Turning carbon dioxide into fuel
We're not able at this time to provide you with a reference link to our earlier dispatch concerning it, but, we have previously reported on the technology being developed at England's fabled Oxford University, technology which would enable us to, instead of treating our Coal Country effluent Carbon Dioxide like a shameful toxic waste, reclaim that Carbon Dioxide and utilize it in a way that reflects what it truly is:
A valuable raw material resource from which we can synthesize a wide variety of useful organic chemicals, including liquid and gaseous hydrocarbon fuels.
Comment follows excerpts from the enclosed link in this dispatch to:
"Turning Carbon Dioxide into Fuel"; Philosophical Transactions of the Royal Society, 2010
by: Z. Jiang, et. al.; Department of Chemistry; University of Oxford; Oxford, UK
Our present dependence on fossil fuels means that, as our demand for energy inevitably increases, so do emissions of greenhouse gases, most notably carbon dioxide (CO2). To avoid the obvious consequences on climate change, the concentration of such greenhouse gases in the atmosphere must be stabilized. But, as populations grow and economies develop, future demands now ensure that energy will be one of the defining issues of this century. This unique set of (coupled) challenges also means that science and engineering have a unique opportunity—and a burgeoning challenge—to apply their understanding to provide sustainable energy solutions. Integrated carbon capture and subsequent sequestration is generally advanced as the most promising option to tackle greenhouse gases in the short to medium term. Here, we provide a brief overview of an alternative mid- to long-term option, namely, the capture and conversion of CO2 to produce sustainable, synthetic hydrocarbon or carbonaceous fuels, most notably for transportation purposes.
Basically, the approach centres on the concept of the large-scale re-use of CO2 released by human activity to produce synthetic fuels, and how this challenging approach could assume an important role in tackling the issue of global CO2 emissions.We highlight three possible strategies involving CO2 conversion by physico-chemical approaches: sustainable (or renewable) synthetic methanol, syngas production derived from flue gases from coal-, gas- or oil-fired electric power stations, and photochemical production of synthetic fuels.
Here, we hope to illustrate that advances in the science and engineering of materials are critical for these new energy technologies ... .
With sufficient advances, and institutional and political support, such scientific and technological innovations could help to regulate/stabilize the CO2 levels in the atmosphere and thereby extend the use of fossil-fuel-derived feedstocks.
(The) focus of this review (is) the idea of using captured, anthropogenically produced CO2 to synthesize liquid renewable or sustainable hydrocarbon and carbonaceous fuels. This approach offers the intriguing possibility of using primary energy from renewable, carbon-free sources (such as electricity derived from solar, wind, wave ...) to convert CO2, in association with hydrogen (or indeed methane), into high-density vehicle fuels compatible with our current transportation infrastructure.
(Via illustrations) we show a generic, idealized energy cycle where one transforms CO2 to ‘carbon-neutral’ liquid fuels in which sustainable or renewable electricity is used to produce hydrogen and the resulting Fischer–Tropsch process yields liquid hydrocarbon fuels.
As noted earlier, the intrinsically high energy density of these fuels and their transportability make them highly desirable.
Importantly, such synthetic fuels do not contain any sulphur.
In addition, methanol (arguably the ‘simplest’ synthetic carbonaceous fuel) is a candidate both as a hydrogen source for a fuel cell vehicle and indeed as a transport fuel, and dimethyl ether is viewed as a ‘superclean’ diesel fuel.
The energy requirement for the production of such renewable liquid fuels depends critically on the method used for the capture of CO2 (invariably from large-scale emitters) and the method used for the production of hydrogen. As long as power generation for our present energy economy using fossil-fuel sources remain, sources of CO2 will be available for use in such proposed recycling systems.
The steam reforming of hydrocarbons to yield syngas and hydrogen is (illustrated as) a classic example:
CH4 + H2O → CO + 3H2
It is important to stress that the above, highly endothermic reaction is used worldwide for the high-volume production of ‘merchant hydrogen’ in the gas, food and fertilizer industries.
The corresponding CO2 reforming of CH4 (so-called ‘dry reforming’) illustrates the important reaction of CO2 with a hydrocarbon, which will be of central importance to our considerations of converting CO2 in flue gases to yield a chemical fuel:
CH4 + CO2 → 2CO + 2H2
The energy input for CO2 reforming of CH4 requires approximately 20 per cent more energy input as compared with steam reforming, but this is certainly not a prohibitive extra energy cost for this chemical reaction.
(We remind you, that, as seen in: Chicago Converts CO2 to Methane | Research & Development; and, in:
Exxon Converts 99% of Coal to Methane | Research & Development; as just two examples out of now many, we can make all of the Methane, CH4, needed, as above, for the conversion of Carbon Dioxide, with Water, into hydrocarbon synthesis gas, i.e., the various blends of CO and H2, from either Coal, or, from Carbon Dioxide itself.)
Importantly, these two reactions give rise to syngas with different H2/CO molar ratios. Both are useful for the formation of syngas, for ultimate liquid fuel production.
Commercially, methanol is produced from syngas using natural gas or coal, mainly containing CO and H2 along with a small amount of CO2. The reaction is usually catalysed by Cu/ZnO-based catalysts that have high reactivity and selectivity.
It is also possible to synthesize methanol directly from CO2 by combining it with hydrogen according to the reaction:
CO2 + 3H2 → CH3OH + H2O.
Interestingly, this can also be viewed as a mechanism for ‘liquefying’ hydrogen chemically using CO2!
(And, as in: Solar-Powered Hydrogen Generation | Research & Development; concerning: "United States Patent 7,726,127 - Solar Power for Thermochemical Production of Hydrogen", we can utilize environmental energy to produce such useful Hydrogen, to make Methanol from Carbon Dioxide, from nothing, essentially, but Water.)
In the same way that biofuels recycle CO2 biologically, a ‘sustainable’, synthetically artificial cycle can also be envisaged where the carbon in the methanol is recycled by extracting and utilizing CO2 from the atmosphere."
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There is considerably more to the report, of course. But, those excerpts represent the essence of the thing:
As these Oxford scientists put it, it is perfectly feasible to capture "anthropogenically produced CO2" and then use it "to synthesize liquid renewable or sustainable hydrocarbon and carbonaceous fuels".