Tuesday, February 26, 2008

Another CO2 roach motel?

As we all know the mystery is solved by tracking down the dog who did not bark in the night? Your challenge, dear anonymice, is to spot the dog in this story which is making its rounds.

UCLA chemists report a major advance in reducing heat-trapping carbon dioxide emissions in the Feb. 15 issue of the journal Science.

The scientists have demonstrated that they can successfully isolate and capture carbon dioxide, which contributes to global warming, rising sea levels and the increased acidity of oceans. Their findings could lead to power plants efficiently capturing carbon dioxide without using toxic materials.

"The technical challenge of selectively removing carbon dioxide has been overcome," said Omar M. Yaghi, UCLA's Christopher S. Foote Professor of Chemistry and co-author of the Science paper. "Now we have structures that can be tailored precisely to capture carbon dioxide and store it like a reservoir, as we have demonstrated. No carbon dioxide escapes. Nothing escapes -- unless you want it to do so. We believe this to be a turning point in capturing carbon dioxide before it reaches the atmosphere."

If you are of teh scientifical bent you can read more in Science
A high-throughput protocol was developed for the synthesis of zeolitic imidazolate frameworks (ZIFs). . . . Members of a selection of these ZIFs (termed ZIF-68, ZIF-69, and ZIF-70) have high thermal stability (up to 390°C) and chemical stability in refluxing organic and aqueous media. Their frameworks have high porosity (with surface areas up to 1970 square meters per gram), and they exhibit unusual selectivity for CO2 capture from CO2/CO mixtures and extraordinary capacity for storing CO2: 1 liter of ZIF-69 can hold ~83 liters of CO2 at 273 kelvin under ambient pressure.
and Nature Materials. Investors can go to the USPTO and look up the patent application. The $64,000 question (Eli is old and cheap) is what's missing in all these write ups?

Bunnies and anonymice can get an idea from the perspective on this in Science by Robert Service

On page 939, Yaghi and colleagues report a new robotic high-throughput scheme for creating MOF relatives known as zeolitic imidazolate frameworks (ZIFs). And Mallouk and others say that the work is again an important blend of fundamental research and a critical application: materials that might help coal-fired power plants filter out carbon dioxide from their smokestacks. Mallouk calls the new work "very clever" because Yaghi and his colleagues have designed their hubs and linkers to mimic the construction of zeolites, a family of natural porous compounds widely used as catalysts and filters in industry. But because ZIFs are stable at high temperatures and are easier to tailor by adding desired chemical functional groups, they may prove even more useful in the long run.

One key race is to create a MOF that can store hydrogen for use in future fuel-cell cars. High-pressure gas tanks do the job fairly well. But pressurizing gases is a big energy drain and can create a hazard if the gas tank is punctured in a crash. By filling part of the tank with a MOF's cagelike network built with hydrogen-absorbent metal hubs and organic struts, however, it is possible-- at least in theory--to store more of the gas at a lower pressure. Slightly raising the temperature or releasing the pressure then liberates the gas. Yaghi's group and Jeffrey Long's group at UC Berkeley both recently created MOFs that can hold up to 7.5% of their weight in hydrogen, better than a benchmark for hydrogen storage set by the U.S. Department of Energy. Unfortunately, they only do so at 77 kelvin (-196°C), making them impractical for real-world use.

In July 2007, researchers led by William Goddard III of the California Institute of Technology in Pasadena reported in the Journal of the American Chemical Society that adding lithium to a MOF should make it possible to store 6% of its weight in hydrogen at room temperature. Long says many groups are working on it, but "it's not trivial." Lithium, he points out, tends to hold strongly to solvent molecules after synthesis, and removing the solvent requires so much energy that it typically blows apart the framework.

To put it bluntly, these things could be roach motels, the CO2 checks in but it can't check out, or the energy bill at check out makes the entire exercise academic. That makes them not very useful since the cost of synthesis and the mass of material needed requires that any capture method has to cycle tons of time. Yaghi says the ZIFs can be cycled, but what is the energy needed to cycle the system, how many times can it be cycled and what is the loss of the ZIF effectiveness per cycle. Eli has seen a lot of pretty chemistry founder on engineering issues and when something like this, a well known issue with respect to hydrogen storage, is not discussed his nose twitches.

UPDATE: A number of other important issues are raised in the comments below. Eli urges you to read them. Among them:
  1. Tim McDermott- So 1 liter of ZIF-69 can capture 155 grams of CO2, which is 44 grams of C. Woot the problem is solved!
  2. How will these things do in the presence of water vapor which screws up zeolites - Bocco
  3. A good point is that the isotherms are constant implying they can handle changing pressure - Bocco
  4. David Benson likes chilled ammonia (he must come from Jupiter!:)
and more. Read the comments.

Yaghi's lab has made a step forward, but much remains to do.


Anonymous said...

How about the billions of dollars worth of subsidies and market protections given to the fossil fuel industry every year.

Until that ends, CO2 Soaker Gizmos are just distractions.


Anonymous said...

So --
What's the density of a chunk of this stuff, fully loaded? Will it sink in water?

If we sink it deep enough in the ocean, can we get sufficient pressure that the CO2 will be a supercritical liquid? (70-something bars?)

If so, will the CO2 slip out of the scaffold, leaving the scaffold in salvageable form?

Just wondering.

Anonymous said...

If this thing can be made to work, will Big Oil Industry start to embrace carbon caps already? Please?

*sound of crickets*

C W Magee said...

price tag?

Anonymous said...

What's missing, let's see ...
22.4 liters/mole at STP;
44 g/mole for CO2;
(12 g Carbon / mole C02);
83 liters CO2 captured /liter ZIF-69;

So 1 liter of ZIF-69 can capture 155 grams of CO2, which is 44 grams of C.

W00t! The crisis is over!

Anonymous said...

One of the things that's missing is that the adsorption experiments they did were not in the precense of H2O, which is almost certain to be present in a real world situation, and if zeolites are anything to go by then that will really mess up the chances of this being used in an application.

Also if you look at the isotherms in the additional online material, which are pretty flat, this means they would be suitable for a system were the adsorption and desorption pressures are changing without having a great energy penalty.

Another thing that is missing is context in terms of other materials that exist. It sounds quite alot, but this is not so spectacular in terms of capacity. They need to bump up the pressure and see how good their isotherms remain.


David B. Benson said...

World has relatively little titanium.

Which I am under the impression those ZIFs require...

Anonymous said...

Ah! But ...

Cymraeg llygoden

Anonymous said...

How much energy is required to produce 1 liter of ZIF -- and carbon dioxide produced, if fossil fuel is used to produce the energy?

Is the volume of carbon dioxide released (at 273k and 1 atm) by the production of 1 liter of ZIF by burning fossil fuel less than 83 liters? (the carbon sequestered by 1 liter of ZIF)

Second: how much does it cost relative to other methods of reducing emissions? (like efficiency improvements, which can actually save money while reducing emissions)

These methods that sound too good to be true usually are. Cold fusion anyone?

Mark said...

It's been a tedious, unproductive day, and I can't remember--how many liters per day does a "typical" power plant produce? Can the zeolite be easily emptied and reused?

Anonymous said...

A 600 MW station consumes about 1.5 million tons of bituminous coal p.a. If coal is 78% carbon, that gives us about 4.3 million tons of CO2.

From tim mcdermott we get a figure of about half a litre per gram of CO2, giving us ~ 2 x 10^12 litres p.a. from our single power plant.

Quite a lot.

David B. Benson said...

S2 --- Bituminous coal is probably less than 78% carbon, by quite a bit.

Doesn't really matter for your calculations.

David B. Benson said...

Chilled ammonia appears quite sensible compared to ZIFs:

Chilled ammonia pilot plant to capture post-combustion CO2

Anonymous said...

I think the original point being made by Eli was if you can't get the CO2 out again "easily" then this material is worth nothing. Exactly because then you would need a ridiculous amount of the stuff for even one power plant. If the stuff can be regenerated (which it apparently can) then it's a question of cost, inventory and make-up due to degeneration of the stuff, because it will be used to make a pure CO2 gas stream that will be pumped into the ground somewhere. So one ZIF will have to be cycled so many hundred/thousand/million times.

This material looks good in terms of CO2 adsorption even in the presence of CO, but I have a feeling that H2O will just plug it all up such that there is nowhere for CO2 to adsorb. That remains to be seen. The method of producing this seems expensive which means it will need to stay active for a very large number of cycles to be judged better than say liquid ammonia or amine scrubbing.

I found nowhere in the articles anything about titanium, only cobalt and zinc. I'd think twice before using Co in any large process.


David B. Benson said...

To put the manitude of the problem in perspective, the latest issue of Sierra states that U.S. utilities produce 2 billion tons of CO2.

I assume that is yearly.

Anonymous said...

I'd much rather have a motel for gaseous pests designed by a botanist than by a chemist.

Anonymous said...

To put the magnitude of the problem into perspective. Then say all the 2 billion tons of CO2 that came from the US came from 600 MW bitumous coal plants (which is of course not the case) then that would mean 500 power stations would need to be fitted with carbon capture. (2 bill/ 4.2 mil, unless this is an american/british billion problem). Suddendly seems a lot less, doesn't it? I'm not calling this problem small but wowing people with the figure of 2 billion tons per year, doesn't exactly help people to figure out what that means - it sounds big, it is big, but what does it mean?

I'd trust an engineer to design a system for gaseous pests, a chemist to tell the engineer the types of materials needed, and a botanist to study the effect of the "cleaner" air on plants. Of course, if we ALL decided (not just me) to get rid of the car, live close to work, insulate our houses, consume a little (lot) less, turn off the airco AND were perpared to pay more than just lip-service to the CO2 problem, i.e. pay real cash, then maybe, maybe "farmers" could ease any upcoming problems with some design help from a botanist/biologist.

The magnitude of the problem is such that we'll need a lot of the currently proposed solutions all together to create a sustainable future. With both botanists and chemists (amongst others) doing the work.

Anonymous said...

Sorry, Anon at 2:07 am was Bocco.


David B. Benson said...

Here is another new CO2 adsorber (if that is the correct term):

Scientists develop low cost material for capturing carbon dioxide from smokestacks

Anonymous said...

I am Aman.

i have ready pretty much of ZIfs and the technology that is presently used in carbon capture from power plants.
The ammonia solution that many of you have mentioned are actually toxic in nature. After adsorbing CXo2 they need to be scrubbed off which again requires a lot of energy.to sum it all about 20-30 percent of the total power plant expenditure goes in trapping Co2 and then releasing it.

As many of you know Co2 is being absorbed so that it can be used in CCS technology.

majority (*80%) of the total cost of CCS is absorbing Co2 at the first place.

Certainly many of the costs involved are not made public , but i really do think that this is the best R&D we had for absorbing Co2 on large scale.