Catalyst and preparation method thereof, and system and method for continuously preparing methylhexahydrophthalic anhydride

Abstract

The invention discloses a catalyst and a preparation method thereof, and a system and a method for continuously preparing methylhexahydrophthalic anhydride, and belongs to the technical field of methylhexahydrophthalic anhydride preparation. The catalyst has a double-layer structure, the outer layer is a stainless steel hollow structure, and the inner layer is a Raney nickel-cobalt metal structure. The catalyst not only has high activity and high hydrogenation efficiency of a Raney nickel catalyst, but also has the advantages of high strength, long service life, strong stability and the like, and can be used for preparing methylhexahydrophthalic anhydride. Besides, according to the system for continuously preparing methylhexahydrophthalic anhydride provided by the invention, the hydrogenation process is divided into two sections, and the catalyst is used for the second-section hydrogenation process, so that higher hydrogenation efficiency, shorter hydrogenation residence time and higher production efficiency can be obtained in this way, the saturation degree of a hydrogenation product is high, and the yield of the product is increased. The method has the advantages of low iodine value, light color number, high purity, higher yield, few byproducts and the like.

Description

Technical Field

[0001] The invention relates to the technical field of methyl hexahydrophthalic anhydride preparation, and in particular to a catalyst and a preparation method thereof, and a system and a method for continuously preparing methyl hexahydrophthalic anhydride. Background Art

[0002] Methylhexahydrophthalic anhydride is a liquid anhydride curing agent obtained by hydrogenating methyltetrahydrophthalic anhydride to saturate olefin bonds. It is mainly used for epoxy resin curing. Because of its characteristics of product stability, light color, strong antioxidant ability, low freezing point, and good high-temperature electrical properties, it is usually used in mid-to-high-end fields such as electronic component potting, material casting, and semiconductor sealing. At present, intermittent kettle hydrogenation is often used to produce methylhexahydrophthalic anhydride.

[0003] The kettle-type intermittent hydrogenation process requires the use of powdered or granular hydrogenation catalysts. The catalyst and materials are mixed in the kettle by stirring. The disadvantages are low product yield, slightly poor saturation, easy breakage of the catalyst, large catalyst loss, the product may carry trace amounts of catalyst, less dissolved hydrogen and uneven mixing, more side reactions, and low product yield.

[0004] In contrast, the continuous hydrogenation process mostly uses fixed-bed catalysts. Hydrogen and methyltetrahydrophthalic anhydride are mixed and then enter the catalyst bed. First, the fixed bed operation lacks stirring, resulting in uneven hydrogen mixing. Second, due to the high viscosity of methylhexahydrophthalic anhydride, it is easier to adhere to the catalyst surface, covering the active center of the hydrogenation catalytic metal. In addition, the catalyst has a small specific surface area and low hydrogenation efficiency. A higher hydrogenation temperature is required to obtain a highly saturated methylhexahydrophthalic anhydride product. Higher temperatures will cause some products to undergo condensation and self-polymerization to generate oligomers or the product will undergo over-hydrogenation saturated carboxyl groups, thereby affecting the actual use effect of the product.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a catalyst and a preparation method thereof, and a system and method for continuously preparing methylhexahydrophthalic anhydride, so as to solve or improve the above technical problems.

[0007] The present invention can be implemented like this:

[0008] In a first aspect, the present invention provides a catalyst having a double-layer structure, wherein the outer layer is a stainless steel hollow structure, and the inner layer is a Raney nickel-cobalt metal structure; the catalyst is spherical or quasi-spherical.

[0009] In an alternative embodiment, the catalyst has at least one of the following characteristics:

[0010] Feature 1: The outer diameter of the catalyst is 0.5 mm to 20 mm, preferably 1 mm to 10 mm;

[0011] Feature 2: The specific surface area of ​​the catalyst is 20m 2 / g~100m 2 / g;

[0012] Feature 3: The thickness ratio of the outer layer to the inner layer is 0.5:1 to 2:1, preferably 0.7:1 to 1.3:1;

[0013] Feature 4: The weight ratio of the outer layer to the inner layer is 0.7:1 to 2:1, preferably 1:1 to 1.5:1.

[0014] In a second aspect, the present invention provides a method for preparing a catalyst as described in the aforementioned embodiment, comprising the following steps: attaching nickel-cobalt-aluminum alloy powder to the surface of a substrate via a first adhesive to obtain a first intermediate; attaching a mixture of stainless steel powder and aluminum powder to the surface of the intermediate via a second adhesive to obtain a second intermediate; sintering the second intermediate and removing the substrate, the first adhesive and the second adhesive to obtain a third intermediate; heating and soaking the third intermediate to remove aluminum to obtain a catalyst.

[0015] In an optional embodiment, the preparation of the catalyst includes at least one of the following features:

[0016] Feature 5: The substrate is spherical or quasi-spherical; preferably, the diameter of the substrate is 0.5 mm to 10 mm, more preferably 0.5 mm to 5 mm; preferably, the substrate is activated carbon;

[0017] Feature 6: The particle size of the nickel-cobalt-aluminum alloy powder is 100 mesh to 300 mesh, preferably 150 mesh to 200 mesh;

[0018] Feature 7: The content of Ni in the nickel-cobalt-aluminum alloy powder is ≥80wt%, the content of Co is 2wt% to 5wt%, and the content of Al is 12wt% to 18wt%;

[0019] Feature 8: The particle size of the stainless steel powder is 100-200 mesh; preferably, the stainless steel powder is 304 stainless steel powder;

[0020] Feature 9: The first adhesive and the second adhesive independently include at least one of solvent adhesive, hot melt adhesive and pressure sensitive adhesive; preferably, the active components in the first adhesive and the second adhesive include at least one of acrylic acid, polyurethane and synthetic rubber; more preferably, the active components in the first adhesive and the second adhesive include acrylic acid;

[0021] Feature 10: The solid contents of the first binder and the second binder are independently 20 wt% to 60 wt%;

[0022] Feature 11: The viscosity of the first adhesive and the second adhesive at 25° C. is independently 300 cp to 2000 cp;

[0023] Feature 12: The surface drying time of the first adhesive and the second adhesive is independently 3 minutes to 15 minutes;

[0024] Feature 13: The coating thickness of the first adhesive on the substrate surface is 5 μm to 50 μm, preferably 5 μm to 15 μm;

[0025] Feature 14: The coating thickness of the second adhesive on the surface of the mixture is 5 μm to 50 μm, preferably 5 μm to 15 μm.

[0026] In an optional embodiment, the preparation of the catalyst further comprises at least one of the following features:

[0027] Feature 15: The sintering temperature is 300°C to 600°C, preferably 400°C to 550°C;

[0028] Feature 16: The temperature of the heating and soaking is 50°C to 180°C, preferably 100°C to 150°C;

[0029] Feature 17: The soaking solution used for heated soaking is a strong alkaline solution, preferably a strong alkaline solution with a concentration of 30wt% to 70wt%, and more preferably, the strong alkaline solution is a sodium hydroxide solution.

[0030] In a third aspect, the present invention provides a system for continuously preparing methyl hexahydrophthalic anhydride, which comprises a first-stage hydrogenation reactor and a second-stage hydrogenation reactor connected in series;

[0031] The first-stage hydrogenation reactor has an inlet for methyltetrahydrophthalic anhydride and hydrogen to enter, and an outlet for outputting the first-stage hydrogenation product; the second-stage hydrogenation reactor has a first inlet connected to the outlet of the first-stage hydrogenation reactor, the second-stage hydrogenation reactor also has a second inlet for hydrogen to enter, and the second-stage hydrogenation reactor also has an outlet for outputting the second-stage hydrogenation product; the catalyst of the aforementioned embodiment is used to be filled in the second-stage hydrogenation reactor.

[0032] In an optional embodiment, the first stage hydrogenation reactor is a fixed bed reactor.

[0033] In an optional embodiment, the first stage hydrogenation reactor is filled with a SiO2-alumina supported nickel catalyst, wherein the carrier is a composite of silica and alumina.

[0034] In an optional embodiment, the content of Ni in the SiO2-alumina supported nickel catalyst is 40 wt% to 60 wt%.

[0035] In an optional embodiment, the SiO2-alumina supported nickel-based catalyst is in the shape of a cloverleaf strip.

[0036] In an optional embodiment, a vertically extending array of tubes is provided in the second-stage hydrogenation reactor, the array of tubes has a reaction chamber, the reaction chamber has a first inlet and a second inlet arranged opposite to each other, wherein the first inlet is used for supplying methyltetrahydrophthalic anhydride, and the second inlet is used for supplying hydrogen, and the catalyst of any of the aforementioned embodiments is used to be loaded in the reaction chamber.

[0037] In an optional embodiment, a plurality of tubes are arranged in parallel in the second-stage hydrogenation reactor; preferably, the number of tubes arranged in the second-stage hydrogenation reactor is 3 to 10; more preferably, the number of tubes arranged in the second-stage hydrogenation reactor is 5 to 8.

[0038] In an optional embodiment, each tube array is provided with a plurality of reaction chambers in series; preferably, the number of reaction chambers provided for each tube array is 5 to 20; more preferably, the number of reaction chambers provided for each tube array is 8 to 15.

[0039] In an optional embodiment, the mass of the catalyst loaded in a single reaction chamber is 0.2% to 3% of the total mass of the first-stage hydrogenation product that theoretically needs to be subjected to the second-stage hydrogenation in the reaction chamber; preferably, the mass of the catalyst loaded in a single reaction chamber is 0.3% to 1% of the total mass of the first-stage hydrogenation product that theoretically needs to be subjected to the second-stage hydrogenation in the reaction chamber.

[0040] In an optional embodiment, the first inlet and the second inlet are mirror-symmetrical.

[0041] In an optional embodiment, a filter is provided at the outlet of each reaction chamber.

[0042] In an alternative embodiment, the bottom of the reaction chamber is horizontal and the top is curved.

[0043] In an optional embodiment, the system further comprises a first preheater and a dynamic mixer;

[0044] The first preheater is used to preheat methyltetrahydrophthalic anhydride. The dynamic mixer is connected to the outlet of the first preheater and has an inlet for introducing hydrogen. The outlet of the dynamic mixer is connected to the inlet of a first-stage hydrogenation reactor.

[0045] In an optional embodiment, the system further comprises a first gas-liquid separation tank; the first gas-liquid separation tank is connected between the first stage hydrogenation reactor and the second stage hydrogenation reactor.

[0046] In an optional embodiment, the system further includes a second gas-liquid separation tank, a second preheater, and a distillation tower;

[0047] The inlet of the second gas-liquid separation tank is connected to the outlet of the second-stage hydrogenation reactor, the outlet of the second gas-liquid separation tank is connected to the inlet of the second preheater, and the outlet of the second preheater is connected to the inlet of the distillation tower.

[0048] In an optional embodiment, the system further comprises a top condenser connected to the top of the distillation tower and a bottom reboiler connected to the bottom of the distillation tower.

[0049] In an optional embodiment, the system further comprises a vacuum buffer tank connected to the outlet of the top condenser.

[0050] In a fourth aspect, the present invention provides a method for continuously preparing methylhexahydrophthalic anhydride, which is prepared using the system of any one of the aforementioned embodiments.

[0051] In an optional embodiment, the preparation conditions include at least one of the following characteristics:

[0052] Feature 18: The hydrogen pressure in the second-stage hydrogenation reactor is 1MPa-8MPa, the hydrogenation temperature is 60°C-120°C, and the residence time of the material in the second-stage hydrogenation reactor is 1h-5h; preferably, the hydrogen pressure in the second-stage hydrogenation reactor is 1MPa-4MPa, and the residence time of the material in the second-stage hydrogenation reactor is 1h-3h;

[0053] Feature 19: The preheating temperature of the second preheater is 140°C to 200°C, preferably 140°C to 170°C.

[0054] Feature 20: The operating pressure of the distillation tower is -0.09 MPa to -0.1 MPa, the bottom temperature of the distillation tower is 210°C to 235°C, the top gas phase temperature is 145°C to 170°C, and the number of plates is 8 to 20; preferably, the bottom temperature of the distillation tower is 213°C to 225°C, the top gas phase temperature is 148°C to 160°C, and the number of plates is 10 to 15;

[0055] Feature 21: The temperature of the product obtained after cooling in the top condenser is 30°C to 120°C, preferably 50°C to 100°C.

[0056] The beneficial effects of the present invention include:

[0057] The present invention creatively proposes a new catalyst, which not only has the high activity and high hydrogenation efficiency of the Raney nickel catalyst, but also has the advantages of high strength, long life, strong stability, etc., and is particularly suitable for preparing methyl hexahydrophthalic anhydride. The system for continuously preparing methyl hexahydrophthalic anhydride provided by the present invention divides the hydrogenation process into two stages, and the catalyst is used for the second stage hydrogenation process. In this way, it is conducive to obtaining a higher hydrogenation efficiency, a shorter hydrogenation residence time, and a higher production efficiency, and the hydrogenation product can also have a high saturation, a low iodine value, a light color number, a high purity, a higher yield, and less by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0059] Figure 1 A schematic structural diagram of a system for continuously preparing methyl hexahydrophthalic anhydride provided by the present invention;

[0060] Figure 2 for Figure 1 An enlarged view of the local reaction chamber in the second-stage hydrogenation reactor.

[0061] Icons: 1-first preheater; 2-dynamic mixer; 3-first stage hydrogenation reactor; 4-first gas-liquid separation tank; 5-second stage hydrogenation reactor; 6-second gas-liquid separation tank; 7-second preheater; 8-distillation tower; 9-tower top condenser; 10-vacuum buffer tank; 11-tower bottom reboiler. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0063] The catalyst and preparation method thereof, and the system and method for continuously preparing methylhexahydrophthalic anhydride provided by the present invention are specifically described below.

[0064] The invention provides a catalyst having a double-layer structure, wherein the outer layer is a stainless steel hollow structure and the inner layer is a Raney nickel-cobalt metal structure; the catalyst is spherical or quasi-spherical.

[0065] In the catalyst, the addition of cobalt in the inner layer can not only improve the hydrogenation activity and efficiency, but also provide a higher strength for the Raney nickel-cobalt catalyst to prevent the catalyst from breaking during multiple uses. At the same time, the outer stainless steel hollow structure can prevent the catalyst from being crushed due to the impact of the reactor wall when the catalyst is driven by the gas to maintain a rotating state, and the hollow structure can also effectively increase the specific surface area of ​​the catalyst. In addition, the spherical or quasi-spherical shape can help the catalyst maintain a highly efficient rotating mixing state, which is more conducive to the uniform mixing of the catalyst in the hydrogenation raw material and improves the hydrogenation efficiency.

[0066] In some optional embodiments, the outer diameter of the catalyst can be 0.5 mm to 20 mm, such as 0.5 mm, 1 mm, 2 mm, 5 mm, 10 mm, 12 mm, 15 mm, 18 mm or 20 mm, etc., or other values ​​within the range of 0.5 mm to 20 mm. In some typical embodiments, the outer diameter of the catalyst is 1 mm to 10 mm.

[0067] In some optional embodiments, the specific surface area of ​​the catalyst is 20 m 2 / g~100m 2 / g, such as 20m 2 / g, 25m 2 / g, 30m 2 / g, 35m 2 / g, 40m 2 / g, 45m 2 / g, 50m 2 / g, 55m 2 / g, 60m 2 / g, 65m 2 / g, 70m 2 / g, 75m 2 / g, 80m 2 / g, 85m 2 / g, 90m 2 / g, 95m 2 / g or 100m 2 / g, etc., can also be 20m 2 / g~100m 2 / Other values ​​within the range of g.

[0068] In some optional embodiments, the thickness ratio of the outer layer to the inner layer can be 0.5:1 to 2:1, such as 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc., or other values ​​within the range of 0.5:1 to 2:1. In some typical embodiments, the thickness ratio of the outer layer to the inner layer is 0.7:1 to 1.3:1.

[0069] In some optional embodiments, the weight ratio of the outer layer to the inner layer can be 0.7:1 to 2:1, such as 0.7:1, 1:1, 1.2:1, 1.5:1, 1.8:1 or 2:1, etc., or other values ​​within the range of 0.7:1 to 2:1. In some typical embodiments, the weight ratio of the outer layer to the inner layer is 1:1 to 1.5:1.

[0070] After the binder is removed, the inner layer of the double-layer catalyst is in direct contact with the outer layer due to gravity. During the sintering process, the two layers are sintered and bonded at the contact point to form a stable spherical hollow metal structure containing two non-concentric layers.

[0071] As mentioned above, the double-layer catalyst provided by the present invention not only has the high activity and high hydrogenation efficiency characteristics of conventional Raney nickel catalysts, but also has the advantages of high strength, long life and strong stability.

[0072] Correspondingly, the present invention also provides a method for preparing the above-mentioned catalyst, which may include the following steps: attaching nickel-cobalt-aluminum alloy powder to the surface of a substrate via a first adhesive to obtain a first intermediate; attaching a mixture containing stainless steel powder and aluminum powder to the surface of the intermediate via a second adhesive to obtain a second intermediate; sintering the second intermediate and removing the substrate, the first adhesive and the second adhesive to obtain a third intermediate; heating and soaking the third intermediate to remove aluminum to obtain a catalyst.

[0073] For example, a layer of adhesive can be coated (e.g., sprayed) on the surface of the substrate, and then a layer of nickel-cobalt-aluminum alloy powder can be coated (e.g., sprayed) to cover the adhesive layer, and then another layer of adhesive can be coated (e.g., sprayed), and then a layer of a mixture of stainless steel powder and aluminum powder can be sprayed on the adhesive layer. After spraying, it is placed at a high temperature for sintering, and the substrate and adhesive are removed at high temperature to obtain an intermediate of a double-layer alloy structure. The substance is placed in an immersion solution for heating and immersion, and the aluminum metal is removed, so that a catalyst of a double-layer hollow alloy structure can be obtained. The outer layer is a stainless steel hollow structure, and the inner layer is a Raney nickel-cobalt metal structure.

[0074] In some optional embodiments, the substrate is spherical or quasi-spherical, and the spherical or quasi-spherical shape can help the catalyst maintain a highly efficient rotating mixed state, which is more conducive to the uniform mixing of the catalyst in the hydrogenation feedstock and improves the hydrogenation efficiency. In some optional embodiments, the diameter of the substrate can be 0.5mm to 10mm, such as 0.5mm, 1mm, 2mm, 4mm, 6mm, 8mm or 10mm, etc., or other values ​​within the range of 0.5mm to 10mm. In some more typical embodiments, the diameter of the substrate is 0.5mm to 5mm. As an example, the above-mentioned substrate can be activated carbon.

[0075] In some optional embodiments, the particle size of the nickel-cobalt-aluminum alloy powder can be 100 mesh to 300 mesh, such as 100 mesh, 150 mesh, 200 mesh, 250 mesh or 300 mesh, etc., or other values ​​within the range of 100 mesh to 300 mesh. In some typical embodiments, the particle size of the nickel-cobalt-aluminum alloy powder is 150 mesh to 200 mesh. Controlling the particle size of the nickel-cobalt-aluminum alloy powder within the above range is beneficial to the sintering process during the catalyst preparation process, and is convenient for the nickel-cobalt-aluminum alloy to form a shell-shaped stable structure. At the same time, the preparation of metal powder with a high mesh number is difficult, and a dense layer will be formed during the sintering process, which is not conducive to the discharge of ash after carbonization of activated carbon, affecting the performance of the catalyst; the preparation of metal powder with a low mesh number is easy, but it will lead to a decrease in the catalyst loading per unit volume and reduce the catalytic activity. Therefore, the particle size of the nickel-cobalt-aluminum alloy powder is controlled within 100 mesh to 300 mesh in the present invention.

[0076] In some optional embodiments, the Ni content in the nickel-cobalt-aluminum alloy powder is ≥80wt% (such as 80wt%, 81wt%, 82wt%, 83wt%, 84wt%, 85wt% or 86wt%, etc.), the Co content is 2wt% to 5wt% (such as 2wt%, 3wt%, 4wt% or 5wt%, etc.), and the Al content is 12wt% to 18wt% (such as 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt% or 18wt%, etc.).

[0077] In some optional embodiments, the particle size of the stainless steel powder can be 100 mesh to 200 mesh, such as 100 mesh, 120 mesh, 150 mesh, 180 mesh or 200 mesh, etc., or other values ​​within the range of 100 mesh to 200 mesh. As an example, the above-mentioned stainless steel powder can be 304 stainless steel powder. Similarly, controlling the particle size of the stainless steel powder within the above range is beneficial to the sintering process during the catalyst preparation process, and is convenient for the 304 stainless steel powder to form a shell-like stable structure. At the same time, the preparation of metal powder with a high mesh number is more difficult, and it is easy to form a dense layer during the sintering process, which is not conducive to the discharge of ash after carbonization of activated carbon, affecting the performance of the catalyst; the preparation of metal powder with a low mesh number is easy, but it will lead to a decrease in the catalyst loading per unit volume and reduce the catalytic activity. Therefore, the particle size of the stainless steel powder is controlled within 100 mesh to 300 mesh in the present invention.

[0078] It should be noted that the mixture containing stainless steel powder and aluminum powder is more conducive to the sintering of metal powder due to the high thermal conductivity of aluminum, making it easier for metal powders such as nickel-cobalt and stainless steel to sinter and bond to form a fixed round shell.

[0079] In some optional embodiments, the first adhesive and the second adhesive may independently include at least one of solvent adhesive, hot melt adhesive and pressure sensitive adhesive. The active ingredients in the first adhesive and the second adhesive may include at least one of acrylic acid, polyurethane and synthetic rubber. That is, the first adhesive and the second adhesive may independently be solvent adhesive, hot melt adhesive or pressure sensitive adhesive prepared from at least one of acrylic acid, polyurethane and synthetic rubber. In some typical embodiments, the active ingredients in the first adhesive and the second adhesive both include acrylic acid.

[0080] In some optional embodiments, the solid contents of the first adhesive and the second adhesive are independently 20wt% to 60wt%, such as 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt% or 60wt%, etc., and may also be other values ​​within the range of 20wt% to 60wt%.

[0081] In some optional embodiments, the viscosity of the first adhesive and the second adhesive at 25° C. may independently be 300 cp to 2000 cp, such as 300 cp, 500 cp, 1000 cp, 1200 cp, 1500 cp, 1800 cp or 2000 cp, etc., or other values ​​within the range of 300 cp to 2000 cp.

[0082] In some optional embodiments, the surface drying time of the first adhesive and the second adhesive is independently 3 min to 15 min, such as 3 min, 5 min, 8 min, 10 min, 12 min or 15 min, etc., or other values ​​within the range of 3 min to 15 min.

[0083] In some optional embodiments, the coating thickness of the first adhesive on the substrate surface can be 5 μm to 50 μm, such as 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, or other values ​​within the range of 5 μm to 50 μm. In some typical embodiments, the coating thickness of the first adhesive on the substrate surface is 5 μm to 15 μm.

[0084] Similarly, the coating thickness of the second adhesive on the surface of the mixture may also be 5 μm to 50 μm. In some typical embodiments, the coating thickness of the second adhesive on the surface of the mixture may also be 5 μm to 15 μm.

[0085] It should be noted that an adhesive that meets the above-mentioned solid content, viscosity, and surface drying time range is conducive to controlling the coating thickness of the adhesive within the above-mentioned range, and is conducive to the adhesive not flowing after being sprayed on the catalyst, having good adhesion, and leaving sufficient operating time for the spraying process before surface drying.

[0086] In some optional embodiments, the sintering temperature may be 300° C. to 600° C., such as 300° C., 350° C., 400° C., 450° C., 500° C., 550° C. or 600° C., or other values ​​within the range of 300° C. to 600° C. In some typical embodiments, the sintering temperature is 400° C. to 550° C.

[0087] In some optional embodiments, the temperature of the heating soaking can be 50° C. to 180° C., such as 50° C., 100° C., 120° C., 140° C., 160° C. or 180° C., or other values ​​within the range of 50° C. to 180° C. In some more typical embodiments, the temperature of the heating soaking is 100° C. to 150° C.

[0088] In some optional embodiments, the soaking solution used for heating and soaking is a strong alkaline solution, for example, a strong alkaline solution with a concentration of 30wt% to 70wt% (such as 30wt%, 40wt%, 50wt%, 60wt% or 70wt%, etc.). As an example, the strong alkaline solution can be a sodium hydroxide solution.

[0089] In addition, the present invention also provides a system for continuously preparing methyl hexahydrophthalic anhydride. Figure 1 The system includes a first-stage hydrogenation reactor 3 and a second-stage hydrogenation reactor 5 connected in series.

[0090] The first-stage hydrogenation reactor 3 has an inlet for methyltetrahydrophthalic anhydride and hydrogen to enter, and an outlet for outputting the first-stage hydrogenation product; the second-stage hydrogenation reactor 5 has a first inlet connected to the outlet of the first-stage hydrogenation reactor 3, and the second-stage hydrogenation reactor 5 also has a second inlet for hydrogen to enter, and the second-stage hydrogenation reactor 5 also has an outlet for outputting the second-stage hydrogenation product; the above-mentioned catalyst is used to be filled in the second-stage hydrogenation reactor 5.

[0091] In some embodiments of the present invention, the hydrogenation feedstock entering the first stage hydrogenation reactor 3 is unisomerized methyltetrahydrophthalic anhydride. Methyltetrahydrophthalic anhydride is usually prepared by Diels-Alder diene synthesis reaction of isoprene, isoprene and maleic anhydride, and the synthetic product is a commercial product of methyltetrahydrophthalic anhydride after acid or basic isomerization, while the present invention does not require isomerization when preparing methylhexahydrophthalic anhydride, and directly uses unisomerized methyltetrahydrophthalic anhydride for hydrogenation. Among them, the mass ratio of isoprene to isoprene in the synthetic raw material can be between 90:10 and 70:30, and the molar ratio of the sum of the moles of trans-isopentadiene and isoprene monomers to maleic anhydride can be between 1.02 and 1.1. During the synthesis process, the less maleic anhydride monomer remains in the methyltetrahydrophthalic anhydride, the better.

[0092] The synthesis reaction formula of above-mentioned methyltetrahydrophthalic anhydride is as follows:

[0093]

[0094] During the specific synthesis, reference may be made to the relevant prior art, and no further elaboration or limitation will be given here.

[0095] The present invention adopts a step-by-step hydrogenation method, which is beneficial to high product yield and less side reactions.

[0096] In some optional embodiments, the first stage hydrogenation reactor 3 is a fixed bed reactor. It should be noted that if the entire methyl hexahydrophthalic anhydride preparation process is only carried out in the first stage hydrogenation reactor 3, the methyl hexahydrophthalic anhydride will have a higher viscosity, a shorter hydrogenation residence time, a lower dissolved hydrogen content, and the iodine value of the product cannot be stably controlled.

[0097] For example, the first stage hydrogenation reactor 3 may be loaded with a SiO2-alumina supported nickel catalyst, wherein the carrier is a composite of silica and alumina.

[0098] In some optional embodiments, the content of Ni in the SiO2-alumina supported nickel catalyst is 40wt% to 60wt%, such as 40wt%, 45wt%, 50wt%, 55wt% or 60wt%, etc., and can also be other values ​​within the range of 40wt% to 60wt%. The SiO2-alumina supported nickel catalyst can be in the shape of a cloverleaf strip.

[0099] The above-mentioned SiO2-alumina supported nickel catalyst can be purchased directly, or can be prepared by oneself with reference to relevant existing technologies.

[0100] In some optional embodiments, combined with Figure 1 and Figure 2 The second-stage hydrogenation reactor 5 is provided with a vertically extending array of tubes, the array of tubes has a reaction chamber, the reaction chamber has a first inlet and a second inlet arranged opposite to each other, wherein the first inlet is used for supplying methyltetrahydrophthalic anhydride, and the second inlet is used for supplying hydrogen, and the catalyst provided by the present invention is used to be loaded in the reaction chamber.

[0101] The number of vertically extending tubes provided in the above-mentioned second-stage hydrogenation reactor 5 may be one or more. When the number of tubes is more than one, the multiple tubes may be provided in parallel in the second-stage hydrogenation reactor 5. For example, the number of tubes provided in the second-stage hydrogenation reactor 5 may be 3 to 10, such as 3, 4, 5, 6, 7, 8, 9 or 10. In some typical embodiments, the number of tubes provided in the second-stage hydrogenation reactor 5 is 5 to 8.

[0102] The number of reaction chambers provided for each of the above-mentioned tubes may be one or more. When the number of reaction chambers provided for a single tube is more than one, the multiple reaction chambers may be provided in series on the tube. For example, the number of reaction chambers provided for each tube may be 5 to 20, such as 5 columns, 8 columns, 10 columns, 12 columns, 15 columns, 18 columns or 20 columns. In some typical embodiments, the number of reaction chambers provided for each tube is 8 to 15.

[0103] It should be noted that the number of the above-mentioned tube arrays and the number of reaction chambers can be adjusted according to actual needs (such as product flow rate, product demand).

[0104] In some optional embodiments, the mass of the catalyst loaded in a single reaction chamber is 0.2% to 3% of the total mass of the first-stage hydrogenation product that theoretically needs to be subjected to the second-stage hydrogenation in the reaction chamber, such as 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5% or 3%, etc., and can also be other values ​​within the range of 0.2% to 3%. In some more typical embodiments, the mass of the catalyst loaded in a single reaction chamber is 0.3% to 1% of the total mass of the first-stage hydrogenation product that theoretically needs to be subjected to the second-stage hydrogenation in the reaction chamber.

[0105] It should be noted that the catalyst can be evenly distributed in each reaction chamber, that is, the filling amount of the catalyst in each reaction chamber is the same. Alternatively, the filling amount of the catalyst in different reaction chambers can be gradually reduced from top to bottom vertically to prevent over-hydrogenation of the product in the reaction chamber with the highest dissolved hydrogen concentration.

[0106] In some optional embodiments, the first inlet and the second inlet are mirror-symmetrical, so that the hydrogen and methyltetrahydrophthalic anhydride can be mixed in mirror-symmetrical manner to improve the mixing effect.

[0107] In some optional embodiments, the outlet of each reaction chamber is provided with a filter, such as a filter screen.

[0108] In some optional embodiments, the bottom of the reaction chamber is horizontal and the top is arc-shaped, which can play a certain role in splash prevention.

[0109] Furthermore, the system for preparing methyl hexahydrophthalic anhydride provided by the present invention further includes a first preheater 1 and a dynamic mixer 2.

[0110] The first preheater 1 is used to preheat methyltetrahydrophthalic anhydride. The dynamic mixer 2 is connected to the outlet of the first preheater 1 and has an inlet for introducing hydrogen. The outlet of the dynamic mixer 2 is connected to the inlet of a first-stage hydrogenation reactor 3.

[0111] Furthermore, the system for preparing methyl hexahydrophthalic anhydride provided by the present invention further comprises a first gas-liquid separation tank 4 ; the first gas-liquid separation tank 4 is connected between the first-stage hydrogenation reactor 3 and the second-stage hydrogenation reactor 5 .

[0112] Furthermore, the system for preparing methyl hexahydrophthalic anhydride provided by the present invention further includes a second gas-liquid separation tank 6 , a second preheater 7 and a distillation tower 8 .

[0113] The inlet of the second gas-liquid separation tank 6 is connected to the outlet of the second-stage hydrogenation reactor 5 , the outlet of the second gas-liquid separation tank 6 is connected to the inlet of the second preheater 7 , and the outlet of the second preheater 7 is connected to the inlet of the distillation tower 8 .

[0114] The above-mentioned system for preparing methyl hexahydrophthalic anhydride further includes a top condenser 9 connected to the top of the distillation tower 8 and a bottom reboiler 11 connected to the bottom of the distillation tower 8. In addition, the system further includes a vacuum buffer tank 10 connected to the outlet of the top condenser 9.

[0115] As mentioned above, the production process of methyl hexahydrophthalic anhydride provided by the present invention comprises: the hydrogenation raw material methyl tetrahydrophthalic anhydride is mixed with hydrogen after passing through the first preheater 1 and the dynamic mixer 2, and then enters the first hydrogenation reactor 3 for hydrogenation; after the hydrogenation is completed, the material enters the second hydrogenation reactor 5, and the second hydrogenation reactor 5 is continuously injected with hydrogen; the hydrogen is mixed with the first hydrogenation product and the second catalyst in the reaction chamber on the tubes distributed inside the second hydrogenation reactor 5 for hydrogenation; after the first stage hydrogenation in the upper reaction chamber is completed, the material enters the next reaction chamber together with the hydrogen for the next stage hydrogenation; the final hydrogenation product enters the gas-liquid separation tank, the hydrogen is recovered to the hydrogen compressor for reuse, the liquid phase product enters the second preheater 7 for preheating, the preheated material enters the distillation tower 8 for material separation, the methyl hexahydrophthalic anhydride product is extracted from the tower top, and the polyanhydride polymer is extracted from the tower bottom; the product extracted from the tower top is cooled and then enters the storage tank for storage, and the tower bottom material is extracted as a by-product.

[0116] The present invention adopts a process of connecting two hydrogenation reactors in series, wherein the first stage is a fixed bed and the second stage is a novel hydrogenation kettle. The method adopts a method in which both hydrogen and hydrogenation raw materials continuously enter the hydrogenation reactor, thereby effectively increasing the dissolved hydrogen content in the hydrogenation raw materials. Meanwhile, hydrogen and the hydrogenation raw materials enter the same reaction chamber in a mirror-symmetrical manner. Driven by hydrogen, the raw materials, hydrogen and catalyst are mixed at a high speed, so that the catalyst is evenly distributed in the hydrogenation raw materials, thereby improving the stability of the hydrogenation product and the hydrogenation efficiency.

[0117] The second section uses an optimized catalytic hydrogenation reactor, in which tubes are arranged, and reaction chambers are distributed in a stepped manner on each tube. A special catalyst is installed in the reaction chamber. Methyltetrahydrophthalic anhydride raw material and hydrogen enter the sides of the reaction chamber respectively. The two raw material feed outlets are mirror-imaged for mixing. Hydrogen enters the reaction chamber at a certain angle, driving the methyltetrahydrophthalic anhydride, catalyst, and hydrogen in the reaction chamber to rotate at high speed, so that the catalyst is evenly dispersed in the methyltetrahydrophthalic anhydride solution. And because hydrogen is continuously injected into the reaction chamber, the new hydrogen gas and the liquid methyltetrahydrophthalic anhydride solution are continuously mixed uninterruptedly, so that the dissolved hydrogen content continues to increase. In an environment with uniform mixing and high dissolved hydrogen content, the hydrogenation efficiency is improved. After the hydrogenation in the first reaction chamber is completed, the material enters the next reaction chamber through a connecting pipeline for re-hydrogenation. The reaction chambers are distributed from top to bottom along the length of the tubes, and catalysts are loaded in each layer of the reaction chamber. A filter is set at the outlet of each reaction chamber to filter the catalyst, and the hydrogenation product finally flows out of the last reaction chamber. Since the catalyst activity of the second-stage reaction is higher and the dissolved hydrogen content is increased, the hydrogenation reaction can be carried out at a lower temperature, and the side reactions such as condensation self-polymerization of methyltetrahydrophthalic anhydride are greatly reduced. Compared with traditional hydrogenated products, it has obvious advantages. After flowing out of the hydrogenation reactor, the product enters the second preheater 7, and after being heated, it enters the distillation tower 8 to remove polymers and heavy components, so as to obtain a methylhexahydrophthalic anhydride hydrogenated product with higher yield and lighter color.

[0118] Accordingly, the present invention also provides a method for continuously preparing methyl hexahydrophthalic anhydride, which is prepared by using the system of any one of the aforementioned embodiments.

[0119] In some optional embodiments, the preheating temperature of the first preheater 1 can be 50°C to 150°C, such as 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc., or other values ​​within the range of 50°C to 150°C. In some typical embodiments, the preheating temperature of the first preheater 1 is 80°C to 130°C.

[0120] In some optional embodiments, the hydrogenation temperature of the first stage hydrogenation reactor 3 can be 80°C to 120°C, such as 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C or 120°C, etc., or other values ​​within the range of 80°C to 120°C.

[0121] The hydrogen pressure of the first-stage hydrogenation reactor 3 may be 1 MPa to 3 MPa, such as 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa or 3 MPa, or may be other values ​​within the range of 1 MPa to 3 MPa.

[0122] The residence time of the material in the first stage hydrogenation reactor 3 can be 5 h to 10 h, such as 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, etc., or can be other values ​​within the range of 5 h to 10 h.

[0123] In some optional embodiments, the hydrogen pressure in the second-stage hydrogenation reactor 5 can be 1MPa to 8MPa, such as 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa or 8MPa, etc., or other values ​​within the range of 1MPa to 8MPa. In some more typical embodiments, the hydrogen pressure in the second-stage hydrogenation reactor 5 is 1MPa to 4MPa.

[0124] The hydrogenation temperature in the second-stage hydrogenation reactor 5 can be 60°C to 120°C, such as 60°C, 70°C, 80°C, 90°C, 100°C, 110°C or 120°C, etc., or other values ​​within the range of 60°C to 120°C.

[0125] The residence time of the material in the second-stage hydrogenation reactor 5 can be 1 h to 5 h, such as 1 h, 2 h, 3 h, 4 h or 5 h, etc., or other values ​​within the range of 1 h to 5 h. In some typical embodiments, the residence time of the material in the second-stage hydrogenation reactor 5 is 1 h to 3 h.

[0126] In some optional embodiments, the preheating temperature of the second preheater 7 can be 140° C. to 200° C., such as 140° C., 150° C., 160° C., 170° C., 180° C., 190° C. or 200° C., or other values ​​within the range of 140° C. to 200° C. In some typical embodiments, the preheating temperature of the second preheater 7 is 140° C. to 170° C.

[0127] In some optional embodiments, the operating pressure of the distillation tower 8 may be -0.09 MPa to -0.1 MPa, such as -0.09 MPa, -0.095 MPa or -0.1 MPa, etc., or may be other values ​​within the range of -0.09 MPa to -0.1 MPa.

[0128] The bottom temperature of the distillation tower 8 can be 210° C. to 235° C., such as 210° C., 215° C., 220° C., 225° C., 230° C. or 235° C., or other values ​​within the range of 210° C. to 235° C. In some typical embodiments, the bottom temperature of the distillation tower 8 is 213° C. to 225° C.

[0129] The gas phase temperature at the top of the tower can be 145° C. to 170° C., such as 145° C., 150° C., 155° C., 160° C., 165° C. or 170° C., or other values ​​within the range of 145° C. to 170° C. In some typical embodiments, the gas phase temperature at the top of the distillation tower 8 is 148° C. to 160° C.

[0130] The number of plates may be 8 to 20, such as 8, 10, 12, 15, 18 or 20, or other values ​​within the range of 8 to 20. In some typical embodiments, the number of plates is 10 to 15.

[0131] In some optional embodiments, the temperature of the product obtained after cooling by the top condenser 9 can be 30°C to 120°C, such as 30°C, 50°C, 80°C, 100°C or 120°C, or other values ​​within the range of 30°C to 120°C. In some more typical embodiments, the temperature of the product obtained after cooling by the top condenser 9 is 50°C to 100°C.

[0132] As mentioned above, the hydrogenation process of the present invention is divided into two stages. The first stage hydrogenation adopts a fixed bed Raney nickel catalyst, and the hydrogenation temperature is not high, so that the amount of condensation self-polymerization products of methyltetrahydrophthalic anhydride in the first stage hydrogenation process is greatly reduced, and only a part of the carbon-carbon double bond addition is carried out, which effectively improves the product yield and product color number. The hydrogen and the first stage hydrogenation product are uniformly mixed in the reaction chamber of the second stage hydrogenation reactor 5, and the catalyst adopts a Raney nickel form with a high specific surface area, the hydrogenation efficiency is higher, the hydrogenation residence time is shorter, the production efficiency is higher, the hydrogenation product saturation is higher, and a lower iodine value and a lighter color number can be obtained; at the same time, the lower hydrogenation temperature and the shorter residence time make the product neither produce self-polymers nor cause the problem of carboxyl being hydrogenated due to over-hydrogenation of the product in the second stage hydrogenation process, and the finished methylhexahydrophthalic anhydride product has a higher purity.

[0133] Therefore, the preparation scheme of methyl hexahydrophthalic anhydride provided by the present invention can obtain a methyl hexahydrophthalic anhydride product with higher yield, less by-products, lower iodine value, lighter color and higher purity, and can operate stably for a long time.

[0134] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0135] Example 1

[0136] This embodiment provides a catalyst, which is prepared by the following method:

[0137] A first adhesive is sprayed on the surface of the spherical activated carbon substrate, and a layer of nickel-cobalt-aluminum alloy powder is sprayed on the adhesive layer to cover the first adhesive layer, and then a second adhesive is sprayed, and then a mixture of 304 stainless steel powder and aluminum powder is sprayed on the second adhesive layer. After spraying, it is sintered at high temperature, and the activated carbon substrate and adhesive are removed at high temperature to obtain an intermediate with a double-layer alloy structure. The intermediate is placed in an immersion solution for heating and immersion to remove aluminum metal to obtain a catalyst with a double-layer hollow alloy structure.

[0138] Among them, the diameter of the matrix is ​​2mm. The particle size of the nickel-cobalt-aluminum alloy powder is 150 mesh. The content of Ni in the nickel-cobalt-aluminum alloy powder is 84wt%, the content of Co is 3wt%, and the content of Al is 13wt%. The particle size of the stainless steel powder and the aluminum powder is 150 mesh. The mass ratio of the outer layer of stainless steel powder and aluminum powder is 2:1. The first adhesive and the second adhesive are the same, both of which are solvent adhesives prepared from acrylic acid, with a solid content of 50wt%, a viscosity of 900cp at 25°C, a surface drying time of 13min, and a spraying thickness of 10μm. The sintering temperature is 520°C, the heating immersion temperature is 120°C, the heating immersion time is 2h, and the immersion solution used for heating immersion is a sodium hydroxide solution with a concentration of 60wt%. After treatment, the outer diameter of the catalyst is 2.2mm~2.6mm, and the specific surface area is 60m 2 / g~85m 2 / g, the thickness ratio of the outer layer to the inner layer is 0.9:1 to 1.1:1, and the weight ratio of the outer layer to the inner layer is 1.15:1 to 1.25:1.

[0139] The outer layer of the catalyst prepared in this example is a spherical double-layer structure, the outer layer is a stainless steel hollow structure, and the inner layer is a Raney nickel-cobalt metal structure.

[0140] Example 2

[0141] The difference between this embodiment and embodiment 1 is that the diameter of the substrate is 0.5 mm. The particle size of the nickel-cobalt-aluminum alloy powder is 180 mesh. The content of Ni in the nickel-cobalt-aluminum alloy powder is 80wt%, the content of Co is 2wt%, and the content of Al is 18wt%. The particle size of the stainless steel powder and the aluminum powder is 100 mesh. The first adhesive and the second adhesive are the same, both of which are solvent adhesives prepared from acrylic acid, with a solid content of 50wt%, a viscosity of 900cp at 25°C, a surface drying time of 13min, and a spraying thickness of 5μm. The sintering temperature is 400°C, the heating soaking temperature is 100°C, the heating soaking time is 2h, and the soaking solution used for heating soaking is a sodium hydroxide solution with a concentration of 30wt%. After treatment, the outer diameter of the catalyst is 0.9mm~1.2mm, and the specific surface area is 65m 2 / g~90m 2 / g, the thickness ratio of the outer layer to the inner layer is 1.05:1 to 1.15:1, and the weight ratio of the outer layer to the inner layer is 1.1:1 to 1.35:1.

[0142] Example 3

[0143] The difference between this embodiment and embodiment 1 is that the diameter of the substrate is 5 mm. The particle size of the nickel-cobalt-aluminum alloy powder is 200 mesh. The content of Ni in the nickel-cobalt-aluminum alloy powder is 83wt%, the content of Co is 5wt%, and the content of Al is 12wt%. The particle size of the stainless steel powder and the aluminum powder is 200 mesh. The first adhesive and the second adhesive are the same, both of which are solvent adhesives prepared from acrylic acid, with a solid content of 50wt%, a viscosity of 900cp at 25°C, a surface drying time of 13min, and a spraying thickness of 15μm. The sintering temperature is 550°C, the heating soaking temperature is 150°C, the heating soaking time is 2h, and the soaking solution used for heating soaking is a sodium hydroxide solution with a concentration of 70wt%. After treatment, the outer diameter of the catalyst is 5.4mm~5.8mm, and the specific surface area is 55m 2 / g~80m 2 / g, the thickness ratio of the outer layer to the inner layer is 0.9:1 to 1.1:1, and the weight ratio of the outer layer to the inner layer is 1.1:1 to 1.22:1.

[0144] Example 4

[0145] The difference between this embodiment and embodiment 1 is that the diameter of the substrate is 8 mm. The particle size of the nickel-cobalt-aluminum alloy powder is 100 mesh. The first adhesive and the second adhesive are the same, both are hot melt adhesives prepared from polyurethane (viscosity at 25°C is 1100 cp, surface drying time is 11 min), and the spraying thickness is 30 μm. The sintering temperature is 300°C, the heating and soaking temperature is 50°C, and the outer diameter of the catalyst after treatment is 8.4 mm to 8.8 mm, and the specific surface area is 50 m 2 / g~75m 2 / g, the thickness ratio of the outer layer to the inner layer is 0.8:1 to 0.9:1, and the weight ratio of the outer layer to the inner layer is 1.08:1 to 1.15:1.

[0146] Example 5

[0147] The difference between this embodiment and embodiment 1 is that the diameter of the substrate is 10 mm. The particle size of the nickel-cobalt-aluminum alloy powder is 300 mesh. The first adhesive and the second adhesive are the same, both are pressure-sensitive adhesives prepared from synthetic rubber (viscosity at 25°C is 850 cp, surface drying time is 15 min), and the spraying thickness is 50 μm. The sintering temperature is 600°C, the heating and soaking temperature is 180°C, and the outer diameter of the catalyst after treatment is 10.5 mm to 11 mm, and the specific surface area is 45 m 2 / g~65m2 / g, the thickness ratio of the outer layer to the inner layer is 1.15:1 to 1.3:1, and the weight ratio of the outer layer to the inner layer is 1.22:1 to 1.4:1.

[0148] Example 6

[0149] Combination Figure 1 The present embodiment provides a system for producing methyl hexahydrophthalic anhydride, which includes a first preheater 1, a dynamic mixer 2, a first gas-liquid separation tank 4, a first-stage hydrogenation reactor 3 and a second-stage hydrogenation reactor 5 connected in series, a second gas-liquid separation tank 6, a second preheater 7, a distillation tower 8, a tower top condenser 9, a tower bottom reboiler 11 and a vacuum buffer tank 10.

[0150] The first preheater 1 is used to preheat the unisomerized methyltetrahydrophthalic anhydride, the dynamic mixer 2 is connected to the outlet of the first preheater 1 and the dynamic mixer 2 also has an inlet for introducing hydrogen, and the outlet of the dynamic mixer 2 is connected to the inlet of a first-stage hydrogenation reactor 3.

[0151] The first-stage hydrogenation reactor 3 is a fixed bed reactor having an inlet for the entry of methyltetrahydrophthalic anhydride and hydrogen and an outlet for the output of the first-stage hydrogenation product. The first-stage hydrogenation reactor 3 is filled with a clover-shaped SiO2-alumina-supported nickel catalyst, the carrier of which is a composite of silica and alumina; the Ni content in the catalyst is 43.5wt%.

[0152] The inlet of the first gas-liquid separator 4 is connected to the outlet of the first stage hydrogenation reactor 3 , and the first gas-liquid separator 4 has an outlet for connecting to the first inlet of the second stage hydrogenation reactor 5 and an outlet for discharging waste hydrogen.

[0153] The second stage hydrogenation reactor 5 has a first inlet connected to the first gas-liquid separation tank 4, and the second stage hydrogenation reactor 5 also has a second inlet for hydrogen to enter, and the second stage hydrogenation reactor 5 also has an outlet for the output of the second stage hydrogenation product. Four vertically extending tubes are arranged in parallel in the second stage hydrogenation reactor 5, each tube has 10 reaction chambers connected in series from top to bottom, and the reaction chamber has a first inlet and a second inlet arranged in mirror symmetry, wherein the first inlet is used for methyltetrahydrophthalic anhydride to enter, and the second inlet is used for hydrogen to enter, each reaction chamber is filled with the catalyst prepared in Example 1, and the outlet of each reaction chamber is provided with a filter; the bottom of each reaction chamber is horizontal, and the top is arc-shaped. The mass of the catalyst filled in a single reaction chamber is 0.5% of the total mass of the first stage hydrogenation product theoretically required for the second stage hydrogenation in the reaction chamber, and the material and hydrogen are transported through pipelines.

[0154] The inlet of the second gas-liquid separation tank 6 is connected to the outlet of the second-stage hydrogenation reactor 5. The second gas-liquid separation tank 6 has an outlet connected to the inlet of the second preheater 7 and an outlet for discharging waste hydrogen. The outlet of the second preheater 7 is connected to the inlet of the distillation tower 8; the top condenser 9 is connected to the top of the distillation tower 8, the bottom reboiler 11 is connected to the bottom of the distillation tower 8, and the outlet of the top condenser 9 is connected to the vacuum buffer tank 10.

[0155] The first preheater 1, the second preheater 7, the tower top condenser 9 and the tower bottom reboiler 11 are respectively provided with a heat transfer oil inlet and a heat transfer oil outlet.

[0156] Example 7

[0157] This embodiment provides a method for preparing methyl hexahydrophthalic anhydride, which is prepared using the system provided in Example 6, and the corresponding preparation conditions include:

[0158] The preheating temperature of the first preheater 1 is 105°C, the temperature of the first stage hydrogenation reactor 3 is 110°C, the hydrogenation pressure is 2MPa, the catalyst loading in the second stage hydrogenation reaction chamber is 0.5% of the raw material mass after the reaction chamber is filled, the temperature of the second stage hydrogenation reactor 5 is 95°C, the hydrogenation pressure is 2.5MPa, and the residence time of the hydrogenation raw material methyltetrahydrophthalic anhydride in the two reactors is 7h and 2h respectively. The hydrogenated product enters the distillation tower 8 after being heated by the second preheater 7, the outlet material temperature of the second preheater 7 is 155°C, the operating pressure of the distillation tower 8 is -0.098MPa, the temperature of the reboiler 11 of the distillation tower 8 is 220°C, the gas phase temperature at the top of the tower is 152°C, the number of plates is 10, and the outlet temperature of the top condenser 9 is 80°C.

[0159] Example 8

[0160] The difference between this embodiment and embodiment 7 is that the temperature of the first stage hydrogenation reactor 3 is 100°C, and the temperature of the second stage hydrogenation reactor 5 is 110°C.

[0161] Example 9

[0162] The difference between this embodiment and embodiment 7 is that the temperature of the first stage hydrogenation reactor 3 is 100°C.

[0163] Example 10

[0164] The difference between this embodiment and embodiment 7 is that the temperature of the first-stage hydrogenation reactor 3 is 100° C. and the hydrogenation pressure is 4 MPa.

[0165] Embodiment 11

[0166] The difference between this embodiment and embodiment 7 is that the temperature of the first-stage hydrogenation reactor 3 is 100° C.; the nickel content of the nickel-cobalt-aluminum alloy powder, the raw material for preparing the catalyst, is 82.5wt%, the cobalt content is 5wt%, and the aluminum content is 12.5wt%.

[0167] Example 12

[0168] The difference between this embodiment and embodiment 7 is that the temperature of the first-stage hydrogenation reactor 3 is 100° C., and the residence time of the hydrogenation raw material methyltetrahydrophthalic anhydride in the two reactors is 7 h and 4 h respectively.

[0169] Embodiment 13

[0170] This embodiment provides a method for preparing methyl hexahydrophthalic anhydride, which is prepared using the system provided in Example 6, and the corresponding preparation conditions include:

[0171] The preheating temperature of the first preheater 1 is 80°C, the temperature of the first stage hydrogenation reactor 3 is 80°C, the hydrogenation pressure is 1MPa, the catalyst loading in the second stage hydrogenation reaction chamber is 0.3% of the raw material mass after the reaction chamber is filled, the temperature of the second stage hydrogenation reactor 5 is 60°C, the hydrogenation pressure is 1MPa, and the residence time of the hydrogenation raw material methyltetrahydrophthalic anhydride in the two reactors is 5h and 1h respectively. The hydrogenated product enters the distillation tower 8 after being heated by the second preheater 7, the outlet material temperature of the second preheater 7 is 140°C, the operating pressure of the distillation tower 8 is -0.09MPa, the temperature of the reboiler 11 of the distillation tower 8 is 213°C, the gas phase temperature at the top of the tower is 148°C, the number of plates is 10, and the outlet temperature of the top condenser 9 is 50°C.

[0172] Embodiment 14

[0173] This embodiment provides a method for preparing methyl hexahydrophthalic anhydride, which is prepared using the system provided in Example 6, and the corresponding preparation conditions include:

[0174] The preheating temperature of the first preheater 1 is 120°C, the temperature of the first stage hydrogenation reactor 3 is 120°C, the hydrogenation pressure is 3MPa, the catalyst loading in the second stage hydrogenation reaction chamber is 1% of the raw material mass after the reaction chamber is filled, the temperature of the second stage hydrogenation reactor 5 is 120°C, the hydrogenation pressure is 4MPa, and the residence time of the hydrogenation raw material methyltetrahydrophthalic anhydride in the two reactors is 10h and 3h respectively. The hydrogenated product enters the distillation tower 8 after being heated by the second preheater 7, the outlet material temperature of the second preheater 7 is 170°C, the operating pressure of the distillation tower 8 is -0.1MPa, the temperature of the reboiler 11 of the distillation tower 8 is 225°C, the gas phase temperature at the top of the tower is 160°C, the number of plates is 15, and the outlet temperature of the top condenser 9 is 100°C.

[0175] Embodiment 15

[0176] The difference between this embodiment and embodiment 7 is that the preheating temperature of the first preheater 1 is 50°C, the catalyst loading amount in the second-stage hydrogenation reaction chamber is 0.2% of the mass of the raw material after the reaction chamber is filled, the hydrogenation pressure is 6MPa, the residence time of the material in the second-stage hydrogenation reactor 5 is 4h, the outlet material temperature of the second preheater 7 is 180°C, the temperature of the bottom reboiler 11 of the distillation tower 8 is 210°C, the top gas phase temperature is 145°C, the number of plates is 8, and the outlet temperature of the top condenser 9 is 30°C.

[0177] Example 16

[0178] The difference between this embodiment and embodiment 7 is that the preheating temperature of the first preheater 1 is 150°C, the catalyst loading amount in the second-stage hydrogenation reaction chamber is 3% of the mass of the raw material after the reaction chamber is filled, the hydrogenation pressure is 8MPa, the residence time of the material in the second-stage hydrogenation reactor 5 is 5h, the outlet material temperature of the second preheater 7 is 200°C, the temperature of the bottom reboiler 11 of the distillation tower 8 is 235°C, the top gas phase temperature is 1670°C, the number of tower plates is 20, and the outlet temperature of the top condenser 9 is 120°C.

[0179] Comparative Example 1

[0180] Methyltetrahydrophthalic anhydride and 2% of Raney nickel catalyst by weight were mixed and added into a high-pressure reactor, and hydrogen was charged to a hydrogen pressure of 5MPa. The hydrogenation temperature was set to 130°C. During the hydrogenation process, the hydrogen pressure would continue to decrease. When the hydrogen pressure decreased to 2MPa, hydrogen was refilled to a pressure of 5MPa. The operation was repeated until the hydrogen pressure did not decrease. The temperature and pressure were maintained for 10 hours. After the reaction was completed, the pressure was released and the product was discharged. After the product was discharged, it was allowed to stand for 3 hours until the upper solution was clarified and the catalyst was completely sunk to the bottom. The upper clear liquid was taken for negative pressure rotary evaporation stripping. The stripping temperature was 185°C and the pressure was -0.095MPa. The gas phase was condensed to obtain the methylhexahydrophthalic anhydride product, and the remaining heavy components were polymeric anhydride and over-hydrogenated products.

[0181] Comparative Example 2

[0182] The experiment was conducted by using the scheme of Example 4 in CN117843598A "A method for preparing methyl hexahydrophthalic anhydride". 2000 g of refined methyl tetrahydrophthalic anhydride was added to a temperature-controlled raw material tank. The air in the reactor was replaced with nitrogen. After replacement for 3 times, 1000 g of refined methyl tetrahydrophthalic anhydride was introduced into an ebullated bed hydrogenation reactor for padding. 32 g of Ni / Co modified catalyst was added according to 3.2% of the material. The catalyst was added after the material residence time was 9 h. The waste catalyst was discharged. The catalyst was added and discharged at an amount of 3 g / h to prepare methyl hexahydrophthalic anhydride by an ebullated bed hydrogenation process. The maximum hydrogen pressure was 5 MPa, the maximum temperature was 125° C., and the residence time was 10 h. The final product was distilled by a thin film evaporator, gas phase cooled to obtain a methyl hexahydrophthalic anhydride product, and liquid phase cooled to obtain a heavy component.

[0183] Comparative Example 3

[0184] The difference between this comparative example and Example 7 is that the catalyst has only a single-layer structure, which is only an inner layer of Raney nickel-cobalt metal structure, and does not have an outer layer of stainless steel hollow structure.

[0185] Comparative Example 4

[0186] The difference between this comparative example and Example 7 is that the catalyst is a single-layer double-layer structure, the outer layer is a stainless steel hollow structure, and the inner layer is Raney nickel. That is, no cobalt is added to the inner layer.

[0187] Comparative Example 5

[0188] The difference between this comparative example and Example 7 is that the inner layer in the catalyst is a Raney nickel-iron metal structure.

[0189] Test Example 1

[0190] Taking the methyl hexahydrophthalic anhydride prepared in Examples 7 to 12 and Comparative Examples 1 to 2 as examples, the chromaticity, purity (chromatography), acid value, iodine value and product yield of the obtained products were compared.

[0191] The chromaticity was tested according to ASTM E313; the purity was tested by chromatography; the acid value was tested according to ASTM D974; the iodine value was tested according to ASTM D5768-02; and the yield was calculated based on the ratio of the liquid product flow rate to the feed flow rate. The results are shown in Table 1.

[0192] Table 1 Test results According to the comparison between Comparative Example 1 and Examples 7 to 12, it can be seen that the methyl hexahydrophthalic anhydride product prepared in the embodiment of the present invention has a higher yield, lighter color, higher acid value, lower iodine value, and higher purity than that of the intermittent hydrogenation process, and the product quality and economic benefits are improved.

[0193] According to the comparison between Comparative Example 2 and Examples 7 to 12, it can be seen that in the process of producing methyl hexahydrophthalic anhydride, no catalyst is continuously discharged in the embodiment of the present invention, the reaction stability is higher, and the product yield is higher and the product purity is higher, which means that the low-temperature operation adopted in the embodiment of the present invention is more conducive to suppressing the occurrence of side reactions, and the amount of by-products generated is significantly reduced. In addition, the actual operating hydrogen pressure of the present invention is relatively low, which means that the dissolved hydrogen content of the embodiment of the present invention under low hydrogen pressure is still higher than that of Comparative Example 2, so the product quality of the present invention is higher and the energy consumption of the device is lower.

[0194] According to the comparison between Examples 8 and 9, it can be seen that after lowering the first stage temperature and increasing the second stage hydrogenation temperature, although the iodine value of the product obtained in Example 8 is slightly lower than that in Example 9, the product yield is significantly reduced, indicating that the increase in the second stage hydrogenation temperature has a greater impact on the product yield, and the mass transfer and heat transfer efficiency of the second stage hydrogenation reactor is better. During the second stage hydrogenation process, about 1% to 2% of methyltetrahydrophthalic anhydride undergoes condensation self-polymerization at high temperature to generate polymers, forming heavy components that remain in the bottom of the distillation tower 8, resulting in a decrease in the final product yield.

[0195] According to the comparison between Example 9 and Example 10, it can be seen that the iodine value of the product decreases slightly after the hydrogen pressure of the first-stage hydrogenation reactor 3 is increased, indicating that the increase of the hydrogen pressure from 2MPa to 4MPa has little effect on the hydrogenation effect of the actual product. It is possible that the hydrogenation capacity of the second-stage hydrogenation reactor 5 is higher, and the iodine value of the first-stage hydrogenation product has little effect on the second-stage hydrogenation product. The second-stage hydrogenation reactor 5 has the ability to fully saturate the product with a slightly higher iodine value.

[0196] According to the comparison of Examples 9 to 11, it can be seen that compared with the method of increasing the hydrogen pressure in Example 10, the method of changing the metal cobalt content in the second-stage catalyst in Example 11 has a more obvious effect, the product chromaticity decreases more, and the product yield decreases insignificantly, indicating that changing the catalyst structure, improving the catalyst hydrogenation activity, and maintaining the process route of hydrogenating methyltetrahydrophthalic anhydride at low temperature is more reasonable.

[0197] According to the comparison between Example 9 and Example 12, when the catalyst of Example 7 is used for hydrogenation, Example 12 only prolongs the residence time of the second-stage hydrogenation reactor 5, and the purity and acid value of the product decrease significantly, while other indicators do not change much. According to the analysis of the hydrogenation method, after the second-stage hydrogenation catalyst improves the hydrogenation activity, the conversion of methyltetrahydrophthalic anhydride to methylhexahydrophthalic anhydride can be completed within a residence time of <4h. However, the excessive hydrogenation time will cause the methylhexahydrophthalic anhydride to further combine with hydrogen, resulting in a side reaction of excessive hydrogenation, and the C=O carbonyl in the methylhexahydrophthalic anhydride is hydrogenated, which ultimately reduces the acid value of the product. At the same time, since the boiling point is close to that of methylhexahydrophthalic anhydride, the separation difficulty is relatively large, and the purity of the final product is also affected.

[0198] Test Example 2

[0199] Taking Example 7 as an example, control groups 1 to 4 were set up. The only difference between control groups 1 to 4 and Example 7 was that the catalysts in the second-stage hydrogenation reactor 5 were replaced with the catalysts prepared in Examples 2 to 5 in sequence.

[0200] The chromaticity, purity (chromatography), acid value, iodine value and product yield of the products obtained in Example 7, Control Groups 1 to 4 and Comparative Examples 3 to 5 were compared using the same test method as in Test Example 1. The results are shown in Table 1.

[0201] Table 2 Test results As can be seen from Table 2, the catalyst provided by the present invention is conducive to obtaining a methyl hexahydrophthalic anhydride product with a higher yield and better quality. However, when the catalyst is improperly set in Comparative Example 3, the catalyst protection is not performed, and only a single-layer catalyst is used, the catalyst is broken during the high-speed mixing process. Although it does not affect the high-efficiency hydrogenation capacity of the catalyst, it will cause the methyl hexahydrophthalic anhydride product to carry a small amount of catalyst powder, and subsequent operations such as sedimentation treatment are required to remove the catalyst powder, which affects the product production efficiency and product quality.

[0202] In summary, the preparation scheme of methyl hexahydrophthalic anhydride provided by the present invention can obtain methyl hexahydrophthalic anhydride products with high yield, few by-products, low iodine value, light color and high purity, and can operate stably for a long time.

[0203] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A catalyst, characterized in that The catalyst has a double-layer structure, the outer layer is a stainless steel hollow structure, and the inner layer is a Raney nickel-cobalt metal structure; the catalyst is spherical or quasi-spherical.

2. The catalyst according to claim 1, characterized in that The catalyst has at least one of the following characteristics: Feature 1: The outer diameter of the catalyst is 0.5 mm to 20 mm, preferably 1 mm to 10 mm; Feature 2: The specific surface area of ​​the catalyst is 20m 2 / g~100m 2 / g; Feature 3: The thickness ratio of the outer layer to the inner layer is 0.5:1 to 2:1, preferably 0.7:1 to 1.3:1; Feature 4: The weight ratio of the outer layer to the inner layer is 0.7:1 to 2:1, preferably 1:1 to 1.5:

1.

3. A method for preparing the catalyst according to claim 1 or 2, characterized in that: The following steps are involved: Nickel-cobalt-aluminum alloy powder is attached to the surface of a substrate via a first adhesive to obtain a first intermediate; a mixture containing stainless steel powder and aluminum powder is attached to the surface of the intermediate via a second adhesive to obtain a second intermediate; the second intermediate is sintered and the substrate, the first adhesive and the second adhesive are removed to obtain a third intermediate; the third intermediate is heated and soaked to remove aluminum to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that: The preparation of the catalyst includes at least one of the following features: Feature 5: The substrate is spherical or quasi-spherical; preferably, the diameter of the substrate is 0.5 mm to 10 mm, more preferably 0.5 mm to 5 mm; preferably, the substrate is activated carbon; Feature 6: The particle size of the nickel-cobalt-aluminum alloy powder is 100 mesh to 300 mesh, preferably 150 mesh to 200 mesh; Feature 7: The content of Ni in the nickel-cobalt-aluminum alloy powder is ≥80wt%, the content of Co is 2wt% to 5wt%, and the content of Al is 12wt% to 18wt%; Feature 8: The particle size of the stainless steel powder is 100-200 mesh; preferably, the stainless steel powder is 304 stainless steel powder; Feature 9: The first adhesive and the second adhesive independently include at least one of solvent adhesive, hot melt adhesive and pressure sensitive adhesive; preferably, the active ingredients in the first adhesive and the second adhesive include at least one of acrylic acid, polyurethane and synthetic rubber; more preferably, the active ingredients in the first adhesive and the second adhesive include acrylic acid; Feature 10: The solid contents of the first binder and the second binder are independently 20 wt% to 60 wt%; Feature 11: The viscosity of the first adhesive and the second adhesive at 25° C. is independently 300 cp to 2000 cp; Feature 12: The surface drying time of the first adhesive and the second adhesive is independently 3 min to 15 min; Feature 13: The coating thickness of the first adhesive on the surface of the substrate is 5 μm to 50 μm, preferably 5 μm to 15 μm; Feature 14: The coating thickness of the second adhesive on the surface of the mixture is 5 μm to 50 μm, preferably 5 μm to 15 μm.

5. The preparation method according to claim 4, characterized in that: The preparation of the catalyst also includes at least one of the following features: Feature 15: The sintering temperature is 300°C to 600°C, preferably 400°C to 550°C; Feature 16: The temperature of the heating and soaking is 50°C to 180°C, preferably 100°C to 150°C; Feature 17: The soaking solution used for heated soaking is a strong alkaline solution, preferably a strong alkaline solution with a concentration of 30wt% to 70wt%. More preferably, the strong alkaline solution is a sodium hydroxide solution.

6. A system for continuously preparing methyl hexahydrophthalic anhydride, characterized in that: It includes a first stage hydrogenation reactor and a second stage hydrogenation reactor connected in series; The first stage hydrogenation reactor has an inlet for methyltetrahydrophthalic anhydride and hydrogen to enter and an outlet for outputting the first stage hydrogenation product; the second stage hydrogenation reactor has a first inlet connected to the outlet of the first stage hydrogenation reactor, the second stage hydrogenation reactor also has a second inlet for hydrogen to enter, and the second stage hydrogenation reactor also has an outlet for outputting the second stage hydrogenation product; the catalyst according to claim 1 or 2 is used to be filled in the second stage hydrogenation reactor; Preferably, the first stage hydrogenation reactor is a fixed bed reactor; Preferably, the first stage hydrogenation reactor is filled with a SiO2-alumina supported nickel catalyst, wherein the carrier is a composite of silicon dioxide and alumina; Preferably, the content of Ni in the SiO2-alumina supported nickel catalyst is 40wt% to 60wt%; Preferably, the SiO2-alumina supported nickel-based catalyst is in the shape of a cloverleaf strip.

7. The system according to claim 6, characterized in that The two-stage hydrogenation reactor is provided with a vertically extending array of tubes, the array of tubes having a reaction chamber, the reaction chamber having a first inlet and a second inlet arranged opposite to each other, wherein the first inlet is used for supplying methyltetrahydrophthalic anhydride, and the second inlet is used for supplying hydrogen, and the catalyst according to claim 1 or 2 is used to be loaded in the reaction chamber; Preferably, a plurality of tubes are arranged in parallel in the second-stage hydrogenation reactor; more preferably, the number of tubes arranged in the second-stage hydrogenation reactor is 3 to 10; further preferably, the number of tubes arranged in the second-stage hydrogenation reactor is 5 to 8; Preferably, each of the tubes is provided with a plurality of reaction chambers in series; more preferably, the number of reaction chambers provided for each of the tubes is 5 to 20; further preferably, the number of reaction chambers provided for each of the tubes is 8 to 15; Preferably, the mass of the catalyst loaded in a single reaction chamber is 0.2% to 3% of the total mass of the first-stage hydrogenation product that theoretically needs to be subjected to the second-stage hydrogenation in the reaction chamber; more preferably, the mass of the catalyst loaded in a single reaction chamber is 0.3% to 1% of the total mass of the first-stage hydrogenation product that theoretically needs to be subjected to the second-stage hydrogenation in the reaction chamber; Preferably, the first inlet and the second inlet are mirror-symmetrical; Preferably, the outlet of each reaction chamber is provided with a filter; Preferably, the bottom of the reaction chamber is horizontal and the top is arc-shaped.

8. The system according to claim 6 or 7, characterized in that: The system also includes a first preheater and a dynamic mixer; The first preheater is used to preheat methyltetrahydrophthalic anhydride, the dynamic mixer is connected to the outlet of the first preheater and the dynamic mixer also has an inlet for introducing hydrogen, and the outlet of the dynamic mixer is connected to the inlet of the first stage hydrogenation reactor; Preferably, the system further comprises a first gas-liquid separation tank; the first gas-liquid separation tank is connected between the first stage hydrogenation reactor and the second stage hydrogenation reactor.

9. The system according to claim 8, characterized in that The system also includes a second gas-liquid separation tank, a second preheater and a distillation tower; The inlet of the second gas-liquid separation tank is connected to the outlet of the second-stage hydrogenation reactor, the outlet of the second gas-liquid separation tank is connected to the inlet of the second preheater, and the outlet of the second preheater is connected to the inlet of the distillation tower; Preferably, the system further comprises a top condenser connected to the top of the distillation tower and a bottom reboiler connected to the bottom of the distillation tower; Preferably, the system further comprises a vacuum buffer tank connected to the outlet of the top condenser.

10. A method for continuously preparing methyl hexahydrophthalic anhydride, characterized in that: Prepared by the system according to any one of claims 6 to 9; Preferably, the preparation conditions include at least one of the following features: Feature 18: The hydrogen pressure in the second-stage hydrogenation reactor is 1MPa-8MPa, the hydrogenation temperature is 60°C-120°C, and the residence time of the material in the second-stage hydrogenation reactor is 1h-5h; preferably, the hydrogen pressure in the second-stage hydrogenation reactor is 1MPa-4MPa, and the residence time of the material in the second-stage hydrogenation reactor is 1h-3h; Feature 19: The preheating temperature of the second preheater is 140°C to 200°C, preferably 140°C to 170°C; Feature 20: The operating pressure of the distillation tower is -0.09 MPa to -0.1 MPa, the bottom temperature of the distillation tower is 210°C to 235°C, the top gas phase temperature is 145°C to 170°C, and the number of plates is 8 to 20; preferably, the bottom temperature of the distillation tower is 213°C to 225°C, the top gas phase temperature is 148°C to 160°C, and the number of plates is 10 to 15; Feature 21: The temperature of the product obtained after cooling in the top condenser is 30°C to 120°C, preferably 50°C to 100°C.

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