Ethylene Electrosynthesis: A Comparative Techno-economic Analysis of Alkaline vs Membrane Electrode Assembly vs CO2-CO-C2H4 Tandems
Ethylene Electrosynthesis: A Comparative Techno-economic Analysis of Alkaline vs Membrane Electrode Assembly vs CO2-CO-C2H4 Tandems
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DOI：
10.1021/acsenergylett.0c02633
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发表时间：
2021-02-16
影响因子：
22
通讯作者：
Sargent, Edward H.
中科院分区：
文献类型：
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作者：
Sisler, Jared;Khan, Shaihroz;Sargent, Edward H.
大气中二氧化碳含量的增加导致全球气温上升，突出表明需要碳中和碳负过程。1− 4从人为CO2排放中生产醇类、烯烃和碳氢化合物等化学品是一种有可能通过使用可再生能源工艺和CO2捕获来减少碳排放的方法。5− 8其中一种化学品乙烯被广泛用作生产聚乙烯、环氧乙烷和乙二醇等许多原材料的原料。电化学CO2还原（CO2 R）制乙烯的最新进展促使研究人员通过技术经济研究确定盈利途径。目前，这样的研究还没有系统地考虑CO2损失;然而，在已公布的实验系统中，由于中性膜电极组件（MEA）中的交叉、碱性流动电池中的碳酸盐形成以及每个中小于100%的CO2单程利用率，显著的CO2损失。在这里，我们发现，即使相对较低的CO2交叉/碳酸盐形成比为1：1（CO2分子损失：CO2分子还原为任何产物），也需要电能效率（eEE）> 65%，以2美分/千瓦时的电力生产1000美元/吨的乙烯。为了解决这个问题，我们然后检查了一个系统，该系统消除了碳酸盐的形成-电解CO2→ CO，然后通过碱性电解CO2 → CO→ C2 H4，并发现它可以生产1000$/吨乙烯，总eEE为1.52%。这意味着，对于80%的CO2→ CO eEE（在商业固体氧化物电池中可实现），CO→ C2 H4阶段必须获得超过40%的eEE，这是一个可实现的目标，因为今天的CO→ C2 H4电解槽报告eEE超过30%。这项工作强调了在电解槽和级联中进行乙烯电合成以获得商业相关性所需的进展。迄今为止，乙烯主要通过石脑油（欧洲，亚洲）和天然气衍生乙烷（北美）的蒸汽裂解生产。这两种方法都存在高能量需求和CO2排放的问题。乙烯的巨大市场规模（2018年为1.8亿吨）9和相对较高的市场价格（600 - 1200美元/吨，取决于地区）10使其成为通过CO2电还原技术生产的有价值的化学品。
Increased atmospheric carbon dioxide (CO2) levels have contributed to a global rise in temperatures, highlighting the need for carbon-neutral and carbon-negative processes. 1− 4 The production of chemicals such as alcohols, olefins, and hydrocarbons from anthropogenic CO2 emissions represents an approach that has the potential to decrease carbon emissions through the use of renewably powered processes and CO2 capture. 5− 8 One such chemical, ethylene, is widely used as a feedstock for the production of many raw materials such as polyethylene, ethylene oxide, and ethylene glycol. Recent improvements in electrochemical CO2 reduction (CO2R) to ethylene have spurred researchers to identify pathways toward profitability through techno-economic studies. Presently, such studies have not taken systematic account of CO2 loss; yet, in published experimental systems, significant CO2 is lost due to crossover in neutral membrane electrode assemblies (MEAs), carbonate formation in alkaline flow cells, and less than 100% CO2 single-pass utilization in each. Here, we find that even relatively low CO2 crossover/carbonate formation ratios of 1: 1 (CO2 molecules lost: CO2 molecules reduced to any product) require electrical energy efficiencies (eEEs)> 65% to produce ethylene at 1000$/tonne with 2¢/kWh electricity. To address this problem, we then examine a system that eliminates carbonate formation electrolytic CO2→ CO followed by CO→ C2H4 via alkaline electrolysis and find it can produce 1000$/tonne ethylene with an overall eEE of∼ 52%. This means that, for a CO2→ CO eEE of 80%(achievable in commercial solid-oxide cells), the CO→ C2H4 stage must obtain∼ 40% eEE, an attainable goal given that today’s CO→ C2H4 electrolyzers report eEE≈ 30%. This work highlights required advances for the electrosynthesis of ethylene in electrolyzer cells and cascades to gain commercial relevance.To date, ethylene is predominantly produced via steam cracking of naphtha (Europe, Asia) and natural-gas-derived ethane (North America). Both of these processes suffer from high energy requirements and CO2 emissions. Ethylene’s large market size (∼ 180 million tonnes in 2018) 9 and relatively high market price (600− 1200$/tonne depending on region) 10 make it a valuable chemical to produce through CO2 electroreduction techniques an approach that offers the