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NNadir

(33,368 posts)
Sun May 8, 2022, 07:26 AM May 2022

LaFeO3 Catalysts for the Oxidation of Nitrogen for Electrochemical Production of Ammonia from Air.

Recently in I have been considering the energy requirements for the zero discharge supercritical desalination of seawater, modeling the urban and agricultural demand for water in California as a tool for this relatively simple calculation to which I've chosen to add some level of complexity.

California and I got divorced nearly thirty years ago, but in my own way, I still love her, but some of what I loved was its spectacular ecology and vistas, many of which have been trashed for access to water and for access to industrial energy.

I view the water problem as a direct opportunity to restore, at least partially, trashed ecosystems.

Supercritical water is a very high energy substance, at temperatures in excess of 373°C, and pressures in excess of 22.1 MPa, and as I envision a process for its generation for the purpose of desalination, the side product would be continuously and reliably produced copious electricity. Electricity is, of course, a thermodynamically degraded form of energy, particularly when it is generated by the combustion of dangerous fossil fuels, as increasingly it is. This is true even for relatively efficient systems, for example combined cycle plants fueled by dangerous natural gas. The thermodynamic degradation of electricity is even worse when attempts are made to store in a chemical form, as in batteries or, for another example along the same terrible idea, as electrolytic hydrogen.

A caveat to the previous paragraph is that when electricity is generated in a process designed to capture entropic losses in heat engines as a form of exergy, which electricity is at least indirectly, it can actually improve thermodynamic efficiency, at least in the case where the electricity is utilized continuously at the time it is generated, foregoing energy storage. I am thus always interested in electrochemical processes where the purpose of the electrochemistry is not to store it, for example as hydrogen, but to rather in processes where it's use is either essential or where the alternatives are even more thermodynamically or materially questionable than electricity itself. Examples of such processes are the Hall-Heroult process by which all the world's aluminum metal is prepared from alumina, Al2O3, an extremely refractory process, as well as the FFC Cambridge process for the preparation of titanium and other metals. I also have interest in the electrochemical process for the preparation of elemental carbon about which I've written elsewhere in this space: Electrolysis of Lithium-Free Molten Carbonates. (In envision this process as a means to replace "Green" electrodes the Hall-Heroult process, which are made from petroleum coke, as well as FFC electrodes.) This electrochemistry, if applied to carbonates derived from air or seawater captured carbon dioxide might also displace – with some research – the carbon content in steel, thus usefully sequestering the element, essentially indefinitely.

It is because of this consideration, the need to recover exergy from thermal desalination via electricity generation that the following paper caught my attention:

Coupling of LaFeO3–Plasma Catalysis and Cu+/Cu0 Electrocatalysis for Direct Ammonia Synthesis from Air, Yi Cui, Hui Yang, Chengyi Dai, Pengju Ren, Chunshan Song, and Xiaoxun Ma Industrial & Engineering Chemistry Research 2022 61 (14), 4816-4823.

The synthesis of ammonia, on which the current world food supply depends, is responsible, depending on one's source, for 1 to 3 percent of the world's energy supply. Currently the world demand for energy is on the order of 600 EJ/year; the Covid lockdowns in Shanghai and other Chinese cities may keep the demand below 600 EJ in 2022 as worldwide Covid lockdowns seems to have done in 2020. This means that the demand for Ammonia represents between 5 and 15 EJ per year, somewhere between the entire energy demand of Great Britain and that of Germany, the latter being largely dependent on Russian fossil fuel sources.

Ammonia is currently industrially synthesized using the Haber-Bosch process, which relies on the high temperature, high pressure catalytic hydrogenation of nitrogen gas. Despite some rather dubious enthusiasm for the fantasy that hydrogen might someday be produced by so called "renewable energy" via the thermodynamic and material nightmare of electrolysis - hydrogen is a currently a very dirty fuel, not that much of of it actually utilized as a fuel except in exotic situations hyped by people who seem not to understand the laws of physics well or at all. I noted elsewhere what the sources and uses of hydrogen are: The current sources and uses of hydrogen.

Here is a graphic from that post:



The caption:

Figure 1. Global current sources of H2 production (a), and H2 consumption sectors (b).


Here is the graphic's source: Progress on Catalyst Development for the Steam Reforming of Biomass and Waste Plastics Pyrolysis Volatiles: A Review Laura Santamaria, Gartzen Lopez, Enara Fernandez, Maria Cortazar, Aitor Arregi, Martin Olazar, and Javier Bilbao Energy & Fuels 2021 35 (21), 17051-17084.

As we can see from the above graphic, hydrogen is a dirty fuel as it is at a minimum 96% dependent on fossil fuels dangerous fossil fuels for production - this at a thermodynamic loss - and depending on the source of electricity, which is also largely dependent on dangerous fossil fuels it may be even more dependent on them than is immediately obvious. (Electrolytic hydrogen is generally produced as a side product from the manufacture of elemental chlorine.)

The Dai and Ren paper under discussion is about the plasma production of fixed nitrogen followed by a electrochemical step. Every winter I attend lectures - except recent winters, lately they've been on line - at the Princeton Plasma Physics Laboratory. It would be disingenuous of me to criticize the hopes for fusion energy to which that national laboratory is mostly dedicated, but to the extent that it may become available (I won't object) or viable, it will be already too late to address the climate disaster, any more than the idiot fantasies of the members of Greenpeace spin about so called "100% renewable energy" "by such and such a year," even as people are dying today from extreme May heat in India and Pakistan.

Today.

Now.

This is why fusion energy will be too late because the climate disaster is underway now; it's on going.

Many of the winter lectures at the Princeton Plasma Physics labs are about all the wonderful things that plasma, a state of matter often referred to as the "4th State of matter" (there are arguably more than 4 states), can do besides run a fusion reactor. I do not recall that any I've attended have focused on the fixation of nitrogen, but in any case were such a lecture to be offered, it would not be about anything new. The nitrogen problem is an old one and was recognized as such - as a cause of soil depletion that, among many other things, famines for instance, that contributed to the outbreak of the American Civil War - early in the history of Chemistry. With the final acceptance of molecular theory, efforts got underway to try to make ammonia once people understood what it was. Mostly they failed. Early attempts to industrially fix nitrogen before the invention of the Haber-Bosch process that were marginally successful, albeit incredibly expensive, utilized electric spark methods; electric sparks are plasma. This is all described in a book I cannot recommend enough Vacslav Smil's Enriching the Earth, Fritz Haber, Carl Bosch, and the Transformation of World Food Production. It is all about the work on the synthesis of ammonia from hydrogen and nitrogen that brought Haber the Nobel Prize and allowed Germany to fight the First World War despite the fact that British blockades prevented Germany from importing Chilean "Salt Peter," (potassium nitrate). This work also allowed humanity to grow beyond Malthusian limits to a population now just shy of 8 billion.

There are more modern methods than spark generation to produce nitrogen plasmas, there are a number of analytical chemistry instruments, for example, that work on "corona discharge" technology involving activated nitrogen, but none of them are used to fix nitrogen at anything competitive with the cost of the Haber Bosch process. The authors of the paper under discussion propose a new catalyst for the production of activated nitrogen plasma, lanthanum ferrate. Whether it would be competitive is not for me to say, but frankly, I'm rather disinterested in the plasma portion of this paper, but am very interested in the electrochemical portion.

The reason is this: At high enough temperatures - especially under pressure - nitrogen burns to form nitrogen oxides; nitrogen oxides are an important component of air pollution. The brown color of smog is, in fact, the color of NO2 gas.

All combustion cycles driven by dangerous fossil fuels produce nitrogen oxides, both in automobiles and trucks, particularly where diesel engines are involved but also in spark (Otto) engines, as well as in power plants. The purpose of catalytic converters - which are never 100% efficient - and the addition of urea to diesel exhaust, the so called "SCR," approach - is to remove nitrogen oxides. Jet engines, which are known as Brayton cycle devices produce nitrogen oxides as do the combustion chambers of dangerous fossil fuel heated Rankine cycle type power plants.

In the presence of water the nitrogen dioxide, the aforementioned NO2, disproportionates into NO gas and nitric acid; the NO gas is rapidly oxidized back to NO2 by oxygen. The net reaction for the formation of nitric acid, a component of "acid rain," in which NO gas is catalytic, is 4NO2 + 2H2O + O2 ? 4HNO3. This is the basis of the Ostwald process for the production of nitric acid from ammonia. The reaction between ammonia is the basis of the widely utilized fertilizer ammonium nitrate which the terrorist Timothy McVeigh used to blow up the Murrah building in Oklahoma. (No one ever called for the banning of agriculture because ammonium nitrate can be diverted to weapons of mass destruction.)

For reasons of high thermodynamic efficiency, the process I imagine for for supercritical water desalination begins not with the heating of seawater, but rather the heating of pressurized air, precisely the conditions under which nitrogen "burns." For a long time I thought about how to address the resultant nitrogen oxides by utilizing approaches to catalysis rather like those utilized in Otto and Diesel internal combustion engines, but this is unsatisfactory in the sense that it wastes fixed nitrogen which takes energy to make and is thus a useful material. One can imagine a closed system under these conditions in which the electrochemical reduction of nitrate and nitrite, formed respectively by the addition of water to nitrogen oxides might be reduced to a useful product.

Shortly I will quote the paper's introduction.

Before doing so, I'd like to make a brief note on the nature of citing papers in connection with a personal issue. If one cites a paper, it does not follow that one agrees either with the contents of the paper or even with the paper's goals. I mention this because recently an abysmal idiot with whom I have a rather unhappy relationship in this space punctuated by ignoring his or her ignorance on and off, commented in one of my posts that I must have Alzheimer's disease because I was mocking a paper I cited in the OP to, um, mock. One sees these sorts of things, and one really doesn’t believe it. Regrettably the comment was removed for violating DU rules, which is sort of sad (but understandable) when someone, not me, alerted on it. Personally I guiltily enjoy it when idiots display idiocy.

The paper in the post was about the issue of flowback water used to frack for dangerous natural gas - a process I oppose in all manifestations - and which the abysmal idiot in question apparently needed to defend, since so called "renewable energy" depends wholly and totally on access to dangerous natural gas and/or other dangerous fossil fuels.

I mention this because, although I think that in many ways, this is a fine paper, there are several points in the introduction with which I decidedly disagree although I suspect that one of them is merely an obeisance paid to what is becoming a culturally universal faith, albeit it one hardly grounded in reality.

The quote from the introduction:

Ammonia (NH3) is one of the most important industrial chemicals in the world. (1) Because of its high hydrogen storage capacity (17.6 wt %), high mass-energy density (22.5 MJ kg–1), and high volumetric energy density (11.5 MJ L–1, higher than 8.491 MJ L–1 of liquid hydrogen), NH3 is considered to be the most attractive energy/hydrogen source carrier. (2?5) At present, industrial NH3 synthesis still relies on the traditional Haber–Bosch (H–B) process. After more than a century, the H–B process has been developed to a very mature state, and its energy efficiency is very close to the theoretical value. (6) Nevertheless, the process operates at high temperature and pressure using a pure feed of nitrogen (N2) and hydrogen (H2) gas. (7) Thus, an extensive industrial infrastructure is required for the process, which leads to a sharp increase in costs. (8) In addition, typical H2 production by natural gas reforming generates large amounts of undesired carbon dioxide (CO2). (9,10) Therefore, using water (H2O) as the H2 source to develop alternative routes for the H–B process under mild conditions has attracted widespread attention.

The electrochemical NH3 synthesis from N2 and H2O using renewable energy sources such as solar and wind energy has emerged as a potential alternative in recent years. (11?13) Compared with the H–B process, significant advantages could include mild reaction conditions, no direct CO2 generation, operability for smaller scale production, and low equipment cost. (14?16) However, because of the extremely low solubility of N2 in H2O and its high triple bond energy (948 kJ mol–1), activating N2 in electrochemical systems is challenging, (17,18) and only low yields (less than 0.1 mg h^(–1)) and faradaic efficiencies for NH3 (less than20%) have been achieved. (12,19)
However, the solubility of nitrate (NO3–) and nitrite (NO2–) in H2O is nearly 40000 times that of N2, ensuring sufficient amounts of N source in the electrolyte. In addition, the energy required for dissociation of the N–O bond is only 21.7% of that of the N2 triple bond. (20) As a result, NOx– can be easier reduced to NH3 than N2. (21?24) Zhang et al. proposed a N2 fixation strategy of oxidation and reduction in electrocatalytic systems. (25) In this work, the yield of NO3– in the electrocatalytic N2 oxidation process is too low to provide an N source for the reduction process directly. Nonthermal plasma (NTP), characterized by its large number of high-energy electrons and a low gas temperature, (26) can promote the activation of N2 under mild conditions. (27,28) Therefore, NTP is applied in the N2 oxidation process in the coupling strategy. (29) Generally, the efficiency of N2 fixation in the NTP can be improved by using a catalyst. (30?32)

Perovskites are used in various reactions, (33?36) especially for oxidation reactions such as the oxidation of nitrogen oxide (35,37,38) and carbon monoxide, (39,40) because of their excellent thermal stability, electronic structure, ionic conductivity, electron mobility, and redox behavior. Consequently, perovskites are expected to display excellent performance in NOx production. Copper-based catalysts are widely used in the electrochemical reduction of NOx–. (41?44) However, copper (Cu) could be deactivated due to excessive adsorption of NO2– on the surface during the reduction of NO3–. Therefore, copper(I) oxide (Cu2O) with special electron-donating characteristics needs to be introduced in environments with high concentrations of NO3– and NO2–. (45)
Considering these aspects, we present an N2 fixation strategy to produce NH3 based on the coupling of N2 oxidation in NTP and electrochemical NOx– reduction in H2O. Briefly, using LaFeO3 as the catalyst, N2 and O2 in the air are first oxidized in NTP to NOx, which enters H2O to produce NO3– and NO2–. Then the NOx– species are electrochemically reduced to NH3 over a Cu+/Cu0 catalyst with considerable activity and excellent faradaic efficiency (FE).


My first objection to the statements herein is that ammonia is a terrible fuel as a "hydrogen carrier" because it is even more dangerous than hydrogen itself; it's only advantage being that it is easily liquified. Many chemists have worked with liquid ammonia and they need to be trained to do so. It boils readily at room temperature releasing a caustic gas that will quickly either blind people painfully, badly damage their lungs and/or kill people. Although it avoids the huge energy penalty associated with the liquefaction of hydrogen that makes adds to the waste of energy and environmental degradation that hydrogen production entails, and is slightly less dangerous from an explosion and leak perspective from hydrogen resulting from hydrogen embrittlement of metals, it is no less unacceptable than hydrogen. The idea of using hydrogen or ammonia as a consumer product borders on insane in my view, although neither of these dumb ideas ever seem to go away.

My second objection is the statement that so called "'renewable energy sources such as wind and solar has emerged as a potential alternative in recent years." This kind of statement is often included in scientific papers these days but on reflection, it's not even close to being "science," so much as a quasi-religious genuflection at the nonsense belief that solar and wind are meaningful and/or sustainable forms of energy. They are not. They have failed, and failed miserably to address climate change and all the wishful rhetoric to the contrary is clearly nonsense. After more than 50 years - more than half a century - of cheering for these forms of energy they produced, as of the 2021 Edition of the International Energy Agency's World Energy Outlook, just 10.4 Exajoules out 587 Exajoules consumed by humanity in 2020, this a Covid lockdown year in which for the first time in recorded history energy demand fell, albeit clearly temporarily. The material and land requirements of the solar and wind industry render them immediately unsustainable, particular with matter and energy wasting systems like the batteries people fall all over themselves to praise in contempt for all future generations. We have spent well over 3 trillion dollars on this stuff in this century for no result other than this:

May 06: 419.61 ppm
May 05: 419.68 ppm
May 04: 421.33 ppm
May 03: 420.48 ppm
May 02: 420.99 ppm
Last Updated: May 7, 2022

Recent Daily Average Mauna Loa CO2

These things are facts. Facts matter, no matter how much wishful thinking and squirming they may produce.

One advantages of the side product of supercritical water desalination being excess electricity is that it will allow for the restoration of wilderness in California - over 1500 square miles of wilderness as of this writing - out of the wind industries industrial parks and allow for the dismantling of that horrible in flight bird fryer at Ivanpah. It is the land requirements for so called "renewable energy" that makes it unsustainable; it is the material (mining) requirements that makes the word routinely attached to it, "renewable" absurd and frankly, a lie.

Despite these statements in the introduction, I think this paper is a valuable one because it addresses the high energy cost of ammonia production even if the Haber Bosch process has approached it's theoretical limits. Most of this energy, as the paper notes, is connected with the need to overcome the energy barrier of breaking NN triple bonds. This is nicely shown by the energy level diagram for the nitrogen and nitrogen-oxygen species contained in the paper:



The caption:

Figure 4. Gibbs free energy profile of N2 reaction on the different surfaces at 50 °C and 1 atm.


It is worth noting that in this energy diagram the activation energy for the production of monoatomic N, reflecting the energy cost of breaking the NN triple bond, is similar in scale to that of breaking the bond in the Haber-Bosch process, which also involves surface chemistry - the catalyst. The N2* refers to the non-thermal plasma. In the process I imagine for SCW desalination the gas phase energy is a side reaction. This said, if the goal of the process is to produce ammonia, however, one can also irradiate the air with gamma rays or x-rays, a source of which might be isolated fission products.

I note that lanthanum is a fission product, but all of its radioactive isotopes are short lived, with the exception of that found naturally, La-138, which has a half life of 0.1 trillion years. After a few weeks, allowing for the decay of La-140 (half-life around 1.68 days) lanthanum isolated from used nuclear fuel would be less radioactive than natural lanthanum, since La-138 does not form to an appreciable extent in nuclear fuels as it is neutron poor. Thus one would need another element as a gamma source to produce N2* radiolytically.

A note on NO: In the presence of oxygen and water, NO gas can react to form nitrous acid, HNO2, as well as nitric acid HNO3. Absorbed into water in a system in which ammonia is being generated, ammonium nitrite will form. Ammonium nitrite is unstable and spontaneously can decompose to nitrogen gas and water. Thus the reaction efficiency is somewhat lower than it is for NO2's reaction to form nitric acid. As the Oklahoma City tragedy perpetrated by the early right wing terrorist Timothy McVeigh showed, ammonium nitrate can also explosively decompose if activated, which McVeigh did by diverting a dangerous fossil fuel, diesel fuel, to a weapon of mass destruction, but in general ammonium nitrate in contrast to ammonium nitrite can be handled and shipped as it often is. It is an important fertilizer on which our food supply depends. Under the right conditions, this electrochemical process can make it without the high temperature and high pressure systems associated with the long practiced industrialized Haber Bosch process.

I have ignored much of the interesting content of the paper in this post, but it's a good one, I think.

From the author's conclusion:

In summary, we adopt a strategy of “oxidation–reduction” to directly produce NH3 from air and H2O under mild conditions. In the oxidation step, N2 and O2 present in the air are converted to NOx– in plasma under perovskite catalysis (LFO-A and LFO-NA). The experimental and theoretical calculations are consistent in that LFO-NA with rich surface-reactive O species can enhance the stability of the species, which promotes NOx– production. In the reduction step, NOx– produced in the previous step is electrochemically reduced to NH3 over MOF-400. High catalytic activity (3.0 mg h–1 cm–2) and FE (83.2%) are obtained at ?0.6 V. The excellent performance is mainly attributed to the presence of both Cu+ and Cu0 species on the surface of MOF-400. Our strategy provides a new approach for distributed small-scale N2 fixation and a new route for the transformation of inert molecules.



I will be celebrating Mother's Day today with the woman of my dreams, who chose to allow me two magnificent sons. I am grateful to have her as a friend, a lover, a friend, and as the parent of my boys. If you are celebrating Mother's Day in some capacity, I wish you a happy one; otherwise I wish you a wonderful afternoon.

3 replies = new reply since forum marked as read
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LaFeO3 Catalysts for the Oxidation of Nitrogen for Electrochemical Production of Ammonia from Air. (Original Post) NNadir May 2022 OP
BMing to read later. The production of NH3 is one area where I would love to be able to ... eppur_se_muova May 2022 #1
I strongly oppose NH3 has a fuel. A far, far, far, far better tool for hydrogen carrier is DME. NNadir May 2022 #2
35,000 gallons of ammonia recently shut down an entire city... hunter May 2022 #3

eppur_se_muova

(36,227 posts)
1. BMing to read later. The production of NH3 is one area where I would love to be able to ...
Sun May 8, 2022, 09:18 AM
May 2022

make my own contribution. Sadly, it seems I'll never have the chance. Besides, the PChem needed is just too far outside my area of expertise. NH3 long ago occurred to me as the best way to store hydrogen, and I know others have been working on this idea (Google ammonia fuel cell). It doesn't seem to catch much attention, which may be a good thing, in some ways -- no overhyped, greenwashed pitch to investors, for example.

NNadir

(33,368 posts)
2. I strongly oppose NH3 has a fuel. A far, far, far, far better tool for hydrogen carrier is DME.
Sun May 8, 2022, 09:41 AM
May 2022

Like ammonia, DME is easily liquified, with a critical point well above the normal boiling point of water, but it's advantages over either ammonia or hydrogen are enormous. DME is non-toxic - it is now a propellant in hair spray having displaced CFC's - it is easily removed from water; it can run diesel engines with very low pollutant generation; it can also run spark engines, it can act as a refrigerant and it fits with minor changes directly into the infrastructure for dangerous natural gas, LPG with minor changes.

Many people are aware of these facts, which are rather obvious, and there is movement to industrialize it for trucks at Volvo/Mack as well as an International DME Association.

Regrettably, beyond Volvo/Mack, the idea has not received the massive attention it clearly deserves.

I am amazed that anyone at all would consider anything else as a product for captive hydrogen, but as noted in the OP, hydrogen as it exists is an exceeding dirty fuel and the hype attached to it is thermodynamically and environmentally disgusting.

I do include thermochemical hydrogen production in my ideas about utilizing heat exchange networks for high efficiency for the purpose of addressing human poverty; it makes sense. Commercial consumer hydrogen is however an extremely dangerous and stupid idea in my view, and the hype disgusts me because it is wholly unnecessary and will ultimately prove environmentally destructive given the energy and material costs of liquifying it.

There are very, very, very serious safety concerns, as is the case with ammonia fuels.

Structures and devices around the world have failed because of hydrogen embrittlement, a well known effect in materials science that I have often discussed with my son.

There was no more obvious failure for hydrogen fuels, of course, than the Challenger disaster, but adding thousands of similar disasters on a smaller scale is not recommended.

We do need ammonia, as you know, for many, many, many applications, but the idea of using as a fuel - which I've seen all over the place - should be a nonstarter. A serious leak could blind an entire neighborhood and might even, under the wrong circumstances, make Bhopal seem like small time.

hunter

(38,264 posts)
3. 35,000 gallons of ammonia recently shut down an entire city...
Sun May 8, 2022, 10:48 AM
May 2022
SALINAS — Evacuation and shelter-in-place orders were lifted early Thursday afternoon after a fire that began Wednesday night at a Taylor Farms processing facility in South Salinas led to the potential for an explosion — which could then release a harmful ammonia cloud.

Sam Klemek, deputy Salinas fire chief and incident commander, said during an afternoon news conference that the blaze had been contained and all of the hazardous materials on scene had been secured.

“Our major concern throughout the fire was that it was going to advance into on-site ammonia storage, approximately 35,000 gallons worth,” he said. “That did prompt us to pull back our resources and evaluate the situation.”

--more--

https://www.mercurynews.com/2022/04/14/taylor-farms-fire-shelter-in-place-order-issued-in-salinas/


There's a reason people who handle ammonia have to be certified. Ammonia is not something you want available at the local fuel station for any idiot to purchase.
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