A composite carrier, a catalyst, a preparation method thereof and a method for removing acetylene in carbon dioxide fraction by front-end hydrogenation

Abstract

This invention relates to the technical field of selective hydrogenation of olefin gases, and more specifically, to a composite support, a catalyst, a method for preparing the same, and a method for hydrogenating and removing alkynes before the C2 fraction. The method for preparing the composite support includes mixing, granulating, and calcining a raw material comprising raw material A, auxiliary agent B, auxiliary agent C, and solvent D to obtain the composite support; raw material A is nanodiamond; auxiliary agent B is a colloidal polymer; and auxiliary agent C is at least one of graphite, polyvinyl alcohol, and carboxymethyl cellulose. The catalyst of this invention is granular, possesses high strength, and can be directly used in industrial applications of acetylene pre-hydrogenation reactions, achieving high acetylene conversion while improving ethylene selectivity. Furthermore, compared to carbon-based catalysts reported in the literature, the reaction temperature required for acetylene conversion in this invention is lower.

Description

Technical Field

[0001] This invention relates to the technical field of selective hydrogenation of olefin gases, and more specifically, to a composite support, a catalyst, a method for preparing the same, and a method for hydrogenating and removing alkynes before the C2 fraction. Background Technology

[0002] Polyolefins are widely used materials, and their current production route involves polymerization of low-carbon olefins such as ethylene and propylene. Therefore, polyolefin production plays a crucial role in modern chemical industry. Ethylene and propylene are typically produced using naphtha and low-carbon alkanes as feedstocks through steam cracking. This process, involving endothermic free radical cracking at high temperatures, achieves efficient production of ethylene and propylene. While thermal cracking can yield high ethylene and propylene yields, the reaction products are difficult to control. The products often contain trace amounts of impurities such as acetylene and propadiene, which not only interfere with downstream olefin polymerization but also jeopardize the safe and stable operation of the equipment itself.

[0003] Commonly used impurity removal methods include solvent extraction and catalytic selective hydrogenation. At present, the main treatment method used in general industrial production is to eliminate alkynes and dienes entrained in cracked gas through catalytic selective hydrogenation, while increasing the production of ethylene and propylene and improving resource utilization.

[0004] Traditional production processes employ sequential separation, first separating hydrogen, then C2 and C3 fractions from the cracking products, followed by removal of acetylene and propadiene from the fractions. In recent years, pre-hydrogenation separation processes have become increasingly common, where impurities such as acetylene and propadiene are selectively hydrogenated before further separation. The hydrogen content in this process is significantly affected by the feedstock from the upstream cracking furnace, reaching over 10%, and the reaction space velocity can reach as high as 12,000 h⁻¹. -1 Under these conditions, the catalyst is required not only to meet the conversion requirements of acetylene and propadiene, but also to have high selectivity in order to reduce the loss of olefins caused by excessive hydrogenation under high hydrogen partial pressure.

[0005] Industrially used selective hydrogenation catalysts are mostly supported metal catalysts, generally consisting of a support and an active component. Common supports include alumina, silica, molecular sieves, activated carbon, magnesium oxide, titanium oxide, diatomaceous earth, etc.; the active component is a metal element with hydrogenation catalytic activity, usually a Group VIII element, such as palladium, platinum, and nickel. Palladium has a strong ability to activate hydrogen and can effectively remove alkynes at relatively low temperatures, making it a commonly used active component in this type of reaction. Currently, industrially used selective hydrogenation catalysts have met the conversion requirements for polymerization-grade olefins, but their selectivity still needs improvement.

[0006] In palladium-catalyzed selective hydrogenation of acetylene, palladium nanoparticles can activate hydrogen at room temperature, but the high activity of hydrogen species generated by the secondary surface particles leads to over-hydrogenation. To improve ethylene selectivity while ensuring the acetylene content at the reactor outlet meets standards, previous researchers have improved ethylene selectivity by poisoning certain sites (Lindlar catalysts) or introducing a second metal for site isolation (PdAg, PdZn catalysts). However, this also results in the waste of precious metal active sites. Therefore, it is necessary to find a method that can improve both the utilization rate of precious metals and the ethylene selectivity, both from the perspective of rational utilization of precious metal resources and catalyst production costs.

[0007] Since Academician Zhang Tao proposed the concept of single-atom catalysis, researchers in the field of acetylene selective hydrogenation have discovered that Pd catalysts existing in the form of single atoms or sub-nano clusters can completely expose Pd on the catalyst surface, eliminating the negative impact of hydrogen species generated by subsurface particles on ethylene selectivity. In recent years, with the continuous deepening of research on carbon-based catalytic materials, defect-rich carbon-based catalyst supports prepared through strategies such as heteroatom doping and surface reconstruction can achieve complete exposure of the supported metal. Bychko et al. achieved 90% acetylene conversion and 85% ethylene selectivity at 350 °C using multi-walled carbon nanotubes as catalysts (10.1002 / cctc.201701234); Dai et al. prepared single-atom Ni catalysts using nitrogen-doped carbon composite supports, achieving >90% acetylene conversion and ethylene selectivity at 200 °C (10.1039 / c7cc04820c); Huang et al. prepared Pd single-atom catalysts using graphene-coated nanodiamonds as supports, achieving 90% acetylene conversion and 85% ethylene selectivity at 60,000 h⁻¹. -1 At high space velocities, 100% acetylene conversion and 90% ethylene selectivity were achieved, but the reaction temperature was as high as 180℃ ( / 10.1021 / jacs.8b07476). The above carbon-based catalysts suffer from insufficient activity at low temperatures, and since they are all in powder form, they not only generate high bed pressure drops leading to additional energy consumption, but are also prone to loss and deactivation under high space velocity industrial application conditions. Therefore, they cannot compete with existing catalysts in industrial applications.

[0008] In summary, although these carbon-based catalytic systems can achieve efficient conversion of alkynes under laboratory conditions, the temperatures of the catalytic reactions are too high, and the carbon-based catalysts are all in powder form with low mechanical strength. They are far from meeting the actual industrial application conditions and cannot meet the actual needs of factories.

[0009] Therefore, how to provide a novel carbon-based catalyst that combines high acetylene conversion and ethylene selectivity, suitable for industrial applications, and meets the actual needs of industrial applications, is a technical problem that needs to be solved. Summary of the Invention

[0010] To address the problems in existing technologies, this invention proposes a composite support, a catalyst, its preparation method, and a method for the hydrogenation removal of alkynes before the C2 fraction. This invention first prepares a composite support, and then prepares a nano-carbon composite hydrogenation catalyst, in which the support is a graphene-coated nanodiamond support. The catalyst of this invention is particulate, possesses high strength, and can be directly used in industrial applications of acetylene pre-hydrogenation reactions. While achieving high acetylene conversion, ethylene selectivity is improved. Furthermore, compared to carbon-based catalysts reported in the literature, the reaction temperature required for acetylene conversion in this invention is lower.

[0011] The first aspect of the present invention is to provide a method for preparing a composite carrier, comprising mixing, molding and granulating, and calcining raw materials including raw material A, auxiliary agent B, auxiliary agent C and solvent D to obtain the composite carrier; wherein the raw material A is nanodiamond;

[0012] The auxiliary agent B is a colloidal polymer;

[0013] The auxiliary agent C is at least one of graphite, polyvinyl alcohol, and carboxymethyl cellulose.

[0014] According to a preferred embodiment of the present invention, the mass ratio of raw material A to auxiliary agent C is 1:1:(0.01-0.12), preferably 1:(0.01-0.1).

[0015] According to a preferred embodiment of the present invention, the total weight of the raw material A, auxiliary agent B and auxiliary agent C is 100 wt%, and the amount of auxiliary agent B is 1-50 wt%, preferably 10-30.5 wt%.

[0016] According to a preferred embodiment of the present invention, the total weight of raw material A, auxiliary agent B and auxiliary agent C to solvent D is in the mass ratio of 1:(0.5-3), preferably 1:(1-2).

[0017] The high-strength composite carrier described above is not a conventional technical adjustment in the field.

[0018] For the molding of powdered carriers and catalysts, conventional binders such as "bentonite, silica sol, coal tar, asphalt, starch, hydroxymethyl cellulose", although they are also binders and can transform powders into particles, are not suitable for the preparation method of the present invention. That is, using the above-mentioned binders to replace the colloidal polymer in the present invention cannot obtain the composite carrier required for the application of composite catalysts.

[0019] The inventors of this invention have confirmed through research that:

[0020] Bentonite and silica sol are commonly used inorganic adhesives, but their material properties differ greatly from those of carbon materials. Experiments have shown that when the method in Example 1 is used to replace additive B in Example 1 with bentonite and silica sol respectively, powdering and peeling will occur after treatment at temperatures above 1000°C, resulting in various problems such as uneven material composition and strength.

[0021] Coal tar and pitch are commonly used binders for carbon materials, especially activated carbon. Materials prepared using coal tar and pitch as binders exhibit extremely high strength and methylene and iodine adsorption values, making them suitable as adsorbents. However, when coal tar and pitch are used to replace additive B in Example 1, the catalytic performance of the resulting catalysts prepared from the composite supports is unstable. This may be because both materials are mixtures containing impurities. The impact of these impurities on the catalyst performance is complex and may have a poisoning effect. Furthermore, the impurity content varies between different batches of materials, leading to fluctuations in material performance.

[0022] A series of natural polymer materials, such as starch and hydroxymethyl cellulose, are commonly used binders for carbon materials in catalyst support molding. However, when starch and hydroxymethyl cellulose are used to replace additive B in Example 1 and are calcined together with nanodiamonds and graphite, it is found that the strength of the resulting support decreases rapidly with increasing processing temperature. The strength of the molded body cannot be improved at the temperature at which the nanodiamond surface undergoes a phase transition, and a high-strength composite support cannot be obtained.

[0023] As can be seen from the known comparison, the present invention uses a colloidal polymer, preferably at least one of phenolic resin, melamine-formaldehyde resin, furan resin, and benzoxazine resin. The resulting composite support not only produces a catalyst with higher strength, but also the catalyst has higher catalytic performance, achieving unexpected technical effects.

[0024] According to a preferred embodiment of the present invention, the additive B is selected from at least one of phenolic resin, melamine-formaldehyde resin, furan resin, and benzoxazine resin.

[0025] According to a preferred embodiment of the present invention, the solvent D is at least one selected from water, ethanol, acetonitrile, acetone, and cyclohexane. According to a preferred embodiment of the present invention,

[0026] The mixing step includes: mixing the raw material A and the auxiliary agent C to obtain mixture A, mixing the auxiliary agent B and the solvent D to obtain mixture B, and then mixing mixture A and mixture B.

[0027] According to a preferred embodiment of the present invention, the additive B is added in the form of an adhesive solution.

[0028] According to a preferred embodiment of the present invention, the particle size range of the nanodiamond is 10-200 nm.

[0029] According to a preferred embodiment of the present invention, the calcination conditions include:

[0030] The calcination is carried out under a protective atmosphere, preferably nitrogen and / or an inert gas.

[0031] According to a preferred embodiment of the present invention, the roasting temperature is 900-1500℃, preferably 900-1300℃.

[0032] According to a preferred embodiment of the present invention, the roasting time is 1-8 hours, preferably 2-6 hours.

[0033] In this invention, the molding process of the composite carrier employs existing conventional molding technologies, such as compression molding, extrusion molding, spray drying molding, oil molding, jet granulation molding, cooling granulation molding, and fibrous carrier molding; and / or,

[0034] Composite carriers use irregularly shaped carriers such as spheres, columns, sheets, toothed spheres, strips, clover or four-leaf clover;

[0035] Preferably, the molding process of the composite carrier adopts existing conventional compression molding and extrusion molding processes;

[0036] And / or, the composite carrier uses a carrier in irregular shapes such as columnar, sheet-like, toothed spherical, strip-like, clover-like, or four-leaf clover-like.

[0037] As an example, the shaped carrier material is placed in a tubular furnace and calcined under a protective atmosphere to produce a composite carrier with graphene-coated nanodiamonds as the main component.

[0038] The graphene-coated nanodiamond has a core-shell structure with graphene as the shell and nanodiamond as the core; in the core-shell structure, the number of graphene shell layers is 1-3.

[0039] As an example, the preparation method of nano-carbon composite carrier can be to fully mix raw material A, auxiliary agent B, auxiliary agent C and solvent D according to a certain ratio, granulate them, and then calcine them under a nitrogen atmosphere at a calcine temperature of 1200℃ for 6 hours. After natural cooling, nano-carbon composite carrier is obtained.

[0040] A second aspect of the present invention is to provide a composite carrier, which is prepared by the preparation method described in the first aspect; preferably,

[0041] The specific surface area of ​​the composite carrier is 100-400 m². 2 / g, preferably 250-400m 2 / g.

[0042] According to a preferred embodiment of the present invention, the lateral compressive strength of the composite carrier is above 65N;

[0043] The composite carrier is irregular in shape, preferably at least one of the following: spherical, columnar, sheet-like, toothed spherical, strip-like, clover-like, and four-leaf clover-like.

[0044] According to a preferred embodiment of the present invention, the composite carrier contains graphene-coated nanodiamonds; more preferably, the composite carrier has a core-shell structure with graphene material as the shell and nanodiamonds as the core; even more preferably, the number of shell layers is 1-3.

[0045] A third aspect of the present invention is to provide a catalyst comprising a composite support and an active component supported on the composite support; the composite support being the composite support described in the second aspect.

[0046] The active component is preferably at least one of Group VIIIB noble metal elements; according to a more preferred embodiment of the present invention, the active component is palladium.

[0047] According to a preferred embodiment of the present invention, the content of the active component is 0.001-10 wt%, preferably 0.01-2 wt%, based on a total catalyst weight of 100 wt%.

[0048] According to a preferred embodiment of the present invention, the content of the composite carrier is 90-99.999 wt%, preferably 98-99.99 wt%.

[0049] A fourth aspect of the present invention is to provide a method for preparing the catalyst described in the third aspect, comprising loading a precursor compound containing the active component onto the composite support, followed by post-processing to obtain the catalyst; preferably,

[0050] The loading method is impregnation.

[0051] According to a preferred embodiment of the invention, the post-treatment includes optional washing followed by drying.

[0052] According to a preferred embodiment of the present invention, the preparation method includes:

[0053] The composite support after vacuum treatment is mixed with a solution of a precursor compound containing the active component, impregnated, optionally washed, and then dried to obtain the catalyst.

[0054] According to a preferred embodiment of the present invention, the content of the metal element in the precursor compound of the active component is 0.001-10 wt%, preferably 0.01-2 wt%, based on a sum of 100 wt% of the mass of the metal element in the precursor compound of the active component and the mass of the composite carrier.

[0055] According to a preferred embodiment of the present invention, the precursor compound of the main active component is selected from palladium salts. Preferably, the palladium salt is selected from at least one of inorganic palladium salts and organic palladium salts. More preferably, the inorganic palladium salt is selected from at least one of palladium chloride, palladium nitrate, and palladium sulfate, and / or, the organic palladium salt is selected from at least one of palladium acetate and palladium acetylacetonate.

[0056] According to a preferred embodiment of the present invention, the impregnation conditions include: an impregnation temperature of 35-55°C. According to a preferred embodiment of the present invention, the impregnation time is 0.5-2 hours.

[0057] According to a preferred embodiment of the present invention, the solvent used in the solution containing the precursor compound of the active component includes an inorganic solvent and / or an organic solvent. Preferably, the inorganic solvent is selected from at least one of water, hydrochloric acid, and nitric acid, and / or the organic solvent is selected from at least one of acetic acid and ethanol.

[0058] According to a preferred embodiment of the present invention, the drying conditions include: a drying temperature of 50-200°C, and / or a drying time of 5-48 hours.

[0059] More preferably, when the inorganic solvent is selected from hydrochloric acid aqueous solution, the molar concentration of the hydrochloric acid aqueous solution is 0.001-0.100; and / or, when the inorganic solvent is selected from nitric acid aqueous solution, the molar concentration of the nitric acid aqueous solution is 0.001-0.100.

[0060] More preferably, the drying temperature in the post-treatment is 80-120°C; and / or, the drying time in the post-treatment is 5-24 hours. In the preparation method of the present invention, drying can be carried out under an air atmosphere or under a vacuum.

[0061] As an example, the preparation method of the nano-carbon selective hydrogenation catalyst can be as follows: A certain amount of nano-carbon composite support is evacuated for 10 minutes. A palladium impregnation solution is prepared and weighed, and diluted with distilled water to 50 mL. The above impregnation solution is added to the support, and the mixture is impregnated and stirred at 60 °C for 1 h. Then, the solvent is removed under reduced pressure using a rotary evaporator. The resulting catalyst is dried in an oven at 60 °C for 12 h to obtain the nano-carbon selective hydrogenation catalyst.

[0062] In the preparation method of this invention, the active component precursor can be loaded onto the support using the impregnation method employed in catalyst preparation, such as equal-volume impregnation or supersaturated impregnation. When using the supersaturated impregnation method, if the active component precursor in the impregnation solution cannot be completely adsorbed by the support, the volume of the impregnation solution and the concentration of the active component should be determined according to the adsorption ratio to ensure that the active component loaded onto the support meets the predetermined requirements.

[0063] The selective hydrogenation catalyst described in this invention can be analyzed using X-ray photoelectron spectroscopy (XPS) to confirm the chemical valence state of the active component of the catalyst.

[0064] A fifth aspect of the present invention is to provide a method for hydrogenating and removing alkynes before a C2 fraction, comprising:

[0065] This includes the selective hydrogenation reaction of acetylene-containing feed gas and hydrogen under the action of a catalyst;

[0066] The catalyst is either the catalyst described in the third aspect or the catalyst prepared by the preparation method described in the fourth aspect.

[0067] According to a preferred embodiment of the present invention, the molar fraction of acetylene in the feed gas is 0.1-10%, preferably 0.1-6%, and / or the molar fraction of hydrogen is 1-30%, preferably 5-25%; preferably, the feed gas is derived from acetylene-containing feed gas in the pre-hydrogenation process of the C2 fraction.

[0068] According to a preferred embodiment of the present invention, the conditions for the selective hydrogenation reaction include: a temperature of 10-180°C, and / or a volume hourly space velocity of 1000-20000 h⁻¹. -1 Preferably, the temperature is 20-120℃ and / or the volumetric hourly space velocity is 4000-20000 h⁻¹. -1 More preferably, the reaction temperature of the selective hydrogenation reaction is 20.0-120.0°C; further preferably 50-120°C; even more preferably 60-120°C; and / or, the volume hourly space velocity is further preferably 5000-20000 h⁻¹. -1 .

[0069] In the selective hydrogenation method described in this invention, as an example, the pre-hydrogenation reaction step includes:

[0070] (A) The above catalyst is loaded into the reactor;

[0071] (B) The feed gas containing acetylene is introduced into the reactor to carry out selective hydrogenation of acetylene.

[0072] In this invention, the reactor is a conventional hydrogenation reactor in the art.

[0073] Compared with the prior art, the present invention has at least the following advantages:

[0074] This invention utilizes a composite support primarily composed of graphene-coated nanodiamonds to prepare a catalyst with high activity. This catalyst can be directly used in the pre-hydrogenation reaction of the C2 fraction, improving the selective hydrogenation of acetylene to ethylene. Furthermore, the catalyst is granular and possesses high strength, meaning it has sufficient mechanical strength to be directly packed into a fixed-bed reactor, better meeting the practical needs of industrial applications compared to powdered catalysts. Additionally, compared to carbon-based catalysts reported in the literature, the catalyst in this invention requires a lower reaction temperature for acetylene conversion; and compared to traditional noble metal Pd selective hydrogenation catalysts, it exhibits higher ethylene selectivity.

[0075] The catalyst of this invention exhibits good catalytic performance at low temperatures and is suitable for industrial production. Detailed Implementation

[0076] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0077] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0078] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0079] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0080] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0081] In this invention, the catalyst can be analyzed using X-ray photoelectron spectroscopy (XPS) to confirm the chemical valence state of the active component of the catalyst.

[0082] The distribution of active components on the surface and cross-section of the support and the shell structure of the support can be observed using a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM); the specific surface area and pore distribution of the catalyst can be confirmed using a physical adsorption analyzer; and the mechanical strength of the catalyst can be tested using a universal strength tester.

[0083] Example 1

[0084] Weigh 10.0g of nanodiamond (particle size range 20-30nm) and 1g of graphite, mix them evenly, and weigh 2.8g of phenolic resin (based on solid content) and dilute with 17g of water. Mix the two mixtures together to form a ball, shape and granulate, and dry in a 60℃ oven for 12h. Place the resulting solid in a tube furnace at 1300℃ for 6h, and after natural cooling, obtain the molded composite carrier A.

[0085] Weigh 8.0 g of the above composite support A, evacuate under vacuum for 10 min, add a 0.25 mg / mL palladium nitrate solution, and dilute with water to 40 mL. Add the solution to the composite support, impregnate and stir at 60 °C for 1 h, cool to room temperature, add 32 mL of ethanol, remove the solvent using a rotary evaporator, and dry the resulting catalyst in a 60 °C oven for 12 h. The final selective hydrogenation catalyst with palladium as the active component is prepared, denoted as catalyst A, with a palladium loading of 0.3 wt‰.

[0086] Examples 2-5

[0087] Following the method of Example 1, except that the proportion of auxiliary agent B in the composite support is different, while the amount of nanodiamond and graphite remains the same, different composite supports B, C, D, and E are obtained. The catalysts prepared according to the method of Example 1 are labeled as catalyst B, catalyst C, catalyst D, and catalyst E, respectively. The specific composition is shown in Table 1. The palladium loading in each catalyst is 0.3 wt‰.

[0088] Examples 6-8

[0089] Following the method of Example 1, except that the type of auxiliary agent B in the composite support is different, different composite supports F, G, and H are obtained. The catalysts prepared according to the method of Example 1 are labeled as catalyst F, catalyst G, and catalyst H, respectively. The specific composition is shown in Table 1. The palladium loading in each catalyst is 0.3 wt‰.

[0090] In Example 9, the mass ratio of raw material A to auxiliary agent C is 1:(0.01-0.12), preferably 1:(0.01-0.1).

[0091] The method of Example 1 was followed, except that the amount of nanodiamond was 10g and the amount of graphite was 0.3g. The resulting composite carrier L was then used to prepare catalyst L according to the method of Example 1.

[0092] The physical and catalytic properties of the catalyst in Example 9 were verified to be comparable to those of the catalyst in Example 1 (the difference in acetylene conversion and ethylene selectivity was no more than 0.5%).

[0093] Example 10

[0094] The method of Example 1 was followed, except that the amount of nanodiamond was 10g and the amount of graphite was 1.15g. The resulting composite support K was then used to prepare catalyst K according to the method of Example 1.

[0095] The physical and catalytic properties of the catalyst in Example 9 were verified to be comparable to those of the catalyst in Example 1 (the difference in acetylene conversion and ethylene selectivity was no more than 0.5%).

[0096] Transmission electron microscopy revealed that the composite carriers in Examples 1-10 all have a core-shell structure with graphene as the shell and nanodiamond as the core, and the number of graphene shell layers in the core-shell structure is 1-3.

[0097] Comparative Example 1

[0098] The method of Example 1 was followed, except that no auxiliary agent B was added to prepare composite support I, and the catalyst prepared thereafter was labeled as catalyst I.

[0099] Comparative Example 2

[0100] Following the method of Example 1, except that no auxiliary agent C was added, composite support J was prepared, and the catalyst prepared thereafter was labeled as catalyst J.

[0101] Comparative Example 3

[0102] A Pd-Ag / Al₂O₃ catalyst was prepared as a comparative example using the equal-volume impregnation method. Palladium nitrate and silver nitrate solutions were prepared according to the appropriate Pd and Ag loadings, and impregnated onto spherical alumina supports with a diameter of 3 mm. The solutions were dried at 120 °C for 8 hours and calcined at 600 °C with air for 4 hours to obtain the Pd-Ag catalyst, denoted as Pd-Ag catalyst, with a palladium loading of 0.3 wt% and a silver loading of 1 wt%.

[0103] Table 1

[0104]

[0105] In Table 1, the total weight of raw material A, auxiliary agent B, and auxiliary agent C is 100 wt%.

[0106] Table 2

[0107]

[0108]

[0109] Table 3

[0110]

[0111] By comparing Comparative Example 1 with Examples 1-8, it can be seen that the catalyst prepared by the composite support of the present invention has a significant improvement in side pressure strength. This result fully demonstrates that the catalyst prepared by the composite support of the present invention has higher strength.

[0112] The high-strength composite carrier described above is not a conventional technical adjustment in the field.

[0113] For the molding of powdered carriers and catalysts, conventional binders such as "bentonite, silica sol, coal tar, asphalt, starch, hydroxymethyl cellulose", although they are also binders and can transform powders into particles, are not suitable for the preparation method of the present invention. That is, using the above-mentioned binders to replace the colloidal polymer in the present invention cannot obtain the composite carrier required for the application of composite catalysts.

[0114] The inventors of this invention have confirmed through research that:

[0115] Bentonite and silica sol are commonly used inorganic adhesives, but their material properties differ greatly from those of carbon materials. Experiments have shown that when the method in Example 1 is used to replace additive B in Example 1 with bentonite and silica sol respectively, powdering and peeling will occur after treatment at temperatures above 1000°C, resulting in various problems such as uneven material composition and strength.

[0116] Coal tar and pitch are commonly used binders for carbon materials, especially activated carbon. Materials prepared using coal tar and pitch as binders exhibit extremely high strength and methylene and iodine adsorption values, making them suitable as adsorbents. However, when coal tar and pitch are used to replace additive B in Example 1, the catalytic performance of the resulting catalysts prepared from the composite supports is unstable. This may be because both materials are mixtures containing impurities. The impact of these impurities on the catalyst performance is complex and may have a poisoning effect. Furthermore, the impurity content varies between different batches of materials, leading to fluctuations in material performance.

[0117] A series of natural polymer materials, such as starch and hydroxymethyl cellulose, are commonly used binders for carbon materials in catalyst support molding. However, when starch and hydroxymethyl cellulose are used to replace additive B in Example 1 and are calcined together with nanodiamonds and graphite, it is found that the strength of the resulting support decreases rapidly with increasing processing temperature. The strength of the molded body cannot be improved at the temperature at which the nanodiamond surface undergoes a phase transition, and a high-strength composite support cannot be obtained.

[0118] As can be seen from the known comparison, the present invention uses a colloidal polymer, preferably at least one of phenolic resin, melamine-formaldehyde resin, furan resin, and benzoxazine resin. The resulting composite support not only produces a catalyst with higher strength, but also the catalyst has higher catalytic performance, achieving unexpected technical effects.

[0119] Application examples

[0120] The prepared catalyst was subjected to a simulated microreactor experiment for the pre-hydrogenation reaction of acetylene under the following reaction conditions:

[0121] 5 mL of catalyst was packed into a stainless steel tube reactor. After reduction with hydrogen, the feed gas simulating pre-ethane removal and pre-hydrogenation was introduced into the reactor. The composition (mole fraction) of the feed gas was: C2H2: 0.102%, C2H6: 12.07%, C2H4 equilibrium, H2: 23.60%, CO: 0.0806%, and the volume hourly space velocity (VHSV) was 8000 h⁻¹. -1 .

[0122] The selective hydrogenation catalytic performance of the above catalysts for acetylene was evaluated, with catalyst AJ in the examples and comparative examples being directly evaluated. The conversion and selectivity of acetylene pre-hydrogenation to ethylene at 60°C are listed in Table 3. The calculation methods for the conversion and selectivity of acetylene pre-hydrogenation to ethylene are as follows:

[0123]

[0124]

[0125] Table 3. Simulation results of the pre-hydrogenation process (average value at 80℃)

[0126]

[0127]

[0128] Verification showed that the conversion rate of acetylene in the above examples and comparative examples was above 99.99%.

[0129] A comparison of the embodiments and comparative examples of the present invention shows that the catalyst of the present invention is granular, has high strength, and can be directly used in industrial applications of acetylene pre-hydrogenation reactions. Application examples demonstrate that the catalyst of the present invention, while maintaining high acetylene conversion, also improves ethylene selectivity.

[0130] By comparing Comparative Examples 1 and 2 with Examples 1-10, it can be seen that the catalyst prepared by the composite support of the present invention has higher selectivity in the pre-hydrogenation reaction.

[0131] At 60℃, the selectivity of the Pd-Ag catalyst in Comparative Example 3 was 32.7%. At 80℃, the selectivity of the Pd-Ag catalyst for ethylene was only -1765.2% because it consumed ethylene. It can be seen that the selectivity of ethylene is higher than that of traditional noble metal Pd selective hydrogenation catalyst.

[0132] In summary, the above results fully demonstrate that the catalyst obtained by the composite support of the present invention has higher selectivity and significantly improved mechanical strength, which better meets the requirements of industrial applications.

[0133] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0134] 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.

[0135] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0136] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0137] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0138] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0139] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A method for preparing a composite support for a catalyst used in the pre-hydrotreating of alkynes in C2 fractions, comprising mixing, granulating, and calcining raw materials including raw material A, auxiliary agent B, auxiliary agent C, and solvent D to obtain the composite support, wherein the composite support contains graphene-coated nanodiamonds; the mixing step includes: The raw material A and the auxiliary agent C are mixed to obtain mixture A. The auxiliary agent B is mixed with solvent D to obtain mixture B. Then, mixture A and mixture B are mixed together. The raw material A is nano-diamond; The auxiliary agent B is a colloidal polymer; The auxiliary agent C is at least one of graphite, polyvinyl alcohol, and carboxymethyl cellulose.

2. The preparation method according to claim 1, characterized in that: The mass ratio of raw material A to auxiliary agent C is 1:(0.01-0.12); and / or, With the total weight of raw material A, auxiliary agent B, and auxiliary agent C being 100 wt%, and the amount of auxiliary agent B being 1-50 wt%; and / or, The total weight ratio of raw material A, auxiliary agent B, and auxiliary agent C to solvent D is 1:(0.5-3); and / or, The additive B is selected from at least one of phenolic resin, melamine-formaldehyde resin, furan resin, and benzoxazine resin.

3. The preparation method according to claim 1, characterized in that: The mass ratio of raw material A to auxiliary agent C is 1:(0.01-0.1); and / or, With the total weight of raw material A, auxiliary agent B, and auxiliary agent C being 100 wt%, and the amount of auxiliary agent B being 10-30.5 wt%; and / or, The total weight ratio of raw material A, auxiliary agent B and auxiliary agent C to solvent D is 1:(1-2).

4. The preparation method according to any one of claims 1-3, characterized in that: The solvent D is at least one selected from water, ethanol, acetonitrile, acetone, and cyclohexane; and / or, The additive B is added in the form of a liquid adhesive; and / or, The nanodiamonds have a particle size range of 10-200 nm.

5. The preparation method according to any one of claims 1-3, characterized in that: The roasting conditions include: The calcination is carried out under a protective atmosphere; and / or, The calcination temperature is 900-1500℃; and / or, The roasting time is 1-8 hours.

6. The preparation method according to any one of claims 1-3, characterized in that: The roasting conditions include: The calcination is carried out under a protective atmosphere, which is nitrogen and / or an inert gas; and / or, The calcination temperature is 900-1300℃; and / or, The roasting time is 2-6 hours.

7. A composite support for a catalyst used in the pre-hydrogenation removal of alkynes from C2 fractions, wherein the composite support is prepared by the preparation method according to any one of claims 1-6; the composite support contains graphene-coated nanodiamond.

8. The composite carrier according to claim 7, characterized in that: The specific surface area of the composite support is between 100 and 400 m 2 / g; and / or, The lateral compressive strength of the composite carrier is above 65N; and / or, The composite carrier is irregular in shape; and / or, The composite carrier contains graphene-coated nanodiamonds.

9. The composite carrier according to claim 7, characterized in that: The specific surface area of ​​the composite carrier is 250-400 m². 2 / g; and / or, The composite carrier is at least one of the following: spherical, columnar, sheet-like, toothed spherical, strip-like, clover-like, and four-leaf clover-like.

10. The composite carrier according to claim 7, characterized in that: The composite carrier contains graphene-coated nanodiamonds. The composite carrier has a core-shell structure with graphene as the shell and nanodiamond as the core.

11. The composite carrier according to claim 10, characterized in that: The shell has 1-3 layers.

12. A catalyst for the hydrogenation removal of alkynes before C2 fractionation, comprising a composite support and an active component supported on the composite support; wherein the composite support is any one of claims 7-11; and the active component is at least one of group VIIIB noble metal elements.

13. The catalyst according to claim 12, characterized in that: The active ingredient is palladium; and / or, Based on a total catalyst weight of 100 wt%, the content of the active component is 0.001-10 wt%; and / or, the content of the composite support is 90-99.999 wt%.

14. The catalyst according to claim 12, characterized in that: Based on a total catalyst weight of 100 wt%, the content of the active component is 0.01-2 wt%; and / or, the content of the composite support is 98-99.99 wt%.

15. A method for preparing a catalyst according to any one of claims 12-14, comprising loading a precursor compound containing the active component onto the composite support, and then performing post-treatment to obtain the catalyst.

16. The method for preparing the catalyst according to claim 15 of the province, characterized in that: The loading method is immersion; and / or the post-treatment includes optional washing followed by drying.

17. The preparation method according to claim 15, characterized in that: The preparation method includes: The composite support after vacuum treatment is mixed with a solution of a precursor compound containing the active component, impregnated, optionally washed, and then dried to obtain the catalyst.

18. The preparation method according to claim 15, characterized in that: Based on the sum of the mass of the metal element in the precursor compound of the active component and the mass of the composite carrier being 100wt%, the content of the metal element in the precursor compound of the active component is 0.001-10wt%.

19. The preparation method according to claim 15, characterized in that: Based on the sum of the mass of the metal element in the precursor compound of the active component and the mass of the composite carrier being 100wt%, the content of the metal element in the precursor compound of the active component is 0.01-2wt%.

20. The preparation method according to claim 15, characterized in that: The precursor compound of the main active component is selected from palladium salts.

21. The preparation method according to claim 20, characterized in that: The palladium salt is selected from at least one of inorganic palladium salts and organic palladium salts.

22. The preparation method according to claim 21, characterized in that: The inorganic palladium salt is selected from at least one of palladium chloride, palladium nitrate, and palladium sulfate, and / or the organic palladium salt is selected from at least one of palladium acetate and palladium acetylacetone.

23. The preparation method according to claim 17, characterized in that: The impregnation conditions include: an impregnation temperature of 35-55°C; and / or an impregnation time of 0.5-2 hours; and / or... The drying conditions include: a drying temperature of 50-200℃, and / or a drying time of 5-48h.

24. The preparation method according to claim 17, characterized in that: The solvents used in the solution of the precursor compound containing the active component include inorganic solvents and / or organic solvents.

25. The preparation method according to claim 24, characterized in that: The inorganic solvent is selected from at least one of water, hydrochloric acid, and nitric acid, and / or the organic solvent is selected from at least one of acetic acid and ethanol.

26. A method for hydrogenating and removing alkynes before the C2 fraction, comprising: This includes the selective hydrogenation reaction of acetylene-containing feed gas and hydrogen under the action of a catalyst; The catalyst is the catalyst according to any one of claims 12-14 or the catalyst prepared by the preparation method according to any one of claims 15-25.

27. The method according to claim 26, characterized in that: The feed gas contains 0.1-10% acetylene and / or 1-30% hydrogen; and / or The conditions for the selective hydrogenation reaction include: a temperature of 10-180°C, and / or a volume hourly space velocity of 1000-20000 h⁻¹. -1 .

28. The method according to claim 26, characterized in that: The feed gas contains 0.1-6% acetylene and / or 5-25% hydrogen; and / or The conditions for the selective hydrogenation reaction include: a temperature of 20-120°C; and / or a volume hourly space velocity of 4000-20000 h⁻¹. -1 .

29. The method according to claim 26, characterized in that: The feed gas is derived from acetylene-containing feed gas from the pre-hydrogenation process of the C2 fraction.

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