Does pressure in a compressed air system increase....

[rtservices]

does pressure in a compressed air system increase when going from a 2" air line to a 1" air line.

 

[Asymptotic]

No.
Consider this experiment. Suppose a pressure gauge labeled 'PSI1' were situated in a 6"pipe directly at the output of a 1485 CFM compressor operating at 100 PSI. A tee is added, and a 1/4" hose barb is coupled to 100 feet of 1/4" diameter air hose with another pressure gauge (labeled 'PSI2') and a graduated needle valve at the far end.

In your experience, with the valve closed, would the pressure at the far end of the hose be higher?

Under no-flow conditions both pressures should be identical.

Now, incrementally open the needle valve while tracking both PSI1 and PSI2 gauges, and plot the resulting pressures against needle valve position (orifice setting). You'll note while pressure at PSI1 drops, that the pressure reduction at PSI2 is far greater as the orifice is progressively made larger.

Except for the no-flow condition, pressure at the far end of the run will always be lower than at the source.
Reducing 2" to 1" will increase air velocity and pressure drop.

Look up "compressed air pipe sizing" and "compressed air distribution".