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facecrockpot t1_j682avo wrote

Reply to comment by kemisage in Researchers unveil the least costly carbon capture system to date - down to $39 per metric ton. by PNNL

I don't think it's chemically as easy as "take oxygen out and connect the carbon" do you have sources for the actual reaction and catalysis? It's probably patented that's why the websites don't tell, but I'm quite curious how they do it.

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kemisage t1_j689tkh wrote

>I don't think it's chemically as easy as "take oxygen out and connect the carbon" do you have sources for the actual reaction and catalysis?

So are you asking for the actual mechanism and the catalyst used? It's different based on which catalyst is used, and there are also several different mechanisms proposed for the formation of carbon-carbon bonds. So it's still up for debate.

The initial dehydration of methanol is actually the easiest step. Such dehydration is performed with many different oxygenates in the industry using either acid-based catalysts or alumina. What comes after is where the debate exists as to what actually happens. That part has been known to be quite efficient using a specific zeolite as a catalyst.

>It's probably patented that's why the websites don't tell

Exactly. There are quite a lot of patents on the catalysts and the process technology. No matter which is used, converting methanol to gasoline is done in a reactor train, so 2-3 reactors are running in parallel with one of them being stopped for catalyst regeneration every now and then while the other two are running.

So far the way we have been designing these plants is to first convert carbon dioxide and hydrogen (or in the case of blue plants, it's natural gas + carbon capture) to synthesis gas (a mixture of carbon monoxide and hydrogen), which is then converted to methanol (or methanol and dimethyl ether) and then subsequently to gasoline. This may also be followed by an upgrading step. The end-result is usually around 85-90% gasoline and 10-15% LPG.

There is plenty of literature if you search for "methanol to gasoline reaction" (example: this), but the source for the overview given above is me. I design this process (and others) for a living.

Edit:

If the technology mentioned in OP can be scaled up and has a high conversion (and rate) for CO2 to methanol, it will bring down the capital costs by a lot. That's why there has been plenty of work on this topic for years now.

The conversion of either natural gas or CO2 to synthesis gas is quite expensive, the most capital-intensive step in the production of gasoline through this route. If it can eliminated (along with another expensive step of separating CO2 from the capture solvent), the economics would become significantly more favorable.

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facecrockpot t1_j68ceof wrote

Thanks for the paper, I'll look into it. I'm actually about to start my PhD researching the hydrogenation of carbondioxide over ruthenium so I appreciate the reliable source.

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kemisage t1_j68fio2 wrote

>I'm actually about to start my PhD researching the hydrogenation of carbondioxide over ruthenium

Nice! I have worked on this until I moved quite recently from the R&D organization in my company to the commercial/sales org. I can't reveal the exact information, but maybe a couple of pointers could help you.

Since you said ruthenium, are you gonna be working with Ru-Macho or its derivatives? The focus of industrial R&D has been (heavily) on using catalysts based on Fe, Mn, and Ni. Cost and abundancy are the factors here. I'd suggest, if possible, to design the equivalent catalyst structure using these cheaper metal ions once you do your initial testing with Ru-based catalysts.

We have noticed a spectacular lack of awareness among different research groups in considering the information published by other groups. This is with respect to the mechanism of CO2 conversion to formic acid, dimethylamine, methanol, etc. A couple of prominent groups have proposed their mechanisms and have focused their observations around their mechanisms, but there are reports out there of contradictory behavior that doesn't match with their proposed mechanisms. I have personally done detailed modeling for the entire mechanistic chain and found that the most widely cited mechanisms are only partially correct. They leave out important information and/or are wrong about the rest of the reaction mechanics.

I know it was a very general description, but don't take the published information on its face value (even if it's from "famous" scientists in the domain). This area is still so new that nobody is 100% correct.

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facecrockpot t1_j68k10w wrote

It's actually Ru/TiO2 because we've found that using light we are able to produce hydrocarbons to at least C6. These preliminary experiments haven't been done by me that's why I'm not that familiar with the mechanisms that person suspected. The focus will definitely be hydrocarbons, no oxygenates.

I'm definitely planning on using other salts in my preliminary experiments. I think the previous research used Ruthenium chloride so if you got experience with a model component for that I'd appreciate your opinion.

I'm still working on my Masters Thesis (FTS with Co@m-SiO and Co@m-AlSiO) thats why my research into Ruthenium has been sparse so far. I appreciate the heads up about the papers. I also got the impression that the very few results there are, are a bit contradictory.

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kemisage t1_j6951hz wrote

Sorry, I am not really familiar with photocatalysis besides my experience with catalytic adsorption of CO2 (no photochemical activation). I worked mostly on homogeneous and heterogeneous thermocatalytic pathways that integrate the CO2 capture and conversion processes, like the one proposed in OP. The photocatalysis group at my company was a lot more connected to and focused on academic research. I believe they were using Cu, Ni, Fe and other metals in the vicinity in their work, even though Ru probably exhibits the highest catalytic activity in general.

It's quite interesting that it can produce hydrocarbons to that length. I have only ever heard of CO and CH4 production via photocatalysis. There was a lot of emphasis on the importance of oxygen vacancies in the research I have heard of (same as it was with thermocatalytic adsorption).

One of the major reasons for contradictory behavior in this domain (again, same as in the case of adsorption) is that many people focus too much on the effect of metals on catalytic activity and selectivity. The support structure plays too big of role to ignore (for example: see this and this), but it's been changing in the recent years, so that's good news.

Anyway, good luck with your theses, both Master's and PhD.

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