RU2141505C1 - Method of preparing winter diesel fuel - Google Patents

Abstract

FIELD: petrochemistry. SUBSTANCE: method comprises atmospheric distillation of petroleum, compounding of fractions and hydrorefining of distillates. Atmospheric distillation of petroleum isolates fraction 98% of which vaporize within 260-370 C and 96% vaporize within 260-370 C, and residual fraction of above 360 C to be distilled under vacuum to isolate fraction 96% of which vaporizes at 220- 370 C; 10-30% of fraction of 260-370 C is subjected to secondary distillation to isolate fractions of 220-330 C and 320-370 C. Fractions of 260-370 C, 320-370 C and 220-370 are mixed at 30:5:5-45:15: 15 ratios and are subjected to hydrorefining; hydrorefined fraction is compounded with fraction of 160-330 C and with fraction of 220-330 C resulting from secondary distillation at 30:30:40-60:20:20 weight ratios, and the resulting base fuel is replenished with 0.005-0.8 wt % of depressor addition agent which is ethylene-vinyl acetate-vinyl propinate copolymer having molecular weight of 2.10²-17.10³ and molecule branching wherein CH₃ is used for 100 C-8-25 carbon atoms. EFFECT: increased yield of the winter diesel fuel. 2 cl, 3 tbl

Description

 The invention relates to the refining industry, in particular to methods for producing winter diesel fuels from products of direct distillation of oil.

 Currently, the production of low-curing diesel fuels does not exceed 12% of the total fuel production, as a result of which, in fact, the need for winter grades of diesel fuels is satisfied only up to 40%. The bulk of winter diesel fuel (39% of its production) is produced according to GOST 305-82 by lowering the boiling point of summer diesel fuel, which leads to a decrease in its resources.

 Along with GOST 305-82, winter diesel fuel developed in accordance with TU 38.401-58-36 with a depressant additive (DZp brand fuel) has been developed for use in temperate regions.

This fuel is recommended for the operation of diesel engines in the winter at an ambient temperature of at least minus 25 ^o C.

 The method of production of winter diesel fuel in the industry is as follows.

The oil is subjected to distillation on an AT or ABT unit with the separation of a fraction of kerosene (120-240 ^o C stripping K-3/1, light diesel fraction (200-320 ^o C), stripping K-3/2 and heavy (240-360 ^o C ) K-3/3 stripping. Part of the mixture of K-3/2 and K-3/3 strips is hydrotreated.

Winter diesel fuel according to GOST 305-82 with a pour point of minus 35 ^o C and a cloud point of minus 25 ^o C is produced by compounding fractions from strips K-3/1 and K-3/2. At the same time, the end of boiling of the K-3/2 stripping fraction does not exceed 320 ^o C. When producing low-sulfur diesel fuel, the fractions are hydrotreated (Fuel, lubricants, technical fluids. / Handbook. M: Chemistry, 1989, p. 65).

 Winter diesel fuel resources largely depend on the use of no less scarce jet fuel (K-3/1 stripping).

 Moreover, the demand for it is growing all the time.

 In this regard, it is important to develop a method for producing winter diesel fuel with minimal use of the fractions used for jet technology in its composition.

A known method of producing diesel fuel by fractionating oil in an atmospheric vacuum direct oil distillation unit with the separation of the kerosene fraction 120-24000 (stripping K-3/1), fraction 200-300 ^o C (stripping K-3/2) and fraction 260- 360 ^o C (stripping K-3/3). Fractions 200-300 ^o C and 260-360 ^o C are mixed in the balance ratio. 20% of this fraction is sent to a secondary distillation unit with the separation of a fraction of 200-320 ^o C, followed by its hydrotreating under known conditions on a GKD-202P zeolite-containing catalyst at a pressure of 25 atm, a temperature of 370 ^o C and a volumetric feed rate of 2.5 h ^-1 . Next, the hydrotreated fraction is subjected to zeolite dewaxing (Parex process) to obtain a denormalizate. Compounding the fraction 180-360 ^o C, 120-240 ^o C (kerosene) and denormalizate produced in a ratio of 25: 30: 45%.

A depressant additive is introduced into the base fuel, which is a product of a radical copolymerization of alkyl methacrylate with vinyl acetate in an amount of 0.2%. The resulting diesel fuel has a limiting filterability temperature of up to minus 40 ^o C and pour point minus 50 ^o C.

At higher concentrations of the 180-360 ^o C fraction, the additive has virtually no effect on the low temperature properties of diesel fuel. Thus, this method of winter diesel fuel involves the involvement of at least 30% of scarce kerosene and up to 45% of expensive denormalizate (Chemistry and technology of fuels and oils. 1986, No. 5, p. 2-4).

The closest in technical essence and the achieved result to the invention is a method for producing winter diesel fuel by fractionating oil in an atmospheric vacuum direct distillation unit with the separation of fractions of kerosene 120-260 ^o C and diesel 160-320 ^o C and 230-360 ^o C ( strippers K-3/1, K-3/2 and K-3/3) (RF patent N 2039791, C 10 G, 55/08, 1995).

The kerosene fraction is subjected to additional distillation to obtain fractions NK-240 ^o C and residual. A part of the mixture of fractions K-3/2 and K-3/3 is sent to the secondary distillation with the separation of the fraction 200-320 ^o C.

The diesel fraction 200-320 ^o C is subjected to catalytic hydrotreating and subsequent dewaxing, and the dewaxed diesel fraction is mixed with a mixture of diesel fractions or the last subjected to additional catalytic hydrotreating, kerosene and residual fraction in the following ratio of components, wt.%:
Dewaxed diesel fraction - 10-20
A mixture of diesel fractions or the last, subjected to additional catalytic hydrotreating - 20-50
Kerosene fraction - 30-50
Residual fraction - up to 100
In this production method, up to 50% of kerosene fractions are involved in winter diesel fuel, which leads not only to a significant reduction in fuel for aviation, but also to the cetane number.

 The aim of this invention is to increase the yield of winter diesel fuel not through the use of kerosene fractions, but by using fuel of a heavier fractional composition and the introduction of depressant additives into it.

According to the proposed method, the oil is subjected to primary distillation with a maximum selection of kerosene fractions 120-280 ^o C (stripping K-3/1), fractions, 98% of which are distilled within 160-300 ^o C (stripping K-3/2), fractions 96% of which is distilled at 260-370 ^o C. 10-30% of the latter is subjected to secondary distillation with the allocation of fractions, 96% of which are distilled at 220-330 ^o C and 320-370 ^o C.

The residual fraction above 360 ^o C is sent to vacuum distillation with the release of distillate, 96% of which boils at a temperature of 220-370 ^o C.

In order to maximize the selection of the diesel fraction from fuel oil (fractions above 360 ^o C) in the K-7 vacuum column, the top temperature is maintained at not lower than 120 ^o C, and the bottom of the column is within 250-280 ^o C with a residual pressure in the column of 600-700 mm RT .art. Such a regime in the column ensures the selection of a diesel fraction with predetermined boiling limits up to 94% of its potential content in fuel oil.

Fractions 260-370 ^o C (straight run), 320-370 ^o C from the secondary distillation and 220-370 ^o C from the vacuum distillation are combined in a ratio of 30: 5: 5 - 45:15: 15 and hydrotreated with alumina-cobalt (nickel) molybdenum the catalyst at a pressure of 3.5 MPa, at a temperature of 345-380 ^o C, the volumetric feed rate of 3.0 hours ^-1 . The hydrotreated fraction is compounded with fractions of 160-330 ^o C and 220-330 ^o C in a ratio of 30:30:40 - 60:20:20.

 The separation of the winter diesel component during the secondary distillation, which is characterized by a low sulfur content and good low temperature properties, as well as its use without the use of a hydrotreating process, will increase the yield of winter diesel fuel. Only heavy distillate fractions are sent for hydrotreating, which contributes to a more qualified use of the hydrotreating unit and an increase in the degree of desulfurization of the fuel. As a result of the proposed method, the selection of kerosene will be more than 70% of its potential content in oil. Base winter diesel fuel has good low temperature properties.

A highly effective depressant additive is introduced into the base fuel, which is a copolymer of ethylene with vinyl acetate and vinyl propinate at a concentration of 0.005-0.8 wt.% Per mol. m 2 • ¹⁰ February -. • 17 March ¹⁰ and branching, characterized by the ratio of CH _3/100 ^o C - 8-25.

The proposed method for producing winter diesel fuel provides maximum extraction of kerosene and winter diesel fuel from oil at the same time. The introduction of additives of a given composition allows to lower the pour point and ultimate filterability, respectively, below minus 35 and minus 25 ^o C (technical requirements).

 Table 1 presents the quality of the fractions. In tables 2 and 3 - data on the composition and quality indicators of winter diesel fuel.

 From the data of table 1 it follows that the distillates of diesel fuel practically do not contain kerosene fractions. Secondary distillation of the heavy diesel fraction allows you to allocate an additional amount of low-curing diesel fuel, and vacuum distillation of fuel oil - diesel distillates. Compounding them in predetermined proportions provides a high-quality base fuel with a high response rate to a depressant additive.

 Changing the specified ratios of the fractions leads to a deterioration in the quality of the fuel or a decrease in its yield.

 When the hydrotreated component in the fuel increases, the cloud point rises (Example 5). With a decrease in its content below predetermined limits, the sulfur content in the fuel increases (Example 4). A change below the specified limits for the content of winter diesel fuel distillates in the fuel leads to a deterioration in low-temperature characteristics, especially cloud point.

 The use of depressant additives with a molecular weight and branching of molecules outside these limits leads to a decrease in the effectiveness of its action. The use of lower concentrations of additives (below 0.005%) does not allow to obtain fuel with the desired low temperature properties (examples 6, 7). Increasing the concentration of the additive above 0.8% leads to an increase in its consumption.

 The proposed method for producing winter diesel fuel allows to increase the yield of winter diesel fuel from 28.3 to 30.1% and improve its operational characteristics (cetane number).

Claims (2)

1. A method of producing winter diesel fuel by atmospheric distillation of oil, compounding fractions and hydrotreating of distillates, characterized in that fractions are isolated during atmospheric distillation of oil, 98% of which boils off within 160 - 330 ^o C and 96% within 260 - 370 ^o C, and the residual fraction above 360 ^o C, subjected to vacuum distillation with the separation of the fraction, 96% of which boils at a temperature of 220 - 370 ^o C; 10-30% of the fraction 260 - 370 ^o C is subjected to secondary distillation with the separation of fractions 220 - 330 ^o C and 320 - 370 ^o C, fractions 260 - 370 ^o C, 320 - 370 ^o C and 220 - 370 ^o C are mixed in a ratio of 30 : 5: 5 - 45: 15: 15 and hydrotreated, the hydrotreated fraction is compounded with a fraction of 160 - 330 ^o С and with a fraction from secondary distillation of 220 - 330 ^o С in a mass ratio of 30: 30: 40 - 60: 20: 20 and 0.005-0.8 wt.% depressant additive, a copolymer of ethylene with vinyl acetate and vinyl propinate mol.m, is introduced into the obtained base fuel. 2 • 10 ² - 17 • 10 ³ and the branching of the molecule, characterized by the ratio of CH ₃ per 100 C 8 - 25 atoms.  2. The method according to claim 1, characterized in that the depressant additive is introduced into the base fuel in the form of a solution in diesel fuel or in aromatic hydrocarbons with a concentration of 1.0 to 80 wt.%.

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