"Carbon Dioxide as a Feedstock
Carol Creutz and Etsuko Fujita
Brookhaven National Laboratory
This chapter is an overview on the subject of carbon dioxide as a starting material for organic syntheses of potential commercial interest and the utilization of carbon dioxide as a substrate for fuel production. It draws extensively on literature sources, particularly the report of a 1999 workshop on the subject of catalysis in CO2 utilization, but with emphasis on systems of most interest to us.
Atmospheric carbon dioxide is an abundant (750 billion tons of carbon in the atmosphere) but dilute source of carbon (only 0.036% by volume), so technologies for utilization at the production source are crucial for both sequestration and utilization. Sequestration—such as pumping CO2 into the seas or the earth—is beyond the scope of this chapter, except where it overlaps utilization—for example, in converting CO2 to polymers. Yet sequestration dominates current thinking on short term solutions to global warming, as should be clear from reports of this and other workshops. (By extrapolation, geologic sequestration of CO2 is short-sighted.) The net anthropogenic increase of 13,000 million tons of carbon dioxide estimated to be added to the atmosphere annually at present can be compared to the 110 million tons of CO2 used to produce chemicals, chiefly urea (75 million tons of CO2), salicylic acid, cyclic carbonates, and polycarbonates. Increased utilization of CO2 as a starting material is, however, highly desirable, because it is an inexpensive, nontoxic starting material. There are ongoing efforts to replace phosgene as a starting material. Creation of new materials and markets for them will increase this utilization, producing an increasingly positive, albeit relatively small, impact on global CO2 levels. The other uses of interest are utilization as a solvent and for fuel production, and these are discussed in turn.
PRINCIPAL CURRENT USES OF CARBON DIOXIDE
Urea synthesis is currently the largest use of carbon dioxide in organic synthesis. Urea, C(O)(NH2)2, is the most important nitrogen fertilizer in the world. Urea is also an intermediate in organic syntheses such as the production of melamine and urea resins, which are used as adhesives and bonding agents. Carbon dioxide is also used to produce salicylic acid, which is found in pharmaceuticals, and cyclic organic carbonates, high melting, but extremely high boiling solvents for natural and synthetic polymers such as lignin, cellulose, nylon, and poly vinyl chloride. The latter are used extensively in the production of polyacrylic fibers and paints. Ethylene and propylene carbonates have many uses in chemical synthesis—among them reactions with ammonia and amines to form carbamates and subsequent reactions with diamines to yield di(hydroxyethyl) carbamates, which can react further with urea to form polyurethanes."
Those are just some of the current uses of Carbon Dioxide. And, although they are currently, relative to CO2 emissions, small uses, the potential seems to be there to expand the applications, especially since versatile modern plastics, such as polycarbonates and polyurethanes, can be made with CO2 as a starting material. Urea, the largest current consumer of CO2, as well, can be used not just as a fertilizer, but as a base material from which some types of plastics can formulated.
The author indicates that capture of CO2 at the production source is crucial to the successful use of CO2 as a base material for further synthesis. We'll note that other research we've reported to you suggests otherwise: That CO2 can feasibly be extracted from the atmosphere for practical use.
And, of course, as we've extensively documented, among other CO2 uses of interest mentioned is it's employment "for fuel production".