Hydrofining catalyst for recovering methanol solvent in HPPO process and preparation process of hydrofining catalyst

Abstract

The invention provides a hydrofining catalyst for recovering a methanol solvent in an HPPO process and a preparation process of the hydrofining catalyst, and belongs to the field of petrochemical engineering. According to the catalyst, Ni is used as a main active component, SiO2 is used as a carrier, and Zn, Ce and the like are doped to serve as structural auxiliaries and electronic auxiliaries, so that the dispersity of the active component is increased, and the hydrogenation performance of the catalyst is improved. The catalyst can be used for efficiently hydrogenating aldehyde ketones, H2O2 and other impurities in the recovered methanol solvent to generate corresponding alcohol and water, so as to obtain the purified methanol solvent in which the aldehyde ketones impurities are basically removed. The impurity removal process is simple, the reaction condition is mild, meanwhile, the non-noble metal is used as the active component, under the condition of high loading capacity of the active component, the high specific surface area and the dispersity of active species can be kept, and efficient removal of impurities in the methanol solvent is achieved.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals and relates to a hydrogenation refining catalyst for recovering methanol solvent in the HPPO process and its preparation process. Background Technology

[0002] Propylene oxide (PO), as an important organic synthesis raw material and chemical intermediate, has now surpassed polypropylene to become the second largest propylene derivative after acrylonitrile. It is widely used in the food, pharmaceutical, and chemical industries to synthesize various chemicals such as polyurethanes, acrylates, polyether polyols, polycarbonates, and propylene glycol monomethyl ether. Furthermore, with the increasing maturity and development of the biodegradable polyester-polypropylene carbonate technology synthesized from propylene oxide and CO2, the demand for propylene oxide in this downstream route is growing, further increasing the requirements for production growth.

[0003] Currently, the main methods for synthesizing propylene oxide include the chlorohydrin method, the co-oxidation method (ethylbenzene co-oxidation, isobutane co-oxidation, isocumene co-oxidation), and the propylene-H₂O₂ oxidation method (HPPO). The chlorohydrin method is an earlier developed technology with relatively mature processes and low investment, but it generates large amounts of chlorine gas, causing severe equipment corrosion and producing large quantities of CaCl₂ waste, which does not align with the principles of green chemical production and has been gradually replaced. The co-oxidation method uses organic peroxides obtained from the oxidation of ethylbenzene as oxidants to further oxidize propylene to produce propylene oxide; however, the process is lengthy and prone to generating large amounts of byproducts. The HPPO process, on the other hand, uses H₂O₂ as an oxidant and titanium-silicon molecular sieves as a catalyst. It features mild reaction conditions, high product selectivity, no co-products, and theoretically, only water as a byproduct. It is a novel, green, and efficient propylene oxide synthesis process that better aligns with the principles of green chemistry and has attracted widespread attention and research from researchers.

[0004] The circulating solvent methanol in the propylene-H₂O₂ oxidation process for propylene oxide synthesis contains various impurities, such as H₂O₂, acetaldehyde, propionaldehyde, and dipropyl methyl ether. These impurities have boiling points close to propylene oxide, making them difficult to separate and extract through simple distillation. During repeated solvent recycling, these impurities gradually accumulate, leading to decreased propylene oxide purity and poor product quality. Aldehydes, in particular, act as polymerization inhibitors for propylene oxide, severely impacting the molecular weight growth of downstream polymers, increasing polymerization pressure, and posing safety hazards. Furthermore, these impurities significantly affect the catalytic activity and selectivity of titanium-silicon molecular sieve catalysts, reducing catalyst lifetime and stability. Therefore, effectively removing impurities from the circulating methanol in the HPPO process is crucial for extending the lifespan and stability of the epoxidation catalyst and improving product yield and quality.

[0005] Currently, some reports have disclosed hydrogenation refining processes for recycled methanol solvents. CN201610473450.1 uses modified zeolite molecular sieves as adsorbents to adsorb aldehyde impurities in propylene oxide solutions, purifying the propylene oxide. Patents CN201110434173.0, CN201910342568.4, CN201910342546.8, and CN201910342529.4 employ modified resins or plasma-modified materials, grafting thiol, hydroxyl, or amino groups to react with aldehydes in the reaction solution, thereby removing impurities from propylene oxide. However, propylene oxide has a certain swelling effect on polymer materials and is easily adsorbed, leading to increased propylene oxide consumption. It also suffers from poor resin stability and fragility. CN201910342601.3 describes a process using ion-exchange modified molecular sieves as a catalyst to react aldehydes and ketones in methanol solvent with methanol, thereby generating the corresponding acetals and ketals, ultimately obtaining purified methanol free of aldehydes and ketones. However, this process consumes methanol solvent, requiring subsequent replenishment of fresh methanol for recycling into the epoxidation process, increasing costs and energy consumption. CN201510125725.8 discloses a process for degrading hydrogen peroxide, using activated carbon as a carrier and precious metals such as Pd and Ag as active components and additives to catalytically hydrogenate and degrade hydrogen peroxide, removing residual oxidants from the solvent. However, precious metal catalysts are expensive and unsuitable for industrial production. Ni-based catalysts have excellent catalytic hydrogenation performance and are inexpensive, widely used in various C=C and C=O hydrogenation processes. However, Ni-based catalysts are prone to metal loss, agglomeration, and sintering problems. Therefore, developing a highly active, highly dispersed, and stable catalyst is an important means of applying it to the HPPO process for impurity removal. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of excessive impurities such as aldehydes and residual H2O2 in the recovered solvent during the HPPO process. It provides a hydrogenation refining catalyst and its preparation method suitable for the recovered solvent in the propylene epoxidation process. This catalyst hydrogenates impurities in the recovered methanol solvent, reducing impurity content and improving methanol solvent purity. The catalyst uses Ni as the main active component, SiO2 as the support, and is doped with Zn, Ce, etc., as structural and electronic aids to increase the dispersion of the active component and improve the hydrogenation performance of the catalyst. This invention achieves improved propylene oxide product quality and catalyst stability through a highly efficient, green, and environmentally friendly purification and impurity removal process.

[0007] To achieve the above objectives, the first aspect of the present invention provides a process for preparing a hydrorefining catalyst, comprising the following steps: (1) Prepare a metal salt solution containing a nickel source, add an alkaline source, and form solution A; (2) Add a silicon source to solution A to form solution B, stir and then age to obtain solution C; (3) Heat solution C under reflux until the pH is neutral, then filter, wash, dry and calcine.

[0008] Furthermore, the metal salt solution also contains an auxiliary metal source, which is selected from at least one of the auxiliary metal nitrate, acetate, sulfate and chloride, and the auxiliary metal is selected from at least one of Zn, Ce, Co and La.

[0009] Furthermore, in the metal salt solution, the mass ratio of nickel oxide to transition metal oxide, calculated as oxides, is 40~80:1~4.

[0010] Furthermore, the nickel source is selected from at least one of nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate.

[0011] Furthermore, the alkali source is selected from at least one of urea, ammonium carbonate, and ammonia water.

[0012] Furthermore, the molar ratio of the nickel source to the alkali source is 0.1~1~1~3.

[0013] Furthermore, the silicon source is selected from at least one of silica sol, water glass, silicon tetrachloride, methyl orthosilicate, ethyl orthosilicate, and fumed silica, and the mass ratio of the nickel source (calculated as NiO) to the silicon source (calculated as SiO2) is 1~10:1~10.

[0014] Furthermore, the stirring time is 2 to 12 hours.

[0015] Furthermore, the aging process takes 3 to 8 hours.

[0016] Furthermore, the temperature of the heating reflux treatment is 70~90℃.

[0017] Furthermore, the drying temperature is 80~120℃, and the time is 6~12 h.

[0018] Furthermore, the drying temperature is 90~110℃.

[0019] Furthermore, the calcination temperature is 300~600℃, and the time is 4~10 h.

[0020] Furthermore, the calcination temperature is 400~550℃, and the calcination time is 4~6 h.

[0021] A second aspect of the present invention provides a hydrorefining catalyst prepared by the above-described preparation process, wherein the hydrorefining catalyst comprises an active component and a support, wherein the active component is NiO and its content is 10% to 60% of the total mass of the catalyst, and the support is SiO2 and its content is 40% to 90% of the total mass of the catalyst.

[0022] Furthermore, the hydrorefining catalyst also includes an auxiliary component, which is an auxiliary metal oxide. The auxiliary metal is selected from at least one of Zn, Ce, Co, and La. The mass ratio of nickel oxide to auxiliary metal oxide is 1~50:0.1~1, and the content of auxiliary metal oxide is 0.1%~10% of the total mass of the catalyst.

[0023] Furthermore, the specific surface area of ​​the hydrorefining catalyst is 380.23~443.86 m². 2 / g, pore volume 0.45~0.89 cm³ 3 / g, with a pore size of 4.86~8.97nm.

[0024] A third aspect of the present invention provides a hydrorefining process for recovering methanol solvent, wherein the hydrorefining process uses the hydrorefining catalyst prepared by the above-described preparation process.

[0025] Further, the hydrorefining catalyst is tableted and granulated, then loaded into a fixed-bed reactor and reduced in a 20% H2 / He mixed atmosphere at 350-450°C for 12-20 h. After reduction, the temperature is purged to 75-95°C with N2 or He and maintained at this temperature. The H2 pressure is set to 1-2 MPa, the gas flow rate to 100-300 mL / min, the methanol solvent recovery feed rate to 0.1-0.8 mL / min, and the mass hourly space velocity to 4-10 h⁻¹. -1 The recovered methanol solvent is hydrogenated to remove impurities.

[0026] Compared with the prior art, the present invention has the following advantages: (1) The catalyst prepared by this invention has excellent hydrogenation performance. When applied to the methanol refining process of solvent recovery, the reaction conditions are mild, and it can effectively remove impurities such as aldehydes, ketones, and H2O2, reducing the impurity content to below 10 ppm. This can improve the quality of propylene oxide products and help extend the service life of epoxidation catalysts. In addition, the catalyst maintains a conversion rate of over 99% even under high-concentration raw material conditions.

[0027] (2) The impurity removal process of this invention is simple, the reaction conditions are mild, and non-precious metals are used as active components. Under high loading of active components, a high specific surface area can still be maintained, which is beneficial to the dispersion of active species and achieves efficient removal of impurities from methanol solvent. This invention provides a low-cost, environmentally friendly catalyst synthesis process that is easy to scale up for production and industrial application. Attached Figure Description

[0028] Figure 1 This is a SEM image of the catalyst prepared in Example 2.

[0029] Figure 2 The image shows the XRD pattern of the catalyst prepared in Example 2. Detailed Implementation

[0030] The invention will be further illustrated by the following examples, but these examples are not intended to limit the invention. Example 1

[0031] 25 g of nickel nitrate was dissolved in 250 mL of water. Then, 41.28 g of urea was added to the solution to form a homogeneous solution. Subsequently, 18.36 g of 30% silica sol was pumped in dropwise over 30 min using a peristaltic pump. The mixture was stirred at room temperature for 4 h, then refluxed at 85 °C until the pH of the solution was neutral. The suspension was filtered, washed three times with deionized water, dried overnight at 100 °C, and calcined in a muffle furnace at 400 °C for 6 h. The specific surface area of ​​the catalyst was 412.28 m². 2 / g, pore volume 0.77cm 3 / g, with a pore size of 7.32 nm. Example 2

[0032] 25 g of nickel nitrate and 0.56 g of zinc nitrate were dissolved in 250 mL of water. Then, 41.28 g of urea was added to the solution to form a homogeneous solution. Subsequently, 18.36 g of 30% silica sol was added dropwise over 30 min using a peristaltic pump. The solution was stirred at room temperature for 4 h, then refluxed at 80 °C until the pH was neutral. The suspension was filtered, washed three times with deionized water, dried overnight at 100 °C, and calcined in a muffle furnace at 400 °C for 6 h. The specific surface area of ​​the catalyst was 395.03 m². 2 / g, pore volume 0.85 cm³ 3 / g, with a pore size of 8.73 nm.

[0033] The SEM and XRD patterns of the catalyst prepared in Example 2 of this invention are as follows: Figure 1 and Figure 2As shown, the catalyst synthesized by this process exhibits a distinct flower-like lamellar structure, with a large specific surface area and high metal dispersion, which is beneficial for improving the catalyst's hydrogenation performance. Example 3

[0034] 22 g of nickel acetate and 0.39 g of cerium nitrate were dissolved in 250 mL of water. Then, 41.28 g of urea was added to the solution to form a homogeneous solution. Subsequently, 18.36 g of 30% silica sol was added dropwise over 30 min using a peristaltic pump. The solution was stirred at room temperature for 4 h, then refluxed at 80 °C until the pH was neutral. The suspension was filtered, washed three times with deionized water, dried overnight at 100 °C, and calcined in a muffle furnace at 400 °C for 6 h. The specific surface area of ​​the catalyst was 398.74 m². 2 / g, pore volume 0.80 cm³ 3 / g, with a pore size of 8.34 nm. Example 4

[0035] 21.4 g of nickel acetate was dissolved in 300 mL of water. Then, 41.28 g of urea was added to the solution to form a homogeneous solution. Subsequently, 20 g of 30% silica sol was pumped in dropwise over 30 min using a peristaltic pump. The mixture was stirred at room temperature for 4 h, then refluxed at 85 °C until the pH of the solution was neutral. The suspension was filtered, washed three times with deionized water, dried overnight at 100 °C, and calcined in a muffle furnace at 350 °C for 8 h. The specific surface area of ​​the catalyst was 421.65 m². 2 / g, pore volume 0.69 cm³ 3 / g, with a pore size of 7.46 nm. Example 5

[0036] 25 g of nickel nitrate was dissolved in 250 mL of water. Then, 5.16 g of urea was added and dissolved completely. Next, a 25% ammonia solution was gradually added until the pH reached 11 and the solution changed from green to blue. Subsequently, 18.36 g of 30% silica sol was pumped in dropwise over 40 min using a peristaltic pump. The mixture was stirred for 5 h at room temperature, then refluxed at 90 °C until the pH was neutral. The suspension was filtered, washed three times with deionized water, dried overnight at 100 °C, and calcined in a muffle furnace at 450 °C for 5 h. The specific surface area of ​​the catalyst was 419.63 m². 2 / g, pore volume is 0.71 cm³ 3 / g, with a pore size of 7.17nm. Comparative Example 1

[0037] Add 11.4 g of sodium carbonate to 150 mL of water, stir thoroughly to dissolve, and then place the solution in a 70°C oil bath with continuous stirring. Slowly add 18.5 g of water glass solution (30% SiO2) to the solution, and continue stirring for 30 min. Add 25 g of nickel nitrate to 75 mL of water, dissolve thoroughly, and then gradually add Ni solution dropwise to the above solution over 2 h. Continue stirring for 4 h, then filter the suspension, wash five times with deionized water, and dry the filter cake overnight in a 110°C oven. Calcinate in a muffle furnace at 550°C for 6 h. The specific surface area of ​​the catalyst is 359.84 m². 2 / g, pore volume is 0.81 cm³ 3 / g, with a pore size of 8.90 nm. Comparative Example 2

[0038] 25 g of nickel nitrate was added to 150 mL of water and stirred thoroughly to dissolve. The solution was then placed in a 70°C oil bath. 12.38 g of ammonium carbonate was added to 100 g of water and dissolved thoroughly to prepare another solution. The ammonium carbonate solution was then added dropwise to the Ni solution along with 18.5 g of 30% silica sol, and the reaction was continued at 70°C for 5 h. The suspension was then filtered, washed five times with deionized water, and the filter cake was dried overnight in a 100°C oven. The catalyst was calcined at 450°C for 6 h. The specific surface area of ​​the catalyst was 370.77 m². 2 / g, pore volume 0.79 cm³ 3 / g, with a pore size of 8.12 nm.

[0039] The catalyst prepared above was granulated into tablets to a mesh size of 20-40 and then packed into a fixed-bed reactor. In situ reduction at 400°C for 6 h under a 20% H₂ / He mixed atmosphere, the catalyst was purged with N₂ to 80°C, and then cooled to the reaction temperature for catalyst performance evaluation. The recovered methanol solvent was then used for 5 h... -1 The hydrogenation reaction was carried out in the reactor at 85℃ and 1 MPa H2 (gas flow rate of 200 mL / min). The contents of various impurities in the methanol solvent are shown in the table below. The catalyst performance evaluation results are shown in Table 1 below: Table 1

[0040] As shown in Table 1, the Ni / SiO2 catalyst synthesized by the homogeneous precipitation method using the technical solution of this invention exhibits good hydrogenation activity. Furthermore, adding auxiliary metals Zn and Ce to the catalyst can improve its hydrogenation performance and further reduce the content of organic peroxides and aldehydes in the recovered solvent to below 10 ppm. After treatment, the removal rates of acetaldehyde and organic peroxides both exceed 99.5%, demonstrating excellent removal efficiency.

[0041] In addition, to further explore the catalyst's tolerance to acetaldehyde and its catalytic ability, the catalyst obtained in Example 2 was used, and the acetaldehyde concentration was further increased to 1.5%. The reaction conditions remained unchanged, and the acetaldehyde content after the reaction was 42 ppm, while the acetaldehyde removal rate remained above 99.5%.

[0042] Examples 6-8 The same preparation method and steps as in Example 2 were used, except that different types of Zn additives were used to obtain Ni-Zn / SiO2 modified with different Zn precursors. Using the same steps and conditions as the evaluation process described above, the results of catalytic hydrogenation for recovering methanol solvent are shown in Table 2.

[0043] Table 2

[0044] As shown in Table 2, adding Zn as a promoter to the Ni / SiO2 catalyst synthesized by the homogeneous precipitation method can effectively isolate metal particles, inhibit the agglomeration process, and thus improve hydrogenation performance. The hydrogenation capacity of different Zn types follows the order: zinc nitrate ≈ zinc acetate > zinc chloride > zinc sulfate.

[0045] Examples 9-10 The same preparation method and steps as in Example 3 were used, except that different types of Ce were used as the auxiliary agent, resulting in Ni-Ce / SiO2 modified with different Ce precursors. Using the same steps and conditions as the evaluation process described above, the catalytic hydrogenation of recovered methanol solvent was applied, and the results are shown in Table 3.

[0046] Table 3

[0047] As shown in Table 3, adding Ce as a promoter to the Ni / SiO2 catalyst synthesized by the homogeneous precipitation method can form oxygen vacancies, which is beneficial to increasing the surface hydrogen concentration and improving the hydrogenation performance. The hydrogenation capacity of different Ce types is in the order of cerium nitrate ≈ cerium acetate > cerium chloride.

[0048] This article uses specific examples to illustrate the structure and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A process for the preparation of a hydrofinishing catalyst, characterized in that, The preparation method comprises the following steps: (1) preparing a metal salt solution containing a nickel source, adding an alkali source to form solution A; (2) adding a silicon source to solution A to form solution B, stirring and aging to obtain solution C; (3) heating and refluxing solution C, filtering, washing, drying and calcining after the pH is neutral.

2. The manufacturing process of claim 1, wherein, The metal salt solution further contains an auxiliary metal source selected from at least one of a nitrate, an acetate, a sulfate and a chloride of an auxiliary metal selected from at least one of Zn, Ce, Co and La. The mass ratio of nickel oxide to transition metal oxide in the metal salt solution is 40-80:1-4.

3. The production process according to claim 1 or 2, characterized in that, The nickel source is selected from at least one of nickel nitrate, nickel acetate, nickel chloride and nickel sulfate. The alkali source is selected from at least one of urea, ammonium carbonate and ammonia water. The molar ratio of the nickel source to the alkali source is 0.1-1:1-3.

4. The production process according to any one of claims 1 to 3, characterized in that, The silicon source is selected from at least one of silica sol, water glass, silicon tetrachloride, methyl orthosilicate, ethyl orthosilicate and fumed silica, and the mass ratio of the nickel source to the silicon source is 1-10:1-10.

5. The production process according to any one of claims 1 to 4, characterized in that, The stirring time is 2-12 h. The aging time is 3-8 h.

6. The production process according to any one of claims 1 to 5, characterized in that, The heating and refluxing temperature is 70-90℃. The drying temperature is 80-120℃, preferably 90-110℃, and the time is 6-12 h. The calcining temperature is 300-600℃, and the time is 4-10 h, preferably, the calcining temperature is 400-550℃, and the calcining time is 4-6 h.

7. A hydrofmishing catalyst produced by the production process according to any one of claims 1 to 6, characterized in that, The hydrofining catalyst comprises an active component and a carrier, the active component is NiO, and the content is 10%-60% of the total mass of the catalyst, and the carrier is SiO2, and the content is 40%-90% of the total mass of the catalyst.

8. The hydrofmishing catalyst of claim 7, wherein, The hydrofining catalyst further comprises an auxiliary component, the auxiliary component is an auxiliary metal oxide, the auxiliary metal is selected from at least one of Zn, Ce, Co and La, the mass ratio of nickel oxide to auxiliary metal oxide is 1-50:0.1-1, and the content of the auxiliary metal oxide is 0.1%-10% of the total mass of the catalyst. And / or, the specific surface area of the hydrofining catalyst is 380.23~443.86m 2 / g, the pore volume is 0.45~0.89cm 3 / g, and the pore size is 4.86~8.97nm.

9. A hydrofining process for recovering methanol solvent, characterized by, The hydrofining process adopts the hydrofining catalyst prepared by the preparation process of any one of claims 1-6.

10. The hydrofinishing process of claim 9, wherein, After the hydrofining catalyst is pressed and granulated, it is loaded into a fixed bed reactor, reduced in a 10-80% H2 / He mixed atmosphere, reduced at 350-450°C for 12-20 h, after reduction treatment, purged with N2 or He to 75-95°C, incubated, set H2 pressure to 1-2 MPa, gas flow to 100-300 mL / min, methanol solvent recovery feed rate to 0.1-0.8 mL / min, mass space velocity to 4-10 h -1 The recovered methanol solvent is hydrogenated to remove impurities.

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