A new cyclic cyclohexylcarbodiimide mediated route to DMC discovered.

[NNadir]

"Molecular organic carbonates (Figure 1) are expected to experience a considerable expansion of their market in the coming years, due to their growing use in the chemical (as solvent and reagent1), pharmaceutical (as intermediates2), and polymer industries.3 Also, the use of dimethyl carbonate (DMC) as an additive to gasoline4 will increase its market by nearly 2 orders of magnitude to an expected 30 Mt per year.5 To satisfy the market demand, new synthetic technologies need to be developed that are not based on phosgene,6 a chemical banned in several countries. The search for newer, safer, environmentally friendly synthetic methodologies has attracted the attention of a large scientific community. Either CO7,8 or CO2 are used as substitutes of phosgene in the scientific and patent literature for the synthesis of linear carbonates, cyclic monomeric carbonates, or polycarbonates.9,10"

The abstract can be found here:

http://pubs.acs.org/cgi-bin/abstract.cgi/joceah/2005/70/i16/abs/jo050392y.html

Green chemistry, more or less, and a fun way to fix carbon dioxide.

[Kraklen]

1. The last step surprises me a bit.

I thought DCU was a nuisance compound.

[NNadir]

2. In the lab its a nuisance, and an undesirable impurity.

Industrially, DCU can be recycled through various dehydration reactions.

I like this reaction because it fixes carbon dioxide. Phosgene is typically made from CO and chlorine, and CO is made either from natural gas or coal. Thus the industrial production of DMC has greenhouse implications. It's probably a small thing, but every little bit helps.

These days anything that fixes CO2 is good.

[Ian David]

3. Can you please translate for mental midgets like me? Thanks! n/t

[NNadir]

4. It's a little esoteric, but the basic idea of "green chemistry" is to...

...substitute toxic compounds with non-toxic compounds.

DMC, dimethyl carbonate is one of those compounds that you don't really experience in every day life, but which nonetheless plays an important role in industry.

Currently this compound has been made from phosgene, COCl2, which was a war gas used extensively in World War I, because it is much heavier than air, sits in trenches, and dissolves lungs.

Phosgene itself is an important industrial chemical, and is necessary for many important processes in the pharmaceutical and other industries. However, it is always a good idea to minimize its use where possible.

I have been some time interested in chemical reactions that "fix" carbon dioxide, particularly those that make use of it in industrial processes to make things that effectively "sequester" it. This seems a more promising way of dealing with the problem than some of the more fanciful things one hears about, like pumping it underground and so forth.

I am also interested in the many applications of the use of carbon dioxide itself as a solvent, something which is done under supercritical conditions. Supercritical conditions are those conditions of pressure and temperature at which there are no distinction between liquids and gases. The supercritical temperature of carbon dioxide is conveniently near room temperature, at 31 degrees centigrade.

I should note that I am proponent of completely banning fossil fuels as soon as is realistically possible. This is the only way to arrest the crisis, and little things, like manufacturing DMC from CO2, or tying up CO2 as a solvent will only palliate, not solve, the crisis.

By the way, I am of the opinion that anyone who expresses any interest whatsoever in a topic like this, especially when it is out of one's area of expertise, hardly can qualify as a "mental midget." Thanks for asking.

[Ian David]

5. Thanks! That seems like cool stuff. I never thought of CO2 as a solvent

CO2 dissolved in water I'd heard of though.

So, if you dissolve something in CO2, then that CO2 can also be sequestered that way, as opposed to dissolving CO2 in something else? Not to mention reducing the need for harsher solvents.

You know, we used to have a very good method of sequestering CO2. What was it called? Oh yeah, trees. What ever happened to those, anyway?

The article you posted looked like they were proposing actually mixing stuff with gasoline to replace things like MBTE. Did I completely misread that?

A while back, someone posted an article about using Silicon Dioxide to sequester large amounts of CO2. Just one more reason why you shouldn't eat those little packets.

Anyway, thanks for translating into English.

[NNadir]

6. Some responses to your questions and remarks.

To the extent that CO2 is tied up for industrial use as a solvent, it is not available for poisoning the atmosphere. There is a limit to how much this can really affect things though. Supercritical carbon dioxide's density varies with pressure, but 0.65 grams/ml is a good working figure, or 650 kg per cubic meter.

It can be shown that a single 1000 MWe coal fired plant puts out about 9.5 billion kg of carbon dioxide in a single year. Thus to contain the output of just one such coal fired plant would require a container that would contain 14.6 million cubic meters. This would be represented by a sphere having a radius of around 222 meters, a diameter of close to half a kilometer.

One application for supercritical CO2 that has been widely proposed, is to use it as a replacement for the trichloroethylene that is used as a dry cleaning solvent. This solvent contaminates much of our nation's water supply. However, given the types of volumes of CO2 put out by power plants it is very unlikely that the use by tens of thousands of dry cleaners would really tie up more than the output of one or two power plants.

Here is the problem with trees as CO2 sequestering agents. First of all forests eventually get into equilibrium with CO2. After a while the trees begin to put out as much as they put in. Secondly, as climate changes, the forests have become less and less healthy. The introduction of new pathogens and pests, the instability of droughts, extreme temperatures, all of these factors are working against out forests which are under extreme pressure almost everywhere. Third habitat destruction and human demand for forest products is creating additional pressure on our forests.

DMC has indeed been used as an oxygenate in fuel. The portion of the molecule that actually burns is the methyl groups provided by methanol in the manufacture of the liquid.

I am extremely dubious of all sequestering schemes I see. I note that they are all really proposals or pilot studies; none is actually working on an industrial scale, unless one counts a few oil wells pressurized with CO2. Sequestering in my opinion will simply not work and it may be extremely dangerous. The solution in my view is to abandon fossil fuels. We may not have much time to do this.

[Celebration]

7. what would happen

If we mix industrial flouride with coal fired plant mercury emissions with chicken and pig crap with carbon dioxide with carbon monoxide with depleted uranium and put it all in a new brand of "Neocon Toothpaste" laced with prions?

[Ian David]

8. My pet idea is to use fusion reactors to reduce toxic waste into plasma

Assuming we somehow managed to build at least as many "fusion furnaces" as we have conventional trash incinerators, how well would that work out?

I know that until we achieve self-sustaining fusion, we'd still have to pump more power into the fusion plants than they create. And that this energy would have to come from somewhere.

Anyway, how useful would it be to turn all the world's non-recyclable trash, toxic and nuclear waste into plasma?

[NNadir]

9. Fusion power doesn't work so far.

Various high temperature trash to fuel schemes have been piloted and in a few cases industrialized. Most of these use the trash itself as a source of heat.

Few of these involve plasmas, unless one considers (with some justification) a flame as a plasma.

Most trash to fuel schemes rely on reformation reactions. In these types of reactions, a carbon source (garbage or whatever) is heated with water to supercritical temperatures. Under these conditions the carbon is oxidized by water to give carbon monoxide and the water is reduced to hydrogen. The resultant mixture of hydrogen and carbon monoxide is called "syn gas" which can be used to make synthetic fuels.

Various companies have been built around such systems. Some have profited more by hype than by actual fuel production.

These schemes are often complicated by corrosive side products, such as acids - usually sulfuric, nitric, or hydrochloric acid, and insoluble materials like salts and metals. This leads to fouling of the systems, and/or system failure.

In general, however, I believe that recent advances in materials science will make such systems increasingly viable, should humanity survive the current climate crisis.

Fusion power remains decades off, (it always seems a few decades off, decade after decade) and in any case any fusion system, if they are made to work, will be entirely dependent on the existence of a much larger fission infrastructure. I believe that one of the few options open to humanity at this point is to cut to the chase and expand the existing fission infrastructure as rapidly as possible. Fission systems are already being built in China that will have reformation capability. This class of reactors are known as high temperature reactors. The famous pebble-bed reactor (of which I am not a particularly huge fan) will also have this capability.