HYDROCARBON PUBLISHING COMPANY
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Publication date:3Q 2018
Just Published. Hydrotreating
Hydrotreating (HT) is a process that has become synonymous with removing impurities from petroleum feedstocks. By mixing hydrogen and feedstocks under controlled conditions in the presence of a catalyst, contaminants in the form of sulfur-, nitrogen-, and oxygen-containing compounds, as well as metals, can be removed. When the catalyst is designed to remove a specific class of compounds, that fact is reflected in the name of the process, e.g., hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), and hydrodearomatization (HDA)/hydrogenation (HYD).
Hydrotreating is suitable for removing contaminants from feedstreams or product streams. For the feedstocks intended for other refinery processes—catalytic cracking, hydrocracking, catalytic reforming, and isomerization—HT protects the sensitive (and costly) catalysts from contamination. To meet product specifications, refiners rely on HT to perform posttreatment in order to meet mandated specifications such as gasoline benzene, sulfur, and also olefins (for European and Californian standards). HDS of diesel is required to satisfy ultra-low sulfur requirements. To a lesser extent, HT may be used to produce 0.1 wt% sulfur bunker fuel oil for the 2020 International Maritime Organization (IMO) mandate. Furthermore, hydrotreaters play a key role in processing unconventional (resid and renewable) feeds to produce more diesel while helping meet stricter environmental regulations. Hydrotreating is not without drawbacks: the capital investment is significant; operating costs (catalysts and hydrogen) can be high; and product quality may be adversely affected by the potential saturation of aromatics and olefins.
Companies and licensers continue to research on and release highly active HDS catalysts that allow for high HDS conversion while limiting the weighted average bed temperature (WABT) of their reactors. Furthermore, the ongoing shale boom and natural gas supply in the US have led to cheaper hydrogen production for refineries, which has opened the door for increased diesel production by increasing the volume swell of a particular unit. New offerings allow for saturation of aromatics in feeds like LCO in order to decrease diesel density and therefore increase the potential gains of incoming crude. Improvement to diesel quality has also been addressed through hydrodewaxing (HDW), which can improve the cloud point and pour point for better cold flow properties. Numerous companies have released technologies which aim to efficiently and effectively dewax a diesel stream through the use of selective catalysts.
Another challenge for refiners comes from the Tier III gasoline standard, in the US which calls for 10 ppm sulfur in gasoline, which is a third of the previous standard. This change greatly impacts the production of FCC gasoline, as it accounts for around a third of the gasoline blending pool, and is the main contributor of sulfur in the final gasoline product. Different refiners and licensers offer technologies and recommendations when deciding between FCC pretreatment and FCC posttreatment. Both options can reduce sulfur levels to meet the new standards, but at a cost. Pretreatment requires reactors to operate at higher severities, which can decrease catalyst cycles by as much as 40%. Companies are releasing and carrying out research into highly active FCC pretreat catalysts that can produce low-sulfur FCC feeds while maintaining desired cycle lengths. Meanwhile, posttreatment of FCC naphtha can lead to olefin saturation and significant octane loss as a result. New offerings and current research aim to find ways to increase HDS activity while decreasing olefin saturation by making the HDS process more selective.
Additionally, the hydrotreating section features the latest trends and technology offerings, including:
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Keywords: hydrogen, hydrotreating, middle distillates, diesel, ULSD, heavy oil, tight oil, fixed-bed, single-stage, two-stage, two-stage with recycle, jet fuel, kerosene, gasoil, gas oil, coker gas oil, coker naphtha, DAO, VGO, HVGO, LCO, resid hydrotreating, renewable hydrotreating, renewable jet fuel, renewable diesel, biodiesel, dewaxing, cold flow properties, cloud point, pour point, cetane, Tier III, gasoline, FCC pretreatment, FCC posttreatment, hydrocracker pretreatment, HDS, hydrodesulfurization, hydrodemetallization, HDM, hydrodenitrogenation, HDN, hydrodearomatization, HDA, hydrogenation, HYD