you can use it. but the polymerize precursor will be not in desired quantity.

Emaraldine polyaniline is distinctively coloured polymer. The coloured (Orange) oxidizing agents (Ammonium dichromate) may have the potency of altering the colour of polyaniline. On the other hands Ammonium dichromate also has the tendency to react violently with a reducing agent. Apart from above mentioned practical problems, Ammonium Dichromate has the ability to oxidize polymerization of aniline to form polyaniline.

http://ac.els-cdn.com/S0030402611007601/1-s2.0-S0030402611007601-main.pdf?_tid=3c865280-6c6a-11e7-80d0-00000aab0f6c&acdnat=1500459099_4720544c60d1b65d2b105945adbf50ed

This is one of the reference where K2Cr2O7 is used as an oxidizer to synthesize Polyaniline. 

Hope this may help.

YOU CAN USE IT, BUT THE PROCESS OF POLYMERIZATION WILL BE VERY VERY SLOW. Yield of polymerize sample will also be very less