RU2141994C1 - Process for production of environmentally safe diesel fuel from sulfur-bearing oils - Google Patents

Abstract

FIELD: petroleum processing and petrochemical processes. SUBSTANCE: fuel is produced by distilling crude oil to isolate kerosene and diesel fractions and catalytic hydrofining of the latter at elevated temperature and hydrogen pressure involving layered charge of aluminum-cobalt-molybdenum and aluminum-nickel-molybdenum catalysts. Process is distinguished by that kerosene and diesel fraction with boiling ranges (160-190)-300 C and (300-310)-390 C, respectively, are isolated and further combined at weight ratio from 70: 30 to 30:70, after which resultant mixture is subjected to hydrofining in presence of, densely arranged in mixture travel direction, catalyst beds: one bed of spherical aluminum-nickel-molybdenum catalyst with grain diameter 2.8- 4.2 mm and two beds of aluminum-cobalt-molybdenum catalyst made in the form of trifolium with diameters 1.8-2.6 and 1.3-1.8 mm, respectively, at weight ratio of the three beds (1.0-1.5):10:(30-35). Catalysts are preliminarily sulfurized with straight-run diesel fraction with shortened end boiling point (no higher than 340 C) and content of sulfur 0.4-1.0 wt %, sulfurization being carried out at gradual temperature rise: to 160-200, 220-240 and 300-340 C and keeping each temperature constant for 2 hr. Hydrofining is carried out at 330-370 C and pressure 2.5-4.0 MPa, liquid space velocity 3.0-4.5 hr^-1. Resulting hydrogenate is stabilized at column top temperature 115-160 C, column bottom temperature 250-320 C, and pressure 0.1-1.2 MPa to produce fraction (160-190)-380 C. EFFECT: increased hydrofining efficiency, increased yield of diesel fuel, and specified technology. 1 tbl

Description

 The invention relates to methods for environmentally friendly diesel fuel from sulfur oils and can be used in the refining and petrochemical industries.

The following methods for producing low-sulfur diesel fuel are known:
- by using an effective hydrotreating catalyst GO-86, providing a residual sulfur content in the target fuel of up to 0.02 wt.% / Oil refining and petrochemicals, 1995, N11, p.15. /,
- by hydrodesulphurization of a straight-run fraction with a sulfur content of not higher than 1.3 wt.% and 95% of which it boils off at a temperature of not higher than 360 ^o C in the presence of a composition catalyst, wt.%: MoO ₃ - 18-19, NiO-4-5% , P ₂ O ₅ - 4.5-5.0%, deposited on an aluminum oxide carrier. Sulfur content in hydrotreated fuel 0.1% wt / Oil refining and petrochemicals 1997, N1, p. 21-22 /,
- by hydrotreating the feedstock in the presence of three layers of catalysts: aluminum-cobalt-molybdenum (AKM), aluminum-nickel-molybdenum (ASM) and aluminum-cobalt-molybdenum (AKM) with a mass ratio of catalysts in the layers of 0.5-1.0: 4.0-4.5: 5.0- 8.0, the catalysts being pre-sulfurized by loading elemental sulfur on top of each layer (3). SU 1801116, 07.03.93)
The disadvantages of the above methods are: increased temperature at which a satisfactory hydrodesulfurization activity of the catalytic system is achieved (above 360 ^o C) and the resulting reduced yield of hydrotreated diesel fuel (93.5-95.2 wt.%).

The closest in technical essence and the achieved result to the present invention is a method for producing low-sulfur diesel fuel obtained by hydrotreating diesel fractions at elevated temperature and pressure in the presence of a layer of aluminum-cobalt-molybdenum catalyst, characterized in that they use a layer of aluminum-cobalt-molybdenum catalyst with a diameter of granules of 3.2-4 , 0 mm in a mixture with elemental sulfur and hydrotreating is carried out additionally in the presence of successive layers of zeolitso holding catalyst with a diameter of granules of 2.0-3.2 mm and aluminum-nickel-molybdenum catalyst taken in a mass ratio of 1: 1: 1.3 - 8.0 and previously activated in a hydrogen-containing gas at 350-400 ^o C (RU, 2005765, 12.12.91).

The disadvantages of this method are the following factors:
- use when loading the catalyst additional reagent - elemental sulfur. The application of this technology leads to technical difficulties when loading the catalyst, the cost of production of low-sulfur diesel fuel,
- the use of a zeolite-containing catalyst in the middle loading layer, which is manufactured by a different technology than the catalysts of the upper and lower layers. The use of a zeolite-containing catalyst leads to increased destruction of the feedstock, resulting in a decrease in the yield of the target fuel. In addition, catalysts of this type are particularly sensitive to poisoning by nitrogen-containing compounds of raw materials, therefore, the use of diesel fuels containing heavier components leads to rapid deactivation of the catalytic system,
- the hydrotreating process to ensure the required degree of removal from raw materials is carried out at elevated pressure of 4 MPa. Most hydrotreating units operate using hydrogen-containing gas from reforming units and the outlet pressure from these units does not exceed 3.5 MPa.

 The aim of this invention is to increase the depth of hydrotreatment of diesel fuel, increase its yield, as well as simplify the production of environmentally friendly fuels by carrying out hydrodesulfurization in mild technological conditions.

The goal is achieved in the following way. The oil is subjected to atmospheric distillation with the separation of fractions (160-190) -300 ^o C and (300-310) -390 ^o C. Then they are combined in a mass ratio of 70: 30-30: 70. The resulting mixture is sent to a hydrotreatment unit with a sequential arrangement of reactors in which two catalysts are densely loaded layer-by-layer tightly using special devices: in the upper layer, a spherical aluminum-nickel-molybdenum catalyst with a diameter of 2.8-4.2 mm and two layers of a trefoil-aluminum-cobalt-molybdenum catalyst with a diameter of 1.8-2.6 and 1.3-1.8 mm, respectively, with a mass ratio of layers (1.0-1.5): 10: (30-35).

To increase the activity of the catalyst, it is specially treated with a straight-run diesel fraction with a boiling end not exceeding 340 ^o C, with a sulfur content of 0.4-1.0 wt. %, with a stepwise rise in temperature to 160-200, 220-240 and 300-340 ^o C with exposure at each temperature for 2 hours.

Hydrotreating of diesel fuel is carried out at a pressure of 2.5 - 4.0 MPa, a temperature of 330 - 370 ^o C, the volumetric feed rate of 3.0-4.5 h ^-1 .

The obtained hydrogenate enters stabilization at a column top temperature of 115-160 ^o C, bottom 260-320 ^o C, at a pressure of 0.1-1.2 MPa to obtain the target fuel fraction (160-190) -380 ^o C.

The proposed method for producing fuel by preparing a catalyst, special loading it, selecting the ratio of fuel fractions can significantly simplify the process of obtaining environmentally friendly fuel, provide the necessary cleaning it from sulfur, expand the limits of the fractional composition of the original fuel by involving fractions with a higher boiling point (up to 390 ^o C) and thereby increase the yield of low sulfur diesel fuel. The table presents data on the main process parameters of the invention and prototype.

 The following are specific examples of the invention.

 Example 1 (prototype).

Hydrotreating is subjected to a diesel fraction of 180-360 ^o C containing 1.6 wt. % sulfur. As an alumina-cobalt-molybdenum catalyst (top layer), a catalyst with a NiO content of 4.1 wt.%, MoO _{3 of} -15.4% is used. The middle layer is a zeolite-containing catalyst with a total content of hydrogenating metals of 17 wt.%, High-silica zeolite (CVM) -5 wt.%. The lower layer is an aluminum-nickel-molybdenum catalyst of the grade DT-005H (TU 38.301-13-91), with a MoO ₃ content of 16, 2 wt.%, NiO - 5.0 wt.% The sulfur content in the upper layer is 20% of the total mass of the upper and middle catalyst. The activation of the catalyst is carried out by elemental sulfur in a hydrogen-containing gas at a temperature of 350-400 ^o C. The ratio between the layers of the catalysts is 1.0: 1.0: 1.3. Hydrotreating is carried out at a pressure of 4 MPa, a temperature of 360 ^o C. The residual sulfur content in the hydrogenate is 0.02 wt.%
Example 2

The oil is subjected to distillation in an atmospheric installation with the separation of fractions (160-190) -300 ^o C (stripping K-3/2) and (300-310) -390 ^o C (stripping K-3/3), mix them in a mass ratio 30:70. The resulting diesel fuel distillate with a sulfur content of 1.6 wt.% Is sent to a hydrotreating reactor loaded sequentially along the feed with AMM catalysts with a diameter of 2.8 mm, AKM with a diameter of 1.8 and 1.3 mm with a catalyst ratio of 1:10:30 .

 As an AKM catalyst (middle and lower layers), an industrial catalyst was used containing oxides, wt.%: Molybdenum - 5.3, cobalt - 1.7, aluminum - the rest was up to 100.

The catalyst was preliminarily blackened with a straight run diesel fraction with a light boiling end (338 ^o C) with a stepwise rise in temperature to 160, 220 and 300 ^o C with exposure at each temperature for 2 hours.

 The process parameters and characteristics of the fractions are given in the table.

 Examples 3 to 4.

 The method according to example 2 is carried out. The ratio between the catalyst layers is 1.5: 10: 35 (example 3) and 1.25: 10: 32 (example 4), respectively. The remaining parameters and characteristics of the fractions are given in the table.

 Examples 5-6.

 The method according to example 4 is carried out by changing the diameter of the catalyst granules and the following ratio between the catalyst layers is 1.25: 10: 32. Reducing the diameter of the granules below those indicated in the invention leads to a decrease in the strength of the catalyst and an increase in pressure in the reactor (Example 5). The sulfur content in the finished fuel is increasing. An increase in the diameter of the granules leads to a decrease in the hydrodesulfurization activity of the catalyst due to a decrease in its total activity (Example 6).

 Examples 7-8.

 The method according to example 4 is carried out by changing the ratio between the catalyst layers beyond the limits specified in the invention, namely 0.9: 9: 28 (example 7) and 1.2: 11: 36 (example 8). In both cases, the activity of the catalyst system decreases. The sulfur content of hydrotreated diesel fuel is increasing.

 Example 9

The method is carried out according to example 4. Sulfurization of the catalyst is carried out with diesel fuel with a higher boiling point (354 ^o C). At the same time, coke formation on the catalysts increases, their activity decreases. The sulfur content in the hydrogenate is increasing.

 Example 10

 The method is carried out as in example 4. Sulfurization of the catalyst is carried out with diesel fuel with a sulfur content of 0.35%. At the same time, the duration of the activation cycle of the catalyst increases, the partial pressure of H2S in the reactor decreases, which leads to less complete sulfurization of the catalyst and a decrease in its activity. The sulfur content in hydrotreated fuels is increasing.

 Example 11

 The method is carried out as in example 4. Sulfurization of the catalyst is carried out without a stepwise rise in temperature with an exposure of 2 hours at each temperature. In this case, intense heat generation and faster coking of the catalyst occur, which leads to a decrease in its activity and an increase in sulfur in the target fuel.

 Examples 12-13.

The method is carried out as in example 4. The conditions for stabilizing the hydrogenate are changed. With a decrease in the temperature of the top and bottom of the stabilization column, as well as pressure, the blow-off time of H2S increases and the hydrotreated fuel does not withstand the corrosion test (Example 12). With an increase in the temperature of stabilization of the top of the column above 320 ^o C (325 ^o C), as well as a decrease in pressure, part of the fraction of diesel fuel left with gasoline fractions. Hydrotreated fuel had an increased cloud point (minus 3-4 ^o C) instead of minus 5 ^o C according to GOST 305-82. The yield of the target fuel is reduced (example 13).

 Example 14-15

The method is carried out as in example 4. Raw materials with a lower content of fractions (160-190) -300 ^o C and higher fractions (300-310) -390 ^o C. were fed to hydrotreatment.

The decrease in the content of fuel fractions (190-200) -300 ^o C leads to a deterioration of desulphurization of diesel fuel and an increase in sulfur content in the target product (example 14).

 The increase in heavy fractions in diesel fuel leads to an increase in the pour point of the target fuel (example 15).

 The low content in the mixture of heavy atmospheric distillation fractions leads to a decrease in the yield of the target product.

Claims (1)

A method of producing environmentally friendly diesel fuel by distillation of oil with the separation of kerosene and diesel fractions, catalytic hydrotreating of the latter at elevated temperature and pressure of hydrogen using layer-loaded alumina-cobalt-molybdenum (AKM) and alumina-nickel-molybdenum (ASM) catalysts, characterized in that fractions ( 160 - 190) - 300 ^o C and (300 - 310) - 390 ^o C, further admixed in a weight ratio of 70: 30 - 30: 70, the resulting mixture is subjected to hydrotreating in the presence of dense LAYOUT catalytic layers along the feed: spherical ASM with a diameter of 2.8 - 4.2 mm and two AKM layers made in the form of a trefoil with a diameter of 1.8 - 2.6 and 1.3 - 1.8 mm, respectively, with a mass ratio of layers (1.0 - 1.5): 10: (30 - 35), and the catalysts are pre-sulfurized with a straight-run diesel fraction with a light boiling point not exceeding 340 ^o C and a sulfur content of 0.4 - 1.0 wt.% With step raising the temperature to 160 - 200, 220 - 240 and 300 -340 ^o C, with holding at each temperature for 2 hours, while hydrotreating the raw materials is carried out at a temperature of 330 - 370 ^o C, d the pressure of 2.5 - 4.0 MPa, the volumetric feed rate of 3.0 - 4.5 h ^-1 , and the resulting hydrogenate is subjected to stabilization at a temperature: top of the column 115 - 160 ^o C, bottom - 250 - 320 ^o C, at a pressure of 0.1 - 1.2 MPa to obtain the target fuel fraction (160 - 190) - 380 ^o C.

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