CN111672512A - A kind of monolithic honeycomb catalyst and its preparation method and application - Google Patents

Abstract

The invention provides an integral honeycomb catalyst and a preparation method and application thereof, wherein the integral honeycomb catalyst comprises acid-washed red mud powder and a forming auxiliary agent as raw materials, wherein the amount of the forming auxiliary agent is 55-80 wt% of the amount of the acid-washed red mud powder, and the forming auxiliary agent comprises: carboxymethyl cellulose, neutral silica sol, glass fiber, active carbon, oleic acid and water. The catalyst has good process formability and excellent denitration performance.

Description

A kind of monolithic honeycomb catalyst and its preparation method and application

technical field

The invention relates to the technical field of catalyst molding, in particular to a monolithic honeycomb catalyst and a preparation method and application thereof.

Background technique

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

The large amount of nitrogen oxides emitted by coal-fired power plants in the industrial production process will cause serious harm to the atmospheric environment and human health. Ammonia selective catalytic reduction (NH ₃ -SCR) technology, as the mainstream nitrogen removal technology in thermal power plants, has the advantages of low operating cost, simple equipment and high nitrogen removal rate. As the core of the technology, the physical and chemical properties of the denitration catalyst directly determine the safety, economy and efficiency of the entire denitration system. At present, the vanadium-titanium-based honeycomb catalysts widely used in coal-fired power plants have a narrow active temperature window and high production costs. At the same time, compounds formed by the reaction of vanadium with alkali metal impurities in flue gas are easily volatilized from the catalyst, causing secondary pollution. Therefore, the research direction of reducing catalyst cost and developing alternative catalysts will be a research hotspot in the field of energy and environmental engineering.

Red mud is a harmful waste residue produced during the processing of bauxite, a common raw material for aluminum production. According to statistics, 1-1.5 tons of red mud is incidentally produced for every 1 ton of alumina produced. A large amount of red mud will not only occupy a lot of land. Due to the strong alkalinity of red mud, its chemical composition penetrates into the ground, which can easily cause soil alkalization and swamping, and also lead to groundwater pollution. Therefore, effective resource utilization of red mud is imperative.

At present, the research on red mud mainly focuses on the production of cement, unburned bricks, concrete, ceramics and other materials, and the recovery of adsorbents, valuable metals and lye. In recent years, studies have found that a large amount of Fe ₂ O ₃ contained in red mud is the main active component of iron-based catalysts, and its main components such as Al ₂ O ₃ and TiO ₂ are also commonly used materials for catalyst supports. In addition, red mud has good porous The skeleton structure, the large difference in the mineral lattice, and the good adsorption performance, so red mud has great potential as a catalyst for SCR denitration.

Studies have shown that pretreatment of red mud (pickling, acid digestion, acid digestion-alkali precipitation, etc.) can not only reduce the alkali content of red mud, but also greatly increase the specific surface area of red mud, improve the pore structure of red mud, and improve denitrification. efficiency. The pretreatment process of red mud is simple and economical, and the pretreated red mud has a good application prospect in the field of catalysis. However, the current research on red mud is still in the preparation and modification of powder catalysts. However, powder catalysts have defects such as inconvenient loading and unloading, high bed pressure drop, and easy to be entrained by flue gas in the process of denitration application in coal-fired power plants. Therefore, it is necessary to It is made into a certain shape by a suitable molding process, so as to reduce the pressure drop of the bed and the amplification effect, and at the same time ensure that the monolithic catalyst can still have good denitration performance. However, in the existing process, it is often necessary to add a carrier alone or the performance of the catalyst is often affected by the addition of a molding aid, so it is difficult to achieve the desired effect.

SUMMARY OF THE INVENTION

Therefore, the purpose of the present invention is to provide a monolithic honeycomb catalyst with good formability and excellent denitration performance and its preparation method and application. The monolithic honeycomb catalyst of the present invention has good mechanical strength, and its axial compression resistance The strength can reach about 2-2.4MPa, which meets the requirements of the national standard GB_T 31587-2015 honeycomb flue gas denitration catalyst (which requires axial compressive strength ≥ 2MPa), and a good NO _x conversion rate, in 325-400 The denitrification efficiency of more than 80% can be always maintained at the working temperature of ℃, and it is easy to be applied in industrialization, and the preparation process is simple and easy to be produced and applied in industrialization. In addition, red mud is a solid waste produced by the aluminum industry, which is harmful to the environment. The effective pretreatment and molding process provided by the invention can recover waste red mud, and use it as an SCR catalyst to remove _NOx , so as to achieve the purpose of "treating waste with waste".

Specifically, the technical solution of the present invention is as follows:

In a first aspect of the present invention, an integral honeycomb catalyst is provided, which comprises using acid-washed red mud powder and a molding aid as raw materials, wherein the amount of the molding aid is 3.5% of that of the acid-washed red mud powder. 55-80 wt%, the forming aids include: carboxymethyl cellulose, neutral silica sol, glass fiber, activated carbon, oleic acid and water.

In the embodiment of the present invention, carboxymethyl cellulose and oleic acid are organic substances, which will be decomposed into H ₂ O and CO ₂ during the catalyst roasting process, and the main substances in neutral silica sol and glass fiber are SiO ₂ and Al ₂ O ₃ , when added to the catalyst, can not only act as a carrier, improve the dispersion of active components, but also provide framework support for the catalyst and improve mechanical strength, and the content of SiO ₂ in neutral silica sol is small, most of which is H ₂ O; activated carbon is an industrial carbon material, which is decomposed into CO ₂ after roasting; H ₂ O is a good solvent, which is beneficial to the mutual fusion between the red mud powder and the molding aid, and the aid combination of the present invention is not only beneficial to the catalyst Forming, to ensure its mechanical strength, but also to ensure that the active components of the catalyst will not be too diluted, so as to ensure the catalytic performance of the catalyst.

In the embodiment of the present invention, the dosages of the forming aids relative to the acid-washed red mud powder are: 1-3wt% of carboxymethyl cellulose, 10-30wt% of neutral silica sol, and 5-20wt% of glass fiber , activated carbon 1-5wt%, oleic acid 3-5wt%, water 30-60wt%. In this paper, relative to the amount of pickling red mud powder, for example, the amount of carboxymethyl cellulose relative to pickling red mud powder is 1-3wt%, that is, the amount of carboxymethyl cellulose is the amount of pickling red mud powder. 1-3wt%.

Further, the dosages of the forming aids relative to the pickling red mud powder are: carboxymethyl cellulose 3wt%, neutral silica sol 20-30wt%, glass fiber 5-15wt%, activated carbon 1-3wt%, Oleic acid 5wt%, water 40-50wt%.

Further preferably, the dosages of the forming aids relative to the pickling red mud powder are: carboxymethyl cellulose 3wt%, neutral silica sol 30wt%, glass fiber 15wt%, activated carbon 3wt%, oleic acid 5wt%, Water 50wt%.

In the embodiment of the present invention, the particle size of the acid-washed red mud powder is below 200 mesh. As the particle size decreases, the strength of the catalyst gradually increases, and the catalytic performance improves, but the smaller particle size will This leads to an increase in production cost; if the particle size is too large, it is not conducive to the full combination of red mud particles and molding aids, resulting in poor molding effect. When the particle size of the pickled red mud powder of the present invention is 200 mesh and below, especially 100-200 mesh, the comprehensive effect is better. The pickling red mud powder of the present invention can adopt conventional pickling red mud, but more preferably, the pickling red mud powder of the present invention is prepared by the following method: mix an appropriate amount of 100-mesh original red mud with 3mol/L The hydrochloric acid solution was evenly mixed at a liquid-solid ratio of 9:1, heated and stirred at a water bath temperature of 70 °C for 2 hours, filtered to pH=7 or so, dried at 105 °C for 12 hours, calcined at 550 °C for 5 hours, and then used a ball mill. Grind it into particles below 200 mesh. After the pickling treatment of the present invention, a large amount of alkali metals and alkaline earth metals in red mud can be removed to a greater extent, which is beneficial to increase the relative content of its active components Fe ₂ O ₃ , carriers Al ₂ O ₃ and SiO ₂ , so that the denitration performance of the pickled red mud powder as a catalyst is improved.

In an embodiment of the present invention, the glass fiber is an alkali-free glass fiber, and its diameter is 0.15 mm or less, such as 0.1-0.15 mm. When the diameter of the glass fiber is large, different degrees of agglomeration will occur inside, and it is difficult to disperse during the molding process, which affects its reinforcement effect. Glass fiber diameters that are too small will not provide maximum strength enhancement.

In the embodiment of the present invention, the addition of both carboxymethyl cellulose and neutral silica sol was particularly selected, and it was found that the plasticity of the mud embryo could be significantly improved. This improvement was achieved when carboxymethyl cellulose alone or neutral not possible with silica sol. In the embodiment of the present invention, carboxymethyl cellulose will decompose and volatilize at high temperature, resulting in more pores inside the red mud catalyst, while avoiding acid sites (especially B acid sites) and excessive adsorption of oxygen At the same time, the addition of neutral silica sol can improve the dispersibility of Fe ₂ O ₃ on the SiO ₂ carrier, improve the crystallinity of Fe ₂ O ₃ , the interaction between the carrier and the active ingredient Fe ₂ O ₃ is enhanced, and the carboxymethyl Under the combined action of the base cellulose and the neutral silica sol, the influence of the binder on the red mud catalyst is minimized on the premise of ensuring the plasticity and mechanical strength. In particular, when the amount of carboxymethyl cellulose is 1-3wt% of the acid-washed red mud powder, and the amount of neutral silica sol is 10-30wt% of the acid-washed red mud powder, the above-mentioned effects that can be achieved are particularly significant, especially , when the carboxymethyl cellulose content is 3wt% and the neutral silica sol content is 10-30wt% (especially 30wt%), the above-mentioned effect can be achieved most significantly.

In the embodiment of the present invention, 100-mesh alkali-free glass fiber is selectively added, and it is found that the use of 100-mesh alkali-free glass fiber can withstand stress and avoid damage and cracking of the honeycomb catalyst. At the same time, it can be used as the carrier of SiO ₂ and Al ₂ O ₃ to increase the carrier content, which is further conducive to the dispersion of red mud active component Fe ₂ O ₃ on the carrier, and improves the crystallinity of Fe ₂ O _3. The carrier and active component Fe _The interaction of _2O3 is enhanced, which reduces the influence of structural additives on the red mud catalyst. At the same time, SiO ₂ and Al ₂ O ₃ are used as the framework of the active components of the catalyst, although they do not have catalytic activity, they can increase the strength of the catalyst. In particular, when the amount of 100-mesh alkali-free glass fiber is 5-20wt% of the acid-washed red mud powder, preferably 5-10wt%, especially 15wt%, the above effect is most significant, and the relationship between strength and catalytic activity is more obvious. balanced.

In the embodiment of the present invention, the selective addition of activated carbon can improve the pore structure inside the red mud catalyst and increase the specific surface area of the catalyst. It is beneficial to increase the number of acid sites and adsorbed oxygen for the red mud catalyst, which is beneficial to the NH ₃ -SCR reaction. When the amount of activated carbon is 1-5wt% (accounting for the amount of pickled red mud powder), with the increase of the amount of activated carbon, the strength of the catalyst decreases slightly within a certain range, while the catalytic activity has slightly different degrees within a certain range. When the amount of activated carbon is 3 wt%, it has relatively better catalytic activity, which shows that the decrease of catalytic conversion rate is less and more gradual when it exceeds 375 °C.

In the embodiment of the present invention, oleic acid is used as a lubricant or an extrusion aid, and volatilizes after being roasted at a high temperature, which basically does not affect the denitration performance of the red mud catalyst.

In the second aspect of the present invention, there is provided a method for preparing the monolithic honeycomb catalyst described in the first aspect, which comprises: mixing acid-washed red mud with carboxymethyl cellulose, neutral silica sol, glass After the fiber and activated carbon are fully mixed, oleic acid and water are added, and the red mud paste is prepared by refining mud. After drying, it is roasted, and it is obtained after cooling.

In the embodiment of the present invention, the vacuum placement of the paste can prevent the plasticity of the green body from being reduced due to the rapid loss of moisture in the catalyst green body, and thus is more conducive to extrusion molding.

In the embodiment of the present invention, the aging can ensure the sufficient absorption of water by the auxiliary agent, which helps to improve the molding efficiency and molding quality.

In an embodiment of the invention, oleic acid is added before water.

In an embodiment of the present invention, the drying temperature is 40-100°C, preferably 40-80°C.

In the embodiment of the present invention, the water loss rate of the catalyst is gradually accelerated with the continuous increase of the drying temperature. At 40-100 °C, the drying of the catalyst embryo can be completed in 3-9 h, but it is worth noting that when the drying temperature is 100 °C and above, the embryo is easily cracked, thereby reducing the yield. In order to improve the yield, the present invention preferably performs drying at 40-80°C.

In the embodiment of the present invention, the aging time is 24-48h.

In the embodiment of the present invention, the roasting adopts two-stage roasting, including raising the temperature to 250-320 °C at a heating rate of 2-8 °C/min and maintaining it for 2-8 h, and then increasing the temperature at a heating rate of 2-8 °C/min. Raised to 450-600°C and maintained for 2-8h.

One-stage roasting can easily make some organic substances remain inside the catalyst and block part of the internal pore structure. In the embodiment of the present invention, the use of two-stage roasting can fully burn and volatilize the organic substances added to the catalyst, which is more conducive to the SCR reaction. progress, and is more conducive to the enhancement of strength.

In a more preferred embodiment of the present invention, the method includes: fully mixing acid-washed red mud with carboxymethyl cellulose, neutral silica sol, glass fiber, and activated carbon, then adding oleic acid and water, and refining the mud to prepare red mud Mud paste, the obtained paste is vacuum-sealed and then extruded to form, and then the extruded embryo is aged at room temperature, and then dried at 60-80 ℃ and then roasted in two stages: including setting the temperature to 4 The heating rate of -6°C/min was raised to 280-300°C and maintained for 3-6h, and then raised to 500-600°C at a heating rate of 4-6°C/min and maintained for 3-6h, after cooling.

In a third aspect of the present invention, an application of the monolithic honeycomb catalyst described in the first aspect above in the field of environmental protection is provided, and the application is catalytic denitration.

Compared with the prior art, the present invention has the following excellent effects:

1. Advantages in formulation: all the molding auxiliaries used are cheap and easy to obtain, and the denitration performance and mechanical properties of the monolithic catalyst are guaranteed with a specific combination and dosage.

2. Technological advantages: The molding and preparation of the red mud honeycomb catalyst is carried out on a simple extrusion molding machine, which is easy to operate and does not need to invest a lot of manpower and material resources.

3. Advantages in performance: The performance indicators of the catalyst (such as denitration efficiency and mechanical strength, etc.) are less different from those of commercial vanadium-titanium catalysts, which are suitable for industrial applications.

4. Industrial production and industrial application: The preparation cost of powdered acid-washing red mud catalyst is low (the red mud used is industrial waste, and the acid species is hydrochloric acid), and the production process and cycle are short, the molding process is simple, and one-step extrusion molding That is, the cost is greatly reduced.

Description of drawings

The accompanying drawings that form a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application and do not constitute improper limitations on the present application. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic diagram of a denitration experimental bench; the catalyst denitration activity tests of the present invention are all carried out under typical operating conditions, and the simulated power plant flue gas composition: each gas pressure is _0.1MPa , N is a carrier gas, and the total gas flow is 2000ml/ min, space velocity ratio 3000h ^-1 , ammonia-nitrogen ratio 1.0, initial concentration of NO and NH ₃ 0.05%, total partial pressure of O ₂ >3.5%, the temperature of the catalyst bed in the experimental reaction section is controlled at room temperature ~ 400 ℃ adjustable.

Fig. 2 is the influence of the neutral silica sol content of embodiment 1 on the denitration performance of honeycomb catalyst;

Fig. 3 is the influence of glass fiber content on the denitration performance of honeycomb catalyst in Example 2;

Fig. 4 is the influence of activated carbon content on the denitration performance of honeycomb catalyst in Example 3;

Fig. 5 is the influence of neutral silica sol content on the denitration performance of honeycomb catalyst in Example 4;

Fig. 6 is the influence of glass fiber content on the denitration performance of honeycomb catalyst in Example 5;

Fig. 7 is the influence of drying temperature on the weight loss rate of honeycomb catalyst in Example 6;

Figure 8 is the effect of drying temperature on the morphology of the honeycomb catalyst in Example 6;

Among them: (a) 40°C, (b) 60°C, (c) 80°C, (d) 100°C;

Fig. 9 is the influence of roasting process on the denitration performance of honeycomb catalyst in Example 8;

Figure 10 is the effect of aging on the denitration performance of the honeycomb catalyst in Example 9;

Figure 11 shows the effect of vacuum sealing on the denitration performance of the honeycomb catalyst in Example 10.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In the following examples, the experimental methods without specific conditions are usually in accordance with conventional conditions or in accordance with the conditions suggested by the manufacturer.

Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with product instructions. In addition, any methods and materials similar or equivalent to those described can be used in the methods of the present invention. Methods and materials for preferred embodiments described herein are provided for illustrative purposes only.

Unless otherwise specified, the particle size of the acid-washed red mud powder used in the following examples is 200 meshes, which is prepared by the following method: an appropriate amount of 100 meshes of original red mud and 3 mol/L hydrochloric acid solution are mixed with a liquid-solid ratio of 9 : 1 Mix evenly, heat and stir at 70°C water bath temperature for 2h, filter it to pH=7 or so, dry at 105°C for 12h, calcine at 550°C for 5h, and then grind it into 200-mesh particles with a ball mill. That's it.

Unless otherwise specified, the alkali-free glass fibers used in the following examples have a diameter of 0.15 mm.

Unless otherwise specified, the amount of deionized water added in the following examples is 50% by weight of the amount of pickled red mud powder.

The denitrification activity involved in the embodiment of the present invention is carried out using the denitration test bench shown in Figure 1; the denitration activity tests are all carried out under typical working conditions, simulating the composition of the power plant flue gas: the pressure of each gas is 0.1MPa, and _N2 is the load The total gas flow was 2000ml/min, the space velocity ratio was 3000h ^-1 , the ammonia-nitrogen ratio was 1.0, the initial concentration of NO and NH ₃ was 0.05%, the total partial pressure of O ₂ was >3.5%, and the temperature of the catalyst bed in the experimental reaction section was controlled at Room temperature ~ 400 ℃ adjustable.

The strength of the catalyst was measured with a Zwick-Z250 strength measuring instrument, the pressure increase rate was 2 mm/min, the deformation amount of 10% was taken as the catalyst failure point, and the average value of three measurements was taken as the final mechanical strength.

Example 1

Take 200g of acid-washed red mud powder (ARM) and mix thoroughly with 3% (mass percentage) binder carboxymethyl cellulose and 10%, 20%, 30% (mass percentage) neutral silica sol, and successively add 5% ( mass percent) of the extrusion aid oleic acid and an appropriate amount of deionized water, and mud was refined to prepare a red mud paste. It was vacuum-sealed for 15 hours and then placed in an extrusion molding machine for extrusion molding. Then, the extruded embryo was placed at room temperature for 48 hours, and then dried at 80 °C. Finally, a two-stage method was adopted. Roasting: the temperature was raised to 300°C at a heating rate of 5°C/min and maintained for 5 hours, and then raised to 550°C at a heating rate of 5°C/min and maintained for 5 hours. After natural cooling, a red mud honeycomb catalyst was obtained. Its denitration performance and mechanical strength are shown in Figure 2 and Table 1.

Table 1 Effect of neutral silica sol content on mechanical strength of honeycomb catalyst

In the formulation without glass fiber and activated carbon, with the increase of silica sol, the catalytic activity will decrease, and the working window temperature will become _narrower . Close to 100%, although the axial mechanical strength will increase, the strength is still too low. Even if the content of silica sol is increased to 30%, the strength is still only 1.372MPa, which cannot be well formed and applied in industry.

Example 2

Take 200g pickling red mud powder (ARM) with 3% (mass percent) binder carboxymethyl cellulose and 30% (mass percent) neutral silica sol, 5%, 10%, 15%, 20% (mass percent) percentage) 100 mesh alkali-free glass fibers are fully mixed, and 5% (mass percent) of oleic acid as an extrusion aid and an appropriate amount of deionized water are added successively, and mud is refined to prepare a red mud paste. It was vacuum-sealed for 15 hours and then placed in an extrusion molding machine for extrusion molding. Then, the extruded embryo was placed at room temperature for 48 hours, and then dried at 80 °C. Finally, a two-stage method was adopted. Roasting: the temperature was raised to 300°C at a heating rate of 5°C/min and maintained for 5 hours, and then raised to 550°C at a heating rate of 5°C/min and maintained for 5 hours. After natural cooling, a red mud honeycomb catalyst was obtained. Its denitration performance and mechanical strength are shown in Figure 3 and Table 2.

Table 2 Effect of glass fiber content on mechanical strength of honeycomb catalyst

In the formulation of this example, the addition of glass fibers can significantly improve the axial mechanical strength. With the increase of glass fibers, the axial mechanical strength will increase, but the catalytic activity will also decrease significantly. At 350-375 ℃ When the NO _x conversion rate is above 70%, it is between 80% and 90% at 375 ℃. When the glass fiber addition is 15%, the NO x conversion rate is about 70% at 325 ℃, and the NO _x conversion rate is about 70% at 350-375 ℃. The NO _x conversion rate was about 80%, and the NO _x conversion rate decreased again at 400°C.

Example 3

Take 200g of acid-washed red mud powder (ARM), 3% (mass percent) binder carboxymethyl cellulose and 30% (mass percent) neutral silica sol, 15% (mass percent) 100-mesh alkali-free glass fiber, 1%, 3%, 5% (mass percent) of activated carbon is fully mixed, and 5% (mass percent) of oleic acid and an appropriate amount of deionized water are added successively, and mud is practiced to prepare red mud paste. It was vacuum-sealed for 15 hours and then placed in an extrusion molding machine for extrusion molding. Then, the extruded embryo was placed at room temperature for 48 hours, and then dried at 80 °C. Finally, a two-stage method was adopted. Roasting: the temperature was raised to 300°C at a heating rate of 5°C/min and maintained for 5 hours, and then raised to 550°C at a heating rate of 5°C/min and maintained for 5 hours. After natural cooling, a red mud honeycomb catalyst was obtained. Its denitration performance and mechanical strength are shown in Figure 4 and Table 3.

Table 3 Effect of activated carbon content on the mechanical strength of honeycomb catalysts

In the formulation of this example, the addition of activated carbon has little effect on the mechanical strength. With the increase of activated carbon, the mechanical strength does not change significantly, but the catalytic activity is improved. The catalyst with activated carbon added NO _x at 375 °C The conversion rate of NO x is close to 90%, especially when the amount of activated carbon is 3%, the conversion rate of NO _x at 325 ℃ is 80%, the conversion rate of NO _x at 350-375 ℃ is above 90%, and when the temperature exceeds 375 ℃, The decrease of the conversion rate is relatively gentle, and the conversion rate can still be maintained above 80% at 400°C. Compared with Example 2, the addition of activated carbon in this example significantly improved the denitration performance; compared with Example 1, the simultaneous addition of activated carbon and glass fiber not only improved the mechanical strength, but also effectively improved the catalytic activity.

Example 4

Take 200g of acid-washed red mud powder (ARM) with 3% (mass percentage) binder carboxymethyl cellulose and 0%, 10%, 20%, 30% (mass percentage) neutral silica sol, 15% (mass percentage) percentage) 100 mesh alkali-free glass fiber, 3% (mass percentage) activated carbon is fully mixed, and 5% (mass percentage) of oleic acid and an appropriate amount of deionized water are added successively, and the red mud paste is prepared by refining mud. It was vacuum-sealed for 15 hours and then placed in an extrusion molding machine for extrusion molding. Then, the extruded embryo was placed at room temperature for 48 hours, and then dried at 80 °C. Finally, a two-stage method was adopted. Roasting: the temperature was raised to 300°C at a heating rate of 5°C/min and maintained for 5 hours, and then raised to 550°C at a heating rate of 5°C/min and maintained for 5 hours. After natural cooling, a red mud honeycomb catalyst was obtained. Its denitration performance and mechanical strength are shown in Figure 5 and Table 4.

Table 4 Effect of neutral silica sol content on mechanical strength of honeycomb catalyst

Example 5

Take 200g of pickled red mud powder (ARM) with 3% (mass percentage) binder carboxymethyl cellulose and 30% (mass percentage) neutral silica sol, 0%, 5%, 10%, 15%, 20 % (mass percentage) of 100 mesh alkali-free glass fiber, 3% (mass percentage) of activated carbon is fully mixed, and 5% (mass percentage) of oleic acid and an appropriate amount of deionized water are added successively, and the red mud paste is prepared by refining mud. . It was vacuum-sealed for 15 hours and then placed in an extrusion molding machine for extrusion molding. Then, the extruded embryo was placed at room temperature for 48 hours, and then dried at 80 °C. Finally, a two-stage method was adopted. Roasting: the temperature was raised to 300°C at a heating rate of 5°C/min and maintained for 5 hours, and then raised to 550°C at a heating rate of 5°C/min and maintained for 5 hours. After natural cooling, a red mud honeycomb catalyst was obtained. Its denitration performance and mechanical strength are shown in Figure 6 and Table 5.

Table 5 Effect of glass fiber content on mechanical strength of honeycomb catalyst

Example 6

Take 200g of acid-washed red mud powder (ARM), 3% (mass percent) binder carboxymethyl cellulose and 30% (mass percent) neutral silica sol, 15% (mass percent) 100-mesh alkali-free glass fiber, 3% (mass percent) activated carbon is fully mixed, and 5% (mass percent) of oleic acid as an extrusion aid and an appropriate amount of deionized water are added successively, and mud is refined to prepare a red mud paste. It was vacuum sealed for 15 hours and then placed in an extrusion molding machine for extrusion molding. Then, the extruded embryo was placed at room temperature for 48 hours, and then placed at 40 °C, 60 °C, 80 °C, and 100 °C. After drying, two-stage roasting was adopted: the temperature was raised to 300°C at a heating rate of 5°C/min and maintained for 5 hours, and then raised to 550°C at a heating rate of 5°C/min and maintained for 5 hours. After natural cooling, the obtained Red mud honeycomb catalyst. Its weight loss rate curve and drying morphology are shown in Figures 7 and 8.

Combining Fig. 7 and Fig. 8, it can be found that the water loss rate of the catalyst increases gradually with the increasing drying temperature. At 40°C, the catalyst body can be dried for 9 hours, at 60°C, the catalyst body can be dried for 7 hours, and at 80°C, the catalyst body can be dried for 5 hours. It is worth noting that when the drying temperature is 100 °C and above, the embryo body is easily cracked, reducing the yield. In order to improve the yield, it is recommended to dry at 40-80°C.

Example 7

Take 200g of pickled red mud powder (ARM) and 30% (mass percentage) of neutral silica sol, 15% (mass percentage) of 100-mesh alkali-free glass fiber, and 3% (mass percentage) of activated carbon, mix thoroughly, and successively add 5% ( mass percent) of the extrusion aid oleic acid and an appropriate amount of deionized water, and mud was refined to prepare a red mud paste. It was placed under vacuum sealing for 15 hours and then placed in an extrusion molding machine for extrusion molding. It was found that the red mud particles could not be aggregated into agglomerates and could not be used for extrusion molding.

Example 8

Take 200g of acid-washed red mud powder (ARM), 3% (mass percent) binder carboxymethyl cellulose and 30% (mass percent) neutral silica sol, 15% (mass percent) 100-mesh alkali-free glass fiber, 3% (mass percent) activated carbon is fully mixed, and 5% (mass percent) of oleic acid as an extrusion aid and an appropriate amount of deionized water are added successively, and mud is refined to prepare a red mud paste. It was vacuum sealed and placed for 15 hours and then placed in an extrusion molding machine for extrusion molding. Then, the extruded molding embryo was placed at room temperature for 48 hours, and then dried at 80 °C. Finally, roasting was used: the The temperature was raised to 550 °C at a heating rate of 5 °C/min and maintained for 5 h. After natural cooling, a red mud honeycomb catalyst was obtained. After testing, its denitration performance and mechanical strength are shown in Figure 9 and Table 6. Results Compared with the two-stage calcination, the mechanical strength and catalytic activity of the catalyst decreased, and the molding efficiency and quality were not high, and the organic additives could not be fully burned and volatilized during the preparation process, remained in the catalyst, and blocked the interior of the catalyst. The pore structure is not conducive to the SCR reaction.

Table 6 Influence of calcination process on mechanical strength of honeycomb catalyst

Example 9

Take 200g of acid-washed red mud powder (ARM), 3% (mass percent) binder carboxymethyl cellulose and 30% (mass percent) neutral silica sol, 15% (mass percent) 100-mesh alkali-free glass fiber, 3% (mass percent) activated carbon is fully mixed, and 5% (mass percent) of oleic acid as an extrusion aid and an appropriate amount of deionized water are added successively, and mud is refined to prepare a red mud paste. It was vacuum-sealed for 15 hours, placed in an extrusion molding machine for extrusion molding, dried at 80 °C, and finally calcined in two stages: the temperature was raised to 300 °C at a heating rate of 5 °C/min and maintained at 80 °C. After 5 h, the temperature was raised to 550 °C at a heating rate of 5 °C/min and maintained for 5 h. After natural cooling, the red mud honeycomb catalyst was obtained. After testing, its denitration performance and mechanical strength are shown in Figure 10 and Table 7. As a result, the mechanical strength and catalytic activity of the catalyst decreased compared with the catalyst obtained by the aging operation, and the water could not be fully absorbed during the preparation process, so it was difficult to improve the molding efficiency and quality of the catalyst.

Table 7 Effects of aging on the mechanical strength of honeycomb catalysts

Example 10

Take 200g of acid-washed red mud powder (ARM), 3% (mass percent) binder carboxymethyl cellulose and 30% (mass percent) neutral silica sol, 15% (mass percent) 100-mesh alkali-free glass fiber, 3% (mass percent) activated carbon is fully mixed, and 5% (mass percent) of oleic acid as an extrusion aid and an appropriate amount of deionized water are added successively, and mud is refined to prepare a red mud paste. Put it in an extrusion molding machine for extrusion molding, and then place the extruded molding embryo at room temperature for 48 hours, then dry it at 80 °C, and finally adopt two-stage roasting: the temperature is set to 5 The heating rate of ℃/min was raised to 300 ℃ and maintained for 5 h, and then increased to 550 ℃ at a heating rate of 5 ℃/min and maintained for 5 h. After natural cooling, the red mud honeycomb catalyst was obtained. After testing, its denitration performance and mechanical strength are shown in Figure 11 and Table 8. Results The mechanical strength and catalytic activity of the catalyst decreased compared with the catalyst obtained by vacuum sealing, and the moisture loss in the catalyst embryo body was too fast during the preparation process, resulting in a decrease in the plasticity of the embryo body, which was not conducive to extrusion molding.

Table 8 Effect of vacuum sealing on mechanical strength of honeycomb catalyst

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still understand the foregoing embodiments. The technical solutions described are modified, or some technical features thereof are equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. An integral honeycomb catalyst comprises acid-washed red mud powder and a forming aid serving as raw materials, wherein the amount of the forming aid is 55-80 wt% of that of the acid-washed red mud powder, and the forming aid comprises: carboxymethyl cellulose, neutral silica sol, glass fiber, active carbon, oleic acid and water.

2. The monolithic honeycomb catalyst according to claim 1, wherein the amounts of the forming aids used relative to the pickled red mud powder are respectively: 1-3 wt% of carboxymethyl cellulose, 10-30 wt% of neutral silica sol, 5-20 wt% of glass fiber, 1-5 wt% of activated carbon, 3-5 wt% of oleic acid and 30-60 wt% of water.

3. The monolithic honeycomb catalyst according to claim 1, wherein the particle size of the acid-washed red mud powder is 200 mesh or less.

4. The monolithic honeycomb catalyst according to claim 1, wherein the glass fibers are alkali-free glass fibers having a diameter of 0.15mm or less.

5. A method of making the monolithic honeycomb catalyst of any one of claims 1-4, comprising: fully mixing acid-washed red mud with carboxymethyl cellulose, neutral silica sol, glass fiber and active carbon, adding oleic acid and water, pugging to prepare a red mud paste, placing the obtained paste in a vacuum seal mode, extruding and molding, aging an extruded and molded blank at room temperature, drying, roasting and cooling to obtain the red mud paste.

6. The method of claim 5, wherein the oleic acid is added prior to the water.

7. The method of claim 5, wherein the drying temperature is 40-100 ℃.

8. The process according to claim 5, characterized in that the aging time is from 24 to 48 h.

9. The method as claimed in claim 5, wherein the two-stage baking comprises raising the temperature to 320 ℃ at a temperature raising rate of 2-8 ℃/min for 2-8h, and raising the temperature to 600 ℃ at a temperature raising rate of 2-8 ℃/min for 2-8 h.

10. Use of a monolithic honeycomb catalyst as claimed in claims 1 to 4 in the field of environmental protection, characterized in that the use is catalytic denitration.

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