Method for preparing hydrogenation catalyst by flame spray pyrolysis

Abstract

The invention belongs to the field of catalysts, and particularly provides a method for preparing a hydrogenation catalyst by flame spray pyrolysis, which comprises the following steps: uniformly mixing acetic acid and 2-ethylhexanoic acid at room temperature to obtain a mixed solvent, then adding precursor salt containing Ni, Mo and Al elements into the mixed solvent, heating and stirring in an oil bath to fully dissolve the precursor salt to obtain a precursor solution; a mixed precursor salt solution is obtained; transferring the mixed precursor salt solution into a flask of a flame spray pyrolysis reactor, injecting the mixed solution into high-temperature flame generated by combustion of premixed gas consisting of CH4 / O2 through a nozzle by using a pump, atomizing the mixed precursor solution by using surrounding oxygen dispersed gas, and performing pyrolysis and oxidation in the high-temperature flame under the pressure of 900 mbar to obtain a NiMo / Al2O3 catalyst; and collecting the NiMo / Al2O3 catalyst, and carrying out sulfuration and reduction to obtain the NiMo / Al2O3 catalyst. The catalyst obtained by the method has high specific surface area, and Ni and Mo are uniformly mixed and closely contacted on the nanoscale, so that the catalyst has high catalytic activity.

Description

Technical Field

[0001] The invention relates to the field of catalysts, and in particular to a method for preparing a hydrogenation catalyst by flame spray pyrolysis. Background Art

[0002] Refineries perform hydroprocessing to remove sulfur (hydrodesulfurization HDS) and nitrogen (hydrodenitrogenation HDN) from heterocyclic compounds. In addition, the hydroprocessing process also hydrogenates some aromatic compounds in petroleum (HYD). The active component of industrial hydroprocessing catalysts is mainly cobalt or nickel-doped molybdenum disulfide (MoS2). The preparation method of this type of catalyst is usually an impregnation method, that is, molybdenum, cobalt, and nickel compounds are impregnated sequentially or simultaneously onto an alumina carrier, and then calcined to obtain a supported metal oxide. The metal oxide is then converted into the real active component, namely the Co-Mo-S or Ni-Mo-S phase, through sulfurization activation. For example, CN95107484A provides a method for preparing a hydrogenation catalyst, wherein a molybdenum-containing carrier having a MoO3 content of 6 to 13 wt% is first prepared by an impregnation method or a kneading method, and then impregnated with an ammonia solution of a Ni-Mo mixture, and then calcined and reduced. The obtained catalyst has a high catalytic hydrogenation activity. However, in this method, after obtaining the molybdenum-containing carrier, the ammonia solution of the Ni-Mo mixture is impregnated, and the distribution effect of the metal on the catalyst is not good.

[0003] Flame spray pyrolysis (FSP) is a promising alternative method for preparing hydrogenation catalysts due to its advantages such as flexibility, rapidity, and scalability.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a hydrogenation catalyst by flame spray pyrolysis.

[0006] The basic concept of the technical solution of the present invention is as follows: A method for preparing a hydrogenation catalyst by flame spray pyrolysis comprises the following steps: (1) Evenly mixing acetic acid and 2-ethylhexanoic acid at room temperature to obtain a mixed solvent, then adding a precursor salt containing Ni, Mo and Al elements to the mixed solvent, heating and stirring in an oil bath to fully dissolve the precursor salt, and obtaining a mixed precursor salt solution; (2) The mixed precursor salt solution is transferred to a flask of a flame spray pyrolysis reactor, and the mixed solution is injected into a high-temperature flame generated by the combustion of a premixed gas composed of CH4 / O2 through a nozzle by a pump, and the mixed precursor solution is atomized by the surrounding oxygen dispersion gas, and pyrolyzed and oxidized in a high-temperature flame at a pressure of 900 mbar to obtain a NiMo / Al2O3 catalyst; (3) collecting the NiMo / Al2O3 catalyst and performing sulfidation to obtain the presulfided catalyst; (4) Reducing the presulfided catalyst under a hydrogen atmosphere to obtain the hydrogenation catalyst.

[0007] As an embodiment, the total concentration of the mixed precursor salt solution is 0.2-0.4 mol / L; the molar ratio of Ni, Mo and Al elements is 1:(1-3):(3-30).

[0008] As an implementation mode, the precursor salt of Ni is nickel 2-ethylhexanoate, the precursor salt of Mo is molybdenum 2-ethylhexanoate, and the precursor salt of Al is aluminum acetylacetonate.

[0009] As an embodiment, in step (1), the volume ratio of acetic acid to 2-ethylhexanoic acid is (0.5~2):1, preferably 1:1.

[0010] As an embodiment, in step (1), the temperature of heating in the oil bath is 30 to 80 o C.

[0011] As an embodiment, in step (2), the atomization method is: the flow rate of the mixed precursor salt solution is 2-4 mL / min, and the flow rate of the oxygen dispersion gas is 5-10 slm.

[0012] As an embodiment, in step (2), in the high-temperature pilot flame, the flow rate of methane is 2-5 slm, and the flow rate of oxygen is twice the flow rate of methane.

[0013] As an embodiment, in step (3), the sulfurization method is: immersing equal volumes of the NiMo / Al2O3 catalyst in an ammonium thiosulfate solution, wherein the molar ratio of S to Mo is (2-5):1, and then drying at 80-110°C for 6-12 hours.

[0014] The present invention also provides a hydrogenation catalyst, which is prepared by any of the methods described above.

[0015] The present invention also provides a use of the hydrogenation catalyst as described above in residual oil hydrogenation.

[0016] Compared with the prior art, the present invention has the following advantages: 1. The NiMo / Al2O3 catalyst prepared by the method of the present invention not only has a high specific surface area, but also realizes uniform mixing and close contact of Ni and Mo components at the nanoscale, which is conducive to the formation of a highly active Ni-Mo-S phase during the sulfurization process. The results of hydrodesulfurization and hydrogenation experiments also verify the high activity of the catalyst prepared by the present invention.

[0017] 2. The method of the present invention uses a mixed solvent of acetic acid and 2-ethylhexanoic acid, and the precursors of Ni and Mo are 2-ethylhexanoic acid nickel and 2-ethylhexanoic acid molybdenum, respectively, which have similar combustion performance in the high-temperature flame process of flame spray pyrolysis and are more conducive to uniform mixing of active components.

[0018] 3. The method for obtaining the NiMo / Al2O3 oxide catalyst of the present invention is a one-step method with a short process flow and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0020] Figure 1 is a TEM image of the catalyst obtained in Example 1 of the present invention.

[0021] Figure 2 is a TEM image of the catalyst obtained in Example 6 of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0023] A method for preparing a hydrogenation catalyst by flame spray pyrolysis comprises the following steps: (1) At room temperature, acetic acid and 2-ethylhexanoic acid are added to a glass flask in a volume ratio of 1:1 and mixed evenly to obtain a mixed solvent; then, appropriate amounts of nickel 2-ethylhexanoate, molybdenum 2-ethylhexanoate and aluminum acetylacetonate are added to the mixed solvent, and the mixture in the flask is heated to 75° C. in an oil bath and stirred to fully dissolve the precursor salts to obtain a mixed precursor salt solution with a total metal concentration of 0.3 mol / L, wherein the molar ratio of Ni, Mo and Al elements is 1:3:20; (2) The mixed precursor salt solution was then transferred to a flask of a flame spray pyrolysis reactor, and the mixed solution was injected into the high-temperature flame through a flame nozzle at a flow rate of 3 mL / min using a plunger pump, and oxygen was used as a dispersion gas to atomize the mixed precursor solution at a flow rate of 9 slm, thereby pyrolyzing in the high-temperature flame to form nano-oxides and obtain NiMo / Al2O3 catalysts. The high-temperature pilot flame was generated by the combustion of a premixed gas composed of CH4 / O2 (flow rates of 3 slm and 6 slm, respectively), while the compressed air around the flame (flow rate of 150 slm) was used as a sheath gas to stabilize the reaction gas flow. The pyrolysis reaction was carried out at a pressure of 900 mbar; (3) The collected NiMo / Al2O3 catalyst was tested and found to have a Mo loading of 19.6wt% and a specific surface area of ​​146m 2 / g. Then, the catalyst was immersed in an ammonium thiosulfate solution with an equal volume, wherein the molar ratio of S to Mo was 3:1, and then dried at 105°C for 8 hours to obtain the presulfurized catalyst; (4) Reducing the presulfided catalyst under a hydrogen atmosphere to obtain the hydrogenation catalyst. Example 2

[0024] The preparation of NiMo / Al2O3 catalyst was the same as in Example 1, with a Mo loading of 20.2 wt% and a specific surface area of ​​139 m 2 / g.

[0025] The difference from Example 1 is that during the presulfurization process of the prepared NiMo / Al2O3 catalyst, the molar ratio of S to Mo is 5:1. Example 3

[0026] The only difference compared with Example 1 is that during the preparation process, the molar ratio of Ni, Mo and Al in the precursor solution is 1:3:80. The loading amount of Mo is 4.8wt% and the specific surface area is 208m 2 / g. Example 4

[0027] Compared with Example 1, during the preparation process, the molar ratio of Ni, Mo and Al in the precursor solution was 1:3:40. The loading amount of Mo was 10.5wt% and the specific surface area was 179m 2 / g. Example 5

[0028] Compared with Example 1, during the preparation process, the molar ratio of Ni, Mo and Al in the precursor solution was 1:3:15. The loading amount of Mo was 31.2wt% and the specific surface area was 131 m 2 / g. Example 6

[0029] Compared with Example 1, the molar ratio of Ni, Mo and Al in the precursor solution is 1: 2: 15. The loading amount of Mo is 18.9wt% and the specific surface area is 152m 2 / g. Comparative Example 1

[0030] The difference from Example 1 is that no Ni additive is added during the catalyst preparation process. The Mo loading of the catalyst is 18.6 wt % and the specific surface area is 157 m 2 / g. . Debugging Example

[0031] The catalyst compositions and specific surface areas of Examples 1-6 and Comparative Example 1 are shown in Table 1.

[0032] The specific surface area was measured by nitrogen adsorption and BET method at 77 K on a Micromeritics ASAP 2000. Before the measurement, the samples were desorbed at 150 °C for 12 h.

[0033] After the catalyst solid was dissolved in HNO3 / HF, the chemical composition of the catalyst was determined using ICP-MS (iCAP RQ ASX-560 model).

[0034]

[0035] As can be seen from Table 1, the catalysts prepared by flame spray pyrolysis have a larger specific surface area, ranging from 130 to 210 m 2 / g. Figure 1 and Figure 2 They are transmission electron micrographs of the catalysts prepared in Example 1 and Example 6 of the present invention. Analysis of the electron micrographs shows that the nano-crystals of the NiMo / Al2O3 catalyst prepared by flame spray pyrolysis are small and generally distributed in the range of 5-10 nm. Effect example

[0036] The residue oil hydrogenation performance of the catalysts of Examples 1-6 and Comparative Example 1 was systematically evaluated using a 300 mL autoclave (Parr Instrument).

[0037] Step 1: 300 mg of the presulfided catalyst was placed in a 300 mL autoclave for the hydrogenation reduction step of the sulfidation reaction, wherein the hydrogen pressure was 30 bar and the heating rate was 3 o C / min, and at 300 o C is maintained for 60 min.

[0038] Step 2, after sulfurization, the autoclave was cooled to room temperature, and then 50g of model diesel was added, the composition of the model diesel was: 3wt% dibenzothiophene, 2wt% naphthalene, and 0.5wt% n-nonane in n-heptane solution. Among them, dibenzothiophene is a representative sulfur compound used to examine the hydrodesulfurization performance of the catalyst, naphthalene is a representative diesel aromatic compound used to examine the hydrogenation performance of the catalyst, and n-nonane is an internal standard for gas chromatography analysis. After nitrogen purging three times, the hydrogen pressure was raised to 50bar, and then the reactor was heated to 350oC and reacted for 4h, with a stirring speed of 700rpm. The product analysis adopted gas chromatography analysis method (GC-FID), the chromatograph was Agilent 7890 model, and the chromatographic column was HP-5ms inert chromatographic column. The obtained reaction data are shown in Table 2.

[0039] The results show that the NiMo / Al2O3 catalyst prepared by flame spray pyrolysis has excellent catalytic performance for the hydrodesulfurization of dibenzothiophene and the hydrogenation of naphthalene. The main products of the hydrodesulfurization of dibenzothiophene are biphenyl and phenylcyclohexane, of which biphenyl is obtained by direct desulfurization, while phenylcyclohexane is obtained by hydrogenating a benzene ring and then desulfurizing. The main products of the hydrogenation of naphthalene are tetralin, trans-decalin and cis-decalin.

[0040]

[0041] Hydrogenation reaction of naphthalene: From the data of Example 1 and Examples 3-5 in Table 2, it can be seen that as the loading of Mo increases from 4.8wt% to 31.2wt%, the conversion rate of naphthalene gradually increases. The comparison between Comparative Example 1 and Example 1 shows that Ni as an additive has a greater effect on the hydrogenation performance of the catalyst than on the hydrodesulfurization performance of the catalyst.

[0042] Hydrodesulfurization reaction of dibenzothiophene: From the data of Example 1 and Examples 3-5 in Table 2, it can be seen that when the molar ratio of Ni:Mo:S is 1:3:9, as the Mo loading increases, the conversion rate of dibenzothiophene hydrodesulfurization basically shows a trend of gradually increasing, wherein the conversion rate is highest when the Mo content is about 20wt%, and when the Mo loading further increases to 31.2wt%, the conversion rate decreases slightly. As for product selectivity, compared with hydrogenation followed by desulfurization, the direct hydrodesulfurization reaction to obtain biphenyl always dominates.

[0043] Comparison of Example 2 with Example 1 shows that, during the sulfurization process, increasing the molar ratio of S:Mo can improve the hydrodesulfurization performance of the catalyst, but the improvement is limited.

[0044] The comparison between Comparative Example 1 and Example 1 shows that Ni, as an additive, is crucial to the hydrodesulfurization performance of the catalyst.

[0045] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted to facilitate understanding of the present invention and are not intended to limit the present invention. Any technician in the field to which the present invention belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for preparing a hydrogenation catalyst by flame spray pyrolysis, comprising the following steps: (1) Evenly mixing acetic acid and 2-ethylhexanoic acid at room temperature to obtain a mixed solvent, then adding a precursor salt containing Ni, Mo and Al elements to the mixed solvent, heating and stirring in an oil bath to fully dissolve the precursor salt, and obtaining a mixed precursor salt solution; (2) The mixed precursor salt solution is transferred to a flask of a flame spray pyrolysis reactor, and the mixed solution is injected into a high-temperature flame generated by the combustion of a premixed gas composed of CH4 / O2 through a nozzle by a pump, and the mixed precursor solution is atomized by the surrounding oxygen dispersion gas, and pyrolyzed and oxidized in a high-temperature flame at a pressure of 900 mbar to obtain a NiMo / Al2O3 catalyst; (3) collecting the NiMo / Al2O3 catalyst and performing sulfidation to obtain a presulfided catalyst; (4) Reducing the presulfided catalyst under a hydrogen atmosphere to obtain the hydrogenation catalyst.

2. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 1, characterized in that: The total concentration of the mixed precursor salt solution is 0.2-0.4 mol / L; the molar ratio of Ni, Mo and Al elements is 1:(1-3):(3-30).

3. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 1, characterized in that: The precursor salt of Ni is nickel 2-ethylhexanoate, the precursor salt of Mo is molybdenum 2-ethylhexanoate, and the precursor salt of Al is aluminum acetylacetonate.

4. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 1, characterized in that: In step (1), the volume ratio of acetic acid to 2-ethylhexanoic acid is (0.5-2):

1.

5. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 4, characterized in that: The volume ratio of acetic acid to 2-ethylhexanoic acid is 1:

1.

6. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 1, characterized in that: In step (1), the temperature of the oil bath is 30 to 80 o C.

7. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 1, characterized in that: In step (2), the atomization method is: the flow rate of the mixed precursor salt solution is 2-4 mL / min, and the flow rate of the oxygen dispersion gas is 5-10 slm.

8. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 1, characterized in that: In step (2), in the high temperature pilot flame, the flow rate of methane is 2-5 slm, and the flow rate of oxygen is twice the flow rate of methane.

9. The method for preparing a hydrogenation catalyst by flame spray pyrolysis according to claim 1, characterized in that: In step (3), the sulfurization method is: immersing equal volumes of the NiMo / Al2O3 catalyst in an ammonium thiosulfate solution, wherein the molar ratio of S to Mo is (2-5):1, and then drying at 80-110°C for 6-12 hours.

10. A hydrogenation catalyst, characterized in that The method is prepared by any one of claims 1 to 9.

11. Use of the hydrogenation catalyst according to claim 10 in hydrogenation of residual oil.

Images