The Collaborative International Dictionary of English v.0.48:

Immaterialize \Im`ma*te"ri*al*ize\, v. t. [Cf. F.
   immat['e]rialiser.]
   To render immaterial or incorporeal.
   [1913 Webster]

         Immateralized spirits.                   --Glanvill.
   [1913 Webster]

WordNet (r) 3.0 (2006):

immaterialize
    v 1: render immaterial or incorporeal [syn: immaterialize,
         immaterialise, unsubstantialize, unsubstantialise]