Cov pob zeb uas ntxeem tau kuj tseem hu ua lim cov pob. Nws yog tsim los ntawm kev ua 20-30% pores sab hauv cov pob zeb tsis muaj zog. Yog li nws tuaj yeem siv tsis tau tsuas yog txhawb nqa thiab npog lub catalyst, tab sis kuj tseem siv rau lim thiab tshem tawm cov khoom tsis huv ntawm cov nplej, gelatin, asphalting, hlau hnyav thiab hlau ions tsawg dua 25um. Yog tias pob ntxeem tau teeb nyob rau sab saum toj ntawm lub reactor, cov impurities tsis raug tshem tawm hauv cov txheej txheem yav dhau los tuaj yeem raug ntxig rau hauv lub qhov hws sab hauv cov khoom, muaj thaum tiv thaiv cov tshuaj tiv thaiv thiab ua kom lub sijhawm ua haujlwm ntawm lub cev. Raws li cov khoom tsis huv nyob hauv cov ntaub ntawv sib txawv, tus neeg siv tuaj yeem xaiv cov khoom los ntawm lawv qhov ntau thiab tsawg, qhov hws thiab porosity, lossis yog tias tsim nyog, ntxiv molybdenum, npib tsib xee thiab cobalt lossis lwm yam khoom xyaw kom tiv thaiv cov catalyst los ntawm coking lossis lom.