RU2206601C2 - Hydrodesulfurization method for catalytic cracking gasoline fraction - Google Patents

Abstract

FIELD: petrochemical processes. SUBSTANCE: gasoline fraction is subjected to rectification separation into three fractions: low-boiling fraction b.p.-60-70 C, middle-boiling fraction 60-70 to 150-160 C, and heavy fraction 150-160 to dry point. The latter is subjected to hydrodesulfurization on oxide-sulfide catalyst and elevated temperature and hydrogen- containing gas pressure and then combined with low-boiling and middle-boiling fractions. EFFECT: decreased sulfur level in catalytic cracking gasoline fractions with no loss in content of olefins and decrease of octane number. 1 dwg, 3 ex

Description

 The invention relates to chemical technology, in particular to methods for hydrotreating gasoline fractions, and can be used in the refining and petrochemical industries.

 Catalytic cracking gasoline (CCF), which is one of the main multi-tonnage components of gasoline and determining the consumer properties of the latter, is characterized by a high content of aromatic (20-30% or more) and olefin (16-40%) hydrocarbons. In cases where non-hydrotreated raw materials are processed at catalytic cracking plants, the high content of sulfur compounds in the resulting gasoline fractions (0.25-0.35 wt.% Or more) makes it difficult to use them for the preparation of marketable gasolines.

 The process of hydrotreating gasoline fractions of CCF is technologically more complicated than the hydrotreating of straight-run gasoline fractions, since hydrogenation reactions of olefinic hydrocarbons should not proceed with simultaneous maximum removal of sulfur compounds. One of the most important factors determining the efficiency of this process is the fractional composition of the raw material. By purging from organosulfur compounds only the high boiling portion of the gasoline fraction of CCF, which does not contain olefinic hydrocarbons, significantly increase the depth of desulfurization, since hydrotreating can be carried out under more severe conditions. In this case, due to the low content of unsaturated hydrocarbons, there is a slight temperature difference at the inlet and outlet of the reactor and there is no drop in the octane number (OR).

 Known methods for hydrodesulfurization of gasoline fractions of CCF [US patent 5 391 288, class. C 10 G 45/00, 69/00; Aladysheva EZ, Peregudova VA, Strom L. D., Khuramshin RT - Chemistry and technology of fuels and oils, 1988, 3, p. 34-35; U.S. Patent 5,397,455, cl. C 10 G 45/02, 69/02], according to which the CCF gasoline fractions containing sulfur and olefins are subjected to hydrodesulfurization at elevated temperature and pressure in the presence of a catalyst containing metals of groups 8 and 6 of the periodic system on an aluminum oxide support, to obtain low sulfur product.

 A disadvantage of the known methods is the reduction in the value of the OCP of gasoline KKF after hydrodesulfurization.

Known [US patent 5318690, cl. C 10 G 35/00, 45/00, 208-89] a method for refining a gasoline fraction of KKF boiling at a temperature above 162 ^{° C.} by initially fractionating a wide gasoline fraction of KKF into low boiling and high boiling. Next, the high boiling gasoline fraction is subjected to catalytic hydrodesulfurization in the presence of hydrogen at elevated temperature and pressure.

 The disadvantage of this method is the low value of the HF product, which forces it to be subjected to additional treatment with an acid catalyst in order to increase the HF of the final product and secondary hydrodesulfurization to obtain a desulfurized product with gas boiling limits.

 Known [application EPO 940464, cl. With 10 G 65/00, publ. September 8, 1999] a method of reducing the sulfur content by separating KKF gasoline into a light fraction constituting 50-80% of the product, a medium boiling fraction constituting 10-30% of the product, and a heavy fraction constituting 5-20% of the product. The heavy fraction is subjected to hydrodesulfurization until S is completely removed. The product is mixed with the medium boiling fraction and again hydrotreated.

 The disadvantage of this method is the need for purification of gasoline in 2 stages, which complicates the technological scheme for producing gasoline CCF with low sulfur content.

 The closest solution to the technical nature and the achieved results is a method of purification of gasoline KKF [RF patent 2134287, cl. With 10 G 55/06, publ. August 10, 1999], according to which the hydrodesulfurization in the presence of an oxide-sulfide catalyst at elevated temperature and pressure of a hydrogen-containing gas is subjected to a heavy unstable gasoline fraction of KKF, which is withdrawn as an upper circulation irrigation from a distillation column of the KKF plant, followed by its return after hydrodesulfurization to this the same distillation column and stabilization in conjunction with a non-hydrotreated light gasoline fraction.

 The disadvantage of the method adopted for the prototype is the relatively low depth of sulfur removal from gasoline CCF, because the fraction subjected to hydrodesulfurization has a higher boiling point and contains 30-50% of the kerosene fraction, which does not need to be subjected to hydrodesulfurization.

 The aim of the invention is to reduce the sulfur content in gasoline fractions of CCF without reducing the content of olefinic hydrocarbons in them and reducing the value of OCh.

This goal is achieved by the method of hydrodesulphurization of the gasoline fraction of KKF in the presence of an oxide-sulfide catalyst at elevated temperature and pressure of a hydrogen-containing gas, according to which the gasoline fraction of KKF by distillation is divided into 3 fractions: low-boiling n.k.- 60-70 ^o C, medium boiling 60-70 - 150-160 ^o With and heavy 150-160 ^o With - ^C. The heavy gasoline fraction is subjected to hydrodesulfurization, followed by mixing it with non-hydrotreated low boiling and medium boiling gasoline fractions.

An essential distinguishing feature of the proposed method is that the gasoline fraction of CCF by distillation is divided into 3 fractions: low boiling N. to. - 60-70 ^o С, medium boiling point 60-70 - 150-160 ^o С and heavy 150-160 ^o С - к. To., The heavy gasoline fraction is subjected to hydrodesulfurization, followed by mixing it with non-purified light boiling and medium boiling gasoline fractions.

 Thus, the claimed method meets the criteria of the invention of "novelty."

 Analysis of known technical solutions for cleaning gasoline fractions KKF allows us to conclude that there are no signs in them that are similar to the essential distinguishing features of the claimed method, that is, the compliance of the proposed method with the requirements of an inventive step.

The essence of the proposed method is as follows (see drawing). The distillate of the vacuum distillation of fuel oil, which has not undergone preliminary hydrotreatment, is subjected to catalytic cracking in the presence of a microspherical zeolite-containing catalyst. On the main distillation column K-1 of the fractionation unit of the KKF unit, cracking products are separated into a wide gasoline fraction of n.k. - 205-215 ^o C (sulfur content before turning on the unit of hydrodesulfurization of 0.22-0.30 wt.%, OHM m.m. 80.6-80.9 points) and gas oil fractions.

A wide gasoline fraction is sent for fractionation to a K-2 distillation column with a conclusion of 3 fractions: low boiling (NK - 60-70 ^o С), medium boiling (60-70 - 150-160 ^o С) and heavy (150-160 ^o S - c.k.). The outputs of the fractions 15-20, 60-65 and 20-25 wt.%, Respectively. The working conditions of the column: top temperature 88-90 ^o C; bottom 224-229 ^o C; top pressure 2.8-3.0 ati; bottom 3.1-3.3 ati.

The heavy gasoline fraction (sulfur content 0.55-0.70 wt.%) Is subjected to hydrodesulfurization in the presence of an oxide-sulfide catalyst at a pressure of 2.8-4.5 MPa and a space velocity of 3-5 h ^-1 . The hydrogenate in the stripping column K-3 undergoes stabilization at a top temperature of 85-90 ^o C, bottom 105-110 ^o C, a pressure of 1.2-1.4 ati.

 After mixing the hydrotreated heavy gasoline fraction with low-boiling and medium boiling gasoline fractions, KKF obtain a stable gasoline fraction with a sulfur content of 0.07-0.09 wt.% While maintaining the value of the RP.

 The advantages of the proposed method are illustrated by the following examples.

Example 1
The distillate of the vacuum distillation of fuel oil fr. 350-540 ^o C, obtained from a mixture of West Siberian, Tatar and Bashkir oils and not previously hydrotreated (sulfur content of 1.66 wt.%, Fractional composition: up to 360 ^o C boils 5%, 95% - 538 ^o C), subjected catalytic cracking at a temperature in the reactor of 520 ^o C in the presence of a microspherical zeolite-containing catalyst Futura-120 GSR. On the main distillation column K-1 of the fractionation unit of the KKF unit, cracking products are separated into a wide gasoline fraction of n.k. - 215 ^o C (sulfur content of 0.30 wt.%, BH m.m. 80.6 points, density 730 kg / m ³ , iodine number 80 g / 100 g) and gas oil fractions.

Wide gasoline fraction n. K. - 215 ^o C (yield 50.3 wt.% for raw materials) sent to fractionation in a distillation column K-2 with the conclusion of 3 fractions: low boiling (n.k. - 60 ^o C), medium boiling (60-150 ^o C ) and heavy (150 ^o C - K. to.). The outputs of the fractions 17, 58 and 25 wt.%, Respectively. The working conditions of the column: top temperature 88 ^o C, bottom 224 ^o C, top pressure 3.0 ati, bottom 3.3 ati.

The heavy gasoline fraction (sulfur content 0.55 wt.%, Density 845 kg / m ³ , iodine number 28 g / 100 g) is subjected to hydrodesulfurization in the presence of Grace 465 aluminum-cobalt-molybdenum catalyst (content, wt.%: Molybdenum oxide - 18.5, cobalt oxide - 4.5, aluminum oxide - the rest is up to 100%). The mixture of raw materials and hydrogen-containing gas (WGS) is heated in a heat exchanger and furnace, from where the gas-raw material mixture heated to a temperature of 250 ^o C is fed to the reactor, where at a pressure of 4.5 MPa and a space velocity of 3 h ^-1 hydrogenation purification of raw materials from sulfur-containing compounds occurs .

 From the reactor, the gas-product mixture is sent to a heat exchanger, where it is cooled in the refrigerator due to heat exchange with the gas-gas mixture and fed to a separator for separating the gas-product mixture into the WGH and unstable hydrogenate.

An unstable hydrogenate from the separator passes through the tube space of the heat exchanger and is sent to the stripping column K-3, where the hydrogenate is degassed with partial removal of moisture, hydrocarbon gases and hydrogen sulfide. The working conditions of the stripping column: top temperature 85 ^o С, bottom 105 ^o С, pressure 1.2 ati.

 After mixing the hydrotreated heavy gasoline fraction with the low-boiling and medium boiling gasoline fractions, KKF obtain a stable gasoline fraction with a sulfur content of 0.07 wt.% Sulfur with the stored value of the OCh m.m. (80.3 points).

Example 2
On the main distillation column K-1 of the fractionating unit of the KKF installation, the cracking products obtained according to Example 1 are separated into a wide gasoline fraction of n.k. - 205 ^o C (sulfur content of 0.22 wt.%, HF m. M. 80.9 points, density 725 kg / m ³ , iodine number 90 g / 100 g) and gas oil fractions.

Wide gasoline fraction n. K. - 205-215 ^o C (yield 49.8% of raw materials) are sent for fractionation in a distillation column K-2 with the conclusion of 3 fractions: low boiling (N. to. - 70 ^o C), medium boiling (70-160 ^o C ) and heavy (160 ^o C - K. to.). The outputs of the fractions 19, 61 and 20 wt.%, Respectively. Column working conditions: top temperature 90 ^o С, bottom 229 ^o С, top pressure 2,8 ati, bottom 3,1 ati.

The heavy gasoline fraction (sulfur content 0.70 wt.%, Density 850 kg / m ³ , iodine number 17 g / 100 g) is subjected to hydrodesulfurization according to example 1 at a temperature of 330 ^o C, a pressure of 2.8 MPa and a space velocity of 5 h ^{- 1} . The working conditions of the stripping column: top temperature 90 ^o C, bottom 110 ^o C, pressure 1.4 ati.

 After mixing the hydrotreated heavy gasoline fraction with low-boiling and medium boiling gasoline fractions, KKF obtain a stable gasoline fraction with a sulfur content of 0.09 wt.% Sulfur with the stored value of the OCh m.m. (80.6 points).

Example 3 (prototype)
On the main distillation column K-1 of the fractionation unit of the KKF plant, the cracking products are separated according to Example 1 into a wide gasoline fraction n. K. - 215 ^o C (sulfur content of 0.26 wt.% before turning on the hydrotreating unit, HF m.m. 80.7 points) and gas oil fractions. To regulate the temperature of the distillation column on the plates using 4 circulation irrigation. The first circulation irrigation is heavy gasoline (FR 110-240 ^o C, sulfur content 0.65 wt.%, Iodine value 5.1 g / 100 g, OHM m. 74.3 points) with 24 plates pumped through air-cooled unit and served on a 26 plate.

 The balance amount of heavy gasoline from the discharge pump of the first circulating irrigation distillation column is discharged into the direct power tank of the hydrotreatment unit, from where it is fed through filters to the feed pumps of the hydrotreatment unit and mixed with VSG.

The mixture of gasoline and HSG is heated in a heat exchanger and furnace, from where the gas-raw material mixture heated to a temperature of 250 ^o C is fed to the reactor, where in the presence of a Grace 465 catalyst (content, wt.%: Molybdenum oxide - 18.5, cobalt oxide - 4, 5, aluminum oxide - the rest is up to 100%) at a pressure of 3 MPa, hydrogenation purification from sulfur-containing compounds occurs. From the reactor, the gas-product mixture is sent to a heat exchanger, where, due to heat exchange with the gas-oil mixture, it is cooled in the refrigerator to a temperature of 45 ^o С and enters the separator for separation of the gas-product mixture into the Wash and unstable hydrogenate.

An unstable hydrogenate from the separator passes through the tube space of the heat exchanger and is sent to a stripping column, where at a pressure of 0.8 atm and a bottom temperature of 185 ^o C, the hydrogenate stabilizes.

The hydrotreated heavy gasoline fraction (sulfur content 0.09 wt.%, Iodine number 2.5 g / 100 g) from the stripper is cooled to a temperature of 45 ^o C and returned to the discharge of the pump upper circulation irrigation distillation column installation KKF. The wide gasoline fraction emitted on this column is an unstable mixture of non-hydrotreated light gasoline fraction n.k. - 110 ^o С and hydrotreated heavy gasoline fraction 110 ^o С - к.к., After stabilization it contains 0.13 wt.% Sulfur and has an OM of m. 79.8 points.

 Thus, when hydrotreating a heavy gasoline fraction of KKF obtained by distillation of low-boiling gasoline fractions from gasoline KKF, after mixing, stable gasoline with a low sulfur content (0.07-0.09 wt.%) Is obtained without reducing the value of the HF m.m. (80.3-80.6 points) (examples 1 and 2). The implementation of the method according to the prototype (example 3) is less effective (sulfur content of 0.13 wt.%, OCh m.m. 79.8 points. This is due to the fact that the fraction subjected to hydrodesulfurization contains, in addition to gasoline, more than 30 wt.% kerosene fraction.

Claims (1)

The method of hydrodesulfurization of the gasoline fraction of catalytic cracking in the presence of an oxide-sulfide catalyst at elevated temperature and pressure of a hydrogen-containing gas, characterized in that the gasoline fraction by distillation is divided into 3 fractions: low boiling n.k. - 60-70 ^o С, medium boiling point 60-70 - 150-160 ^o С and heavy 150-160 - к.к., The heavy gasoline fraction is subjected to hydrodesulfurization, followed by mixing it with non-purified light boiling and medium boiling gasoline fractions.