CN1912063A - Method of producing catalytic reforming raw material - Google Patents

Abstract

The invention is a method for producing catalytic reforming raw material, cutting secondary gasoline raw material into light gasoline fraction, medium gasoline fraction and heavy gasoline fraction, where the medium gasoline fraction, optional virgin naphtha and hydrogen gas contact with first hydrofining catalyst to make alkene saturated reaction, the resultant effluent is not separated but directly contacts with second hydrofining catalyst to make hydrodesulfurization and hydro- denitrogenation reactions, and the extracted hydrogen-enriched gas is recycled and the extracted liquid enters a distillation dehydrating tower and is purified to obtain naphtha. And it can process secondary gasoline with high sulfur, nitrogen and alkene contents, and provides qualified raw material with sulfur and nitrogen contents both less than 0.5 mug/g for catalytic reforming.

Description

A method for producing catalytic reforming feedstock

Technical field

This invention pertains to a process for the refining of hydrocarbon oils in the presence of hydrogen, and more particularly to a process for the production of catalytic reforming feedstock.

Background technique

According to different sources, gasoline can be roughly divided into two categories, namely, straight-run gasoline and secondary processed gasoline. Secondary processed gasoline mainly includes catalytic cracking gasoline, coking gasoline, hydrocracking gasoline, pyrolysis gasoline and reformed gasoline. In my country, more than 80% by weight of the components in the gasoline pool come from FCC gasoline, and some refineries even have 100% by weight of FCC gasoline. Therefore, how to reduce the sulfur and olefin content of FCC gasoline is the key point for refineries to produce clean gasoline that meets the new environmental protection standards. Reformed gasoline is basically sulfur-free, nitrogen-free, olefin-free, and has a high octane number. It is a high-quality gasoline blending component. If the catalytic cracking gasoline is fractionated, the middle distillate section is cut out as the reforming raw material, and then reformed gasoline is produced through the reforming process, the sulfur and olefin content in gasoline can be effectively reduced while maintaining a high octane number .

Catalytic reforming process is one of the important processes in oil refining and petrochemical industry. It takes C ₆ ~ C ₁₁ naphtha fraction as raw material, and generates reformed oil rich in aromatics through hydrogen catalytic reaction, and at the same time produces hydrogen by-product. The reformed oil can be directly used as a blending component of high-octane gasoline, and can also be used to produce low-molecular-weight aromatic products as basic raw materials for petrochemicals; by-product hydrogen is an important source of hydrogen for refineries. At present, the raw material for catalytic reforming is mainly straight-run naphtha, but the crude oil in my country is mostly heavy crude oil, and the extraction rate of straight-run naphtha is low, and straight-run naphtha is the main raw material for steam cracking to ethylene . Therefore, the insufficient source of raw materials has become a major factor restricting the development of catalytic reforming technology in my country.

The catalytic reforming process usually adopts dual (multiple) noble metal catalysts such as platinum-rhenium and platinum-iridium. In order to prevent catalytic reforming catalyst poisoning, the sulfur and nitrogen content in the feed are required to be less than 0.5 μg/g. Therefore, the catalytic reforming process includes a naphtha hydrofinishing (reforming pre-hydrogenation) unit to remove impurities in the raw oil that are harmful to the catalytic reforming catalyst, including sulfur, nitrogen, olefins, and arsenic, lead, and copper. and moisture etc.

At present, the reforming pre-hydrogenation unit is designed to deal with straight-run naphtha feedstock. Since the nitrogen content in straight-run naphtha feedstock is usually less than 1μg/g, the design pressure of the hydrogenation reactor is usually 2MPa around or lower. The nitrogen content of catalytic cracking gasoline is much higher than that of straight-run naphtha, usually reaching 10-100 μg/g. Even if it is mixed with straight-run naphtha and put into the pre-hydrogenation reactor together, the nitrogen content of the mixed oil is 2-20 μg/g. If such a high content of nitrogen is reduced to below 0.5 μg/g, the required pressure should usually be high. at 3MPa. In addition, different from straight-run naphtha, catalytic gasoline has a higher olefin content. Even if it is mixed with straight-run naphtha, the olefin content of the mixed raw material is 5% to 20% by volume. Due to the H ₂ generated in the reaction S will regenerate mercaptans with olefins, so too high alkene content will cause the sulfur content of the product to exceed the standard. Therefore, it is very difficult for the current reforming pre-hydrogenation unit to process catalytic cracking gasoline and other secondary processed gasoline, especially the depth of hydrodenitrogenation reaction is not enough.

EP0022883 discloses a process for producing high-octane gasoline. After the sulfur-containing heavy distillate raw material is subjected to catalytic cracking reaction in the first cracking section, catalytic cracked gasoline with an olefin content of 10 to 60% by weight is generated; the extracted catalytic cracked gasoline is Re-cracking reaction is carried out in the second cracking section to remove part of its sulfur impurities and saturate 50% by weight of olefins; the product of the second cracking section is subjected to hydrotreating to further remove sulfur impurities and reduce olefins, this hydrorefining The product can be used as a reformate. For example, distilling fractions with a distillation range of 93-177°C from catalytic cracking gasoline, using Co-Mo/Al ₂ O ₃ catalysts and suitable operating conditions, the obtained sulfur and nitrogen are less than 1 μg/g, and the bromine index is less than 1. The hydrorefined product can be used as a feedstock for platinum-iridium reforming catalysts. Since the reformed material is produced by this method, the catalytic cracking gasoline has to go through the process of catalytic cracking again, and then hydrofining, so the process is complicated, the investment and operation cost is high, and the yield is low.

CN1319644A discloses a gasoline desulfurization method, which firstly carries out selective hydrodediolefinization to full fraction gasoline (preferably catalytically cracked gasoline), and then separates the gasoline into four fractions, wherein the second fraction and the fourth Fractions (heavy fractions) are blended for selective hydrodesulfurization; while a third fraction undergoes catalytic reforming after hydrofinishing. For example, it is mentioned that the fraction with a distillation range between 95 and 150°C is extracted from the whole distillate gasoline after de-diolefins, and the reaction temperature is 300°C, the partial pressure of hydrogen is 3.5MPa, and the volume ratio of hydrogen to oil is 150Nm ³ /m ³ and under the condition of volume space velocity 3h ^-1 , the fraction was hydrotreated with Procatalyse's HR306 catalyst (Co-Mo/Al ₂ O ₃ ), the sulfur content in the product was less than 1 μg/g, and the olefin content was 0.9 volume %, nitrogen content No data provided. This product can be used as a feed for platinum-tin continuous reforming catalysts. The reformed material obtained by this method must go through two hydrogenation processes, so there are problems such as complicated process and high investment and operation costs.

Contents of the invention

The purpose of the present invention is to provide a method for producing catalytic reforming feedstock on the basis of the prior art.

The method provided by the invention is: cutting the secondary processed gasoline feedstock into light gasoline fraction, medium gasoline fraction and heavy gasoline fraction; Catalyst for hydrogen refining, reacting under the conditions of average reaction temperature 200-380℃, reaction pressure 1.2-4.0MPa, volume space velocity 2-25h ^-1 , hydrogen-oil volume ratio 90-200Nm ³ /m ³ , the reaction flows out The product is directly contacted with the second hydrotreating catalyst without separation, at an average reaction temperature of 200-380°C, a reaction pressure of 1.2-4.0MPa, a volume space velocity of 2.5-25h ^-1 , and a hydrogen-to-oil volume ratio of 90-200Nm ³ /m The reaction is carried out under the conditions of ³ , the generated reaction effluent is cooled and separated, the separated hydrogen-rich gas is recycled, and the separated liquid enters the distillation dehydration tower to obtain naphtha after removing impurities.

Using the method, secondary processed gasoline with high sulfur content, nitrogen content and high olefin content can be processed under low pressure conditions, and qualified raw materials with sulfur content and nitrogen content less than 0.5 μg/g can be provided for catalytic reforming.

Detailed ways

Method provided by the invention is implemented like this:

The secondary gasoline feedstock is cut into a light gasoline fraction, a medium gasoline fraction and a heavy gasoline fraction. The initial boiling point of the medium gasoline fraction is 65-100°C, and the dry point is 150-180°C. The light fraction below the initial boiling point contains more olefins. If it enters the reforming prehydrogenation reactor, it will increase the hydrogen consumption and affect the sulfur content in the product. The heavy distillate above 180°C is easy to deposit carbon on the reforming catalyst, shortening the production cycle.

The middle gasoline fraction, optional straight-run naphtha and hydrogen are contacted with the first hydrotreating catalyst together, at an average reaction temperature of 200-380°C, preferably 280-350°C, and a reaction pressure of 1.2-4.0MPa, preferably 1.5- Under the conditions of 2.5MPa, volumetric space velocity of 2-25h ^-1 , preferably 3-16h ^-1 , and hydrogen-oil volume ratio of 90-200Nm ³ /m ³ , mainly carry out olefin saturation reaction and a small amount of hydrogenation desulfurization and hydrogenation desulfurization Nitrogen reaction, the reaction effluent is directly contacted with the second hydrofinishing catalyst without separation, at an average reaction temperature of 200-380°C, preferably 280-350°C, reaction pressure of 1.2-4.0MPa, preferably 1.5-2.5MPa, volume space velocity 2.5-25h ^-1 , preferably 3-12h ^-1 , under the condition that the volume ratio of hydrogen to oil is 90-200Nm ³ /m ³ , carry out hydrodesulfurization and hydrodenitrogenation reactions, and cool and separate the resulting reaction effluent, The separated hydrogen-rich gas is recycled, and the separated liquid enters the distillation dehydration tower to obtain naphtha after removing impurities such as H ₂ S, NH ₃ and moisture. The naphtha is qualified for catalytic reforming feed requirements raw material.

The gasoline raw material for secondary processing is any one of catalytic cracking gasoline, coker gasoline, pyrolysis gasoline, hydrocoking gasoline and hydrocracking naphtha or a mixture of several of them. The weight ratio of the middle gasoline fraction to the straight-run naphtha is 5:95˜90:10.

Secondary processed gasoline such as catalytically cracked gasoline and coker gasoline has a high olefin content. When used as a raw material for catalytic reforming, this part of olefin must be saturated. This is because, due to the deep dehydrogenation and aromatic condensation reaction in the catalytic reforming process, carbon deposits will inevitably occur on the catalyst. The presence of olefins will lead to increased carbon deposition. In addition, in the hydrodesulfurization process of reforming pre-hydrogenation, olefins will combine with H ₂ S generated by hydrodesulfurization to regenerate mercaptans, and the reaction formula is: . Moreover, the amount of mercaptans in the hydrogenation product is closely related to the amount of olefins in the raw material, that is, it increases with the increase of the olefin content.

The preferred first hydrorefining catalyst of the present invention is a metal-supported catalyst, the carrier is alumina, and the metal component is selected from group VIII cobalt and/or nickel, group VIB molybdenum and/or tungsten and alkali Metal. Calculated by oxide and based on the catalyst, the composition is 1-6% by weight of nickel, 4-12% by weight of molybdenum and/or tungsten, 2-8% by weight of alkali metal, and the balance is aluminum oxide. The catalyst is a hydrogenation catalyst with high selectivity to olefins, especially to diolefins, which can hydrogenate most of the olefins in the saturated feed oil, thereby effectively reducing the content of olefins in the hydrogenation products and preventing Olefins recombine with H ₂ S generated by hydrodesulfurization to form mercaptans.

The content of sulfur and nitrogen impurities in secondary processed gasoline such as catalytic cracked gasoline and coker gasoline is much higher than that of straight-run naphtha. To meet the requirements of catalytic reforming feed, it is necessary to increase the severity of the reaction of the reforming pre-hydrogenation unit. In particular, it is necessary to increase the depth of the hydrogenation denitrogenation reaction, and reduce the sulfur and nitrogen content in the hydrogenation product to below 0.5 μg/g.

The preferred second hydrorefining catalyst of the present invention is a metal-loaded catalyst, the carrier is alumina, the active component is selected from group VIII nickel and cobalt and tungsten from group VIB, and the promoter component is selected from magnesium , zinc, iron, calcium in any element. Calculated by oxide and based on the catalyst, the composition is 1-7% by weight of nickel, 0.01-1.0% by weight of cobalt, 10-30% by weight of tungsten, 0.1-10% by weight of cocatalyst components, and the balance is alumina. The catalyst has excellent hydrodesulfurization and hydrodenitrogenation properties, and can effectively remove sulfur, nitrogen and other impurities in inferior secondary processed gasoline raw materials. The main metal active components selected by the catalyst are nickel and tungsten. Because of its high hydrogenation activity, it is helpful for the hydrogenation denitrogenation reaction, and can convert the higher content of secondary processed gasoline raw materials under lower reaction pressure. The nitrogen-containing impurities are removed to less than 0.5 μg/g, which meets the requirements of catalytic reforming feed.

The first hydrofinishing catalyst and the second hydrofinishing catalyst in the present invention can be packed in two reactors respectively, and the first hydrofinishing catalyst can also be placed on the top of the second catalyst and packed in one reactor implement. The loading volume ratio of the first hydrofinishing catalyst to the second hydrofinishing catalyst is 20:80˜80:20, preferably 30:70˜60:40.

Both catalysts need to be presulfided before use, and the sulfidation method is the same as that of conventional hydrorefining catalysts reported in the literature. For example, under a certain reaction pressure and a certain hydrogen flow rate, add carbon disulfide (CS ₂ ) or dimethyl disulfide (CH ₃ -SS-CH ₃ , DMDS) into straight-run naphtha as sulfurized oil, and the sulfurized The temperature is 230-370°C, and the vulcanization time is 8-24 hours.

The advantage of the inventive method is:

1. Two kinds of hydrofinishing catalysts with different active metal components are used for combined loading. The first hydrofinishing catalyst is an olefin selective hydrogenation catalyst, which can hydrogenate most of the olefins in the saturated feedstock oil, so that it can effectively Reduce the content of olefins in the product and prevent the recombination of olefins with H ₂ S generated by hydrodesulfurization to form mercaptans. The second hydrorefining catalyst has high hydrodenitrogenation activity, and can remove the nitrogen content in the raw oil to 0.5 μg/g under low pressure conditions. The method of the invention can process secondary processed gasoline with high sulfur content, nitrogen content and high olefin content under low pressure conditions, and provide qualified raw materials with sulfur content and nitrogen content less than 0.5 μg/g for catalytic reforming.

2. Adopt the method of the present invention, can make up the deficiency of the raw material of catalytic reforming unit, or replace straight-run naphtha and be used for steam cracking raw material to produce chemical products such as ethylene. The hydrogen produced in the catalytic reforming process can be used in the hydrogenation unit, reducing the cost of hydrogen consumption in the refinery hydrogenation unit.

3. The present invention adopts a process of single-stage serial connection and one-pass process and non-precious metal catalyst, which has simple process flow, mature technology, low investment and flexible operation. This method is applicable to reforming pre-hydrogenation units that have been built and are under construction, and is also applicable to the transformation of old units. The invention can be implemented under lower reaction pressure, which reduces equipment investment and operation cost.

The following examples will further illustrate the method, but the method is not limited thereby.

The trade name of the hydrofinishing catalyst G used in the examples and comparative examples is RGO-2, and the trade name of the hydrofinishing catalyst S is RS-1, both of which are produced by the Catalyst Factory of Sinopec Changling Branch. Comparative Hydrofining Catalyst O is a Co-Mo containing distillate hydrogenation catalyst.

Hydrofinishing catalyst G, hydrofinishing catalyst S and comparative hydrofining catalyst O adopt conventional presulfurization method, and the sulfurized oil is a mixed oil of straight-run gasoline mixed with 2% by weight of carbon disulfide (CS ₂ ). The pre-vulcanization conditions are: reaction pressure 2.0 MPa, vulcanized oil volume space velocity 3.0h ^-1 , maximum vulcanization temperature 290°C, vulcanization time 8 hours.

Comparative example 1

A medium-weight gasoline fraction (distillation range of 95-163°C) is obtained after catalytic cracking gasoline is fractionated, and the medium-weight gasoline fraction is mixed with a straight-run naphtha at a weight ratio of 20:80 to obtain raw material A , and its properties are shown in Table 1. The raw material oil A is contacted with the hydrotreating catalyst S, and the reaction is carried out under the conditions of the reaction pressure 3.2MPa, the average reaction temperature 300°C, the volume space velocity 3.5h ^-1 , and the volume ratio of hydrogen to oil 150Nm ³ /m ³ , and the oil produced by the reaction is After cooling, separating, and removing impurities, naphtha product is obtained, and its process conditions and product properties are shown in Table 2.

It can be seen from Table 2 that the nitrogen content in naphtha products is less than 0.5 μg/g, which meets the feed requirements of catalytic reforming units, while the sulfur content is 6.3 μg/g, which is much higher than the index of <0.5 μg/g. From the analysis results of the type and content of sulfur-containing compounds listed in Table 2, all the sulfur-containing compounds in naphtha products are mercaptans, which shows that the reaction between olefins and H ₂ S generated by hydrodesulfurization reaction regenerates Mercaptans.

Example 1

The raw material used in this embodiment is the same as the raw material A used in Comparative Example 1. Feed oil A is contacted with hydrofinishing catalyst G and hydrofinishing catalyst S in sequence to carry out olefin saturation, hydrodesulfurization and hydrodenitrogenation reactions, and the reaction effluent is cooled, separated and removed to obtain naphtha products. The loading volume ratio of the hydrofinishing catalyst G and the hydrofinishing catalyst S is 40:60. Average reaction temperature, volume space velocity and hydrogen oil volume ratio in the reaction condition of embodiment 1 are identical with comparative example 1, and reaction pressure drops to 2.0MPa, and its reaction condition and product property are as shown in table 2.

It can be seen from Table 2 that the sulfur and nitrogen contents in the naphtha product oil are both less than 0.5 μg/g, meeting the feed requirements of the catalytic reforming unit.

Example 2

A kind of catalytic cracking gasoline and a kind of hydrocoking gasoline are mixed in a weight ratio of 66:34, and after fractionation, a middle-quality gasoline fraction (distillation range is 70-168°C) is obtained, and then the middle-quality gasoline fraction is mixed with a direct Distilled naphtha was mixed at a weight ratio of 50:50 to obtain feed oil B, the properties of which are shown in Table 1. It can be seen from Table 1 that the nitrogen content in raw oil B is relatively high, reaching 17 μg/g.

Feed oil B is contacted with hydrofinishing catalyst G and hydrofinishing catalyst S in sequence, under the conditions of reaction pressure 1.8MPa, average reaction temperature 300°C, volume space velocity 3.0h ^-1 , hydrogen oil volume ratio 150Nm ³ /m ³ Carry out olefin saturation, hydrodesulfurization and hydrodenitrogenation reactions, the reaction effluent is cooled, separated and removed to obtain naphtha products, and the loading volume ratio of hydrofinishing catalyst G and hydrofinishing catalyst S is 40: 60, its reaction conditions and product properties are shown in Table 3.

It can be seen from Table 3 that the sulfur and nitrogen contents in the naphtha product are both less than 0.5 μg/g, meeting the feed requirements of the catalytic reforming unit.

Comparative example 2

The raw material used in this comparative example is the same as the raw material oil B used in Example 2. Feed oil B is contacted with hydrofinishing catalyst G and comparative hydrofinishing catalyst O in sequence to carry out olefin saturation, hydrodesulfurization and hydrodenitrogenation reactions, and the reaction effluent is cooled, separated and removed to obtain naphtha products , The loading volume ratio of hydrofinishing catalyst G and comparative hydrofinishing catalyst O is 40:60, and the reaction conditions are the same as in Example 2 in this comparative example, and its reaction conditions and product properties are shown in Table 3.

It can be seen from Table 3 that the sulfur content in the naphtha product is 0.6 μg/g, and the nitrogen content is 2 μg/g. Therefore, the sulfur and nitrogen content in the naphtha product of this comparative example do not meet the feed requirements of the catalytic reforming unit.

Table 1 Raw Oil A Raw oil B Density (20℃), g/ ^cm3 0.7194 0.7432 Sulfur, μg/g 402 523 Nitrogen, μg/g 3 17 Bromine value, gBr/100g 11.7 20.6 Olefin, weight % 7.9 7.3 Distillation range ASTM D-86, ℃ initial boiling point 55 53 50% 120 110 do it 177 158

Table 2 Comparative example 1 Example 1 catalyst type S G/S Catalyst loading volume ratio 100 40/60 Process conditions: Reaction pressure, MPa 3.2 2.0 Average reaction temperature, ℃ 300 300 Volumetric space velocity, h ^-1 3.5 3.5 Hydrogen oil volume ratio, Nm ³ /m ³ 150 150 Naphtha product properties: Sulfur, μg/g 6.3 <0.5 Nitrogen, μg/g <0.5 <0.5 Sulfide analysis, μg/g Methyl mercaptan 1.1 - ethanethiol 1.4 - tert-butylmercaptan 0.5 - n-propanethiol 2.8 - Isopentyl mercaptan 0.5 -

table 3 Example 2 Comparative example 2 catalyst type G/S G/O Catalyst loading volume ratio 40/60 40/60 Process conditions: Reaction pressure, MPa 1.8 1.8 Average reaction temperature, ℃ 300 300 Volumetric space velocity, h ^-1 3.0 3.0 Hydrogen oil volume ratio, Nm ³ /m ³ 150 150 Naphtha product properties: Sulfur, μg/g <0.5 0.6 Nitrogen, μg/g <0.5 2.1

Claims (10)

1. A method for producing catalytic reforming feedstock, which cuts secondary processed gasoline feedstock into light gasoline fraction, medium gasoline fraction and heavy gasoline fraction, characterized in that the medium gasoline fraction, optional straight-run naphtha Oil and hydrogen are in contact with the first hydrorefining catalyst together, at an average reaction temperature of 200-380°C, a reaction pressure of 1.2-4.0MPa, a volume space velocity of 2-25h ^-1 , and a volume ratio of hydrogen to oil of 90-200Nm ³ /m ³ The reaction is carried out under certain conditions, and the reaction effluent is directly contacted with the second hydrorefining catalyst without separation. The average reaction temperature is 200-380°C, the reaction pressure is 1.2-4.0MPa, the volume space velocity is 2.5-25h ^-1 , and the hydrogen oil volume The reaction is carried out under the condition of a ratio of 90-200Nm ³ /m ³ , the generated reaction effluent is cooled and separated, the separated hydrogen-rich gas is recycled, and the separated liquid enters the distillation dehydration tower to obtain naphtha after removing impurities Oil. 2. The method according to claim 1, characterized in that the gasoline raw material for secondary processing is any one or more of catalytic cracked gasoline, coker gasoline, cracked gasoline, hydrocoked gasoline and hydrocracked naphtha A blend of oils. 3. The method according to claim 1, characterized in that the initial boiling point of the medium gasoline fraction is 65-100°C, and the dry point is 150-180°C. 4. The method according to claim 1 or 3, characterized in that the weight ratio of the middle gasoline fraction to straight-run naphtha is 5:95-90:10. 5. The method according to claim 1, characterized in that the reaction conditions for hydrofining are: average reaction temperature 280-350°C, reaction pressure 1.5-2.5MPa, volume space velocity of the first hydrofining catalyst 3-16h ^-1 , the volume space velocity of the second hydrotreating catalyst is 3-12h ^-1 . 6. The method according to claim 1, characterized in that the first hydrorefining catalyst is a metal-supported catalyst, the carrier is alumina, and the metal component is selected from group VIII cobalt and/or nickel , molybdenum and/or tungsten and alkali metals of Group VIB. 7. The method according to claim 1 or 6, characterized in that said first hydrotreating catalyst, calculated as oxides and based on the catalyst, consists of 1-6% by weight of nickel, molybdenum and/or 4-12% by weight of tungsten, 2-8% by weight of alkali metal, and the balance is alumina. 8. The method according to claim 1, characterized in that the second hydrorefining catalyst is a metal-supported catalyst, the carrier is alumina, and the active component is selected from group VIII nickel and cobalt and group VIII For tungsten in group VIB, the promoter component is any element selected from magnesium, zinc, iron, and calcium. 9. The method according to claim 1 or 8, characterized in that said second hydrotreating catalyst, calculated as oxides and based on the catalyst, consists of nickel 1-7 wt%, cobalt 0.01-1.0 % by weight, 10-30% by weight of tungsten, 0.1-10% by weight of the co-catalyst component, and the balance is aluminum oxide. 10. The method according to claim 1, characterized in that the loading volume ratio of the first hydrofinishing catalyst and the second hydrofinishing catalyst is 20:80-80:20.