No salt was formed after gassing? What was the amine smell?
I wouldn't think that a Urushibara catalyst generated in situ would cleave nitro-compound.
Maybe there was just enough amine formed to stink, but not enough to crystalize. Or perhaps the filteration process to get rid of the Al2O3 and Ni was done crappy, so a lot of the product got left behind.
The Urushibara reduction of the oxime worked, but the nitro-reduction did not? That sounds weird.
I quote the text from the Rhodium page:
'"U-N-AA
U-N-AA is prepared by warming the precepitated nickel which is
deposited from nickel chloride solution by aluminium grains, with
acetic acid saturated with sodium chloride. It consists of aluminium
grains coated by nickel metal, as the nickel metal deposited on
aluminium grains does not separate from the latter, which remain
undisolved after acetic acid treatment owing to the mild reaction
between aluminium metal and acetic acid. As the aluminium grains which
support the the nickel metalact as a carrier, U-N-AA can most
conveniently be used for a vapor-phase reduction. It has been noted
that the use of U-N-AA is not confined to vapor-phase reduction; it is
also suitable for liquid-phase hydrogenation at room tempature and
atmosphere presure. This can be seen from the reduction of
nitrobenzene in EtOH in the presence of U-N-AA, gives aniline in 70%
yield."'
And the method of preparation that he uses should be more active... With the exception that the reduction is carried out in a basic medium! Maybe that's it.
Try the same reduction but add H2SO4 instead of the NaOH. Gas evolution will be less vigorous, but the reaction will be acid catalyzed. Maybe the formation of a NaOH-nitro complex is inhebiting the reduction. This complex wouldn't be formed with the oxime, therefore being consistant with the experimental outcome (the oxime is also more easily reduced, but let's ignore that for now)
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