CN113145163A - All-silicon molecular sieve supported palladium methane oxidation catalyst and preparation method thereof - Google Patents
All-silicon molecular sieve supported palladium methane oxidation catalyst and preparation method thereof Download PDFInfo
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- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 title claims abstract description 91
- 239000003054 catalyst Substances 0.000 title claims abstract description 84
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 66
- 239000002808 molecular sieve Substances 0.000 title claims abstract description 38
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 38
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 38
- 239000010703 silicon Substances 0.000 title claims abstract description 36
- 229910052763 palladium Inorganic materials 0.000 title claims abstract description 26
- 230000003647 oxidation Effects 0.000 title claims abstract description 13
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 13
- 238000002360 preparation method Methods 0.000 title abstract description 22
- 238000006243 chemical reaction Methods 0.000 claims abstract description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000002105 nanoparticle Substances 0.000 claims abstract description 17
- 229910052751 metal Inorganic materials 0.000 claims abstract description 6
- 239000002184 metal Substances 0.000 claims abstract description 6
- 229910003445 palladium oxide Inorganic materials 0.000 claims abstract description 3
- JQPTYAILLJKUCY-UHFFFAOYSA-N palladium(ii) oxide Chemical compound [O-2].[Pd+2] JQPTYAILLJKUCY-UHFFFAOYSA-N 0.000 claims abstract description 3
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 29
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 29
- 238000003756 stirring Methods 0.000 claims description 26
- 238000000034 method Methods 0.000 claims description 16
- 239000008367 deionised water Substances 0.000 claims description 15
- 229910021641 deionized water Inorganic materials 0.000 claims description 15
- 239000000243 solution Substances 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 11
- USFZMSVCRYTOJT-UHFFFAOYSA-N Ammonium acetate Chemical compound N.CC(O)=O USFZMSVCRYTOJT-UHFFFAOYSA-N 0.000 claims description 8
- 239000005695 Ammonium acetate Substances 0.000 claims description 8
- 229940043376 ammonium acetate Drugs 0.000 claims description 8
- 235000019257 ammonium acetate Nutrition 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 8
- 238000002425 crystallisation Methods 0.000 claims description 7
- 230000008025 crystallization Effects 0.000 claims description 7
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 6
- 239000007864 aqueous solution Substances 0.000 claims description 6
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 6
- LPSKDVINWQNWFE-UHFFFAOYSA-M tetrapropylazanium;hydroxide Chemical compound [OH-].CCC[N+](CCC)(CCC)CCC LPSKDVINWQNWFE-UHFFFAOYSA-M 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 5
- -1 polytetrafluoroethylene Polymers 0.000 claims description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 2
- 229910017053 inorganic salt Inorganic materials 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 2
- 239000012279 sodium borohydride Substances 0.000 claims description 2
- 229910000033 sodium borohydride Inorganic materials 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims 1
- 239000000377 silicon dioxide Substances 0.000 claims 1
- 230000003197 catalytic effect Effects 0.000 abstract description 11
- 238000006555 catalytic reaction Methods 0.000 abstract description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 231100000252 nontoxic Toxicity 0.000 abstract description 4
- 230000003000 nontoxic effect Effects 0.000 abstract description 4
- 230000007613 environmental effect Effects 0.000 abstract description 3
- 230000005540 biological transmission Effects 0.000 abstract description 2
- 239000001569 carbon dioxide Substances 0.000 abstract description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 abstract description 2
- 230000036541 health Effects 0.000 abstract description 2
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 abstract description 2
- 239000007789 gas Substances 0.000 description 26
- 230000000694 effects Effects 0.000 description 8
- 238000005470 impregnation Methods 0.000 description 8
- 238000007084 catalytic combustion reaction Methods 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 229910021536 Zeolite Inorganic materials 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 239000010457 zeolite Substances 0.000 description 5
- DHMQDGOQFOQNFH-UHFFFAOYSA-N Glycine Chemical compound NCC(O)=O DHMQDGOQFOQNFH-UHFFFAOYSA-N 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- RCFVMJKOEJFGTM-UHFFFAOYSA-N cerium zirconium Chemical compound [Zr].[Ce] RCFVMJKOEJFGTM-UHFFFAOYSA-N 0.000 description 4
- 239000011247 coating layer Substances 0.000 description 4
- 239000000084 colloidal system Substances 0.000 description 4
- 229910052593 corundum Inorganic materials 0.000 description 4
- 229910000510 noble metal Inorganic materials 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- 229910001845 yogo sapphire Inorganic materials 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 229910003158 γ-Al2O3 Inorganic materials 0.000 description 3
- 239000004471 Glycine Substances 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000008030 elimination Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 229910052741 iridium Inorganic materials 0.000 description 2
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 239000002912 waste gas Substances 0.000 description 2
- NLOAOXIUYAGBGO-UHFFFAOYSA-N C.[O] Chemical compound C.[O] NLOAOXIUYAGBGO-UHFFFAOYSA-N 0.000 description 1
- 230000010718 Oxidation Activity Effects 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- MCMNRKCIXSYSNV-UHFFFAOYSA-N ZrO2 Inorganic materials O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000009841 combustion method Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000002173 high-resolution transmission electron microscopy Methods 0.000 description 1
- 150000002471 indium Chemical class 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000003223 protective agent Substances 0.000 description 1
- 238000004445 quantitative analysis Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
- B01J29/44—Noble metals
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/20—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state
- B01J35/23—Catalysts, in general, characterised by their form or physical properties characterised by their non-solid state in a colloidal state
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/396—Distribution of the active metal ingredient
- B01J35/399—Distribution of the active metal ingredient homogeneously throughout the support particle
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
- B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
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- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/16—Reducing
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
- F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
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Abstract
The invention relates to an environmental catalysis technology, and aims to provide a palladium-loaded all-silicon molecular sieve methane oxidation catalyst and a preparation method thereof. The catalyst takes an all-silicon ZSM-5 molecular sieve as a carrier, and metal palladium oxide in a nano-particle form as an active component is uniformly loaded on the carrier; wherein the active component accounts for 1 percent of the mass ratio of the catalyst. The preparation process of the invention adopts nontoxic and harmless components, which can not cause harm to human health and ecological environment, and the preparation method is simple and easy. The carrier used by the catalyst has super-strong hydrophobicity, and is beneficial to product transmission and reaction promotion. The catalyst of the invention has very high catalytic activity, and can completely oxidize methane into nontoxic and harmless carbon dioxide and water at the temperature below 400 ℃ and under the condition of set space velocity.
Description
Technical Field
The invention relates to the technical field of environmental catalysis, in particular to a palladium-loaded methane oxidation catalyst with an all-silicon molecular sieve and a preparation method thereof.
Background
The catalytic combustion of methane is of great significance on the one hand when it is used as a clean fuel; on the other hand, the gas generated in working areas such as mines and the like and the tail gas of natural gas automobiles and the like can emit a certain amount of methane, and catalytic combustion elimination is the most effective method for controlling the waste gas, so that the greenhouse effect related to the waste gas is effectively reduced.
The supported noble metal catalyst is one of the catalysts having the best methane elimination activity, and the noble metal Pd has proved to have the best cost performance. When different carriers are loaded with the active component Pd, the activity of the obtained catalyst is also very different. Wherein, Al2O3Is a common carrier. However, Al2O3As a carrier, its drawbacks are also apparent. When moisture is present in the reaction gas, Al2O3The supported Pd catalyst was severely deactivated. Therefore, the development of a catalyst with strong water resistance and high stability is one of the key points of a methane catalytic combustion catalyst and is one of the great challenges in the field of environmental catalysis at present.
CN107362791B discloses a non-stoichiometric perovskite type methane catalytic combustion catalyst and a preparation method thereof. The preparation of the catalyst is carried out by adopting a self-propagating gel combustion method, taking glycine as fuel and complexing agent and taking inorganic yttrium and indium salt as raw materials. By controlling the combustion and volatilization speed of the glycine fuel, the prepared sample has larger specific surface area and high-temperature thermal stability; in addition, the defect sites of the material are increased by non-stoichiometric doping at the A or B sites, and the active oxygen migration capacity and the activation capacity are improved.
CN107262093B provides a methane catalytic combustion catalyst and a preparation method thereof, the catalyst comprises a carrier and an active component loaded on the carrier, the outside of the active component is coated with a coating layer for providing oxygen vacancy for the active component, the catalyst also comprises a catalytic assistant cerium zirconium solid solution, on one hand, the coating layer is coated on the outside of the active component, which is beneficial to the oxygen molecules stored in the coating layer to be timely transferred to the active component, thereby maintaining the high temperature stability of the active component of the catalyst; on the other hand, the catalyst also comprises a catalytic assistant cerium-zirconium solid solution, and the cerium-zirconium solid solution can generate more oxygen vacancies and can effectively store oxygen in time, so that the high-temperature stability of the active component of the catalyst can be improved; in addition, the coating layer, the cerium-zirconium solid solution and the carrier are mutually dispersed and contacted, so that the mutual blocking effect is realized, the sintering of the carrier is inhibited, and the high-temperature thermal stability and the catalytic activity of the catalyst are improved.
CN111686723A discloses an iridium-containing bimetallic catalyst for methane catalytic combustion and a preparation method thereof. The catalyst is prepared from Ir metal or oxide, M metal or oxide and TiO2、ZrO2And the M is one of Pd, Pt, Ru or Ag. The weight percentage of the noble metal Ir is 0.05-10 percent and the weight percentage of the metal M is 0.05-10 percent based on the weight of the catalyst as 100 percent. The iridium-containing bimetallic catalyst for methane combustion is obtained by drying and roasting a precursor solution of bimetallic IrM or a mixed precursor solution of bimetallic IrM which is directly impregnated on a carrier step by step.
However, the above prior arts have respective disadvantages, such as difficulty in obtaining raw materials and complicated preparation process. Therefore, it is necessary to develop a methane catalytic combustion catalyst having excellent low-temperature activity and hydrothermal stability and high cost performance.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a palladium-loaded all-silicon molecular sieve methane oxidation catalyst and a preparation method thereof.
In order to solve the technical problem, the solution of the invention is as follows:
the all-silicon molecular sieve supported palladium methane oxidation catalyst is characterized in that the catalyst takes an all-silicon ZSM-5 molecular sieve as a carrier, and metal palladium oxide in a nanoparticle form as an active component is uniformly supported on the carrier; wherein the active component accounts for 1 percent of the mass ratio of the catalyst.
In the invention, the all-silicon ZSM-5 molecular sieve is an MFI type ten-membered ring molecular sieve.
The invention further provides a preparation method of the catalyst, which comprises the following steps:
(1) dissolving polyvinyl alcohol and a palladium active component in deionized water according to a mass ratio of 1.2-2.4: 1, wherein the palladium active component is an inorganic salt of palladium or a palladium complex; stirring at 0 deg.C for 0.5h, rapidly adding NaBH under vigorous stirring4Aqueous solution, NaBH4The amount of Pd2+The mass ratio of (A) to (B) is 2.45: 1; stirring for 1h at 0 ℃ continuously, and reducing Pd to obtain PVA protected palladium nano particles (Pd NPs);
(2) adding an all-silicon ZSM-5 molecular sieve used as a carrier into the Pd NPs solution obtained in the step (1), and then adding ammonium acetate, wherein the mass ratio of the Pd NPs to the all-silicon ZSM-5 molecular sieve to the ammonium acetate is 0.0116:1.15: 7; continuously stirring for 5 hours to load the Pd NPs on the carrier; and (4) carrying out centrifugal treatment, washing with ionized water, drying, and then carrying out roasting to remove PVA, thus obtaining the all-silicon molecular sieve supported palladium methane oxidation catalyst.
In the invention, the drying refers to drying at 100 ℃ for 12h, and the roasting refers to roasting at 550 ℃ in an air atmosphere for 4 h.
In the invention, the all-silicon ZSM-5 molecular sieve is prepared by a hydrothermal method, and comprises the following steps: deionized water, tetrapropylammonium hydroxide (TPAOH) and Tetraethoxysilane (TEOS) are taken according to the volume ratio of 96.72:16.62:30.39, and are uniformly mixed and stirred for 5.5 hours at room temperature; transferring the mixture into a polytetrafluoroethylene reaction kettle, and carrying out crystallization reaction for 4 days at 180 ℃; and after crystallization is finished, centrifuging, washing and drying the product, and roasting at 550 ℃ for 4 hours to remove the organic template agent to obtain the all-silicon ZSM-5 molecular sieve (marked as ZSM-5-Si).
Description of the inventive principles:
in the invention, the zeolite molecular sieve supported palladium catalyst simultaneously has zeolite moleculesThe dual advantages of the sieve and the noble metal show a very high catalytic activity. Research has shown that the all-silicon molecular sieve has excellent hydrophobicity and is beneficial to enhancing the adsorption capacity of the catalyst to reactants. In addition, as the hydrophobicity of the catalyst gradually increases, H of one of the reaction products2O can be far away from the catalytic center more quickly, thereby promoting the reaction.
The palladium is innovatively loaded on the all-silicon ZSM-5 molecular sieve, and the palladium nano particles with proper size and uniform distribution are obtained by using a protective agent polyvinyl alcohol PVA (PVA), so that the activity of methane on the catalyst is greatly improved, and the catalyst can be used under the conditions of temperature (380 ℃) below 400 ℃, 60,000 mL/(g.h) and space velocity below (1500ppm CH)4,5％O2,N2Balance gas, total gas mass flow 100mL/min) to achieve complete oxidation of methane.
The all-silicon ZSM-5 molecular sieve is prepared by a hydrothermal method and can also be expanded to the all-silicon ZSM-5 molecular sieve obtained by a solvent-free method.
Compared with the prior art, the invention has the following advantages:
1. the preparation process of the invention adopts nontoxic and harmless components, which can not cause harm to human health and ecological environment, and the preparation method is simple and easy.
2. The carrier used by the catalyst has super-strong hydrophobicity, and is beneficial to product transmission and reaction promotion.
3. The catalyst of the invention has very high catalytic activity, and can be used for preparing a catalyst under the conditions of temperature (380 ℃) below 400 ℃, 60000 mL/(g.h) and space velocity below (1500ppm CH4, 5% O)2,N2Balance gas, total gas mass flow 100mL/min) completely oxidize methane into non-toxic and harmless carbon dioxide and water.
Drawings
FIG. 1 shows Pd/ZSM-5-Si and Pd/gamma-Al2O3XRD pattern of (a).
FIG. 2 is a high power transmission electron micrograph HRTEM of Pd/ZSM-5-Si with a scale bar of 10 nm;
FIG. 3 shows Pd/ZSM-5-Si and Pd/γ -Al2O3Methane oxygen ofComparative activation plots.
FIG. 4 is a graph showing the distribution of the particle size of PVA-protected Pd NPs.
Detailed Description
To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, the invention provides the following exemplary but non-limiting examples.
Catalytic performance test methods in the examples:
the invention uses catalyst particles (20-40 meshes) on a fixed bed micro reaction device to examine the catalytic oxidation activity of methane. The diameter of the reaction tube of the fixed bed micro-reaction device is 6mm, the loading amount of the catalyst is 0.1g, and the composition of the raw material gas is 1500ppm CH4/5％O2/N2Balance gas, gas mass flow 100 mL/min. The thermocouple for controlling the reaction temperature is positioned in the center of the catalyst bed layer in the quartz tube. The catalyst was not subjected to any pretreatment before the reaction. Each temperature point was reacted for 30min to stabilize the catalyst activity. Gas chromatography was used for quantitative analysis. The following examples were all evaluated for performance according to this method.
Example 1
Preparation of the carrier: the all-silicon ZSM-5 was synthesized by a hydrothermal method. Adding 96.72mL of deionized water into the beaker, and then adding 16.62mL of TPAOH solution; stirring for 15min at room temperature, and then adding 30.39mL TEOS; stirring at room temperature for 5.5h, transferring the mixture into a polytetrafluoroethylene reaction kettle, and crystallizing at 180 ℃ for 4 days. After crystallization is finished, the ZSM-5 zeolite molecular sieve product is centrifuged, washed, dried and roasted at 550 ℃ for 4 hours to remove the organic template agent to obtain the all-silicon ZSM-5 molecular sieve which is marked as ZSM-5-Si, and the product can be judged to be the MFI type ten-membered ring molecular sieve from the XRD diagram.
Preparation of the catalyst: the all-silicon ZSM-5 supported Pd catalyst (Pd/ZSM-5-Si) was obtained by a colloid impregnation method. 21mg of PVA (polyvinyl alcohol, molecular weight 1000) and 1.35ml of Na were added2PdCl4(80.8mmol/L) was dissolved in 60ml of deionized water, stirred at 0 ℃ for 0.5h, and 5ml of freshly prepared NaBH was added rapidly with vigorous stirring4And (3) stirring the aqueous solution (0.1mol/L) at 0 ℃ for 1h, and reducing Pd to obtain the PVA protected Pd nano-particles. Reciprocating systemAdding 1.15g of carrier into the obtained Pd nano-particle solution, adding 7g of ammonium acetate, continuously stirring for 5 hours to load the Pd nano-particles on the carrier, centrifuging, washing with a large amount of deionized water, drying in an oven at 100 ℃ for 12 hours, and roasting in air at 550 ℃ for 4 hours to remove PVA, thereby obtaining the target catalyst. Wherein the active component accounts for 1 percent of the mass ratio of the catalyst.
The catalyst has a catalyst dosage of 0.1g and a feed gas composition of 1500ppm CH4/5％O2/N2The catalytic reaction performance of the balance gas under the condition that the gas mass flow is 100mL/min is as follows:
| temperature (. degree.C.) | 200 | 240 | 280 | 320 | 360 | 380 | 400 |
| CH4 conversion (%) | 1.94 | 6.18 | 39.57 | 83.95 | 98.31 | 100 | 100 |
Example 2
Preparation of the carrier: the all-silicon ZSM-5 was synthesized by a hydrothermal method. Adding 96.72mL of deionized water into the beaker, and then adding 16.62mL of TPAOH solution; stirring for 15min at room temperature, and then adding 30.39mL TEOS; stirring at room temperature for 5.5h, transferring the mixture into a polytetrafluoroethylene reaction kettle, and crystallizing at 180 ℃ for 4 days. After crystallization is finished, the ZSM-5 zeolite molecular sieve product is centrifuged, washed, dried and roasted at 550 ℃ for 4 hours to remove the organic template agent, and then the all-silicon ZSM-5 molecular sieve is obtained and is marked as ZSM-5-Si.
Preparation of the catalyst: the all-silicon ZSM-5 supported Pd catalyst (Pd/ZSM-5-Si) was obtained by a colloid impregnation method. 14mg of PVA (polyvinyl alcohol, molecular weight 1000) and 1.35ml of Na were added2PdCl4(80.8mmol/L) was dissolved in 60ml of deionized water, stirred at 0 ℃ for 0.5h, and 5ml of freshly prepared NaBH was added rapidly with vigorous stirring4And (3) stirring the aqueous solution (0.1mol/L) at 0 ℃ for 1h, and reducing Pd to obtain the PVA protected Pd nano-particles. Adding 1.15g of carrier into the prepared Pd nano-particle solution, adding 7g of ammonium acetate, continuously stirring for 5 hours to load the Pd nano-particles on the carrier, centrifuging, washing with a large amount of deionized water, drying in an oven at 100 ℃ for 12 hours, and roasting in air at 550 ℃ for 4 hours to remove PVA, thereby obtaining the target catalyst. Wherein the active component accounts for 1 percent of the mass ratio of the catalyst.
The catalyst has a catalyst dosage of 0.1g and a feed gas composition of 1500ppm CH4/5％O2/N2The catalytic reaction performance of the balance gas under the condition that the gas mass flow is 100mL/min is as follows:
| temperature (. degree.C.) | 200 | 240 | 280 | 320 | 360 | 400 | 420 |
| CH4 conversion (%) | 0 | 0.80 | 15.09 | 62.94 | 94.69 | 99.33 | 100 |
Example 3
Preparation of the carrier: the all-silicon ZSM-5 was synthesized by a hydrothermal method. Adding 96.72mL of deionized water into the beaker, and then adding 16.62mL of TPAOH solution; stirring for 15min at room temperature, and then adding 30.39mL TEOS; stirring at room temperature for 5.5h, transferring the mixture into a polytetrafluoroethylene reaction kettle, and crystallizing at 180 ℃ for 4 days. After crystallization is finished, the ZSM-5 zeolite molecular sieve product is centrifuged, washed, dried and roasted at 550 ℃ for 4 hours to remove the organic template agent, and then the all-silicon ZSM-5 molecular sieve is obtained and is marked as ZSM-5-Si.
Preparation of the catalyst: the all-silicon ZSM-5 supported Pd catalyst (Pd/ZSM-5-Si) was obtained by a colloid impregnation method. 28mg of PVA (polyvinyl alcohol, molecular weight 1000) and 1.35ml of Na were added2PdCl4(80.8mmol/L) was dissolved in 60ml of deionized water, stirred at 0 ℃ for 0.5h, stirred vigorously5ml of fresh NaBH is added rapidly under stirring4And (3) stirring the aqueous solution (0.1mol/L) at 0 ℃ for 1h, and reducing Pd to obtain the PVA protected Pd nano-particles. Adding 1.15g of carrier into the prepared Pd nano-particle solution, adding 7g of ammonium acetate, continuously stirring for 5 hours to load the Pd nano-particles on the carrier, centrifuging, washing with a large amount of deionized water, drying in an oven at 100 ℃ for 12 hours, and roasting in air at 550 ℃ for 4 hours to remove PVA, thereby obtaining the target catalyst. Wherein the active component accounts for 1 percent of the mass ratio of the catalyst.
The catalyst has a catalyst dosage of 0.1g and a feed gas composition of 1500ppm CH4/5％O2/N2The catalytic reaction performance of the balance gas under the condition that the gas mass flow is 100mL/min is as follows:
| temperature (. degree.C.) | 200 | 240 | 280 | 320 | 360 | 400 |
| CH4 conversion (%) | 0 | 2.25 | 17.23 | 65.07 | 94.85 | 100 |
As can be seen from the catalytic performance test, the catalyst of the invention can be used for preparing a catalyst at the temperature of below 400 ℃ (380 ℃), and under the conditions of 60,000 mL/(g.h) space velocity (1500ppm CH)4,5％O2,N2Balance gas, total gas mass flow 100mL/min) to achieve complete oxidation of methane.
In the above embodiment, changing the amount of PVA has no effect on the quality of Pd NPs in the Pd nanoparticle solution, and the raw material mass ratio relationship of a fixed ratio can be maintained; however, the change of the amount of PVA can affect the particle size distribution of the nano particles, thereby affecting the activity of the catalyst; the purpose of varying the amount of PVA in the different examples was therefore to find the optimum PVA values at different catalytic reaction temperatures, so that the catalysts obtained have the most excellent catalytic properties in comparison. If it is desired to vary the active ingredient mass fraction, this can be achieved by adjusting (increasing/decreasing) the carrier mass.
Comparative example 1:
commercial gamma-Al2O3Preparation of supported Pd catalyst: 21mg of PVA (polyvinyl alcohol) and 1.35ml of Na were added2PdCl4(80.8mmol/L) was dissolved in 60ml of deionized water, stirred at 0 ℃ for 0.5h, and 5ml of freshly prepared NaBH was added rapidly with vigorous stirring4The aqueous solution (0.1mol/L) was stirred at 0 ℃ for 1h to reduce Pd and thus obtain PVA protected Pd NPs. To the prepared Pd NPs solution was added 1.15g of commercial gamma-Al2O3And then adding 7g of ammonium acetate, continuously stirring for 5h to load Pd NPs on the carrier, centrifuging, washing with a large amount of deionized water, drying in an oven at 100 ℃ for 12h, and roasting in air at 550 ℃ for 4h to remove PVA, thereby obtaining the target catalyst.
The catalyst has a catalyst dosage of 0.1g and a feed gas composition of 1500ppm CH4/5％O2/N2The catalytic reaction performance of the balance gas under the condition that the gas mass flow is 100mL/min is as follows:
| temperature (. degree.C.) | 200 | 240 | 280 | 320 | 380 | 440 | 500 | 560 |
| CH4 conversion (%) | 0 | 1.91 | 7.01 | 36.31 | 75.80 | 92.99 | 97.45 | 100 |
Comparative example 2:
compared with the traditional impregnation method (without PVA protection), the Pd loaded on ZSM-5-Si by the impregnation method has the mass fraction of 1 percent, the catalyst obtained by the impregnation method has the catalyst dosage of 0.1g, and the raw material gas composition is 1500ppm CH4/5％O2/N2Balance gas, gas mass flow rate is 100mL/minThe following catalytic reaction properties were as follows:
| temperature (. degree.C.) | 200 | 240 | 280 | 320 | 360 | 400 | 420 |
| CH4 conversion (%) | 0 | 0.24 | 5.23 | 42.16 | 90.43 | 98.33 | 100 |
Comparing the data of the comparative example with the data of the inventive example, it can be seen that: (1) the all-silicon ZSM-5 molecular sieve is an excellent methane oxidation catalyst carrier; (2) the performance of the catalyst obtained by the colloid impregnation method is obviously superior to that of the catalyst prepared by the traditional impregnation method.
The applicant indicates that the present invention is illustrated by the above examples to describe the detailed application of the present invention, but the present invention is not limited to the above detailed application, i.e. it does not mean that the present invention must rely on the above detailed method to be carried out. It will be apparent to those skilled in the art that the reaction conditions, equivalent changes of equipment, and changes of auxiliary conditions, selection of modes, etc. of the present invention are within the protection scope and disclosure of the present invention.
Claims (5)
1. An all-silicon molecular sieve supported palladium methane oxidation catalyst is characterized in that the catalyst takes an all-silicon ZSM-5 molecular sieve as a carrier, and metal palladium oxide in a nanoparticle form as an active component is uniformly supported on the carrier; wherein the active component accounts for 1 percent of the mass ratio of the catalyst.
2. The catalyst of claim 1, wherein the all-silicon ZSM-5 molecular sieve is an MFI-type ten-membered ring molecular sieve.
3. The method of preparing an all-silica molecular sieve supported palladium methane oxidation catalyst of claim 1, comprising the steps of:
(1) dissolving polyvinyl alcohol and a palladium active component in deionized water according to a mass ratio of 1.2-2.4: 1, wherein the palladium active component is an inorganic salt of palladium or a palladium complex; stirring at 0 deg.C for 0.5h, rapidly adding NaBH under vigorous stirring4Aqueous solution, NaBH4The amount of Pd2+The mass ratio of (A) to (B) is 2.45: 1; continuously stirring for 1h at 0 ℃, and reducing Pd to obtain PVA-protected palladium nano-particles;
(2) adding an all-silicon ZSM-5 molecular sieve used as a carrier into the Pd NPs solution obtained in the step (1), and then adding ammonium acetate, wherein the mass ratio of the Pd NPs to the all-silicon ZSM-5 molecular sieve to the ammonium acetate is 0.0116:1.15: 7; continuously stirring for 5 hours to load the Pd NPs on the carrier; and (4) carrying out centrifugal treatment, washing with ionized water, drying, and then carrying out roasting to remove PVA, thus obtaining the all-silicon molecular sieve supported palladium methane oxidation catalyst.
4. The method according to claim 3, wherein the drying is drying at 100 ℃ for 12h, and the roasting is roasting at 550 ℃ in an air atmosphere for 4 h.
5. The method of claim 3, wherein the all-silicon ZSM-5 molecular sieve is prepared by a hydrothermal method comprising: taking deionized water, tetrapropylammonium hydroxide and tetraethoxysilane according to the volume ratio of 96.72:16.62:30.39, uniformly mixing, and stirring at room temperature for 5.5 hours; transferring the mixture into a polytetrafluoroethylene reaction kettle, and carrying out crystallization reaction for 4 days at 180 ℃; and after crystallization is finished, centrifuging, washing and drying the product, and roasting at 550 ℃ for 4 hours to remove the organic template agent to obtain the all-silicon ZSM-5 molecular sieve.
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| CN115445651A (en) * | 2022-09-14 | 2022-12-09 | 浙江大学 | Pure silicon molecular sieve supported palladium catalyst for methane catalytic combustion and preparation method thereof |
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