Preparation method and application of modified hopcalite catalyst

Abstract

The present invention discloses a modified hopcalite catalyst and its preparation method and application. SOLUTION: The preparation method of modified hopcalite catalyst includes the following steps: mix solutions containing copper source, manganese source and aluminum source to obtain a mixed solution, co-precipitate the mixed solution under alkaline conditions to obtain a precipitate, and roast the obtained precipitate to obtain a modified hopcalite catalyst. By doping with Al, the modified hopcalite catalyst disclosed in the present invention has Al with Cu and Mn to form a new spinel structure to act as a carrier, allowing more Cu2+ and Mn4+ to be scattered on the catalyst surface, resulting in a stable structure, good low-temperature contact activity and high catalytic stability. The preparation method disclosed in the present invention has a simple process and high stability of the product.

Description

[Technical Field]

[0001] The present invention relates to the technical field of catalytic combustion CO catalysts. [Background technology]

[0002] In industrial production and construction work, machinery generates large amounts of CO due to incomplete combustion. Colorless and odorless CO gas binds easily with hemoglobin in human blood, leading to serious and irreversible consequences such as hemiplegia, aphasia, and even death due to oxygen deprivation in the brain. Carbon monoxide poisoning accidents are frequent in applications such as coal-fired boilers and factory equipment operation, as well as in the oxidative decomposition of materials, making CO treatment an urgent issue.

[0003] To date, the catalysts used for CO catalytic combustion are mainly precious metal catalysts, but their high cost has significantly limited their commercial application. Therefore, the development of non-precious metal catalysts with high low-temperature activity, high stability, and low cost will greatly advance the commercial application of catalytic combustion.

[0004] Hopcalite catalysts, which are non-precious metal catalysts and are primarily composed of Cu and Mn oxides and their composite oxides, have shown high catalytic activity in catalytic combustion studies. Hopcalite catalysts, primarily composed of MnO2 and CuO, are widely used in sealed submarine cabins and can convert CO to CO2 in the combustion chamber at 320°C. This reaction has the advantage of not generating secondary toxic pollutants (Christopher et al. Applied Catalysis B: Environmental, 2017, (203) 533-540). Conventional hopcalite catalysts are made from CuMn2O4 spinel, which is composed of Cu and Mn. Therefore, most of the Cu and Mn elements are present in the catalyst mainly as carriers, and Cu atoms can be dispersed and released on the surface of the catalyst to form catalytically active centers. 2+ and Mn 4+ Therefore, it is difficult to obtain the desired low temperature catalytic activity with hopcalite catalysts. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a modified hopcalite catalyst in which Al doping forms a new spinel structure with Cu and Mn, acting as a carrier, allowing more Cu2+ and Mn4+ to be dispersed on the catalyst surface, resulting in a stable structure, good low-temperature catalytic activity, and high catalytic stability; a preparation method for the catalyst that is simple and produces a stable product; and a method for applying the catalyst. [Means for solving the problem]

[0006] In order to achieve one of the above objects, the present invention provides the following technical solutions.

[0007] A modified hopcalite catalyst containing a composite oxide consisting of CuAl2O4, MnAl2O4 and oxides of Cu and Mn.

[0008] In some embodiments of the present invention, the Cu, Mn oxide is CuMnO2.

[0009] In some examples of the present invention, the ratio of the amounts of Cu, Mn and Al in the composite oxide is 1-10:1-10:0.2-5.

[0010] Preferably, the ratio of the amounts of Cu, Mn and Al is 5:1:0.2-3, more preferably 5:1:0.5-1.

[0011] In order to achieve the second of the above objects, the present invention provides the following technical solutions.

[0012] The preparation method of the catalyst includes the following steps: co-precipitating a mixed solution containing Cu ions, Mn ions and Al ions, and roasting the obtained precipitate.

[0013] In some embodiments of the present invention, the mixed solution is an acid solution containing a compound of Cu, a compound of Mn, and a compound of Al.

[0014] Preferably, the acid solution is a nitric acid solution.

[0015] In some embodiments of the present invention, the roasting temperature is between 300 and 500°C.

[0016] In some embodiments of the present invention, the roasting time is 6 to 10 hours.

[0017] In some embodiments of the present invention, the co-precipitation is carried out under alkaline conditions.

[0018] Preferably, the alkaline conditions are pH=8 to 9, more preferably pH=8 to 8.5.

[0019] In some embodiments of the present invention, the co-precipitating alkali is the precipitating agent, and the alkali is one or more of sodium hydroxide, sodium carbonate, and ammonia.

[0020] In some embodiments of the present invention, the alkali has a concentration of 0.3 to 3 mol L -1 is located.

[0021] Preferably, the alkali has a concentration of 1.5 to 2.5 mol L. -1 is located.

[0022] In some embodiments of the present invention, the co-precipitation is carried out at a temperature of 10 to 30°C.

[0023] Preferably, the coprecipitation is carried out at a temperature of 15 to 20°C.

[0024] In some examples of the present invention, after coprecipitation, the mixed solution is allowed to stand for 10 to 20 hours.

[0025] In some examples of the present invention, the ratio of the amounts of Cu, Mn and Al in the composite oxide is 1-10:1-10:0.2-5.

[0026] Preferably, the ratio of the amounts of Cu, Mn and Al is 5:1:0.5-1.

[0027] In some embodiments of the present invention, the mixed solution has a total metal ion concentration of 0.5 to 1.5 mol L -1 is located.

[0028] In some embodiments of the present invention, the Cu compound is either copper nitrate (Cu(NO3)2·3H2O) and / or copper sulfate (CuSO4).

[0029] In some embodiments of the present invention, the Mn compound is either manganese nitrate (MnN2O6·4H2O) and / or manganese nitrate solution (Mn(NO3)2).

[0030] In some embodiments of the present invention, the compound of Al is aluminum nitrate (Al(NO3)3·9H2O).

[0031] In some embodiments of the present invention, the preparation procedure for the mixed solution includes dissolving the copper source, manganese source, and aluminum source in distilled water in that order to obtain the mixed solution.

[0032] In order to achieve the above three objects, the present invention provides the following technical solutions.

[0033] The catalyst described above or the catalyst prepared according to the preparation method described above is applied to CO catalytic combustion.

[0034] In some embodiments of the present invention, the catalyst has a particle size of 20-60 mesh.

[0035] Specifically, in the above application, the low-temperature oxidation of CO is at a temperature of 20°C. [Effects of the Invention]

[0036] (1) In the present invention, a new hopcalite catalyst for CO catalytic combustion was obtained. (2) Compared with the conventional hopcalite catalyst, the present invention also dopes the existing hopcalite catalyst with Al2O3, improving the dispersion of the active center components Cu2+ and Mn4+. At the same time, the doping effect of the metal ions improves the bonding strength between CO and Cu and Mn, thereby significantly improving the low-temperature activity and catalytic efficiency of the catalyst. (3) In the present invention, the catalyst has a low-temperature activity used in the CO catalytic combustion reaction that is higher than that of the conventional hopcalite catalyst, and can achieve 100% conversion of CO at room temperature of 20°C. (4) Doping with Al not only improves the low-temperature catalytic activity of the catalyst, but also reduces the preparation cost of hopcalite catalyst. The co-precipitation preparation process is easy to operate and has strong feasibility. [Brief explanation of the drawings]

[0037] [Figure 1] XRD spectrum of Example 5 [Figure 2] Comparison of Example 5 and commercial Hopcalite catalyst H2-TPR DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will now be described in detail in conjunction with examples. It should be understood that the above examples and drawings are merely for illustrative purposes only and do not constitute any limitations on the scope of the present invention. Any appropriate transformation or combination consistent with the purpose of the present invention is within the scope of the claims of the present invention.

[0039] The catalyst used in each of the following examples was prepared according to the following procedure.

[0040] Add appropriate amounts of copper nitrate, manganese nitrate, and aluminum nitrate to appropriate amounts of distilled water and mix thoroughly to obtain a transparent metal ion mixed solution. The amounts of each raw material should be such that the molar ratio of Cu:Mn:Al is 5:1:x, where x = 0~1. In the obtained mixed solution, the total concentration of metal ions is 1 mol L. -1 The solution should be 2 mol L. -1The NaOH solution was used as a precipitant, and the metal ion mixture and NaOH precipitant were simultaneously added dropwise to a 5L beaker under stirring conditions to allow for co-precipitation. The reaction temperature was room temperature, and the pH was adjusted to 8-8.5. The pH of the reaction solution was adjusted by adjusting the addition rate during titration. Once the metal ion solution was completely added, the NaOH precipitant addition was stopped. The mixture was then stirred at room temperature for 2 hours and allowed to age for 15 hours. The precipitate was then filtered and washed to a pH of approximately 7. The filter cake was then air dried at 100°C and roasted at 400°C for 6-10 hours to obtain the CuO-MnO2-xAl2O3 catalyst. The catalyst granules were then sieved to 20-60 mesh and used in fixed-bed CO catalytic combustion reactions.

[0041] In each of the following examples, the combustion reaction using a fixed-bed CO catalyst is as follows:

[0042] Five grams of the sieved catalyst granules were loaded into a fixed-bed reactor and pre-activated with air at 350°C for approximately 6 hours. The bed temperature was then adjusted to the required reaction temperature, and the catalyst was then added at a rate of 30 mL min -1 CO is introduced into a fixed-bed reactor through a mass flow meter at a flow rate of 0.05 to carry out a catalytic combustion reaction, and the reaction product gas is directly introduced into a gas chromatograph for detection. The catalytic combustion reaction temperature is 20 to 200°C, and the Al doping amount (calculated as metal ion Al / (Cu+Mn)%) of the CuO-MnO2-xAl2O3 catalyst under consideration is 0 to 30%. [Example]

[0043] The combustion reaction activity of CO catalyst was investigated against commercial Hopcalite catalyst. -1 A mixed gas consisting of 1.6% CO, 21.4% oxygen and 77.0% nitrogen was passed through the reactor at a reaction air flow rate of 360 h -1 The CO catalytic combustion reaction is carried out under normal pressure and a reaction temperature of 15°C. After the temperature has stabilized for 15 minutes, sampling begins. Online analysis is performed using a TCD detector on an SC-2000 gas chromatograph, and the CO conversion rate of the reaction product is evaluated using the following formula: X CO(%) = ([CO] in -[CO] out ) / [CO] in *100% X CO : CO conversion rate, [CO] in : CO concentration at the reactor inlet; [CO] out : CO concentration at reactor outlet

[0044] The temperature is then raised by 5°C per sampling, and the reaction is stopped when the CO conversion rate reaches 100%.

[0045] According to the reaction results, at 125°C mixed gas After entering the catalyst bed, the CO conversion rate reached 100%. [Example]

[0046] A Cu-Mn-Al composite oxide was prepared as a catalyst with a molar ratio of Cu:Mn:Al = 5:1:0.2. The catalyst was then reacted in a fixed-bed reactor at a rate of 30 mL min -1 A mixed gas consisting of 1.6% CO, 21.4% oxygen and 77.0% nitrogen was passed through the reactor at a reaction air flow rate of 360 h -1 The CO catalytic combustion reaction was carried out under normal pressure and a reaction temperature of 15°C, and after the temperature had stabilized for 15 minutes, sampling was started and online analysis was carried out using a TCD detector on an SC-2000 gas chromatograph.

[0047] According to the reaction results, at 85°C mixed gas After entering the catalyst bed, the CO conversion rate reached 100%. [Example]

[0048] A Cu-Mn-Al composite oxide with a molar ratio of Cu:Mn:Al = 5:1:0.4 was prepared as a catalyst. The catalyst was reacted in a fixed-bed reactor at a rate of 30 mL min -1 A mixed gas consisting of 1.6% CO, 21.4% oxygen and 77.0% nitrogen was passed through the reactor at a reaction air flow rate of 360 h -1The CO catalytic combustion reaction was carried out under normal pressure and a reaction temperature of 15°C, and after the temperature had stabilized for 15 minutes, sampling was started and online analysis was carried out using a TCD detector on an SC-2000 gas chromatograph.

[0049] According to the reaction results, at 55°C mixed gas After entering the catalyst bed, the CO conversion rate reached 100%. [Example]

[0050] A Cu-Mn-Al composite oxide with a molar ratio of Cu:Mn:Al = 5:1:0.6 was prepared as a catalyst. The catalyst was reacted in a fixed-bed reactor at a rate of 30 mL min -1 A mixed gas consisting of 1.6% CO, 21.4% oxygen and 77.0% nitrogen was passed through the reactor at a reaction air flow rate of 360 h -1 The CO catalytic combustion reaction was carried out under normal pressure and a reaction temperature of 15°C, and after the temperature had stabilized for 15 minutes, sampling was started and online analysis was carried out using a TCD detector on an SC-2000 gas chromatograph.

[0051] According to the reaction results, at 35°C mixed gas CO conversion rate reached 100% after entering the catalyst bed layer. [Example]

[0052] A Cu-Mn-Al composite oxide with a molar ratio of Cu:Mn:Al = 5:1:0.8 was prepared as a catalyst. It was reacted in a fixed-bed reactor at a rate of 30 mL min -1 A mixed gas consisting of 1.6% CO, 21.4% oxygen and 77.0% nitrogen was passed through the reactor at a reaction air flow rate of 360 h -1 The CO catalytic combustion reaction was carried out under normal pressure and a reaction temperature of 15°C, and after the temperature had stabilized for 15 minutes, sampling was started and online analysis was carried out using a TCD detector on an SC-2000 gas chromatograph.

[0053] According to the reaction results, at 20°C mixed gas After entering the catalyst bed, the CO conversion rate reached 100%. [Example]

[0054] A Cu-Mn-Al composite oxide was prepared with a molar ratio of Cu:Mn:Al = 5:1:1 and used as a catalyst. The catalyst was then reacted in a fixed-bed reactor at a rate of 30 mL min -1 A mixed gas consisting of 1.6% CO, 21.4% oxygen and 77.0% nitrogen was passed through the reactor at a reaction air flow rate of 360 h -1 The CO catalytic combustion reaction was carried out under normal pressure and a reaction temperature of 15°C, and after the temperature had stabilized for 15 minutes, sampling was started and online analysis was carried out using a TCD detector on an SC-2000 gas chromatograph.

[0055] According to the reaction results, at 45°C mixed gas After entering the catalyst bed, the CO conversion rate reached 100%. [Example]

[0056] We investigated the preparation process of Cu-Mn-Al composite oxides using commercial hopcalite catalysts with Cu:Mn:Al molar ratios of 5:1:0.2, 5:1:0.4, 5:1:0.6, 5:1:0.8, and 5:1:1, respectively. Example 5, which showed the best low-temperature activity, was used to simulate the X-ray diffraction of the catalyst. The XRD spectrum shown in Figure 1 was obtained. The figure shows that the primary crystalline structure in the Cu-Mn-Al catalyst is a spinel structure formed by the interconnection of Cu, Mn, and Al. At the same time, the formation of CuMnO2 composite oxide was also observed. It was found that the addition of Al to the newly formed Cu-Mn-Al composite oxide catalyst resulted in the replacement of the CuMn2O4 spinel structure with CuAl2O4 or MnAl2O4, using Al as a carrier. This improved the dispersion of Cu and Mn, resulting in better catalytic activity. H2-TPR results also confirmed this rule. In Example 5, the catalyst and commercial hopcalite catalyst were subjected to the H2 procedure to increase the temperature and reduce the catalyst. The H2-TPR comparison spectra shown in Figure 2 were obtained. The figure shows that the Cu-Mn catalyst is more easily reduced by doping with Al. This is due to the Cu content in the catalyst. 2+ , Mn 2+At the same time, the doping of Al effectively reduces the interaction between the active component and the carrier, and the free Cu as the active component on the catalyst surface. 2+ , Mn 4+ This improves the degree of dispersion of the catalyst, thereby improving the low-temperature reducibility of the catalyst and increasing the reaction activity of catalytic combustion.

[0057] The above examples are merely preferred methods for carrying out the present invention, and the claims of the present invention are not limited to the above examples. All technical solutions consistent with the concept of the present invention are included in the claims of the present invention. Improvements and modifications made by those skilled in the art without departing from the principles of the present invention are also included in the claims of the present invention.

Claims

1. Follow the steps below: mixing solutions containing a copper source, a manganese source, and an aluminum source to obtain a mixed solution; co-precipitating the mixed solution under alkaline conditions to obtain a precipitate; and roasting the obtained precipitate to obtain a modified hopcalite catalyst; The temperature at which the mixed solution is coprecipitated under the alkaline condition is 10 to 30°C; A method for preparing a modified hopcalite catalyst, characterized in that the ratio of the amount of Cu element in the copper source, the amount of Mn element in the manganese source, and the amount of Al element in the aluminum source is 5:1:(0.5-1).

2. The method for preparing a modified hopcalite catalyst according to claim 1, wherein the copper source is an acid solution of a compound containing Cu ions, the manganese source is an acid solution of a compound containing Mn ions, and the aluminum source is an acid solution of a compound containing Al ions.

3. 3. The method for preparing a modified hopcalite catalyst according to claim 2, wherein the acid solution of the compound of Cu ions comprises copper nitrate and / or copper sulfate.

4. 3. The method for preparing a modified hopcalite catalyst according to claim 2, wherein the acid solution of the compound containing Mn ions contains manganese nitrate.

5. 3. The method for preparing a modified hopcalite catalyst according to claim 2, wherein the acid solution of the compound of Al ions comprises aluminum nitrate.

6. The method for preparing a modified hopcalite catalyst according to any one of claims 1 to 5, characterized in that the roasting temperature is 300 to 500°C and the roasting time is 6 to 10 hours.

7. The method for preparing modified hopcalite catalyst according to any one of claims 1 to 5, characterized in that the alkaline conditions include pH=8-9, using alkali as precipitant, and the concentration of alkali is 1-3 mol / L.

8. The method for preparing a modified hopcalite catalyst according to claim 1, wherein the temperature at which the mixed solution is coprecipitated under the alkaline conditions is 15 to 20°C.

9. The method for preparing a modified hopcalite catalyst according to any one of claims 1 to 5, characterized in that the mixed solution is co-precipitated under alkaline conditions and allowed to stand for 10 to 20 hours to obtain the precipitate.

10. A modified hopcalite catalyst comprising a composite oxide of CuAl 2 O 4 , MnAl 2 O 4 and oxides of Cu and Mn, wherein the ratio of the amounts of Cu, Mn and Al is 5:1:0.5-1.

11. 11. Use of the modified hopcalite catalyst of claim 10 in the catalytic combustion of CO.

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