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Author: Subject: Diesel => NOx + water = Nitric acid?
ecos
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[*] posted on 21-1-2019 at 09:33
Diesel => NOx + water = Nitric acid?


I was reading about the new regulations in Europe to ban diesel cars with high emissions.

The main reason was that diesel has high NOx emissions compared to petrol fuel.

New modern cars use catalyst converter to reduce the NOx emissions.

I found on wiki that NOx (NO and NO2) are soluble in water. :)

I thought why don't we pass the NOx to cold water as a filtration process (or even combine it with the catalytic converter)?
the result will be nice. water contaminated with NOx = Nitric acid
people can sell this water later to companies.

would that work ?

a nice PDF about diesel and nitric acid : https://www.tandfonline.com/doi/pdf/10.1080/00022470.1983.10...



[Edited on 21-1-2019 by ecos]

[Edited on 21-1-2019 by ecos]

[Edited on 21-1-2019 by ecos]
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[*] posted on 21-1-2019 at 10:37


Wow, you think just like me! Seems like a waste to try and destroy (with a catalytic converter) something as valuable as nitrogen oxides. A while back I did some earnest research on this, and found a few reasons why no one has tried to convert NOx emissions into something useful.

For one, the amount of NOx emitted by a diesel powered vehicle is pretty small; bad emissions were measured in hundreds of milligrams per kilometer. Also, the reaction 2NO+O2-> 2NO2 works much better (faster) at a high NOx concentration than a low one. I'll try to find a reference for this. Third, the absorption tank needed to process large volumes of exhaust would be very inconvenient. If placed in the vehicle, there would be an unacceptable risk of gas leakage causing poisoning or suffocation, and if placed under the vehicle the tank might be damaged. Finally, the combined cost of the apparatus, and fuel economy losses from increased weight and restriction of exhaust flow would probably cost you more than it would to buy much cleaner nitric acid (assuming it is legal for individuals to purchase it in your area.)

Even so, I would love to see a proof of concept demonstrated for such a "self propelled liquid fuel multipurpose Birkeland Eyde reactor"

Edit: found my references, (although yours is just as good or better)
https://www.tandfonline.com/doi/pdf/10.1080/00022470.1964.10...
Something I found very fascinating here is "Table IV—Calculated Conversion
Rates of NO to NO2 in Atmosphere" It seems to show that the rate of conversion of NO to NO2 in an oxygen containing environment is not directly proportional to the concentration of NO, but rather the square of its concentration. This means that the time it takes for 1 ml of NO diluted in a 10l of air to be mostly converted (e.g. 80%) into NO2 will be far longer than the time it takes for a ml of NO diluted in 1l of air to make the same conversion. Very fascinating, if true.

Oh, and I think that if someone did figure out how to make grams of nitric acid using a diesel motor, the EU would be even more inclined to restrict it then they would for simple air pollution.

[Edited on 22-1-2019 by Vomaturge]
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[*] posted on 21-1-2019 at 11:28


this is just useless, expensive an inefficient.
1) concentration of NO2 in the exhaust gas is expressed in ppm (aka very low)
2) NO2 dissolves in water formin nitric acid AND NO again, so you need multiple absorbtion/oxidation stages
3) the gas must be in intimate contact with the water. the high flow rate of exhast gas means a big absorpion "tower" or low absorption rate (plus lots of splashing and loss of eater from the carrying gas)
4) nobody would ever buy dirty low concentration nitric acid that need lots of processing
5) just stupid idea, at this point you could put a giant compressor in your car to store the exhaust CO2 and sell it to make carbonated drinks





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[*] posted on 21-1-2019 at 11:39


Better idea, prepare Mg(NO3)2 from mixing aqueous MgSO4 (Epsom Salt) and KNO3 (stump remover) and freeze out the K2SO4 hydrate. I have done this previously as adding aqueous ammonia leads to aqueous NH4NO3 and a suspension of Mg(OH)2.

Then, for HNO3 without acid per Wikipedia (https://en.wikipedia.org/wiki/Magnesium_nitrate) to quote:

"Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt, but rather its decomposition into magnesium oxide, oxygen, and nitrogen oxides:

2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2.

The absorption of these nitrogen oxides in water is one possible route to synthesize nitric acid. Although inefficient, this method does not require the use of any strong acid."

Interestingly, per Wiki magnesium nitrate is moderately soluble in ethanol, so also one could dissolve some in ethanol, set on fire, and collect the NO2 rich fumes. Note, it may be a bit too energetic if there is no water in the the ethanol!

[Edited on 21-1-2019 by AJKOER]
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[*] posted on 21-1-2019 at 12:30


Quote: Originally posted by AJKOER  
Better idea, prepare Mg(NO3)2 from mixing aqueous MgSO4 (Epsom Salt) and KNO3 (stump remover) and freeze out the K2SO4 hydrate. I have done this previously as adding aqueous ammonia leads to aqueous NH4NO3 and a suspension of Mg(OH)2.

Then, for HNO3 without acid per Wikipedia (https://en.wikipedia.org/wiki/Magnesium_nitrate) to quote:

"Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt, but rather its decomposition into magnesium oxide, oxygen, and nitrogen oxides:

2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2.

The absorption of these nitrogen oxides in water is one possible route to synthesize nitric acid. Although inefficient, this method does not require the use of any strong acid."

Interestingly, per Wiki magnesium nitrate is moderately soluble in ethanol, so also one could dissolve some in ethanol, set on fire, and collect the NO2 rich fumes. Note, it may be a bit too energetic if there is no water in the the ethanol!

[Edited on 21-1-2019 by AJKOER]


how is this relevant to the topic "nitric acid from diesel engine exhaust gases"???





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[*] posted on 21-1-2019 at 14:20


Add to the issues that the exhaust gases are at high temperature where they are less soluble in water.
Any straightforward process would also have CO2 being dissolved -- or more importantly driving the NOx out of solution.
Your water will heat up pretty quickly with all of that gas passing through it.

Nice tidy ideas do not often conform to all of the engineering constraints. (cough hyperloop cough.)
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[*] posted on 21-1-2019 at 15:01


Quote: Originally posted by Ubya  
Quote: Originally posted by AJKOER  
Better idea, prepare Mg(NO3)2 from mixing aqueous MgSO4 (Epsom Salt) and KNO3 (stump remover) and freeze out the K2SO4 hydrate. I have done this previously as adding aqueous ammonia leads to aqueous NH4NO3 and a suspension of Mg(OH)2.

Then, for HNO3 without acid per Wikipedia (https://en.wikipedia.org/wiki/Magnesium_nitrate) to quote:

"Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt, but rather its decomposition into magnesium oxide, oxygen, and nitrogen oxides:

2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2.

The absorption of these nitrogen oxides in water is one possible route to synthesize nitric acid. Although inefficient, this method does not require the use of any strong acid."

Interestingly, per Wiki magnesium nitrate is moderately soluble in ethanol, so also one could dissolve some in ethanol, set on fire, and collect the NO2 rich fumes. Note, it may be a bit too energetic if there is no water in the the ethanol!

[Edited on 21-1-2019 by AJKOER]


how is this relevant to the topic "nitric acid from diesel engine exhaust gases"???

I like how diesel or exhaust fumes are not mentioned once. It is clear that AJOEKER is a troll like phd. At least give him a title warning beginners his information isn't valid.




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[*] posted on 22-1-2019 at 04:35


Quote: Originally posted by ecos  

I found on wiki that NOx (NO and NO2) are soluble in water. :)


Interesting, when did you first hear the terms "acid rain" ?

This is not a troll or a taunt. I'm just feeling a wee bit old and wondered if you were (much) younger than me.
Acid rains have been in the news since late 80's as I can recall and I learned about nitric and sulphuric acid production that way.
It was only much much later I understood how catalytic exhausts produced nitrogen and oxygen.
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[*] posted on 22-1-2019 at 05:36


Quote: Originally posted by Herr Haber  
Quote: Originally posted by ecos  

I found on wiki that NOx (NO and NO2) are soluble in water. :)


Interesting, when did you first hear the terms "acid rain" ?

This is not a troll or a taunt. I'm just feeling a wee bit old and wondered if you were (much) younger than me.
Acid rains have been in the news since late 80's as I can recall and I learned about nitric and sulphuric acid production that way.
It was only much much later I understood how catalytic exhausts produced nitrogen and oxygen.


I was thinking about other solutions that catalytic converter.
I read an article that catalytic converter produce sometimes ammonia gas not just N or O.

if water can reduce the NO a little bit then car makers can use it as next step combined with the expensive catalytic converter.

hmmmm...

I think ammonia gas is more soluble in water than NOx :)
if the exhaust NOx can be formed to NH3 then passed to water ... wouldn't that be better?!
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[*] posted on 22-1-2019 at 07:01


Quote: Originally posted by ecos  
Quote: Originally posted by Herr Haber  
Quote: Originally posted by ecos  

I found on wiki that NOx (NO and NO2) are soluble in water. :)


Interesting, when did you first hear the terms "acid rain" ?

This is not a troll or a taunt. I'm just feeling a wee bit old and wondered if you were (much) younger than me.
Acid rains have been in the news since late 80's as I can recall and I learned about nitric and sulphuric acid production that way.
It was only much much later I understood how catalytic exhausts produced nitrogen and oxygen.


I was thinking about other solutions that catalytic converter.
I read an article that catalytic converter produce sometimes ammonia gas not just N or O.

if water can reduce the NO a little bit then car makers can use it as next step combined with the expensive catalytic converter.

hmmmm...

I think ammonia gas is more soluble in water than NOx :)
if the exhaust NOx can be formed to NH3 then passed to water ... wouldn't that be better?!


again, it seems that you are not reading, all that "pass through water" stuff is not feasible, end of story.
as J_Sum1 said, exhaust gases are hot, most of the energy produced in a combustion engine goes to heating the exhaust gases, if you want to bubble ANY of the gases through water you are INEVITABLY going to heat it lowering the solubility. but wait, we just need to cool the water right? the car already has a radiator, so to sell some really dilute ammonia or nitric acid (or ammonium nitrate) solution we just need to install to every car a separate acid resistant tank to contain the water, multiple absorbtion towers and catalytic converters to transform that little NOx produced in "usefull" ammonia or nitric acid, then we need a huge radiator possibly with active cooling because we like our water cold, and we need to consider the efficiency loss of the engine given the exhaust gases high back pressure and the ton of weight the car now has to travel with. an upgrade of just a few thousand dollars, but hey you'll be able to sell 10 liters of dirty and really diluted ammonium nitrate solution for maybe a few cents every 1000 miles, THAT'S A STEAL DEAL

[Edited on 22-1-2019 by Ubya]





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[*] posted on 22-1-2019 at 10:15


Quote: Originally posted by AJKOER  
Better idea, prepare Mg(NO3)2 from mixing aqueous MgSO4 (Epsom Salt) and KNO3 (stump remover) and freeze out the K2SO4 hydrate. I have done this previously as adding aqueous ammonia leads to aqueous NH4NO3 and a suspension of Mg(OH)2.

Then, for HNO3 without acid per Wikipedia (https://en.wikipedia.org/wiki/Magnesium_nitrate) to quote:

"Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt, but rather its decomposition into magnesium oxide, oxygen, and nitrogen oxides:

2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2.

The absorption of these nitrogen oxides in water is one possible route to synthesize nitric acid. Although inefficient, this method does not require the use of any strong acid."

Interestingly, per Wiki magnesium nitrate is moderately soluble in ethanol, so also one could dissolve some in ethanol, set on fire, and collect the NO2 rich fumes. Note, it may be a bit too energetic if there is no water in the the ethanol!

[Edited on 21-1-2019 by AJKOER]


This is one of AJOEKER's more coherent and sensible posts if you omit the ethanol part. At least I see the connection with the diesel/NO2/water story. The crystallization of potassium sulfate works and magnesium nitrate is boiled down to decomposition (330 degrees) to generate NO2 and O2, bubbled through stirred water and you even get some extra NO2 from the NO and oxygen. Aka nitric acid. Diluted and inefficient but it works, at least better than leading exhaust gasses through water.

Potassium sulfate contamination shouldn't even be a problem, just get most of it out to keep volumes down. Just start leading the gasses through water as soon a it turns brown.

[Edited on 22-1-2019 by Tsjerk]
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