PRODUCTION OF HIGH QUALITY DIESEL FUEL AND LUBRICANT FROM HIGH BOILING AROMATIC CARBONACEOUS MATERIAL

Abstract

A broad embodiment of the present disclosure relates to a process for removal of at least 20%, 40% or 80% of the aromatics content of the fraction boiling above 190° C. from a heavy hydrocarbonaceous feedstock comprising at least 30 wt % aromatics, at least 3000 wt ppm nitrogen and at least 0.5 wt % oxygen said method being carried out in a single stage in which no intermediate stream is withdrawn and comprising the steps of a. providing a hydrotreater feed by combining said heavy hydrocarbonaceous feedstock with excess hydrogen, providing a hydrotreater feed, b. providing a hydrotreated hydrocarbon product comprising less than 30 wt ppm nitrogen, less than 20 wt ppm nitrogen or less than 10 wt ppm nitrogen by hydrotreating said hydrotreater feed by contacting it with a material catalytically active in hydrotreatment under hydrotreatment conditions, c. providing a hydrotreated product either as the hydrotreated hydrocarbon product of step b or by fractionation as a fraction of said hydrotreated hydrocarbon product, with the associated benefit of a process providing a low level of nitrogen in the hydrocarbon product also providing a high potential for dearomatization. The aromatics content of the heavy hydrocarbonaceous feedstock may typically be between 30 wt % aromatics and 90 wt % aromatics. The nitrogen content of the heavy hydrocarbonaceous feedstock may typically be between 3000 wt ppm and 10000 wt ppm. The oxygen content of the heavy hydrocarbonaceous feedstock may typically be between 0.5 wt % and 10 wt %. The removal of aromatics content from the fraction boiling above 190° C. may be from 20%, 40% or 80% to 99% or 100%.

Claims

1. A process for removal of at least 20%, 40% or 80% of the aromatics content of the fraction boiling above 190° C. from a heavy hydrocarbonaceous feedstock comprising at least 30 wt % aromatics, at least 3000 wt ppm nitrogen and at least 0.5 wt % oxygen said method being carried out in a single stage in which no intermediate stream is withdrawn and comprising the steps of a. providing a hydrotreater feed by combining said heavy hydrocarbonaceous feedstock with excess hydrogen, b. providing a hydrotreated hydrocarbon product comprising less than 30 wt ppm nitrogen, less than 20 wt ppm nitrogen or less than 10 wt ppm nitrogen by hydrotreating said hydrotreater feed by contacting it with a material catalytically active in hydrotreatment under hydrotreatment conditions, c. providing a hydrotreated product either as the hydrotreated hydrocarbon product of step b or by fractionation as a fraction of said hydrotreated hydrocarbon product.

2. A process according to claim 1 in which the material catalytically active in hydrotreatment comprises a group VIII metal, a group VIB metal and an oxidic support, taken from the group consisting of alumina, silica, titania and combinations thereof.

3. A process according to claim 1, in which the hydro-treatment conditions involve a hydrogen pressure from 120, 140 or 160 to 200 bar.

4. A process according to claim 1, in which the hydro-treatment conditions involve a temperature from 340° C. or 360° C. to 400 or 420° C.

5. A process according to claim 1, in which the hydro-treatment conditions involve a liquid hourly space velocity of 0.1 hr.sup.−1 or 0.2 hr.sup.−1 to 0.5 hr.sup.−1, 0.6 hr.sup.−1 or 1.0 hr.sup.−1.

6. A process for production of a hydroprocessed product comprising the steps of claim 1, and the further steps of d. a further hydroprocessing step, directing said hydrotreated product or a fraction thereof to contact a further material catalytically active in hydroprocessing, under hydroprocessing conditions providing a hydroprocessed hydrocarbon and e. providing a hydroprocessed product either as the hydroprocessed hydrocarbon product of step (d) or as a fraction of said hydroprocessed hydrocarbon product.

7. A process according to claim 6 in which the material catalytically active in hydroprocessing is a material catalytically active in hydrocracking such as a material comprising a metal component selected from Group VIII and/or VIB of the Periodic System and being supported on a carrier containing one or more oxides taken from the group consisting of alumina, silica, titania, silica-alumina, molecular sieves, zeolites, ZSM-11, ZSM-22, ZSM-23, ZSM-48, SAPO-5, SAPO-11, SAPO-31, SAPO-34, SAPO-41, MCM-41, zeolite Y, ZSM-5, and zeolite beta.

8. A process according to claim 7 in which the reaction step in the presence of a material catalytically active in hydrocracking is carried out at a temperature between 2000° C. and 400° C., a pressure between 15 and 200 bar, a liquid hourly space velocity between 0.2 hr−1 and 5 hr−1, and a hydrogen to hydrocarbon ratio between 100 and 2000 Nm.sup.3/m.sup.3.

9. A process according to claim 1, in which at least 80 wt % of either said hydrotreated product or said hydroprocessed product is a fraction boiling above 360° C.

10. A process according to claim 9 in which said hydroprocessed product fraction boiling above 360° C. is a lubricant or a lubricant base stock having a viscosity index of at least 110 or 120.

11. A process according to claim 1, in which at least 80 wt % of either said hydrotreated product or said hydroprocessed product is a fraction boiling between 150 and 350° C.

12. A process according to claim 11 in which said fraction boiling between 150 and 350° C. is a diesel or a diesel blend stock having a cetane index of at least 35, 38 or 40.

Description

BRIEF DESCRIPTION OF FIGURES

[0060] FIG. 1 illustrates the present disclosure, and

[0061] FIG. 2 illustrates a process employing an embodiment of the present disclosure.

NUMBERS REFERRED TO IN THE FIGURES

[0062] Raw coal tar 2 [0063] Feed fractionation column 4 [0064] Heavy asphalt fraction 6 [0065] Coal tar 8 [0066] Pump 10 [0067] Pressurized coal tar 12 [0068] Hydrogen rich stream 14 [0069] Hydrotreatment feedstock 16 [0070] Heat exchanger 18 [0071] Fired heater 20 [0072] Hydrodemetallization (HDM) reactor 22 [0073] Metal guard material 24 [0074] Quench hydrogen 26 [0075] Demetallized feedstock 28 [0076] Heat exchanger 30 [0077] Heavy hydrocarbonaceous feedstock 32 [0078] Hydrotreatment reactors 34, 40, 46 [0079] Intermediate cooling 38, 44 and 50 [0080] Partially hydrotreated hydrocarbon products 36, 42 and 48. [0081] Bypass line 52 [0082] Hydrotreated product 54 [0083] Further hydroprocessing reactor 56 [0084] By-pass line 62 [0085] Hydroprocessed hydrocarbon product 58 [0086] Cooler 60 [0087] High pressure separator 66 [0088] Product stream 68 [0089] Vapor stream 72 [0090] Compressor 74 [0091] Make-up hydrogen 76 [0092] Low pressure separator 70 [0093] Hydroprocessed product recycle stream 78 [0094] Hydroprocessed product 80 [0095] Fractionator 82 [0096] Fuel gas stream 84 [0097] Naphtha stream 86 [0098] Middle distillate (or diesel) stream 88 [0099] Unconverted oil (or lubricant base stock) stream 90.

[0100] In FIG. 1 an embodiment of the present disclosure is illustrated. According to FIG. 1 a heavy hydrocarbonaceous feedstock 32, having a high content of nitrogen, oxygen and aromatics, such as pretreated coal tar, is directed to a single hydrotreatment reactor 34 having one or more reactor beds, with optional addition of hydrogen 26 from a hydrogen rich gas 14 which mainly for temperature control may be done between reactor beds. From the hydrotreatment reactor a deep hydrotreated product may be withdrawn, which has a low nitrogen content, and thus high dearomatization has been possible in the zones furthest downstream in the reactor. Therefore the hydrotreated hydrocarbon product 48 has a low content of aromatics.

[0101] In FIG. 2 a process, employing an embodiment of the present disclosure is illustrated, including a number of optional elements, included to illustrate one way of pretreating a raw coal tar prior to deep hydrotreatment. A raw coal tar 2 is directed as feed to an optional feed fractionation column 4, in which a heavy asphalt fraction 6 may be withdrawn, before the coal tar 8 is directed to a pump 10, after which the pressurized coal tar 12 is combined with a hydrogen rich recycle stream 14, providing a hydrotreatment feedstock 16. The hydrotreatment feedstock 16, is heated in heat exchanger 18 and fired heater 20, before being directed to a hydrodemetallization (HDM) reactor 22, comprising a metal guard material 24, having a high metal absorption capacity and a hydrotreatment activity. To the HDM reactor, and other reactors quench hydrogen 26 is added mainly for temperature control from a hydrogen rich stream 14. The temperature of demetallized feedstock effluent 28 may be appropriately adjusted in heat exchanger 30 and directed as a heavy hydrocarbonaceous feedstock 32 to three hydrotreatment reactors in series 34, 40, 46, with optional intermediate cooling, 38, 44 and 50 of the partially hydrotreated hydrocarbon products 36, 42 and 48. In the illustration in FIG. 2 3 reactors are shown in series, each with 3 reactor beds, but in practice it may be fewer reactors or more reactors, and fewer or more reactor beds. The catalyst in the three reactors comprises in general a material catalytically active in hydrotreatment, but the specific composition in each reactor or each reactor bed may be tailored to the specific heavy hydrocarbonaceous feedstock, e.g. based on the amount of oxygen in the feedstock, which would be hydrogenated in exothermal hydrodeoxygenation reactions. At the outlet of the third hydrotreatment reactor a hydrotreated hydrocarbon product 48 is provided. The third reactor 46 may however also be fully or partially bypassed by line 52 if so required, e.g. until the conditions require that the third reactor is put in use, e.g. due to deactivation of the first and second reactors. The hydrotreated hydrocarbon product is directed as a hydrotreated product 54 to a further hydroprocessing reactor 56, or alternatively the further hydroprocessing reactor is by-passed by line 62. The further hydroprocessing reactor 56, may be either operating as a hydroisomerisation reactor, or as a hydrocracking reactor. If the further hydroprocessing reactor 56 is operating as a hydrocracking reactor, the product 58 will have reduced boiling point and a reduced yield of high boiling products, as these will be hydrocracked to form especially middle distillate products for e.g. diesel. Typically a hydrocracking reactor will involve a certain amount of yield loss, by conversion into light hydrocarbons.

[0102] If the further hydroprocessing reactor 56 is operating as a hydroisomerisation reactor, the product 58 will have only moderate change in boiling point, but instead a conversion of linear paraffins to branched paraffins will occur, which is beneficial as the cold flow properties of the isomerized product will be improved; i.e. the pour point will be lower. However, a reduction of viscosity index may also be observed as a result of paraffin isomerization. The yield loss will be moderate, but very often hydroisomerisation will be carried out only on a specific fraction after fractionation not shown in the figures, in a separate reactor to reduce yield loss even further. Typically the hydroisomerisation catalyst is similar to a hydrocracking catalyst, but selectivity is increased by operating at less severe conditions.

[0103] The hydroprocessed hydrocarbon 58 may be cooled in cooler 60 and separated in a high pressure separator 66, to a vapor stream 72 and a product stream 68. The vapor stream 72 is pressurized in compressor 74 and combined with make-up hydrogen 76. The product stream is depressurized in a low pressure separator (or optionally more), and an amount 78 may be directed for liquid recycle. Another amount of a hydroprocessed product 80 is directed to a fractionator 82.

[0104] According to FIG. 2 the fractionator is fractionating the product based on boiling point into a fuel gas stream 84, a naphtha stream 86, a middle distillate (or diesel) stream 88 and an unconverted oil (or lubricant base stock) stream 90.

[0105] In further embodiments, not illustrated in figures, the stream 48 may be separated into a heavy and a lighter stream. Often the lighter stream may be directly available as a diesel product or possibly require isomerization to improve the cold flow properties, whereas the heavy stream may require hydrocracking to yield a product in a desirable boiling range. By separating the hydrotreated product into a light fraction and a heavy fraction, it becomes possible to treat each fraction of the hydrotreated product optimally—which may or may not involve hydroprocessing of that fraction. This can reduce one or more of the total reactor size, the yield loss and the consumption of hydrogen, and it may even lead to a more attractive product mix. By providing a fractionator prior to the further hydroprocessing it may also be possible to avoid the fractionator 82 downstream further hydroprocessing.

[0106] In further embodiments, one or both of the optional separations may be carried out in simple gas liquid separators, operating at suitable pressure and temperature, or in a more complex distillation based fractionator operating at low pressure, providing a better separation. It may be beneficial to maintain an elevated pressure during separation as this will be more energy efficient, since the pressure in downstream reactors may not have to be re-established.

EXAMPLES

[0107] Three experiments were conducted to demonstrate the effect of highly effective hydrodenitrogenation and dearomatization processes.

[0108] A hydrotreatment catalyst was made as follows. Alumina powder, alumina gel and diluted nitric acid are mixed for 12 minutes and extruded, in 1/20″ trilobe shape. The extrudates are dried for 2 hours at 200° C. and then calcined at 550° C. The extrudates are then impregnated with an acidic NiMo solution prepared with phosphoric acid, molybdenum trioxide and nickel carbonate, adjusting the amounts to produce a catalyst with 16 wt % Ni, 3 wt % Mo and 3 wt % P. The catalyst is calcined at 370° C. for 2 hours.

[0109] The experiments were carried out in a unit with two isothermal reactors in series. The first reactor was loaded with 63 ml of commercial demetallization catalyst TK-743, followed by commercial dearsenation catalyst TK-47, whilst the second reactor was loaded with commercial hydrotreatment catalyst TK-609T HyBRIM™ from Haldor Topsøe A/S. The catalyst beds in both reactors were diluted by 40 vol % inert carborundum (SiC) prior to loading in order to improve the liquid distribution of the reactors. Pure hydrogen was used in once-through mode.

[0110] A straight-run fossil diesel spiked with TBDS was used for sulfiding the catalysts. Conditions at three different pressures were tested (168 barg, 120 barg and 100 barg) were tested. Results from the experiments are shown in Table 2.

[0111] The feed for the experiments was a tar from gasification of coal, having the properties of Table 1. The determination of aromatic content was carried out according to method ASTM D6591.

TABLE-US-00001 TABLE 1 Property Method Unit SG 60/60 D 4052 1.0144 Density @ 40 oC D 4052 g/cm3 0.9969 S D 4294 wt ppm 2498 N D 4629 wt ppm 6605 H D 7171H wt % 8.85 O Elementary wt % 5.72 Aromatics D 6591 wt % 50.1 1 Ring D 6591 wt % 6.3 2 Ring D 6591 wt % 13.19 3+ Ring D 6591 wt % 30.61

[0112] Experiments 1, 2 and 3 were carried out in two isothermal reactors in series, with the conditions of the hydrotreatment reactor being stated in Table 2.

TABLE-US-00002 TABLE 2 EXAMPLE 1 2 3 Operating conditions Weight average ° C. 362 360 361 temperature Pressure barg 168 120 100 Overall LHSV 1/h 0.41 0.41 0.35 H.sub.2/oil Nl/l 2247 2227 2235 Total liquid AP1 product SG 60/60F 0.8507 0.8630 0.8736 Hydrogen wt % 13.52 12.93 12.51 Sulfur wt ppm 9.5 13.8 20.2 Nitrogen wt ppm 1.10 0.62 1.75 Total Aromatics Monoaromatics wt % 8.01 27.40 38.60 Diaromatics wt % 0.38 1.81 3.52 3+ ring Aromatics wt % 0.06 0.45 0.91 Aromatics saturation % HD mono % 83.9 42.7 15.5 aromatics % HD di % 97.1 86.3 73.3 aromatics % HD tri+ % 99.8 98.5 97.0 aromatics Yields Naphtha yield wt % FF 16.79 15.38 14.33 Middle distillate wt % FF 72.29 73.23 75.23 yield Lube base oil wt % FF 5.51 5.86 6.56 yield Middle distillate D4737 38.30 35.10 33.50 cetane index Lube base oil VI D 2270 152.9 135.9 115.4

[0113] The results of Table 2 demonstrate that a significant yield of a high viscosity index lubricant is possible.

[0114] When compared to the prior art it is seen that the product according to Experiment 1 is having a 5 wt % yield of a fraction with excellent lubricant base stock properties, as well as about 70 wt % diesel of good quality. Also the product of experiments 2 and 3 were deeply hydrotreated, and included middle distillate and lube base oil of good quality, but the lower severity of hydrotreatment was reflected in a higher aromatic content. This was reflected in a lower product quality; for the middle distillate a lower cetane index and for the lube base oil a lower VI. In comparison, the lubricant products according to the prior art were documented to have inferior VI of only 105. This is assumed to be due to insufficient dearomatization, which again is believed to be related to insufficient hydrodenitrogenation.

[0115] All three examples fall under the present disclosure; examples 1 and 2 show a high extent of saturation of all aromatics, while example 3 shows a high extent of saturation of di-aromatics and tri-aromatics.

[0116] The high viscosity index lubricant fraction of the present disclosure indicates that this fraction has a high content of paraffins. Similarly the middle distillate of experiment 1 has a higher cetane index that the middle distillates of experiments 2 and 3, which is also believed to indicate a high paraffin content.