Pyrolysis gasoline first-stage catalyst and preparation method thereof

Abstract

The invention discloses a pyrolysis gasoline first-stage catalyst and a preparation method thereof. The catalyst comprises an aluminum oxide and niobium oxyphosphate composite carrier and hydrogenation active component nickel, the total acid amount of infrared acid of the catalyst is 0.45-0.75 mmol / g, and the acid amount of L acid is 0.40-0.70 mmol / g. The preparation method comprises the following steps: (1) adding niobic acid and phosphoric acid into bottom water of a reactor, adding an aluminum salt aqueous solution and a precipitant in a parallel flow manner, carrying out a gel forming reaction, adding a solution containing basic nickel carbonate and citric acid into slurry after the reaction is finished, then adding organic acid, carrying out an aging reaction, and washing, filtering and drying an aging product to obtain modified aluminum oxide dry glue powder; and (2) mixing the modified alumina dry glue powder, a peptizing agent and an extrusion aid, performing extrusion molding, drying and roasting to obtain the catalyst. According to the catalyst disclosed by the invention, relatively high diene hydrogenation selectivity of a pyrolysis gasoline first-stage catalyst is realized through a synergistic effect of NbOx species, acidity and nickel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of clean refining, and particularly relates to a cracking gasoline first-stage catalyst and a preparation method thereof. BACKGROUND

[0002] Cracking gasoline contains diene, mono-olefin, olefinic aromatic hydrocarbon, sulfur, nitrogen, oxygen, chlorine, heavy metal and other compounds. With the increasing production of ethylene cracking by-product cracking gasoline, the hydrogenation of cracking gasoline becomes more important. Diene in cracking gasoline is easy to polymerize at high temperature. Therefore, the hydrogenation of cracking gasoline can be divided into two stages. The first stage is mainly to saturate diene, followed by mono-olefin and a small amount of styrene. The activity of the first-stage cracking gasoline hydrogenation catalyst should not be too high, and it is required to have high diene hydrogenation selectivity, to reduce the strong exothermic reaction of mono-olefin hydrogenation, and to avoid the generation of carbon deposition.

[0003] Although noble metal palladium catalysts are mostly selected in industry for selective hydrogenation to remove highly unsaturated hydrocarbons, the noble metal catalysts are significantly affected by impurity content, resulting in a shortened operation cycle of the device. Non-noble metal nickel-based catalysts have a better market application prospect due to their relatively good impurity resistance and price advantage.

[0004] Nickel catalysts are usually prepared by the impregnation method, and most of them use soluble metal salts to prepare the impregnation solution, and then perform 1-3 times of impregnation, drying, calcination process on the carrier, and then reduction to obtain the catalyst. CN103769104A discloses a nickel-based selective hydrogenation catalyst, its preparation method and application. The nickel-based selective hydrogenation catalyst is prepared by using nickel as the active component and Al2O3 as the carrier. The catalyst contains 8-20wt% of NiO, and the balance is Al2O3, calculated by the weight of the oxide. The carrier is a mixed carrier of θ-Al2O3 and δ-Al2O3. The active component nickel still uses the conventional impregnation method of soluble metal salt.

[0005] Compared to the conventional impregnation method, the kneading method eliminates the impregnation process, directly adding the active component during support molding. After molding, the catalyst is obtained through a single drying, calcination, and reduction process. However, the current kneading method suffers from the problem that nickel salts readily react strongly with the catalyst, forming nickel-aluminum spinel that is difficult to reduce, thus affecting the catalyst's activity. CN115990483A discloses a cracked gasoline hydrogenation catalyst, its preparation method, and its application. The catalyst includes a support and an active component, nickel. The support comprises alumina and silica, wherein the alumina contains α-phase alumina and θ-phase alumina. The active component, nickel, is added during support molding. The nickel source used is soluble nickel sources such as nickel nitrate, nickel acetate, and nickel sulfate. Inorganic or organic acids such as nitric acid, sulfuric acid, acetic acid, phosphoric acid, and citric acid are also added, resulting in a simple dissolution process. Although the above method improves the selective hydrogenation performance of the first-stage catalyst for cracked gasoline to some extent through changes in both the support and the preparation method of the active metal, further improvements are still needed. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a primary catalyst for pyrolysis gasoline and its preparation method. The catalyst of this invention introduces special seed crystals during the alumina gelation process, along with a solution prepared from specific metal salts and additives. Through the good matching of the active metal with the support and special substances in the catalyst, it exhibits high hydrogenation activity and selectivity when applied to the primary selective hydrogenation process of pyrolysis gasoline.

[0007] The first-stage catalyst for cracked gasoline of the present invention comprises an alumina and niobium oxyphosphate composite support and a hydrogenation active component, nickel. Based on the weight of the catalyst, the nickel content as oxide is 10.0-25.0%, preferably 12.0-23.0%, the niobium oxyphosphate content is 2.0%-10.0%, preferably 3.0%-8.0%, and the alumina content is 65.0%-88.0%, preferably 69.0%-85.0%. The total acidity of the catalyst in infrared radiation is 0.45-0.75 mmol / g, preferably 0.50-0.70 mmol / g, and the L acid content is 0.40-0.70 mmol / g, preferably 0.35-0.65 mmol / g.

[0008] The pore volume of the primary catalyst for cracked gasoline of the present invention is 0.45~1.30 mL / g, and the specific surface area is 180~400 m². 2 / g.

[0009] The first-stage catalyst for cracked gasoline of the present invention may further include additives such as Ti, Zr, V, Cu, Zn, and Si. The additive content is 0.5% to 7% based on the total weight of the catalyst, and the sum of the contents of all components of the catalyst is 100%.

[0010] The method for preparing the first-stage catalyst for cracked gasoline of the present invention includes the following: (1) Niobic acid and phosphoric acid are added to the bottom water of the reactor, and then aluminum salt aqueous solution and precipitant are added in parallel to carry out the gelation reaction. After the gelation reaction is completed, a solution containing basic nickel carbonate and citric acid is added to the slurry, and then organic acid is added to carry out the aging reaction. The aging product is washed, filtered, and dried to obtain alumina dry glue powder with active metal modification. (2) The active metal modified alumina dry adhesive powder, adhesive solvent and extrusion aid in step (1) are mixed evenly, extruded into strips, and then dried and calcined to obtain the catalyst product.

[0011] In the method of the present invention, the temperature of the bottom water in step (1) is 50~90℃, and the amount of bottom water added is determined according to the amount of reactants in the gelation reaction, which is generally well known to those skilled in the art.

[0012] In the method of the present invention, the amount of niobic acid and phosphoric acid added in step (1) is completely converted into the amount of niobium oxyphosphate according to the chemical synthesis ratio.

[0013] In the method of the present invention, the aluminum salt in step (1) is an aqueous solution of aluminum sulfate, and the concentration of the aqueous solution of aluminum sulfate is 4~12g / 100mL based on aluminum oxide; the precipitant is an aqueous solution of sodium aluminate, and the concentration of the aqueous solution of sodium aluminate is 12~40g / 100mL based on aluminum oxide.

[0014] In the method of the present invention, the gelation reaction conditions in step (1) are: time of 0.4 to 1.5 hours and pH value of 7.0 to 9.5.

[0015] In the method of the present invention, in the solution containing basic nickel carbonate and citric acid in step (1), the molar ratio of basic nickel carbonate (calculated as nickel oxide) to citric acid is 1.5 to 1.0.

[0016] In the method of the present invention, the organic acid added in step (1) is one or more of citric acid, lactic acid, glycolic acid, ethylenediaminetetraacetic acid, etc., and the amount added is 0.6 to 1.0 times the molar content of basic nickel carbonate (calculated as nickel oxide).

[0017] In the method of the present invention, the aging reaction time in step (1) is 0.2 to 1 hour.

[0018] In the method of this invention, the washing in step (1) generally involves washing with deionized water until SO4 is reached. 2- ≤2.5%, Na + ≤0.05%, Fe 3+ If the concentration is less than 0.25%, it generally requires 2-5 washes. In the method of the present invention, the drying conditions in step (1) are: drying temperature 90~130℃, drying time 5~34 hours.

[0019] In the method of the present invention, the extrusion aid in step (2) can be one or more of guar gum powder, cellulose, starch, polymeric surfactant, etc., and the amount used accounts for 0.1% to 20.0% of the dry basis weight of the alumina dry adhesive powder containing active metal in step (1); the adhesive solvent can be one or more of aluminum sulfate, citric acid, nitric acid, acetic acid, oxalic acid, etc., and the amount used accounts for 0.1% to 20.0% of the dry basis weight of the alumina dry adhesive powder in step (1).

[0020] In the method of the present invention, the drying and calcination conditions in step (3) are as follows: drying at 100~120℃ for 1~5 hours and calcining at 350~550℃ for 1~5 hours.

[0021] The application of the catalyst of this invention in the first stage selective hydrogenation process of cracked gasoline.

[0022] (1) This invention utilizes the synergistic effect of three active centers—NbOx species, acidic sites, and non-noble metal nickel—to achieve high diene hydrogenation selectivity in the first stage catalyst for cracked gasoline. During the preparation process, niobium oxyphosphate formed from niobic acid and phosphoric acid is used as a seed crystal for the neutralization reaction, which facilitates the formation of a larger pore volume and higher specific surface area on the support, as well as a significant increase in the total acidity of the support, especially the L-acid content, thereby enhancing the catalyst's hydrogenation capacity. The Nb-O-Nb chains on the support surface exhibit significant internal tension, causing local Nb-O bonds to tend to break to release this tension, making it easier for dienes to form on the NbO-Ox support. x H2 is adsorbed onto the Ni metal, then adsorbed, dissociated, and overflows onto the Nb-OC bond, forming NbO. x The surface has better adsorption capacity and lower dissociation activation energy, which can better realize the dissociation of hydrogen in the hydrogenation reaction and further improve the activity of the catalyst in removing dienes. (2) In this invention, after the gelation reaction is completed, a solution containing basic nickel carbonate and citric acid is added to the slurry, followed by the addition of organic acid to form a nickel citrate complex gel precipitate and age it. This enhances the uniform dispersion of the active component nickel in the alumina slurry, thereby enhancing the directional and orderly dispersion of the active metal Ni during the calcination and decomposition process, and further increasing the hydrogenation performance of the catalyst. The niobium phosphate component, existing in the form of seed crystals, can form a stable structure with alumina and be uniformly dispersed in the support. It can hinder the interaction between Ni and the support, suppress the formation of the NiAl2O4 phase, make Ni dispersion more uniform, and increase Ni 2+ The number of ions. Detailed Implementation

[0023] In this invention, the specific surface area and pore volume were determined using a cryogenic liquid nitrogen adsorption method, while the total acid content, Brønsted acid content, and Lewis acid content were determined using pyridine infrared adsorption spectroscopy. In this invention, % represents mass percentage. The catalyst composition was determined using a colorimetric method.

[0024] The catalysts used in this invention are described in detail below using examples. Example 1

[0025] 6.0g of niobic acid and 5.2g of phosphoric acid were added to 1L of water. 600mL of aluminum sulfate aqueous solution and 200mL of sodium aluminate aqueous solution were neutralized at 80℃ for 1.0h, with the pH value of the neutralization reaction controlled at 8.8~9.0. 100mL of a mixed solution containing 30g of basic nickel carbonate and 32g of citric acid was added to the slurry, followed by the addition of 42g of citric acid. The mixture was aged for 0.5h, and after two washing and filtration, a filter cake was obtained. The cake was dried at 110℃ for 24h and then ground to obtain the catalyst dry gel powder. The dry gel powder was extruded into strips, dried at 110℃ for 3h, and then calcined at 500℃ for 3h to obtain the finished catalyst A. Example 2

[0026] First, add 7.0g of niobic acid and 6.1g of phosphoric acid to 1L of water. Then, neutralize 600mL of aluminum sulfate aqueous solution and 200mL of sodium aluminate aqueous solution at 80℃ for 1.0h, controlling the pH of the neutralization reaction to be 8.8~9.0. Add 100mL of a mixed solution containing 34g of basic nickel carbonate and 43g of citric acid to the slurry, then add 35g of citric acid, age for 0.5h, and obtain a filter cake after two washing and filtration. Dry the filter cake at 110℃ for 24h, and grind it to obtain the catalyst dry gel powder. The dry gel powder is extruded into strips, dried at 110℃ for 3h, and then calcined at 500℃ for 3h to obtain the finished catalyst B. Example 3

[0027] First, add 9.0g of niobic acid and 7.8g of phosphoric acid to 1L of water. Then, neutralize 600mL of aluminum sulfate aqueous solution and 200mL of sodium aluminate aqueous solution at 80℃ for 1.0h, controlling the pH of the neutralization reaction to be 8.8~9.0. Add 100mL of a mixed solution containing 38g of basic nickel carbonate and 53g of citric acid to the slurry, then add 40g of citric acid, age for 0.5h, and obtain a filter cake after two washing and filtration. Dry the filter cake at 110℃ for 24h, and grind it to obtain the catalyst dry gel powder. The dry gel powder is extruded into strips, dried at 110℃ for 3 hours, and then calcined at 450℃ for 3 hours to obtain the finished catalyst C. Example 4

[0028] 7.6g of niobic acid and 6.6g of phosphoric acid were added to 1L of water. 600mL of aluminum sulfate aqueous solution and 200mL of sodium aluminate aqueous solution were neutralized at 80℃ for 1.0h, with the pH value of the neutralization reaction controlled at 8.8~9.0. 100mL of a mixed solution containing 42g of basic nickel carbonate and 47g of citric acid was added to the slurry, followed by the addition of 53g of citric acid. The mixture was aged for 0.5h. The filter cake obtained after two washing and filtration was dried at 110℃ for 24h and then ground to obtain catalyst dry gel powder. The dry gel powder was extruded into strips, dried at 110℃ for 3h, and then calcined at 480℃ for 3h to obtain the finished catalyst D.

[0029] Comparative Example 1 Catalyst E was prepared using the same method as in Example 1, except that niobic acid and phosphoric acid were not added.

[0030] Comparative Example 2 Catalyst F was prepared using the same method as in Example 3, except that 100 mL of an aqueous solution containing 79 g of nickel nitrate and 53 g of citric acid was added to the slurry.

[0031] Comparative Example 3 Catalyst G was prepared using the same method as in Example 1, except that 100 mL of a mixed solution containing 30 g of basic nickel carbonate and 32 g of citric acid was added to the slurry, except that 42 g of citric acid was not added.

[0032] Comparative Example 4 Catalyst H was prepared using the same method as in Example 1, except that 6.0 g of niobic acid and 20.1 g of oxalic acid were first added to 1 L of water. Example 5

[0033] This example compares the physicochemical properties of the catalysts prepared in the above examples with the results of operating the above examples on a small-scale hydrogenation unit for 600 hours, as shown in Tables 1 and 2.

[0034] Table 1. Main properties of the catalyst Catalyst properties A B C D E F G H [NbOPO4, wt%] 4.6 5.4 6.9 5.8 - 6.9 4.6 C 10 H5NbO 20 ]]> 12.1 NiO, wt% 15 17 19 21 15 Leaching Leaching 15 Total IR acid, mmol / g 0.612 0.632 0.639 0.643 0.241 0.648 0.633 0.421 B acid, mmol / g 0.110 0.121 0.125 0.117 0.097 0.111 0.126 0.163 L acid, mmol / g 0.502 0.511 0.514 0.526 0.144 0.537 0.507 0.258 Pore volume, mL / g 0.56 0.55 0.54 0.53 0.41 0.63 0.62 0.59 Specific surface area, m 2 / g]] 241 237 229 208 213 359 341 256 Table 2. Selective hydrogenation activity of catalysts Item Feed oil A B C D E F G H Diene, g iodine / 100 g oil 25 1.3 1.0 1.0 0.9 5.8 - - 3.9 Bromine value, g bromine / 100 g oil 36 28 29 27 29 30 - - 31 Note: The reaction conditions were evaluated after catalyst reduction: P = 2.5 MPa; LHSV = 1.5 h. -1 H2 / Oil = 100 Nm 3 / m 3 ; Reaction temperature = 80℃.

[0035] The hydrogenation reaction test results in Table 2 show that the catalyst of this invention significantly reduces the diene content in cracked gasoline, and the olefins are slightly saturated. The catalyst of this invention exhibits excellent selective hydrogenation performance for dienes.

Claims

1. A cat cracker naphtha catalyst characterized by: The catalyst comprises alumina and niobium phosphate composite carrier and hydrogenation active component nickel, the content of nickel in the form of oxide is 10.0-25.0% by weight of the catalyst, preferably 12.0-23.0%, the content of niobium phosphate is 2.0%-10.0%, preferably 3.0%-8.0%, the content of alumina is 65.0%-88.0%, preferably 69.0%-85.0%; the total infrared acid content of the catalyst is 0.45-0.75 mmol / g, preferably 0.50-0.70 mmol / g, the L acid content is 0.40-0.70 mmol / g, preferably 0.35-0.

65.

2. The catalyst of claim 1, wherein: The pore volume is 0.45-1.30 mL / g, and the specific surface area is 180-400 m2 / g. 2 / g.

3. The catalyst of claim 1, wherein: The catalyst further comprises one or more of Ti, Zr, V, Cu, Zn, Si additives, the content of the additive is 0.5%-7% by weight of the total catalyst, and the sum of the contents of the components of the catalyst is 100%.

4. A process for preparing the naphtha primary catalyst of claim 1, characterized by The method comprises the following steps: (1) adding niobium acid and phosphoric acid into the bottom water of a reactor, then adding aluminum salt aqueous solution and precipitant to carry out gelation reaction, adding a solution containing basic nickel carbonate and citric acid into the slurry after the gelation reaction, and then adding organic acid to carry out aging reaction, and washing, filtering and drying the aging product to obtain active metal modified alumina dry gel powder; (2) uniformly mixing the active metal modified alumina dry gel powder, a peptizing agent and a extrusion aid, and then extruding and shaping, and then drying and calcining to obtain the catalyst product.

5. The method of claim 4, wherein: The temperature of the bottom water in step (1) is 50-90 ℃, and the amount of the bottom water is determined according to the amount of the reaction material of the gelation reaction.

6. The method of claim 4, wherein: The aluminum salt in step (1) is aluminum sulfate aqueous solution, and the concentration of the aluminum sulfate aqueous solution is 4-12 g / 100 mL in terms of alumina; the precipitant is sodium metaaluminate aqueous solution, and the concentration of the sodium metaaluminate aqueous solution is 12-40 g / 100 mL in terms of alumina.

7. The method of claim 4, wherein: The gelation reaction conditions in step (1) are as follows: the time is 0.4-1.5 hours, and the pH value is 7.0-9.

5.

8. The method of claim 4, wherein: The solution containing basic nickel carbonate and citric acid in step (1) contains basic nickel carbonate and citric acid, and the molar ratio of nickel oxide in the basic nickel carbonate to citric acid is 1.5-1.

0.

9. The method of claim 4, wherein: The organic acid in step (1) is one or more of citric acid, lactic acid, glycolic acid and ethylenediaminetetraacetic acid, and the amount of the organic acid is 0.6-1.0 times the molar content of nickel oxide in the basic nickel carbonate.

10. The method of claim 4, wherein: The aging reaction time in step (1) is 0.2-1 hour.

11. The method of claim 4, wherein: The washing in step (1) is done with deionized water to SO4 2- ≯2.5%, Na + ≯0.05%, Fe 3+ ≯0.25%.

12. The method of claim 4, wherein: The drying conditions in step (1) are as follows: the drying temperature is 90-130 ℃, and the drying time is 5-34 hours.

13. The method of claim 4, wherein: The extrusion aid in step (2) is one or more of sesbania powder, cellulose, starch and high molecular surfactant, and the amount of the extrusion aid is 0.1%-20.0% of the dry weight of the active metal modified alumina dry gel powder in step (1); the peptizing agent is one or more of aluminum sulfate, citric acid, nitric acid, acetic acid and oxalic acid, and the amount of the peptizing agent is 0.1%-20.0% of the dry weight of the modified alumina dry gel powder in step (1).

14. The method of claim 4, wherein: The drying and calcining conditions in step (3) are as follows: drying at 100-120 ℃ for 1-5 hours, and calcining at 350-550 ℃ for 1-5 hours.

15. Use of the catalyst of claim 1 in a one-stage selective hydrogenation process of pyrolysis gasoline.