Cov roj dawb yog ib hom nyias nyias ntawm tshuab xaws. Cov li ntawd -hu ua cov roj dawb feem ntau yog hais txog cov roj ntxhia dawb. Nws yog ib tug ntxhia roj uas tau tshwj xeeb refined. Cov roj dawb tsis muaj xim, tsis muaj ntxhiab, tshuaj lom neeg tsis muaj zog, thiab muaj lub teeb pom kev zoo.
Lub hauv paus muaj pes tsawg leeg yog saturated hydrocarbon qauv, thiab muaj ntxhiab hydrocarbons, nitrogen, oxygen, sulfur, thiab lwm yam tshuaj nyob ze rau xoom. Vim qhov no super refining qhov tob, nws yog ib qho nyuaj rau kev siv cov feem ntau hnyav nyob rau hauv cov txheej txheem tsim tiag, yog li qhov hnyav molecular ntawm cov roj dawb feem ntau nyob rau hauv thaj tsam ntawm 250-450. Nws muaj qhov zoo oxidation stability, tshuaj stability, lub teeb stability, tsis muaj xim, tsis muaj ntxhiab, thiab tsis corrode fiber ntau textiles.
