It is NOT advisable. I asked the same thing and got this from Marco at Aguilar:
Thank you for using the Filter Twin & the Octamizer.
There would be no advantage here – they are 9V pedals. Using an improper power supply could cause damage to the pedals.
Please let me know if I can assist further.
Fuzzrocious Club #194
Brubaker Brute Squad #18
Spector Club #224 (USA NS-5MM, NS-2J)