CN116239364A

CN116239364A - Zeolite molecular sieve powder shaping method

Info

Publication number: CN116239364A
Application number: CN202111516879.1A
Authority: CN
Inventors: 刘浩; 田志坚; 曲炜; 王从新; 王琳; 陈欣; 李鹏
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2021-12-07
Filing date: 2021-12-07
Publication date: 2023-06-09

Abstract

The invention relates to a zeolite molecular sieve powder forming method, and belongs to the technical field of molecular sieve material preparation. The method is characterized in that a mixture containing powder to be formed, a high polymer binder and a dispersing agent is subjected to steps of aging, compression forming, solidification and the like before carbonization. Aging and compression molding are carried out to promote the air occluded in the mixture, especially zeolite molecular sieve pore canal to be fully discharged, and the high molecular adhesive is fully contacted with zeolite molecular sieve powder; through solidification, the molecular connection of the high molecular adhesive is promoted to be more compact. The above operation contributes to obtaining a zeolite molecular sieve molded body having a complete structure and high strength. The powder forming process provided by the invention is simple and convenient to operate, and is easy to realize in the preparation process of molecular sieve materials with different scales such as experimental research and industrial production.

Description

Zeolite molecular sieve powder shaping method

Technical Field

The invention relates to a zeolite molecular sieve powder forming method, and belongs to the technical field of molecular sieve material preparation.

Background

Based on intensive studies on the composition and structure of natural zeolite, the international association of mineralogy has defined the zeolite as follows (The Canadian Mineralogist,1997, 35, 1571):

zeolite minerals are crystalline substances with a frame-like structure, the framework of which is formed by connecting tetrahedra consisting of central cations and four oxygen atoms around the central cations, and the zeolite minerals have a porous or cage-like open cavity. These cavities are typically occupied by water molecules and extra-framework cations, which are typically exchangeable. The pore canal has larger size and can allow the passage of the object substances. The aqueous phase thereof is dehydrated upon heating to a temperature typically not higher than 400 c and the process is largely reversible. Its backbone may be blocked by OH or F groups that occupy positions at vertices of tetrahedra that are not shared with other tetrahedra.

The above definition emphasizes three structural features of zeolites as opposed to other minerals: (1) having a rack-like structure; (2) having an open cavity; and (3) the framework is formed by connecting tetrahedral structural units. Various types of natural minerals and synthetic materials having zeolite structural features are collectively referred to as zeolite molecular sieves. The central cations of the zeolite molecular sieve framework are usually silicon, phosphorus and aluminum, and can also be main group cations or transition metal cations such as beryllium, boron, magnesium, gallium, germanium, arsenic and the like. In addition to oxygen, nitrogen, sulfur, chlorine, etc. may also be used as bridging anions to connect the central cations.

Because the zeolite molecular sieve has pore channels with molecular size, high specific surface area, exchangeable cations outside the framework, adjustable composition and structure and higher framework stability, the zeolite molecular sieve is widely applied to the processes of ion exchange, catalysis, adsorption separation and the like. The total amount of artificially synthesized zeolite molecular sieves consumed annually worldwide exceeds one million tons. In the use process, particularly in the catalysis and adsorption separation process of large industrial devices, zeolite molecular sieves are required to have not only excellent performance, but also ideal micro-macro structure and mechanical strength. The satisfaction of these requirements requires a suitable molding process as a support. Zeolite molecular sieves are typically in powder form and need to be formed into particles having a specific shape. In order to achieve the required molding effect, a binder is added to the zeolite molecular sieve powder during the molding process to improve the adhesiveness and cohesiveness thereof. Adhesives are generally classified into matrix adhesives, film adhesives, and chemical adhesives.

The organic matter may be used as matrix binder or film binder for powder molding. For example, patent document CN111266137a discloses a manganese oxide-based catalyst for removing formaldehyde and volatile organic compounds. The catalyst is prepared by mixing manganese oxide, bentonite, polymer binder and other components, extruding or coating on a solid substrate. Patent document CN107282139B discloses an industrial molding binder for powder catalysts. The adhesive comprises methyltrimethoxysilane, dimethyldimethoxysilane, ethylene glycol butyl ether, a cross-linking agent, an ester plasticizer, an ester solvent, methanol, silica sol and the like. The adhesive can be used for bonding catalysts to plate-type, honeycomb-type and corrugated plate-type carriers. Patent document CN109433191a discloses a method of binding a powder catalyst. The method uses nanocellulose to bond the powder catalyst to the conductive substrate.

The chemical adhesive is different from the matrix adhesive and the film adhesive in that the chemical adhesive plays a role in bonding by generating new species through chemical reaction. Common chemical binders include magnesia-magnesium chloride, water glass-calcium chloride, aluminum sol, silica sol, and the like. The organic matter is oxidized and decomposed by high-temperature roasting, so that the organic matter is not used as a chemical binder in the traditional powder forming process. By changing the heat treatment mode of the powder, some organic matters can also play a role in chemical bonding. Patent document CN1181917C discloses a mixed metal catalyst comprising a combustible binder. The combustible binder is formed by pyrolysis of an organic polymer at 300-600 ℃ in an inert atmosphere. Patent document CN108927146B discloses a poor-quality heavy oil hydrogenation catalyst using spherical granular carbon as a carrier. The spherical granular carbon is obtained by kneading active carbon powder and an organic binder into balls, and then carrying out acid washing and carbonization. Patent document CN107029668B discloses a honeycomb type molecular sieve-activated carbon composite adsorbent. The adsorbent is prepared from a Y-type molecular sieve, activated carbon powder, expanded graphite, silica sol, an organic binder and deionized water through the steps of mixing, pugging, vacuum pugging, aging, honeycomb extrusion molding, low-temperature microwave shaping, microwave vacuum sintering and the like. Patent document CN109675632a discloses a preparation method of a carbon-based ZIF composite catalyst. The method uses polyvinylpyrrolidone or polyethyleneimine as an adhesive and applies high-temperature carbonization to the adhesive. Patent document CN111186837a discloses a method for preparing a nitrogen-doped molded activated carbon used as a catalyst carrier. The method takes woody biomass as a raw material and comprises the steps of nitrogen doping, binder adding, kneading, forming, carbonization, activation and the like. The binder is phenolic resin, coal tar, polyvinyl alcohol or carboxymethyl cellulose. Patent document CN111115631a discloses a preparation method of a coffee grounds-based molded porous carbon material. The method takes coffee grounds as raw materials, mixes the coffee grounds with solvent, extrusion aid, adhesive and structure reinforcing agent, and prepares porous carbon through kneading, extrusion molding, drying, carbonization and activation. The binder is starch, sodium carboxymethyl starch or montmorillonite, sepiolite, silicate, silica sol, sodium silicate, dilute nitric acid and phosphoric acid.

Disclosure of Invention

The invention aims to provide a forming method which overcomes the defects of the prior art and is suitable for zeolite molecular sieve powder. The molding method comprises the following steps:

step a, pretreating a raw material zeolite molecular sieve to obtain powder to be molded;

step b, weighing 2-30 parts by weight of the powder to be molded obtained in the step a, 3-20 parts by weight of the polymer binder and 1-50 parts by weight of the dispersing agent, and uniformly mixing the powder and the dispersing agent;

step c, aging the mixture obtained in step b in air at a temperature of 5-100deg.C, preferably 10-80deg.C, more preferably 20-60deg.C for 0.2-48 hr, preferably 1-36 hr, more preferably 5-24 hr;

step d, compressing and molding the aged mixture obtained in the step c, wherein the molding pressure is more than or equal to 10MPa, preferably more than or equal to 20MPa, and more preferably more than or equal to 40MPa;

step e, curing the molded body obtained in the step d in an oxidizing atmosphere at a curing temperature of 20-200 ℃, preferably 60-160 ℃, more preferably 100-120 ℃ for a curing time of 0.2-48 hours, preferably 1-36 hours, more preferably 5-24 hours;

and f, carbonizing the cured molding obtained in the step e in a non-oxidizing atmosphere to obtain a carbonized molding, wherein the carbonizing temperature is 400-1000 ℃, preferably 500-900 ℃, more preferably 600-800 ℃, and the carbonizing time is 0.5-12h, preferably 1-10h, more preferably 2-8h.

In the zeolite molecular sieve powder forming method provided by the invention, the pretreatment process in the step a is one or more of drying, crushing, roasting, solvent extraction, acid washing, alkali washing, water washing, ion exchange, hydrothermal treatment, steam treatment and impregnation.

In the zeolite molecular sieve powder forming method provided by the invention, the raw material zeolite molecular sieve skeleton type in the step a is one or more than two of AEI, AEL, AFI, AFO, ATO, ATS, BEA, BEC, CHA and CLO, EDI, ERI, EUO, FAU, FER, GIS, HEU, LAU, LTA, LTL, MER, MFI, MOR, MTT, MTW, MWW, NES, RHO, TON. The central cation of the skeleton is one or more of silicon, phosphorus, aluminum, beryllium, boron, magnesium, gallium, germanium, arsenic, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc.

In the zeolite molecular sieve powder molding method provided by the invention, the particle size of the powder to be molded obtained in the step a is less than or equal to 1000 mu m, preferably less than or equal to 500 mu m, and more preferably less than or equal to 100 mu m.

In the zeolite molecular sieve powder molding method provided by the invention, the polymer binder in the step b is one or more than two of gum, dextrin, cellulose, hemicellulose, methylcellulose, carboxymethyl cellulose, ethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl hydroxypropyl cellulose, starch, alginic acid, lignin, sesbania powder, animal glue, polyethylene glycol, polyethylene, polyvinyl chloride, polyvinyl alcohol, polypropylene, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, polybutene, polybutadiene, polychloroprene, polyisoprene, polystyrene, polyurethane, polyphenyl ether, polyphenylene sulfide, phenolic resin, epoxy resin, organic silicon epoxy resin and nitrile rubber.

In the zeolite molecular sieve powder molding method provided by the invention, the dispersing agent in the step b is one or more than two of water, methanol, ethanol, propanol, butanol, glycol, glycerol, ethyl acetate, diethyl ether, benzene, toluene, xylene, pentane, hexane, cyclohexane, heptane, octane, acetone, cyclohexanone, dichloromethane, chloroform, acetonitrile and pyridine.

In the method for forming zeolite molecular sieve powder provided by the invention, the oxidizing atmosphere in the step e contains oxygen and inert gas. Wherein the volume fraction of oxygen is 0.5% to 30%, preferably 1% to 20%, more preferably 5% to 10%. The inert gas contains one or more of helium, carbon dioxide, nitrogen and argon. Air is also an oxidizing atmosphere suitable for this step.

In the zeolite molecular sieve powder molding method provided by the invention, the non-oxidizing atmosphere in the step f contains one or more than two of hydrogen, helium, methane, carbon monoxide, carbon dioxide, nitrogen and argon.

According to the requirement, the zeolite molecular sieve powder forming method provided by the invention can be further optimized. Specifically, the carbonized molded body obtained in the step f may be activated in an oxidizing atmosphere. The activation temperature is-20-400 ℃ and the activation time is 0.2-48h. The oxidizing atmosphere comprises oxygen and an inert gas. Wherein the volume fraction of oxygen is 1% -10%, and the inert gas contains one or more than two of helium, carbon dioxide, nitrogen and argon.

The most obvious difference between the zeolite molecular sieve powder forming method provided by the invention and the prior art is that the mixture containing the powder to be formed, the high polymer binder and the dispersing agent is subjected to aging, compression forming, solidification and other steps before carbonization. The invention has the following beneficial effects:

aging and compression molding are carried out to promote the air occluded in the mixture, especially zeolite molecular sieve pore canal to be fully discharged, and the high molecular adhesive is fully contacted with zeolite molecular sieve powder; through solidification, the molecular connection of the high molecular adhesive is promoted to be more compact. The above operation contributes to obtaining a zeolite molecular sieve molded body having a complete structure and high strength. The powder forming process provided by the invention is simple and convenient to operate, and is easy to realize in the preparation process of molecular sieve materials with different scales such as experimental research and industrial production.

Drawings

FIG. 1 is a photograph of a compression molded zinc-containing Beta molecular sieve tablet of example 1 after curing at 110℃for 24 hours.

FIG. 2 is an X-ray diffraction pattern of the molded TS-1 molecular sieve obtained in example 3.

FIG. 3 is a nitrogen adsorption-desorption isotherm of the molded TS-1 molecular sieve obtained in example 3.

FIG. 4 is a graph showing the pore distribution of the molded TS-1 molecular sieve obtained in example 3.

FIG. 5 is a nitrogen adsorption-desorption isotherm of the TS-1 molecular sieve powder described in example 3.

FIG. 6 is a graph showing the pore distribution of the TS-1 molecular sieve powder described in example 3.

Detailed Description

The following examples will illustrate the invention further. The present invention is not limited to the following examples.

Example 1

The method described in reference (Chinese Journal of Catalysis,2017, 38, 1207) synthesizes zinc-containing Beta molecular sieves. At the time of synthesis, cobalt nitrate in the synthetic route described in the literature was replaced with equimolar zinc nitrate. The obtained molecular sieve is white powdery crystal, the grain size is less than or equal to 50 mu m, and the molecular sieve is roasted for 24 hours at 550 ℃ before being used. The molecular sieve has BEA type framework, and the central cation of the framework is silicon.

15.3g of the zinc-containing Beta molecular sieve, 2.6g of cellulose and 6.7g of starch are taken out, placed in a mortar, 30.0g of water is added, and the mixture is ground into slurry. The mixture was aged in an oven at 45℃for 18 hours, and then compressed and molded to prepare an ingot of about 2.2 g/tablet. The molding pressure was 30MPa, and a cylindrical die having an inner diameter of 12mm was used for pressing. And (3) placing the ingot into a baking oven at 110 ℃ for curing for 24 hours, and then placing the ingot into a quartz reaction tube for heat treatment. The treatment conditions are as follows: 50mL/min argon atmosphere, 640 ℃ and 7h. After cooling to room temperature, the resulting solidified ingot was taken out. Figure 1 of the accompanying drawings gives a photograph of the resulting ingot after curing at 110℃for 24 hours. As can be seen from the photographs, the obtained zinc-containing Beta molecular sieve ingot has complete structure after solidification, smooth surface and no crack. The ingot piece is still complete in structure after carbonization, the surface is still smooth and has no cracks, and only the color is changed from pale yellow after heat preservation to black.

Example 2

10 of the carbonized zinc-containing Beta molecular sieve ingots obtained in example 1 were randomly extracted for radial strength testing. The test results are shown in Table 1.

TABLE 1

Tablet numbering	Ingot thickness (mm)	Pressure (N)	Radial compressive Strength (N/cm)
				1	3.0	358	1193
2	3.0	434	1447
				3	2.7	245	907
4	2.9	314	1083
				5	3.1	399	1287
6	3.0	326	1087
				7	2.9	295	1017
8	2.9	327	1128
				9	3.1	422	1361
10	3.0	359	1197

The radial strength test result shows that the formed zinc-containing Beta molecular sieve prepared by the powder forming method provided by the invention has uniform texture and high mechanical strength.

Comparative example 1

2.2g of the zinc-containing Beta molecular sieve described in example 1 was taken and compression molded. The compression molding conditions are as follows: room temperature, 45MPa,0.1h. The mold used was the same as in example 1. The columnar aggregate is crushed after light touch.

Comparative example 2

The procedure for the preparation of the shaped zinc-containing Beta molecular sieves described in example 1 was repeated, but without aging. Directly compression molding after mixing, and placing the tablet obtained by compression molding into a 110 ℃ oven for curing. And when the ingot is solidified for 1h, the ingot is cracked, and the surface is peeled layer by layer.

The results of examples 1 and 2 and comparative examples 1 and 2 show that the zeolite molecular sieve powder molding method provided by the invention is helpful for obtaining a complete and high-strength molded body.

Example 3

The TS-1 molecular sieves were synthesized according to the methods described in literature (The Journal of Physical Chemistry B,2006, 110, 15080). The resulting molecular sieve was calcined at 550 ℃ for 24 hours and sieved through a 200 mesh sieve before use. The molecular sieve has MFI type framework, and the cation in the center of the framework is silicon or titanium.

Mixing 100g of TS-1 molecular sieve, 45g of phenolic resin (water soluble type, mass fraction is 70%) and 20g of glycol, and kneading.

The above mixture was aged in an oven at 80℃for 32 hours, and then, an ingot of about 2 g/tablet was produced by compression molding. The molding pressure was 30MPa. A cylindrical die with an inner diameter of 12mm was used for pressing. The obtained ingot is put into a quartz reaction tube for heat treatment. The treatment conditions are as follows: 100mL/min oxygen-nitrogen mixed atmosphere (oxygen volume fraction is 5%, nitrogen volume fraction is 95%), 200 ℃ for 3h;200mL/min nitrogen atmosphere at 600℃for 5h. After cooling to room temperature, the mixture was treated at 200℃for 2 hours in a mixed atmosphere of oxygen and nitrogen (oxygen volume fraction: 5% and nitrogen volume fraction: 95%) of 100 mL/min. After cooling to room temperature again, the obtained carbonized ingot pieces are crushed, and 10-20 mesh particles are sieved. Thus obtaining the formed TS-1 molecular sieve.

Example 4

The shaped TS-1 molecular sieve phase obtained in example 3 was identified using a PANalytical X' pert Pro powder X-ray diffractometer. The obtained X-ray diffraction pattern is shown in figure 2 of the specification. The powder X-ray diffraction result shows that the TS-1 molecular sieve crystal phase is not changed in the forming process.

Example 5

The nitrogen adsorption-desorption isotherms of the molded TS-1 molecular sieve obtained in example 3 were determined using a Micromeritics ASAP 2420 physical adsorption instrument. The obtained nitrogen adsorption-desorption isotherm and pore distribution curve are shown in figures 3 and 4 of the specification.

Comparative example 3

The nitrogen adsorption-desorption isotherms of the TS-1 molecular sieve powder described in example 3 were determined using the apparatus described in example 5. The obtained nitrogen adsorption-desorption isotherm and pore distribution curve are shown in figures 5 and 6 of the specification.

The results of example 5 and comparative example 3 show that the zeolite molecular sieve powder forming method provided by the invention has no obvious influence on the zeolite molecular sieve pore structure.

Claims

1. The zeolite molecular sieve powder forming method is characterized by comprising the following steps:

2. The method for forming zeolite molecular sieve powder according to claim 1, wherein the pretreatment process in step a is one or more of drying, pulverizing, roasting, solvent extraction, acid washing, alkali washing, water washing, ion exchange, hydrothermal treatment, steam treatment and impregnation.

3. The method for forming zeolite molecular sieve powder according to claim 1 or 2, wherein in step a, the zeolite molecular sieve skeleton type of the raw material is one or more than two of AEI, AEL, AFI, AFO, ATO, ATS, BEA, BEC, CHA and CLO, EDI, ERI, EUO, FAU, FER, GIS, HEU, LAU, LTA, LTL, MER, MFI, MOR, MTT, MTW, MWW, NES, RHO, TON; the central cation of the skeleton is one or more of silicon, phosphorus, aluminum, beryllium, boron, magnesium, gallium, germanium, arsenic, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc.

4. A process for the formation of a zeolite molecular sieve powder according to claim 1, 2 or 3, wherein the particle size of the powder to be formed obtained in step a is less than or equal to 1000 μm, preferably less than or equal to 500 μm, more preferably less than or equal to 100 μm.

5. The method for molding zeolite molecular sieve powder according to claim 1, wherein the polymer binder in the step b is one or more of gums, dextrins, celluloses, hemicelluloses, methylcellulose, carboxymethylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylhydroxypropylcellulose, starches, alginic acid, lignin, sesbania powder, gelatin, polyethylene glycol, polyethylene, polyvinyl chloride, polyvinyl alcohol, polypropylene, polyacrylonitrile, polyacrylamide, polymethyl methacrylate, polybutene, polybutadiene, polychloroprene, polyisoprene, polystyrene, polyurethane, polyphenylene oxide, polyphenylene sulfide, phenolic resin, epoxy resin, silicone epoxy resin, and nitrile rubber.

6. The method for forming zeolite molecular sieve powder according to claim 1 or 5, wherein the dispersant in the step b is one or more of water, methanol, ethanol, propanol, butanol, ethylene glycol, glycerin, ethyl acetate, diethyl ether, benzene, toluene, xylene, pentane, hexane, cyclohexane, heptane, octane, acetone, cyclohexanone, dichloromethane, chloroform, acetonitrile, pyridine.

7. The method of forming a zeolite molecular sieve powder according to claim 1, wherein the oxidizing atmosphere of step e comprises oxygen and an inert gas; wherein the volume fraction of oxygen is 0.5% to 30%, preferably 1% to 20%, more preferably 5% to 10%; the inert gas contains one or more of helium, carbon dioxide, nitrogen and argon.

8. The method of forming zeolite molecular sieve powder according to claim 1, wherein the non-oxidizing atmosphere in step f comprises one or more of hydrogen, helium, methane, carbon monoxide, carbon dioxide, nitrogen, and argon.

9. The method for forming zeolite molecular sieve powder according to claims 1 to 8, wherein the carbonized molded body obtained in step f is activated in an oxidizing atmosphere at a temperature of-20 to 400 ℃ for 0.2 to 48 hours; the oxidizing atmosphere comprises oxygen and inert gas, wherein the volume fraction of the oxygen is 1-10%, and the inert gas comprises one or more than two of helium, carbon dioxide, nitrogen and argon.