A coal tar hydrodesulfurization and denitrification phosphorus-doped catalyst and its preparation method

Abstract

The present invention discloses a phosphorus-doped catalyst for hydrodesulfurization and denitrification of coal tar and a preparation method thereof. In the catalyst obtained by the present invention, the weight ratio of the phosphorus content (recorded as P2O5) to the γ-alumina support is 0.1-8%, the weight ratio of the molybdenum content (recorded as MoO3) to the γ-alumina support is 1-25%, and the weight ratio of the magnesium content (recorded as MgO) to the γ-alumina support is 0.5-5%; in the preparation method of the present invention, the simultaneous use of ammonium phosphate, mannitol and tetramethylammonium bicarbonate can inhibit the damage to the pore structure during the catalyst forming process, inhibit the plugging of the pore structure of the support by the metal active components in the impregnation solution, retain the pore structure similar to that of the support, and promote the loading and dispersion of the active components; due to the use of molybdenum and magnesium active components, the phosphorus-doped catalyst has high removal rates for hydrodesulfurization and denitrification of coal tar after being modified by phosphorus doping with mannitol and tetramethylammonium bicarbonate, with a desulfurization rate as high as 99.27% and a denitrification rate as high as 99.33%.

Description

Technical Field

[0001] The invention relates to the field of hydrogenation catalysts, and in particular to a coal tar hydrodesulfurization, denitrogenation and phosphorus-doped catalyst and a preparation method thereof. Background Art

[0002] Coal tar is a byproduct of coking, coal gasification and coal chemical industry. It is a complex mixture of various substances. According to the different coal pyrolysis and distillation temperatures and process methods, coal tar can be divided into low-temperature coal tar and high-temperature coal tar. Due to the difficulty of subsequent treatment, most coal tar is not effectively utilized. Except for a part of high-temperature coal tar used to extract chemicals, most of the medium- and low-temperature coal tar and a small amount of high-temperature coal tar are used as fuel for extensive combustion. However, compared with heavy petroleum fractions, coal tar raw materials have the characteristics of high sulfur, high nitrogen, high ash, high aromatic content, high colloid and high asphaltene; a large amount of sulfides and nitrides will be produced during combustion, causing serious environmental pollution; therefore, the fine processing and effective utilization of coal tar have become more important, and the hydrogenation catalytic process can effectively remove sulfur, nitrogen and other impurities in coal tar; however, the coal tar hydrogenation catalyst faces the problem that the water produced by deoxygenation during the hydrogenation process has an adverse effect on the catalyst activity, stability and strength. At the same time, coal tar has high sulfur and nitrogen content and contains a large amount of aromatics, and the desulfurization and denitrification rates are not high. In order to catalyze aromatics, desulfurization and denitrification, the catalyst is required to have a suitable pore structure and the synergistic effect of the desulfurization and denitrification active components.

[0003] Chinese patent CN113198500A discloses a novel crude benzene hydrorefining desulfurization and denitrification catalyst, which has cobalt, molybdenum and P as main components, and aims to solve the technical problems of high cost, low catalyst activity and low life of the existing crude benzene hydrorefining desulfurization and denitrification catalyst.

[0004] Chinese patent CN102626635A discloses the preparation and application of a coal tar denitrification catalyst; it is prepared by an equal volume impregnation method using Mo and W as hydrogenation active components and mesoporous alumina as a carrier; the catalyst in this invention is mainly developed for the high nitrogen content of coal tar; it has a large specific surface area, a large pore size and a concentrated distribution, and thus exhibits the advantages of high denitrification activity and good stability, and is a special catalyst suitable for coal tar hydrodenitrogenation treatment.

[0005] Chinese patent CN114425448A discloses a hydrodesulfurization catalyst and its preparation method and application. The catalyst comprises: a carrier, a molybdenum element and a Group VIII metal element, wherein the molybdenum element is at least partially present in the catalyst in the form of carbonyl molybdenum, and the Group VIII metal element is present in the catalyst in the form of a Group VIII metal porphyrin compound. The hydrodesulfurization catalyst is used in the heavy oil fixed bed hydrodesulfurization process, can selectively hydrogenate and remove sulfur-containing compounds, and can also reduce hydrogen consumption and save energy, and can be used in the process of heavy oil fixed bed hydrogenation to produce marine fuel oil.

[0006] The above patents all use a variety of heavy metal active components, and the active components are unevenly dispersed on the carrier. Excessive loading and unsaturated dispersion will increase the cost of the catalyst and reduce its activity. The desulfurization and denitrification effects also need to be further improved, and it is impossible to achieve efficient desulfurization and denitrification effects at the same time. Summary of the invention

[0007] In view of the deficiencies of the prior art, the present invention provides a coal tar hydrodesulfurization and denitrification phosphorus-doped catalyst and a preparation method thereof. The catalyst obtained by the method of the present invention promotes the catalytic activity of magnesium and molybdenum active components under the action of mannitol, ammonium phosphate and tetramethylammonium bicarbonate, and has efficient desulfurization and denitrification activity for the hydrogenation catalysis of coal tar.

[0008] The present invention provides a coal tar hydrodesulfurization, denitrification and phosphorus-doped catalyst and a preparation method thereof, which is characterized by comprising the following process:

[0009] Step 1: Preparation of impregnation solution: Weigh a certain amount of ammonium phosphate, mannitol, and tetramethylammonium bicarbonate into a beaker, dissolve them with deionized water, and prepare an aqueous solution containing ammonium phosphate, mannitol, and tetramethylammonium bicarbonate; add magnesium source and molybdenum source catalytic active components and stir them thoroughly to obtain an impregnation solution containing active components.

[0010] Step 2: Preparation of precursor Weigh a certain amount of dried γ-alumina and put it into the above impregnation solution. Place it in a closed condition, stir it at 50-80°C for 1-4 hours, and then cook it at 100-120°C for 1-4 hours to obtain a catalyst precursor.

[0011] Step 3: Preparation of catalyst: Place the above precursor in a muffle furnace, keep it at 80-120°C for 1-4 hours, use a programmed temperature method to heat it to 450-600°C at a rate of 5-10°C / min, and calcine it for 6-12 hours to obtain a coal tar hydrodesulfurization, denitrogenation and phosphorus doped catalyst.

[0012] In the preparation method of the present invention, the molar concentration of ammonium phosphate in the aqueous solution is 0.025 moL / L - 1 moL / L, the molar concentration of mannitol is 0.05 moL / L - 2 moL / L, and the molar concentration of tetramethylammonium bicarbonate is 0.05 moL / L - 5 moL / L.

[0013] In the preparation method of the present invention, the molar concentration of the molybdenum source in the impregnating solution containing the active component is 0.01 moL / L - 1 moL / L, and the molar concentration of the magnesium source is 0.01 moL / L - 2 moL / L.

[0014] In the preparation method of the present invention, the magnesium source is selected from one or more of magnesium nitrate, magnesium chloride, magnesium sulfate, and magnesia.

[0015] In the preparation method of the present invention, the molybdenum source is selected from one or more of molybdic acid and ammonium molybdate tetrahydrate.

[0016] In the preparation method of the present invention, in step 3, the precursor stays at 110 - 120 °C for 3 - 4 hours.

[0017] In the preparation method of the present invention, the programmed temperature rise is calcined at 500 - 550 °C for 8 - 10 hours.

[0018] In the catalyst obtained by the present invention, the weight ratio of the phosphorus content (recorded as P2O5) to the γ-alumina carrier is 0.1 - 8%, the weight ratio of the molybdenum content (recorded as MoO3) to the γ-alumina carrier is 1 - 25%, and the magnesium content

[0019] (recorded as MgO) to the weight ratio of the γ-alumina carrier is 0.5 - 5%.

[0020] The application of the catalyst obtained by the preparation method of the present invention in the hydrodesulfurization and denitrification of coal tar has a desulfurization rate as high as 99.27% and a denitrification rate as high as 99.33%.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The use of mannitol and tetramethylammonium bicarbonate can inhibit the damage to the pore structure during the catalyst forming process. During the drying and calcination processes of mannitol and tetramethylammonium bicarbonate, due to volatilization and decomposition, the generated gases flow in the carrier pores, which will inhibit the blockage of the metal active components in the impregnating solution to the carrier pore structure, promote the impregnating solution to enter the catalyst carrier pore structure, and retain a pore structure similar to that of the carrier.

[0023] 2. Steaming the precursor followed by drying and calcination can further improve the catalytic activity. During the steaming process of the precursor, the slow decomposition of mannitol, tetramethylammonium bicarbonate, and ammonium phosphate occurs, and the generated gas flows through the pores of the carrier, increasing the dispersion amount of the active component and the carrier, and enabling the active component to be more uniformly and saturatedly loaded on the surface of the carrier, with less impact on the pore structure of the carrier.

[0024] 3. The use of mannitol and tetramethylammonium bicarbonate increases the loading distribution of the active component of the catalyst on the carrier, increases the catalytic activity of the catalyst, can reduce the use of the active component, and reduces the catalyst cost.

[0025] 4. The simultaneous use of ammonium phosphate, tetramethylammonium bicarbonate, and mannitol can inhibit the damage to the pore structure during the catalyst forming process. The volatilization and decomposition of the above substances will inhibit the blocking of the pore structure of the carrier by the heavy metal active component in the impregnating solution, and retain the pore structure similar to that of the catalyst and the carrier.

[0026] 5. Due to the use of molybdenum and magnesium active components, the phosphorus-doped catalyst has high removal rates for both hydrodesulfurization and denitrification of coal tar under the modification of mannitol and tetramethylammonium bicarbonate. The desulfurization rate is as high as 99.27%, and the denitrification rate is as high as 99.33%. Description of the Drawings

[0027] Figure 1 It is a scanning electron microscope photograph of the catalyst prepared in Example 3.

[0028] Figure 2 It is the X-ray energy spectrum analysis (EDS) of the catalyst prepared in Example 3.

[0029] Figure 3 It is the X-ray energy spectrum analysis (EDS) of the catalyst prepared in Comparative Example 2.

[0030] Figure 4 It is a scanning electron microscope photograph of the catalyst prepared in Comparative Example 6. Detailed Embodiments

[0031] The functions and effects of the method of the present invention will be further described below in conjunction with embodiments, but are not limited to the following embodiments.

[0032] For the preparation of the γ-alumina carrier of the present invention, a certain mass of alumina powder is weighed and mixed with water, extruded into a clover shape, and then dried and calcined at 600 °C for later use; the pore structure of the γ-alumina carrier is: BET specific surface area 205.7681 m 2 / g, pore volume 0.5105 mL / g, and average pore diameter 9.9239 nm.

[0033] Example 1

[0034] Weigh 7.5 g of ammonium phosphate, 9.1 g of mannitol, and 13.5 g of tetramethylammonium bicarbonate and place them in a beaker. Add 100 ml of deionized water to the beaker and stir magnetically until the solid substances are completely dissolved to obtain an aqueous solution. Add 7.4 g of magnesium nitrate and 24.7 g of ammonium molybdate tetrahydrate (CAS: 12054-85-2) to the above solution and stir well to obtain an impregnation solution containing magnesium and molybdenum active components. Weigh 100 g of γ-alumina support dried at 120 °C and impregnate it with the above impregnation solution. Under closed conditions, stir at 50 °C for 2 hours and then cook at 100 °C for 4 hours to obtain a catalyst precursor. Place the precursor in a muffle furnace, stay at 110 °C for 4 hours, and use the programmed heating method to heat to 550 °C at a rate of 10 °C / min and calcine for 10 hours to obtain a coal tar hydrodesulfurization and denitrification phosphorus-doped catalyst.

[0035] Example 2

[0036] Weigh 7.5 g of ammonium phosphate, 13.7 g of mannitol, and 13.5 g of tetramethylammonium bicarbonate and place them in a beaker. Add 100 ml of deionized water to the beaker and stir magnetically until the solid substances are completely dissolved to obtain an aqueous solution. Add 7.4 g of magnesium nitrate and 24.7 g of ammonium molybdate tetrahydrate (CAS: 12054-85-2) to the above solution and stir well to obtain an impregnation solution containing magnesium and molybdenum active components. Weigh 100 g of γ-alumina support dried at 120 °C and impregnate it with the above impregnation solution. Under closed conditions, stir at 50 °C for 2 hours and then cook at 100 °C for 4 hours to obtain a catalyst precursor. Place the precursor in a muffle furnace, stay at 110 °C for 4 hours, and use the programmed heating method to heat to 550 °C at a rate of 10 °C / min and calcine for 10 hours to obtain a coal tar hydrodesulfurization and denitrification phosphorus-doped catalyst.

[0037] Example 3

[0038] Weigh 7.5 g of ammonium phosphate, 18.2 g of mannitol, and 13.5 g of tetramethylammonium bicarbonate and place them in a beaker. Add 100 ml of deionized water to the beaker and stir magnetically until the solid substances are completely dissolved to obtain an aqueous solution. Add 7.4 g of magnesium nitrate and 24.7 g of ammonium molybdate tetrahydrate (CAS: 12054-85-2) to the above solution and stir well to obtain an impregnation solution containing magnesium and molybdenum active components. Weigh 100 g of γ-alumina support dried at 120 °C and impregnate it with the above impregnation solution. Under closed conditions, stir at 50 °C for 2 hours and then cook at 100 °C for 4 hours to obtain a catalyst precursor. Place the precursor in a muffle furnace, stay at 110 °C for 4 hours, and use the programmed heating method to heat to 550 °C at a rate of 10 °C / min and calcine for 10 hours to obtain a coal tar hydrodesulfurization and denitrification phosphorus-doped catalyst.

[0039] Example 4

[0040] Weigh 7.5 g of ammonium phosphate, 18.2 g of mannitol and 13.5 g of tetramethylammonium bicarbonate and place them in a beaker. Add 100 ml of deionized water to the beaker and stir magnetically to completely dissolve the solid substances to obtain an aqueous solution. Add 14.8 g of magnesium nitrate and 24.7 g of ammonium molybdate tetrahydrate (CAS: 12054-85-2) to the above solution and stir well to obtain an impregnation solution containing magnesium and molybdenum active components. Weigh 100 g of γ-alumina support dried at 120 °C and impregnate it with the above impregnation solution. Under airtight conditions, stir at 50 °C for 2 hours and then cook at 100 °C for 4 hours to obtain a catalyst precursor. Place the precursor in a muffle furnace, stay at 110 °C for 4 hours, and use the programmed heating method to raise the temperature to 550 °C at a rate of 10 °C / min and calcine for 10 hours to obtain a coal tar hydrodesulfurization and denitrogenation phosphorus-doped catalyst.

[0041] Example 5

[0042] The same method as in Example 3 is adopted, except that 12.4 g of ammonium molybdate is used.

[0043] Example 6

[0044] The same method as in Example 3 is adopted, except that 3.8 g of ammonium phosphate is used.

[0045] Example 7

[0046] The same method as in Example 3 is adopted, except that 6.75 g of tetramethylammonium bicarbonate is used.

[0047] Comparative Examples 1-5

[0048] The same method as in Example 3 is adopted, except that in Comparative Examples 1-3, ammonium phosphate, mannitol and tetramethylammonium bicarbonate are not added respectively, in Comparative Example 4, 3.6 g of mannitol is used, and in Comparative Example 5, 3.6 g of mannitol and 6.75 g of tetramethylammonium bicarbonate are used.

[0049] Comparative Example 6

[0050] Weigh 7.5 g of ammonium phosphate, 18.2 g of mannitol and 13.5 g of tetramethylammonium bicarbonate and place them in a beaker. Add 100 ml of deionized water to the beaker and stir magnetically to completely dissolve the solid substances, obtaining an aqueous solution. Add 7.4 g of magnesium nitrate and 24.7 g of ammonium molybdate tetrahydrate (CAS: 12054-85-2) to the above solution and stir thoroughly to obtain an impregnating solution containing magnesium and molybdenum active components. Weigh 100 g of γ-alumina support dried at 120 °C and impregnate it with the above impregnating solution. Stir at 50 °C for 2 hours to obtain a catalyst precursor. Place the precursor in a muffle furnace, stay at 110 °C for 4 hours, and use a programmed heating method to heat to 550 °C at a rate of 10 °C / min and calcine for 10 hours to obtain a phosphorus-doped catalyst for coal tar hydrodesulfurization and denitrification.

[0051] Comparative Example 7

[0052] Weigh 7.5 g of ammonium phosphate, 18.2 g of mannitol and 13.5 g of tetramethylammonium bicarbonate and place them in a high-pressure reactor. Add 100 ml of deionized water to the reactor and stir magnetically to completely dissolve the solid substances, obtaining an aqueous solution. Add 7.4 g of magnesium nitrate and 24.7 g of ammonium molybdate tetrahydrate (CAS: 12054-85-2) to the above solution and stir thoroughly to obtain an impregnating solution containing magnesium and molybdenum active components. Weigh 100 g of γ-alumina support dried at 120 °C and impregnate it with the above impregnating solution to obtain a catalyst precursor. Place the precursor in a muffle furnace, stay at 180 °C for 4 hours, cool to room temperature, filter and wash with water to obtain a catalyst semi-finished product, dry at 120 °C for 4 hours, and then calcine at 550 °C for 10 hours to obtain a phosphorus-doped catalyst for coal tar hydrodesulfurization and denitrification.

[0053] Table 1 Composition and pore structure distribution of the catalysts prepared according to the examples and comparative examples of the present application

[0054]

[0055] Coal tar hydrotreating experimental evaluation of the catalysts prepared according to Examples 1-7 and Comparative Examples 1-7 of the present application:

[0056] Hydrotreating experiment: Place the catalyst in a reactor and pre-sulfurize it at 160 °C for 10 hours. The sulfurizing solution is kerosene containing 2.5% carbon disulfide. Using the prepared coal tar for the modulation experiment as the raw material, under the conditions of a temperature of 460 °C, a pressure of 11.2 MPa, a volume space velocity of 0.4 h -1 , and a hydrogen-oil ratio of 1800:1, use the catalysts prepared in the examples and comparative examples of the present invention for catalytic hydrotreating experiments. Use 0.1 g of catalyst for every 1000 g of the coal tar for the modulation experiment.

[0057] The properties of the prepared coal tar for the modulation experiment are as follows:

[0058]

[0059]

[0060] Table 2 Properties of the coal tar effluent after hydrocatalytic hydrogenation

[0061]

[0062] As can be seen from Table 1, the surface pore structure of the catalyst support will change after being impregnated to prepare the catalyst. The addition of mannitol, ammonium phosphate, and tetramethylammonium bicarbonate inhibits the damage of the impregnating solution to the pore structure of the support. In Comparative Example 2, mannitol was not used, and the specific surface area of the obtained catalyst decreased by up to 63%, and the pore volume decreased by up to 29%. As the amount of mannitol used increased within a certain range, the pore structure of the catalyst was better protected; Example 6 showed that the decrease in the amount of ammonium phosphate used would also reduce the specific surface area of the support; Comparative Examples 3-5 showed that the addition and change in the amount of tetramethylammonium bicarbonate would also affect the pore structure, and ammonium phosphate, mannitol, and tetramethylammonium bicarbonate need to be controlled within a certain range.

[0063] As can be seen from Tables 1-2, the catalyst has high desulfurization and denitrification efficiencies at the same time. The desulfurization rate is as high as 99.27%, and the denitrification rate is as high as 99.33%; comparing Comparative Examples 1-5 with the Examples, it can be seen that phosphorus doping can improve the desulfurization and denitrification efficiencies, and the catalytic activity of the catalyst without phosphorus is lower; comparing Comparative Examples 6-7 with the Examples shows that steaming the catalyst precursor can improve the catalytic activity. At the same time, steaming the precursor also has higher activity compared to hydrothermal treatment.

[0064] From Figure 2-3 it can be seen that the X-ray energy spectrum analysis (EDS) of the catalyst without using mannitol, tetramethylammonium bicarbonate, etc. shows that the content of the Mo active component decreases. Combining its pore structure, it can be seen that the active component may block the pores, resulting in the support being unable to load more active components, which is also an explanation for the decrease in the activity of the above catalyst.

[0065] From Figure 1 and Figure 4 it can be seen that the surface particles of the catalyst obtained without going through the steaming process formed agglomerates, resulting in a large change in the pore structure.

[0066] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a coal tar hydrodesulfurization and denitrification phosphorus-doped catalyst, characterized in that It includes the following processes: Step 1: Preparation of the impregnation solution. Weigh a certain amount of ammonium phosphate, mannitol, and tetramethylammonium bicarbonate and place them in a beaker. Dissolve them with deionized water to prepare an aqueous solution containing ammonium phosphate, mannitol, and tetramethylammonium bicarbonate. Add the magnesium source and molybdenum source catalytic active components and stir well to obtain an impregnation solution containing the active components; Step 2: Preparation of the precursor. Weigh a certain amount of dried γ-alumina and put it into the above impregnation solution. Place it under closed conditions and stir at 50 - 80°C for 1 - 4 hours, then cook at 100 - 120°C for 1 - 4 hours to obtain the catalyst precursor; Step 3: Preparation of the catalyst. Place the above precursor in a muffle furnace, stay at 80 - 120°C for 1 - 4 hours for drying, and use the programmed temperature rising method to raise the temperature to 450 - 600°C at a rate of 5 - 10°C / min and calcine for 6 - 12 hours to obtain the coal tar hydrodesulfurization and denitrogenation phosphorus-doped catalyst.

2. The method according to claim 1, wherein The molar concentration of ammonium phosphate in the aqueous solution is 0.025 moL / L - 1 moL / L, the molar concentration of mannitol is 0.05 moL / L - 2 moL / L, and the molar concentration of tetramethylammonium bicarbonate is 0.05 moL / L - 5 moL / L.

3. The method according to claim 1, wherein In the impregnation solution containing the active components, the molar concentration of the molybdenum source is 0.01 moL / L - 1 moL / L, and the molar concentration of the magnesium source is 0.01 moL / L - 2 moL / L.

4. The method according to claim 1, characterized in that The magnesium source is selected from one or more of magnesium nitrate, magnesium chloride, magnesium sulfate, and magnesia.

5. The method according to claim 1, wherein The molybdenum source is selected from one or more of molybdic acid and ammonium molybdate tetrahydrate.

6. The method according to claim 1, wherein In Step 2, after stirring at 50°C for 1 - 2 hours, cook at 100 - 120°C for 4 hours.

7. The method according to claim 1, characterized in that In Step 3, the precursor stays at 110 - 120°C for 4 hours for drying.

8. The method according to claim 1, wherein After the programmed temperature rising, calcine at 500 - 550°C for 8 - 10 hours.

9. The coal tar hydrodesulfurization and denitrogenation phosphorus-doped catalyst prepared by the method according to any one of claims 1 - 8, wherein the weight ratio of the phosphorus content (recorded as P2O5) to the γ-alumina carrier in the catalyst is 0.1 - 8%, the weight ratio of the molybdenum content (recorded as MoO3) to the γ-alumina carrier is 1 - 25%, and the weight ratio of the magnesium content (recorded as MgO) to the γ-alumina carrier is 0.5 - 5%.

10. The application of the catalyst prepared by the method according to any one of claims 1 - 8 or the catalyst according to claim 9 in coal tar hydrodesulfurization and denitrogenation, with a desulfurization rate as high as 99.27% and a denitrogenation rate as high as 99.33%.

Images