CN112808291B - Preparation method of Co-Zn/C-N catalyst and application of Co-Zn/C-N catalyst in CO 2 Application of hydrogenation methanol synthesis reaction - Google Patents
Preparation method of Co-Zn/C-N catalyst and application of Co-Zn/C-N catalyst in CO 2 Application of hydrogenation methanol synthesis reaction Download PDFInfo
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 title claims abstract description 174
- 239000003054 catalyst Substances 0.000 title claims abstract description 86
- 229910020521 Co—Zn Inorganic materials 0.000 title claims abstract description 70
- 238000005984 hydrogenation reaction Methods 0.000 title claims abstract description 19
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 238000003786 synthesis reaction Methods 0.000 title description 7
- LXBGSDVWAMZHDD-UHFFFAOYSA-N 2-methyl-1h-imidazole Chemical compound CC1=NC=CN1 LXBGSDVWAMZHDD-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 12
- XURCIPRUUASYLR-UHFFFAOYSA-N Omeprazole sulfide Chemical compound N=1C2=CC(OC)=CC=C2NC=1SCC1=NC=C(C)C(OC)=C1C XURCIPRUUASYLR-UHFFFAOYSA-N 0.000 claims abstract description 11
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 8
- ONDPHDOFVYQSGI-UHFFFAOYSA-N zinc nitrate Chemical compound [Zn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ONDPHDOFVYQSGI-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims description 21
- 239000011701 zinc Substances 0.000 claims description 19
- XIOUDVJTOYVRTB-UHFFFAOYSA-N 1-(1-adamantyl)-3-aminothiourea Chemical compound C1C(C2)CC3CC2CC1(NC(=S)NN)C3 XIOUDVJTOYVRTB-UHFFFAOYSA-N 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 239000007864 aqueous solution Substances 0.000 claims description 6
- YZZFBYAKINKKFM-UHFFFAOYSA-N dinitrooxyindiganyl nitrate;hydrate Chemical compound O.[In+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O YZZFBYAKINKKFM-UHFFFAOYSA-N 0.000 claims description 6
- 238000003756 stirring Methods 0.000 claims description 6
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- SLCITEBLLYNBTQ-UHFFFAOYSA-N CO.CC=1NC=CN1 Chemical compound CO.CC=1NC=CN1 SLCITEBLLYNBTQ-UHFFFAOYSA-N 0.000 claims description 4
- NVLDSCWHEUSPCV-UHFFFAOYSA-N [Co++].CO.[O-][N+]([O-])=O.[O-][N+]([O-])=O Chemical compound [Co++].CO.[O-][N+]([O-])=O.[O-][N+]([O-])=O NVLDSCWHEUSPCV-UHFFFAOYSA-N 0.000 claims description 4
- 238000002390 rotary evaporation Methods 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 239000008367 deionised water Substances 0.000 claims description 3
- 229910021641 deionized water Inorganic materials 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- 239000002994 raw material Substances 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 abstract description 31
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 10
- 230000000694 effects Effects 0.000 abstract description 8
- RAXXELZNTBOGNW-UHFFFAOYSA-N imidazole Natural products C1=CNC=N1 RAXXELZNTBOGNW-UHFFFAOYSA-N 0.000 abstract description 6
- 229910021536 Zeolite Inorganic materials 0.000 abstract description 2
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 abstract description 2
- 229910001981 cobalt nitrate Inorganic materials 0.000 abstract description 2
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 abstract description 2
- 239000010457 zeolite Substances 0.000 abstract description 2
- 239000011261 inert gas Substances 0.000 abstract 2
- 239000010941 cobalt Substances 0.000 description 24
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 24
- 229910017052 cobalt Inorganic materials 0.000 description 22
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 18
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 15
- 229910052725 zinc Inorganic materials 0.000 description 13
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 10
- 239000011787 zinc oxide Substances 0.000 description 9
- 241000282326 Felis catus Species 0.000 description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- 238000011156 evaluation Methods 0.000 description 5
- 238000005470 impregnation Methods 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 238000003917 TEM image Methods 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 229910052738 indium Inorganic materials 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- QNRATNLHPGXHMA-XZHTYLCXSA-N (r)-(6-ethoxyquinolin-4-yl)-[(2s,4s,5r)-5-ethyl-1-azabicyclo[2.2.2]octan-2-yl]methanol;hydrochloride Chemical compound Cl.C([C@H]([C@H](C1)CC)C2)CN1[C@@H]2[C@H](O)C1=CC=NC2=CC=C(OCC)C=C21 QNRATNLHPGXHMA-XZHTYLCXSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical compound [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 description 3
- HSSJULAPNNGXFW-UHFFFAOYSA-N [Co].[Zn] Chemical compound [Co].[Zn] HSSJULAPNNGXFW-UHFFFAOYSA-N 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000006555 catalytic reaction Methods 0.000 description 3
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- AMBYFCFKKPUPTB-UHFFFAOYSA-N cobalt indium Chemical compound [Co].[In] AMBYFCFKKPUPTB-UHFFFAOYSA-N 0.000 description 2
- 229910000428 cobalt oxide Inorganic materials 0.000 description 2
- 235000019441 ethanol Nutrition 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000003213 activating effect Effects 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000002816 fuel additive Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 239000002638 heterogeneous catalyst Substances 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- ZULISPCCQYDDNG-UHFFFAOYSA-N zinc methanol dinitrate Chemical compound CO.[N+](=O)([O-])[O-].[Zn+2].[N+](=O)([O-])[O-] ZULISPCCQYDDNG-UHFFFAOYSA-N 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B01J35/394—
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
- B01J37/082—Decomposition and pyrolysis
- B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/15—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively
- C07C29/151—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases
- C07C29/153—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used
- C07C29/156—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of oxides of carbon exclusively with hydrogen or hydrogen-containing gases characterised by the catalyst used containing iron group metals, platinum group metals or compounds thereof
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
Abstract
The invention relates to the technical field of catalysts, and particularly discloses a preparation method of a Co-Zn/C-N catalyst and a method for catalyzing CO 2 Application in the reaction of synthesizing methanol by hydrogenation. The catalyst is prepared by coordinating cobalt nitrate, zinc nitrate and 2-methylimidazole to form a ZIF-67@ ZIF-8 zeolite imidazole framework structure, and roasting in inert gas. Simultaneously, indium nitrate is dipped into ZIF-67@ ZIF-8 and is roasted under inert gas to prepare the In-Co-Zn/C-N catalyst, and the Co-Zn/C-N and In-Co-Zn/C-N catalysts can be used for CO 2 The hydrogenation reaction for synthesizing methanol can obtain higher CO under a milder condition 2 Conversion and methanol selectivity. The catalyst has high activity and stability under mild conditions, and has good industrial application prospect.
Description
Technical Field
The invention relates to the technical field of catalysts, in particular to a preparation method of a Co-Zn/C-N catalyst and application thereof in CO 2 Application in the reaction of synthesizing methanol by hydrogenation.
Background
CO 2 Is both a greenhouse gas and the most abundant carbon resource on earth. Catalysis of CO 2 The methanol synthesized by hydrogenation can effectively reduce CO 2 The concentration of the methanol is reduced, the global greenhouse effect is relieved, the produced methanol can be used as a fuel substitute and a fuel additive, and important chemical raw materials are widely applied.
CO 2 The hydrogenation for synthesizing the methanol is an exothermic reaction, and the reaction is more favorable to be carried out in the forward direction due to the lower temperature in thermodynamics, but because CO is generated 2 The chemical inertness of (2) and the low-temperature methanol yield of the conventional catalyst. The methanol synthesis in industry adopts Cu/Zn/Al 2 O 3 Catalyst, under the conditions of 220 ℃ and 300 ℃ and 5-10MPa, synthesizing gas (CO, H) 2 And a small amount of CO 2 ) And (4) carrying out a reaction. In CO 2 Cu/Zn/Al in the hydrogenation synthesis of methanol 2 O 3 The selectivity and yield of methanol as the catalyst still need to be improved. The porous carbon-nitrogen material has higher specific surface area, and the doped nitrogen element increases the alkaline sites of the material and effectively promotes CO 2 Absorption of (2). Cobalt-based catalysts are widely used for the production of hydrocarbons from synthesis gas (fischer-tropsch synthesis). The previous work results of the applicant show that cobalt nitrate and 2-methylimidazole are coordinatedFormation of ZIF-67 Zeolite imidazole framework Structure, N 2 The Co/C-N catalyst prepared by lower roasting has excellent CO 2 Hydrogenation activity, but high methane selectivity and low methanol selectivity in the product.
Disclosure of Invention
Aiming at the defects In the prior art, the invention aims to provide a method for preparing Co-Zn/C-N and In-Co-Zn/C-N catalysts and application thereof In CO 2 Application in synthesizing methanol by hydrogenation.
The invention provides a preparation method of a Co-Zn/C-N catalyst, which comprises the following steps:
(1) respectively dissolving cobalt nitrate hexahydrate and 2-methylimidazole in a proper amount of methanol, quickly adding a cobalt nitrate methanol solution (the step of quickly adding refers to the fact that the cobalt nitrate methanol solution is added within 60 seconds, the description is omitted below) into the 2-methylimidazole methanol solution, and then stirring at room temperature until the mixed solution is gradually changed from black to purple for about 10 min;
(2) respectively dissolving zinc nitrate hexahydrate and 2-methylimidazole in methanol, quickly adding a methanol solution of 2-methylimidazole into the purple solution obtained in the step (1), quickly adding a methanol solution of zinc nitrate into the solution, stirring at room temperature for 30-60min, standing for 12-36h to obtain a purple black solution, centrifuging, washing, and drying to obtain ZIF-67@ ZIF-8-X, wherein X is the molar ratio of Zn to Co in the added raw materials;
(3) and (3) roasting the ZIF-67@ ZIF-8-X obtained in the step (2) for 4-6h at the temperature of 600 ℃ and 800 ℃ in an inert atmosphere to obtain the Co-Zn/C-N-X catalyst.
Further, X is 0.5 to 4;
furthermore, the mass ratio of the cobalt nitrate hexahydrate, the 2-methylimidazole in the step (1), the zinc nitrate hexahydrate and the 2-methylimidazole in the step (2) is (4-5) g: (9-10) g: (2-20) g: (2-20) g, most preferably (4.3-4.4) g: (9.7-9.8) g: (2.2-17.7) g: (2.4-19.6) g.
Further, the specific operation of step (3) is: putting the ZIF-67@ ZIF-8-X obtained in the step (2) into a tube furnace, and adding N 2 Or heating to 600-800 ℃ at the temperature of 10 ℃/min under Ar atmosphere, and roasting at 600-800 ℃ for 4-6h (preferably, roasting at 600 ℃ for 5h) to obtain the Co-Zn/C-N-X catalyst。
Further, the washing in the step (2) is as follows: washed three times with methanol and the temperature of the drying was 60 ℃.
Furthermore, the ZIF-67@ ZIF-8-X, Co-Zn/C-N-X catalyst is of a rhombic dodecahedron structure.
The invention also provides a preparation method of the In-Co-Zn/C-N catalyst, which comprises the following steps:
(a) dropwise adding an indium nitrate aqueous solution into the prepared ZIF-67@ ZIF-8-X, carrying out rotary evaporation In a water bath, drying, and roasting at 800 ℃ for 4-6h under an inert atmosphere to obtain the In-Co-Zn/C-N-X catalyst.
Further, the preparation of the indium nitrate aqueous solution comprises the following steps: dissolving indium nitrate hydrate in deionized water, wherein the mass ratio of the indium nitrate hydrate to ZIF-67@ ZIF-8-X is 0.4: (1-2), preferably 0.43: 1.5.
further, the roasting in the step (a) comprises the following specific steps: in N 2 Or heating to 600-800 ℃ at the temperature of 10 ℃/min under Ar atmosphere, and roasting at 600-800 ℃ for 4-6h (preferably, roasting at 600 ℃ for 5h) to obtain the In-Co-Zn/C-N-X catalyst.
Further, the temperature of the water bath rotary evaporation in the step (a) is 50 ℃, and the temperature of the drying is 100 ℃.
The invention also provides a Co-Zn/C-N or In-Co-Zn/C-N catalyst prepared by the preparation method In CO 2 The application in the methanol synthesis by hydrogenation comprises the following specific steps of:
adding the catalyst into a fixed bed reactor, and introducing CO with the volume fraction of 22.5 percent 2 、 67.5％H 2 And 10% N 2 Gradually increasing the pressure in the reactor to 2MPa and the space velocity of 6Lg cat -1 h -1 Raising the temperature of the reactor to 275 or 300 ℃ at the speed of 2 ℃/min for continuous reaction, starting the timing of reaction time after the conversion rate is stable and the emptying, carrying out online analysis by an Agilent GC3000 gas-phase product, selecting the data of 50h after the reaction is stable, and calculating CO 2 Conversion and gas phase product selectivity. Collected by a cold trapThe liquid-phase product is analyzed by Agilent GC4890, and the selectivity of the liquid-phase product is calculated by taking the average value of 50 h;
CO in product evaluation 2 The conversion and selectivity calculation formula is as follows:
X CO2 :CO 2 conversion, n CO2,in :CO 2 Inlet molar amount, n CO2,out :CO 2 The molar mass of the outlet(s),
n Product,out : number of carbons per product outlet molar quantity carbon number per product.
STY MeOH Space-time yield of methanol, F CO2,in :CO 2 Inlet flow (ml/min), S MeOH : and (4) methanol selectivity.
m cat : catalyst mass (g).
Compared with the prior art, the invention has the following advantages and beneficial effects:
(1) according to the preparation method, zinc is used as an auxiliary agent, so that the dispersion degree of Co In the material is effectively improved, the interaction of Co and In can be reduced, and the selectivity of methanol is improved. Meanwhile, the hydrogenation effect of the metal cobalt is stronger, and the cobalt has high hydrogenation activity in CO 2 Methane is mainly generated in the hydrogenation reaction, so that the selectivity of methanol is improved. In the experiment, XPS detection shows that the Zn/Co molar ratio on the surface of the obtained material is far greater than the actually added content, which indicates that Zn is mainly on the surface of the catalyst, and Co with a lower surface can weaken the stronger hydrogenation capacity, thereby reducing the methane selectivity and improving the methanol selectivity. Meanwhile, Co and Zn have certain interaction, so that Co and Zn are difficult to reduce,the metal particles are also smaller.
(2) The continuous reaction of the fixed bed heterogeneous catalyst proves that the catalyst prepared by the method has good activity, high methanol selectivity and good stability.
(3) The preparation method of the catalyst is relatively simple, the reaction condition is mild, and the scale amplification is easy.
Drawings
FIGS. 1 and 2 are transmission electron micrographs of ZIF-67@ ZIF-8, Co-Zn/C-N catalysts at different ratios of zinc to cobalt. From FIG. 1, it can be seen that ZIF-67@ ZIF-8 is a rhombohedral structure, with the rhombohedral diameter increasing with increasing zinc to cobalt ratio. After being roasted at 600 ℃, as shown in figure 2, the Co-Zn/C-N-0.5 structure is damaged, while the Co-Zn/C-N-1, Co-Zn/C-N-2 and Co-Zn/C-N-4 still keep a better rhombic dodecahedron structure, and cobalt and zinc particles are uniformly distributed on a carbon nitrogen carrier.
FIG. 3 is an XRD pattern of the Co-Zn/C-N catalyst, in which characteristic peaks of metallic cobalt (JCPDS15-0806) and zinc oxide (JCPDS 36-1451) can be detected from Co-Zn/C-N-0.5. No characteristic peak of carbon and nitrogen was observed, indicating that carbon and nitrogen are amorphous structures. The sizes of the Co-Zn/C-N-0.5 catalyst metal cobalt and zinc oxide grains are respectively 10nm and 20nm through calculation of a sheller formula. With the increase of the zinc content, the characteristic peak of zinc oxide in the Co-Zn/C-N-1, Co-Zn/C-N-2 and Co-Zn/C-N-4 catalysts disappears, and the cobalt-zinc carbide Co disappears 3 ZnC (JCPDS 29-0524) characteristic peak appears. The crystal grains of the metal cobalt are slightly reduced, and the sizes of the crystal grains of the metal cobalt of the three catalysts are respectively 7nm, 7nm and 9 nm.
FIG. 4 shows the results of the activity evaluation of Co-Zn/C-N catalyst at 275 deg.C, from which it can be seen that CO increases with the ratio of zinc to cobalt 2 The conversion rate is rapidly reduced, and the selectivity of methanol and CO is rapidly increased. The space-time yields of methanol of the four catalysts are calculated to be 1.4, 2.7, 1.9 and 1.0mmol/g respectively cat /h。
FIG. 5 is a transmission electron micrograph of an In-Co-Zn/C-N catalyst. It can be seen from the figure that the catalyst rhombohedral structure is destroyed after impregnation with indium nitrate.
FIG. 6 is an XRD pattern of the In-Co-Zn/C-N catalyst, and it can be seen that after the catalyst is impregnated with indium nitrate, the catalyst detects characteristic peaks of metallic cobalt (JCPDS15-0806) and cobalt indium carbide (JCPDS 89-7234) and is accompanied with a small amount of zinc oxide (JCPDS 36-1451).
FIG. 7 shows the evaluation results of the activity of In-Co-Zn/C-N catalyst at 300 ℃ after impregnation with indium, catalyst CO 2 The conversion rate is obviously reduced, namely the reaction temperature is increased to 300 ℃, and CO is reduced 2 The conversion rate is only about 10%. But the methane selectivity in the product is significantly reduced, with the major products being CO and methanol. The space-time yields of methanol of the four catalysts are calculated to be 1.2, 0.6, 1.3 and 2.4mmol/g respectively cat H is used as the reference value. Wherein the In-Co-Zn/C-N-4 catalyst is CO at 300 DEG C 2 The conversion rate is 9.1%, the methanol selectivity is 46.6%, and the methanol space-time yield is highest.
Detailed Description
The present invention will be described in detail with reference to specific examples, examples 5 to 8, in which CO is evaluated in the product evaluation 2 The calculation formulas of the conversion rate and the selectivity are described in the technical scheme of the invention.
InN with Allantin reagent as indium nitrate hydrate used in the examples 3 O 9 ·xH 2 O，MW＝300.83。
Example 1 a Co-Zn/C-N-0.5 catalyst was prepared by the following procedure:
(1) 4.32g of cobalt nitrate hexahydrate and 9.75g of 2-methylimidazole are respectively weighed and dissolved in 150ml of methanol, the cobalt nitrate methanol solution is quickly added into the 2-methylimidazole methanol solution, the mixture is stirred for 10min at room temperature, and the mixed solution gradually changes from black to purple.
(2) Weighing 2.23g of zinc nitrate hexahydrate and 2.46g of 2-methylimidazole, respectively dissolving in 150ml of methanol, quickly adding the 2-methylimidazole methanol solution into the purple solution obtained in the step (1), stirring at room temperature for 1min, quickly adding the zinc nitrate methanol solution into the solution, stirring at room temperature for 30min, standing for 24h to obtain a purple solution, centrifuging, washing with methanol for three times, and drying at 60 ℃ to obtain ZIF-67@ ZIF-8-0.5.
(3) Placing the obtained ZIF-67@ ZIF-8-0.5 in a tube furnace under N 2 Heating to 600 ℃ at a speed of 10 ℃/min under the atmosphere, and then roasting for 5h to obtain the Co-Zn/C-N-0.5 catalyst.
Example 2 a Co-Zn/C-N-1 catalyst was prepared by the following procedure:
the use amounts of zinc nitrate hexahydrate and 2-methylimidazole in the step (2) of the example 1 are respectively increased to 4.46g and 4.93g to obtain ZIF-67@ ZIF-8-1, and the rest steps are the same as the example 1 to finally obtain the Co-Zn/C-N-1 catalyst.
Example 3 a Co-Zn/C-N-2 catalyst was prepared by the following procedure:
the use amounts of zinc nitrate hexahydrate and 2-methylimidazole in the step (2) of the example 1 are respectively increased to 8.92g and 9.76g to obtain ZIF-67@ ZIF-8-2, and the rest steps are the same as the example 1 to finally obtain the Co-Zn/C-N-2 catalyst.
Example 4 a Co-Zn/C-N-4 catalyst was prepared by the following procedure:
the use amounts of zinc nitrate hexahydrate and 2-methylimidazole in the step (2) of the example 1 are respectively increased to 17.84g and 19.50g, and the rest steps are the same as the example 1, so that ZIF-67@ ZIF-8-4 is obtained, and finally the Co-Zn/C-N-4 catalyst is obtained.
FIGS. 1 and 2 are transmission electron micrographs of ZIF-67@ ZIF-8, Co-Zn/C-N catalysts prepared in examples 1-4, in that order, and in different ratios of zinc to cobalt. The ZIF-67@ ZIF-8 can be seen to be a rhombohedral structure, with the rhombohedral diameter increasing with the proportion of zinc and cobalt. After being roasted at 600 ℃, the Co-Zn/C-N-0.5 (figure 2) structure is damaged, the catalysts Co-Zn/C-N-1, Co-Zn/C-N-2 and Co-Zn/C-N-4 still keep a better rhombic dodecahedron structure, and cobalt and zinc are uniformly distributed on a carbon nitrogen carrier.
FIG. 3 is an XRD pattern of the Co-Zn/C-N catalysts prepared in examples 1-4, in which it can be seen that characteristic peaks of metallic cobalt (JCPDS15-0806) and zinc oxide (JCPDS 36-1451) were detected from Co-Zn/C-N-0.5, and no characteristic peak of carbon and nitrogen was observed, indicating that carbon and nitrogen are amorphous structures. The grain diameters of the Co-Zn/C-N-0.5 catalyst surface metal cobalt and the zinc oxide grain are respectively 10nm and 20nm through calculation of a sheller formula. With the increase of the zinc content, the characteristic peak of zinc oxide in the Co-Zn/C-N-1, Co-Zn/C-N-2 and Co-Zn/C-N-4 catalysts disappears, and the cobalt-zinc carbide Co disappears 3 ZnC (JCPDS 29-0524) characteristic peak appears. The crystal grains of the metallic cobalt are slightly reduced, and the sizes of the crystal grains of the metallic cobalt of the three catalysts are respectively 7nm, 7nm and 9nm。
Examples 5 to 8:
example 5: catalysis of CO Using the catalysts prepared in examples 1-4 2 The method for synthesizing the methanol by hydrogenation comprises the following steps:
0.2g of the Co-Zn/C-N-0.5 catalyst prepared in example 1 was charged into a fixed bed reactor (made of stainless steel, 47cm long and 1/4 inches in inner diameter), and 22.5% by volume of CO was introduced into the reactor 2 、67.5％H 2 And 10% N 2 The pressure of the reactor is increased to 2MPa within 3h, and the space velocity is 6Lg cat -1 h -1 And then the temperature of the reactor is increased to 275 ℃ (the temperature increase rate is 2 ℃/min), and the reaction time is timed after the conversion rate is stable and the air is discharged. Performing on-line analysis on the gas-phase product by an Agilent GC3000, selecting data after the reaction is stabilized for 50h to calculate CO 2 Conversion and gas phase product selectivity. Collecting the liquid phase product by a cold trap, analyzing by Agilent GC4890, and taking the average value of reaction for 50h to calculate the selectivity of the liquid phase product.
Examples 6 to 8: the catalysts of examples 2 to 4 were subjected to the application test in the same manner.
Examples 5-8 CO at 275 deg.C 2 The results of the conversion and the product selectivity evaluations are shown in FIG. 4. It can be seen from the figure that CO increases with the ratio of zinc to cobalt 2 The conversion rate is rapidly reduced, and the selectivity of methanol and CO is rapidly increased. Illustrates that metallic cobalt is beneficial to activating CO 2 However, too much metallic cobalt catalyzes mainly CO 2 Production of methane (CO) 2 +4H 2 →CH 4 +2H 2 O). While the interface of cobalt and zinc oxide or cobalt zinc carbide mainly generates methanol (CO) 2 +3H 2 →CH 3 OH+H 2 O) or CO (CO) 2 +H 2 →CO+H 2 O). The methanol space-time yields of the four catalysts of examples 1 to 4 were calculated to be 1.4, 2.7, 1.9, 1.0mmol/g, respectively cat /h。
In fig. 4: s CO (ii) a CO Selectivity, S CH4 : methane selectivity, S C2+HC : c2 and above hydrocarbon selectivity, S MeOH : selectivity to methanol, S C2H5OH : ethanol selectivity, STY MeOH : methanol space time yield.
Example 9: the In-Co-Zn/C-N-0.5 catalyst is prepared by the following specific steps:
dissolving 0.43g of indium nitrate hydrate in 0.6g of deionized water to obtain an indium nitrate aqueous solution, slowly dropwise adding the indium nitrate aqueous solution into 1.5g of ZIF-67@ ZIF-8-0.5 prepared in example 1, carrying out water bath rotary evaporation at 50 ℃, drying at 100 ℃, placing the obtained product in a tubular furnace, and carrying out N-ion exchange in a N-ion exchange column 2 Heating to 600 ℃ at a speed of 10 ℃/min under the atmosphere, and then roasting for 5h to obtain the In-Co-Zn/C-N-0.5 catalyst.
Example 10: the In-Co-Zn/C-N-1 catalyst is prepared by the following specific steps:
the ZIF-67@ ZIF-8-0.5 In example 9 was replaced with the same amount of ZIF-67@ ZIF-8-1 prepared In example 2, and the other steps were not changed to obtain an In-Co-Zn/C-N-1 catalyst.
Example 11: the In-Co-Zn/C-N-2 catalyst is prepared by the following specific steps:
the ZIF-67@ ZIF-8-0.5 catalyst obtained In example 9 was replaced with the same amount of ZIF-67@ ZIF-8-2 catalyst obtained In example 3 to obtain an In-Co-Zn/C-N-2 catalyst.
Example 12: the In-Co-Zn/C-N-4 catalyst is prepared by the following specific steps:
the amount of ZIF-67@ ZIF-8-0.5 used In example 9 was replaced with the same amount of ZIF-67@ ZIF-8-4 as that used In example 4 to obtain an In-Co-Zn/C-N-4 catalyst.
FIG. 5 is a transmission electron micrograph of In-Co-Zn/C-N catalysts prepared In examples 9 to 12, In that order. It can be seen from the figure that the catalyst has a broken rhombohedral structure after impregnation with indium nitrate.
FIG. 6 is an XRD pattern of the In-Co-Zn/C-N catalyst prepared In examples 9-12, In which it can be seen that after impregnation with indium nitrate, the catalyst detects characteristic peaks of metallic cobalt (JCPDS15-0806) and cobalt indium carbide (JCPDS 89-7234) accompanied by characteristic peaks of a small amount of zinc oxide (JCPDS 36-1451).
Examples 13 to 16: catalysis of CO Using the catalysts prepared in examples 9-12 2 A process for the hydrogenation of methanol, which comprises the same steps as in examples 5 to 8, except that: the reaction temperature was fixed at 300 ℃.
From the figure7 it can be seen that the catalyst CO after impregnation with indium 2 The conversion rate is obviously reduced, namely, the reaction temperature is increased to 300 ℃, and CO is added 2 The conversion rate is only about 10%. But the methane selectivity in the product is significantly reduced, with the major products being CO and methanol. Indicating that indium is beneficial for catalyzing CO 2 Hydrogenation produces CO and methanol. The methanol space-time yields of the four catalysts obtained in examples 9 to 12 were calculated to be 1.2, 0.6, 1.3, 2.4mmol/g cat H is used as the reference value. Wherein the In-Co-Zn/C-N-4 catalyst is at 300 ℃ and CO 2 The conversion rate is 9.1 percent, the methanol selectivity is 46.6 percent, and the space-time yield of the methanol is the highest and reaches 2.4mmol/g cat /h。
Claims (7)
1. A preparation method of an In-Co-Zn/C-N catalyst comprises the following steps:
(1) respectively dissolving cobalt nitrate hexahydrate and 2-methylimidazole in methanol, quickly adding a cobalt nitrate methanol solution into a 2-methylimidazole methanol solution, and then stirring at room temperature until the mixed solution is gradually changed from black to purple;
(2) respectively dissolving zinc nitrate hexahydrate and 2-methylimidazole in methanol, quickly adding a methanol solution of 2-methylimidazole into the purple solution obtained in the step (1), quickly adding the methanol solution of zinc nitrate, stirring at room temperature for 30-60min, standing for 12-36h to obtain a purple black solution, centrifuging, washing, and drying to obtain ZIF-67@ ZIF-8-X, wherein X is the molar ratio of Zn to Co in the added raw materials;
(3) dropwise adding an indium nitrate aqueous solution into ZIF-67@ ZIF-8-X, carrying out rotary evaporation In a water bath, drying, and roasting at the temperature of 600-.
2. The method of claim 1, wherein X = 0.5-4.
3. The preparation method according to claim 2, wherein the mass ratio of the cobalt nitrate hexahydrate, the 2-methylimidazole in the step (1), the zinc nitrate hexahydrate and the 2-methylimidazole in the step (2) is (4-5): (9-10): (2-20): (2-20).
4. The method of claim 1, wherein said ZIF-67@ ZIF-8-X is a rhombohedral structure.
5. The method of claim 1 wherein the aqueous solution of indium nitrate is prepared by: dissolving indium nitrate hydrate in deionized water, wherein the mass ratio of the indium nitrate hydrate to ZIF-67@ ZIF-8-X is 0.4: (1-2).
6. The preparation method according to claim 1, wherein the roasting in the step (3) comprises the following specific steps: in N 2 Or heating to 600-800 ℃ at a speed of 10 ℃/min under Ar atmosphere, and roasting at 600-800 ℃ for 4-6h to obtain the In-Co-Zn/C-N-X catalyst.
7. An In-Co-Zn/C-N-X catalyst prepared by the preparation method of any one of claims 1 to 6 In CO 2 Application in synthesizing methanol by hydrogenation.
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| CN108722460A (en) * | 2018-04-08 | 2018-11-02 | 湖北大学 | NiCo@N-C bi-functional oxygen electrode catalyst based on MOFs and preparation method thereof |
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