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1、Increasing diesel production from the FCCUSulphur concentration in the gasoline pool is being reduced in many parts of the world. In Europe, Euro V regulations, implemented in 2009, require less than 10 ppm sulphur in gasoline. Since 2008, the gasoline sulphur specification in the US and Canada has
2、been less than 30 ppm on average, and a further reduction to 10 ppm is under consideration in the US. In Europe and North America, diesel with a sulphur content in this range is referred to as ultra-low sulphur diesel (ULSD). In Russia, the gasoline sulphur content will be reduced to 10 ppm by 2015.
3、 It is likely the sulphur specification in the rest of the world will also become more stringent over time.Gasoline is a complex product, with many important parameters determining its quality, aside from sulphur concentration; these include vapour pressure, benzene concentr-ation, boiling range and
4、 octane rating. In some regions, such as the EU and India, demand for diesel is higher than for gasoline. In others, including the US, demand for diesel is projected to grow while gasoline demand declines, as shown in Figure 1, which also illustrates the future projected change in the global gasolin
5、e-to-distillate ratio.To reduce gasoline product and increase diesel product, some refiners produce lower end-point gasoline, routing the heavier cut of the full-range gasoline to the diesel pool. This results in higher capacity requirements for the diesel hydro-treaters, which are often already ful
6、ly utilised.To remove sulphur from FCC gasoline, CDTECH offers the FCC naphtha desulphurisation technology produces low-sulphur heavy catalytic naphtha as a separate product for blending into the diesel poolMauriCe KorpelShoeK, Gary podrebaraC, Kerry roCK and rajeSh SaMarth CDTeChcommercially proven
7、 LCN (light catalytic naphtha) CDHydro and CDHDS processes. These processes, which employ the principle of catalytic distillation, conduct selective hydro-desulphurisation in a distillation environment. The full-range gasoline is split into three different cuts, giving the refiner blending flexibili
8、ty. It is possible to use the CDHDS process to tailor the sulphur content of the distillate and bottom product, making it feasible to produce 10 ppm low end-point gasoline and a separate heavier cut that meets the less than 10 ppm sulphur specification for blending into the diesel pool. This flexibi
9、lity can provide significant value by debottlenecking the diesel hydrotreater.properties of FCC gasolineFigure 2 shows a plot of the concentrations of total sulphur, mercaptan sulphur (RSH) and olefins (measured via bromine number) as a function of the boiling point of the FCC gasoline. At the light
10、 end of the gasoline, the olefin concentration is high and the total sulphur concentration is relatively low. Nearly all the total sulphur is in the form of RSH. As the boiling point increases, the sulphur concentration begins to increase quite significantly, while the RSH concentration actually dec
11、lines. At the heaviest end, most of the sulphur is contained in compounds such as benzothiophene and methyl benzothiophene. Conversely, the olefin concentration profile follows the opposite trend: the lighter end of gasoline is olefin-rich, while the heavier end contains very few olefins.The data pl
12、otted in Figure 2 illustrate the challenge involved in treating the light end of the PTQ Q1 2010 75Global gasoline-to-distillate ratioNorth Americangasoline demand, Mt/a9EAR MUNNASNOT-DNAMEDENILOSAOITARETALLITSIDOTENILOSAFigure 1 Decline in gasoline demand loss. As Figure 3 shows, the first step is
13、 to treat the lightest fraction of the gasoline in a LCN CDHydro unit, where the RSH is non-destructively removed. The LCN CDHydro unit is not a hydro-desulphurisation step. It operates at very mild conditions, resulting in no measurable olefin loss. Part of the rectification section of the LCN CDHy
14、dro column contains catalyst packed in a distillation structure. The rest of the column contains conventional distillation trays. The LCN CDHydro unit works by performing an additional reaction between the RSH and the contained diolefins over the catalyst to form a heavier sulphide (RSR). The heavy
15、sulphide goes to the bottom of the LCN CDHydro column and exits with the bottom product.The light product from the LCN CDHydro column has a very low RSH content, very high olefin concentration, a high octane rating and a relatively high Reid vapour pressure (RVP). Some refiners choose to isolate this fraction in order to increase flexibility in the blending operation.The LCN CDHydro column bottoms go to the CDHDS
