Effects of Size and Location of Nanoparticles in Catalysis - Krijn de Jong

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Summary

In a captivating talk by Krijn de Jong at Aalto University, the focus is on the fascinating world of nanoparticle catalysis. De Jong unravels how the size and location of nanoparticles, such as those made from cobalt, iron, and copper, significantly affect catalytic processes. By understanding these details, researchers can optimize catalysts for their activities, improve efficiency, and even aid in efforts like carbon capture and renewable energy transitions. De Jong underscores the importance of these advancements towards a sustainable future.

Highlights

De Jong elaborates on the relationship between nanoparticle size and catalytic activity, demonstrating with cobalt and iron nanoparticles. 🔬
He underscores the significance of nanoparticle distribution on support materials and its impact on catalytic performance. 🧭
The talk highlights the dual role of size and composition in achieving desired catalyst properties. 🏗️
There's a fascinating dive into the effect of environmental treatments on nanoparticle formation. 🌱
De Jong presents cutting-edge methods to control nanoparticle size for better industrial applications, like methanol synthesis. 🔧

Key Takeaways

Understanding nanoparticle size is crucial for optimizing catalytic efficiency. 🧪
Location and distribution of nanoparticles greatly influence their effectiveness. 📍
The balance between nanoparticle stability and activity is essential in catalysis. ⚖️
Promotors can significantly modify the activity of nanoparticles depending on their size. 🔍
The potential of nanoparticles extends to diverse areas like energy storage and carbon capture. 🌍

Overview

Krijn de Jong's lecture at Aalto University delves into the critical aspects of nanoparticle design in catalysis. He starts by explaining how the size of nanoparticles drastically influences the catalytic processes, showcasing research findings involving metals like cobalt and iron. The takeaway is clear: size isn't just a number; it's a fundamental factor in catalytic efficiency!

Next, de Jong talks about the often-overlooked aspect of nanoparticle distribution on their support materials. He illustrates how the proximity and evenness of these particles on supports can make or break a catalyst's performance. This attention to the spatial arrangement emphasizes that where a nanoparticle resides is as pivotal as its size.

The talk also offers a glimpse into future possibilities where nanoparticle catalysts could revolutionize energy solutions, highlighting their potential role in carbon capture and utilization. It's a reminder of the important strides chemistry and materials science are making towards a more sustainable and efficient future.

Chapters

00:00 - 04:30: Introduction and Climate Change The chapter begins with a warm welcome and gratitude expressed towards Professor Peruvian and the young forum for catalysis scientists of the Finnish Catalysis Society for their invitation. The speaker reflects on the previous evening's discussions about the innovative idea of bringing young researchers together, emphasizing the opportunities it presents.
04:30 - 27:04: Nanoparticle Size in Catalysis This chapter discusses the role and significance of nanoparticle size in the field of catalysis. Despite being a plenary talk within the day, the speaker emphasizes the importance of engaging with young scientists in the field. The chapter encourages active participation and dialogue from the audience, particularly young researchers, to foster a deeper understanding and excitement towards catalysis.
27:04 - 48:07: Impact of Nanoparticle Location The chapter titled 'Impact of Nanoparticle Location' involves a session where attendees are encouraged to prepare questions in advance of the discussion. The speaker emphasizes the importance of engaging in the talk by preparing at least one question to ask during the poster break or at the end of the talk. The speaker expresses anticipation in discussing the attendees' perspectives on the talk and their own research. The chapter highlights the interactivity and the participatory expectations of the session.
48:07 - 53:09: Catalyst Preparation Techniques This chapter discusses the preparation techniques for catalysts with a focus on the effects of nanoparticles size and location. The chapter begins with introductory remarks and touches on the relevance of research in the field of catalysis in relation to climate change, followed by the challenges faced in catalysis.
53:09 - 54:30: Discussion and Questions The chapter titled 'Discussion and Questions' delves into the conversion of synthesis gas and touches upon the broader topic of climate change. A pivotal slide is referenced, borrowed from a publication two years ago, which encapsulates the debate in the Senate regarding climate change, plotting temperature increase since pre-industrial times. The discussion provides a synthesis of climate data beginning from the year 1900.
54:30 - 58:00: Nitric Oxide in Catalyst Preparation The chapter 'Nitric Oxide in Catalyst Preparation' discusses the impact of human activities, particularly the emission of carbon dioxide (CO2), on the environment. It focuses on the cumulative amount of CO2 emitted, which has reached approximately 1500 gigatons, primarily due to the burning of fossil fuels. This significant emission level is analyzed in the context of its environmental consequences.

Effects of Size and Location of Nanoparticles in Catalysis - Krijn de Jong Transcription

00:00 - 00:30 so good morning to all of you first of all thank you very much professor Peruvian for your kind introduction and invitation to come to our University and the young forum for catalysis scientists of the Finnish catalysis society yesterday evening we were talking that it is such an excellent idea I think to bring together the young researchers and to give you the opportunity also to
00:30 - 01:00 present your own work and then as in every measurement there's one outlier and that is this talk which is then the plenary talk on of this of this day but I do think that the interaction with you as young people and young scientists working in the field of catalysis is also very exciting for me so I'm looking forward that each of you asked me at
01:00 - 01:30 least one question that can be in the end of the talk that can be during the poster break and be careful if you don't ask it I will ask you what was your question so be prepared right at least one question or remember it memorize it because I'm looking forward to it too to discuss with you how you view a talk like this or your about your own research so once more thank you very much for your kind invitation the topic
01:30 - 02:00 that I indicate here is about nanoparticles effects of size and location and what I would like to do is it go along this line a few introductory remarks and then on size in a non location of nanoparticles so first on the introduction these days when you do research also in the field of catalysis you cannot avoid saying a few words on climate change so I will do so then the challenges of for catalysis and I will
02:00 - 02:30 focus in the examples are derived from that particularly on the conversion of so-called synthesis gas so first climate change in one slide and this is a slide that I took from a publication two years ago which summarizes in the sends the whole debate in the Senate on the vertical axis is the temperature increase relative to pre-industrial times so we start from zero at around 19 the year 1900 or so and we plot and I
02:30 - 03:00 use the top horizontal axis the cumulative amount of co2 emitted due to let's say activities of people and that's in gigatons so billions of tons of co2 so now we are about here we have emitted about 1500 gigatons of co2 due to mainly burning fossil fuels and that has brought about we think because
03:00 - 03:30 that's not a fully proven but there's a considerable body of evidence that has brought about a temperature increase of about 1 degree C on our planet now if the Paris agreement holds we will stick to 2 degrees C or below and then we can read out how many co2 still to go which is another roughly speaking a thousand gigatons well you may say okay that's not you know that's a lot but don't forget that every year we emit about 35 gigatons of co2 so it's only 30
03:30 - 04:00 years to grow on the current level and this is called the carbon budget and that puts enormous constraints on the rate of implementation of renewables on declining the use of fossil fuels and so forth but this is basically how you could summarize that the challenges ahead while catalysis cannot do everything but it can contribute in a certain way and there are three aspects one is do or contribute to reduction of co2 emission
04:00 - 04:30 by bringing about more efficient processes or higher efficiencies in the end use of products and fossil fuels and also carbon capture and storage so that is to take co2 from flue gases and store them at the safe place so this is something where catalysis plays a role in the kind of transition periods other feedstocks may come in other than fossil fuels for example biomass and I will I
04:30 - 05:00 will talk about synthesis gas version in that context on the next slide and ultimately of course we would like to go fully to what some people called light-harvesting basically the NSE comes from the Sun being it wind or or light it both brought about by the solar radiation so a large harvesting and catalysis and plays a role in conversion and storage of energy so the the agenda is clear but how to fill out that agenda that's the challenge so one
05:00 - 05:30 aspect that we work on of the only with there are many many aspects to these challenges but that I will use here as an example is the use of synthesis gas that's a mixture of CO and hydrogen and any carbon containing feedstock can bring you to that intermediate synthesis gas its intermediate because it's generated from a range of feedstocks and it can produce a range of products so any carbon containing feedstock coal natural gas let's say fossil fuel-based
05:30 - 06:00 and you can move along and say we will use biomass to get the reduced carbon footprint or some people say you could even use co2 I know the two talks today on co2 so I def I put in one slide on co2 hundreds in Asia so you can make with all these feats you can make synthesis gas and depending on the metal nanoparticles that you use you can make a variety of products that are indicated here when it's moving into long-chain
06:00 - 06:30 alkanes we often call it fischer-tropsch synthesis and when it's short ray chain alkenes olefins it's called FDI officiator of dolphins so that's the conversion that I'm going to particular talk about so on the right hand side use these metal nanoparticles to bring about these products one on co2 hydrogenation I cannot resist the temptation to talk a little bit about that because I see more and more
06:30 - 07:00 conferences on the topics because these days carbon capture and utilisation CCU rather than CCS so with CCS we store it underground somewhere somehow and with CCU we're going to convert the co2 and I to review many papers on that topic and often the first sentences I'm going to save the planet and then I write to the editor is this really true question mark and why do i debate because let's face it thermodynamics is serious science much
07:00 - 07:30 more serious than catalysis catalysis you can tweak thermodynamics is a given no yes so you better you better study it carefully so when you hydrogenate co2 and for example you make methanol you can also do hydrocarbons you can do me saying I saw methanation on the on the list today that doesn't matter but you make a product these reactions are exothermic all of them that implies that you
07:30 - 08:00 convert chemical energy levels in these molecules into heat that inevitably implies that the energy content the chemical energy in the product molecule is less than in the feedstock this is first law thermodynamics cannot be tweaked no fake news about thermodynamics so more efficient so then my statement is it's more efficient to use hydrogen directly and thereby prevent formation
08:00 - 08:30 of co2 than to first make co2 and then go to solve the problem afterwards so let's take the example to see you two comes from a power station and you might say I'm going to capture the co2 I'm going to hydrogenate it but you could also say I'll use that hydrogen say the hydrogen is from a renewable source and solar electrolysis with hydrogen with a small carbon footprint that hydrogen can also be used to now generate power close
08:30 - 09:00 down the carbon the coal based power station and then you have your power without co2 formation yes so so it's very difficult to defend this on the basis of climate change possible there's background in energy storage and liquid transportation but we can talk about it but let's be very critical ourselves on this topic so sorry for preaching but now I move on to the science that I'm
09:00 - 09:30 going to talk about so nano particle size size is very important and I'm going to talk about the background how we control nano particle size and the effects they're off so first the nano particle size so if we have a number of atoms let's say over the thousand atoms we have already three nanometer particle and that can grow all the way let's say to eleven nanometer in this example with more than sixty thousand atoms you might say what's the difference in these in these particles
09:30 - 10:00 well a very important difference is that the details composition and structure of the surface changes as a function of size this is known from the 1960s from Hardy felt in particular that that seminal work on on this and Peter from hell.the from Sasol and South Africa it's a very good paper that I really advise to study carefully if you are studying particle science effects hooli did a lot of this work and it combines density functional theory on the details
10:00 - 10:30 of atom atom interactions together with longer scale modeling to get data like this so this is a nanoparticle and we consider for example what we call a B 5 B site that's a very specific site where if a molecule absorbs it will interact with five metal atoms it is what we call a step edge side so there's a terrace here and then an H and yet and other terrorists so B finds B side if you plot the side fraction of those specific
10:30 - 11:00 sites as a function of the diameter of the particle you go from virtually zero to let's say something like 7% from six nanometers and onwards and what's what's Abel shown in this paper that in the range size range of one to say six nanometers the largest changes take place and that's important and therefore we control want to control particle size and we can do that in various way so I'll give three different approaches by
11:00 - 11:30 which we varied the size so the metal loading the metal loading can be varied on the support that's a classical way of very nano particle size and we did this for cobalt and we did this for iron for the applications indicated so cobalt is very well known so if you have cobalt conversion of synthesis gas to to ultra clean diesel the synthesis gas being produced from me saying in this case from natural gas and this is the world
11:30 - 12:00 largest planet like this which is called gas to liquid so methane or natural gas to liquid hydrocarbons Ultra Clean Diesel is the main application if you make five million tons per annum of this synthetic diesel you need a plant of this this full size it's an enormous complex if you visit wow this is big stuff and you need more than fifty five hundred metric tons of power to run the plant more than 10 to the power 25 nanoparticles mornings and stars in the
12:00 - 12:30 universe you need a lot of cobalt so what where this is relevant if the size is off by a factor of 2 it mainly that you need the thousand metric tons rather than 500 metric tons so this is really relevant what is the optimal size so that problem we studied by simply changing the weight loading one way to send 13 way to send with carbon nanofibers for all kinds of reasons this is high aspect ratio graphitic carbon as support material and we vary the load
12:30 - 13:00 and then here we have three nanometer particles and here about eight nanometer particles and using this technique with different precursors and an impregnation techniques we could vary the size from 3 to 25 nano particles if you didn't have the activity for this overall reaction the activity normalized program of cobalt as a function of the coal particle size you get this plot with a very distinct maximum around 6 nanometers now you may recall the 6 nano
13:00 - 13:30 meters from the from helden plot so above 6 nanometers the activity drops and scales with one over the diameter but before that you might say that relationship breaks down and we get an enormous decrease of what we call the turnover frequency so this is an important parameter its activity now per surface atom of cobalt of those nano particles as a function of size and we get the kind of hockey stick relationship with the horizontal from six nanometers and above over a wide range of conditions and below six
13:30 - 14:00 nanometers it decreases my effector of dem we worked with the Holmen group in transient in those days and we did a transient kinetic studies and from that the overall conclusion was that basically what happens at the small nanoparticles that at the edges and the corners the co molecules are bonded too strongly so they're bonded so strongly that they basically don't contribute to catalysis so only the relatively small
14:00 - 14:30 terraces contribute with less step edges and that was the combined effect of this factor of ten in lower activity so another study we did was on synthesis gas to lower olefins so now the alkenes are the molecules researching for a particular c2 to c4 olefins the major building blocks of the chemical industry and with this kind of overall syngas
14:30 - 15:00 conversion data like co conversion high olefin selectivity and low median selectivity we could were able to achieve that by combining the the active phase iron with promoters sodium and sulfur the size of the iron particles is relevant and the support how many talked about now about the promoters and about the size of the iron nanoparticles again by varying the weight loading from 2 to 20 rate to sent on again carbon
15:00 - 15:30 nanofiber support with promoters in the blueprint and a red without the promoters we could vary the size from say 3 to 10 nanometers or so what we found for activity was not the reverse from cobalt so the smallest particles have the highest turnover frequency we can discuss about that later but I would like to to focus now on selectivity product selectivity so lower olefins are the desired products meeting is
15:30 - 16:00 undesired and when we make smaller particles our promoted nanoparticles are effective at larger size to suppress meeting and enhance the lower olefin selectivity with but at the smallest sizes it doesn't matter whether this promoter around or not so clearly the promoters are only effective with larger particles and not with smaller particles and that we have been digging into and in particular this
16:00 - 16:30 paper we sorted out this using again working with the people in Toronto the transient kinetic techniques but also density functions theory if you take the sodium sulphide so the sulfur is here in yellow and the sodium atoms in in orange on the iron carbide surface then we found out that the sodium sulphide molecule so to speak the promoter atoms inject electron density into the iron carbide surface that weakens the carbon
16:30 - 17:00 hydrogen bonds and strengthen the iron hydrogen bond but overall it leads to a lower hydrogen properties confirmed by sitcom measurements and that brings a higher barrage barrier to meet the information and a lower barrier to ethylene formation so with that we start now to understand also particle size effects combined with the presence or absence of promoters and I think that is a significant step forward so these were two examples may be very simply very
17:00 - 17:30 metal loading a well developed technique you might say we also took approaches that are used less often one is to vary the support pore diameter and these nanoparticles are am placed on a support material in many cases and we vary the thermal treatment of the precursors that are in that are used and I'll give you a couple of examples of that so here we use an ordered misreported silica with about ten nanometer pores and we fill
17:30 - 18:00 those pores with the nickel nitrate solution we evaporate the water we get nickel nitrate crystallizing in confinement and we can deduce it also from x-ray diffraction line broadening but also from TM and basically what we get if you have the average crystallite size and nanometers and you have the support pore diameter and for this nickel nickel nitrate we base it he had a beautiful one-to-one relationship offer a range of let's say 3 to 10 nanometers or so confirmed by
18:00 - 18:30 dark field TEM the bright lines is the nickel nitrate and the diameter of those lines of those nano wires if you like is very close to that of the pore diameter in this case about 10 nanometers so if we take them the average crystallite size Minard we decompose the nickel nitrate into nickel oxide which is essential step on our way to nickel nanoparticles then we had this the green a data point so that's the one-to-one relationship between nickel nitrate crystallite size and support for
18:30 - 19:00 diameter if we decompose it in air we the black points give almost an erratic relationship with pore diameter and the nickel oxide when we do it with traces of nitric oxide in our gas stream gives again a correlation with a radiation with the support pore diameter although no longer one-to-one relationship because of shrinkage of nickel nitrate to nickel oxide and we see a dark field TEM that the nickel nanoparticles are
19:00 - 19:30 well embedded in the Mesa pores while if we do the air calcination we get these structures with nano rods inside the meat support and larger particles outside the me supports so a dramatic effect on the way how we decompose a precursor you've done a lot of work on that and using the nitrogen flow we can get therefore on average thomsonite 8 to 9 nanometers and a nitric oxide containing flow we decompose the nickel
19:30 - 20:00 nitrate into three to four nickel part nanometer particles what I want to emphasize now is the stability of these catalysts the stability of this catalyst for methanation in this case from synthesis gas here the activity is plotted program of needle and methanation of nickel is not very structured sensitive and that implies that we would expect that of course the initial activity of the blue data points that's the three nanometer nanoparticles
20:00 - 20:30 initial size is the highest and this is with eight nanometers the black points and we start over here much lower activity but what we see after a few hours time on stream than the blue one the smallest particles have the lowest activity yeah so for the Chris huh why is that why is that why have the smallest particle in Italy a lower activity after some time on stream well the answer is it's in also Auto happening in particular nickel carbonyl
20:30 - 21:00 is a transport mechanism from small particles to launch in nano nano particles and as we all know smaller nano particles have a higher thermodynamic potential and that's in the so called Kelvin equation so the higher thermodynamic potential of the small particles in play implies that we have a higher concentration of monomers in this case the nickel carbonyl then with the large one so we have a gradient in thermodynamic potential gradient in concentration and thereby a net
21:00 - 21:30 transport from small to large and we end up with large particles and and few or non small ones so this can be modeled because the two conditions under which this can take place as long as what we call unhindered growth the system can just grow to infinity and ultimately be a single crystal in the bottom of your reactor or it can be confined growth it hits the poor walls well this is a long story it's in the supporting information
21:30 - 22:00 of this paper and what we found that if you start with small particles that the driving force for growth is so large that it can crush the support in other words it can break the poor walls and you get very large particles in fact you get unconfined growth you might say if you start from large particles the driving force is small the elastic forces can cope with the growth and you grow until you hit the poor walls and the growth stops and this implies why
22:00 - 22:30 this grows tremendously and activity drops very low much lower than when you start initially larger and you get some growth but much more modest and you are leveling off to a quite stable system so larger is better and this we have seen in other systems today we'll talk about aqueous phase reforming and we for nickel that if you start very small the ratio of final over initial size goes up above 24 small particles and
22:30 - 23:00 it's only a factor of 2 or so growth when you start with large particles so when there's also typing there may be benefits in starting with somewhat larger particles copper for methanol synthesis copper for methanol synthesis my second example of thermal treatments but now it will be the reduction step that we will consider first so copper catalysts are very important and the methanol synthesis industry is an enormous one rapidly growing in
23:00 - 23:30 particular of 40 to 65 million tons per annum in only five years why is that because there's lots of shale gas in the u.s. being converted to methanol shipped to China and then convert it into olefins in China it's a very interesting logistic chain of of feedstocks but then it burned about this high-pressure this is the range of temperatures and the question we wanted to answer is their structure sensitivity
23:30 - 24:00 also a methanol synthesis is their impact of the size of the nanoparticles well experimentally it was not observed we check the literature but all the particle studies were effectively larger than 10 nanometers but from a theory theoretical studies it has been predicted they should be structured sensitivity so we explored the size range below 10 nanometers but how can we control the copper nano particle size and what is the impact of size on catalysis so we started first to study
24:00 - 24:30 the reduction of a copper precursor so there's variation there in size that we can get and then other methods such as heat treatments of copper nitrate and using different supports now we study both copper and copper zinc because link oxide is a well-known promoter of copper in in the methanol synthesis so first the copper precursor the copper precursor in this case is a mixed compound of the copper precursor and the
24:30 - 25:00 supportt precursors on this case the final product is copper nanoparticles on the silica support but this is a mixed compound so it's a co precipitate you might say and this is the way we produce that but basically what you get is a quiet layer like compound the fillo silicates or free laurel leaves leave like a compound copperfield silicate that we is our starting place it is a very uniform precursor if you produce it like this way but you have to still generate the nanoparticles and we wanted
25:00 - 25:30 to do that to study that in real time using in situ TEM so we worked with the people at how the topside and they have this dedicated machine where you have a bead at low pressure but you can expose the sample to hydrogen with differential pumping still put the protector your electron source and while the electron beam travels through your sample you can study the system responding to the Hardison so now we're going to look to
25:30 - 26:00 material during reduction and these are the conditions one millibar of addition 282 see and what we are going to watch is a video in which this is the original copper feel of silicate and this is since this bright field T and we will see dark dots you will see dark dots and if you focus on one or two you will see them grow in the real time and this is for an ensemble of nanoparticles and I think for the very first time we were able to image that and and grow the
26:00 - 26:30 nanoparticles and analyze their growth in a quantitative fashion on an individual nanoparticle basis what you will also see is there there's no particle mobility so my image of growing any particle always that they were a kind of vacuum cleaners so they were walking around and picking up monomers no no they're stuck so the monomers have to travel so that's an enormous advantage if you want to model something that you know or that the basic premises of these things so the fusion of copper
26:30 - 27:00 species possibly copper two-plus and new creation most the only during the first few minutes and growth ceases after about 20 minutes so enjoy the movie off we go this is minutes so it's accelerated you see a particle growing see many you can pick one and you see it growing in real time for about 20 minutes and now it's more or less fixed so the size but we see a whole ensemble of nano particles that we can now
27:00 - 27:30 analyze and we we analyze an on an individual basis so we can NFI analyze them in a collective way as we did in the past with every individual particle in this case 25 particles we can have the size of the particle as a function of time and we can test our model not only on the collective appearance of top or what we could do also in the past but now on individual nano particle and thereby accept or reject certain
27:30 - 28:00 mechanisms as too much detail now but look at the auto catalysis plays a key role to explain the growth phenomena that we observe well you can do these things and people say beautiful nice but is it relevant for my catalyst preparation in the lab so it occurs almost a year to work out the conditions that we get the same particle size distribution in our microscope and in a laboratory experiment like you would do it in a tubular reactor and blood flow
28:00 - 28:30 and everything like that so exit on in-situ reaction I don't think that's that's a big challenge and you can talk about that later if needed so we're so we're on our way so reduction is one one important step and we can control that and understand that describe rate model eight but we need it much more to do with different supports with copper and copper zinc on silicon carbon and alumina so you might say we had to work harder nicer you get these kind of
28:30 - 29:00 tables and we had multiple of these tables there are lots of work to do so I'll jump to the final results and the turn over frequency so again the activity per surface atom of copper per second as a function of the size gives three discrete lines one is for copper one is for copper supported on zinc silicate and one is the conventional copper zinc oxide with or without alumina and with copper zinc oxides we
29:00 - 29:30 have clearly the highest maximum turnover frequency and it is about a factor of 10 compared to copper and that's that's known from the literature copper zinc oxide brings you about a factor 10 5 to 10 a activity and Hounds bonds and that's very significant and what we see is that the structure sensitivity of copper is there but there's not as strong as with cobalt here you might even argue you know in terms of the variations is this you know decreasing well we have produced a lot
29:30 - 30:00 of samples at 3 nanometers so we think there is some impact but small the most distinct was with the copper zinc silicate but the copper zinc oxide we were not able to make the smallest particles so the effects of promote or are much more important enough particle size in the case of copper which dies in if some with some of the theoretical predictions done in the past so science effects are significant we studied a number of those and we see many studies
30:00 - 30:30 ongoing also for other systems these days a topic that they studied much less and that I like very much because we work on it lately a lot is the net effect of the nanoparticle location because you might say size matters well of course size matters if you buy a house and what do you see how big is the house but the second thing you should check is where is the house located because you cannot easily change that so
30:30 - 31:00 you better take care the so the nanoparticle location has two distinct relevance as you might say for catalysis one is how Earth's additions to the next nanoparticles so again with houses what's the distance through your neighbor and what's the nature of the neighbor not unimportant when you buy a house anyway so the distance between the nanoparticles is relevant and the other one if it's bifunctional catalysis what's the distance to another catalytic
31:00 - 31:30 function so we will see two of those examples so one is nanoparticle location with respect to each other suppose this is my support area and here are the nanoparticles and and they're more or less cluster together they're very close together so I have a large support surface area where there's no nanoparticles and some have high density domains of nanoparticles this is a more uniform distribution of the nanoparticles and this matters for the overall performance of my catalyst as we
31:30 - 32:00 will see in a minute so how do we control the location well often we don't I I note in many papers that people not even consider location so how was the distribution of my nanoparticles but it matters so we control it by the drying step after impregnation and again the thermal treatment of the precursor during sorry after impregnation and drying and we'll give an example of that in the case of of copper so copper on
32:00 - 32:30 silica thermal treatment if you have copper nitrate deposited so you impregnate the copper nitrate solution evaporates the solvent you get copper nitrate and in many cases you have patches indicated in red patches of copper nitrate and other RMT it's very non-uniform this is something that happens a lot in catalyst preparation so you're impregnate you dry and then you get what we call the coffee stain effect now you know the coffee stain effects so you spill some coffee on your white clothes and you think ah
32:30 - 33:00 yeah it's reasonably uniform it doesn't I don't note it but the next morning you come back it's a brown ring very distinct in your white clothes yeah yeah you know the coffee's anything otherwise you can do it during the break and and this this happens and that that reorganizes your your copper nitrate or whatever the precursor in many cases so you get a non-uniform distribution now the question is are you happy with that well if you're happy with that and you
33:00 - 33:30 leave it like that but sometimes you want a more uniform distribution like this and the simple how you decompose the copper nitrate is key and again nitric oxide plays a role now the nitric oxide helps you to keep the footprint of the nanoparticles very much related to that of the copper nitrate so more or less it mobilizes the copper nitrate you decompose you get these great particles but but clustered or close to graduation say high-density domains and other areas
33:30 - 34:00 are empty here I get a much more uniform distribution of my copper oxide nanoparticles so with the nitric oxide calcination short inter particle spacing with nitrogen calcination or air large inter particle spacing it's in the in the nitrate chemistry when you make a basic copper hydroxide nitrate or a anhydrous rather mobile species that that that redistributes off your support
34:00 - 34:30 so that's in this paper we sorted it out and then we started to apply this to our copper zinc systems which are very interesting for methanol synthesis and we used an ordered misreported support and we impregnated with copper and zinc nitrate solutions we dried then we do the heat treatment in two ways nitrogen get uniform distributions or nitric oxide high density domains and then we do the catalysis and we see the impact so first this is from the electron tomography so we tilt samples andreakms
34:30 - 35:00 the whole 3-dimensional object the Narges in calcination uniform and out calcination non-uniform we will see the order the Me's reports in this direction and dark dots are the nanoparticles so off we go and here we see a quite uniform distribution here you see certain ports very much stuffed with nanoparticles and all the pores are empty so we have an enormous redistribution during drying and after an hour calcination that is maintained and here we have the redistribution of
35:00 - 35:30 the nanoparticles and we get a very uniform distribution of nanoparticles the size is very close six versus eight nanometers and the loading the overall copper loading is the same in both systems we can also do fall you meandering so this is the uniform distribution and this is the very much non-uniform distribution well this is from election time tomography and this is very small sample size so is it relevant for my overall overall catalyst
35:30 - 36:00 well we published later on that with small angle x-ray scattering we can analyze the differences first of all of the the support we get this very discreet diffraction pattern and the Bragg diffraction of our poor system but the the background carries information on how uniform the electron density is in and how periodical it is and when you get a uniform distribution of
36:00 - 36:30 nanoparticles you get some announcement of overall non-uniform but not stronger when some pores are filled and all the pores are empty so from this background we could model the extent to which pores are filled or pores are empty so it's not only electron tomography also small-angle x-ray scattering gives it information if you do that the catalysis not surprisingly uniform distribution stable rather this table catalyst high density domains you get a
36:30 - 37:00 much stronger deactivation so most likely there's some particle diffusion and coalescence occurring in in these systems so particle distribution matters we went on to study other examples where we used iron adsorption vs. iron exchange I'll explain in a minute what we are talking about and now we have bi-functional catalysis so I'll focus now on platinum alumina combined with
37:00 - 37:30 zeolite so here is now the the the concept of you have a zeolite and the zeolite is a solid acid and the solid acid carries acidic proton branch at acid sites and and they're important in carbenium ion chemistry but how do we get Robinho Mayans well usually because we have metal or metal sulphides particles and these metals are active in alkane dehydrogenation so we will see on the
37:30 - 38:00 next slide but the platinum particles can be on the alumina binder as we call it so usually in c-lite catalysis we glue the zeolite crystals together using an alumina binder to make a strong next to date and the Platinum can be present on the binder or the Platinum can be inside the zeolite and the binder is just there for mechanical purposes nothing else and all the catalysis takes place inside the zeolite this we will call nanoscale intimacy and these are
38:00 - 38:30 called closest intimacy so these by functional catalysts are very important for all kinds of by functional hydrocracking by functional hydro isomerisation etc so we're being recorded for the noise from the newspaper here yeah so by functional catalysts are here's an example so we have asset sites in the zeolite we have metal sites inside the zeolite in this
38:30 - 39:00 case this is for isomerization and crackling this is for hydrogenation the origination to make that even a bit more explicit so we have an alkane that becomes an alkyne plus hydrogen that's on the metal side and the alkenes can be protonated much more easily of course in alkanes so at a relatively low temperature these alkenes will be promoted sorry will be protonated we get carbenium ions and the
39:00 - 39:30 cabina ions can be isomerized to give us iso alkenes or can be correct two smaller fragments hydrocracking yang takes place but this is still unsaturated compounds the olefins they have to diffuse back from the asset side to the metal side and then our hydrogenated to gives us the highest moral correct alkanes this has been practiced and known for for many many decades so I cited Paul why so in the nineteen
39:30 - 40:00 sixties already said look this is a kind of modulated or Mada adapted Thiele modulus type concept so if we have a distance between the metal sites and the asset size this L this distance between the two should be smaller than a given expression which is in fact a variation on the Thiele modulus and for the chemical engineers here very well-known so you can fill out the partial pressure of the olefins the diffusion coefficient absolute temperature and the reaction rate and here's a typical reaction rate sorry
40:00 - 40:30 here we use the typical reaction rate and if you do that then the L is smaller than say five micrometers or so so you're doing well because most of the zeolite crystals are smaller than five micrometers they're more like half a micrometer or so so no worries people will say it doesn't matter where the metal is so what then people started to do and recently we scouted the industrial literature very interesting we digged into the literature it's and we found out that almost everybody
40:30 - 41:00 applies the following rule closer is better and people said let's not take any risk I'll put my metal function inside the zeolite because then I have the closest distance and whatever I do I'm in good shape yeah because my L is the smallest I can get so we'll put the Platinum in the zeolite now we were a bit stubborn because we said look all these in there steel catalysts and I'll give you hear a bit enlarged picture so if you if you take a
41:00 - 41:30 slice of an extra day so the macroscopic the macroscopic catalyst body but you you cut it in small pieces but you maintain the mechanical integrity at the micrometer scale you see these zero art so this is a zeolite why crystals of about half a micrometer or so and every every see like crystal is coated with a thin layer of alumina and that's the art of extrusion because you extrude the zeolite together with the binders but you have also domains of alumina you see that is
41:30 - 42:00 in rats this is from EDX aluminium mapping is read silicon mapping is green so now we can if you see this image and this we can do easily now with modern EDX detectors in the TEM then we thought well why not put the platinum on the alumina and compare it with platinum on the zero marks so and that can be done very easily because if you take H 2 PT CL 6s precursor you may drive the
42:00 - 42:30 alumina based on point of cedar charge and all these well-known concepts from colloidal chemistry if you select the the pH properly the h2 pineal six in particular the PTC of 6 to minus will just elect be the electro statically bonded to the protonated or age groups of the alumina so you below the point of zero charge you have a positively charged net positive charge on your luminal surface and your interact with
42:30 - 43:00 the N eyes and so the regular boot or group in particular study this at length I would say as you know the literature so we know very well how to do that but the funny thing is that the bronsted acid sides of the zeolites are ready to go for exchange with cations so if you take the PT nh3 for 2 plus cation it will just exchange and again you have to tweak pH and do things but just for simplicity it's simply ion exchanging this precursor to the protons and then
43:00 - 43:30 what you get is this it's this is really from the first experiment so we have our stem EDX and now in green is Silicon mapping so that's the zeolite to see like why with the silicon through aluminium range of 30 so dominated by silicon so this is silicon this is alumina that's in red and the yellow dots is the elemental mapping using EDX so you see it is as if you have beef and vegetables and today you want to pepper on the beef
43:30 - 44:00 and the next day you say I'll put the pepper on the vegetables and see how it tastes that's catalysis right we like to compare it to a food preparation anyway the so the catalyst preparation now gets really precise in the sensor at the nanometer scale on a macroscopic sample because you can do these things easily in surface science with masks and things that's very easy but on a powder it's it's new stuff so we were very interesting about it the platinum on the
44:00 - 44:30 binder platinum on the zeolite and we went to Johann Martens your Martin's is a world leading expert in mine are you cracking and we said no one we did a fun experiment on Friday afternoon you know platinum on binder platinum on the zeolite could use investigate this in your advanced hydrocracking Ted research he said of course but I already know the answer this will be the best catalyst said well but check it anyway so he did and I'll skip the experience so I'll
44:30 - 45:00 just go to the catalysis and what did he find he found that if you use NC 10 as feedstock and then and C 19 as feedstock and I'll focus on those this is a branch molecule complicated stuff let's make the normal alkanes you see the activity for red red where's platinum on the alumina and green is platinum on the zeolite activity-wise very close like Paul Weiss predicted the tillow modulus behaves but the
45:00 - 45:30 selectivity was the other way around and expected we get much more isomerization the filled symbols in the case of the platinum on the alumina the nano scale intimacy recall and even more importantly for example if you take NC 10 and you give a 35 to send the hydrocracking conversion you get identical product pattern between the two the referee asked is this really not the same data no it was two different samples but you got identical data for the selectivity while with NC 19 we see
45:30 - 46:00 that for example C for formation and starting from C 19 so secondary hydrocracking much more pronounced from the Platinum's in this year light and outside so now we are continuing this research and will I'll show you here platinum on theism five with normal heptane a much lighter feedstock and here we see since this is diffusion limited process we know that from all all kind of literature so that the conversion as a function of temperature is very different when you put the platinum inside the zealot it's
46:00 - 46:30 much less active so at teeth 50 let's say it's a 30 degree C difference or something like that when you put the platinum on the binder so what's the current thinking behind this and we're digging deeper into it if you have a zeolite crystal here indicated that only the outer surface of the zeolite is really contributing to this catalysis and that implies if I have my platinum on the binder in red I get my olefins on
46:30 - 47:00 the binder they have to diffuse to the poor not I get a gradient in either olefins back to the Platinum only a short diffusion distance and I get high selectivity to isomerization here I do everything inside the zeolite and it goes forth and back and forth and back so the chance that my eyes or elephants are not protected by a hydrogenation but get secondary reactions are enhanced so that's the current proposal that we have we doing a lot of research on that to dig deeper into this so we talked about
47:00 - 47:30 size so as I said like houses size matters but don't forget location we have a host of techniques to control these things and we're making nothing progress in that I would like to acknowledge our funding which is on the one hand from the world of science and on the other hand on the world of Industry but perhaps even more important acknowledgement of the people the cooperations nationally and internationally but from our university
47:30 - 48:00 postdocs peas these students also I mention your Hari better now moved to one in a university professor Petra DeYoung and please note the silent h no only professional relationship so professor Petra Dion who worked with me for a long time is now professor in the field of nanomaterials and catalysis and associa system professor you've run as a ship each who
48:00 - 48:30 works at the interface of electron microscopy and catalysis that I discussed a lot and finally thank you for your attention and welcome to Utrecht and and it's great to be here thank you very much thank you very much for a very interesting presentation in the formation of the nanoparticles of
48:30 - 49:00 nickel and platinum so you you test upon the loading and you know method of impregnation and thermal treatment but how about if you take is your light for instance you have wise your light with three different silicate aluminum ratio and you take MGM 41 with again three different silica element ratio and you try to put platinum and nickel where will we get the largest particle and the smallest particle yeah so the examples I
49:00 - 49:30 gave for the nickel nitrate impinge on silica you're very close to the point of unit charge so this acid-base properties of your sport have little impact close to the point of cereal charge so I think what we what we around ado here is disclose some of the basic rules and then have to rethink all of these four specific cases because if you have said if you have aluminium containing SPF 15 you have an acidic material you have a very much
49:30 - 50:00 more acidic than a pure silicon material so you have to rethink and an ion exchange can be very well used for example on those materials while on pure silica ion exchange won't work so it's horses for courses but I do think that with the things we've learned over the last ten years or so I think we can for a quite a large number of systems design size and location as I said the platinum alumina zeolite we designed it on paper
50:00 - 50:30 and then made it so so I think we're making pro now where we can control a lot of these parameters much more than in the past [Music] and how contagion effects the dispersion
50:30 - 51:00 of these particles and you talked about nitrogen oxide and nitrogen or air and maybe we go to the slide we see better but my question is could you elaborate a bit on how this difference is finally achieved what is the effect of real effect chemical effect on those gas streams on the dispersion here so this
51:00 - 51:30 one so your question is what is the impact of the nitric oxide and it's twofold it's very complicated story that's two PSD to full PhD thesis on that so nitric oxide has two impacts one is it it accelerates the conversion of a methyl nitrate to a metal hydrogen nitrate that's basically acid-base chemistry so if you convert a metal nitrate to a metal hydrogen nitrogen you
51:30 - 52:00 emit or you produce hno3 nitric acid and if you bring a now around you only produce no.2 so it just changes the chemistry of the decomposition and accelerates this conversion so what it does there now comes in it becomes a metal hydroxide nitrate and then it's stuck so this has still the possibility to become mobile as you'll see in a second but this is stuck and then a decomposes to individual nanoparticles
52:00 - 52:30 depth the hydroxy nitrite to the metal oxide that is also affected by a no but that's a radical chemistry so different teases and and we studied it for nickel and for copper and for cobalt and it has a great impact on the the rate of decomposition so the rate of decomposition is moderated in the case of of an all being present because of different radical chemistry while if I
52:30 - 53:00 know is no present it's almost an explosion so metal nitrates if you decompose them give entropic explosions it's endothermic chemistry but entropic in the sense of making lots of gas and that we see in the differential scanning calorimetry as a as a spike in our endothermic decomposition if there's a now around you that a very moderated peak for the for the heat consumption of the decomposition so it's very different chemistry it's very exciting I could talk for hours about that but that's so
53:00 - 53:30 that's now here this is very peculiar for copper it's not true for nickel not true for cobalt it is anhydrous copper nitrate so the PhD student one day I came into my lap and showed the reactor which she did it and she had a black ring on the reactor I said ah now we know there has been volatilization of the copper compounds she dipped into the literature and founders