LSX type and A type molecular sieve composite adsorbent and seed-crystal-free controllable preparation method

Abstract

The invention discloses an LSX type and A type molecular sieve composite adsorbent and a seed-crystal-free controllable preparation method. The preparation method comprises the following steps: uniformly mixing kaolin and a pore-enlarging agent, and carrying out auxiliary molding by using an ammonium salt solution; drying and roasting a formed sample, uniformly dispersing the formed sample into alkali liquor, carrying out low-temperature aging and high-temperature crystallization, and then washing, drying and roasting to obtain the LSX type and A type molecular sieve composite adsorbent. Wherein low-temperature aging and high-temperature crystallization are controlled to be performed in a static state, a dynamic state or a combination of the static state and the dynamic state, so that the ratio of the LSX type molecular sieve to the A type molecular sieve in the obtained composite adsorbent is regulated and controlled. Kaolin is used as a main raw material, a large number of molecular sieves, silicon sources and aluminum sources do not need to be additionally added, and the preparation cost of the adsorbent is greatly reduced; the ammonium salt solution is added into the kaolin powder in the forming process, so that kaolin forming can be promoted; the ratio of the LSX type molecular sieve to the A type molecular sieve in the molecular sieve composite adsorbent is regulated and controlled in a static and dynamic aging (crystallization) manner.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molecular sieve adsorbents, in particular to a LSX type and A type molecular sieve composite adsorbent and a seed-free controllable preparation method. BACKGROUND

[0002] Molecular sieve adsorbents have the advantages of large specific surface area, uniform pore size, easy ion modification, strong adsorption performance, etc., and are the core components of pressure swing adsorption purification devices, and are widely used in the fields of gas adsorption and separation and purification.

[0003] Molecular sieve composite adsorbents have rich pore sizes and pore structures, can increase the types of gas adsorption and improve the gas adsorption capacity compared with pure crystal molecular sieves, can produce a synergistic effect on the adsorption of multiple gases, and have application potential in the adsorption and separation of mixed gases. However, a large amount of molecular sieve raw powder is usually added as a seed during the preparation of the molecular sieve composite adsorbent, and a silicon source or an aluminum source is introduced according to the type of the molecular sieve adsorbent to be prepared, resulting in high preparation cost and difficulty in large-scale production. In addition, when the amount of molecular sieve raw powder in the raw material combination is reduced or no molecular sieve raw powder is used during the preparation of the molecular sieve composite adsorbent, the raw material will face the problem of molding difficulty, resulting in the inability to prepare a molded adsorbent with certain strength, and thus the inability to be applied to a pressure swing adsorption purification device.

[0004] CN116078346A discloses a preparation method of an X type molecular sieve and an A type molecular sieve composite adsorbent. The technology uses the binder in the 13X molecular sieve adsorbent to provide the required aluminum source, and under the conditions of an additional silicon source and an alkali solution, an X type molecular sieve and an A type molecular sieve composite adsorbent are prepared by hydrothermal synthesis. However, the 13X molecular sieve adsorbent contains 80% to 90% of 13X molecular sieve raw powder, and the introduction of an external silicon source results in high raw material cost and difficulty in large-scale industrialization.

[0005] CN109485058A discloses a preparation method of a binder-free LSX molecular sieve, which uses LSX molecular sieve powder and kaolin as raw materials, mixes and shapes, dries and calcines, and then crystallizes in an alkali solution, and after sodium ion exchange, a binder-free NaLSX molecular sieve is obtained. A large amount of LSX molecular sieve powder is added during the preparation of the binder-free LSX molecular sieve adsorbent, resulting in high preparation cost and unsuitability for industrial production.

[0006] CN101524637B discloses a method for preparing a binder-free adsorbent rich in LSX molecular sieves. The method involves mixing KNaLSX with binder components, slurrying, filtering, washing, drying, adding a silicon source, molding, and then heating in a sodium hydroxide solution to crystallize into X-type zeolite. Finally, cation exchange is performed using a sodium-soluble salt solution. This technology introduces a large amount of KNaLSX molecular sieves as seed crystals, adds an external silicon source, and uses sodium salts for exchange, increasing raw material costs and preparation steps, and is time-consuming, making it unsuitable for industrial production.

[0007] CN116408044A discloses an attapulgite / molecular sieve composite adsorbent, its preparation method, and its application. Using NaX molecular sieve powder as raw material, attapulgite and an aluminum source are added for crystallization. After drying, an attapulgite / molecular sieve composite adsorbent precursor is obtained. After metal cation exchange, it is further shaped and activated to obtain the composite adsorbent. The raw materials for preparing the adsorbent contain NaX molecular sieve powder and an exogenous aluminum source, making the raw materials complex and uneconomical.

[0008] To address the problems of excessive raw material types, high cost, and complex preparation processes caused by the additional addition of large amounts of molecular sieve powder as seed crystals, external silicon sources, and aluminum sources during the preparation of molecular sieve composite adsorbents using kaolin as raw material, this invention provides a seedless LSX-type and A-type molecular sieve composite adsorbent and its preparation method. Summary of the Invention

[0009] The purpose of this invention is to provide a seedless and controllable preparation method for an LSX-type and A-type molecular sieve composite adsorbent. Compared with existing technologies for preparing molecular sieve composite adsorbents, the preparation method of this invention uses kaolin as the main raw material, eliminating the need for adding large amounts of molecular sieves, silicon sources, and aluminum sources, thus significantly reducing the cost of adsorbent preparation. Adding ammonium salt solution to the kaolin powder during the molding process promotes kaolin molding. Furthermore, the ratio of LSX-type and A-type molecular sieves in the molecular sieve composite adsorbent can be controlled through static and dynamic aging (crystallization) methods.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] This invention provides a seedless and controllable preparation method for an LSX-type and A-type molecular sieve composite adsorbent, wherein the preparation method includes the following steps:

[0012] After the kaolin and the pore-expanding agent are mixed evenly, the molding is assisted by ammonium salt solution. After the molded sample is dried and calcined, it is evenly dispersed in alkaline solution and subjected to low-temperature aging and high-temperature crystallization treatment. Then it is washed, dried and calcined to obtain LSX-type and A-type molecular sieve composite adsorbent.

[0013] The ratio of LSX-type and A-type molecular sieves in the resulting composite adsorbent is adjusted by controlling low-temperature aging and high-temperature crystallization under static, dynamic, or combined static and dynamic conditions.

[0014] Specifically, dynamic aging and crystallization processes tend to synthesize more LSX-type molecular sieves, while static aging and crystallization processes tend to synthesize A-type molecular sieves.

[0015] According to the seedless controllable preparation method of the present invention, preferably, the silicon-aluminum molar ratio of the kaolin is (1.8-2.2):1.

[0016] According to the seedless controllable preparation method of the present invention, preferably, the pore-expanding agent is selected from at least one of sodium carboxymethyl cellulose, urea, calcium carbonate, and starch.

[0017] According to the seedless controllable preparation method of the present invention, preferably, the amount of the pore-expanding agent added is 1% to 10% of the mass of kaolin; more preferably, it is 2% to 5%.

[0018] According to the seedless controllable preparation method of the present invention, preferably, the ammonium salt is selected from ammonium chloride, ammonium carbonate, and ammonium sulfate; the concentration of the ammonium salt solution is 0.1–5 mol / L, more preferably 0.5–2 mol / L. Those skilled in the art will understand that the solvent of the ammonium salt solution is water.

[0019] According to the seedless controllable preparation method of the present invention, preferably, the molding method is rolling granulation, extrusion granulation, etc.

[0020] According to the seedless controllable preparation method of the present invention, preferably, the drying temperature of the molded sample is 100-120°C, and the drying time is 1-5 hours. For example, drying at 120°C for 2 hours is sufficient to achieve the drying purpose.

[0021] According to the seedless controllable preparation method of the present invention, preferably, the calcination temperature of the shaped sample is 650-800°C and the calcination time is 1-3 hours.

[0022] According to the seedless controllable preparation method of the present invention, preferably, the alkaline solution is a mixed alkaline solution of sodium hydroxide and potassium hydroxide.

[0023] More preferably, the amount of kaolin is calculated based on silicon dioxide, and the amount of the mixed alkaline solution is calculated based on the sum of sodium oxide and potassium oxide. In the mixed alkaline solution, the molar ratio of water to the sum of sodium oxide and potassium oxide is (15-20):1, and the molar ratio of potassium oxide to the sum of sodium oxide and potassium oxide is (0.1-0.4):1. In the addition ratio of the mixed alkaline solution and kaolin, the molar ratio of the sum of sodium oxide and potassium oxide to silicon dioxide is (2.0-4.0):1.

[0024] According to the seedless controllable preparation method of the present invention, preferably, the aging temperature of the low-temperature aging is 40-70°C, more preferably 50-60°C, and the aging time is 3-18 hours.

[0025] According to the seedless controllable preparation method of the present invention, preferably, the crystallization temperature of the high-temperature crystallization is 80-100°C, more preferably 90-95°C, and the crystallization time is 2-15 hours.

[0026] According to the seedless controllable preparation method of the present invention, preferably, the sum of the aging time of the low-temperature aging and the crystallization time of the high-temperature crystallization is 15-20 hours.

[0027] According to the seedless controllable preparation method of the present invention, preferably, static aging or static crystallization involves placing the reaction raw materials in a polytetrafluoroethylene liner, sealing the reaction vessel, and then placing it in a forced-air drying oven for aging or crystallization reaction.

[0028] According to the seedless controllable preparation method of the present invention, preferably, dynamic aging or dynamic crystallization involves placing the reaction raw materials in a polytetrafluoroethylene liner, sealing the reaction vessel, and then placing it in a homogeneous reactor for aging or crystallization reaction, wherein the rotation speed of the homogeneous reactor is 50-200 r / min.

[0029] According to the seedless controllable preparation method of the present invention, the washing is specifically water washing; preferably, water washing is performed until pH < 9.

[0030] According to the seedless controllable preparation method of the present invention, the drying method can be any conventional drying method, and the present invention does not limit it. For example, drying at 100-120°C for 1-5 hours is sufficient to achieve the drying purpose.

[0031] In another aspect, the present invention provides an LSX-type and A-type molecular sieve composite adsorbent, which is obtained by any of the above-mentioned seedless controllable preparation methods.

[0032] The beneficial effects of this invention include:

[0033] 1) This invention uses kaolin as the sole silicon and aluminum source to prepare LSX-type and A-type molecular sieve composite adsorbents, eliminating the need for additional LSX-type or A-type molecular sieves, silicon sources, and aluminum sources, thus significantly reducing raw material costs and simplifying the process.

[0034] 2) In this invention, an ammonium salt solution is added during the kaolin molding process to promote the bonding and molding of kaolin powder. Kaolin has a negative surface zeta potential in a neutral or alkaline environment, and its surface is primarily negatively charged. NH4+ + It can be adsorbed onto the surface of kaolin through electrostatic interactions. In addition, NH4... +Hydrogen atoms in kaolin can form hydrogen bonds with oxygen atoms in the silicon-oxygen tetrahedra and aluminum-oxygen octahedra of the kaolin structure. Therefore, adding ammonium salt solution to kaolin powder during rolling granulation or when kneading materials before extrusion granulation helps to shape the kaolin.

[0035] 3) This invention can control the ratio of LSX-type and A-type molecular sieves in a molecular sieve composite adsorbent by combining static and dynamic aging (crystallization). The static crystallization process tends to form A-type molecular sieves with stable crystal structure, tightly connected structural units, and small pore size, while the dynamic crystallization process tends to form LSX-type molecular sieves with loose crystal structure and large pore size. Attached Figure Description

[0036] Figure 1 The XRD patterns are those of the products from Examples 1 and 2.

[0037] Figure 2 The image shows the static CO2 adsorption diagrams of the products from Examples 1 and 2. Detailed Implementation

[0038] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0039] All numerical specifications in this invention (e.g., temperature, time, concentration, and weight, including ranges for each) are generally approximate values ​​that may be changed (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about".

[0040] Source of raw materials or equipment:

[0041] In this embodiment of the invention, the kaolin is analytical grade, with a silicon-to-aluminum molar ratio of 2.05, and is manufactured by Suzhou Kaolin Co., Ltd., China; the ammonium chloride is analytical grade (≥99.5%), and is manufactured by Sinopharm Chemical Reagent Co., Ltd.; the ammonium sulfate is analytical grade (≥99.0%), and is manufactured by Sinopharm Chemical Reagent Co., Ltd.; the ammonium carbonate is analytical grade, and is manufactured by Sinopharm Chemical Reagent Co., Ltd.; the sodium carboxymethyl cellulose is chemically pure, with a viscosity of 800–1200 mPa·s, and is manufactured by Sinopharm Chemical Reagent Co., Ltd.; the calcium carbonate is analytical grade (≥99%), and is manufactured by Sinopharm Chemical Reagent Co., Ltd.; the urea is analytical grade (≥99.5%), and is manufactured by Sinopharm Chemical Reagent Co., Ltd.; the sodium hydroxide is analytical grade (≥96%), and is manufactured by Sinopharm Chemical Reagent Co., Ltd.; and the potassium hydroxide is analytical grade (≥85%), and is manufactured by Sinopharm Chemical Reagent Co., Ltd. The coating machine, model BY300A, is manufactured by Shanghai Huanghai Pharmaceutical Testing Instruments Co., Ltd.; the single-screw extruder, model DJ-26, is manufactured by Guangzhou Huagong Opto-Mechatronics Technology Co., Ltd.; the X-ray diffractometer, model X Pert PRO, is manufactured by Panaco (Netherlands); the X-ray fluorescence spectrometer, model ZSX primusⅡ, is manufactured by Rigaku (Japan); and the static physicochemical adsorption analyzer, model ASAP2020 HD88, is manufactured by Micron Instruments (USA).

[0042] Example 1

[0043] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A1, including the following steps:

[0044] 800g of kaolin ground into fine powder was mixed evenly with 16g of sodium carboxymethyl cellulose and then rolled into granules in a coating machine. During the granulation process, 0.5mol / L ammonium chloride solution was sprayed into the powder until most of the powder formed spherical particles. The spherical samples were dried at 120℃ for 2h and calcined at 650℃ for 3h before use.

[0045] Dissolve 105g NaOH and 49.5g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0046] 60.2 g of the calcined spherical sample was added to the mixed alkaline solution and stirred until homogeneous. Under static conditions, the sample was aged at 60℃ for 13 h, crystallized at 90℃ for 3 h, filtered, washed with water until pH < 9, dried at 120℃ for 2 h, and calcined at 500℃ for 2 h to obtain the LSX / A-A1 molecular sieve composite adsorbent. XRD patterns are shown below. Figure 1 The static CO2 adsorption curve is shown in the figure. Figure 2 .

[0047] Example 2

[0048] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A2, including the following steps:

[0049] 1 kg of kaolin ground into fine powder was mixed evenly with 50 g of sodium carboxymethyl cellulose and then rolled into a coating machine for granulation. During the granulation process, 1 mol / L ammonium chloride solution was sprayed into the powder until most of the powder formed spherical particles. The spherical samples were dried at 120℃ for 2 h and calcined at 700℃ for 2 h before use.

[0050] Dissolve 89g NaOH and 42.1g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0051] 52.5g of the calcined spherical sample was added to the mixed alkaline solution and stirred until homogeneous. The mixture was aged at 60℃ for 5 hours at a constant dynamic rotation speed of 100 rpm, crystallized at 95℃ for 12 hours, filtered, washed with water until pH < 9, dried at 120℃ for 2 hours, and calcined at 500℃ for 2 hours to obtain the LSX / A-A2 molecular sieve composite adsorbent. XRD patterns are shown below. Figure 1 The static CO2 adsorption curve is shown in the figure. Figure 2 .

[0052] from Figure 1 It can be seen that LSX / A-A1 and LSX / A-A2 exhibit characteristic diffraction peaks of type X molecular sieve at 2θ values ​​of 6.1°, 11.7°, 15.4°, 18.4°, 20.0°, 23.3°, 26.6°, 30.3°, 30.9°, and 33.5°, and characteristic diffraction peaks of type A molecular sieve at 2θ values ​​of 7.2°, 12.5°, 16.1°, 21.7°, 24.0°, 26.1°, 27.1°, and 29.9°, indicating that the products possess the crystal structures of both type LSX and type A molecular sieves. This method successfully prepared composite adsorbents of type LSX and type A molecular sieves.

[0053] from Figure 2 It can be seen that the carbon dioxide adsorption capacities of LSX / A-A1 and LSX / A-A2 are 118.1 cm⁻¹, respectively. 3 / g and 114.5cm 3 / g indicates that the LSX-type and A-type molecular sieve composite adsorbent has excellent carbon dioxide adsorption capacity.

[0054] Example 3

[0055] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A3, including the following steps:

[0056] 1 kg of finely ground kaolin was mixed evenly with 50 g of calcium carbonate, and then 2 mol / L ammonium sulfate solution was added to knead it into a plastic body. The mixture was then extruded in an extruder, dried at 120°C for 2 hours, and calcined at 750°C for 2 hours before use.

[0057] Dissolve 105g NaOH and 49.5g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0058] 86.6g of the calcined strip sample was added to the mixed alkaline solution and stirred until homogeneous. The sample was then aged at 50℃ for 10 hours under static conditions, followed by crystallization at 95℃ for 5 hours at a dynamic speed of 100r / min. After filtration and washing with water until pH < 9, the sample was dried at 120℃ for 2 hours and calcined at 500℃ for 2 hours to obtain the LSX / A-A3 molecular sieve composite adsorbent.

[0059] Example 4

[0060] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A4, including the following steps:

[0061] 2 kg of finely ground kaolin was mixed evenly with 40 g of urea, and then a 2 mol / L ammonium carbonate solution was added to knead it into a plastic body. The mixture was then extruded in an extruder, dried at 120°C for 2 hours, and calcined at 800°C for 1 hour before being put into use.

[0062] Dissolve 99g NaOH and 46.8g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0063] 56.6g of the calcined strip sample was added to the mixed alkaline solution and stirred until homogeneous. The sample was aged at 70℃ for 3 hours at a dynamic speed of 100 r / min, then crystallized at 80℃ for 15 hours under static conditions. After filtration and washing with water until pH < 9, the sample was dried at 120℃ for 2 hours and calcined at 500℃ for 2 hours to obtain the LSX / A-A4 molecular sieve composite adsorbent.

[0064] Example 5

[0065] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A5, including the following steps:

[0066] 800g of kaolin ground into fine powder was mixed evenly with 16g of sodium carboxymethyl cellulose and then rolled into granules in a coating machine. During the granulation process, 0.5mol / L ammonium chloride solution was sprayed into the powder until most of the powder formed spherical particles. The spherical samples were dried at 120℃ for 2h and calcined at 650℃ for 3h before use.

[0067] Dissolve 105g NaOH and 49.5g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0068] 60.2g of the calcined spherical sample was added to the mixed alkaline solution and stirred until homogeneous. The mixture was aged at 60℃ for 13h under a dynamic rotation speed of 50r / min throughout the process, crystallized at 90℃ for 3h, filtered, washed with water until pH < 9, dried at 120℃ for 2h, and calcined at 500℃ for 2h to obtain the LSX / A-A5 composite molecular sieve adsorbent.

[0069] Example 6

[0070] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A6, including the following steps:

[0071] 1 kg of kaolin ground into fine powder was mixed evenly with 50 g of sodium carboxymethyl cellulose and then rolled into a coating machine for granulation. During the granulation process, 1 mol / L ammonium chloride solution was sprayed into the powder until most of the powder formed spherical particles. The spherical samples were dried at 120℃ for 2 h and calcined at 700℃ for 2 h before use.

[0072] Dissolve 89g NaOH and 42.1g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0073] 52.5g of the calcined spherical sample was added to the mixed alkaline solution and stirred until homogeneous. Under static conditions, the sample was aged at 60℃ for 5h, crystallized at 95℃ for 12h, filtered, washed with water until pH < 9, dried at 120℃ for 2h, and calcined at 500℃ for 2h to obtain the LSX-type and A-type molecular sieve composite adsorbent LSX / A-A6.

[0074] Example 7

[0075] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A7, including the following steps:

[0076] 1 kg of finely ground kaolin was mixed evenly with 20 g of starch and then rolled into a coating machine for granulation. During the granulation process, 0.5 mol / L ammonium chloride solution was sprayed into the powder until most of the powder formed spherical particles. The spherical samples were dried at 120℃ for 2 h and calcined at 750℃ for 2 h before use.

[0077] Dissolve 139g NaOH and 24.4g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0078] 59.7g of the calcined spherical sample was added to the mixed alkaline solution and stirred until homogeneous. Under static conditions, the sample was aged at 40℃ for 18h, crystallized at 100℃ for 2h, filtered, washed with water until pH < 9, dried at 120℃ for 2h, and calcined at 500℃ for 2h to obtain the LSX-type and A-type molecular sieve composite adsorbent LSX / A-A7.

[0079] Example 8

[0080] This embodiment prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A8, including the following steps:

[0081] 1 kg of finely ground kaolin was mixed evenly with 20 g of starch and then rolled into a coating machine for granulation. During the granulation process, 0.5 mol / L ammonium chloride solution was sprayed into the powder until most of the powder formed spherical particles. The spherical samples were dried at 120℃ for 2 h and calcined at 700℃ for 2 h before use.

[0082] Dissolve 82g NaOH and 86.1g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0083] 105.1g of the calcined spherical sample was added to the mixed alkaline solution and stirred until homogeneous. The mixture was aged at 40℃ for 18h at a dynamic rotation speed of 200r / min throughout the process, crystallized at 100℃ for 2h, filtered, washed with water until pH < 9, dried at 120℃ for 2h, and calcined at 500℃ for 2h to obtain the LSX / A-A8 composite adsorbent of LSX and A-type molecular sieves.

[0084] Comparative Example 1

[0085] This comparative example includes the following steps:

[0086] 800g of kaolin ground into fine powder was placed in a coating machine for granulation. During the granulation process, an aqueous solution was sprayed into the powder. The powder was difficult to form spherical particles, making it impossible to carry out subsequent experimental steps such as drying, calcination, aging, and crystallization.

[0087] Comparative Example 2

[0088] This comparative example includes the following steps:

[0089] 1 kg of finely ground kaolin was mixed evenly with 50 g of calcium carbonate, and then an aqueous solution was added to knead it into a plastic body. However, it was difficult to extrude strip-shaped samples into the plastic body in the extruder, making it impossible to carry out subsequent experimental steps such as drying, calcination, aging, and crystallization.

[0090] Comparative Example 3

[0091] This comparative example prepares an LSX-type and A-type molecular sieve composite adsorbent LSX / A-A9, including the following steps:

[0092] 1 kg of kaolin ground into fine powder was placed in a coating machine for granulation. During the granulation process, 1 mol / L ammonium chloride solution was sprayed into the powder until most of the powder formed spherical particles. The spherical samples were dried at 120℃ for 2 hours and calcined at 700℃ for 2 hours before use.

[0093] Dissolve 89g NaOH and 42.1g KOH in 500mL of water to prepare a mixed alkaline solution, and cool to room temperature.

[0094] 52.5g of the calcined spherical sample was added to the mixed alkaline solution and stirred until homogeneous. The sample was aged at 60℃ for 5 hours at a dynamic rotation speed of 100r / min throughout the process, crystallized at 95℃ for 12 hours, filtered, washed with water until pH < 9, dried at 120℃ for 2 hours, and calcined at 500℃ for 2 hours to obtain the LSX / A-A9 molecular sieve composite adsorbent.

[0095] The specific preparation conditions of LSX-type and A-type molecular sieve composite adsorbents, the proportions of the two molecular sieves, the silicon-aluminum ratio, and the static CO2 adsorption capacity in the adsorbents of Examples 1-8 and Comparative Example 3 are shown in Tables 1 and 2.

[0096] Table 1 Preparation conditions of LSX-type and A-type molecular sieve composite adsorbents

[0097]

[0098]

[0099] Table 2. Molecular sieve content, silica-alumina ratio, and static CO2 adsorption capacity of LSX-type and A-type molecular sieve composite adsorbents.

[0100] Sample LSX type molecular sieve (%) A type molecular sieve (%) Silica to alumina ratio Static CO2adsorption capacity LSX / A-A1 52 48 2.06 118.1 LSX / A-A2 42 58 2.04 114.5 LSX / A-A3 67 33 2.07 122.2 LSX / A-A4 56 44 2.05 119.5 LSX / A-A5 75 25 2.07 124.8 LSX / A-A6 21 79 2.03 110.1 LSX / A-A7 27 73 2.04 112.7 LSX / A-A8 40 60 2.04 114.4 LSX / A-A9 42 58 2.04 92.8

[0101] As can be seen from Examples 1 and 5, Examples 2 and 6, Examples 7 and 8, the dynamic aging and crystallization process tends to synthesize more LSX-type molecular sieves, while the static aging and crystallization process tends to synthesize A-type molecular sieves.

[0102] As can be seen from Example 1 and Comparative Example 1, Example 3 and Comparative Example 2, using an aqueous solution instead of an ammonium salt solution during the adsorbent forming process will make it difficult to form the adsorbent and make it impossible to carry out subsequent experimental steps.

[0103] As can be seen from Example 2 and Comparative Example 3, if sodium carboxymethyl cellulose is not added to the molding raw material as a pore expander, the number of adsorption sites on the inner surface of the adsorbent is reduced, which significantly reduces the static CO2 adsorption capacity of the LSX-type and A-type molecular sieve composite adsorbent, resulting in a decrease in gas adsorption effect.

[0104] The experimental results above show that, without the addition of molecular sieves, silicon sources, or aluminum sources, the shaped adsorbent made primarily of kaolin can be directly crystallized to obtain LSX-type and A-type molecular sieve composite adsorbents. The silicon-aluminum molar ratio is basically consistent with that of the kaolin raw material, exhibiting good adsorption effect on CO2. This significantly reduces production costs, simplifies the process, and is suitable for industrial production. It can be applied in the field of PSA gas separation and purification.

[0105] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for the seed-free controllable preparation of a composite adsorbent of LSX and A type molecular sieves, wherein, The seed-free controllable preparation method comprises the following steps: After the kaolin and the pore-expanding agent are uniformly mixed, the ammonium salt solution is used for auxiliary molding; after the molded sample is dried and calcined, it is uniformly dispersed into lye, and then low-temperature aging and high-temperature crystallization treatment are carried out, and then washing, drying and calcination are carried out to obtain the LSX type and A type molecular sieve composite adsorbent. The low-temperature aging and high-temperature crystallization are controlled to be carried out in static state, dynamic state or a combination of static state and dynamic state, so as to control the proportion of the LSX type and A type molecular sieve in the obtained composite adsorbent.

2. The seedless controllable preparation method according to claim 1, wherein, The pore-expanding agent is at least one selected from sodium carboxymethyl cellulose, urea, calcium carbonate and starch.

3. The seedless controllable preparation method according to claim 1, wherein, The addition amount of the pore-expanding agent is 1% to 10% of the mass of the kaolin.

4. The seedless controllable preparation method according to claim 1, wherein, The ammonium salt is selected from ammonium chloride, ammonium carbonate and ammonium sulfate; and the concentration of the ammonium salt solution is 0.1 to 5 mol / L.

5. The seedless controllable preparation method according to claim 1, wherein, The calcination temperature of the molded sample is 650 to 800 DEG C, and the calcination time is 1 to 3 h.

6. The seedless controllable preparation method according to claim 1, wherein, The lye is a mixed lye of sodium hydroxide and potassium hydroxide.

7. The seedless controllable preparation method according to claim 6, wherein, The amount of the kaolin is calculated based on silicon oxide, and the amount of the mixed lye is calculated based on the total amount of sodium oxide and potassium oxide; in the mixed lye, the molar ratio of water to the total amount of sodium oxide and potassium oxide is (15 to 20) to 1, and the molar ratio of potassium oxide to the total amount of sodium oxide and potassium oxide is (0.1 to 0.4) to 1; in the addition ratio of the mixed lye and the kaolin, the molar ratio of the total amount of sodium oxide and potassium oxide to silicon oxide is (2.0 to 4.0) to 1.

8. The seedless controllable preparation method according to claim 1, wherein, The aging temperature of the low-temperature aging is 40 to 70 DEG C, and the crystallization temperature of the high-temperature crystallization is 80 to 100 DEG C. The sum of the aging time of the low-temperature aging and the crystallization time of the high-temperature crystallization is 15 to 20 h.

9. The seedless controllable preparation method according to claim 1, wherein, The static aging or static crystallization is that the reaction raw material is placed in a polytetrafluoroethylene inner container, the reaction kettle is sealed, and then the aging or crystallization reaction is carried out in a forced air drying oven; The dynamic aging or dynamic crystallization is that the reaction raw material is placed in a polytetrafluoroethylene inner container, the reaction kettle is sealed, and then the aging or crystallization reaction is carried out in a homogeneous reactor, and the rotating speed of the homogeneous reactor is 50 to 200 r / min. 10.A LSX type and A type molecular sieve composite adsorbent obtained by the seed-free controllable preparation method according to any one of claims 1 to 9.

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