A process for preparing a hydrodesulfurization catalyst

Abstract

The application discloses a preparation method of a hydrodesulfurization catalyst, which comprises the following steps: (1) preparing a phosphorus-modified gamma phase alumina carrier; (2) immersing the phosphorus-modified gamma phase alumina carrier into an epoxy propane aqueous solution to perform low-temperature and high-temperature two-stage sealed heat treatment, and then performing drying treatment to obtain a composite crystal phase alumina carrier; and (3) immersing the composite crystal phase alumina carrier into an active component impregnation solution, and performing drying and calcination on the immersed material to obtain the hydrodesulfurization catalyst. The alumina carrier of the hydrodesulfurization catalyst has flaky pseudo-boehmite crystal grains which grow in situ on the outer surface of the alumina carrier, the flaky crystal grains are firmly combined with the main body of the alumina, and the pores formed by the stacking of the flaky crystal grains are wide; and the hydrodesulfurization catalyst prepared by using the alumina as the carrier has high hydrodesulfurization activity and metal capacity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalyst preparation, and particularly relates to a preparation method of a heavy oil hydrodesulfurization catalyst. BACKGROUND

[0002] In recent years, with the heavyization of crude oil resources, the increasing demand for fuel oil consumption and the increasingly stringent environmental regulations, the use of hydrogenation technology to convert heavy oil including residual oil into high-quality fuel oil and chemical products helps to improve the processing depth of crude oil, reduce environmental pollution, improve light oil yield and improve product quality. Fixed bed residual oil hydrogenation technology is an effective means to realize efficient conversion of heavy oil. Most of the metals, sulfur, nitrogen and residual carbon impurities in crude oil are mainly enriched in residual oil after atmospheric and vacuum distillation. Due to the complex molecular composition, high viscosity and high impurity content of residual oil, the hydrogenation reaction is difficult, and it is required to effectively remove the metal, sulfur, nitrogen and residual carbon impurities in the residual oil through catalytic reaction. Residual oil hydroprocessing catalysts usually include protective catalysts, metal removal catalysts, desulfurization catalysts and denitrification catalysts, each of which has other functions. Residual oil hydrodesulfurization catalysts should have a large pore size and pore volume to facilitate the diffusion of macromolecular reactants and not be easily blocked by metal and coke.

[0003] CN104646008A discloses a poor-quality heavy oil hydrodesulfurization and demetallization catalyst and a preparation method thereof. The catalyst uses alumina as a carrier, and VIB and VIII elements, particularly Ni-Mo, as active components. The catalyst has a pore volume of 0.61-0.70 mL / g, a specific surface area of 155-200 m 2 / g, and an average pore diameter of 13.0-18.0 nm. The average pore diameter gradually increases from the center to the outer surface of the catalyst particle in the radial direction. The preparation method of the catalyst is to treat the formed and calcined carrier particles with an acid solution with continuously increasing concentration, but the metal capacity of the catalyst needs to be further improved.

[0004] CN111822011A discloses a carrier for hydrodesulfurization, a catalyst and a preparation method thereof. The carrier is an auxiliary-alumina-containing carrier, which comprises a main body alumina and rod-like alumina, the main body alumina is an alumina with micron-sized channels, at least part of the rod-like alumina is distributed on the outer surface and the micron-sized channels of the main body alumina, the auxiliary phosphorus and / or boron is distributed in the micron-sized channels, and the auxiliary titanium is distributed on the surface of the rod-like alumina on the outer surface of the carrier. The preparation method of the carrier is as follows: a physical pore-expanding agent is adsorbed into a solution containing auxiliary phosphorus and / or boron, and then mixed and kneaded with pseudo-boehmite to form a carrier intermediate, which is dried and calcined; the carrier intermediate is immersed in an ammonium bicarbonate solution, sealed and heat-treated, and dried; a solution containing auxiliary titanium is sprayed on the outer surface of the material for impregnation, and dried and calcined to obtain an alumina carrier. The catalyst prepared by the method has a rod-like structure on the surface, but the degree of firmness of the rod-like alumina grown on the surface combined with the main body alumina needs to be further improved. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a preparation method of a hydrodesulfurization catalyst, which in-situ grows flaky pseudo-boehmite grains on the outer surface of an alumina carrier of the hydrodesulfurization catalyst, the flaky grains are firmly combined with the main body alumina, and the pores formed by the accumulation of the flaky grains are wide, so that the hydrodesulfurization catalyst prepared by using the alumina as the carrier has high hydrodesulfurization activity and metal capacity.

[0006] The preparation method of the hydrodesulfurization catalyst of the present application comprises the following steps: (1) preparing a phosphorus-modified gamma-phase alumina carrier; (2) immersing the phosphorus-modified gamma-phase alumina carrier in an aqueous propylene oxide solution for low-temperature and high-temperature two-stage sealed heat treatment, and then drying to obtain a composite crystal phase alumina carrier; the low-temperature sealed heat treatment conditions are as follows: the temperature is 60-100℃, and the sealed heat treatment is performed for 1-4 hours; the high-temperature sealed heat treatment conditions are as follows: the temperature is 110-180℃, preferably 120-160℃, and the treatment is performed for 8-12 hours; (3) impregnating the composite crystal phase alumina carrier with an active component impregnation solution, and drying and calcining the impregnated material to obtain a hydrodesulfurization catalyst.

[0007] In the method, the phosphorus-modified gamma phase alumina carrier in step (1) can be prepared by adding the modified element phosphorus at any step in the preparation process of the alumina carrier precursor, such as adding during kneading and shaping of the carrier, or loading on the alumina carrier by impregnation. The content of the phosphorus is 1.5 wt% to 4.5% of the carrier weight, and the modified element phosphorus can be a phosphate salt such as ammonium phosphate, ammonium hydrogen phosphate, or phosphoric acid. Preferably, the phosphoric acid is loaded on the gamma phase alumina carrier by impregnation, and the material after impregnation needs to be dried and calcined. The drying temperature is 100-160°C, the drying time is 1-8 hours, and the calcination temperature is 450-600°C, and the calcination time is 1-8 hours. The preparation method of the gamma phase alumina carrier is known in the art, and generally comprises kneading, shaping, drying, and calcining of pseudo-boehmite.

[0008] In the method, the mass percentage concentration of the propylene oxide aqueous solution in step (2) is 2.5% to 12%, preferably 4% to 8%, and the mass ratio of the propylene oxide aqueous solution to the phosphorus-modified gamma phase alumina carrier is 3:1 to 10:1, preferably 4:1 to 8:1.

[0009] In the method, the sealing heat treatment in step (2) is generally carried out in an autoclave, and the high-temperature sealing heat treatment temperature is preferably 120-160°C.

[0010] In the method, the drying temperature in step (2) is 100-160°C, and the drying time is 2-8 hours.

[0011] In the method, the composite crystal phase alumina carrier has the following properties: the alumina carrier is a mixed phase of gamma-Al2O3 and AlOOH, the AlOOH crystal grains have a flaky structure and are in situ oriented growth on the outer surface of the alumina carrier, the coverage rate of the flaky AlOOH crystal grains on the outer surface of the alumina carrier is 50% to 80%, and the coverage rate refers to the percentage of the surface occupied by the flaky AlOOH crystal grains on the outer surface of the alumina carrier. The size of the flaky AlOOH crystal grains is 50-400 nm, the ratio H of the grain size of the crystal face corresponding to the AlOOH (120) peak to the grain size of the crystal face corresponding to the gamma-Al2O3 (440) peak is 2.5-3.5, and H=D AlOOH (120) / D γ-Al2O3 (440), wherein D(120) represents the grain size of the crystal face corresponding to the AlOOH (120) peak in the XRD spectrum; the 120 peak refers to the characteristic peak with 2θ of 25.5-29.9° in the XRD spectrum; D(440) represents the grain size of the crystal face corresponding to the gamma-Al2O3 (440) peak in the XRD spectrum; and the 440 peak refers to the characteristic peak with 2θ of 63.6-69.1° in the XRD spectrum.

[0012] In the method of the present application, the active component impregnation solution in step (3) is a solution containing Group VIB and Group VIII metals, the Group VIB metal is selected from one or more of W and Mo, and the Group VIII metal is selected from one or more of Co and Ni. The content of the Group VIB metal in the impregnation solution is 8.5-20.0 g / 100 mL in terms of metal oxide, and the content of the Group VIII metal is 2.5-6.0 g / 100 mL in terms of metal oxide.

[0013] In the method of the present application, the drying temperature in step (3) is 100-160°C, the drying time is 2-8 hours, the calcination temperature is 450-550°C, and the calcination time is 4-6 hours.

[0014] The specific surface area of the hydrodesulfurization catalyst of the present application is 200-350 m 2 / g, the pore volume is 0.7-1.1 mL / g, the most probable pore diameter is 10-20 nm, and the 10-20 nm pores account for 50%-75% of the total pore volume. The MoO3 content is 13.5-18.5 g / 100 g, the NiO content is 3.0-4.5 g / 100 g, and the remainder is an alumina carrier.

[0015] Compared with the prior art, the present application has the following advantages:

[0016] (1) The present application first applies phosphorus elements to modify the alumina precursor, and preferably uses a phosphoric acid solution to impregnate the γ-phase alumina carrier. During impregnation, the phosphoric acid solution acts on the alumina grains on the surface of the pores of the carrier, increasing the macropore content and the connectivity of the pores. On the other hand, due to the addition of phosphorus, the content and strength of L acid on the surface of the alumina carrier are increased, and the hydrogenation activity of the corresponding catalyst is improved.

[0017] (2) The phosphorus-modified alumina carrier is subjected to two-stage sealed heat treatment in a propylene oxide solution. During low-temperature sealed heat treatment, propylene oxide is hydrolyzed to form an alcohol solution, and the solution is weakly alkaline. During high-temperature sealed hydrothermal treatment, the alumina carrier surface grains grow outward in situ under alkaline and alcohol solution conditions and form flaky AlOOH grains. The coverage of AlOOH grains on the outer surface of the alumina carrier is moderate, the ratio of the grain size of the crystal plane corresponding to the AlOOH (120) peak to the grain size of the crystal plane corresponding to the γ-Al2O3 (211) peak is appropriate, and 30-150 nm open pores are formed on the surface of the carrier. At the same time, the flaky grain structure is uniform, the binding force with the surface of the carrier is strong, and the formed pores are firm.

[0018] (3) The hydrogen desulfurization catalyst prepared by using the alumina as the carrier in the present application, the surface sheet AlOOH crystal grains of the carrier are transformed into γ-Al2O3 during the calcination, the active metal components impregnated on the surface of the AlOOH crystal grains are coordinated with the phase transformation process of the AlOOH crystal grains, the interaction between the active metal components and the alumina carrier is adjusted, the formation of nickel-aluminum spinel phase is reduced, and the catalytic activity of the catalyst is improved.

[0019] (4) The outer surface of the catalyst in the present application is accumulated by sheet crystal grains, which is beneficial to the contact of the residual oil reactant molecules, improves the catalyst activity, in addition, the pore structure of the catalyst surface is wide, which is beneficial to the diffusion of the macromolecular reactants to the inside of the carrier, so that the catalyst has high anti-metal deposition capacity. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 XRD spectra of the phosphorus modified alumina carrier (A) and the alumina carrier (B) prepared in Example 1.

[0021] Figure 2 Low-magnification SEM image of the surface of the alumina carrier prepared in Example 1.

[0022] Figure 3 SEM image of the surface of the alumina carrier prepared in Comparative Example 2. DETAILED DESCRIPTION

[0023] The technical solutions and technical effects of the present application will be further illustrated below in combination with examples, but are not limited to the following examples. In the present application, wt% represents mass fraction.

[0024] BET method: N2 physical adsorption-desorption is used to characterize the pore structure of the carriers in the examples and comparative examples, and the specific operation is as follows: an ASAP-2420 type N2 physical adsorption-desorption instrument is used to characterize the pore structure of the samples. A small amount of sample is vacuum treated at 300℃ for 3-4 hours, and finally the product is placed in liquid nitrogen at low temperature (-200℃) for nitrogen adsorption-desorption test. The specific surface area is obtained according to the BET equation, and the distribution rate of the pore volume and the pore diameter below 30nm is obtained according to the BJH model.

[0025] The scanning electron microscope is used to characterize the microstructure of the alumina carrier, and the specific operation is as follows: the JSM-7500F scanning electron microscope is used to characterize the microstructure of the carrier, the acceleration voltage is 5kV, the acceleration current is 20μA, and the working distance is 8mm.

[0026] Example 1

[0027] (1) Take 500 grams of pseudo-boehmite (prepared by aluminum sulfate-sodium metaaluminate method), add 2 grams of sesbania powder, then add an appropriate amount of 0.5% acetic acid solution to the mixture and knead uniformly, extrude into strips, dry the formed material at 120°C for 8 hours, and calcine at 500°C for 5 hours to obtain an alumina carrier precursor. Dip the carrier in a 8.5% phosphoric acid solution, filter the carrier after impregnation, dry at 120°C for 8 hours, and calcine at 500°C for 5 hours to obtain a phosphorus-modified alumina carrier precursor. The XRD spectrum of the carrier is shown in Figure A of Figure 1 .

[0028] (2) Take 100 grams of the phosphorus-modified alumina carrier precursor of step (1), add 550 grams of a 6.6% propylene oxide aqueous solution, and transfer the mixture into an autoclave. After sealing, place the autoclave in an oven and seal-treat at 75°C for 3 hours, then raise the temperature to 130°C and seal-treat for 10 hours. After treatment, cool, wash, and filter the material, and dry the solid material at 140°C for 6 hours to obtain an alumina carrier S1. The XRD spectrum of the carrier is shown in Figure B of Figure 1 , and the properties of the carrier are shown in Table 1. The outer surface scanning electron micrograph of the carrier is shown in Figure Figure 2 .

[0029] (3) Take 50 grams of the alumina carrier S1, and impregnate the alumina carrier with a saturated impregnation method using a molybdenum oxide concentration of 15.2 g / 100 mL and a nickel oxide concentration of 3.7 g / 100 mL. Dry the impregnated material at 120°C for 6 hours and calcine at 450°C for 5 hours to obtain a hydrodesulfurization catalyst Cat-1.

[0030] Example 2

[0031] The same as Example 1, except that the concentration of the phosphoric acid solution in step (1) is 12%. The concentration of propylene oxide in step (2) is 5.7%, and the solution amount is 680 grams. During hydrothermal treatment, first treat at 85°C for 2 hours, then at 145°C for 9 hours to obtain an alumina carrier S2 and a hydrodesulfurization catalyst Cat-2 of the present application. The properties of the carrier are shown in Table 1.

[0032] Example 3

[0033] The same as Example 1, except that the concentration of the phosphoric acid solution in step (1) is 5.2%. The concentration of propylene oxide in step (2) is 7.8%, and the solution amount is 410 grams. During hydrothermal treatment, first treat at 65°C for 4 hours, then at 155°C for 8 hours to obtain an alumina carrier S3 and a hydrodesulfurization catalyst Cat-3 of the present application. The properties of the carrier are shown in Table 1.

[0034] Example 4

[0035] Same as Example 1, except that the concentration of phosphoric acid solution in step (1) is 13.5%. In step (2), the concentration of propylene oxide is 4.5%, the amount of solution used is 730 grams, and the hydrothermal treatment is first carried out at 95°C for 1.5 hours, and then at 120°C for 11.5 hours to obtain the alumina support S4 and the hydrodesulfurization catalyst Cat-4 of the present invention. The properties of the support are shown in Table 1.

[0036] Comparative Example 1

[0037] Same as Example 1, except that in step (2) the aqueous propylene oxide solution was replaced with an aqueous ammonia solution of the same mass concentration to prepare comparative alumina support S5 and comparative hydrodesulfurization catalyst Cat-5. The properties of the alumina support are shown in Table 1.

[0038] Comparative Example 2

[0039] Same as Example 1, except that in step (2), the propylene oxide aqueous solution was replaced with an ethylene oxide solution of the same concentration to prepare the comparative alumina support S6 and the comparative hydrodesulfurization catalyst Cat-6. The properties of the alumina support are shown in Table 1, and the scanning electron microscope images of the outer surface of the support are shown in Table 2. Figure 3 .

[0040] Comparative Example 3

[0041] Same as Example 1, except that the concentration of propylene oxide in step (2) is 0.8%, and comparative alumina support S7 and comparative hydrodesulfurization catalyst Cat-7 are prepared. The properties of the alumina support are shown in Table 1.

[0042] Comparative Example 4

[0043] Same as Example 1, except that step (2) hydrothermal treatment is a one-step hydrothermal treatment with a heat treatment temperature of 65°C and a treatment time of 14 hours, to obtain comparative alumina support S8 and comparative hydrodesulfurization catalyst Cat-8. The properties of the alumina support are shown in Table 1, and the hydrodemetallization catalyst is shown in Table 3.

[0044] Table 1 Properties of Alumina Supports

[0045]

[0046] From the data in Table 1 and Figures 2-3 As can be seen, compared with the comparative alumina support, the alumina support prepared by the method of the present invention has a higher 10-20nm pore content and a wider surface pore.

[0047] Example 5

[0048] The hydrodesulfurization catalysts Cat-1, Cat-2, Cat-3, Cat-4 prepared by the present application and the hydrodesulfurization catalysts Cat-5, Cat-6, Cat-7, Cat-8 prepared by the comparative examples were respectively filled into a fixed bed hydrogenation reactor, and the raw materials (see Table 2) were treated. The test conditions were as follows: reaction temperature 384℃, hydrogen / oil volume ratio 700, liquid hourly space velocity 0.5h-1, hydrogen partial pressure 14.0MPa, continuous operation 2000 hours, and the impurity removal properties were shown in Table 3. -1

[0049] Table 2 Raw material oil properties

[0050] Item Density (20°C), g / cm 3 ]] 0.97 S, wt% 3.9 N, wt% 0.21 Ni, pg / g 28.6 V, pg / g 73.9

[0051] Table 3 Evaluation results of catalysts

[0052] Protecting catalyst Cat-1 Cat-2 Cat-3 Cat-4 Cat-5 Cat-6 Cat-7 Cat-8 Relative desulfurization rate, % 127 125 122 126 100 98 106 104 Relative Ni+V removal rate, % 119 125 122 127 100 103 105 99

[0053] From the results in Table 3, it can be seen that the hydrodesulfurization catalyst prepared by the method of the present application has higher desulfurization activity and higher Ni and V removal activity compared with the comparative hydrodesulfurization catalysts.​

Claims

1. A process for the preparation of a hydrodesulfurization catalyst, characterized in that The preparation method comprises the following steps: (1) preparing a phosphorus-modified gamma phase alumina carrier; (2) immersing the phosphorus-modified gamma phase alumina carrier into an aqueous propylene oxide solution for low-temperature and high-temperature two-stage sealed heat treatment, and then drying to obtain a composite crystal phase alumina carrier; the low-temperature sealed heat treatment condition is that the temperature is 60-100 ℃, and the sealed heat treatment is performed for 1-4 hours; the high-temperature sealed heat treatment condition is that the temperature is 110-180 ℃, and the treatment is performed for 8-12 hours; (3) immersing the composite crystal phase alumina carrier in an active component impregnation solution, and then drying and calcining the immersed material to obtain a hydrodesulfurization catalyst; the aqueous propylene oxide solution has a mass percentage concentration of 2.5%-12%; the mass ratio of the aqueous propylene oxide solution to the phosphorus-modified gamma phase alumina carrier is 3:1-10:1; the composite crystal phase alumina carrier has the following properties: the alumina carrier is a mixed phase of gamma-Al2O3 and AlOOH, the AlOOH crystal grains have a sheet structure, are in situ oriented growth on the outer surface of the alumina carrier, and have a coverage rate of 50%-80% on the outer surface of the alumina carrier; the sheet AlOOH crystal grains have a size of 50-400 nm; the ratio H of the grain size of the crystal face corresponding to the AlOOH (120) peak to the grain size of the crystal face corresponding to the gamma-Al2O3 (440) peak is 2.5-3.5, H=D AlOOH (120) / D γ-Al2O3 (440), wherein D (120) represents the grain size of the crystal face corresponding to the AlOOH (120) peak in the XRD spectrum; the 120 peak refers to a characteristic peak with 2θ of 25.5-29.9° in the XRD spectrum; D (440) represents the grain size of the crystal face corresponding to the gamma-Al2O3 (440) peak in the XRD spectrum; the 440 peak refers to a characteristic peak with 2θ of 63.6-69.1° in the XRD spectrum; the active component impregnation solution in step (3) is a solution containing a group VIB metal and a group VIII metal, the group VIB metal is selected from one or more of W and Mo, and the group VIII metal is selected from one or more of Co and Ni; the content of the group VIB metal in the impregnation solution is 8.5-20.0 g / 100 mL in terms of metal oxide, and the content of the group VIII metal is 2.5-6.0 g / 100 mL in terms of metal oxide.

2. The method of claim 1, wherein: The phosphorus modified gamma phase alumina carrier in step (1) has a phosphorus content of 1.5 wt% to 4.5% by weight of the carrier.

3. The method of claim 1, wherein: The mass percentage concentration of the propylene oxide aqueous solution in step (2) is 4% to 8%, and the mass ratio of the propylene oxide aqueous solution to the phosphorus modified gamma phase alumina carrier is 4:1 to 8:

1.

4. The method of claim 1, wherein: The drying temperature in step (2) is 100 to 160°C, and the drying time is 2 to 8 hours.

5. The method of claim 1, wherein: The drying temperature in step (3) is 100 to 160°C, the drying time is 2 to 8 hours, the calcination temperature is 450 to 550°C, and the calcination time is 4 to 6 hours.

6. The method of claim 1, wherein: The specific surface area of the hydrodesulfurization catalyst is 200-350 m 2 / g, the pore volume is 0.7-1.1 mL / g, the most probable pore diameter is 10-20 nm, and the pores of 10-20 nm account for 50%-75% of the total pore volume.

7. The method of claim 1, wherein: The MoO3 content is 13.5 to 18.5 g / 100 g, the NiO content is 3.0 to 4.5 g / 100 g, and the rest is an alumina carrier, based on the weight of the hydrogen desulfurization catalyst.

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