CN100352788C - Method for producing iolite-based and mullite-based tubular ceramic separation membrane - Google Patents

Abstract

The present invention relates to a method for preparing a cordierite base mullite base tubular ceramic separation membrane, which belongs to the technical field of the separation membrane preparation. First, slurry prepared by fine cordierite particles is used for the surface modification on coarse particle raw material powder, coarse grain cordierite powder and mullite powder are respectively dipped in the fine particle cordierite powder slurry for mechanical stirring, after 1 to 2 hours, the powder is filtered out and is dried, the mass percent of the powder weight increment is between 8 and 15%, the particle size of the fine particle cordierite powder is smaller than 10 micrometers, and the volume ratio of the coarse particle cordierite or mullite powder to the slurry is 1/3 to 5; then, an extrusion forming method is used for preparing a macropore ceramic tube supporter, and a membrane layer is prepared on the supporter. The present invention uses the fine particle cordierite powder slurry for the surface modification treatment on the coarse particle raw materials, so large particle aggregate powder is sintered. Thus, the cordierite base mullite base tubular ceramic separation membrane manufactured by the method has the advantages of high mechanical strength, high thermal shock resistance, large pore diameter, high flux, small osmotic resistance, etc. The method has the advantages of short preparation period and low cost, and is suitable for industrial application.

Description

Preparation method of cordierite-based or mullite-based tubular ceramic separation membrane

technical field

The invention relates to the technical field of preparation of ceramic separation membranes.

Background technique

High-temperature ceramic membrane filtration and separation technology is an advanced hot gas purification technology developed in the 1980s. It is used in the removal of high-temperature smoke and dust in the chemical, chemical, metallurgical, and ceramic industries, the purification of gases, and the recovery of various ceramic powders, etc. The field has broad application prospects. As the key material of this type of technology - high-temperature ceramic filter membrane material, it is usually required to have high temperature resistance, good thermal and chemical stability, high filtration and dust removal accuracy, easy regeneration, stable operation and other properties. The manufacture of this kind of ceramic separation membrane is usually to first make the large-pore ceramic membrane into a tubular shape, and then prepare one or more separation layers with smaller pore diameters on the outer surface or inner surface to form the so-called asymmetric membrane element. This tubular asymmetric separation membrane element not only has high gas flow rate, but also ensures high dust removal and separation effect and structural strength, and is especially welcomed by users.

Commercialized porous ceramic membranes are made of Al ₂ O ₃ , ZrO ₂ , and TiO ₂ . The raw materials are expensive and the manufacturing cost is high, which limits their large-scale application, such as dust removal and environmental protection. Moreover, its thermal shock resistance is poor, and it cannot be used in high-temperature gas-solid separation processes such as high-temperature dust removal and dust collection. On the other hand, their sintering temperature is high, which brings great difficulties to the preparation, especially the large-pore porous ceramic membrane with high gas flow rate.

In addition to the general advantages of porous ceramics, cordierite (2MgO·2Al ₂ O ₃ ·5SiO ₂ ) and mullite (3Al ₂ O ₃ ·2SiO ₂ ) porous ceramics also have the advantages of low thermal expansion coefficient and good thermal shock resistance , so it can be widely used in high temperature dust removal, catalyst carrier for automobile exhaust treatment and other fields. Traditional cordierite porous ceramics mostly use expensive artificial reagents as raw materials. After firing at a certain temperature, they are crushed and classified, and then molded for secondary sintering. The raw materials of the product are expensive and the preparation process is complicated. At present, there have been reports of sintering cordierite materials with talc or industrial waste fly ash as raw materials at a certain temperature, for example, CN03128180. Cordierite Porous Ceramic Membrane. Synthetic cordierite and mullite powders with large particle size have poor activity during sintering, and their high melting point requires high temperature to sinter large particles, which not only increases the manufacturing cost, but also cannot guarantee sufficient mechanical strength.

"Inorganic Synthesis and Preparation Chemistry" (edited by Xu Ruren, etc., pages 550-558) published by Higher Education Press provides the preparation method of the commonly used tubular ceramic membrane: first prepare the tubular support with extrusion molding (extrusion) , and then deposit one or more layers of film on its outer surface or inner surface by dip-coating. In order to prepare a support body with a large pore size, ceramic powder with a large particle size should be used. However, their sintering activity is poor. To sinter into macroporous ceramics with sufficient strength, a high sintering temperature is required. For example, the sintering temperature of alumina porous supports exceeds 1650°C, which is one of the reasons for the high price of alumina ceramic membranes. . In the practice of firing ceramics, it is generally necessary to add a sintering aid with a low melting point. For example, when preparing a macroporous alumina support film, a small amount of kaolin should be added as a sintering aid. However, such additives cannot be used in the manufacture of high-temperature ceramic membrane supports, because the phase formed by the sintering aid has poor thermal shock resistance and corrosion resistance.

In the prior art, cordierite porous ceramics have been widely used as three-way catalyst supports for automobile exhaust, but they are limited to fine-pore honeycomb ceramics with a submicron pore size. There has been no report on cordierite porous ceramics with large pore sizes. Mullite As a well-known high-temperature resistant ceramic, it has also been widely used, but there are no related reports on the preparation of macroporous ceramics.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, to realize the preparation of high temperature resistant cordierite or mullite-based support ceramic membranes with low temperature sintering through surface modification of large-grained powder raw materials, and to use industrial waste materials Fly ash is used as raw material, basic magnesium carbonate is added, and porous cordierite ceramic film is synthesized in situ by reaction sintering, or the film is prepared by physical sintering of industrial cordierite powder, so that cordierite-based or mullite-based tubular ceramic separation membrane.

The preparation method of the cordierite-based or mullite-based tubular ceramic separation membrane of the present invention includes preparing a cordierite-based or mullite-based macroporous support by extrusion molding, and preparing a separation membrane layer on the support, which It is characterized in that the steps are: (1) first use the fine-grained cordierite powder slurry to modify the surface of the coarse-grained raw material powder: respectively impregnate the coarse-grained cordierite and mullite powders into the fine-grained cordierite powder After mechanical stirring in the slurry for 1-2 hours, the coarse powder is filtered out, dried, and the above steps are repeated, so that the weight percentage of the cordierite-based or mullite powder is 8-15%. The particle size of the fine cordierite powder of the active agent is 5-10 microns; the fine cordierite powder slurry is made of coarse cordierite powder and organic additives (dispersant) suspended and dispersed in the water medium by wet method Formed by ball milling for 5-20 hours, the solid content of the slurry is 10-20% (mass percentage); the organic additive is a polymer dispersant, such as PEG or PAA, a binder PVA, and a plasticizer glycerin; Wherein, the volume ratio of coarse-grained cordierite or mullite powder and fine-grained cordierite powder in the slurry is 1:3-5; the particle size of the coarse-grained cordierite and mullite raw material powder is 50 -500 microns; (2) Extrude the ceramic tube base body on the extruder with existing technology, sinter 3-4 hours under 1380 ℃, air atmosphere, obtain the tubular macroporous support body after cooling; (3) then Prepare the membrane layer on the tubular macroporous support by using the existing technology: the outer membrane is prepared by thermal spraying (spray-coating), or the outer membrane and inner membrane are prepared by dip-coating, or The modified layer is prepared by suspending slurry dipping coating technology; the slurry used is the same as the above-mentioned fine-grained cordierite powder slurry; the thermal spraying used refers to the suspended particle slurry spraying technology in the prior art, and the surrounding temperature is controlled Cool naturally at 80-90°C, and then sinter at high temperature to get the finished product.

For the preparation of fine-grained cordierite slurry, in order to reduce costs, it is not necessary to use chemical reagents as raw materials to prepare powders by chemical synthesis, but to use: 1) commercially available cheap 400-mesh standard sieve Add water to cordierite industrial powder to make a slurry, and after settling for several hours, take the suspended particles in the supernatant liquid as the powder raw material for preparing fine-grained slurry; or 2) mix industrial waste fly ash with stoichiometric industrial basic magnesium carbonate (Analytical pure) mixed as a powder raw material for preparing fine-grained slurry, wherein the mass ratio of fly ash to basic magnesium carbonate is between 5:1-3:1.

The preparation method of the cordierite-based or mullite-based tubular ceramic separation membrane of the present invention, because in the step of preparing the cordierite-based or mullite-based porous support body, the slurry prepared with fine-grained cordierite powder The coarse-grained raw material powder has undergone surface modification treatment, so the large-grained aggregate powder can be sintered at a lower temperature, endowing the support with good mechanical strength and thermal shock resistance, and its preparation conditions and other energy It is more convenient to control, and its pore size, porosity, permeation flux and other parameters can be selected by selecting the original powder particle size. It has the advantages of stable quality, strong repeatability, short preparation cycle and low cost, and is suitable for industrial applications.

The cordierite-based or mullite-based tubular ceramic separation membrane prepared by the preparation method of the invention has large pore size, high flux, low permeation resistance, high mechanical strength and good thermal shock resistance.

Further description is given below by way of examples.

Example 1: Preparation of a full cordierite-based ceramic membrane (outer membrane) using fly ash and basic magnesium carbonate as modifiers

(1) Impregnation modification of powder:

The 6% fly ash dispersion slurry was settled for 4 hours, the fine powder of the supernatant liquid was discarded, dried and ground to obtain a powder, the average particle size was about 6.5 μm, and the fly ash powder and basic magnesium carbonate were mixed by 3 : 1 ratio, add PVA as binder, PEG-10000 as dispersant, glycerin as plasticizer, ball mill and mix for 12 hours, and prepare fine slurry with 20% solid content.

Put commercial synthetic cordierite powder through a standard sieve, take the powder between 100-300 μm, put it in the above-mentioned fine slurry, and stir it mechanically for 1 hour, so that a layer of slurry is evenly immersed around the powder particles, Then dry, repeat 4 times, powder body weight gain is 10%.

(2) Extrusion molding: use the usual method to mix the impregnated powder, methyl cellulose and appropriate amount of starch by dry ball milling, add warm water to make mud, refine it on a mud kneader to make plastic mud, and stale for 3 days . Vacuum practice mud 4 times, stale for 2 days. Prepare a ceramic tube blank with an outer diameter of 40mm on the extruder, dry it for 72 hours, use a program-controlled electric furnace to raise the temperature from room temperature to 400°C at 2°C/min, keep it warm for 1 hour, and then rise to 1380°C at 4°C/min ℃, keep it warm for 4 hours, and then take it out of the furnace after cooling with the furnace to obtain a tubular cordierite support.

(3) Preparation of film layer:

The 5% fly ash dispersion slurry was settled for 5 hours, the fine powder of the supernatant liquid was discarded, dried and ground to obtain a powder with an average particle size of 6.0 μm. By coal ash powder: basic magnesium carbonate: PVA: glycerol=1: 0.2: 0.08: 0.001 (mass ratio) ratio preparation suspension slurry, the solid content of slurry is 15%, adopts thermal spray technology, in above-mentioned place The outer surface of the prepared support was spin-coated with a layer of wet film blank, and dried at 70° C. under an air atmosphere for 1 hour; the obtained dried green film was burned at 900° C. under an air atmosphere for 1 hour. Then soak in the above slurry with 10% solid content, and dry at room temperature for 3 days at a relative humidity of 80. Sintering for 1 hour at 1150° C. under air conditions, with a heating rate of 1° C./min, to obtain a full cordierite-based porous separation membrane with a thickness of 100-130 μm.

Example 2: Preparation of a cordierite-based asymmetric membrane (inner membrane) using cordierite fine powder as a modifier.

(1) Impregnation modification of powder:

Settling the 10% cordierite fine powder dispersion slurry for 4 hours, discarding the fine powder in the supernatant liquid, drying and grinding to obtain a powder with an average particle size of about 7 μm. Cordierite fine powder, binder PVA, dispersant PEG-10000, plasticizer glycerin, ball milling and mixing for 12 hours to prepare a fine slurry with a solid content of 17%.

Put the commercial cordierite powder through a standard sieve, take the powder between 200-350μm, put it in the above-mentioned fine slurry, stir it mechanically for 1 hour, so that a layer of slurry is uniformly impregnated around the powder particles, and then dry , repeated 5 times, the powder weight gain was 12%.

(2) molding by the extrusion molding method of embodiment 1, drying, sintering. The sintering temperature is 1360°C, the temperature is kept for 4 hours, and the tubular cordierite support is obtained after cooling with the furnace.

(3) Preparation of film layer:

The 8% cordierite fine powder dispersion slurry was settled for 6 hours, the fine powder in the supernatant was discarded, dried and ground to obtain a powder with an average particle size of 6.5 μm. Prepare the suspension slurry in the ratio of coal ash powder: basic magnesium carbonate (analytical pure): PVA: glycerol=1: 0.2: 0.08: 0.001 (mass ratio), the solid content of the slurry is 15%, in the above-mentioned support body Prepare a layer of wet film on the surface by dip coating with suspended particles, dry at room temperature for 3 days at a relative humidity of 80, and then dry at 70°C for 1 hour in an air atmosphere. Sintering at 1150° C. under air conditions for 1 hour with a heating rate of 1° C./min to obtain a full cordierite-based porous separation membrane.

Example 3: Preparation of cordierite outer membrane supported by mullite macroporous ceramics.

(1) Impregnation of powder:

Cordierite fine powder is used as the modifier of the powder, and the preparation of the fine slurry is according to (1) in Example 2.

Put the commercialized synthetic mullite powder through a standard sieve, take the powder between 100-300 μm, put it in the above slurry, and stir it mechanically for 2 hours, so that a layer of slurry is evenly impregnated around the powder particles, and then Drying was repeated 5 times, and the weight gain of the powder was 12%.

(2) Mix the impregnated powder with MC-400 (methyl cellulose) and starch by dry ball milling at a ratio of 1:0.05:0.006 (mass ratio). Make mud with warm water, refine it on a clay kneader for 50 minutes to form plastic mud, and stale for 3 days. Vacuum practice mud 4 times, stale for 3 days. A single-channel porous ceramic membrane body was prepared in an extruder, dried for 72 hours at a constant temperature of 20°C and a relative humidity of 80°C, and constrained to dry in a constant temperature oven at 40°C for 12 hours. Rise to 400°C at 2°C/min, hold for 1 hour, then rise to 1450°C at 4°C/min, hold for 4h, cool with the furnace, and then take out the furnace to obtain a tubular mullite support.

(3) Preparation of the film layer: the preparation of the film layer can refer to Example 1 to obtain the finished product.

Claims (3)

1. A method for preparing a cordierite-based or mullite-based tubular ceramic separation membrane, comprising preparing a cordierite-based or mullite-based macroporous support by extrusion molding, and preparing a separation membrane layer on the support, It is characterized in that the steps are (1) Firstly, use the fine-grained cordierite powder slurry to modify the surface of the coarse-grained raw material powder: respectively immerse the coarse-grained cordierite or mullite powder in the fine-grained cordierite powder slurry and mechanically stir for 1 After 2 hours, the coarse powder is filtered out, dried, and the above steps are repeated, so that the weight percentage of the coarse cordierite or mullite powder is 8-15%, wherein the fine cordierite used as a modifier The particle size of the powder is 5-10 microns; the fine-grained cordierite powder slurry is made by suspending and dispersing coarse-grained cordierite powder and organic additives in an aqueous medium and wet ball milling for 5-20 hours. The solid content mass percent of the material is 10-20%; the organic additive is a polymer dispersant; wherein, the volume ratio of the coarse cordierite or mullite powder and the fine cordierite powder in the slurry is 1 : 3-5; the particle size of the coarse-grained cordierite or mullite raw material powder is 50-500 microns; (2) extrude the ceramic tube blank on the extruder with the prior art, through 1380 ℃, air Sintering under the atmosphere for 3-4 hours, after cooling, the tubular macroporous support is obtained; (3) reusing the existing technology to prepare the film layer on the tubular macroporous support: the outer film is prepared by thermal spraying process, or the suspension slurry is used The outer film and the inner film are prepared by dipping coating technology, or the modified layer is prepared by using the suspension slurry dipping coating technology; the slurry used is the same as the above-mentioned fine-grained cordierite powder slurry; the thermal spraying used refers to the prior art The suspended particle slurry spraying technology in the process, the ambient temperature is controlled within 80-90°C, cooled naturally, and then sintered at high temperature to obtain the finished product. 2. the preparation method of cordierite-based or mullite-based tubular ceramic separation membrane as claimed in claim 1, is characterized in that, the powder raw material in described fine-grained cordierite powder slurry is made of standard sieve The cordierite industrial powder is the particle suspended in the upper liquid phase after adding water to slurry and settling. 3. the preparation method of cordierite-based or mullite-based tubular ceramic separation membrane as claimed in claim 1, is characterized in that, the powder raw material in described fine-grained cordierite powder slurry is made of industrial waste pulverized coal The ash is mixed with chemically pure metered industrial basic magnesium carbonate, and the mass ratio of fly ash to basic magnesium carbonate is between 5:1 and 3:1.