Citation V/Ultra/Encore (C560)
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 83; Flight Crew Total 10416; Flight Crew Type 1241
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Landed As Precaution
Aircraft
Enroute at FL310 approximately 35 minutes from [destination]; we heard a loud pop and the cabin pressurization rate of climb went to 4;000 fpm. A descent was requested from ATC; approved; and initiated.  EMERGENCY procedures were initiated and completed.  Aircraft diverted to [a nearby alternate] with the cabin altitude stabilized at approximately 13;000 feet until the descent was completed.
A CE-560 Captain reported diverting to a nearby alternate after experiencing loss of cabin pressure.