Preparation method of wide-temperature-threshold deoxidation platinum-palladium molecular sieve catalyst

Abstract

The invention discloses a preparation method of a wide temperature threshold deoxidation platinum-palladium molecular sieve catalyst, which is characterized in that a combination of a platinum base and a palladium base is coated with stilbite, and the catalyst has a deoxidation effect in a wide temperature range of 25-800 DEG C. And the platinum and the palladium have strong conductive power when being combined with positive charge ions in the stilbite, and the desorption condition of the electrolysis process is wider. The device can be used for deoxidizing molten iron in smelting, and is mainly accumulated beside a molten iron flowing channel to form a low-oxygen area around the molten iron channel, so that the oxygen content in the molten iron is reduced; the aluminum-based adhesive has excellent high-temperature resistance, and the shrinkage rate of the aluminum-based adhesive in high-temperature roasting is about 35% lower than that of other adhesives; the binder used as the molecular sieve catalyst increases the compressive strength and wear resistance of the product.

Description

Technical Field

[0002] The invention relates to the technical field of molecular sieve catalysts, in particular to a method for preparing a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst. Background Art

[0003] Deoxygenated molecular sieve catalysts are crucial in the fields of smelting and chemical industry, but existing deoxygenated molecular sieve catalysts face the problems of narrow active temperature range and poor versatility. To solve these problems, it is necessary to improve catalyst materials and formulations.

[0004] Natural stilbite belongs to the family of aluminosilicate minerals with a hydrated framework structure. The cations in its crystal lattice are weakly bonded to the aluminosilicate framework and can be reversibly replaced by other cations. In this regard, it can protect the stability of the zeolite crystal structure and also possess the special ion exchange properties of the catalyst. As a molecular sieve catalyst carrier, stilbite has high oxidizability and stability.

[0005] Polyaluminium chloride has strong high temperature resistance, low shrinkage, high bonding strength, and wear resistance. It has good bonding and anti-aging properties in the production of catalysts. It increases the mechanical strength of the catalyst in fluid catalytic cracking and other catalysts, and also has the ability to resist metal pollution and high coke selectivity, providing the catalyst with medium and large pores to enhance diffusion performance.

[0006] It is of great economic significance to develop a high- and low-temperature deoxygenation molecular sieve catalyst with a wide active temperature range and good versatility based on the above-mentioned prior art material properties. Summary of the invention

[0007] The present invention aims to at least partially overcome the above technical problems and / or other potential problems existing in the prior art: to provide a method for preparing a wide-temperature threshold deoxidized platinum-palladium molecular sieve catalyst with a wide active temperature range and good versatility.

[0008] The technical solution of the present invention is as follows: A method for preparing a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst comprises the following steps: 1) Weigh the following raw materials in parts by weight: 75-80 parts of natural stilbite; 15-20 parts of clay mineral; 6-8 parts of polyaluminium chloride; 2) The raw materials in step 1) are mixed and crushed and then granulated. After granulation, the granules are dried at 120-160° C. until the moisture content of the granules is less than 10wt%, and then calcined at 620-650° C. for 3-4h, and cooled to room temperature to obtain a molecular sieve carrier; 3) Platinum-based and palladium-based materials are mixed to prepare a precious metal solution, the molecular sieve carrier prepared in step 2) is placed in the precious metal solution and immersed for 2-3 hours to obtain a molecular sieve catalyst, and then the impregnated molecular sieve catalyst is placed in an oven at 120-160° C. for homogeneous conversion for 12-24 hours, and finally the molecular sieve catalyst is activated at a temperature of 360-420° C. for 4-6 hours to obtain a high-low temperature deoxidized platinum-palladium molecular sieve catalyst.

[0009] As an optimization, the platinum-based concentration in the precious metal solution is 0.005-0.01 mol / L.

[0010] As an optimization, the palladium concentration in the precious metal solution is 0.01-0.03 mol / L.

[0011] The above concentrations are addition concentrations, i.e., the molar addition amount of platinum or palladium per liter of solution.

[0012] As an optimization, the clay mineral is a mixture of one or more of pyroxene, sepiolite, palygorskite and kaolin.

[0013] As an optimization, the platinum group is H 6 N 4 O 4 One or both of Pt and platinum (Pt).

[0014] As an optimization, the palladium group is palladium chloride (PdCl 2 )、palladium oxide (PdO), palladium sulfate (PdSO 4 ), one or more of palladium nitrate.

[0015] The beneficial effects of the present invention are as follows: the present invention uses platinum and palladium as the deoxygenation catalytic activity sources of the catalyst, the platinum-based catalytic activity is relatively low, and is generally used for low-temperature reactions. The palladium-based catalytic activity is relatively high, and is generally used for high-temperature reactions. Therefore, the present invention uses stilbite molecular sieve as the carrier of the catalyst, making full use of the high activity of many cations in stilbite, and the catalyst can effectively accelerate the deoxygenation reaction and effectively improve the catalytic activity of platinum and palladium. Under negative pressure conditions, stilbite can first absorb water and impurities, so that platinum and palladium can ensure deep desorption performance.

[0016] The present invention adopts a combination of platinum and palladium, and has a wide temperature range of 25-800°C without losing the deoxidation effect. When platinum and palladium are combined with positively charged ions in stilbite, they have strong conductive power, and the desorption conditions in the electrolysis process are relatively wide. The present invention can be applied to deoxidize molten iron in smelting, mainly accumulating beside the channel where the molten iron flows to form a low-oxygen zone around the channel, thereby reducing the oxygen content in the molten iron.

[0017] Aluminum-based adhesives have excellent high-temperature resistance and their shrinkage rate during high-temperature calcination is about 35% lower than that of other adhesives. As a binder for molecular sieve catalysts, they not only increase the compressive strength and wear resistance of the product, but also have good activity and anti-aging properties under high-temperature conditions. They also have resistance to metal pollution and high coke selectivity, which improves the diffusion properties of the catalyst in the medium and large pores, and further improves the comprehensive performance of the deoxidation catalyst. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with specific examples, but the present invention is not limited to the following specific examples.

[0019] Example 1 The wide temperature threshold deoxidation platinum palladium molecular sieve catalyst was prepared according to the following steps: 1) Weigh the following raw materials: 80 kg natural stilbite; 15 kg kaolin; 5 kg palygorskite; 8 kg polyaluminium chloride; 2) The raw materials in step 1) are first placed in a mixer and mixed for 5 hours, and then crushed to 325 mesh for granulation; the diameter of the granules after granulation is 3-5 mm, the granules are dried at 120° C. for 8-12 hours until the moisture content of the granules is less than 10wt%, and then calcined at 650° C. for 4 hours, and cooled to room temperature to obtain a molecular sieve carrier; 3) Platinum (Pt) and palladium oxide (PdO) are dissolved in aqua regia and diluted with water to prepare a precious metal solution, wherein the concentration of platinum (Pt) added in the precious metal solution is 0.01 mol / L, and the concentration of palladium oxide (PdO) added is 0.03 mol / L. The molecular sieve carrier prepared in step 2) is immersed in the precious metal solution for 3 hours to obtain a molecular sieve catalyst, and then the immersed molecular sieve catalyst is placed in an oven at 120°C for homogeneous conversion for 24 hours, and finally the molecular sieve catalyst is activated at a temperature of 420°C for 6 hours to obtain a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst.

[0020] The catalyst was tested at a temperature of 25-800°C and had the following indicators: compressive strength 90-110 N / particle; bulk density 0.78-0.86 m 3 / g; specific surface area 640-780m 2 / g; deoxidation amount 6.5-7.0wt%; pore volume 0.45-0.82cm 3 / g; porosity 50-68%.

[0021] Example 2 The wide temperature threshold deoxidation platinum palladium molecular sieve catalyst was prepared according to the following steps: 1) Weigh the following raw materials: 80kg natural stilbite; 15kg sepiolite; 5kg stilbite; 8kg polyaluminium chloride; 2) The raw materials in step 1) are first placed in a mixer and mixed for 5 hours, and then crushed to 325 mesh for granulation; the diameter of the granules after granulation is 3-5 mm, the granules are dried at 120° C. for 8-12 hours until the moisture content of the granules is less than 10wt%, and then calcined at 650° C. for 4 hours, and cooled to room temperature to obtain a molecular sieve carrier; 3) Platinum (Pt) and palladium oxide (PdO) are dissolved in aqua regia and diluted with water to prepare a precious metal solution, wherein the concentration of platinum (Pt) added in the precious metal solution is 0.01 mol / L, and the concentration of palladium oxide (PdO) added is 0.03 mol / L. The molecular sieve carrier prepared in step 2) is immersed in the precious metal solution for 3 hours to obtain a molecular sieve catalyst, and then the immersed molecular sieve catalyst is placed in an oven at 120°C for homogeneous conversion for 24 hours, and finally the molecular sieve catalyst is activated at a temperature of 420°C for 6 hours to obtain a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst.

[0022] The catalyst has the following indicators at a temperature threshold of 25-800°C: compressive strength 85-100N / particle; bulk density 0.78-0.85m 3 / g; specific surface area 630-770m 2 / g; deoxidation amount 5.85-6.10wt%; pore volume 0.4-0.76cm 3 / g; porosity 43-46%.

[0023] Example 3 The wide temperature threshold deoxidation platinum palladium molecular sieve catalyst was prepared according to the following steps: 1) Weigh the following raw materials: 75 kg natural stilbite; 15 kg kaolin; 5 kg palygorskite; 6 kg polyaluminium chloride; 2) The raw materials in step 1) are first placed in a mixer and mixed for 5 hours, and then crushed to 325 mesh for granulation; the diameter of the granules after granulation is 3-5 mm, the granules are dried at 160° C. for 8-12 hours until the moisture content of the granules is less than 10wt%, and then calcined at 620° C. for 3 hours, and cooled to room temperature to obtain a molecular sieve carrier; 3) Platinum (Pt) and palladium oxide (PdO) are dissolved in aqua regia and diluted with water to prepare a precious metal solution, wherein the concentration of platinum (Pt) added in the precious metal solution is 0.005 mol / L, and the concentration of palladium oxide (PdO) added is 0.01 mol / L. The molecular sieve carrier prepared in step 2) is immersed in the precious metal solution for 3 hours to obtain a molecular sieve catalyst, and then the immersed molecular sieve catalyst is placed in an oven at 160°C for homogeneous conversion for 12 hours, and finally the molecular sieve catalyst is activated at 360°C for 4 hours to obtain a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst.

[0024] The catalyst was tested at a temperature of 25-800°C and had the following indicators: compressive strength 80-90N / particle; bulk density 0.76-0.82m 3 / g; specific surface area 621-747m 2 / g; deoxidation amount 6.5-7.6wt%; pore volume 0.4-0.68cm 3 / g; porosity 47-50%.

[0025] Comparative Example 1 The deoxidized platinum-palladium molecular sieve catalyst was prepared according to the following steps: 1) Weigh the following raw materials: 80 kg natural stilbite; 15 kg kaolin; 5 kg palygorskite; 8 kg polyaluminium chloride; 2) Mix the raw materials in step 1) and put them into a kneader; 3) Dissolve platinum (Pt) and palladium oxide (PdO) in aqua regia and dilute with water to prepare a precious metal solution, wherein the concentration of platinum (Pt) added in the precious metal solution is 0.01 mol / L, and the concentration of palladium oxide (PdO) added is 0.03 mol / L. In step 2), put 35-38% of the total weight of the raw materials into the kneading machine and knead for 2-3 hours, and then extrude and granulate. The extrusion die for this time is: 1 / 8 of the diameter 3.1-3.3mm. Put the extruded particles into a medium temperature oven at 160°C for curing for 24 hours. Then roast the cured molecular sieve catalyst at a temperature of 650°C and keep the temperature constant for 4 hours to obtain the molecular sieve catalyst product; The catalyst has the following indicators at a temperature threshold of 25-800°C: compressive strength 75-85N / particle; bulk density 0.52-0.67m 3 / g; specific surface area 440-580m 2 / g; deoxidation amount 4.5-5.0wt%; pore volume 0.35-0.65cm 3 / g; porosity 35-43%.

[0026] It can be seen from this that the kneading process will cause the overall performance of the catalyst to decline and is not suitable for the preparation of deoxidized platinum-palladium molecular sieve catalysts.

[0027] Comparative Example 2 The deoxidized platinum-palladium molecular sieve catalyst was prepared according to the following steps: 1) Weigh the following raw materials: 80kg natural stilbite; 15kg kaolin; 5kg palygorskite; 8kg sodium carboxymethyl cellulose; 2) The raw materials in step 1) are first placed in a mixer and mixed for 5 hours, and then crushed to 325 mesh for granulation; the diameter of the granules after granulation is 3-5 mm, the granules are dried at 120° C. for 8-12 hours until the moisture content of the granules is less than 10wt%, and then calcined at 650° C. for 4 hours, and cooled to room temperature to obtain a molecular sieve carrier; 3) Platinum (Pt) and palladium oxide (PdO) are dissolved in aqua regia and diluted with water to prepare a precious metal solution, wherein the concentration of platinum (Pt) added in the precious metal solution is 0.01 mol / L, and the concentration of palladium oxide (PdO) added is 0.03 mol / L. The molecular sieve carrier prepared in step 2) is immersed in the precious metal solution for 3 hours to obtain a molecular sieve catalyst, and then the immersed molecular sieve catalyst is placed in an oven at 120°C for homogeneous conversion for 24 hours, and finally the molecular sieve catalyst is activated at a temperature of 420°C for 6 hours to obtain a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst.

[0028] The catalyst was tested at a temperature of 25-800°C and had the following indicators: compressive strength 66-80N / particle; bulk density 0.72-0.76m 3 / g; specific surface area 540-670m 2 / g; deoxidation amount 4.5-6.0wt%; pore volume 0.52-0.65cm 3 / g; porosity 30-45%.

[0029] It can be seen that conventional cellulose binders lead to reduced catalyst performance relative to polyaluminium chloride.

[0030] Comparative Example 3 The deoxidized platinum-palladium molecular sieve catalyst was prepared according to the following steps: 1) Weigh the following raw materials: 80 kg of artificial zeolite; 15 kg of kaolin; 5 kg of palygorskite; 8 kg of polyaluminium chloride; 2) The raw materials in step 1) are first placed in a mixer and mixed for 5 hours, and then crushed to 325 mesh for granulation; the diameter of the granules after granulation is 3-5 mm, the granules are dried at 120° C. for 8-12 hours until the moisture content of the granules is less than 10wt%, and then calcined at 650° C. for 4 hours, and cooled to room temperature to obtain a molecular sieve carrier; 3) Platinum (Pt) and palladium oxide (PdO) are dissolved in aqua regia and diluted with water to prepare a precious metal solution, wherein the concentration of platinum (Pt) added in the precious metal solution is 0.01 mol / L, and the concentration of palladium oxide (PdO) added is 0.03 mol / L. The molecular sieve carrier prepared in step 2) is immersed in the precious metal solution for 3 hours to obtain a molecular sieve catalyst, and then the immersed molecular sieve catalyst is placed in an oven at 120°C for homogeneous conversion for 24 hours, and finally the molecular sieve catalyst is activated at a temperature of 420°C for 6 hours to obtain a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst.

[0031] The catalyst was tested at a temperature of 25-800°C and had the following indicators: compressive strength 80-90N / particle; bulk density 0.77-0.81m 3 / g; specific surface area 620-650m 2 / g; deoxidation amount 5.5-6.2wt%; pore volume 0.42-0.65cm 3 / g; porosity 40-45%.

[0032] It can be seen from this that natural zeolite has a greater deoxygenation gain on the catalyst than artificial zeolite, thanks to the fact that the natural zeolite-coated platinum-palladium catalyst has higher activity under high and low temperature conditions, effectively accelerating the deoxygenation reaction.

[0033] The above are only examples of the features of the present invention and do not constitute any limitation on the protection scope of the present invention. Any technical solution formed by equivalent exchange or equivalent replacement falls within the protection scope of the present invention.

Claims

1. A method for preparing a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst, characterized in that: The following steps are involved: 1) Weigh the following raw materials in parts by weight: 75-80 parts of natural stilbite; 15-20 parts of clay mineral; 6-8 parts of polyaluminium chloride; 2) The raw materials in step 1) are mixed and crushed and then granulated. After granulation, the granules are dried at 120-160° C. until the moisture content of the granules is less than 10wt%, and then calcined at 620-650° C. for 3-4h, and cooled to room temperature to obtain a molecular sieve carrier; 3) Platinum-based and palladium-based materials are mixed to prepare a precious metal solution, the molecular sieve carrier prepared in step 2) is placed in the precious metal solution and immersed for 2-3 hours to obtain a molecular sieve catalyst, and then the impregnated molecular sieve catalyst is placed in an oven at 120-160° C. for homogeneous conversion for 12-24 hours, and finally the molecular sieve catalyst is activated at a temperature of 360-420° C. for 4-6 hours to obtain a high-low temperature deoxidized platinum-palladium molecular sieve catalyst.

2. The method for preparing a wide temperature threshold deoxidized platinum palladium molecular sieve catalyst according to claim 1, characterized in that: The platinum concentration in the noble metal solution is 0.005-0.01 mol / L.

3. The method for preparing the wide temperature threshold deoxidized platinum palladium molecular sieve catalyst according to claim 2, characterized in that: The palladium concentration in the noble metal solution is 0.01-0.03 mol / L.

4. The method for preparing the wide temperature threshold deoxidized platinum palladium molecular sieve catalyst according to claim 3, characterized in that: The clay mineral is a mixture of one or more of pyroxene, sepiolite, palygorskite and kaolin.

5. The method for preparing the wide temperature threshold deoxidized platinum palladium molecular sieve catalyst according to claim 4, characterized in that: The platinum base is one or both of H6N4O4Pt and platinum (Pt).

6. The method for preparing the wide temperature threshold deoxidized platinum palladium molecular sieve catalyst according to claim 5, characterized in that: The palladium base is one or more of palladium chloride (PdCl2), palladium oxide (PdO), palladium sulfate (PdSO4), and palladium nitrate.