KR0130153B1 - High dispersing heterogenous catalyst production using microwave - Google Patents

Abstract

The first step of the impregnation is to saturate in the matrix, the precursor solution in which activated material, the precursor is melted. For this method, spray, vaporization dry, initial wetting, absorption , or the like are considered based on the contacting method of the precursor solution and matrix. The next step of the catalyst production after impregnation is the drying step to eliminate the catalyst remaining in the pore of the matrix. The drying employing the microwave can be conducted in a short time since the catalyst is evaporated at a fast speed by the direct heating from the microwave and by the indirect heating of the matrix and the catalyst.

Description

Method for producing a highly dispersed heterogeneous catalyst using microwaves and apparatus therefor

1 is an exemplary view showing an example of a batch catalyst production apparatus of the present invention.

2 is an exemplary view showing an example of the continuous catalyst production apparatus of the present invention.

3 is a graph showing an example of temperature control in firing the catalyst using the batch catalyst production apparatus of FIG.

Figure 4 is a graph showing the oxidation activity of the Co ₃ O ₄ / activated carbon catalyst for benzene fired in conventional and microwave heating apparatus.

5 is a graph showing the activity according to the calcination time of Co ₃ O ₄ / activated carbon catalyst.

* Explanation of symbols for main parts of the drawings

1: resonator 2: microwave generator

3: power meter 4: waveguide

5: matching device 6: impregnation part

7: Hopper 8: Sprayer

9: Conveyor Belt 10: Spray Nozzle

11: conveyor belt 12: recovery tank

13: reservoir 14: dry firing unit

15: metal barrier wall 16: metal barrier wall

17: microwave generator 18: waveguide

19: microwave inlet 20, 21: optical temperature measuring instrument

22: air inlet 23: by-product gas outlet

24: product hopper 25: cooling nozzle

The present invention relates to a method for producing a heterogeneous catalyst comprising a metal or a metal oxide catalyst component and a support that supports the same. In particular, the present invention relates to a method for producing a catalyst having a very high dispersion of catalyst components by using microwave in the drying and / or firing step in the production of a heterogeneous catalyst by impregnation.

The impregnation method used in the production of heterogeneous catalysts impregnates a solution containing a precursor of a desired catalyst component in a porous porous carrier, dries the solvent in the impregnating solution through a drying process, and then calcinates the catalyst precursor ( precursor) is converted into a catalyst component to form a catalyst on the surface of the carrier and the pore wall surface inside. In addition, the degree of dispersion indicates how well the catalyst component is dispersed on the surface of the carrier and the pore wall. In the case of the supported catalyst, the ratio of the number of metal atoms exposed to the metal surface and the total number of metal atoms contained in the entire metal Say. Therefore, it can be said that the smaller the size of the particles or crystals of the catalyst component supported on the support, the higher the dispersion degree.

Since the catalytic reaction occurs on the surface of the catalyst component particles, it is expected that the higher the dispersion degree, the higher the activity of the catalyst. This is not necessarily true for all reactions, however, for example, in reaction systems where the mass transfer of reactants in the pores inside the carrier dominates the overall reaction rate, the catalyst component is concentrated in the pores near the surface rather than evenly distributed throughout the pores of the carrier. Rather it is advantageous to the reaction.

In the structure sensitive reaction, it is generally known that the activity of the catalyst is independent of the degree of dispersion, and even in the structure sensitive reaction that exhibits the activity at specific positions such as corners and vertices, there is no significant relationship with the dispersion degree.

In addition, even in a reaction in which the activity of the catalyst depends on the crystal size, the optimum crystal size, i.e., superdispersity exists, and when the dispersion exceeds an appropriate value, the catalyst is changed due to changes in the coordination number of surface atoms or binding energy to the adsorbate. There is a gradual decrease in activity.

However, the greater the dispersion degree, the more reactions with a higher reaction rate, and the larger the dispersion degree, the more advantageous the catalyst is in terms of production cost, poisoning phenomenon, and loss due to wear. In the case of a low concentration catalyst having a small loading amount, the situation is different from that of a high concentration catalyst. The low loading catalyst may not completely cover the surface of the carrier depending on the preparation conditions.

In this case, the activity of the catalyst is inevitably inferior to that of the complete catalyst, and if the catalyst components are packed together in large particles, the degree of surface coverage is greatly reduced and the activity is fatally reduced. Therefore, in the case of a low concentration catalyst, it is important to secure the optimum crystal size, but it is more important to secure a wide active point. If the size of the catalyst component crystal is not a problem, the larger the dispersion, the less the amount of loading, which would be advantageous in terms of manufacturing price. This is especially true for catalysts containing platinum group precious metals, such as reforming catalysts and catalysts in fluidized bed catalyst cracking (FCC) processes, which are widely used in petrochemical industries. If it can be cut in half, the savings in manufacturing costs are very large. On the other hand, high dispersibility of the catalyst component is required in the liquid environmental catalyst used in the environmental industry. Liquid environmental catalysts are prepared by adsorbing an oxidizing catalyst component for complete oxidation reaction on the surface of an adsorbent as a carrier.The oxidizing catalyst component carrying harmful components adsorbed in gaseous atmosphere after selectively adsorbing liquid harmful components to the adsorbent. As it is completely oxidized and removed at low temperature, it is designed to be used continuously through repeated processes of adsorption and regeneration.

This catalyst is advantageous in the function of the adsorbent because the larger the dispersion degree, the smaller the amount of the oxidation catalyst component should be supported in the range of activity to maintain the large surface area of the adsorbent. In addition, for many reasons many catalysts require a high degree of dispersion. The impregnation method of such a heterogeneous catalyst production method is the simplest and most inexpensive manufacturing method, but has not been generally used for the production of high dispersion catalysts due to the defect that the catalyst components are unevenly distributed on the carrier.

If the adsorption power of the carrier to the catalyst component is too strong, it is concentrated in the vicinity of the surface of the carrier during the production of low concentration catalyst.In contrast, if the adsorption power is too weak, it is impregnated into the carrier depending on variables such as temperature and heating rate in the drying step after impregnation. This is because the distribution of the catalyst precursor as a solute in solution changes (JR Anderson, Structure of Netallic Catalysis, Academic Press Inc., 1975, pp. 171-176).

If the adsorption force of the carrier is very weak, the distribution of the catalyst component in the carrier during the drying step, i.e., the solvent removal step of the impregnating solution, depends on the method of removing the solvent under the interaction between the capillary force and the pore size distribution.

When the solvent evaporates momentarily, the solute deposits on the walls of neighboring pores close to its original location, so that the distribution of the solute becomes uniform throughout. On the other hand, in the evaporation conditions, the evaporation of the solvent occurs as it gradually diffuses into the micropores from the macropores toward the surface of the carrier having a relatively high vapor pressure.

In this case, when the liquid evaporates, the solute is gradually accumulated in the micropores because the impregnation solution in the neighboring macropores is continuously filled by the capillary force. Thus, the solute as a whole of the carrier is biased toward the micropores and toward the center rather than toward the surface of the carrier. However, the distribution of solutes, in addition to the initial saturation of the solution, the degree of connection of the liquid transport path, the carrier and the physical properties of the solution as a function of various variables, such as the actual impregnation method, many commercially available catalysts require uniform distribution Nevertheless, it is known that the concentration is higher on the surface rather than the center of the carrier (CNSstterfield, Hdterogerneous Catalysis in Industrial Practice, 2nd ed., McGraw, pp. 108-109). There are two major drawbacks of the heterogeneous distribution of catalyst components, which are divided into two types: macroscopic and non-uniform distributions concentrated at the surface or center of the carrier and micro-uniform distributions concentrated at specific locations within the pores.

Because of these drawbacks of impregnation, special methods have been used for the preparation of catalysts that require high dispersibility. However, these methods have a disadvantage in that the process is complicated and the manufacturing cost is higher than the impregnation method. Precipitation requires more filtration, water washing, molding, and the like than impregnation, and it is difficult to precisely control the pH.

Because of this, the equipment cost is high and the waste disposal cost is higher than the impregnation method by using acid or alkali. The ion exchange method is also complicated by the pH control and is only possible if the carrier has ion exchange capacity. PH control in the ion exchange method is known to be difficult when both the problem of stabilizing ions and the problem of carrier attack by a strong acid or strong alkali solution are considered simultaneously.

Other special methods also have complex processes and are more expensive than impregnation. It would not be efficient to use such expensive manufacturing methods to improve dispersion in the production of low concentration catalysts such as FCC catalysts which are loaded at less than 2%. The same is true of environmental catalysts that must be manufactured and distributed as cheaply as possible.

And most of all, the precipitation method, the ion exchange method, etc., unlike the impregnation method, is difficult to prepare one or more catalyst components, so there is a problem in the use in the production of two-component or multi-component catalyst.

Therefore, the present inventors have made the present invention in order to solve the non-uniform distribution of the catalyst component, which is a major drawback of the impregnation method, to make a high-dispersion catalyst cheap. Another object of the present invention is to provide a method for producing a catalyst which can simultaneously and continuously treat the impregnation, drying, and calcined acid systems of the impregnation method.

Microwave refers to electromagnetic waves in the electromagnetic spectrum in the frequency range 300 MHz to 300 GHz and wavelengths in the range of 1 m to 1 mm. Microwaves with a frequency of 915 MHz or 2,450 MHz are commonly used for heating. When a dielectric such as H ₂ O is placed in the electric field of the wave, the molecular dipoles of the dielectric change their orientation by responding to the electric field change of the microwave.

In this process, the molecular dipoles do not respond instantaneously to changes in the electric field of the microwave and are oriented in time, which creates a kind of frictional heat inside the dielectric. The principle of heat generation, in which heat is generated on an object by waves propagating at the speed of light, is applied to household and industrial electronic ovens. This heating method is faster than conventional methods and has a dielectric having a permanent dipole. Is selectively heated. In addition, the material transfer is improved in chemical reactions and processes due to effects other than heat.

The improvement of material transfer by microwave has proved feasible through accurate comparison of diffusion coefficients: solid-solid, solid-liquid and solid-based chemistry, sintering, crystal growth Etc. It has been reported in the field of reactions and processes mainly involving solids.

Although the principle of improving material transfer by microwaves is not known in detail, it is believed to be improved by a similar principle of heating a dielectric. In the field difficult to interpret due to the complexity of phenomena such as crystal growth and sintering, this is called a microwave effect.

The present inventors can effectively produce high dispersion metal and metal oxide catalysts by applying the high-speed heating and material transfer enhancement properties of microwaves to the drying or firing step of impregnation method where the catalyst components are unevenly distributed. The effect was confirmed experimentally.

The method of producing a catalyst using microwaves is different from that of other applications. It is important to improve the transfer rate of a substance by microwaves in a material or crystal boundary layer in chemical reaction and sintering. The main purpose is to disperse the catalyst components as evenly and finely as possible on the solid surface and the pores.

In view of the internal pore, the main purpose of the ammonia production is to distribute the pores widely and evenly from the wall surface of the pores instead of being transferred to the carrier through the pore wall surface which is the catalyst component.

Until now, microwaves have been known to increase only the material transfer rate of a specific component in a solid material. However, the present inventors have found that the catalyst component deposited on the surface of the porous solid used as a carrier of the catalyst and the wall of the inner pores in the surface and wall directions. It was confirmed that the effect of dispersion is very large.

The mass transfer in the carrier surface and the pore wall direction has been shown to be high speed in comparison with the mass transfer in the material. Accordingly, the present invention solves the problem of non-uniform distribution of catalyst components on the carrier surface and the pore wall surface, which is a drawback of the impregnation method, by using the property of dispersing the material together with the property of heating the object of microwave rapidly.

The improvement in the degree of dispersion of the catalyst according to the invention is achieved independently or in combination in two stages: drying and firing. In the drying step, the microwave heating effect and the microwave effect of dispersing the catalyst component are used, and in the firing step, the microwave effect related to the calcination reaction and powder phase of the catalyst particles is used. Hereinafter, the present invention will be described in detail in the order of preparation of the catalyst by the impregnation method.

The first step of the impregnation method is to impregnate (support) the precursor solution in which the precursor, the active substance, is dissolved, in the carrier. The appropriate method is selected in consideration of the type of carrier and precursor solution to be prepared and the required loading amount. As the impregnation method, a spraying method, an evaporation drying method, an incipient wetness meyhod, an adsorption method, and the like may be considered depending on the contact method between the carrier and the precursor solution.

Spraying is a method in which the precursor solution is sprayed into a small particle size to uniformly contact the carrier, and evaporation drying is a method in which the carrier is put in an evaporator and stirred or shaken. In the initial wet method, it is necessary to add a solution in which the precursor material of the solvent is dissolved in the amount of the precursor pore volume to the dried carrier. The adsorption method is a method in which a carrier is immersed in a precursor solution to adsorb and support an active material as a precursor on a carrier surface.

The amount of loading in these impregnation methods decreases in the order of evaporation drying method, initial impregnation method and adsorption method. Water is generally used as a solvent for the preparation of the precursor solution. When the solubility of the precursor in water is low, an organic solvent may be used. Water and most organic solvents are very well heated in the microwave, so any solvent may be used in the present invention.

The catalyst preparation step after impregnation is a drying step to remove the solvent contained in the pores of the carrier. As described above, the catalyst production by the impregnation method has a problem in that the catalyst components are unevenly distributed at this stage. This problem occurs because the bonding strength between the carrier and the catalyst precursor is very weak in the impregnation method, unlike the ion exchange method or the precipitation method in which the carrier and the catalyst precursor are strongly bound by the ionic bond. Table 1 shows a typical batch microwave heater.

The apparatus is composed of a resonator 1, a microwave generator 2, a power meter 3, a waveguide 4, and a matcher 5. The resonator 1 is a part corresponding to the furnace of the electric furnace, and the waveguide 4 is a tube made of a metal that induces microwave propagation so that the microwaves generated by the microwave generator 2 reach the resonator 1. to be.

Drying of the catalyst using such a microwave heating device is completed in a very short time compared to the conventional heating method. The reason for this is that, as described above, the microwave heating method is a heating method in which the object itself generates heat directly at a very high speed by waves propagating at a speed of light, unlike the conventional heating method, which is heated through a heat transfer medium.

From the moment the catalyst is exposed to microwaves, the solvent in the carrier begins to evaporate at a rapid rate by direct heating or in some cases by indirect heating by the invention of the carrier and catalyst components. The rapid evaporation rate of these solvents helps to distribute the catalyst components evenly on the carrier. As described above, when the solvent absorbs microwaves and evaporates at a high speed, the catalyst components on the surface of the carrier and the pores remain in their original uniform supporting state. As a result, the solvent evaporation rate is relatively slow, and thus the solvent is evaporated in the carrier. Compared with the conventional heating method in which the movement of the catalyst component occurs, the dispersion degree of the catalyst is improved.

In parallel with the supply of energy by microwaves, the drying atmosphere pressure may be maintained in a vacuum in order to increase the evaporation rate of the solvent or to reduce the required thermal energy. However, a more fundamental reason for the improved dispersion of the catalyst by microwaves in the drying step is due to the nature of the microwaves to improve mass transfer. As will be discussed later, it is well supported by the fact that the degree of dispersion is enhanced by microwaves in the firing step after the solvent is removed.

In the drying step, the degree of dispersion of the catalyst is improved regardless of whether the carrier and the catalyst precursor are heated when the solvent is heated to the microwave. As can be seen in Examples 3 and 4, when the solvent is water that is well heated in the microwave, the dispersibility is improved even if both the carrier and the catalyst precursor are not heated.

Even if the catalyst precursor is not heated in the microwave in the solid state, it is dissolved in the polar solvent and ionized or when the molecules are polarized, it absorbs the microwave and starts to heat partially. Therefore, the solvent and the catalyst precursor are substantially heated at the beginning of drying, which is a factor in improving the dispersion of the catalyst even if the catalyst precursor in the solid state is not heated in the microwave. The present invention which improves the degree of dispersion of the catalyst by using microwave in the drying step is not limited to whether the carrier and the catalyst precursor are heated, and thus can be applied to most catalysts prepared by the impregnation method.

Apart from this, microwaves also have independent effects in the firing process. Firing, which is the catalyst preparation step following drying, is a step in which the catalyst precursor is decomposed to form crystals of the catalyst component as is known. Oxygen is required at this stage in the preparation of the metal oxide catalyst, but in the production of the metal catalyst, depending on the precursor, the reducing atmosphere must be maintained.

The degree of dispersion of the catalyst is sufficiently improved in the drying step, but much more in the firing step. Therefore, even if the catalyst is dried in the conventional heating apparatus and fired using the microwave heating apparatus only in the firing step, the dispersion degree is greatly improved. The improvement of the dispersion degree in the calcination step is achieved by the microwave effect between the carrier and the catalyst component regardless of the solvent.

Example 1 is a good example that can specifically confirm this microwave effect. Example 1 compares the difference in dispersion of catalysts calcined through the two heaters by drying the catalyst impregnated with 2% Co ₃ O ₄ in activated carbon in a conventional heating apparatus and then firing the catalyst in the conventional and microwave heating apparatus. It is to see.

As a result of analyzing the prepared Co ₃ O ₄ / activated carbon catalyst by electron microscopy, the crystal size of the catalyst component fired in the microwave heating device was in the range of nm (nanometer), whereas the catalyst component fired in the conventional heating device was micrometer (micrometer). ), The degree of dispersion of the calcined catalyst in the microwave heater was found to be 1000 times higher.

As a result of adapting the catalysts prepared at various firing times and firing temperatures to the oxidation reaction of benzene, the catalysts fired in the conventional heating apparatus showed little activity as catalysts, but the catalysts fired in the microwave heater showed very high activity.

The dispersion of the catalyst particles deposited on the carrier surface and the pore wall surface in the carrier surface and the pore wall surface direction cannot be confirmed by the same mechanism as the material transfer in the replacement. It was predicted that the dispersion coefficient in the wall direction was so large that it could not be compared with the dispersion coefficient inside the solid.

From this it can be seen that the microwave can be used more useful in the field of catalyst production of the present invention than any other field. In order to reduce the required microwave energy within a range that does not impair the effects of such microwaves, the required zero energy may be supplemented by using hot air or an inert gas.

In the present invention, calcination is possible when either of the carrier or the catalyst precursor is heated to the microwave, but since the catalyst precursors composed of C 1, NO ₃ , and NH ₄ , which are generally used in the impregnation method, are hardly heated to the microwave, the carrier is actually a carrier. Is possible only after heating.

If the carrier is not heated, the firing should be carried out in a conventional heating apparatus, and the dispersion degree is improved only through the drying step. In general, activated carbon in the carrier is well heated in microwave, while silica, alumina, zeolite, etc. of ultra high purity are not heated well at room temperature. However, these materials contain a small amount of impurities, unless they are of high purity, and the microwaves are well heated, and if necessary, the microwave heating efficiency can be improved by mixing the carrier with a material having high microwave absorption rate. In terms of improving the dispersion degree, it is more advantageous that the catalyst precursor is not heated because microwave lowers the activation energy of the crystal growth to increase the crystal growth rate of the catalyst component. As shown in Example 1, even if the precursor is not heated, if the carrier is heated in the microwave, it is possible to improve the dispersion degree in the firing step.

In addition to improving the dispersion degree in the firing step, the microwave has the effect of increasing the firing rate as shown in Example 1. The increase in firing rate was shown to be partly related to the improvement in dispersion.

If the degree of dispersion is large, the firing rate will be increased by increasing the reaction area of the gas-solid reaction and decreasing the crystal size. Due to the increased firing rate, the catalyst production method of the present invention has a lower energy cost than the conventional method and shortens the time of exposure to heat, thereby greatly reducing the risk of deactivation of the catalyst due to solidification. In addition, the production time is shortened, the catalyst production rate is high.

The present invention having such an advantage can be easily used to prepare a heterogeneous catalyst by the impregnation method, which can be used independently of each of the commonly used batch drying process or the calcination process, so that the conventional impregnation method can be easily improved. have.

In addition, since the drying and firing rate is much higher than the conventional method, the present invention can be easily applied even when the catalyst is continuously produced using the impregnation method instead of the batch production method. Table 2 will be a representative example of such a continuous catalyst production apparatus to which the present invention is applied.

The impregnation method in Table 2 is a device that can collectively process the impregnation, drying and firing steps. In the case of the metal catalyst system, there is a reduction step after firing, but the present invention deals only with the firing step related to the dispersion degree improvement.

In the apparatus of Table 2 the impregnation of the catalyst components is by spraying. However, other methods may be used to impregnate and introduce a catalyst into the conveyor 9 of the apparatus. When the carrier stored in the hopper 7 is supplied to the conveyor 9 via the sprayer 8, the catalyst precursor solution is impregnated through the spray nozzle 10.

In this case, the impregnation time may be determined by appropriately adjusting the length of the impregnation part 6, the number of spray nozzles 10, and the moving speed of the conveyor 9. The sprayer 8 makes it possible to widen the carrier by electromotive force such that the carrier particles from the hopper 7 are supplied to the conveyor 9 at a constant thickness.

Conveyor (9) is a porous plate or net of a material capable of preventing the leakage of metal or microwaves, or the filtrate of the precursor solution sprayed as a belt (11) consisting of the storage tank 13 through the recovery tank 12 between the belts It is intended to be flown down and recovered. The filtrate of the precursor solution collected in the reservoir 13 is reused after the concentration is adjusted.

The impregnated catalyst is moved to the dry firing unit 14, and drying and firing are started by microwaves. Metal barrier walls 15 and 16 are provided on the left and right sides of the drying and firing sections 14 to prevent microwaves from propagating to other places. The double right barrier wall 15 serves to separate the impregnation part, the drying part and the firing part. The microwaves generated by the microwave generator 17 are dried and supplied to the baking unit 14 through the waveguide 18. At this time, the microwave may be supplied at any position on the side or top of the drying, firing unit (14). Microwaves can use either 2450MHz or 915MHz. On the other hand, the control of the firing temperature is made by the temperature controller in the optical temperature measuring system 20, 21 and the microwave generator 17.

The air or inert gas necessary for the production of the metal oxide enters through the gas inlet 22, and the excess air exits through the outlet 23 together with the by-product gas of the steam and calcining reaction in the drying step. The calcined catalyst is dried and exited from the calcined portion 14 to enter the product hopper 24. Finally, the conveyor belt heated in the drying and firing unit 14 is cooled by the cooling water sprayed from the cooling nozzle 25 and then enters the impregnation unit 6 again.

Such a highly disperse heterogeneous catalyst production method of the present invention is characterized in that the dispersibility is improved by the energy source used in the drying and / or firing step so that the catalyst can be efficiently produced at low cost using the impregnation method. have.

Thus, the catalyst of high dispersion can be produced by the present invention without using the precipitation method, the ion exchange method, or other special methods, which are complicated in manufacturing process, have a large amount of waste discharge, are difficult to operate, and are expensive to manufacture. In addition, the advantages of the impregnation method can be utilized to the maximum, it is possible to easily prepare a heterogeneous catalyst having one or more components as a catalyst component. The catalyst component and the dispersion of the catalyst according to the present invention are improved regardless of the physical properties and the loading of the carrier such as pore size, structure and adsorption capacity.

Therefore, the present catalyst production method is very effective in the case of preparing a low loading catalyst by impregnating a low concentration of precursor solution in a carrier having a very high adsorptive power, and in particular, a general metal containing platinum group precious metal in activated carbon silica, alumina, and zeolite having a large surface area. And it is very effective when preparing a low supported catalyst by carrying a small amount of metal oxide. In addition, the degree of dispersion is independent or complex in two stages of drying and firing, and even if both the carrier and the catalyst component are not heated in the microwave, the degree of dispersion can be improved through the drying step, so that it is applicable to most catalysts prepared by the impregnation method. Can be.

In addition, since the firing rate is increased by the microwave effect, the firing can be performed at a lower temperature than the conventional heating method, and thus the risk of deactivation of the catalyst in the manufacturing process by the sintering phenomenon is greatly reduced. Due to the shortening of the firing time, the drying time is greatly shortened due to the microwave's high-speed heating characteristics of the polar solvent, so the overall process time is greatly reduced and economical.

This enables batch processing and continuous processing as in the apparatus of the present invention. The present invention is also very effective compared to other methods for the production of multicomponent catalysts of metals and metal oxides, since the degree of dispersion can be improved regardless of the number of catalyst components.

As described above, the present invention may be economically and variously applied because it is possible to supplement necessary thermal energy by using hot air or an inert gas in order to reduce the required microwave energy in a range that does not impair the effect of microwaves.

Example 1

To prepare a catalyst loaded with Co ₃ O ₄ on activated carbon, 8.84 g of Co (NO ₃ ) ₂ · 6H ₂ O was added to 775 g of distilled water to prepare a precursor solution, which was then placed in a rotary evaporator. Slowly add 190 g of activated carbon of size

At room temperature, the precursor solution was impregnated into activated carbon. As a result of examining the impregnation amount with an ultraviolet absorbance analyzer, it was confirmed that the catalyst component was impregnated with 1.84 wt% based on Co ₃ O ₄ . After drying for 2 hours at 110 ° C in a conventional air circulation dryer, the catalyst was calcined using a conventional muffle furnace and the microwave heating apparatus shown in Table 2, and the dispersion degree was compared.

In the muffle furnace, the temperature was raised to the desired firing temperature in advance, and the catalyst was baked in a 100 ml beaker with a thickness of 2 mm. In a microwave heating apparatus, the catalyst was also placed in a beaker of the same size with a thickness of 2 mm. It baked while adjusting temperature while raising temperature. Preliminary experiments showed that activated carbon was very well heated in microwave, while Co (NO ₃ ) ₂ · 6H ₂ O was not well heated.

Properties of Activated Carbon Used in Catalyst Preparation

The dispersion of the catalysts was compared by comparing the oxidation activity of benzene and scanning electron microscope (SEM) analysis. The oxidation reaction of benzene was carried out while adsorbing a certain amount of benzene on the calcined catalyst, and then placing it in a micro-pulse reaction apparatus, 0.1000 g, and supplying oxygen in pulses of 2 ml.

The micro-pulse reactor consists of a six-cylinder valve, a reactor, and a gas chromatograph analyzer. The six-cylinder valve is an electrically driven type with a timer that can supply oxygen every 20 minutes at 2 ml intervals. It is made of 1/4 inch inner diameter pipe. Gas chromatographic analyzers are used to measure the amounts of reaction products and unreacted oxygen, and were set up to calculate the oxidation conversion rate for each oxygen supply.

FIG. 4 shows benzene in activated carbon without CoO, a catalyst fired at 250, 300, 350, and 400 ° C. for 10 minutes in a conventional muffle furnace, and a catalyst fired for 10 minutes at a temperature path in FIG. 3 in a microwave heating apparatus. The adsorption of each and oxidation reaction at the reaction temperature of 260 ℃ is shown as the reaction conversion rate according to the number of oxygen supply. Compared with the activated carbon that does not support the catalyst component, it can be seen that all of the catalysts calcined in the muffle furnace have little activity.

On the other hand, the catalyst calcined in the microwave heating device was found to have a very high activity even after firing for 10 minutes. 5 is an experimental result of investigating the effect of calcining time calcined for 10 minutes, 2 hours, and 10 hours in a muffle furnace at 300 ° C, respectively. It has been shown that the catalyst fired in the conventional heating apparatus has little activity regardless of the firing time.

From these results, it can be seen that the catalyst calcined in the conventional heating apparatus has a problem in the supported state, and it can be confirmed through SEM analysis. SEM analysis showed that the calcined catalyst in the muffle furnace was packed with large particles of micron size (μm), while the calcined catalyst in the microwave heating device was loaded with nanometer (nm) size particles.

On the other hand, in order to compare the firing rate of the conventional heating method of microwave heating method, the precursor was impregnated with 5.2 wt% based on CoO and fired at 300 ° C. while changing the time using two heating apparatuses. In addition, FTIR and XPS analyzes were performed on the two catalysts to determine whether the firing was completed by the presence or absence of NO or N in the precursor. As a result of the analysis, precursors of all catalysts calcined for 10, 30, and 60 minutes in the muffle furnace were found to be precursors, but catalysts calcined for 20 minutes in the microwave heater did not appear. From these results, it can be seen that the firing speed in the microwave heating apparatus is three times faster, and the microwave effect is found in the firing step of the catalyst.

Example 2

To prepare a catalyst of 2% MoO / activated carbon in the same manner as in Example 1, the precursor solution was impregnated with activated carbon and then dried at 110 ° C. for 2 hours in a conventional heating apparatus. The precursor (NH) MoO.4HO used in the preparation of these catalysts was not well heated in the microwave.

As in Example 1, baking was carried out using a conventional and microwave heating apparatus, and oxidative reaction activity and benzene dispersity of benzene were compared for benzene. As a result of the analysis, the catalyst calcined in the conventional heating apparatus showed little oxidation reaction to benzene due to the large particle supported, whereas the catalyst calcined in the microwave heating apparatus showed very good activity.

Example 3

In order to prepare 2% CrO / activated carbon catalyst in the same manner as in Example 1, the precursor solution was impregnated with activated carbon and then dried at 110 ° C. for 2 hours in a conventional heating field. The precursor (NH) CrO used in the preparation of these catalysts was not heated to microwaves.

As in Example 1, baking was carried out using a conventional and microwave heating apparatus, and oxidative reaction activity and benzene dispersity of benzene were compared for benzene. As a result of the analysis, the catalyst calcined in the conventional heating apparatus showed little oxidation reaction to benzene due to the large particle supported, whereas the catalyst calcined in the microwave heating apparatus showed very good activity.

Example 4

In the same manner as in Example 1, the precursor solution was impregnated with activated charcoal to prepare a CoO-MoO / activated carbon and a two-component catalyst having a total of 2% by 1% each of catalyst components, followed by 2 hours at 110 ° C. in a conventional heating apparatus. Dried over.

As in Example 1, baking was carried out using a conventional and microwave heating apparatus, and oxidative reaction activity and benzene dispersity of benzene were compared for benzene. As a result of the analysis, the catalyst calcined in the conventional heating apparatus showed little oxidation reaction to benzene due to the large particle supported, whereas the catalyst calcined in the microwave heating apparatus showed very good activity. The two-component catalysts fired in the microwave heating apparatus showed different reaction characteristics from those of the two single-component catalysts, indicating that the crystal sizes of the two catalyst components were reduced to similar levels.

Example 5

In the same manner as in Example 1, to prepare a bicomponent catalyst of CoO-CrO / activated carbon having a total of 2% by 1% of the catalyst component, the precursor solution was impregnated with activated carbon and then heated at 110 ° C. in a conventional heating apparatus for 2 hours. Dried over.

As in Example 1, baking was carried out using a conventional and microwave heating apparatus, and oxidative reaction activity and benzene dispersity of benzene were compared for benzene. As a result of the analysis, the catalyst calcined in the conventional heating apparatus showed little oxidation reaction to benzene due to the large particle supported, whereas the catalyst calcined in the microwave heating apparatus showed very good activity.

Example 6

A 0.5% Pd / γ-AlO catalyst was prepared to see the effect of heating on dispersion in the drying step of impregnation. Impregnation was performed by using Pd (NO) aqueous solution in alumina of physical properties as shown in Table 1. The impregnated catalysts were then dried using conventional and microwave heaters, and the two catalysts were calcined in conventional heaters. In the microwave apparatus, drying was performed at 110 ° C. for 10 minutes, and in the conventional heating apparatus, at 110 ° C. for 1 hour. Firing was carried out for 2 hours at 440 ° C. for both catalysts.

Properties of Commercial Alumina

Comparison of dispersion degree was performed by hydrogen chemisorption method. Before hydrogen chemisorption, the catalyst was reduced at 400 ° C. for 2 hours while flowing hydrogen at a flow rate of 70 cc / min. As a result of hydrogen compound adsorption, the crystal size of the catalyst dried in the microwave heater was 2 nm, assuming that one H atom was adsorbed on the surface source of Pd, while the catalyst dried in the conventional heater was 7 nm.

Example 7

A 4% NI / SiO catalyst was prepared by impregnating Davison 57 silica Ni (NO) solution with a specific surface area of 300 m 2 / g, pore volume of 1.0 cc / g, packing density of 4 g / cc, and particle size of 40/80 mesh. As in Example 6, the catalyst was dried using a conventional and microwave heating apparatus and the crystal sizes were compared by hydrogen adsorption. Drying was carried out at a temperature of 100 ° C. for 10 minutes in a microwave heating apparatus and at a temperature of 100 ° C. for 1 hour in a conventional heating apparatus. Firing was carried out for 2 hours at 400 ° C. for both catalysts and reduction at 360 ° C. for 2 hours. As a result of the hydrogen chemical adsorption, the crystal size of the dried catalyst in the microwave heater was 5 nm, but the dried catalyst in the conventional heater was 14 nm.

Example 8

The activated carbon of Table 1 was impregnated with an aqueous solution of HPtCl and drying firing was performed in a conventional and microwave heating apparatus to prepare a 2% Pt / activated carbon catalyst. In the conventional heating apparatus, the resultant was dried at 110 ° C. for 1 hour and then calcined at 280 ° C. for 2 hours, and in the microwave heating apparatus, dried at 110 ° C. for 10 minutes, and then calcined at 280 ° C. for 10 minutes. The crystal size of the two catalysts after reduction at 250 ° C. was analyzed by electron microscopy. As a result, the crystals of the catalyst dried and calcined in the microwave heating apparatus were 3 nm or less, but the catalyst dried and calcined in the conventional heating apparatus was 5 nm or more.

Example 9

To a carrier such as alumina, silica, or zeolite, a series of metal and metal oxide catalysts having one or more components of Ag, Au, Fe, Ta, Sr, v, Zn, W, Mg, Mn, Ba, Al Each was prepared using conventional and microwave heating apparatus. In addition, the relative sizes of the catalyst components of the catalysts prepared by the two heating apparatuses were measured by measuring the chemical adsorption amount of the gas adsorbed thereto.

When the gas chemisorption amount measurement results indicate that the adsorption amount of the catalyst prepared in the microwave heating apparatus is x1 and the coalescence amount of the catalyst prepared in the conventional apparatus is x2, that is, 100 (x1-x2) / x2. It is shown in Table 3 as the gas chemical adsorption amount increase or decrease of the catalyst, it can be seen that the gas chemisorption amount of all the catalysts produced by the present invention in Table 3 is greatly increased. From these results, it can be seen that the catalyst prepared in the microwave heating apparatus has a smaller crystal size of the catalyst component than the catalyst prepared in the conventional apparatus.

Example 10

CoO / activated carbon catalysts were prepared using a continuous manufacturing apparatus. At this time, activated carbon as a carrier was supplied to the impregnation unit 6 at a rate of 1 kg / 1 minute, and a Co (NO) · 6HO solution having a concentration of 2% at a rate of 4 kg / 1 minute through the spray nozzle 10, and air or inert gas. The dry through the air inlet 22 at a rate of 20l / 1 min based on 30 ℃, was supplied to the firing unit (14). In this way, the catalyst precursor solution was impregnated into the carrier by the spraying method, and the drying and firing of the catalyst was continuously performed using microwave energy in one chamber. At this time, the temperature of the drying and baking part 14 where drying and firing was performed. Was maintained at 250 ° C. by adjusting the output of the microwaves.

Moreover, the moving speed of the conveyor belt 11 was adjusted so that the residence time of the catalyst during drying and firing, i.e., the time until the catalyst entered the drying and firing 14 and exited again was about 15 minutes. The CoO / activated carbon catalyst thus prepared was analyzed by electron microscopy and oxidation activity for benzene as in Example 1, and the crystal size was similar to that of the catalyst prepared in the microwave heating apparatus of FIG. The dispersion was much higher than the catalyst.

Gas chemisorption measurement result

Claims (15)

In the heterogeneous preparation containing the metal and the metal oxide catalyst component by the impregnation method, in a carrier selected from among activated carbon, silica, alumina and zeolanit, Group II a, Group IV a, Group I b, and Impregnating a catalyst precursor solution comprising one or more metals of Group II b, Group III b, Group VIII b, Group VI b, Group b b, and Group b b Method of producing a highly dispersed heterogeneous catalyst using a microwave, characterized in that by putting into the resonator (1) and produced by drying and firing batchwise with the microwave generated from the microwave generator (2). The method for producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein the Group II a element is Mg, Ca, Sr, or Ba. The method for producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein Sn is used as a Group IV-a element. The method for producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein the Group b element is Cu, Ag, or Au. The method for producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein Zn is a Group II b element. The method for producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein La is a Group III-b element. 2. The method for producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein the group B element is V or Ta. The method of producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein the Group b element is Cr, Mo, or w. The method for producing a highly disperse heterogeneous catalyst using microwaves according to claim 1, wherein Mn is a group b element. The method for producing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein the element b is Fe, Co, Ni, or Pt or Pd. The method of manufacturing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein microwave energy is saved by simultaneously supplying hot air or an inert gas into the electromagnetic field together with the microwave energy supply. The method for preparing a highly dispersed heterogeneous catalyst using microwaves according to claim 1, wherein the microwave frequency is 915 MHz or 2450 MHz. In the apparatus for producing a heterogeneous catalyst containing a catalyst component of the metal oxide by the impregnation method, the catalyst precursor solution is impregnated into the carrier and then dried in the resonator (1) to guide the microwave wave generated in the microwave generator (2) (4) is introduced into the resonator (1), and the catalyst is fired batchwise, or is supplied to the dried and baked portion (14) through the microwave waveguide (18) and the microwave inlet (19) generated from the microwave generator (17). The carrier and precursor solution were supplied to the impregnation part 6 provided with the endless conveyor belt for rotating the spray nozzle 10 to be dried and fired while being transferred to the drying and baking part 14 by the rotating belt 11. Apparatus for continuous production of heterogeneous catalysts of cross-dispersity using microwaves. The microwave and hot air or inert gas supplied to the drying / firing portion of the microwave generated by the microwave generator 17 through the waveguide 18 and the microwave inlet port 19 through the gas inlet 22. Apparatus for continuously producing a highly dispersed heterogeneous catalyst using microwaves, characterized in that the catalyst is calcined while being supplied to a drying and firing portion (14). In the production of heterogeneous catalysts containing metal and metal oxide catalyst components by impregnation, Group II a element, Group IV a element, Group I b element, and Group 1 are selected from the group consisting of activated carbon, silica, alumina and zeolite. Dry one or more metals of Group II b, Group III b, Group V b, Group VI b, Group b b, and Group b b. The carrier is continuously supplied to the conveyor belt 11 turning the impregnation part 6 and impregnated by impregnating the carrier with the spray nozzle 10 in the impregnation part 6 with the carrier solution. 14) is produced in the microwave generator 17 is produced by drying and firing with microwaves introduced through the waveguide 18 and the microwave inlet port 19 and introduced into the firing section 14, the high dispersion degree using microwaves Method for the preparation of heterogeneous catalysts.