Abstract: “Carbon dioxide emissions, known to exacerbate climate change, have been increasing rapidly over the past century. One strategy to alleviate this issue is carbon capture and utilization (CCU), in which atmospheric CO2 is used to produce more valuable compounds. An attractive target is sodium acrylate, the building block of superabsorbent polymers found in many common goods. Researchers have sought a reaction coupling CO2 and ethylene, which would produce acrylate from sustainable starting materials. Nickel catalysts have been able to facilitate this coupling but suffer from low efficiency, due to the formation of a nickelalactone intermediate. This has a very stable ring structure that resists the release of acrylate from the catalyst. My project aims to develop supporting ligands for the catalyst that provide appropriate steric bulk and electron density to the nickel center to promote efficient nickelalactone ring-opening. Current work focuses on N-heterocyclic carbene (NHC) ligands, which are very electron-donating and highly modular. Preliminary experiments on a simple bis(NHC) nickelalactone and computational investigation of other ligand systems with varying properties predicts that strong electronic asymmetry and broad steric bulk are vital to ligand design for destabilizing nickelalactones. These NHC ligands could be the key to efficient nickel catalysts coupling CO2 and ethylene for sodium acrylate production, thus contributing to global CCU efforts.”
East Central IL ACS Undergraduate Research Conference
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Hi Vennela, I enjoyed your talk! You were very well-spoken and communicated your thoughts very clearly so that someone outside your field (like me) was able to easily understand your work. I have a couple questions. How efficient is the traditional process of making sodium acrylate that you mention in slide 4? In other words, what is the percent yield to “beat.” Also, from a structural standpoint, can you speculate why the species in the blue dotted square on slide 13 demonstrates better theoretical results compared to the structures immediately above or to the left of it?
Thank you for your kind comment and your questions! For the efficiency of the traditional acrylate synthesis, acrylic acid is generally made with over 90% conversion from propylene, while the conversion to the sodium salt is often in situ with polymerization and hard to quantify. This could be the benchmark to beat in terms of ethylene conversion, if we’re comparing petroleum cracking feedstocks, even though the CO2 incorporation is the more interesting part of the target reaction.
For my speculation on why the dotted blue nickelalactone isomer has such a low predicted deprotonation energy profile, I honestly don’t have a lot to say. It directly contradicts some of my initial assumptions. My guess would be that somehow the sterics of this particular isomer enable a lactone ring distortion better able to distribute negative charge during deprotonation. I am currently running more calculations that might be able to elucidate this result.
Hello!
I enjoyed your presentation a lot. About density functional theory calculation, can you elaborate on your choice of level of theory and basis set? Besides the two that you’ve used, did you venture out to other basis sets that are potentially more powerful?
Hello, thanks for your question!
I mainly chose the BP86 functional and these basis sets because they are not too computationally intensive but still work decently well for these types of systems (e.g. in comparison to X-ray diffraction crystal structures obtained for some nickelalactones). I have not really played around with more powerful basis sets, but it is possible that those will provide better reactivity estimates. It is certainly something I can look into in the future to see whether the trends I’ve observed differ.
How much CO2 can be foreseen to be able to be taken out of the atmosphere?
Hello, thank you for the question, that’s a really important thing to consider! It is sort of difficult to predict. With the acrylate market exceeding 2 million metric tons per year, maybe 1 million tons of CO2 could be used? In the largest example of current CO2 utilization, 112 million of the 150 million tons of urea produced annually are made from CO2. While these sorts of things make a very small dent in overall atmospheric CO2 levels, it is one step toward more sustainable industrial practices.