Hydrogenation catalyst, method for producing the same, and method for selectively hydrogenating carbon three fraction

Abstract

The present application provides a kind of hydrogenation catalyst and its preparation method and carbon three fraction selective hydrogenation method.The composite oxide and palladium are included in the hydrogenation catalyst, wherein the composite oxide includes alumina and titanium dioxide, the specific surface area of the composite oxide is expressed as X m 2 / g, the average pore size of the composite oxide is expressed as Y nm, wherein the ratio of X to Y is 5 to 30; in the composite oxide, the anatase crystalline phase of titanium dioxide accounts for 95wt% to 100wt% of the total titanium dioxide. The hydrogenation catalyst provided by the present application has high acetylene saturation activity, good selectivity, high low-temperature activity, good resistance to impurity poisoning and good raw material adaptability. The present application provides a kind of carbon three fraction selective hydrogenation method, which has high conversion rate and hydrogenation selectivity, and effectively removes MAPD in carbon three fraction.

Description

Technical Field

[0001] This invention relates to a hydrogenation catalyst and a selective hydrogenation method for C3 fractions. Background Technology

[0002] Propylene is an important basic chemical raw material that can be used to produce polypropylene, acrylonitrile, propylene oxide, acrolein, acrylic acid, etc. Its downstream products have wide applications in films, fibers, rubber, resins, coatings and other fields.

[0003] Propylene is typically obtained in petroleum cracking to ethylene production units. The C3 fraction in the cracked gas usually consists of 93-96% propylene, 2.9-3.5% propane, and 1-5% propyne (MA) and propadiene (PD). MAPD is a toxic substance that affects downstream propylene applications; therefore, removing MAPD is essential for obtaining high-purity propylene. MAPD in the C3 fraction is usually selectively hydrogenated to propylene, with some side reactions producing propane. Industrial removal of MAPD from the C3 fraction mainly includes gas-phase catalytic selective hydrogenation, liquid-phase catalytic selective hydrogenation, and catalytic distillation. Currently, liquid-phase selective hydrogenation is commonly used due to its simple process flow, low reaction temperature, low energy consumption, safety, environmental friendliness, and ease of operation. Selective hydrogenation of the C3 fraction requires high precision in catalyst selection and reaction process control. Currently, industrial selective hydrogenation catalysts for the C3 fraction are supported catalysts with palladium as the main active component and alumina as the carrier; some also add auxiliaries such as silver, gold, and copper to improve propylene selectivity.

[0004] CN 107970933 A discloses a selective hydrogenation catalyst for C3 fractions, its preparation method, and the hydrogenation method. The catalyst comprises: a support and an active component supported on the support; the support is Mn and Ce modified Al2O3; the main active component is Pd, and the co-active component is Ga-Ga2O3, wherein the co-active component Ga2O3 exists in an amorphous γ-crystalline phase; the co-active component Ga is obtained by partial reduction of Ga2O3; the degree of reduction of Ga in Ga2O3 is 10-70%; the crystal form of the Al2O3 modified on the support contains a θ phase, and the proportion of the θ phase is >30%; the Pd content is 0.1-1.0 wt% of the total mass of the support; in the co-active component Ga-Ga2O3, the total Ga content is 0.05-2.0 wt% of the total mass of the support. This catalyst exhibits tolerance to trace amounts of organic sulfur and high activity and selectivity towards alkynes and dienes, and can effectively perform liquid-phase selective hydrogenation and removal of MAPD from C3 fractions.

[0005] CN 104098427 A discloses a method for selective hydrogenation of C3 fractions, wherein the C3 fractions enter an adiabatic bed reactor for selective hydrogenation to remove propyne and propadiene. The method is characterized by a selective hydrogenation catalyst support that is alumina or primarily alumina, with a bimodal pore distribution structure containing dual active components Pd and Ni. During catalyst preparation, the anti-coking component Ni enters the macropores of the support in the form of a microemulsion. The anti-coking component Ni is mainly distributed in the macropores of the support, significantly reducing the degree of coking on the catalyst surface. Hydrogenated compounds gradually diffuse out of the catalyst channels without causing blockage, thus greatly extending the catalyst's operating life. This method significantly reduces green oil formation and catalyst coking, improving the economic efficiency of the plant operation.

[0006] CN 105727990 A This invention relates to a method for preparing a palladium-copper supported catalyst. The catalyst contains palladium and copper, and the support contains Al2O3. The method is characterized by impregnating an Al2O3-based support in an organic solution of a hydroxyl-containing bipyridine derivative, drying the support, then impregnating it again with a mixed cationic solution of Pd and Cu, drying again, and calcining to obtain a Pd-Cu catalyst. Because the preparation method overcomes the adverse effects of surface tension and solvation on the dispersion of palladium and copper in the impregnation solution, the prepared catalyst is more conducive to the formation of palladium-copper alloys and exhibits excellent activity, selectivity, and anti-coking properties.

[0007] Hydrogenation catalysts developed using TiO2 as a support exhibit high activity, good low-temperature activity, and strong resistance to poisoning. However, TiO2 also has some weaknesses as a catalyst support, such as a relatively small specific surface area, the tendency of the active anatase type to transform into an inert rutile structure at high temperatures, poor mechanical strength, and weak acidity. These shortcomings are generally overcome by generating composite oxides such as TiO2-Al2O3 as supports to meet industrial application standards. The structure and shape of TiO2-based catalytic materials can significantly affect the light absorption efficiency of photocatalytic materials. Coral reefs possess excellent light absorption and reflection structures, thus providing a three-dimensional (3D) environment for many marine plants and animals and absorbing small particles, supporting approximately one-quarter of known marine life. Coral-like 3D layered structures can have a higher specific surface area, resulting in more active sites and stronger light-harvesting capabilities, and have been shown to have better photocatalytic performance than other structures.

[0008] There are currently no reports on the synthesis of coral cluster 3D microstructures on the surface of composite oxide supports such as TiO2-Al2O3. Utilizing unique microstructure structures can enhance the co-catalytic effect of TiO2 as an electronic promoter on the support, thereby improving the catalyst activity and enabling the catalyst to exhibit higher catalytic performance in industrial applications. Summary of the Invention

[0009] This invention provides an alumina-titanium dioxide composite oxide support with a coral cluster 3D microstructure. Under the same pore size distribution and pore volume conditions, this support can provide a higher specific surface area, thereby having more active sites and stronger electron capture ability, ultimately improving the co-catalytic effect of TiO2 as an electron aid.

[0010] This invention aims to provide a cheap and readily available selective hydrogenation catalyst for C3 fractions suitable for industrial production. The catalyst has a specific structure, with TiO2 uniformly dispersed on the support surface. It exhibits good low-temperature activity and high hydrogenation activity at high space velocities.

[0011] First, the present invention provides a hydrogenation catalyst comprising a composite oxide and palladium, wherein the composite oxide comprises aluminum oxide and titanium dioxide, and the specific surface area of ​​the composite oxide is expressed as X m. 2 / g, the average pore size of the composite oxide is expressed as Y nm, where the ratio of X to Y is 5 to 30. Preferably, in the composite oxide, the anatase phase titanium dioxide accounts for 96 wt% to 100 wt% of the total titanium dioxide. Preferably, in the composite oxide, the anatase phase titanium dioxide accounts for 97 wt% to 100 wt% of the total titanium dioxide. Preferably, in the composite oxide, the anatase phase titanium dioxide accounts for 98 wt% to 100 wt% of the total titanium dioxide. Preferably, in the composite oxide, the anatase phase titanium dioxide accounts for 99 wt% to 100 wt% of the total titanium dioxide.

[0012] In this invention, the proportion of anatase phase titanium dioxide to total titanium dioxide can be measured by X-ray diffraction analysis.

[0013] In this invention, the specific surface area of ​​the composite oxide can be determined by the BET method.

[0014] According to some embodiments of the composite oxide of the present invention, the diffraction peak area representing the crystal structure of anatase titanium dioxide, as measured by X-ray diffraction analysis, accounts for 95 wt% to 100 wt% of the diffraction peak area of ​​all titanium dioxide crystal structures.

[0015] According to some embodiments of the composite oxide of the present invention, the diffraction peak area representing the crystal structure of anatase titanium dioxide, as measured by X-ray diffraction analysis, accounts for 96 wt% to 100 wt% of the diffraction peak area of ​​all titanium dioxide crystal structures.

[0016] According to some embodiments of the composite oxide of the present invention, the diffraction peak area representing the crystal structure of anatase titanium dioxide, as measured by X-ray diffraction analysis, accounts for 97 wt% to 100 wt% of the diffraction peak area of ​​all titanium dioxide crystal structures.

[0017] According to some embodiments of the composite oxide of the present invention, the diffraction peak area representing the crystal structure of anatase titanium dioxide, as measured by X-ray diffraction analysis, accounts for 98 wt% to 100 wt% of the diffraction peak area of ​​all titanium dioxide crystal structures.

[0018] Preferably, the ratio of X to Y is 5 to 15. More preferably, the ratio of X to Y is 5 to 10.

[0019] According to some embodiments of the present invention, the pore volume of the composite oxide is Z mL / g, and the ratio of X to Z is 220 to 400, preferably 250 to 350. In some embodiments, the ratio of X to Z is 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, or within any combination thereof.

[0020] According to some embodiments of the invention, X is 90 to 150. In some embodiments, X is 90, 100, 110, 120, 130, 140, 150 or a range of any two thereof.

[0021] According to some embodiments of the present invention, Y is 9 to 20, preferably 12 to 16. In some embodiments, Y is 12, 13, 14, 15, 16, or any combination thereof.

[0022] According to some embodiments of the present invention, Z is 0.3 to 0.5, preferably 0.3 to 0.4. In some embodiments, Z is 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, or any combination thereof.

[0023] According to some embodiments of the present invention, the composite oxide contains 5 wt% to 21 wt% titanium dioxide. In some embodiments, the composite oxide contains 5 wt%, 6 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, 20 wt%, 21 wt% or any combination thereof of titanium dioxide.

[0024] According to some embodiments of the present invention, the palladium content in the catalyst is 0.1%-20% by mass. In some embodiments, the palladium content is 0.1%, 0.3%, 0.5%, 1.5%, 2.0%, 5%, or 8% by mass.

[0025] According to some embodiments of the present invention, the method for preparing the composite oxide includes the following steps:

[0026] Step I. Dissolve soluble aluminum salts in water to form an aluminum salt solution, dissolve titanium salts in an acid solution to form a titanium salt solution, and mix ammonium salts and alkaline solutions to form a mixed alkaline solution;

[0027] Step II. (a) Add the titanium salt solution and the mixed alkaline solution to the aluminum salt solution, so that the mixture is maintained at the first pH value for a first time period; (b) Stop adding the titanium salt solution and continue adding the mixed alkaline solution, so that the mixture is maintained at the second pH value for a second time period; (c) Stop adding the mixed alkaline solution and add the titanium salt solution, so that the mixture is maintained at the third pH value for a third time period.

[0028] Step III. After step II.(c), the temperature of the mixture is raised and maintained for a fourth time period to obtain a precipitate;

[0029] Step IV. The precipitate is dried and calcined to obtain a composite oxide containing alumina and titanium dioxide. Preferably, the precipitate is also washed and filtered before drying (to remove unwanted impurities).

[0030] According to some embodiments of the present invention, in step II, the first pH value is less than 5, preferably 3 to 4. According to some embodiments of the preparation method of the present invention, in step II, the second pH value is greater than 8.5, preferably 9 to 10. According to some embodiments of the preparation method of the present invention, in step II, the third pH value is greater than 7 and less than 9, preferably 7.5 to 8.5.

[0031] According to some embodiments of the present invention, in step II, the first time period, the second time period, and the third time period are 5 to 20 minutes, preferably 10 to 15 minutes.

[0032] According to some embodiments of the present invention, in step II, the fourth time period is 20 minutes to 60 minutes.

[0033] According to some embodiments of the present invention, in step III, the operating temperature is 25°C to 60°C, preferably 50°C to 60°C.

[0034] According to some embodiments of the present invention, in step III, the temperature is raised to 80°C to 150°C, preferably 80°C to 100°C. In some embodiments, in step III, the temperature is raised to 80°C, 85°C, 90°C, 92°C, or 95°C.

[0035] According to some embodiments of the present invention, in step IV, the drying temperature is 110°C to 130°C.

[0036] According to some embodiments of the present invention, in step IV, the calcination temperature is between 800°C and 1000°C. In some embodiments, in step IV, the calcination temperature is within the range of 800°C, 850°C, 900°C, 950°C, or any combination thereof.

[0037] According to some embodiments of the present invention, the concentration of the aluminum salt is from 0.5 to 2.5 mol / L. The aluminum salt is a soluble aluminum salt, selected from one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, and other organic salts of aluminum.

[0038] According to some embodiments of the present invention, the concentration of the titanium salt is 0.2 to 1.2 mol / L. According to some embodiments of the present invention, the concentration of the ammonium salt is 0.1 to 0.3 mol / L. The ammonium salt may be selected from one or more of ammonium bicarbonate, ammonium carbonate, and other organic ammonium salts.

[0039] According to some embodiments of the present invention, the concentration of the alkaline solution is 0.2 to 0.4 mol / L. The alkaline solution may be one or more of ammonia, sodium hydroxide, potassium hydroxide, and other organic bases.

[0040] According to some embodiments of the present invention, the acid solution may be selected from one or more of sulfuric acid, nitric acid, hydrochloric acid, and other organic acids.

[0041] According to some embodiments of the present invention, in step IV, the precipitate washing process includes washing with deionized water until the acid radical ions are undetectable.

[0042] According to some embodiments of the present invention, in step IV, the drying temperature is 100°C to 120°C, and the drying time is 4°C to 12 hours.

[0043] According to some embodiments of the present invention, in step IV, the calcination temperature is 800°C to 1000°C.

[0044] According to some embodiments of the present invention, the composite oxide has a coral-like 3D layered structure. The coral-like 3D layered structure can have a higher specific surface area, thus possessing more active sites and stronger light-harvesting ability. In the TiO2-Al2O3 support, titanium dioxide is uniformly distributed on the alumina surface, and the support surface possesses a coral-like 3D microstructure. While retaining pore volume and pore size distribution, the specific surface area is increased, and the surface electronic activity of the support is improved, greatly enhancing the low-temperature activity and stability of the catalyst, thereby improving the hydrogenation performance of the catalyst. This catalyst is suitable for hydrogenation of C2 and C3 fractions, and its hydrogenation performance is better than that of existing catalysts, showing great promise for industrial applications.

[0045] Furthermore, the present invention also provides a method for preparing the hydrogenation catalyst as described above, which includes impregnating the composite oxide with a palladium compound solution, reducing the impregnated product with hydrazine hydrate, drying and calcining the product after hydrazine hydrate reduction, and reducing the calcined product to obtain the Pd / TiO2-Al2O3 catalyst, i.e., the hydrogenation catalyst of the present invention.

[0046] According to some embodiments of the present invention, the calcined product is reduced for 6 to 8 hours at a hydrogenation temperature of 100 to 150°C, a hydrogen pressure of 2.6 to 3.0 MPa, and a hydrogen flow rate of 35 to 65 mL / min.

[0047] According to some embodiments of the present invention, the preparation method of the hydrogenation catalyst includes pre-soaking the above-synthesized alumina-titanium dioxide composite oxide in deionized water at 1 to 1.5 times its volume for 0.3 to 1 hour, filtering and draining the water, then impregnating it with a palladium compound solution equal to the amount of palladium metal contained in the catalyst for 14 hours, wherein the amount of the solution is at least equal to the total pore volume of the composite support, then adding 30-40% by weight of hydrazine hydrate at 1 to 2 times the volume of the composite support for reduction for 1 to 2 hours, filtering and washing with deionized water; drying the obtained product at 100-150°C for 4 to 10 hours, and then calcining it at 400-600°C for 4 to 8 hours to obtain the Pd / TiO2-Al2O3 catalyst.

[0048] In addition, the present invention provides a method for selective hydrogenation of C3 fractions, which includes selectively hydrogenating the distillate oil in the presence of the above-mentioned hydrogenation catalyst.

[0049] According to some embodiments of the present invention, the reaction temperature is 20–50°C, the mol ratio of hydrogen to alkyne is 1:1–2.5:1, the pressure is 0.5–0.8 MPa, and the recycle ratio is 10:1–30:1.

[0050] Compared with existing catalysts, the hydrogenation catalyst provided by this invention has higher low-temperature activity in the field of C3 fraction hydrogenation and hydrogenation activity at high space velocities. Attached Figure Description

[0051] Figure 1 The 3D microstructure of the coral reef prepared by the alumina-titanium dioxide composite oxide in Example 1 is shown.

[0052] Figure 2 The XRD pattern of the alumina-titanium dioxide composite oxide prepared in Example 1 is shown. Detailed Implementation

[0053] To facilitate understanding of the present invention, the present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not limited to the scope of application of the present invention.

[0054] Unless otherwise specified, all raw materials or components used in this invention can be obtained through commercial means or conventional methods.

[0055] The specific surface area and pore structure of the composite oxides were determined using an ASAP 2020 adsorption analyzer (N2 adsorption method) from Micron Instruments, USA. Before testing, the composite oxide samples were degassed at 623 K for 4 h, and nitrogen was adsorbed at liquid nitrogen temperature. Sample data were processed using AMSM software, and the specific surface area was obtained using the Brunauer-Emmet-Teller (BET) method. The average pore size was obtained from the nitrogen adsorption isotherm using the Barrett-Joyner-Halenda (BJH) method, and the pore volume was obtained using the P / Po single-point desorption curve.

[0056] The morphology of the composite oxide was observed using a QUANTA 200 scanning electron microscope from FEI.

[0057] The crystal structure of the composite oxide was characterized using an EMPYREAN X-ray diffractometer from Panaco GmbH, Netherlands. The radiation source was Cu Kα, with an X-ray tube voltage of 40 kV, a tube current of 40 mA, a slit width of 10 mm, a scanning range of 5–90°, and a scanning speed of 0.013° / s.

[0058] Example 1

[0059] 328.02 g of Al2(SO4)3 was dissolved in deionized water to prepare 1000 mL of aluminum sulfate solution. 21.14 g of TiO(OH)2 was dissolved in sulfuric acid solution, and deionized water was added to prepare 500 mL of dilute sulfuric acid solution containing metatitanic acid. 18 g of NH4HCO3 was dissolved in 600 mL of deionized water to prepare ammonium bicarbonate solution, then 250 mL of 24–28 wt% ammonia solution was added, stirred until homogeneous, and then deionized water was added to prepare 1000 mL of mixed alkali solution.

[0060] At atmospheric pressure and 55°C, the dilute sulfuric acid solution of the above-mentioned metatitanic acid and the mixed alkali solution were added concurrently to the aluminum sulfate solution while maintaining vigorous stirring. The pH of the mixed solution was maintained within the range of 3 to 4 for 15 minutes. The addition of the dilute sulfuric acid solution of metatitanic acid was then stopped, and the mixed alkali solution was continued to be added until the pH reached 9 to 10. This was maintained for 15 minutes. The addition of the mixed alkali solution was then stopped, and the dilute sulfuric acid solution of the above-mentioned metatitanic acid was added again to adjust the pH to 7.5 to 8.5. This was maintained for 6 to 10 minutes. The temperature was then raised to 92°C and maintained for 20 minutes. The mixture was filtered, and the filter cake was washed five times with 20 times its volume of deionized water. The washed filter cake was dried at 110°C for 6 hours and then calcined at 850°C for 5 hours. 114.3 g of a composite oxide with a TiO2 content of 15.0% was obtained. Figure 1SEM images show that the surface microstructure of the composite oxide exhibits a coral-like 3D layered structure. Figure 2 The XRD pattern of the alumina-titanium dioxide composite oxide prepared in Example 1 is shown. For titanium dioxide, the characteristic diffraction peak of anatase only appears at 2θ = 25.4° and no diffraction peaks of other crystal phases appear at other positions, indicating that the TiO2 component in the composite oxide exists in the form of anatase crystal phase. That is to say, the anatase crystal phase of titanium dioxide accounts for 100 wt% of the total titanium dioxide.

[0061] Example 2

[0062] 256.04 g of Al₂(SO₄)₃ was dissolved in deionized water to prepare 1000 mL of aluminum sulfate solution. 32.15 g of Ti(SO₄)₂ was dissolved in dilute sulfuric acid to prepare 500 mL of titanium sulfate solution in dilute sulfuric acid. 18 g of NH₄HCO₃ was dissolved in 600 mL of deionized water to prepare ammonium bicarbonate solution. Then, 250 mL of 24–28 wt% ammonia solution was added, stirred until homogeneous, and then diluted with deionized water to prepare 1000 mL of mixed alkali solution.

[0063] At atmospheric pressure and 60°C, the dilute sulfuric acid solution of titanium sulfate and the mixed alkali solution were added concurrently to the aluminum sulfate solution while maintaining vigorous stirring. The pH of the mixed solution was kept within the range of 3 to 4 for 15 minutes. The addition of the dilute sulfuric acid solution of titanium sulfate was then stopped, and the mixed alkali solution was continued to be added until the pH reached 9 to 10. This was maintained for 15 minutes. The addition of the mixed alkali solution was then stopped, and the dilute sulfuric acid solution of titanium sulfate was added to adjust the pH to 7.5 to 8.5. The temperature was raised to 85°C and maintained for 40 minutes. The mixture was filtered, and the filter cake was washed five times with 20 times its volume of deionized water. The washed filter cake was dried at 110°C for 6 hours and then calcined at 950°C for 5 hours. 86.8 g of an alumina-titanium dioxide composite oxide with a TiO2 content of 12.3% was obtained.

[0064] Example 3

[0065] The preparation process of the titanium dioxide-alumina composite oxide in Example 1 was repeated, except that 379.79g of Al(NO) was used. 3)3 A 1000 mL aluminum nitrate solution was prepared by dissolving the aluminum nitrate in deionized water. 25.99 g of Ti(OCH3CH2)4 was dissolved in anhydrous ethanol to prepare a 500 mL tetraethyl titanate ethanol solution. Finally, a 9.1% aluminum oxide-titanium dioxide composite oxide was obtained.

[0066] Example 4

[0067] The preparation process of the titanium dioxide-alumina composite oxide in Example 1 was repeated, except that 396.92 g of Al(NO3)3 was dissolved in deionized water to prepare 1000 mL of aluminum nitrate solution. 6.13 g of TiO(OH)2 was dissolved in sulfuric acid solution, and deionized water was added to prepare 500 mL of dilute sulfuric acid solution containing metatitanic acid. Finally, a 5.0% alumina-titanium dioxide composite oxide was obtained.

[0068] Example 5

[0069] The preparation process of the titanium dioxide-alumina composite oxide in Example 1 was repeated, except that 374.13 g of AlCl3·6H2O was dissolved in deionized water to prepare 1000 mL of aluminum chloride solution. 59.99 g of Ti(OCH3CH2)4 was dissolved in anhydrous ethanol to prepare 500 mL of tetraethyl titanate ethanol solution. Finally, an alumina-titanium dioxide composite oxide with a content of 21.0% was obtained.

[0070] Scanning electron microscopy and XRD results show that the composite oxides prepared in Examples 2-5 are similar to those in Example 1, with a surface microstructure of coral cluster 3D layered structure, and the TiO2 component in the composite oxides exists in the form of anatase crystal phase.

[0071] Comparative Example 1

[0072] 268.46 g of Al2(SO4)3 was dissolved in deionized water to prepare 1000 mL of aluminum sulfate solution. 24.5 g of TiO(OH)2 was dissolved in sulfuric acid solution, and deionized water was added to prepare 1000 mL of dilute sulfuric acid solution containing metatitanic acid. 18 g of NH4HCO3 was dissolved in 600 mL of deionized water to prepare ammonium bicarbonate solution, then 250 mL of 24–28 wt% ammonia solution was added, stirred until homogeneous, and then deionized water was added to prepare 1000 mL of mixed alkali solution.

[0073] Under normal pressure and at a temperature of 70-75℃, the above-mentioned three solutions—a deionized aqueous solution of aluminum sulfate, a dilute sulfuric acid solution of metatitanic acid, and a mixed alkaline solution—were co-precipitated in parallel flow. The flow rate of the mixed alkaline solution was controlled to maintain the pH of the precipitate within the range of 5.0-6.0 for 8 minutes. Then, the flow rate of the mixed alkaline solution was increased to maintain the pH of the mixed solution within the range of 8.5-9.5 for 8 minutes. Next, the flow rate of the mixed alkaline solution was decreased to maintain the pH of the mixed solution within the range of 5.0-6.0 for 8 minutes. The flow rate of the mixed alkaline solution was then increased again to maintain the pH of the precipitate within the range of 8.5-9.5. This process was repeated until all solutions A1 and B1 were added. The reaction solution was allowed to stand at 70℃ for 30 minutes, filtered, and the filter cake was washed with 15 times its volume of deionized water for 30 minutes. This process was repeated four times. Finally, the filter cake was dried at 100-120℃ for 8-12 hours and calcined at 950℃ for 5 hours to obtain the titanium dioxide-alumina composite. Its structure and properties are shown in Table 1.

[0074] Comparative Example 2

[0075] Take 401.88g of analytically pure AlCl3·6H2O and dissolve it in 1000ml of deionized water to prepare solution A1; take 43.25g of chemically pure Ti(OCH2CH3)4 and dissolve it in 500ml of benzene (benzene content is 99.8(wt)%) to prepare solution B1; take 18g of analytically pure NH4HCO3 and dissolve it in 600ml of deionized water, add 250ml of ammonia water with a concentration of 24-28wt%, stir and mix evenly, and then add deionized water to prepare 1000ml of solution C1.

[0076] Under normal pressure and at a temperature of 70-75℃, solutions A1, B1, and C1 were co-precipitated by parallel flow. The flow rate of solution C1 was controlled to maintain the pH of the precipitate in the range of 5.0-6.0 for 8 minutes. Then, the flow rate of solution C1 was increased to maintain the pH of the mixed solution in the range of 8.5-9.5 for 8 minutes. Then, the flow rate of solution C1 was decreased to maintain the pH of the mixed solution in the range of 5.0-6.0 for 8 minutes. Then, the flow rate of solution C1 was increased again to maintain the pH of the precipitate in the range of 8.5-9.5. This process was repeated until all solutions A1 and B1 were added. The reaction solution was allowed to stand at 70℃ for 30 minutes, filtered, and the filter cake was washed with 15 times the volume of deionized water for 30 minutes. This process was repeated four times. Finally, the filter cake was dried at 100-120℃ for 8-12 hours and calcined at 550℃ for 5 hours to obtain 42.7g of titanium dioxide-alumina composite. The results of its structure and performance are shown in Table 1.

[0077] Comparative Example 3

[0078] The preparation process of the titanium dioxide-alumina composite oxide in Comparative Example 2 was repeated, except that the calcination temperature after drying was changed to 950℃.

[0079] Scanning electron microscopy and XRD results show that the composite oxides prepared in Comparative Examples 1-3 do not have a coral cluster 3D layered structure, and the TiO2 crystal phase is mainly rutile titanium dioxide.

[0080] Table 1. Analytical data of titanium dioxide-alumina composites

[0081]

[0082]

[0083] Catalyst preparation:

[0084] Example 6

[0085] 100 g of the titanium dioxide-alumina composite support prepared in Example 1 was pre-impregnated with 160 mL of deionized water for 0.5 hours, filtered, and the water was drained. The solution was then immersed in 80 mL of a 0.636 g / 100 mL aqueous solution of palladium chloride for 1 hour. After 1 hour, the solution was removed and reduced with 145 mL of 40% (by weight) hydrazine hydrate for 1 hour. Chloride ions were washed away with deionized water. The solution was dried at 120 °C for 6 hours and then calcined at 500 °C for 4 hours. Finally, it was reduced for 8 hours under hydrogen conditions of 28 MPa pressure, 110 °C temperature, and 40 mL / min hydrogen flow rate. A palladium / titanium dioxide-alumina catalyst A with a palladium content of 0.3% (by weight) was obtained.

[0086] Example 7

[0087] 100 g of the titanium dioxide-alumina composite support prepared in Example 2 was pre-impregnated with 150 mL of deionized water for 0.5 hours, filtered, and the water was drained. The solution was then immersed in 80 mL of a 0.636 g / 100 mL aqueous solution of palladium chloride for 1 hour. After 1 hour, the solution was removed and reduced with 150 mL of 40% (by weight) hydrazine hydrate for 1 hour. Chloride ions were washed away with deionized water. The solution was dried at 120 °C for 6 hours and then calcined at 500 °C for 4 hours. Finally, it was reduced for 8 hours under hydrogen conditions of 28 MPa pressure, 110 °C temperature, and 40 mL / min hydrogen flow rate. A palladium / titanium dioxide-alumina catalyst B with a palladium content of 0.3% (by weight) was obtained.

[0088] Example 8

[0089] 120 g of the titanium dioxide-alumina composite support prepared in Example 5 was pre-impregnated with 180 mL of deionized water for 0.5 hours, filtered, and the water was drained. The solution was then immersed in 80 mL of a 0.636 g / 100 mL aqueous solution of palladium chloride for 1 hour. After 1 hour, the solution was removed and reduced with 180 mL of 40% (by weight) hydrazine hydrate for 1 hour. Chloride ions were washed away with deionized water. The solution was dried at 120 °C for 6 hours and then calcined at 500 °C for 4 hours. Finally, it was reduced for 8 hours under hydrogen conditions of 28 MPa pressure, 110 °C temperature, and 40 mL / min hydrogen flow rate. A palladium / titanium dioxide-alumina catalyst C with a palladium content of 0.3% (by weight) was obtained.

[0090] Comparative Example 4

[0091] 100 g of the titanium dioxide-alumina composite support prepared in Comparative Example 1 was pre-impregnated with 160 mL of deionized water for 0.5 hours, filtered, and dried. The sample was then immersed in 80 mL of a 0.636 g / 100 mL aqueous solution of palladium chloride for 1 hour. After 1 hour, the sample was removed and reduced with 145 mL of 40% (by weight) hydrazine hydrate for 1 hour, followed by washing with deionized water to remove chloride ions. The sample was dried at 120 °C for 6 hours and then calcined at 500 °C for 4 hours. Finally, it was reduced for 8 hours under hydrogen conditions of 28 MPa pressure, 110 °C temperature, and 40 mL / min hydrogen flow rate. This yielded a palladium / titanium dioxide-alumina catalyst D with a palladium content of 0.3% (by weight).

[0092] Comparative Example 5

[0093] 100 g of the titanium dioxide-alumina composite support prepared in Comparative Example 2 was pre-impregnated with 160 mL of deionized water for 0.5 hours, filtered, and the water was drained. The support was then immersed in 80 mL of a 0.636 g / 100 mL aqueous solution of palladium chloride for 1 hour. After 1 hour, the support was removed and reduced with 145 mL of 40% (by weight) hydrazine hydrate for 1 hour. Chloride ions were washed away with deionized water. The support was dried at 120 °C for 6 hours and then calcined at 500 °C for 4 hours. Finally, it was reduced for 8 hours under hydrogen conditions of 28 MPa pressure, 110 °C temperature, and 40 mL / min hydrogen flow rate. A palladium / titanium dioxide-alumina catalyst E with a palladium content of approximately 0.3% (by weight) was obtained.

[0094] Comparative Example 6

[0095] 100 g of the titanium dioxide-alumina composite support prepared in Comparative Example 3 was pre-impregnated with 160 mL of deionized water for 0.5 hours, filtered, and dried. The sample was then immersed in 80 mL of a 0.636 g / 100 mL aqueous solution of palladium chloride for 1 hour. After 1 hour, the sample was removed and reduced with 145 mL of 40% (by weight) hydrazine hydrate for 1 hour, followed by washing with deionized water to remove chloride ions. The sample was dried at 120 °C for 6 hours and then calcined at 500 °C for 4 hours. Finally, it was reduced for 8 hours under hydrogen conditions of 28 MPa pressure, 110 °C temperature, and 40 mL / min hydrogen flow rate. This yielded a palladium / titanium dioxide-alumina catalyst F with a palladium content of approximately 0.3% (by weight).

[0096] Example 9

[0097] This example demonstrates the application of a catalyst in the selective hydrogenation reaction of C3 fractions.

[0098] The catalysts used in this embodiment are those described in Examples 6, 7, 8, and Comparative Examples 4-6.

[0099] The composition of the raw materials used in this embodiment is shown in Table 2.

[0100] Table 2. Composition of feedstocks for selective hydrogenation of C3 fractions.

[0101]

[0102] In this embodiment, a fixed-bed pilot-scale evaluation device from Tuochuan Scientific Equipment Co., Ltd. was used, with 50 mL of catalyst loaded, to carry out a selective hydrogenation reaction of C3 fraction.

[0103] Reaction conditions: reaction pressure 0.5-0.7 MPa, hydrogen flow rate 1.92 L / h, reactor inlet temperature 25℃, recycle ratio 20:1, feed rate 25 mL / h.

[0104] The catalyst was evaluated under the same conditions, and the results of selective hydrogenation are shown in Table 3.

[0105] Table 3 Results of selective hydrogenation of C3 fraction

[0106]

[0107] MAPD conversion rate = (MAPD in feed - MAPD in product) / (MAPD in feed)

[0108] MAPD selectivity = (propylene in product - propylene in feedstock) / (MAPD in feedstock - MAPD in product)

[0109] As can be seen from the table above, the hydrogenation catalyst provided by this invention exhibits high alkyne saturation activity, good selectivity, high low-temperature activity, good resistance to impurity poisoning, and good feedstock adaptability. The selective hydrogenation method for C3 fractions provided by this invention has high conversion rate and hydrogenation selectivity, and can effectively remove MAPD from C3 fractions.

[0110] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A hydrogenation catalyst comprising a composite oxide and palladium, wherein, The composite oxide comprises aluminum oxide and titanium dioxide, and the specific surface area of ​​the composite oxide is expressed as X m. 2 / g, the average pore size of the composite oxide is expressed as Y nm, wherein the ratio of X to Y is 5 to 30, and in the composite oxide, anatase phase titanium dioxide accounts for 95 wt% to 100 wt% of the total titanium dioxide; The pore volume of the composite oxide is expressed as Z mL / g, and the ratio of X to Z is 220 to 400. The composite oxide has a coral-like 3D layered structure; The preparation method of the composite oxide includes the following steps: Step I. Dissolve soluble aluminum salts in water to form an aluminum salt solution, dissolve titanium salts in an acid solution to form a titanium salt solution, and mix ammonium salts and alkaline solutions to form a mixed alkaline solution; Step II. (a) Add the titanium salt solution and the mixed alkali solution to the aluminum salt solution, so that the mixture is maintained at the first pH value for a first time period; (b) Stop adding the titanium salt solution and continue adding the mixed alkali solution, so that the mixture is maintained at the second pH value for a second time period; (c) Stop adding the mixed alkali solution and add the titanium salt solution, so that the mixture is maintained at the third pH value for a third time period. Step III. After step II.(c), the temperature of the mixture is raised and maintained for a fourth time period to obtain a precipitate; Step IV. The precipitate is dried and calcined to obtain a composite oxide containing alumina and titanium dioxide; The first pH value is less than 5, the second pH value is greater than 8.5, and the third pH value is greater than 7 and less than 9. The first, second, and third time periods are 5 to 20 minutes each; the fourth time period is 20 to 60 minutes.

2. The hydrogenation catalyst according to claim 1, characterized in that, The ratio of X to Z is between 250 and 350.

3. The hydrogenation catalyst according to claim 1, characterized in that, X is 90 to 150; and / or Y is 9 to 20; and / or Z is 0.3 to 0.5; and / or the composite oxide contains 5 wt% to 21 wt% titanium dioxide.

4. The hydrogenation catalyst according to claim 3, characterized in that, Y is 12 to 16; and / or Z is 0.3 to 0.

4.

5. The hydrogenation catalyst according to claim 1, characterized in that, In step IV, washing and filtration are performed before drying.

6. The hydrogenation catalyst according to claim 1, characterized in that, In step II, the first pH value is 3 to 4, and / or the second pH value is 9 to 10, and / or the third pH value is 7.5 to 8.

5.

7. The hydrogenation catalyst according to claim 1, characterized in that, The first, second, and third time periods are each 10 to 15 minutes long.

8. The hydrogenation catalyst according to claim 1, characterized in that, In step II, the operating temperature is 25°C to 60°C; and / or in step III, the temperature is increased to 80°C to 150°C; and / or in step IV, the drying temperature is 110°C to 130°C; and / or the calcination temperature is 800°C to 1000°C.

9. The method for preparing the hydrogenation catalyst according to any one of claims 1-8, characterized in that, The process includes impregnating the composite oxide with a palladium compound solution, reducing the impregnated product with hydrazine hydrate, drying and calcining the product after hydrazine hydrate reduction, and then reducing the calcined product.

10. The preparation method according to claim 9, characterized in that, The Pd / TiO2-Al2O3 catalyst was prepared by reduction for 6-8 hours at a hydrogenation temperature of 100-150℃, a hydrogen pressure of 2.6-3.0MPa, and a hydrogen flow rate of 35-65mL / min.

11. A method for selective hydrogenation of a C3 fraction, comprising selectively hydrogenating the fraction oil in the presence of a hydrogenation catalyst as described in any one of claims 1-8 or a hydrogenation catalyst obtained by the preparation method described in claim 9 or 10.

12. The hydrogenation method according to claim 11, wherein, The reaction temperature is 20~50℃, the mol ratio of hydrogen to alkyne is 1:1~2.5:1, the pressure is 0.5~0.8MPa, and the recycle ratio is 10:1~30:1.

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