Carbon Capture — Is it legit?
Methane and carbon dioxide are the gases of the 21st century
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Note: A reader asked me a few weeks ago to write about carbon capture and its definitely something that fits in with some recent news, especially from Occidental. Do you have any topics you want me to cover? Just reply to this email, email me at firstname.lastname@example.org or tweet at me @Tpolymerist
In The News
Occidental Investing In Direct Air Carbon Capture
Last week in the Oil News Special I wrote about how Occidental is investing in Direct Air Carbon Capture or DAC. You can see the original Bloomberg article here. Essentially what Occidental and their partner companies want to do is take carbon dioxide directly from the air and then pump it into the ground to push oil out.
Sounds like a carbon neutral way to get oil, but how much carbon dioxide is actually in our atmosphere I wondered?
I think this graph from Climate.gov shows two important things. The first is that we have more carbon dioxide in our atmosphere than the average from the last 800,000 years at 409.8 ppm. The second important thing here is that the carbon dioxide content in the atmosphere is 409.8 ppm or 0.0409% of the total.
To selectively pull the carbon dioxide out of the air and then sequester it underground sounds crazy to me right now, especially when we have low oil prices and other projects that seemed more viable get canceled for lack of profitability. Melody Bomgardner for C&EN1 reported this summer that Petra Nova would be idling their coal plant CO2 capture operation because of low oil prices:
A joint venture between NRG and Japan’s JX Nippon, Petra Nova is backed by $190 million in US Department of Energy grants and over $300 million in loans from Japanese banks. In its 3 years of operation it captured 3.5 million metric tons of CO2, according to the DOE.
The facility used an amine-containing solvent system developed by Mitsubishi Heavy Industries to absorb CO2 from low-pressure, oxygen-containing flue gas.
The project’s abrupt halt shows how reliant large carbon-capture projects are on demand for CO2 from the oil sector. Oil production and prices have nosedived due to the economic impact of the COVID-19 pandemic.
The shutdown shows that “the outlook for industrial CO2 capture for enhanced oil recovery applications does not look positive,” concludes an analysis by the market research firm Lux Research. Lux says the project won’t be economical again until oil prices reach $70 per bbl. They are currently below $45 per bbl.
At my first job out of school the inventor and co-founder of the company would always tell us “you can’t polish a turd.” I get similar polishing vibes here by Occidental and any oil company seeking to extract carbon dioxide and push it into the ground to get more oil. There might be a better way to utilize that carbon dioxide that I think is getting more traction and has already gotten some commercial traction. Use carbon dioxide as a starting material for chemistry.
Carbon Dioxide and Methane As Chemical Feedstocks
Let’s start with Methane
Let’s start our story with me attending a research group meeting when I was an undergraduate back in 2008/2009. Someone was presenting about one of the research group’s central research themes, which was C-H activation of methane. The concept was if you can turn methane to methanol then you can unlock a new methane economy that even now in 2020 is not possible.
Methane has a higher global warming potential than carbon dioxide and is a main constituent of natural gas. It is often considered a waste product at crude oil wells. The global warming potential or GWP of methane is compared to carbon dioxide, nitrous oxide, and tetrafluoromethane in the table below. The higher the number the the worse it is for the environment.
I won’t get into the other two gases, but carbon dioxide and methane are sometimes inextricably connected to each other and dealing with these gases is going to be a way for us bridge the gap from a fossil fuel energy economy to one that is primarily renewable. The first step is transitioning coal fired energy generation to natural gas and then from natural gas to renewables. We do not have a robust storage solution for renewables, yet.
Natural gas is about 94% methane2 and is often a byproduct of crude oil extraction and instead of letting that methane go directly to atmosphere it is typically burned off at a flare tower like in the picture below. Natural gas powerplants burn this gas to generate power in a steam turbine and the major byproduct of this process is carbon dioxide. Flare towers are actually probably better overall for the environment than just letting the natural gas go directly to atmosphere even though they can make it look like you have entered Mordor on a rainy day.
The best scenario here would be that we have chemistry that can unlock methane activation for us as well as carbon dioxide. For those that want to talk carbon capture capture we need to also talk about methane.
Methane → Methanol and an Introduction to C-H Activation
Oxidizing methane to methanol would supplant our current process of methanol generation, which is hydrogenation of carbon monoxide or reacting what is known as “synthesis gas.” With methanol we can get a “fuel” in the form of a liquid that is easy to transport and we can do more chemistry to methanol such as further oxidation to formaldehyde or reduce it and make something else.
Industrially, this is how we make methanol right now from natural gas from the Methanol Institute3:
Today, methanol is typically produced on an industrial scale using natural gas as the principal feedstock. A world-scale methanol plant produces 5,000 metric tons per day — 600 million gallons/2.3 billion liters per year — by reforming natural gas with steam and then putting the resulting synthesis gas through conversion into liquid methanol.
To say the least the current method is somewhat energy intensive. This is where concepts such as transition metal catalysis and the concept of small molecule activation or alkyl C-H activation have become important concepts to explore.4 Robert Bergman helped start our modern understanding of this concept. If we can capture methane directly from natural gas and turn it into methanol without having to reform natural gas with steam and then hydrogenation with hydrogen produced from that reaction then we can make methanol generation easier and less energy intensive (you still need to generate heat to do the reforming).
If it is easier to make methanol out of methane then the costs go down over the long term and a feedstock that would once get burned at a flare tower to produce carbon dioxide would become more valuable than ever before. This is even more critical in the event that we might get to a future where extracting oil for fossil fuels is not economical, which could in turn eventually raise prices on chemical feedstocks if the supply is severely constrained from current levels.
Remember ~9% of all oil that is extracted goes to the chemical industry. Because the amount of oil needed to generate chemicals is relatively small the chemical industry takes advantage of the economies of scale in big oil, which helps keeps costs low. As the need for oil drops companies will have to cut production and refinement to boost prices until eventually the only buyers are chemical companies. This is why I think the oil companies should try and buy as many chemical companies as possible.
The other useful product of synthesis gas or “syn gas” as those in the industry might call it is for Fischer-Tropsch chemistry. If you ever see a “gas to liquids” phrase (GTL) or “gas to fuels” phrase you can bet that a Fischer-Tropsch reaction is going to probably be in there somewhere. This type of chemistry was pioneered by Fischer and Tropsch, two German chemists, and was a critical route to obtaining replacement fuel feedstocks due to scarcity of petroleum during WWII for the Germans.5 While, in the future we hopefully will not be using Fischer-Tropsch chemistry to make fuel we could be using it to make higher order alkanes such as ethane, propane, which are the starting materials to make ethylene and propylene — the starting materials for polyethylene and polypropylene as well as required precursors to polystyrene and phenol.
Modern C-H Activation. Turning Methane Into Something Useful
The community of C-H activation chemists is huge. I am by no means going to cover all of it here. That would be crazy. If you have just discovered C-H activation here then great. The references are a good place to start. Tang and coworkers6 have a review on C-H activation that I will attempt to distill for you here. There are three main routes to doing C-H activation from methane that could produce some useful products:
- Complete C-H bond removal and the partial oxidation of carbon: production of CO and H2 (syn gas)
- Complete C-H bond removal: production of Carbon black and hydrogen
- Partial C-H bond removal and C-C bond formation: production of hydrocarbons
Complete C-H bond removal and partial oxidation of carbon gives us synthesis gas and all of the useful stuff I wrote about above can be done here such as Fischer-Tropsch chemistry. We already make synthesis gas industrially, but it is very energy intensive. Developing new catalysts and process methodologies could enable us to make synthesis gas at lower temperatures for less money than it costs now. This could further reduce the energy required and make the process better for the environment, or maybe more portable (i.e. take it to Mars).
Complete C-H bond removal is a route to carbon black and hydrogen. This is already being done at demonstration scale in the past few years and is also known as a “Turquoise Hydrogen” route. For instance Ekona Power just raised $3 million in funding to do a pumped methane pyrolysis to make hydrogen.7 Hydrogen has been touted as a clean fuel replacement for most fossil fuels, but producing and storing hydrogen has been somewhat of a challenge.
Partial C-H bond removal and C-C bond formation for production of hydrocarbons is maybe the most exciting for synthetic chemists (or it is for me anyway) because this is where you can make things like ethane, propane, butane, and benzene. If we can do this third route of synthesis at scale and at low cost then we have a very big abundant natural feedstock of methane here on Earth that we can use to do all of the traditional chemistry we have gotten used to over the past 100 years.
Modern catalysis routes for C-H activation have been explored through noble metal catalysis or other transition metal catalysis, but there is also a potential biological way, specifically a family of enzymes called cytochrome P450s. Frances Arnold has an excellent review on P450s and her pioneering work on doing C-H activation of hydrocarbons with them8:
In nature, enzymes catalyze regio- and stereoselective C–H bond functionalization using transformations ranging from hydroxylation to hydroalkylation under ambient reaction conditions. The efficiency of these enzymes relative to analogous chemical processes has led to their increased use as biocatalysts in preparative and industrial applications. Furthermore, unlike small molecule catalysts, enzymes can be systematically optimized via directed evolution for a particular application and can be expressed in vivo to augment the biosynthetic capability of living organisms.
If Frances Arnold’s name sounds familiar its because she won the Nobel Prize in Chemistry in 2018 for her work in directing the evolution of enzymes. She has also been appointed to lead The Council of Advisors on Science and Technology.9 Congrats Frances! Anyway, enough of C-H bond activation, let’s talk about carbon dioxide.
Carbon Dioxide — The Other Carbon Gas
So despite everything I wrote above about methane activation and how we have abundant methane sources and there is potential to do this type of chemistry with evolution directed enzymes we still need to figure out a way to utilize carbon dioxide. Being able to use carbon dioxide is not important insofar as its abundance, but rather it is a byproduct of many industrial processes that are critical to building infrastructure. Carbon dioxide is in the gas that we emit when we breathe so in a Elon Musk/Jeff Bezos space future being able to utilize carbon dioxide seems important despite Mars having methane.10
There are many industrial processes that emit carbon dioxide, but there are a few that we will have to figure out for the long term viability of certain processes like cement production and short to medium term like natural gas power plants. Getting around the carbon dioxide problem in cement is not easy primarily because the conversion of calcium carbonate to calcium oxide releases CO2 as a byproduct. Natural gas powerplants will probably be our best bet in transitioning power generation from coal until we can develop energy sustainable storage technologies to pair with renewable energy generation and as we know from above burning methane yields CO2.
Point source capture of carbon dioxide is going to be the most preferred since the concentration of CO2 to the other gases is higher coming directly out of a natural gas power plant or cement plant. As above, this is also done chemically with scrubbers based on amines, but once you get this CO2 what can you actually do with it?
There are a couple of options the first being related to methane activation above by turning carbon dioxide into methane via a process called methanation11:
CO2 conversion into CH4 (further denoted as CO2 methanation) is a process with high technological readiness levels. Its reaction over Ni is the classical reaction discovered by the French chemist Paul Sabatier in the early 1900s (also referred to as the Sabatier reaction) and one that can be applied in the so-called Power-to-Gas (PtG) principle. Here, point source CO2 emissions can be employed as cheap, or even negative cost carbon feedstock to demodulate the mismatch in renewable electricity demand and supply, while reducing harmful CO2 emissions in the atmosphere via a closed-cycle process.
Since this reaction needs a high amount of energy 300–400 C, one could think of using renewable energy to power it when there is excess energy capacity. Then if we know how to activate and utilize methane we can turn that carbon source into something more useful. So in a sense carbon capture could also be a way to indirectly store energy.
I actually didn’t even know about methanation until I started writing this newsletter. The Vogt and coworkers article I cite here is primarily why I needed to write about methane activation and uses above. If we can turn CO2 back into methane then all of the chemistry we can do from methane is available to us, but this of course takes energy and installation of new capacity. Is there a more immediate way to utilize CO2 right now?
Putting Carbon Dioxide into Polymers and Materials
All of the above strategies sound amazing right? The issue many might have here is that they are still perhaps years away if we get billions of dollars of funding into commercializing the technologies that have already been developed. If you know any billionaires feel free to forward this newsletter them. Until that reality comes into existence there is a more immediate way to utilize carbon dioxide if we can get our hands on it.
The concept of inserting carbon dioxide in epoxide moieties has been around for awhile and this is primarily how we synthesize ethylene carbonate and propylene carbonate (useful solvents) from ethylene oxide and propylene oxide.12 This process of synthesizing cyclic carbonates with an epoxide and carbon dioxide could be further expanded into synthesizing linear polycarbonates with special catalysts as Geoff Coates has shown to be possible.13
With the right catalysts one could think about polymerizing glycidyl methacrylate and carbon dioxide to make a thermoplastic that could be crosslinked later.14 People have already polymerized glycidyl methacrylate and then pushed carbon dioxide into those polymers where there is a pendant cyclic carbonate.15 Alternatively, we might be able to first insert that carbon dioxide and then polymerize a thermoplastic with a pendant cyclic carbonate or we could mix and match this monomer with a different acrylates to fine tune a specific coating properties for paints. I am not sure that polymer exists yet, but those who are synthetically inclined might see some of the possibilities here.
Covestro already has polymers and polyols that utilize carbon dioxide under the trade name of Cardyon. The amount of CO2 in Cardyon polymers can go as high as 20% by weight according to Covestro. For those interested here is one of their patents covering the production of carbon dioxide polymers.16
Covestro is not the only company making polymers and plastics from carbon dioxide. Ashai Kasei, Empower, and Sabic to name a few are also in the pursuit of turning carbon dioxide into high performance specialty polymers according to the nova-institute.17 Even Avantium, the company I wrote about two weeks ago is pursuing activation of carbon dioxide by making glyoxylic and glycolic acid.18 Hopefully, this primer in carbon capture will make me writing about those companies in the future make more sense.
We are going to need to burn natural gas and make cement for the foreseeable future, at least probably in my lifetime. While we continue to develop the chemistry and technology to take us towards the zero emission future we are going to need to figure out how to utilize gases like carbon dioxide and methane in the near term to reduce our need to either burn methane at flare towers or capture carbon dioxide at point of generation at a cement plant. Being able to make useful stuff out of methane and carbon dioxide will also put more value on these gases and make them less likely to be burned off or allowed to escape out into the atmosphere.
If we hope to build a colony on Mars or spend any lengthy period of time in space then we definitely need to figure out how to utilize these gaseous carbon sources since they will probably be the only carbon sources we might be able to find readily outside of planet Earth.
Talk to you Friday,
The views here are my own and do not represent those of my employer nor should they be considered investment advice.
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