A method for preparing aromatic hydrocarbons from methanol

Abstract

The present invention relates to a method for preparing aromatic hydrocarbons from methanol, belonging to the technical field of methanol to aromatic hydrocarbons. In the present invention, two inorganic acids (selenic acid and boric acid) and two metal salts (magnesium salt and bismuth salt) are used to modify the HZSM-5 molecular sieve after alkalization treatment with ammonia water, which can effectively improve the conversion rate of methanol aromatization reaction, the yield of BTX, the yield of trimethylbenzene and the yield of total aromatic hydrocarbons.

Description

Technical Field

[0001] The present invention relates to a method for preparing aromatic hydrocarbons from methanol, belonging to the technical field of methanol to aromatic hydrocarbons. Background Art

[0002] Aromatic hydrocarbons are organic compounds containing benzene rings. Aromatic hydrocarbons were originally sourced from crude benzene and coal tar in the coal coking industry in the early days, and were later replaced by petroleum catalytic reforming and gasoline cracking. Currently, they account for more than 90% of all aromatic hydrocarbon sources. In China, however, petroleum and natural gas resources are extremely scarce, while coal resources are relatively abundant. Therefore, the process of preparing aromatic hydrocarbons from methanol has become a research hotspot. The conversion process of preparing aromatic hydrocarbons from methanol is as follows: First, methanol is dehydrated to form dimethyl ether; then, methanol / dimethyl ether is catalytically converted to light olefins on the acid sites of the catalyst; finally, the light olefins are converted into a mixture of long-chain olefins, alkanes, aromatic hydrocarbons, etc. through reactions such as dehydrogenation, cyclization, and hydrogen transfer.

[0003] Due to its optimal acidity and appropriate pore size, ZSM-5 molecular sieve is widely used as a catalyst for methanol to aromatic hydrocarbons. However, currently, the conversion rate and aromatic hydrocarbon yield of catalytically preparing aromatic hydrocarbons from methanol using conventional ZSM-5 molecular sieve are both relatively low. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing aromatic hydrocarbons from methanol to solve the problem of relatively low conversion rate and aromatic hydrocarbon yield in the current preparation of aromatic hydrocarbons from methanol.

[0005] The present invention provides a method for preparing aromatic hydrocarbons from methanol, comprising the following steps: subjecting methanol to aromatization reaction using a catalyst, and the preparation method of the catalyst is as follows: immersing the original powder of HZSM-5 molecular sieve in ammonia water with a concentration of 0.8 - 1.2 mol / L for a mixing reaction, and then immersing it in ammonium nitrate solution for a displacement reaction to obtain alkali-treated molecular sieve powder; then adsorbing the modified agent solution on the alkali-treated molecular sieve powder, drying, and calcining to obtain the catalyst. The modified agent solution is composed of selenic acid, boric acid, magnesium nitrate, bismuth nitrate, and water. The mass ratio of the alkali-treated molecular sieve powder, the mass of selenium element in selenic acid, the mass of boron element in boric acid, the mass of magnesium element in magnesium nitrate, and the mass of bismuth element in bismuth nitrate is 100:(0.4 - 0.6):(0.8 - 1):(0.9 - 1.2):(0.7 - 0.9).

[0006] Preferably, the volume of ammonia water corresponding to every 10 g of the original powder of HZSM-5 molecular sieve is 120 - 150 mL.

[0007] Preferably, the molar ratio of SiO2 to Al2O3 in the original powder of HZSM-5 molecular sieve is 38 - 60, and the specific surface area is 350 - 355 m 2 / g.

[0008] Preferably, the temperature of the mixing reaction is 60 - 70°C and the time is 1 - 1.5 h.

[0009] Preferably, after the mixing reaction is completed, solid-liquid separation is carried out. The solid obtained from the solid-liquid separation is washed, dried, immersed in an ammonium nitrate solution for a displacement reaction. After the displacement reaction is completed, solid-liquid separation is carried out again. The solid obtained from the solid-liquid separation is washed and dried to obtain the alkali-treated molecular sieve powder.

[0010] Preferably, the displacement reaction includes a first displacement reaction and a second displacement reaction; the temperature of the first displacement reaction is 80 - 90°C and the time is 4 - 6 h; the temperature of the second displacement reaction is 80 - 90°C and the time is 4 - 6 h.

[0011] Preferably, the temperature of the drying is 80 - 90°C.

[0012] Preferably, the temperature of the calcination is 580 - 620°C and the time is 4 - 6 h.

[0013] Preferably, the particle size of the catalyst is 60 - 80 mesh.

[0014] Preferably, the temperature for the aromatization reaction of methanol is 340 - 500°C and the pressure is 0.02 - 0.06 MPa.

[0015] The beneficial effects of the present invention are as follows:

[0016] (1) By using ammonia water with an appropriate concentration to alkalize the HZSM-5 molecular sieve, the present invention can increase the mesoporous channels of the HZSM-5 molecular sieve, which is beneficial to the later loading and fixation of metal and non-metal ions and the progress of the methanol aromatization reaction, thereby improving the conversion rate of methanol, the yield of BTX, the yield of trimethylbenzene, and the yield of total aromatics.

[0017] (2) By using a combination of selenic acid and boric acid, the present invention can improve the conversion rate of the methanol aromatization reaction, the yield of BTX, the yield of trimethylbenzene, and the yield of total aromatics more effectively than the combination of either of them with phosphoric acid.

[0018] (3) By using magnesium salts and bismuth salts to modify the HZSM-5 molecular sieve, the present invention can work together with selenic acid and boric acid to improve the conversion rate of the methanol aromatization reaction, the yield of BTX, the yield of trimethylbenzene, and the yield of total aromatics.

[0019] (4) By using two inorganic acids (selenic acid and boric acid) and two metal salts (magnesium salt and bismuth salt) to modify the HZSM-5 molecular sieve after alkalization treatment with ammonia water, the present invention can enable each step to play a synergistic role before and after, effectively improving the conversion rate of methanol aromatization reaction, the yield of BTX, the yield of trimethylbenzene, and the yield of total aromatics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the comparison results of the average value of methanol conversion rate, the average value of the yield of BTX (benzene, toluene, and xylene), the average value of the yield of trimethylbenzene, and the average value of the yield of total aromatics in the preparation methods of each example and comparative example in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following examples are intended to further illustrate the content of the present invention rather than limit the protection scope of the present invention.

[0022] Example 1

[0023] The method for preparing aromatics from methanol in this example includes the following steps:

[0024] (1) Add 10 g of the original powder of HZSM-5 molecular sieve (the molar ratio of SiO2 to Al2O3 is 38, and the specific surface area is 352 m 2 / g) into 120 mL of ammonia water with a concentration of 0.8 mol / L, stir evenly, then heat up to 60 °C, stir and reflux for 1 h. After cooling to room temperature, filter. First, rinse the filter cake with dilute hydrochloric acid to neutralize the weak base solution on the surface of the molecular sieve, then wash it with distilled water until neutral, and then put it into a blast drying oven and dry it at 100 °C for 12 h to obtain the alkaline molecular sieve.

[0025] (2) Place the alkaline molecular sieve obtained in step (1) into 200 mL of ammonium nitrate solution with a concentration of 1 mol / L, stir evenly, then heat to 80 °C, stir and reflux for 4 h, filter. Then place the filter cake into 300 mL of ammonium nitrate solution with a concentration of 1 mol / L, stir evenly, then heat to 80 °C, stir and reflux for 4 h, filter. Place the filter cake into a blast drying oven and dry it at 100 °C for 12 h to obtain the alkali-treated molecular sieve powder.

[0026] (3) According to the equal-volume impregnation method, the modifier solution was uniformly dropped onto the alkali-treated molecular sieve powder, and the mass of water in the modifier solution was equal to the saturated water adsorption capacity of the alkali-treated molecular sieve; the modifier solution was prepared by mixing selenic acid, boric acid, magnesium nitrate, bismuth nitrate and water. The mass ratio of the alkali-treated molecular sieve, the mass of selenium element in selenic acid, the mass of boron element in boric acid, the mass of magnesium element in magnesium nitrate and the mass of bismuth element in bismuth nitrate was 100:0.4:0.8:0.9:0.7; then the molecular sieve powder adsorbed with the modifier solution was placed in an ultrasonic cleaner for ultrasonic treatment to uniformly disperse the modifier solution in the molecular sieve powder; then the molecular sieve powder adsorbed with the modifier solution was dried at 80 °C for 12 h, and finally the dried solid was ground and placed in a muffle furnace and calcined at 580 °C for 4 h. After cooling to room temperature, the modified HZSM-5 molecular sieve was obtained. The modified HZSM-5 molecular sieve was tableted, ground, sieved, and the particles with a particle size of 60-80 mesh were collected to obtain the catalyst.

[0027] (4) 7 g of the catalyst and 3 g of inert carrier quartz sand were stirred evenly and filled into the middle constant temperature section of a stainless steel reactor with an inner diameter of 10 mm and a length of 900 mm. Then, inert carrier quartz sand was filled at the upper and lower ends of the reactor. Then, nitrogen was introduced into the reactor at a flow rate of 30 mL / min. At the same time, the reactor was heated to the reaction temperature and purged for 2 h. Then, raw material methanol was pumped in with a double plunger micro pump to make methanol contact and react with the catalyst in the reactor. The reaction temperature was 340 °C, the reaction pressure was 0.02 MPa, and the methanol mass space velocity was 0.8 / h.

[0028] Example 2

[0029] The method for preparing aromatics from methanol in this example includes the following steps:

[0030] (1) 10 g of the original powder of HZSM-5 molecular sieve (the molar ratio of SiO2 and Al2O3 was 46, and the specific surface area was 355 m 2 / g) was added to 130 mL of ammonia water with a concentration of 1 mol / L, stirred evenly, then heated to 65 °C, stirred and refluxed for 1.2 h. After cooling to room temperature, it was filtered. The filter cake was first rinsed with dilute hydrochloric acid to neutralize the weak base solution on the surface of the molecular sieve, then washed with distilled water to neutrality, and then placed in a blast drying oven and dried at 100 °C for 12 h to obtain the alkaline molecular sieve.

[0031] (2) The alkaline molecular sieve obtained in step (1) is placed in 200 mL of ammonium nitrate solution with a concentration of 1 mol / L, stirred evenly, heated to 85 °C, stirred and refluxed for 5 h, filtered, and then the filter cake is placed in 300 mL of ammonium nitrate solution with a concentration of 1 mol / L, stirred evenly, heated to 85 °C, stirred and refluxed for 5 h, filtered, and the filter cake is placed in a blast drying oven and dried at 100 °C for 12 h to obtain an alkali-treated molecular sieve powder.

[0032] (3) According to the equal-volume impregnation method, the modifier solution is evenly dropped onto the alkali-treated molecular sieve powder, and the mass of water in the modifier solution is equal to the saturated water adsorption capacity of the alkali-treated molecular sieve; the modifier solution is prepared by mixing selenic acid, boric acid, magnesium nitrate, bismuth nitrate and water, and the mass ratio of the alkali-treated molecular sieve, the mass of selenium element in selenic acid, the mass of boron element in boric acid, the mass of magnesium element in magnesium nitrate and the mass of bismuth element in bismuth nitrate is 100:0.5:0.9:1:0.8; then the molecular sieve powder adsorbed with the modifier solution is placed in an ultrasonic cleaner for ultrasonic treatment to make the modifier solution evenly dispersed in the molecular sieve powder; then the molecular sieve powder adsorbed with the modifier solution is dried at 85 °C for 12 h, and finally the dried solid is ground and placed in a muffle furnace and calcined at 600 °C for 5 h, and after cooling to room temperature, a modified HZSM-5 molecular sieve is obtained. The modified HZSM-5 molecular sieve is tableted, ground, sieved, and particles with a particle size of 60-80 mesh are collected to obtain a catalyst.

[0033] (4) 7 g of the catalyst and 3 g of inert carrier quartz sand are stirred evenly and filled into the middle constant temperature section of a stainless steel reactor with an inner diameter of 10 mm and a length of 900 mm, and then inert carrier quartz sand is filled at the upper and lower ends of the reactor respectively. Then, nitrogen is introduced into the reactor at a flow rate of 30 mL / min, and at the same time, the reactor is heated to the reaction temperature and purged for 2 h. Then, raw material methanol is pumped in with a double plunger micro pump to make methanol contact and react with the catalyst in the reactor. The reaction temperature is 400 °C, the reaction pressure is 0.04 MPa, and the methanol mass space velocity is 1 / h.

[0034] Example 3

[0035] The method for preparing aromatics from methanol in this example includes the following steps:

[0036] (1) 10 g of the original powder of HZSM-5 molecular sieve (the molar ratio of SiO2 and Al2O3 is 60, and the specific surface area is 350 m 2(g) was added to 150 mL of ammonia water with a concentration of 1.2 mol / L, stirred evenly, then heated to 70 °C, stirred and refluxed for 1.5 h. After cooling to room temperature, it was filtered. The filter cake was first rinsed with dilute hydrochloric acid to neutralize the weak base solution on the surface of the molecular sieve, then washed with distilled water until neutral, and then placed in a blast drying oven and dried at 100 °C for 12 h to obtain basic molecular sieve.

[0037] (2) The basic molecular sieve obtained in step (1) was placed in 200 mL of ammonium nitrate solution with a concentration of 1 mol / L, stirred evenly and heated to 90 °C, stirred and refluxed for 6 h, filtered, and then the filter cake was placed in 300 mL of ammonium nitrate solution with a concentration of 1 mol / L, stirred evenly and heated to 90 °C, stirred and refluxed for 6 h, filtered, and the filter cake was placed in a blast drying oven and dried at 100 °C for 12 h to obtain alkali-treated molecular sieve powder.

[0038] (3) According to the equal-volume impregnation method, the modifier solution was evenly dropped onto the alkali-treated molecular sieve powder. The mass of water in the modifier solution was equal to the saturated water adsorption capacity of the alkali-treated molecular sieve. The modifier solution was prepared by mixing selenic acid, boric acid, magnesium nitrate, bismuth nitrate and water. The mass ratio of the alkali-treated molecular sieve, the mass of selenium element in selenic acid, the mass of boron element in boric acid, the mass of magnesium element in magnesium nitrate and the mass of bismuth element in bismuth nitrate was 100:0.6:1:1.2:0.9. Then the molecular sieve powder adsorbed with the modifier solution was placed in an ultrasonic cleaner for ultrasonic treatment to make the modifier solution evenly disperse in the molecular sieve powder. Then the molecular sieve powder adsorbed with the modifier solution was dried at 90 °C for 12 h. Finally, the dried solid was ground and placed in a muffle furnace and calcined at 620 °C for 6 h. After cooling to room temperature, modified HZSM-5 molecular sieve was obtained. The modified HZSM-5 molecular sieve was tableted, ground, sieved, and the particles with a particle size of 60 - 80 meshes were collected to obtain the catalyst.

[0039] (4) 7 g of the catalyst and 3 g of inert carrier quartz sand were stirred evenly and filled into the middle constant temperature section of a stainless steel reactor with an inner diameter of 10 mm and a length of 900 mm. Then inert carrier quartz sand was filled at the upper and lower ends of the reactor respectively. Then nitrogen was introduced into the reactor at a flow rate of 30 mL / min. At the same time, the reactor was heated to the reaction temperature and purged for 2 h. Then raw material methanol was pumped in with a double plunger micro pump to make methanol contact and react with the catalyst in the reactor. The reaction temperature was 500 °C, the reaction pressure was 0.06 MPa, and the methanol mass space velocity was 1.5 / h.

[0040] Comparative Example 1

[0041] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, magnesium nitrate is replaced with aluminum nitrate.

[0042] Comparative Example 2

[0043] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, magnesium nitrate is replaced with iron nitrate.

[0044] Comparative Example 3

[0045] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, magnesium nitrate is replaced with potassium nitrate.

[0046] Comparative Example 4

[0047] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, magnesium nitrate is replaced with zinc nitrate.

[0048] Comparative Example 5

[0049] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, magnesium nitrate is replaced with cadmium nitrate.

[0050] Comparative Example 6

[0051] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, magnesium nitrate is replaced with lanthanum nitrate.

[0052] Comparative Example 7

[0053] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, magnesium nitrate is replaced with cobalt nitrate.

[0054] Comparative Example 8

[0055] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, bismuth nitrate is replaced with aluminum nitrate.

[0056] Comparative Example 9

[0057] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, bismuth nitrate is replaced by iron nitrate.

[0058] Comparative Example 10

[0059] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, bismuth nitrate is replaced by potassium nitrate.

[0060] Comparative Example 11

[0061] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, bismuth nitrate is replaced by zinc nitrate.

[0062] Comparative Example 12

[0063] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, bismuth nitrate is replaced by cadmium nitrate.

[0064] Comparative Example 13

[0065] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, bismuth nitrate is replaced by lanthanum nitrate.

[0066] Comparative Example 14

[0067] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, bismuth nitrate is replaced by cobalt nitrate.

[0068] Comparative Example 15

[0069] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, boric acid is replaced by phosphoric acid.

[0070] Comparative Example 16

[0071] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, selenic acid is replaced by phosphoric acid.

[0072] Comparative Example 17

[0073] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that the concentration of ammonia water used in step (1) of the method for preparing aromatic hydrocarbons from methanol in this comparative example is 0.6 mol / L.

[0074] Comparative Example 18

[0075] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that the concentration of ammonia water used in step (1) of the method for preparing aromatic hydrocarbons from methanol in this comparative example is 1.4 mol / L.

[0076] Comparative Example 19

[0077] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (1) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, ammonia water is replaced with a tetramethylammonium hydroxide solution of the same concentration.

[0078] Comparative Example 20

[0079] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (1) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, ammonia water is replaced with a sodium hydroxide solution of the same concentration.

[0080] Comparative Example 21

[0081] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, the modifier solution is prepared by mixing selenic acid, boric acid, magnesium nitrate and water, and the mass ratio of the alkali-treated molecular sieve, the mass of selenium element in selenic acid, the mass of boron element in boric acid and the mass of magnesium element in magnesium nitrate is 100:0.6:1:2.1.

[0082] Comparative Example 22

[0083] The difference between the method for preparing aromatic hydrocarbons from methanol in this comparative example and the method for preparing aromatic hydrocarbons from methanol in Example 1 is only that in step (3) of the method for preparing aromatic hydrocarbons from methanol in this comparative example, the modifier solution is prepared by mixing selenic acid, boric acid, bismuth nitrate and water, and the mass ratio of the alkali-treated molecular sieve, the mass of selenium element in selenic acid, the mass of boron element in boric acid and the mass of bismuth element in bismuth nitrate is 100:0.6:1:2.1.

[0084] Comparative Example 23

[0085] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, the modifier solution is prepared by mixing selenic acid, magnesium nitrate, bismuth nitrate and water, and the mass ratio of the alkali-treated molecular sieve, the mass of selenium element in selenic acid, the mass of magnesium element in magnesium nitrate and the mass of bismuth element in bismuth nitrate is 100:1.6:1.2:0.9.

[0086] Comparative Example 24

[0087] The difference between the method for preparing aromatics from methanol in this comparative example and the method for preparing aromatics from methanol in Example 1 is only that in step (3) of the method for preparing aromatics from methanol in this comparative example, the modifier solution is prepared by mixing boric acid, magnesium nitrate, bismuth nitrate and water, and the mass ratio of the alkali-treated molecular sieve, the mass of boron element in boric acid, the mass of magnesium element in magnesium nitrate and the mass of bismuth element in bismuth nitrate is 100:1.6:1.2:0.9.

[0088] The reaction products of each example and comparative example at a total of three sampling times of 1 h, 2 h and 3 h of the reaction were subjected to chromatographic analysis. According to the analysis results, the methanol conversion rate, the yields of BTX (benzene, toluene and xylene), the yield of trimethylbenzene and the yield of total aromatics at each sampling time were calculated. The average value of the methanol conversion rate, the average value of the yield of BTX (benzene, toluene and xylene), the average value of the yield of trimethylbenzene and the average value of the yield of total aromatics at the three sampling times were calculated. The results are shown in Table 1 and Figure 1 as shown.

[0089] Table 1 Average values of methanol conversion rate, average values of yields of BTX, average values of yields of trimethylbenzene and average values of yields of total aromatics in each example and comparative example

[0090]

[0091] As can be seen from Table 1 and Figure 1 It can be seen that compared with other metal elements, modifying the HZSM-5 molecular sieve with magnesium element and bismuth element together with selenic acid and boric acid can effectively improve the yields of BTX, trimethylbenzene and total aromatics in the preparation of aromatics from methanol; compared with phosphoric acid, modifying the HZSM-5 molecular sieve with selenic acid and boric acid simultaneously can effectively improve the yields of BTX, trimethylbenzene and total aromatics in the preparation of aromatics from methanol; by selecting an appropriate concentration of ammonia water, the mesoporous channels of the HZSM-5 molecular sieve can be increased, which is conducive to the loading and fixation of metal and non-metal ions and the progress of the methanol aromatization reaction, thereby improving the methanol conversion rate, the yields of BTX, trimethylbenzene and total aromatics.

Claims

1. A method for preparing aromatics from methanol, characterized in that: The following steps are involved: A catalyst is used to carry out an aromatization reaction of methanol. The preparation method of the catalyst is as follows: HZSM-5 molecular sieve raw powder is immersed in ammonia water with a concentration of 0.8-1.2 mol / L for a mixed reaction. After the mixed reaction is completed, solid-liquid separation is performed, and the solid obtained by the solid-liquid separation is washed and dried. The solid is immersed in an ammonium nitrate solution for a replacement reaction. After the replacement reaction is completed, the solid-liquid separation is performed, and the solid obtained by the solid-liquid separation is washed and dried to obtain an alkali-treated molecular sieve powder; the alkali-treated molecular sieve powder is then adsorbed with a modifier solution. , dried, and calcined to obtain a catalyst, wherein the modifier solution consists of selenic acid, boric acid, magnesium nitrate, bismuth nitrate and water, and the ratio of the mass of the alkali-treated molecular sieve powder, the mass of the selenium element in the selenic acid, the mass of the boron element in the boric acid, the mass of the magnesium element in the magnesium nitrate and the mass of the bismuth element in the bismuth nitrate is 100:(0.4-0.6):(0.8-1):(0.9-1.2):(0.7-0.9); the volume of ammonia water used for every 10g of the HZSM-5 molecular sieve raw powder is 120-150mL.

2. The method for preparing aromatics from methanol according to claim 1, characterized in that: The molar ratio of SiO2 to Al2O3 in the HZSM-5 molecular sieve raw powder is 38-60, and the specific surface area is 350-355m 2 / g.

3. The method for preparing aromatics from methanol according to claim 1, characterized in that: The temperature of the mixed reaction is 60-70° C. and the time is 1-1.5 h.

4. The method for preparing aromatics from methanol according to claim 1, characterized in that: The replacement reaction includes a first replacement reaction and a second replacement reaction; the temperature of the first replacement reaction is 80-90° C. and the time is 4-6 hours; the temperature of the second replacement reaction is 80-90° C. and the time is 4-6 hours.

5. The method for preparing aromatics from methanol according to claim 1, characterized in that: The drying temperature is 80-90°C.

6. The method for preparing aromatics from methanol according to claim 1 or 5, characterized in that: The calcination temperature is 580-620° C. and the calcination time is 4-6 hours.

7. The method for preparing aromatics from methanol according to claim 1, characterized in that: The particle size of the catalyst is 60-80 mesh.

8. The method for preparing aromatics from methanol according to claim 1, characterized in that: The temperature for aromatization of methanol is 340~500℃ and the pressure is 0.02~0.06MPa.

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