RU2436838C1 - Procedure for de-mercaptanisation of kerosene fractions - Google Patents

Abstract

FIELD: gas and oil production. ^ SUBSTANCE: invention refers to procedure of de-mercaptanisation of kerosene fractions by contacting raw stock (kerosene fraction) and hydrogen in zone of preliminary treated catalyst of hydro-fining of activity not over 50% of guaranteed nominal activity at temperature 220-240C, pressure 0.4-1.2 MPa, volume rate of gas-raw stock supply 3.5-7 h-1 and multiplicity hydrogen/raw stock not less, than 4:1 nm3/m3. Also, there is performed preliminary preparation of production of straight-run kerosene fraction by extraction of oil AT or AVT at installations of primary processing by means of rectification with calculated parametres of mode of operation of columns C-1 and C-2. Origin of oil raw stock, qualitative-quantitative fraction-by fraction distribution of mercaptans, straight-run benzene fractions containing maximal amount of mercaptans and a straight-run kerosene fraction are taken in consideration during calculation of the parametres. The kerosene fraction is subjected to process of de-mercaptanisation by contacting a descending flow of mixture of raw stock with hydrogen in a reactor of axial type equipped with a distributor of gas-raw stock mixture of catalyst of hydro-fining. ^ EFFECT: achieving content of mercaptans in kerosene fraction not over 10 ppm at maintaining initial level of total sulphur; simultaneous reduction of operational expenditures and increased flexibility of process of reactive fuel production. ^ 1 ex, 4 tbl

Description

The invention relates to the field of oil refining and can be used to purify kerosene fractions from mercaptans.

Current requirements for the content of mercaptans in fuels are extremely stringent. The technical regulation “On requirements for automobile and aviation gasoline, diesel and marine fuel, jet fuel and heating oil” requires the content of mercaptans in jet fuel not exceeding 30 ppm. The British standard DEF STAN 91-91 / 4-2002, which regulates the requirements for jet fuel Jet Ai, sets the requirements for the content of mercaptans at a level of no more than 30 ppm. In addition, both regulatory documents establish requirements for such quality indicators as thermo-oxidative stability, and DEF STAN also for the quality indicator characterizing the lubricity of the fuel. Russian standards for jet fuel TS-1 do not establish requirements for lubricity, however, these requirements are included in the set of qualification assessment methods (KMKO) and are mandatory when setting fuel for production.

A known method of removing mercaptans from kerosene fractions by alkalization with an aqueous solution of sodium hydroxide and oxidation with oxygen in the presence of aqueous alkaline solutions of phthalocyanine catalysts, followed by separation of the catalyst solution from the purified feedstock, is the Merox process [Sittig M. Processes for the oxidation of hydrocarbon feedstocks. - M.: Chemistry, 1970. - 300 p.]. The main disadvantage of this method is the formation of persistent emulsions of the kerosene fraction with alkaline solutions.

Known methods for purifying petroleum products from mercaptans (demercaptanization) by converting mercaptans with aqueous solutions of alkalis to mercaptides followed by oxidation of mercaptans with atmospheric oxygen to disulfides in the presence of catalysts, as well as by treating them with sodium hypochlorite solutions, hydrogen peroxide, organic peroxides, oxydisulfide and dimethoxide . Chemistry of organic sulfur compounds. - M.: Chemistry, 1975. - S. 98-103, 512].

A known method of purification of petroleum distillates from mercaptans (RF patent No. 2145972) by oxidative treatment in a reactor with a stationary catalyst bed containing metalphthalocyanine on a solid support in the presence of an alkaline agent. Next, the spent alkaline agent is separated from the purified fraction, concentrated and recycled to the reactor to the purification step.

A known method of demercaptanization of petroleum distillates (RF patent No. 2106387) by treating them with atmospheric oxygen in the presence of a heterogeneous catalyst containing copper sulfate deposited on carbon fiber fabric. After 50-200 hours of operation, the catalyst is periodically impregnated with an aqueous solution of sodium hydroxide.

A disadvantage of the known methods is the complexity of their implementation, which requires the creation of special multi-stage industrial plants.

A known method of demercaptanization of kerosene fractions (RF patent No. 2179573), in which demercaptanization of kerosene fractions is carried out by heating to 150-250 ° C a mixture containing feedstock and hydrocarbon gas (contains 4-20 wt.% Hydrogen), taken in a ratio of 5: 50 nm ³ / m ^{3 of} raw materials and further contacting this mixture at a pressure of 0.1-0.5 MPa with a catalyst containing metal oxides of groups 6 and 8 of the Periodic Table of the Elements. In this case, the catalyst is pretreated for 12-48 hours with a solution containing 0.5-1.0 wt.% Polysulfides in the kerosene fraction, at a temperature of 150-250 ° C, a pressure of 0.1-0.3 MPa and a hydrocarbon gas supply (contains 4-20 wt.% H ₂ ) not less than 10 nm ³ / m ^{3 of} kerosene fraction.

The disadvantage of this method is that the process of hydrotreating kerosene fractions, which leads to a decrease in the total sulfur content, which, as is known, in turn leads to a decrease in the lubricity of the fuel and a deterioration in its thermo-oxidative stability, occurs simultaneously with the process of demercaptanization. In addition, this process involves a fairly large consumption of hydrogen.

The closest in technical essence and the achieved result to the proposed invention is a method for demercaptanization of kerosene fractions (RF patent No. 2381257), which is carried out by contacting the feedstock and hydrogen in the zone of the pre-treated catalyst in countercurrent mode at a temperature of 220-230 ° C, volumetric feed rate 5-7 h ^-1 , multiples of hydrogen / feed (30-50): 1, followed by removal of light hydrocarbons and hydrogen sulfide, while these operations are carried out in one reactor.

However, this method has a number of significant drawbacks, such as the complex hardware design of the process, which combines two processes with different technological modes in one device: demercaptanization of kerosene fractions and stripping of light hydrocarbons and hydrogen sulfide. This leads to significant losses of material flows due to the carry-over of the kerosene fraction by the upward flow of hydrogen, the range of productivity of the apparatus is significantly reduced due to the need to conduct the process at a volumetric feed rate of 5-7 h ^-1 and, in addition, also involves a significant consumption hydrogen for the process.

The aim of the invention is to provide a method for the demercaptanization of kerosene fractions, which allows to achieve a mercaptan content of not more than 10 ppm while maintaining the initial level of total sulfur while reducing operating costs and increasing the flexibility of the jet fuel production process.

This goal is achieved by the method of demercaptanization of kerosene fractions (feedstock) by contacting the feedstock and hydrogen at elevated temperature and pressure in the zone of the pre-treated catalyst, while the proposed method is characterized in that it includes a preliminary stage of preparation of distillates at the primary oil refining plants AT or ABT, when by distillation, methyl, ethyl, partially propyl, butyl and heavier mercaptans and straight-run to rosin fraction, demercaptanization of which is carried out by contacting the downward flow of a mixture of raw materials with hydrogen in an axial type reactor equipped with a gas-raw material mixture distributor and the process is conducted on a catalyst using a hydrotreating catalyst with an activity of not more than 50% of the guaranteed nominal activity at a temperature of 220-240 ° C , a pressure of 0.4-1.2 MPa, a volumetric feed rate of a gas-raw material mixture of 3.5-7 h ^-1 and a hydrogen / feed ratio of at least 4: 1 nm ³ / m ³ .

At the same time, distillates of AT, ABT installations - straight-run gasoline and kerosene fractions are obtained by distillation of the feedstock in columns K-1 and K-2 at such parameters of the technological mode of operation of the columns that are determined by calculation depending on the origin of the feedstock and the distribution of mercaptans by fractional composition of raw materials.

Salient features of the proposed method are:

- the presence of a preliminary preparation stage for the production of distillates during the initial distillation of crude oil at AT or AWT units by distillation of crude oil using certain calculation methods, depending on the composition of the crude oil and the fractional distribution of mercaptans, the operating conditions of the K-1 preliminary topping columns and the main distillation column K -2 in order to maximize the selection, together with fractions of straight-run gasoline, of compounds of methyl-, ethyl-, partially propyl-, butyl- and heavier mercaptans and obtain I partially demercaptanized straight-run kerosene fraction, which then, in a mixture with hydrogen, is sent to an axial type reactor, which is equipped with a gas-feed mixture distributor, directly for carrying out the process of demercaptanization on a catalyst loaded in the reactor and pre-sulphided, which use a hydrotreating catalyst with activity no more 50% of guaranteed nominal activity. The process is carried out at the following process parameters: at a temperature of 220-240 ° C, a pressure of 0.4-1.2 MPa, a volumetric feed rate of a gas-raw material mixture of 3.5-7 h ^-1 and a hydrogen / feed ratio of at least 4: 1 nm ³ / m ³ .

Analysis of the available literature did not reveal technical solutions similar to the proposed method.

These distinctive features of the proposed technical solution determine its novelty. Thus, the claimed method meets the criterion of "novelty." Analysis of the known solutions for the methods of demercaptanization of kerosene fractions allows us to conclude that they lack features similar to the significant distinguishing features of this method.

The method is as follows.

Crude oil is fed to the K-1 preliminary topping column of the ABT primary oil distillation unit. From the top of the K-1 column, a gasoline fraction containing methyl, ethyl and partially propyl, butyl and heavier mercaptans is isolated from petroleum feed. Next, the bottoms product of the K-1 column - partially stripped oil is fed to the main distillation column K-2, where the further process of separation of partially stripped oil into straight-run fractions is ongoing. Subject to the calculation of the selected technological regime, the gasoline fraction is separated from the top of the K-2 column, with which some mercaptans are also removed, and the straight-run kerosene fraction of jet fuel is removed to the K-3/1 stripping column. The technological parameters of the process depend on the origin of the crude oil, the content of mercaptans and their fractional distribution and determine them individually for various oil mixtures, by preliminary calculation. The calculation of the parameters of the technological regime of distillation columns K-1 and K-2 is carried out in such a way as to achieve a minimum content of mercaptans in the output straight-run kerosene fraction by maximizing their output together with other straight-run fractions: gasoline, diesel. So, for a mixture of Ukhta and Eastern oils (with a ratio of 30:70 wt.%), It is advisable to carry out the process at a temperature of the top of the K-1 column in the range of 149-168 ° C, the bottom of the K-1 column in the range of 272-275 ° C, the top of the K-2 column is 138-142 ° C.

Further, the straight-run kerosene fraction obtained in the above method in a mixture with a hydrogen-containing gas (contains hydrogen up to 99 vol%) with a volume ratio of hydrogen-containing gas: raw materials of at least 4: 1 is fed to an axial type reactor equipped with a gas-raw material mixture distributor. At the same time, the gas-raw material mixture distributor is a series of hollow truncated cones installed coaxially.

The gas-raw material mixture is contacted in the reactor in a downward flow at a temperature of 220-240 ° C, a pressure of 0.4-1.2 MPa and with a volumetric feed rate of 3.5 to 7 h ^-1 on a catalyst, which is used as traditional, containing metal oxides of groups 6 and 8 of the Periodic system of elements (such as alumina-cobalt-molybdenum, alumina-nickel-molybdenum) hydrotreating catalysts with activity reaching not more than 50% of the guaranteed nominal activity. In this case, the catalyst used, for example, alumina-cobalt-molybdenum GO-70, is pre-sulfidized for 12-48 hours with a solution containing 0.5-1.0 wt.% Polysulfides in the kerosene fraction, at a temperature of 150-250 ° С, pressure 0.1 -0.3 MPa and the supply of hydrocarbon gas (contains 4-20 wt.% H ₂ ) not less than 10 nm ³ / m ^{3 of the} kerosene fraction.

After passing through the reactor, the gas product mixture is sent to a stripping column for stripping from hydrogen sulfide.

Examples of execution.

The results of the invention are presented in tables 1-4. The method is carried out according to the above process sequence.

After carrying out a physico-chemical study of the crude oil processed at the AVT plants of OAO Slavneft-YANOS and consisting of a mixture of Ukhta and East oils at a ratio of 30:70 wt.%, Revealing the fractional distribution of mercaptans in the crude oil and selected straight-run fractions (table 1), simulating the process using the HYSIS program, the selection of the optimal parameters of the technological mode for using the method on an industrial scale was carried out.

Physico-chemical studies of petroleum feedstocks showed the presence of mercaptans in all fractions of the feedstock: from light (dry gas, PBP) to diesel and heavier petroleum fractions. The spectrum of these compounds is wide: from light mercaptans C ₁ -C ₅ to heavy C ₁₀ -C ₁₃ having a boiling point of 250-340 ° C.

Table 2 shows examples of the technological modes of operation of the K-1 topping column and the K-2 main distillation column of the ABT unit when selecting a work option with the aim of removing a significant amount of methyl-, ethyl- and partially propyl-, butyl- together with gasoline fractions and heavier mercaptans, thereby allowing to receive the already partially demerkaptanizirovannuyu straight-run kerosene fraction, wherein the mercaptans are present C ₂ -C _10, the largest number of them are mercaptans C ₅ -C ₆ tempo rature boiling in the range 125-150 ° C. Therefore, increasing the end of boiling of the K-2 gasoline fraction and, accordingly, the beginning of boiling of the kerosene fraction, we increase the removal of C ₅ -C ₆ mercaptans with the gasoline fraction, thereby reducing their content in the kerosene fraction.

The optimum top temperature of the K-2 column is 138-142 ° С, a decrease in temperature below 138 ° С leads to an increase in the content of mercaptans in the straight-run kerosene fraction, and an increase in temperature above 142 ° С leads to a violation of the GOST requirements for the beginning of the boiling point of straight-run kerosene fractions.

The distribution of mercaptans in the flow of the K-3/1 stripping column of the ABT unit (straight-run kerosene fraction) according to the calculations of the HYSIS program is presented in table 3.

Table 4 shows the results of the process at the laboratory installation of kerosene demercaptanization using GO-70 hydrotreating catalyst with 50% activity from its nominal value.

The test results showed that the optimal temperature of the process of demercaptanization of kerosene fractions is 220-240 ° C. Lowering the temperature of the demercaptanization process below 220 ° C reduces the degree of purification from mercaptans, and when the temperature rises to 250 ° C, the hydrotreating process begins, which leads to a decrease in the total sulfur content in the hydrogenate (in the hydrodemercaptanized kerosene fraction) and, therefore, the operational characteristics of jet fuel deteriorate.

Volumetric feed rate of raw materials and hydrogen: 3.5-7.0. Conducting the process in a wide range of space velocities increases the flexibility of the demercaptanization process for capacity utilization depending on seasonal demand and market conditions. Examples of performance showed: at a space velocity of 3.5 h ^-1 and a temperature of up to 240 ° C, the process proceeds without reducing the total sulfur content, that is, without compromising lubricity and thermo-oxidative stability.

The pressure in the reactor can be maintained within a wide range: 0.4-1.2 MPa, since an increase in pressure above 1.2 MPa leads to a decrease in the total sulfur content in the hydrogenate (in the hydrodemercaptanized kerosene fraction), which leads to a decrease in lubricity and thermo-oxidative stability. At a pressure in the apparatus below 0.4 MPa, the mercaptan sulfur content increases.

The process achieves the target with a hydrogen / feed feed ratio of 4: 1 when using a WASH containing hydrogen up to 99% vol. At lower multiplicity, the content of mercaptans in the hydrodemercaptanized kerosene fraction exceeds 10 ppm.

Table 1 Distribution of mercaptans in the products of the AVT-3 installation as calculated in the HYSYS program (example 1 from table 3). Mercaptans Content, ppm in oil in gasoline K-1 in gasoline K-2 jet fuel in K-3/2 in K-3/3 C1 45 234 490 0 one one C2 40 157 767 2 2 one C3 43 247 376 5 2 one C4 35 172 424 16 four 2 C5 12 47 119 31 3 one C6 5 fifteen 9 31 3 one C7 2 four fourteen 2 one C8 2 3 13 5 one C9 3 2 fifteen eleven 3 C10 6 3 37 fourteen C11 6 26 21 C12 5 10 21 C13 one one four the amount ∑205 ∑881 ∑2185 ∑130 ∑107 ∑72

Table 3 Distribution of mercaptans in the K-3/1 stream (straight-run kerosene fraction) of the AVT-3 unit as calculated in the HYSYS program Mercaptans Content, ppm Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 C1 0 0 0 0 0 0 0 0 C2 2 2 2 2 2 one 2 one C3 5 5 5 5 3 3 3 2 C4 16 fifteen fourteen 12 eleven 9 9 7 C5 31 25 twenty 17 16 12 eleven 9 C6 31 thirty 28 25 21 16 fourteen 13 C7 fourteen fifteen fifteen 16 fourteen fourteen 13 fifteen C8 13 13 fourteen fourteen fourteen 16 fifteen eighteen C9 fifteen fifteen fifteen 16 19 21 21 21 C10 3 3 3 3 6 5 eleven 5 C11 0 0 0 0 0 0 0 0 C12 0 0 0 0 0 0 0 0 C13 0 0 0 0 0 0 0 0 the amount ∑130 ∑123 ∑116 ∑110 ∑107 ∑97 ∑100 ∑91

Table 4 Test results at a laboratory unit for hydrodemercaptanization of jet fuel No. The temperature in the reaction zone, ° C Volumetric speed, h ^-1 The multiplicity of hydrogen / raw materials, nm ³ / m ³ Pressure, MPa The content of mercaptan sulfur in the feed, ppm The content of mercaptan sulfur in the hydrogenate, ppm The total sulfur content in raw materials, wt.% The total sulfur content in the hydrogenate, wt.% one 200 3,5 four 0.4 91 fourteen 0.18 0.18 2 210 3,5 10 0.4 91 12 0.18 0.18 3 220 3,5 3 0.4 91 eleven 0.18 0.18 four 220 3,5 four 0.3 91 eleven 0.18 0.18 5 220 8 four 0.4 91 eleven 0.18 0.18 6 220 3,5 fifteen one 91 7 0.18 0.18 7 220 7 10 one 130 9 0.18 0.18 8 240 3,5 8 0.4 91 four 0.18 0.18 9 240 7 10 0.6 91 5 0.18 0.18 10 240 7 8 0.7 130 5 0.18 0.18 eleven 240 5 10 0.6 152 5 0.18 0.18 12 240 3 four 0.4 91 four 0.18 0.17 13 240 7 four 1,2 91 2 0.18 0.18 fourteen 240 7 four 1.3 91 one 0.18 0.16 fifteen 250 7 10 0.6 91 four 0.18 0.17 16 250 3,5 four 0.4 91 four 0.18 0.17

Thus, the process of demercaptanization of straight-run kerosene fractions by the proposed method in comparison with the prototype allows you to:

- due to the presence of the preliminary preparation stage for the production of distillates during the initial distillation of oil at ABT and AT units, which leads to the intensification of the separation of methyl, ethyl and, partially, propyl, butyl and heavier mercaptans together with gasoline fractions and, thus, preliminary demercaptanization of the straight-run kerosene fraction, which allows the hydrodemercaptanization of the kerosene fraction to be carried out directly under milder conditions and at a significantly reduced hydrogen consumption;

- apply the previously used hydrotreating catalyst with a 50% degree of activity in the downward flow of the gas-raw material mixture in the reactor, which ensures a minimum hydrogen consumption and the absence of additional hydrotreatment reactions of the kerosene fraction, which means that the total sulfur compounds are preserved, thereby preserving antioxidant and lubricating properties of the resulting commercial fuel;

- eliminate material losses by eliminating the partial ablation of the fraction of straight-run kerosene in comparison with a reactor with an upward flow of hydrogen;

- to provide the possibility of carrying out the process in a wide range of space velocities, which increases the flexibility of the demercaptanization process for capacity utilization depending on seasonal demand and market conditions;

- to carry out the process of stripping hydrogen sulfide from hydrodemercaptanized fuel according to the traditional scheme at a lower pressure compared to the prototype, which ensures lower metal consumption of the equipment;

- technological parameters of the process make it possible to carry out demercaptanization of not only kerosene, but other fractions of jet fuel (for example, Jet Ay 1).

The proposed method is simple to implement and can be easily implemented on standard equipment of oil refineries.

Claims (1)

The method of demercaptanization of kerosene fractions by contacting the feedstock and hydrogen at elevated temperature and pressure in the zone of the pre-treated catalyst, followed by removal of hydrogen sulfide, characterized in that it is preliminarily refined at the primary oil refining units at the design parameters of K-1 columns and K-2, taking into account the origin of the crude oil and the qualitatively-quantitative fractional distribution of mercaptans, emit straight-run gasoline fractions containing mercaptans and straight-run kerosene fraction, demercaptanization of which is carried out by contacting the downward flow of a mixture of raw materials with hydrogen in an axial type reactor equipped with a gas-raw mixture distributor on a hydrotreating catalyst with an activity of not more than 50% of the guaranteed nominal activity at a temperature of 220-240 ° C, pressure 0, 4-1.2, MPa, a volumetric feed rate of a gas-raw material mixture of 3.5-7 h ^-1 and a hydrogen / feed ratio of at least 4: 1 nm ³ / m ³ .