A kind of mesoporous alumina molecular sieve containing molybdenum and its preparation method and application

Abstract

The present invention discloses a molybdenum-containing mesoporous alumina molecular sieve and its preparation method and application. Based on the weight of the molybdenum-containing mesoporous alumina molecular sieve, the molybdenum content is 10wt% to 35wt%, preferably 20wt% to 25wt%; the specific surface area of ​​the molybdenum-containing mesoporous alumina molecular sieve is 250 to 450m 2 / g, pore volume is 0.20~0.35cm 3 / g. The present invention successfully introduces molybdenum into the mesoporous alumina molecular sieve in one step through a one-step gel method, and by using an additive, the interaction between alumina and molybdenum particles is enhanced, the molybdenum is evenly dispersed on the alumina, the accumulation of molybdenum on the alumina is avoided, the increase of particle size is suppressed, and combined with the regulation of preparation conditions, a molybdenum-containing mesoporous alumina molecular sieve with high molybdenum dispersion and high specific surface area can be obtained at a lower temperature. The molybdenum-containing mesoporous alumina molecular sieve of the present invention is particularly suitable as a catalytic material for the hydrodesulfurization of sulfur-containing hydrocarbons.

Description

Technical Field

[0001] The invention belongs to the field of catalytic technology, and particularly relates to an aluminum oxide material and a preparation method thereof, as well as an application in a hydrodesulfurization process. Background Art

[0002] Molecular sieves not only have good physical and structural properties, but also have good hydrothermal stability and chemical properties. It has high adsorption capacity, strong selectivity, high temperature resistance, and has the functions of screening molecules, adsorption, ion exchange and catalysis. It is widely used in petrochemical and organic chemicals. Molecular sieves can be divided into natural zeolites and synthetic zeolites. Most natural zeolites are formed by the reaction of volcanic tuff and tuffaceous sedimentary rocks in marine or lacustrine environments. At present, more than 1,000 zeolite mines have been discovered, and the more common ones are clinoptilolite, mordenite, erionite and chabazite. They are mainly distributed in the United States, Japan, France and other countries. China has also discovered a large number of mordenite and clinoptilolite deposits. Japan is the country with the largest amount of natural zeolite mining. Because natural zeolites are limited by resources, synthetic zeolites have been widely used since the 1950s. Molecular sieves are used as solid adsorbents in the chemical industry. The substances adsorbed by them can be desorbed, and the molecular sieves can be regenerated after use. They can also be used for drying, purification, separation and recovery of gases and liquids. It has been used as a cracking catalyst in the petroleum refining industry since the 1960s, and now a variety of molecular sieve catalysts suitable for different catalytic processes have been developed.

[0003] In recent years, non-silicon mesoporous materials such as alumina and titania have become research hotspots in the fields of heterogeneous catalysis, environmental protection and clean energy. Alumina, as a cheap catalyst or catalyst carrier, is widely used in petrochemicals such as hydrocracking, hydrodesulfurization, fine chemicals and organic synthesis.

[0004] CN109894125A discloses a preparation method and application of a supported sulfided Co-Mo / γ-A2O3 bimetallic catalyst. The catalyst is prepared by the following steps: using a pipette to absorb an appropriate amount of deionized water, dripping it onto a unit mass of γ-A2O3, and measuring the water absorption of the carrier γ-A2O3; then measuring the volume of the unit carrier water absorption, adding a certain amount of (NH4)6Mo7O 24·4H2O and Co(NO3)2·6H2O are completely dissolved; the dissolved solution is slowly added to the unit mass of the carrier γ-A2O3 and allowed to stand for 12 hours; then, after drying and calcination, an oxidized Co-Mo / γ-A2O3 bimetallic catalyst is obtained; finally, the oxidized catalyst is sulfurized to obtain a sulfurized catalyst that is easy to prepare, has good utilization performance and high catalytic activity, and is used for the catalytic removal of heteroatoms in coal-related model compounds dibenzyl ether, furan, thiophene and quinoline. The catalyst is loaded with molybdenum by impregnation, and its loading amount is limited, and the pore structure of the carrier is greatly affected, thereby affecting the improvement of catalyst performance.

[0005] The pore size distribution of traditional alumina materials is wide, which is not conducive to shape-selective catalytic reactions. Therefore, the synthesis of mesoporous alumina molecular sieves with larger specific surface area and narrower pore size distribution has important significance and broad application prospects. The synthesis methods of mesoporous alumina molecular sieves mainly include hydrothermal method, template method, and sol-gel method. For example, CN1958450A discloses a synthesis method of mesoporous alumina molecular sieves. The synthesis method uses organic aluminum as an aluminum source, a straight-chain carboxylic acid containing 12 to 18 carbon atoms as a template agent, alcohol as a solvent, and water as a catalyst. The precursor is synthesized at room temperature using an anion template method, and then filtered, washed with ethanol, dried, and a programmed temperature calcination method is used to obtain a mesoporous alumina molecular sieve. However, the research on mesoporous alumina molecular sieves is still in an immature stage, and how to prepare a catalytic material suitable for hydrodesulfurization needs further in-depth research. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a molybdenum-containing mesoporous alumina molecular sieve and its preparation method and application. The molybdenum-containing mesoporous alumina molecular sieve is a mesoporous alumina molecular sieve material with high molybdenum dispersion, high specific surface area and good pore size distribution, and is particularly suitable for use as a hydrodesulfurization catalytic material.

[0007] The first aspect of the present invention provides a molybdenum-containing mesoporous alumina molecular sieve, wherein the molybdenum content is 10wt% to 35wt% based on the weight of the molybdenum-containing mesoporous alumina molecular sieve; the specific surface area of ​​the molybdenum-containing mesoporous alumina molecular sieve is 250 to 450m 2 / g, pore volume is 0.20~0.35cm 3 / g.

[0008] Furthermore, the molybdenum-containing mesoporous alumina molecular sieve preferably has a molybdenum content of 20wt% to 25wt% based on the weight of the molybdenum-containing mesoporous alumina molecular sieve.

[0009] Furthermore, the molybdenum in the molybdenum-containing mesoporous alumina molecular sieve exists in the form of molybdenum oxide.

[0010] Furthermore, in the molybdenum-containing mesoporous alumina molecular sieve, the mesopore diameter is 2.0 to 4.0 nm, preferably 2.5 to 4.0 nm.

[0011] Furthermore, no MoO3 characteristic peak is found in the XRD spectrum of the molybdenum-containing mesoporous alumina molecular sieve.

[0012] Furthermore, in the molybdenum-containing mesoporous alumina molecular sieve, the particle size of MoO3 grains is 2.0 to 4.5 nm, preferably 2.5 to 4.5 nm.

[0013] The second aspect of the present invention provides a method for preparing a molybdenum-containing mesoporous alumina molecular sieve, comprising:

[0014] (1) Mixing an aluminum source, a molybdenum source and water to prepare a solution A;

[0015] (2) slowly adding an auxiliary agent to the solution A obtained in step (1) to obtain a gel B;

[0016] (3) Gel B is aged, dried, and heat treated to obtain a molybdenum-containing mesoporous alumina molecular sieve.

[0017] Furthermore, the molybdenum in the molybdenum-containing mesoporous alumina molecular sieve obtained in step (3) exists in the form of molybdenum oxide.

[0018] Furthermore, in the above method for preparing the molybdenum-containing mesoporous alumina molecular sieve, step (1) is preferably to dissolve the aluminum source and the molybdenum source in water respectively, and then mix them to obtain solution A.

[0019] Furthermore, in the above-mentioned method for preparing molybdenum-containing mesoporous alumina molecular sieve, the aluminum source in step (1) is an aluminum-containing inorganic salt, which can be specifically selected from one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride, preferably aluminum nitrate.

[0020] Furthermore, in the above-mentioned method for preparing molybdenum-containing mesoporous alumina molecular sieve, the molybdenum source in step (1) is one or more of ammonium dimolybdate, ammonium tetramolybdate, and ammonium heptamolybdate, preferably ammonium heptamolybdate.

[0021] Furthermore, in the above-mentioned method for preparing molybdenum-containing mesoporous alumina molecular sieve, the water is deionized water.

[0022] Furthermore, in the above-mentioned method for preparing molybdenum-containing mesoporous alumina molecular sieve, the weight ratio of the molybdenum source in terms of Mo, the aluminum source in terms of Al2O3 and water in step (1) is 10-35:65-90:40-60, preferably 20-30:70-80:45-55.

[0023] Furthermore, in the preparation method of the molybdenum-containing mesoporous alumina molecular sieve, the auxiliary agent in step (2) is one or more of ammonia water, ammonium carbonate, and ammonium bicarbonate, preferably ammonium carbonate. The concentration of the auxiliary agent is 0.5 to 3.0 mol / L, preferably 0.7 to 2.5 mol / L, and more preferably 1.0 to 2.0 mol / L.

[0024] Furthermore, in the above-mentioned preparation method of molybdenum-containing mesoporous alumina molecular sieve, the method of slowly adding the auxiliary agent in step (2) is 50 to 70 mL relative to solution A, and the flow rate of the auxiliary agent is controlled to be 0.05 to 3.0 mL / min, preferably 0.08 to 2.5 mL / min, and more preferably 1.0 to 2.0 mL / min. The pH value of gel B is adjusted to be 4.0 to 9.0 by adjusting the amount of auxiliary agent added, preferably 4.5 to 8.0, and more preferably 5.0 to 7.0. The slow addition of the auxiliary agent can be carried out by dropwise addition.

[0025] Furthermore, in the above-mentioned method for preparing molybdenum-containing mesoporous alumina molecular sieve, when the auxiliary agent is added in step (2), the temperature of solution A is controlled at 40-90°C (specific examples include but are not limited to: 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C), preferably 45-80°C, and more preferably 50-70°C.

[0026] Furthermore, in the above-mentioned preparation method of molybdenum-containing mesoporous alumina molecular sieve, the aging treatment conditions in step (3) are as follows: the aging temperature is 25 to 60°C, preferably 30 to 55°C, and more preferably 35 to 45°C; the aging time is 12 to 36h, preferably 15 to 30h, and more preferably 20 to 25h.

[0027] Furthermore, in the above-mentioned method for preparing molybdenum-containing mesoporous alumina molecular sieve, the drying conditions in step (3) are as follows: the drying temperature is 90 to 150°C, preferably 100 to 140°C, and more preferably 110 to 130°C; the drying time is 12 to 24h, preferably 14 to 22h, and more preferably 16 to 20h.

[0028] Furthermore, in the above-mentioned preparation method of molybdenum-containing mesoporous alumina molecular sieve, the heat treatment conditions in step (3) are as follows: the heat treatment temperature is 400-750°C, preferably 450-700°C, and more preferably 500-650°C; the heat treatment time is 3-16h, preferably 5-14h, and more preferably 8-12h. The heat treatment is carried out in an oxygen-containing atmosphere (such as an air atmosphere). The heat treatment equipment is preferably a muffle furnace.

[0029] A third aspect of the present invention provides a catalytic material for hydrodesulfurization, wherein the catalytic material for hydrodesulfurization comprises the above-mentioned molybdenum-containing mesoporous alumina molecular sieve or the molybdenum-containing mesoporous alumina molecular sieve obtained by the above-mentioned preparation method.

[0030] The fourth aspect of the present invention provides a hydrodesulfurization catalyst, comprising: a mesoporous alumina molecular sieve containing molybdenum carbide, wherein the molybdenum content is 10wt% to 35wt%, preferably 20wt% to 25wt%, based on the weight of the mesoporous alumina molecular sieve containing molybdenum carbide; the specific surface area of ​​the mesoporous alumina molecular sieve containing molybdenum carbide is 180 to 400 m 2 / g, pore volume is 0.18~0.40cm 3 / g.

[0031] Furthermore, the mesopore diameter of the mesoporous alumina molecular sieve containing molybdenum carbide is 2.0-4.0 nm.

[0032] Furthermore, no diffraction peak of molybdenum carbide is found in the XRD spectrum of the mesoporous alumina molecular sieve containing molybdenum carbide.

[0033] Furthermore, the particle size of the molybdenum carbide-containing grains is 2.0 to 4.5 nm.

[0034] Furthermore, the mesoporous alumina molecular sieve containing molybdenum carbide is obtained by carbonizing the above-mentioned mesoporous alumina molecular sieve containing molybdenum. Specifically, the mesoporous alumina molecular sieve containing molybdenum carbide (Mo2C) is obtained by carbonizing and passivating the mesoporous alumina molecular sieve containing molybdenum carbide obtained in step (3).

[0035] Furthermore, the carbonization is carried out in the presence of a carbonizing atmosphere, the carbonizing atmosphere includes a carbonizing gas and hydrogen, the carbonizing gas can be selected from one or more of C1-C4 alkanes, preferably methane and / or ethane; the volume ratio of the carbonizing gas to hydrogen is 1:2-5. The carbonization treatment temperature is 550-750°C, and the carbonization treatment time is 3-8h. The carbonization process adopts a programmed temperature increase method, and further preferably includes two stages of temperature increase, wherein the first stage is heated to 250-350°C, and the first stage heating rate is controlled at 4-6°C / min; the second stage is heated to the carbonization temperature, and the second stage heating rate is generally controlled at 0.5-2°C / min, and further preferably the first stage heating rate is 3-5°C / min higher than the second stage heating rate.

[0036] Furthermore, the passivation is carried out under the passivation atmosphere, which is a mixed gas of an inert gas and oxygen, wherein the inert gas is selected from one or more of nitrogen, argon, etc. The oxygen concentration in the passivation atmosphere can be 0.5 v% to 1 v%. The passivation treatment temperature is 15 to 40° C., and the passivation treatment time is 4 to 8 hours.

[0037] The hydrodesulfurization catalyst of the present invention can be used in the hydrodesulfurization process of sulfur-containing hydrocarbons, such as gasoline hydrodesulfurization, diesel hydrodesulfurization, etc.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1. The molybdenum-containing mesoporous alumina molecular sieve of the present invention has a mesoporous alumina molecular sieve material with high molybdenum dispersion, high specific surface area and good pore size distribution, and is particularly suitable as a catalytic material for hydrodesulfurization.

[0040] 2. The present invention successfully introduces molybdenum into the mesoporous alumina molecular sieve in one step through a one-step gel method to prepare the molybdenum-containing mesoporous alumina molecular sieve, thereby simplifying the preparation steps.

[0041] 3. The preparation method of the molybdenum-containing mesoporous alumina molecular sieve of the present invention is to use an additive to enhance the interaction between alumina and molybdenum particles, uniformly disperse the molybdenum on the alumina, avoid the accumulation of molybdenum on the alumina, inhibit the increase of particle size, and combine with the regulation of preparation conditions to obtain a molybdenum-containing mesoporous alumina molecular sieve with high molybdenum dispersion and high specific surface area at a lower temperature.

[0042] 4. The molybdenum-containing mesoporous alumina molecular sieve of the present invention is a mesoporous catalytic material with special catalytic properties, which can be used as a hydrodesulfurization catalytic material and can show good activity and selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 XRD diagram of the molybdenum-containing mesoporous alumina molecular sieve sample prepared in Example 1-7 of the present invention;

[0044] Figure 2 XRD diagram of the molybdenum-containing mesoporous alumina molecular sieve samples prepared in Comparative Examples 1-3 of the present invention;

[0045] Figure 3 The nitrogen adsorption-desorption isotherm and pore size distribution diagram of the molybdenum-containing mesoporous alumina molecular sieve sample prepared in Example 1 of the present invention;

[0046] Figure 4 This is a TEM image of the molybdenum-containing mesoporous alumina molecular sieve sample prepared in Example 2 of the present invention;

[0047] Figure 5 The XRD diagrams of the catalyst samples obtained in Examples 8 and 9 of the present invention and Comparative Example 4;

[0048] Figure 6 This is a SEM image of the catalyst sample obtained in Example 8 of the present invention;

[0049] Figure 7 This is a TEM image of the catalyst sample obtained in Example 8 of the present invention;

[0050] Figure 8 This is a diagram showing the evaluation results of the catalysts obtained in Examples 8 and 9 of the present invention and Comparative Example 4. DETAILED DESCRIPTION

[0051] In order to further illustrate the present invention, the molybdenum-containing mesoporous alumina molecular sieve and the preparation method thereof provided by the present invention are described in detail below in conjunction with the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0052] In the present invention, the specific surface area, pore volume and pore diameter are measured by low temperature liquid nitrogen adsorption method on Micromeritics ASAP2020 physical adsorption instrument, wherein the specific surface area is measured by BET method, the pore volume is measured by single point adsorption total pore volume method, and the pore diameter is measured by BJH method.

[0053] In the present invention, XRD analysis was performed on a Rigaku D / MAX-2200 powder X-ray diffractometer, with a graphite monochromator, Cu Kα radiation, a tube voltage of 40 kV, a tube current of 40 mA, and a scanning speed of 2 o ·min -1 The scanning range 2θ is 10 ~ 90°. The positions of the standard MoO3 characteristic peaks are as follows: 2θ = 12.7°, 23.3°, 25.8°, 27.2°, 34.1°, 35.4°, 45.7°, 46.6°, 54.7° (JCPDS card no. 05-0508).

[0054] In the present invention, the measurement is performed using a JEM-2100 transmission electron microscope (TEM) manufactured by JEOL Ltd. The grain size of molybdenum oxide is obtained by statistically analyzing 20 TEM images (the number of grains is greater than 200).

[0055] In the present invention, the scanning electron microscope image (SEM) is obtained by a scanning electron microscope Nova Nano SEM 450 model produced by FEI Company of the United States.

[0056] Example 1

[0057] 19.14 g Al(NO3)3·9H2O was dissolved in 50 mL deionized water to obtain solution A1. 2.57 g (NH4)6Mo7O 24·4H2O was dissolved in 10mL of deionized water and stirred to dissolve to obtain solution A2; the above solution A1 and solution A2 were mixed to obtain solution A, and then placed in a 40°C water bath and stirred to mix evenly. After the mixed solution was heated to 40°C, a 3mol / L ammonia solution was added to the mixed aqueous solution at a rate of 0.05mL / min through a peristaltic pump under stirring until a gel was formed and the pH was measured to be 4, and then the titration was stopped to obtain a gel; the formed gel was then aged at 25°C for 36h, and then dried in an oven at 150°C for 12h to obtain a dry gel; finally, the obtained dry gel was calcined in a muffle furnace at 400°C for 16h to obtain a molybdenum-containing mesoporous alumina molecular sieve sample, and the XRD pattern of the molecular sieve sample is shown as follows Figure 1 As shown in the figure, the nitrogen adsorption-desorption isotherm and pore size distribution of the molecular sieve sample are shown in Figure 3 The specific properties of the samples are shown in Table 1.

[0058] Example 2

[0059] 7.89 g AlCl3 was dissolved in 40 mL deionized water to obtain solution A1, and 1.72 g (NH4)2Mo4O 13 ·2H2O was dissolved in 10mL of deionized water and stirred to dissolve to obtain solution A2; the above solution A1 and solution A2 were mixed to obtain solution A, and then placed in a 60°C water bath and stirred to mix evenly. After the mixed solution was heated to 60°C, 1.5mol / L (NH4)2CO3 solution was added to the above mixed aqueous solution at a rate of 1mL / min through a peristaltic pump under stirring until a gel was formed and pH=6 was measured, and then the titration was stopped to obtain a gel; the formed gel was then aged at 40°C for 24h, and then dried in an oven at 120°C for 18h to obtain a dry gel; finally, the obtained dry gel was calcined at 550°C in a muffle furnace for 9h to obtain a molybdenum-containing mesoporous alumina molecular sieve sample, and the XRD pattern of the molecular sieve sample is shown as follows Figure 1 As shown, the TEM characterization of the molecular sieve sample is as follows Figure 4 The specific properties of the samples are shown in Table 1.

[0060] Example 3

[0061] 24.37g Al2(SO4)3 was dissolved in 30mL deionized water to obtain solution A1, and 0.71g (NH4)2Mo2O7 was dissolved in 10mL deionized water and stirred to dissolve to obtain solution A2; the above solutions A1 and A2 were mixed to obtain solution A, and then placed in a 90°C water bath and stirred to mix them evenly. After the mixed solution was heated to 90°C, 0.5mol / L NH4HCO3 solution was added to the mixed aqueous solution at a rate of 3mL / min through a peristaltic pump under stirring until a gel was formed and pH=9 was measured, and then the titration was stopped to obtain a gel; the formed gel was then aged at 60°C for 12h, and then dried in a 90°C oven for 24h to obtain a dry gel; finally, the obtained dry gel was calcined at 700°C in a muffle furnace for 3h to obtain a molybdenum-containing mesoporous alumina molecular sieve sample, and the XRD pattern of the molecular sieve sample is shown as follows Figure 1 The specific properties of the samples are shown in Table 1.

[0062] Embodiment 4-7

[0063] The amount of molybdenum salt was changed to prepare molybdenum contents of 15wt%, 18wt%, 20wt%, and 30wt%, respectively. The remaining steps were the same as in Example 2 to obtain molybdenum-containing mesoporous alumina molecular sieve samples. The XRD pattern of the molecular sieve samples is shown in FIG. Figure 1 The specific properties of the samples are shown in Table 1.

[0064] Comparative Example 1

[0065] The same as Example 1, the only difference is that no auxiliary agent is used in Comparative Example 1, and no ammonia water is added. The XRD pattern of the molecular sieve sample is as follows Figure 2 The specific properties of the samples are shown in Table 1.

[0066] Comparative Example 2

[0067] The same as Example 2, the only difference is that no auxiliary agent is used in Comparative Example 1, and no ammonium carbonate is added. The XRD pattern of the molecular sieve sample is as follows: Figure 2 The specific properties of the samples are shown in Table 1.

[0068] Comparative Example 3

[0069] The same as Example 3, the only difference is that no auxiliary agent is used in Comparative Example 1, and no ammonium bicarbonate is added. The XRD pattern of the molecular sieve sample is as follows: Figure 2 The specific properties of the samples are shown in Table 1.

[0070] Table 1 Properties of the molybdenum-containing mesoporous alumina molecular sieve samples obtained in various examples and comparative examples

[0071] Mo content (wt%) <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Mesopore diameter (nm) <![CDATA[Average particle size (nm) of MoO3 grains]]> Example 1 35 369.1 0.29 3.0 3.5 Example 2 25 442.6 0.34 3.3 3.2 Example 3 10 263.7 0.27 2.6 4.3 Example 4 15 301.3 0.30 2.9 2.8 Example 5 18 329.8 0.28 3.1 2.9 Example 6 20 344.1 0.29 3.2 3.0 Example 7 30 360.4 0.32 3.2 3.3 Comparative Example 1 35 121.7 0.20 2.1 5.7 Comparative Example 2 25 180.4 0.23 2.3 6.4 Comparative Example 3 10 92.6 0.19 2.0 7.3

[0072] The properties of the molecular sieve samples prepared in Examples 1-7 and Comparative Examples 1-3 are shown in Table 1. As can be seen from Table 1, the molecular sieve samples (Examples 1-7) prepared by the one-step gel method using ammonia water, ammonium carbonate or ammonium bicarbonate as an auxiliary agent have a larger specific surface area (250-450 m 2 / g), the pore volume and pore size distribution are good, while the specific surface area, pore volume and pore size of the molecular sieve samples prepared without adding additives (Comparative Examples 1-3) are significantly reduced.

[0073] The XRD patterns of the molecular sieve samples prepared in Examples 1-7 are as follows: Figure 1 As shown. Figure 1 It can be seen that the molecular sieve sample prepared by the one-step gel method using additives has only alumina diffraction peaks at high Mo loading (10~35wt%), and no obvious MoO3 diffraction peaks, indicating that the molecular sieve sample prepared by this method has good molybdenum dispersion in the alumina carrier even at high loading levels and the molybdenum particles are smaller.

[0074] The XRD patterns of the molecular sieve samples prepared in Comparative Examples 1-3 are as follows: Figure 2 As shown. Figure 2 It can be seen that the XRD of the molecular sieve prepared without additives has an obvious MoO3 diffraction peak, indicating that the dispersion of molybdenum in the alumina carrier is poor and the molybdenum particles are large.

[0075] The nitrogen adsorption-desorption isotherm and pore size distribution of the molecular sieve sample prepared in Example 1 are shown in Figure 3 As shown. Figure 3 (a) It can be seen that the nitrogen adsorption-desorption isotherm of the molybdenum-containing mesoporous alumina molecular sieve presents an H1-type hysteresis loop, showing obvious characteristics of mesoporous materials; Figure 3 (b) It can be seen that the molybdenum-containing mesoporous alumina molecular sieve has a narrow pore size distribution and uniform pore size.

[0076] The TEM characterization of the molecular sieve sample prepared in Example 2 is as follows Figure 4 As shown. Figure 4 It can be seen that the molybdenum-containing mesoporous alumina molecular sieve particles are small and highly dispersed, with an average particle size of about 3 nm, which is consistent with its XRD results.

[0077] Example 8

[0078] The molybdenum-containing mesoporous alumina molecular sieve sample obtained in Example 2 was carbonized in a mixed gas of CH4 and H2 (CH4:H2=1:4, volume ratio), firstly heated to 300°C at a heating rate of 5°C / min, then adjusted to a heating rate of 1°C / min from 300°C to 600°C, and carbonized for 5h; after the carbonization process was completed, the temperature was cooled to room temperature (20°C), and passivated in a 1v% O2 / N2 atmosphere for 6h to obtain a highly dispersed molybdenum carbide catalyst supported on a mesoporous alumina molecular sieve. The catalyst properties are shown in Table 2, and the XRD pattern of the catalyst sample is shown in Table 2. Figure 5 ; SEM characterization of the prepared catalyst is shown in Figure 6 The TEM characterization of the catalyst is shown in Figure 7 shown.

[0079] Example 9

[0080] The same as Example 8, except that the molybdenum-containing mesoporous alumina molecular sieve sample obtained in Example 2 is replaced by the molybdenum-containing mesoporous alumina molecular sieve sample obtained in Example 3 to prepare a catalyst.

[0081] Comparative Example 4

[0082] The same as Example 8, except that the molybdenum-containing mesoporous alumina molecular sieve sample obtained in Example 2 is replaced by the molybdenum-containing mesoporous alumina molecular sieve sample obtained in Comparative Example 2 to prepare a catalyst.

[0083] Table 2 Properties of the catalysts obtained in various examples and comparative examples

[0084] <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Pore volume (cm 3 / g)]]> Mesopore diameter (nm) <![CDATA[Average grain size (nm) of Mo3C grains]]> Example 8 218.4 0.23 3.3 2.7 Example 9 191.3 0.20 2.5 4.1 Comparative Example 4 123.1 0.21 2.2 5.8

[0085] Evaluation test

[0086] Using 1wt% thiophene n-octane solution as the simulated raw material, the same reaction conditions (280℃, 3MPa, liquid hourly volume space velocity of 4h -1 The catalysts obtained in Example 8, Example 9 and Comparative Example 4 were evaluated for reaction under the conditions of 1:1, 2:5:1, and the conversion rate of thiophene, i.e., the desulfurization rate, was obtained by gas chromatography analysis. Figure 8 .

[0087] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for those skilled in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A molybdenum-containing mesoporous alumina molecular sieve for hydrodesulfurization, wherein the molybdenum content is 20wt% to 35wt% based on the weight of the molybdenum-containing mesoporous alumina molecular sieve; the specific surface area of ​​the molybdenum-containing mesoporous alumina molecular sieve is 301.3 to 450m 2 / g, pore volume is 0.20~0.35cm 3 / g; the mesopore diameter is 2.9~4.0nm; in the molybdenum-containing mesoporous alumina molecular sieve, the particle size of MoO3 grains is 2.0~4.5nm; the molybdenum in the molybdenum-containing mesoporous alumina molecular sieve exists in the form of molybdenum oxide, and no MoO3 diffraction peak is found in its XRD spectrum; The preparation method of the molybdenum-containing mesoporous alumina molecular sieve comprises: (1) Mixing an aluminum source, a molybdenum source and water to prepare a solution A; (2) slowly adding an auxiliary agent to the solution A obtained in step (1) to obtain a gel B; (3) Gel B is aged, dried, and heat treated to obtain a molybdenum-containing mesoporous alumina molecular sieve; The auxiliary agent in step (2) is one or more of ammonia water, ammonium carbonate and ammonium bicarbonate.

2. The molecular sieve according to claim 1, characterized in that The molybdenum mesoporous alumina molecular sieve has a molybdenum content of 20wt% to 25wt% based on the weight of the molybdenum-containing mesoporous alumina molecular sieve.

3. The molecular sieve according to any one of claims 1-2, characterized in that: In the molybdenum-containing mesoporous alumina molecular sieve, the particle size of MoO3 grains is 2.5-4.5 nm.

4. The method for preparing the molecular sieve according to any one of claims 1 to 3, comprising: (1) Mixing an aluminum source, a molybdenum source and water to prepare a solution A; (2) slowly adding an auxiliary agent to the solution A obtained in step (1) to obtain a gel B; (3) Gel B is aged, dried, and heat treated to obtain a molybdenum-containing mesoporous alumina molecular sieve; The auxiliary agent in step (2) is one or more of ammonia water, ammonium carbonate and ammonium bicarbonate.

5. The preparation method according to claim 4, characterized in that: The process of step (1) is to dissolve the aluminum source and the molybdenum source in water respectively, and then mix them to obtain solution A.

6. The preparation method according to claim 4, characterized in that: The aluminum source in step (1) is one or more selected from aluminum nitrate, aluminum sulfate, and aluminum chloride; And / or, the molybdenum source is one or more of ammonium dimolybdate, ammonium tetramolybdate, and ammonium heptamolybdate; And / or, the weight ratio of the molybdenum source calculated as Mo, the aluminum source calculated as Al2O3 and water is 10-35:65-90:40-60.

7. The preparation method according to claim 6, characterized in that: The weight ratio of the molybdenum source as Mo, the aluminum source as Al2O3 and water is 20-30:70-80:45-55.

8. The preparation method according to claim 4, characterized in that: The concentration of the auxiliary agent in step (2) is 0.5-3.0 mol / L.

9. The preparation method according to claim 8, characterized in that: The concentration of the auxiliary agent in step (2) is 0.7-2.5 mol / L.

10. The preparation method according to claim 8, characterized in that: The concentration of the auxiliary agent in step (2) is 1.0-2.0 mol / L.

11. The preparation method according to claim 4, characterized in that: The method of slowly adding the auxiliary agent in step (2) is 50 to 70 mL relative to solution A, and the flow rate of the auxiliary agent is controlled to be 0.05 to 3.0 mL / min; And / or, the pH value of gel B is adjusted and controlled to be 4.0-9.0 by adding an auxiliary agent.

12. The preparation method according to claim 11, characterized in that: In step (2), the auxiliary agent is slowly added in an amount of 50 to 70 mL relative to solution A, and the flow rate of the auxiliary agent is controlled to be 0.08 to 2.5 mL / min.

13. The preparation method according to claim 11, characterized in that: In step (2), the auxiliary agent is slowly added in an amount of 50 to 70 mL relative to solution A, and the flow rate of the auxiliary agent is controlled to be 1.0 to 2.0 mL / min.

14. The preparation method according to claim 11, characterized in that: The pH value of gel B is adjusted and controlled to be 4.5-8.0 by adding the auxiliary agent.

15. The preparation method according to claim 11, characterized in that: The pH value of gel B is adjusted and controlled to be 5.0-7.0 by adding the auxiliary agent.

16. The preparation method according to claim 4, characterized in that: When the auxiliary agent is added in step (2), the temperature of solution A is controlled at 40-90°C.

17. The preparation method according to claim 16, characterized in that: When the auxiliary agent is added in step (2), the temperature of solution A is controlled at 45-80°C.

18. The preparation method according to claim 16, characterized in that: When the auxiliary agent is added in step (2), the temperature of solution A is controlled at 50-70°C.

19. The preparation method according to claim 4, characterized in that: The aging treatment conditions in step (3) are as follows: the aging temperature is 25 to 60° C., and the aging time is 12 to 36 hours; And / or, the drying conditions are as follows: the drying temperature is 90-150° C., and the drying time is 12-24 hours.

20. The preparation method according to claim 4, characterized in that: The aging treatment conditions in step (3) are as follows: aging temperature is 30 to 55° C.; aging time is 15 to 30 hours; And / or, the drying conditions are as follows: the drying temperature is 100-140° C.; the drying time is 14-22 hours.

21. The preparation method according to claim 4, characterized in that: The aging treatment conditions in step (3) are as follows: the aging temperature is 35 to 45° C.; the aging time is 20 to 25 hours; And / or, the drying conditions are as follows: the drying temperature is 110-130° C.; the drying time is 16-20 hours.

22. The preparation method according to claim 4, characterized in that: The heat treatment conditions are as follows: the heat treatment temperature is 400-750° C., and the heat treatment time is 3-16 hours.

23. The preparation method according to claim 22, characterized in that: The heat treatment conditions are as follows: the heat treatment temperature is 450-700° C., and the heat treatment time is 5-14 hours.

24. The preparation method according to claim 22, characterized in that: The heat treatment conditions are as follows: the heat treatment temperature is 500-650° C.; the heat treatment time is 8-12 hours.

25. A catalytic material for hydrodesulfurization, comprising the molybdenum-containing mesoporous alumina molecular sieve according to any one of claims 1 to 3 or the molybdenum-containing mesoporous alumina molecular sieve obtained by the preparation method according to any one of claims 4 to 24.

26. A hydrodesulfurization catalyst comprising: A mesoporous alumina molecular sieve containing molybdenum carbide, wherein the mesoporous alumina molecular sieve containing molybdenum carbide is obtained by carbonizing the molybdenum-containing mesoporous alumina molecular sieve according to any one of claims 1 to 3 or the molybdenum-containing mesoporous alumina molecular sieve obtained by the preparation method according to any one of claims 4 to 24; the molybdenum content is 20wt% to 35wt% based on the weight of the mesoporous alumina molecular sieve containing molybdenum carbide; the specific surface area of ​​the mesoporous alumina molecular sieve containing molybdenum carbide is 180 to 400m 2 / g, pore volume is 0.18~0.40cm 3 / g.

27. The catalyst according to claim 26, characterized in that The hydrodesulfurization catalyst comprises: a mesoporous alumina molecular sieve containing molybdenum carbide, wherein the molybdenum content is 20wt% to 25wt% based on the weight of the mesoporous alumina molecular sieve containing molybdenum carbide.

28. The catalyst according to claim 26, characterized in that No diffraction peak of molybdenum carbide was found in the XRD spectrum of the mesoporous alumina molecular sieve containing molybdenum carbide; And / or, the particle size of the molybdenum carbide-containing grains is 2.0 to 4.5 nm.

29. Use of the hydrodesulfurization catalyst according to any one of claims 26 to 28 in the hydrodesulfurization of sulfur-containing hydrocarbons.

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