Efficiently Producing Fuels from Waste CO2 and Off-peak Wind or Other Renewable Energy

Updated 8/18/2012

Others' Related Patents.

Nuclear Methanol and Gasoline.
Nuclear Diesel
Sea Fuels
CO2 Electrolysis
Junk Science
Conventional FTS
(Click here for the References page)

Nuclear Methanol and Gasoline. Martin and Kubic of Los Alamos National Laboratories suggested in 2007 that a novel approach to electrolytic rejuvenation of an aqueous solution of CO2-laden K2CO3 may permit lower-cost separation of CO2 from the atmosphere. They then propose that this CO2, along with hydrogen from water electrolyzed by nuclear energy, be converted to methanol and then to gasoline in a process they call “Green Freedom™”. (It does not appear there has been anything significant done on this plan since then.)

Their primary innovation would appear to be an improved method of separating CO2 from the atmosphere, though it is not clear from the available information that they have made a significant improvement here. Martin’s process, like most others, would require enormous amounts low-cost high-quality water in their stripping tower. It would probably be 10 times more expensive than using conventional technologies (but better optimized) to separate CO2 from point sources (shale gas, cement plants, biofuels plants, the exhaust of natural gas or coal-fired power plants) where the concentration of CO2 is nearly three orders of magnitude higher than in the atmosphere, as we will do.

The next problem would appear to be what they propose to do with the CO2. They clearly have not figured out how to make the RWGS reaction work efficiently (as we have); so they propose to make methanol from a syngas consisting of just CO2 and H2 (mostly from electrolyzed water) rather than using the more efficient processes that usually have a ratio of CO/CO2 greater than 3 and have always had this ratio greater than 1. It is true that methanol can be synthesized without CO in the syngas, but the process has not been commercialized because it hasn’t worked as well. Mitsui is attempting to demonstrate CO2-to-methanol in a very small pilot plant in which at least some of the hydrogen is generated by solar photolysis and some will probably come from solar PV. Almost no technical details are being made public, but the catalyst being used appears to be the same as that used in a bench-scale demonstration more than a decade ago (Kenji Ushikoshi et al, Applied Organometallic Chemistry 14, 819-825, 2000), Cu/ZnO/ZrO2/Al2O3/SiO2. The process achieved very high selectivity, but very low conversion per pass, so it still required separations, recompression, and recirculation. Indeed, the process is much simpler than fully recycled FTS, but the product is just methanol. Several other CO2-to-methanol processes are also in development, including one that apparently has useful yield at room temperature, but it starts with an expensive hydrosilane precursor. There will be no shortage of cheap methanol from coal and methane for at least the next 25 years, so “green” methanol simply won’t compete. (See FTS-Perspectives for comments on some others’ efforts to make carbon-neutral methanol.)

Another (and bigger) problem is that Martin plans to power the plant using a huge nuclear reactor – four times larger than most that have been built. Nuclear power has never been cheap, and it is steadily becoming more expensive. It has competed thus far only because of enormous subsidies (in the research, development, fuel processing, security, waste storage, etc.), and these are increasingly harder to support politically. The Union of Concerned Scientists and most other environmental organizations do not support ramping up nuclear energy – primarily for safety reasons.

Their nuclear-generated methanol cannot compete with fossil-derived methanol. The price of methanol has spiked severely on a few occasions in recent history, largely due to some process plant problems in Chile and natural gas price spikes in the U.S. However, methanol plants are being built fast enough in China, Qatar, Iran, Russia, and elsewhere to insure that the price of methanol (per unit energy) should average well below the cost of all other transportation fuels for many years.

Recent research indicates that electrical energy will cost about $90/MWhr ($25/GJ) from new nuclear plants in most countries other than China and France – or over five times as much as off-peak wind energy. If we assume 55% conversion efficiency and add (very conservatively) about 25% for a few other cost components, the “nuclear methanol” from their process will cost about $1/kg. The mean price of methanol for 2012 was ~$0.42/kg. No one will pay over twice as much for “nuclear methanol” as for methanol from natural gas or coal. Their “nuclear gasoline” would cost at least $7/gal.

Since methanol has not been accepted as a major component of gasoline in the U.S. and most industrialized nations, they propose to convert the methanol to gasoline using conventional processes (such as the ExxonMobil MTG process). These processes have achieved 85% efficiency in production of gasoline. Undoubtedly, the processes can be improved, and methanol-to-gasoline processes are likely to play a larger role in the future as renewable methanol becomes more available.

Finally, it is important to return to a sub-theme in the first point – the fundamental market reason for abandoning the CO2-to-methanol route that has been advocated by Nobel Laureate George Olah for many years. Mid-alcohols and light olefins have been 20%-70% more expensive per unit energy than methanol over most of the past decade and that relationship is likely to continue – partly because of an undeniable trend in agricultural commodities. If expensive energy is to be used to make carbon-neutral products, the products should be mostly those with the highest value per unit energy – jet fuel, diesel, mid-alcohols, gasoline, and light olefins. We have shown that these more valuable products can ultimately be made at higher efficiency than others have yet achieved in the production of methanol.

Nuclear Diesel. Severinsky is to be commended for the valiant efforts in his pending patents (U.S. published application 2006/0211777, etc.), as his work is mostly sound – to the extent that it can really be evaluated. Basically, he has attempted to patent the general process of making carbon-neutral fuels (diesel and gasoline) using the RWGS reaction and the FTS reaction. He thinks the best source of the hydrogen would be nuclear reactors electrolyzing water, but he realizes other renewable energy and other processes could also be used.

The problem of course is that the above general concepts have been discussed since the mid-1970’s. Severinsky collects a lot of relevant technical information and presents a variety of different plant designs in very general and confusing language. He makes claims about efficiencies that he thinks are possible, but provides no clear explanations of how or why his ideas are better than what has been done before. While most of the details on the various components he describes are sound, his system designs (which is what he is attempting to claim) are completely unintelligible (even to an expert who has spent years trying to understand such things).

One test is to ask: “Is there anything in his patent of value that was not really present in the prior literature?”. Another is to ask: “Is it likely that anyone on a technical team designing and developing an RFTS plant would ever take a second glance at his patent when trying to scope out the design, understand the plant, or optimize some process?” The answer to both is a resounding no.

It is not surprising that the initial PCT written opinion (9/2007) stated that none of his claims contained an inventive step. He did end up getting some highly restricted claims issued (USP # 818476764, and others) that will never be of any value or of any concern to Windfuels.

Sea Fuels. Behrens has proposed in US Pat 7,302,903 (12/2007) that wind energy could be used to produce hydrocarbons from seawater in floating vessels. One of the showstoppers with his concept is that it utilizes CO2 that has already been sequestered in the ocean, so it is no better for the climate than fossil fuels. Another showstopper is that it would add the cost of a ship the size of an aircraft carrier to the cost of the small RFTS plant that it would support. And there are numerous other technical problems too, but there is no point in continuing here. However, Behrens’ patent does provide an interesting example of how severely the scope of the claims must be limited in this subject area when substantive technical innovation is not supported in the patent’s specification.

The idea of taking CO2 from seawater and making fuels from it is actually more flawed than the notion of taking CO2 from the atmosphere. The atmosphere is approaching 400 ppm CO2, but ocean surface waters are typically only 90 ppm CO2 (including H2CO3, carbonic acid) by mass so an enormous amount of seawater would need to be handled, cleaned, and de-gassed. (The advocates of this approach like to say the concentration of CO2 in seawater is 140 times its concentration in air. That is roughly true in terms of kg/m3, but that is irrelevant when it comes the to cost of the separation problem.) The theoretical minimum amount of energy required to separate CO2 from the atmosphere and compress it to 100 bar is about twice as much as from point sources, but in practice it has taken over 15 times more energy thus far (in spite of many valiant efforts by many very capable teams). Behrens’ proposed vacuum methods for separating CO2 from the ocean fail to appreciate that even after separating the enormous amount of H2O vapor (85-98%, depending mostly on the temperature selected, preferably just above freezing) from the flash overhead, the non-condensable gas in the overhead will still be under 15% CO2, with the balance being N2, O2, and Ar. Hence, complex gas separations will still be required. We estimate that, in practice, taking CO2 from the ocean will take 30 times as much energy as separating CO2 from point sources, though we have not looked carefully at all process optimization possibilities.

More Sea Fuels and Methanol Routes at the DoD. Dennis Hardy, in US Patent 7,420,004, claims the synthesis of hydrocarbons via a CO2 to methanol to hydrocarbons process using Fischer-Tropsch catalysts. The independent claim is extremely broad, and probably wouldn’t survive a court challenge, as there is virtually no substantive, innovative material in the specification. Some of the dependent claims might survive, such as those that require taking the CO2 from seawater – but that is a very bad idea, as discussed above. They mention various renewable energy sources, but the primary focus is nuclear.

The independent claim requires first producing methanol for feeding into the FT reactor. This route from methanol to hydrocarbons is less effective than many other options (such as the ExxonMobil MTG process). Perhaps more importantly, no one is going to make expensive renewable methanol from expensive energy and CO2 for at least the next 25 years, as fossil methanol will remain too cheap. Of course, the WindFuels process will produce some methanol, but it will also be producing larger streams of other, more valuable products – jet fuel, diesel, gasoline, and ethanol.

A recent publication by a research team that includes Hardy at the Naval Research Laboratories (NRL) has generated some media attention. Their focus has apparently turned to hydrocarbons via direct hydrogenation of CO2, but with less success than others have achieved, as the unwanted methane selectivity is very high.

We have a few comments in
http://www.dotyenergy.com/PDFs/Doty-90362-RWGS-ASME-ES10.pdf showing why it is extremely unlikely that direct hydrogenation of CO2 will ever compete with the RWGS route.

CO2 Electrolysis. Stoots et al in US Pub 2008002338 disclose a method of producing a CO+H2 syngas by electrolyzing a steam/CO2 mixture at high temperatures. One of the showstopper problems with their invention is that is requires a ceramic electrolyte, and the best option that anyone has come up with over the past two decades of related work in high-temperature steam electrolysis is zirconia.

Few companies have more experience with zirconia at high temperatures and high stresses than Doty Scientific. We know all too well how fragile and expensive zirconia is. Reliance on zirconia ensures that neither steam electrolysis nor steam/CO2 electrolysis will ever work in the real world. Even if they could make it work with acceptable lifetime (irrespective of the cost of the electrolytes), it does not appear that they could offer any efficiency advantage in an RFTS plant. There has simply been too much progress recently in water electrolysis, and off-peak electricity is becoming too cheap for anything else to compete.

Junk Science. An enormous amount of junk science related to bizarre hydrogen production methods, CO2-to-fuels, direct solar fuels, and especially algal oil has appeared on the web over the past decade. Some of that has let to patents, some has been published, and some has been supported by ARPA-E. We’ve posted many sound and objective analyses in the past, but we’ve concluded that at least for now we don’t have the time to try to respond to scam artists with junk science, so we’ve taken most of that material down (though it can be made available to potential investors upon request). Here, we’ll comment only on one example patent.

Seymour’s work in US Patent 7,238,728 (7/2007) and elsewhere is a classic example of the kind of stuff that gives patenting a bad name. Most patents simply prove to be uncompetitive in the real world; but some, like this one, are poorly conceived or vague ideas by individuals with just enough technical expertise to convince an unqualified patent attorney that they have a good idea. (They sometimes are even able to convince investors.)

Seymour seems to understand that syngas (CO and H2) can be converted to liquid hydrocarbons in an FTS reactor and that the combination of partial combustion and pyrolysis of biomass can produce syngas. He apparently also understands that the mixture ratio may need adjustment, and that electrolysis of water produces hydrogen and oxygen which should be able to be used in the process. So he proposes to: (A) send some of the H2 and O2 along with some waste CO2 into a gas turbine; (B) generate heat to assist in the pyrolysis; (C) reduce some of the CO2 to CO; (D) separate the CO from the turbine products; (E) feed a proper syngas mixture into the FTS reactor; and (F) collect the reaction products.

There is no way such a process could ever be made to work at efficiencies even a quarter of what we’ll achieve. For starters, one cannot have turbine exit conditions that permit the combination of (A) efficient utilization of its remaining enthalpy in pyrolysis, (B) high CO fraction in the turbine exhaust, and (C) efficient separation of the turbine products (CO, CO2, and H2O). It also seems silly to deliberately design an inefficient turbine (as needed to get the desired pyrolysis heat), especially when burning electrolysis hydrogen; and there are a host of other detail issues that the inventor has not begun to think about.

The patent examiners don’t worry about patents like this as long as they don’t obviously violate the second law of thermodynamics. They might suggest some claim language that is clearly of no value and quickly have the patent allowed to get it off their desk. This one issued only 11 months after it was submitted. It is completely worthless and of no concern to us.

Conventional FTS. Andre Steynberg and colleagues disclose in pending US patent 2007/0142481 an improvement on a two-stage FTS reactor arrangement. In this design, the syngas first partially reacts in a 3-phase LT-FTS reactor, and its tail gas (some products and un-reacted syngas) then go to a 2-phase HT-FTS reactor for further reaction. This approach appears optimum for their desired balance of mostly lubricants, high-quality waxes, linear alkyl-benzenes, gasoline, diesel, and some light olefins and oxygenates from coal-syngas. This is a beautifully written reference by the world’s best team in fossil-based FTS, but there is little here that can be applied to renewable, carbon-neutral products. Two other nice reference patents on fossil FTS are US Pat # 7,001,927 by Zhang and US Pat # 7,115,670 by Hensman and Newton.

Green Freedom™
FJ Martin and WL Kubic, Los Alamos National Laboratories

“Nuclear Methanol” or “how to make methanol more toxic and less competitive”.

Take a look at real costs being quoted today for nuclear power plants.

Gasoline by this process would cost at least $7/gal – more likely, over $9/gal.

Who is going to lay out $50B for the first demonstration facility?

Severinsky’s nuclear diesel – Good attempt. The problem is, it is still nuclear and has a very inefficient RWGS reactor and product separations process.
Sea Fuels – Just another idea – it is simply too expensive and there is no climate benefit.
CO2 ElectrolysisVery inefficient, extremely expensive electrolytes.
Junk Science “how to use biomass extremely inefficiently”
Conventional FTS Excellent examples of a practical fossil-based FTS processes. Limited relevance to carbon neutral renewable fuels.
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