The number of binary post-AGB stars known in the Galaxy is significant, yet their evolutionary, status is far from understood. Evidence is growing that all these evolved binaries are surrounded by circumbinary Keplerian dusty disks. We present the first results of our 2D-SED-modeling and detailed study of the mineralogy using Spitzer-IRS and TIMMI2 spectra. Our analyses show that the spectra indicate a very high degree of processing of the dust grains, both with respect to grain size and crystallinity. Whether this processing is the result of the long storage time in the disk and/or due to a special thermal history at formation is not yet clear.