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.