CN112958098B - Sulfur-mercury oxidation resistant catalyst, preparation method thereof and flow electrode device - Google Patents

Abstract

The invention provides a sulfur-resistant mercury oxidation catalyst, a preparation method thereof and a flowing electrode device, wherein the sulfur-resistant mercury oxidation catalyst is CeO with a core-shell structure₂@ CuO, of which CeO₂Is used as an inner core and CuO is used as a shell layer. The catalyst of the invention is of a core-shell structure and is in SO₂Exhibits excellent zero-valent mercury oxidation capability in the presence of conditions. The invention also provides a preparation method of the sulfur-resistant mercury oxidation catalyst, which is prepared by adopting a flowing electrode method to carry out reaction. Compared with the existing solution precipitation method and other methods, the method has the advantages of simplicity and controllability, capability of preparing a complete and uniform core-shell structure and wide application range.

Description

A kind of anti-thiomercuric oxidation catalyst and preparation method thereof, flow electrode device

technical field

The invention relates to the technical field of environmental protection, in particular to an anti-thiomercuric oxidation catalyst, a preparation method thereof, and a flow electrode device.

Background technique

Mercury, commonly known as mercury, is a heavy metal that can exist in both gaseous and liquid forms at room temperature. Mercury is highly toxic and can migrate and accumulate in the biological chain over long distances, which is extremely harmful to the environment and human health. Among them, the coal-fired industry, non-ferrous metal industry, waste incineration, and cement industry are the main sources of man-made emissions.

Mercury mainly exists in three forms in industrial flue gas: gaseous elemental mercury (Hg ⁰ ), gaseous active mercury (Hg ²⁺ ) and particulate mercury ⁽ Hg _p ⁾ . Removal is an important part of solving industrial flue gas mercury pollution emissions. Since Hg ⁰ can be converted into Hg ²⁺ and then removed, for example, in the coal-fired industry, Hg ²⁺ can be cooperatively removed by subsequent wet desulfurization equipment. Therefore, the key to removing mercury from flue gas is to provide a sulfur-resistant and efficient The Hg ⁰ oxidation catalyst converts Hg ⁰ to Hg ²⁺ in the presence of SO ₂ .

Existing mercury oxidation catalysts are usually composite structures, such as the catalysts disclosed in CN102698753A, which are copper-based composite oxide catalysts and/or copper-based composite halide catalysts, or carrier-supported structures, such as the mercury oxidation catalysts disclosed in CN102470345A. ₂ is that the carrier supports V ₂ O ₅ and MoO ₃ as active components, but the anti-sulfur performance or oxidation efficiency of the above catalysts needs to be further improved.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the prior art, the present invention provides an anti-thiomercury oxidation catalyst, a preparation method thereof, and a flow electrode device. The catalyst exhibits excellent zero-valent mercury oxidation ability in the presence of SO ₂ .

The present invention adopts the following technical solutions:

The invention provides an anti-thiomercuric oxidation catalyst, which is CeO ₂ @CuO with a core-shell structure, wherein CeO ₂ is the core and CuO is the shell.

In the present invention, it is found through experiments that the core-shell structure CeO ₂ @CuO is used as a catalyst, and its shell CuO can react with SO ₂ so as to have a good anti-sulfur effect. After the reaction, the inner core CeO with strong zerovalent mercury oxidation ability ₂ can be contacted with zero-valent mercury in the flue gas to convert Hg ⁰ into Hg ²⁺ , so the catalyst of the present invention is an excellent anti-thiomercuric oxidation catalyst.

Preferably, the inner core is a spherical particle with a particle size of 50-200 nm.

Preferably, the mass ratio of Cu:Ce in the anti-thiomercuric oxidation catalyst=1:(15-25).

The present invention also provides a preparation method of the above-mentioned anti-thiomercuric oxidation catalyst. The preparation method provided by the present invention adopts the flow electrode method for reaction preparation.

In the prior art, most of the materials for preparing core-shell structures adopt a two-step method. The first step uses traditional hydrothermal method, sol-gel method, impregnation method, co-precipitation method and other methods to first synthesize the target core, and the second step The encapsulation of shell particles to core particles mainly includes metal vapor deposition (MOCVD), electrochemical deposition (EPD), continuous ionic layer adsorption (SILAR) and solution precipitation. Among them, the reactants of MOCVD are expensive, and the products after the reaction need to be treated harmlessly; EPD is difficult to prepare metal oxide core-shell structures with low conductivity; SILAR is mainly suitable for synthesizing shell particles with strong adsorption to core particles The more commonly used solution precipitation method mainly uses the particles prepared in the first step as the condensation core, and by adjusting the amount of salt added in the solution or adjusting the pH of the solution, the shell particles are promoted to use the core particles as the core particles in the solution. The template is deposited and grown, but the existence of ion concentration gradient and pH gradient in the reaction process of this method interferes with the precipitation and formation of shell particles on the surface of the inner core, making the reaction process uneven, and it is difficult to synthesize a uniform core-shell structure.

Flow electrode method is a sewage treatment method that uses electrodes and semi-permeable membranes to make ions in liquid move in a directional manner, thereby selectively removing ions in solution, and is generally used in the field of water treatment. Through research, the present invention unexpectedly finds that the material of the core-shell structure can be prepared by using the flowing electrode method. The method is simple and controllable. Compared with the existing solution precipitation method and other methods, a more complete and uniform core-shell structure can be prepared, and is suitable for wider range.

Specifically, in the preparation method of the present invention, the CeO ₂ solution is used as the electrode solution, and the copper salt solution is used as the flowing solution. Among them, the electrode liquid flows through the cathode chamber and the anode chamber, and the flowing liquid flows through the middle desalination chamber. Under the action of the electric field, the Cu ²⁺ will move to the outer electrode chamber and be captured by the suspended CeO ₂ nuclei. The CeO ₂ @CuO structure is finally formed.

Preferably, the copper salt solution is a copper nitrate solution.

In the prior art, copper acetate is generally used as a precursor for synthesizing copper shells. In the present invention, copper nitrate can be used to avoid side reactions as much as possible, such as reactions with electrodes.

Preferably, the electrode solution also contains sodium sulfate, and the mass ratio of the sodium sulfate to CeO ₂ is 1:(2-4), more preferably 1:3.

In the present invention, adding sodium sulfate to the electrode solution can improve the conductivity of the CeO ₂ solution, and the sodium sulfate is quite stable, basically maintains the form of Na ²⁺ and SO ₄ ^2- during the flow process, and does not participate in the electrode reaction, thereby oxidizing the catalyst. Ability has minimal impact. Further research in the present invention finds that the addition amount of sodium sulfate is strongly related to the structural integrity and uniformity of the obtained core-shell structure catalyst, and the effect is better when the addition amount of sodium sulfate is controlled within the above range.

Preferably, in the preparation process, a constant voltage mode is adopted, and the voltage is preferably 4-5V, more preferably 4.5V.

In the present invention, the reaction rate and energy consumption are integrated, and it is found that the constant voltage mode is better. Moreover, when the voltage is controlled within the above range, it is beneficial to obtain a core-shell structure with complete and uniform encapsulation.

Preferably, the electrode solution sequentially flows through the cathode chamber and the anode chamber which are connected in series.

In the prior art, in order to facilitate rapid desalination, the cathode chamber and the anode chamber are connected in parallel. In the present invention, since part of the CeO ₂ core is larger than 100 nm, it will slowly and naturally deposit in the solution, which is not conducive to the reaction. Therefore, the two external electrode chambers (cathode chamber and anode chamber) through which CeO ₂ flows are connected in series to reduce the flow rate. channel length, thereby improving the catalyst synthesis efficiency.

After the improvement of the present invention, the electrode solution containing CeO2 enters from the cathode chamber, and then flows out from the anode chamber, the copper salt solution flows through the middle chamber, and the ^Cu2+ _enters the cathode chamber through the cation exchange membrane under the action of voltage , and then reduced to Cu ⁰ or indirectly with OH ^- to form Cu(OH) ₂ driven by electrons, and part of Cu ²⁺ was captured by the action of the electric double layer on the surface of CeO _2. After subsequent burning treatment, The Cu ⁰ on the catalyst surface will be oxidized to CuO by air, while the Cu(OH) ₂ will be decomposed into CuO at high temperature, and part of the CuO will be generated in situ during the reaction, thereby preparing the CeO ₂ @CuO catalyst, the schematic diagram is shown in the figure 1 shown.

Preferably, after the reaction time reaches 6 hours, the outflowing electrode liquid is separated into solid and liquid, and the obtained solid is calcined.

The length of the reaction time has an effect on the amount of Cu deposition on the surface of CeO ₂ . The study found that the reaction time longer than 6 hours is beneficial to obtain a complete core-shell structure. And as mentioned above, the present invention found that after the flow electrode reaction, the surface of CeO ₂ not only has CuO, but also part of Cu ⁰ and/or Cu(OH) ₂ , so further burning treatment is required, which is also conducive to stabilizing the crystal form . Preferably, the firing temperature is 400-600°C. Further, in order to remove the influence of impurity ions in the solution, the solid obtained after solid-liquid separation needs to be cleaned and dried before burning.

In a preferred embodiment of the present invention, the parameters in the preparation process using the flow electrode method are: the concentration range of the CeO ₂ solution and the Cu(NO ₃ ) ₂ solution is 30-40 g/L; additionally adding Na ₂ to the CeO ₂ solution The concentration range of SO ₄ , Na ₂ SO ₄ in the solution is 10～15g/L; the constant voltage power supply mode is used in the reaction process, the voltage range is 4.0～5.0V; the flow rate range of CeO ₂ solution is 2～4ml/min, Cu The flow rate of (NO ₃ ) ₂ was 1-3 ml/min, and the reaction time was 6 hours.

More preferably, the concentration of the CeO ₂ solution and the Cu(NO ₃ ) ₂ solution is 37.5g/L, and Na ₂ SO ₄ is additionally added to the CeO ₂ solution, and the concentration of Na ₂ SO ₄ in the solution is 12.5g/L, and the reaction During the process, the constant voltage power supply mode was used, the voltage was 4.5V, the flow rate of CeO ₂ solution was 3ml/min, the flow rate of Cu(NO ₃ ) ₂ was 2ml/min, and the reaction time was 6 hours.

The present invention effectively controls the deposition process and deposition valence state of Cu ²⁺ on the surface of the CeO ₂ core by adjusting the above-mentioned parameters in the preparation process of the flowing electrode method, so as to form a uniform CuO shell.

The invention also provides a flow electrode device, comprising a left terminal fixing plate, a left current collector, an anode chamber, a cation exchange membrane, a desalination chamber, an anion exchange membrane, a cathode chamber, a right side The collector and the right terminal fixing plate are connected in series with the anode chamber and the cathode chamber.

The traditional flow electrode device is shown in Figure 2, including the left tail plate, the left current collector (graphite plate), the anode chamber (plastic flow channel), the cation exchange membrane, the desalination chamber (plastic substrate), the anion exchange Membrane, cathode chamber (plastic flow channel), right current collector (graphite plate) and right tail plate. The anode chamber and the cathode chamber are connected in parallel, the electrode liquid flows through the anode chamber and the cathode chamber respectively, and the solution to be desalted flows through the desalination chamber. According to the research of the present invention, it is found that changing the anode chamber and the cathode chamber to be connected in series is beneficial to reduce the length of the flow channel, thereby improving the catalyst synthesis efficiency.

Preferably, the left current collector and the right current collector are both titanium meshes. Titanium mesh and wire can be connected with titanium sheet. In the present invention, the current collector is replaced from a graphite plate to a titanium mesh, which can effectively prevent Cu ²⁺ from reacting on the electrode and precipitating.

Preferably, both the anode chamber and the cathode chamber are formed by hollow plastic flow channels. The invention hollows out the plastic flow channel, which is more favorable for Cu ²⁺ to preferentially contact with CeO ₂ in the solution in the process of moving to the charged titanium mesh, and further grow on its surface.

Preferably, the desalination chamber is formed by a silica gel flow channel between the cation exchange membrane and the anion exchange membrane, and further preferably, the desalination chamber further includes a nylon mesh. The traditional plastic substrate has a larger width, which increases the distance between the two electrodes. After the present invention is replaced with a silica gel flow channel, the width is reduced and the voltage utilization efficiency is improved. The additional addition of nylon mesh allows for a more even distribution of water while preventing the water circuit in the chamber from being interrupted.

The invention also provides the application of the flow electrode method in preparing the core-shell structure material.

The present invention provides an anti-thiomercuric oxidation catalyst, which has a core-shell structure and exhibits excellent zero-valent mercury oxidation ability in the presence of SO ₂ . The present invention also provides a preparation method of the sulfur-mercury oxidation-resistant catalyst, which is prepared by reaction with a flowing electrode method. The method is simple and controllable, and compared with the existing solution precipitation method, a more complete and uniform core-shell structure can be prepared, and the application range is wider.

Description of drawings

Fig. 1 is the principle diagram that the present invention adopts the flow electrode method to prepare catalyst;

2 is a schematic diagram of a conventional flow electrode device;

3 is a schematic diagram of the flow electrode device provided in Embodiment 1 of the present invention;

Fig. 4 is the TEM (a) and SEM (b) morphology diagrams of CeO ₂ @CuO obtained in Example 2 of the present invention;

Fig. 5 is the element distribution of CeO ₂ @CuO obtained in Example 2 of the present invention;

6 is a diagram showing the distribution of copper element content and between CeO ₂ solution and Cu(NO ₃ ) ₂ solution in the synthesis process of Example 2 of the present invention;

Fig. 7 is the variation diagram of pH and electric current with time in the reaction process of embodiment 2 of the present invention;

8 is a TEM morphology diagram of spherical CeO ₂ and CeO ₂ @CuO obtained in Example 3 of the present invention;

9 is a topography diagram of spherical CeO ₂ , CeO ₂ @CuO provided by Example 2 and Cu _0.05 CeO _x provided by Comparative Example 1;

10 is a graph showing the test results of Hg ⁰ oxidation performance of spherical CeO ₂ , CeO ₂ @CuO provided in Example 2, and Cu _0.05 CeO _x provided in Comparative Example 1.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of them. Example. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

This embodiment provides a flow electrode device, the schematic diagram of which is shown in a in FIG. 3 , including a left terminal fixing plate, a left current collector, an anode chamber, a cation exchange membrane, and a desalination chamber that are closely arranged in sequence. chamber, anion exchange membrane, cathode chamber, right current collector and right terminal fixing plate. Among them, the left terminal fixing plate and the right terminal fixing plate are arranged in parallel and opposite (not shown in the figure); the left current collector and the right current collector are both titanium meshes, and the titanium meshes are connected to the wires with titanium sheets; Both the anode chamber and the cathode chamber are formed by hollow plastic flow channels (as shown in b in Figure 3), and the anode chamber and the cathode chamber are connected in series; the desalination chamber is composed of cation exchange membrane and anion exchange membrane. Silica gel flow channels are formed between, further desalination chambers also include nylon grids.

Further, in this embodiment, the size of the titanium mesh is 90mm×90mm×4mm, 13 flow grooves (44mm×2mm×2mm) are engraved on the plastic flow channel, and epoxy resin adhesive is used for sealing at each interface. shown in c in Figure 3.

Example 2

The present embodiment provides an anti-thiomercuric oxidation catalyst, which is CeO ₂ @CuO with a core-shell structure, and the preparation method thereof is as follows:

The flow electrode device provided in Example 1 was adopted, and the CeO ₂ solution added with Na ₂ SO ₄ was used as the electrode solution, which entered from the cathode chamber and then flowed out from the anode chamber, and the Cu(NO ₃ ) ₂ solution was used as the flowing solution to flow through Desalination chamber in the middle. Among them, the concentration of CeO ₂ solution and Cu(NO ₃ ) ₂ solution is 37.5g/L; the concentration of Na ₂ SO ₄ in the electrode solution is 12.5g/L; the constant voltage power-on mode is used in the reaction process, and the voltage is 4.5 V; the flow rate of CeO ₂ solution is about 3 mL/min, and the flow rate of Cu(NO ₃ ) ₂ is about 2 mL/min, and the reaction time is 6 hours. After the reaction, the electrode liquid flowing out from the anode chamber was separated into solid-liquid, and the obtained solid was washed and dried, and then calcined in an air atmosphere at 500 °C to obtain CeO ₂ @CuO.

Element content characterization by ICP-AES found that the mass ratio of Cu to Ce elements on CeO ₂ @CuO was about 1:20.

CeO ₂ in this embodiment is spherical particles, which can be obtained commercially or synthesized by template method. The specific preparation method is as follows:

Dissolve 1.997g Ce(NO ₃ ) ₃ ·6H ₂ O in 56mL of ethylene glycol solution, stir until Ce(NO ₃ ) ₃ ·6H ₂ O is completely dissolved, slowly add 0.8g polyvinylpyrrolidone (PVP), keep Stir to avoid PVP consolidation, then add 8 mL of water and stir for 30 minutes. The prepared suspension was added to the polytetrafluoroethylene lining of the reactor, and then reacted at 160 ° C for 24 hours. After the reaction was completed, the reactor was cooled at room temperature, and then centrifuged and washed with deionized water in turn. 3 times, washed 3 times with anhydrous ethanol, after washing, drying at 80°C overnight, and calcining at 600°C for 4 hours. The spherical CeO ₂ with a particle size of 50-200 nm and a uniform shape was obtained.

The TEM and SEM morphological results of CeO ₂ @CuO obtained in this example are shown in Fig. 4. It can be seen from a in Fig. 4 that the outer surface of CeO ₂ @CuO is more sparse than the inner layer, and the surface has a fluid layer. It may be caused by the incomplete crystallization process of CuO on it, which is the intersection of CuO and CeO ₂ interface; it can be seen from b in Fig. 4 that the overall synthesis of CeO ₂ @CuO is quite uniform, and the size is similar to that of CeO ₂ . ₂ There is obvious CuO "armor" formation on the surface.

The TEM element distribution of CeO ₂ @CuO obtained in this example is shown in Fig. 5. It can be seen from a in Fig. 5 that CeO ₂ @CuO still maintains the spherical structure of CeO _2. In the HAADF imaging mode, the image intensity It is positively related to the square of the atomic number, and an obvious intensity drop layer can be seen from the inner core to the interface, while the atomic number of Ce is 58 and the atomic number of Cu is 29, so the drop at the interface also confirms the appearance of the surface CuO layer; It can be seen from the element distribution diagram of bd in Figure 5 that the distribution of Ce, Cu and O elements is quite uniform, because the present invention adopts a two-step method to synthesize the core-shell structure, and CeO ₂ is stable after burning at 600 °C crystal form, it can be considered that even if the doping of Cu to the CeO2 lattice occurs, it is mainly carried out _on the outer surface of CeO2 _; the rather uniform Cu element distribution image shows that _CuO covers the outer layer of the CeO2 core, and the distribution of Cu fairly uniform, strongly demonstrating the successful preparation of the CeO2@ _CuO core-shell structured catalyst.

In order to further study the solution change and stability during the flow electrode reaction, the current, pH, and Cu ion concentration changes during the reaction were measured.

During the reaction, the CeO ₂ solution and the Cu(NO ₃ ) ₂ solution were sampled respectively, and the Cu element was measured by ICP-AES, wherein the CeO ₂ solution was centrifuged to take the supernatant before the test. Figure 6 shows the content of copper and the distribution between the CeO ₂ and Cu(NO ₃ ) ₂ solutions during the synthesis. From the beginning of the reaction to 2 hours, the Cu content in the CeO ₂ solution was extremely low, while the Cu content in the Cu(NO ₃ ) ₂ solution continued to decrease, which indicated that at the beginning of the reaction, the Cu(NO ₃ ) ₂ solution passed through the cation exchange membrane The Cu ²⁺ flowing to the CeO ₂ solution may be adsorbed and intercepted by the exchange membrane, thereby leaving the equilibrium state in the solution. At the same time, the Cu content in the two solutions that persists is poor, which also indicates that the cation exchange membrane has good performance and maintains a certain voltage. The passing rate of Cu ²⁺ and the migration of Cu ²⁺ are less affected by the concentration difference. From 1 hour after the start of the reaction to the end of 6 hours, the copper content in the solution continued to decrease. At the same time, Cu elements also appeared in the CeO ₂ solution, and the proportion continued to increase. This result indicates that in the negative electrode, the solution Cu ²⁺ is not all converted into CuO or Cu ⁰ , Cu ₂ O is deposited on the surface of CeO ₂ , and some Cu ²⁺ exists in the solution.

Because the cation exchange membrane is not a differential pressure membrane, the ion migration on both sides is mainly driven by voltage. It can be considered that the migration rate of Cu ²⁺ is constant, and the Cu species entering the CeO ₂ solution flows mainly to the electrode plate and the surface of CeO ₂ deposition, and continue to exist in the solution; since the traditional graphite flow channel is replaced by a plastic flow channel in the device, the deposition ratio of the electrode plate should be effectively controlled, so the copper concentration existing in the solution rises faster, mainly from the _Decrease in the deposition rate to the CeO surface. Judging from the proportion of copper distribution in the three time periods of 0-2 hours, 2-4 hours and 2-6 hours, the proportion of copper content in the CeO ₂ solution increased by 1%, 4% and 3% respectively every two hours, indicating that it is possible There is a process in which the copper deposition rate is accelerated and then slowed down in the reactor.

In order to study the changes of pH and current during the reaction, and to explore the reasons for the change of copper deposition rate and different types of deposition, the pH and current in the CeO ₂ solution were measured every 0.5 hours from the beginning of the reaction, and the measurement results are shown in Figure 7. At the beginning of the reaction, the pH is greater than 7, mainly because the pH electrode uses a saturated calomel electrode to measure the pH value by the difference in conductivity, while the ion concentration in ultrapure water is extremely low, making the measurement inaccurate, and in Na ₂ SO ₄ After the addition of , the pH returned to normal; and the pH continued to decrease as the reaction continued, until the reaction was terminated, at about 4.3.

During the reaction process, the reduction of water at the cathode leads to the generation of OH ^- , which increases the pH of the solution, which leads to the deposition of Cu ²⁺ to form Cu(OH) ₂ , while the oxidation of water occurs in the anode to lose electrons, And H ⁺ is generated, which makes the pH of the solution drop, which leads to the decomposition of Cu(OH) ₂ , which is converted into Cu ²⁺ . In theory, when the two are in equilibrium, the pH of the solution should remain at 7 after flowing through the anode cell and the cathode cell. However, it was actually observed that the pH of the solution kept decreasing, which indicated that the anodic H ⁺ -producing reaction was not in equilibrium with the cathodic ^OH- producing reaction. On the one hand, it may come from the combination of the above-mentioned ^OH- and Cu ²⁺ to generate Cu(OH) ₂ , and on the other hand, it may come from the reduction of Cu ²⁺ to Cu ⁰ and Cu ₂ O. In the process of capacitive deionization, it is found that the pH reduction can effectively promote the formation of Cu ⁰ and inhibit the formation of Cu ²⁺ on the electrode. In the formation of Cu ₂ O, H ⁺ is also formed. Therefore, as the reaction goes on, the formation of Cu(OH) ₂ in the solution will continue to decrease, and the equilibrium will shift in the direction of the reduction of Cu ²⁺ .

From the change of the current during the reaction, it can also be found that the current decreases continuously at the beginning of the reaction, from 7 mA to 2 mA after 4 hours. From the point of view of the turning point, it is not only similar to the change rate of Cu content, but also to the aforementioned pH. drop, leading to the inference that Cu ²⁺ favors Cu ₂ O and Cu ⁰ in agreement. Therefore, it can be speculated that the reaction reached the turning point of Cu ²⁺ to Cu(OH) ₂ and Cu ⁰ at about 4 hours of reaction; since the conductivity of Cu(OH) ₂ is significantly lower than that of Cu ⁰ , the increase in current indicates that in addition to ions After a long time reaction, in addition to the enrichment of the electrode plate, there is also a part due to the formation of Cu ⁰ with high conductivity.

From the changes of Cu content and distribution, solution pH, and current during the reaction, it is strongly proved that there are two reaction zones in the synthesis process: at the beginning of the reaction, the flow electrode device is in the Cu(OH) ₂ generation zone, and the Cu ²⁺ The formation of Cu(OH) ₂ is dominant; after a period of reaction, the flow electrode device is in the formation region of Cu ⁰ , and the formation of Cu ²⁺ to Cu ⁰ and Cu ₂ O is dominant.

Example 3

This embodiment provides an anti-thiomercuric oxidation catalyst, which is CeO ₂ @CuO with a core-shell structure, which is prepared by using a traditional flow electrode device (as shown in FIG. 2 ), and the preparation process parameters are the same as those in Embodiment 2.

As a result, the TEM morphology of CeO ₂ @CuO obtained is shown in b in Figure 8 , where a is the TEM morphology of spherical CeO ₂ prepared by the same preparation method as in Example 2. It can be seen that the uniformity of the catalyst shell layer prepared by using the traditional flow electrode device is worse than that of Example 2.

Example 4

This embodiment provides an anti-thiomercuric oxidation catalyst, which is CeO ₂ @CuO with a core _- shell structure. The concentration of SO ₄ in the electrode solution was 12.5 g/L, and the reaction time was 6 hours.

Example 5

This embodiment provides an anti-thiomercury oxidation catalyst, which is CeO ₂ @CuO with a core _- shell structure. The concentration of SO ₄ in the electrode solution was 6.5 g/L, and the reaction time was 6 hours.

Results The shell integrity and uniformity of the CeO ₂ @CuO catalysts obtained in Examples 4-5 were slightly worse than those in Example 2.

Comparative Example 1

This comparative example provides a copper-cerium composite catalyst Cu _0.05 CeO _x prepared by a co-precipitation method, and the copper-cerium ratio is the same as that of Example 2, specifically, the mass ratio of Cu to Ce elements is about 1:20.

Morphology characterization and performance testing

Fig. 9 is the morphological diagram of spherical CeO ₂ , CeO ₂ @CuO provided in Example 2 and Cu _0.05 CeO _x provided in Comparative Example 1, wherein a is the appearance morphological diagram of three catalysts, and b is CeO ₂ @CuO The TEM morphology of , is basically the same as that of spherical CeO ₂ , and c is the TEM morphology of Cu _0.05 CeO _x , which shows an uneven distribution with a particle size of around 10-20 nm.

10 is a graph showing the test results of Hg ⁰ oxidation performance of spherical CeO ₂ , CeO ₂ @CuO provided in Example 2, and Cu _0.05 CeO _x provided in Comparative Example 1. The test conditions are: Hg: 80 μg/m ³ , O ₂ : 4%, SO ₂ : 100 ppm, N ₂ as equilibrium gas, space velocity: 200000 h ⁻¹ .

Results In the temperature range from 150 to 400 °C, CeO ₂ @CuO catalysts showed the best Hg ⁰ oxidation activity, and could reach 91% Hg ⁰ oxidation efficiency at 300 °C; while Cu _0.05 CeO _x had lower activity, as The activity of Cu-Ce composite metal oxide catalysts is lower than that of spherical CeO ₂ in the temperature range of 150-400 ℃. This result strongly proves the necessity of structural optimization of the catalyst (improved to core-shell structure).

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (7)

1. The preparation method of sulfur-resistant mercury oxidation catalyst is characterized by adopting a flowing electrode method to carry out reaction preparation, and CeO is used₂The solution is an electrode solution, and a copper salt solution is used as a flowing liquid;

the electrode solution also contains sodium sulfate, the sodium sulfate and CeO₂The mass ratio of (1): (2-4) of a first step,

the electrode solution sequentially flows through a cathode chamber and an anode chamber which are connected in series;

the sulfur-resistant mercury oxidation catalyst is CeO with a core-shell structure₂@ CuO, of which CeO₂Is an inner core and CuO is a shell layer.

2. The method according to claim 1, wherein the inner core is a spherical particle having a particle diameter of 50 to 200nm,

and/or the mass ratio of Cu to Ce in the sulfur-resistant mercury oxidation catalyst is =1 (15-25).

3. The preparation method of the sulfur-resistant mercury oxidation catalyst according to claim 1, wherein a constant voltage mode is adopted in the preparation process, and the voltage is 4.0-5.0V.

4. The method for preparing the sulfur-resistant mercury oxidation catalyst according to any one of claims 1 to 3, wherein after the reaction time reaches 6 hours, the liquid and solid of the electrode flowing out are separated, and the obtained solid is burned.

5. A flow electrode device, which is used for the preparation method of the sulfur-resistant mercury oxidation catalyst according to any one of claims 1 to 4, and comprises a left terminal fixing plate, a left current collector, an anode chamber, a cation exchange membrane, a desalination chamber, an anion exchange membrane, a cathode chamber, a right current collector and a right terminal fixing plate which are arranged in close contact in sequence, wherein the anode chamber and the cathode chamber are connected in series.

6. The flow electrode assembly of claim 5, wherein the left and right current collectors are both titanium mesh;

and/or the anode chamber and the cathode chamber are both formed by hollow plastic runners.

7. A flow electrode device according to claim 5 or 6, wherein the desalination chamber is formed by a silica gel flow channel between the cation exchange membrane and the anion exchange membrane, the desalination chamber further comprising a nylon mesh therein.

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