Linking Catalyst & Process Development with TEA in the Conversion of Biomass to High-Octane Gasoline


>>Dan Ruddy: Thank you, everyone, for joining
us today. My name’s Dan Ruddy. I’m a senior scientist here at NREL, and it’s
a pleasure to discuss with you today how we’ve linked catalyst and process development with
aspects of techno-economic analysis and process modeling in a research project that we’ve
been exploring around biomass conversion to high-octane gasoline. So, most of us are quite familiar with this
approach to catalyst development and catalyst science, where we can couple theory, synthesis,
and characterization of new materials with catalytic testing, and the results from each
one of these aspects can feed back to one another to help improve computational models,
design new materials to access your synthesis and characterization, and new reactions to
run to understand catalytic performance. But, what I want to talk about today is how
we’ve linked a second cycle around techno-economic analysis that can actually link back to this
first more traditional catalyst development cycle. By understanding some of the more high-cost
aspects of the process, we can understand and gain information that can lead toward
catalyst scaling and pilot-scale testing, but also, the results from the techno-economic
analyses can feed back to that traditional loop in all aspects of catalyst testing, synthesis
of new materials, and theoretical models that need to be developed. And that’s what I’m gonna focus on today. And all of our research and the conversion
of biomass really comes back to this grand challenge, that stems from the complex functionality
of biomass. You can see here—cellulose, hemicellulose,
and lignin biopolymers that are highly complex oxygenates. But, in comparison, the fuels that we might
wish to compare from this biomass are quite simple alkanes/alkenes, some minimal branching,
maybe some aromatics, but, at the molecular level, these structures are quite different. So, it’s difficult to envision a direct pathway
that can convert biomass to these alkanes and alkenes. So, rather, what we seek to do is identify
intermediates along the way that we can access, and in this case, thermochemically. What I’ll focus on is the gasification route. These intermediates, we want to have—we
want to be able to access them in high yield, and we want to balance the stability of these
intermediates with the reactivity to be able to further convert these and tailor the structures
to the fuel molecules that we want to make. So, if we’re considering gasification technologies,
the intermediate is syngas—carbon monoxide and hydrogen—which is fairly well accessed
from feedstock, gasification, and clean up. From here, there are three routes that are
flight mature, we would consider, in the conversion of syngas to fuels. First is Fischer-Tropsch, which directly converts
the syngas intermediate to gasoline and distillates. The second route goes through a methanol intermediate,
a secondary intermediate. Quite well understood—conversion of syngas
to methanol via copper zinc oxide on [inaudible] catalyst. And from methanol, two routes: MTG—methanol-to-gasoline,
and MODG—Mobil olefins-to-gasoline-and-distillates—are quite well known to access a variety of different
fuels. Because these three technologies are pretty
mature, we also understand the drawbacks associated with them that limits their industrial relevance. So, in the case of Fischer-Tropsch, there’s
costly catalytic upgrading to produce quality fuels. You get a lot of straight chain and you get
some waxes, so you need to further break those down to fuel molecules. And, in the case of the methanol routes, they
tend to be capital intensive with either a high aromatics content in gasoline, or also,
a high number of process steps to get your products. So, using process models and techno-economic
analysis, we can look at these types of processes starting from biomass—including biomass
gasification cleanup, and then further conversion. And, if we consider the net cost of production
from biomass, we can see that even in the case of these mature technologies, the Fischer-Tropsch
or MOGD were at $3.82 per gallon or $4.80 per gallon—not really cost competitive with
today’s market, and really highlighting the difficulty in generating cost-competitive
biofuels. And so, this really motivates us to seek new
advanced catalyst and advanced processes to produce cost-competitive biofuels. And so, one route that we’ve been exploring
as an alternative to FT or MTG or MOGD, but still utilizing the methanol intermediate
is what we call the high-octane gasoline pathway—or the HOG pathway. And some methanol, we can develop a market
responsive biorefinery concept. And what this means is that we can access
all three of our common fuels from methanol. So, for example, dehydrative coupling of methanol-to-DME
generates DME as a diesel fuel, which has been approved for use—especially in California. You can also take that DME and convert it
to hydrocarbons to generate a high-octane gasoline product, and that’s what I’ll focus
most of our talk on today. But, you can also take the olefins from that
high-octane gasoline product and couple those to a jet fuel. And so, we have the opportunity to balance
the production of each of these types of fuels to meet market needs. And, alternatively, we’re not confined only
to biomass. Going through a syngas intermediate and methanol
intermediate opens up routes to use other waste sources such as MSW or other renewable
sources such as biogas. So, we’re looking at the overview of this
DME to hydrocarbons process. [inaudible], we didn’t develop this here at
NREL. This was work that was funded out of BP, and
some really excellent, ground-breaking work about 10 years ago out of Enrique Iglesia’s
lab showing the conversion of dimethyl ether over a large-pore acidic zeolite such as beta-zeolite
under mild conditions of just 200 Celsius, and usually closer to the one or two bar than
high pressure. The product is a branch hydrocarbon mixture
of C4 and C7s—typical product selectivities shown in the bar chart there—high selectivity
to C4 and C7 with good selectivity to C5 and C6 as well, where the C5+ products would be
considered the high-octane gasoline product that we desired to produce. A few key points here. As I mentioned, DME-to-methanol—we have
a variety of routes to get there, and quite versatile. The total product is great as a fuel mixture
because of the variety of isomers that are produced. And, I’ll highlight a little bit later, there
are just some key differences between this type of process and MTG. And finally, this high-octane product is really
attractive as a refinery alkylate blendstock, really bringing this high-octane fuel to the
market. And again, the opportunity to couple the olefins
to distillate. So, we’re often asked, “How does this really
differ from MTG? What are some of the key differences?” And so, we highlight here—on the left—I
must say, the methanol-to-gasoline pathway is a very excellent example of being able
to convert methanol to what really resembles a finished gasoline product, having a mixture
of alkanes, alkenes, and aromatics. But, it turns out, those aromatics can kind
of work against you. In what we call the HOG pathway—the high-octane
gasoline pathway—we favor branch hydrocarbon products with very minimal aromatics. We get a different product because we use
a different catalyst—in this case, utilizing a beta zeolite catalyst—and we also utilize
lower severity conditions, that which also has the added benefit of a lower coking rate. Again, this leads to a product with the higher
octane numbers—both in research octane and motor octane—and it really resembles a high-octane
synthetic alkylate, which is one of the more valuable streams at a refinery. And, importantly, because of these lower severity
conditions, lower coking rate, if we look at these two processes from a biomass front-end,
we actually have the opportunity to access a higher yield of 65 gallons per ton in the
HOG pathway versus 55 in MTG. So, we can work with our process modeling
group here at NREL and techno-economic analysis group, put together an Aspen model for the
full conversion from biomass to this HOG product. And the great thing about this gasification
technology is we can leverage commercial technologies all the way around from biomass to the production
of DME in the bottom right-hand corner of the screen. And then, we can assert this new technology
of DME to high-octane gasoline, and we can look at some long-term targets, making assumptions
about catalyst performance. And so, in particular, we can target 65 gallons
per dry ton of biomass at a cost of production of $3.41 per gallon. Now, as you note, this $3.41 is lower than
those traditional syngas conversion routes—even Fischer-Tropsch. But, if you look at putting the typical performance
metrics of HBEA catalyst into this process model, we see that we only get a yield of
about 40 gallons per dry ton biomass, and the cost of production is $5.20 per gallon. So, we don’t really come anywhere close to
these long-term targets with the parent beta catalyst. So, if we look more closely into the TEA model,
we understand some of the sensitivity around the catalyst development and the catalyst
performance. So, here are four of the most—of the highest
contributing cost to the hydrocarbon synthesis. And if you notice, the yield has the highest
contribution. So, what we’re looking at here is that the
center zero line would be the base case scenario. So, shown on the right—65 gallons per ton. If we were able to increase that to 70—in
this case, green is good, and we would reduce the production cost by 7.2 percent. However, if that yield drops to just 60 gallons
per ton, we would expect an 8 percent increase in the cost of production. We see the catalyst cost is important as well
as the catalyst lifetime. Interesting, from this analysis, is that the
single-pass DME conversion has only a minor effect on the cost of production. So, if we model it at 40 percent single pass,
if that drops to just 25 percent, we see that only has about a 1.7 percent increase in the
expected cost of production from this process. So, what this analysis really highlights is
the importance of developing an inexpensive catalyst with a long lifetime that demonstrates
a high selectivity to C5 products to increase the product yield. And selectivity is much more important than
conversion. So, considering the HBEA catalyst and the
chemistry that’s occurring over that catalyst, what really limits the performance to only
40 gallons per ton, for example? Well, the first off, when you look at the
chemistry, it’s hydrogen deficient. If you take a DME molecule and you pull water
out of it—which you know the catalyst does—you’re left with two CH2 units. And so, you’re short on hydrogen to produce
the alkanes that we see coming out of the reactor. And the way the BEA catalyst compensates for
this is by generating a hexamethylbenzene as a key hydrocarbon aromatic product. So, if you write a balanced equation out,
you would start with 33 DME molecules; you can generate six of these very high-value
trimethylbutane C7 compounds; 33 waters, which would make 2 hexamethylbenzene. So, this contributes significantly to yield
loss that is not coming out of your C5+ products. Some really excellent work has been done—in
particular, from Aditya Bhan’s group—looking at the mechanism of this type of reaction. These are details of the mechanism. They’re not really important for today’s talk,
but mostly to highlight we do need to generate aromatics in the catalyst on the left hand
side of the aromatic’s carbon tool so that we can generate propylene that enters in the
right-hand side of the mechanism, in order to grow the methylation to grow the hydrocarbon
chain up to the C5, C6, and C7 products that we want to form. And so, if we consider some of the limitations
of HBEA and how we would address these from catalyst development, we need to shift products
away from that aromatic cycle and push more of the carbon into this olefin cycle. We initially have [inaudible] we could do
this and address the hydrogen deficiency by co-feeding a molecular hydrogen and that we
could activate that with catalyst modifications to get it to participate in the reaction,
but key to that would be maintaining that C5+ selectivity, as highlighted by the sensitivity
analysis. And then finally, I showed earlier, there’s
a high selectivity to C4, and those are really key. We need to be able to reactivate those and
get those back into the chain growth cycle to really realize this maximum of C5+ yield. So, through the more traditional side of catalyst
development—couple linked synthesis theory and catalytic testing—well, we generated
a number of different catalyst targets. We tested those, and screened those, and what
we found was that modification of the beta-zeolite with copper resulted in a two- to threefold
increase in the hydrocarbon production rate—as shown in the top left chart there—and an
extended lifetime. So, the red markers in the top left are the
typical HBEA performance, and we have to stop the reaction after about 20 or 24 hours, because
we’ve built up too much hexamethylbenzene in the reactor. However, after copper modification, we see
an increase in the total hydrocarbon productivity, and we can run this reaction for longer than
100 hours. In this particular case, we stopped at 100,
regenerated the catalyst, and the light blue markers—you can see that those match quite
well to the beginning of the reaction. Very important—we haven’t changed the selectivity
too much, and, if anything, we have a slightly higher selectivity to the C5, C6, and C7 products,
which is advantageous. Looking more at the mechanism and pulling
out some of the product ratios to understand where the product are coming from relative
to the aromatics or the olefin cycle, we can see that for HBEA or HBEA with co-fed hydrogen,
only about 20 to 25 percent of the products come out of the aromatic cycle, and almost
80 come out of the olefin cycle. However, when we add copper modification,
we drive down the products from the aromatic cycle down less than 10 percent with over
90 percent of the carbon coming from the olefin cycle. We have a decrease in the HMB, as we expected,
being able to run for a much longer time in the reaction and we’ve really favored these
olefin cycle products. So, this copper catalyst seems to achieve
the first two goals that we set out in catalyst improvement. We’ve looked very deeply to try and figure
out the role of copper is in this catalyst, and we worked closely with collaborators at
Argonne National Lab to do X-ray absorption spectroscopy. And interestingly, we see contributions from
both metallic and ionic copper in the catalyst. And so, we have this multifunctional catalyst
now, where we have metallic copper that we hypothesize, activates the hydrogen, and we
see an increased paraffin-to-olefin ratio resulting from that reaction. But, we also have cationic copper that we
think facilitates the hydrogen transfer and dehydrogenation inside the catalyst cores. We explored this experimentally doing the
reaction with deuterium, and as you can see in the left here, running just a para-beta
catalyst with deuterium and looking at this major C7 triptane product. There’s no deuterium in the product. Deuterium’s not activated over the regular
zeolite catalyst. But, after copper modification running the
reaction with deuterium, we now see deuterium all over this triptane product and throughout
the mass spectrum. With respect to the cationic copper, we also
looked at this dehydrogenation reaction feeding just isobutane over the copper BEA catalyst
or the HBEA catalyst, and monitoring hydrogen production. And, as you can see, the HBEA catalyst doesn’t
produce any hydrogen under these conditions, but the copper BEA catalyst produces hydrogen
quite extensively over—even up to 8 or 9 hours time on stream. So, considering this dehydrogenation, we’re
quite intrigued by that, and it’s a very interesting reaction. It’s something that’s very popular in literature,
so, we went back to the process model to understand what kind of importance this would have within
the TEA. And, it turns out, it’s a critical component
to the TEA. Because of the high selectivity to the C4
products, we have to be able to recycle those and get those back into the chain growth pathway. Looking on the right, we’ve put metrics now
to what that importance would mean. This is just the high-octane gasoline synthesis
cost—just that last portion of the process model. With an HBEA catalyst, that would contribute
$1.01 to the cost of the finished fuel. And that’s with no C4 recycle. If we have a moderate amount of reactivation
of the C4 products and reincorporation of the C5+ products, over the copper BEA catalyst,
we can drop that down to $0.67. And, if we can really recycle this all the
way to extinction, we could reach our target goal of just $0.38 per gallon for the hydrocarbon
synthesis cost. So, this recycle is a critical component in
the TEA to achieve these high yields and really realize those lower costs in production. But why is it so difficult? Well, over the parent beta-zeolite catalyst,
mechanisms have been studied extensively. Some really nice work out Enrique Iglesia’s
group has shown that alkanes are considered terminal products and no re-incorporation. So, if you look at the highlighted area in
green, that highlights you’re doing a chain growth in propylene, and once you get the
HT step to the butanes—isobutane or n-butane—that arrow only points one way, and those products
do not come back into the cycle for further chain growth—the terminal products. Well, we’ve already shown that we can get
some activation of isobutane over our copper BEA catalyst, so we wanted to study this more
deeply—more on that more traditional left side of catalyst development looking at computational
aspects and experimental aspects over the copper BEA catalyst. So, what we did was we tried to isolate the
different functionalities present in this multifunctional catalyst. We know we had metallic copper and we have
cationic copper from the X-ray absorption. So, we made five materials to explore the
difference between metallic copper and copper oxide on silica without any Brønsted acid
sites, and we can control either copper oxide particles or copper metal just by the pre-treatment—whether
oxidative or reductive. We can look at our regular HBEA catalyst,
and then, we prepared two catalysts with just ionic copper. And we wanted to explore both copper(II) and
copper(I). And again, we can control the copper(II) or
copper(I) speciation just by the pre-treatment of the same ion exchanged copper BEA, where
now, we have the Brønsted acid sites, copper ionic sites, but no metallic copper. Looking just at the dehydrogenation reaction,
feeding isobutane—which is major product from the DME-to-hydrocarbon C4 products—we
can do this reaction at 300 degrees in a u-tube type reactor. And what we see is—I already showed the
data that the HBEA catalyst was inactive, but it turns out that both copper and silica
or copper oxide and silica are also inactive for this reaction, and no hydrogen was observed. However, both catalysts with ionic copper
generate hydrogen in this reaction, and so, this tells us these ionic copper species are
really the active sites for isobutane dehydrogenation. The copper oxide particles, copper metal,
or Brønsted sites are not active. To look more closely at copper(II) versus
copper(I), we again went back to Argonne National Lab, and we had them do operando XAS experiments
under essentially identical conditions as to what we did in our lab—feeding isobutane
and monitoring the products. I show here on the top right the representative
characteristic spectra for copper(I) and copper(II)—copper(II) in red; copper(I) in blue. So, you can see this clear shift in the XANES,
so, these are indicative, and we’ll be able to follow the copper fraction during the course
of the reaction, which is shown on the bottom right. And these are the results over the copper(II)
catalyst, and you can see that almost immediately, we have conversion from copper(II) to copper(I). In just 2 minutes, 80 percent of the copper
is in the copper(I) state, and after two hours, 100 percent of it is. If we load the copper(I) catalyst and do that
pre-treatment, it remains copper(I) throughout the whole reaction. And at no point was metallic copper observed
for these two materials. So, this really allows us to state that ionic
copper(I) species are responsible for the observed dehydrogenation. And so, we can take this information now and
feed it back into these theoretical calculations and we can look at reaction mechanisms and
energetics to look at the reaction of isobutane to isobutene, only now that we know, it’s
a copper(I) site in the beta-zeolite. So, we look at the mechanism of isobutane
and explored both breaking at the primary CH bond first versus the tertiary CH bond
first. Turns out, the primary route is slightly lower
in energy, because the alkane is carbanion not a carbocation in this case. But we can go through this mechanism where
we can see primary CH bond activation. We can put that—that goes to a Brønsted
acid site on the zeolite. And then, that reaction with the tertiary
CH to form isobutene ad hydrogen. And what’s important from these is we can
look at these energetics, and we can compare to known dehydrogenation catalysts such as
gallium or zinc in a zeolite, and what we find out is that these copper(I) species have
higher barriers, and therefore, we would expect them to be less active in something like gallium
or zinc. And this is important, because now we can
move forward in the catalyst design and we can think about trying to improve this dehydrogenation
performance by making bimetallic catalysts that maybe incorporate the species like gallium
or zinc in these cation [inaudible]. So, this is really simulated to understand
how dehydrogenation was occurring over this copper catalyst and at these ionic copper
sites. So, we wanted to now look at experiments where
we can simulate the recycle of isobutane in the presence of DME and hydrogen and try to
get information that we can feed back into the process model in the techno-economic analysis. So, what we did was we took our regular reaction
conditions feeding DME and hydrogen, and now, we fed one percent of isobutane, representative
of a recycle stream. And we did experiments with and without isobutane
co-feed. We did them at a regular reaction conditions
of 200 degrees and at a low pressure or a high pressure. And, importantly, we used isotopically labeled
isobutane, because this would allow us to track 13-label carbon in the progress. And so, if we look at the conversion and the
selectivity, there’s not a very large effect in going with or without the isobutane co-feed,
only a minor decrease in the conversion yield. But what we see—particularly in the case
of the isobutene product—if we do this reaction with just the HBEA catalyst, we see the mass
spectrum that matches the missed spectrum for isobutene. However, when you use the copper BEA catalyst,
now we see evidence of this isotopically labeled carbon in the isobutene product. So, this confirms the dehydrogenation activity
and that this reaction is occurring, even in the presence of DME and hydrogen over this
catalyst. But, it’s not good enough just to dehydrogenate
isobutene. We have to show this product gets into the
C5+ products. So, again, we can look at the mass spectra
of C5 and C6 products from this reaction, and we see that in the cases of all three
of these, we see the evidence of the isotopically labeled carbon in the C5 and C6 products when
we use the copper BEA catalyst, and no evidence of isotopically labeled isobutane incorporation
with just the HBEA catalyst. So, this indicates not only the reactivation
of isobutane under these conditions, but reincorporation into these C5+ products. So, now, I’m gonna go back to our process
design. We can take the performance metrics that we’ve
measured over copper data, we can put them in, and to remind you, with the regular parent
beta catalysts, we achieve about 40 gallons per ton yield at $5.20 per gallon. But now, with the performance of the copper
BEA, we can achieve a yield of 56 gallons per drive time at $4.54 per gallon. This is a 13 percent reduction versus the
parent zeolite, a 40 percent increase in yield versus the parent zeolite, and it really requires
both high productivity of the copper BEA catalyst and this unique ability to reactivate isobutane
and reincorporating the C5+ products. And remember, I mentioned at the beginning
that a process like MOGD for methanol, from the biomass front end, is around $4.80 per
gallon. So, again, we’re starting—we’re even competing
with these more mature technologies. It’s interesting to look at these C4 conversions
and what we measured and what we would have expected to measure. So, under both of our conditions—at low
pressure and high pressure—we measure isobutane conversion of about 14.5 percent and just
over 23 percent at higher pressure. And these are remarkably high compared to
the thermodynamic limitations of isobutane dehydrogenation that you would expect at 200
degrees. We would expect less than one percent conversion. So, this really suggests to us that the reactivity
is kinetically controlled. We have a lot more to do to track this down
and follow-up experiments to understand this, but presumably, it’s through the consumption
of both products isobutene—as evidenced by the heavy carbon in the C5+ products—and
hydrogen, which we know the catalyst also activates at the metallic copper sites. This would be similar to other product removal
concepts to drive reactions. And, we could also—understanding now the
structure of the catalyst, having cationic copper inside the zeolite core, we can start
to hypothesize that maybe having that copper inside the core is important for dehydrogenation
and generation of that alkene in close proximity to a Brønsted acid site that can really rapidly
convert it and drive this reaction forward. We have to do a little bit of a stand and
check and compare it to what’s out there about isobutene methylation rates and high through
transfer rates. And there’s some great work from Dante Simonetti
when he was with Enrique Iglesia’s group, where they looked at these two rates of isobutene
over the HBEA catalyst. And they had values at 33 and 38 micromoles
per mole aluminum per second. If we look at our isobutane conversion rates,
they’re somewhat lower at about 7 or 11.5 micromoles per mole aluminum per second, but
this intuitively makes sense, because we have to do the dehydrogenation stuff as well. And it shows that we’re roughly in the same
order of magnitude for this type of conversion over this catalyst. So, let’s shift gears in adjust this last
step of process design where we can take these olefins and couple them to a jet fuel. What we’ve done is taken a representative
mixture of the DME to hydrocarbon’s reaction where the mole percents here are shown near
their representative structures—high NC4, NC7—and we’ve developed a process over a
simple commercial Amberlyst catalyst under mild conditions to generate a couple of products
that have hydrocarbon numbers in the distillate range. We’ve looked at carbon distribution analysis
of this product, and the raw material coming out of the reactor still has some light contribution
from unreactive C7 to C8, possibly dimerizations of C4. But a very simple back end distillation removes
those light ends, and we get the distribution in red, which matches very nicely with their
representative jet fuel example. Might be a little bit off right in the very
center of the distribution, but what’s important is that there’s no heavy molecules out past
C22. That would really be problematic for something
like jet fuel. We took this mixture and we did a variety
of different ASTM tests for it, and it meets the specifications for density, viscosity,
heat of combustion—very importantly, freeze point—and distillation curve. And so, while these branch compounds wouldn’t
be very attractive as a diesel fuel, it is, actually, quite attractive as a jet fuel blendstock. So, again, we can go back to our process model,
and we can update, just again, that keeping all the front end the same, starting just
from our DME conversion, we can insert a couple new process steps where we take the C4s and
rather than recycling them, we can put them through a dehydrogenation unit and we can
put all of our olefins through an olefin coupling unit. And now, we can generate both a high-octane
gasoline and a distillate product. Again, in the HOG only case, we’re at 56
gallons per ton—$4.54 per gallon. In the case of HOG plus distillate, we still
get 29 gallons of the HOG product, 20 gallons of jet product, at a price of $4.71 per gallon. So, we do suffer a slight decrease in the
total yield and an increase in the cost versus HOG only. It makes sense, we’re adding additional capital. This is a whole new process and additional
steps along the process. And inherently, we have a yield on the distillate—distillate
yield is limited by the paraffin olefin ratio that degenerate in the HOG product. You can only convert the olefins that degenerate. But still, we’re competitive with the MOGD
as a benchmark at $4.80. So, in summary, I hope I’ve highlighted how
we’ve utilized TEA and really coupled this with our R&D to both direct topics of research,
but also, understanding the value of catalyst improvements that we’ve made. We’ve developed this inexpensive copper BEA
catalyst with a higher productivity and extended lifetime than the parent BEA catalyst, and
importantly, we’ve shown that reactivates and re-incorporates isobutane, even in the
presence of DME and hydrogen. This unique reactivity results in a 40 percent
increase in yield and 13 percent reduced cost versus the HBEA in the process model. We’ve also shown that distillates can be produced
from the olefins, but with an additional cost, since it requires additional capital. And ongoing R&D in this project—again, we
could take these results from the computation that I showed that zinc and gallium should
be more active for isobutane dehydrogenation than our copper(I) species that we identified. So we’ve been looking to develop bimetallic
catalysts that can help control that paraffin-to-olefin ratio in the HOG product, and this benefits
us twofold. We can control the HOG fuel properties by
having olefins present that can help tune in the motor octane number, but also, we can
direct more olefins to the distillate yield if we can generate more olefins in that process. So, all the research that I presented today
has been a great team effort—both the people here at NREL and collaborators at our National
Labs. Great effort from our techno-economic analysis
team and fuel property analysis collaborators here at NREL, as well as, again, our X-ray
absorption spectroscopy collaborators at Argonne. This research was funded by the Department
of Energy Bioenergy Technologies Office, and also, through ChemCatBio—a division of the
Energy Materials Network. Thank you. [Applause]>>Moderator: We can take questions if anyone
has them. Just let me take a second to come over to
you with a mic.>>Audience: Dan, can you comment on what you
think might be limiting you to further increase the productivity of the high-octane gasoline? Like, what fundamental reaction steps could
we further look at to improve that yield?>>Dan Ruddy: Right. So, we can take a little bit from the sensitivity
case there where the single-pass DME conversion might not be as important, because we can
recycle the DME. But, the key areas are increasing that C4
recycle conversion. Right now, at around 23 percent, there’s still
quite a bit of a recycle stream. So, we can push that recycle conversion higher—say,
to 40 percent, 50 percent. Now, we can start to generate a higher yield,
less recycle cost, and that would drive down the cost and increase, essentially, again,
the productivity, as you mentioned.>>Audience: Yeah—follow on question to that. What is your theoretical maximum yield you
could get if everything was perfect?>>Dan Ruddy: I think it’s pretty close to
the 65 gallons per ton. Just based on carbon efficiency, known carbon
efficiency losses through the gasification cleanup step. We’re kind of in that 65 range.>>Audience: Okay.>>Moderator: If there are no other questions,
I will thank everyone for joining us today. Sorry about the technical difficulties. So, thank you, Dan.>>Dan Ruddy: Okay. Thank you. [Applause]

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