RU2402594C1 - Hydrocarbon desulphuration method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method for desulphuration of two streams containing hydrocarbon material involving the following steps: (a) reaction of a first hydrocarbon material-containing stream (1), containing hydrocarbon components which boil above 343°C, and hydrogen (28), with a desulphuration catalyst in a desulphuration zone (3) used in desulphuration conditions to produce an outgoing stream (4) from the desulphuration zone; (b) feeding the outgoing stream from the desulphuration zone into vapour-liquid separator (5) which provides a vaporous stream (17) and a first liquid hydrocarbon-containing stream (6); (c) feeding the vaporous stream (17) and a second hydrocarbon-containing stream (18) into a hydrocracking zone (21) to produce an outgoing stream from the hydrocracking zone. (d) feeding the outgoing stream from the hydrocracking zone and the hydrocarbon-containing stream (16) of a repeated cycle into a hydrogenation zone (22) to produce an outgoing stream (23) from the hydrogenation zone; (e) fractionation of the outgoing stream (23) from the hydrogenation zone to produce an ultralow-sulphur hydrocarbon-containing stream (38); and (f) fractionation of the first liquid hydrocarbon-containing stream (6) extracted from step (b) to obtain a hydrocarbon-containing stream (16) of the repeated cycle, and a second liquid hydrocarbon-containing stream (17) containing hydrocarbon components and having low sulphur concentration.

EFFECT: obtaining ultralow-sulphur hydrocarbon products.

7 cl, 1 ex, 3 tbl, 1 dwg

Description

FIELD OF THE INVENTION

The technical field to which the present invention belongs is the desulfurization of hydrocarbon feedstocks to low sulfur levels.

State of the art

In order to produce more valuable hydrocarbon-containing streams, such as, for example, naphtha, gasoline, kerosene and diesel fuel having lower concentrations of sulfur and nitrogen, refiners used hydrodesulfurization methods. The feedstock, most often subjected to hydrotreating or desulfurization, is usually a liquid hydrocarbon-containing streams, such as, for example, naphtha, kerosene, diesel fuel, gas oil, vacuum gas oil (VGO) and oil without light fractions. In order to create an improvement sufficient to produce a marketable product or feedstock suitable for downstream processing, the degree of hydrodesulfurization is usually chosen. Over the years, it has been recognized that due to environmental concerns and recently adopted rules and regulations, products sold must comply with increasingly lower limits for pollutants such as sulfur and nitrogen. Recently, new regulations have been proposed in the United States and Europe that basically require the complete removal of sulfur from liquid hydrocarbons, which are used as transport fuels such as gasoline and diesel.

Desulfurization is usually achieved by contacting a hydrocarbon-containing feedstock in a reaction vessel or desulfurization zone with a suitable desulfurization catalyst under conditions of elevated temperature and pressure in the presence of hydrogen to result in a product containing the desired maximum sulfur limits. The quality of the desulfurized products is influenced by the operating conditions and desulfurization catalysts within the desulfurization reactor.

Although a wide variety of process flow schemes, operating conditions, and catalysts have been used in commercial desulfurization activities, there is always a demand for new desulfurization processes that provide lower costs and product quality. With regard to the desired low sulfur transport fuels, the method of the present invention significantly improves the economic benefits of producing low sulfur fuels.

US 5114562 B1 discloses a method in which the middle distillate oil streams are hydrotreated to produce a low sulfur and low aromatic product in two successive reaction zones. The effluent of the first reaction zone is purified from hydrogen sulfide by purification with hydrogen and then reheated by indirect heat exchange. The second reaction zone uses a sulfur-sensitive noble metal hydrogenation catalyst.

SUMMARY OF THE INVENTION

The present invention is an improved method for producing low sulfur hydrocarbon products. First, a hydrocarbon-containing feedstock comprising hydrocarbon components boiling above 343 ° C. and hydrogen is reacted in the first desulfurization zone to produce an effluent of the first desulfurization zone, which is introduced into a vapor-liquid separator that is operated at elevated temperature to form a vapor stream, comprising low boiling hydrocarbon compounds and hydrogen, and a liquid hydrocarbon containing stream comprising hydrocarbon components having a reduced concentration sulfur. A vapor stream comprising low boiling hydrocarbon compounds, hydrogen and a second hydrocarbon containing feed comprising hydrocarbon components boiling below 371 ° C. is reacted in a hydrocracking zone to form a hydrocracking zone effluent which is introduced together with a hydrocarbon containing recycle stream boiling preferably in a range from 149 ° C to 371 ° C, into the hydrogenation zone to obtain an effluent of the hydrogenation zone, which is fractionated to produce ultra-low ernisty hydrocarbon stream boiling in the range of preferably from 149 ° C to 371 ° C. The liquid hydrocarbon-containing stream formed by the vapor-liquid separator is fractionated to form a hydrocarbon-containing recycle stream boiling preferably in the range of 149 ° C to 371 ° C and a liquid hydrocarbon-containing stream comprising hydrocarbon components boiling above 371 ° C and having a reduced sulfur concentration .

Other embodiments of the present invention cover additional details, such as types and descriptions of feedstocks, desulfurization catalysts, hydrocracking catalysts and preferred operating conditions including temperatures and pressures, all of which are disclosed further in the following discussion of each of these aspects of the present invention.

The drawing is a simplified diagram of a process diagram of a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that a more efficient and economical production of ultra-low sulfur hydrocarbon products, including ultra low sulfur diesel fuel, can be achieved and used in the above-described integrated hydrodesulfurization and hydrocracking process.

In accordance with the present invention, the first feed which is introduced into the first desulfurization zone preferably contains components boiling above 343 ° C and more preferably boiling above 371 ° C and includes, for example, straight-run gas oils, vacuum gas oils, cracked gas oils, products distillation of coking plants, products of direct distillation, solvent-derived debituminized oils obtained during oil pyrolysis, high-boiling synthetic oils and products of distillation of catalytic cracking plants. The preferred feedstock is gas oil or other fractions having at least 50 wt.% And most usually at least 75 wt.% Of its components boiling at a temperature between 315 ° C and 538 ° C.

The first feed is reacted with hydrogen in a first desulfurization zone containing a desulfurization catalyst operating under desulfurization conditions. Preferred desulfurization conditions include a temperature of from 204 ° C. to 482 ° C. and a hourly average volumetric feed rate of a hydrocarbon-containing feed liquid from 0.1 h ^-1 to 10 h ^-1 .

Suitable desulfurization catalysts for use in the present invention are any conventional conventional hydrotreating catalysts known and include those consisting of at least one group VIII metal, preferably iron, cobalt and nickel, more preferably cobalt and / or nickel, and at least at least one Group VI metal, preferably molybdenum and tungsten, on a carrier material with a high surface area, preferably alumina. Other suitable desulfurization catalysts include zeolite catalysts as well as noble metal catalysts, where the noble metal is selected from palladium and platinum. It is within the scope of the present invention that more than one type of desulfurization catalyst is used in the same reaction vessel. Group VIII metal is usually present in an amount ranging from 2 to 20 wt.%, Preferably from 4 to 12 wt.%. Group VI metal will usually be present in an amount ranging from 1 to 25 wt.%, Preferably from 2 to 25 wt.%. Typical desulfurization temperatures range from 204 ° C. to 482 ° C. at pressures from 2.1 MPa to 17.3 MPa, preferably from 2.1 MPa to 13.9 MPa.

The resulting effluent from the first desulfurization zone is introduced into a vapor-liquid separator, preferably operated at a temperature of more than 288 ° C, to provide a steam stream comprising hydrogen, hydrogen sulfide and low boiling hydrocarbon-containing compounds boiling up to 371 ° C, and a first liquid hydrocarbon-containing stream, including hydrocarbon components boiling above 371 ° C and having a reduced sulfur concentration. This first liquid hydrocarbon-containing stream, which also contains a portion of hydrocarbons boiling in the range of 149 ° C to 371 ° C, is preferably introduced into the hot pulse zone, then into the cold pulse zone and subsequently fractionated to provide a hydrocarbon-containing recycle stream containing hydrocarbons, boiling in the range from 149 ° C to 371 ° C, and a second liquid hydrocarbon-containing stream comprising hydrocarbon components boiling above 371 ° C and having a reduced sulfur concentration. This second liquid hydrocarbon-containing stream is preferably used as a suitable feedstock for a catalytic cracking process in a fluid. A vapor phase stream comprising hydrogen, hydrogen sulfide and low boiling hydrocarbon compounds boiling up to 371 ° C and a second hydrocarbon containing feed comprising hydrocarbon components boiling below 371 ° C are fed to a hydrocracking zone containing a hydrocracking catalyst to obtain an hydrocracking zone effluent . The second hydrocarbon-containing feedstock may be any suitable feedstock boiling below 371 ° C, and preferably boiling in the range of 177 ° C to 371 ° C. Such suitable feedstocks include, for example, a straight run middle distillation product, kerosene and diesel boiling range hydrocarbons, a distillation product of coking plants, and light recycle gas oil.

The hydrocracking zone may contain one or more layers of the same or different catalysts. In one embodiment, when the preferred products are medium distillation products, the preferred hydrocracking catalysts use amorphous or low zeolite bases combined with one or more hydrogenation components based on Group VIII or VI metals. In another embodiment, when the preferred products are in the boiling range of gasoline, the hydrocracking zone comprises a catalyst that includes, in general, any crystalline cracking zeolite base on which a minor amount of a hydrogenation component based on a Group VIII metal is deposited. Additional hydrogenation components for inclusion in the zeolite base may be selected from Group VI. In the art, cracking zeolite bases are sometimes referred to as molecular sieves and usually consist of silica, alumina and one or more exchangeable cations, such as sodium, magnesium, calcium, rare earth metals, etc. In addition, they are characterized by crystalline pores with a relatively constant diameter of 4 to 14 angstroms. It is preferable to use zeolites having a relatively high molar ratio of silica / alumina from 3 to 12. Suitable zeolites found in nature include, for example, mordenite, stilbit, heylandite, ferrierite, daciardite, chabazite, erionite and faujasite. Suitable synthetic zeolites include, for example, crystalline types B, X, Y, and L, for example, synthetic faujasite and mordenite. Preferred zeolites are those having a crystal pore diameter of from 8 to 12 angstroms, in which the silica / alumina molar ratio is from 4 to 6. The best example of a zeolite falling in a preferred group is a type Y molecular sieve.

Naturally occurring zeolites are usually found in sodium form, alkaline rare earth form, or mixed forms. Synthetic zeolites are almost always prepared first in sodium form. In any case, for use as a cracking base, it is preferable that most or all of the original monovalent zeolite metals are ion-exchanged with the multivalent metal and / or ammonium salt, followed by heating to decompose the ammonium ions bound to the zeolite, leaving instead hydrogen ions and / or exchange centers, which were actually purified from cations (“decationized”) by further removal of water. Being in hydrogen form or “decationized” type Y zeolites of this nature are described in more detail in US-A-3130006.

Multivalent metal-hydrogen zeolites can be prepared by ion exchange, first with an ammonium salt, then by partial reverse exchange with a multivalent metal salt, and then by calcination. In some cases, as in the case of synthetic mordenite, hydrogen forms can be prepared by direct acid treatment of the alkali metal zeolites. Preferred cracking bases are those that are at least 10 percent and preferably 20 percent deficient in metal cations, based on the initial ion exchange capacity. Particularly desirable and stable classes of zeolites are those in which at least 20 percent of the ion exchange capacity is filled with hydrogen ions.

The active metals used in the preferred hydrocracking catalysts of the present invention as hydrogenation components are Group VIII metals, i.e. iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. In addition to these metals, other promoters can also be used in combination with them, including Group VI metals, for example, molybdenum and tungsten. The amount of hydrogenating metals in the catalyst can vary widely. Generally speaking, any amount from 0.05 to 30 weight percent can be used. In the case of noble metals, from 0.05 to 2 weight percent is usually preferably used. A preferred method of introducing the hydrogenation metal is to contact the zeolite base material with an aqueous solution of a suitable compound of the desired metal in which the metal is present in cationic form. Following the addition of the selected hydrogenation metal or metals, the resulting catalyst powder is filtered off, dried, granulated with added lubricants, binders or the like, if desired, and calcined in air at a temperature of, for example, 371-648 ° C, to activate the catalyst and decompose the ions ammonium Alternatively, the zeolite component may first be granulated, followed by the addition of a hydrogenating component and activation by calcination. The above catalysts can be used in pure form, or the ground zeolite catalyst can be mixed and co-granulated with other relatively less active catalysts, additives or binders, such as alumina, silica gel, co-alumina gels, activated clays etc. in proportions ranging between 5 and 90 wt. percent. These additives may be used as such, or they may contain a small proportion of the added hydrogenation metal, such as a metal of group VI B and / or group VIII.

Additional metal-cured hydrocracking catalysts may also be used in the process of the present invention, which include, for example, aluminophosphate molecular sieves, crystalline chromosilicates and other crystalline silicates. Crystalline chromosilicates are more fully described in US-A-4363718.

Hydrocracking is carried out in the presence of hydrogen, and preferably under hydrocracking conditions, which include a temperature of 232 ° C to 468 ° C, a pressure of 3548 kPa to 20785 kPa, an average hourly space velocity of a liquid (LHSV) of 0.1 to 30 h ^-1 and a circulation speed hydrogen from 337 m ³ / m ³ at nu up to 4200 m ³ / m ³ at n.a.

The hydrocracking zone effluent and the hydrocarbon-containing recycle stream, preferably boiling in the range of 232 ° C to 371 ° C, are preferably fed directly to the hydrogenation zone containing the hydrogenation catalyst to produce a hydrogenation zone effluent. The hydrogenation catalyst may be selected from any known hydrogenation or desulfurization catalyst. This catalyst may be the same or different from the desulfurization catalyst used in the desulfurization zone, and may be selected from known desulfurization catalysts, such as, for example, those described above. Preferred hydrogenation conditions may be selected from those ranges that have been explained for the desulfurization zone, and may be more, less, or equal in severity to the reaction conditions selected for the desulfurization zone.

The resulting hydrogenation zone effluent is partially condensed and introduced into a cold vapor-liquid separator operated at a temperature of from 21 ° C. to 60 ° C. to produce a hydrogen-rich gas stream containing hydrogen sulfide and a liquid hydrocarbon-containing stream. The resulting hydrogen-rich gas stream is preferably passed through an acid gas purification zone to lower the concentration of hydrogen sulfide in order to produce a purified hydrogen-rich gas stream, a portion of which can then be returned when it is desired or necessary. The liquid hydrocarbon-containing stream from the cold vapor-liquid separator is preferably introduced into a cold evaporation drum to remove dissolved hydrogen and usually gaseous hydrocarbons, and subsequently directed to the fractionation zone to produce a stream of the obtained low sulfur diesel fuel. Preferably, the stream of diesel fuel obtained contains less than 50 parts by weight per million sulfur, more preferably 10 parts by weight per million sulfur. Fresh hydrogen can be introduced into the process at any convenient position.

We turn now to the drawing; a feed stream comprising a heavy vacuum gas oil enters the process through line 1 and is mixed with the hydrogen rich gas stream supplied through line 28, and the resulting mixture is introduced via line 2 into desulfurization zone 3. Hydrogen supply to the desulfurization zone 3 is provided through lines 30 and 31. The resulting effluent from the desulfurization zone 3 is transported through line 4 and introduced into the hot vapor-liquid separator 5. A gaseous stream including hydrogen, hydrogen sulfide and low boiling hydrocarbons is removed from the hot vapor-liquid separator 5 along line 17 and mixed with a light recycle gas oil, which is introduced through line 18 and which boils in the range of medium distillation products, the resulting mixture is transported through line 19 and introduced into the reaction a torus 20, in which this stream is in contact with the hydrocracking zone 21. The resulting effluent from the hydrocracking zone 21 is fed directly to the hydrogenation zone 22, which is located inside the reaction zone 20. The resulting effluent from the hydrogenation zone 22 is passed through line 23 and introduced into the heat exchanger 24. The resulting cooled and partially condensed stream is diverted from the heat exchanger 24 25 and introduced into the cold vapor-liquid separator 26. The hydrogen-rich gas stream is withdrawn from the cold vapor-liquid separator 26 via line 27 and introduced into the desulfurization zone 3 via lines 28, 29, 30 and 31, as described above. A liquid hydrocarbon-containing stream is withdrawn from the cold vapor-liquid separator 26 via line 32 and introduced into the cold evaporation drum 33. A gas stream including hydrogen and usually gaseous hydrocarbons is diverted from the cold evaporation drum 33 through line 34. A liquid stream comprising hydrocarbons of the boiling range of diesel fuel, removed from the cold evaporation drum 33 via line 35 and introduced into the fractionation zone 36. The ultra-low sulfur diesel stream is recovered from fractionation zone 36 and diverted therefrom via line 38. A hydrocarbon containing stream including compounds boiling below the diesel boiling range is diverted from fractionation zone 36 via line 37 and recovered. The liquid stream is withdrawn from the hot vapor-liquid separator 5 via line 6 and introduced into the hot evaporation drum 7. The steam stream, including hydrogen and low boiling hydrocarbons, is removed from the hot evaporation drum 7 via line 8 and recovered. A liquid hydrocarbon-containing stream containing hydrocarbons boiling at a temperature above 371 ° C and hydrocarbons in the boiling range of diesel fuel is withdrawn from the hot evaporation drum 7 via line 9 and introduced along with the above-described steam stream supplied through line 34, and the resulting mixture is introduced via line 10 to the cleaning zone 11. A stream comprising hydrogen, gaseous hydrocarbons under normal conditions, and hydrocarbons in the boiling range of gasoline is removed from purification zone 11 via line 12 and recovered. A liquid hydrocarbon-containing stream containing hydrocarbons boiling at a temperature above 371 ° C and hydrocarbons in the boiling range of diesel fuel is diverted from purification zone 11 via line 13 and introduced into fractionation zone 14. A stream comprising low boiling hydrocarbons is removed from fractionation zone 14 via line 15 and recovered. A liquid hydrocarbon-containing stream, including hydrocarbons boiling at a temperature above 371 ° C., is removed from the fractionation zone 14 via line 17 and recovered. A liquid stream including hydrocarbons of the boiling range of diesel fuel is removed from fractionation zone 14 via line 16 and introduced into reaction zone 20, as described above.

EXAMPLE

Desulfurization was carried out for two hydrocarbon-containing feed streams, one of which is a feed type of a mixture of heavy gas oils having the composition and properties shown in Table 1, the other is a feed stream of a type of light recycle gas oil having the composition and properties shown in Table 2.

The process conditions in the reaction zones are shown in Table 3.

The resulting sulfur concentration in diesel fuel was less than 50 wt. ppm With an increase in temperature and a decrease in space velocity, an ultra-low sulfur diesel fuel with a sulfur content of 10 wt. ppm

Table 1 A mixture of heavy straight run and vacuum gas oil Type of feedstock HAGO (Heavy straight run gas oil) HVGO (Heavy Vacuum Gas Oil) HAGO / HVGO Flow rate, barrels per day of work for each installation 12056 76394 88450 about.% 13.63 86.37 100.0 wt.% 13.25 86.75 100.0 API (American Petroleum Institute Method Density) 24.6 19.5 20,2 Relative density 0.9065 0.9368 0.9327 Sulfur, wt.% 2.49 3.05 2.98 Nitrogen, parts by weight / million 750 1275 1205 Carbon in composition
condensed compounds, wt.% 0.15 1.30 1.15 Asphaltenes C ₇ , wt.% 0.03-0.05 0.15-0.20 0.13-0.18 Metals, parts by weight / million Ni + V 1,0 5,0 4.47 Si - - - UOP K (K content determined by the method of UOP - Universal Oil Products) 11.78 11.79 11,784 Distillation, ° С D 2887 D 2887 TBP / D1160 IBP (starting boiling point) 245 342 242/252 10% 334 397 393/404 thirty% 376 440 430/435 fifty% 408 473 463/463 70% 430 504 495/495 90% 464 552 553/553 EP (end boiling point) 523 614 611/611

table 2 Light recycle gas oil LCO feedstock (light recycle gas oil) Cracking Raw Materials (w / EHS OH) Speed, barrels per day of work 12000 API 15,5 Sp. Gr. (specific gravity) 0.9624 Sulfur, ppm 6145 Nitrogen, ppm 500 Flash point, ° C 73 The point of yield loss, ° C <-15 Cetane index twenty ASTM D-86 IBP, C (initial boiling point according to ASTM D-86, ° C) 182 5% 221 10% 230 thirty% 253 fifty% 274 70% 294 90% 339 95% 351 FBP (final boiling point) 359

Table 3 Reaction conditions for reaction zones Hydrotreating Plant Hydrocracking Diesel Fuel Hydrotreating The speed of raw materials, barrels per day of installation work 104557 12000 57806 Pound / h (kg / h) 1,433,629 (650,283.2) 168679 (76511.5) LHSV FF, h ^-1 Volume (Hourly average volumetric fluid velocity) Catalyst volume
cube foot. (m ³ ) LHSV FF, h ^-1 (Hourly average volumetric fluid velocity) Volume rolled
congestion
cube foot. (m ³ ) LHSV FF, h ^-1 (Hourly average volumetric fluid velocity) Volume rolled
congestion
cube foot. (m ³ ) Hydrotreating 1.18 20757 (587.77) 1.33 2116 (59.91) 3 3374 (95.54) Hydrocracking - - 1.85 1520 (43.04) - - The average temperature of the layer, ° F (° C) 696 (369) 700/700 (371/371) 690 (366) Pressure (HPS) psi (kPa) 1041 (7177) The purity of fresh N ₂ mol.% 99.9 Scrubber Circular
gas Yes The content of H ₂ in the circulating gas, mol.% 94.3

The preceding description, example, and drawing clearly illustrate the advantages encompassed by the method of the present invention and the benefits that will be obtained by using it.

Claims (7)

1. The method of desulfurization of two hydrocarbon-containing streams of raw materials, which includes the following stages:
(a) reacting the first hydrocarbon-containing stream (1) of a feed containing hydrocarbon components boiling above 343 ° C. and hydrogen (28) with a desulfurization catalyst in a desulfurization zone (3) operating under desulfurization conditions to produce an effluent (4) desulfurization zones;
(b) introducing a desulfurization zone effluent into a vapor-liquid separator (5) operated at a temperature higher than 288 ° C. to provide a vapor stream (17) containing hydrogen, hydrogen sulfide and low boiling hydrocarbon compounds boiling up to 371 ° C., and a first liquid hydrocarbon-containing stream (6) containing hydrocarbon components boiling above 371 ° C. and having a reduced sulfur concentration;
(c) feeding a vapor stream (17) containing hydrogen, hydrogen sulfide and low boiling hydrocarbon-containing compounds boiling up to 371 ° C, and a second hydrocarbon-containing stream (18) of raw materials including hydrocarbon components boiling below 371 ° C, into zone (21) hydrocracking to produce a hydrocracking zone effluent;
(d) feeding the effluent of the hydrocracking zone and a hydrocarbon-containing recycle stream (16) boiling in the range of 149 to 371 ° C. into the hydrogenation zone (22) to produce the hydrogenation zone effluent (23);
(e) fractionating the effluent (23) of the hydrogenation zone to produce an ultra-low hydrocarbon containing stream (38) boiling in the range of 149 to 371 ° C; and
(f) fractionating the first liquid hydrocarbon-containing stream (6) recovered in step (b) to produce a hydrocarbon-containing recycle stream (16) boiling in the range of 149 to 371 ° C. and a second liquid hydrocarbon-containing stream (17) containing hydrocarbon components boiling above 371 ° C, and having a reduced sulfur concentration. 2. The method according to claim 1, in which the first hydrocarbon-containing stream (1) of the feedstock is selected from the group consisting essentially of straight-run gas oil, vacuum gas oil, distillation products of coking units subjected to cracking of gas oil and mixtures thereof. 3. The method according to claim 1, in which the operating conditions for the zone (5) of desulfurization include a temperature of from 204 to 482 ° C, a pressure of from 2.1 to 17.3 MPa and an hourly average volumetric flow rate of a liquid from 0.1 to 10 hours ^{- 1} . 4. The method according to claim 1, in which the operating conditions for the hydrogenation zone (22) include a temperature of from 204 to 482 ° C, a pressure of from about 2.1 to 17.3 MPa, and an average hourly space velocity of the liquid from 0.1 to 10 hours ^-1 . 5. The method according to claim 1, in which the ultra-low hydrocarbon-containing stream (38) obtained in stage (e) contains less than 50 parts by weight of sulfur per million. 6. The method according to claim 1, in which the ultra-low hydrocarbon-containing stream (38) obtained in stage (e) contains less than 10 parts by weight per million sulfur. 7. The method according to any one of claims 1 to 6, in which the second feed stream (18) is selected from the group consisting of light recycle gas oil, straight-run middle distillate, kerosene and hydrocarbons in the boiling range of diesel fuel and distillation product of coking plants.