I am sure that just about all of the compressors can operate an impact wrench - its just a question of for how long.
When looking at 120 volt air compressors, check more than the tank size and SCFM ratings. Have a look at the motor. One of the ways that vendors achieve high SCFM values is with high speed motors direct driving a compressor. High compressor speeds make for better SCFM ratings and for an equivalent SCFM rating, a lighter compressor; however, they also make for shorter compressor life.
The larger 120v / 240 v dual voltage rating compressors equipped with belt drive separate two cylinder compressors are probably pretty durable. However, being 120v the largest induction motor that can be used utilized on a common 15 amp branch circuit is about 1.5 hp. If you look at the specs on these compressors the SCFM of the compressor are typically a nudge above 5 SCFM at 90 psi. 1/2" drive impact wrenches run 5 - 8 SCFM @ 90 psi; however, those ratings are a bit screwy because they appear to be based upon a 25% duty cycle (15 seconds of operation per minute) - somebody missed the cubic feet per minute in SCFM. In recognition of this, the application guides say pick a compressor with an SCFM rating at least 125- 150% of your tool. On that basis the best 120 v compressors are probably at the bottom of the SCFM rating for typical 1/2 wrenches. Larger tanks can help - a bit. A tank fully charged to 140 psi will permit some continuous operation of the tool before the tank pressure drops to the cut-in pressure. At that point, if you continue to run your wrench and your wrench SCFM is equal to or greater than compressor SCFM rating, the tank pressure will continue to decay and the wrench performance will go in the toilet. So, once the compressor kicks in on a smallish compressor you generally have to sit and let the compressor recover. If the whole point of using an air tool was to speed things up, this kind of scenario probably makes a 1/2" breaker bar faster! Also, remember that when examining the SCFM ratings, the wrench is looking at the psi rating at its entrance and the compressor is rated at the discharge from the port on the compressor head (not downstream of the regulator). 90 psi at the compressor head will not give you 90 psi at the tool (if the regulator has tank and outlet and pressure gauges, watch the outlet pressure drop when you operate the tool) which is another reason why you need that 150% margin between the compressor and tool SCFM ratings.
I have a 240 volt, 2 cyl, 3 hp (I think) 60 gal compressor with a rating of 12.5 SCFM @ 100 psi with a peak tank pressure of either 140 or 150 psi. Its probably the realistic minimum that I would consider for regular operation of a 1/2" impact wrench. Doing the winter / summer tire change thing, I can get one wheel on and off and a second mostly off before the compressor is in to cycling. If it were not for the fact that I need the compressor to top up the tires after they have been in storage, the impact wrench does not really speed things up a huge amount compared to using a breaker bar, particularly since I always do the final tightening with a torque wrench.
The final consideration is that if you go to the max 1.5 hp motor size on a 120 volt 15 amp branch circuit, that needs to be a dedicated branch circuit for the compressor. If you plug your 1.5 hp air compressor into a wall outlet that also happens to be on the same circuit supplying the lights and other outlets in the garage, I can pretty much guarantee you that you are going to be tripping the branch circuit breaker PDQ.
Edit
Just noted your point about axle nuts and I assume 'crank' nuts. You are not doing those with a 1/2 " impact. Up the SCFMs significantly for a 1" impact driver!
