CN103566965A - Molybdenum-based molecular sieve catalyst, and preparation method and application of catalyst - Google Patents

Abstract

The invention relates to a molybdenum-based molecular sieve catalyst and its preparation method and application. The mass percent of the molybdenum-based molecular sieve catalyst is: Mo ₂ C: 1.06%-10.6%; HZSM-5 molecular sieve: 89.4%-98.94%. The catalyst is prepared by adopting an impregnation method, modifying the HZSM-5 molecular sieve with water-soluble molybdenum salt, and then obtaining the molybdenum-based molecular sieve Mo ₂ C/HZSM-5 catalyst through carburizing and passivation treatment. The catalyst can be directly used in the selective conversion of dimethyl ether to produce aromatics, and has excellent dimethyl ether aromatization performance. The preparation method of the catalyst is simple, the metal doping amount is small, the cost is low, and the catalyst has good industrial application prospect.

Description

A kind of molybdenum-based molecular sieve catalyst and its preparation method and application

technical field

The invention relates to a molecular sieve catalyst, in particular to a molybdenum-based molecular sieve catalyst used for the aromatization of dimethyl ether, and also relates to a preparation method of the catalyst and an application in the aromatization of dimethyl ether.

Background technique

Aromatics are an important class of basic organic chemical raw materials, and their derivatives are widely used in the production of chemical fibers, plastics, rubber and other chemical products and fine chemicals. With the continuous development of petrochemical and textile industries, the demand for light aromatics around the world The volume keeps growing. Moreover, aromatics are the octane components of gasoline. With the enhancement of people's awareness of environmental protection, there is an urgent need to increase the octane number of gasoline to meet the needs of clean gasoline.

Aromatics resources mainly come from the by-products of crude benzene and coal tar in the coking industry, reformed oil in the petroleum refining industry and pyrolysis gasoline in the co-product of the olefin manufacturing industry. Due to the serious pollution and low utilization rate of the former, it will no longer meet the demand for aromatic hydrocarbon raw materials in the development of organic chemical industry. will be severely restricted. In this context, the technology of producing aromatics from natural gas emerged as the times require. Methane is a mineral with abundant reserves in my country, and its aromatization has been widely studied in the past few decades, and some remarkable results have been obtained. However, due to the difficulty in activation of CH ₄ and the limitation of thermodynamic equilibrium, the low conversion rate and low yield of aromatics in the aromatization process have become the bottleneck restricting the industrial production of methane aromatization.

Dimethyl ether is a non-toxic green chemical product, containing CH ₃ and CH ₃ O groups in the molecule, and has similar reactivity to methanol. my country's coal and natural gas resources are very rich. Today, the industrial process development of one-step preparation of dimethyl ether from coal or natural gas through synthesis gas is becoming more and more mature. Using dimethyl ether to synthesize aromatics can provide a new way for the utilization of coal resources. The way to reduce environmental pollution can also reduce the dependence on oil resources and ensure the country's energy security. It is a technical route with sustainable development and high economic benefits. The research on dimethyl ether aromatization is just in its infancy, and the core of vigorously developing dimethyl ether aromatization technology is to find a catalyst with high conversion rate and high yield of aromatics.

Although the HZSM-5 molecular sieve catalyst in the prior art can successfully realize the aromatization of dimethyl ether, there is generally a defect that the catalytic efficiency is not high, and the dimethyl ether aromatization process itself generates a large amount of water. The existing HZSM-5 Molecular sieve catalysts are unstable and easily deactivated in high-temperature hydrothermal environments, resulting in a significant drop in the yield of aromatics.

Contents of the invention

In order to overcome the shortcomings of the above-mentioned catalysts, the present invention uses molybdenum salts to modify the HZSM-5 molecular sieve catalyst, and then obtains a new type of HZSM-5 molecular sieve catalyst through carburizing and passivation treatment, and uses it in the aromatization process of dimethyl ether , with high catalytic activity, long catalyst life and excellent stability. At present, research in this area has not been reported.

An object of the present invention is to provide a molybdenum-based molecular sieve catalyst molecule with high selectivity and high conversion rate, and the molybdenum-based molecular sieve catalyst contains the following weight percentage components:

Mo ₂ C: 1.06% to 10.6%;

HZSM-5 molecular sieve: 89.4% to 98.94%.

Preferably, the molybdenum-based molecular sieve catalyst contains the following components in weight percent:

_Mo2C : 3.18%;

HZSM-5 molecular sieve: 96.82%.

Another object of the present invention is to provide the preparation method of the above-mentioned catalyst, which is characterized in that the HZSM-5 molecular sieve is modified by water-soluble molybdenum salt, and then the molybdenum-based molecular sieve catalyst is obtained through carburizing and passivation treatment.

Preferably, the above method comprises the following preparation steps:

(1) The raw HZSM-5 molecular sieve powder is roasted to remove the physically adsorbed impurities, pulverized and set aside;

(2) According to the weight percentage composition of each component of the catalyst to be prepared, weigh a certain amount of water-soluble molybdenum salt and dissolve it in an appropriate amount of deionized water to form an impregnation solution, and then stir and mix the impregnation solution with the HZSM-5 molecular sieve catalyst , stand still, spare;

(3) Dry the impregnated catalyst, then roast it, and obtain the modified Mo/HZSM-5 catalyst after cooling down;

(4) Carburizing the Mo/HZSM-5 catalyst obtained in step (3), and obtaining the molybdenum-based molecular sieve Mo ₂ C/HZSM-5 catalyst after passivation.

More preferably, the above method comprises the following preparation steps:

(1) Roast HZSM-5 molecular sieve raw powder, the calcination temperature is raised from room temperature to 773K at a rate of 5-10K/min, then kept at 773K for 2-4 hours, and finally dropped to room temperature naturally;

(2) According to the weight percentage composition of each component of the catalyst to be prepared, weigh a certain amount of water-soluble molybdenum salt and dissolve it in an appropriate amount of deionized water to form an impregnation solution, and then mix the impregnation solution with the HZSM-5 molecular sieve catalyst in a rapid Thoroughly mix on a mixer, then sonicate at room temperature for 0.5 to 1 hour, and then stand still for 8 to 12 hours;

(3) Put the impregnated catalyst in an oven at 353-393K to dry for 8-12 hours, then roast at 673-873K for 2-4 hours, and obtain the modified Mo/HZSM-5 catalyst after cooling down;

(4) Heat the modified Mo/HZSM-5 catalyst obtained in step (3) from room temperature to 900K at a rate of 1K/s under 10%v/v C ₂ H ₆ /H ₂ atmosphere, and then switch to Ar Cool to room temperature under atmosphere, and finally passivate under 1%v/v O ₂ /He atmosphere for 0.5-1h, to obtain the molybdenum-based molecular sieve Mo ₂ C/HZSM-5 catalyst.

Preferably, the water-soluble molybdenum salt used in the above method is ammonium molybdate.

Preferably, the carburizing and passivation steps in the above method are carried out in a temperature-programmed tube furnace under normal pressure.

The third object of the present invention is to provide the application of the above catalyst in the aromatization process of dimethyl ether.

Preferably, the conditions for the molybdenum-based molecular sieve catalyst to catalyze the selective conversion of dimethyl ether to aromatics are as follows: the reaction temperature is 633K, and the space velocity is 1500h ^-1 .

After the preparation method of the invention uses the water-soluble molybdenum salt to modify the HZSM-5 molecular sieve and performs carburizing treatment, the performance of the catalyst in catalyzing the aromatization of dimethyl ether is significantly improved. When the Mo ₂ C loading was 3% (calculated by the mass fraction of Mo), the yield of total aromatics was as high as 95.5%. At the same time, the stability of the molecular sieve catalyst prepared by the invention is also improved.

The high-efficiency and low-load Mo ₂ C/HZSM-5 catalyst prepared by the invention can be directly used to convert dimethyl ether into aromatics. The preparation method of the catalyst is simple, the metal doping amount is small, the cost is low, and the catalyst has good industrial application prospect.

Description of drawings

Fig. 1 is the XRD spectrum of the Mo ₂ C/HZSM-5 catalyst example of the present invention.

Figure 2 is the XPS spectrum of Mo3d electrons and O1s electrons in the Mo/HZSM-5 catalyst of Example 3 of the present invention.

Fig. 3 is the pyridine adsorption FT-IR spectra of the catalysts HZSM-5 and 3Mo ₂ C/HZSM-5 according to the embodiment of the present invention.

Fig. 4 is the NH ₃ -TPD spectrograms of HZSM-5 and 3Mo ₂ C/HZSM-5 catalysts according to the examples of the present invention.

Fig. 5 is the effect of Mo ₂ C loading on the performance of DME aromatization on Mo ₂ C/HZSM-5 catalyst of Example 3 of the present invention.

Fig. 6 shows the effect of reaction temperature on the performance of DME aromatization on the Mo ₂ C/HZSM-5 catalyst of Example 3 of the present invention.

Fig. 7 is a stability test chart of the Mo ₂ C/HZSM-5 catalyst of Example 3 of the present invention.

Detailed ways

The content of the present invention is further described below in conjunction with the examples, but the examples should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, any modifications or replacements made to the methods, steps or conditions of the present invention fall within the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

Example 1

Preparation of 1Mo ₂ C/HZSM-5 catalyst:

(1) Carrier pretreatment: at a temperature of about 773K, bake the HZSM-5 molecular sieve in a muffle furnace for 3 hours to remove organic matter such as residual templates, cool down, and set aside.

(2) Preparation of Mo/HZSM-5 catalyst: Weigh 0.93g of ammonium molybdate, add it into a beaker containing 49.07g of deionized water, and prepare an ammonium molybdate solution with a mass concentration of 1.86%, and then weigh The solution and 3g of the pretreated HZSM-5 molecular sieve in step (1) (calculated based on the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 1%), mixed in a rapid mixer Mix evenly, then ultrasonic at room temperature for 30min, stand still for 12h, air-dried at 393K for 12h, and finally calcined at 773K in a muffle furnace for 3h to obtain the Mo/HZSM-5 catalyst.

(3) Preparation of Mo ₂ C/HZSM-5 catalyst: The Mo/HZSM-5 catalyst obtained in step (2) was heated in a temperature-programmed tube furnace in an atmosphere of 10% v/v C ₂ H ₆ /H ₂ heated from room temperature to 900K at a rate of 1K/s, switched to Ar atmosphere and cooled to room temperature, and then passivated in 1%v/v O ₂ /He atmosphere for 30min to obtain Mo ₂ C/HZSM-5 catalyst ( Calculated by the mass fraction of Mo ₂ C, the doping amount m _Mo2C /m _HZSM-5 mass ratio is 1.06%), the catalyst is labeled as 1Mo ₂ C/HZSM-5 (calculated by the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 1%).

Preparation of 3Mo ₂ C/HZSM-5 catalyst:

(1) Carrier pretreatment: at a temperature of about 773K, bake the HZSM-5 molecular sieve in a muffle furnace for 3 hours to remove organic matter such as residual templates, cool down, and set aside.

(2) Preparation of Mo/HZSM-5 catalyst: Weigh 2.79g of ammonium molybdate, add it into a beaker containing 47.21g of deionized water, and prepare an ammonium molybdate solution with a mass concentration of 5.58%, and then weigh The solution and 3g of the pretreated HZSM-5 molecular sieve in step (1) (calculated based on the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 3%), mixed in a rapid mixer Mix well, then ultrasonic at room temperature for 1h, let it stand for 8h, blow dry at 353K for 8h, and finally bake in muffle furnace at 873K for 4h to obtain Mo/HZSM-5 catalyst.

(3) Preparation of Mo ₂ C/HZSM-5 catalyst: The Mo/HZSM-5 catalyst obtained in step (2) was heated in a temperature-programmed tube furnace in an atmosphere of 10% v/v C ₂ H ₆ /H ₂ Heating from room temperature to 900K at a rate of 1K/s, switching to Ar atmosphere and cooling to room temperature, and then passivating in 1%v/v O ₂ /He atmosphere for 1h to obtain Mo ₂ C/HZSM-5 catalyst ( Calculated by the mass fraction of Mo ₂ C, the doping amount m _Mo2C /m _HZSM-5 mass ratio is 3.18%), the catalyst is labeled as 3Mo ₂ C/HZSM-5 (calculated by the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 3%).

Preparation of 5Mo ₂ C/HZSM-5 catalyst:

(1) Carrier pretreatment: at a temperature of about 773K, the HZSM-5 molecular sieve was roasted in a muffle furnace for 2 hours to remove organic matter such as residual templates, cooled, and set aside.

(2) Preparation of Mo/HZSM-5 catalyst: Weigh 4.65g of ammonium molybdate, add it into a beaker filled with 45.36g of deionized water, and prepare an ammonium molybdate solution with a mass concentration of 9.30%, and then weigh Take this solution and 3g each of the HZSM-5 molecular sieve pretreated in step (1) (calculated based on the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 5%), mix and mix quickly Mix on the instrument, then ultrasonic at room temperature for 1h, stand still for 10h, air-dried at 373K for 10h, and finally baked in a muffle furnace at 673K for 2h to obtain the Mo/HZSM-5 catalyst.

(3) Preparation of Mo ₂ C/HZSM-5 catalyst: The Mo/HZSM-5 catalyst obtained in step (2) was heated in a temperature-programmed tube furnace in an atmosphere of 10% v/v C ₂ H ₆ /H ₂ Heating from room temperature to 900K at a rate of 1K/s, switching to Ar atmosphere and cooling to room temperature, and then passivating in 1%v/v O ₂ /He atmosphere for 1h to obtain Mo ₂ C/HZSM-5 catalyst ( Calculated by the mass fraction of Mo ₂ C, the doping amount m _Mo2C /m _HZSM-5 mass ratio is 5.3%), the catalyst is labeled as 5Mo ₂ C/HZSM-5 (calculated by the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 5%).

Preparation of 10Mo ₂ C/HZSM-5 catalyst:

(1) Carrier pretreatment: at a temperature of about 773K, bake the HZSM-5 molecular sieve in a muffle furnace for 3 hours to remove organic matter such as residual templates, cool down, and set aside.

(2) Preparation of Mo/HZSM-5 catalyst: Weigh 9.30g of ammonium molybdate, add it into a beaker filled with 41.70g of deionized water, and prepare an ammonium molybdate solution with a mass concentration of 18.6%, then weigh Take this solution and 3g of the pretreated HZSM-5 molecular sieve in step (1) (calculated based on the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 10%), mix and mix quickly Mix on the instrument, then ultrasonic at room temperature for 30min, stand still for 12h, air-dry at 373K for 12h, and finally bake in a muffle furnace at 773K for 3h to obtain the Mo/HZSM-5 catalyst.

(3) Preparation of Mo ₂ C/HZSM-5 catalyst: The Mo/HZSM-5 catalyst obtained in step (2) was heated in a temperature-programmed tube furnace in an atmosphere of 10% v/v C ₂ H ₆ /H ₂ Heating from room temperature to 900K at a rate of 1K/s, switching to Ar atmosphere and cooling to room temperature, and then passivating in 1%v/v O ₂ /He atmosphere for 1h to obtain Mo ₂ C/HZSM-5 catalyst ( Calculated by the mass fraction of Mo ₂ C, the doping amount m _Mo2C /m _HZSM-5 mass ratio is 10.6%), the catalyst is labeled as 10Mo ₂ C/HZSM-5 (calculated by the mass fraction of molybdenum, the doping amount m _Mo /m _HZSM-5 mass ratio is 10%).

Performance test of Mo ₂ C/HZSM-5 catalyst:

1. XRD characterization

Carry out XRD characterization of four kinds of Mo ₂ C/HZSM-5 catalysts and HZSM-5 molecular sieve raw powder with different doping amounts in the above example 1, as shown in Figure 1, curve 1 is HZSM-5 molecular sieve, curve 2-5 They are Mo ₂ C/HZSM-5 catalysts with loadings of 1%, 3%, 5%, and 10% (calculated by mass fraction of molybdenum), respectively. The XRD characterization results show that all catalysts have the characteristic diffraction peaks of HZSM-5 raw powder, and the peak intensity does not change significantly, indicating that the loading of Mo ₂ C with different mass fractions does not destroy the crystal phase structure of HZSM-5, HZSM-5 molecular sieve The crystallinity did not decrease. No other diffraction peaks are found in the figure, indicating that the Mo species are uniformly distributed on the support.

2. XPS characterization

Carry out XPS characterization to the 3Mo ₂ C/HZSM-5 catalyst in the above-mentioned example 1, the result is shown in Figure 2, the XPS spectrum of the Mo3d electron of the Mo species in 3Mo ₂ C/HZSM-5 has three peaks, and its binding energy is respectively are 228.6eV, 232.6eV, and 235.9eV, and the integral areas of the latter two are obviously larger than the former. The Mo3d signal with a binding energy of 228.6eV can be attributed to the +2-valent molybdenum in Mo ₂ C, while the binding energies of 232.6eV and 235.9eV can be attributed to the +4-valent and +6-valent molybdenum species in molybdenum oxide, respectively. It can be seen that the passivation during the preparation of the Mo ₂ C catalyst converts most of the Mo ₂ C on the surface of the catalyst into molybdenum oxide, forming a protective layer and preventing the oxidation of Mo ₂ C in the inner layer and in the pores.

3. Py-IR characterization

The 3Mo ₂ C/HZSM-5 catalyst and the HZSM-5 molecular sieve raw powder in the above Example 1 were characterized by Py-IR at a test temperature of 373K, and the results are shown in FIG. 3 . It can be seen from Figure 3 that the two catalysts have strong absorption in the predetermined area, indicating that there are B acid and L acid on the surface of the two catalysts, and the absorption peak at ~1450cm ^-1 is the absorption peak of pyridine at the L acid position, ~1488cm ^-1 is the superimposition of the pyridine absorption peaks at the B acid and L acid, ~1540cm ^-1 is the pyridine absorption peak at the B acid site, ~1619cm ^-1 and 1635cm ^-1 represent the pyridine at the L acid site and the B acid site, respectively absorption peak. It can be seen from the size of the absorption peak that the B acid sites and L acid sites of the HZSM-5 catalyst loaded with Mo ₂ C are both reduced, that is, the total acid content is reduced.

4. Characterization of NH ₃ -TPD

The NH ₃ -TPD characterization of the 3Mo ₂ C/HZSM-5 catalyst _and the HZSM-5 molecular sieve raw powder in the above example 1 was carried out, and the results are shown in Figure 4. Regular changes. There are two peaks in the temperature-programmed desorption spectrum, which are low-temperature peak (weak acid site) and high-temperature peak (strong acid site), that is, the acid center of the catalyst is composed of weak acid center and strong acid center. From the peak area, the weak acid center is the main acid center of the catalyst, and the percentage of strong acid center is relatively small. In addition, it can be seen from the figure that the weak acid sites and strong acid sites of the molecular sieve catalyst are significantly reduced after loading Mo ₂ C, which is consistent with the analysis results of Py-IR.

Example 2

The effect of loading on the performance of Mo ₂ C/HZSM-5 catalyst for DME aromatization:

Take an appropriate amount of 1Mo ₂ C/HZSM-5, 3Mo ₂ C/HZSM-5, 5Mo ₂ C/HZSM-5, 10Mo ₂ C/HZSM-5 powder prepared in Example 1, press into tablets, mash, and sieve A granular catalyst of 40-60 meshes was obtained. Then 0.3 g of the catalyst was filled into a fixed-bed reactor with a reaction temperature of 633K and a space velocity of 1500 h ^-1 . The catalyst was first treated in N ₂ atmosphere at 633K for 30 min, and then switched to 15% DME/N ₂ raw material gas for reaction. The reaction product was analyzed online by GC-9790 gas chromatograph, and the reaction results are shown in Figure 5. The conversion rate of dimethyl ether was 100%, and the selectivity of the product aromatics of the 3Mo ₂ C/HZSM-5 catalyst reached 95.5% ( That is, the yield is 95.5%). It can be seen that the doping amount _mMo2C /m _HZSM-5 mass ratio is 3.18%, which is calculated by the mass fraction of Mo in _{Mo 2 C} /HZSM-5. When the doping amount m _Mo /m _HZSM-5 mass ratio is 3%, the catalytic efficiency of the molecular sieve catalyst is the best.

Comparative example 1

Take an appropriate amount of HZSM-5 powder, roast it in a muffle furnace at 773K for 3 hours, and then press it into tablets, crush it, and sieve it to obtain the HZSM-5 granular molecular sieve catalyst with a particle size of 40-60 mesh. The dimethyl ether aromatization performance of the catalyst was tested using the same evaluation method as in Example 2 above. The results show that the yield of aromatic products on this catalyst is 52.6%, which is much lower than 95.5% of 3Mo ₂ C/HZSM-5.

Comparative example 2

The same as the preparation method of the 3Mo/HZSM-5 catalyst in Example 1, prepare the Zn/HZSM-5 catalyst (calculated based on the mass fraction of zinc, the doping amount m _Zn /m _HZSM-5 mass ratio is 3%), the only difference The point is: replace ammonium molybdate with zinc nitrate. The dimethyl ether aromatization performance of the catalyst was detected by the evaluation method of the above-mentioned Example 2. The results show that the yield of aromatic products in this catalyst is 68.0% higher than that of HZSM-5 catalyst, but still much lower than 95.5% yield of 3Mo ₂ C/HZSM-5.

Example 3

Effect of reaction temperature on the performance of 3Mo ₂ C/HZSM-5 catalyst for aromatization of dimethyl ether:

Change the reaction temperature, use the evaluation method of Example 2 to evaluate the dimethyl ether aromatization performance of the 3Mo ₂ C/HZSM-5 catalyst, the results are shown in Figure 6, it can be seen that the Mo ₂ C/HZSM-5 catalyst The optimal reaction temperature is 633K.

Example 4

Catalyst Stability Test:

At a reaction temperature of 683K, the stability of the 3Mo ₂ C/HZSM-5 catalyst was evaluated. The evaluation method was the same as in Example 2, and the results are shown in FIG. 7 . It can be seen that the catalyst has good stability.

Claims (9)

1. a molybdenum based molecular sieve catalyst, is characterized in that described molybdenum based molecular sieve catalyst contains following percentage by weight component:

Mo ₂C：1.06％～10.6％；

HZSM-5 molecular sieve: 89.4%～98.94%.

2. a molybdenum based molecular sieve catalyst, is characterized in that described molybdenum based molecular sieve catalyst contains following percentage by weight component:

Mo ₂C：3.18％；

HZSM-5 molecular sieve: 96.82%.

3. prepare a method for molybdenum based molecular sieve catalyst as claimed in claim 1, it is characterized in that utilizing water-soluble molybdenum salt pair HZSM-5 molecular sieve to carry out modification, then obtain described molybdenum based molecular sieve catalyst by carburizing and Passivation Treatment.

4. the preparation method of molybdenum based molecular sieve catalyst as claimed in claim 3, is characterized in that comprising being prepared as follows step:

(1) HZSM-5 molecular screen primary powder is removed to the impurity of its physical absorption through roasting, pulverized, standby;

(2) according to the percentage by weight of the catalyst components of required preparation, form, take a certain amount of water-soluble molybdenum salt and be dissolved in appropriate deionized water formation maceration extract, then this maceration extract and HZSM-5 molecular sieve catalyst are uniformly mixed, standing, standby;

(3) catalyst after dipping is dry, then roasting, obtains modification Mo/HZSM-5 catalyst after cooling down;

(4) the Mo/HZSM-5 catalyst obtaining in step (3) is carried out to Carburization Treatment, after passivation, obtain described molybdenum based molecular sieve Mo ₂c/HZSM-5 catalyst.

5. the preparation method of molybdenum based molecular sieve catalyst as claimed in claim 3, is characterized in that comprising being prepared as follows step:

(1) by the roasting of HZSM-5 molecular screen primary powder, sintering temperature rises to 773K with the speed of 5～10K/min by room temperature, then under 773K condition, keeps 2～4h, is finally naturally down to room temperature;

(2) according to the percentage by weight of the catalyst components of required preparation, form, take a certain amount of water-soluble molybdenum salt and be dissolved in appropriate deionized water formation maceration extract, again this maceration extract and HZSM-5 molecular sieve catalyst are fully mixed on quick blending instrument, then ultrasonic 0.5～1h at room temperature, more standing 8～12h;

(3) catalyst after dipping is put into the dry 8～12h of baking oven of 353～393K, then roasting 2～4 hours under 673～873K, obtains modification Mo/HZSM-5 catalyst after cooling down;

(4) by the resulting modification Mo/HZSM-5 of step (3) catalyst in 10%v/v C ₂h ₆/ H ₂speed with 1K/s under atmosphere is heated to 900K from room temperature, then switches under Ar atmosphere and is cooled to room temperature, finally at 1%v/v O ₂passivation 0.5～1h under/He atmosphere, obtains described molybdenum based molecular sieve Mo ₂c/HZSM-5 catalyst.

6. the preparation method of the molybdenum based molecular sieve catalyst as described in claim 4 or 5, is characterized in that: in described step (2), water-soluble molybdenum salt used is ammonium molybdate.

7. the preparation method of the catalyst as described in claim 4 or 5, is characterized in that: described step (4) is in temperature programming tube furnace, to carry out under normal pressure.

8. the application of molybdenum based molecular sieve catalyst as claimed in claim 1 or 2 in dimethyl ether selective conversion aromatic hydrocarbons processed.

9. application as claimed in claim 8, is characterized in that the condition of described molybdenum based molecular sieve catalyst dimethyl ether selective conversion aromatic hydrocarbons reaction processed is: reaction temperature is 633K, and air speed is 1500h ^-1.

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