A catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons and its use method

Abstract

The present application discloses a catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons and a method for using the catalyst, which relates to the field of catalytic environmental protection technology and specifically comprises active components Co3O4 and MnO2 and carriers TiO2 or SiO 2， Wherein, the molar ratio of manganese element to cobalt element in manganese nitrate and cobalt nitrate hexahydrate is (2‑4): 1 according to the loading amount. In the present application, by first mixing and rolling the carrier with the precursor solid, the precursor can be more evenly distributed on the carrier surface, and in the subsequent impregnation and precipitation process, the precursor can more evenly penetrate into the pores of the carrier, thereby improving the dispersion and utilization rate of the active sites of the catalyst.

Description

Technical Field

[0001] The present invention relates to the field of catalytic environmental protection technology, and in particular to a catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons and a method for using the catalyst. Background Art

[0002] Non-methane hydrocarbons (NMHC) refer to all volatile hydrocarbons other than methane, such as alkanes, alkenes, aromatic hydrocarbons and oxygenated hydrocarbon components. When NMHC in the environment exceeds a certain concentration, it will directly harm human health, and many volatile organic compounds are carcinogenic to humans. When non-methane hydrocarbons produce photochemical smog and ozone through chemical reactions under light conditions, they cause immeasurable damage to the human environment.

[0003] Sulfur dioxide is the most common and simplest sulfur oxide, with the chemical formula SO2. It is a colorless, transparent gas with a pungent odor and is soluble in water, ethanol and ether. Sulfur dioxide is one of the main atmospheric pollutants and is also produced in many industrial processes. When sulfur dioxide dissolves in water, it forms sulfurous acid, which is further oxidized in the presence of PM2.5 to quickly and efficiently generate sulfuric acid.

[0004] Nitrogen oxides refer to compounds composed of only two elements, nitrogen and oxygen, and include a variety of compounds. Except for nitrous oxide and nitrogen dioxide, other nitrogen oxides are unstable. When exposed to light, moisture or heat, they turn into nitrogen dioxide and nitric oxide, and nitric oxide turns into nitrogen dioxide. Nitrogen oxides are toxic to varying degrees.

[0005] Such as the Chinese patent, application number, CN201910471905.X A catalyst for removing non-methane total hydrocarbons in total hydrocarbons, its preparation method and application. The catalyst is a supported cobalt tetroxide catalyst, the catalyst carrier is one of TiO2 / SiO2, and the active component is one or two of Co3O4 / MnO2. Among them, the percentage of the active component is 30%-50% based on the mass ratio of Co3O4 or MnO2 to the carrier TiO2 / SiO2. The catalyst described in the present invention can completely convert non-methane total hydrocarbons in total hydrocarbons into CO2 and H2O at a certain temperature, while methane is not converted or the conversion rate is less than 5%. The catalyst described in the invention can be used in the detection equipment of non-methane total hydrocarbons to quantitatively detect the content of non-methane total hydrocarbons in total hydrocarbons, which greatly simplifies the structure of the current detection equipment used for non-methane total hydrocarbons and has a wide operating temperature window.

[0006] However, due to the low concentration of the precursor aqueous solution, the carrier is immersed in the precursor solution, the contact probability between the carrier and the precursor is low, and there is still a large amount of precursor that is not loaded and is easy to agglomerate, which ultimately leads to a reduction in the catalytic effect of the catalyst. Summary of the invention

[0007] The embodiments of the present application solve the problem of low catalyst loading in the prior art by providing a catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons and a method for using the catalyst, thereby achieving a high loading.

[0008] The present invention provides a catalyst for the integrated treatment of SO2, NOx, and non-methane total hydrocarbons, including active components Co3O4 and MnO2 and a carrier TiO2 or SiO 2， Among them, the molar ratio of manganese nitrate and cobalt nitrate hexahydrate to manganese element and cobalt element is (2-4):1 according to the loading amount.

[0009] Further, the preparation comprises the following steps:

[0010] S1. Weigh a certain mass of TiO2 or SiO2 carrier respectively; calculate the mass of the required precursors cobalt nitrate hexahydrate and manganese nitrate according to the mass of TiO2 or SiO2 and the loading amount of Co3O4 and MnO2 of 30%-50%;

[0011] Wherein, the molar ratio of manganese nitrate and cobalt nitrate hexahydrate to cobalt nitrate is (2-4):1 according to the loading amount;

[0012] S2, rolling and grinding the weighed cobalt nitrate hexahydrate and manganese nitrate solution with the carrier until the mixture is uniform to obtain a mixed powder;

[0013] S3, adding deionized water to the mixed powder to dissolve the precursor, obtaining an impregnation solution, and impregnating overnight;

[0014] S4. Under stirring conditions at 80°C, add sodium carbonate solution dropwise to the support impregnated with the precursor, adjust the pH to 9, and continue stirring for 2 hours to obtain a precipitate;

[0015] S5. The obtained precipitate is filtered, washed with deionized water, and dried overnight at 60°C;

[0016] S6. Grind the dried precursor into fine powder, and calcine at 500-600° C. for 4 h to obtain the catalyst.

[0017] Furthermore, the concentration of the sodium carbonate aqueous solution prepared in step S4 is 0.1 mol / L.

[0018] Furthermore, the concentration of cobalt nitrate hexahydrate in the impregnation solution in step S3 is 0.45 mol / L.

[0019] Furthermore, in step S2, the weighed cobalt nitrate hexahydrate and manganese nitrate solution are rolled together with the carrier, ground until mixed evenly, and then deionized water is added, rolled again, ground and mixed to obtain a mixed powder of solid and liquid;

[0020] S3. Deionized water is added to the mixed powder of solid and liquid to completely dissolve the precursor, thereby obtaining an impregnation solution, and impregnation is performed overnight.

[0021] Furthermore, the amount of deionized water added is sufficient to dissolve 40-60% of the total mass of the precursor.

[0022] Furthermore, the deionized water is added in batches in step S2, and the mixture is crushed, ground and mixed again after each addition of deionized water until the precursor is completely dissolved to obtain a completely dissolved mixed powder.

[0023] Furthermore, the amount of deionized water added each time is sufficient to dissolve 10-20% of the total mass of the precursor.

[0024] Further, water is added and rolled until the precursor is dissolved by 60-70%, and then the mixed powder is heated, and ground once every 10-25°C until the precursor is completely dissolved. After keeping warm for 10 minutes, it is cooled to 0-20°C to allow part of the precursor to precipitate, thereby obtaining an incompletely dissolved mixed powder, and then the mixed powder is impregnated at a fixed volume.

[0025] The above-mentioned method of using the catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons is used under the temperature condition of 170°C-250°C.

[0026] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0027] First, by first mixing and rolling the carrier and the precursor solid, the precursor can be more evenly distributed on the carrier surface, so that in the subsequent impregnation and precipitation process, the precursor can more evenly penetrate into the pores of the carrier, thereby improving the dispersion and utilization rate of the active sites of the catalyst; the rolling process will increase the contact area between the carrier and the precursor, strengthen the interaction between them, and form a more stable active component structure during the calcination process, thereby improving the stability and activity of the catalyst; mixed rolling also increases the surface roughness or produces more micropores, so that the precursor and the carrier are physically embedded, increasing their loading capacity, improving their catalytic effect, and ultimately increasing the temperature window;

[0028] Second, deionized water is added for secondary rolling and grinding to further promote the distribution of the precursor on the surface of the carrier and form a preliminary wet state to prepare for the subsequent impregnation process; part of the precursor is dissolved to form a saturated solution, so that the precursor can penetrate into the pores of the carrier more quickly. Compared with solid powder, the precursor in the solution is easier to distribute on the entire surface of the carrier, thereby improving the impregnation effect and the dispersion of cobalt;

[0029] Third, through repeated rolling and grinding, the precursor and the carrier are mixed at the molecular level, so that the precursor is more evenly distributed on the surface and inside of the carrier, which provides a basis for the subsequent preparation of high-performance catalysts;

[0030] Fourth, by raising the temperature after the precursor is dissolved by 60-70%, the mixed solution is supersaturated, which increases the distribution of precursor molecules on the carrier. There are a large number of hydroxyl groups on the surface of the carrier, which can form hydrogen bonds with the precursor molecules; the cations generated by salt ionization increase the viscosity of the carrier, and the cations form a double electric layer on the surface of the carrier particles, affecting the charge distribution on the carrier surface and the activity of the hydroxyl groups; BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the catalytic effect of non-methane total hydrocarbons in Example 1 of the present invention;

[0032] Figure 2 This is a schematic diagram of the catalytic effect of non-methane total hydrocarbons in Example 2 of the present invention;

[0033] Figure 3 This is a schematic diagram of the catalytic effect of non-methane total hydrocarbons in Example 3 of the present invention;

[0034] Figure 4 This is a schematic diagram of the catalytic effect of non-methane total hydrocarbons in Example 4 of the present invention. DETAILED DESCRIPTION

[0035] To facilitate the understanding of the present invention, the present application will be described more comprehensively below with reference to the relevant drawings; the drawings show preferred embodiments of the present invention, but the present invention can be implemented in many different forms and is not limited to the embodiments described herein; on the contrary, the purpose of providing these embodiments is to enable a more thorough and comprehensive understanding of the disclosed content of the present invention.

[0036] It should be noted that the terms “vertical”, “horizontal”, “up”, “down”, “left”, “right” and similar expressions used in this document are only for illustrative purposes and do not represent the only implementation method.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the term "and / or" used herein includes any and all combinations of one or more related listed items. Embodiment 1

[0038] The present application discloses a catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons, which is a supported cobalt tetraoxide-manganese dioxide catalyst, the carrier of which is TiO2 or SiO2, and the active components of which are Co3O4 and MnO2;

[0039] The percentage of active components is 30%-50% based on the mass ratio of active components Co3O4 and MnO2 to carrier TiO2 or SiO2;

[0040] The method comprises the following steps:

[0041] S1. Weigh a certain mass of TiO2 or SiO2 carrier respectively; calculate the mass of the required precursors cobalt nitrate hexahydrate and manganese nitrate according to the mass of TiO2 or SiO2 and the loading amount of Co3O4 and MnO2 of 30%-50%;

[0042] Wherein, the molar ratio of manganese nitrate and cobalt nitrate hexahydrate to cobalt nitrate is (2-4):1 according to the loading amount;

[0043] S2, rolling and grinding the weighed cobalt nitrate hexahydrate and manganese nitrate solution with the carrier until the mixture is uniform to obtain a mixed powder;

[0044] S3, adding deionized water to the mixed powder to dissolve the precursor, obtaining an impregnation solution, and impregnating overnight;

[0045] The concentration of cobalt nitrate hexahydrate in the impregnation solution was 0.45 mol / L;

[0046] S4. Under stirring conditions at 80°C, add sodium carbonate solution dropwise to the support impregnated with the precursor, adjust the pH to 9, and continue stirring for 2 hours to obtain a precipitate;

[0047] The concentration of the prepared sodium carbonate aqueous solution is 0.1 mol / L;

[0048] S5. The obtained precipitate is filtered, washed with deionized water, and dried overnight at 60°C;

[0049] S6. Grind the dried precursor into fine powder, and calcine at 500-600° C. for 4 h to obtain the catalyst.

[0050] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0051] By first mixing and rolling the carrier and the precursor solid, the precursor can be more evenly distributed on the carrier surface, so that in the subsequent impregnation and precipitation process, the precursor can more evenly penetrate into the pores of the carrier, thereby improving the dispersion and utilization rate of the active sites of the catalyst; the rolling process will increase the contact area between the carrier and the precursor, strengthen the interaction between them, and form a more stable active component structure during the calcination process, thereby improving the stability and activity of the catalyst; mixed rolling also increases the surface roughness or produces more micropores, so that the precursor and the carrier are physically embedded, increasing their loading capacity, improving their catalytic effect, and ultimately increasing the temperature window;

[0052] Deionized water is added directly after rolling to increase the concentration of the solution that the carrier contacts from low to high. The low-concentration solution can better infiltrate the carrier, making it easier to load the subsequent precursor.

[0053] By increasing the amount of precursor, a large number of precursor molecules are distributed near the carrier during the impregnation process, thereby increasing the loading rate. A low-concentration sodium carbonate solution is subsequently added to provide a large amount of solvent to prevent a large amount of gas generated by excessive reaction and some precursors from remaining unreacted. Embodiment 2

[0054] The above scheme is further improved by rolling the precursor and the carrier together to improve the catalytic effect and ultimately increase the temperature window to improve the impregnation efficiency.

[0055] S2, rolling the weighed cobalt nitrate hexahydrate and manganese nitrate together with the carrier, grinding until the mixture is uniformly mixed, then adding deionized water, rolling again, grinding and mixing, to obtain a mixed powder of a solid-liquid mixture;

[0056] The amount of deionized water added is sufficient to dissolve 40-60% of the total mass of the precursor;

[0057] S3, adding deionized water to the mixed powder of solid and liquid to completely dissolve the precursor, obtain an impregnation solution, and impregnate overnight;

[0058] The concentration of cobalt nitrate hexahydrate in the impregnation solution was 0.45 mol / L;

[0059] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0060] Deionized water is added for secondary rolling and grinding to further promote the distribution of the precursor on the surface of the carrier and form a preliminary wet state to prepare for the subsequent impregnation process; part of the precursor is dissolved to form a saturated solution, so that the precursor can penetrate into the pores of the carrier more quickly. Compared with solid powder, the precursor in the solution is easier to distribute on the entire surface of the carrier, thereby improving the impregnation effect and the dispersion of cobalt;

[0061] By controlling the amount of deionized water added to 40-60% of the total mass of the precursor, it can be ensured that part of the precursor begins to dissolve at this stage, thereby forming a solid-liquid mixed state, which is beneficial to the initial distribution of the precursor on the carrier and can prevent the precursor from being completely dissolved and separated from the carrier due to excessive water. After adding water, since part of the cobalt nitrate has been dissolved in the water, the cobalt ions can reach a state of equilibrium faster during the impregnation process, thereby reducing the time required to achieve the ideal impregnation effect.

[0062] During the mixing and rolling process, the cobalt ions in the solution and the solid cobalt nitrate powder work together to make the distribution of cobalt on the carrier more uniform, thereby improving the activity of the catalyst. Embodiment 3

[0063] Example 2 The speed and effect of impregnation are improved by adding deionized water for secondary rolling and grinding; in order to improve the uniformity of the load, further improvements are made;

[0064] S2, rolling the weighed cobalt nitrate hexahydrate and manganese nitrate solution together with the carrier, grinding until mixed evenly, then adding deionized water, rolling again, grinding and mixing, repeating the steps of adding deionized water, and rolling and grinding and mixing until the precursor is completely dissolved to obtain a completely dissolved mixed powder;

[0065] The amount of deionized water added each time is 10-20% of the total mass of the precursor;

[0066] S3, adding deionized water to the completely dissolved mixed powder to make the impregnation solution reach the target concentration, obtaining an impregnation solution, and impregnating overnight;

[0067] The concentration of cobalt nitrate hexahydrate in the impregnation solution was 0.45 mol / L;

[0068] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0069] Through repeated rolling and grinding, the precursor and the carrier are mixed at the molecular level, so that the precursor is more evenly distributed on the surface and inside of the carrier, providing a basis for the subsequent preparation of high-performance catalysts.

[0070] Gradually adding a small amount of deionized water can control the dissolution rate of the precursor, avoid adding too much water at one time and causing the local concentration to be too high or too low, and ensure the uniformity and controllability of the dissolution process; compared with adding enough water at one time, gradually adding water reduces the total volume of the impregnation solution, thereby improving the impregnation efficiency. A smaller volume of the impregnation solution means that less solvent needs to be removed, shortening the time of the subsequent drying and calcination process; through multiple rolling and grinding, the physical and chemical interaction between the precursor and the carrier can be strengthened, which helps to improve the stability and activity of the catalyst.

[0071] As the amount of saturated precursor solution increases, more precursor can penetrate into the mixed powder, thereby increasing the loading amount of the precursor on the carrier, forming more active components in the subsequent calcination process, and improving the catalytic performance of the catalyst; gradiently increasing the amount of precursor solution makes the precursor more evenly distributed in the mixed powder, forming uniform catalyst active sites in the subsequent calcination step, thereby improving the efficiency and selectivity of the catalyst. Embodiment 4

[0072] Example 3: The precursor is more evenly distributed on the surface and inside of the carrier through repeated rolling and grinding. In order to improve the bonding degree between the precursor and the carrier, further improvements are made;

[0073] S2, the weighed cobalt nitrate hexahydrate and manganese nitrate are rolled together with the carrier, ground until mixed evenly, then deionized water is added, rolled again, ground and mixed, deionized water is added repeatedly, and the steps of rolling and grinding and mixing are repeated until the precursor is dissolved by 60-70%, and then the mixed powder is heated, and each time the temperature is increased by 10-25°C, it is ground once until the precursor is completely dissolved, and after keeping warm for 10 minutes, it is cooled to 0-20°C to precipitate part of the precursor to obtain an incompletely dissolved mixed powder;

[0074] The amount of deionized water added each time is 10-20% of the total mass of the precursor;

[0075] S3, adding deionized water to the mixed powder that is not completely dissolved to make the impregnation solution reach the target concentration, obtaining an impregnation solution, and impregnating overnight;

[0076] The concentration of cobalt nitrate hexahydrate in the impregnation solution was 0.45 mol / L;

[0077] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0078] By raising the temperature after the precursor is dissolved by 60-70%, the mixed solution is supersaturated, increasing the distribution of the precursor molecules on the carrier. There are a large number of hydroxyl groups on the carrier surface, which can form hydrogen bonds with the precursor molecules. The cations generated by salt ionization increase the viscosity of the carrier, and the cations form a double electric layer on the surface of the carrier particles, affecting the charge distribution on the carrier surface and the activity of the hydroxyl groups.

[0079] The salt ions directly form hydrogen bonds with the hydroxyl groups on the surface of the carrier or the salt ions are connected to the hydroxyl groups on the surface of the carrier through water molecules, thereby increasing the viscosity; when the temperature of the supersaturated solution drops and the precursor precipitates, the salt ions and the water molecules of the hydroxyl groups on the surface of the carrier no longer combine, and the salt ions are directly connected to the hydroxyl groups on the surface of the carrier through hydrogen bonds, which greatly increases the stability of the load, improves the degree of bonding between the precursor and the carrier, and increases the service life of the catalyst.

[0080] Catalyst activity test:

[0081] A methane / propane mixed gas was used to simulate the methane and non-methane total hydrocarbon pollutant gas, and the catalysts in Examples 1-4 were used for the catalytic combustion of methane and non-methane total hydrocarbons. The activity evaluation of the catalyst used for catalytic combustion was carried out in a fixed bed microreactor (quartz tube with an inner diameter of 3 mm). The amount of catalyst used was 100 mg, and the temperature was automatically controlled by a K-type thermocouple. A methane / propane standard mixed gas was mixed with air and entered the reactor for combustion. The total flow rate was controlled by a mass flowmeter, the concentration of methane and propane was 100 ppm, air was used as the carrier gas, the oxygen concentration was 10%, the reaction temperature was 50-350°C, and it was carried out under normal pressure. The relationship between the conversion rate of methane and propane and the reaction temperature in Example 1-Example 4 is shown in the figure. Figure 1-Figure 3 shown.

[0082] It can be seen from the activity curves of Examples 1-4 that the catalyst of the present invention exhibits good catalytic oxidation activity for non-methane total hydrocarbons in total hydrocarbons, and can achieve complete catalytic oxidation of propane without converting methane at a relatively low temperature and in a relatively wide temperature range (170°C-250°C).

[0083] Catalytic effect on nitrogen oxides:

[0084] The catalysts were installed on the downstream side of the diesel engine stand, and the average NO was measured while repeating a steady operation in which fuel was injected to change the environment from an oxidizing environment (too lean). X The purification rate (%) was measured. X The purification rate is calculated by the following mathematical formula.

[0085] NOx purification rate (%) = {engine outlet NO X (ppm)-catalyst outlet NO X(ppm)} / engine outlet NO X (ppm)×100%;

[0086] The purification rates of the catalysts obtained in Examples 1 to 4 for nitrogen oxides are all not less than 61%;

[0087] Catalytic effect on sulfur dioxide:

[0088] Referring to the chemical industry standards of the People's Republic of China HG / T2089-2014 (sulfur dioxide oxidation to sulfuric acid catalyst activity test method) and HG / T2086-2013 (sulfur dioxide oxidation to sulfuric acid catalyst), the activity of the catalysts of Examples 1 to 4 was measured, and the conversion rates of sulfur dioxide after heat resistance were not less than 83%.

[0089] Catalyst activity loading test:

[0090] The impregnated support is filtered out, the remaining impregnation solution is dried to precipitate the remaining precursor, and the loading amount is calculated;

[0091] Loading amount = 1-precursor remaining amount / precursor calculated amount × 100%, the results are shown in Table 1;

[0092] Table 1 Catalyst active loading

[0093]

[0094] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons, characterized in that: It includes active components Co3O4 and MnO2 and carriers TiO2 or SiO 2， Wherein, the molar ratio of manganese nitrate and cobalt nitrate hexahydrate to the loaded amount is (2-4):1; The method comprises the following steps: S1. Weigh a certain mass of TiO2 or SiO2 carrier respectively; calculate the mass of the required precursors cobalt nitrate hexahydrate and manganese nitrate according to the mass of TiO2 or SiO2 and the loading amount of Co3O4 and MnO2 of 30%-50%; Wherein, the molar ratio of manganese nitrate and cobalt nitrate hexahydrate to cobalt nitrate is (2-4):1 according to the loading amount; S2, the weighed cobalt nitrate hexahydrate and manganese nitrate are rolled together with the carrier, ground until mixed evenly, then deionized water is added, rolled again, ground and mixed, deionized water is added repeatedly, and the steps of rolling and grinding and mixing are repeated until the precursor is dissolved by 60-70%, and then the mixed powder is heated, and each time the temperature is increased by 10-25°C, it is ground once until the precursor is completely dissolved, and after keeping warm for 10 minutes, it is cooled to 0-20°C to precipitate part of the precursor to obtain an incompletely dissolved mixed powder; The amount of deionized water added each time is 10-20% of the total mass of the precursor; S3, adding deionized water to the mixed powder of solid and liquid to completely dissolve the precursor, obtain an impregnation solution, and impregnate overnight; S4. Under stirring conditions at 80°C, add sodium carbonate solution dropwise to the support impregnated with the precursor, adjust the pH to 9, and continue stirring for 2 hours to obtain a precipitate; S5. The obtained precipitate is filtered, washed with deionized water, and dried overnight at 60°C; S6. Grind the dried precipitate into fine powder, and calcine at 500-600° C. for 4 h to obtain the catalyst.

2. The catalyst for integrated treatment of SO2, NOx and non-methane total hydrocarbons as claimed in claim 1, characterized in that: The concentration of the sodium carbonate solution prepared in step S4 is 0.1 mol / L.

3. The catalyst for integrated treatment of SO2, NOx and non-methane total hydrocarbons as claimed in claim 1, characterized in that: The concentration of cobalt nitrate hexahydrate in the impregnation solution in step S3 is 0.45 mol / L.

4. A method for using the catalyst for integrated treatment of SO2, NOx, and non-methane total hydrocarbons as claimed in any one of claims 1 to 3, characterized in that: The catalyst is used under the temperature condition of 170°C-250°C.

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