Ultra-deep desulfurization and denitrification hydrotreating catalyst and preparation method thereof
Technical Field
The invention belongs to a catalyst preparation technology, and particularly relates to an ultra-deep desulfurization and denitrification hydrotreating catalyst and a preparation method thereof.
Technical Field
With the intensive research on the ultra-deep hydrodesulfurization reaction of diesel oil, people find that the hydrotreating catalyst prepared by using a porous low-acidity molecular sieve or composite alumina (CN 103349995A, CN102631934A, CN105251527A, J.Catal.317(2014) 303-. However, the molecular sieve-alumina composite carrier has more micropores and mesopores, and the capillary force with larger difference is caused by the inconsistency of the pore sizes, so that the metal diffusion is not uniform easily in the process of dipping the active metal solution. In addition, the catalyst used for the ultra-deep desulfurization and denitrification reaction has high metal content, so that the concentration of the impregnating solution is high in the preparation process, and the property of the impregnating solution can influence the diffusion behavior of the metal in the impregnation process.
CN108620081A discloses a hydrogenation catalyst impregnation liquid and a preparation method thereof, wherein the impregnation liquid comprises, in terms of oxides, 5-70 g/100mL of VIB group metal oxides, 1-30 g/100mL of VIII group metal oxides, the molar ratio of organic acid to VIII group metal atoms is 0.1-1, and the molar ratio of organic amine to VIB group metal atoms is 0.1-2. CN 106607039A, CN108568305A, CN102994141A, CN103769125A, CN103769222A, etc. also disclose similar methods of adding complexing/chelating agents to prepare the impregnation liquid, and the diffusion behavior of the active metal is changed by changing the surface tension and viscosity of the impregnation liquid.
In the existing preparation method of the impregnation liquid, active component metals are dissolved in an aqueous solution, and corresponding complexing agents/chelating agents are added, in order to ensure the metal content and the solubility performance of the complexing agents, a two-stage complexation impregnation method is adopted in CN106607097A, CN106607096A, CN 103769220B and the like, the steps are complex, and a certain dissolution interval exists due to the solubility.
For preparing the composite carrier hydrotreating catalyst for ultra-deep desulfurization and denitrification, a more appropriate impregnation solution is required.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a super-deep desulfurization and denitrification complex hydrotreating catalyst and a preparation method thereof. The catalyst has high content of active metal components and better metal dispersion effect, and is suitable for ultra-deep hydrodesulfurization and denitrification reactions of diesel oil.
According to the ultra-deep desulfurization and denitrification hydrotreating catalyst, on the basis of the total weight of the catalyst, the VIB group metal is 20-45% in terms of oxide, preferably 23-40%, the VIII group metal is 3-10% in terms of oxide, preferably 3.5-9%, the phosphorus is 3-9% in terms of oxide, the molecular sieve is 6-18%, and the alumina is 18-68%; the molecular sieve is one or more of Y-type molecular sieve, beta zeolite, ZSM series molecular sieve, TS series molecular sieve, SAPO series molecular sieve, MCM series molecular sieve or SBA series molecular sieve, and preferably is beta zeolite, ZSM series molecular sieve, TS series molecular sieve or SAPO series molecular sieve; the VIB group element is preferably Mo and/or W, and the VIII group element is preferably Co and/or Ni; the weight ratio of the VIII group metal/(VIB group metal + VIII group metal) calculated by oxide is 0.01-0.90, and the mass ratio of phosphorus calculated by oxide to VIII group metal oxide is 0.2-6.
The ultra-deep desulfurization and denitrification hydrotreating catalyst has the following properties: the total acid amount of the catalyst is 0.3-0.6 mmol/g, wherein the medium-strength acid amount at 250-450 ℃ is 0.1-0.3 mmol/g; the specific surface area of the catalyst is 100-400 m2Preferably 150 to 300 m/g2The pore volume is 0.1-0.7mL/g, preferably 0.2-0.5mL/g, and the average pore diameter is 2-10 nm, preferably 4-8 nm.
The preparation method of the ultra-deep desulfurization and denitrification hydrotreating catalyst comprises the following steps:
(1) uniformly mixing pseudo-boehmite precursor slurry, a molecular sieve and organic alcohol to obtain slurry A;
(2) adding a silane coupling agent into the slurry A obtained in the step (1), uniformly mixing, and then adjusting the pH value of the slurry to 7.5-11 to obtain slurry B;
(3) aging the slurry B obtained in the step (2) under a certain pressure, filtering the material after aging to remove a certain amount of water, adding organic amine and a silane coupling agent, kneading into a plastic body, and forming, drying and roasting to obtain a composite carrier;
(4) preparing an impregnation liquid, namely adding VIB group active metal salt into an organic solvent, adding organic phosphide, slowly heating to dissolve, keeping the temperature constant, adding VIII group active metal salt, mixing and dissolving to obtain an active metal impregnation liquid;
(5) and (4) dipping the active metal dipping solution prepared in the step (4) on the composite carrier prepared in the step (3), and drying and roasting to obtain a catalyst product.
In the method, the pseudoboehmite precursor slurry in the step (1) is a gelatinizing material which is not aged after gelatinizing in the process of preparing the pseudoboehmite in the field, and the gelatinized material is filtered and washed, and then is uniformly mixed with certain deionized water again to obtain the slurry. The methods for preparing pseudoboehmite in the field are generally aluminum alkoxide hydrolysis or acid-base neutralization. The acid-base neutralization process generally adopts an operation mode of parallel-flow gelling of two materials, or an operation mode of continuously adding one material into a gelling tank and the other material into gelling. The gelling material typically comprises a source of aluminum (Al)2(SO4)3、AlCl3、Al(NO3)3And NaAlO2One or more of the above), precipitant (NaOH, NH)4OH or CO2Etc.), can be selected according to different gelling processes. The conventional operation modes mainly comprise: (1) acid aluminium salt ((Al)2(SO4)3、AlCl3、Al(NO3)3) With alkaline aluminium salts (NaAlO)2) Or alkaline precipitants (NaOH, NH)4OH) inAnd gelling, (2) alkaline aluminium salt (NaAlO)2) With acidic precipitants (CO)2) Neutralizing to form gel. The above methods are well known to those skilled in the art.
In the method, the solid content of the pseudo-boehmite precursor slurry in the step (1) is 1-25 wt%, preferably 5-20 wt% in terms of alumina.
In the method, the mass ratio of the organic alcohol in the step (1) to the water in the pseudo-boehmite precursor slurry is 50-800: 100, preferably 100-600: 100.
In the method, the molecular sieve in the step (1) is selected from one or more of Y-type molecular sieve, beta zeolite, ZSM series molecular sieve, TS series molecular sieve, SAPO series molecular sieve, MCM series molecular sieve or SBA series molecular sieve, and preferably the beta zeolite, the ZSM series molecular sieve, the TS series molecular sieve and the SAPO series molecular sieve; the molecular sieve has preferable specific surface area>300m2G, pore volume>0.4mL/g, total acid amount<0.5mmol/g。
In the method of the present invention, the organic alcohol in step (1) is an organic alcohol with a carbon number less than 4, such as one or more of methanol, ethanol, propanol, isopropanol, ethylene glycol and glycerol, preferably ethanol, propanol, isopropanol and ethylene glycol.
In the method, the silane coupling agent in the step (2) and the step (3) is oxygen-containing organosilane with the carbon atom number less than 8; may be one or more of trimethoxysilane, tetramethoxysilane, methyldiethoxysilane, dimethylethoxysilane, triethoxysilane, tetraethoxysilane, dimethyldiethoxysilane, dimethylvinylethoxysilane or trimethylallyloxysilane, preferably one or more of tetramethoxysilane, methyldiethoxysilane, dimethylethoxysilane, triethoxysilane, tetraethoxysilane, dimethyldiethoxysilane, dimethylvinylethoxysilane. The silane coupling agent in the step (2) and the silane coupling agent in the step (3) may be the same or different.
In the method, the mass ratio of the silane coupling agent in the step (2) to the organic alcohol in the slurry A is 0.1-5: 100, preferably 0.2-4: 100.
in the method of the present invention, in step (2), organic base and/or inorganic base may be used to adjust the pH, organic amine is preferably used, and organic amine with carbon number less than 15, such as one or more of ethylamine, propylamine, dimethylamine, ethylenediamine, dipropylamine, butylamine, diethylamine, diisopropylamine, hexyldiamine, 1, 2-dimethylpropylamine, sec-butylamine, 1, 5-dimethylhexylamine, ethylenediamine, 1, 2-propylenediamine, 1, 4-butylenediamine, monoethanolamine, diethanolamine, triethanolamine, 3-propanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide or tetrapropylammonium hydroxide, is further preferably used.
In the method, the pH value is preferably adjusted to 8-10 in the step (2).
In the method of the present invention, the aging process of step (3) is generally performed in a pressure-resistant vessel, such as a high-pressure reaction vessel; the aging conditions are as follows: the aging temperature is 100-200 ℃, preferably 150-200 ℃, and the aging time is 6-48 hours, preferably 12-36 hours; the aging pressure is the autogenous pressure of the system.
In the method, the water content in the filter cake subjected to certain water removal in the step (3) is 25-70 wt%, and preferably 35-55 wt%.
In the method, the organic amine in the step (3) is an organic amine with a carbon atom number less than 6, and can be one or more of ethylamine, propylamine, dimethylamine, ethylenediamine, dipropylamine, butylamine, diethylamine or diisopropylamine, preferably ethylamine, propylamine, dimethylamine and ethylenediamine; based on the total weight of the pseudo-boehmite precursor and the molecular sieve, the adding amount of the organic amine is 1wt% -10 wt%, preferably 2wt% -7 wt%, and the adding amount of the silane coupling agent is 1wt% -10 wt%, preferably 2wt% -7 wt%, wherein the pseudo-boehmite precursor is calculated by alumina.
In the method, the drying temperature in the step (3) is 80-150 ℃, and the drying time is 2-8 hours; the roasting temperature is 300-900 ℃, and the roasting time is 2-8 hours.
In the method of the present invention, the organic solvent in step (4) is ethers, alcohols, ketones or organic acids, such as one or more of ethyl ether, methanol, ethanol, propanol, butanol, ethylene glycol, acetone, acetic acid or propionic acid, preferably one or more of ethanol, propanol, acetone or acetic acid; the VIB group active metal salt is preferably one or more soluble salts such as phosphomolybdic acid, phosphotungstic acid, ammonium phosphomolybdate, ammonium molybdate, ammonium metatungstate and ammonium phosphotungstate; the group VIII active metal salt is preferably one or more of soluble salts such as cobalt nitrate, nickel nitrate, cobalt acetate and nickel acetate; the solubility is the solubility in the above organic solvents.
In the method of the present invention, the organophosphate in step (4) is a phosphide containing benzene and/or ester group, preferably one or more of tricresyl phosphate, triphenyl phosphite, triphenylphosphine oxide, triphenyl phosphate, and di-n-butyl phosphite.
In the method, after the organic phosphide is added in the step (4), the temperature is slowly increased to 15-90 ℃, and preferably 20-65 ℃.
In the method of the present invention, the impregnation method in step (5) is a well-known scheme to those skilled in the art, for example, an equal volume impregnation scheme is adopted; the drying condition in the step (5) is 60-140 ℃, and the roasting condition is 300-800 ℃.
The application of the ultra-deep desulfurization and denitrification hydrotreating catalyst in the diesel hydrotreating reaction generally has the following process conditions: the pressure is 4-8 MPa, the temperature is 320-400 ℃, and the volume airspeed is 0.5-4 h-1The hydrogen-oil ratio is 50-1000.
Compared with the prior art, the invention has the following advantages:
1. by controlling the silane coupling agent hydrolysis rate to be matched with the pseudo-boehmite crystal nucleus crystallization rate, the alumina and the molecular sieve are combined in order, the phenomenon of non-uniformity in the reaction process is avoided, and the prepared molecular sieve-alumina composite carrier has the advantages that the alumina and the molecular sieve are firmly bonded, the surface acidity is high, and the distribution is uniform.
2. The active metal impregnation liquid prepared by the organic solvent has small surface tension, is more suitable for uniform impregnation of a carrier with more micropores and mesopores, and the prepared ultra-deep desulfurization and denitrification hydrotreating catalyst has high active metal content, uniform distribution of active metal components, no generation of concentrated crystalline phase and higher catalyst activity.
Drawings
Fig. 1 is an XRD spectrum of the catalysts prepared in example 2, comparative example 2 and comparative example 3.
Detailed Description
The following examples further illustrate the present invention and the effects thereof, but are not intended to limit the present invention. The percentages in the examples of the present invention and comparative examples are by mass unless otherwise specified.
The infrared acid amount of the catalyst is tested according to a Q/SHFRIPP 040024-one 2001 method, specifically, pyridine reagent is adopted to carry out gas-solid adsorption under certain steam pressure, then the change of an adsorbed vibration band and a sample pressure surface acid hydroxyl band is measured by infrared spectrum, and the acid amount of different types is calculated according to the absorption coefficient. The specific surface area, pore volume and pore diameter of the catalyst are tested according to the method of GB/T19587-2017. The content of elements on the catalyst is analyzed by X-ray fluorescence spectrometry.
Example 1
1L of aluminum sulfate solution (with the concentration of 0.2 mol/L) and 1L of sodium metaaluminate solution (with the concentration of 0.3 mol/L) are respectively placed in a raw material tank, 1L of purified water is placed in a reaction tank to be used as a base solution, the temperature of the reaction tank is controlled to be 70 ℃ through water circulation, and a small amount of sodium hydroxide is added to ensure that the pH value of the solution is 8.1. The aluminum sulfate solution was injected into the reactor at a rate of 10 mL/min, and simultaneously, the sodium metaaluminate solution was injected and the rate was adjusted so that the pH of the reactor solution was constant at 8.8. And (3) finishing neutralization after 60min, fully washing to remove Na + ions and SO 42-ions, and adding a certain amount of deionized water to obtain the pseudo-boehmite slurry A with the solid-to-liquid ratio of 15% (calculated by alumina).
Example 2
50g of ZSM-5 molecular sieve (specific surface area 405 m)2Per g, pore volume of 0.44mL/g, total acid amount of 0.35 mmol/g) was added to 667g of the pseudo-boehmite slurry A obtained in example 1, followed by stirring well, addition of 800g of ethanol, continuous stirring well, addition of 8g of tetraethoxysilane,after stirring was continued, a small amount of tetramethylammonium hydroxide was added to adjust the pH of the slurry to 8.5. Placing the mixture into a closed high-pressure kettle, aging the mixture for 24 hours at 185 ℃, taking out the mixture, filtering the mixture until the water content of a filter cake is 39 percent, adding 8g of ethylenediamine and 6g of tetraethoxysilane, kneading the mixture into a plastic body, extruding the plastic body into strips, forming the strips, drying the strips at 100 ℃ for 3 hours, and roasting the strips at 500 ℃ for 4 hours to obtain the composite carrier.
125g of phosphomolybdic acid was placed in a multi-neck flask, and 80g of ethanol and 90g of tricresyl phosphate were added thereto, followed by stirring. And slowly heating after uniformly stirring, keeping the temperature of the solution at 30 ℃ for 0.1-2 h, adding 80g of nickel acetate after the solution is clarified, stirring continuously, and diluting the solution to 140mL by using acetic acid after the solution is completely dissolved.
Atomizing, spraying and soaking the prepared soaking liquid onto the prepared composite carrier, drying at 110 ℃, and roasting at 500 ℃ to obtain the finished product catalyst Cat-1.
Example 3
20g of beta-molecular sieve (specific surface area 557 m)2Per g, pore volume of 0.46mL/g, total acid amount of 0.42 mmol/g) was added to 667g of the pseudo-boehmite slurry A obtained in example 1, after stirring well, 1500g of isopropyl alcohol was added, after stirring well, 50g of dimethylvinylethoxysilane was added, after stirring well, a small amount of triethanolamine was added to adjust the pH of the slurry to 9.0. Placing into a closed high-pressure kettle, aging at 160 ℃ for 20h, taking out, filtering until the water content of a filter cake is 52%, adding 4g of diethylamine and 3.5g of dimethylethoxysilane, kneading into a plastic body, extruding into strips, molding, drying at 100 ℃ for 3h, and roasting at 500 ℃ for 4h to obtain the composite carrier.
60g of ammonium phosphomolybdate was placed in a multi-neck flask, and 80g of acetone and 20g of di-n-butyl phosphite were added thereto and stirred. And slowly heating after uniformly stirring, keeping the temperature of the solution at 40 ℃ for 0.1-2 h, adding 20g of nickel nitrate after the solution is clarified, stirring continuously, and diluting the solution to 110mL by using acetone after the solution is completely dissolved.
Atomizing, spraying and soaking the prepared soaking liquid onto the prepared composite carrier, drying at 110 ℃, and roasting at 500 ℃ to obtain the finished product catalyst Cat-2.
Example 4
35g of TS-1 molecular sieve (specific surface area 503 m)2Per gram, pore volume of 0.62mL/g, total acid amount of 0.28 mmol/g) was added to 667g of the pseudo-boehmite slurry A obtained in example 1, after stirring well, 3000g of propanol was added, after stirring well, 20g of dimethylethoxysilane was added, after stirring well, a small amount of tetraethylammonium hydroxide was added to adjust the pH of the slurry to 9.5. Placing the mixture into a closed high-pressure kettle, aging the mixture for 30h at 175 ℃, taking out the mixture, filtering the mixture until the water content of a filter cake is 46 percent, adding 6g of dimethylamine and 4g of triethoxysilane, kneading the mixture into a plastic body, extruding the plastic body into strips, forming the strips, drying the strips for 3h at 100 ℃, and roasting the strips for 4h at 500 ℃ to obtain the composite carrier.
100g of ammonium phosphomolybdate was placed in a multi-neck flask, and 80g of acetic acid and 60g of triphenyl phosphite were added thereto, followed by stirring. Slowly heating after uniformly stirring, keeping the temperature of the solution at 30 ℃ for 0.1-2 h, adding 80g of nickel acetate after the solution is clarified, stirring continuously, and diluting the solution to 120mL by using acetic acid after the solution is completely dissolved.
Atomizing, spraying and soaking the prepared soaking liquid onto the prepared composite carrier, drying at 110 ℃, and roasting at 500 ℃ to obtain the finished product catalyst Cat-3.
Comparative example 1
The synthesis scheme of example 2 was repeated but instead the molecular sieve was added in the usual manner.
50g of ZSM-5 molecular sieve (specific surface area 405 m)2Per gram, pore volume of 0.44mL/g, total acid amount of 0.35 mmol/g) was put into 667g of the pseudo-boehmite slurry A obtained in example 1, put into a closed autoclave, aged at 185 ℃ for 24 hours, taken out, filtered until the water content of the filter cake was 39%, added with 8g of ethylenediamine and 6g of tetraethoxysilane, kneaded into a plastic mass, extruded into a bar, dried at 100 ℃ for 3 hours, and calcined at 500 ℃ for 4 hours to obtain a composite carrier.
125g of phosphomolybdic acid was placed in a multi-neck flask, and 80g of ethanol and 90g of tricresyl phosphate were added thereto, followed by stirring. And slowly heating after uniformly stirring, keeping the temperature of the solution at 30 ℃ for 0.1-2 h, adding 80g of nickel acetate after the solution is clarified, stirring continuously, and diluting the solution to 140mL by using acetic acid after the solution is completely dissolved.
Atomizing, spraying and soaking the prepared soaking liquid onto the prepared composite carrier, drying at 110 ℃, and roasting at 500 ℃ to obtain the finished product catalyst Cat-4.
Comparative example 2
The synthetic scheme of example 2 was repeated, but the impregnation solution was changed to a conventional method of preparing an aqueous solution of Mo-Ni-P.
50g of ZSM-5 molecular sieve (specific surface area 405 m)2Per gram, pore volume of 0.44mL/g, total acid amount of 0.35 mmol/g) was added to 667g of the pseudo-boehmite slurry A obtained in example 1, followed by stirring uniformly, addition of 800g of ethanol, continuous stirring uniformly, addition of 8g of tetraethoxysilane, continuous stirring uniformly, addition of a small amount of tetramethylammonium hydroxide to adjust the pH of the slurry to 8.5. Placing the mixture into a closed high-pressure kettle, aging the mixture for 24 hours at 185 ℃, taking out the mixture, filtering the mixture until the water content of a filter cake is 39 percent, adding 8g of ethylenediamine and 6g of tetraethoxysilane, kneading the mixture into a plastic body, extruding the plastic body into strips, forming the strips, drying the strips at 100 ℃ for 3 hours, and roasting the strips at 500 ℃ for 4 hours to obtain the composite carrier.
114.5g of molybdenum oxide and 119.4g of basic nickel carbonate were placed in a multi-neck flask, and 30.3g of phosphoric acid and 180mL of deionized water were added thereto, followed by stirring. And slowly heating after stirring uniformly, keeping the temperature of the solution at 90 ℃ for 0.5-2 h, and converting the solution into clear solution. Naturally cooling and diluting to 300 mL.
Atomizing, spraying and soaking the prepared soaking liquid onto the prepared composite carrier, drying at 110 ℃, and roasting at 500 ℃ to obtain the finished product catalyst Cat-5.
Comparative example 3
The synthesis scheme of example 2 was repeated, but instead of adding tricresyl phosphate to the impregnation solution, phosphoric acid containing the same amount of phosphorus was added to obtain the finished catalyst Cat-6.
Comparative example 4
The synthesis scheme of example 2 is repeated, but the carrier forming process is changed into the forming process that the powder is mixed and kneaded with the conventional extrusion aid, peptizer and water after being dried.
50g of ZSM-5 molecular sieve (specific surface area 405 m)2Per g, pore volume 0.44mL/g, total acid amount 0.35 mmol/g) was added to 667g of the pseudo-boehmite slurry A obtained in example 1, and 800g of the mixture was added thereto after stirring wellAnd (3) adding 8g of tetraethoxysilane after the ethanol is continuously and uniformly stirred, and adding a small amount of tetramethylammonium hydroxide to adjust the pH value of the slurry to 8.5 after the ethanol is continuously and uniformly stirred. Putting the mixture into a closed high-pressure kettle, aging the mixture for 24 hours at 185 ℃, taking the mixture out, filtering and drying the mixture, wherein the drying temperature is 100 ℃, and obtaining the composite powder.
Adding 2.5g of sesbania powder, 24g of 10% nitric acid and 145ml of deionized water into the composite powder, kneading into a plastic body, extruding into strips, drying at 100 ℃ for 3h, and roasting at 500 ℃ for 4h to obtain the composite carrier.
125g of phosphomolybdic acid was placed in a multi-neck flask, and 80g of ethanol and 90g of tricresyl phosphate were added thereto, followed by stirring. And slowly heating after uniformly stirring, keeping the temperature of the solution at 30 ℃ for 0.1-2 h, adding 80g of nickel acetate after the solution is clarified, stirring continuously, and diluting the solution to 140mL by using acetic acid after the solution is completely dissolved.
Atomizing, spraying and soaking the prepared soaking liquid onto the prepared composite carrier, drying at 110 ℃, and roasting at 500 ℃ to obtain the finished product catalyst Cat-7.
The physicochemical properties and composition of the catalyst are shown in Table 1.
TABLE 1 physicochemical Properties and compositions of the catalysts
The catalyst evaluation was carried out on a 100mL small-scale hydrogenation apparatus, and the catalyst was presulfided before the activity evaluation. The evaluation process conditions of the catalyst are that the pressure is 6.0 MPa, and the liquid hourly volume space velocity is 2.0h-1The volume ratio of hydrogen to oil is 300:1, and the reaction temperature is 350 ℃. Activity evaluation the properties of the raw oil are shown in Table 2, and the results of activity evaluation are shown in Table 3.
Table 2 properties of the feedstock.
Table 3 results of activity evaluation.
Therefore, under the condition of the same active metal content, the catalyst prepared by the scheme has higher ultra-deep desulfurization and denitrification activity.