Thermal and catalytic cracking of whole crude oils at high severity

Abstract

The catalytic and thermal cracking of three types of whole crude oils, having API gravity at 34° (AL), 39° (AXL) and 51° (ASL), were investigated via a fixed-bed micro-activity test (MAT) unit at high temperature between 600 and 650 °C. Equilibrium FCC catalyst (E-Cat)/ZSM-5 additive was used for catalytic cracking tests at 30 s and catalyst/oil (C/O) ratio of 2.0–6.0. For both thermal and catalytic cracking of all crude oils, the increase in reaction temperature resulted in higher conversion and enhanced yields of C2-C4 light olefins, LPG, coke, and dry gas at the expense of naphtha, heavy cycle oil (HCO), and light cycle oil (LCO). In thermal cracking, the yields of C2-C4 olefins at 650 °C were as follows: AL (22.8 wt.%) > AXL (19.0 wt.%) > ASL (18.8 wt.%) associated with naphtha yields of 34.4, 38.1 and 48.0 wt.%, respectively. Compared with thermal, catalytic cracking over E-Cat/ZSM-5 enhanced conversion, doubled the yields of light olefins and showed an increase in aromatics content of naphtha fraction. Contrary to thermal cracking, the yields of C2-C4 olefins in catalytic cracking were as follows: ASL (42.9 wt.%) > AXL (41 wt.%) > AL (39.1 wt.%) associated with naphtha yields of 31.7, 27.5, and 23.0 wt.%, respectively.