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!