Hydrodesulfurization Of Light Cycle Oil Research Articles

Influence of arsenic on light cycle oil hydrodesulfurization over a CoMo catalyst

Samples of a commercial hydrotreating catalyst with different initial arsenic content were used in the study light cycle oil (LCO) feed in a hydrotreating unit operating at high pressure (350 °C, 3 MPa) to evaluate the conversion and selectivity of the catalyst in the presence of arsenic. It was determined that arsenic in the catalyst modifies the textural properties and has the strongest influence on the conversion of the HDS reaction. For the first time, evidence is provided that the arsenic replaces cobalt in CoMoS phase. The incorporation of As is proposed to occur in “edge” sites of the molybdenum sulfide disfavoring the C–S cleavage during the HDS reaction, while hydrogenation sites would be favored.

Kinetic Features of Light Cycle Oil Hydrodesulfurization Reactions in the Presence of a Co6–PMO12(S)/Al2O3 Catalyst

The group kinetics of reactions of organic sulfur compounds present in light cycle oil (LCO) in the hydrotreating process over a Co6–PMo12(S)/Al2O3 sulfide catalyst based on phosphomolybdic heteropoly acid as a function of hydrogen pressure (4, 5, and 6 MPa) at varying temperature (300–360°C in 20°C increments) and space velocities of 0.5, 1.0, and 3.0 h–1 has been studied. Total sulfur content in the feedstock and the hydrogenation products has been determined. The obtained data on the kinetics of hydrodesulfurization (HDS) reactions can be used to select optimum modes of the LCO hydrotreating process. Using the coefficient of determination and Fisher’s ratio test values, the adequacy of the pseudo-first-order and 1.5-order kinetic models and the Langmuir–Hinshelwood model has been determined. A kinetic model describing the hydrodesulfurization of LCO by hydrotreating in the presence of the Co6–PMo12(S)/Al2O3 catalyst has been selected, and the kinetic characteristics of the HDS of the compounds constituting LCO have been determined.

Effects of Nitrogen and Aromatics on Hydrodesulfurization of Light Cycle Oil Predicted by a System Dynamics Model

The production of ultralow-sulfur diesel from light cycle oil (LCO) by hydrotreatment is promising. Unfortunately, hydrodesulfurization (HDS) of LCO is seriously inhibited by the coexistence of organic nitrogen and aromatic compounds during the hydrotreating process. It is of great interest to understand this inhibition confidently by simulations. In this study, the inhibition effects from both organonitrogen and aromatic compounds are simulated by a proposed system dynamics (SD) model for the first time. The axial profiles of the concentrations of organic sulfur, nitrogen, and aromatics in the hydrotreating reactor are predicted by the SD model. Impact factors for nitrogen and aromatic compounds respectively are used to characterize their inhibition effects. Studies were also conducted on the variation of the impact factors along the axial position of the hydrotreator. The simulation results of HDS, with consideration of the nitrogen and aromatic inhibition effects, are compared with published experimental data. The influence of the operating conditions such as inlet system temperature and liquid hourly space velocity on the impact factors is also investigated.

Kinetic modeling of the hydrotreatment of light cycle oil and heavy gas oil using the structural contributions approach

The kinetics of the hydrodesulfurization of light cycle oil (LCO) and heavy gas oil (HGO) over a CoMo/Al 2O 3 catalyst were investigated in a perfectly mixed flow reactor with stationary basket of the Robinson-Mahoney type at temperatures of 330, 310 and 290 °C, H 2/HC molar ratios of 2.8, 3.6 and 7.2 and a pressure of 65 bar. Hougen-Watson type rate equations were derived for the conversion of dibenzothiophene, substituted (di)benzothiophene and their products. To avoid having to deal with a huge number of model parameters, a methodology based upon structural contributions was applied. In the absence of own kinetic data on key components a number of kinetic and adsorption parameters were taken from published work on a very similar catalyst. For a given value of H 2/HC only a small number of experiments was required to determine the value of the very complex denominators DEN σ and DEN τ appearing in the rate equations for the hydrodesulfurization of LCO and of HGO and of their evolution with the conversion of the feedstock. With the rate equations constructed in this way the calculated total conversion of DBT, its conversion into biphenyl and into cyclohexylbenzene were in excellent agreement with the experimental values.

Selective hydrodesulfurization of light cycle oil over high porous TiO2 supported catalysts

Selective hydrodesulfurization of light cycle oil over high porous TiO2 supported catalysts

An approach to the deep hydrodesulfurization of light cycle oil

Deep HDS of LCO to be <10ppm was achieved by fractionating HDS. An LCO fraction having boiling point lower than 340°C was easily hydrodesulfurized to be <10ppmS under conventional HDS conditions because the hydrodesulfurization of the reactive sulfur species contained in the fraction was hardly inhibited by the aromatic compounds. In contrast, the heavier fraction was very hard to be hydrodesulfurized since its refractory sulfur species were strongly inhibited by large content of aromatic components. Dilution of the heavier fraction with common solvents showed higher reactivity over NiMo/Al2O3 catalyst than itself alone. Decalin, which showed the highest dilution effect, was believed to strip the strongly adsorbed aromatics off from the catalyst surface.

MCM-41-supported Co-Mo catalysts for deep hydrodesulfurization of light cycle oil

Light cycle oil (LCO), a by-product of the fluid catalytic cracking (FCC) process in a petroleum refinery, can be used as a blendstock for the production of diesel and jet fuels. Regulatory and operational issues result in need for new and more active catalysts for the deep hydrodesulfurization (HDS) of diesel feedstocks, such as LCO. This paper reports the activity of a mesoporous molecular sieve MCM-41-supported Co-Mo catalyst in comparison to a commercial γ-alumina (Al 2O 3)-supported Co-Mo catalyst for the desulfurization of a LCO with a sulfur content of 2.19 wt.%. The HDS of dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene—polyaromatic sulfur compounds present in LCO—and their relative reactivities in terms of conversion were examined as a function of time on stream in a fixed-bed flow reactor. The MCM-41-supported catalyst demonstrates consistently higher activity for the HDS of the refractory dibenzothiophenic sulfur compounds, particularly 4,6-dimethyldibenzothiophene. The presence of a large concentration of aromatics in LCO appears to inhibit the HDS of the substituted dibenzothiophenes.