Abstract
The effect of the chemical composition of the hydrotreated light cycle oil (HDT LCO) on the benzene, toluene, ethylbenzene, and xylene (BTEX) production by a hydrocracking (HCK) procedure, is presented. Six different types of HDT LCOs were obtained by submitting two types of LCOs to hydrotreating (HDT) with different catalysts and experimental conditions. The products were analyzed as mono-, di- and tri-aromatic compounds using the supercritical fluid chromatography (SFC) method (ASTM D5186). The HDT LCOs were subjected to HCK with a 50/50 in weight mixture of nickel-molybdenum on alumina (NiMo/Al2O3) and H-ZSM5 (NiMo/H-ZSM5, 50/50) at 375 °C, 7.5 MPa, 1.2 h−1, and 750 m3/m3 H2/Oil. The HCK products were analyzed by gas chromatography with a flame ionization detector (GC-FID) and divided into five groups: gas, light hydrocarbons (LHCs), BTEX, middle hydrocarbons (MHCs), and heavy hydrocarbons (HHCs).The results showed that the BTEX formation ranged from 27.0 to 29.8 wt.% and it did not show a significant dependence on the mono-aromatic (59.9 and 75.6 wt.%), total aromatic (61.1–84.2 wt.%) contents or MHCs conversion (58.3–64.3 wt.%) from the departing HDT LCO feedstock. This result implies that, contrary to previous expectations, the BTEX formation does not directly depend on the amounts of total or mono-aromatic compounds when departing from real feedstocks. A GC-PIONA (paraffin, isoparaffin, olefin, naphthene, aromatic) characterization method (ASTM D6623) for mechanism understanding purpose was also carried out.
Highlights
The present work is the continuation of the studies on benzene, toluene, and xylene (BTX) production from light cycle oil (LCO) [1,2,3,4]
LCO has lost market as a part of diesel feedstock because of its inherent low quality [5,6,7], which makes the resulting fuel, usually as part of diesel, difficult to comply with strict environmental regulations around the world [8, 9]
According to the context described above, the main objective of this work is to study the effect of the chemical composition, in terms of total and mono-aromatic contents or composition of middle hydrocarbons (MHCs) in six different hydrotreated light cycle oil (HDT LCO) samples, on the benzene, toluene, ethylbenzene, and xylene (BTEX) yield
Summary
The present work is the continuation of the studies on benzene, toluene, and xylene (BTX) production from light cycle oil (LCO) [1,2,3,4]. The chemical nature of LCO is being highly aromatic. LCO from Mexican refineries contains up to 90 wt.% of mono-, di-, and tri-aromatic compounds (Fig. 1) [7]. Most of the aromatic compounds are di-aromatic-type hydrocarbons, i.e., naphthalene derivatives (Fig. 1). Among the alternatives for LCO upgrading is the BTX production after successive hydrotreating (HDT) and hydrocracking (HCK) procedures (Fig. 2) [1, 2, 10]. Laredo et al [2] presented
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