CN114849764A

CN114849764A - Medium oil type hydrocracking catalyst and preparation method thereof

Info

Publication number: CN114849764A
Application number: CN202110158194.8A
Authority: CN
Inventors: 余颖龙; 袁晓亮; 王晶晶; 王延飞; 赵梓贺; 张雅琳; 王燕; 张占全; 乔柯; 阎子峰
Original assignee: Petrochina Co Ltd; China University of Petroleum East China
Current assignee: Petrochina Co Ltd; China University of Petroleum East China
Priority date: 2021-02-04
Filing date: 2021-02-04
Publication date: 2022-08-05

Abstract

The invention relates to a medium oil type hydrocracking catalyst, which comprises the following components in percentage by weight based on the weight of the catalyst: 10-20% of a composite modified Y-type molecular sieve, 55-60% of amorphous silicon-aluminum and a binder, and 25-30% of active metal calculated by oxides, wherein the active metal is a metal in a VIB group and a VIIIB group; wherein the mass ratio of the amorphous silicon-aluminum to the binder is 3-10; the composite modified Y-type molecular sieve is obtained by modifying a Y-type molecular sieve by a composite dealumination modifier consisting of organic acid and a chelating agent. The invention also relates to a preparation method of the medium oil type hydrocracking catalyst. The composite modified Y-shaped molecular sieve provided by the invention is modified by adopting the composite dealumination modifier, so that the higher crystallinity of the composite modified Y-shaped molecular sieve is kept, and the higher silicon-aluminum ratio of the composite modified Y-shaped molecular sieve is also ensured.

Description

Medium oil type hydrocracking catalyst and preparation method thereof

Technical Field

The invention relates to a hydrocracking catalyst for producing more middle distillate and a preparation method thereof, wherein a modified Y-type molecular sieve prepared by an organic acid-chelating agent composite system is adopted, and the prepared modified USY-type molecular sieve has the structural characteristics of small unit cell parameter, large specific surface area, high silicon-aluminum ratio and good crystallinity maintenance, and the medium oil hydrocracking catalyst adopting the composite modified Y-type molecular sieve has the characteristic of producing more light distillate.

Background

The trend that crude oil is heavier and has poorer and poorer quality is increasingly prominent, and the hydrocracking process is a very effective means for converting heavy and poor heavy oil into light and high-quality products. Compared with catalytic cracking, the hydrocracking process has high raw material adaptability and becomes a core process of modern oil refining enterprises. In order to meet the increasing demand of light distillate oil worldwide, the research and development of novel high-yield light oil hydrocracking catalysts become the core and key of the technology. From the current state of research, the structure and acid properties of the catalyst determine the hydrocracking performance of heavy oil.

ZL97121663.0 discloses a hydrocracking catalyst especially suitable for producing middle distillate, which comprises an amorphous silica-alumina component and a small-pore alumina adhesive, wherein the content of amorphous silica-alumina is 30-60 wt%, at least one VIB group element and at least one VIII group element, the total content of hydrogenation metal oxides is 20-35 wt%, and the balance is the small-pore alumina adhesive, and the hydrocracking catalyst is characterized in that the specific surface area of the catalyst is 150-300 m- ² The specific surface area is 0.25-0.50 ml/g, the pore volume is 0.25-0.50 ml/g, the pore distribution of 4-15 nano-pores is 60-90%, and the infrared acidity is 0.30-0.50 mmol/g.

CN102030351A discloses macroporous alumina with bimodal pore distribution, wherein the pore volume of the macroporous alumina is 0.6-3.0 ml/g, and the specific surface area of the macroporous alumina is 90-300 m ² And/g, wherein the pores with the diameter of 35-100 angstroms account for 20-55% of the total pore volume, and the most probable pore diameter is 300-600 angstroms. The preparation process of the aluminum oxide adopts a two-step aging method for preparation.

CN107029779A discloses a Y-type molecular sieve-containing hierarchical pore hydrocracking catalyst, wherein the pore volume of pores with the pore diameter of less than 2 nanometers accounts for 2-50% of the total pore volume, the pore volume of pores with the pore diameter of 2-100 nanometers accounts for 20-85% of the total pore volume of the catalyst, and the pore volume of pores with the pore diameter of more than 100 nanometers accounts for 3-70% of the total pore volume of the catalyst.

Therefore, the preparation of molecular sieves with hierarchical pore structures and suitable acidity is an effective method for improving the activity and selectivity of hydrocracking catalytic reaction and improving the heavy oil conversion capacity.

Most of the existing industrialized hydrocracking catalysts contain molecular sieves, and the size of the pore diameter of the catalyst is an important factor influencing the conversion of raw oil in the process of heavy oil hydrogenation or residual oil hydrocracking. Firstly, the influence rule of the molecular sieve pore structure on the hydrocracking reaction needs to be determined. In current hydrocracking catalysts, the molecular sieve serves as both an active component and a part of the carrier. The microporous molecular sieve usually has a regular pore channel structure, has the characteristics of certain acidity, shape selectivity, good thermal stability, adjustable performance and the like, and has good catalytic performance. Despite the many advantages of microporous pore structures, a single microporous structure also brings about significant limitations. The raw materials contain a large amount of asphaltene and metals, and the sizes of reactants and products are larger than the pore diameter of the microporous molecular sieve, so that the diffusion resistance in the molecular sieve crystal is large, and the reactants and the products are difficult to contact with the active sites of the catalyst. Even the smaller molecules in the reactants or products are diffusion limited during the catalytic process. Therefore, the aperture of the catalyst is too small, the reduction of the diffusion rate of reaction intermediate products and byproducts in the microporous pore channels of the molecular sieve can cause polymerization reaction or the active sites of the molecular sieve are blocked; metals and carbon deposits on the outer surface of the catalyst, which may cause the catalyst to lose catalytic activity or even to deactivate.

The molecular sieve crystallite size and unit cell parameters are also key parameters in determining the molecular sieve structure. Molecular sieves typically have a crystallite size thousands of times the pore size, and under such diffusion-limited conditions, less than 10% of the active sites of the molecular sieve are available to participate in the catalytic reaction, and these active sites are typically located at the outer edges of the molecular sieve. The small-grain molecular sieve has the advantages of increasing the specific surface area, increasing the proportion of surface atoms and active sites and shortening the length of a grain pore passage due to the reduction of the grain diameter, increasing the accessibility of heavy oil macromolecules, improving the intra-crystalline diffusion rate of reactants and products, reducing the excessive cracking of the products and reducing the coking rate of a catalyst. The grain size of the molecular sieve has a significant impact on hydrocracking activity and yield of middle distillates. However, compared with the common molecular sieve, the small-grain molecular sieve has large surface energy and poor structural stability. Especially, the loss of crystallinity is serious in the dealumination process, and the reduction of hydrothermal stability is obvious. The unit cell size of the molecular sieve is reduced, the thermal and hydrothermal stability of the molecular sieve is increased, the diffusion resistance from the surface of the molecular sieve to an internal pore passage is reduced, and meanwhile, the method can play a role in adjusting acidity, is beneficial to reducing coking, and improves the conversion rate of raw oil.

The preparation of the modified Y-type molecular sieve with high silica-alumina ratio by various methods is the first choice of the current industrial modified molecular sieve technology. The modification method of the Y-type molecular sieve is summarized into three methods: (1) high temperature hydrothermal method; (2) a chemical method; (3) a method combining high-temperature hydrothermal and chemical methods. High temperature hydrothermal method is simple and easy, and can produce partIn the second pore, the aluminum removed from the framework does not leave the molecular sieve, but exists in the pore channels of the molecular sieve in various forms, so that the pore distribution of the molecular sieve is unreasonable, and the loss of crystallinity is large. Chemical methods, in which a skeleton portion is dealuminated by treating it with a chemical agent, can be classified into two types: one is dealuminization and silicon supplementation, namely, when dealuminization is carried out by a chemical reagent method, silicon atoms are filled in the dealuminized positions, and higher crystallinity can be kept. Typical of the process is SiCl ₄ Gas phase dealuminization silicon and (NH) ₄ ) ₂ SiF ₆ Liquid phase dealuminization and silicon supplement, and the other is pure dealuminization by using the action of inorganic acid and molecular sieve, namely HCl and HNO ₃ And H2SO ₄ Dealuminizing by inorganic acid only depends on H ⁺ The crystallinity is greatly reduced due to dealumination, and the acid concentration and the modification time must be strictly controlled in the modification process. In order to improve the modification effect and avoid the defects of the modification by the traditional chemical method, a composite modification method of mutually matching organic acid and chelating agent under proper concentration is provided.

Chinese patent CN201711119061.X discloses a modified Y-Y isomorphous molecular sieve and a preparation method thereof, wherein an organic alkali solution is adopted to treat the Y-Y isomorphous molecular sieve. The molecular sieve has a core-shell structure, wherein the shell structure is a nano Y-type molecular sieve; the total pore volume is 0.56-1.25 mL/g; the mesoporous volume is 0.45-0.95 mL/g; the mesopore volume accounts for 40-80% of the total pore volume; the molar ratio of the silicon oxide to the aluminum oxide is 6-25; specific surface area 580 and 950m ² /g。

The literature reports that the industrial application contrastive analysis of a hydrocracking catalyst FC-76 using a mesoporous Y-type molecular sieve and an FC-32 catalyst containing a conventional USY-type molecular sieve (contrastive analysis of the industrial application of the hydrocracking catalyst FC-76 and the FC-32, Lishiwei, oil refining technology and engineering, volume 49, 6 th in 2019) reduces the reaction temperature of the FC-76 catalyst by 6 ℃, improves the total space velocity by 10 percent, reduces the light hydrocarbon yield by 0.3 percent, reduces the light naphtha by 2.4 percent, reduces the yield of middle distillate oil (aviation kerosene and diesel oil) by 0.5 percent and reduces the BMCI of hydrogenated tail oil by 1.9 units. The catalyst simultaneously strengthens the hydrogenation ring-opening reaction and the hydrogenation isomerization reaction in the hydrocracking process, and can produce high-quality lubricating oil base oil products.

Disclosure of Invention

Based on the above, the invention aims to provide a medium oil type hydrocracking catalyst and a preparation method thereof, the Y-type molecular sieve of the catalyst is modified by adopting an organic acid-chelating agent composite modifier, and an industrial Y-type molecular sieve is used as a raw material to synthesize the composite modified Y-type molecular sieve with the structural characteristics of small unit cell parameter, large specific surface area, high silicon-aluminum ratio, good crystallinity and the like, so that the defects of the traditional Y-type molecular sieve can be avoided.

In order to achieve the above object, the present invention provides a medium oil type hydrocracking catalyst, comprising, based on the weight of the catalyst: 10-20% of composite modified Y-type molecular sieve, 55-60% of amorphous silicon-aluminum and binder, 25-30% of active metal calculated by oxide,

wherein the active metal is a group VIB metal and a group VIIIB metal;

wherein the mass ratio of the amorphous silicon-aluminum to the binder is 3-10;

the composite modified Y-type molecular sieve is obtained by modifying a Y-type molecular sieve by a composite dealumination modifier consisting of organic acid and a chelating agent.

The hydrocracking catalyst of the invention preferably has the specific surface area of 650m ² /g～700m ² A silicon-aluminum ratio of 20 to 30 and a unit cell parameter of

Compared with the content of the framework aluminum in the unit cell of the composite modified Y-shaped molecular sieve, the reduction range can reach more than 60 percent.

The hydrocracking catalyst of the invention is preferably characterized in that the composite modified Y-type molecular sieve is modified by the following method:

(1) putting the Y-shaped molecular sieve into the composite dealumination modifier, and stirring to obtain a milky white suspension;

(2) and washing the suspension to be neutral, and drying to obtain a white powder product.

Wherein, the feeding sequence of the organic acid and the chelating agent in the composite dealuminizing agent can be sequentially added or simultaneously added; the molar ratio of the organic acid to the chelating agent is 1: 0.2-1.5.

The hydrocracking catalyst provided by the invention has the advantages that the solid-liquid ratio of the USY type molecular sieve to the composite dealumination modifier is 1: 10-50, the stirring temperature is 70-100 ℃, and the stirring time is 3-6 h.

The hydrocracking catalyst of the present invention, wherein preferably, the drying conditions are: the temperature is 80-120 ℃, and the time is 8-16 h.

In the hydrocracking catalyst of the present invention, it is preferable that the organic acid includes at least one of citric acid, succinic acid, oxalic acid, malic acid and tartaric acid.

In the hydrocracking catalyst of the present invention, preferably, the chelating agent is disodium ethylenediaminetetraacetate.

In the hydrocracking catalyst of the present invention, it is preferable that the concentration of the composite dealumination modifier is 0.1 to 1mol/L, the concentration of the organic acid is 0.04 to 0.85mol/L, and the concentration of the chelating agent is 0.17 to 0.60 mol/L.

In the hydrocracking catalyst of the present invention, it is preferable that the binder is alumina.

In the hydrocracking catalyst of the present invention, preferably, the group VIB metal is tungsten, and the group VIIIB metal is nickel.

In order to achieve the above object, the present invention also provides a method for preparing the above middle oil type hydrocracking catalyst, comprising the steps of:

(S1) mixing the composite modified Y-shaped molecular sieve with a binder and amorphous silicon-aluminum, molding, drying and roasting to obtain a carrier;

(S2) fully contacting the carrier with a salt solution containing active metals, and drying to obtain a hydrocracking catalyst;

preferably, the drying conditions in the steps (S1) and (S2) are temperature of 110 ℃ and 150 ℃, time of 4-12 h; the roasting condition is 400-550 ℃ and the time is 2-6 h.

The preparation method of the medium oil type hydrocracking catalyst provided by the invention specifically comprises the following steps:

(1) weighing raw materials of an industrial Y-type molecular sieve at room temperature, adding a composite dealumination modifier under the stirring condition, and removing a large amount of non-framework aluminum and partial framework aluminum species through organic coordination reaction;

(2) continuously stirring for a certain time to obtain milky white suspension after the reaction is finished;

(3) filtering the milky white turbid liquid, washing the precipitate to be neutral, and drying to obtain a white powder product, namely the composite modified Y-shaped molecular sieve which can keep a higher silica-alumina ratio and has higher crystallinity;

(4) the medium oil type hydrocracking catalyst is obtained by mixing, kneading, molding and loading the composite modified Y-shaped molecular sieve with a binder and amorphous silicon-aluminum, can improve the conversion capability of heavy oil macromolecules, increases the yield of light distillate oil such as gasoline, aviation kerosene and the like, and realizes the remarkable increase of the conversion capability of heavy oil and the yield of the light distillate oil.

The invention has the following beneficial effects:

(1) according to the composite modified Y-type molecular sieve provided by the invention, the composite dealumination modifier is used for modification, so that strong damage of inorganic medium and strong acid to a molecular sieve framework is avoided, and higher crystallinity of the composite modified Y-type molecular sieve is kept; the chelating agent component with good water solubility and weak acidity in the solution is consistent with the acidic environment of the modifier, so that non-framework aluminum species are effectively removed, and a high silicon-aluminum ratio is ensured.

(2) The composite modified Y-type molecular sieve has the characteristics of small unit cell parameter, large specific surface area, high silicon-aluminum ratio and good crystallinity, forms rich secondary pore structures, has smooth pore channels and can improve the utilization rate of an active center.

(3) All raw materials in the preparation method of the composite modified Y-type molecular sieve provided by the invention can be from industrial raw materials, and the preparation operation is simple. Therefore, the method has obvious practicability and superiority and has good industrial application prospect.

(4) According to the preparation method of the composite modified Y-type molecular sieve, the organic acid and the chelating agent are combined, so that the unit cell parameters are reduced under the low-concentration condition, the strong damage of inorganic medium and strong acid to the molecular sieve framework is avoided, and the higher crystallinity is kept; the chelating agent component with good water solubility and weak acidity in the solution is consistent with the acidic environment of the modifier, effectively removes non-framework aluminum species, and ensures higher silicon-aluminum ratio.

(5) When the hydrocracking catalyst provided by the invention is used for processing heavy raw materials, the conversion capability of heavy oil macromolecules can be improved, the yield of light distillate oil such as gasoline, aviation kerosene and the like can be increased, and the conversion capability of the catalyst on the heavy oil macromolecules and the yield of gasoline and kerosene can be improved.

Drawings

FIG. 1 is an XRD spectrum of Y-type molecular sieves treated with different organic acids of examples 1-1 to 1-5;

FIG. 2 is a partial magnified view of FIG. 1;

FIG. 3 is a graph showing the relative proportions of aluminum atoms in different coordination environments;

FIG. 4 shows N of example 5-1 to example 5-3 and industrial USY type molecular sieve raw material ₂ Adsorption and desorption isotherms.

Detailed Description

The following examples illustrate the invention in detail: the present example is carried out on the premise of the technical scheme of the present invention, and detailed embodiments and processes are given, but the scope of the present invention is not limited to the following examples, and the experimental methods without specific conditions noted in the following examples are generally performed according to conventional conditions.

Example 1

In this example, the selection of organic acid components in the composite modifier is examined, and five common organic acids, namely tartaric acid, citric acid, oxalic acid, succinic acid and malic acid, are adopted to treat the same commercial USY type molecular sieve under the condition of 0.3mol/L concentration. The USY represents a commercial ultrastable Y-type molecular sieve, and DAY-N, DAY-H, DAY-C, DAY-P and DAY-J respectively represent samples prepared by treating the Y-type molecular sieve with citric acid, succinic acid, oxalic acid, malic acid and tartaric acid.

Example 1-1

5g of commercial USY type molecular sieve was placed in a 250mL three-necked flask at room temperature, and 25mL of 0.3 mol. L was added ^-1 Citric acid solution, stirring vigorously at 80 deg.C for 4 h. After the reaction is finished, filtering the obtained milky white suspension, washing to be neutral, and drying at 110 ℃ for 12 hours to obtain the acid modified Y-type molecular sieve, wherein the specific surface area and the pore structure of the acid modified Y-type molecular sieve are shown in Table 1. Sample number "DAY-N".

Examples 1-2 to examples 1-5

The difference from example 1-1 was only that the citric acid solution was replaced with succinic acid solution, oxalic acid solution, malic acid solution, and tartaric acid solution in this order. The sample numbers are "DAY-H", "DAY-C", "DAY-P" and "DAY-J" in this order.

TABLE 1 specific surface area and pore structure data for molecular sieves

The results in table 1 show that the framework aluminum of the molecular sieve can be effectively removed by treating the Y-type molecular sieve with the organic acid, and both the organic acid and the organic acid can play a role in pore expansion, and the acid strength of the organic acids is as follows from high to low: oxalic acid, citric acid, tartaric acid, malic acid and succinic acid. Proper concentration proportion is needed for different organic acids, and collapse of a molecular sieve framework caused by excessive dealumination is avoided. For example, in this example, the majority of samples had increased pore content compared to the molecular sieve before acid treatment, reflecting the framework aluminum removal effect. However, the specific surface area and pore volume of the micropores of the succinic acid-treated sample at the concentration are reduced, and the pore volume of the secondary pores is greatly increased by nearly 50%, which indicates that the secondary pores are caused by skeleton collapse and have influence on the reaction performance.

In addition, as can be seen from fig. 1 and fig. 2, the characteristic diffraction peak of the USY molecular sieve is still maintained after the USY molecular sieve is treated with the organic acid. Without causing substantial disruption of the molecular sieve structure. The appropriate acid concentration and the matching acid species are key influencing factors in the modification process.

Example 2

This example examines the effect of the composite modifier and compares it with the samples of citric acid modified, chelating agent modified and industrial USY type molecular sieve modified samples for structural performance.

Example 2-1

5g of commercial USY type molecular sieve was placed in a 250mL three-necked flask at room temperature, and 25mL of 0.3 mol. L was added ^-1 Adding 0.3 mol.L of citric acid solution at the same time ^-1 The solution of disodium edetate is 25mL, and is stirred vigorously at 80 ℃ for 4 h. And after the reaction is finished, filtering the obtained milky white suspension, washing to be neutral, and drying at 110 ℃ for 12 hours to obtain the composite modified Y-type molecular sieve, wherein the crystal structure of the composite modified Y-type molecular sieve is shown in Table 2, and the specific surface area and the pore structure of the composite modified Y-type molecular sieve are shown in Table 3. Sample number "DAY-EN" represents the composite modification.

Comparative example 1

5g of industrial USY type molecular sieve was placed in a 250mL three-necked flask at room temperature, followed by addition of 0.3 mol. L ^-1 The solution of disodium edetate is 25mL, and is stirred vigorously at 80 ℃ for 4 h. And after the reaction is finished, filtering the obtained milky white suspension, washing to be neutral, and drying at 110 ℃ for 12 hours to obtain the chelating agent modified Y-type molecular sieve, wherein the crystal structure of the chelating agent modified Y-type molecular sieve is shown in Table 2, and the specific surface area and the pore structure of the chelating agent modified Y-type molecular sieve are shown in Table 3. Sample number "DAY-E" represents disodium EDTA modification.

TABLE 2 Effect of different modifiers on the crystal structure of USY-type molecular sieves

Sample (I)	USY	DAY-E	DAY-N	DAY-EN
					The parameters of the unit cell are as follows,	24.485	24.465	24.387	24.351
SiO ₂ /Al ₂ O ₃	9.4	10.2	15.0	18.8
					Al _framework	28.32	26.08	17.31	13.26
degree of crystallinity	67.1％	78.5％	66.0％	65.8％

As is clear from the results in Table 2, the skeleton Si/Al ratios of the samples "USY", "DAY-E", "DAY-N" and "DAY-EN" were successively higher and the cell parameters were successively lower. The single chelator modified sample "DAY-E" showed that it was primarily removing non-framework aluminum species, with relatively poor removal of framework aluminum. The silicon-aluminum ratio of the framework of the compound treated molecular sieve sample DAY-EN is improved from 9.4 to 18.8, which is twice of that of the industrial USY type molecular sieve; the aluminum content of the single unit cell framework is reduced from 28.32 to 13.26, which is reduced by about 53 percent, compared with a sample 'DAY-N' prepared by monocitric acid, the unit cell parameter is smaller, the dealumination degree is higher, and the crystallinity of the molecular sieve is kept stable. The result shows that the composite agent can effectively remove the framework aluminum of the molecular sieve and successfully prepare the high-silica-alumina ratio small-unit cell modified Y-type molecular sieve.

TABLE 3 Effect of different modifiers on the specific surface area and pore structure data of Y-type molecular sieves

The results in table 3 show that the chelating agent disodium ethylene diamine tetraacetate has obvious effect of removing non-framework aluminum species and can promote the formation of micropores, but the kinetic diameter of the chelating agent disodium ethylene diamine tetraacetate is large after the molecules are dissolved, the chelating agent disodium ethylene diamine tetraacetate is difficult to enter into the internal cavity of the molecular sieve for reaction, the complexation with aluminum is more concentrated on the outer surface of the molecular sieve, and the chelating agent disodium ethylene diamine tetraacetate has no effect on the pore volume of the micropores when being used alone. The citric acid dealuminization is effectual, and when using jointly with the chelator, effective dealuminization on the one hand, on the other hand in time clears up the non-skeleton aluminium that takes off the formation through the chelator, and the synergism produces the reaming effect, and is obvious to the clearance and the promotion effect of well hole capacity of pipeline.

Meanwhile, referring to fig. 3, it can be seen that in the sample prepared from the single citric acid and the proportion of Al atoms in different coordination environments, the proportion of penta-coordination non-framework aluminum is reduced, the proportion of hexa-coordination non-framework aluminum is increased, the ionic aluminum species is converted to the polymeric aluminum species, and the removed framework aluminum is aggregated around the crystal in the polymeric state. The proportion of five-coordinate and six-coordinate non-framework aluminum of DAY-E and DAY-EN is obviously reduced in all samples with chelating agents participating in the reaction, which shows that EDTA has strong complexing effect on the non-framework five-coordinate and six-coordinate aluminum and can effectively remove the non-framework aluminum. The DAY-EN sample prepared by the composite treatment of the chelating agent and the organic acid has the four-coordinate framework aluminum accounting for 88 percent of the total content of aluminum species, which is far higher than that of a parent Y-type molecular sieve and a molecular sieve sample prepared by a single dealuminating agent, and the removal of non-framework aluminum is also ensured.

Example 3

In this example, the influence of experimental conditions on the modification effect is examined, the parameters such as the concentration of the modifier, the reaction time and the reaction temperature are mainly examined, the framework Si/Al ratio is used as a reference index, and SiO is used as a reference index ₂ /Al ₂ O ₃ The higher the molecular weight, the more suitable the modified Y-type molecular sieve with small unit cell and high stability is.

Example 3-1 to example 3-16

The only difference from example 2-1 is that: the concentration of the citric acid solution, the concentration of the disodium ethylene diamine tetraacetate solution, the reaction time and the reaction temperature are shown in table 4. The sample numbers obtained in examples 3-1 to 3-16 were S01 to S16 in this order.

TABLE 4 Effect of different modifiers on the crystal structure of USY-type molecular sieves

From the results in table 4, the influence of each element on the silica-alumina ratio after modification of the Y-type molecular sieve is as follows: the concentration of the citric acid solution is more than the reaction time and the concentration of the ethylene diamine tetraacetic acid solution is more than the reaction temperature. For the preparation of the composite modifier, the influence of the addition amount of the citric acid on the silica-alumina ratio of the framework of the molecular sieve is large.

According to the above examples 3-1 to 3-16, the preferable modification conditions of the present invention are: the citric acid concentration is 0.5mol/L, the EDTA concentration is 0.5mol/L, the reaction time is 3h, and the reaction temperature is 70 ℃.

Example 4

This example examines the comparison of the structural parameters of the modified sample and the industrial USY type molecular sieve under the preferred synthesis conditions.

This example differs from example 2-1 in that: the concentration of the citric acid solution and the concentration of the ethylene diamine tetraacetic acid solution are both 0.5mol/L, the reaction time is 3 hours, the reaction temperature is 70 ℃, and the solid-to-liquid ratio is 1:10, the modified Y-type molecular sieve sample prepared was designated as Optisize-E.

TABLE 5 comparison of preferred modified samples with the structural parameters of commercial USY type molecular sieves

As can be seen from the results in Table 5, the optimal sample has a further reduced Optize-E cell size, with silicon to aluminum ratio of SiO ₂ /Al ₂ O ₃ The temperature is increased from 9.4 to 22.1, and the increase amplitude reaches 135 percent; the crystallinity is slightly lower than that of the starting material. The content of framework aluminum in the molecular sieve unit cell is reduced from 28.89 to 9.78, the reduction amplitude reaches 66 percent, and the dealumination effect is obvious. The composite modifier is proved to be capable of effectively removing framework aluminum and non-framework aluminum of the molecular sieve.

Example 5

This example examines the reproducibility of the sample modification effect under different raw material throughput conditions.

Example 5-1 to example 5-3

The difference from example 4 is that: the addition amount of the USY type molecular sieve is 3, 8 and 12g in sequence, the addition amount of the citric acid solution is 25, 25 and 20mL in sequence, and the addition amount of the ethylene diamine tetraacetic acid solution is 5,25 and 30mL in sequence. The obtained sample numbers are respectively 'E-1', 'E-2' and 'E-3', and 'USY' represents a raw material industrial USY type molecular sieve. The structural parameters of each molecular sieve are shown in table 6.

TABLE 6 repeatability results of sample modification effect at different raw material throughput conditions

From the results in table 6, it can be seen that the unit cell parameters of the composite modified Y-type molecular sieves obtained in examples 5-1 to 5-3 are significantly reduced, the silica-alumina ratio is improved by more than one time, and the crystallinity retention rate is more than 80% compared to the USY-type molecular sieve. The cell parameter is significantly reduced within the range

Referring to fig. 3, fig. 3 is a low-temperature nitrogen adsorption and desorption curve of the composite modified Y-type molecular sieve and the industrial USY-type molecular sieve raw material, the adsorption capacity of the composite modified Y-type molecular sieve is significantly higher than that of the industrial USY-type molecular sieve raw material, and the composite modified Y-type molecular sieve raw material is at a relative pressure (P/P) ₀ ) The absorption and desorption curve shows obvious trend and becomes steep in the range of 0.8-1.0, which indicates that the modified sample has a better secondary pore structure, and the pore channel is smooth and is beneficial to the reaction mass transfer process. From the results, the composite modifier has high repeatability of the modification result of the industrial USY type molecular sieve, stable effect and feasible technical route.

Example 6

(1) Taking 15g of E-1 molecular sieve, mixing with 85.7g of amorphous silicon-aluminum dry glue powder (dry basis is 70%) and 30g of alumina binder, forming, drying (120 ℃, 4 hours) and roasting (450 ℃, 4 hours) to prepare a carrier;

(2) preparing a metal impregnation solution containing 32g of nickel nitrate hexahydrate and 30g of ammonium metatungstate, fully contacting and impregnating the carrier obtained in the step (1) with the metal impregnation solution, drying at 110 ℃ for 20 hours, and then roasting at 500 ℃ for 2 hours to obtain the hydrocracking catalyst MC-1. See table 7 for catalyst composition.

Example 7

(1) Mixing 20g of E-2 molecular sieve, 64.3g of amorphous silicon-aluminum dry glue powder (dry basis is 70%) and 35g of alumina binder, forming, drying (150 ℃, 6 hours) and roasting (500 ℃, 3 hours) to prepare a carrier;

(2) preparing a metal impregnation solution containing 26g of nickel nitrate hexahydrate and 31g of ammonium metatungstate, fully contacting and impregnating the carrier obtained in the step (1) with the metal impregnation solution, drying at 140 ℃ for 8 hours, and then roasting at 350 ℃ for 6 hours to obtain the hydrocracking catalyst MC-2. See table 7 for catalyst composition.

Example 8

(1) Mixing 32g of E-3 molecular sieve, 85.7g of amorphous silicon-aluminum dry glue powder (dry basis is 70%) and 30g of alumina binder, forming, drying (110 ℃, 12 hours) and roasting (550 ℃, 6 hours) to prepare a carrier;

(2) preparing a metal impregnation solution containing 44.7g of nickel nitrate hexahydrate and 43.3g of ammonium metatungstate, fully contacting and impregnating the carrier obtained in the step (2) with the metal impregnation solution, drying at 110 ℃ for 20 hours, and then roasting at 500 ℃ for 2 hours to obtain the hydrocracking catalyst MC-3. See table 7 for catalyst composition.

Comparative example 1

(1) Adopts a literature report (Catalyst Design by NH) ₄ OH Treatment of USY Zeolite, adv. Funct. Mater.,2015,25,7130-7144) to obtain modified Y-type molecular sieve DY-1. Taking 15g of DY-1 molecular sieve, mixing with 85.7g of amorphous silicon-aluminum dry glue powder (dry basis is 70%) and 30g of binder, forming, drying and roasting to prepare a carrier;

(2) preparing a metal impregnation solution containing 32g of nickel nitrate hexahydrate and 30g of ammonium metatungstate, fully contacting and impregnating the carrier obtained in the step (2) with the metal impregnation solution, drying at 110 ℃ for 20 hours, and then roasting at 500 ℃ for 2 hours to obtain the hydrocracking catalyst C-1. See table 7 for catalyst composition.

Comparative example 2

(1) The industrial USY type molecular sieve is treated by a Chinese patent CN201711119061.X method to obtain the modified Y type molecular sieve DY-2. Mixing 20g of DY-2 molecular sieve, 64.3g of amorphous silicon-aluminum dry glue powder (dry basis is 70%) and 35g of binder, molding, drying and roasting to prepare a carrier;

(2) preparing a metal impregnation solution containing 26g of nickel nitrate hexahydrate and 31g of ammonium metatungstate, fully contacting and impregnating the carrier obtained in the step (1) with the metal impregnation solution, drying at 140 ℃ for 8 hours, and then roasting at 350 ℃ for 6 hours to obtain the hydrocracking catalyst C-2. See table 7 for catalyst composition.

Comparative example 3

(1) Taking 32g of unmodified industrial USY type molecular sieve, mixing with 85.7g of amorphous silicon-aluminum dry glue powder (dry basis is 70%) and 30g of binder, molding, drying and roasting to prepare a carrier;

(2) preparing a metal impregnation solution containing 44.7g of nickel nitrate hexahydrate and 43.3g of ammonium metatungstate, fully contacting and impregnating the carrier obtained in the step (2) with the metal impregnation solution, drying at 110 ℃ for 20 hours, and then roasting at 500 ℃ for 2 hours to obtain the hydrocracking catalyst C-3. See table 7 for catalyst composition.

Example 9

Evaluation of hydrocracking Performance

The evaluation apparatus was carried out using a 100mL small-sized hydrogenation apparatus, and the catalyst was presulfided before the activity evaluation. Under the pressure of 15.0Mpa, the reaction temperature is raised to 140 ℃ from room temperature for 2 hours; when the reaction temperature reaches 140 ℃, vulcanized oil (2% DMDS) is added, and the temperature is raised after the constant temperature is kept for 4 hours. Then the temperature is raised to 220 ℃ at the rate of 20 ℃/h, and the temperature is kept constant at 220 ℃ for 8 hours. And continuously heating to 320 ℃ at the speed of 20 ℃/h, keeping the temperature of 320 ℃ for 12 hours, and ending the vulcanization. And then, continuously feeding vulcanized oil, raising the temperature to a set temperature at the speed of 30 ℃/h, switching evaluation raw materials, and carrying out evaluation. The properties of the raw oil and the reaction conditions used for evaluating the catalyst activity are shown in tables 8 and 9, and the comparative catalyst reaction performance is shown in table 10. When the catalyst is evaluated, raw oil firstly passes through a hydrofining catalyst bed layer and then directly enters a hydrocracking catalyst bed layer, and the organic nitrogen content in the raw oil is controlled to be lower than 10ppm when the raw oil passes through the hydrofining catalyst bed layer.

TABLE 7 catalyst composition

TABLE 8 Process conditions

Reaction pressure	15MPa
		Volume ratio of hydrogen to oil	1000∶1
Airspeed	1.5h ^-1

TABLE 9 Properties of the raw materials

Day of the item	Analysis results
		Density (20 ℃ C.), g/cm ³	0.9205
Range of distillation range, deg.C	314-539
		S，μg/g	10100
N，μg/g	1920
		Carbon residue in wt%	0.18
Freezing point, deg.C	33

TABLE 10 catalyst reactivity

The results of the hydrocracking reactions in table 10 show that, compared with the comparative catalyst, the catalyst of the present invention has the same conversion rate, low reaction temperature, increased liquid yield, reduced light naphtha yield, improved middle distillate selectivity, and improved tail oil BMCI. The hydrocracking catalyst prepared by the method has good hydrocracking performance.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore intended that all such changes and modifications as fall within the true spirit and scope of the invention be considered as within the following claims.

Claims

1. A medium oil type hydrocracking catalyst, which is characterized by comprising the following components in percentage by weight based on the weight of the catalyst: 10-20% of composite modified Y-type molecular sieve, 55-60% of amorphous silicon-aluminum and binder, 25-30% of active metal calculated by oxide,

wherein the active metal is a group VIB metal and a group VIIIB metal;

wherein the mass ratio of the amorphous silicon-aluminum to the binder is 3-10;

2. The hydrocracking catalyst of claim 1, wherein the composite modified Y-type molecular sieve has a specific surface area of 650m ² /g～700m ² A silicon-aluminum ratio of 20 to 30 and a unit cell parameter of

3. The hydrocracking catalyst according to claim 2, wherein the composite modified Y-type molecular sieve is modified by the following method:

(2) washing the suspension to be neutral, and drying to obtain a white powder product;

4. The hydrocracking catalyst according to claim 3, wherein the solid-to-liquid ratio of the USY molecular sieve to the composite dealumination modifier is 1: 10-50, the stirring temperature is 70-100 ℃, and the stirring time is 3-6 h.

5. Hydrocracking catalyst according to claim 3, characterized in that the drying conditions are: the temperature is 80-120 ℃, and the time is 8-16 h.

6. The hydrocracking catalyst of claim 1, wherein the organic acid comprises at least one of citric acid, succinic acid, oxalic acid, malic acid and tartaric acid.

7. Hydrocracking catalyst according to claim 1, characterized in that the chelating agent is disodium ethylenediaminetetraacetic acid.

8. The hydrocracking catalyst of claim 1, wherein the concentration of the composite dealumination modifier is 0.1-1mol/L, wherein the concentration of the organic acid is 0.04-0.85mol/L and the concentration of the chelating agent is 0.17-0.60 mol/L.

9. Hydrocracking catalyst according to claim 1, characterized in that the binder is alumina.

10. The hydrocracking catalyst of claim 1, wherein the group VIB metal is tungsten and the group VIIIB metal is nickel.

11. A process for preparing the medium oil type hydrocracking catalyst as set forth in claim 1, which comprises the steps of:

(S1) mixing the composite modified Y-shaped molecular sieve with a binder and amorphous silicon-aluminum, kneading, molding, drying and roasting to obtain a carrier;