Can you put a 15 amp rated receptacle on a 20 amp circuit?

Answer:

Yes,  if it is duplex type receptacle.

               Duplex Receptacle Single Receptacle

210.21 Outlet Devices

(B) Receptacles.

(3) Receptacle Ratings.

Where connected to a branch circuit supplying two or more receptacles or outlets, receptacle ratings shall conform to the values listed in Table 210.21(B)(3), or, where rated higher than 50 amperes, the receptacle rating shall not be less than the branch-circuit rating.

If it was a single receptacle then it would have to be rated not less than the circuit supplying it.

210.21 (B)(1) Single Receptacle on an Individual Branch Circuit.