CN109082303B - A kind of FCC gasoline cleaning method - Google Patents

Abstract

The invention relates to a FCC gasoline cleaning method, the catalytic cracking gasoline passes through a pre-hydrogenation reactor under the action of a pre-hydrogenation catalyst to carry out mercaptan etherification and double bond isomerization reaction, the effluent of the pre-hydrogenation reaction is cut and fractionated into light gasoline fraction and heavy gasoline fraction, the light gasoline fraction carries out superposition reaction under the action of a superposition catalyst, the heavy gasoline fraction carries out selective hydrodesulfurization under the action of a hydrodesulfurization-isomerization catalyst, and simultaneously linear chain olefin is isomerized into single-branch olefin or single-branch paraffin; the reacted heavy gasoline fraction enters an octane number recovery unit and is subjected to double-branched chain isomerization reaction under the action of an isomerization catalyst; finally blending the light gasoline fraction and the heavy gasoline fraction to obtain a clean gasoline product with low olefin, ultralow sulfur content and high octane number.

Description

A kind of FCC gasoline cleaning method

technical field

The invention relates to a method for cleaning FCC gasoline.

Background technique

FCC gasoline is a mixture of C ₄ -C ₁₂ hydrocarbons and trace amounts of sulfides, oxides and metal arsenides. A mixture of olefins, 12-20v% aromatic hydrocarbons and alkanes, and the octane number characteristic of each component is aromatics>olefins≈isoparaffins>paraffins. my country's high sulfur, high olefin content and low octane FCC gasoline accounts for about 70%, while the proportion of low sulfur content, low olefin content, high octane number of alkylated oil, isomerized oil and reformate oil This makes the cleaning of FCC gasoline in our country need to carry the triple task of desulfurization, olefin reduction and maintenance of octane number at the same time.

CN201010224554.1 provides a method for producing ultra-low sulfur and high octane gasoline. The production method comprises the following steps: entering a low-quality full-distillate gasoline raw material into a reactive distillation column, contacting with a thioetherification catalyst, generating a thioetherification reaction, and performing fraction cutting, so as to convert low-boiling mercaptans and thiophenes and other sulfides into high-boiling sulfides. thioether is transferred to heavy distillate gasoline, and the cutting and fractionation temperature of light distillate gasoline and heavy distillate gasoline is 50-90 °C; light distillate gasoline is contacted with hydrocarbon multi-branched isomerization catalyst; heavy distillate gasoline and selective addition The hydrodesulfurization catalyst is contacted with the supplementary desulfurization-hydrocarbon isomerization/aromatization catalyst; the treated light-distillate gasoline and heavy-distillate gasoline are mixed to obtain ultra-low-sulfur and high-octane gasoline. The invention is suitable for the upgrading of inferior gasoline, especially for inferior catalytic cracking gasoline with ultra-high sulfur and high olefin, good desulfurization and olefin reduction effect can be obtained, and after the reaction, the octane number of the product can be maintained or improved and kept relatively high product yield.

At present, among the gasoline quality upgrading technologies commonly used by domestic refineries, the highly selective desulfurization process represented by Prime-G technology adopts pre-hydrogenation-light and heavy gasoline cutting-heavy gasoline selective hydrodesulfurization-heavy gasoline supplementary desulfurization process principle. However, due to the different composition and content of specific gasoline raw materials, as well as different gasoline product standards, the gasoline upgrading process and the catalyst used are also quite different.

SUMMARY OF THE INVENTION

The invention provides a method for cleaning FCC gasoline. Specifically, FCC gasoline is pre-hydrogenated and cut into light and heavy gasoline fractions. Method for cleaning gasoline with low olefins, ultra-low sulfur content, and high octane number.

A method for cleaning FCC gasoline. Under the action of a pre-hydrogenation catalyst, the FCC gasoline passes through a pre-hydrogenation reactor to undergo mercaptan etherification and double bond isomerization, and the pre-hydrogenation reaction effluent is cut into light and heavy Gasoline fraction, light gasoline fraction undergoes superposition reaction under the action of superposition catalyst, heavy gasoline fraction undergoes selective hydrodesulfurization under the action of hydrodesulfurization-isomerization catalyst, and straight-chain olefins are isomerized into single-branched olefins or Mono-branched paraffins; the reacted heavy gasoline fractions then enter the octane number recovery unit to carry out double-branched isomerization reactions under the action of isomerization catalysts; finally, the light and heavy gasoline fractions are blended to obtain clean gasoline.

The pre-hydrogenation reaction effluent is cut and fractionated into light and heavy gasoline fractions, and the temperature of cutting and fractionation is 50-70°C.

The above-mentioned catalytically cracked gasoline is subjected to a pre-hydrogenation reactor for mercaptan etherification and double bond isomerization reaction. The reaction conditions are as follows: the reaction temperature is 80-160°C, the reaction pressure is 1-5MPa, the liquid volume space velocity is 1-10h ^-1 , The volume ratio of hydrogen to oil is 3-8:1; the pre-hydrogenation catalyst includes a carrier and an active component, and the carrier comprises 75-95wt% alumina composite carrier with macroporous structure and 5-25wt% selected from ZSM-5, ZSM-11 , ZSM-12, ZSM-35, mordenite, amorphous silica-alumina, SAPO-11, MCM-22, Y molecular sieve or beta molecular sieve, one or more, the alumina composite carrier with macroporous structure contains 0.1～ 12wt% of tungsten-doped lanthanum ferrite, alumina composite carrier mesopores account for 1-85% of the total pores, and macropores account for 1-70% of the total pores. Preferably, the mesopores account for 5-70% of the total pores, and preferably the macropores account for 5-45% of the total pores. One or more of active components cobalt, molybdenum, nickel and tungsten are supported on the surface of the carrier, in terms of oxides, the content of the active components is 0.1-15.5%.

Further preferably, the reaction conditions are as follows: the reaction temperature is 90-145°C, the reaction pressure is 1-4MPa, the liquid volume space velocity is 1-8h ^-1 , and the hydrogen-oil volume ratio is 3-6:1.

The pre-hydrogenation reaction of the present invention is mainly that under the action of a pre-hydrogenation catalyst, small molecular mercaptans and thioethers undergo a thioetherification reaction with diolefins, and at the same time, double bond isomerization (that is, terminal olefins are converted into internal olefins), and The remaining diolefins were saturated. In addition to mercaptan etherification and double bond isomerization, side reactions such as olefin polymerization and excessive cracking are inhibited to improve catalyst activity and selectivity and improve liquid yield.

The alumina composite carrier with macroporous structure contains 0.1-12wt% of tungsten-doped lanthanum ferrite, the carrier mesopores account for 1-85% of the total pores, and the macropores account for 1-70% of the total pores. Preferably, the mesopores account for 5-70% of the total pores, and preferably the macropores account for 5-45% of the total pores.

A method for preparing an alumina composite carrier with a macroporous structure. The aluminum source and succulent powder are added into a kneader and mixed evenly, an inorganic acid solution and an organic polymer are added, and the kneading is uniform, and then tungsten-doped lanthanum ferrite is added. , after kneading evenly, through extrusion, molding, drying and calcination, the alumina carrier is obtained.

The above alumina composite carrier powder with macroporous structure and one of ZSM-5, ZSM-11, ZSM-12, ZSM-35, mordenite, SAPO-11, MCM-22, Y molecular sieve or beta molecular sieve powder or The mixtures are mixed evenly, then add succulent powder and deionized water to mix, add inorganic acid, stir, dry, and roast to obtain a mixed carrier. The active components cobalt, molybdenum, nickel, and tungsten are then loaded. The cobalt, molybdenum, nickel, and tungsten in the catalyst are recorded as oxides, and the content is 0.1-15.5%.

In the above preparation of the alumina carrier, the aluminum source is one or more of pseudoboehmite, alumina, and aluminum sulfate. The aluminum source can also be one or more of kaolin, rectorite, perlite, and montmorillonite.

Further improvement of the carrier, an improved alumina carrier, the carrier contains 0.1-12wt% of silicon oxide, tungsten-doped lanthanum ferrite is 0.1-10wt%, the carrier mesopores account for 1-80% of the total pores, and the macropores account for 1-80% of the total pores. 1 to 55% of the total pores. Preferably, the mesopores account for 1-65% of the total pores, more preferably 5-55%, preferably the macropores account for 5-45% of the total pores, more preferably 10-35%, and the micropores, mesopores and macropores of the carrier do not Evenly distributed.

Preferably, the tungsten-doped lanthanum ferrite in the alumina carrier is 0.3-9wt%, more preferably 0.3-5wt%, and the tungsten in the tungsten-doped lanthanum ferrite accounts for 0.1-8wt% of the tungsten-doped lanthanum ferrite.

The organic polymer is one or more of polyvinyl alcohol, sodium polyacrylate, polyethylene glycol, and polyacrylate, preferably polyacrylic acid or sodium polyacrylate.

Compared with adding lanthanum ferrite (LaFeO ₃ ), tungsten-doped lanthanum ferrite is added to the alumina carrier, and then the products selected from ZSM-5, ZSM-11, ZSM-12, ZSM-35, mordenite, amorphous silica-alumina are introduced. , SAPO-11, MCM-22, Y molecular sieve or beta molecular sieve or one or more of them to prepare a composite carrier, load cobalt, molybdenum, nickel, tungsten active components, the catalyst effectively promotes the thioetherification reaction, while double bond isomerization (ie, the terminal olefins are converted to internal olefins), and the remaining diolefins are saturated. In particular, the double bond isomerism selectivity is relatively high.

The carrier is further improved, and the preparation method of adding silicon oxide to the alumina carrier is preferred. The pseudo-boehmite and succulent powder are added to the kneader and mixed uniformly, and the inorganic acid or organic acid solution and the organic polymer are added, kneaded uniformly, and then Then add tungsten-doped lanthanum ferrite, and mix evenly to obtain an alumina precursor for use; add a silicon source to the acid solution of the organic polymer, after mixing uniformly, mix with the alumina precursor, and the unit content of the organic polymer in the alumina precursor is organic polymerization. The content of the organic polymer is more than 1.5 times higher than that of the silicon source, and the alumina carrier is obtained by extrusion, molding, drying and roasting. The silicon source can be sodium silicate or silicon micropowder, and the tungsten-containing compound includes ammonium tungstate, ammonium metatungstate, ammonium paratungstate, and the like. The inorganic acid is nitric acid, hydrochloric acid and sulfuric acid, and the organic acid is oxalic acid, citric acid, nitrilotriacetic acid, tartaric acid, acetic acid or malic acid.

Further improvement of the above alumina carrier, the silicon source can be sodium silicate or silicon micropowder, or one or both of diatomite and opal, and the aluminum source can also be kaolin, rectorite, perlite , one or more of montmorillonite.

The sub-molten salt medium in the activation process of kaolin, rectorite, perlite and montmorillonite powder is NaOH-H ₂ O, and the bauxite powder and sub-molten salt medium are mixed uniformly according to the mass ratio of 1:0.2-2, Under the temperature of 100～400℃, the activation time is 0.5～4h. The activation process of diatomite and opal is to roast diatomite at a temperature of 500-1000℃ for 1-10h. The tungsten-doped lanthanum ferrite in the above alumina carrier preferably has micro-mesopores, and the catalyst prepared by introducing tungsten-doped lanthanum ferrite with micro-mesoporous pores is conducive to inhibiting the occurrence of side reactions such as hydrocarbon cracking, and improving the selectivity of the target product .

A preparation method of tungsten-doped lanthanum ferrite with micro-mesoporous, citric acid is dissolved in deionized water, stirred and dissolved, then lanthanum nitrate and ferric nitrate are added to citric acid, stirred and dissolved, sodium polyacrylate or polyacrylic acid is added, The amount of sodium polyacrylate or polyacrylic acid added is 0.1-9 wt % of the tungsten-doped lanthanum ferrite, preferably 0.1-6.0 wt %. A tungsten-containing compound is then added, in terms of oxides, tungsten accounts for 0.1-8wt% of the tungsten-doped lanthanum ferrite, stirred, and after the reaction, the finished product is obtained by drying, roasting and grinding.

The alumina carrier of the present invention is an alumina composite carrier with a macroporous structure.

In the preparation process of the improved alumina carrier, the unit content of the organic polymer in the alumina precursor is more than 1.5 times higher than the content of the organic polymer in the silicon source, which can effectively improve the pore structure of the carrier. The pores and macropores are unevenly distributed, which reduces the occurrence of side reactions such as olefin polymerization and excessive cracking, improves the selectivity, and has a high gasoline yield, which is beneficial to the long-term operation of the device; on the other hand, it is beneficial to generate more active sites on the surface of the carrier. center to improve catalyst activity.

The pre-hydrogenation catalyst carrier of the present invention comprises an alumina composite carrier with a macroporous structure and is selected from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-35, mordenite, amorphous silica-alumina, SAPO-11, One or more of MCM-22, Y molecular sieve or beta molecular sieve, loaded with one or more of cobalt, molybdenum, nickel, and tungsten, used for gasoline removal of diolefins, mercaptans, sulfides, and double bond Isomerically terminal olefins are converted to internal olefins; and remaining diolefins are saturated. The catalyst not only effectively promotes the conversion of terminal olefins into internal olefins and increases the octane number, but also helps to reduce the recracking reaction of low-carbon isomers, reduce the occurrence of side reactions such as olefin polymerization, improve the activity selectivity, and increase the gasoline yield.

The above-mentioned active components of cobalt, molybdenum, nickel and tungsten can be their various salts or one or more of their respective oxides, sulfides, nitrides and phosphides.

The preparation method of the catalyst to be hydrogenated includes the following steps: preparing the active components containing cobalt, molybdenum, nickel and tungsten into an impregnating liquid, impregnating the carrier, drying at 120-180 ° C for 4-8 hours, 450-800 ° C Lower calcination for 3-9 hours to obtain a pre-hydrogenation catalyst.

The pre-hydrogenation catalyst is further improved, and the pre-hydrogenation catalyst also includes ZSM-5, ZSM-11, ZSM-12, ZSM-35, mercerized, SAPO-11, MCM-22, Y molecular sieve or beta molecular sieve one or more of them.

The heavy gasoline fraction reaction effluent of the present invention is selectively hydrodesulfurized under the action of a hydrodesulfurization-isomerization catalyst, and the reaction process conditions for the isomerization of linear olefins into single-branched olefins or single-branched paraffins are as follows: reaction The temperature is 190-330°C, the reaction pressure is 1.2-3.5MPa, the volumetric space velocity is 2.5-5h ^-1 , and the volume ratio of hydrogen to oil is 160-460:1.

Catalytic cracking gasoline selective hydrodesulfurization-isomerization catalyst, including carrier and active components, the carrier is the carrier used for the pre-hydrogenation catalyst, the surface of the carrier supports phosphomolybdic acid, phosphotungstic acid or phosphomolybdic acid, and phosphomolybdic acid in the catalyst , phosphotungstic acid or phosphomolybdotungstic acid is recorded as oxide, and the content is 0.1 to 16.5%.

Further improvement, the above-mentioned hydrodesulfurization-isomerization catalyst surface is impregnated with active components to obtain an improved hydrodesulfurization-isomerization catalyst, and the improved hydrodesulfurization-isomerization catalyst includes 0.1% to 14.5% of metal activity by weight percentage. The components and active components are selected from one or more of cobalt, molybdenum, nickel and tungsten.

The hydrodesulfurization-isomerization catalyst of the present invention uses macroporous alumina containing tungsten-doped lanthanum ferrite as a carrier, supports tungsten phosphomolybdate, phosphotungstic acid or phosphomolybdotungstic acid and/or cobalt, molybdenum, nickel, One or more of tungsten is used for selective desulfurization and isomerization of gasoline hydrogenation, which not only effectively promotes single branched chain isomerization, improves octane number, but also helps to reduce the recracking reaction of low-carbon isomerized hydrocarbons, reducing Side reactions such as olefin polymerization and excessive cracking occur, the activity selectivity is improved, and the gasoline yield is high.

The hydrodesulfurization-isomerization reaction effluent of the heavy gasoline fraction then enters the octane number recovery unit, and under the action of the isomerization catalyst, double-branched isomerization is carried out. The reaction conditions are: reaction temperature 180-450 ℃, reaction pressure 0.6 -4.8MPa, airspeed 0.5-8h ^-1 , hydrogen oil volume ratio 50-450:1.

The double-branched isomerization includes the isomerization of single-branched olefins or single-branched paraffins to double-branched paraffins.

The isomerization catalyst comprises ZSM-5 molecular sieve, and the isomerization catalyst comprises 32-88% weakly acidic mesoporous H-type Zn-ZSM-5 molecular sieve or improved weakly acidic mesoporous H-type Zn-ZSM by weight percentage -5 molecular sieve, preferably 42-83%; 0-66% pseudoboehmite, macroporous alumina or zinc-aluminum hydrotalcite binder as carrier, preferably 8-55%; impregnation 0.5-16% metal activity component, preferably 1-12%; the metal active component is one or more of Fe, Co, Ni, Mo and W, and the loading method is impregnation method, preferably equal volume impregnation method or multiple impregnation Law.

In the present invention, the weakly acidic mesoporous H-type Zn-ZSM-5 molecular sieve has a mesopore diameter of 4.5-36 nm, a specific surface area of 320-650 m ² /g, and a zinc oxide content of 0.15-36 nm of the total weight of the molecular sieve. 12%.

In the present invention, the improved weakly acidic mesoporous Zn-ZSM-5 molecular sieve has a mesopore diameter of 4.5-36 nm, a specific surface area of 320-650 m ² /g, and a zinc oxide content of 0.15-36 nm of the total weight of the molecular sieve. 12%, the zinc content on the surface of the molecular sieve is higher than the zinc content inside the molecular sieve, preferably 0.2-2 times higher.

The present invention also provides a preparation method of mesoporous Zn-ZSM-5 molecular sieve, comprising the following steps:

(1) At a certain temperature, the deionized water, aluminum source, zinc source, acid source, template agent (SDA) and silicon source are mixed uniformly under stirring conditions to prepare a gel, and the material molar ratio is adjusted to (0.003-0.07 ) Al ₂ O ₃ : (0.03-0.3) Na ₂ O: 1SiO ₂ : (8-45) H ₂ O: (0.05-0.2) SDA: (0.001-0.15) ZnO;

(2) the gel obtained in the step (1) is aged and transferred to a stainless steel reactor containing a polytetrafluoroethylene lining for sealing and crystallization, after the crystallization is completed, the crystallization product is cooled, filtered to remove the mother liquor, and filtered. The cake is washed with deionized water until neutral, and dried to obtain Zn-ZSM-5 molecular sieve;

(3) The Zn-ZSM-5 molecular sieve obtained in the step (2) is subjected to a series of treatments such as exchange, filtration, drying, calcination, etc., to obtain the H-type Zn-ZSM-5 molecular sieve.

The invention further improves the mesoporous Zn-ZSM-5 molecular sieve. After obtaining the H-type Zn-ZSM-5 molecular sieve, the surface of the H-type Zn-ZSM-5 molecular sieve is then impregnated with a zinc-containing compound for modification by the impregnation method, so that the surface of the molecular sieve is modified. The zinc content is higher than the zinc content inside the molecular sieve, and it is preferably impregnated with equal volume to obtain an improved H-type Zn-ZSM-5 molecular sieve modified with Zn, that is, an improved Zn-ZSM-5 molecular sieve. Wherein, the zinc-containing compound is one or more of zinc nitrate, zinc acetate, zinc chloride and zinc sulfate, preferably zinc acetate.

The silicon source described in the step (1) can be a conventional commercially available silicon source, or one or both of diatomite and opal, and the aluminum source can be a conventional commercially available aluminum source, or kaolin, rector One or more of soil, perlite and montmorillonite, and the zinc source can also be one or two of smithsonite and red zinc ore.

SDA described in step (1) is one or more of trimethylamine (TMA), methylethylamine, pyrrole, morpholino, and can also be commonly used tetrapropyl ammonium hydroxide (TPAOH), tetrapropyl bromide One or more of ammonium (TPABr), 1,6-hexanediamine, n-butylamine, and hexanediol, preferably one or more of trimethylamine (TMA), methylethylamine, pyrrole, and morphine.

The aging temperature in step (2) is 30-85°C, preferably 40-80°C; the aging time is 1-24h, preferably 2-16h.

The crystallization temperature described in the step (2) is 120-210 ° C, preferably 130-185 ° C; the temperature is programmed in 1-5 sections, preferably 1-3 sections; it is best to perform subsection unequal temperature rise, non-isothermal subsection Heating treatment, the heating rate is fast first and then slow. Before 100 °C, the temperature is increased at a heating rate of 6-8 °C/min, 20-30 °C is a heating section, and the processing time in the temperature section is 0.5-5 hours; 100-200 °C The temperature is increased at a heating rate of 3-5 °C/min, 10-20 °C is a heating section, and the treatment time in the temperature section is 0.5-8 hours. The invention adopts non-isothermal subsection heating treatment, which is beneficial to the control of nucleation rate and growth rate in the crystallization process of Zn-ZSM-5 molecular sieve, and can control the size and number of mesopores, thereby improving the activity of the catalyst and the selectivity of the target product. . The crystallization time is 10-96h, preferably 24-72h.

The roasting temperature described in the step (3) is 420-780°C, preferably 450-650°C; the roasting time is 1-8h; the exchange reagent is one of hydrochloric acid, nitric acid, sulfuric acid, ammonium chloride or ammonium nitrate;

The surface modification of the molecular sieve described in the step (3) adopts the same volume of impregnation with a zinc-containing compound, wherein the mass fraction of ZnO is 0.5-15%, preferably 0.5-10%.

The isomerization catalyst of the invention comprises one-step synthesis of Zn-ZSM-5 molecular sieve with Zn in the framework. The synthesis method of the molecular sieve is simple, the crystal structure is changed due to the entry of Zn into the framework of the molecular sieve, mesopores are generated, and the dispersibility of Zn is improved at the same time. This will reduce the diffusion resistance of reactants and improve the resistance to carbon deposition.

The zinc content on the surface of Zn-ZSM-5 molecular sieve is higher than that in the interior of the molecular sieve. The interaction between the surface Zn atom and the Al hydroxyl group leads to the weakening of the strong acid strength to medium strong acid, which reduces the acid strength of the molecular sieve and reduces the side reactions such as hydrocarbon cracking from the root. occurs, improving the selectivity of multi-branched isomeric hydrocarbons.

The cut light gasoline fraction of the present invention undergoes a superposition reaction under the action of the FCC gasoline superposition catalyst, thereby reducing the olefin content of the catalytically cracked gasoline light gasoline fraction.

FCC gasoline stacking catalyst, by weight percentage, comprising 30-85% H-type mesoporous Zn-ZSM-5 molecular sieve or improved mesoporous Zn-ZSM-5 molecular sieve and selected from mordenite, SAPO-11, MCM-22 One or more of Y molecular sieve or beta molecular sieve is a composite carrier, impregnated with 0.2-14% metal active components, preferably 0.8-8%; the metal active components are V, Fe, Ni, Mo and One or more of W, the loading method is dipping method, preferably multiple dipping method.

The H-type mesoporous Zn-ZSM-5 molecular sieve or the improved mesoporous Zn-ZSM-5 molecular sieve is the molecular sieve of the octane number recovery isomerization catalyst of the present invention.

The preparation method of the FCC gasoline superimposed catalyst of the present invention is as follows: mesoporous H-type Zn-ZSM-5 molecular sieve or improved Zn-ZSM-5 molecular sieve is mixed with mordenite, SAPO-11, MCM-22, Y molecular sieve or beta molecular sieve One or more of the composite catalysts are mixed and formed, and then the metal active components are impregnated and calcined to obtain a composite catalyst. The superimposed catalyst of the present invention is suitable for the superposition reaction of light olefins in catalytic cracking gasoline, catalytic cracking gasoline and delayed coking gasoline to produce gasoline components. At 9～150℃, 0.5～4.5MPa, and space velocity of 0.8～30h ^-1 , the conversion rate of C4 olefin is higher than 86%, and the selectivity of C8 olefin is not less than 85%.

The present invention provides a method for producing clean gasoline with low olefin, ultra-low sulfur content and high octane number, in particular to the pre-hydrogenation of FCC gasoline, cutting light and heavy gasoline fractions, and the light gasoline fractions are subjected to a superposition reaction, and the heavy gasoline fractions undergo a superposition reaction. A method for producing clean gasoline with low olefin, ultra-low sulfur content and high octane number through the process of hydrodesulfurization-isomerization of gasoline fractions, double-branched isomerization, and blending of light and heavy gasoline fractions. The method of the invention further reduces the olefin content of the gasoline and maintains the octane number of the gasoline while realizing the ultra-deep desulfurization of the FCC gasoline, thereby obtaining the clean gasoline meeting the National VI standard, thereby significantly improving the economic benefit of the refinery.

Detailed ways

The present invention will be described in further detail below by means of examples, but these examples should not be construed as limiting the present invention. The raw materials and reagents used in the present invention are all commercially available products.

1. Preparation of pre-hydrogenation catalyst

(1) Preparation of pre-hydrogenation catalyst 1

1. Preparation of tungsten-doped lanthanum ferrite with micro-mesopores

Under stirring conditions, dissolve 2.2mol La(NO ₃ ) ₃ in 100 mL of water, add citric acid and stir to dissolve; then add 4.2 mol Fe(NO ₃ ) ₃ , then add 160 g of sodium polyacrylate, and then add 10 g of metatungstic acid The aqueous solution of ammonium is continuously stirred for 30 minutes, and the micro-mesoporous tungsten-doped lanthanum ferrite is obtained by drying, roasting and grinding.

2. Preparation of alumina carrier

2.2g of micro-mesoporous tungsten-doped lanthanum ferrite was added with citric acid for later use, 300g of pseudo-boehmite powder and 20.0g of succulent powder were added to the kneader, and mixed evenly, then nitric acid and 8g of sodium polyacrylate were added. Knead uniformly, then add micro-mesoporous tungsten doped lanthanum ferrite, mix uniformly, and shape into a clover shape through kneading and extrusion. It was dried at 120°C for 8 hours and calcined at 700°C for 4 hours to obtain alumina carrier 1 containing micro-mesoporous tungsten-doped lanthanum ferrite. The pore structure of the carrier is shown in Table 1.

3. Preparation of pre-hydrogenation catalyst 1

Alumina carrier 1 is kneaded and stirred with succulent powder, acidified amorphous silica-alumina, and deionized water, dried and roasted to obtain composite carrier 1-1, and ammonium heptamolybdate and nickel nitrate are added to distilled water to form an impregnating liquid to impregnate the above composite carrier. For carrier 1-1, the obtained catalyst precursor was dried at 140° C. and then calcined at 500° C. for 6 hours to obtain catalyst 1. The main composition of catalyst 1: the alumina carrier containing micro-mesoporous tungsten doped lanthanum ferrite is 73.2wt%, the alumina content is 4.8wt%, the silicon oxide content is 5.2wt%, the nickel oxide content is 7.7wt%, the molybdenum oxide content is 7.7wt%, The content was 9.1 wt%.

(2) Preparation of pre-hydrogenation catalyst 2

1. Preparation of tungsten-doped lanthanum ferrite

Under stirring conditions, 2.2 mol La(NO ₃ ) ₃ was dissolved in 100 mL of water, and citric acid was added to stir and dissolve; then 4.2 mol of Fe(NO ₃ ) ₃ was added, and then an aqueous solution containing 10 g of ammonium metatungstate was added, and the stirring was continued for 30 min. After drying, roasting and grinding, the tungsten-doped lanthanum ferrite is obtained.

2. Preparation of alumina carrier

2.2g of tungsten-doped lanthanum ferrite was added with citric acid, 300g of pseudo-boehmite powder and 20.0g of succulent powder were added to the kneader, mixed evenly, then nitric acid and 8g of sodium polyacrylate were added, kneaded evenly, and then The tungsten-doped lanthanum ferrite is added, mixed uniformly, and formed into a clover shape through kneading and extrusion. It was dried at 120°C for 8 hours and calcined at 700°C for 4 hours to obtain alumina carrier 2 containing tungsten-doped lanthanum ferrite. The pore structure of the carrier is shown in Table 1.

3. Preparation of pre-hydrogenation catalyst 2

Same as catalyst 1, introduce zsm-5 into the carrier to obtain composite carrier 2-1, impregnate composite carrier 2-1 with the impregnation solution containing molybdenum and cobalt, and the obtained catalyst precursor is dried at 140 ℃ and then calcined at 530 ℃ for 5h , to obtain catalyst 2. The main composition of catalyst 2: the alumina carrier containing tungsten-doped lanthanum ferrite is 71.5wt%, the zsm-5 content is 7wt%, the molybdenum oxide is 10.8wt%, and the cobalt oxide is 10.7wt%.

(3) Preparation of pre-hydrogenation catalyst 3

The preparation of the alumina carrier 3 containing the micro-mesoporous tungsten-doped lanthanum ferrite is the same as that of the catalyst 1, except that the micro-mesoporous tungsten-doped lanthanum ferrite accounts for 6 wt% of the carrier. The preparation of the catalyst is the same as that of catalyst 1, and the activated montmorillonite is used as the aluminum source. The difference is that the active components are molybdenum and tungsten, and catalyst 3 is mainly composed of: the alumina carrier containing micro-mesoporous tungsten doped lanthanum ferrite is 75.6wt%, the alumina content is 4.0wt%, and the silicon oxide content is 4.0wt% %, molybdenum oxide 10.1wt%, tungsten oxide 6.3wt%.

(4) Preparation of pre-hydrogenation catalyst 4

Preparation of improved alumina carrier

2g of sodium polyacrylate was dissolved in nitric acid, then 28g of silicon micropowder was added, and the mixture was evenly stirred to obtain a silicon micropowder-sodium polyacrylate mixture, and 1/10 of the amount was used for later use, and 2.0g of micro-mesoporous tungsten-doped lanthanum ferrite was added with citric acid spare. Add 310g of pseudo-boehmite powder and 22.0g of succulent powder into the kneader, add nitric acid, then add 28g of sodium polyacrylate nitric acid solution, mix well, then add the above-mentioned silicon micropowder-sodium polyacrylate mixture, knead evenly, Then, the micro-mesoporous tungsten-doped lanthanum ferrite is added, mixed uniformly, and formed into a clover shape through kneading and extrusion. Drying at 130° C. for 7 hours, and calcining at 650° C. for 5 hours, a micro-mesoporous tungsten-doped lanthanum ferrite and silicon oxide alumina carrier 4 was obtained.

The preparation of the catalyst is the same as that of catalyst 2, except that the active components are tungsten, nickel and molybdenum. The main components of catalyst 4 are: the alumina carrier containing micro-mesoporous tungsten doped lanthanum ferrite is 71.7wt%, and the content of zsm-5 is 5wt%. %, tungsten oxide 7.8wt%, nickel oxide 3.2wt%, molybdenum oxide 12.3wt%.

(5) Preparation of pre-hydrogenation catalyst 5

Under stirring conditions, 2.0 mol La(NO ₃ ) ₃ was dissolved in 100 mL of water, and citric acid was added to stir and dissolve; then 4.0 mol of Fe(NO ₃ ) ₃ was added, and an aqueous solution containing 12 g of ammonium metatungstate was added, and the stirring was continued for 30 min. After drying, roasting and grinding, the tungsten-doped lanthanum ferrite is obtained.

The preparation of alumina carrier 5 containing tungsten-doped lanthanum ferrite is the same as catalyst 4, except that tungsten-doped lanthanum ferrite accounts for 3 wt% of the carrier, and activated diatomite and kaolin are used as silicon and aluminum sources. Catalyst 5 is mainly composed of: 74.0wt% of alumina carrier containing tungsten-doped lanthanum ferrite and silicon oxide, 4wt% of zsm-5, 12.9wt% of molybdenum oxide, and 9.1wt% of tungsten oxide.

(6) Preparation of pre-hydrogenation catalyst 6

The catalyst preparation is the same as that of catalyst 4, except that mordenite is added to the catalyst. Catalyst 6 is mainly composed of: the content of alumina carrier 4 containing micro-mesoporous tungsten doped lanthanum ferrite and silica is 80.1 wt%, and the content of mordenite is 6.8 wt%. , molybdenum oxide 10.4wt%, tungsten oxide 2.7wt%. Activated diatomite and kaolin are used as silicon source and aluminum source.

(7) Preparation of pre-hydrogenation catalyst 7

The preparation of the catalyst is the same as that of catalyst 6, except that beta molecular sieve is added to the catalyst. The main composition of catalyst 7 is: the content of alumina carrier 4 containing micro-mesoporous tungsten doped lanthanum ferrite and silicon oxide is 72.8wt%, and the content of beta molecular sieve is 6.7wt% , molybdenum oxide 10.4wt%, nickel oxide 10.1wt%. Activated diatomite and kaolin are used as silicon source and aluminum source.

(8) Preparation of pre-hydrogenation comparative catalyst 1

The preparation of the carrier is the same as that of catalyst 4, except that lanthanum ferrite is added. The preparation of the catalyst is the same as that of catalyst 4, and the reaction conditions are the same as that of catalyst 4. The reaction results are shown in Table 2.

2. Preparation of hydrodesulfurization-isomerization catalyst

(1) Preparation of hydrodesulfurization-isomerization catalyst 1

Using the carrier of the pre-hydrogenation catalyst 1 as a carrier, impregnating phosphomolybdotungstic acid, the obtained catalyst precursor was dried at 140°C, and then calcined at 600°C for 7 hours to obtain the hydrodesulfurization-isomerization catalyst 1. The main composition of the catalyst 1: the alumina carrier containing micro-mesoporous tungsten doped lanthanum ferrite is 90.2 wt %, and the phosphorus molybdenum tungsten oxide is 9.8 wt %.

(2) Preparation of hydrodesulfurization-isomerization catalyst 2

Using the carrier of the pre-hydrogenation catalyst 3 as a carrier, impregnated with phosphomolybdic acid, the obtained catalyst precursor was dried at 140° C. and then calcined at 630° C. for 5 hours to obtain catalyst 2. The hydrodesulfurization-isomerization catalyst 2 is mainly composed of: the alumina carrier containing tungsten doped lanthanum ferrite is 85.2wt%, and the phosphorus molybdenum oxide is 14.8wt%.

(3) Preparation of hydrodesulfurization-isomerization catalyst 3

The carrier of the pre-hydrogenation catalyst 4 is used as the carrier, impregnated with phosphotungstic acid and ammonium molybdate (the weight of molybdenum oxide accounts for 4.1% of the catalyst). wt%, phosphotungsten oxide 7.0wt%.

(4) Preparation of hydrodesulfurization-isomerization catalyst 4

Using the carrier of the pre-hydrogenation catalyst 4 and the mordenite as the carrier, impregnating phosphomolybdotungstic acid and cobalt nitrate (the weight of cobalt oxide accounts for 3.6% of the catalyst), and using the activated diatomite and kaolin as the silicon source and aluminum source. The main composition of the catalyst 4: the alumina carrier containing tungsten-doped lanthanum ferrite and silicon oxide is 86.8 wt%, and the phosphorus-molybdenum-tungsten oxide is 9.6 wt%.

3. Preparation of isomerization catalyst in octane recovery unit

1. Preparation of mesoporous Zn-ZSM-5 molecular sieves

(1) Dissolve 0.44g NaAlO2 and 2.14g Zn(NO3)2 6H2O in 49.55g deionized water, then add dropwise 2.00g sulfuric acid (3mol/L), stir for 5min, add 0.93g TMA, stir for 1h, add 14.20g water glass (containing 27.6wt% SiO2, 7.1wt% Na2O and 65.3wt% H2O) was mixed and stirred at room temperature for 2h, the molar composition of the mixture was 0.003Al2O3:0.25Na2O:1SiO2:50H2O:0.24SDA : 0.11ZnO.

(2) The mixture obtained in step (1) was heated to 75°C for aging for 6 hours, then the solution was poured into a stainless steel crystallization kettle with a polytetrafluoroethylene lining, the temperature was raised to 130°C for crystallization for 12 hours, and then the temperature was raised to 180°C ℃ static crystallisation for 24h. After the crystallization, the mother liquor was removed by cooling and filtration, washed until neutral, and dried at 120° C. to obtain the crystallization product Zn-ZSM-5 molecular sieve.

(3) The Zn-ZSM-5 molecular sieve was added to the ammonium chloride solution with a concentration of 1 mol/L according to the solid-to-liquid ratio of 1:10, mixed and stirred at 60 ° C for 4 h, suction filtered, dried, and then repeated in the same way. After one exchange, it was put into a muffle furnace and calcined at a high temperature of 550 °C for 6 h to obtain H-type Zn-ZSM-5 molecular sieve, which was then impregnated with ZnO with a mass fraction of 5%.

2. Preparation of Ni-Mo/Zn-ZSM-5-Y molecular sieve catalyst

Mix 30g of the above-treated Zn-ZSM-5 molecular sieve and 11g of Y molecular sieve with 30g of deionized water uniformly, then extrude into strips, dry at 120 °C for 4 hours, and bake at 550 °C for 5 hours to obtain a molecular sieve carrier, which is then impregnated several times. The Ni-Mo/Zn-ZSM-5 catalyst was prepared by impregnating 7.0wt% of NiO and 6.0wt% of MoO3.

4. Preparation of superimposed catalysts

Taking the mesoporous Zn-ZSM-5 molecular sieve of the isomerization catalyst in the octane number recovery unit as a carrier, 40 g of the above-treated Zn-ZSM-5 molecular sieve and 11 g of Y molecular sieve were mixed with 30 g of deionized water uniformly, and then squeezed. The strips were formed, dried at 120 °C for 4 h, calcined at 550 °C for 5 h to obtain a molecular sieve carrier, and then impregnated with 7.5 wt% NiO and 6.5 wt% MoO ₃ by multiple dipping method to prepare Ni-Mo/Zn-ZSM-5 catalyst.

Table 1 Specific surface area and pore size distribution of macroporous alumina supports

Table 2 Catalyst pre-hydrogenation reaction results

FCC gasoline is processed through a pre-hydrogenation reactor under the action of a pre-hydrogenation catalyst to remove diolefins, mercaptans, and thioethers, and at the same time, double bond isomerization (ie, end olefins are converted into internal olefins), and the remaining diolefins are removed. Olefin saturation. The reaction temperature was 115°C, the reaction pressure was 1.8MPa, the liquid volume space velocity was 5h ^-1 , and the hydrogen-oil volume ratio was 4:1. The reaction results are shown in Table 2. The reaction effluents of pre-hydrogenation catalysts 2, 3, 4, and 7 are cut into light and heavy gasoline fractions at 44°C, and the light gasoline fractions undergo a superimposition reaction under the action of the superposition catalyst. The reaction temperature is 91°C and the reaction pressure is 3.0 MPa, the liquid volume space velocity is 20h ^-1 , the superposition reaction results show that the C4 olefin conversion (%) is 91.3, 90.4, 89.5, 92.1; the C8 olefin selectivity (%) is 89.4, 87.9, 87.7, 89.9, ; The carbon deposition rate (%) is 0.04, 0.02, 0.03, 0.03 respectively. The heavy gasoline fraction is selectively hydrodesulfurized under the action of hydrodesulfurization-isomerization catalysts 1-4, and the linear olefins are isomerized into single-branched olefins or single-branched paraffins. The reaction process conditions are: reactor temperature 265 ℃ , the reaction pressure is 1.5MPa, the volume space velocity is 2.5h ^-1 , and the volume ratio of hydrogen to oil is 320. After about 150 hours of reaction, samples were taken for analysis, and the results are shown in Table 3. The reaction effluents of catalysts 2, 3 and 4 then enter the octane number recovery unit, where the double branched chain isomerization reaction is carried out under the action of the isomerization catalyst. The reaction temperature is 360°C, the reaction pressure is 1.8MPa, the space velocity is 0.8h ^-1 , The volume ratio of hydrogen to oil is 280:1. After the reaction, the double-branched paraffin increases by more than 5.1%, and the sulfur content obtained after the light and heavy gasoline fractions are reconciled are 8mg/kg, 7mg/kg, 6mg/kg respectively, and the olefin content is respectively 13v%, 10v%, 11v%; The clean gasoline with alkane loss of 0.2, 0.3 and 0.3 respectively meets the National VI standard.

It can be seen from Table 2 that the pre-hydrogenation catalysts 1-7 have low octane number loss, high gasoline yield, high mercaptan removal rate and good activity. The catalyst can effectively inhibit the occurrence of side reactions such as olefin polymerization and excessive cracking, and inhibit the occurrence of low carbon In the cracking reaction of hydrocarbons, the yield of gasoline is high, which is conducive to the long-term operation of the device; the surface of the catalyst carrier produces more active site load centers, which effectively improves the catalyst's removal of diolefins, mercaptans, sulfides, and double bond isomerization. The catalyst has good activity and selectivity. The reaction runs for 600h, the removal rates of mercaptans from pre-hydrogenation catalysts 4 and 7 are 98.2% and 98.6%, the octane number loss is 0.2 units and 0.3 units, the carbon deposition rates are 0.3 and 0.2, and the liquid yield is 99.6% and 99.6%. 99.0%. The increase of internal olefin is 0.37% and 0.42%, the removal rate of diene content is 100% and 98.2%, and the catalyst reaction performance is stable. The hydrodesulfurization-isomerization catalyst 1-4 has high desulfurization rate and good activity. The catalyst can effectively inhibit the occurrence of side reactions such as olefin polymerization and excessive cracking, reduce the recracking reaction of low-carbon isomerized hydrocarbons, and the surface of the catalyst carrier produces more The active site loading center can effectively improve the desulfurization-isomerization activity of the catalyst, and the catalyst has good hydrodesulfurization-isomerization activity and selectivity.

Table 3 Catalyst hydrodesulfurization-isomerization results

Of course, the present invention can also have other various embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformation should belong to the protection scope of the present invention.

Claims (11)

1. A method for cleaning FCC gasoline is characterized in that: the method comprises the following steps: under the action of a pre-hydrogenation catalyst, catalytically cracked gasoline passes through a pre-hydrogenation reactor to carry out mercaptan etherification and double bond isomerization reaction, the pre-hydrogenation reaction effluent is cut and fractionated into light gasoline fractions and heavy gasoline fractions, the light gasoline fractions carry out superposition reaction under the action of a superposition catalyst, the heavy gasoline fractions carry out selective hydrodesulfurization under the action of a hydrodesulfurization-isomerization catalyst, and simultaneously straight-chain olefin is isomerized into single-branch olefin or single-branch paraffin; the reacted heavy gasoline fraction enters an octane number recovery unit and is subjected to double-branched chain isomerization reaction under the action of an isomerization catalyst; finally blending the light gasoline fraction and the heavy gasoline fraction to obtain clean gasoline; the pre-hydrogenation catalyst comprises a carrier and an active component, wherein the carrier comprises 75-95wt% of an alumina composite carrier with a macroporous structure and 5-25wt% of one or more selected from ZSM-5, ZSM-11, ZSM-12, ZSM-35, mordenite, amorphous silicon-aluminum, SAPO-11, MCM-22, Y molecular sieve or beta molecular sieve, the alumina composite carrier with the macroporous structure contains 0.1-12wt% of tungsten doped lanthanum ferrite, the mesopores of the alumina composite carrier account for 1-85% of the total pores, the macropores of the alumina composite carrier account for 1-70% of the total pores, and the surface of the carrier is loaded with one or more of the active components cobalt, molybdenum, nickel and tungsten, wherein the content of the active component is 0.1-15.5% in terms of oxide.

2. The FCC gasoline clean-up method of claim 1, wherein: the pre-hydrogenation reaction conditions were as follows: the reaction temperature is 80-160%^oC, reaction pressure is 1-5MPa, liquid volume space velocity is 1-10h^-1The volume ratio of hydrogen to oil is 3-8: 1.

3. The FCC gasoline clean-up method of claim 1, wherein: the alumina composite carrier with the macroporous structure comprises 0.1-12wt% of silicon oxide and 0.1-10wt% of tungsten-doped lanthanum ferrite, wherein mesopores account for 1-80% of total pores, macropores account for 1-70% of the total pores, and micropores, mesopores and macropores in the carrier are not uniformly distributed.

4. A FCC gasoline cleaning process as claimed in claim 3, characterized in that: the silicon source of the alumina is one or two of diatomite and opal, and the aluminum source of the alumina is one or more of kaolin, rectorite, perlite and montmorillonite.

5. The FCC gasoline clean-up method of claim 1, wherein: the selective hydrodesulfurization reaction process conditions are as follows: the reaction temperature is 190 ℃ and 330 ℃, the reaction pressure is 1.2-3.5MPa, and the volume space velocity is 2.5-5h^-1The hydrogen-oil volume ratio is 160-460: 1.

6. The FCC gasoline clean-up method of claim 1, wherein: the hydrodesulfurization-isomerization catalyst comprises a carrier and an active component, wherein the carrier comprises an alumina composite carrier with a macroporous structure, the alumina composite carrier contains 0.1-12wt% of tungsten-doped lanthanum ferrite, mesoporous pores of the alumina composite carrier account for 1-85% of total pores, macroporous pores of the alumina composite carrier account for 1-70% of the total pores, and phosphomolybdic acid, phosphotungstic acid or phosphomolybdotungstic acid is loaded on the surface of the carrier, and the content of the phosphomolybdic acid, the phosphotungstic acid or the phosphomolybdotungstic acid in the catalyst is 0.1-16.5% in terms of oxide in percentage by weight.

7. The FCC gasoline clean-up method of claim 1, wherein: and cutting and fractionating the prehydrogenation reaction effluent into light gasoline fraction and heavy gasoline fraction at 50-70 ℃.

8. The FCC gasoline clean-up method of claim 1, wherein: the isomerization catalyst in the octane number recovery unit comprises 32-88% of weak acid mesoporous H-type Zn-ZSM-5 molecular sieve or improved weak acid mesoporous H-type Zn-ZSM-5 molecular sieve and 0-66% of pseudo-boehmite, macroporous alumina or zinc-aluminum hydrotalcite binder which are taken as carriers, and 0.5-16% of metal active components are impregnated in the isomerization catalyst, wherein the metal active components are one or more of Fe, Co, Ni, Mo and W.

9. The FCC gasoline clean-up method of claim 1, wherein: the octane number recovery unit double-branched chain isomerization reaction conditions are as follows: reaction temperature 180-^oC, reaction pressure of 0.6-4.8MPa and airspeed of 0.5-8h^-1And the volume ratio of hydrogen to oil is 50-450: 1.

10. The FCC gasoline clean-up method of claim 1, wherein: the laminated catalyst comprises, by weight, 30-85% of an H-type mesoporous Zn-ZSM-5 molecular sieve or an improved mesoporous Zn-ZSM-5 molecular sieve and one or more selected from mordenite, SAPO-11, MCM-22, a Y molecular sieve or a beta molecular sieve as a composite carrier, and 0.2-14% of a metal active component is impregnated in the composite carrier, wherein the metal active component is one or more selected from V, Fe, Ni, Mo and W.

11. A FCC gasoline cleaning process as claimed in claim 3, characterized in that: the preparation method of the alumina composite carrier with the macroporous structure comprises the following steps: adding an aluminum source and sesbania powder into a kneader, uniformly mixing, adding an inorganic acid or organic acid solution and an organic polymer, uniformly kneading, then adding tungsten-doped lanthanum ferrite, and uniformly mixing to obtain an aluminum oxide precursor for later use; adding a silicon source into the acid solution of the organic polymer, uniformly mixing, mixing with an alumina precursor, wherein the content of the organic polymer in the alumina precursor per unit content is more than 1.5 times higher than that of the organic polymer in the silicon source, and extruding, forming, drying and roasting to obtain the alumina carrier.