I would like to try some home chemistry experiments to catch CO2 from the air and turn it into methanol (or another convenient liquid hydrocarbon).
It could also be methane (or propane or butane or similar) if there was some way to store it and e.g. demonstrate it burning.
Not looking to do it all at once of course. Just some of the important steps to start with. E.g. I know I can make CO2 easily by mixing vinegar and baking soda. So that could be a starting point for an experiment in turning that into something else.
Although I am quite interested in that first step, too. I know CO2 dissolves in water and even easier in a strong base. (Carbonic acid) How to get the CO2 gas out of there, or get it to react further? Can I get it to form methanol in the water and then distill it out?
Today there are businesses offering installations on a commercial scale (just two that I happen to have read about, Climeworks or Carbon Engineering) so those processes would be interesting to do, or I could use different processes if easier in a home setting.
What could be some simple home experiments that would form steps for capturing and converting athmospheric CO2?
BTW not looking to “grow plants and then ferment them”, I’m not into plants. Although I might consider something with store bought yeast, but I don’t want to distill ethanol And the carbon has to come from the air, not from other added chemicals.
Yeast will do pretty much the opposite of what you want - it will produce CO2. Does ‘growing plants’ include algae? - because that opens up some possibilities - some algae produce oils and fats directly.
I don’t like plants or growing plants, I’m a tech nerd. But if I could make it a little more… technological… suppose I had a closed vat with “chemicals” (including algae) in it. Bubble air through it for a month, or put it out in sunlight, or on a (solar electricity) electric heater. And find that afterwards the mass of the chemicals had increased by 1kg. That would work. Especially if I could then purify the chemicals into a jar of oils.
Can I buy a suitable vat, algae and chemicals somewhere? What would be suitable ingredients?
To use carbon dioxide (CO[SUB]2[/SUB]) to produce methanol (CH[SUB]3[/SUB]OH) you first have to convert it to carbon monoxide (CO) using a catalyst and then combine with hydrogen to make syngas. This is because the covalent bond of the oxygen atoms is so strong that CO[SUB]2[/SUB] has no affinity to combine with anything else. Methanol is frequently used as an intermediate to steam reformation to produce hydrogen, but in this case you’d have to separate the hydrogen first which is an energy negative (and typically atmospheric carbon positive) reaction depending on where you get the hydrogen from.
I would also caution against working with with gaseous hydrogen unless you are very experienced in gas chemistry lab technique AND have prior experience handling hydrogen. Gaseous hydrogen can be very dangerous because of its low denotability threshold and high range of flammability and denotability limits. If you do work with hydrogen, you need to do so in an area with high ceilings and excellent ventilation.
Wonder how easy that would be to do if the catalysts were just commercially available somewhere.
I did know about the Fischer Tropsch process. I thought it used high pressures, high temperatures and exotic catalysts. Not ideal for home experimentation. Is there any way of doing an equivalent reaction with some simpler means?
I also realize that hydrocarbons give off lots of energy when burned to CO2, and you have to put that energy back in somehow to go the other way. But OTOH the reaction of hydrogen and oxygen also gives off lots of energy which is easy to put back in with simple electrolysis. Is there a law of physics that says you can’t put the energy back into the CO2 without high temperatures and pressures? (ETA: But then again, plants do it all the time…)
It isn’t that you need high temperatures and/or pressures to turn reactants into CO[SUB]2[/SUB], but the most efficient extraction of that energy in a heat engine requires getting a reaction at the highest possible temperature and the fastest possible expansion to reduce thermal energy losses and get as close to adiabatic expansion as possible, e.g. a Carnot cycle. Using a fuel cell you can extract energy by direct electrochemical reaction producing a charge differential between the anode and cathode without the same temperatures or pollution byproducts of combustion processes, but the tradeoff is that fuel cells are generally limited in how much specific power they can produce, the temperatures at which they can operate without the electrolyte breaking down, and the sensitivity of the catalyst to contamination (depending on the type of fuel and catalyst material).
“Simple electrolysis” is a clean process from a byproduct standpoint (as long as you use distilled water) but it is not very efficient because of the thermal losses. These could be recovered with regeneration systems and the heat used for other purposes, but it inevitably results in a lot of waste. If you have something like a mid-ocean solar platform that you want to use to generate fuel for transportation use then you might just accept the losses, but it isn’t something you’d want to use a power production source that relies on a fuel that has significant cost and supply limitations, e.g. nuclear fission.
The Fischer-Tropsch process is quite inefficient and not cost effective compared to even the most difficult tar sand extraction process. It was famously used by Nazi Germany in the waning days of WWII simply because they had lost access to Middle East oil fields and other sources of petroleum. It is not a sustainable means of mass liquid hydrocarbon fuel production.
If you are interested in hydrocarbon fuel synthesis, two books you should read are Beyond Oil and Gas: The Methanol Economy by Nobel laureate George Olah et al, and Synthetic Fuels by Probstein and Hicks. The former is a cogent analysis of energy supplies, both natural and synthetic, largely focused on transportation fuels. Olah examines natural reserves of petrochemical resources, the use of renewable and atomic energy sources with their advantages and limitations, the “hydrogen economy” and its substantial limitations as medium for transportation energy, and the methanol and dimethyl ether (DME) economy as a fuel carrier. Although he is a cautious advocate for methanol and DME for transportation use, he is realistic about both the practical and political limitations and does not advocate a one-size-fits-all strategy for future energy policy, advocating instead for wider research and a diverse portfolio of potential sources and carriers. The latter book is more of a survey of conventional synthetic fuel production and is an excellent reference if a little dated (not that problematic as there have not been great practical advances in synthetic fuels since the 2005 edition was published despite all the promises of fuel from biomass and hydrocarbon-producing-algae).
This may be more academic than the kitchen table experimentation that the o.p. was looking for but it is good to have an understanding of the basic limitations of hydrocarbon fuel synthesis and why there has not emerged a clear choice as a replacement for natural petroleum sources. I find the work of Vaclav Smil to be instructive as well, although his focus is more systematic and at a survey level rather than the research detail that Olah et al go into.
Not ever so sure, however, whenever I tried keeping fish, it seemed like I was keeping algae - I think you could probably start from a sample of pondwater - add it to a large container of water, plus some NPK plant food and bubble air through it and add sunlight - you’re almost certain to produce biomass that way and I think if there’s enough of it, you could just filter it, dry it out and process it as one does to produce woodgas - probably horribly inefficient, but I reckon you’ll get some kind of result.
Thanks for the recommendation. I am not interested in the fossil fuel aspects of that book but it seems to have interesting info about methanol (which I myself have also concluded works better than hydrogen).
Although I’m not so much interested in a methanol “economy” as in, where can I buy the equipment today to use for myself right now?
E.g. I could use methanol today (in principle) in something like the Ecoy Comfort, a direct methanol fuel cell that you can buy today and use to create electricity (and heat, I assume). 10 liters of methanol would heat my house for 2 days in autumn and provide a significant % of the electricity as well (not counting electric heating).
Even better would be something like the Viesmann Vitovalor PA2 home CHP (heating + electricity) methane fuel cell. Would have been perfect for my house (slightly too big), but I don’t have natural gas service and wouldn’t ever want to use fossil natural gas anyway.
Thanks Mangetout, maybe I could try it with an aquarium, filled with pond water and fertilizer and put out in the sun. With a lid on it against evaporation and keeping it topped up with tap water. Would be interesting to see if there’s any appreciable increase in biomass.
Is there any particular reason why we can’t reverse CO2 without high pressures, high temperatures and exotic catalysts? Even though plants do it all the time? Or is it just that nobody has invented it yet?
It’s just that there are no free lunches. The amount of energy released from burning carbon and combining it with oxygen cannot exceed the energy required to break them apart.
When we do it industrially, it seems like we have to dump a whole load of energy into the process, but the same thing is happening on a molecular scale when plants do it - the process that plants use to transform CO2 and water into sugars and oxygen is just as brutally energetic and strenuous - it’s just that it happens at a very tiny scale, so we don’t notice it.
Most methanol today is produced from syngas derived from natural gas stock, however it is possible to produce methanol from biomass. The problem is scaling this up because the relative density of suitable biomass is low, and it generally has to be harvested, processed (mulched and chemically or thermally decomposed) and then distilled to extract methanol of suitable purity (especially if it is to be used in a fuel cell). it is generally denatured as well to prevent it from being incidentally consumed, and has to be stored in a sealed, dehumidifed environment because of how hygroscopic methanol is. All of that said, methanol and derivative DME is desirable as a next generation hydrocarbon fuel because they are relatively easy to store and can be used with conventional Otto, Atkinson, and Diesel cycle engines with few modifications other than changing the mixture ratio, using chemically more robust seals in the fuel delivery system, and (for DME) adding a lubricity agent.
This isn’t scientific but it will probably work better than anything you can do in your house: plant oak and walnut trees and let them grow to be more than 100 years old. You’ll trap several tonnes of carbon for several centuries.
Another is invest in an all-wood house. Make sure it’s fire-safe, and maintain it for at least 100 years. That’s another very good way to store carbon.
Please provide a cite. I have worked on methanol extensively about 3 years back and at that time China was the leader in production as well as end user for Methanol. Most of Chinese methanol comes from coal I.e. syngas derived from coal.
You may well be correct. I was looking at North American production of methanol which is heavily based on steam reforming of natural gas because of how available it is in that region and how relatively clean the process is, but China (as a major industrial user of methanol and hydrogen in various chemical synthesis processes) is doubtless focused on coal because it is cheaper and more readily available domestically.
The point remains that methanol from biomass, while technically feasible, has a lot of challenges to scale up to any sustainable amout of production. The use of lignocellulosic biomass (colloqually ‘hog fuel’) as a feedstock for methanol is often promoted as waste-to-fuel (instead of crop-to-fuel like corn to ethanol) and is technically feasible but because of the handling and processing of low density material it is not practical without a large scale investment in an entire processing infrastructure, and even then will never match current petroleum production volumes.