Molecular Characteristics of Light Cycle Oil Hydrodesulfurization over Silica–Alumina-Supported NiMo Catalysts

Abstract

A detailed understanding of the catalytic upgrading of light cycle oil (LCO) is important to achieve effective deep hydrodesulfurization (HDS) when LCO is mixed with straight run gas oil in the diesel pool. Herein, HDS of polyaromatic-rich LCO was studied at the molecular level over three NiMo catalysts on silica–alumina supports, which were synthesized on the pilot scale using different silica/alumina mixing procedures. Gas chromatography with atomic emission detection and two-dimensional gas chromatography with time-of-flight mass spectrometry were used to evaluate the HDS performance through determining the feed and product compositions, respectively, at the molecular level. Furthermore, the textural properties of the catalysts were evaluated using Raman spectroscopy, transmission electron microscopy, and the temperature-programmed desorption of NH3. The performance of the best catalyst was attributed to its higher content of octahedrally coordinated Mo oxide species, a lower number of layered stacks, and the more acidic sites on the surface. In addition, the hydrotreating reactivity of various family groups in LCO over the catalyst was investigated.

Comparative Study of Light Cycle Oil and Naphthalene as an Adequate Additive to Improve the Stability of Marine Fuels

“…This concentrated the naphthalene from the initial 0.62 rel % (according to the GC × GC-TOFMS profile in Figure ; retention time 1290 s) in the LCO stream to 30 wt % in the additive, which resulted in a reduction of the effective dose from 3 wt % for LCO to 1.5 wt % for the additive. This reduction in the effective dose indicated that unsubstituted naphthalene had a greater effect on improving the colloidal stability compared with other diaromatics, such as substituted naphthalenes, biphenyls, dibenzothiophenes, or fluorenes present in the LCO fraction. , The effectiveness of the additive based on the substituted (alkyl) naphthalene has also been studied by other research teams in the past; however, it has been found that this additive (coded as VNII NP 200) loses its effect if the fuel contains a large number of unstable components . This information confirms our finding of a higher effect of unsubstituted naphthalene on the stability of marine fuels.…”

Molecular Characteristics of Catalytic Nitrogen Removal from Coal Tar Pitch over γ-Alumina-Supported NiMo and CoMo Catalysts

“…The commercial catalysts (NMA and CMA) were used as received from JGC Catalysts and Chemicals (JGC C&C, Kawasaki, Japan) in the single-stage reaction. To address the active sites [26,27], the active sites over NiMo and CoMo can be elucidated to symmetric stretching of the Mo-O bond in bridged or two-dimensional polymeric forms of octahedrally coordinated Mo oxide species. Such Mo oxide species have been shown to interact weakly with supports, resulting in higher reducibility and activity in hydrotreating reactions [26].…”

“…The distribution of MoS slabs over support materials is closely related to the presence of promoters such as Ni and Co, although the sulfidation of calcined catalysts may lead to the redistribution of surface species. The lower number of layered stacks (MoS) leads to a shorter distance between the active sites and the support materials, thereby resulting in improved HDS via effective hydrogenolysis [27]. As-received NMA and CMA catalysts have been characterized by XRF (ZSX Primus IV, Tokyo, Japan), N 2 -sorption isotherm (TriStar II3020, Norcross, GA, USA), TEM (HITACHI HF5000, Tokyo, Japan), Raman (LabRAM HR-800, Tokyo, Japan), and NH 3 -TPD (BELL CAT II, Osaka, Japan) and are presented in the Supplementary Information together with chemical stability data.…”