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Who Cares About Making Ammonia? You Do.

This paper comes under the heading of “early days, but possibly of great interest”. It demonstrates room-temperature synthesis of ammonia from nitrogen gas using a samarium/molybdenum system, and chemists of all sorts will sit up and that news and say “Hold it. Ammonia is the Haber-Bosch process, isn’t it?”

That it is. And that’s a reaction that keeps over half the human race alive, through its use in fertilizer production. This is a prime example of one of the absolute foundation stones of modern existence that most people are completely unaware of. All over the world, there are huge reactors running at high pressures and temperatures, full of carefully-worked-out iron-based catalysts, that are pulling nitrogen and hydrogen in and pushing ammonia out at a rate (worldwide) of nearly 300 tons per minute. Until Haber worked out that reaction (and Bosch improved it for industrial scale), the only creatures on Earth that could do that were certain types of bacteria. In 1909, we became the second. Note that those bacteria are also (and still) keeping large swathes of the human race alive, since they’re the nitrogen-fixers found around the roots of legumes. And if either of these things stopped working, the bacteria or our industrial ammonia plants, we’d be looking at mass famines within months with effects on the human population not seen since the Black Death. Both going down at once would have a decent shot at collapsing our civilization.

The Haber process has a reputation of being pretty severe, what with those temperatures (>400 C) and pressures (around 400 atmospheres), but as this commentary on the new paper makes clear, it’s really a pretty good setup. Thermodynamically, it makes very efficient use of its energy input and wastes very little on side processes. The problem is the size of those inputs: running a Haber-Bosch plant is an energy-intensive undertaking, and it’s even more so when you consider the energy that has to go into making the hydrogen starting material as well. A new catalytic route that lowered the energy barriers involved would be very desirable from a power-consumption and carbon-emissions view.

This new reaction doesn’t use hydrogen gas at all – rather, the H atoms in the ammonia product come from water, with the samarium iodide allowing it to serve as such a source. Under normal conditions that’s not such an easy reaction – about 111 kcal/mole for O-H dissociation in bulk water – but in hydrated samarium iodide the O-H bond strength is knocked down to 26 kcal/mole. It also looks like other OH-containing molecules (such as ethylene glycol) can also serve. So the samarium end of the reaction furnishes the hydrogen, and the molybdenum end activates the nitrogen (indeed, it’s an important element in the bacterial nitrogenase enzymes as well). The reaction turns over at greater than 100x per minute, which may not sound too impressive compared to an enzymatic process, but that actually approaches the ammonia production of nitrogenase, because it’s obviously not an easy reaction under any conditions.

What it doesn’t approach is the throughput of the Haber-Bosch, of course, and as it stands the reaction isn’t really suitable for industrial scaleup. But it’s of potential importance, as mentioned, because of the non-hydrogen-gas aspect. This is new way to get ammonia to form, and it already works at least 10x better than any other artificial system that’s not a Haber-Bosch variant, and this at atmospheric pressure and room temperature. Thermodynamically, it still has a way to go when you add up the total energy involved versus ammonia production, but this looks very much like an area to pursue. The Haber plants are going to be with us for a while to come (they’d better), but there could be better ways. . .

 

68 comments on “Who Cares About Making Ammonia? You Do.”

  1. judw says:

    A few extracts on the tainted history of Fritz Haber from wikipedia and a BBC article :

    “Haber is also considered the “father of chemical warfare” for his years of pioneering work developing and weaponizing chlorine and other poisonous gases during World War I, especially his actions during the Second Battle of Ypres.”

    “It was not just the poison gas. There was one other area of research in the 1920s in which Haber and his colleagues were successful: developing pesticide gases. Of Haber’s legacies, this was the bitterest. For this research was later developed into the Zyklon process, used by the Nazis to murder millions in their death camps, including his own extended family.”

    references: (https://en.wikipedia.org/wiki/Fritz_Haber), (https://www.bbc.com/news/world-13015210)

    1. Derek Lowe says:

      Haber is indeed a tainted figure. He seems to have been very enthusiastic about his chemical warfare work, and his wife at the time (Clara Immerwahr) shot herself, apparently partly because of Haber’s military work and also because of the general problems of living with him and his domineering style.

      1. Isidore says:

        I do not think “tainted” is fair by the standards of a century ago. At that time all countries were considering chemical warfare to be a more humane way to kill your enemy than shooting him or blowing him to bits. Remember that this was the time before antibiotics, when a simple injury would frequently result in a painful slow death. And all combatants, not just the Germans, employed chemical warfare during WWI, in fact the French used chemical agents first, albeit of lower lethality and on a smaller scale than the German did.
        I think Haber was a tragic figure, a decorated German patriot who found himself without a country because he was Jewish, when his contributions to his homeland and to the world meant nothing to the Nazi rulers. Interestingly, Bosch, who was not Jewish, was systematically deprived of his positions and honors by the Nazis of whom he was no friend.
        There is a pretty good book on Haber “Master Mind: The Rise and Fall of Fritz Haber, the Nobel Laureate Who Launched the Age of Chemical Warfare”.

        1. Isidore says:

          I should add that the notion that chemical means of killing someone were more humane than conventional weapons evaporated, so to speak, quickly after the actual results of their use were seen and experienced first hand. But at the beginning of the war people did believe so sincerely.

          1. KazooChemist says:

            Coincidentally, there was an anhydrous ammonia leak from a farm vehicle near Chicago this morning. Over three dozen individuals were sent to the hospital. Seven are listed as being in critical condition. Some of the injured included first responders who attempted to rescue others from the vapor cloud and were themselves overcome. I recall seeing a safety video with exactly that scenario when I went through Hazmat training. You must don personal protection equipment prior to attempting a rescue or there might be two casualties instead of one.

          2. b says:

            “Please secure your own mask before helping others”

        2. loupgarous says:

          Part of the lower lethality of French CW initially was their use of hydrocyanic acid (“Forestite”) and acrolein (“Papite”) as weapon fills.

          But the French learning curve was short – they introduced cyanogen chloride and they, the other Allies and the Germans introduced phosgene.

          1. loupgarous says:

            Sorry, I left out why hydrocyanic acid and acrolein, two very toxic chemicals, weren’t very lethal in the field as chemical warfare agents – their persistence on target wasn’t great, so enemy troops tended not to be badly affected.

          2. Nick K says:

            HCN wasn’t great as a war gas as its molecular weight is only 27, making it lighter than nitrogen or oxygen. When used in WW1 it simply diffused upwards rather than filling trenches like the much heavier chlorine.

          3. loupgarous says:

            @Nick, which was my point about HCN’s lack of persistence, that in French use it dispersed on the winds just after laydown.

            Later Soviet doctrine still had a use for larger quantities of HCN for just that reason, say, taking enemy airbases and other places they wanted to use just after a gas attack. By contrast, even the least persistent nerve agents persist longer in an given area than HCN and require deconning with propionic acid and/or supertropical bleach before it’s safe to occupy those areas.

          4. milkshake says:

            HCN was weaponized by the Japanese Imperial Army during WWII, the soldiers defending Okinawa were issued grapefruit-sized round thick-walled glass vials to be used as a chemical hand grenade when fighting in caves and bunkers. Each glass grenade contained about half liter of liquid HCN with some copper powder as a stabilizer. It was not very effective because Americans famously used the flamethrowers, and HCN is flammable.

      2. milkshake says:

        Haber’s counterpart in French chemical warfare was one Victor Grignard, who early in the WWI improved the process for making phosgene on large scale. Grignard was indeed the father of chemical warfare – he developed bromoacetate and benzyl bromide teargases and their use in the trenches early in the war got the whole chemical warfare going. Yet no one keeps saying Grignard is tainted. With haber there is the nice morality story about his wife killing herself and Haber being jewish and later persecuted by Nazis. Frankly I am very tired hearing again about “Haber the father of modern chemical warfare.”

        1. dearieme says:

          “Grignard was indeed the father of … teargases and their use in the trenches early in the war got the whole chemical warfare going.”

          Are you really arguing that it makes sense to equate the use of tear gas to the use of lethal gas?

          1. Hap says:

            Scaling the manufacture of phosgene would seem to be a big contribution, though, since there wasn’t any polymer chemistry to use it for at that scale.

          2. milkshake says:

            ethyl bromoacetate and xylyl bromides are quite toxic, and once you spray people in trenches with noxious stuff on which they can choke to death, and can cause bleeding in brain, it undercuts the spirit of the chemical weapon convention. French were the first to use chemical weapons, even if with a mixed result. Germans then found a loophole in the convention (which banned only the chemical shells) and sent a cloud of chlorine from gas tanks downwind. And soon both sides were gassing each other without worrying about subtleties of international law.

          3. loupgarous says:

            Adamsite (diphenylaminechlorarsine, or “agent DM”) was distributed to US forces in containers marked “not to be used where fatalities are unacceptable”, even though its formal classification was as a riot control agent. A co-worker of mine who served in the Louisiana Army National Guard told me DM was stored at the New Orleans armory (Jackson Barracks) in fifty-five gallon drums as late as the early-mid 1980s, against the possibility of widespread civil disorder.

      3. Nick K says:

        If we add up the number of lives saved through Haber’s ammonia work versus the number lost by his promotion of chemical warfare, I think we can safely call him a hero.

        Incidentally, why is poisoning a person considered so much more heinous than shredding him or her with high explosive?

        1. DanielT says:

          Nick I think if you were exposed to Mustard gas you might have a different opinion. I find it hard to imagine a worse way to die.

          1. Nick K says:

            Neither appeals, thanks all the same.

          2. A Nonny Mouse says:

            Unfortunately, I was allowed usage of a large cylinder of phosgene when I started my PhD which was pre-Health and Safety!

            I do not recommend checking the liquid nitrogen traps by smelling what is in there.

          3. Derek Lowe says:

            Jaysus. No, I don’t recommend that course of action, either. Glad you’re still with us!

        2. Dionysius Rex says:

          Indeed – war might not be so popular if the protagonists were all forced to go about it with nothing but steak knives.

        3. loupgarous says:

          James Bryant Conant, one of the first war gas chemists at Edgewood Arsenal during the first World War, a leading American chemist between the wars, and later a central figure in the Manhattan Project, put it this way:

          “I did not see in 1917, and do not see in 1968, why tearing a man’s guts out by a high-explosive shell is to be preferred to maiming him by attacking his lungs or skin. All war is immoral. Logically, the 100 percent pacifist has the only impregnable position. Once that is abandoned, as it is when a nation becomes a belligerent, one can talk sensibly only in terms of the violation of agreements about the way war is conducted, or the consequences of a certain tactic or weapon.”

          It’s significant that even so, Conant opposed development of the hydrogen bomb after the second World War – as he did not believe the survival of the nation was sufficiently at risk to warrant such a leap in destructive capacity beyond nuclear weapons using solely fission as an energy source.

          1. milkshake says:

            One of the discussions Conant was involved was possibility of dumping radiological waste from spent nuclear fuel on Nazi Germany, to poison the food supply and to make industrial areas inhabitable, as it was unclear at that time if the reactors in Hanford would produce enough plutonium, or if the plutonium bomb could be built. Oppenheimer too was involved in doing calculations for the proposal. Everyone was disgusted by it because it sounded too much like chemical warfare, but done on civilian population

          2. loupgarous says:

            @milkshake – The “dusting” proposal actually made its way into wartime science fiction. Robert Heinlein (writing as “Anson MacDonald”) wrote the short story “Solution Unsatisfactory” for Astounding Science Fiction magazine in 1941, the same year Conant brought the idea up at a National Academy of Science meeting.

            The story’s main characters include Clyde C. Manning, a US Army commanding officer with a striking resemblance to the Manhattan Project’s Gen. Leslie Groves, and Dr. Estelle Karst, a scientific head whose academic history (a refugee from Germany who’d worked with Otto Hahn) is similar to Lise Meitner.

            Where the story veers off from the Manhattan Project is that the radioactive dust idea is accepted for lack of alternatives (apparently the Project had kept the use plutonium and U-235 for bombs a domestic secret, even if the Germans had figured them out on their own). General Manning, the Leslie Groves-like figure, eventually extorts control of the necessary bombers to distribute the dust from the world’s armies, flown by an international corps of pilots, with the idea of enforcing a postwar peace by all means necesary.

            This was one of Robert Heinlein’s early stories, written not very long after Heinlein was associated with Upton Sinclair’s “EPIC” socialist political movement. His stories “Solution Unsatisfactory”, “The Long Watch”, “Space Cadet” and others take a view common just after Hiroshima and Nagasaki that nuclear weapons should be internationalized.

      4. Peter Kenny says:

        One piece of chemical trivia that may be of interest is that Clara Immerwahr was a close friend of Otto Sackur (of the Sackur-Tetrode equation) who died in 1914 as the result of a laboratory explosion at the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry where Haber was the director. I’ve linked ‘Clara Immerwahr: A Life in the Shadow of Fritz Haber’ as the URL for this comment.

      5. loupgarous says:

        Clara Immerwahr was the first woman to earn a doctorate in chemistry in Germany. She was active in pacifism and women’s rights, but became a mother and housewife in an increasingly troubled marriage to Haber, who was increasingly gone to wage chemical war against the Allies – a bone of contention between them.

        One of the sad notes there is the translation of Clara Immerwahr’s family name – “always true”.
        One wonders if she felt the only way to be true to herself was suicide.

  2. Uncle Al says:

    with a turnover frequency of around 117 per minute” Turnover number is s^(-1). Remember Hartrees measuring ab intio calculation quality? Off by a C-C bond dissociation energy is some 86 kcal/mol (very bad) or 0.137 Hartree (fantastic!). ““early days, but possibly of great interest”” indeed.

    https://bionumbers.hms.harvard.edu/files/Maximum%20turnover%20numbers%20of%20some%20enzymes.pdf

  3. Barry says:

    about 2% of the WORLD’S energy budget is spent on Haber-Fosch ammonia synthesis.
    https://aip.scitation.org/doi/am-pdf/10.1063/1.4985090

    any improvement on that would mean more coal could be left in the ground

    1. Ken says:

      Or used to mine bitcoins.

    2. milkshake says:

      there is better catalyst than iron for Haber Bosh, which allows you to run it at lower temperature and half the pressure. The catalyst is ruthenium based and given the commodity price of ammonia, it is too costly, despite ruthenium being the cheapest platinum metal.

  4. tlp says:

    Other cool wikipedia excerpt: “Nearly 50% of the nitrogen found in human tissues originated from the Haber-Bosch process.”

    1. Jim Hartley says:

      That is way cool!

  5. DCM says:

    hmm not ostensible enough….nominally

  6. DTX says:

    A very engaging book that covers chemical & biological warfare, including Haber’s efforts, is called “A higher form of killing.” I believe the title was based on a quote from Haber (along the lines Isidore noted). A few snippets from the book:

    The laxity of safety was amazing. In the UK, several workers were transporting a chemical warfare agent between sites. The container started to leak, so they tied a string it and hung it out the window.

    Towards the end of WWI, one of the things that held research back was the lack of fresh human skill to test the chemical warfare agents on (i.e., all of the workers on-site had already had substances tested on them).

    During WWII, the Germans had the nerve agents, Toban, Soman, & Sarin. These chemicals were orders of magnitude more toxic than the weapons of WWI. The Allies had no antidotes, because they didn’t know the nerve agents existed. Yet, despite the many horrors done by the Germans during WWII, they never used these agents in battle. Why? The book offers: During WWI, a young German artillery corporal was hit by mustard gas and temporarily blinded. It was thought to have turned him away from using chemical weapons. His name was Adolf Hitler.

    1. Illegal thoughts says:

      Gee, it almost makes you wonder if the other stories you heard about him (and them) were, so to speak, exaggerated

    2. John Dallman says:

      The actual reason is a little more complicated. Hitler was always concerned with effects on public opinion in Germany, and that meant gas warfare wasn’t the first choice. By the time he was willing to consider it, the Allied bomber offensive was underway, and German cities were horribly vulnerable to gas bombing. The Allies did not have nerve gasses, but the Germans didn’t know that, and assumed they did.

      1. Icefox says:

        They may not have had sarin but sure as heck had plenty of other chemical weapons, including phosgene. A glance at Wikipedia suggests that, neither side wanted it used against them and so neither side wanted to use it first. As it should be.

      2. Icefox says:

        They sure as heck had phosgene. From Wikipedia, neither side wanted to use chemical weapons because neither side wanted them used back. As it should be.

        1. DTX says:

          I was giving a short summary of part of the book. Yes, there were other reasons the Germans didn’t use chemical weapons. The toxicity of the nerve agents far exceeded those used in WWI.

          Both sides considered using chemical weapons. The book includes an actual copy of the 2nd letter from Churchill to his chief’s of staff imploring them to switch to chemical weapons. Part of Churchill’s justification was that nations switched to chemical weapons during the WWI and this was no different than a “woman changing the length of their skirt.” (this changed my view of Churchill considerably).

          Churchill asked for a “cold-blooded” estimate of how quickly they could end the war by dousing Germany with chemical weapons. Churchill noted they could hit Germany with 20 tons for each ton launched at England. Fortunately, his chief’s of staff rejected his plea.

          You need to read the book to get the full flavor. My snippets don’t give it justice. It’s an amazingly engaging book with some insightful perspectives.

          1. loupgarous says:

            Churchill was pushing gas warfare with a memo a month at his most prolific, as well as promiting work with biological weapons such as anthrax. During WW2, the Vigo Ordnance Plant near Terre Haute, Indiana was built to mass-produce anthrax bombs for Britain, but the war ended before the plant got past the stage of making the anthrax simulant bacillus globigii. It was sold to Pfizer, who made antibiotics there. Pfizer shut the place down in 2008.

      3. loupgarous says:

        Interestingly, the Manhattan Project served (inadvertently) as a deterrent to the German use of nerve agents.

        German intelligence was aware that the US Government was buying a LOT of fluorine (as a way of gasifying uranium for enrichment, but the Germans weren’t thinking about that because they early on had chosen manufacture of plutonium in natural uranium heavy water reactors). They assumed it was destined for nerve agent manufacture – and reasoned that we could make more nerve gas than they could and that retaliation would be harsh.

        1. Bill Smathers says:

          Do you have a source for this? Sounds fascinating.

          1. loupgarous says:

            “Speer, who was strongly opposed to the introduction of tabun, flew Otto Ambros, I.G.’s authority on poison gas as well as synthetic rubber, to the meeting. Hitler asked Ambros, “What is the other side doing about poison gas?” Ambros explained that the enemy, because of its greater access to ethylene, probably had a greater capacity to produce mustard gas than Germany did. Hitler interrupted to explain that he was not referring to traditional poison gases: “I understand that the countries with petroleum are in a position to make more [mustard gas], but Germany has a special gas, tabun. In this we have a monopoly in Germany.” He specifically wanted to know whether the enemy had access to such a gas and what it was doing in this area. To Hitler’s disappointment Ambros replied, “I have justified reasons to assume that tabun, too, is known abroad. I know that tabun was publicized as early as 1902, that Sarin was patented and that these substances appeared in patents. ” (…)Ambros was informing Hitler of an extraordinary fact about one of Germany’s most secret weapons. The essential nature of tabun and sarin had already been disclosed in the technical journals as far back as 1902 and I.G. had patented both products in 1937 and 1938. Ambros then warned Hitler that if Germany used tabun, it must face the possibility that the Allies could produce this gas in much larger quantities. Upon receiving this discouraging report, Hitler abruptly left the meeting. The nerve gases would not be used, for the time being at least, although they would continue to be produced and tested.”

            — Joseph Borkin, The Crime and Punishment of IG Farben, 1978, New York: Free Press. ISBN 978-0-02-904630-2. OCLC 3845685

      4. The Lunatic says:

        Indeed. And the reason the Germans assumed that the Allies would have nerve gasses is that the basic pesticide work was published in the open scientific literature in the 1930s. The German scientists figured their Allied counterparts would easily solve the same problems they did. It was quite parallel to why the Allies expected the Germans would have an advanced atomic bomb program.

    3. MCS says:

      The story I’ve heard several places is that the German Army was dependent on horse drawn transport. They were unable to develop an equine gas mask. The respiratory tract of a horse is pretty fragile. I suspect that even tear gas could kill a horse.

      1. loupgarous says:

        Supposedly, a German general being interrogated as to why they hadn’t used gas early and often to beat the Normandy invasion back replied simply “die Pferde”.

      2. Anonymous says:

        I think coal powered trains and extensive use of military horses was a deliberate policy choice forced by a lack of internal petroleum supplies.

        1. loupgarous says:

          Correct. German petroleum and synthetic fuels were, as much as possible, reserved for war machines such as tanks and military aircraft; coal powered the railways and the steel mills of the Ruhr, while horses and oxen required no fuel, merely forage and grain, and could pull heavy loads (toward the end of the war, Junkers Jumo turbojets traveled by ox-cart to the Messerschmitt works, where they were fitted to Me 262 fighters).

  7. Peter S. Shenkin says:

    You may know the Lotka-Voltera equations for predator-prey populations over time. Alfred Lotka was an insurance actuary who founded the field of mathematical biology in his spare time. In the 19-teens, he predicted that the fixation of nitrogen via the Haber process would outpace that from natural processes in only a few years. He may have been off, but the figure cited by @tip indicates that we may be close now.

  8. Haber Borscht says:

    I love how all discussions so far are about WWI, Haber’s tainted past and chemical warfare.

    I will be the first one to say, pretty cool paper indeed. Nothing that gonna revolutionize anything in the closest future, but an interesting new research avenue to follow up on.

  9. Scott says:

    “This is new way to get ammonia to form, and it already works at least 10x better than any other artificial system that’s not a Haber-Bosch variant, and this at atmospheric pressure and room temperature. Thermodynamically, it still has a way to go when you add up the total energy involved versus ammonia production, but this looks very much like an area to pursue.”

    Wouldn’t just cranking up the temperature and pressure speed things up greatly? Obviously not all the way to H-B levels (400degC and 400bar is pretty nuts, mostly the 400bar pressure), but to maybe 200degC and 100bar?

    1. chimaera says:

      Perhaps, but you run into a few issues pretty quickly.

      More heat and pressure means switching to a pressure vessel over a simple tank, so capital costs go up. The H&S people also start getting a bit edgy in these situations.

      The kinetics may not be that favourable either: it could be a diminishing returns situation. Couple that with the capital expense involved and the crossover point might arrive faster than you’d like.

      The final potential pitfall is the thermal stability of the catalyst. No point cranking up the temperature if your catalyst falls apart.

  10. anon says:

    What about those 5 equivalents of SmI2? Isn’t that more expensive than ammonia?

  11. DriveBy says:

    Yet bacteria do the same (fix nitrogen) under remarkably less strenuous conditions. Is that what the basic theme of the next great human lurch forward in scientific progress will be? – moving from the heroic conditions (solvents, heat, pressure) of past synthetic chemistry processes to the more languid assembly conditions preferred by bio-engineered critters? Yes, that’s oversimplifying a lot (at this juncture), but that would be an amazing leap forward, putting humans more in harmony with the earth, perhaps?

    1. x says:

      The earth has no harmony, only an endless orgy of murder and consumption with a few merciless negative feedback mechanisms to control runaway feedback loops. If you want to be in closer harmony with the earth, burn your antibiotics and feed yourself to a tiger.

  12. loupgarous says:

    India takes advantage of their need for lots of ammonia and the electricity formed by their nuclear power reactors to drive a monothermal reaction to separate deuterium from the mass of hydrogen passing through their ammonia plants:
    https://cns-snc.ca/media/Bulletin/A_Miller_Heavy_Water.pdf

    “Processes Based on Chemical Exchange
    The remaining processes in Table 1 all depend on the separation factors between two
    chemical species influencing a reaction of the type:
    HX + DY ↔ DX + HY.
    Monothermal versus Bithermal Processes
    One species is a gas, the other a liquid. Quite large separation factors exist for the pairs
    of chemical species listed and they can be exploited in two approaches: monothermal and
    bithermal processes. These are illustrated in Figure 3.4
    Monothermal processes are very simple. Equilibrium favours deuterium in the liquid
    species. So, by converting the liquid into the gas, the gas can then be used to enrich the
    incoming liquid in D. The effect can be amplified by countercurrent flow of the liquid,
    prior to its conversion, with the gas, after conversion. Quite short exchange columns can
    achieve high deuterium enrichments because the gas enters the exchange column at the
    same concentration as the liquid leaving it and so is far removed from equilibrium. Note
    too that a substantial part of the deuterium in the liquid can be extracted since the D
    concentration in the gas leaving can be as low as 1/a of the feed concentration. There is only one problem with monothermal processes: a simple conversion process has to exist and it has to be very low cost since it will have to treat the entire feed flow. For two of
    the four processes in Table 1, there is no practicable conversion process. However, both
    water and ammonia can be converted into hydrogen. Ammonia is comparatively easy to
    dissociate thermally, requiring 45 kJ/mol. Plants using this monothermal process have
    been built in India and Argentina.”

  13. Scott says:

    I have a potentially-stupid question:

    Do most H-B processes use electrical heat or gas heat?

    Because if they use gas heat, why wouldn’t you try generating electricity using the waste heat of the process? Might as well recover some costs if you can.

    1. Nick K says:

      I believe most Haber-Bosch plants use methane as a source of the hydrogen (steam reforming reaction), so it would make sense to use the gas as an energy source as well.

      1. milkshake says:

        you are right, natural gas -derived hydrogen is considerably cheaper than electrolysis-produced hydrogen, so it is used almost exclusively in the commodity manufacture. And methane-derived hydrogen is not perfectly pure, and this can have effect on catalytic processes (for example if the used catalyst is sensitive to traces of CO). If you are working on a hydrogenation process to be scaled up in a plant, it makes good sense to try natural gas-derived grade H2 too

    2. loupgarous says:

      Gas is the direct, economical approach, for heating and as a feedstock for all sorts of things. Among other things made where I grew up (the parishes just upriver from New Orleans, also known as “petrochemical alley”) were ammonia and various nitrates, because methane and other hydrocarbons were there to be used for the purpose. Using electricity would just entail Joule heating losses and other inefficiencies, even though Entergy has a nuclear power plant there, too.

    3. zero says:

      In order to make the chemical process as efficient as possible, that residual heat is used to heat incoming reactants. The products after passing through a heat exchanger will be nearly ambient temps, not enough energy available to bother with in most cases.

      Given the multiple conversion steps and limited thermodynamic efficiency, it would be more efficient to run things like pumps and fans from the grid than to run them from a fraction of the product flow through a Carnot engine.

  14. Thomas Hager says:

    Interesting thread. Yes, Haber-Bosch synthetics now outstrip natural nitrogen fixation. For those who want to know more, my book “The Alchemy of Air” — finalist for the National Academies communications prize — describes the history of the technology and offers insights into the personal stories of the two scientists. Carl Bosch, the forgotten man here, is just as interesting as Haber . . . . and far more important in the industrialization that is changing our world with reactive nitrogen.

  15. loupgarous says:

    The reason the new pathway to ammonia isn’t going to displace Haber-Bosch is economics. But let’s say Elon Musk succeeds in settling Mars. The settlers may well need more ammonia than they have, but must husband what energy they have wisely. And there your new process is, not requiring huge, energy-guzzling reactor vessels.

    As Man goes beyond our Moon and neighbor planets and their moons, he’ll remain a protein-driven animal. Ammonia is something you don’t hear discussed much as a vital commodity for, say, Martian or lunar colonies, but if the colonies grow as their planners hope they will, they’ll need to overcome losses in recyclable biomass somehow.

    The new process may well be “right-sized” to replace lost nitrates in biomass recycling – less prodigious than Haber-Bosch, but less demanding, certainly less energy-dependent, and possibly MUCH less massive.

    1. Scott says:

      Oooh, good call on the viability of this in space exploration or planetary colonization.

      While (solar) energy is extremely abundant in space, a 400bar reactor vessel that can handle 400degC is *very* heavy.

      1. loupgarous says:

        Agreed, and reactors like this have an advantage over the natural approach of speed of synthesis (if only modest throughput). They won’t replace natural nitrogen fixation, but could be a life-saving supplement in the event recyclable biomass falls short or is lost to a leak somewhere in the system

        In honesty, through, NASA has studied rhizome nitrogen fixation in space under extreme conditions such as “etioliation” (depriving plants of light).

        Some of their findings:

        “NanoRacks-SyNRGE3 is a follow-on experiment to the NASA BRIC-SyNRGE study flown on the STS‐135 Space Shuttle mission in July 2011 that demonstrated the symbiosis between etiolated plants (i.e., plants grown without light) and bacteria was negatively affected by microgravity. The NanoRacks-SyNRGE3 experiment uses the model legume species Medicago truncatula (M. truncatula) (i.e., barrel medic) and the nitrogen-fixing bacterium Sinorhizobium meliloti (S. meliloti) to determine the genetic maintenance of communication and reciprocity within a microbiome to further investigate the events associated with the effect of microgravity on biological nitrogen fixation in M. truncatula. The experiment tests the hypothesis that the rate of infection of M. truncatula L. cv. Jemalong A17 (Enod11::gus) by its symbionts S. meliloti ABS7 and 1021 is less in microgravity than in normal gravity on Earth.”

        NASA also has flown experiments testing the hypothesis

        “that the rate of infection of Medicago truncatula by Sinorhizobium meliloti is higher in microgravity than in 1g.”

        and identifying

        “mechanistic responses that trigger host-symbiont signaling and infection”

        One takeaway from current research is that it’s at least possible to have working rhizome-based nitrogen fixation in microgravity, but still a matter for more research. It might not be unreasonable to develop the pathway to ammonia in the paper Derek describes as another means to fix nitrogen to ammonia in low-gravity or other extraterrestrial ecologies.

  16. Matthew says:

    About 5 years ago I visited Heidelberg where there is a museum dedicated to the life and work of Carl Bosch. I highly recommend it to those who are interested in chemistry and chemical engineering.

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