Ordered multichannel network structure cellulose / molecular sieve composite material and preparation method thereof

Abstract

The invention relates to the technical field of porous materials, in particular to an ordered multichannel network structure cellulose / molecular sieve composite material and a preparation method thereof.The composite material is of a stable porous framework structure formed by cellulose, molecular sieves are evenly distributed in the three-dimensional network structure of the composite material, the pore volume is larger than 0.2 cm < 3 > / g, and the composite material is composed of macropores (gt; 50 nm), mesopores (2-50 nm) and micropores (lt; the porous material can be used in a plurality of fields such as gas adsorption, purification and separation, and the like. The preparation method comprises the following steps: uniformly mixing cellulose and a zeolite molecular sieve which are used as raw materials, directionally freezing and co-assembling, and freeze-drying to obtain the cellulose / molecular sieve composite porous material with a macroscopic three-dimensional network structure and directional multiple channels. The prepared cellulose / molecular sieve composite material not only has a self-supporting network skeleton, a rich pore structure and a relatively high specific surface area, but also has directionally arranged pore channels, and the composite material has good flexibility and elasticity.

Description

Technical Field

[0001] The present invention relates to the technical field of porous materials, and particularly relates to an ordered multi-channel network structure cellulose / molecular sieve composite material and a preparation method thereof. Background Art

[0002] At present, hydrogen production by ammonia cracking is widely regarded as one of the important solutions to break through the bottleneck of hydrogen energy storage and transportation due to its advantages of no carbon emission, high hydrogen storage density and low cost. However, the adsorption and separation technology required to obtain high-purity hydrogen and extremely low ammonia residue is the core problem. Therefore, the development of low-cost and high-performance adsorption materials has become the key.

[0003] Zeolite molecular sieves are a class of inorganic materials with regular pore structures, strong acidity and high hydrothermal stability, and are widely used in the fields of adsorption and purification. However, the molecular sieve materials usually used for hydrogen separation and purification have a small pore size and are disorderly stacked in the tower, resulting in a lack of good mass transfer channels for gases in the separation tower, causing a large resistance and high operating pressure; moreover, traditional molecular sieve forming technologies have problems such as binder plugging of pores, resulting in a low effective specific surface area and affecting the separation efficiency. Cellulose is a macromolecular polysaccharide composed of glucose, which is widely distributed in nature and insoluble in water. Due to the strong intermolecular forces between its molecular chains, it has good rigidity and is suitable as a self-supporting skeleton. Also, due to its good biocompatibility, easy degradability and no pollution, it has great application value. By generating a composite porous material by the freeze co-assembly method of molecular sieve and cellulose, the network structure formed by cellulose cross-linking provides a supporting skeleton, the long-range ordered pore structure formed by the growth orientation of ice crystals provides a good mass transfer channel, and the uniformly dispersed molecular sieve provides a high specific surface area adsorption platform. Therefore, the ordered multi-channel network structure cellulose / molecular sieve composite material proposed by the present invention has a high adsorption capacity, high mass transfer and high adsorption efficiency.

[0004] At present, the methods for optimizing the structure of porous materials using the freeze co-assembly method mainly include: the preparation method of layered carbon-derived wave-absorbing materials disclosed in Patent CN118894520A: by first placing the prepared ZIF-8 nanoparticles in pure water for freezing, and then freeze-drying them in a freeze dryer and calcining them at a high temperature in a nitrogen atmosphere to obtain layered carbon-derived wave-absorbing materials. A two-dimensional interwoven layered material of fluorinated graphite-nanocellulose and its preparation method and application disclosed in Patent CN117511624A: by mixing the prepared cellulose nanofibrils with fragmented fluorinated graphite for freezing, and freeze-drying them at a certain temperature to obtain a micro-nano two-dimensional interwoven layered material of fluorinated graphite-nanocellulose. The preparation method of superhydrophobic chitosan-based aerogel disclosed in Patent CN115245795A: by dispersing carbon nanotubes modified by chitosan and chitosan in acetic acid solution and slowly dropping glutaraldehyde solution to form a gel, then freezing it under low-temperature conditions and freeze-drying it, and finally performing chemical vapor deposition in a closed environment to obtain superhydrophobic chitosan-based aerogel. The hybrid manganese dioxide aerogel and its preparation method and application disclosed in Patent CN115364818A: by dispersing MnO2 nanosheets prepared by mixing sodium dodecyl sulfate with hydrochloric acid and potassium permanganate and cellulose nanofibers prepared by drying bamboo powder extracted by benzene / ethanol and treated with acidified NaCl2 and KOH in ultrapure water for freezing and then freeze-drying to obtain hybrid manganese dioxide aerogel. The above preparation processes have long flow charts and are difficult for large-scale production.

[0005] Therefore, to solve the above technical problems, it is necessary for this application to propose an ordered multi-channel network structure cellulose / molecular sieve composite material and its preparation method. Summary of the Invention

[0006] The purpose of the present invention is to solve the disadvantages existing in the prior art, and to propose an ordered multi-channel network structure cellulose / molecular sieve composite material and its preparation method. The prepared cellulose-molecular sieve porous material has a large specific surface area, a more optimized pore structure, and long-range ordered pores.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] An ordered multi-channel network structure cellulose / molecular sieve composite material, the composite material is composed of cellulose and molecular sieve, the mass ratio of cellulose to molecular sieve is 1:8 to 1:30, and the BET specific surface area of the composite material is 380 - 850m 2 / g, and the pore size distribution is in the range of 0.5nm to 100μm.

[0009] The present invention also provides a preparation method of an ordered multi-channel network structure cellulose / molecular sieve composite material, including the following steps:

[0010] Step 1, Mixing: Stir and mix a certain amount of cellulose dispersion liquid with the molecular sieve raw powder to obtain a mixed suspension. The mixing temperature is 15 - 55°C, and the mixing time is 4 - 12 h; the mass ratio of cellulose to the molecular sieve is 1:8 - 1:30.

[0011] Step 2, Directional Freezing Co - assembly: Place the mixed suspension obtained in Step 1 above into a freezing tube, and then vertically place the freezing tube with a heat - insulating layer on a low - temperature stage to make the mixed suspension freeze directionally from bottom to top to obtain a frozen solid. The freezing temperature is - 80 - - 20°C, and the freezing time is 2 - 10 h.

[0012] Step 3, Drying: Place the solid obtained in Step 2 above into a vacuum freeze - dryer for drying. The drying temperature is - 50 - - 40°C, and the drying time is 12 - 72 h to obtain a composite.

[0013] Step 4, Baking: Place the composite obtained in Step 3 above into an oven for baking to obtain a multi - channel and multi - level pore network structure cellulose - molecular sieve composite material. The baking temperature is 60 - 120°C, and the baking time is 12 - 72 h.

[0014] Preferably, in Step 1, the cellulose dispersion liquid is an aqueous solution with a solid content of 0.3% - 1.0%.

[0015] Preferably, in Step 2, the freezing tube is a plexiglass tube with a diameter of 1 - 5 cm and a height of 2 - 8 cm.

[0016] By adopting the above technical solutions: Using cellulose and zeolite molecular sieve as raw materials, through uniform mixing and then directional freezing co - assembly, and then freeze - drying, a cellulose / molecular sieve composite porous material with a macroscopic three - dimensional network structure and directional multi - channels is obtained. The prepared cellulose / molecular sieve composite material not only has a self - supporting network skeleton, rich pore structures, a relatively high specific surface area, but also has directionally arranged pores, and the composite material has good flexibility and elasticity. Among them, a self - supporting three - dimensional network structure is formed by cellulose cross - linking, and it provides rich pores. During the freezing co - assembly process, due to the guiding growth of ice crystals, directional and continuous pores are formed. The molecular sieve is uniformly dispersed in the cellulose network structure, providing rich micropores, so a multi - level pore composite material with an ordered multi - channel network structure is formed. Among them, the molecular sieve is uniformly distributed in its three - dimensional network structure, and the pore volume > 0.2 cm 3 / g, and the multi - level pore network structure is jointly composed of macropores (>50 nm), mesopores (2 - 50 nm) and micropores (<2 nm). This porous material can be used in multiple fields such as gas adsorption and purification separation.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. In the present invention, cellulose and molecular sieve are directly mixed and stirred, and then co-assembled by freezing followed by freeze-drying to obtain a composite porous material. No additives are required, and no pretreatment of the material is necessary. The preparation conditions are mild, significantly simplifying the process, reducing the production difficulty, having low cost, and being convenient for industrial production.

[0019] 2. The porous composite material prepared by the present invention has a rich pore structure. The three-dimensional network structure formed by cellulose cross-linking can serve as a good self-supporting framework, enabling the molecular sieve to be evenly dispersed in its framework structure, avoiding problems such as a reduction in active sites and a decrease in the effective specific surface area caused by molecular sieve accumulation and pore blockage. During the freeze co-assembly process, oriented and continuous ordered pores are formed due to the growth orientation of ice crystals, providing good mass transfer channels. In addition, cellulose is easily degradable, has good biocompatibility, is pollution-free, and is environmentally friendly. The cellulose / molecular sieve composite material has good formability, good mechanical properties and flexibility, and is extremely easy to realize industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is the SEM image of the cellulose / molecular sieve porous material of the present invention;

[0021] Figure 2 is a schematic diagram of the cellulose / molecular sieve composite material sample of the present invention; wherein, (a) is a cross-sectional view and (b) is a radial view. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings, so that those skilled in the art can better understand the advantages and features of the present invention, and thus more clearly define the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] Please refer to Figure 1 , an ordered multi-channel network structure cellulose / molecular sieve composite material provided by an embodiment of the present invention is composed of cellulose and zeolite molecular sieve, and the mass ratio of cellulose to zeolite molecular sieve is 1:8 - 1:30, and it can be applied to fields such as gas adsorption and separation.

[0024] The present invention also provides a preparation method for the above-mentioned ordered multi-channel network structure cellulose / molecular sieve composite material, which specifically includes the following steps:

[0025] Step 1, Mixing: A certain amount of cellulose dispersion is stirred and mixed with the molecular sieve raw powder to obtain a mixed suspension. The mixing temperature is 15 - 55°C, and the mixing time is 4 - 12 h; the mass ratio of cellulose to the molecular sieve is 1:8 - 1:30.

[0026] Step 2, Directional Freezing Co-Assembly: The mixed suspension obtained in Step 1 above is placed in a freezing tube, and then the freezing tube with a heat-insulating layer is vertically placed on a low-temperature stage to freeze the mixed suspension from bottom to top directionally, obtaining a frozen solidified product. The freezing temperature is -80 - -20°C, and the freezing time is 2 - 10 h.

[0027] Step 3, Drying: The solidified product obtained in Step 2 above is placed in a vacuum freeze-dryer for drying. The drying temperature is -50 - -40°C, and the drying time is 12 - 72 h to obtain a composite.

[0028] Step 4, Baking: The composite obtained in Step 3 above is placed in an oven for baking to obtain a multi-channel multi-stage pore network structure cellulose - molecular sieve composite material. The baking temperature is 60 - 120°C, and the baking time is 12 - 72 h.

[0029] The structure of the ordered multi-channel network structure cellulose / molecular sieve composite material prepared by the above method observed under a scanning electron microscope is as Figure 1 shown.

[0030] Example 1

[0031] Cellulose produced by Weifang Lite Composite Materials Co., Ltd. and 13X zeolite molecular sieve produced by Jianlong Micro-Nano in Yanshi, Henan are used, and they are mixed at a mass ratio of cellulose to zeolite molecular sieve of 20:1, placed in an organic glass tube with a diameter of 2 cm and a height of 5 cm, and vertically placed on a low-temperature stage at -45°C for 4 h of freezing. Then, the obtained frozen solidified product is placed in a freeze-drying oven at -45°C for 18 h of freeze-drying. Finally, the solid is baked in an oven at 80°C for 48 h to obtain an ordered multi-channel network structure cellulose / molecular sieve composite porous material.

[0032] Example 2

[0033] Cellulose produced by Wuqiao Qiyuan Cellulose Co., Ltd. and 13X zeolite molecular sieve produced by Dalian Haixin Chemical Co., Ltd. are used, and they are mixed at a mass ratio of cellulose to zeolite molecular sieve of 30:1, placed in an organic glass tube with a diameter of 3 cm and a height of 4 cm, and vertically placed on a low-temperature stage at -60°C for 6 h of freezing. Then, the obtained frozen solidified product is placed in a freeze-drying oven at -60°C for 24 h of freeze-drying. Finally, the solid is baked in an oven at 90°C for 24 h to obtain an ordered multi-channel network structure cellulose / molecular sieve composite porous material.

[0034] Example 3

[0035] Cellulose produced by Weifang Lite Composite Materials Co., Ltd. and 13X zeolite molecular sieve produced by Dalian Haixin Chemical Co., Ltd. were used. They were mixed at a mass ratio of cellulose to zeolite molecular sieve of 10:1 and placed in an organic glass tube with a diameter of 3 cm and a height of 6 cm. Then, it was vertically placed on a low-temperature stage at -50°C and frozen for 8 h. After that, the obtained frozen solid was placed in a freeze dryer at -50°C and freeze-dried for 12 h. Finally, the solid was dried in an oven at 100°C for 12 h to obtain an ordered multi-channel network structure cellulose / molecular sieve composite porous material.

[0036] In summary, the ordered multi-channel network structure cellulose / molecular sieve composite material prepared by the present invention has good flexibility, a high specific surface area, and a long-range ordered pore structure. At the same time, the present invention simplifies the preparation process, eliminates the need for pretreatment of raw materials, reduces the production difficulty, lowers the production cost, and is easy to industrialize.

[0037] The descriptions and practices disclosed in the present invention are easy to think about and understand for those of ordinary skill in the art. Without departing from the principle of the present invention, several improvements and refinements can also be made. Therefore, the modifications or improvements made without departing from the spirit of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. An ordered multi-channel network structure cellulose / molecular sieve composite material, characterized in that, The composite material is composed of cellulose and molecular sieve, and the mass ratio of cellulose to molecular sieve is 1:8 to 1:

30. The BET specific surface area of the composite material is 380 to 850 m 2 / g, and the pore size distribution is in the range of 0.5 nm to 100 μm.

2. The preparation method of an ordered multi-channel network structure cellulose / molecular sieve composite material according to claim 1, characterized in that, It includes the following steps: Step 1, mixing: Stir and mix a certain amount of cellulose dispersion liquid with molecular sieve raw powder to obtain a mixed suspension. The mixing temperature is 15-55°C, and the mixing time is 4-12 h; the mass ratio of cellulose to molecular sieve is 1:8-1:30; Step 2, directional freezing co-assembly: Place the mixed suspension obtained in the above step 1 into a freezing tube, and then vertically place the freezing tube with a heat-insulating layer on a low-temperature stage to freeze the mixed suspension from bottom to top directionally to obtain a frozen solid. The freezing temperature is -80 to -20°C, and the freezing time is 2-10 h; Step 3, drying: Place the solid obtained in the above step 2 into a vacuum freeze dryer for drying. The drying temperature is -50 to -40°C, and the drying time is 12-72 h to obtain a composite; Step 4, baking: Place the composite obtained in the above step 3 into an oven for baking to obtain a multi-channel multi-stage pore network structure cellulose-molecular sieve composite material. The baking temperature is 60-120°C, and the baking time is 12-72 h.

3. The preparation method of an ordered multi-channel network structure cellulose / molecular sieve composite material according to claim 2, characterized in that, In step 1, the cellulose dispersion liquid is an aqueous solution with a solid content of 0.3%-1.0%.

4. The preparation method of an ordered multi-channel network structure cellulose / molecular sieve composite material according to claim 2, characterized in that, In step 2, the freezing tube is a plexiglass tube with a diameter of 1-5 cm and a height of 2-8 cm.

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