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U-Know! Forum » Where do carbon dioxide & nitrous oxide come from? |
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Merrick 2148 posts |
Jul 21, 2008, 11:50
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Well not in the strict sense, I mean what's the raw material for industrial uses? Given that these things are not filtered out of the atmosphere, there's gotta be a raw material that I'm guessing is likely to be fossil sourced. Which means their production and use is actively contributing to climate change. I just blogged a musing on it, with Grufty Jim's knowledge on carbon dioxide, but as for nitrous we're totally in the dark. http://bristlingbadger.blogspot.com/2008/07/stop-burping-stop-climate-change.html Any ideas or info (with references) gratefully received.
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Rhiannon 5291 posts |
Jul 22, 2008, 12:37
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If people want to make chemicals with nitrogen in I imagine vaguely that they use the Haber process which fixes the nitrogen in the air into ammonia. And then go from there, making whatever nitrogenous thingies you fancy. This is sheer speculation. I could swear blind that when I was at school we watched a video about it with John Cleese explaining it all. But maybe I have imagined this totally. But burning fossil fuel is where most of the no2 pollution comes from innit, I think.
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PMM 3155 posts |
Jul 22, 2008, 12:45
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Manufacture... Nitrous oxide is most commonly prepared by careful heating of ammonium nitrate, which decomposes into nitrous oxide and water vapor.[4] The addition of various phosphates favors formation of a purer gas at slightly lower temperatures. One of the earliest commercial producers was George Poe in Trenton, New Jersey. NH4NO3(s) → 2 H2O(g) + N2O(g) This reaction occurs between 170 - 240°C, temperatures where ammonium nitrate is a moderately sensitive explosive and a very powerful oxidizer. Above 240 °C the exothermic reaction may accelerate to the point of detonation, so the mixture must be cooled to avoid such a disaster. Superheated steam is used to reach reaction temperature in some turnkey production plants.[6] Downstream, the hot, corrosive mixture of gases must be cooled to condense the steam, and filtered to remove higher oxides of nitrogen. Ammonium nitrate smoke, as an extremely persistent colloid, will also have to be removed. The cleanup is often done in a train of 3 gas washes; namely base, acid and base again. Any significant amounts of nitric oxide (NO) may not necessarily be absorbed directly by the base (sodium hydroxide) washes. The nitric oxide impurity is sometimes chelated out with ferrous sulfate, reduced with iron metal, or oxidised and absorbed in base as a higher oxide. The first base wash may (or may not) react out much of the ammonium nitrate smoke, however this reaction generates ammonia gas, which may have to be absorbed in the acid wash. [edit] Other routes The direct oxidation of ammonia may someday rival the ammonium nitrate pyrolysis synthesis of nitrous oxide mentioned above. This capital-intensive process, which originates in Japan, uses a manganese dioxide-bismuth oxide catalyst:[7] 2 NH3 + 2 O2 → N2O + 3 H2O Higher oxides of nitrogen are formed as impurities. In comparison, uncatalyzed ammonia oxidation (i.e. combustion or explosion) goes primarily to N2 and H2O. Nitrous oxide can be made by heating a solution of sulfamic acid and nitric acid. A lot of gas was made this way in Bulgaria.[citation needed][8] HNO3 + NH2SO3H → N2O + H2SO4 + H2O There is no explosive hazard in this reaction if the mixing rate is controlled. However, as usual, toxic higher oxides of nitrogen form. Nitrous oxide is produced in large volumes as a by-product in the synthesis of adipic acid; one of the two reactants used in nylon manufacture.[9][10] This might become a major commercial source, but will require the removal of higher oxides of nitrogen and organic impurities. Currently much of the gas is decomposed before release for environmental protection. Greener processes may prevail that substitute hydrogen peroxide for nitric acid oxidation; hence no generation of oxide of nitrogen by-products. Hydroxylammonium chloride can react with sodium nitrite to produce N2O as well: NH3OH+Cl− + NaNO2 → N2O + NaCl + H2O If the nitrite is added to the hydroxylamine solution, the only remaining byproduct is salt water. However, if the hydroxylamine solution is added to the nitrite solution (nitrite is in excess), then toxic higher oxides of nitrogen are also formed. http://en.wikipedia.org/wiki/Nitrous_oxide That seemed too easy. I can't believe you didn't look there, so my apologies if this doesn't actually answer your question.
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grufty jim 1978 posts |
Jul 22, 2008, 14:51
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That all sounds pretty correct to me, though to be honest I never use Wikipedia as a reference source. I could head on over there and alter one or more of those chemical equations and it probably wouldn't be picked up for a couple of days. When it's not a controversial subject, you can often rely upon Wikipedia, but even then, there are people who spend their free time adding inaccuracies to random Wikipedia articles (I know one of them. He does it in the name of discordianism). On the specific subject of manufacturing nitrous oxide from fertiliser (ammonia nitrate), I knew a chemistry postgrad who made some cash on the side by selling nitrous to heads. This guy was one of the best chemists I'd ever met, and even he damn near killed himself one evening. Heat the stuff too quickly and it'll explode rather forcefully. Heat it too slowly (his mistake that night) and you start to get all manner of ammonia-derived vapours being emitted. Inhale them and you're in very serious trouble!
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Rhiannon 5291 posts |
Jul 23, 2008, 09:13
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are you really asking about nitrogen dioxide (no2) though - that's what I assumed you were interested in, rather than nitrous oxide (n2o). Though I guess they're both pollutants. Or are you talking about NOx ie nitrogen oxide NO and nitrogen dioxide NO2. got to be specific with chemical names haven't you.
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grufty jim 1978 posts |
Edited Jul 23, 2008, 12:06
Jul 23, 2008, 12:04
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Rhiannon wrote: are you really asking about nitrogen dioxide (no2) though - that's what I assumed you were interested in, rather than nitrous oxide (n2o). Though I guess they're both pollutants. Or are you talking about NOx ie nitrogen oxide NO and nitrogen dioxide NO2. got to be specific with chemical names haven't you. Definitely nitrous oxide (N2O) we're talking about Rhiannon. The others are also pollutants as you point out, but they don't tend to be consumed recreationally by heads. Having said that, and thought about it a bit more, I'm not sure that's really a big issue. As Merrick points out, the 'greenhouse' effect of N2O is almost 300 times worse than CO2. But: (a) the amount consumed recreationally, compared to the amount of CO2 produced, must be damn near negligible (even taking the 300x multiplier into account). (b) the N2O that gets inhaled won't be expelled to atmosphere as N2O. I haven't checked out what does get expelled, but the fact that you get high off the stuff implies that a chemical reaction has taken place, almost certainly resulting in the N2O being converted to something else. Which isn't to say that releasing N2O into the atmosphere is a good idea. Merely that we should probably minimse the energy we spend campaigning against munters and their N2O balloons, so long as global industry is still boiling the planet alive.
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PMM 3155 posts |
Jul 23, 2008, 12:08
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Nitrous oxide is only lightly metabolised upon inhalation. Most of it is exhaled again as nitrous oxide. Dentists and their staff used to sometimes be affected by prolonged exposure in poorly ventilated surgeries.
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grufty jim 1978 posts |
Jul 23, 2008, 12:17
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PMM wrote: Nitrous oxide is only lightly metabolised upon inhalation. Most of it is exhaled again as nitrous oxide. Dentists and their staff used to sometimes be affected by prolonged exposure in poorly ventilated surgeries. Thanks for that PMM. All the same, I still think the quantities we're talking about, in comparison to CO2, make it very much a second priority (hell, third priority after methane).
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Merrick 2148 posts |
Jul 23, 2008, 20:15
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Ta for that (the nylon thing's a mad one), but nope, it doesn't answer the question. That remains: what is the feedstock? Heat that ammonium nitrate to make nitrous oxide, fine, but what's the ammonium nitrate made of? Wikipedia says ammonia gas and concentrated nitric acid. Fine, but what's that made from? My big question is; is this stuff adding new greenhouse gases to the atmosphere (a la burning coal), or is it coming from source that doesn't add any (a la burning wood)? Yes Jim, it's not as big an issue as whether one uses aeroplanes or whatever, but it's just something I'm curious about and the answer doesn't come readily to hand. And, though it be a small choice, if a few minutes feeling fuzzy has such a big greenhouse impact, certainly there are people who would like to choose to lay off it. (The next question would be what's the comparitive climate impacts of a balloon of nitrous and, say, a can of beer with all its aluminium and stuff - smelters dish out greenhouse gases tens of thousands of times more potent than CO2)
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Merrick 2148 posts |
Jul 23, 2008, 20:23
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Wikipedia (I know, Jim) says that modern ammonia production is natural gas or liquid petroleum gas. http://en.wikipedia.org/wiki/Ammonia#Synthesis_and_production But still the question remains; is the stuff used as a propellant and by munters and so on - like CO2 for fizzy drinks - taken as a by-product in processes that would otherwise have vented it to the atmosphere, or is it specially made?
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