Light Cycle Oil Upgrading to Benzene, Toluene, and Xylenes by Hydrocracking: Studies Using Model Mixtures

Reactivity of Sulfur and Nitrogen Compounds of FCC Light Cycle Oil in Hydrotreating over CoMoS and NiMoS Catalysts

NiMoS and CoMoS catalysts were synthesized and applied to hydrotreating (HDT) of FCC light cycle oils (FCC-LCO) in an autoclave batch reactor at 613 K and 8.6 MPa H2. The S and N compounds in LCO were classified into four and three groups, respectively, in terms of the HDT reactivity. The individual and the competitive reactivities of the S and N compounds in the HDS and the HDN were investigated over the conventional CoMoS and NiMoS catalysts using S and N model compounds (dibenzothiophene, DBT, and carbazole, CBZ). In the HDS of DBT, both the direct desulfurization (DDS) and pre-hydrogenation pathway (HYD) were found to proceed, whereas the HYD pathway was favored for the HDN of CBZ. As a result, the NiMoS catalyst that facilitates the HYD pathway showed better activity in the HDN of LCO than the CoMoS (k = 10.20 × 10−2 vs. 1.80 × 10−2 h−1). Indeed, the HDS of LCO over the NiMoS was more favorable than that over the CoMoS catalyst (k = 4.3 × 10−1 vs. 3.6 × 10−1 h−1).

The Effect of Y Zeolites with Different Pores on Tetralin Hydrocracking for the Production of High-Value Benzene, Toluene, Ethylbenzene and Xylene Products

A series of Y zeolites with different pore properties was prepared as a support for hydrocracking catalysts for the production of BTEX (benzene, toluene, ethyl-benzene, and xylene) from tetralin. Some important characterizations, including N2 adsorption–desorption, NH3-TPD, Py-IR, and HRTEM, were applied to obtain the properties of different catalysts. Meanwhile, the tetralin hydrocracking performances of those catalysts were investigated on a high-pressure fixed-bed microreactor. The results showed that Si/Al ratio is the core property of zeolites and that the increase in the Vmicro/Vmeso of zeolites could facilitate the formation of BTEX products by hydrocracking tetralin. The method of hydrocracking tetralin was proposed. It was also found that the hydrogenation–cracking path was controlled by aromatic saturation thermodynamics, and strong acidity aided the backward shift of equilibrium temperature.

Effect of the chemical composition of six hydrotreated light cycle oils for benzene, toluene, ethylbenzene, and xylene production by a hydrocracking process

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.

Selective hydrogenation of light cycle oil for BTX and gasoline production purposes

The study of the best experimental conditions and catalyst for the hydrogenation (HYD) of light cycle oil (LCO) for upgrading purposes was carried out. The objective was to examine the ability of two commercial hydrotreatment (HDT) catalysts for selective aromatic saturation. The effect of the hydrotreatment operation parameters (temperature, pressure, liquid hourly space velocity, H2/HC ratio) on the sulfur and nitrogen contents and in the saturation of aromatic hydrocarbons was also investigated. The goal was to obtain the highest conversion to mono-aromatic hydrocarbons from this di-aromatic (naphthalene derivatives) type feedstock, and at the same time to get reasonable hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) performance to avoid contaminant hydrocarbons for the next step (usually hydrocracking, HCK). An appropriate hydrotreated product with the highest concentration of mono-aromatic derivatives, a minimum reduction on the total aromatic content, and suitable decrements of sulfur and nitrogen compounds, was achieved using a cobalt-molybdenum supported on alumina catalyst, at 330 °C, 5.5 MPa, and a liquid hourly space velocity of 1.1 h−1. Additionally, the kinetics of the HDA was studied, assuming a lump characterization into tri-, di- and mono-aromatic and aliphatic hydrocarbons, pseudo-first-order reaction rates between these conversions, and thermal losses and diffusional resistances to be undetectable.

Waste Refinery: The Valorization of Waste Plastics and End-of-Life Tires in Refinery Units. A Review

This review collects a wide range of initiatives and results that expose the potential of the refineries to be converted into waste refineries. Thus, they will use their current units for the valorization of consumer society wastes (waste plastics and end-of-life tires in particular) that are manufactured with petroleum derivatives. The capacity, technological development, and versatility of fluid catalytic cracking (FCC) and hydroprocessing units make them appropriate for achieving this goal. Polyolefinic plastics (polyethylene and polypropylene), the waxes obtained in their fast pyrolysis, and the tire pyrolysis oils can be cofed together with the current streams of the industrial units. Conventional refineries have the opportunity of operating as waste refineries cofeeding these alternative feeds and tailoring the properties of the fuels and raw materials produced to be adapted to commercial requirements within the oil economy frame. This strategy will contribute in a centralized and rational way to the recycling of the consumer society wastes on a large scale. Furthermore, the use of already existing and, especially, depreciated units for the production of fuels and raw materials (such as light olefins and aromatics) promotes the economy of the recycling process.

Effect of the catalyst in the BTX production by hydrocracking of light cycle oil

Catalysts to produce the important petrochemicals like benzene, toluene, and xylene (BTX) from refinery feedstocks, like light cycle oil (LCO) are reviewed here by covering published papers using model mixtures and real feeds. Model compounds experiments like tetralin and naphthalene derivatives provided a 53–55% total BTX yield. Higher yields were never attained due to the inevitable gas formation and other C9+-alkylbenzenes formed. For tetralin, the best catalysts are those conformed by Ni, CoMo, NiMo, or NiSn over zeolite H-Beta. For naphthalene derivatives, the best catalysts were those conformed by W and NiW over zeolite H-Beta silylated. Real feeds produced a total BTX yield of up to 35% at the best experimental conditions. Higher yields were never reached due to the presence of other types of hydrocarbons in the feed which can compete for the catalytic sites. The best catalysts were those conformed by Mo, CoMo, or NiMo over zeolite H-Beta. Some improvements were obtained by adding ZSM-5 to the support or in mixtures with other catalysts.

In Situ Generated Nanosized Sulfide Ni-W Catalysts Based on Zeolite for the Hydrocracking of the Pyrolysis Fuel Oil into the BTX Fraction

The hydrocracking reaction of a pyrolysis fuel oil fraction using in situ generated nano-sized NiWS-sulfide catalysts is studied. The obtained catalysts were defined using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The features of catalytically active phase generation, as well as its structure and morphology were considered. The catalytic reactivity of in situ generated catalysts was evaluated using the hydrocracking reaction of pyrolysis fuel oil to obtain a light fraction to be used as a feedstock for benzene, toluene, and xylene (BTX) production. It was demonstrated that the temperature of 380 °C, pressure of 5 MPa, and catalyst-to-feedstock ratio of 4% provide for a target fraction (IPB −180 °C) yield of 44 wt %, and the BTX yield of reaching 15 wt %.

Effect of the experimental conditions on BTX formation from hydrotreated light cycle oil

The study of a light cycle oil (LCO) upgrading alternative involving hydrotreating and hydrocracking/transalkylation procedures for obtaining a benzene, toluene and xylene (BTX) enriched fraction is presented. The research work was focused on the effect of the experimental conditions on the hydrocracking of an hydrotreated light cycle oil (HDT LCO) in order to produce the highest amounts of BTX, when the catalysts consisted of a mixture (50/50 in weight) of nickel–molybdenum on alumina (NiMo/Al2O3) and ZSM-5 materials (NiMo/ZSM-5 (50)). It was found that 7.4 MPa, up to 375 °C, LHSV of 1.2 h−1 and a H2/Oil value of 442 m3/m3 were the optimal experimental conditions for producing an enriched BTX fraction (31%). In order to facilitate the analysis, the study was carried out considering four types of hydrocarbons as lumps for the feed and HCK products: light hydrocarbons (LHC) composed by C4–C7 non-aromatic compounds, BTX, middle hydrocarbons (MHC) consisting of C7–C10 paraffins and isoparaffins, alkylbenzenes, tetralin and naphthalene derivatives and a small amount of high molecular weight hydrocarbons (HHC). Based on this description, HDT LCO used as feedstock for the hydrocracking (HCK) procedure, presents a 99% of a MHC fraction. The HCK conversion, BTX selectivity and yields were obtained from the chromatographic analysis of the products. A simple kinetic model considering only the MHC conversion was carried out. The obtained activation energy confirmed the endothermic nature of the HCK process. The activity decay of the catalytic mixture was also studied by varying the time on stream.

Bridging the gap between academic and industrial hydrocracking: on catalyst and operating conditions' effects

This work aims at bridging the knowledge gap between the well-studied Pt/zeolite catalysts and the industrially-employed NiMoS/(Al₂O₃ + zeolite) ones.

Mechanism of tetralin conversion on zeolites for the production of benzene derivatives

The influences of acidity and textural properties of the zeolites on the activity and selectivity were revealed in tetralin conversion.

Effect of the catalytic system and operating conditions on BTX formation using tetralin as a model molecule

Light cycle oil (LCO) is an inexpensive feedstock for the production of high-added-commercial-value-mono-aromatic compounds such as benzene, toluene and xylenes (BTX). To extend the knowledge on the processing of LCO for BTX production, the hydrocracking reaction was studied using a commercial NiMo/Al2O3 catalyst, ZSM-5 zeolite and their mechanical mixtures (20/80, 30/70 and 50/50) for processing tetralin as model feedstock in a bench-scale-trickle-bed reactor at 450–500 °C, 3.9–5.9 MPa, 1.3 1/h and H2/feed volume ratio of 168–267 m3/m3. Accessible, well-dispersed and strong Brönsted acid sites eased the hydrocracking of tetralin to BTX and the metallic hydrogenation functions from nickel–molybdenum catalysts were also required to minimize deactivation. To achieve suitable tetralin conversions (86–95 wt%), high BTX selectivity in the liquid phase (44–70 wt%) and suitable catalytic activities for coke precursor hydrogenation (to reduce deactivation), NiMo/Al2O3//ZSM-5 mixtures (50–80 ZSM-5) were employed, which probed to be effective.