Abstract. Oxygenates are becoming vital petrochemicals for high octane blending stocks in the 1990s gasoline era. Feedstocks for oxygenates are needed by the refiners worldwide. Catalytic cracking of VGO and/or heavier feeds, using special catalysts and novel technologies, can maximize the yield of light olefins to an extent which doubles or triples that of conventional FCC. Two processes were commercialized in China, namely DCC and MGG. Another new process, MIO, is under pilot scale study.
DCC converts HVGO to about 50 wt% (on FF, the same below) gaseous products, in which CT 13-23 wt%, Ci 10-17 wt%, depending on feed character. By changing operating mode and catalyst, the yield of ici +iCg can be over 12 wt%, in which iCi/Ci - 0.42, iCt/Ct - 0.69.
MGG process is aimed at producing Maximum liquefied Gas plus Gasoline from VGO or VGO + VR. The yield of LPG reaches 23-35 wt%, in which Cg is 7–11 wt%, Ch is 7.6–13 wt%, and naphtha 42-46 wt% (RON 92-95, MON 80-83) depending on feed and operating mode. The catalyst is so selective that dry gas + coke yield is only about 10 wt% at conversion 85 wt%. MIO (Maximum Iso-Olefins) can yield ici + iCg over 13 wt%. Catalysts play vital roles in these processes. Novel catalytic materials were employed in the catalyst formulation.
To blend oxygenates in gasoline is becoming a general trend in the 1990's gasoline market. Clean Air Act Amendment of United States mandates an oxygen content and requires lower Rvp, aromatics, Sulfur and VOC etc. in gasoline. Other developed countries too are using oxygenates as substitutes of TEL. The demand of oxygenates in the market is, therefore, increasing rapidly. The key raw materials for oxygenates are propylene, butylene, isoamylenes.
A process that can economically produce more such light olefins is anxiously being pursued by the refiners. Catalytic cracking of VGO and/or heavier feeds, using a special catalyst and novel technologies, can maximize the yield of light olefins to the extent which doubles or triples that of conventional FCC. Two processes were commercialized in China in recent years, and other one is under development. Promising results were obtained. The process scheme is similar to that of FCC, i.e. atmospheric pressure reaction and self heat balance. It consists of a reactionregeneration zone and a fractionation zone. The reactor could be a riser plus a fluidized dense bed or just a riser, depending on operating mode and catalyst employed. DCC-I is for maximum propylene DCC Process' production, while DCC-II is for maximizing butylene and amylene. Table I shows the test result of various feedstocks in a 2 b/d pilot unit operated with DCC-I mode. It is seen from Table I, for highly paraffnic feedstocks