EFFECTS OF VAPOR-LIQUID-EQUILIBRIA ON COKE DEPOSITION IN TRICKLE-BED REACTORS DURING HEAVY OIL PROCESSING .1. EXPERIMENTAL RESULTS

The deposition of coke onto catalysts during the conversion of heavy v acuum gas oil has been investigated in a trickle-bed reactor at elevat ed temperatures (ca. 450-degrees-C) and moderate hydrogen pressures (3 0 bar). It is argued that coke is formed via two parallel routes, viz. ,(i) thermal condensation reactions of aromatic moieties and (ii) cata lytic dehydrogenation reactions. The amount of coke deposited onto the catalyst shows a distinct maximum as a function of both temperature a nd hydrogen/oil ratio. These maxima are induced by the vapor-liquid eq uilibria in the reactor. A qualitative description involving the conce ntration of heavy coke precursors present in the oil phase is given.