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HYDROTREATING AND CATALYTIC REFORMING
Publication date:3Q 2017
Just Published. Hydrotreating and Catalytic Reforming
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 the 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:
Catalytic reforming transforms naphthenes and paraffins into aromatics and isoparaffins. This process serves two main objectives in the refinery: production of high-octane reformate for gasoline blending and production of high-value aromatics for the petrochemical industry. In addition to benzene and xylene, reformate also contains toluene and heavier aromatics, which can be converted to benzene and desired xylenes via hydrodealkylation, disproportionation, transalkylation, isomerization, or alkylation. Reformers also supply considerable amounts of hydrogen needed for hydrotreating, hydrocracking, and isomerization; H2 supply coming from the reformer is becoming an increasingly important contributor to the refinery hydrogen network as more stringent fuel specifications are put in place necessitating greater H2 use in hydroprocessing units to meet these ultra-low requirements. Straight-run naphtha from the crude unit is the most common feedstock, but gasoline-range streams from catalytic crackers, hydrocrackers, cokers, and visbreakers can be routed to the reformer to increase octane.
Catalytic reforming processes are classified as semi-regenerative, cyclic, or continuous (CCR) depending upon the frequency of catalyst regeneration. Operating conditions, average cycle length, catalyst composition, and product slate can all vary depending on the type of unit that is used.
Since its inception, the primary focus of catalytic reforming was gasoline production. However, the sluggish gasoline demand in developed countries combined with new blending components and processing of non-traditional crudes (tight oil) have reduced the role catalytic reforming in a modern refinery. Furthermore, ethanol blending into the gasoline pool has been on an upward trend around the world, and blending ethanol displaces reformate in the gasoline pool, hence decreasing its demand. The main issue with ethanol blending is increased volatility due to high RVP. Usually reformate would be used to reduce RVP but there are other options, such as alkylate and ETBE, that are available in the industry.
Despite a decrease in gasoline demand, there are opportunities for refiners with catalytic reformers to shift operations and take advantages of current market opportunities, namely increased production of aromatics. The aromatics market is on an upswing with strong demand growth and many are now realizing the potential for increasing profits through catalytic reforming. Some refiners already switched operating conditions to maximize aromatics production instead of reformate.
In addition to benzene and xylene, reformate also contains toluene and heavier aromatics, which can be converted to benzene and desired xylenes via hydrodealkylation, disproportionation, transalkylation, isomerization, or alkylation. By 2025, the aromatics market will account for 35% of the total naphtha supply, an increase from 27% in 2012 as the demand growth will outpace the supply, tightening markets. With the market ripe for aromatics, catalytic reforming is still an important unit. This is evidenced by the significant patent activity in the last four years centering on aromatics-selective reforming processes, novel catalyst compositions to boost aromatics yields and the use of reforming in conjunction with other processes for aromatics production. Going forward, refiners may opt for integration with other processing units within their facility or with a nearby PC plant to boost aromatics output in order to maximize the value of their existing reforming assets.
Additionally, the catalytic reforming 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, platinum catalysts, Pt catalysts, Sn, tin, reformate, high octane, octane, gasoline blending, aromatics production, byproduct hydrogen, semi-regenerative, cyclic, continuous, CCR, catalyst regeneration, benzene, toluene, xylene, paraxylene, PX, BTX aromatics, Reid vapor pressure, RVP, oxygenate blending, ethanol, refinery-petrochemical integration, multimetallic catalysts, zeolite, promoter, additive, platinum recovery