity analyses reveal the most important factors regarding the economic viability of the technology. We have compared the RTI CO2 oxidation process with the state of art partial oxidation process and found that the new process can be economically favorable depending on market conditions.
(1) Chongterdtoonskul, A.; Schwank, J. W.; Chavadej, S. Journal of Molecular Catalysis A: Chemical 2013, 372.
(2) Kolb, K. E.; Kolb, D. Journal of Chemical Education 1983, 60, 57.
(3) Shen, J. P.; Mobley, P. D.; Douglas, L. M.; Peters, J. E.; Lail, M.; Norman, J. S.; Turk, B. RSC Advances 2014, 4, 45198.
Keywords: CO2 Utilization, Ethylene Epoxidation