CN117861658B - Catalyst preparation method based on supergravity reactor - Google Patents

Abstract

The present invention relates to the technical field of catalyst preparation, and provides a catalyst preparation method based on an ultra-gravity reactor, comprising: preparing a first solution and a second solution, wherein the first solution contains ferrous ions, and the second solution is an alkaline hydrogen peroxide solution; the packed bed rotates, and the first solution and the second solution are introduced into a reaction cavity; the packed bed is controlled to operate at a plurality of different rotation speeds, so that the packed bed generates flow fields with different gravity levels, and the first solution and the second solution are mixed and reacted in real time under the flow fields with different gravity levels, so as to generate nano-scale porous amorphous iron oxides at different gravity levels, wherein part of the iron oxides exist in the form of quantum dots. The present invention solves the defects of the existing iron oxide preparation technology being complex and inefficient and having insufficient surface active sites, and can "one-step" regulate the surface properties of the iron oxide to generate nano-scale porous amorphous iron oxides at different gravity levels by only adjusting the gravity level, thereby improving the catalytic activity and improving the production efficiency.

Description

Catalyst preparation method based on ultra-gravity reactor

Technical Field

The invention relates to the technical field of catalyst preparation, and in particular to a catalyst preparation method based on a supergravity reactor.

Background technique

Iron oxide catalyst is a common catalyst, which is often used in many chemical reactions such as redox reaction, acid-base catalysis reaction, organic synthesis reaction, etc. Iron is one of the abundant elements on earth, so iron-based catalysts are usually more economical than rare metal catalysts (such as rhodium, palladium, platinum, etc.). Due to the relatively abundant iron resources, iron-based catalysts help to ensure the continuous supply of catalysts, which is conducive to the sustainable development of industry. Iron is a relatively environmentally friendly element, and its mining, refining and processing processes have less impact on the environment compared with some rare metals. Although iron may not be as active as some rare metals, iron-based catalysts still show good catalytic performance in some reactions, and their activity and selectivity can be further improved by improving the design and structure of the catalyst. These advantages of iron-based catalysts make it one of the ideal choices in many reactions.

The surface structure of iron-based catalysts is crucial to their performance. However, traditional structural regulation methods, such as metal doping or artificial defect preparation, are often complicated to operate (e.g., multiple steps such as high temperature and high pressure precursor preparation of metal loading are required), which affects the generation of active sites on the catalyst surface and the catalytic activity, and has low production efficiency (e.g., the reaction process is complicated and the prepared catalyst is unstable).

Therefore, the existing methods for preparing iron oxides need to be improved.

Summary of the invention

The present invention provides a method for preparing a catalyst based on a supergravity reactor. The present invention solves the defects of the existing iron oxide preparation technology, which is complex and inefficient and has insufficient surface active sites. The surface properties of the iron oxide can be regulated by simply adjusting the gravity level to generate nanoscale porous amorphous iron oxides under different gravity levels, thereby improving the catalytic activity of the iron oxide and improving production efficiency.

The present invention provides a catalyst preparation method based on a supergravity reactor, wherein the supergravity reactor is provided with a reaction cavity, and a packing bed is provided in the reaction cavity;

The catalyst preparation method comprises:

preparing a first solution and a second solution, wherein the first solution contains ferrous ions and the second solution is an alkaline hydrogen peroxide solution;

The packed bed rotates, the first solution and the second solution are introduced into the reaction cavity, and the first solution and the second solution move from the inside to the outside of the packed bed under the action of centrifugal force;

The packed bed is controlled to run at a plurality of different rotational speeds, and the packed bed generates flow fields with different gravity levels at different rotational speeds, so that the first solution and the second solution are mixed and reacted in real time under the flow fields with different gravity levels, so as to generate nano-scale porous amorphous iron oxides at different gravity levels, wherein part of the iron oxides exist in the form of quantum dots.

According to the catalyst preparation method based on the supergravity reactor provided by the present invention, the first solution and the second solution are introduced into the reaction cavity, comprising:

The first solution and the second solution are sprayed against each other and then enter the reaction cavity.

According to the catalyst preparation method based on the high-gravity reactor provided by the present invention, the high-gravity reactor includes a first liquid inlet and a second liquid inlet arranged opposite to each other, and the first liquid inlet and the second liquid inlet are both connected to the reaction cavity.

According to the catalyst preparation method based on the supergravity reactor provided by the present invention, the liquid inlet angles of the first liquid inlet and the second liquid inlet are adjustable.

According to the catalyst preparation method based on the supergravity reactor provided by the present invention, the spray angle between the first liquid inlet and the second liquid inlet ranges from 25° to 180°.

According to the catalyst preparation method based on the supergravity reactor provided by the present invention, the concentration of ferrous ions in the first solution ranges from 0.75 mM to 2.25 mM, the concentration of hydroxide in the second solution ranges from 0.75 mM to 4.5 mM, and the concentration of hydrogen peroxide in the second solution ranges from 0.75 mM to 3.75 mM.

According to the catalyst preparation method based on the supergravity reactor provided by the present invention, the inlet flow rates of the first solution and the second solution range from 0.09 L/min to 0.21 L/min.

The catalyst preparation method based on the high gravity reactor provided by the present invention also includes:

The suspension generated by the reaction of the first solution and the second solution at different gravity levels is centrifuged to obtain a sample precipitate.

The catalyst preparation method based on the high gravity reactor provided by the present invention also includes:

The sample pellet is frozen.

The catalyst preparation method based on the high gravity reactor provided by the present invention also includes:

The frozen sample is precipitated and freeze-dried in a vacuum environment to obtain iron oxide samples at different gravity levels.

The catalyst preparation method based on the supergravity reactor provided by the present invention comprises the following steps: introducing the prepared first solution and the second solution into the supergravity reactor; during the rotation of the packed bed, under the action of centrifugal force, the first solution and the second solution move from the inside to the outside of the packed bed; in this process, the fluid is cut to generate small droplets of micrometer level; the small droplets wrap nanometer-level iron oxide to generate countless droplet reaction micro-elements; the droplets undergo multiple collisions, renewals, separations and recombination in the packed bed; and by controlling the packed bed to run at multiple different rotation speeds, flow fields with different gravity levels are generated, so that the first solution and the second solution are mixed and reacted in real time under the flow fields with different gravity levels to generate nanometer-level porous amorphous iron oxides with different gravity levels; wherein part of the iron oxides exist in the form of quantum dots; the nanometer-level porous amorphous iron oxides have a small particle size and a high specific surface area, can provide more active sites, and the porous structure can increase the exposure of the active sites, increase the contact area between the reactants and the catalyst, and thus improve the catalytic activity. The present invention solves the defects of the existing iron oxide preparation technology, which is complex and inefficient and has insufficient surface active sites. The surface properties of the iron oxide can be regulated by simply adjusting the gravity level to generate nanoscale porous amorphous iron oxides under different gravity levels, giving the iron oxides a uniform surface pore structure, a large specific surface area, _a high surface Fe(II) content, a nanoscale, and a monodentate _SO4 ^2- coordination mode, etc., thereby achieving efficient catalysis of _H2O2 and improving production efficiency.

Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is an experimental schematic diagram of a high gravity reactor provided in an embodiment of the present invention;

FIG2 is a schematic flow diagram of a catalyst preparation method based on an ultra-gravity reactor provided by the present invention;

3 is a schematic diagram of the spraying of the first solution and the second solution in the catalyst preparation method based on the supergravity reactor provided by the present invention;

4 is an XRD spectrum corresponding to iron oxide prepared by a packed bed at 0 rpm and 500 rpm in a catalyst preparation method based on a supergravity reactor provided by the present invention;

5 is a TEM morphology and particle size distribution diagram of iron oxide prepared by a packed bed at 0 rpm and 500 rpm in a catalyst preparation method based on a supergravity reactor provided by the present invention;

FIG6 is a nitrogen adsorption-desorption curve corresponding to the iron oxide prepared by the packed bed at 0 rpm and 500 rpm respectively in the catalyst preparation method based on the high gravity reactor provided by the present invention;

7 is an infrared spectrum corresponding to iron oxide prepared by the packed bed at 0 rpm and 500 rpm in the catalyst preparation method based on the supergravity reactor provided by the present invention;

8 is an XPS spectrum corresponding to iron oxide prepared at 0 rpm and 500 rpm respectively in the catalyst preparation method based on the high gravity reactor provided by the present invention;

9 is a diagram showing the change in characteristic peaks of the fluorescent substance TPOH generated in the process of preparing iron oxide in the step of the packed bed at 0 rpm and 500 rpm in the catalyst preparation method based on the high gravity reactor provided by the present invention, and (c) a schematic diagram showing the change in superoxide anion content.

Reference numerals:

1. Reactor body; 2. Driving device; 3. Packing bed; 4. Liquid outlet storage device; 5. First solution storage device; 6. Second solution storage device; 7. First driving pump; 8. Second driving pump.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

The catalyst preparation method based on the supergravity reactor provided by the present invention is described below in conjunction with Figures 1 to 9.

Before describing the catalyst preparation method based on the high gravity reactor provided by the present invention, the high gravity reactor is firstly specifically illustrated by an example.

As shown in Figure 1, in this embodiment, the ultra-gravity reactor includes a reactor body 1, a driving device 2 (such as a motor), a packing bed 3, a liquid outlet storage device 4, a first solution storage device 5, a second solution storage device 6, a first driving pump 7 and a second driving pump 8.

The reactor body 1 has a reaction cavity, and the packing bed 3 is arranged in the reaction cavity and has a packing (such as a porous wire mesh packing). The first solution storage device 5 and the second solution storage device 6 are both connected to the reaction cavity through a pipeline, and the liquid outlet storage device 4 is connected to the reaction cavity through a pipeline and is used to collect the mixed liquid after the reaction. The first driving pump 7 is arranged on the pipeline connecting the first solution storage device 5 and the reaction cavity, and the second driving pump is arranged on the pipeline connecting the second solution storage device 6 and the reaction cavity. The first driving pump 7 and the second driving pump 8 are used to drive the first solution and the second solution into the reaction cavity respectively.

The driving device 2 is transmission-connected to the packed bed 3 and is used to drive the packed bed 3 to rotate at high speed. The speed of the packed bed 3 can be adjusted by adjusting the speed of the output end of the driving device to form flow fields with different gravity levels in the packed bed.

The supergravity reactor also has a first liquid inlet, a second liquid inlet and a liquid outlet, the first liquid inlet, the second liquid inlet and the liquid outlet are all connected to the reaction cavity, the first liquid inlet is used to pass the first solution into the reaction cavity, and the second liquid inlet is used to pass the second solution into the reaction cavity. Among them, the first liquid inlet and the second liquid inlet are both located near the center of the supergravity reactor (inside the packing bed 3), and the liquid outlet is located at the bottom of the supergravity reactor, which is used to collect and process the liquid after the reaction.

In this embodiment, the first liquid inlet and the second liquid inlet are arranged opposite to each other. When the first solution and the second solution are driven into the reaction cavity by the first driving pump 7 and the second driving pump 8 respectively, the first solution and the second solution can be sprayed against each other, so that the first solution and the second solution can be fully mixed when entering the reaction cavity, which is convenient for subsequent reaction.

In this embodiment, the liquid inlet angles of the first liquid inlet and the second liquid inlet are adjustable. In this way, the liquid inlet angles of the first solution and the second solution can be adjusted. By adjusting the liquid inlet angles of the first solution and the second solution, the angle at which the mixed liquid after the first solution and the second solution are sprayed against each other enters the packed bed can be adjusted, and the moving path length and reaction time of the mixed liquid after the first solution and the second solution are sprayed against each other in the packed bed can be adjusted. By adjusting the reaction time of the first solution and the second solution in the packed bed, the reaction products of the first solution and the second solution can also be controlled.

It should be noted that, in a specific implementation, the first liquid inlet and the second liquid inlet can be rotated to adjust the liquid inlet angles of the first solution and the second solution respectively, and the spraying angle of the first solution and the second solution can be adjusted, thereby controlling the direction of the liquid after the first solution and the second solution are sprayed and mixed when entering the packed bed.

The following is a description of the catalyst preparation method based on the high gravity reactor provided by the present invention. The catalyst preparation method based on the high gravity reactor described below and the high gravity reactor described above can be referenced to each other.

As shown in FIG2 , the present invention provides a method for preparing a catalyst based on a supergravity reactor, comprising:

S210, preparing a first solution and a second solution, wherein the first solution contains ferrous ions, and the second solution is an alkaline hydrogen peroxide solution;

S220, the packed bed rotates, the first solution and the second solution are introduced into the reaction cavity, and the first solution and the second solution move from the inside to the outside of the packed bed under the action of centrifugal force;

S230, controlling the packing bed to run at a plurality of different rotational speeds, so that the packing bed generates flow fields with different gravity levels at different rotational speeds, so that the first solution and the second solution are mixed and reacted in real time under the flow fields with different gravity levels, so as to generate nano-scale porous amorphous iron oxides at different gravity levels, wherein part of the iron oxides exist in the form of quantum dots.

Traditional iron oxide synthesis and structure control methods are often complicated (specifically, multiple steps such as high temperature and high pressure precursor preparation of metal loading are required) and not efficient enough (specifically, the reaction process is complicated, and the prepared catalyst is unstable ₎ . The catalyst preparation method based on the supergravity reactor provided by the present invention can "one-step" generate nano-scale porous amorphous iron oxide in real time and control the surface properties of iron oxide in real time by simply adjusting the gravity level, thereby achieving efficient catalysis of _H2O2 . Compared with iron oxides generated under normal gravity field, the supergravity field gives iron oxides smaller nano-size, more uniform nano-surface pore structure, and more surface divalent iron content, so that the iron oxides generated under the supergravity field can produce more active oxygen species such as hydroxyl radicals and superoxide anion radicals when catalyzing hydrogen peroxide.

After the first solution and the second solution enter the reaction cavity, since the packing bed is in a rotating state, under the action of centrifugal force, the first solution and the second solution are thrown out from the inside of the packing bed 3 to the outside of the packing bed 3. In this process, the fluid is cut to generate small droplets of micron level, and the small droplets wrap the nano-scale iron oxide to generate countless droplet reaction micro-elements, which experience multiple collisions, renewals, separations and recombination in the packing bed, and by controlling the packing bed to run at multiple different speeds, flow fields with different gravity levels are generated, so that the first solution and the second solution are mixed and reacted in real time under the flow fields with different gravity levels to generate nano-scale porous amorphous iron oxides at different gravity levels, wherein part of the iron oxides exist in the form of quantum dots, and the nano-scale porous amorphous iron oxides have a small particle size and a high specific surface area, which can provide more active sites, and the porous structure can increase the exposure of the active sites, increase the contact area between the reactants and the catalyst, and thus improve the catalytic activity.

The reaction principle is as follows:

After the Fe ²⁺ solution (first solution) and the alkaline hydrogen peroxide solution (second solution) are simultaneously introduced into the supergravity reactor, the Fe ²⁺ immediately reacts with hydrogen peroxide to generate Fe ³⁺ . Due to the presence of sodium hydroxide, the Fe ³⁺ ions precipitate quickly. And Fe ²⁺ can also directly react with sodium hydroxide to produce precipitation. Compared with the traditional iron oxide precipitation process, the strong fluid flow generated by the rotation of the packed bed in the supergravity reactor cuts and crushes the iron oxide precipitate, affecting the structure of the iron oxide precipitate. The extremely short growth time limits the growth of the iron oxide, resulting in the formation of amorphous (low crystallinity) hydrated iron oxide.

The reaction equation is as follows:

The catalyst preparation method based on the ultra-gravity reactor provided by the present invention greatly improves the surface active sites of the iron oxide, thereby improving the catalytic activity of the iron oxide and significantly improving the production efficiency of the iron oxide.

Specifically, according to some embodiments of the present invention, in step S210, a set amount of FeSO ₄ ·H ₂ O may be dissolved in deionized water to obtain a first solution containing a set concentration of ferrous ions. A set amount of sodium hydroxide may be dissolved in deionized water, and then a set amount of hydrogen peroxide solution is added to the solution containing sodium hydroxide, and the mixture is quickly stirred to obtain an alkaline hydrogen peroxide solution (second solution).

According to some embodiments of the present invention, the first solution and the second solution are introduced into the reaction cavity, comprising: the first solution and the second solution are sprayed against each other and then enter the reaction cavity, so that the first solution and the second solution can be fully mixed when entering the reaction cavity, which is convenient for subsequent reaction.

Specifically, in this embodiment, the first solution and the second solution enter the reaction cavity through the first liquid inlet and the second liquid inlet respectively. When the first driving pump and the second driving pump are started, the first solution and the second solution flow out through the first liquid inlet and the second liquid inlet respectively. Since the first liquid inlet and the second liquid inlet are arranged relative to each other, the first solution and the second solution are sprayed against each other, so that the first solution and the second solution can be fully mixed when entering the reaction cavity, which is convenient for subsequent reactions.

It should be noted that the above-mentioned "counter-spraying" specifically refers to the first solution and the second solution being sprayed in opposite directions and mixed. Among them, the first liquid inlet and the second liquid inlet can be arranged opposite to each other (the angle between the two is 180°). In this case, the first solution and the second solution are directly contacted and mixed after being sprayed and enter the packed bed in a direction perpendicular to the packed bed. The first liquid inlet and the second liquid inlet can also be arranged at an angle (the angle between the two is less than 180°). In this case, the first solution and the second solution are directly contacted and mixed after being sprayed and enter the packed bed in a direction with a certain inclination angle (less than 90°) with the packed bed, thereby extending the movement path of the mixed liquid of the first solution and the second solution in the packed bed.

It should be noted that, since the physical properties (density, viscosity, surface tension, etc.) of the first solution and the second solution are similar, the two solutions can be mixed together and flow in a new direction after being sprayed in a set direction.

According to some embodiments of the present invention, the liquid inlet angles of the first liquid inlet and the second liquid inlet are adjustable. By adjusting the liquid inlet angles of the first solution and the second solution, the angle at which the mixed liquid after the first solution and the second solution are sprayed against each other enters the packed bed can be adjusted, and the length of the moving path of the mixed liquid after the first solution and the second solution are sprayed against each other in the packed bed can be adjusted, thereby adjusting the reaction time and reaction product of the first solution and the second solution.

As shown in Fig. 3, according to some preferred embodiments of the present invention, the value range of the spray angle between the first liquid inlet and the second liquid inlet is 25° to 180°. By setting the spray angle between the first liquid inlet and the second liquid inlet within the above range, the mixed liquid after the spraying of the first solution and the second solution can enter the packed bed at an appropriate angle for reaction, and the reaction path of the first solution and the second solution can be controlled within a reasonable range.

It should be noted that the movement path of the mixed liquid after the first solution and the second solution are sprayed against each other in the packing bed is not only related to the angle at which the mixed liquid enters the packing bed, but also related to the rotation speed of the packing bed and the type of packing. During specific implementation, the angle at which the mixed liquid after the first solution and the second solution are sprayed against each other enters the packing bed can be specifically set according to the rotation speed of the packing bed and the type of packing.

According to some preferred embodiments of the present invention, the concentration of ferrous ions in the first solution ranges from 0.75 mM to 2.25 mM, the concentration of hydroxide in the second solution ranges from 0.75 mM to 4.5 mM, and the concentration of hydrogen peroxide in the second solution ranges from 0.75 mM to 3.75 mM. By controlling the amount of ferrous ions, sodium hydroxide and hydrogen peroxide, firstly, the molar ratio between the reactants can be optimized, thereby improving the reaction efficiency; secondly, the amount of waste generated can be reduced; and thirdly, the amount of reactants can be reduced, thereby saving costs.

According to some preferred embodiments of the present invention, the inlet flow rate of the first solution and the second solution ranges from 0.09L/min to 0.21L/min. By controlling the inlet flow rate of the first solution and the second solution within the above range, firstly, the first solution and the second solution can be evenly mixed, which is convenient for the subsequent reaction in the packed bed; secondly, the flow rate of the first solution and the second solution can be controlled within a reasonable range, which is convenient for the first solution and the second solution to enter the packed bed in a set direction after the spraying and mixing, and avoid the situation where the flow direction of the first solution and the second solution after the spraying and mixing is abnormal due to the flow rate being too large or too small.

According to some embodiments of the present invention, the catalyst preparation method based on the ultra-gravity reactor further includes: centrifuging the suspension generated by the reaction of the first solution and the second solution at different rotation speeds to obtain a sample precipitate (yellow solid substance). By centrifuging the suspension, the sample precipitate can be quickly separated from the liquid after the reaction, which is convenient for subsequent freezing and drying of the sample precipitate.

Specifically, in this embodiment, a centrifuge is used to centrifuge the suspension generated by the reaction of the first solution and the second solution at different gravity levels. The centrifugal force of the centrifuge can be set to 3220×g (rotation speed is 4000rpm). After the centrifugation is completed, the supernatant is removed, and the sample precipitate is washed several times with distilled water and anhydrous ethanol to remove liquid impurities remaining on the sample precipitate.

According to some embodiments of the present invention, the catalyst preparation method based on the ultra-gravity reactor further includes: freezing the sample precipitate in a vacuum environment. By freezing the sample precipitate, the sample precipitate can be free of obvious liquid flow, which is convenient for subsequent freeze-drying.

Specifically, in this embodiment, the sample precipitate is placed in a -80°C environment (such as a refrigerator) and frozen for 3 days.

According to some embodiments of the present invention, the catalyst preparation method based on the supergravity reactor further includes: freeze-drying the sample precipitate after freezing treatment to obtain iron oxide samples under different gravity levels. By freeze-drying the sample precipitate after freezing treatment, the water in the iron oxide can be fully removed. During the freezing process, the water solidifies in the form of ice, and the water is removed under vacuum conditions to maintain the morphology and structural integrity of the iron oxide, maintain the activity and stability of the iron oxide, and reduce possible phase changes or chemical reactions.

Specifically, in this embodiment, the frozen sample precipitate is placed in a vacuum freeze dryer at -70°C for freeze drying for 7 days, and the freeze-dried sample is ground to obtain iron oxide samples under different gravity levels. The sample needs to be stored in a sealed jar away from light.

The following is a specific example of the catalyst preparation method based on the supergravity reactor provided by the present invention.

At room temperature, 0.4448 g of FeSO ₄ ·H ₂ O and 0.12 g of sodium hydroxide were dissolved in deionized water to obtain a first solution containing a set concentration of ferrous ions and a sodium hydroxide solution of a set concentration. 0.225 ml of hydrogen peroxide solution was added to the sodium hydroxide solution and stirred rapidly to obtain a second solution.

The first solution and the second solution are introduced into the reaction cavity through the first liquid inlet and the second liquid inlet respectively by the first driving pump 7 and the second driving pump 8, and the first solution and the second solution are sprayed against each other when flowing out through the first liquid inlet and the second liquid inlet, so that the first solution and the second solution are evenly mixed and the mixed liquid is adjusted to a set angle to enter the packing bed for reaction.

The rotation speed of the packed bed was controlled to be 0 rpm and 500 rpm, respectively, to obtain sample A and sample B having a gravity level of 1 g and a gravity level of 8.37 g, respectively.

The iron oxide morphology, surface properties, hydroxyl content, and superoxide anion radical content of sample A and sample B were characterized respectively.

The experimental results show that the increase in gravity level reduces the average particle size of sample A from 281.7nm to 25.7nm of sample B. The average pore size changes from a dispersed distribution of 8.572nm to a concentrated distribution of 3.037nm, the surface pore size distribution tends to be uniform, the specific surface area increases from ^98.124m2 /g to ^135.905m2 /g, and the surface divalent iron content increases from 30.74% to 65.81%. It can be seen that the catalyst preparation method based on the supergravity reactor provided by the present invention can improve the catalytic activity of iron oxide and improve production efficiency.

As shown in Figure 4, the X-ray diffraction (XRD) patterns of the iron oxide samples synthesized under different gravity levels show characteristic peaks that show ridges like hills and mounds, lacking obvious diffraction peaks. This indicates that the generated samples may have an amorphous structure. Compared with the known standard cards, the diffraction peaks are similar to those of Schwatman ore (Sch), but the XRD signals are weaker due to the smaller crystal size of the samples. As the gravity level increases, the diffraction peaks become broader, indicating that the increase in gravity level induces poor crystallinity.

As shown in Figure 5, the size of iron oxides generated under normal gravity conditions ranges from 200nm to 300nm, and is elliptical or circular, as shown in Figure 5 (a). As the gravity level increases, the size distribution and morphological characteristics of the iron oxides become more uniform, showing a rice grain shape with no obvious edges and corners, a length of 100nm, and a width of about 25nm. The supergravity reactor generates a microscopic mixing field by cutting the liquid, so that the reactants are instantly mixed and evenly mixed. Under normal gravity levels, mixing mainly comes from forced convection caused by stirring and rotation, which is not conducive to the formation of uniform structures under some conditions. In a supergravity environment, the increase in gravity levels shortens the mixing time, resulting in a shorter mixing time and a more uniform mass distribution of the product. When the size of the catalyst is reduced to the nanoscale, its physical and chemical properties may be significantly different from its macroscopic counterparts.

Table 1 Changes in surface pore structure and specific surface area of iron oxides prepared at different rotation speeds

As shown in Figure 6, according to the classification of the International Union of Pure and Applied Chemistry (IUPAC), the curve corresponding to the iron oxide generated at 0 rpm conforms to the type IV isotherm, showing a typical H4-type hysteresis loop and lacking an obvious saturated adsorption platform, which indicates that the pore structure is irregular in shape and the hysteresis loop is located later, suggesting a larger pore size. The adsorption-desorption curve corresponding to the iron oxide generated at 500 rpm can be classified as a mixture of type IV and type II isotherms with both H2-type hysteresis loops, indicating that there are both micropores and mesopores in the material. Table 1 shows that the surface pore size and pore volume of the iron oxide generated under normal gravity conditions (0 rpm) are large but the specific surface area is small, indicating that the pores are isolated and dispersed. The pore size distribution of the iron oxide generated under supergravity conditions (500 rpm) is more concentrated, mainly distributed in mesopores of near-micrometer size, with a larger pore volume, forming an iron oxide with a porous structure. The porous nanostructure has the advantages of high adsorption, high permeability and good transfer capacity, which may interact more effectively with other molecules and help improve catalytic performance.

As shown in Figure 7, the characteristic peaks from 996 cm ^-1 to 1164 cm ^-1 correspond to the stretching vibration of sulfate ions. Under supergravity, the three weakly symmetrical characteristic bands of Sch at 996 cm ^-1 , 1081 cm ^-1 and 1153 cm ^-1 correspond to the characteristic peaks of sulfate in the form of non-protonated monodentate inner sphere, and the adsorption process is shown in Equation (1). The presence of the structure makes the iron oxide surface negatively charged. The peak at 1083cm ^-1 of the iron oxide generated under normal gravity conditions has a significant split, and this trend corresponds to the bridged bidentate adsorption of non-protonated sulfate on the Sch surface. The change in the coordination mode of the sulfate ion shows that the increase in rotation speed leads to the transformation of the bidentate complex to the monodentate complex. Compared with the bidentate complex, the monodentate complex is more flexible and easier to transfer electrons to the central iron atom, and has better catalytic activity.

(1)

As shown in Figure 8, the Fe 2p3/2 peak and Fe 2p1/2 peak of Fe(Ⅱ) appear at around 707eV and 721eV respectively, and the peak area ratio represents the proportion of iron. As shown in Figure 8, as the speed increases from 0rpm to 500rpm, the proportion of Fe(Ⅱ) increases from 30.74% to 65.81%. In the heterogeneous reaction mechanism, the reaction of Fe(Ⅱ) with H ₂ O ₂ to generate hydroxyl (HO·) is an effective step in removing pollutants, so the increase in speed is conducive to the generation of HO·.

As shown in Figure 9, benzoic acid reacts with hydroxyl radicals to generate hydroxybenzoic acid, which shows fluorescence at a specific wavelength. This property is used to measure the content of hydroxyl radicals generated at different rotation speeds. As shown in Figure 9 (a) and (b), as the rotation speed increases, the characteristic peak signal of hydroxybenzoic acid increases, which means that more free radicals are generated. NBT reacts with superoxide anion radicals to produce colored formazan derivatives with a characteristic peak at a wavelength of 285cm ^-1 . This characteristic is used to measure superoxide anion radicals at different rotation speeds, and the results are shown in Figure 9 (c). As the rotation speed increases, more NBT is reduced, which means that the increase in rotation speed leads to the generation of more superoxide anion radicals.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (7)

1. A method for preparing a catalyst based on a high gravity reactor, characterized in that the high gravity reactor has a reaction cavity, and a packing bed is provided in the reaction cavity; The catalyst preparation method comprises: preparing a first solution and a second solution, wherein the first solution contains ferrous ions and the second solution is an alkaline hydrogen peroxide solution; The packed bed rotates, the first solution and the second solution are sprayed against each other and then introduced into the reaction cavity, and the first solution and the second solution move from the inside to the outside of the packed bed under the action of centrifugal force; Controlling the packed bed to run at a plurality of different rotational speeds, the packed bed generates flow fields with different gravity levels at different rotational speeds, so that the first solution and the second solution are mixed and reacted in real time under the flow fields with different gravity levels, so as to generate nano-scale porous amorphous iron oxides at different gravity levels, wherein part of the iron oxides exist in the form of quantum dots; The ultra-gravity reactor comprises a first liquid inlet and a second liquid inlet which are arranged opposite to each other, and the first liquid inlet and the second liquid inlet are both connected to the reaction cavity; The liquid inlet angles of the first liquid inlet and the second liquid inlet are adjustable. 2. The catalyst preparation method based on the supergravity reactor according to claim 1 is characterized in that the spray angle between the first liquid inlet and the second liquid inlet ranges from 25° to 180°. 3. The method for preparing a catalyst based on a supergravity reactor according to claim 1, characterized in that the concentration of ferrous ions in the first solution ranges from 0.75 mM to 2.25 mM, the concentration of hydroxide in the second solution ranges from 0.75 mM to 4.5 mM, and the concentration of hydrogen peroxide in the second solution ranges from 0.75 mM to 3.75 mM. 4. The catalyst preparation method based on the high gravity reactor according to claim 1 is characterized in that the inlet flow rate of the first solution and the second solution ranges from 0.09 L/min to 0.21 L/min. 5. The method for preparing a catalyst based on an ultra-gravity reactor according to any one of claims 1 to 4, characterized in that it further comprises: The suspension generated by the reaction of the first solution and the second solution at different gravity levels is centrifuged to obtain a sample precipitate. 6. The method for preparing a catalyst based on a high gravity reactor according to claim 5, characterized in that it also comprises: The sample pellet is frozen. 7. The method for preparing a catalyst based on a high gravity reactor according to claim 6, characterized in that it also comprises: The frozen sample is precipitated and freeze-dried in a vacuum environment to obtain iron oxide samples at different gravity levels.