Anhydrous ethylene glycol is not avaliable commercially and therefore is not easy to obtain.
Urea can undergo a decomposition reaction to produce NH3 + biuret + cyanuric acid near it's melting point of 132 oC. And urea is hyrated. Eg. urea.2H2O
The advantage of this method is that there's no water produced, as in the standard ammonium salt neutralization
(NH4)2SO4 + Ca(OH)2 =Heat=> 2 NH3 + CaSO4 + 2H2O
The 2 NH3 is passed through a drying agent to ensure completely anhydrous.