Selective hydrogenation catalyst for alkynes and dienes and method for its preparation and use

Abstract

This invention relates to the field of selective hydrogenation technology, specifically to a selective hydrogenation catalyst for alkynes and dienes, its preparation method, and its application. The catalyst provided by this invention uses a modified composite oxide as a support, on which active components are loaded; wherein the modified composite oxide uses a composite oxide as a support, on which alkali metal hydroxides are loaded; the composite oxide includes alumina and zirconium oxide; the active components include nickel, iron, lead, and selenium. The catalyst provided by this invention not only possesses high reactivity and high selectivity, but also avoids excessive hydrogenation to form alkanes, while inhibiting or preventing olefin isomerization to form other isomers. Furthermore, it exhibits high stability, a long single-pass life, and does not require frequent regeneration.

Description

Technical Field

[0001] This invention relates to the field of selective hydrogenation technology, specifically to a selective hydrogenation catalyst for alkynes and dienes, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Low-carbon monoolefins are important chemical raw materials widely used in polymer synthesis in industry. The main production method for low-carbon olefins is the cracking of petroleum hydrocarbons and crude oil, including heavy fractions. However, the cracking process is carried out at high temperatures, generating impurities along with low-carbon olefins. The presence of dienes / alkynes not only affects the further processing of monoolefins but also poisons the low-carbon monoolefin polymerization catalyst. In industry, diene / alkyne impurities must be controlled below 10 ppm. Therefore, in industry, the purification of low-carbon monoolefin feedstocks must be achieved through heterogeneous selective catalytic hydrogenation of alkynes / dienes on the surface of a supported metal catalyst.

[0004] High activity and high selectivity are important factors in the design of alkyne / dien hydrogenation catalysts. Maintaining high catalyst activity while suppressing or avoiding excessive hydrogenation of alkynes / dienes to alkanes, and simultaneously suppressing or avoiding olefin isomerization to other isomers, is crucial for achieving high selectivity for the desired low-carbon monoolefins.

[0005] Currently, the main hydrogenation catalysts selected are precious metal Pd-based catalysts and non-precious metal Cu or Ni-based catalysts. The former has higher production costs and is easily deactivated in feed atmospheres containing impurities such as sulfur and water, exhibiting poor resistance to impurities. Therefore, when using precious metal hydrogenation catalysts, the types and contents of impurities in the feedstock are subject to very strict requirements, often requiring pretreatment, which increases equipment investment and operating costs. Non-precious metal catalysts not only have lower production costs but also stronger resistance to impurities such as sulfur and water; however, they suffer from low activity, low selectivity, poor stability, and the need for frequent regeneration. Summary of the Invention

[0006] To overcome the above problems, the present invention provides a selective hydrogenation catalyst for alkynes and dienes, its preparation method and application.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a catalyst having a modified composite oxide as a support and an active component loaded on its surface; The modified composite oxide uses a composite oxide as a carrier to support alkali metal hydroxides; the composite oxide includes alumina and zirconium oxide. The active components include nickel, iron, lead, and selenium.

[0008] In one or more embodiments, the alkali metal hydroxide includes one or more of sodium hydroxide or potassium hydroxide.

[0009] A second aspect of the present invention provides a method for preparing the catalyst described in the first aspect, comprising the following steps: (1) After mixing macroporous pseudoboehmite, microporous pseudoboehmite, basic zirconium carbonate and guar gum powder evenly, add citric acid solution and knead into block solid, dry and calcine to obtain composite oxide; (2) The composite oxide is immersed in an alkali metal hydroxide solution. After the solution is completely adsorbed, it is dried to obtain the modified composite oxide. (3) The modified composite oxide is immersed in a mixed solution containing active components, dried and then calcined to obtain the precursor material; (4) The precursor material is reduced in a hydrogen atmosphere to obtain the catalyst.

[0010] In one or more embodiments, in step (1), the macroporous pseudoboehmite has a pore volume > 0.9 mL / g and a specific surface area > 290 m². 2 / g, particle size ≥200 mesh, SiO2 content <0.15%; In one or more embodiments, in step (1), the pore volume of the small-pore boehmite is >0.4 mL / g, and the specific surface area is >270 μm. 2 / g, particle size ≥200 mesh, SiO2 content <0.15%.

[0011] In one or more embodiments, in step (1), the mass ratio of macroporous pseudoboehmite to microporous pseudoboehmite is 5:5 to 7:3.

[0012] In one or more embodiments, in step (1), the mass ratio of basic zirconium carbonate to macroporous pseudoboehmite and microporous pseudoboehmite is 1:99 to 2:98.

[0013] In one or more embodiments, in step (1), guar gum powder accounts for 2 to 5% of the total mass of macroporous boehmite, microporous boehmite, basic zirconium carbonate and guar gum powder.

[0014] In one or more embodiments, in step (1), the mass fraction of the citric acid solution is 2-3%.

[0015] In one or more embodiments, in step (1), the mass ratio of citric acid solution to the total mass of macroporous boehmite, microporous boehmite, basic zirconium carbonate and guar gum powder is (0.7~0.8):1.

[0016] In one or more embodiments, in step (1), the shape of the blocky solid includes clover-shaped, toothed, spherical, or cylindrical.

[0017] In one or more embodiments, in step (1), the drying temperature is 120~200℃ and the drying time is 2~4 h.

[0018] In one or more embodiments, in step (1), the calcination temperature is 800~900℃ and the calcination time is 3~4 h.

[0019] In one or more embodiments, in step (2), the mass ratio of alkali metal hydroxide to composite oxide is (0.5~1%):1.

[0020] In one or more embodiments, step (2) involves preparing the alkali metal hydroxide solution by: The amount of solvent water in the alkali metal hydroxide solution is obtained based on the water absorption rate of the composite oxide; then the alkali metal hydroxide is dissolved in water to obtain the alkali metal hydroxide solution.

[0021] In one or more embodiments, in step (2), the drying temperature is 150~200℃ and the drying time is 3~4 h.

[0022] In one or more embodiments, in step (3), the method for preparing the mixed solution containing active components includes: dispersing a nickel source, an iron source, a lead source and a selenium source in water to obtain a mixed solution containing active components; Preferably, the nickel source comprises nickel nitrate; the iron source comprises ferric nitrate; the lead source comprises lead nitrate; and the selenium source comprises selenium dioxide. More preferably, the molar ratio of nickel source, iron source, lead source and selenium source is (5~6):(0.8~1.5):(0.2~0.4):(0.3~0.5).

[0023] More preferably, the mass ratio of solvent water to modified composite oxide in the mixed solution containing the active component is (1.4~1.6):1; More preferably, the concentration of the nickel source is 0.35~0.45 mol / L.

[0024] In one or more embodiments, in step (3), the drying temperature is 150~200℃ and the drying time is 2~3 h.

[0025] In one or more embodiments, in step (3), the calcination temperature is 350~450℃ and the calcination time is 3~4 h.

[0026] In one or more embodiments, in step (4), the reduction temperature is 350~450℃ and the reduction time is 8~10 h.

[0027] A third aspect of the present invention provides the application of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in the selective hydrogenation of alkynes and dienes to prepare monoolefins.

[0028] In one or more embodiments, the conditions for selective hydrogenation of mixed C4 alkynes and dienes are: temperature 30-100°C, reaction pressure 1-2 MPa, and gross hourly space velocity 10-20 h⁻¹. -1 The ratio of the number of moles of hydrogen to the total number of moles of alkynes and dienes (hydrogen ratio) is (1.2~2):1.

[0029] In one or more embodiments, the conditions for selective hydrogenation of mixed C5 alkynes and dienes are: temperature 30–100°C, reaction pressure 1–2 MPa, and gross hourly space velocity 6–10 h⁻¹. -1 The hydrogen ratio is (1.5~2.5):1.

[0030] The beneficial effects of this invention are as follows: The catalyst provided by this invention not only has high reactivity and high selectivity, but also avoids excessive hydrogenation to form alkanes, while inhibiting or preventing olefin isomerization to form other isomers. In addition, it has high stability, long single-pass life, and does not require frequent regeneration.

[0031] For high activity: the highly dispersed and uniquely geometrically distributed nickel active sites (nickel concentrated on the catalyst surface) and the synergistic enhancement of Fe, Pb, and Se electronic structures improve catalyst activity. Specifically, this invention employs a "Ni-Fe-Pb-Se" multi-metal active component to achieve an "active center isolation" strategy. The presence of Fe, Pb, and Se acts as a "barrier," preventing the migration and aggregation of Ni particles during high-temperature calcination and reduction. This stable, highly dispersed state of the promoter allows for more Ni atoms per unit mass of catalyst to serve as active centers, directly increasing the specific activity of the catalyst. Furthermore, zirconium oxide itself possesses certain surface defect sites and moderate electronic effects. It not only stabilizes the active metal particles but may also promote the dissociation of hydrogen molecules and the migration of hydrogen atoms to active centers through a "spillover" effect. This means that the concentration of active hydrogen species required for the reaction is higher around the Ni active centers, thereby accelerating the hydrogenation cycle rate. Moreover, the tunable electronic structures of Fe, Pb, and Se optimize the activation ability of Ni for reactants (d-band center optimization) while accelerating product desorption to free up active sites.

[0032] For high selectivity: Traditional hydrogenation catalysts (such as pure Ni) have continuous active sites on their surface, leading to strong adsorption of both reactants and products, resulting in over-hydrogenation. In this catalyst, Fe, Pb, and Se act as promoters, geometrically "diluting" the main active component Ni, forming isolated active centers. This structure forces alkynes / dienes to adsorb only in specific ways, making deep hydrogenation difficult. Furthermore, Fe, Pb, and Se, as promoters, can modify the electronic properties of Ni, modulating its adsorption energies for reactants and products. This allows the catalyst to maintain high activity for the target unsaturated hydrocarbons (alkynes / dienes) but has weak adsorption capacity for the product mono-olefins. Once the product is formed, it is rapidly desorbed, thus ensuring extremely high selectivity. Moreover, alkali metals, as electronic promoters, can donate electrons to the active metal Ni, increasing its electron density and weakening the binding force between Ni and the carbon-carbon double bonds (which have high electron cloud density) in mono-olefins. This effectively prevents mono-olefins from remaining on the catalyst surface and being further hydrogenated to alkanes.

[0033] To inhibit or avoid the isomerization of olefins into other isomers: the isomerization of monoolefins is usually initiated by acidic sites on the support surface. Alkali metal hydroxides can neutralize the acidic centers on the support (especially alumina) surface, passivating the active sites of the isomerization reaction. Therefore, the resulting olefin can maintain its original structure, without double bond migration or skeletal isomerization, ensuring the uniqueness of the product.

[0034] For high stability and long catalyst single-pass lifetime: the composite oxide support undergoes alkali metal treatment, neutralizing the acidic centers of the support and inhibiting the polymerization of alkynes, dienes, and olefins, thus preventing the formation of large amounts of carbon deposits and significantly extending the single-pass lifetime. Furthermore, the Pb and Se in the active components, in addition to modulating selectivity, also inhibit side reactions that lead to carbon deposition, reducing deactivation factors at their source. Moreover, the introduction of the zirconium oxide support enhances the thermal stability and mechanical strength of the support; the strong interaction between the active component Ni and the support and additives effectively inhibits the migration and aggregation of Ni particles during the reaction process, allowing the active centers to maintain a highly dispersed state for a long time, which is fundamental to the long-term activity of the catalyst. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0038] In the following examples, the macroporous pseudoboehmite has a pore volume of 0.92 mL / g and a specific surface area of ​​297 μm. 2 / g, particle size ≥200 mesh, SiO2 content 0.13%, small-pore boehmite pore volume 0.413 mL / g, specific surface area 284 m 2 / g, particle size ≥200 mesh, SiO2 content 0.11%.

[0039] Example 1 Catalyst preparation: 60 kg of macroporous boehmite, 40 kg of microporous boehmite, 1.5 kg of basic zirconium carbonate, and 3 kg of guar gum powder were added to a kneader and mixed evenly. Then, 75 kg of a 2% (w / w) citric acid aqueous solution was added, and the mixture was kneaded for 30 min. The kneaded material was then extruded into 3 mm clover-shaped pieces using an extruder. The mixture was dried at 150℃ for 2 h and calcined at 850℃ for 4 h to obtain a composite oxide. The composite oxide had a bulk density of 0.66 g / mL and a water absorption rate of 66.5%.

[0040] (2) Dissolve 100 g of sodium hydroxide in 6.65 kg of deionized water to prepare an alkali metal hydroxide solution; place 10 kg of composite oxide from step (1) in a sugar coating pan, start the sugar coating pan, slowly add the alkali metal hydroxide solution into the sugar coating pan, and after the solution is completely adsorbed onto the composite oxide, dry it at 200℃ for 4 h to obtain the modified composite oxide.

[0041] (3) Disperse 1700 g nickel nitrate hexahydrate, 510 g ferric nitrate nonahydrate, 110 g lead nitrate and 40 g selenium dioxide in 15 kg deionized water, stir until completely dissolved, add 10 kg modified composite oxide, impregnate for 60 min, then drain the excess water, dry at 150℃ for 2 h, calcine at 400℃ for 4 h to obtain the precursor material.

[0042] (4) The precursor material was reduced in a hydrogen atmosphere to obtain the catalyst. The reduction temperature was 450℃ and the reduction time was 10 h.

[0043] The active component is on the surface of the modified composite oxide, and the thickness of the active component is 0.18 mm.

[0044] Comparative Example 1 Compared with Example 1, in step (3), only nickel, iron and selenium are added to the active ingredients, and the other methods are the same as in Example 1.

[0045] Comparative Example 2 Compared with Example 1, in step (3), only nickel, lead and selenium are added to the active ingredients, and the other methods are the same as in Example 1.

[0046] Comparative Example 3 Compared with Example 1, in step (3), only nickel, lead and iron are added to the active ingredients, and the other methods are the same as in Example 1.

[0047] Comparative Example 4 Compared with Example 1, in step (2), no alkali metal hydroxide modification was performed, but the other methods were the same as in Example 1, and the prepared catalyst nickel was uniformly distributed on the support.

[0048] Comparative Example 5 Compared with Example 1, in step (1), basic zirconium carbonate was not added, but the other methods were the same as in Example 1.

[0049] Experimental Example 1 30 g of the catalyst prepared in Example 1 was loaded into an isothermal fixed-bed reactor for hydrogenation performance evaluation. A bubbling bed reaction was adopted, with 3 mm ceramic rings filling the upper and lower parts of the catalyst bed. Mixed C4 rich in alkynes was used as raw material. The specific temperature and parameter conditions are shown in Table 1, and the hydrogenation performance evaluation results are also shown in Table 1.

[0050] Table 1 Evaluation results of mixed C4 hydrogenation

[0051] Note: The reaction pressure is 1 MPa, the circulation ratio is 10, and the hydrogen ratio refers to the molar ratio of hydrogen to butyne and butadiene in the feed. Butyne includes 1-butyne, 2-butyne and vinylacetylene, and butadiene includes 1,2-butadiene and 1,3-butadiene.

[0052] As can be seen from Table 1, the catalyst prepared in this invention has high activity when used for selective hydrogenation of mixed C4 materials rich in alkynes, and the butane content in the product increases only slightly, indicating high butene selectivity. The increase in 1-butene content in the product indicates that the catalyst has low activity in hydrogen-induced double bond isomerization reactions.

[0053] Experiment Example 2 The feedstock in Experiment 1 was replaced with C5 coal chemical (1,4-pentadiene 0.89%, 1-pentene 9.07%, n-pentane 41.63%, trans-pentene 7.92%, cis-pentene 3.64%, 1,3-trans-pentadiene 1.58%, cyclopentadiene 3.12%, cyclopentene 11.34%, cyclopentane 1.97%). The specific temperature and parameter conditions are shown in Table 2, and the hydrogenation performance evaluation results are also shown in Table 2.

[0054] Table 2 Evaluation Results of C5 Hydrogenation in Coal Chemical Industry

[0055] Note: Reaction temperature 40℃, reaction pressure 1 MPa.

[0056] As can be seen from Table 2, the catalyst prepared in this invention has high reactivity when used for selective hydrogenation of mixed C5 molecules. Under suitable conditions, it can remove dienes from mixed C5 molecules to 500 ppm or less.

[0057] Experimental Example 3 The catalyst in Experimental Example 1 was replaced with the catalysts in Comparative Examples 1-5. Mixed C4 rich in alkynes was used as raw material. The specific temperature and parameter conditions were as follows: catalyst loading 30g, reaction pressure 1MPa, feed rate 30g / h, recycle ratio 10, hydrogen ratio 1.5. The hydrogenation performance evaluation results are shown in Table 3.

[0058] Table 3 Evaluation results of mixed C4 hydrogenation

[0059] As shown in Table 3, the catalyst activity and selectivity both decrease when iron, selenium, and lead are lacking in the active components. This is because highly dispersed nickel active sites with a specific geometric distribution cannot be formed, and the electronic structures modulated by Fe, Pb, and Se cannot be formed either. Without alkali metal hydroxide modification, the catalyst selectivity decreases, and olefin isomerization cannot be suppressed or avoided.

[0060] Experiment Example 4 The catalysts in Experimental Example 1 and Comparative Example 5 were subjected to stability tests using mixed C4 hydrocarbons rich in alkynes as raw materials. The specific temperature and parameter conditions were as follows: catalyst loading 30g, reaction pressure 1MPa, feed rate 30g / h, recycle ratio 10, hydrogen ratio 1.5, and the test ran for 500h. Afterward, the catalyst was removed, dried at 200℃ for 2h, and weighed. The hydrogenation performance evaluation results are shown in Table 4.

[0061] Table 4. Evaluation results of hydrogenation performance

[0062] The catalyst was removed and dried at 200°C for 2 hours. The catalysts used in Example 1 and Comparative Example 5 increased in weight by 0.25% and 0.75%, respectively. According to the data comparison, the catalyst support without the addition of basic zirconium carbonate had slightly lower catalyst activity and slightly higher catalyst carbon deposition, indicating that the single-pass operation cycle of the catalyst was shortened.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A catalyst, characterized in that, It uses modified composite oxides as a carrier and loads active components; The modified composite oxide uses a composite oxide as a carrier and has alkali metal hydroxide loaded on its surface; the composite oxide includes alumina and zirconium oxide. The active components include nickel, iron, lead, and selenium.

2. The catalyst according to claim 1, characterized in that, The alkali metal hydroxide includes one or more of sodium hydroxide or potassium hydroxide.

3. The method for preparing the catalyst according to claim 1 or 2, characterized in that, Includes the following steps: (1) After mixing macroporous pseudoboehmite, microporous pseudoboehmite, basic zirconium carbonate and guar gum powder evenly, add citric acid solution and knead into block solid, dry and calcine to obtain composite oxide; (2) The composite oxide is immersed in an alkali metal hydroxide solution. After the solution is completely adsorbed, it is dried to obtain the modified composite oxide. (3) The modified composite oxide is immersed in a mixed solution containing active components, dried and then calcined to obtain the precursor material; (4) The precursor material is reduced in a hydrogen atmosphere to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that, In step (1), the mass ratio of macroporous pseudoboehmite to microporous pseudoboehmite is 5:5~7:3; Alternatively, in step (1), the mass ratio of basic zirconium carbonate to macroporous pseudoboehmite and microporous pseudoboehmite is 1:99~2:

98. Alternatively, in step (1), the guar gum powder accounts for 2-5% of the total mass of macroporous boehmite, microporous boehmite, basic zirconium carbonate, and guar gum powder; Alternatively, in step (1), the mass fraction of the citric acid solution is 2-3%; Alternatively, in step (1), the mass ratio of citric acid solution to the total mass of macroporous boehmite, microporous boehmite, basic zirconium carbonate and guar gum powder is (0.7~0.8):

1.

5. The preparation method according to claim 3, characterized in that, In step (1), the drying temperature is 120~200℃ and the drying time is 2~4 h; Alternatively, in step (1), the calcination temperature is 800~900℃ and the calcination time is 3~4 h.

6. The preparation method according to claim 3, characterized in that, In step (2), the mass ratio of alkali metal hydroxide to composite oxide is (0.5~1%):1; Alternatively, in step (2), the method for preparing the alkali metal hydroxide solution includes: The amount of solvent water in the alkali metal hydroxide solution is obtained based on the water absorption rate of the composite oxide; then the alkali metal hydroxide is dissolved in water to obtain the alkali metal hydroxide solution.

7. The preparation method according to claim 3, characterized in that, In step (3), the method for preparing the mixed solution containing active components includes: dispersing a nickel source, an iron source, a lead source and a selenium source in water to obtain a mixed solution containing active components.

8. The preparation method according to claim 7, characterized in that, The nickel source includes nickel nitrate; the iron salt includes ferric nitrate; the lead source includes lead nitrate; and the selenium source includes selenium dioxide. Preferably, the molar ratio of the nickel source, iron source, lead source, and selenium source is (5~6):(0.8~1.5):(0.2~0.4):(0.3~0.5). Preferably, the mass ratio of solvent water to modified composite oxide in the mixed solution containing the active component is (1.4~1.6):1; Preferably, the concentration of the nickel source is 0.35~0.45 mol / L.

9. The preparation method according to claim 3, characterized in that, In step (3), the calcination temperature is 350~450℃ and the calcination time is 3~4 h; Alternatively, in step (4), the reduction temperature is 350~450℃ and the reduction time is 8~10 h.

10. The application of the catalyst according to claim 1 or 2 or the catalyst prepared by the preparation method according to any one of claims 3 to 9 in the selective hydrogenation of alkynes and dienes to prepare monoolefins.

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