Selective catalytic oxidation catalysts, methods of making and using the same
By preparing a mixture of Cu-based catalysts A and B, the problems of poor selectivity and NOx generation in the treatment of nitrogen-containing VOCs were solved, achieving high conversion rate and high N2 selectivity, which is suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2022-11-22
- Publication Date
- 2026-07-21
AI Technical Summary
Existing catalytic oxidation catalysts lack selectivity when treating nitrogen-containing VOCs, have narrow temperature windows, are prone to generating NOx, and suffer from problems such as high cost, complex processing technology, and difficulty in handling gases with complex compositions.
Catalysts A and B, containing Cu as the active component, and supported by a mixture of alumina, titanium dioxide, and cerium dioxide, were used to prepare selective catalytic oxidation catalysts with a Dv90 of 1-20 μm by mechanical grinding. The catalysts utilize the synergistic effect of Cu to oxidize nitrogen-containing VOCs to N2 and reduce NOx to N2 in situ.
It achieves high conversion rate and high N2 selectivity, produces almost no NOx, has a simple and low-cost catalyst preparation, is suitable for large-scale industrial production, and can handle complex gases with high oxygen and water vapor content.
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Figure CN118059932B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of volatile organic compound (VOC) treatment technology, specifically to a selective catalytic oxidation catalyst, its preparation method and application, and a method for treating nitrogen-containing VOCs. Background Technology
[0002] Volatile organic compounds (VOCs) are organic compounds with boiling points between 50-260℃ and saturated vapor pressures exceeding 133.3 Pa at room temperature. In terms of classification, VOCs mainly include aliphatic hydrocarbons, oxygen-containing hydrocarbons, aromatic hydrocarbons and their derivatives, and hydrocarbons containing heteroatoms (Cl, S, N, etc.). Nitrogen-containing VOCs belong to heteroatom-containing volatile organic compounds and mainly include amines, amides, nitriles, and nitro hydrocarbons. Nitrogen-containing VOCs often have a pungent or irritating odor and are more harmful to human health than conventional VOCs, and are also more difficult to treat.
[0003] For conventional VOCs, catalytic oxidation is currently the most common method for treatment, which can oxidize VOCs into non-toxic carbon dioxide and water. However, in the conventional catalytic oxidation process, the nitrogen in nitrogen-containing VOCs is converted into NO. x (NO, NO2 and N2O). NO x Nitrogenous VOCs are another major type of air pollutant, causing severe air pollution such as acid rain and smog. Therefore, the catalytic oxidation of nitrogen-containing VOCs often requires further treatment methods after conventional catalytic oxidation units to remove NO. x .
[0004] Currently, organic amines are frequently used as template agents or alkaline media in the production process of molecular sieves. For example, ethylenediamine is widely used in the synthesis of molecular sieves such as ZSM-5, ZSM-35, and MCM-41. During the degassing, drying, and calcination stages after molecular sieve crystallization, ethylenediamine is emitted into the tail gas. The presence of nitrogen-containing VOCs makes the clean treatment of the tail gas quite difficult.
[0005] Currently, the treatment of nitrogen-containing VOCs is receiving increasing attention. For example, Ma et al. (Catalysis Today, 2020, 339:181-191.) used different preparation methods (in-situ synthesis, wet impregnation, and grafting) to produce SiO2 with different specific surface areas (537m²). 2 / g and 1540m 2A Pd / SiO2 catalyst with a Pd loading of 0.3-0.5 wt% was prepared by in-situ synthesis and used for the catalytic oxidation of n-butylamine. The catalyst prepared on a high specific surface area using this method exhibits high n-butylamine oxidation activity (T90 of 240℃) and low NO content. x The yield was 0.99% at T90, while other catalysts showed higher NO yields. x Yield. The Pd / SiO2 catalyst prepared by in-situ synthesis involves a series of processes, including crystallization of Pd, silicon source, and template agent, calcination in an oxidizing atmosphere, and calcination in a reducing atmosphere. The preparation process is relatively complex, and the use of the precious metal Pd results in high raw material and preparation costs for the catalyst.
[0006] CN103212419A discloses a catalyst for treating acrylonitrile (C3H3N)-containing waste gas, its preparation method, and its application. The catalyst uses a perovskite crystal material with an ABO3 structure, and through specific reaction conditions, acrylonitrile is primarily converted into CO2, H2O, and N2. However, when the O2 content in the reaction atmosphere increases, the N2 selectivity of this catalyst decreases significantly, greatly limiting its application in treating waste gas with high O2 content.
[0007] Overall, existing catalytic oxidation catalysts lack selectivity in treating nitrogen-containing VOCs, have narrow temperature windows, and readily generate NO. x Furthermore, it suffers from problems such as high cost, complex processing technology, and difficulty in handling gases with complex compositions. Therefore, there is an urgent need to develop selective catalytic oxidation catalysts for nitrogen-containing VOCs. Summary of the Invention
[0008] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a selective catalytic oxidation catalyst, its preparation method, and its application. Using the selective catalytic oxidation catalyst provided by this invention, nitrogen-containing VOCs can be selectively catalytically oxidized, exhibiting both high conversion rate of nitrogen-containing VOCs and high N2 selectivity, while producing almost no NO during the process. x .
[0009] To achieve the above objectives, a first aspect of the present invention provides a selective catalytic oxidation catalyst, comprising catalyst A and catalyst B, wherein catalyst A comprises a first support and a first active component supported on the first support, and catalyst B comprises a second support and a second active component supported on the second support, wherein both the first and second active components contain Cu; the first support is one or more of alumina, titanium dioxide, cerium dioxide, zirconium dioxide, cerium oxide-zirconium oxide solid solution, and silica; the second support is one or more of ZSM-5 molecular sieve, SSZ-13 molecular sieve, β-type molecular sieve, SAPO-34 molecular sieve, and Y-type molecular sieve; the weight ratio of catalyst A to catalyst B is 1:0.2-5, and the Dv90 of the selective catalytic oxidation catalyst is 1-20 μm.
[0010] Preferably, the first active component is Cu.
[0011] Preferably, the second active component is Cu.
[0012] Preferably, the first carrier is cerium dioxide and / or cerium oxide-zirconia solid solution, more preferably cerium dioxide.
[0013] Preferably, the second carrier is a ZSM-5 molecular sieve and / or a β-type molecular sieve, more preferably a ZSM-5 molecular sieve.
[0014] Preferably, the weight ratio of catalyst A to catalyst B is 1:0.4-3, more preferably 1:0.5-2.
[0015] Preferably, the selective catalytic oxidation catalyst has a Dv90 of 3-15 μm, more preferably 3-10 μm.
[0016] Preferably, based on the total weight of catalyst A, the content of the first active component, expressed as elemental metal, is 0.5-20% by weight, more preferably 3-15% by weight, and even more preferably 5-10% by weight.
[0017] Preferably, based on the total weight of catalyst B, the content of the second active component, expressed as elemental metal, is 0.5-15% by weight, more preferably 3-10% by weight, and even more preferably 3-6% by weight.
[0018] A second aspect of the present invention provides a method for preparing the selective catalytic oxidation catalyst described in the first aspect of the present invention, the method comprising the step of mechanically grinding the catalyst A and the catalyst B.
[0019] Preferably, the mechanical grinding is performed using one or more of dry ball milling, dry rod milling, air jet milling, and impact milling, with dry ball milling being more preferred.
[0020] Preferably, the ball milling time is 0.5-24 hours.
[0021] Preferably, the mechanical milling results in a Dv90 of 1-20 μm for the selective catalytic oxidation catalyst, more preferably 3-15 μm, and even more preferably 3-10 μm.
[0022] The third aspect of the present invention provides the application of the selective catalytic oxidation catalyst described in the first aspect of the present invention in the treatment of nitrogen-containing VOCs.
[0023] Preferably, the nitrogen-containing VOCs are one or more of ethylenediamine, n-butylamine, ethanolamine, diethylamine, and triethylamine, and more preferably ethylenediamine.
[0024] The fourth aspect of the present invention provides a method for treating nitrogen-containing VOCs in a gas, the method comprising: contacting the gas to be treated with the selective catalytic oxidation catalyst described in the first aspect of the present invention.
[0025] Preferably, the nitrogen-containing VOCs are one or more of ethylenediamine, n-butylamine, ethanolamine, diethylamine, and triethylamine, more preferably ethylenediamine.
[0026] Preferably, the concentration of nitrogen-containing VOCs in the gas to be treated is 10-10,000 ppm, more preferably 100-5,000 ppm.
[0027] Preferably, the contact conditions include: a contact temperature of 225-550°C and a volume hourly space velocity of 2,000-300,000 h⁻¹. -1 The flow rate of the gas to be treated is 100-5,000 mL / min; more preferably, the contact conditions include: a contact temperature of 250-450°C and a volume hourly space velocity of 5,000-150,000 h⁻¹. -1 The flow rate of the gas to be treated is 200-3,000 mL / min.
[0028] Preferably, the contact results in a conversion rate of nitrogen-containing VOCs of 95% or higher, more preferably 98% or higher.
[0029] Preferably, the contact results in an N2 selectivity of 95% or more, more preferably 98% or more.
[0030] In the selective catalytic oxidation catalyst of this invention, the presence of catalyst A containing Cu and a first support enables efficient oxidation of nitrogen-containing VOCs during the catalytic oxidation process. Simultaneously, through the synergistic effect of catalyst B containing Cu and a second support, nitrogen-containing VOCs are further catalytically oxidized. Furthermore, the NO generated during the reaction can be neutralized by the VOCs themselves or by NH3 and hydrocarbon fragments produced during the cracking process. x In-situ reduction is performed to convert it into N2, thereby ensuring that the final processed product does not contain NO. x This allows the selective catalytic oxidation catalyst of the present invention to possess both high conversion rate of nitrogen-containing VOCs and high N2 selectivity.
[0031] Furthermore, in the selective catalytic oxidation catalyst of the present invention, by selecting a specific Dv90 and the weight ratio of catalyst A to catalyst B, the number and relative distance of active sites in catalyst A and catalyst B can be controlled. This allows different active sites to perform their independent functions without interfering with each other, while maintaining an optimal relative distribution to exert a synergistic effect, thereby reducing the NO generated during the catalytic process. x It can be rapidly and selectively catalytically reduced in the vicinity, thus ensuring NO x It can be promptly restored to N2.
[0032] On the other hand, the catalyst preparation method of the present invention is simple and low in cost, making it particularly suitable for large-scale industrial production. Furthermore, the catalyst has a low oxidation temperature for reactants, is resistant to high temperatures, tolerates H2O and O2 in the atmosphere, and has good stability. It exhibits excellent selective catalytic oxidation activity for nitrogen-containing VOCs, such as ethylenediamine, n-butylamine, ethanolamine, diethylamine, and triethylamine, and has good industrial applicability. Attached Figure Description
[0033] Figure 1 The curves show the ethylenediamine conversion rate as a function of temperature for the selective catalytic oxidation catalysts prepared in Example 1 and Comparative Examples 1-4.
[0034] Figure 2 The curves show the N2 selectivity as a function of temperature for the selective catalytic oxidation catalysts prepared in Example 1 and Comparative Examples 1-4.
[0035] Figure 3 This is a curve showing the change in ethylenediamine conversion rate over time for the selective catalytic oxidation catalyst prepared in Example 1;
[0036] Figure 4 This is the curve showing the change in N2 selectivity over time for the selective catalytic oxidation catalyst prepared in Example 1. Detailed Implementation
[0037] 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.
[0038] In this invention, Dv90 refers to the particle size corresponding to the cumulative particle size distribution of the sample reaching 90%, and its specific value can be determined by laser particle size distribution method.
[0039] The first aspect of this invention provides a selective catalytic oxidation catalyst, wherein the selective catalytic oxidation catalyst comprises catalyst A and catalyst B, catalyst A comprises a first support and a first active component supported on the first support, and catalyst B comprises a second support and a second active component supported on the second support, wherein both the first active component and the second active component contain Cu; the first support is one or more of alumina, titanium dioxide, cerium dioxide, zirconium dioxide, cerium oxide-zirconium oxide solid solution, and silica; the second support is one or more of ZSM-5 molecular sieve, SSZ-13 molecular sieve, β-type molecular sieve, SAPO-34 molecular sieve, and Y-type molecular sieve; the weight ratio of catalyst A to catalyst B is 1:0.2-5, and the Dv90 of the selective catalytic oxidation catalyst is 1-20 μm.
[0040] The inventors of this invention unexpectedly discovered during their research that when catalyst A, containing Cu as an active component and supported by one or more of alumina, titanium dioxide, cerium dioxide, zirconium dioxide, cerium oxide-zirconia solid solution, and silica, and catalyst B, containing Cu as an active component and supported by one or more of ZSM-5 molecular sieves, SSZ-13 molecular sieves, β-type molecular sieves, SAPO-34 molecular sieves, and Y-type molecular sieves, are mixed in a specific ratio, and the particle size of the mixture is controlled within the range of Dv90 of 1-20 μm, the resulting new catalyst, when used for the treatment of nitrogen-containing VOCs, can selectively catalytically oxidize nitrogen in nitrogen-containing VOCs to N2, with almost no NO emission. x Furthermore, the selective catalytic oxidation catalyst obtained thereby exhibits excellent catalytic activity and a wide temperature window.
[0041] The selective catalytic oxidation catalyst of the present invention will now be described in detail.
[0042] As described above, the selective catalytic oxidation catalyst of the present invention contains catalyst A and catalyst B, wherein catalyst A is a supported catalyst containing a first support and a first active component supported on the first support.
[0043] The first support is one or more of alumina, titanium dioxide, cerium dioxide, zirconium dioxide, cerium oxide-zirconia solid solution, and silicon dioxide. In order to better synergize with the first active component and thereby further improve the catalytic performance of the selective catalyst of the present invention and increase the conversion rate of nitrogen-containing VOCs, preferably, the first support is cerium dioxide and / or cerium oxide-zirconia solid solution.
[0044] In a particularly preferred embodiment of the present invention, the first carrier is cerium dioxide, which can significantly improve the conversion rate of nitrogen-containing VOCs while ensuring that the N2 selectivity is at a high level.
[0045] Furthermore, in catalyst A, the first active component contains Cu, preferably Cu. The inventors of this invention have discovered that Cu dispersed on the surface of the first support, especially on the surface of cerium dioxide, exhibits high catalytic oxidation activity, enabling more efficient oxidation of nitrogen-containing VOCs.
[0046] In addition, the content of the first active component in catalyst A can vary within a wide range. For example, based on the total weight of catalyst A, the content of the first active component, expressed as elemental metal, is 0.5-20% by weight, preferably 3-15% by weight, and more preferably 5-10% by weight.
[0047] When the content of the first active component is controlled within the above range, the performance of the selective catalytic oxidation catalyst can be further guaranteed, and the conversion rate of nitrogen-containing VOCs and N2 selectivity can be significantly improved.
[0048] On the other hand, catalyst B is also a supported catalyst, containing a second support and a second active component supported on the second support.
[0049] In catalyst B, the second support is one or more of ZSM-5 molecular sieve, SSZ-13 molecular sieve, β-type molecular sieve, SAPO-34 molecular sieve, and Y-type molecular sieve, preferably ZSM-5 molecular sieve and / or β-type molecular sieve. This allows for better synergistic interaction with the second active component and ensures the synergistic effect between catalyst B and catalyst A, thereby further improving the catalytic performance of the catalyst described in this invention, increasing the conversion rate of nitrogen-containing VOCs and the N2 selectivity.
[0050] In a particularly preferred embodiment of the present invention, the second carrier is a ZSM-5 molecular sieve, which can further significantly improve the conversion rate of nitrogen-containing VOCs and the N2 selectivity.
[0051] Furthermore, in catalyst B, the second active component contains Cu, and preferably, the second active component is Cu. By supporting Cu on the second support to obtain catalyst B, and mixing it with catalyst A, NO obtained from the oxidation of catalyst A can be oxidized through the synergistic effect of specific active sites. x The nitrogen is reduced to N2, thus avoiding the production of NO during the catalytic process. x It is very suitable for industrial production.
[0052] Furthermore, in catalyst B, based on the total weight of catalyst B and calculated as elemental metal, the content of the second active component can be 0.5-15% by weight, preferably 3-10% by weight, and more preferably 3-6% by weight. When the content of the second active component is controlled within the above range, the performance of the selective catalytic oxidation catalyst can be further guaranteed, and the N2 selectivity can be significantly improved while ensuring the conversion rate of nitrogen-containing VOCs.
[0053] On the other hand, in this invention, the weight ratio of catalyst A to catalyst B can be 1:0.2-5, specifically 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.
[0054] Preferably, the weight ratio of catalyst A to catalyst B is 1:0.4-3, more preferably 1:0.5-2. This allows for better synergistic effects between catalysts A and B, thereby further improving the conversion rate of nitrogen-containing VOCs and the N2 selectivity.
[0055] Furthermore, the particle size distribution of the selective catalytic oxidation catalyst plays a crucial role in the distribution of active sites. In this invention, the Dv90 of the selective catalytic oxidation catalyst is 1-20 μm. Specifically, the Dv90 of the selective catalytic oxidation catalyst can be, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, ... 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm m, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, 20μm, etc.
[0056] Preferably, the Dv90 of the selective catalytic oxidation catalyst is 3-15 μm, more preferably 3-10 μm. This allows for better control of the active sites of the catalyst, further improving the conversion rate of nitrogen-containing VOCs and the N2 selectivity of the selective catalytic oxidation catalyst.
[0057] According to a first aspect of the present invention, the selective catalytic oxidation catalyst does not require conventional and expensive precious metals such as Pd and Pt. It only requires catalyst A and catalyst B containing Cu as active components. By selecting a specific support and controlling the weight ratio of catalyst A and B and the Dv90 of the selective catalytic oxidation catalyst within the range of 1-20 μm, the active sites can be regulated. This allows different active sites to not only play their respective roles efficiently but also to synergize with each other, thereby exhibiting excellent nitrogen-containing VOCs conversion rate and N2 selectivity. It is very suitable for the treatment of nitrogen-containing VOCs, especially for the treatment of ethylenediamine.
[0058] In a particularly preferred embodiment of the present invention, the selective catalytic oxidation catalyst is a mixture of catalyst A and catalyst B, wherein the support of catalyst A is cerium dioxide and the active component is Cu, and the support of catalyst B is ZSM-5 molecular sieve and the active component is Cu. Such a selective catalytic oxidation catalyst exhibits excellent conversion rates of nitrogen-containing VOCs and N2 selectivity, a wide temperature window, and high-temperature resistance, making it highly suitable for the treatment of nitrogen-containing VOCs, especially for the treatment of ethylenediamine.
[0059] A second aspect of the present invention provides a method for preparing the selective catalytic oxidation catalyst described in the first aspect of the present invention, the method comprising the step of mechanically grinding the catalyst A and the catalyst B.
[0060] According to a second aspect of the present invention, catalyst A can be prepared according to conventional methods for preparing supported catalysts, and preferably, catalyst A is prepared according to the following method:
[0061] 1) Impregnate the first carrier with a first impregnation solution containing the first active component precursor;
[0062] 2) The impregnated product is subjected to a first drying and a first roasting treatment in sequence.
[0063] The selection of the first active component and the first carrier is consistent with that described in the first aspect of the present invention, and will not be repeated here.
[0064] According to a second aspect of the present invention, the first active component is preferably Cu. In this case, the first active component precursor is preferably selected from one or more of copper chloride, copper nitrate, copper sulfate, copper acetate and their corresponding crystalline hydrates, more preferably one or more of copper nitrate, copper acetate and their corresponding crystalline hydrates; and even more preferably one or more of copper nitrate and their corresponding crystalline hydrates.
[0065] According to the present invention, the conditions for the first drying are not particularly limited and can be conventionally selected in the art. For example, the conditions for the first drying may include: a temperature of 80-120°C and a time of 4-48 hours. Preferably, the conditions for the first drying may include: a temperature of 100-120°C and a time of 8-24 hours.
[0066] In this invention, the conditions for the first roasting are not particularly limited and can be conventional choices in the art. In this invention, the conditions for the first roasting may include: a temperature of 300-800℃ and a time of 2-24h, preferably a temperature of 400-600℃ and a time of 4-8h.
[0067] According to a second aspect of the present invention, the catalyst B can be prepared according to conventional methods for preparing supported catalysts, and preferably, the catalyst B is prepared according to the following method:
[0068] 1) Impregnate the second carrier with the second impregnation solution containing the second active component precursor;
[0069] 2) The impregnated product is subjected to a second drying treatment and a second calcination treatment in sequence.
[0070] The selection of the second active component and the second carrier is consistent with that described in the first aspect of the present invention, and will not be repeated here.
[0071] According to a second aspect of the present invention, the second active component is preferably Cu. In this case, the precursor of the second active component is preferably selected from one or more of copper chloride, copper nitrate, copper sulfate, copper acetate and their corresponding crystalline hydrates, more preferably one or more of copper nitrate, copper acetate and their corresponding crystalline hydrates; and even more preferably one or more of copper nitrate and their corresponding crystalline hydrates.
[0072] According to the present invention, the conditions for the first drying are not particularly limited and can be conventionally selected in the art. For example, the conditions for the first drying may include: a temperature of 80-120°C and a time of 4-48 hours. Preferably, the conditions for the first drying may include: a temperature of 100-120°C and a time of 8-24 hours.
[0073] In this invention, the conditions for the second calcination are not particularly limited and can be conventional choices in the art. In this invention, the conditions for the second calcination may include: a temperature of 300-800℃ and a time of 2-24h, preferably a temperature of 400-600℃ and a time of 4-8h.
[0074] Furthermore, according to a second aspect of the present invention, the selective catalytic oxidation catalyst is prepared by mechanically grinding the catalyst A and the catalyst B.
[0075] In addition, in order to control the Dv90 of the selective catalytic oxidation catalyst to be 1-20 μm, catalyst A and catalyst B can be mechanically ground separately and then mixed to obtain a Dv90 of 1-20 μm for the mixed catalytic oxidation catalyst; alternatively, mechanical grinding can be performed simultaneously during the mixing process to obtain a Dv90 of 1-20 μm for the obtained catalytic oxidation catalyst.
[0076] Furthermore, the specific method of mechanical grinding in this invention is not particularly limited, as long as the above-mentioned objective can be achieved. For example, one or more of the following methods can be used: dry ball milling, dry rod milling, air jet milling, and impact milling. Preferably, the mechanical grinding is performed using dry ball milling.
[0077] There are no particular restrictions on the specific operation of the dry ball milling, as long as the Dv90 of catalyst A and catalyst B after ball milling is 1-20 μm, preferably 3-15 μm, and more preferably 3-10 μm.
[0078] For example, the ball milling can be carried out using a UBE-V2 / 4L planetary ball mill from Changsha Deco Instrument Equipment Co., Ltd., using zirconia ceramic balls with a particle size of 2-5mm as grinding balls, and the weight ratio of grinding balls to catalyst can be 3-6:1, and the ball milling time can be 0.5-24h.
[0079] Furthermore, in this invention, when mechanically grinding catalyst A and catalyst B, the weight ratio of catalyst A to catalyst B is such that the prepared catalytic oxidation catalyst meets the requirements described in the first aspect of this invention, which will not be described separately here.
[0080] The third aspect of the present invention provides the application of the selective catalytic oxidation catalyst described in the first aspect of the present invention in the treatment of nitrogen-containing VOCs.
[0081] When the selective catalytic oxidation catalyst described in the first aspect of this invention is applied to the treatment of nitrogen-containing VOCs, the synergistic effect of the first and second active components at specific sites can prevent NO from being oxidized. x The generation of this process allows for the selective in-situ reduction of intermediate products to N2 while simultaneously oxidizing nitrogen-containing VOCs. This avoids the need for further NO removal after oxidation, as is required in conventional technologies for treating nitrogen-containing VOCs. x The emission problem is greatly reduced, and the complexity of the treatment process is significantly reduced. Furthermore, the catalytic oxidation catalyst provided by this invention can achieve a conversion rate of over 95% for nitrogen-containing VOCs, preferably over 98%; at the same time, the selectivity for N2 can reach over 95%, preferably over 98%, demonstrating excellent performance.
[0082] In addition, the catalyst described in this invention has a wide temperature window, enabling it to be applied to the treatment of complex gases with high oxygen and water vapor content, making it very suitable for industrial applications.
[0083] A fourth aspect of the present invention provides a method for treating nitrogen-containing VOCs in a gas, wherein the method includes: contacting the gas to be treated with the selective catalytic oxidation catalyst described in the first aspect of the present invention.
[0084] In this invention, there is no particular limitation on the nitrogen-containing VOCs, which can be various nitrogen-containing VOCs commonly found in the art. For example, the nitrogen-containing VOCs can be one or more of ethylenediamine, n-butylamine, ethanolamine, diethylamine, and triethylamine. Preferably, the nitrogen-containing VOCs are ethylenediamine.
[0085] In addition, the concentration of nitrogen-containing VOCs in the gas to be treated is not particularly limited in this invention. For example, it can be 10-10,000 ppm, preferably 20-5,000 ppm, and more preferably 100-5,000 ppm.
[0086] In this invention, there is no particular limitation on the location of the contact; any conventional choice in the art can be made. Preferably, the contact takes place within a fixed-bed reactor.
[0087] Furthermore, there are no particular limitations on the contact conditions. Preferably, the contact conditions include: a contact temperature of 225-550°C and a volume hourly space velocity of 2,000-300,000 h⁻¹. -1 The flow rate of the gas to be treated is 100-5,000 mL / min; more preferably, the contact conditions include: a contact temperature of 250-450°C and a volume hourly space velocity of 5,000-150,000 h⁻¹. -1 The flow rate of the gas to be treated is 200-3,000 mL / min.
[0088] By conducting the contact under the above conditions, the conversion rate of nitrogen-containing VOCs and the selectivity of N2 can be further improved.
[0089] According to a fourth aspect of the present invention, by contacting a gas to be treated containing nitrogen-containing VOCs with the catalyst described in the first aspect of the present invention, the nitrogen-containing VOCs in the gas can be oxidized to produce NO. x And immediately cause the generated NO x It is further reduced to N2 in situ without emitting NO. x .
[0090] Furthermore, the method described in the fourth aspect of the present invention can be used to treat gases containing nitrogen-containing VOCs, such that the conversion rate of nitrogen-containing VOCs is 95% or more, preferably 98% or more.
[0091] Furthermore, the method described in the fourth aspect of the present invention can achieve a N2 selectivity of 95% or more, preferably 98% or more, in a gas containing nitrogen-containing VOCs after oxidation.
[0092] The present invention will be described in detail below through embodiments, but the present invention is not limited to the following embodiments.
[0093] In the following examples, unless otherwise specified, all raw materials used are commercially available products or prepared using conventional methods.
[0094] In the following examples and comparative examples, the ball milling was carried out using a UBE-V2 / 4L planetary ball mill from Changsha Deco Instrument Equipment Co., Ltd., with zirconia ceramic balls of 2-5 mm particle size as grinding balls, and the weight ratio of grinding balls to catalyst was 4:1.
[0095] In the following examples and comparative examples, Dv90 was determined using the laser particle size distribution method (using a Malvern Mastersizer 3000 laser particle size analyzer).
[0096] Example 1
[0097] 1) Add 20.28g of copper nitrate trihydrate to 200g of deionized water and stir until the copper nitrate trihydrate is fully dissolved. Then mix it with 100g of cerium dioxide support, stir and impregnate at 25℃ for 60min, heat at 90℃ for 120min, transfer it to a forced-air drying oven and dry at 110℃ for 12h, then calcine at 550℃ in a muffle furnace for 5h. After natural cooling, catalyst A1 is obtained. The Dv90 of the obtained catalyst A1 is 101.2μm and the copper content is 5% by weight.
[0098] 2) Add 20.28g of copper nitrate trihydrate to 200g of deionized water and stir until the copper nitrate trihydrate is fully dissolved. Then mix it with 100g of ZSM-5 molecular sieve support, stir and impregnate at 25℃ for 60min, heat at 90℃ for 120min, transfer it to a forced-air drying oven and dry at 110℃ for 12h, then calcine at 550℃ in a muffle furnace for 5h. After natural cooling, catalyst B1 is obtained. The Dv90 of the obtained catalyst B1 is 80.8μm and the copper content is 5% by weight.
[0099] Steps 1) and 2) do not have a specific order;
[0100] 3) Catalyst A1 and catalyst B1 were loaded into a ball mill jar at a weight ratio of 1:0.5 and dry-milled for 5 hours to obtain selective catalytic oxidation catalyst C1 with a Dv90 of 9.7 μm.
[0101] Example 2
[0102] 1) Add 33.81g of copper nitrate trihydrate to 200g of deionized water and stir until the copper nitrate trihydrate is fully dissolved. Then mix it with 100g of cerium dioxide support, stir and impregnate at 25℃ for 60min, heat at 90℃ for 120min, transfer it to a forced-air drying oven and dry at 110℃ for 12h, then calcine at 550℃ in a muffle furnace for 5h. After natural cooling, catalyst A2 is obtained. The Dv90 of the obtained catalyst A2 is 105.3μm and the copper content is 8% by weight.
[0103] 2) Add 11.86g of copper nitrate trihydrate to 200g of deionized water, stir until the copper nitrate trihydrate is fully dissolved, mix it with 100g of ZSM-5 molecular sieve support, stir and impregnate at 25℃ for 60min, heat at 90℃ for 120min, transfer to a forced-air drying oven and dry at 110℃ for 12h, then calcine at 550℃ in a muffle furnace for 5h, and obtain catalyst B2 after natural cooling. The obtained catalyst B2 has a Dv90 of 73.5μm and a copper content of 3% by weight.
[0104] Steps 1) and 2) do not have a specific order;
[0105] 3) Catalyst A2 and catalyst B2 were loaded into a ball mill jar at a weight ratio of 1:1 and dry-milled for 5 hours to obtain selective catalytic oxidation catalyst C2 with a Dv90 of 8.7 μm.
[0106] Example 3
[0107] 1) Add 43.49g of copper nitrate trihydrate to 200g of deionized water and stir until the copper nitrate trihydrate is fully dissolved. Then mix it with 100g of cerium dioxide support, stir and impregnate at 25℃ for 60min, heat at 90℃ for 120min, transfer it to a forced-air drying oven and dry at 110℃ for 12h, then calcine at 550℃ in a muffle furnace for 5h. After natural cooling, catalyst A3 is obtained. The Dv90 of the obtained catalyst A3 is 105.3μm and the copper content is 10% by weight.
[0108] 2) Add 24.67g of copper nitrate trihydrate to 200g of deionized water and stir until the copper nitrate trihydrate is fully dissolved. Then mix it with 100g of ZSM-5 molecular sieve support, stir and impregnate at 25℃ for 60min, heat at 90℃ for 120min, transfer it to a forced-air drying oven and dry at 110℃ for 12h, then calcine at 550℃ in a muffle furnace for 5h. After natural cooling, catalyst B3 is obtained. The Dv90 of the obtained catalyst B3 is 87.1μm and the copper content is 6% by weight.
[0109] Steps 1) and 2) do not have a specific order;
[0110] 3) Catalyst A3 and catalyst B3 were loaded into a ball mill jar at a weight ratio of 1:2 and dry ball milled for 5 hours to obtain selective catalytic oxidation catalyst C3 with a Dv90 of 8.3 μm.
[0111] Example 4
[0112] The procedure is carried out according to the method of Example 1, except that...
[0113] In step 3), the weight ratio of catalyst A1 and catalyst B1 is 1:1 to obtain selective catalytic oxidation catalyst C4 with a Dv90 of 9.4 μm.
[0114] Example 5
[0115] The procedure is carried out according to the method of Example 1, except that...
[0116] In step 1), the cerium dioxide support is replaced with an equal weight of cerium oxide-zirconia solid solution to obtain catalyst A5.
[0117] The obtained catalyst A5 has a Dv90 of 97.8 μm;
[0118] In step 3), catalyst A1 is replaced with an equal weight of catalyst A5 to obtain selective catalytic oxidation catalyst C5, which has a Dv90 of 9.5 μm.
[0119] Example 6
[0120] The procedure is carried out according to the method of Example 1, except that...
[0121] In step 2), the ZSM-5 molecular sieve is replaced with an equal weight of β molecular sieve to obtain catalyst B6.
[0122] The obtained catalyst B6 has a Dv90 of 78 μm;
[0123] In step 3), catalyst B1 is replaced with an equal weight of catalyst B6 to obtain selective catalytic oxidation catalyst C6, which has a Dv90 of 9.6 μm.
[0124] Example 7
[0125] The procedure is carried out according to the method of Example 1, except that...
[0126] In step 2), 43.47g of copper nitrate trihydrate is added to 200g of deionized water.
[0127] Catalyst B7 was obtained, with a Dv90 of 105.3 μm and a copper content of 10% by weight.
[0128] In step 3), catalyst B1 is replaced with an equal weight of catalyst B7 to obtain selective catalytic oxidation catalyst C7, which has a Dv90 of 9.8 μm.
[0129] Example 8
[0130] The procedure is carried out according to the method of Example 1, except that...
[0131] In step 3), the weight ratio of catalysts A1 and B1 is 1:5 to obtain selective catalytic oxidation catalyst C8 with a Dv90 of 8.1 μm.
[0132] Example 9
[0133] The procedure is carried out according to the method of Example 1, except that...
[0134] In step 3), the weight ratio of catalyst A1 to B1 is 1:0.2, resulting in selective catalytic oxidation catalyst C9 with a Dv90 of 9.9 μm.
[0135] Example 10
[0136] The procedure is carried out according to the method of Example 1, except that...
[0137] In step 3), dry ball milling for 2 hours yields a selective catalytic oxidation catalyst C10 with a Dv90 of 16.8 μm.
[0138] Example 11
[0139] The procedure is carried out according to the method of Example 1, except that...
[0140] In step 3), dry ball milling for 24 hours yields a selective catalytic oxidation catalyst C11 with a Dv90 of 3.5 μm.
[0141] Comparative Example 1
[0142] The catalyst A1 prepared in step 1) of Example 1 was used as catalyst D1.
[0143] Comparative Example 2
[0144] Catalyst B1 prepared in step 2) of Example 1 was used as catalyst D2.
[0145] Comparative Example 3
[0146] The procedure was carried out according to Example 1, except that catalysts A1 and B1 were not mixed and ball-milled; A1 and B1 were used directly for the tests described later.
[0147] Comparative Example 4
[0148] The procedure is carried out according to the method of Example 1, except that...
[0149] In step 3), instead of ball milling catalyst A1 and catalyst B1, the two catalyst powders are thoroughly mixed by stirring with a spatula for 1 hour to obtain catalyst D4. The Dv90 of the obtained catalyst D4 is 75.5 μm.
[0150] Comparative Example 5
[0151] The procedure is carried out according to the method of Example 1, except that...
[0152] In step 3), the weight ratio of catalyst A1 to B1 is 1:10 to obtain catalyst D5, and the Dv90 of the obtained catalyst D5 is 8.6 μm.
[0153] Comparative Example 6
[0154] The procedure is the same as in Implementation 1, except that...
[0155] In step 1), 35.09 g of palladium nitrate solution (calculated as palladium, with a palladium content of 15% by weight) was added to 200 g of deionized water and stirred evenly to obtain an impregnation solution. This solution was then mixed with 100 g of cerium dioxide support for subsequent operations to obtain catalyst A'6. The obtained catalyst A'6 has a Dv90 of 98.4 μm and a palladium content of 5% by weight.
[0156] 2) Add 35.09g of palladium nitrate solution (calculated as elemental palladium, palladium content is 15% by weight) to 200g of deionized water, stir evenly to obtain impregnation solution, mix it with 100g of ZSM-5 molecular sieve support for subsequent operations to obtain catalyst B'6. The obtained catalyst B'6 has a Dv90 of 85.6μm and a palladium content of 5% by weight.
[0157] 3) Catalyst A'6 and catalyst B'6 were loaded into a ball mill jar at a weight ratio of 1:0.5 and dry-milled for 5 hours to obtain catalyst D6 with a Dv90 of 9.2 μm.
[0158] Test Example 1
[0159] Before conducting activity tests, the powdered catalyst was granulated and sieved to obtain catalyst particles of 60-80 mesh, ensuring that the reactant gas could flow normally through the catalyst bed. 200 mg of the 60-80 mesh granulated samples of the catalysts prepared in Examples 1-11, Comparative Examples 1-2, and Comparative Examples 4-6 were placed in a quartz tube with an inner diameter of 5 mm. 200 mg of the 60-80 mesh granulated samples of catalysts A1 and B1 from Comparative Example 3 were loaded into a fixed bed in two sections at a weight ratio of 2:1, with the reactant gas flowing first through catalyst A1 and then through catalyst B1.
[0160] A gas to be treated is introduced, which contains 0.2 vol% ethylenediamine, 20 vol% oxygen, 5 vol% water vapor, and the balance nitrogen. The total flow rate of the gas to be treated is 1,000 mL / min, and the space velocity is 150,000 h⁻¹. -1 The temperature of the catalyst reaction bed was controlled by adjusting the furnace temperature. An isothermal reaction activity test was conducted under atmospheric pressure, with the reaction stabilized at each temperature point for 20 minutes. The tail gas products were detected using a gas chromatograph and an infrared gas analyzer. The concentrations of ethylenediamine and NO in the reaction products were used to determine the optimal reaction conditions. x The ethylenediamine conversion rate and N2 selectivity were calculated based on the concentration of NH3. The ethylenediamine conversion rate was calculated according to formula (1), and the N2 selectivity was calculated according to formula (2).
[0161]
[0162]
[0163] The reaction temperatures and N2 selectivity at which ethylenediamine conversions were 50% (T50), 90% (T90), and 99% (T99) are shown in Table 1.
[0164] All catalysts can achieve complete oxidation of ethylenediamine at 450℃, and the N2 selectivity of each catalyst at 450℃ is shown in Table 1.
[0165] Table 1
[0166]
[0167] As shown in Table 1, compared with Comparative Examples 1-6, the selective catalytic oxidation catalysts in Examples 1-11 provided by the invention have significantly better overall performance. The ethylenediamine conversion rate and N2 selectivity are both at a high level, and the catalysts have strong high temperature resistance, making them more suitable for the treatment of nitrogen-containing VOCs.
[0168] Specifically, compared with selective catalytic oxidation catalysts D2 and D5, selective catalytic oxidation catalysts C1-C11 have significantly better catalytic activity. The T50, T90, and T99 values of the catalyst for converting ethylenediamine are lower, and the conversion of ethylenediamine can be achieved at a lower temperature, indicating that catalysts A and B in the selective catalytic oxidation catalyst have a good synergistic effect in terms of oxidation performance.
[0169] Meanwhile, compared with selective catalytic oxidation catalysts D1 and D3, selective catalytic oxidation catalysts C1-C11 have better N2 selectivity, and their N2 selectivity at 450℃ is significantly higher than that of catalysts D1 and D3, indicating that catalysts A and B in the selective catalytic oxidation catalysts have a significant synergistic effect in improving N2 selectivity.
[0170] Furthermore, through Figure 1 and Figure 2 Comparing the ethylenediamine conversion rate and N2 selectivity of selective catalytic oxidation catalyst C1 and selective catalytic oxidation catalysts D1-D4 in the temperature range of 180-560℃, it can be seen that selective catalytic oxidation catalyst C1 has both good catalytic activity and N2 selectivity throughout the entire temperature range, and its overall performance is significantly better than that of the comparative example.
[0171] Furthermore, as demonstrated by the test results of Examples 1 and 5-6 in this invention, by selecting cerium dioxide as the first support and ZSM-5 molecular sieve as the second support, the catalytic activity of the prepared selective catalytic oxidation catalyst can be further improved.
[0172] Furthermore, the test results of Examples 1 and 7 show that by controlling the content of the second active component to be 3-6% by weight, the N2 selectivity of the obtained selective catalytic oxidation catalyst can be further improved, resulting in a selective catalytic oxidation catalyst with better overall performance.
[0173] Furthermore, as can be seen from Examples 1 and 8-9, by controlling the weight ratio of catalysts A1 and B1 within the range of 1:0.5-2, a selective catalytic oxidation catalyst with both good catalytic activity and N2 selectivity can be obtained.
[0174] Furthermore, the results of Examples 1 and 10-11 show that by controlling the Dv90 of the selective catalytic oxidation catalyst to 3-10 μm, the ethylenediamine conversion rate and N2 selectivity of the catalyst can be further improved, resulting in a selective catalytic oxidation catalyst with superior performance.
[0175] Test Example 2
[0176] Following the method described in Test Example 1, the selective catalytic oxidation catalyst C1 obtained in Example 1 was subjected to a long-term activity test at 350°C. The conversion rate of ethylenediamine and the N2 selectivity were as follows: Figure 3 and Figure 4 As shown.
[0177] Depend on Figure 3 and Figure 4 It can be seen that after 100 hours of testing, the ethylenediamine conversion rate and N2 selectivity of the selective catalytic oxidation catalyst remained above 99%, indicating that even after long-term use, it still has excellent catalytic performance, long catalyst life, and is very suitable for industrial production.
[0178] 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 selective catalytic oxidation catalyst, characterized in that, The selective catalytic oxidation catalyst comprises catalyst A and catalyst B, wherein catalyst A comprises a first support and a first active component supported on the first support, and catalyst B comprises a second support and a second active component supported on the second support. Both the first active component and the second active component contain Cu; The first carrier is one or more of alumina, titanium dioxide, cerium dioxide, zirconium dioxide, cerium oxide-zirconium oxide solid solution, and silicon dioxide; The second carrier is one or more of ZSM-5 molecular sieve, SSZ-13 molecular sieve, β-type molecular sieve, SAPO-34 molecular sieve and Y-type molecular sieve; The weight ratio of catalyst A to catalyst B is 1:0.2-5. The selective catalytic oxidation catalyst has a Dv90 of 1-20 μm.
2. The selective catalytic oxidation catalyst according to claim 1, wherein, The first active component is Cu.
3. The selective catalytic oxidation catalyst according to claim 1, wherein, The second active component is Cu.
4. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The first carrier is cerium dioxide and / or cerium oxide-zirconia solid solution.
5. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The first carrier is cerium dioxide.
6. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The second carrier is a ZSM-5 molecular sieve and / or a β-type molecular sieve.
7. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The second carrier is a ZSM-5 molecular sieve.
8. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The weight ratio of catalyst A to catalyst B is 1:0.4-3.
9. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The weight ratio of catalyst A to catalyst B is 1:0.5-2.
10. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The selective catalytic oxidation catalyst has a Dv90 of 3-15 μm.
11. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, The selective catalytic oxidation catalyst has a Dv90 of 3-10 μm.
12. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, Based on the total weight of catalyst A, the content of the first active component, expressed as elemental metal, is 0.5-20% by weight.
13. The selective catalytic oxidation catalyst according to any one of claims 1-3, wherein, Based on the total weight of catalyst B, the content of the second active component, expressed as elemental metal, is 0.5-15% by weight.
14. A method for preparing the selective catalytic oxidation catalyst according to any one of claims 1-13, characterized in that, The method includes the step of mechanically grinding the catalyst A and the catalyst B.
15. The preparation method according to claim 14, wherein, The mechanical grinding is carried out using one or more of the following methods: dry ball milling, dry rod milling, air jet milling, and impact milling.
16. The preparation method according to claim 14, wherein, The mechanical milling process results in a Dv90 of 1-20 μm for the selective catalytic oxidation catalyst.
17. The use of the selective catalytic oxidation catalyst according to any one of claims 1-13 in the treatment of nitrogen-containing VOCs.
18. The application according to claim 17, wherein, The nitrogen-containing VOCs are one or more of ethylenediamine, n-butylamine, ethanolamine, diethylamine, and triethylamine.
19. A method for treating nitrogen-containing VOCs in a gas, characterized in that, The method includes contacting the gas to be treated with the selective catalytic oxidation catalyst according to any one of claims 1-13.
20. The processing method according to claim 19, wherein, The nitrogen-containing VOCs are one or more selected from ethylenediamine, n-butylamine, ethanolamine, diethylamine, and triethylamine; The concentration of nitrogen-containing VOCs in the gas to be treated is 10-10,000 ppm.
21. The processing method according to claim 19, wherein, The contact conditions include: a contact temperature of 225-550°C and a volume hourly space velocity of 2,000-300,000 h⁻¹. -1 The flow rate of the gas to be treated is 100-5,000 mL / min.
22. The processing method according to any one of claims 19-21, wherein, The contact process results in a conversion rate of over 95% for nitrogen-containing VOCs.
23. The processing method according to any one of claims 19-21, wherein, The contact results in an N2 selectivity of over 95%.