In a previous post, I said that I would go into more detail on the “Methanol Economy”. This is a concept developed by Nobel Laureate Prof. George Olah, and is recently gaining traction throughout the world. The core idea is very simple. Since we are running out of fossil fuel reserves (estimates on the rate of depletion and the amount left will vary from person to person depending on their agenda), it behooves us to find alternate sources of energy. Modern civilization has been built on the foundation of cheap, plentiful energy, and in order to ensure the continued growth and progress of our species, this must continue. Fossil fuels are a gift left to us by nature; they took billions of years to form and literally represent the most raw form of chemical energy (fossil fuels in this case refers to deposits of coal, crude petroleum, or natural gas). To put it another way, the situation with fossil fuels is like taking free energy out of the ground. The components of these fossil fuels are hydrocarbons; they are also valuable as feedstocks for chemical synthesis. In fact, Mendeleev’s oft-repeated statement that “to use petroleum as a fuel is like firing a furnace with banknotes” still rings true today. Since we have become used to using hydrocarbons as a source of energy, we need to look within that class for an alternate, sustainable energy source. C1 and C2 (hydrocarbons with 1 or 2 carbons, respectively) compounds are the ideal candidates, since they can be made with minimum effort through current technologies. However, ethanol (the prototype C2 compound) met with dismal failure after government experiments with promoting “bio-based” ethanol. Diverting food crops for other purposes is never a good idea. Thus, out of the C1 compounds, methanol is the most promising, if not the best.
Methanol is a liquid at ambient temperature and pressure, and has a convenient boiling point (65 deg C). Existing infrastructure for the transportation of alkane hydrocarbons can be used for methanol with little modifications. In fact, for a long time, California used a blend of methanol and gasoline for cars (this was discontinued in the 80’s for some reason); this was called “M85”. Methanol has a very good energy density, although not nearly as high as octane-based gasoline. For those interested in hydrogen fuels, methanol also has a much higher density of hydrogen than liquid hydrogen! This is simply due to the extremely low density of liquid hydrogen, and the fact that 1 mole of methanol contains 4 moles of hydrogen.
Critics of the methanol economy often cite the toxicity of methanol as a potential issue. However, this is offset by other factors, such as it’s ready biodegradation in the environment, and the fact that methanol fires can be extinguished with plain water. Also, methanol is miscible with water in all proportions, making it a lot easier to handle. In fact, methanol is used as the fuel of choice in the Indianapolis 500 for these safety reasons. It burns with an invisible flame, thus posing less problems to drivers from visible obstruction due to the smoke and fire.
Of course, there are challenges to get this system off the ground. The most ideal, renewable feedstock for the synthesis of methanol (a C1 compound) is carbon dioxide (another C1 compound). CO2 levels have been rising lately (from 350 ppm in the 1950’s to 400+ ppm now), and this has major implications for global warming and climate change. Using CO2 as a carbon feedstock would go a long way to mitigating this situation. Of course, the selective reduction of CO2 to methanol is very difficult (usually mixtures of C1 compounds – such as formic acid, formaldehyde, methanol, and methane result), just as the selective oxidation of methane to methanol is very difficult. In fact, on a side note, one of the few proven experimental conditions for the selective oxidation of methane to methanol is in superacid media! The methanol, once formed, gets immediately protonated in the medium to form the methyloxonium ion, preventing further oxidation. Of course, this remains a subject of academic curiosity, since handling large amounts of highly corrosive acids on scale is not trivial. There are other groups continuing this line of research, including that of Roy Periana at Scripps Florida, but success has largely been very limited.
Even though we always hear about continuously rising CO2 levels, we have to keep in mind that CO2 is still a trace gas in our atmosphere! 400 ppm is only 0.04%, after all. For those who don’t know, Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% (credit to wikipedia). The cheap, large-scale separation of carbon dioxide, a trace gas in the atmosphere, is still a major challenge. Currently, CO2 is separated from air through cryogenic means, although this is still rather expensive if one wants to consider CO2 as a starting material for chemical synthesis. Some people in our group have made promising steps in this direction, coming up with cheaper adsorbents for the selective separation of carbon dioxide from air – see this paper.
This is just a small overview of the methanol economy. I’m not an expert in this area, but I have some knowledge of this field since I have read a lot about it and work with people who are doing research in this area. Those who are interested and wish to read more should first check out this paper, and if they have further interest, this book.