De-NOx sorbents, methods for removing nitrogen oxides

Abstract

The application relates to the technical field of gas purification, and discloses a denitration adsorbent and a nitrogen oxide removal method, wherein the adsorbent comprises an active component, a carrier and a noble metal additive; the active component is selected from at least one of a molecular sieve active component, a silicon active component, an activated carbon active component, a calcium active component, a barium active component and an aluminum active component; the content of the active component is 5-40 wt% in terms of the total weight of the adsorbent, the content of the carrier is 50-94 wt%, and the content of the additive is 0.1-10 wt% in terms of the noble metal element. The adsorbent has deep denitration capacity through cooperation of the active component, the additive and the carrier, and can effectively remove nitrogen oxides in gas to the ppb level.

Description

Technical Field

[0001] This invention relates to the field of gas purification application technology, specifically to a method for removing nitrogen oxides from a denitrification adsorbent. Background Technology

[0002] Gas purification has important applications in fields such as feedstock gas refining, trace component enrichment, and electronic gas purification. Taking electronic gases as an example, a purity level of 6N is typically required, meaning that impurity content must be reduced to the ppb level. This plays a decisive role in the quality of electronic devices, directly impacting various fields such as semiconductors, display panels, and photovoltaics. However, due to process limitations, feedstock gases may contain nitrogen oxides at ppm levels or even higher. The depth of removal of these components directly determines the quality of the purified gas.

[0003] Currently, common techniques for removing impurities from high-purity gases include cryogenic treatment, chemical reactions, and adsorption. For example, CN115010132A discloses a method for purifying high-purity carbon monoxide gas, which uses cryogenic distillation and flash evaporation to remove impurities from the obtained carbon monoxide gas. This patent application does not mention the deep removal of nitrogen oxides, and the obtained carbon monoxide has a purity of 5N with an impurity content of 50 ppm, which is relatively high. CN214261301U discloses a system for removing oxygen impurities, which mainly uses molecular sieves for deoxygenation, achieving a gas concentration of 4N purity, i.e., an oxygen concentration of less than 100 ppm, but with a relatively high residual impurity content. CN110040686A discloses a method for reducing the moisture content in hydrogen chloride gas from the ppm level to the ppb level using a chemical reaction, but this method is not suitable for the deep removal of nitrogen oxides.

[0004] Currently, there are no publicly available materials that provide direct reference and guidance for the deep purification of gases to remove nitrogen oxides down to the ppb level. Therefore, a denitrification purification adsorbent capable of removing nitrogen oxides to the ppb level is needed. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of poor removal effect and high impurity content of denitrification products in the existing technology of denitrification purification adsorbents, and to provide a denitrification adsorbent and nitrogen oxide removal method. The adsorbent has deep denitrification capability through the combination of active components, additives and carriers, and can effectively remove nitrogen oxides from the gas to the ppb level.

[0006] To achieve the above objectives, the first aspect of the present invention provides a denitrification adsorbent, wherein the adsorbent comprises an active component, a carrier, and a noble metal additive;

[0007] The active component is selected from at least one of molecular sieve active components, silicon active components, activated carbon active components, calcium active components, barium active components, and aluminum active components;

[0008] Based on the total weight of the adsorbent, the auxiliary agent, calculated as precious metal elements, has the following contents: the content of the active component is 5-40 wt%, the content of the carrier is 50-94 wt%, and the content of the auxiliary agent is 0.1-10 wt%.

[0009] Preferably, based on the total weight of the adsorbent, the auxiliary agent (calculated as a precious metal element) contains 8-25 wt% of the active component, 70-90 wt% of the carrier, and 0.5-5 wt% of the auxiliary agent.

[0010] Preferably, the carrier is selected from at least one of silicon dioxide, aluminum oxide, cerium oxide, and clay.

[0011] Preferably, the precious metal additive is selected from at least one of Pt, Pd, Rh, Au and Ag, and more preferably Pt and / or Pd.

[0012] Preferably, the active component is selected from at least one of molecular sieve active components, calcium active components, and barium active components.

[0013] Preferably, the active component is obtained by calcining an active component source.

[0014] Preferably, the active component source is selected from at least one of molecular sieves, silica sol, activated carbon, calcium compounds, barium compounds, and aluminum compounds.

[0015] A second aspect of the present invention provides a method for removing nitrogen oxides, wherein the method includes the following steps:

[0016] In the presence of the denitrification adsorbent described in the first aspect, the gas containing nitrogen oxides is denitrified;

[0017] The denitrification conditions include: a denitrification temperature of 50-300℃;

[0018] The gas containing nitrogen oxides includes both nitrogen oxides and oxygen.

[0019] Preferably, the gas containing nitrogen oxides also includes at least one of nitrogen, water vapor, and carbon dioxide.

[0020] Preferably, the volume concentration of oxygen in the gas containing nitrogen oxides is 0.1-50 vol%, more preferably 5-25 vol%.

[0021] Preferably, the volume concentration of water vapor in the nitrogen oxide-containing gas is 0-30 vol%, more preferably 5-15 vol%.

[0022] Preferably, the volume concentration of nitrogen oxides in the gas containing nitrogen oxides is 1-1000 ppm, more preferably 1-100 ppm.

[0023] Preferably, the denitrification conditions include a denitrification temperature of 100-200℃.

[0024] Preferably, the method further includes: regenerating the denitrified adsorbent in the presence of a reducing atmosphere.

[0025] Preferably, the reducing atmosphere is an inorganic reducing atmosphere and / or an organic gaseous compound.

[0026] Preferably, the inorganic reducing atmosphere includes at least one of H2 and / or CO.

[0027] Preferably, the regeneration conditions include: a regeneration temperature of 50-400℃, more preferably 100-400℃; and a regeneration time of 0.5-72h, more preferably 0.5-2h.

[0028] Preferably, the volume concentration of H2 in the reducing atmosphere is 0.1-20 vol%.

[0029] The beneficial effects of the above technical solution are as follows:

[0030] (1) The present invention provides a denitrification adsorbent that, through the combination of active components, additives and carrier, has deep denitrification capability and can effectively remove nitrogen oxides in gas to the ppb level. The denitrification adsorbent has a wide range of applications, low penetration concentration, and good environmental tolerance to complex gases.

[0031] (2) In this invention, preferably, the method for removing nitrogen oxides involves denitrifying with a nitrogen oxide-containing gas at a specific temperature to effectively remove nitrogen oxides from the gas. After the reaction is completed, the denitrification adsorbent is regenerated by a reducing atmosphere. After multiple cycles of regeneration, the performance of the denitrification adsorbent remains at a high level. Attached Figure Description

[0032] Figure 1 The adsorption performance test curve of the denitrification adsorbent was obtained by infrared spectroscopy under the first set of test conditions in Example 1.

[0033] Figure 2 This is the adsorption performance test curve of the denitrification adsorbent obtained by mass spectrometry under the second set of test conditions in Example 1;

[0034] Figure 3 This is a partially enlarged view of the adsorption performance test curve of the denitrification adsorbent under the second set of test conditions in Example 1;

[0035] Figure 4 The adsorption performance test curve of the denitrification adsorbent of Example 11 after fourteen consecutive cycles of regeneration-denitrification is shown.

[0036] Figure 5 This is the regeneration gas concentration-temperature-time curve of the denitrification adsorbent in Example 11;

[0037] Figure 6 This is the regeneration gas concentration-temperature-time curve of the denitrification adsorbent in Example 12;

[0038] Figure 7 This is the breakthrough curve of the denitrification test for the denitrification adsorbent in Example 12. Detailed Implementation

[0039] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0040] The first aspect of the present invention provides a denitrification adsorbent, wherein the adsorbent comprises an active component, a carrier, and a noble metal additive;

[0041] The active component is selected from at least one of molecular sieve active components, silicon active components, activated carbon active components, calcium active components, barium active components, and aluminum active components;

[0042] Based on the total weight of the adsorbent, the auxiliary agent, calculated as precious metal elements, has the following contents: the content of the active component is 5-40 wt%, the content of the carrier is 50-94 wt%, and the content of the auxiliary agent is 0.1-10 wt%.

[0043] In this invention, the denitrification adsorbent, through the combination of active components, precious metal additives and carrier, has a deep denitrification capability and can effectively remove nitrogen oxides from the gas to the ppb level. The denitrification adsorbent has a wide range of applications, good adsorption effect, and good environmental tolerance to complex gases.

[0044] In this invention, the nitrogen oxides are defined in the conventional sense of the art as compounds composed of nitrogen and oxygen, including at least one of nitrous oxide (N₂O), nitric oxide (NO), nitrogen dioxide (NO₂), dinitric oxide (N₂O₃), dinitric oxide (N₂O₄), and dinitric oxide (N₂O₅). In this invention, the nitrogen oxides primarily refer to nitric oxide (NO) and nitrogen dioxide (NO₂).

[0045] In this invention, the ppb level has the conventional interpretation in the art, referring to a volume concentration of nitrogen oxides in the range of one part per billion to one part per million.

[0046] According to the present invention, preferably, based on the total weight of the adsorbent, the auxiliary agent, calculated as a precious metal element, contains 8-25 wt% of the active component, 70-90 wt% of the support, and 0.5-5 wt% of the auxiliary agent. More preferably, based on the total weight of the adsorbent, the auxiliary agent, calculated as a precious metal element, contains 10-20 wt% of the active component, 78-88 wt% of the support, and 1-2 wt% of the auxiliary agent.

[0047] In this invention, the composition of the denitrification adsorbent meets the above-mentioned limitations. The nitrogen oxides are further removed by the oxidation of nitrogen oxides through the oxidation of nitrogen oxides by the noble metal catalysis of the auxiliary agent and the chemical adsorption of the oxidized nitrogen oxides by the active component.

[0048] In this invention, the content of each component in the gas during the adsorbent performance test is determined by infrared spectroscopy (refer to GB / T 25930-2010, GB / T 32198-2015 and GB / T6040-2019) or mass spectrometry (refer to GB / T 6041-2020). The content of each component in the adsorbent is determined by X-ray fluorescence spectroscopy (GB / T 30905-2014).

[0049] In this invention, when the active component is selected from at least one of calcium, barium, and aluminum active components, the content of the active component is expressed as the equivalent of the oxide of the corresponding metal element. For example, when the active component is barium, the content of the active component is expressed as BaO equivalent.

[0050] In this invention, when the active component is selected from at least one of molecular sieve active components, silicon active components, and activated carbon active components, the content of the active component is based on the total weight of the active components. For example, when the active component is a molecular sieve, the content of the active component is based on the weight of the molecular sieve, and the content of the silicon active component is based on silicon dioxide.

[0051] According to the present invention, the type and source of the carrier are not particularly limited, and it can be a conventional carrier material in the art, which can be commercially available or prepared by existing methods. The carrier is selected from at least one of silicon oxide, alumina, cerium oxide and clay, preferably alumina.

[0052] In this invention, the carrier serves to support the active components and has abundant pores, which can promote the uniform dispersion of the active components on the carrier and increase the contact area between the adsorbent and the gas containing nitrogen oxides.

[0053] In this invention, the clay has the conventional meaning in the art, and the range of types of clay that can be selected is relatively wide, preferably selected from at least one of kaolin, montmorillonite and quartz.

[0054] According to the present invention, preferably, the noble metal additive is selected from at least one of Pt, Pd, Rh, Au and Ag, and more preferably Pt and / or Pd.

[0055] In this invention, precious metals are used as additives, which help to catalyze the oxidation of NO in nitrogen oxides to NO2, so that nitrogen oxides can come into more complete contact with active components, effectively removing nitrogen oxides to a low concentration at the ppb level, and have deep denitrification capabilities.

[0056] According to the present invention, the range of types of active components is relatively wide. Preferably, the active components are selected from at least one of molecular sieve active components, calcium active components, and barium active components.

[0057] According to the present invention, preferably, the active component is obtained by calcining an active component source. In the present invention, the calcination conditions are not particularly limited, but preferred calcination conditions include: a calcination temperature of 400-700℃, more preferably 500-650℃; and a calcination time of 1-72h, more preferably 2-8h.

[0058] In this invention, the composition and structure of the active component are not particularly limited. Calcining the active component source yields an alkaline material, which adsorbs the oxidation products of nitrogen oxides via chemical adsorption, avoiding the removal of nitrogen oxides and further reducing their concentration. Through synergy with additives, in addition to easily adsorbed NO2, difficult-to-adsorb NO in the gas source can also achieve good adsorption and removal effects.

[0059] According to the present invention, preferably, the active component source is selected from at least one of molecular sieves, silica gel, activated carbon, calcium compounds, barium compounds and aluminum compounds.

[0060] According to the present invention, the type and source of the molecular sieve are not particularly limited, and it can be a conventional molecular sieve in the art, which can be commercially available or prepared using existing methods. Preferably, the molecular sieve is selected from at least one of the following groups: MFI group molecular sieves, BEA group molecular sieves, LTA group molecular sieves, CHA group molecular sieves, and FAU group molecular sieves. The molecular sieve only needs to satisfy the above-mentioned structure, for example, the MFI group molecular sieve is ZSM-5 molecular sieve, the LTA group molecular sieve is type A molecular sieve, the CHA group molecular sieve is SSZ-13 molecular sieve, and the FAU group molecular sieve is type Y molecular sieve.

[0061] In this invention, the type and source of the silica gel are not particularly limited, and it is a conventional silica gel material in the art. The silica gel can be commercially available or prepared using existing methods. Those skilled in the art can adapt the weight percentage of SiO2 in the silica gel. The activated carbon is a conventional activated carbon material in the art.

[0062] According to the present invention, the type and source of the calcium compound are not particularly limited. The active component of the adsorbent mainly needs to use calcium as a cation, and the form of the cation is not limited. The calcium compound is a conventional organic calcium compound and / or inorganic calcium compound in the art. The calcium compound is selected from at least one of calcium carbonate, calcium oxide, calcium chloride, calcium hydroxide, calcium nitrate, calcium phosphate, calcium sulfate, calcium oxalate, calcium gluconate, calcium lactate, calcium citrate and calcium acetate.

[0063] According to the present invention, the type and source of the barium compound are not particularly limited. The active component of the adsorbent mainly needs to use barium as a cation, and its form is acceptable. The barium compound is a conventional organic barium compound and / or inorganic barium compound in the art. The barium compound is selected from at least one of barium carbonate, barium oxide, barium chloride, barium hydroxide, barium nitrate, barium sulfate, barium phosphate, barium oxalate, barium gluconate, barium lactate, barium citrate, and barium acetate.

[0064] In this invention, the range of aluminum compounds that can be selected is relatively wide, and can be conventional organoaluminum compounds and / or inorganic aluminum compounds in the art. The inorganic aluminum compounds are selected from at least one of alumina, aluminum carbonate, aluminum chloride, aluminum hydroxide, basic alumina, aluminum nitrate, aluminum phosphate, and aluminum sulfate. The organoaluminum compounds are selected from at least one of aluminum oxalate, aluminum gluconate, aluminum lactate, aluminum citrate, and aluminum acetate.

[0065] In this invention, the preparation method of the denitrification adsorbent is not particularly limited. Those skilled in the art can choose conventional preparation methods that can load the active component and additives onto the carrier. For example, it can be selected from at least one of impregnation, precipitation, ion exchange, sol-gel, and hydrothermal methods, with impregnation being preferred. The impregnation conditions are not particularly limited.

[0066] According to a preferred embodiment of the present invention, the method for preparing the denitrification adsorbent includes: impregnating an active component source and an auxiliary agent source onto a carrier, and then drying and calcining them to obtain the denitrification adsorbent.

[0067] In this invention, the source and amount of the active component, auxiliary agent, and carrier are not particularly limited, as long as the obtained denitrification adsorbent meets the above limitations.

[0068] In this invention, the type and source of the auxiliary agent source are not particularly limited, but are preferably selected from at least one of precious metal nitrates, chlorides, sulfates, acidic complexes formed with hydrochloric acid, and acetylacetone salts. More preferably, they are selected from at least one of palladium nitrate, platinum nitrate, palladium chloride, platinum chloride, chloropalladic acid, chloroplatinic acid, and ruthenium nitrate. The amount of the auxiliary agent source used is sufficient to ensure that the content of the precious metal auxiliary agent meets the above-mentioned limitations.

[0069] In this invention, preferably, the drying conditions include: a drying temperature of 80-150℃ and a drying time of 1-6 hours.

[0070] In this invention, preferably, the roasting conditions include: a roasting temperature of 400-700℃, more preferably 500-650℃; and a roasting time of 1-72h, more preferably 2-8h. In this invention, the roasting time refers to the roasting time calculated from the point when the roasting temperature is reached.

[0071] In this invention, the heating rate of the roasting is not particularly limited. According to a preferred embodiment of the invention, the heating rate is 1-5℃ / min.

[0072] In this invention, preferably, the denitrification adsorbent is used to denitrify gases containing nitrogen oxides. In this invention, the denitrification adsorbent can effectively and deeply remove nitric oxide and nitrogen dioxide.

[0073] In this invention, preferably, the gas containing nitrogen oxides comprises nitrogen oxides and oxygen. Referring to the foregoing description, the nitrogen oxides are preferably nitric oxide and / or nitrogen dioxide.

[0074] In this invention, preferably, the denitrification temperature is 50-300℃.

[0075] A second aspect of the present invention provides a method for removing nitrogen oxides, wherein the method includes the following steps:

[0076] In the presence of the denitrification adsorbent described in the first aspect, the gas containing nitrogen oxides is denitrified;

[0077] The denitrification conditions include: a denitrification temperature of 50-300℃;

[0078] The gas containing nitrogen oxides includes both nitrogen oxides and oxygen.

[0079] In this invention, preferably, the denitrification adsorbent is used to remove nitrogen oxides. The denitrification adsorbent is subjected to denitrification with a gas containing nitrogen oxides at a specific temperature. First, nitric oxide is catalytically oxidized to obtain NO2. Then, the difficult-to-remove nitrate is obtained by chemical adsorption through the active component of the adsorbent.

[0080] According to the present invention, preferably, the gas containing nitrogen oxides further includes at least one of nitrogen, water vapor and carbon dioxide.

[0081] In this invention, oxygen can promote the oxidation of nitric oxide in nitrogen oxides, and fully oxidize nitric oxide to obtain NO2, which is easier to be adsorbed. Water vapor can promote the nitrogen oxides to obtain a stable and difficult-to-remove state after adsorption, and at the same time, it can make the regeneration conditions of the adsorbent more mild.

[0082] By using the denitrification adsorbent of the present invention, the denitrification adsorbent can be used to denitrify a gas containing nitrogen oxides. First, the nitrogen oxides are catalytically oxidized on the additive to oxidize NO to NO2. Then, the difficult-to-remove nitrates are obtained by chemical adsorption through the active component of the adsorbent. Thus, nitrogen oxides can be removed to the ppb level.

[0083] As described above, since the denitrification adsorbent of the present invention oxidizes NO to NO2 by first catalytically oxidizing nitrogen oxides, it is particularly suitable for treating gases containing oxygen in the nitrogen oxide-containing gas. In particular, when the volume concentration of oxygen in the nitrogen oxide-containing gas is 0.1-50 vol%, the presence of sufficient oxygen allows NO to be fully oxidized to NO2, which is then further chemically adsorbed to obtain nitrates that are difficult to remove, thus removing nitrogen oxides to the ppb level.

[0084] According to the present invention, preferably, the volume concentration of oxygen in the gas containing nitrogen oxides is 0.1-50 vol%, for example, 1 vol%, 2 vol%, 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol%, 50 vol%, or any range between the two, preferably 5-25 vol%. In the present invention, the gas containing nitrogen oxides contains oxygen, which is capable of fully oxidizing NO in the nitrogen oxides to NO2.

[0085] In this invention, the source of oxygen is not particularly limited; it can be oxygen gas or an oxygen precursor that can decompose to produce oxygen under denitrification conditions.

[0086] According to the present invention, preferably, the volume concentration of water vapor in the gas containing nitrogen oxides is 0-30 vol%, for example, 1 vol%, 2 vol%, 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, or any range between the two, preferably 5-15 vol%.

[0087] In this invention, the gas containing nitrogen oxides contains water vapor, which can further adsorb NO2 obtained from the oxidation of nitrogen oxides, thus aiding adsorption. Simultaneously, in the subsequent adsorbent regeneration stage, the adsorbed water can contribute a large number of hydrogen bridge structures to the adsorbent, activating reactions involving hydrogen atom transfer, including the hydrogenation reduction of nitrates to ammonia, allowing the subsequent denitrification adsorbent to be regenerated under mild conditions.

[0088] In this invention, preferably, the remaining portion of the gas containing nitrogen oxides comprises nitrogen and / or carbon dioxide.

[0089] According to the present invention, preferably, the volume concentration of nitrogen oxides in the gas containing nitrogen oxides is 1-1000 ppm, for example, 1 ppm, 5 ppm, 10 ppm, 15 ppm, 20 ppm, 25 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm, 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, or any range between the two, preferably 1-100 ppm. In the present invention, the volume concentration of nitrogen oxides refers to the volume concentration of nitric oxide and nitrogen dioxide, primarily nitric oxide.

[0090] In this invention, during the engineering design process, those skilled in the art can adjust the amount of denitrification adsorbent added according to the concentration of nitrogen oxides to achieve sufficient adsorption and removal of nitrogen oxides.

[0091] According to the present invention, preferably, the denitrification conditions include: a denitrification temperature of 100-200℃, for example 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any range between the two.

[0092] In this invention, if the denitrification temperature is too high, the adsorption effect will decrease due to the thermal equilibrium of denitrification, resulting in a shorter breakthrough time; if the denitrification temperature is too low, the catalytic oxidation activity of the adsorbent will be low at low temperatures, resulting in a shorter breakthrough time and a poorer adsorption effect.

[0093] According to a preferred embodiment of the present invention, the denitrification process includes: in the presence of a denitrification adsorbent, first introducing at least one of water vapor, nitrogen and carbon dioxide and oxygen, heating to the denitrification temperature and stabilizing, and then introducing nitrogen oxides for denitrification.

[0094] According to the present invention, preferably, the method further includes: regenerating the denitrified adsorbent in the presence of a reducing atmosphere.

[0095] In this invention, the denitrification adsorbent is regenerated and recycled. The regeneration method is simple, the conditions are controllable, and the regeneration effect of the adsorbent is good. After multiple regeneration cycles, it can maintain a good nitrogen oxide adsorption capacity. During regeneration, taking hydrogen as an example, the auxiliary agent can play a catalytic role in hydrogenation decomposition, re-hydrogenating nitrates back to the original active center structure, while nitrogen is hydrogenated into ammonia.

[0096] According to the present invention, preferably, the reducing atmosphere is an inorganic reducing atmosphere and / or an organic gaseous compound, wherein the inorganic reducing atmosphere is at least one of H2 and / or CO, and the organic gaseous compound is an organic compound that is gaseous under reducing conditions, as is commonly known in the art. Examples include at least one of alkanes, alkenes, alkynes, alcohols, aldehydes, acids, ethers, ketones, amines, esters, nitriles, halogens, thiols, sulfonates, nitrogenous impurities, boronous impurities, and sulfurous impurities. More preferably, it is selected from at least one of C1-C4 alkanes, C2-C4 alkenes, C2-C4 alkynes, methanol, ethanol, 1,2-ethylenediol, 1-propanol, 2-propanol, 1,3-propanediol, formaldehyde, acetaldehyde, formic acid, acetic acid, acetone, methylamine, dimethylamine, trimethylamine, ethylamine, ethylenediamine, diethylamine, and triethylamine.

[0097] In this invention, the regeneration of the denitrification adsorbent using the aforementioned reducing atmosphere can accelerate the removal of adsorbed nitrogen oxides. Heating the denitrification adsorbent after denitrification under a reducing atmosphere restores the adsorption capacity of the active components, achieving an ideal regeneration effect.

[0098] According to the present invention, preferably, the volume concentration of H2 in the reducing atmosphere is 0.1-20 vol%, for example, 0.1 vol%, 0.2 vol%, 0.5 vol%, 0.7 vol%, 1 vol%, 2 vol%, 3 vol%, 4 vol%, 5 vol%, 6 vol%, 7 vol%, 8 vol%, 9 vol%, 10 vol%, 15 vol%, 20 vol%, or any range between the two, preferably 2-10 vol%.

[0099] In this invention, preferably, the reducing atmosphere further includes a protective atmosphere, which is selected from at least one of nitrogen, helium, and argon.

[0100] According to a preferred embodiment of the present invention, the regeneration of the denitrification adsorbent includes the following steps: after denitrification is completed, the gas containing nitrogen oxides is switched to a reducing atmosphere, and the temperature is raised to the regeneration temperature and then kept constant for regeneration.

[0101] According to the present invention, preferably, the regeneration conditions include: a regeneration temperature of 50-400℃, more preferably 100-400℃; and a regeneration time of 0.5-72h, more preferably 0.5-2h.

[0102] In this invention, the provided denitrification adsorbent is used to remove nitrogen oxides, which can reduce the NO concentration in nitrogen oxides to 100 ppbv, achieving deep purification and removal of nitrogen oxides. The NO and NO2 concentrations of nitrogen oxides and the NO and NO2 concentrations of the denitrification products are measured using an Antaris IGS (Thermo) online gas phase infrared spectrometer (refer to GB / T25930-2010, GB / T32198-2015 and GB / T6040-2019).

[0103] According to a particularly preferred embodiment of the present invention, a method for removing nitrogen oxides includes the following steps:

[0104] In the presence of a denitrification adsorbent, gases containing nitrogen oxides are denitrified.

[0105] The denitrification conditions include: a denitrification temperature of 100-200℃;

[0106] The gas containing nitrogen oxides includes both nitrogen oxides and oxygen.

[0107] The volume concentration of oxygen in the gas containing nitrogen oxides is 5-25 vol%.

[0108] The adsorbent includes an active component, a carrier, and a noble metal additive;

[0109] Based on the total weight of the adsorbent, the auxiliary agent, calculated as precious metal elements, has the following contents: the content of the active component is 8-25 wt%, the content of the carrier is 70-90 wt%, and the content of the auxiliary agent is 0.5-5 wt%.

[0110] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.

[0111] Example 1

[0112] Preparation of the denitrification adsorbent: An alumina support was prepared according to the method disclosed in Example 1 of CN116020334A. The specific surface area of ​​the prepared support was 91.2 m². 2 / g, pore volume is 0.42mL / g, and average pore size (calculated according to BJH desorption) is 13.6nm.

[0113] Platinum nitrate and barium nitrate were selected as impregnation components, respectively. After impregnation with equal volumes and drying, the denitrification adsorbent was obtained by calcining at 600℃ for 2h with a heating rate of 2℃ / min. The content of the auxiliary agent Pt was 2wt%; the content of the active component calculated as BaO was 20wt%; and the remainder was alumina as the carrier.

[0114] First set of test conditions:

[0115] 400 mg of adsorbent was used for testing. A mixed gas was prepared by mixing H2O water vapor, O2, and N2, with an H2O volume concentration of 15 vol% and an O2 to N2 volume ratio of 1:4 (O2 volume concentration of 17 vol%, N2 volume concentration of 68 vol%). The gas flow rate was 150 mL / min, and the mixture was heated to 200 °C and stabilized for 0.5 h. NO was then injected into the mixed gas to obtain a gas containing nitrogen oxides, with a concentration of 80 ppmv. The NO concentration in the exhaust gas was continuously measured.

[0116] NO concentration was measured using an Antaris IGS (Thermo) online gas phase infrared spectrometer. A typical test curve is shown below. Figure 1 As shown, from Figure 1 As can be seen, the blue curve represents the NO breakthrough that occurs at t=0 when the device is not filled with adsorbent ("breakthrough" means that the NO concentration exceeds 10 ppmv). The NO breakthrough curve for the test gas is the green curve, which breaks through at 4000 s. The red curve represents the NO2 concentration curve observed in the adsorption experiment. According to the 10 ppmv test threshold definition, the NO2 breakthrough time is 17000 s. The results are shown in Table 1.

[0117] Second set of test conditions:

[0118] To further demonstrate that the adsorbent in this embodiment can reduce NO to 100 ppbv, mass spectrometry was used for testing. The test conditions were: adsorbent dosage 600 mg, NO concentration 100 ppmv, flow rate 225 mL / min, H₂O volume concentration 15 vol%, and O₂ to N₂ volume ratio 1:4 (O₂ volume concentration 17 vol%, N₂ volume concentration 68 vol%). The test results are shown below. Figure 2 and Figure 3 As can be seen, the blue curve is the NO breakthrough curve, and the red curve is the observed NO2 concentration curve. Under these test conditions, NO takes 430 seconds to reach 100 ppbv. The adsorbent can reduce nitrogen oxides to below 100 ppbv within a certain time.

[0119] Example 2

[0120] The adsorbent was prepared according to the method of Example 1, except that the content of Pt was adjusted to 0.3 wt%; the content of the active component, calculated as BaO, was 20 wt%; and the remainder was a support, namely alumina.

[0121] Denitrification conditions: 400 mg of adsorbent was used for testing. A mixed gas was prepared by mixing H2O water vapor, O2, and N2, with an H2O volume concentration of 15 vol% and an O2 to N2 volume ratio of 1:4 (O2 volume concentration of 17 vol% and N2 volume concentration of 68 vol%). The gas flow rate was 150 mL / min, and the mixture was heated to 150 °C and stabilized for 0.5 h. NO was then injected into the mixed gas to obtain a gas containing nitrogen oxides, with a concentration of 80 ppmv. The NO concentration in the tail gas was continuously measured, and the results are shown in Table 1.

[0122] Example 3

[0123] The adsorbent was prepared according to the method of Example 1, except that the content of Pt was adjusted to 0.75 wt%, the content of active component (calculated as BaO) was 20 wt%, and the remainder was a support, namely alumina.

[0124] The denitrification conditions were the same as in Example 2, and the results are shown in Table 1.

[0125] Example 4

[0126] The adsorbent was prepared according to the method of Example 1, except that the content of Pt was adjusted to 1 wt%, the content of active component (calculated as BaO) was 20 wt%, and the remainder was a support, namely alumina.

[0127] The denitrification conditions were the same as in Example 2, and the results are shown in Table 1.

[0128] Example 5

[0129] The adsorbent was prepared according to the method of Example 1, except that the content of Pt was adjusted to 1 wt%; the content of the active component, calculated as BaO, was 5 wt%; and the remainder was a support, namely alumina.

[0130] The denitrification conditions were the same as in Example 2, and the results are shown in Table 1.

[0131] Example 6

[0132] The adsorbent was prepared according to the method of Example 1, except that the content of Pt was adjusted to 1 wt%; the content of the active component, calculated as BaO, was 10 wt%; and the remainder was a support, namely alumina.

[0133] The denitrification conditions were the same as in Example 2, and the results are shown in Table 1.

[0134] Example 7

[0135] The adsorbent was prepared according to the method of Example 1, except that the content of Pt was adjusted to 1 wt%; the content of the active component, calculated as BaO, was 15 wt%; and the remainder was a support, namely alumina.

[0136] The denitrification conditions were the same as in Example 2, and the results are shown in Table 1.

[0137] Example 8

[0138] The denitrification adsorbent prepared in Example 1 was used for denitrification, the difference being that the gas containing nitrogen oxides did not contain water vapor, the volume ratio of O2 to N2 was 1:4, the volume concentration of O2 was 20 vol%, and the volume concentration of N2 was 80 vol%. The denitrification conditions were the same as the first set of test conditions in Example 1, and the results are shown in Table 1.

[0139] Example 9

[0140] The denitrification adsorbent prepared in Example 1 was used for denitrification, except that the volume concentration of water vapor in the gas containing nitrogen oxides was 5 vol%, with the remainder being O2 and N2, the volume ratio of O2 to N2 was 1:4, the volume concentration of O2 was 19 vol%, and the volume concentration of N2 was 76 vol%. The denitrification conditions were the same as the first set of test conditions in Example 1, and the results are shown in Table 1.

[0141] Example 10

[0142] The denitrification adsorbent prepared in Example 1 was used for denitrification, except that the denitrification temperature was 150℃, and other denitrification conditions were the same as the first group of test conditions in Example 1. The results are shown in Table 1.

[0143] Example 11

[0144] The adsorbent after denitrification in Example 4 was regenerated. After denitrification in Example 4 was completed, the gas containing nitrogen oxides was switched to a mixture of H2 and N2 with a volume concentration of 5 vol%. The temperature was increased to 400°C at 5°C / min and held for 1 hour. After cooling back to room temperature, the gas containing nitrogen oxides was switched back, and denitrification was performed again according to the test conditions of Example 4.

[0145] The above regeneration-denitrification cycle was repeated fourteen times. The test results are as follows: Figure 4 ,from Figure 4 As can be seen, the penetration time increased after the first few tests, and stabilized at around 4900s after the fourth test. The summary data of the last test results are shown in Table 1.

[0146] Figure 5 To monitor the change curve of exhaust gas composition over time when using H2 / N2 regeneration, from Figure 5As can be seen, at approximately 800 seconds, corresponding to a temperature of about 50°C, a large amount of NH3 is generated, with almost no other nitrogen oxides. This indicates that although the nitrogen oxides were adsorbed as nitrates in the previous step, a hydrogenation reaction occurred under the regeneration conditions. The auxiliary agent, acting as a hydrogenation center, caused the adsorbed nitrogen to be converted into NH3 and removed. The short-term NH3 concentration can reach 250,000 ppm. At approximately 1500 seconds, corresponding to a temperature of about 100°C, no more NH3 or other nitrogen oxides are generated. At this point, the regeneration process is complete, and the nitrogen on the adsorbent is completely removed. Therefore, 100°C can be expected to be the minimum acceptable regeneration temperature.

[0147] Example 12

[0148] The adsorbent after denitrification in Example 8 was regenerated. After denitrification in Example 8 was completed, the gas containing nitrogen oxides was switched to a mixture of H2 and N2, wherein the volume concentration of H2 was 5 vol%. The temperature was increased to 400°C at 5°C / min and held for 1 hour. After cooling back to room temperature, the gas containing nitrogen oxides was switched back, and denitrification was performed again according to the test conditions of Example 8.

[0149] Figure 6 To monitor the change curve of exhaust gas composition over time when using H2 / N2 regeneration, from Figure 6 As can be seen from the data, when the regeneration temperature rises to 400℃, no more substances are desorbed from the adsorbent. Therefore, it can be expected that 400℃ is the lowest acceptable regeneration temperature under the conditions of this embodiment, indicating that no water vapor is added during the denitrification process, so the temperature required for the regeneration of the denitrification adsorbent is relatively high.

[0150] The second and third regeneration-denitrification processes are carried out according to the above regeneration process: the gas containing nitrogen oxides is adjusted to contain 20 vol% O2 + 80 vol% N2, and the volume concentration of NO is 80 ppmv;

[0151] Fourth regeneration - denitrification: Adjust the gas containing nitrogen oxides to 5 vol% H2O + 19 vol% O2 + 76 vol% N2, and the volume concentration of NO to 80 ppmv;

[0152] Fifth to seventh regeneration-denitrification: Adjust the gas containing nitrogen oxides to 15 vol% H2O + 17 vol% O2 + 68 vol% N2, and the volume concentration of NO to 80 ppmv;

[0153] After the seventh denitrification, the breakthrough time was 10,000 s. The summary data of the final test is shown in Table 1. The test breakthrough curve is shown in... Figure 7 ,from Figure 7As can be seen, after seven cycles of regeneration-denitrification under different conditions, the adsorbent still maintains a high breakthrough time level, especially increasing from approximately 4000 s initially to 10000 s. This indicates that the adsorbent has very good stability and further demonstrates that the adsorbent performs well under different water content test conditions, especially exhibiting superior adsorption performance after multiple cycles at a water vapor content of 15 vol%.

[0154] Example 13

[0155] Preparation of denitrification adsorbent: Alumina support was prepared according to the method disclosed in CN116020334A, as in Example 1.

[0156] SSZ-13 molecular sieve was synthesized according to the method described on page 178 of the book "Verified Syntheses of Zeolitic Materials" (ISBN: 978-0-692-68539-6) published by the International Society for the Study of Zeolitic Materials.

[0157] A mixed slurry containing a certain amount of palladium nitrate and SSZ-13 molecular sieve was mixed with an alumina support, dried, and then calcined at 600℃ for 2 hours at a rate of 2℃ / min to obtain a denitrification adsorbent. The adsorbent contained 1.7wt% Pd as an additive, 20wt% SSZ-13 molecular sieve as the active component, and the remainder was the support, namely alumina.

[0158] 120 mg of adsorbent was used for testing. A gas containing nitrogen oxides was prepared by mixing H₂O, O₂, and N₂, with an H₂O volume concentration of 3 vol% and an O₂ to N₂ volume ratio of 1:5.9 (O₂ volume concentration of 14 vol% and N₂ volume concentration of 83 vol%). The flow rate of the nitrogen oxide-containing gas was 300 mL / min, and the mixture was heated to 100 °C and stabilized for 0.5 h. Subsequently, NO and NO₂ were injected into the nitrogen oxide-containing gas, with NO volume concentration of 200 ppmv and NO₂ volume concentration of 20 ppmv. The nitrogen oxide concentration in the exhaust gas was continuously measured (recorded as the sum of NO and NO₂ concentrations).

[0159] Example 14

[0160] The denitrification adsorbent prepared in Example 1 was used for denitrification, except that the volume concentration of O2 in the gas containing nitrogen oxides was 0.2 vol%, the volume concentration of N2 was 84.8 vol%, and the volume concentration of water vapor was 15 vol%. The denitrification conditions were the same as the first set of test conditions in Example 1, and the results are shown in Table 1.

[0161] Comparative Example 1

[0162] Denitrification was performed according to the first set of test conditions in Example 1, except that no denitrification adsorbent was loaded. The denitrification results are shown in Table 1.

[0163] Comparative Example 2

[0164] The denitrification adsorbent prepared in Example 1 was used for denitrification. The denitrification conditions were the same as the first group of test conditions in Example 1, except that the test gas for denitrification contained only N2. Other conditions were the same as in Example 1. The denitrification results are shown in Table 1.

[0165] Comparative Example 3

[0166] The denitrification adsorbent prepared in Example 1 was used for denitrification. The denitrification conditions were the same as those in the first group of tests in Example 1, except that the denitrification temperature was adjusted to 10°C. The denitrification results are shown in Table 1.

[0167] Comparative Example 4

[0168] The denitrification adsorbent prepared in Example 1 was used for denitrification. The denitrification conditions were the same as those in the first group of tests in Example 1, except that the denitrification temperature was adjusted to 250℃. The denitrification results are shown in Table 1.

[0169] Comparative Example 5

[0170] The denitrification adsorbent was prepared according to the method in Example 1, except that no additives were added, the active component content was 20 wt% based on BaO, and the remainder was a carrier, namely alumina.

[0171] The denitrification conditions were the same as in Example 2, and the denitrification results are shown in Table 1.

[0172] Table 1

[0173]

[0174] As can be seen from the results in Table 1, the denitrification adsorbent provided by this invention has a longer penetration time and better removal effect under the same test conditions for the removal of nitrogen oxides.

[0175] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A denitrification adsorbent, characterized in that, The adsorbent includes an active component, a carrier, and a noble metal additive; The active component is selected from at least one of molecular sieve active components, silicon active components, activated carbon active components, calcium active components, barium active components, and aluminum active components; Based on the total weight of the adsorbent, the auxiliary agent, calculated as precious metal elements, has the following contents: the content of the active component is 5-40 wt%, the content of the carrier is 50-94 wt%, and the content of the auxiliary agent is 0.1-10 wt%.

2. The adsorbent according to claim 1, wherein, Based on the total weight of the adsorbent, the auxiliary agent, calculated as precious metal elements, has the following contents: the content of the active component is 8-25 wt%, the content of the carrier is 70-90 wt%, and the content of the auxiliary agent is 0.5-5 wt%.

3. The adsorbent according to claim 1 or 2, wherein, The carrier is selected from at least one of silicon dioxide, aluminum oxide, cerium oxide, and clay; Preferably, the precious metal additive is selected from at least one of Pt, Pd, Rh, Au and Ag, and more preferably Pt and / or Pd.

4. The adsorbent according to any one of claims 1-3, wherein, The active component is selected from at least one of molecular sieve active components, calcium active components, and barium active components; Preferably, the active component is obtained by calcining an active component source; Preferably, the calcination conditions include: a calcination temperature of 400-700℃, more preferably 500-650℃; and a calcination time of 1-72h, more preferably 2-8h. Preferably, the active component source is selected from at least one of molecular sieves, silica gel, activated carbon, calcium compounds, barium compounds, and aluminum compounds.

5. The adsorbent according to claim 4, wherein, The molecular sieve is selected from at least one of the following molecular sieves: MFI group, BEA group, LTA group, CHA group, and FAU group. Preferably, the calcium compound is selected from at least one of calcium carbonate, calcium oxide, calcium chloride, calcium hydroxide, calcium nitrate, calcium phosphate, calcium sulfate, calcium oxalate, calcium gluconate, calcium lactate, calcium citrate, and calcium acetate. Preferably, the barium compound is selected from at least one of barium carbonate, barium oxide, barium chloride, barium hydroxide, barium nitrate, barium sulfate, barium phosphate, barium oxalate, barium gluconate, barium lactate, barium citrate, and barium acetate.

6. A method for removing nitrogen oxides, wherein, The method includes the following steps: In the presence of the denitrification adsorbent according to any one of claims 1-5, the gas containing nitrogen oxides is denitrified; The denitrification conditions include: a denitrification temperature of 50-300℃; The gas containing nitrogen oxides includes both nitrogen oxides and oxygen.

7. The method according to claim 6, wherein, The gas containing nitrogen oxides also includes at least one of nitrogen, water vapor, and carbon dioxide; Preferably, the volume concentration of oxygen in the gas containing nitrogen oxides is 0.1-50 vol%, more preferably 5-25 vol%. Preferably, the volume concentration of water vapor in the nitrogen oxide-containing gas is 0-30 vol%, more preferably 5-15 vol%.

8. The method according to claim 6 or 7, wherein, The volume concentration of nitrogen oxides in the gas containing nitrogen oxides is 1-1000 ppm, preferably 1-100 ppm; Preferably, the denitrification conditions include a denitrification temperature of 100-200℃.

9. The method according to any one of claims 6-8, wherein, The method further includes: regenerating the adsorbent to be regenerated after denitrification in the presence of a reducing atmosphere; Preferably, the reducing atmosphere includes inorganic reducing atmospheres and / or organic gaseous compounds; Preferably, the inorganic reducing atmosphere is at least one of H2 and / or CO.

10. The method according to claim 9, wherein, The regeneration conditions include: a regeneration temperature of 50-400℃, preferably 100-400℃; and a regeneration time of 0.5-72h, preferably 0.5-2h. Preferably, the volume concentration of H2 in the reducing atmosphere is 0.1-20 vol%.

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