CN115869944A - Catalytic oxidation catalyst applied to high-moisture environment and preparation method thereof - Google Patents
Catalytic oxidation catalyst applied to high-moisture environment and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 89
- 230000003197 catalytic effect Effects 0.000 title claims abstract description 53
- 230000003647 oxidation Effects 0.000 title claims abstract description 28
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 28
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 83
- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 61
- 239000011248 coating agent Substances 0.000 claims abstract description 28
- 238000000576 coating method Methods 0.000 claims abstract description 28
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims abstract description 27
- 229910052684 Cerium Inorganic materials 0.000 claims abstract description 26
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 14
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052763 palladium Inorganic materials 0.000 claims abstract description 13
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 7
- 239000002002 slurry Substances 0.000 claims description 64
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 35
- 239000010970 precious metal Substances 0.000 claims description 32
- 238000003756 stirring Methods 0.000 claims description 24
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 claims description 20
- 239000012752 auxiliary agent Substances 0.000 claims description 18
- 239000000919 ceramic Substances 0.000 claims description 18
- 229910052878 cordierite Inorganic materials 0.000 claims description 15
- JSKIRARMQDRGJZ-UHFFFAOYSA-N dimagnesium dioxido-bis[(1-oxido-3-oxo-2,4,6,8,9-pentaoxa-1,3-disila-5,7-dialuminabicyclo[3.3.1]nonan-7-yl)oxy]silane Chemical group [Mg++].[Mg++].[O-][Si]([O-])(O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2)O[Al]1O[Al]2O[Si](=O)O[Si]([O-])(O1)O2 JSKIRARMQDRGJZ-UHFFFAOYSA-N 0.000 claims description 15
- RQPZNWPYLFFXCP-UHFFFAOYSA-L barium dihydroxide Chemical group [OH-].[OH-].[Ba+2] RQPZNWPYLFFXCP-UHFFFAOYSA-L 0.000 claims description 14
- 229910001863 barium hydroxide Inorganic materials 0.000 claims description 14
- 238000011068 loading method Methods 0.000 claims description 14
- 239000006255 coating slurry Substances 0.000 claims description 12
- 239000012153 distilled water Substances 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 12
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 6
- 238000000498 ball milling Methods 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- 229910017604 nitric acid Inorganic materials 0.000 claims description 6
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 claims description 6
- NWAHZABTSDUXMJ-UHFFFAOYSA-N platinum(2+);dinitrate Chemical compound [Pt+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O NWAHZABTSDUXMJ-UHFFFAOYSA-N 0.000 claims description 6
- 238000005303 weighing Methods 0.000 claims description 6
- 238000000034 method Methods 0.000 claims description 5
- 239000002923 metal particle Substances 0.000 abstract description 12
- 229910001404 rare earth metal oxide Inorganic materials 0.000 abstract description 10
- 239000002245 particle Substances 0.000 abstract description 9
- 150000001335 aliphatic alkanes Chemical class 0.000 abstract description 8
- 230000000694 effects Effects 0.000 abstract description 8
- -1 cerium modified aluminum oxide Chemical class 0.000 abstract description 6
- 238000001179 sorption measurement Methods 0.000 abstract description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 4
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- 230000008021 deposition Effects 0.000 abstract description 3
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- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
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- 239000002912 waste gas Substances 0.000 description 2
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- VVQNEPGJFQJSBK-UHFFFAOYSA-N Methyl methacrylate Chemical compound COC(=O)C(C)=C VVQNEPGJFQJSBK-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
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- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
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- 231100000252 nontoxic Toxicity 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
The invention relates to a catalytic oxidation catalyst applied to a high-moisture environment and a preparation method thereof, belonging to the technical field of catalyst preparation. The cerium modified aluminum oxide is used, the cerium oxide is a rare earth oxide, the surface adsorption capacity of the catalyst can be improved by doping the cerium modified aluminum oxide, the utilization efficiency of O2 is improved, the carbon deposition resistant effect is improved, the rare earth oxide and the noble metal particles are interacted, so that the noble metal particles can form more dispersed particles with smaller particle size, and the catalytic effect is improved; due to the addition of the new theta-alumina, the stability of the whole coating/catalyst in high-temperature operation is greatly ensured, the activity of the fresh catalyst is ensured, and the influence of hydrothermal aging on the catalyst is reduced as much as possible. Meanwhile, the addition of the platinum/palladium double-system noble metal is adopted, so that the removal efficiency of the platinum/palladium double-system noble metal on alkane organic matters under the high-temperature condition is improved.
Description
Technical Field
The invention relates to a catalytic oxidation catalyst applied to a high-moisture environment and a preparation method thereof, belonging to the technical field of catalyst preparation.
Background
At present, the catalytic oxidation technology is one of the mainstream process technologies currently used for treating exhaust gas containing organic volatile compounds (VOC), and the main basic principle is that the exhaust gas is subjected to a series of purification measures, then is heated to a proper temperature range, is introduced into a catalytic oxidation reactor containing a catalyst, and is treated by a matched catalytic oxidation catalyst, wherein organic volatile gas mainly containing hydrocarbon is completely converted into carbon dioxide and water, so that the purification purpose is achieved. Therefore, the development and type selection of the catalytic oxidation catalyst becomes more critical.
The related technology of the catalytic oxidation catalyst is mainly derived from the related technology of the automobile exhaust treatment catalyst, and through the long-term development of many years, corresponding matching schemes are provided for various organic matters such as benzene series, alkane components, esters, alcohols and the like. When the catalytic oxidation catalyst is applied to the field of tail gas emission control of chemical devices, certain special working conditions in the industry provide new requirements for the prior formula.
The catalytic oxidation catalyst mainly comprises a coating, a noble metal component and an inert carrier. The carrier is composed of a metal carrier and a cordierite ceramic carrier, and the carrier mainly provides good support for the catalyst. The coating is mostly composed of metal/nonmetal oxides, and the formed porous form has a high specific surface area, and can effectively adsorb organic volatile matters in the waste gas and capture the volatile matters on the surface of the catalyst by adsorption. Then, organic volatile matter molecules are combined with oxygen atoms on the surface of the noble metal particles, finally, heat is released, and water and carbon dioxide which are nontoxic and harmless are generated through reaction.
The exhaust gas of some chemical devices such as acrylic acid, methyl methacrylate and other chemical production devices contains a large amount of water, and the water content is generally about 10 percent and can reach 17 percent at most. The actual use effect of the catalytic oxidation catalyst can be seriously influenced by overhigh water content in the waste gas, and the main influence is that the coating falls off, the microstructure of the coating collapses, the active component noble metal particles are agglomerated and inactivated, and the like. Thereby seriously affecting the use effect of the catalytic oxidation device and the service life of the catalyst.
The existing catalytic oxidation catalyst has single noble metal type, adopts single-component platinum mostly, and has lower conversion efficiency aiming at alkane gaseous organic matters at high temperature. The coating formula mostly adopts a zirconia-based formula, has certain limitation, macroscopically, the whole coating falling rate of the catalyst is higher, and the catalyst is more obvious under the condition of high water content. In addition, the pore structure is easy to collapse under high temperature. The carrier is usually a metal carrier, the surface water absorption of which is not high, and the coating is not easy to coat. And because the catalyst is higher in the use temperature of the relevant scenes mentioned in the application, the expansion coefficient of the catalyst is higher, and the catalyst is easy to deform during operation.
Therefore, the development of a catalyst product with stronger hydrothermal stability performance is of great significance, on one hand, the service life of the catalytic oxidation catalyst can be prolonged to reduce the operation cost of users, and on the other hand, the improvement of the coating layer can also provide the operation stability of the catalyst, so that the long-term stable operation of the system is ensured.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a catalytic oxidation catalyst applied to a high-moisture environment and a preparation method thereof. The catalyst is specially suitable for catalytic oxidation catalysts used in high-moisture environments, and mainly solves the problems that the long-period running performance of the existing catalyst is reduced in the high-moisture environments, a coating falls off and the like.
The catalytic oxidation catalyst applied to the high-moisture environment comprises a carrier and precious metal slurry, wherein the loading capacity of the precious metal slurry is 50-150g/L, the precious metal slurry contains precious metals Pt and Pd, the content of the precious metals is 0.5-2.5 wt%, and the precious metal slurry contains alumina, cerium modified alumina and an auxiliary agent. The cerium oxide is a rare earth oxide, the surface adsorption capacity of the catalyst can be improved by doping the cerium oxide, the utilization efficiency of O2 is improved, the carbon deposition resistant effect is improved, and the rare earth oxide and the noble metal particles interact with each other, so that the noble metal particles can form more dispersed particles with smaller particle size, and the catalytic effect is improved; the noble metal palladium has better catalytic performance for alkane at high temperature, and has low hydroxylation degree with water at high water content, so that excessive catalytic active ingredients are not occupied, and the catalytic effect of the catalyst can be improved;
further, the crystalline form of alumina is theta-alumina. Because the theta-alumina has the regularity and the high-temperature stability of the unique pore channel structure, the addition of the theta-alumina can effectively ensure the high stability of the pore channel structure of the catalyst carrier, greatly ensure the stability of the whole coating/catalyst in operation at high temperature and further improve the catalytic effect of the catalyst;
further, the carrier is a cordierite ceramic honeycomb carrier.
Further, the auxiliary agent is a barium hydroxide solution.
Further, the mass ratio of alumina, cerium-modified alumina and an auxiliary agent in the noble metal slurry is 40.
A preparation method of a catalytic oxidation catalyst applied to a high-moisture environment comprises the following specific preparation steps:
(1) Preparation of cerium-modified alumina: weighing 80-90 parts of theta-alumina, adding the theta-alumina into 160-300 parts of distilled water, stirring for 1.5-6 h, adding 1-10 parts of cerium oxide into a mixture of alumina and water, continuously stirring for 2-8 h, drying at 140-180 ℃, and roasting at 500-700 ℃ for 2.0-5.0 zxft 8978 to obtain cerium modified alumina;
(2) Preparation of slurry: adding theta-alumina and cerium modified alumina into distilled water, stirring for 2-6 h, dropping the prepared barium hydroxide solution serving as an auxiliary agent into the slurry, adjusting the pH to 1-5, and then performing ball milling until the slurry D90 is 20-60 mu m to obtain coating slurry; wherein the mass ratio of the theta-alumina to the cerium-modified gamma-alumina to the auxiliary agent barium hydroxide solution is 40;
(3) Preparation of noble metal slurry: adding noble metals into the prepared coating slurry, wherein the noble metals are platinum nitrate and palladium nitrate, and the weight of the noble metals accounts for 0.5-2.5% of the weight of the coating material, adding dilute nitric acid after the noble metals are added into the slurry, and stirring and adjusting for 8-20 h until the pH of the slurry is stabilized to 1-3 to obtain noble metal slurry;
(4) Coating a carrier: taking a cordierite ceramic honeycomb carrier, uniformly loading the noble metal slurry on the cordierite ceramic honeycomb carrier by adopting a negative pressure method according to the loading capacity of the noble metal slurry of 50-150g/L, drying for 2-4 h at 150-180 ℃, and finally roasting the carrier for 1-5 h at 450-550 ℃ to obtain the finished catalyst.
By the scheme, the invention at least has the following advantages:
(1) The cerium modified alumina is used, the cerium oxide is a rare earth oxide, the surface adsorption capacity of the catalyst can be improved by doping the cerium modified alumina, the utilization efficiency of O2 is improved, the carbon deposition resistant effect is improved, the rare earth oxide and the noble metal particles interact with each other, so that the noble metal particles can form more dispersed particles with smaller particle size, and the catalytic effect is improved;
(2) Because the theta-alumina has the regularity and the high-temperature stability of the unique pore channel structure, the addition of the theta-alumina can effectively ensure the high stability of the pore channel structure of the catalyst carrier, greatly ensure the stability of the whole coating/catalyst in operation at high temperature and further improve the catalytic effect of the catalyst;
(3) The noble metal palladium has better catalytic performance for alkane at high temperature, and has low hydroxylation degree with water at high water content, so that excessive catalytic active ingredients are not occupied, and the catalytic effect of the catalyst can be improved;
(4) The invention greatly ensures the stability of the coating/catalyst overall operation at high temperature due to the addition of the new theta-alumina, ensures the activity of the fresh catalyst and simultaneously reduces the influence of hydrothermal aging on the catalyst as much as possible. Meanwhile, the addition of the platinum/palladium double-system noble metal is adopted, so that the removal efficiency of the platinum/palladium double-system noble metal on alkane organic matters under the high-temperature condition is improved.
The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.
Detailed Description
The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
(1) Preparation of cerium-modified alumina: weighing 80-90 parts of theta-alumina with a high specific area, adding the theta-alumina into 160-300 parts of distilled water, stirring for 1.5-6 h, taking 1-10 parts of cerium oxide, adding the cerium oxide into a mixture of the alumina and the water, continuously stirring for 2-8 h, drying at the temperature of 140-180 ℃, and roasting at the temperature of 500-700 ℃ for 2.0-5.0 zxft 8978 to obtain cerium modified alumina; cerium oxide is a rare earth oxide, and the doping thereof can improve the surface adsorption capacity of the catalyst and improve O 2 The utilization efficiency and the carbon deposit resistance are improved, the rare earth oxide and the noble metal particles interact with each other, so that the noble metal particles can form more dispersed particles with smaller particle size, and the catalytic effect is improved;
(2) Preparation of slurry: adding theta-alumina and cerium modified alumina into distilled water in a certain proportion, stirring for 2-6 h, dropping the prepared barium hydroxide solution serving as an auxiliary agent into the slurry, adjusting the pH to 1-5, and then ball-milling until the slurry D90 is 20-60 mu m to obtain coating slurry; wherein the mass ratio of the theta-alumina to the cerium modified theta-alumina to the auxiliary agent barium hydroxide solution is (40); because the theta-alumina has the regularity and the high-temperature stability of the unique pore channel structure, the addition of the theta-alumina can effectively ensure the high stability of the pore channel structure of the catalyst carrier, greatly ensure the stability of the whole coating/catalyst in operation at high temperature and further improve the catalytic effect of the catalyst;
(3) Preparation of noble metal slurry: adding noble metals into the prepared coating slurry, wherein the noble metals are platinum nitrate and palladium nitrate, and the weight of the noble metals accounts for 0.5-2.5% of the weight of the coating material, adding dilute nitric acid after the noble metals are added into the slurry, and stirring and adjusting for 8-20 h until the pH of the slurry is stabilized to 1-3 to obtain noble metal slurry; the noble metal palladium has better catalytic performance for alkane at high temperature, and has low hydroxylation degree with water at high water content, so that excessive catalytic active ingredients are not occupied, and the catalytic effect of the catalyst can be improved;
(4) Coating a carrier: taking a cordierite ceramic honeycomb carrier, uniformly loading the noble metal slurry on the cordierite ceramic honeycomb carrier by adopting a negative pressure method according to the loading capacity of the noble metal slurry of 50-150g/L, drying for 2-4 h at 150-180 ℃, and finally roasting the carrier for 1-5 h at 450-550 ℃ to obtain the finished catalyst.
Example 1
A catalytic oxidation catalyst used in high-water content environment is a ceramic honeycomb carrier with a specification of 150 x 100mm, a volume of 2.25L and 400 meshes per square foot, and a coating is made of alumina modified by noble metal Pt, noble metal Pd and cerium.
(1) Preparation of cerium-modified alumina: weighing 80 parts of theta-alumina with a high specific area, adding the theta-alumina into 160 parts of distilled water, stirring for 1.5 hours, adding 1 part of cerium oxide into a mixture of the alumina and the water, continuously stirring for 2 hours, drying at the temperature of 140 ℃, and roasting at the temperature of 500 ℃ for 2.0 hours to obtain cerium modified alumina;
(2) Preparation of slurry: adding theta-alumina and cerium modified alumina into distilled water in a certain proportion, stirring for 2h, dropping the prepared barium hydroxide solution serving as an auxiliary agent into the slurry, adjusting the pH to 1, and then ball-milling until the slurry D90 is 20 microns to obtain coating slurry; wherein the mass ratio of the theta-alumina to the cerium modified theta-alumina to the auxiliary agent barium hydroxide solution is 40;
(3) Preparation of noble metal slurry: adding precious metals into the prepared coating slurry, wherein the precious metals are platinum nitrate and palladium nitrate, the weight of the precious metals accounts for 0.5% of the weight of the coating material, adding the precious metals into the slurry, adding dilute nitric acid, and stirring and adjusting for 8 hours until the pH value of the slurry is stabilized to 1 to obtain precious metal slurry;
(4) Carrier coating: taking a cordierite ceramic honeycomb carrier, uniformly loading noble metal slurry on the cordierite ceramic honeycomb carrier according to the loading capacity of the noble metal slurry of 50g/L, drying for 2h at 150 ℃, and finally roasting the carrier for 1h at 450 ℃ to obtain the finished catalyst.
Example 2
A catalytic oxidation catalyst used in high-moisture environment is a ceramic honeycomb carrier with the specification of 150 x 100mm, the volume of 2.25L and 400 meshes per square foot, and a coating is made of alumina modified by noble metal Pt, noble metal Pd and cerium.
(1) Preparation of cerium-modified alumina: weighing 85 parts of theta-alumina with a high specific area, adding the theta-alumina into 200 parts of distilled water, stirring for 3 hours, adding 5 parts of cerium oxide into a mixture of the alumina and the water, continuously stirring for 5 hours, drying at the temperature of 140-180 ℃, and roasting at 600 ℃ for 3.5 h to obtain cerium modified alumina;
(2) Preparation of slurry: adding theta-alumina and cerium modified alumina into distilled water in a certain proportion, stirring for 4h, dropping the prepared barium hydroxide solution serving as an auxiliary agent into the slurry, adjusting the pH to 3, and then carrying out ball milling until the slurry D90 is 40 mu m to obtain coating slurry; wherein the mass ratio of the theta-alumina to the cerium modified theta-alumina to the auxiliary agent barium hydroxide solution is 50;
(3) Preparation of noble metal slurry: adding precious metals into the prepared coating slurry, wherein the precious metals are platinum nitrate and palladium nitrate, the weight of the precious metals accounts for 1.5% of the weight of the coating material, adding the precious metals into the slurry, adding dilute nitric acid, and stirring and adjusting for 14 hours until the pH value of the slurry is stabilized to 2 to obtain precious metal slurry;
(4) Carrier coating: taking a cordierite ceramic honeycomb carrier, uniformly loading the noble metal slurry on the cordierite ceramic honeycomb carrier according to the loading capacity of the noble metal slurry of 100g/L, drying at 165 ℃ for 3h, and finally roasting the carrier at 500 ℃ for 3h to obtain the finished catalyst.
Example 3
A catalytic oxidation catalyst used in high-moisture environment is a ceramic honeycomb carrier with the specification of 150 x 100mm, the volume of 2.25L and 400 meshes per square foot, and a coating is made of alumina modified by noble metal Pt, noble metal Pd and cerium.
(1) Preparation of cerium-modified alumina: weighing 90 parts of theta-alumina with a high specific area, adding the theta-alumina into 300 parts of distilled water, stirring for 6 hours, taking 10 parts of cerium oxide, adding the cerium oxide into a mixture of the alumina and the water, continuously stirring for 8 hours, drying at the temperature of 140-180 ℃, and roasting at 700 ℃ for 5.0 h to obtain cerium modified alumina;
(2) Preparation of slurry: adding theta-alumina and cerium modified alumina into distilled water in a certain proportion, stirring for 6h, dropping the prepared barium hydroxide solution serving as an auxiliary agent into the slurry, adjusting the pH to 5, and then carrying out ball milling until the slurry D90 is 60 microns to obtain coating slurry; wherein the mass ratio of the theta-alumina to the cerium modified theta-alumina to the auxiliary agent barium hydroxide solution is 60;
(3) Preparation of noble metal slurry: adding precious metals into the prepared coating slurry, wherein the precious metals are platinum nitrate and palladium nitrate, the weight of the precious metals accounts for 2.5% of the weight of the coating material, adding the precious metals into the slurry, adding dilute nitric acid, and stirring and adjusting for 20 hours until the pH of the slurry is stabilized to 3 to obtain precious metal slurry;
(4) Coating a carrier: taking a cordierite ceramic honeycomb carrier, uniformly loading noble metal slurry on the cordierite ceramic honeycomb carrier according to the loading capacity of the noble metal slurry of 150g/L, drying at 180 ℃ for 4h, and finally roasting the carrier at 550 ℃ for 5h to obtain the finished catalyst.
Comparative example
Comparative example 1: comparative example 1 was prepared substantially in the same manner as in inventive example 1, except that no cerium-modified alumina was used, and a catalyst was prepared in the same manner;
comparative example 2: comparative example 2 was prepared substantially in the same manner as in inventive example 1, except that a catalyst was prepared in the same manner by using gamma-alumina in place of theta-alumina according to the present invention;
comparative example 3: comparative example 3 was prepared in substantially the same manner as in inventive example 1, except that no noble metal palladium was added to the coating layer, and the catalyst was prepared in the same manner;
performance testing experiments:
the catalysts of examples 1 to 3 of the present invention and comparative examples 1 to 3 were subjected to performance testing, which was classified into fresh state testing and thermal aging testing, and the performance testing conditionsThe following were used: 600ppm propane, 10% O 2 ，15% H 2 O, using N as balance gas 2 The reaction temperature is between room temperature and 500 ℃, and the space velocity is 25000h -1 . The aging conditions were: and (4) carrying out heat aging for 24h at 750 ℃. Performance testing gives the T of the catalyst sample 50 And T of the catalyst sample 100 And a conversion of 450 ℃ T 50 And T 100 Lower values indicate better catalyst performance, and specific results are shown in table 1.
TABLE 1 Performance test results
As can be seen from the detection data in the table above, the T50 and T100 average values of the catalysts prepared in examples 1 to 3 are low in both the fresh state and the aged state, so that the catalysts have excellent catalytic effects, and the technical scheme of the present application is proved to have high feasibility;
comparing the measured data of comparative example 1 with example 1, the catalyst was also prepared due to the use of cerium-modified alumina in comparative example 1, resulting in a decrease in the catalytic effect of the final catalyst, and thus it can be confirmed that cerium oxide is a rare earth oxide, the incorporation of which can improve the surface adsorption capacity of the catalyst, improve the utilization efficiency of O2 and increase the anti-coking effect, and the interaction of the rare earth oxide with the noble metal particles can form more dispersed noble metal particles with smaller particle size, improving the catalytic effect;
then, the detection data of the comparative example 2 is compared with that of the example 1, and the catalyst is prepared by using gamma-alumina to replace the theta-alumina of the invention in the comparative example 2, so that the catalytic effect of the final catalyst is reduced, and therefore, the fact that the theta-alumina has the regularity and the high-temperature stability of the unique pore channel structure can be confirmed, the high stability of the pore channel structure of the catalyst carrier can be effectively ensured by adding the theta-alumina, the stability of the operation of the coating/catalyst at high temperature is greatly ensured, and the catalytic effect of the catalyst is further improved;
finally, the detection data of the comparative example 3 is compared with that of the example 1, and since the catalyst is prepared in the same way without adding the noble metal palladium in the comparative example 3, the catalytic effect of the final catalyst is also reduced, so that the catalytic performance of the noble metal palladium on alkane at high temperature is better, the hydroxylation degree of the noble metal palladium with water at high water content is low, excessive catalytic active ingredients are not occupied, and the catalytic effect of the catalyst can be improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (6)
1. A catalytic oxidation catalyst applied to a high-moisture environment is characterized in that: the carrier and the precious metal slurry are included, the loading capacity of the precious metal slurry is 50-150g/L, the precious metal slurry contains precious metals Pt and Pd, the content of the precious metals is 0.5-2.5 wt%, and the precious metal slurry contains alumina, cerium modified alumina and an auxiliary agent.
2. A catalytic oxidation catalyst for use in high water environments according to claim 1, wherein: the crystalline form of alumina is theta alumina.
3. The catalytic oxidation catalyst for use in high moisture environments of claim 1, wherein: the carrier is a cordierite ceramic honeycomb carrier.
4. The catalytic oxidation catalyst for use in high moisture environments of claim 1, wherein: the auxiliary agent is barium hydroxide solution.
5. The catalytic oxidation catalyst for use in high moisture environments of claim 1, wherein: the mass ratio of the alumina to the cerium modified alumina to the auxiliary agent in the noble metal slurry is (40).
6. The method for preparing a catalytic oxidation catalyst for use in high water content environments of claim 1, comprising the steps of:
(1) Preparation of cerium-modified alumina: weighing 80-90 parts of theta-alumina, adding the theta-alumina into 160-300 parts of distilled water, stirring for 1.5-6 h, adding 1-10 parts of cerium oxide into a mixture of alumina and water, continuously stirring for 2-8 h, drying at 140-180 ℃, and roasting at 500-700 ℃ for 2.0-5.0 zxft 8978 to obtain cerium modified alumina;
(2) Preparation of slurry: adding theta-alumina and cerium modified alumina into distilled water, stirring for 2-6 h, dropping the prepared barium hydroxide solution serving as an auxiliary agent into the slurry, adjusting the pH to 1-5, and then performing ball milling until the slurry D90 is 20-60 mu m to obtain coating slurry; wherein the mass ratio of the theta-alumina to the cerium-modified gamma-alumina to the auxiliary agent barium hydroxide solution is 40;
(3) Preparation of noble metal slurry: adding precious metals into the prepared coating slurry, wherein the precious metals are platinum nitrate and palladium nitrate, the weight of the precious metals accounts for 0.5-2.5% of the weight of the coating material, adding dilute nitric acid after the precious metals are added into the slurry, and stirring and adjusting for 8-20 h until the pH value of the slurry is stabilized to 1-3 to obtain precious metal slurry;
(4) Coating a carrier: taking a cordierite ceramic honeycomb carrier, uniformly loading noble metal slurry on the cordierite ceramic honeycomb carrier by adopting a negative pressure method according to the loading capacity of the noble metal slurry of 50-150g/L, drying for 2-4 h at 150-180 ℃, and finally roasting the carrier for 1-5 h at 450-550 ℃ to obtain the finished catalyst.
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