asphalt (Britannica Concise):

Black or brown petroleum-like material that has a consistency varying from viscous liquid to glassy solid.

It is obtained either as a residue from the distillation of petroleum or from natural deposits. Asphalt consists of compounds of hydrogen and carbon with minor proportions of nitrogen, sulfur, and oxygen. It softens when heated and is elastic under certain conditions. Used principally in road surfacing, asphalt is also used for roofs, coatings, floor tilings, and waterproofing, and in industrial products.

de- prefix -- denoting removal

removal of hydrocarbon

--------------------------------------------------
Note added at 24 mins (2006-10-16 05:06:51 GMT)
--------------------------------------------------

Solvent deasphalting is a unique separation process in
which residue is separated by molecular weight (density),
instead of by boiling point, as in the vacuum distillation
process.

"Pelarut Bebas Residu" adalah juga bisa jadi option
Lihat:
http://www.uop.com/objects/29 Deasphalting.pdf

awaaspalan = menyingkirkan kandungan aspal

Bahasa yg digunakan :
Kamus Minyak dan Gas Bumi (Lemigas)

Ini terjemahan yang saya pikir belum dikenal. Pas untuk coba2 (experimentation); kali2 aja populer nanti.

luruh-aspal = unsur aspalnya luruh / gugur / luntur.

Pilihan sejenis:
- luruh-aspal akibat larut