Platinum-rhodium alloy catalytic gauze for producing HCN and preparation method of platinum-rhodium alloy catalytic gauze

Abstract

The invention discloses a platinum-rhodium alloy catalytic gauze for producing HCN (hydrogen cyanide) and a preparation method of the platinum-rhodium alloy catalytic gauze. The platinum-rhodium alloy catalytic gauze is prepared from a platinum-rhodium alloy wire with the wire diameter of 0.076 + / -0.002 mm, the content of Pt is 89.7-90.3 w%, the content of Rh is 9.7-10.3 w%, and the content of other impurities is smaller than or equal to 0.05 w%. The tensile strength of the platinum-rhodium alloy wire is larger than or equal to 700 Mpa, and the ductility is larger than or equal to 7%. The weaving mode of the platinum-rhodium alloy catalysis net is plain weaving, and the mesh number is 40 / 80; the diameter of the platinum rhodium alloy catalysis net is 1100 to 2800mm; the filling amount of the platinum-rhodium alloy catalytic nets in the oxidation furnace is 15-90 kg, the number of filling layers is 40-50, and 80 meshes and 40 meshes are combined up and down to be used in a complete set and stacked mode. When the Pt-Rh alloy catalytic gauze provided by the invention is used for producing HCN, the service life of the catalytic gauze is 8-9 months, and the conversion rate reaches 70-72%. The preparation process flow of the Pt-Rh alloy catalytic gauze is controllable in the whole process, the process is smooth, and the platinum-rhodium alloy catalytic gauze with high catalytic capacity can be produced in batches.

Description

Technical Field

[0001] The invention belongs to the technical field of precious metal alloy catalytic materials, and in particular relates to a platinum-rhodium alloy catalytic mesh for producing HCN and a preparation method thereof. Background Art

[0002] Hydrocyanic acid (HCN) is a special and important chemical intermediate raw material, mainly used in the production of downstream products such as sodium cyanide, adiponitrile, acetone cyanohydrin and methionine. Its production methods mainly include: Anger method, acrylonitrile by-product method, light oil cracking method, etc. Among them, Anger method is mature in technology, economical and reasonable, and uses natural gas (methane) directly as raw material, which is the mainstream chemical synthesis method. With the vigorous development of my country's chemical industry, downstream derivatives of hydrocyanic acid continue to expand to different fields, and the domestic market usage increases dramatically every year. The demand for platinum-rhodium alloy catalytic mesh as a catalyst is increasing, and the technical requirements for the catalytic mesh are also getting higher and higher. For manufacturers who use Anger method to produce hydrocyanic acid, the catalytic mesh is the second largest cost after natural gas and ammonia. While innovating and transforming production technology and stabilizing the production process, manufacturers also urge platinum-rhodium alloy catalytic mesh to develop in the direction of saving platinum, reducing consumption, high conversion rate and long service life.

[0003] At present, most of the hydrocyanic acid manufacturers in my country use methane, ammonia and air as raw materials in the Ansler method. The furnace body adopts a normal pressure furnace, the reaction temperature is about 1000~1150℃, and the catalyst used is a platinum palladium rhodium ternary alloy catalytic mesh, the grade is Pt-4Pd-3.5Rh, the wire diameter is Ø0.090mm, the weaving method is plain weave, and the mesh number is 80 mesh. At present, the platinum palladium rhodium alloy wire used in the platinum palladium rhodium ternary alloy catalytic mesh has poor mechanical properties, with a tensile strength between 300~400Mpa and an elongation between 4%~5%. The catalytic mesh prepared with this wire is prone to several problems in the HCN production process: 1) low high temperature strength, easy to tear, and sometimes even need to replace a new mesh in less than one cycle; 2) low conversion rate, generally only about 64%~66%; 3) short service life, a cycle is only 4~6 months, resulting in frequent shutdowns, affecting production and subsequent derivative production processes.

[0004] The present invention aims to provide a platinum-rhodium alloy catalytic mesh for producing HCN by methane ammonia oxidation process (Angstrom process) under high temperature conditions, which has high strength, high conversion rate and long service life. Summary of the invention

[0005] The first object of the present invention is to provide a platinum-rhodium alloy catalytic mesh for producing HCN, and the second object of the present invention is to provide a method for preparing the rhodium alloy catalytic mesh.

[0006] The first object of the present invention is achieved by providing a platinum-rhodium alloy catalytic mesh for producing HCN, characterized in that the platinum-rhodium alloy catalytic mesh is prepared by platinum-rhodium alloy wire with a wire diameter of 0.076±0.002mm, wherein the Pt content is 89.7~90.3w%, the Rh content is 9.7~10.3w%, and the content of other impurities is ≤0.05w%; the platinum-rhodium alloy wire has a tensile strength of ≥700Mpa and an elongation of ≥7%; The platinum-rhodium alloy catalytic mesh is woven in a plain weave, with a mesh size of 40 / 80 meshes; The diameter of the platinum-rhodium alloy catalytic mesh is Ø1100~Ø2800mm; the loading amount of the platinum-rhodium alloy catalytic mesh in the oxidation furnace is 15~90kg, the number of loading layers is 40~50 layers, and an 80-mesh + 40-mesh combination is used in a stacked set.

[0007] The second object of the present invention is achieved by the method for preparing the platinum-rhodium alloy catalytic mesh for producing HCN, characterized in that the method for preparing the catalytic mesh comprises the following steps: continuous warping, machine loading, threading → plain weaving → crimping welding and shaping → pre-activation → inspection → platinum-rhodium alloy catalytic mesh; Among them, in the continuous warping, machine loading and threading process, the longitudinal slice sequence is 1, 2, 1, 2 cross circulation, and the reed mesh number is 40 / 80; In the curling welding and shaping process, the curling size is 10~12mm and the welding seam width is 10~12mm.

[0008] The beneficial effects of the present invention are: 1. The preparation method of the platinum-rhodium alloy wire provided by the present invention has overcome the key technology of the preparation of platinum-rhodium alloy filaments and the adjustment of mechanical properties. In the wire drawing process, the wire drawing performance is improved and the wire breakage probability is reduced by reducing the deformation amount per pass and reducing the internal stress generated during the cold drawing of the wire. After the wire diameter is reduced, the obtained platinum-rhodium alloy wire can obtain higher strength and longer service life at high temperature, and has less impurities, smooth surface, and mechanical properties that meet the requirements of subsequent processes.

[0009] 2. When the Pt-Rh alloy catalytic net provided by the present invention is used to catalytically produce HCN, the service life of the catalytic net is 8 to 9 months, and the conversion rate is 70-72%. The present invention reduces platinum consumption and prolongs service life while ensuring or even improving catalytic efficiency through comprehensive consideration and reasonable design of factors such as the catalytic net component ratio, weaving method, wire diameter, number of installation layers and position, and can be used as a key catalytic material for producing HCN using the methane ammonia oxidation method (Ansler method). The preparation process of the Pt-Rh alloy catalytic net of the present invention is controllable throughout the process, the process is smooth, and a platinum-rhodium alloy catalytic net with high catalytic ability can be mass-produced. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The as-cast structure diagram of the Pt-Rh alloy after recrystallization annealing in step 3 of Example 1 of the present invention; Figure 2 The upper and lower parts of the Pt-Rh alloy catalytic screen prepared in Example 1 of the present invention are a set of 80 mesh + 40 mesh in the oxidation furnace; Figure 3 This is a scanning electron microscope image of the texture of the Pt-Rh alloy catalytic mesh prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0011] The present invention discloses a platinum-rhodium alloy catalytic mesh for producing HCN. The platinum-rhodium alloy catalytic mesh is prepared by using a platinum-rhodium alloy wire material with a wire diameter of 0.076±0.002 mm, wherein the Pt content is 89.7-90.3w%, the Rh content is 9.7-10.3w%, and the content of other impurities is ≤0.05w%; the platinum-rhodium alloy wire material has a tensile strength of ≥700Mpa and an elongation of ≥7%; The platinum-rhodium alloy catalytic mesh is woven in a plain weave, with a mesh size of 40 / 80 meshes; The diameter of the platinum-rhodium alloy catalytic mesh is Ø1100~Ø2800mm; the loading amount of the platinum-rhodium alloy catalytic mesh in the oxidation furnace is 15~90kg, the number of loading layers is 40~50 layers, and an 80-mesh + 40-mesh combination is used in a stacked set.

[0012] The platinum-rhodium alloy wire preparation method comprises the following steps: melting and casting → hot forging → recrystallization annealing → cold rolling → annealing → rough drawing → annealing → medium drawing → fine drawing → continuous annealing, and the specific method is as follows: a. Prepare the metal raw materials according to the composition ratio, with Pt content of 89.7~90.3w%, Rh content of 9.7~10.3w%, and the rest of the impurities controlled to ≤0.05w%. Put the metal raw materials into the smelting device for melting, with a pre-melting power of 8kW, a time of 1h, a smelting power of 20kW, and a smelting number of 3 times. Obtain a platinum-rhodium alloy solid solution, cast into a cylindrical ingot, and form a machinable ingot after water cooling, with a diameter of Ø35mm; b. Perform hot forging on the ingot. Use an air forging hammer to forge the ingot multiple times, forging the ingot from Ø35mm to Ø18mm. The single deformation is 10%~20%. Annealing is required after each hammer forging. The annealing temperature is 1000~1100℃; c. Carry out recrystallization annealing treatment on the ingot in a box-type high-temperature furnace at a recrystallization annealing temperature of 1000-1100°C for 30 minutes, and then cool to room temperature by air cooling; d. Roll the ingot from Ø18mm to Ø4mm bar on a rolling mill, and then perform stress relief annealing; e. Rough drawing is performed on a disc wire drawing machine from Ø4mm to Ø1.4mm, followed by stress relief annealing; f. Conduct wire drawing on a multi-mode water tank wire drawing machine, with the wire diameter ranging from Ø1.4mm to Ø0.3mm, using 25 dies and a surface reduction rate of 11~13%; g. Fine drawing of wires is performed on a fine drawing machine, with the wire diameter being drawn from Ø0.3mm to Ø0.076mm, using a 24 die, with a surface reduction ratio of 8-10%, and the wire diameter is tested to meet the tolerance requirements: Ø0.076mm±0.002mm; the tensile strength of the fine wire is tested to be ≥700Mpa, and the elongation is ≥7%. Then continuous annealing is performed.

[0013] The present invention further provides a method for preparing the platinum-rhodium alloy catalytic mesh for producing HCN, comprising the following steps: continuous warping, machine loading, yarn threading → plain weaving → crimping welding and shaping → pre-activation → inspection → platinum-rhodium alloy catalytic mesh, and the specific steps are: a. Calculate the length of the platinum-rhodium alloy filaments according to the length of the weaving net, and arrange the wires evenly and continuously on the rewinding machine. Arrange dozens of shafts of filaments on the creel after the arrangement is completed. On the warp cylinder, according to the width of the weaving net, hundreds or thousands of metal filaments are evenly distributed, and dozens or hundreds of turns are continuously rewound. The tension of the metal filaments remains consistent. Put the warp cylinder on the weaving machine to thread the yarn, thread the longitudinal slices, and the sequence of the longitudinal slices is 1, 2, 1, 2 cross-circulation. Thread the reed, and select the mesh number of the reed to be 40 / 80. Each filament corresponds to a needle hole, and prepare for weaving the net; b. On the weaving machine, release the filaments of the warp cylinder one by one, divide them into several small bundles, tie each bundle tightly with cotton thread and pull it, set the weft density and tension: the weft density is 16~35 wefts / cm, the tension is 900~950N, and weave the metal mesh. During the weaving process, it is necessary to deal with problems such as broken wires and loose wires to ensure the smooth completion of the weaving work; c. After weaving, cut the net from the net weaving machine and cut it into a circle according to the diameter size on the sorting platform. To prevent the net edge from loosening, it is necessary to perform hemming welding and shaping. The entire circumference is hemmed, and the hemming size is 10~12mm. It is pressed with a spot welder, and the welding seam width is controlled at 10~12mm. Ensure that the edge of the net is not loose, and then use a straight bar press plate to press the net surface flat and wrinkle-free; d. Hang the round net flat on the rack and let it hang naturally. Use hydrogen flame for pre-activation. Adjust the flame to the appropriate temperature between 800~900℃ and the speed between 0.5~0.8m. 2 / min, reciprocate on the metal mesh surface at a uniform speed to activate it, making sure that the entire mesh surface is activated; e. Check the net for various indicators, including but not limited to: net diameter, thickness, net defects, etc., and form a platinum-rhodium alloy catalytic net when the requirements are met. The loading amount of Pt-Rh alloy catalytic net in the oxidation furnace is controlled at 15~90kg, and the number of loading layers is 40~50 layers. 80 mesh + 40 mesh are used as a set of stacking for the production of HCN by Anscher method.

[0014] The present invention is further described in detail below in conjunction with specific embodiments: Example 1 1) The metal raw materials are prepared according to the composition ratio, with a Pt content of 89.7w%, a Rh content of 10.3w%, and the rest of the impurities controlled to ≤0.05w%. The metal raw materials are loaded into a smelting device for melting, with a pre-melting power of 8kW, a time of 1h, a smelting power of 20kW, and a smelting number of 3 times. A platinum-rhodium alloy solid solution is obtained, and then the solid solution is cast into a cylindrical ingot with a diameter of 35mm, and a processable ingot is formed after water cooling; 2) The ingot is hot forged, and the ingot is forged multiple times with an air forging hammer, and the ingot is forged from Ø35mm to Ø18mm, and the single deformation is 10%. Annealing treatment is required after each hammer forging, and the annealing temperature is 1000℃; 3) The ingot is subjected to recrystallization annealing treatment in a box-type high-temperature furnace with a recrystallization annealing temperature of 1050°C and a holding time of 30 minutes. The ingot is then cooled to room temperature by air cooling. The test results show that the platinum-rhodium alloy forms equiaxed crystals ( Figure 1 ); 4) Roll the ingot from Ø18mm to Ø7mm and then to Ø4mm bars on the rolling mill, and then perform stress relief annealing; 5) Rough drawing is performed on a disc wire drawing machine from Ø4mm to Ø1.4mm, followed by stress relief annealing; 6) The wire is drawn on a multi-mode water tank wire drawing machine, with the wire diameter being drawn from Ø1.4mm to Ø0.3mm, using 25 dies and an area reduction rate of 11%; 7) The wire is finely drawn on a fine drawing machine, with the wire diameter being drawn from Ø0.3mm to Ø0.076mm, using a 24 die and an area reduction rate of 8%. The wire diameter is tested to meet the tolerance requirement: Ø0.076mm±0.002mm, and then continuous annealing is performed.

[0015] 8) Calculate the length of the platinum-rhodium alloy filaments according to the length of the weaving net, and arrange the wires evenly and continuously on the rewinding machine. Arrange dozens of shafts of filaments on the creel after the arrangement is completed. On the warp cylinder, according to the width of the weaving net, hundreds or thousands of metal filaments are evenly distributed, and dozens or hundreds of circles are continuously rewound. The tension of the metal filaments remains consistent. Put the warp cylinder on the weaving machine to thread the yarn, thread the longitudinal slices, and the sequence of the longitudinal slices is 1, 2, 1, 2 cross-circulation. Thread the reed, and select the mesh number of the reed to be 40 meshes. Each filament corresponds to a needle hole, and prepare for weaving the net; 9) On the weaving machine, release the filaments of the warp cylinder one by one, divide them into several small bundles, tie each bundle tightly with cotton thread and pull it, set the weft density and tension: the weft density is 17 wefts / cm, the tension is 950N, and weave the metal mesh. During the weaving process, it is necessary to deal with problems such as broken wires and loose wires to ensure the smooth completion of the weaving work; 10) After weaving, cut the net from the net weaving machine and cut it into a circle with a diameter of Ø1890mm on the finishing platform. To prevent the net edge from loosening, it is necessary to perform hemming welding and shaping. The entire circumference is hemmed with a hemming size of 10mm, and spot welded with a weld seam width of 10mm. Ensure that the edge of the net is not loose, and then use a straight bar press plate to press the net surface flat and wrinkle-free; 11) Hang the circular net flat on the rack and let it hang naturally. Use hydrogen flame for pre-activation. Adjust the flame to the appropriate temperature between 850℃ and the speed to 0.6m. 2 / min, reciprocate on the metal mesh surface at a uniform speed to activate it, making sure that the entire mesh surface is activated; 12) The mesh is inspected for various indicators, including but not limited to: mesh diameter, thickness, mesh defects, etc. Once the requirements are met, a platinum-rhodium alloy catalytic mesh is formed.

[0016] When the catalytic net prepared in this embodiment is used to produce HCN, the oxidation furnace is loaded with 40 kg and 42 layers, and an 80 mesh + 40 mesh upper and lower combination is used as a set ( Figure 2 ).

[0017] Example 2 1) The metal raw materials are prepared according to the composition ratio, with a Pt content of 90w%, a Rh content of 10w%, and the rest of the impurities controlled to ≤0.05w%. The metal raw materials are loaded into a smelting device for melting, with a pre-melting power of 8kW, a time of 1h, a smelting power of 20kW, and a smelting number of 3 times. A platinum-rhodium alloy solid solution is obtained, and then the solid solution is cast into a cylindrical ingot with a diameter of 35mm, which is then water-cooled to form a processable ingot; 2) The ingot is hot forged, and the ingot is forged multiple times with an air forging hammer, and the ingot is forged from Ø35mm to Ø18mm, with a single deformation of 15%. Annealing treatment is required after each hammer forging, and the annealing temperature is 1050℃; 3) The ingot is subjected to recrystallization annealing treatment in a box-type high-temperature furnace at a recrystallization annealing temperature of 1080°C for 30 minutes, and then air-cooled to room temperature. The test results show that the platinum-rhodium alloy forms equiaxed crystals; 4) Roll the ingot from Ø18mm to Ø7mm and then to Ø4mm bars on the rolling mill, and then perform stress relief annealing; 5) Rough drawing is performed on a disc wire drawing machine from Ø4mm to Ø1.4mm, followed by stress relief annealing; 6) The wire is drawn on a multi-mode water tank wire drawing machine, with the wire diameter being drawn from Ø1.4mm to Ø0.3mm, using 25 dies and a surface reduction rate of 12%; 7) The wire is finely drawn on a fine drawing machine, with the wire diameter being drawn from Ø0.3mm to Ø0.076mm, using a 24 die and a surface reduction rate of 9%. The wire diameter is tested to meet the tolerance requirement: Ø0.076mm±0.002mm, and then continuous annealing is performed.

[0018] 8) Calculate the length of the platinum-rhodium alloy filaments according to the length of the weaving net, and arrange the wires evenly and continuously on the rewinding machine. Arrange dozens of shafts of filaments on the creel after the arrangement is completed. On the warp cylinder, according to the width of the weaving net, hundreds or thousands of metal filaments are evenly distributed, and dozens or hundreds of circles are continuously rewound. The tension of the metal filaments remains consistent. Put the warp cylinder on the weaving machine to thread the yarn, thread the longitudinal slices, and the sequence of the longitudinal slices is 1, 2, 1, 2 cross-circulation. Thread the reed, and select the mesh number of the reed to be 40 meshes. Each filament corresponds to a needle hole, and prepare for weaving the net; 9) On the weaving machine, release the filaments of the warp cylinder one by one, divide them into several small bundles, tie each bundle tightly with cotton thread and pull it, set the weft density and tension: the weft density is 17.5 wefts / cm, the tension is 900N, and the metal mesh is woven. During the weaving process, problems such as broken wires and loose wires need to be handled to ensure the smooth completion of the weaving work; 10) After weaving, cut the net from the net weaving machine and cut it into a circle with a diameter of Ø2000mm on the finishing platform. To prevent the net edge from loosening, it is necessary to perform hemming welding and shaping. The entire circumference is hemmed with a hemming size of 11mm, and spot welded with a welding seam width of 12mm. Ensure that the edge of the net is not loose, and then use a straight bar press plate to press the net surface flat and wrinkle-free; 11) Hang the circular net flat on the rack and let it hang naturally. Use hydrogen flame for pre-activation. Adjust the flame to the appropriate temperature between 80℃ and 70℃, and the speed is 0.7m. 2 / min, reciprocate on the metal mesh surface at a uniform speed to activate it, making sure that the entire mesh surface is activated; 12) The mesh is inspected for various indicators, including but not limited to: mesh diameter, thickness, mesh defects, etc. Once the requirements are met, a platinum-rhodium alloy catalytic mesh is formed.

[0019] When the catalytic net prepared in this embodiment is used to produce HCN, the loading amount of the oxidation furnace is 45 kg, the number of loading layers is 46, and an 80-mesh + 40-mesh combination is used in a stacked set.

[0020] Example 3 1) The metal raw materials are prepared according to the composition ratio, with a Pt content of 90.3w%, a Rh content of 9.7w%, and the rest of the impurities controlled to ≤0.05w%. The metal raw materials are loaded into a smelting device for melting, with a pre-melting power of 8kW, a time of 1h, a smelting power of 20kW, and a smelting number of 3 times. A platinum-rhodium alloy solid solution is obtained, and then the solid solution is cast into a cylindrical ingot with a diameter of 35mm, and a processable ingot is formed after water cooling; 2) The ingot is hot forged, and the ingot is forged multiple times with an air forging hammer, and the ingot is forged from Ø35mm to Ø18mm, with a single deformation of 20%. Annealing treatment is required after each hammer forging, and the annealing temperature is 1100℃; 3) The ingot is subjected to recrystallization annealing treatment in a box-type high-temperature furnace at a recrystallization annealing temperature of 1100°C for 30 minutes, and then air-cooled to room temperature. The test results show that the platinum-rhodium alloy forms equiaxed crystals; 4) Roll the ingot from Ø18mm to Ø7mm and then to Ø4mm bars on the rolling mill, and then perform stress relief annealing; 5) Rough drawing is performed on a disc wire drawing machine from Ø4mm to Ø1.4mm, followed by stress relief annealing; 6) The wire is drawn on a multi-mode water tank wire drawing machine, with the wire diameter being drawn from Ø1.4mm to Ø0.3mm, using 25 dies and a surface reduction rate of 13%; 7) The wire is finely drawn on a fine drawing machine, with the wire diameter being drawn from Ø0.3mm to Ø0.076mm, using a 24 die and a surface reduction rate of 10%. The wire diameter is tested to meet the tolerance requirement: Ø0.076mm±0.002mm, and then continuous annealing is performed.

[0021] 8) Calculate the length of the platinum-rhodium alloy filaments according to the length of the weaving net, and arrange the wires evenly and continuously on the rewinding machine. Arrange dozens of shafts of filaments on the creel after the arrangement is completed. On the warp cylinder, according to the width of the weaving net, hundreds or thousands of metal filaments are evenly distributed, and dozens or hundreds of circles are continuously rewound. The tension of the metal filaments remains consistent. Put the warp cylinder on the weaving machine to thread the yarn, thread the longitudinal slices, and the sequence of the longitudinal slices is 1, 2, 1, 2 cross-circulation. Thread the reed, and select the mesh number of the reed to be 80 meshes. Each filament corresponds to a needle hole, and prepare for weaving the net; 9) On the weaving machine, release the filaments of the warp cylinder one by one, divide them into several small bundles, tie each bundle tightly with cotton thread and pull it, set the weft density and tension: the weft density is 32 wefts / cm, the tension is 920N, and the metal mesh is woven. During the weaving process, problems such as broken wires and loose wires need to be handled to ensure the smooth completion of the weaving work; 10) After weaving, cut the net from the net weaving machine and cut it into a circle with a diameter of Ø2500mm on the finishing platform. To prevent the net edge from loosening, it is necessary to perform hemming welding and shaping. The entire circumference is hemmed with a hemming size of 12mm, and the spot welder is used for pressure welding, and the welding seam width is controlled at 11mm. Ensure that the edge of the net is not loose, and then use a straight bar press plate to press the net surface flat and wrinkle-free; 11) Hang the circular net flat on the rack and let it hang naturally. Use hydrogen flame for pre-activation. Adjust the flame to the appropriate temperature between 900℃ and the speed to 0.8m. 2 / min, reciprocate on the metal mesh surface at a uniform speed to activate it, making sure that the entire mesh surface is activated; 12) The mesh is inspected for various indicators, including but not limited to: mesh diameter, thickness, mesh defects, etc. Once the requirements are met, a platinum-rhodium alloy catalytic mesh is obtained.

[0022] When the catalytic net prepared in this embodiment is used to produce HCN, the oxidation furnace is loaded with 60 kg of material and 48 layers of material are loaded, and an 80-mesh + 40-mesh combination is used in a stacked manner.

[0023] Comparative Examples 1-6 The differences between the catalytic screens prepared in Comparative Examples 1-6 and Example 1 are shown in Table 1.

[0024] Table 1 Preparation of Comparative Examples 1-4 Test Example Performance Test of Pt-Rh Alloy Catalytic Net Prepared in Example 1-3 1. Physical performance testing The Pt-Rh alloy wires prepared in Examples 1 to 3 were sampled and tested for physical properties. The diameter of the wires was tested with an X-ray detector, and the tensile strength and elongation of the wires were tested with a universal mechanical properties tester. Three samples were tested for each example, and the test results are shown in Table 2.

[0025] Table 2 Pt-Rh alloy wires prepared in Examples 1-3 It can be seen from Table 1 that the tensile strength of the Pt-Rh alloy wires prepared in Examples 1-3 is ≥700 MPa, and the elongation is ≥7%.

[0026] 2. Conversion rate and service life test The conversion rate test was conducted on the Pt-Rh alloy catalytic mesh prepared in Examples 1-3 and Comparative Examples 1-6. Under normal pressure and reaction temperature of 1100°C, a mixture of methane, ammonia and air raw materials was passed into a wire mesh catalyst bed made of a platinum-rhodium alloy catalyst for an ammonia oxidation reaction, and the reaction formula is: 2CH4+2NH3+3O2→2HCN+6H2O. The test device is a catalyst performance test device for HCN production by an HCN manufacturer, and has a full process for producing HCN. The test device can comprehensively evaluate the catalytic performance of the catalytic mesh: the conversion rate is calculated based on the test data, and the service life is calculated based on the real-time conversion rate change of the catalytic mesh. The test results of each embodiment are shown in Table 3.

[0027] Table 3 Conversion rate and service life of the catalytic screens prepared in Examples 1-3 and Comparative Examples 1-6 Test results: The conversion rate of the Pt-Rh alloy catalytic mesh prepared in Examples 1-3 is 70~72%, and the service life is 8~9 months. After comparative analysis: The mechanical properties of the single wire of the Pt-Rh alloy catalytic mesh prepared in Examples 1-3 of the present invention are significantly improved compared with those in Comparative Examples 1-4, and the conversion rate and service life are also greatly improved compared with Comparative Examples 1-6. Its preparation method has overcome the key technologies of preparation and mechanical property adjustment of platinum-rhodium alloy filaments. After the wire diameter is reduced, higher strength and longer service life can be obtained under high temperature conditions. The alloy wire has less impurities, a smooth surface, and mechanical properties that meet the requirements of subsequent processes. In the wire drawing process, the wire drawing performance is improved and the probability of wire breakage is reduced by reducing the deformation amount per pass and reducing the internal stress generated during cold drawing of the wire.

[0028] The alloy filaments with a diameter of 0.076 mm are more difficult to weave, and the warp is easy to break. The present invention improves the defects of loose mesh, deformation, uneven mesh, etc. by improving the weaving forming process, and obtains a catalytic mesh with high uniformity mesh, which overcomes the key technology of catalytic mesh forming. Compared with the Pt-Pd-Rh alloy catalytic mesh used in the traditional methane ammonia oxidation method to produce HCN, the catalytic mesh provided by the present invention is changed from a ternary alloy to a binary alloy, palladium is removed, and rhodium with high temperature resistance strength is added. At the same time, the wire diameter is changed from the original Ø0.09mm to Ø0.076mm, and the mesh surface is firstly combined with 80+40 meshes to be stacked into a set of meshes and then loaded in the oxidation furnace for use. Therefore, under the high temperature environment of the reaction temperature of 1000~1100℃, the high temperature strength of the catalytic mesh can be effectively improved, the specific surface area of ​​the catalytic mesh can be increased, and the permeability of the airflow in the furnace can be increased, thereby increasing the contact area between the catalytic mesh and the reaction gas, enhancing the catalytic activity, and increasing the conversion rate to 70%~72%, extending the service life to 8~9 months, and improving the production efficiency of HCN.

[0029] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A platinum-rhodium alloy catalytic screen for producing HCN, characterized in that: The platinum-rhodium alloy catalytic mesh is made of platinum-rhodium alloy wire with a wire diameter of 0.076±0.002mm, wherein the Pt content is 89.7~90.3w%, the Rh content is 9.7~10.3w%, and the content of other impurities is ≤0.05w%; the platinum-rhodium alloy wire has a tensile strength of ≥700Mpa and an elongation of ≥7%; The platinum-rhodium alloy catalytic mesh is woven in a plain weave, with a mesh size of 40 / 80 meshes; The diameter of the platinum-rhodium alloy catalytic mesh is Ø1100~Ø2800mm; the loading amount of the platinum-rhodium alloy catalytic mesh in the oxidation furnace is 15~90kg, the number of loading layers is 40~50 layers, and an 80-mesh + 40-mesh combination is used in a stacked set.

2. The platinum-rhodium alloy catalytic screen for producing HCN according to claim 1, characterized in that: The method for preparing the platinum-rhodium alloy wire comprises the following steps: melting and casting → hot forging → recrystallization annealing → cold rolling → annealing → rough drawing → annealing → medium drawing → fine drawing → continuous annealing; Wherein, in the hot forging process, the deformation amount per pass is 10-20%, and the annealing temperature is 1000-1100°C; In the recrystallization annealing process, the recrystallization annealing temperature is 1000-1100°C and the holding time is 30 minutes; In the intermediate drawing process, the wire diameter is drawn from Ø1.4 mm to Ø0.3 mm, a 25 die is used, and the area reduction rate is 11-13%.

3. The platinum-rhodium alloy catalytic screen for producing HCN according to claim 2, characterized in that: In the melting and casting process, the pre-melting power is 8 kW and the time is 1 hour; the melting power is 20 kW and the melting times are 3 times.

4. The platinum-rhodium alloy catalytic screen for producing HCN according to claim 2, characterized in that: In the fine drawing process, the wire diameter is drawn from Ø0.3mm to Ø0.076mm, a 24-die is used, and the surface reduction rate is 8-10%.

5. The method for preparing the platinum-rhodium alloy catalytic screen for producing HCN according to claim 1, characterized in that: The preparation method of the catalytic net comprises the following steps: continuous warping, machine loading, yarn threading → plain weaving → crimping welding and shaping → pre-activation → inspection → platinum-rhodium alloy catalytic net; Among them, in the continuous warping, machine loading and threading process, the longitudinal slice sequence is 1, 2, 1, 2 cross circulation, and the mesh number of the steel reed is 40 / 80; In the curling welding and shaping process, the curling size is 10~12mm and the welding seam width is 10~12mm.

6. The method for preparing a platinum-rhodium alloy catalytic screen for producing HCN according to claim 5, characterized in that: In the plain weaving process, the weft density is 16-35 wefts / cm, and the tension is 900-950N.

7. The method for preparing a platinum-rhodium alloy catalytic screen for producing HCN according to claim 5, characterized in that: In the pre-activation process, hydrogen flame pre-activation is used, the temperature is 800~900℃, the speed is 0.5~0.8m 2 / min.

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