0:00:01   Hello everyone. My name is Wilson McNeary and I'm a postdoc at NREL, in the catalytic carbon
0:00:06   transformation and scallops center. I'm going to talk today about some of our work using atomic
0:00:11   layer deposition to improve biomass conversion catalysts.
0:00:18   So as the world utilizes greater amounts of renewable energy, there is increasing discussion about
0:00:25   the hard to de carbonized sectors of the economy. These are areas such as heavy industry and
0:00:32   transport, which require large amounts of oil and oil products. There's a shift underway in
0:00:39   transportation for light duty transport towards electric vehicles. However, other methods of
0:00:47   transport, such as air travel and heavy shipping are going to be really hard to electrify. So
0:00:53   there's a need for research into carbon neutral or carbon negative fuels. one way in which this need
0:01:01   could be met is through the conversion of biomass into biofuels and bioproducts. This typically
0:01:07   involves a synthesis and upgrading step, which uses heterogeneous catalysts to convert the chemical
0:01:13   intermediates into the final bioproducts. In this step, the catalysts are often exposed to a number
0:01:20   of different stressors such as high temperature a condensed phase environment which may promote
0:01:26   leaching of the catalyst and impurities such as sulfur, which can deactivate the catalysts. So
0:01:33   there's great interest in developing a tailored catalyst solution that can mitigate all of these
0:01:38   different degradation pathways
0:01:44   here at in real we've been working to use atomic layer deposition or L. D. To protect catalyst in
0:01:51   these type of reactions. If you're watching this talk, I'm sure you're probably familiar with the
0:01:55   concept of a L. D. And how it works. But just as a general overview, this is a coding process in
0:02:01   which you can coat a starting surface using the four step process outlined below where you dose in a
0:02:10   metal organic precursor followed by a purge followed by a counter reactant, followed by another
0:02:15   purge that constitutes a single a lady cycle And you can repeat that as many times as you want. Some
0:02:22   of the unique aspects of a lady or that it's self limiting, which allows you to deposit formal films
0:02:28   on a range of different substrates. In particular, the ability to coat High surface area three
0:02:34   dimensional bulk powders has enabled a wide space of application around using L. D. Coatings to
0:02:40   protect catalytic nanoparticles.
0:02:46   one of the first examples of using led to protect catalysts was from a group at Argonne National
0:02:52   Laboratory. They showed that alumina L. D. Could help to preserve the small size of palladium
0:02:58   nanoparticles even when exposed to high temperatures for long amounts of time. They also found that
0:03:07   they had a lot of flexibility and how many cycles of A. L. D. They could put down on the catalyst
0:03:11   without degrading the catalytic activity. So up to 15 or so cycles, they found that the L. D.
0:03:18   Preferentially deposited on low coordination sites of the palladium nanoparticle, which were not
0:03:23   themselves active for the reaction they were looking at so they could get the protective effect of
0:03:30   the L. D. Film without negatively impacting reactivity. When they tested these catalysts in their
0:03:39   desire reaction, they found that they maintain their activity for a much longer time than uncoated
0:03:45   catalyst under really high temperatures and long reaction times.
0:03:53   This laid the groundwork for the work that we've been doing it in real trying to use a lady to
0:03:58   improve catalytic performance in reactions that are relevant to biomass conversion. Our first foray
0:04:05   into this was in collaboration with forged nano and johnson Matthey and we were looking at using L.
0:04:10   D. Coatings to improve performance in the Konik acid hydrogenation reaction. We found that aluminum
0:04:18   L. D. Could help to preserve the activity of these catalyst over long reaction times. It also helped
0:04:25   to impede the phase transition of the T. O. To support at high temperatures. It helped to preserve
0:04:32   the small size of the palladium nanoparticles and it had the added benefit of mitigating leaching of
0:04:38   the palladium in the acidic reaction environment.
0:04:44   The work I'm going to discuss today is a continuation of this, where we were looking at L. D.
0:04:48   Catalyst for use and aromatic hydrogenation reactions. Aromatic hydrogenation is an important step
0:04:55   in the production of biofuel. It's required to decrease aromatics in the final fuel, which in turn
0:05:03   allows for lower emissions when that fuel is burned.
0:05:09   The catalyst that we were looking at were done with an over coating procedure in which T 02 L. D.
0:05:14   Was deposited on a palladium supported on alumina catalyst. After an initial catalyst screening, we
0:05:21   found that the best performer of that bunch was one with 10 cycles of T. 02 which I'll be calling 10
0:05:28   c t 02 in this talk, that's the one I'm going to primarily focus on day today as we did a lot of in
0:05:35   depth characterization, reaction testing and computational modeling with this catalyst.
0:05:43   So when we examine this 10 C. T. 02 catalyst after the L. D. Procedure, we found that there was
0:05:49   about nine weight percent of T. I on the surface. Looking at the microscopy and E. DS maps, we can
0:05:56   see that there's a can formal layer of T 02 across the surface and the aluminum support was pretty
0:06:01   evenly coated. We did notice some, some significant changes in the kidneys option uptake both with
0:06:09   hydrogen and carbon monoxide. This indicates that the plane sites were at least partially covered by
0:06:16   the L. D. Process, although from just the kidneys option in the my Crosby images, we, the extent is
0:06:24   somewhat unclear, but this kind of brought us to our first big question in this work was how does
0:06:31   this coverage of the palladium by the T. O. To impact the reactivity.
0:06:41   We set out to examine these catalysts in batch reactions. Initially using a couple of different
0:06:48   aromatic molecules benzene, styrene and naphthalene. We found that in every case the 10 C. T. 02
0:06:55   actually had considerably higher conversion at the same time points than did the uncoated palladium
0:07:02   aluminum. We dug into this a little bit further with the napoli hydrogenation reaction. I'm showing
0:07:09   on the right the tetra land productivity of each catalyst, the 10 C. T. O. To the uncoated palladium
0:07:17   alumina and a palladium titania control catalyst. And you can see that the 10 C. T. 02 has higher
0:07:25   performance than those two uncoated materials. When we look at turnover frequency, which is
0:07:32   normalizing by the ceo kim absorption numbers that I showed on the previous slide. The difference is
0:07:38   even more stark with the 10 cto to drastically outperforming the other two catalysts. This is
0:07:44   because as we saw, there are fewer available palladium sites on this 10 C. T. 02 catalyst, but it's
0:07:50   doing more reaction with those fewer sites.
0:07:57   So this was an interesting finding that we kind of didn't expect, given that we knew we were going
0:08:02   to be covering some of the palladium sites. We wanted to make sure that we could replicate this in
0:08:07   flow reactions. So we tested napoli hydrogenation in a trickle bed reactor with those same three
0:08:13   catalysts and we found very similar trends where the 10 C. T. 02 outperformed both the uncoated
0:08:20   palladium alumina and the palladium titanium control case.
0:08:26   The 10 C. T. 02 ended up having about a 1.7 X. Higher activity than its uncoated base material. So
0:08:33   the application of the L. D. Layer alone is enough to increase the activity by that. Much.
0:08:39   Additionally, looking at the difference between the 10 C. T. 02 and the palladium supported on
0:08:46   titania, we can tell that there's there's a difference between the the L. D. Layer and its effect on
0:08:53   the catalytic performance versus just A T. 02 crystal and support. So there's something special
0:08:59   about having the close contact between the L. D. Layer and the palladium. So this brought us to our
0:09:07   next big question, which is why does the T. 02 L. D. Layer boost the activity?
0:09:17   We first aimed to address this question by characterizing the electronic structure of the catalyst
0:09:22   with XPS. And you can see here for the palladium uh segment of the XPS spectra, the binding energy
0:09:33   didn't really change when the 10 CT 02 L. D layer was added. We additionally got some X A. S done on
0:09:43   these catalysts and we found that the coordination number between palladium was exactly the same for
0:09:49   10 C. T. 02 versus the uncoated catalyst. So in both of these cases, application of the L. D layer
0:09:56   doesn't appear to really be changing the electronic structure of palladium itself. We also got some
0:10:03   I. S. S analysis done and we found for the aluminum and titanium peaks. Kind of the expected
0:10:11   behavior where for the 10 C t 02 and blew the alumina is almost entirely covered and there is the
0:10:18   emergence of a. T. I peak relative to the uncoated palladium alumina, additionally, zooming in on
0:10:25   the palladium peak in the spectrum. We can see evidence more evidence of the coating of palladium,
0:10:32   given that the intensity of the peak is slightly less than half for the 10 c t 02 catalyst.
0:10:43   So, since our experimental evidence pointed to no significant changes in the electronic structure,
0:10:49   but definite coverage of the palladium, we decided to look at this from a different angle. Using
0:10:55   some computational modeling. Our collaborators here at in real, developed a few different model
0:11:00   surfaces to test the absorption of different reaction intermediates on The one I'm going to focus on
0:11:08   is what we call the truncated T. 0 2 layer on palladium. Uh we expect that this is closest to the
0:11:16   experimental system we were working with, given that there's still available available platinum, but
0:11:21   it is partially covered by T. 02 We calculated the absorption energies of hydrogen, naphthalene and
0:11:29   petrol in on this truncated surface, which is shown in the right as the blue bars compared to bear
0:11:36   palladium. We saw some interesting shifts in the binding energy for these intermediates. The
0:11:44   hydrogen didn't really change. Um if anything, it got slightly more stable. However, the nazi lean
0:11:50   and petrol in got considerably less stable with the addition of that truncated T. 0. 2 Layer. We
0:11:58   believe this is because these molecules prefer to absorb in a flat configuration and they can't do
0:12:04   this is easily with the T. 02 blocking some of the large palladium domains on the surface. So we
0:12:15   believe that this combination of hydrogen binding in the hydrogenation reaction not really changing,
0:12:22   and a substantial decrease in the strongly bound aromatics, particularly the tetra lin product, have
0:12:31   the combined effect of increasing the rate of hydrogenation and giving us the phenomenon we're
0:12:37   seeing in our experiments,
0:12:43   as I mentioned, we were also interested in studying the stability of these catalysts with the L. D.
0:12:48   Layer. So we exposed them to a few different stressors and then retested them for naphthalene
0:12:54   hydrogenation activity. We took a subset of catalyst and exposed them to sulfur during the reaction
0:13:02   using dimethyl sulfide additive, we took some catalyst and expose them to a couple different thermal
0:13:10   treatments under dry air and we also exposed some catalyst to a hydrothermal treatment in liquid
0:13:17   water. Here, I'm showing the tetra in productivity of the catalyst after each of these different
0:13:24   treatments for the sulfide catalyst, we saw that they all lost some of their activity. However, the
0:13:32   ale decoded catalyst lost the least amount.
0:13:36   There were some interesting trends with The 450 c in the 750 c thermal treatment uh but one of the
0:13:44   biggest takeaways was that the 10 C. T. 02 catalyst not only retained its initial activity but
0:13:50   actually increased in activity over these different treatment steps. The hydrothermal treatment was
0:13:57   pretty detrimental to all of the catalysts shown in yellow, including the L. D. Catalyst, and we
0:14:03   believe a lot of that is due to evidence of support collapse and palladium centering in the
0:14:11   hydrothermal treatment. However, there were some interesting trends with the 10 C. T. 02 catalyst in
0:14:20   the ceo to I'm sorry ceo uptake, we found that it increased for each of these different treatments,
0:14:28   including the hydrothermal treatment. So we wanted to investigate that a little bit further
0:14:35   in order to dig into this further, we got some microscopy of the catalyst after the 7 50 C.
0:14:43   treatment and the 200 C hydrothermal treatment, you can see for the 10 C. T. O. Two, there is not a
0:14:51   significant change in the particle size which is for the 7 50 C. Thermal treatment, which is
0:14:56   promising, indicating that the L. D. Layer helped to preserve the palladium particles. But we do see
0:15:04   this really substantial increase in SEO uptake despite no real change in the particle size, We
0:15:10   believe this may be due to the formation of pores in the T. 02 layer. This calculation could open up
0:15:16   pores in the layer and expose more of the palladium, thereby increasing both the activity and the
0:15:22   ceo uptake. Mhm. The 200 C. Hydrothermal treatment as you saw, was really Detrimental to all the
0:15:30   catalysts, including the 10 c. t. 0. 2. We saw evidence of support collapse as well as in X. Rd
0:15:36   evidence of the alumina phase transition to bow My, which is known to be really detrimental to
0:15:41   catalytic performance. Interestingly though, in the 10 C. T. 02 we didn't see that much
0:15:48   agglomeration of the palladium as we did in the uncoated material. But there was a collaboration of
0:15:53   the A. L. D. Layer. You see those large chunks of T. I. On the surface indicate that the L. D. Layer
0:16:00   was unstable in that hot liquid water environment and a glom aerated together. So that's an area of
0:16:07   research. We're going to be following up on what the limitations are of these T. 02 L. D. Layers in
0:16:13   an Aquarius reaction environment and how much we can affect the stability and and keep those layers
0:16:21   from from showing the behavior that they had here.
0:16:27   Finally, we wanted to put some thought into the value proposition of ale de Forca Tallis is
0:16:32   specifically whether L. D. Would be worth it in the application of this hydrogenation catalyst. Our
0:16:40   collaborators at forge nano came up with a few different cost estimates for a 10 c t 02 L decoding
0:16:47   depending on the price of the L. D. Precursor and the capacity of the equipment used to do the
0:16:52   coding. We used a cost estimate of 43 84 per kilogram kind of as a worst case scenario, combine that
0:17:03   with a catalyst cost estimate from Israel's cat cost program and fed that into a simple techno
0:17:10   economic model of an aromatic hydrogenation process.
0:17:15   Were used this model to run a number of different scenarios in which we change the way to really
0:17:21   space velocity and the catalyst lifetime parameter. And these were meant to represent the different
0:17:29   performance improvements that might result from an ale decoding with waiter really. Space velocity
0:17:33   being an increased activity and catalyst lifetime being an increase in durability savings were found
0:17:43   in the positive direction for both of these parameters. In the case of weight over the space
0:17:46   velocity due to decreased operational and capital expenses and the case of catalyst lifetime due to
0:17:52   decreased catalyst purchase price, we found relative to the baseline that the cost of an L decoding
0:18:01   could be neutralized by just a two X increase in either of these parameters. So if the weight of the
0:18:08   space velocity or catalyst lifetime are doubled, the addition of an ale decoding more than pays for
0:18:15   itself, we think that a two X increase particularly weight early space velocity is achievable based
0:18:21   on the one point seven x activity increase that we saw experimentally in this work and of course Any
0:18:29   any increase in both parameters or beyond two x. Just compounds the benefit of the L. D. Coding even
0:18:37   further. So we think this is a really promising analysis that suggests LD coatings can be a feasible
0:18:44   option for catalytic processes if they increase the performance By at least two X or more.
0:18:59   So in conclusion, I've shown you that we can applying nail decoding to change the service absorption
0:19:05   energetic of aromatic molecules which can lead to improve process economics and we hope will
0:19:11   eventually lead to decreased harmful emissions by making it easier to remove aromatics from both bio
0:19:18   and fossil fuels. We're taking this work a step further right now by trying to use L. D. Catalyst in
0:19:28   the production of sustainable aviation fuels. And we're focused on a pathway to bio jet fuel that
0:19:35   involves making volatile fatty acids or V. F. A. S. From arrested anaerobic digestion and then
0:19:44   converting those into al canes for jet fuel through hydro de oxygenation or H. D. O. Given that HBO
0:19:53   has many similar mechanistic steps as hydrogenation. We felt that LD catalysts would also be
0:20:02   effective in that reaction. So far. We've done some preliminary where confound that with an L
0:20:08   decoded catalyst, we can dramatically shift the product distribution towards al canes in this multi
0:20:14   step reaction. Which is really promising and uh further indicates that there's utility of L. D.
0:20:21   Catalyst in the production of sustainable aviation fuel. Additionally, we've been working to use L.
0:20:29   D. Catalyst in oxidation reactions for making bio based chemicals such as glue connick acid. These
0:20:37   are challenging reaction environments given the oxidative atmosphere and the Aquarius Phase. So
0:20:45   we've been focused on reducing catalyst leaching. We found that in 15 hour leaching tests, LD
0:20:52   coatings can help to dramatically reduce leaching of the active metal species. Which is also
0:20:58   promising for this application as well.
0:21:05   I'd like to acknowledge funding for this work from the U. S. Department of Energy's bioenergy
0:21:09   Technologies office as well as our collaborators at forge nano and johnson Matthey. My group at in
0:21:16   real has led by Derek Vardon. And I'd also like to thank all of the collaborators in our group that
0:21:21   helped bring this work together.
0:21:25   I'd also like to thank you for your attention. I hope you enjoy the rest of the A. I. C. Summit and
0:21:30   I'd love to hear from you if you have any questions.