Nitrocellulose (flash paper) synthesis without Sulfuric Acid?

Question

According to the Wikipedia page on Nitrocellulose:

The process uses nitric acid to convert cellulose into cellulose nitrate and water:
$$\ce{3HNO3 + C6H10O5 ->[H2SO4] C6H7(NO2)3O5 + 3H2O}$$ The sulfuric acid is present as a catalyst to produce the nitronium ion, $\ce{NO2+}$. The reaction is first order and proceeds by electrophilic substitution at the C−OH centers of the cellulose.^[8]

Since I have been on quarantine, I have lost access to the lab and therefore must carry out reactions from the comforts of my home. I have some sulfuric acid drain cleaner that is sufficient for many at-home applications. However, it consists of only about 93% $\ce{H2SO4}$, and contains a lot of dark dyes. I am trying to synthesize nitrocellulose paper from letter printer paper and envelopes, for the purpose of developing a self-destructing letter that burns away when the letter is returned to the envelope after being removed. However, the dyes in the sulfuric acid severely discolor the paper, and make it stand out considerably in a pile of mail, defeating the purpose of secrecy. So, at least until the quarantine is lifted, I may need an alternative catalyst to Sulfuric acid to synthesize the nitronium ions in vitro. Does anyone have an alternative to $\ce{H2SO4}$, or a way to eliminate the dyes without distillation? (because I broke my condenser column, and can't use the lab's)

Update: I'm still curious about my question, but it might not even be legal to send nitrocellulose envelopes through the mail. One spark and you could end up with flaming mail processing machines. Yikes!

Answer 1

I do not think it will be possible to form nitrate esters of cellulose without sulfuric acid present, I am sure that you need the strong bronsted acid to make the reaction work. But I think that there is another issue here, your safety / health / the law on energetic materials.

I hate to have to say this, but I do not think it is safe to make energetic materials using nitric acid at home. You should also consider for a moment the question of "is it legal" to make the energetic material at home.

Keep in mind years ago some "home chemists" would make explosives / fireworks and it was regarded as "boys will be boys". But nowadays the "boys in blue" (Police) are very keen to chase after people who make explosives / things which go bang etc.

I think that the distillation of sulfuric acid at home does not sound like a good idea, I think that you would need to work in a good fume hood. Most school labs would be unlikely to have the equipment required to do it.

With all due respect I think you should choose another chemical project to pass the time while you are on "lockdown".

Answer 2

An interesting photolysis experiment, to be performed in small amounts only, as you may actually produce a higher yield of an energetic than you expect with available reagents.

Dissolve KNO3 in dilute H2O2 (or, just water as any released electrons via photolysis can also scavenge the nitrate radical) with a bit of B-12 Vitamin (or, try substituting a B-complex).

Soak cotton in the mix. Flatten out the treated cotton and place it at the center of a plastic bowl lined with aluminum foil.

Place in sunlight until the color vanishes (less than a couple of hours).

Let the treated cotton dry in the dark (no Al foil contact).

Test lite the product.

You may wish to compare the results to only KNO3 treated cotton.

Chemistry:

The B-12 photocatalyst produces electron holes (h+), which react with water creating hydroxyl radicals.

$\ce{H2O2 + h+ -> H+ + .OH }$

The latter reacts with NO3- to form the nitrate radical which may attack the cotton.

$\ce{NO3- + .OH -> .NO3 + OH- }$

Similarly, the H2O2 may be attacked by electrons also released from the photocatalyst. The one-electron reduction of the hydrogen peroxide can also produce the hydroxyl radical as follows:

$\ce{H2O2 + e- -> .OH + OH- }$

A not favored reaction resulting in associated loss of the nitrate radical:

$\ce{ .NO3 + e- -> NO3- }$

You may wish to test the results from several photolysis samples, some of which were repeatedly subject to the B-12/H2O2/KNO3 sunlight treatment.

Does anyone wish to know which is a more powerful nitrating agent in practice, strong nitric acid or the transient nitrate radical? It may be time to discover!

To assist, here is an interesting source, 'Nitrate radicals and biogenic volatile oxidation, mechanisms, and organic aerosol', to quote:

Abstract. Oxidation of biogenic volatile organic compounds (BVOC) by the nitrate radical (NO3) represents one of the important interactions between anthropogenic emissions related to combustion and natural emissions from the biosphere. This interaction has been recognized for more than 3 decades, during which time a large body of research has emerged from laboratory, field, and modeling studies.

Here is a mention of a non-photolysis creation path (but, my preference would be nitrate in a reaction mix of copper with HOCl in the presence of graphite):

The nitrate radical (NO3) arises from the oxidation of nitrogen dioxide (NO2) by ozone (O3) and occurs principally in the nighttime atmosphere due to its rapid photolysis in sunlight and its reaction with NO (Wayne et al., 1991; Brown and Stutz, 2012). The nitrate radical is a strong oxidant, reacting with a wide variety of volatile organic compounds, including alkenes, aromatics, and oxygenates as well as with reduced sulfur compounds. Reactions of NO3 are particularly rapid with unsaturated compounds (alkenes) (Atkinson and Arey, 2003).

A possible important implication of the above, in the current proposed experiment, is not to overdue the photolysis (assuming that it is, at all, successful, else investigate non-photolysis paths).