Alumina ceramic membrane support with high thermal shock resistance and method for producing the same

Abstract

The application provides an alumina ceramic membrane support with high thermal shock resistance, characterized in that the support is prepared by mixing raw materials of alumina, NTE oxide and pore-forming agent, binder, plasticizer, lubricant and water, pugging, extrusion and calcination; the mass ratio of the alumina, NTE oxide and pore-forming agent in the mixed powder is 75-98:2-10:0-15; the binder is 3-10% of the total mass of the mixed powder; the plasticizer is 1-3% of the total mass of the mixed powder; the lubricant is 0.1-2% of the total mass of the mixed powder; and the water is 10-30% of the total mass of the mixed powder. By introducing molybdate with near-zero / negative thermal expansion coefficient, the alumina ceramic membrane support with ultra-low or near-zero thermal expansion coefficient is prepared, so that the thermal shock resistance of the alumina porous ceramic support is significantly improved; the NTE oxide of molybdate can also be used as a sintering aid of alumina to promote the sintering of the alumina support; in addition, the NTE oxide has good acid and alkali corrosion resistance, and the prepared alumina ceramic membrane support has excellent mechanical properties and corrosion resistance, and can be used in the fields of high temperature and high pressure and gas-solid separation.

Description

A highly thermally shock resistant alumina ceramic film support and its preparation method Technical Field

[0001] This invention relates to the technical field of ceramic separation membranes, and specifically to a highly thermally shock resistant alumina ceramic membrane support and its preparation method. Background Technology

[0002] Inorganic ceramic membranes possess advantages such as high mechanical strength, good chemical stability, antimicrobial ability, high separation efficiency, and long service life, and are widely used in industries such as biomedicine, food and beverage, petrochemicals, metallurgy, electronics, and environmental water treatment. Ceramic membranes consist of a porous ceramic support and a separation membrane layer. The ceramic support serves as the carrier for the separation membrane layer, and its performance plays a crucial role in the overall performance of the ceramic membrane. Currently, the more mature commercial ceramic membranes are mainly made of alumina, titanium dioxide, zirconium oxide, and silicon carbide. Among them, the support for alumina, titanium dioxide, and zirconium oxide ceramic membranes is alumina. Alumina material has a high coefficient of thermal expansion (8*10). -6 ( / ℃) and low thermal conductivity (10-30 W·m) -1 ·K -1 This results in poor thermal shock resistance, thus limiting the application of alumina ceramic membranes in harsh conditions (high temperature, high pressure, etc.) and in gas-solid separation.

[0003] Currently, common methods for addressing the poor thermal shock resistance of dense or porous alumina ceramics include adding metal or metal alloy particles to improve thermal conductivity, and adding cordierite, mullite, aluminum titanate, or nepheline to reduce their coefficient of thermal expansion, thereby improving the thermal shock resistance of alumina ceramics. However, the interface between metal particles and alumina is poorly matched. For alumina ceramic film supports, excellent acid and alkali corrosion resistance is required. Adding cordierite, mullite, aluminum titanate, or nepheline will affect the alkali corrosion resistance of the alumina ceramic film support, so these conventional methods are not suitable for alumina ceramic film supports.

[0004] The literature review "Negative thermal expansion: a review" describes NTE-type oxides (with a negative average linear thermal expansion coefficient), which are oxides with good high-temperature thermal stability and resistance to acid and alkali corrosion. However, their application in the field of alumina ceramic films has never been reported. Therefore, there is an urgent need for a method to utilize the aforementioned NTE-type oxides to achieve high seismic resistance in alumina ceramic film supports. Summary of the Invention

[0005] The existing alumina ceramic membrane support has shortcomings, namely its poor thermal shock resistance, which limits the application of alumina ceramic membranes under harsh conditions (high temperature, high pressure, etc.) and in gas-solid separation. This invention improves the thermal shock resistance of the alumina ceramic membrane support by introducing NTE oxide, which has a negative coefficient of thermal expansion, good thermal stability, and excellent resistance to acid and alkali corrosion. Simultaneously, it also possesses excellent mechanical properties and corrosion resistance.

[0006] A highly thermally shock resistant alumina ceramic membrane support is disclosed. The support comprises a mixture of alumina, NTE oxide, and a pore-forming agent, a binder, a plasticizer, a lubricant, and water, which are mixed, kneaded, extruded, and then calcined. The mass ratio of alumina, NTE oxide, and pore-forming agent in the mixed powder is 75–98:2–10:0–15. The binder constitutes 3%–10% of the total mass of the mixed powder. The plasticizer constitutes 1%–3% of the total mass of the mixed powder. The lubricant constitutes 0.1%–2% of the total mass of the mixed powder. The water constitutes 10%–30% of the total mass of the mixed powder.

[0007] The NTE oxide powder contains at least ZrMo2O8, ZrV2O7, and Y2Mo3O. 12 Zr2Mo4O 15 One of its modified compounds;

[0008] The NTE oxide powder can be pre-synthesized by solid-state method or wet chemical method, or it can be directly mixed with alumina in the form of raw material oxide according to stoichiometric ratio.

[0009] The alumina powder has a particle size of 2-50 μm;

[0010] The pore-forming agent is one or more of starch, carbon powder, graphite powder, etc.

[0011] The binder is one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, and hydroxyethyl cellulose; the plasticizer is glycerin; and the lubricant is one or more of castor oil, oleic acid, and paraffin wax.

[0012] A method for preparing a high-thermal-shock-resistant alumina ceramic film support includes the following steps:

[0013] 1) Mix alumina powder, NET oxide, and pore-forming agent to obtain a mixed powder;

[0014] 2) The mixed powder is kneaded and shaped with binder, plasticizer, lubricant and water, and then extruded and dried to obtain the green body of the support.

[0015] 3) Calcine the alumina support green body to prepare the alumina ceramic film support.

[0016] In step 2) above, the extrusion temperature is 20-40℃ and the extrusion pressure is 1-10 MPa;

[0017] In step 2) above, the support preform can be a single-channel or multi-channel tubular membrane, or a single-layer or multi-layer flat sheet membrane.

[0018] In step 2) above, the green body is dried using microwave drying or electric heating blast drying;

[0019] In step 3) above, the calcination temperature is 1200-1500℃ and the calcination time is 2-6h.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: by introducing molybdates with a negative coefficient of thermal expansion, an alumina ceramic film support with an ultra-low or near-zero coefficient of thermal expansion is prepared, thereby significantly improving the thermal shock resistance of the porous alumina ceramic support; and molybdate-based NET oxides can also act as sintering aids for alumina to promote the sintering of the alumina support; in addition, NTE oxides have good resistance to acid and alkali corrosion, which makes the prepared alumina ceramic film support have excellent mechanical properties and corrosion resistance. Attached Figure Description

[0021] Figure 1 is a cross-sectional scanning electron microscope image of the sample from Example 1.

[0022] Figure 2 shows a cross-sectional scanning electron microscope image of the sample from Example 2.

[0023] Figure 3 shows a cross-sectional scanning electron microscope image of the sample from Comparative Example 1.

[0024] Figure 4 shows a cross-sectional scanning electron microscope image of the sample from Comparative Example 2. Detailed Implementation

[0025] The present invention will be further explained and described below with reference to specific embodiments.

[0026] Example 1:

[0027] The mixed powder of the support of the present invention is alumina powder (30μm), ZrMo2O8 and graphite powder, with a mass ratio of 80:10:10; the binder, plasticizer, lubricant and water are 3%, 1%, 0.5% and 20% of the total mass of the mixed powder, respectively.

[0028] The preparation method includes the following steps:

[0029] 1) Add alumina powder, ZrMo2O8 powder and graphite powder to a mixer and mix them to obtain a mixed powder;

[0030] 2) The mixed powder is kneaded and slurried with binder, plasticizer, lubricant and water, and then extruded and dried through an extruder at 5MPa to obtain a green body of multi-channel tubular membrane support;

[0031] 3) The green body of the multi-channel tubular membrane support was calcined at 1200℃ for 4 hours to prepare the alumina ceramic membrane support.

[0032] Example 2:

[0033] The mixed powder of the support of the present invention is alumina powder (5μm) and ZrV2O7 in a mass ratio of 98:2; the binder, plasticizer, lubricant and water are 5%, 3%, 0.5% and 25% of the total mass of the mixed powder, respectively.

[0034] The preparation method includes the following steps:

[0035] 1) Add alumina powder and ZrV2O7 powder to a high-power mixer for mixing to obtain a mixed powder;

[0036] 2) The mixed powder is kneaded and slurried with binder, plasticizer, lubricant and water, and then extruded and dried through a screw extruder at 2MPa to obtain a multi-channel tubular membrane support green body;

[0037] 3) The green body of the multi-channel tubular membrane support is calcined at 1500℃ for 2 hours to prepare the alumina ceramic membrane support.

[0038] Example 3:

[0039] The mixed powder of the support in this invention is alumina powder (20μm) and Y2Mo3O. 12 The mixture contains toner and carbon powder in a mass ratio of 91:4:5; the binder, plasticizer, lubricant, and water constitute 6%, 1%, 0.2%, and 15% of the total mass of the mixed powder, respectively.

[0040] The preparation method includes the following steps:

[0041] 1) Alumina powder, Y2Mo3O 12 Powder and toner are added to a mixer for mixing to obtain a mixed powder;

[0042] 2) The mixed powder is kneaded and slurried with binder, plasticizer, lubricant and water, then extruded and dried through an extruder at 7MPa to obtain a green sheet film support;

[0043] 3) The green sheet film support was calcined at 1400℃ for 4 hours to prepare the alumina ceramic film support.

[0044] Example 4:

[0045] The mixed powder of the support in this invention is alumina powder (50μm) and Zr2Mo4O. 15 The mixture contains starch in a mass ratio of 89:6:5; the binder, plasticizer, lubricant, and water constitute 4%, 2%, 0.6%, and 25% of the total mass of the mixed powder, respectively.

[0046] The preparation method includes the following steps:

[0047] 1) Alumina powder, Zr2Mo4O 15 Powder and starch are added to a mixer and mixed to obtain a mixed powder;

[0048] 2) The mixed powder is kneaded and slurried with binder, plasticizer, lubricant and water, and then extruded and dried through an extruder at 5MPa to obtain a single-channel tubular membrane support green body;

[0049] 3) The single-channel tubular membrane support green body was calcined at 1350℃ for 3 hours to prepare the alumina ceramic membrane support.

[0050] Comparative Example 1

[0051] The mixed powder of the support of the present invention is alumina powder (30μm) and starch in a mass ratio of 95:5; the binder, plasticizer, lubricant and water are 4%, 2%, 0.6% and 25% of the total mass of the mixed powder, respectively.

[0052] The preparation method includes the following steps:

[0053] 1) Add alumina powder and starch to a mixer and mix them to obtain a mixed powder;

[0054] 2) The mixed powder is kneaded and slurried with binder, plasticizer, lubricant and water, and then extruded and dried through an extruder at 5MPa to obtain a green body of multi-channel tubular membrane support;

[0055] 3) The multi-channel tubular membrane support green body was calcined at 1350℃ for 3 hours to prepare the alumina ceramic membrane support.

[0056] Comparative Example 2

[0057] The mixed powder of the support of the present invention is alumina (30μm), sintering aid and starch, in a mass ratio of 89:6:5; the binder, plasticizer, lubricant and water are 4%, 2%, 0.6% and 25% of the total mass of the mixed powder, respectively.

[0058] The preparation method includes the following steps:

[0059] 1) Add alumina powder, sintering aid and starch to a mixer and mix to obtain mixed powder;

[0060] 2) The mixed powder is kneaded and slurried with binder, plasticizer, lubricant and water, then extruded and dried through an extruder at 10MPa to obtain a green body of multi-channel tubular membrane support;

[0061] 3) The multi-channel tubular membrane support green body was calcined at 1350℃ for 3 hours to prepare the alumina ceramic membrane support.

[0062] The thermal shock resistance of ceramic materials is often characterized by the coefficient of thermal expansion, the critical thermal shock temperature difference, and the residual strength after cyclic thermal shock. The smaller the coefficient of thermal expansion, the larger the critical thermal shock temperature difference ΔT, and the higher the residual strength after multiple cyclic thermal shocks, the better the thermal shock resistance.

[0063] The tubular / flat ceramic membrane supports from the above embodiments and comparative examples were cut into standard samples of 3*4*36mm, and their linear thermal expansion coefficients were tested using a thermal dilatometer. After the heated ceramic samples were rapidly cooled in water, the maximum temperature difference ΔT was determined when the flexural strength did not decrease significantly after a single thermal shock. The thermal shock resistance cycle test employed a water-cooled thermal cycle, with one cycle consisting of holding at 250℃ for 1 hour and then cooling in water for 5 minutes. The data for each embodiment and comparative example are shown in the table below.

[0064] Table 1. Performance test results of alumina ceramic film support specimens prepared in various embodiments of the present invention.

[0065]

[0066] A comparison of the examples and comparative examples shows that adding NTE-type oxides can reduce the coefficient of thermal expansion of the alumina ceramic film support, increase the critical thermal shock temperature difference and residual strength after multiple thermal shock cycles, and significantly improve the thermal stability of the alumina ceramic film support. The residual flexural strength after 20 thermal shock cycles is 40-50% higher than that of the comparative example. Due to their negative coefficient of thermal expansion, NET-type molybdates exhibit opposite expansion and contraction characteristics to alumina ceramics during thermal shock cycles, which can release and eliminate residual thermal stress, thereby improving the residual strength after multiple thermal shock cycles. Furthermore, electron micrographs also show that the added NTE-type oxides act as sintering aids, forming effective sintering necks between particles, increasing particle bonding, and promoting sintering.

[0067] Comparative Examples 1 and 2 show that the alumina support has low strength without sintering aids and does not meet the requirements. After adding commonly used sintering aids, a liquid phase is formed between the particles to increase the bonding between the particles and promote sintering. However, the bonding between the particles is not tight enough. During the cyclic thermal shock process, the bonding between the particles weakens under the action of thermal stress.

Claims

1. A highly thermally shock resistant alumina ceramic film support, characterized in that... The support is made from a mixture of alumina, NTE oxide, and a pore-forming agent, a binder, a plasticizer, a lubricant, and water, which are mixed, kneaded, extruded, and then calcined. The mass ratio of alumina, NTE oxide, and pore-forming agent in the mixed powder is 75–98:2–10:0–15. The binder constitutes 3%–10% of the total mass of the mixed powder. The plasticizer constitutes 1%–3% of the total mass of the mixed powder. The lubricant constitutes 0.1%–2% of the total mass of the mixed powder. The water constitutes 10%–30% of the total mass of the mixed powder. The NTE oxide powder contains at least ZrMo₂O₈, ZrV₂O₇, and Y₂Mo₃O₃. 12 One of Zr2Mo4O15 and its modified compounds.

2. The support body according to claim 1, characterized in that... The NTE oxide powder is pre-synthesized by solid-state method or wet chemical method, or directly mixed with alumina in the form of raw material oxide according to stoichiometric ratio.

3. The support body according to claim 1, characterized in that... The alumina powder has a particle size of 2-50 μm.

4. The support body according to claim 1, characterized in that... The pore-forming agent is selected from one or more of starch, carbon powder, and graphite powder.

5. The support body according to claim 1, characterized in that... The binder is one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, and hydroxyethyl cellulose; the plasticizer is glycerin; and the lubricant is one or more of castor oil, oleic acid, and paraffin wax.

6. A method for preparing the alumina ceramic film support with high thermal shock resistance as described in claim 1, comprising the following steps: 1) Mix alumina powder, NTE oxide and pore-forming agent to obtain a mixed powder; 2) The mixed powder is kneaded and slurried with binder, plasticizer, lubricant and water, and then extruded and dried to obtain a green support body; 3) The green alumina support body is calcined to prepare an alumina ceramic film support body.

7. The method according to claim 6, characterized in that... In step 2) above, the extrusion temperature is 20-40℃ and the extrusion pressure is 1-10Mpa.

8. The method according to claim 6, characterized in that... In step 2) above, the support preform is a single-channel or multi-channel tubular membrane, or a single-layer or multi-layer flat sheet membrane.

9. The method according to claim 6, characterized in that... In step 2) above, the green body is dried using microwave drying or electric heating blast drying; in step 3), the calcination temperature is 1200-1500℃ and the calcination time is 2-6h.

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