A composite adsorbent with a core-shell structure for separating carbon monoxide by pressure swing adsorption

Abstract

The present invention relates to a composite adsorbent for pressure swing adsorption separation of carbon monoxide with a core-shell structure, which uses microspheres with high specific heat capacity and non-porous structure as the core and zeolite exchanged with divalent copper loaded with cuprous salt as the shell. The composite adsorbent comprises the following raw materials in parts by mass: 5-10 parts of microspheres with high specific heat capacity and non-porous structure, 70-90 parts of copper-based adsorbent precursor, and 5-10 parts of binder. The copper-based adsorbent precursor is a mixture of cuprous salt and zeolite exchanged with divalent copper in a mass ratio of 0.5-0.7:1. By adding an inert core, the present invention improves the specific heat capacity of the adsorbent, can control the adverse temperature gradient generated during adsorption and desorption, reduces the temperature change during the adsorption and desorption process, and makes the pressure swing adsorption process easier to control; the binder is more firmly combined, improving the physical strength of the adsorbent, thereby extending the service life of the adsorbent.

Description

Technical Field

[0001] The present invention belongs to the field of carbon monoxide adsorbents, and particularly relates to a composite adsorbent with a core-shell structure for separating carbon monoxide by pressure swing adsorption. Background Art

[0002] Types of CO adsorbents include zeolite molecular sieves, activated carbon, metal-organic framework materials, π-complexing adsorbents, etc. In the 1970s and 1980s, researchers utilized the principle that transition metal ions such as Cu + , Ag + etc. can undergo π-complexing interactions with CO, and loaded and dispersed metal ions on porous materials with high specific surface areas such as zeolite molecular sieves and activated carbon to prepare special CO adsorbents. Such adsorbents are customarily referred to as π-complexing adsorbents. Since the complexing ability of Cu + with CO is stronger than that of Ag + , thus Cu +Supported adsorbents can achieve higher adsorption capacity and selectivity. π-complexation belongs to the category of weak chemical bonds. Therefore, compared with traditional physical adsorption using van der Waals forces or electrostatic forces, it has stronger interaction forces and higher adsorption selectivity. And compared with general chemical adsorption, its weak chemical bond nature enables the desorption process to be easily achieved by reducing pressure or increasing temperature. π-complexation adsorption separation combines the strong chemical action of π-complexation with adsorption separation, and has the characteristics of high selectivity, low energy consumption, and low cost. Therefore, it has become an important frontier field for improving traditional separation technologies. The adsorbents applied to the pressure swing adsorption separation of CO process are mainly copper-loaded adsorbents. The research on them originated in the 1970s and 1980s. Subsequently, the adsorption capacity or selectivity of CO has been continuously improved by means of improving the adsorbent carrier, using different active components, and improving the preparation method, so as to develop adsorbents with more excellent performance. Nippon Steel & Sumitomo Metal Corporation (NKK) (European Patent.0170884A1, 1986.) loaded an appropriate amount of CuCl onto Cu(I)Y zeolite, improving the adsorption selectivity and adsorption amount of CO. This adsorbent can separate high-purity CO from steel plant tail gas through a single pressure swing adsorption and has been industrialized. Kansai Thermal Engineering Co., Ltd. (Patent DE3631396A1) improved the carrier structure of the adsorbent. Taking the carrier composed of SiO2 or / and Al2O3 as the core, an organic matter carbonized layer was formed on its surface to form a composite carrier, and then copper was loaded onto the composite carrier. The presence of the carbonized layer effectively prevented the oxidation of copper, thus extending the service life of the adsorbent. Xie Youchang et al. from Peking University (Xie Youchang, Zhang Jiaping, Tong Xianzhong, etc. High-efficiency carbon monoxide adsorbent CuCl / zeolite [J]. Chemical Journal of Chinese Universities, 1997, 18(7): 1159-1165) dispersed CuCl on carriers such as 13X, NaY, and CuY zeolites by solid mixing and heating using the principle of spontaneous monolayer dispersion to prepare high-efficiency CO adsorbents. The adsorption capacities of CuCl / NaY and CuCl / CuY adsorbents are as high as 90 mL / g carrier and 100 mL / g carrier respectively at 20 °C and a CO partial pressure of 60 kPa. The developed high-efficiency CO adsorbent PU-1 has been successfully used in industrial pressure swing adsorption separation of CO. CN86102838A uses a monovalent copper compound loaded on a high specific surface area carrier, at room temperature and a partial pressure of CO or unsaturated hydrocarbon of 10 -2- Under the condition of -760 mmHg, its adsorption capacity is generally 1 - 4 mmol / g of adsorbent, and can ultimately reach 7.0 mmol / g of adsorbent. The preparation method of the monolayer CuCl / activated carbon adsorbent for CO adsorption and separation in CN108704609A is to dissolve Cu2(OH)2CO3 and CuCl2 in formic acid to obtain a divalent copper salt solution, and impregnate it on the surface of activated carbon to obtain an adsorbent precursor; then heat-treat the precursor in a vacuum environment or in a flowing inert atmosphere of N2 or Ar to prepare the monolayer CuCl / activated carbon adsorbent. The monolayer CuCl / activated carbon adsorbent prepared by this patented method has high CO adsorption capacity, selectivity and regenerability, and can be used for the separation and purification of various gases containing CO. Advantages such as mild operating conditions required for the adsorption process, general process requirements for equipment, and recyclability of the adsorbent make the adsorption process widely favored in the field of industrial production. In the process of adsorption separation, the structural properties of the adsorbent itself are the key factors affecting the adsorption separation performance. In industry, the pressure swing adsorption separation process is used to recover CO. It is a technology that utilizes the characteristic that the adsorption capacity of the adsorbent for each component in the gas mixture varies with pressure to separate and purify the required gas components from the gas mixture (mainly industrial waste gas) or to purify the gas mixture. Due to advantages such as low energy consumption, simple process, high purity of product gas, high degree of automation of the device, and simple operation, the PSA technology has been rapidly promoted and applied in industries such as chemical engineering, petrochemical engineering, chemical fertilizer, metallurgy, electronics, food, coal, machinery, and light industry.

[0003] Currently, the adsorbents for pressure swing adsorption separation of CO mainly consist of single homogeneous adsorbents. The single homogeneous adsorbent technology mainly has the following problems: 1) The cost of the adsorbent is relatively high, and the physical strength of the adsorbent is poor. 2) Poor thermal stability: The heat capacity of the single adsorbent is fixed. During use, the temperature changes significantly, the system temperature is prone to fluctuate, and it is not easy to control. 3) Low mass transfer coefficient: As the molecules diffuse towards the center of the adsorbent, the diffusion resistance becomes greater. Therefore, there is an urgent need to design an adsorbent with high removal efficiency, high strength, long life, and good thermal stability. Summary of the Invention

[0004] The present invention relates to a core-shell structured composite adsorbent with high adsorption performance and high physical strength. Compared with the existing copper-based adsorbents, the adsorbent prepared in the present invention has strong carbon monoxide adsorption ability, and the adsorbent has a large specific heat capacity, reducing the temperature change during the use of the adsorbent. The performance improvement is achieved by uniquely introducing a composite adsorbent with a core-shell structure. Such core-shell structured adsorbents not only improve the mass transfer rate, but also improve the temperature adaptability of the adsorbent, thereby suppressing the thermal gradient in the bed during the PSA cycle, and further increasing the working capacity of the adsorbent. The present invention uses a non-porous microsphere with a high heat capacity as the core, which can absorb more heat during the adsorption process, thereby increasing the adsorption capacity; and uses a shell containing CuY / X zeolite and an appropriate amount of inorganic binder, with a stable framework, reducing the wear during the use of the adsorbent and improving the mass transfer rate.

[0005] The object of the present invention is to improve the existing copper-based adsorbent for carbon monoxide, and prepare a composite adsorbent using an effective component with an adsorption ability for CO and an inert material with a large specific heat capacity but no adsorption ability for CO, which not only retains the high-efficiency adsorption ability for CO, but also increases the specific heat capacity of the adsorbent, and at the same time can reduce the loss of the existing active component during the adsorption process and reduce the temperature change during the adsorption and desorption process.

[0006] The present invention realizes the above object through the following technical solutions:

[0007] A composite adsorbent for pressure swing adsorption separation of carbon monoxide with a core-shell structure, with a microsphere having a high specific heat capacity and a non-porous structure as the core and a molecular sieve exchanged with divalent copper loaded with cuprous salt as the shell. The composite adsorbent comprises the following raw materials in parts by mass: 5-10 parts of a microsphere having a high specific heat capacity and a non-porous structure, 70-90 parts of a copper-based adsorbent precursor, and 5-10 parts of a binder. The copper-based adsorbent precursor is a mixture of cuprous salt and a molecular sieve exchanged with divalent copper in a mass ratio of 0.5-0.7:1.

[0008] Further, the microsphere having a high specific heat capacity and a non-porous structure has a particle size of 1-3 mm, a porosity <10%, and a density of 2-4 g / cm 3 , and a mass specific heat capacity of 0.7-0.9 J / g·°C; or a volume specific heat capacity of 1.5-3.5 J / cm 3 ·°C. Preferably, the microsphere having a high specific heat capacity and a non-porous structure has a porosity of 1-5%, such as 2%, 3%, 4%; and a density of 2.8-3.7 g / cm 3 . Specifically, the microsphere having a high specific heat capacity and a non-porous structure is selected from magnesia microspheres, alumina microspheres, glass microspheres, silica microspheres, and ceramic microspheres.

[0009] Further, the cuprous salt is at least one of CuCl, CuBr, and CuI, and the divalent copper-exchanged molecular sieve is at least one of Cu(II)Y and Cu(II)X. Further still, the divalent copper-exchanged molecular sieve is obtained by ion exchange in an aqueous solution of an X-type molecular sieve and / or a Y-type molecular sieve and a Cu(II) solution; the X-type molecular sieve is 13X, the Y-type molecular sieve is NaY, the solute of the Cu(II) solution is at least one of CuCl2, CuBr2, and Cu(NO3)2, and the concentration of Cu(II) in the Cu(II) solution is 0.5-0.8 mol / L; further still, the total amount of the molecular sieve (the total of the X-type molecular sieve and the Y-type molecular sieve) and the amount of the Cu(II) solution are such that the solid-liquid ratio is 1:10-30.

[0010] In a specific embodiment of the present invention, the conditions for the ion exchange of the X-type molecular sieve and / or the Y-type molecular sieve and the Cu(II) solution in an aqueous solution are at pH = 4-5 (for example, the pH is adjusted with ammonia water), and the ion exchange is carried out at 60-90 °C (for example, 70 °C, 75 °C, 80 °C) for 3-5 times, each time for 1-5 h.

[0011] Further, the binder is selected from at least one of clay and silicone resin. Preferably, the binder is natural clay with a particle size of 20-50 μm. Further, the clay is selected from at least one of kaolin, metakaolin, montmorillonite, sericite, bentonite, and sepiolite; the silicone resin is selected from polymethyl silicone resin and polyethyl silicone resin; preferably, it is methyl MQ-type silicone resin, and more preferably, the M:Q ratio of the methyl MQ-type silicone resin is 0.5-0.7, and the weight-average molecular weight is 5000-10000 g / mol.

[0012] In a preferred technical solution of the present invention, the binder is a mixture of kaolin and methyl MQ-type silicone resin in a mass ratio of 5-7:1-1.4. The inventors have found that the core-shell structure composite adsorbent prepared with the above-mentioned compounded binder has a more stable core-shell structure, high strength, and does not affect the adsorption and separation of carbon monoxide, significantly improving the stability of the composite adsorbent.

[0013] Further, the composite adsorbent further includes 1-2 parts by mass of a binder aid, and the binder aid is at least one of polyvinyl alcohol, hydroxypropyl methylcellulose, phenolic resin, acrylic resin, dextran, sodium silicate, and arabic gum. Preferably, it is a compound of hydroxypropyl methylcellulose and sodium silicate in a mass ratio of 4-7:1. The binder aid and the clay binder are used in combination, which can significantly improve the strength and abrasion resistance of the composite adsorbent. The inventors have also unexpectedly found that the above-mentioned compounded binder aid of hydroxypropyl methylcellulose and sodium silicate not only improves the strength of the core-shell structure of the composite adsorbent, but also improves the dispersion uniformity of the shell coating, making the catalyst stability more excellent.

[0014] The composite adsorbent for pressure swing adsorption separation of carbon monoxide with a core-shell structure provided by the present invention has an inert dense core and a shell with adsorption capacity. The advantages of using an inert core in the present invention are: first, after adding the inert core, the specific heat capacity of the adsorbent is increased, the unfavorable temperature gradient generated during adsorption and desorption can be controlled, the temperature change during adsorption and desorption is reduced, and the pressure swing adsorption process is easier to control. Second, inert particles are used as cores, and a proper amount of adhesive and copper salt are added to prepare a CO complex adsorbent. The adhesive is more firmly bonded, which improves the physical strength of the adsorbent, thereby extending the service life of the adsorbent and reducing the specific cost of the adsorbent. Third, after using an inert non-porous core, compared with a homogeneous adsorbent, it has a higher mass transfer rate and a lower pressure drop. In the PSA / VPSA system and process, due to the fast mass transfer rate, the cycle time can be reduced, and then the power consumption is reduced and the adsorbent productivity is increased.

[0015] The second object of the present invention is to provide a method for preparing the composite adsorbent for separating carbon monoxide by pressure swing adsorption of the core-shell structure, comprising the following steps:

[0016] (S1) mixing NaY and / or 13X molecular sieves with a Cu(II) solution at a certain solid-liquid ratio, adjusting the pH value to weak alkalinity with aqueous ammonia, and performing slurry exchange multiple times at 70-90° C. to obtain a divalent copper-exchanged molecular sieve;

[0017] (S2) mixing and grinding a divalent copper-exchanged molecular sieve and a cuprous salt, and auxiliary heating the resulting mixture at 350-500° C. and 10-50 KPa for 5-10 h to obtain a copper-based adsorbent precursor;

[0018] (S3) coating the microspheres with high specific heat capacity and non-porous structure, the copper-based adsorbent precursor obtained in step (S2), and a binder to prepare a composite adsorbent precursor having the microspheres with high specific heat capacity and non-porous structure as the core and the divalent copper-exchanged molecular sieve loaded with cuprous salt as the shell;

[0019] (S4) reducing the composite adsorbent precursor under a CO or H2 atmosphere at 150-250°C for 5-10 hours to obtain the composite adsorbent with core-shell structure for pressure swing adsorption separation of carbon monoxide.

[0020] Furthermore, in step (S1), the concentration of Cu(II) in the Cu(II) solution is 0.5-0.8 mol / L; the solid-liquid ratio of the molecular sieve to the Cu(II) solution is 1:10-30; the weak alkalinity is pH 4-6, preferably 4.2-5.5, and the molecular sieve is 13X and / or NaY.

[0021] Furthermore, in step (S2), the mass ratio of the cuprous salt to the molecular sieve exchanged with divalent copper is 0.5-0.7:1, preferably 0.58-0.66:1.

[0022] Furthermore, the coating process in step (S3) includes a mechanical ball rolling method and a roller coating method. Furthermore, the process parameters of the mechanical ball rolling method are a power of 250-400W and a rotation speed of 90-130rpm.

[0023] The present invention enhances mass transfer inside the adsorbent beads without increasing the pressure drop through the adsorbent container containing the adsorbent. The core of the inner layer is made of a material with a higher thermal conductivity / capacity, which increases the rate of heat dissipation conducted through the interior of the adsorbent beads, thereby improving the performance of adsorption processes (such as PSA and TSA). Improvements in mass transfer and heat transfer will produce better performance in the adsorption separation process. Another advantage is that the use of a higher density dense non-porous (porosity <10%) material in the inner layer allows for higher gas feed flow rates without fluidizing the adsorbent. Low pressure drop saves more electrical energy, and from a process design perspective, the increased fluidization limit allows the use of smaller containers and higher gas throughput, both of which increase productivity and reduce investment costs.

[0024] The composite adsorbent of the present invention has the following characteristics:

[0025] 1. By adding inert cores, the specific heat capacity of the adsorbent is increased, the unfavorable temperature gradient generated during adsorption and desorption can be controlled, the temperature change during the adsorption and desorption process is reduced, and the pressure swing adsorption process is easier to control.

[0026] Second, with the inert core as the center, a proper amount of binder and copper salt are added to obtain a carbon monoxide complex adsorbent. The binder is more firmly bonded, which improves the physical strength of the adsorbent, thereby extending the service life of the adsorbent and reducing the specific cost of the adsorbent.

[0027] 3. The composite adsorbent of the present invention has a higher mass transfer rate and a lower pressure drop. In the PSA / VPSA system and process, due to the fast mass transfer rate, the cycle time can be reduced, and then the power consumption can be reduced and the adsorbent productivity can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The XRD patterns of the original NaY powder and the original adsorbent, the composite adsorbent prepared in Example 1, analytically pure CuCl, and the added alumina;

[0029] Figure 2 is a photograph of the composite adsorbent prepared in Example 2;

[0030] Figure 3 This is a graph showing the adsorption and desorption of CO by the composite adsorbent prepared in Example 2 at different pressures;

[0031] Figure 4 are the temperature changes during 5 pressure swing adsorption cycles of Example 2 and Comparative Example 1. Detailed implementation manners

[0032] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. The following examples facilitate a better understanding of the present invention, but do not limit the present invention. The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0033] The natural clay is attapulgite clay, purchased from Guoxing Attapulgite Co., Ltd., and the particle size D50 is 24.8 μm.

[0034] Example 1

[0035] (S1) Mix the NaY molecular sieve raw powder with 0.8 mol / L CuCl2 solution at a solid-liquid ratio of 1:20; adjust the pH to 4.2 with ammonia water; exchange at 70 °C for 5 times, 2 h each time, and dry in an oven to obtain Cu(II)Y;

[0036] (S2) Mix the Cu(II)Y obtained in step (S1) with CuCl at a solid weight ratio of 1:0.57 and grind for 0.5 h, and perform vacuum-assisted heat treatment at 350 °C and 30 kPa for 5 h to obtain a copper-based adsorbent precursor;

[0037] (S3) Using the mechanical rolling ball method, add 10 parts by mass of silica microspheres (porosity 5%, density 2.3 g / cm 3 , particle size 2.5 mm), 5 parts by mass of kaolin, 1 part by mass of methyl MQ silicone resin (M:Q = 0.6, weight average molecular weight 8000 g / mol, the same in the following examples), 2 parts by mass of polyvinyl alcohol, and 85 parts by mass of the copper-based adsorbent precursor obtained in step (S2) for coating to obtain a composite adsorbent precursor;

[0038] (S4) Reduce the composite adsorbent precursor obtained in step (S3) in a carbon monoxide atmosphere at 100 KPa and 150 °C for 6 h to prepare a composite adsorbent with a core-shell structure for pressure swing adsorption separation of carbon monoxide.

[0039] Figure 1 are the XRD patterns of the NaY raw powder, the original adsorbent, the composite adsorbent prepared in Example 1, analytical pure CuCl, and the added alumina. It can be seen from the figure that no characteristic peak pattern of CuCl is observed in the core-shell adsorbent, which proves that the core-shell adsorbent has good dispersibility. Compared with the original adsorbent, an alumina peak pattern can be clearly seen at 65-70°, which proves that the core-shell adsorbent can observe the alumina core of the microspheres.

[0040] Example 2

[0041] (S1) Mix the 13X molecular sieve raw powder with 0.5 mol / L CuCl₂ solution at a solid-liquid ratio of 1:30; adjust the pH to 4.6 with ammonia water; exchange at 80 °C for 5 times, 2 h each time, to obtain Cu(II)X;

[0042] (S2) Mix the Cu(II)X obtained in step (S1) with CuCl at a solid weight ratio of 1:0.62 and grind for 0.5 h, then perform vacuum-assisted heat treatment at 500 °C and 10 kPa for 7 h to obtain the copper-based adsorbent precursor;

[0043] (S3) Using the mechanical rolling ball method, add 5 parts by mass of alumina microspheres (porosity 3%, density 3.8 g / cm 3 , particle size 2.1 mm), 5 parts by mass of kaolin, 1 part by mass of methyl MQ silicone resin, 2 parts by mass of hydroxypropyl methylcellulose, and 90 parts by mass of the copper-based adsorbent precursor obtained in step (S2) for coating to obtain the composite adsorbent precursor;

[0044] (S4) Reduce the composite adsorbent precursor obtained in step (S3) in a hydrogen atmosphere at 150 kPa and 250 °C for 5 h to prepare the product, a composite adsorbent for pressure swing adsorption separation of carbon monoxide with a core-shell structure.

[0045] Figure 2 is a photo of the composite adsorbent prepared in Example 2.

[0046] Figure 3 is the adsorption and desorption diagram of CO by the composite adsorbent prepared in Example 2 at different pressures.

[0047] Example 3

[0048] (S1) Mix the 13X molecular sieve raw powder with 0.7 mol / L CuCl₂ solution at a solid-liquid ratio of 1:20; adjust the pH to 5.5 with ammonia water; exchange at 90 °C for 5 times, 2 h each time, to obtain Cu(II)X;

[0049] (S2) Mix the Cu(II)X obtained in step (S1) with CuCl at a solid weight ratio of 1:0.66 and grind for 0.5 h, then perform vacuum-assisted heat treatment at 400 °C and 20 kPa for 6 h to obtain the copper-based adsorbent precursor;

[0050] (S3) Using the mechanical rolling ball method, add 5 parts by mass of alumina microspheres (porosity 3%, density 3.8 g / cm 3, 7 parts by mass of kaolin with a particle size of 2.1 mm, 1.4 parts by mass of methyl MQ silicone resin, 2 parts by mass of sodium silicate, and 90 parts by mass of the copper-based adsorbent precursor obtained in step (S2) are wrapped to obtain a composite adsorbent precursor;

[0051] (S4) The composite adsorbent precursor obtained in step (S3) is reduced in a hydrogen atmosphere at 150 kPa and 250 °C for 5 h to prepare a composite adsorbent with a product core-shell structure for pressure swing adsorption separation of carbon monoxide.

[0052] Example 4

[0053] (S1) 13X molecular sieve raw powder is mixed with 1 mol / L CuCl2 solution at a solid-liquid ratio of 1:15; the pH is adjusted to 4.6 with ammonia water; exchanged 5 times at 80 °C for 2 h each time to obtain Cu(II)X;

[0054] (S2) The Cu(II)X obtained in step (S1) is mixed and ground with CuCl at a solid weight ratio of 1:0.63 for 0.5 h, and vacuum-assisted heat treatment is carried out at 450 °C and 30 kPa for 7 h to obtain a copper-based adsorbent precursor;

[0055] (S3) Using the mechanical rolling ball method, 10 parts by mass of alumina microspheres (porosity 3%, density 3.8 g / cm 3 , particle size 2.1 mm), 5 parts by mass of kaolin, 1 part by mass of methyl MQ silicone resin, 1 part by mass of hydroxypropyl methyl cellulose, and 80 parts by mass of the copper-based adsorbent precursor obtained in step (S2) are wrapped to obtain a composite adsorbent precursor;

[0056] (S4) The composite adsorbent precursor obtained in step (S3) is reduced in a hydrogen atmosphere at 150 kPa and 250 °C for 5 h to prepare a composite adsorbent with a product core-shell structure for pressure swing adsorption separation of carbon monoxide.

[0057] Example 5

[0058] Other conditions and operations are the same as in Example 2, except that 2 parts by mass of hydroxypropyl methyl cellulose are replaced by a compound of 1.6 parts by mass of hydroxypropyl methyl cellulose and 0.4 parts by mass of sodium silicate.

[0059] Example 6

[0060] Other conditions and operations are the same as in Example 5, except that methyl MQ silicone resin is not added.

[0061] Example 7

[0062] Other conditions and operations are the same as in Example 2, except that 2 parts by mass of hydroxypropyl methyl cellulose are replaced by a compound of 1.75 parts by mass of hydroxypropyl methyl cellulose and 0.25 parts by mass of sodium silicate.

[0063] Example 8

[0064] Other conditions and operations are the same as those in Example 2, except that 2 parts by mass of hydroxypropyl methylcellulose are replaced by a compound of 1.6 parts by mass of hydroxypropyl methylcellulose and 0.4 parts by mass of phenolic resin.

[0065] Example 9

[0066] Other conditions and operations are the same as those in Example 2, except that 2 parts by mass of hydroxypropyl methylcellulose are replaced by a compound of 1.6 parts by mass of hydroxypropyl methylcellulose and 0.4 parts by mass of acrylic resin.

[0067] Comparative Example 1

[0068] (S1) Mix 13X molecular sieve raw powder with 0.5 mol / L CuCl2 solution at a solid-liquid ratio of 1:30; adjust the pH to 4.6 with ammonia water; exchange at 80 °C for 5 times, 2 h each time, to obtain Cu(II)X;

[0069] (S2) Mix the Cu(II)X obtained in step (S1) with CuCl at a solid weight ratio of 1:0.62 and grind for 0.5 h, and perform vacuum-assisted heat treatment at 500 °C and 10 kPa for 7 h to obtain a copper-based adsorbent precursor;

[0070] (S3) Using the mechanical rolling ball method, add 5 parts by mass of clay, 2 parts by mass of hydroxypropyl methylcellulose, and 90 parts by mass of the copper-based adsorbent precursor obtained in step (S2) to the rolling ball machine for coating to obtain a composite adsorbent precursor;

[0071] (S4) Reduce the composite adsorbent precursor obtained in step (S3) in a hydrogen atmosphere at 150 kPa and 250 °C for 5 h to prepare a composite adsorbent with a core-shell structure for pressure swing adsorption separation of carbon monoxide.

[0072] Effect Example

[0073] Perform the following performance tests on the composite adsorbents obtained in the above examples and comparative examples, and the results are shown in Table 1 below.

[0074] 1. Mechanical strength: Refer to Part 3 of GB / T 30202.3-2013, compressive strength, and use a ZQJ-II intelligent particle strength tester (manufactured by Dalian Intelligent Testing Machine Factory, supervised by the National Chemical Catalyst Testing Center). Randomly select 20 composite adsorbent microspheres to test the compressive strength and take the average value.

[0075] 2. Abrasion rate: Refer to GB / T 10505.2-1989, the determination method of the abrasion rate of 3A molecular sieve, and calculate according to the formula abrasion rate = mass difference between the samples before and after abrasion / mass of the sample before abrasion × 100%.

[0076] 3.CO adsorption capacity is tested at 25°C and 1 atmosphere using a Micromertics ASAP 2050 Xtended Pressure Sorption Analyzer.

[0077] 4. Pressure swing adsorption stability of adsorbent. The composite adsorbents of the embodiments and comparative examples are subjected to the steps of adsorption, pressure equalization and decompression, inversion, vacuuming, pressure equalization and decompression, and final pressure increase.

[0078] Figure 4 It is the change of the temperature of the adsorbent layer in Example 2 and Comparative Example 1 after 5 pressure swing adsorption cycles (each cycle is 100s, and the temperature of the adsorption and desorption bed is controlled at 70°C). It can be seen that using the composite adsorbent with a core-shell structure of the present invention, the temperature change of the composite adsorbent of Example 2 during the entire pressure swing adsorption / desorption process is much lower than that of the homogeneous adsorbent of Comparative Example 1. In the PSA / VPSA system and process, due to the fast mass transfer rate, the cycle time can be reduced, and then the power consumption is reduced and the adsorbent productivity is increased, thereby improving the use efficiency of the adsorbent. At the same time, due to the large specific heat capacity of the adsorbent, the thermal gradient in the adsorption bed during the PSA cycle is suppressed, the working capacity of the adsorbent bed is increased, the pressure drop is reduced, and the power consumption is reduced.

[0079] Table 1 Composite adsorbent performance test results

[0080]

[0081]

[0082] It can be seen that the composite adsorbent for separating carbon monoxide by pressure swing adsorption with a core-shell structure of the present invention, by adding an inert core with high specific heat capacity, significantly reduces the temperature change of the adsorbent during the pressure swing adsorption process without significantly reducing the CO adsorption capacity, thereby significantly improving the stability. The introduction of the core-shell structure, on the one hand, reduces the loss rate of the adsorbent during operation, and on the other hand, improves the phenomenon of the adsorption capacity of the adsorbent decreasing due to temperature changes during the pressure swing adsorption process, thereby greatly extending the service life of the adsorbent.

Claims

1. A composite adsorbent with a core-shell structure for separating carbon monoxide by pressure swing adsorption, characterized in that, It uses microspheres with high specific heat capacity and a non-porous structure as the core, and zeolites exchanged with divalent copper loaded with cuprous salts as the shell. The composite adsorbent comprises the following raw materials in parts by mass: 5 - 10 parts of microspheres with high specific heat capacity and a non-porous structure, 70 - 90 parts of copper-based adsorbent precursor, and 5 - 10 parts of binder. The copper-based adsorbent precursor is a mixture of cuprous salt and zeolite exchanged with divalent copper in a mass ratio of 0.5 - 0.7:1; the binder is a mixture of kaolin and methyl MQ silicone resin in a mass ratio of 5 - 7:1 - 1.4; the microspheres with high specific heat capacity and a non-porous structure have a particle size of 1 - 3 mm, a porosity < 10%, and a density of 2 - 4 g / cm 3 , and a mass specific heat capacity of 0.7 - 0.9 J / g·°C or a volume specific heat capacity of 1.5 - 3.5 J / cm 3 ·°C; The composite adsorbent further comprises 1-2 parts by mass of a binding aid, and the binding aid is a compound of hydroxypropyl methylcellulose and sodium silicate in a mass ratio of 4-7:

1.

2. The composite adsorbent according to claim 1, wherein The porosity of the microspheres with high specific heat capacity and non-porous structure is 1-5%, and the density is 2.8-3.7 g / cm 3 .

3. The composite adsorbent according to claim 1, wherein The microspheres with high specific heat capacity and non-porous structure are selected from magnesia microspheres, alumina microspheres, glass microspheres, silica microspheres, and ceramic microspheres.

4. The composite adsorbent according to claim 1, characterized in that, The cuprous salt is at least one of CuCl, CuBr, and CuI, and the divalent copper-exchanged molecular sieve is at least one of Cu(II)Y and Cu(II)X.

5. The composite adsorbent according to claim 4, wherein, The divalent copper-exchanged molecular sieve is obtained by ion exchange of X-type molecular sieve and / or Y-type molecular sieve with a Cu(II) solution in an aqueous solution; the X-type molecular sieve is 13X, the Y-type molecular sieve is NaY, the solute of the Cu(II) solution is at least one of CuCl2, CuBr2, and Cu(NO3)2, and the concentration of Cu(II) in the Cu(II) solution is 0.5-0.8 mol / L; the total amount of the molecular sieve and the amount of the Cu(II) solution satisfy a solid-liquid ratio of 1:10-30; the total amount of the molecular sieve is the sum of the X-type molecular sieve and the Y-type molecular sieve.

6. The composite adsorbent according to claim 1, wherein The M:Q ratio of the methyl MQ silicone resin is 0.5-0.7, and the weight average molecular weight is 5000-10000 g / mol.

7. The preparation method of the composite adsorbent for pressure swing adsorption separation of carbon monoxide with the core-shell structure according to any one of claims 1-6, characterized in that, It includes the following steps: (S1) Mix NaY and / or 13X type molecular sieve with a Cu(II) solution at a certain solid-liquid ratio, adjust the pH value to 4-6 with ammonia water, and perform multiple pulping exchanges at 70-90 °C to obtain a divalent copper-exchanged molecular sieve. (S2) Mix and grind the divalent copper-exchanged molecular sieve with the cuprous salt, and assist in heating the obtained mixture at 350-500 °C and 10-50 KPa for 5-10 h to obtain a copper-based adsorbent precursor. (S3) Perform a coating process on the microspheres with high specific heat capacity and non-porous structure, the copper-based adsorbent precursor obtained in step (S2), and the binder to prepare a composite adsorbent precursor with the microspheres with high specific heat capacity and non-porous structure as the core and the divalent copper-exchanged molecular sieve loaded with the cuprous salt as the shell. (S4) Reduce the composite adsorbent precursor in a CO or H2 atmosphere at 150-250 °C for 5-10 h to obtain the composite adsorbent for pressure swing adsorption separation of carbon monoxide with a core-shell structure.

8. The preparation method according to claim 7, characterized in that, In step (S1), the concentration of Cu(II) in the Cu(II) solution is 0.5-0.8 mol / L; the solid-liquid ratio of the molecular sieve and the Cu(II) solution is 1:10-30; the pH value is adjusted to 4.2-5.5 with ammonia water, and the molecular sieve is 13X and / or NaY.

9. The preparation method according to claim 7, characterized in that, In step (S2), the mass ratio of the cuprous salt to the divalent copper-exchanged molecular sieve is 0.5-0.7:

1.

10. The preparation method according to claim 7, characterized in that, In step (S2), the mass ratio of the cuprous salt to the divalent copper-exchanged molecular sieve is 0.58-0.66:1.

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