Hydrodesulfurization of Fluid Catalytic Cracking Decant Oils in a Laboratory Flow Reactor and Effect of Hydrodesulfurization on Subsequent Coking

Abstract

This study investigates the hydrodesulfurization (HDS) of fluidized catalytically cracked decant oils used as feedstock for needle coke production. Three decant oils, representing a high (4.0 wt %), medium (2.5 wt %), and low (0.9 wt %) sulfur content, were hydrotreated in a fixed-bed flow reactor. Removing sulfur from larger ring systems in decant oils is the most effective way of reducing the needle coke sulfur content, because large aromatics are significant contributors to the coke product obtained from delayed coking. Two commercial catalysts with different pore size distributions were tested for their hydrodesulfurization activities, selectivities for specific sulfur-containing species, and hydrogenation of constituent polyaromatic hydrocarbons (PAHs) under different operating conditions. The decant oils and hydrotreated products were analyzed by GC/ MS to determine changes in molecular compositions of the feedstocks. Following HDS, the decant oils and their hydrotreated products were carbonized to produce a semicoke, and the coke was evaluated for mesophase formation and quality. The desirable outcome of decant oil HDS is sulfur removal, particularly from large polyaromatic ring systems, with minimum hydrogen consumption and hydrogenation. The results showed that the desired level of 0.5 wt % of sulfur in both low-and medium-sulfur decant oils could be achieved through HDS over a commercial CoMo catalyst. Furthermore, hydrogenation of the PAH during HDS appeared to slightly improve the mesophase development seen upon subsequent carbonization.

Reactivity of sulfur compounds in FCC decant oils for hydrodesulfurization over CoMoS2/Al2O3 catalysts

“…FCC-DO is a highly aromatic product composed 70-90% of aromatics that also contains 0.5-3.5% sulfur, 0.1-0.3% nitrogen, and 1-3% asphaltenes [1][2][3]. Since FCC-DO has a moderate molecular size and high aromaticity, it is considered as a raw material for producing needle cokes [4][5][6][7]. Also, FCC-DO is used as a feedstock for mesophase pitch to produce a carbon fiber [8,9] and raw material for carbon black [10].…”

Synthesis and Characterization of New Inorganic‐Organic Hybrid Nanocomposite PMo11Cu@MgCu2O4@CS as an Efficient Heterogeneous Nanocatalyst for ODS of Real Fuel

“…In order to reduce air impurities, strict regulations have been imposed to reduce the OSCs of liquid fuels to a very low level . To obtain the quality demands of liquid fuels with low‐level of OSCs, many alternative technologies have been used such as selective adsorption, extraction, biodesulfurization, hydrodesulfurization, and oxidative desulfurization (ODS) . Among these processes, the ODS has gained attention from the scientific community worldwide due to mild reaction conditions such as lower reaction temperature and atmospheric pressure, lower investment, operating costs, and simpler process .…”

Carbon Nanostructure Curvature Induced from the Rapid Release of Sulfur upon Laser Heating

“…As such, sulfur imparts a relatively unobservable impact on the nanostructure, but rather acts to cause micro-cracks upon rapid evolution in the form of H 2 S and CS 2 upon subsequent graphitization heat treatment. The micro-cracks result in an observed volume increase, and therefore, the process has been termed puffing [28][29][30]. Puffing has been evaluated on the micro-and macro-length scales.…”

“…The structural defects imparted on the carbon from oxygen removal set the stage for the trajectory of lamellae growth upon additional heat treatment, whereas in the case of sulfur, the lamellae are significantly annealed with trajectory set after heat treatment at 1000 • C. As such, sulfur imparts a relatively unobservable impact on the nanostructure, but rather, acts to cause micro-cracks upon release upon subsequent graphitization heat treatment, in the forms of H 2 S and CS 2 . The micro-cracks result in an observed volume increase, and therefore, the process has been termed puffing [28][29][30]. This is primarily a problem for the needle coke industry as needle coke is often used as the primary filler in the production of graphite electrodes and micro-cracks, acting to reduce the electrodes' desired properties [28][29][30].…”

“…The micro-cracks result in an observed volume increase, and therefore, the process has been termed puffing [28][29][30]. This is primarily a problem for the needle coke industry as needle coke is often used as the primary filler in the production of graphite electrodes and micro-cracks, acting to reduce the electrodes' desired properties [28][29][30]. The added thermal stability of sulfur in carbon versus oxygen is understood by the enthalpy of formation of the leaving species.…”