Holding up a 40psf live load on the 2nd floor, plus say a 10lb dead load, plus the roof over the second floor at say 40psf, yields a total of 90psf. At 46', you'd be picking up 23' per lf with a single beam down the center, or 2,070 lbs per lf on the beam. The biggest challenge is going to be keeping the deflection to a reasonable amount- at 32', L/360 deflection allow the floor to bounce over an inch, so I'd suggest getting down to L/720, which would be closer to 1/2".
The smallest beam that span tables even show for a 32' span is a W14x53, which is going to give you a beam weighing over 3,000lbs. You really need to get a structural engineer to look at this.