CN1952058A - Method for FCC gasoline proceeding hydrodesulphurization and olefin removal - Google Patents

Abstract

The invention relates to a work-starting method of FCC gasoline hydrodesulfurization to degrade the alkenes. According to the invention, on the basis of regular wet process thiolaction, it adopts reformed generating oil as the sulfurized oil so as to avoid the extra high temperature in the early starting time, decrease the carbon deposition of the catalyst and increase the stability and activity of the catalyst. The invention can be used in different kinds of gasoline that contains molecular sieve reforming catalyst thiolaction, especially the gasoline that contains high molecular sieve.

Description

A start-up method of FCC gasoline hydrodesulfurization and olefin reduction technology

technical field

The invention relates to a start-up method of FCC gasoline hydrodesulfurization and olefin reduction technology, in particular to a start-up method of full fraction FCC gasoline hydrodesulfurization and olefin reduction technology.

Background technique

In order to reduce the emission of harmful substances in automobile exhaust, countries successively legislated to impose stricter restrictions on sulfur and olefins in gasoline. Around 2005, the sulfur content of gasoline in Europe, the United States and other countries and regions will be reduced to 30-50 μg/g, and even put forward the suggestion of 5-10 μg/g "sulfur-free gasoline"; olefins will be reduced to about 10.0v%. FCC gasoline generally contains more sulfur and contains a large amount of olefins, especially full-cut FCC gasoline. Full-fraction FCC gasoline aromatization to reduce olefins is a new technology for upgrading full-fraction FCC gasoline. It is characterized in that it can greatly reduce the olefin content while achieving desulfurization, but still maintain a high gasoline yield. And lower octane loss, can produce gasoline that meets Euro III emission standards. As described in technologies such as CN1458235A, CN1488722A, CN1488724A, CN1488728A, CN1552811A, CN1552821A.

On the one hand, the metal oxide content of the gasoline reforming catalyst used in FCC gasoline aromatization and olefin reduction technology is low, ranging from 1.0w% to 10.0w%, while the content of molecular sieves is relatively high, generally ranging from 50.0w% to 90.0w%. On the other hand, FCC gasoline has a higher olefin content. Olefins mainly undergo desired reactions such as isomerization and aromatization in the acidic center of molecular sieves, and undesired coking and carbon deposition reactions also occur. At the same time, because of the low content of active metals, the function of inhibiting coking and carbon deposition is not very prominent. Especially in the process of catalyst sulfidation, since the active metal is not yet in the state of optimal performance, the phenomenon of coking and carbon deposition is more serious at this time.

At present, gasoline reforming devices generally adopt the usual wet vulcanization method, that is, adding a vulcanizing agent into vulcanized oil to vulcanize the gasoline reforming catalyst. The main function of vulcanized oil is to carry a large amount of heat generated during the vulcanization process. Generally, straight-run oil with low impurity content and unsaturated hydrocarbons is selected as the benchmark.

Due to the special composition of the gasoline reforming catalyst, straight-run gasoline cannot be used as vulcanized oil. The main reason is that during the vulcanization period, straight-run gasoline will undergo a type-selective cracking reaction of n-alkanes, which will generate a large amount of gas and reduce the purity of circulating hydrogen, which is not conducive to vulcanization. At the same time, the reaction releases a large amount of heat, which is not conducive to the control operation; nor can FCC gasoline be used as vulcanized oil. Fly warm. It is very important to choose what kind of raw material oil as vulcanized oil.

US4177136 discloses a hydrotreating process using elemental sulfur to presulfide a hydrogenation catalyst, using elemental sulfur to presulfide the catalyst. The disadvantage of this method is that the solid element sulfur has been completely converted into hydrogen sulfide at a lower temperature, but the catalyst cannot be completely vulcanized at a low temperature, and sufficient sulfur cannot be supplied to the catalyst at a high temperature, that is, the supply rate of hydrogen sulfide cannot be accurately controlled. , so that the amount of sulfur on the catalyst is low. This method is not suitable for the sulfidation of gasoline upgrading catalysts.

US5215954, US5681787 disclose the preparation method of presulfided catalyst. Although the activity of the presulfided catalyst has been improved, with the improvement of the activity, the catalyst is more prone to carbon deposition, which directly affects the stability of the catalyst in use.

CN1351110A discloses a hydrogenation catalyst presulfurization method, which mainly performs wet presulfurization on the hydrogenation catalyst, which can significantly reduce the amount of carbon deposits on the catalyst during the hydrogenation reaction and improve the activity stability of the catalyst. Sulfurized oil is kerosene or light diesel oil, which is not suitable for sulphurizing gasoline reforming catalysts. CN1362289A discloses a method for presulfiding a hydrogenation catalyst. Compared with the traditional vulcanization method, the inventive method can only significantly reduce the vulcanization cost. It does not solve the problems that a large number of reactions occur during the vulcanization process of the FCC gasoline reforming catalyst, the heat release is relatively large, and it is difficult to control.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention proposes a start-up method of FCC gasoline, especially the technology of hydrodesulfurization and olefin reduction of full fraction FCC gasoline. Especially in the process of wet vulcanization, choosing suitable raw materials as vulcanized oil can significantly improve the activity and stability of the catalyst.

The method for starting the FCC gasoline desulfurization and olefin reduction process of the present invention includes: under pre-sulfurization conditions, contacting the vulcanizing agent, hydrogen and sulfurized oil with the gasoline reforming catalyst at a temperature of 150°C to 460°C, preferably 200°C to 350°C, contacting The pressure is 0.5MPa-10.0MPa, the contact time is 10-50 hours, preferably 10-25 hours, the hydrogen-oil volume ratio is 50-5000, preferably 50-1000, and the liquid hourly space velocity is 0.5h ^- 1-15.0 h ^-1 . After the pre-sulfurization is completed, the raw material of FCC gasoline is replaced. When switching to FCC gasoline raw materials, it is generally operated in a gradually increasing manner in proportion, such as gradually switching to 25W%, 50W%, 75W%, 100W% FCC gasoline, and strictly controlling the temperature of the catalyst bed to prevent overheating. Among them, sulfurized oil is reformed oil.

The reformed oil is a product obtained from the catalytic reforming process of naphtha. Generally, the content of aromatics is about 75m%, the content of naphthenes is about 17m%, the content of paraffins is about 7m%, and the content of olefins is 1m%. %the following.

The vulcanizing agent can be a vulcanizing agent commonly used in the art, such as one or more of carbon disulfide, organic sulfide, disulfide or polysulfide, thiophene compound, elemental sulfur and hydrogen sulfide, etc., liquid phase vulcanizing agent or elemental Sulfur is added to sulfurized oil when it is used, and hydrogen sulfide is added to hydrogen gas when it is used. The conditions of vulcanization are well known to those skilled in the art, and can be carried out under one condition, or can be carried out under different conditions in several stages. For example, it can be carried out in three stages, constant temperature at 120-200°C for 1-10 hours, constant temperature at 210-280°C for 5-20 hours, constant temperature at 290-400°C for 5-20 hours, and a heating rate of 10-15°C/h . When the vulcanizing agent is added to the vulcanized oil, the content of the vulcanizing agent in the vulcanized oil is 0.1w%-15w%. When hydrogen sulfide is used as the sulfurizing agent, the volume concentration of hydrogen sulfide in the hydrogen gas is 0.01% to 5%.

The method of the present invention can be applied to the presulfurization process of various catalysts with higher molecular sieve content, such as FCC gasoline hydrodesulfurization and olefin reduction catalyst: the metal oxide content is 1.0w% to 10.0w%, and the molecular sieve content is 50.0w% to 90.0 w%; the balance is binder; the metal is selected from one or more of zinc, iron, manganese, nickel, cobalt, molybdenum, tungsten, magnesium, calcium, barium, etc., and the molecular sieve has a grain size of 20nm to 800nm Hydrogen-type molecular sieve with small grain size within the range; specific surface area of the catalyst is 300m ² /g-600m ² /g, and pore volume is 0.15ml/g-0.55ml/g. The molecular sieve component is preferably HZSM-5 and/or Hbeta, and the appropriate type of molecular sieve can also be determined according to different reaction types.

Compared with the prior art, the inventive method has the following advantages:

A. Select the reformed oil as sulfurized oil. Because it is rich in aromatics and naphthenes, and less in olefins and paraffins, there is no reactive component for the acidic catalyst with a molecular sieve content of 50.0w% to 90.0w%. During the pre-sulfurization process, these components can be prevented from reacting on the acidic sites, the vulcanization process is stable, and the vulcanization temperature is easy to control, which is beneficial to the catalyst vulcanization. Charcoal amount.

B. There is no special requirement on the decomposition temperature of the vulcanizing agent. The vulcanizing agent can be all sulfides such as carbon disulfide, organic sulfide, disulfide or polysulfide, thiophene compound.

C. Select the reformed oil as vulcanized oil, and its vulcanization temperature can be carried out within a wide range. Below 330°C, the polymerization reaction of olefin saturated olefins can be avoided; above 330°C, the type-selective cracking reaction of linear alkanes can be avoided, which is beneficial to reduce the carbon deposition of acidic catalysts. The method overcomes the problem that the curing temperature is limited and the catalyst cannot be fully presulfurized when other types of sulfurized oil are used in the prior art.

D, the method of the present invention is particularly applicable to the start-up process of gasoline reforming catalysts with HZSM-5 and/or Hbeta molecular sieves as active components, and molecular sieve content above 50%, to reduce the carbon deposition amount of this type of catalyst during use , improving the service life of such catalysts has a very prominent effect.

Description of drawings

Fig. 1 is the temperature rise of the vulcanization process when different vulcanized oils are used in Example 1.

Detailed ways

The technical scheme of the present invention will be further described below in conjunction with examples. The reformed oil and raw materials used are shown in Table 1. The composition and properties of the gasoline upgrading catalyst are shown in Table 2.

     Table 1. Properties of raw oil and reformed oil

project FCC Gasoline Feedstock reformate oil Distillation range, ℃ 34～183 50～167 Composition by fluorescence method/v% saturated hydrocarbon 28.9 23.6 Of which naphthenes 6.8 16.5 Olefin 52.9 0.6 Aromatics 18.4 75.8 Sulfur, μg/g 986 ＜0.5 Nitrogen, μg/g 57 ＜0.5 Diolefins, gI/100g 2.54 - RON 93.8 MON 80.4

                       Table 2. Composition and properties of gasoline upgrading catalysts

project MQ-A MQ-B MQ-C Composition and content, w% NiO 3.0%MgO 0.5% NiO 1.5%MgO 0.25% NiO 6.0% MgO 1.0% ZnO 0.50% 70% of HZSM-5(A) with 100-500nm SiO ₂ /Al ₂ O ₃ molar ratio of 27 The Hbeta (B) of the SiO ₂ /Al ₂ O ₃ molar ratio of 33 with a grain size of 70-150nm is 60% A: 40% B: 35% Al ₂ O ₃ balance Al ₂ O ₃ balance Al ₂ O ₃ balance Specific surface area, m ² /g 335 505 397 Pore volume, ml/g 0.23 0.40 0.33

In Example 1, three different raw materials were selected as sulfurized oil, and the gasoline reforming catalyst was MQ-A.

The vulcanization conditions and process are:

Vulcanization conditions

Partial pressure: 3.4MPa; volumetric space velocity: 2.0h ^-1 ; hydrogen-to-oil volume ratio: 400; circulating hydrogen purity: 70v%; vulcanized oil: reformed oil; vulcanized agent: C ₂ H ₆ S ₂ ; final vulcanized Temperature: 340°C.

The vulcanization process is as follows:

After the inlet temperature of the reactor rises to 150°C, start the feed pump, feed vulcanized oil into the system at a volumetric space velocity of 2.0h ^-1 to carry out closed-circuit circulation of the vulcanized oil, and start injecting C ₂ H ₆ S ₂ into the vulcanized oil at a uniform speed. The content of C ₂ H ₆ S ₂ in the vulcanized oil was 4%, and the temperature was kept constant for 3 hours. Raise the inlet temperature of the reactor to 230° C. at a heating rate of 15° C./h, and vulcanize at a constant temperature for 8 hours. During the heating process, H ₂ S will penetrate the reactor bed. Raise the inlet temperature of the reactor to 340°C at a heating rate of 10°C/h, and vulcanize at a constant temperature for 8 hours to complete the vulcanization. From reformed oil to 100% fresh raw material oil, it should be carried out in four steps. Replace 25% fresh raw material oil every step, and keep the total feed amount constant. There should be a sufficient time interval for each oil change (depending on the temperature rise of the bed, not less than 5 hours), so as to keep the smooth operation of oil change at start-up.

It can be seen from the graph of the influence of the operating oil on the reaction temperature rise (Fig. 1) that the temperature rise of the reformed oil is very low, and the temperature rise is about 60°C after switching to FCC gasoline at 340°C. The temperature rise of the other two start-up oils is above 100°C, and switching to FCC gasoline at this time is extremely unfavorable for start-up.

In Example 2, see Table 3 for the operation results and catalyst carbon deposits after switching to catalytically cracked gasoline with three starting oils. The process conditions are: inlet temperature 340°C, reaction pressure 3.5MPa, liquid hourly volume space velocity 2h ^-1 , hydrogen-oil volume ratio 400:1.

                   Table 3 The reaction results of the three start-up oils after switching to FCC gasoline

Start oil name straight run naphtha FCC gasoline            Device running time, h 500 400 500 2000 Distillation range, ℃ 45～202 43～204 45～198 45～195 Composition by fluorescence method/v% saturated hydrocarbon 55.8 55.3 59.4 56.8 Olefin 18.8 22.6 9.2 13.4 Aromatics 25.4 22.1 31.2 29.8 Sulfur, μg/g 278 302 180 220 Nitrogen, μg/g 34 41 15 18 RON 90.8 90.2 92.0 91.8 MON 79.2 79.0 80.1 79.9 Catalyst carbon deposit, wt% 20.4 22.8 10.3 12.4

It can be seen from the reaction results after the three kinds of starting oils are switched to catalytic cracked gasoline that due to the low carbon deposits in the reformed oil, there is little difference in the various indicators of the products after 500-2000 hours; the catalyst carbon deposits of the other two starting oils are high , affecting the activity and stability of the catalyst.

In Example 3, the selective reforming oil produced by MQ-B and MQ-C catalysts was used as the start-up oil. The vulcanization process was the same as in Example 1, and the process conditions were the same as in Example 2. Table 4 shows the operation results and the amount of carbon deposited on the catalyst.

Table 4 The reaction results of MQ-B and MQ-C catalysts after treating FCC gasoline

Start oil name                    catalyst MQ-B MQ-C Device running time, h 2000 2000 Distillation range, ℃ 45～199 45～193 Composition by fluorescence method/v% saturated hydrocarbon 59.4 58.4 Olefin 10.4 12.9 Aromatics 30.2 28.7 Sulfur, μg/g 240 200 Nitrogen, μg/g 17 14 RON 91.6 91.4 MON 79.8 79.6 Catalyst carbon deposit, wt% 12.2 13.6

Claims (10)

1. A start-up method for FCC gasoline hydrodesulfurization and olefin reduction technology, comprising: under pre-sulfurization conditions, contacting a sulfurizing agent, hydrogen and sulfurized oil with a gasoline reforming catalyst at a temperature of 150°C to 460°C and a contact pressure of 0.5MPa～10.0MPa, contact time is 10 hours～50 hours, hydrogen oil volume ratio is 50～5000, liquid hourly space velocity is 0.5 hours ^-1 ～15.0 hours ^-1 , after the pre-sulfurization is completed, replace it with FCC gasoline raw material; It is characterized in that the sulfurized oil is reformed oil. 2. The method according to claim 1, characterized in that the temperature is 200°C-350°C, the contact time is 10-25 hours, and the volume ratio of hydrogen to oil is 50-1000. 3. The method according to claim 1, characterized in that when the FCC gasoline raw material is replaced, it is operated in a manner of gradually increasing in proportion. 4. The method according to claim 1, characterized in that said reformed oil is a product obtained from naphtha catalytic reforming process. 5. The method according to claim 1, characterized in that the sulfurizing agent is one or more of carbon disulfide, organic sulfide, disulfide or polysulfide, thiophene compound, elemental sulfur and hydrogen sulfide, and the liquid Phase vulcanizing agent or elemental sulfur is added to vulcanized oil when used, and hydrogen sulfide is added to hydrogen gas when used. 6. The method according to claim 5, characterized in that when the vulcanizing agent is added to the vulcanized oil, the content of the vulcanizing agent in the vulcanized oil is 0.1w% to 15w%, and when hydrogen sulfide is used as the vulcanizing agent, the hydrogen sulfide The volume concentration in hydrogen is 0.01% to 5%. 7. The method according to claim 1, characterized in that the gasoline upgrading catalyst is an FCC gasoline hydrodesulfurization and olefin reduction catalyst. 8. The method according to claim 1 or 7, characterized in that the metal oxide content of the gasoline upgrading catalyst is 1.0w% to 10.0w%, and the molecular sieve content is 50.0w% to 90.0w%; the metal is selected from One or more of zinc, iron, manganese, nickel, cobalt, molybdenum, tungsten, magnesium, calcium, barium, etc. The molecular sieve is a hydrogen-type molecular sieve with a small grain size in the range of 20nm to 800nm. 9. The method according to claim 8, characterized in that the gasoline upgrading catalyst has a specific surface area of 300m ² /g-600m ² /g and a pore volume of 0.15ml/g-0.55ml/g. 10. The method according to claim 8, characterized in that said molecular sieve is HZSM-5 and/or Hbeta molecular sieve.