Carbon monoxide separation:past, present and future

Large amounts of carbon monoxide are produced by industrial processes such as biomass gasification and steel manufacturing. The CO present in vent streams is often burnt, this produces a large amount of CO2, e.g., oxidation of CO from metallurgic flue gasses is solely responsible for 2.7% of manmade CO2 emissions. The separation of N2 from CO due to their very similar physical properties is very challenging, meaning that numerous energy-intensive steps are required for CO separation, making the CO separation from many process streams uneconomical in spite of CO being a valuable building block in the production of major chemicals through C1 chemistry and the production of linear hydrocarbons by the Fischer-Tropsch process. The development of suitable processes for the separation of carbon monoxide has both industrial and environmental significance. Especially since CO is a main product of electrocatalytic CO2 reduction, an emerging sustainable technology to enable carbon neutrality. This technology also requires an energy-efficient separation process. Therefore, there is a great need to develop energy efficient CO separation processes adequate for these different process streams. As such the urgency of separating carbon monoxide is gaining greater recognition, with research in the field becoming more and more crucial. This review details the principles on which CO separation is based and provides an overview of currently commercialised CO separation processes and their limitations. Adsorption is identified as a technology with the potential for CO separation with high selectivity and energy efficiency. We review the research efforts, mainly seen in the last decades, in developing new materials for CO separation via ad/bsorption and membrane technology. We have geared our review to both traditional CO sources and emerging CO sources, including CO production from CO2 conversion. To that end, a variety of emerging processes as potential CO2-to-CO technologies are discussed and, specifically, the need for CO capture after electrochemical CO2 reduction is highlighted, which is still underexposed in the available literature. Altogether, we aim to highlight the knowledge gaps that could guide future research to improve CO separation performance for industrial implementation.</p

Design and development of a downstream separation process for ethylene recovery within the e-Refinery framework

Electroreduction of CO2 into high-valued chemicals is a promising way to reduce CO2 emissions while simultaneously producing bulk chemicals currently produced from fossil-fuel feedstocks. The downside of this process is that conversion rates are low, meaning the resulting product stream is a complex gas mixture consisting primarily of reactants and by-products and a relatively small amount of product. This study focuses on the development of a new downstream separation process to capture ethylene from a mock-up reaction mixture (mole fractions C2H4/CO2/CO/H2/H2O : 20/55/15/15/5), based on low driving forces and suitable for application in a 100kW test case within the e-Refinery. An extensive literature study of numerous separation techniques for gases was conducted and adsorption was chosen as the most suitable option. After screening of various adsorbents, active carbon was selected as the most potential sorbent. Based on a selectivity analysis, the primary focus was on the behaviour of C2H4/CO2 on active carbon. Using a simple, custom-build set-up, transient breakthrough experiments were performed for this gas mixture and the resulting selectivity for an equivolume feed, yielded a lower separation performance than expected based on the ideal adsorption solution theory, respectively a selectivity of 1.5–1.7 versus 3.2–3.5. Additionally a theoretical model was developed using MATLAB, which described the velocity profile inside the adsorber column and could qualitatively predict breakthrough behaviour. Further analysis led to the conclusion that for a more accurate quantitative match between experimental and numerical results, isotherm parameters should be obtained from the same type of active carbon. Ultimately this technique could be used to increase the ethylene content in a CO2-bearing stream and pave the way for a new, energy-efficient method to obtain hydrocarbons, ethylene in this case, from an electrolyzer cell

Carbon monoxide separation: past, present and future

Large amounts of carbon monoxide are produced by industrial processes such as biomass gasification and steel manufacturing. The CO present in vent streams is often burnt, this produces a large amount of CO2, e.g., oxidation of CO from metallurgic flue gasses is solely responsible for 2.7% of manmade CO2 emissions. The separation of N2 from CO due to their very similar physical properties is very challenging, meaning that numerous energy-intensive steps are required for CO separation, making the CO separation from many process streams uneconomical in spite of CO being a valuable building block in the production of major chemicals through C1 chemistry and the production of linear hydrocarbons by the Fischer-Tropsch process. The development of suitable processes for the separation of carbon monoxide has both industrial and environmental significance. Especially since CO is a main product of electrocatalytic CO2 reduction, an emerging sustainable technology to enable carbon neutrality. This technology also requires an energy-efficient separation process. Therefore, there is a great need to develop energy efficient CO separation processes adequate for these different process streams. As such the urgency of separating carbon monoxide is gaining greater recognition, with research in the field becoming more and more crucial. This review details the principles on which CO separation is based and provides an overview of currently commercialised CO separation processes and their limitations. Adsorption is identified as a technology with the potential for CO separation with high selectivity and energy efficiency. We review the research efforts, mainly seen in the last decades, in developing new materials for CO separation via ad/bsorption and membrane technology. We have geared our review to both traditional CO sources and emerging CO sources, including CO production from CO2 conversion. To that end, a variety of emerging processes as potential CO2-to-CO technologies are discussed and, specifically, the need for CO capture after electrochemical CO2 reduction is highlighted, which is still underexposed in the available literature. Altogether, we aim to highlight the knowledge gaps that could guide future research to improve CO separation performance for industrial implementation.ChemE/Catalysis EngineeringComplex Fluid ProcessingChemE/Transport Phenomen