CN116603525A - Silver-based catalyst and preparation method and application thereof - Google Patents
Silver-based catalyst and preparation method and application thereof Download PDFInfo
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- CN116603525A CN116603525A CN202310457411.2A CN202310457411A CN116603525A CN 116603525 A CN116603525 A CN 116603525A CN 202310457411 A CN202310457411 A CN 202310457411A CN 116603525 A CN116603525 A CN 116603525A
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- Prior art keywords
- silver
- based catalyst
- carrier
- cerium
- cerium oxide
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- 239000004332 silver Substances 0.000 title claims abstract description 190
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 title claims abstract description 189
- 229910052709 silver Inorganic materials 0.000 title claims abstract description 189
- 239000003054 catalyst Substances 0.000 title claims abstract description 145
- 238000002360 preparation method Methods 0.000 title claims abstract description 32
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 78
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 78
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims abstract description 57
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 50
- JVTAAEKCZFNVCJ-UHFFFAOYSA-M Lactate Chemical compound CC(O)C([O-])=O JVTAAEKCZFNVCJ-UHFFFAOYSA-M 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 29
- LOMVENUNSWAXEN-UHFFFAOYSA-N Methyl oxalate Chemical compound COC(=O)C(=O)OC LOMVENUNSWAXEN-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 22
- 235000012239 silicon dioxide Nutrition 0.000 claims abstract description 20
- 238000005984 hydrogenation reaction Methods 0.000 claims abstract description 18
- 239000002105 nanoparticle Substances 0.000 claims abstract description 11
- 239000002245 particle Substances 0.000 claims description 52
- 238000006243 chemical reaction Methods 0.000 claims description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- -1 specifically Substances 0.000 claims description 22
- 238000001035 drying Methods 0.000 claims description 20
- 230000009467 reduction Effects 0.000 claims description 20
- 230000001588 bifunctional effect Effects 0.000 claims description 18
- 239000002243 precursor Substances 0.000 claims description 18
- 238000003756 stirring Methods 0.000 claims description 17
- 239000012695 Ce precursor Substances 0.000 claims description 14
- 239000001257 hydrogen Substances 0.000 claims description 14
- 229910052739 hydrogen Inorganic materials 0.000 claims description 14
- 150000003839 salts Chemical class 0.000 claims description 14
- 239000007789 gas Substances 0.000 claims description 11
- 229910002011 hydrophilic fumed silica Inorganic materials 0.000 claims description 11
- CQLFBEKRDQMJLZ-UHFFFAOYSA-M silver acetate Chemical compound [Ag+].CC([O-])=O CQLFBEKRDQMJLZ-UHFFFAOYSA-M 0.000 claims description 11
- 229940071536 silver acetate Drugs 0.000 claims description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- 239000012018 catalyst precursor Substances 0.000 claims description 10
- 239000008367 deionised water Substances 0.000 claims description 10
- 229910021641 deionized water Inorganic materials 0.000 claims description 10
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims description 10
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 8
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 claims description 8
- 238000002390 rotary evaporation Methods 0.000 claims description 8
- 229910052710 silicon Inorganic materials 0.000 claims description 8
- 239000010703 silicon Substances 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 7
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 6
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 5
- 229910001961 silver nitrate Inorganic materials 0.000 claims description 5
- 229910021529 ammonia Inorganic materials 0.000 claims description 4
- XMPZTFVPEKAKFH-UHFFFAOYSA-P ceric ammonium nitrate Chemical compound [NH4+].[NH4+].[Ce+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O XMPZTFVPEKAKFH-UHFFFAOYSA-P 0.000 claims description 4
- OZECDDHOAMNMQI-UHFFFAOYSA-H cerium(3+);trisulfate Chemical compound [Ce+3].[Ce+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O OZECDDHOAMNMQI-UHFFFAOYSA-H 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 239000011148 porous material Substances 0.000 claims description 4
- 239000002244 precipitate Substances 0.000 claims description 4
- 239000001569 carbon dioxide Substances 0.000 claims description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 3
- 229910021485 fumed silica Inorganic materials 0.000 claims description 3
- 150000002431 hydrogen Chemical class 0.000 claims description 3
- 229910000161 silver phosphate Inorganic materials 0.000 claims description 3
- FJOLTQXXWSRAIX-UHFFFAOYSA-K silver phosphate Chemical compound [Ag+].[Ag+].[Ag+].[O-]P([O-])([O-])=O FJOLTQXXWSRAIX-UHFFFAOYSA-K 0.000 claims description 3
- 229940019931 silver phosphate Drugs 0.000 claims description 3
- LMEWRZSPCQHBOB-UHFFFAOYSA-M silver;2-hydroxypropanoate Chemical compound [Ag+].CC(O)C([O-])=O LMEWRZSPCQHBOB-UHFFFAOYSA-M 0.000 claims description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 2
- LGZVIFDFEQVAKL-UHFFFAOYSA-N azane cerium(3+) trinitrate Chemical compound N.[Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O LGZVIFDFEQVAKL-UHFFFAOYSA-N 0.000 claims description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 238000011068 loading method Methods 0.000 abstract description 17
- 230000003197 catalytic effect Effects 0.000 abstract description 11
- 239000012752 auxiliary agent Substances 0.000 abstract description 7
- 230000000694 effects Effects 0.000 description 32
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 19
- 229910052684 Cerium Inorganic materials 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 11
- 238000011156 evaluation Methods 0.000 description 11
- 239000000243 solution Substances 0.000 description 10
- HKVFISRIUUGTIB-UHFFFAOYSA-O azanium;cerium;nitrate Chemical group [NH4+].[Ce].[O-][N+]([O-])=O HKVFISRIUUGTIB-UHFFFAOYSA-O 0.000 description 8
- LVMBEXJKZGJYRH-UHFFFAOYSA-N [Ag].[Ce] Chemical compound [Ag].[Ce] LVMBEXJKZGJYRH-UHFFFAOYSA-N 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 7
- 239000001301 oxygen Substances 0.000 description 7
- 229910052760 oxygen Inorganic materials 0.000 description 7
- 230000008569 process Effects 0.000 description 7
- 238000004873 anchoring Methods 0.000 description 6
- 230000009977 dual effect Effects 0.000 description 6
- 238000002173 high-resolution transmission electron microscopy Methods 0.000 description 6
- 230000003993 interaction Effects 0.000 description 6
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 5
- XNRNVYYTHRPBDD-UHFFFAOYSA-N [Si][Ag] Chemical compound [Si][Ag] XNRNVYYTHRPBDD-UHFFFAOYSA-N 0.000 description 5
- 230000007423 decrease Effects 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 239000006185 dispersion Substances 0.000 description 4
- 238000009904 heterogeneous catalytic hydrogenation reaction Methods 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 238000005245 sintering Methods 0.000 description 4
- 229920000954 Polyglycolide Polymers 0.000 description 3
- 238000005054 agglomeration Methods 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 3
- 239000003245 coal Substances 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000004633 polyglycolic acid Substances 0.000 description 3
- 239000010453 quartz Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 208000012839 conversion disease Diseases 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000002194 synthesizing effect Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 238000004176 ammonification Methods 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- OTMRNYIQCFEMDQ-UHFFFAOYSA-N cerium(3+) dioxosilane oxygen(2-) Chemical compound [O-2].[Ce+3].[Si](=O)=O.[O-2].[O-2].[Ce+3] OTMRNYIQCFEMDQ-UHFFFAOYSA-N 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 238000012854 evaluation process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000013067 intermediate product Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 229910001923 silver oxide Inorganic materials 0.000 description 1
- YPNVIBVEFVRZPJ-UHFFFAOYSA-L silver sulfate Chemical compound [Ag+].[Ag+].[O-]S([O-])(=O)=O YPNVIBVEFVRZPJ-UHFFFAOYSA-L 0.000 description 1
- 229910000367 silver sulfate Inorganic materials 0.000 description 1
- 235000013599 spices Nutrition 0.000 description 1
- 230000007480 spreading Effects 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
Classifications
-
- 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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/66—Silver or gold
-
- 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
- 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
- B01J35/391—Physical properties of the active metal ingredient
- B01J35/393—Metal or metal oxide crystallite size
-
- 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
- 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
-
- 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
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
-
- 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
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
-
- 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
- B01J37/0009—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)
-
- 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
- B01J37/02—Impregnation, coating or precipitation
- B01J37/0201—Impregnation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
- C07C67/31—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by introduction of functional groups containing oxygen only in singly bound form
-
- 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
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Catalysts (AREA)
Abstract
The invention discloses a silver-based catalyst and a preparation method and application thereof, wherein the silver-based catalyst comprises a carrier and an active component, the active component is a silver species, and the carrier is a difunctional carrier; the difunctional carrier comprises cerium oxide and silicon dioxide, and the silver-based catalyst has the structure that: the cerium oxide is uniformly dispersed on the surface of the silicon dioxide nano particles in the form of nano islands, and the silver species are located on the cerium oxide nano islands in the form of nano particles. The method successfully prepares the silver-based catalyst with a special structure by a two-step loading method, and in the preparation process, the method improves the dispersity of cerium oxide by adding the citric acid auxiliary agent, and simultaneously, the silver species is selectively dispersed on the cerium oxide nanometer islands by a method of pre-reducing the difunctional carrier. The silver-based catalyst provided by the invention has the advantages of low silver loading, high catalytic activity, high selectivity and high stability when being used for preparing methyl glycolate through dimethyl oxalate hydrogenation.
Description
Technical Field
The invention belongs to the technical field of catalysts, relates to a silver-based catalyst and a preparation method and application thereof, and in particular relates to a silver-based catalyst for preparing Methyl Glycolate (MG) through dimethyl oxalate hydrogenation and a preparation method and application thereof.
Background
Methyl glycolate is an important chemical raw material intermediate, can be used for synthesizing high-added-value chemicals such as medicines, cosmetics, spices, pesticides and the like, and has wide application prospects. Polyglycolic acid has strong environmental degradability, and can be degraded into carbon dioxide and water within 1-3 months in nature, so that the demand is huge, and the mass production of the raw material methyl glycolate for synthesizing the polyglycolic acid is important. However, the traditional methyl glycolate production process route has the problems of serious pollution, harsh reaction conditions and the like, and can not realize the large-scale production of methyl glycolate. In recent years, the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol via a coal-based route has become one of the most representative coal chemical technologies. The methyl glycolate is a preliminary hydrogenation product of the dimethyl oxalate, the selective regulation and control of the hydrogenation reaction product of the oxalic ester is expected to realize the large-scale production of coal-based polyglycolic acid routes, and the process has high atom economy, green and environment-friendly performance, and has good development prospect and economic value.
The silver-based catalyst shows excellent catalytic activity in preparing methyl glycolate through dimethyl oxalate hydrogenation at present, and has wide industrial application prospect. Compared with a copper-based catalyst, the hydrogenation capacity of silver is weaker, so that the hydrogenation reaction of dimethyl oxalate can stay in the first step, and in addition, the adsorption of silver methyl glycolate is weaker than that of the copper-based catalyst, so that the product methyl glycolate is prevented from further hydrogenation to generate by-product glycol, and the selectivity of methyl glycolate by adopting the silver-based catalyst can reach more than 85%. However, the silver-based catalysts currently have the following problems: 1. in order to ensure that the silver species present as metallic silver shows excellent catalytic activity, silver loading in silver-based catalysts is generally high, and the price and the cost are high; 2. the Tasman temperature of silver is only 345 ℃, silver particles are easy to migrate due to high temperature, and silver species catalysts are easy to agglomerate into large particles in the use process, so that the catalysts are poor in stability and easy to deactivate, and industrial application of the catalysts is hindered.
The present invention aims to solve the above-mentioned problems.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a silver-based catalyst with a dual-function carrier, aiming at the problems of high silver load and poor stability of the silver-based catalyst in the technology for preparing methyl glycolate by hydrogenating dimethyl oxalate. The method successfully prepares the silver-based catalyst with a special structure by a two-step loading method, and in the preparation process, the method improves the dispersity of cerium oxide by adding the citric acid auxiliary agent, and simultaneously, the silver species is selectively dispersed on the cerium oxide nanometer islands by a method of pre-reducing the difunctional carrier. The silver-based catalyst provided by the invention has the characteristics of low silver loading, high catalytic activity, high selectivity and high stability when being used for preparing Methyl Glycolate (MG) through dimethyl oxalate hydrogenation.
The technical scheme adopted by the invention is as follows:
the first aspect of the invention provides a silver-based catalyst comprising a support and an active component, the active component being a silver species, the support being a bifunctional support; the difunctional carrier comprises cerium oxide and silicon dioxide, and the silver-based catalyst has the structure that: the cerium oxide is uniformly dispersed on the surface of the silicon dioxide nano particles in the form of nano islands, and the silver species are located on the cerium oxide nano islands in the form of nano particles.
The cerium oxide nano islands herein mean cerium oxide particles dispersed on silicon oxide like islands, similar to cerium oxide nano particles. The reason for using cerium oxide nano islands instead of cerium oxide nano particles is that the cerium oxide particles are uniformly dispersed on silicon dioxide like islands, the adhesion condition between nano islands is relatively small, and corresponding silver species cannot cross from one nano island to another nano island.
Preferably, the silver species comprises 1-20wt.% of the total mass of the silver-based catalyst, and the bifunctional support comprises 80-99wt.% of the total mass of the silver-based catalyst; further, the silver species comprises 2-5wt.% of the total mass of the catalyst, and the difunctional carrier comprises 95-98wt.% of the total mass of the catalyst. The cerium oxide accounts for 1-40wt.% of the total mass of the dual-function carrier, and the silicon dioxide accounts for 60-99wt.% of the total mass of the dual-function carrier; further, the cerium oxide accounts for 1-10wt.% of the total mass of the carrier, and the silicon dioxide accounts for 90-99wt.% of the total mass of the carrier. The reason why the cerium oxide is required to limit the total mass of the bifunctional support to the above range is that: 1. the cerium oxide content is high, the particle sizes of cerium oxide and silver species are correspondingly increased, and the exposure of active sites on the surfaces of the silver species is reduced, so that the activity is reduced; 2. the cerium oxide content increases, resulting in an increase in the silver valence state and a decrease in the activity of the catalyst.
The specific surface area of the silver-based catalyst is 50-200m 2 Per gram, average pore volume of 0.7-1.4cm 3 And/g, the average pore diameter is 10-30nm.
Preferably, the particle size of the silver species is 1.0-20nm, and the cerium oxide nano island size is 2.0-30nm; further, the particle size of the silver species is 2-5nm, and the cerium oxide nano island size is 2-6nm; still further, the silver species has a particle size of 4-5nm and the cerium oxide nanoislands have a size of 4-6nm.
A second aspect of the present invention provides a method for preparing the silver-based catalyst according to the first aspect of the present invention, comprising the steps of:
(1) Dissolving silver precursor salt in deionized water, and stirring to obtain silver precursor solution;
(2) Dispersing the difunctional carrier in the precursor solution obtained in the step (1), and stirring in a dark place;
(3) And (3) removing water in the mixture obtained in the step (2) through rotary evaporation to obtain a catalyst precursor precipitate, and drying and roasting the catalyst precursor to obtain the silver-based catalyst.
Preferably, the silver precursor salt is selected from any one of silver nitrate, silver phosphate, silver lactate or silver acetate, preferably selected from silver acetate;
the stirring time in the step (1) is 10-20min; stirring time in the step (2) is 10-40h; the drying conditions in the step (3) are as follows: the drying temperature is 80-130 ℃ and the drying time is 12-24 hours; the roasting temperature is 300-700 ℃ and the roasting time is 2-6h.
Preferably, the preparation method of the bifunctional vector in step (2) comprises the following steps:
(a) Dissolving cerium precursor salt in deionized water, and stirring to obtain cerium precursor solution;
(b) Dispersing a silicon source in the cerium precursor solution obtained in the step (a), and stirring;
(c) Removing water in the mixture obtained in the step (b), performing rotary evaporation to obtain a difunctional carrier precursor precipitate, and drying and roasting the difunctional carrier precursor to obtain the difunctional carrier.
Preferably, the cerium precursor salt is any one of cerium nitrate, cerium sulfate or cerium ammonia nitrate, more preferably selected from cerium ammonium nitrate; the silicon source is any one of hydrophilic fumed silica, lipophilic fumed silica, alkaline silica sol or ammonia silica sol, and is more preferably selected from hydrophilic fumed silica;
the stirring time in the step (a) is 10-20min; stirring in the step (b) for 10-40h; the drying conditions in step (c) are: the drying temperature is 80-130 ℃ and the drying time is 12-24 hours; the roasting temperature is 300-700 ℃ and the roasting time is 2-6h.
Preferably, the precursor solution in the step (a) contains citric acid, specifically, cerium precursor salt and citric acid are dissolved in deionized water, and the mixture is stirred to obtain cerium precursor solution;
the molar ratio of the cerium precursor salt to the citric acid is 1:1.25-0.5.
Preferably, the bifunctional support is used for preparing the silver-based catalyst after reduction, specifically: reducing the difunctional carrier obtained in the step (c) in reducing gas at high temperature, transferring the reduced difunctional carrier into inert gas for protection, and taking out the difunctional carrier when the difunctional carrier is used in the step (2);
the reduction treatment conditions are as follows: the reduction temperature is 300-700 ℃, the reduction time is 2-10h, and the reducing gas is selected from hydrogen, carbon monoxide or ammonia, more preferably hydrogen;
the inert gas is selected from argon, nitrogen, helium or carbon dioxide, more preferably from argon.
According to a third aspect of the invention, there is provided the use of a silver-based catalyst according to the first aspect of the invention for the catalytic selective hydrogenation of dimethyl oxalate to methyl glycolate;
the method comprises the following steps: introducing mixed gasified dimethyl oxalate and hydrogen into a reactor packed with the silver-based catalyst for reaction;
the reaction pressure is 0.5-3.5MPa; the reaction temperature is 200-240 ℃; the mass airspeed of the dimethyl oxalate is 0.1-4.0h -1 The method comprises the steps of carrying out a first treatment on the surface of the The molar ratio of the hydrogen ester (hydrogen ester ratio for short) is 60-150.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention successfully prepares the silver-based catalyst with a special structure, and the special structure is as follows: the cerium oxide is dispersed on the surface of the silicon dioxide nano-particles in the form of nano-islands, the silver species are located on the cerium oxide nano-islands in the form of nano-particles instead of being located on the surface of the silicon dioxide nano-particles, and meanwhile, the sizes of the silver species and the cerium oxide nano-islands are moderate, specifically, the particle size of the silver species is 1.0-20nm, and the size of the cerium oxide nano-islands is 2.0-30nm; further, the particle size of the silver species is 2-5nm, and the cerium oxide nano island size is 2-6nm; still further, the silver species has a particle size of 4-5nm and the cerium oxide nanoislands have a size of 4-6nm.
2. The silver-based catalyst has high stability when being used for heterogeneous hydrogenation reaction of dimethyl oxalate, and the reason is that: the cerium oxide is uniformly dispersed on the silicon dioxide in the form of nanometer islands, the silicon dioxide provides a large specific surface area, the cerium oxide nanometer islands are favorable for dispersion, ag species fall on the cerium oxide nanometer islands, the cerium oxide is a strong interaction carrier of silver, the function of anchoring the silver species is provided, and sintering of silver particles can be prevented. The silicon dioxide is a weak interaction carrier and is not easy to age through monoatomic migration, so that the Ostwald aging of metallic silver is prevented, the structure of the silver-based catalyst ensures that the problem of silver particle growth does not exist in the long-term use process, the stability of the catalyst is improved, and the catalyst replacement cost is greatly reduced in industry.
3. The silver-based catalyst has high catalytic activity when being used for heterogeneous hydrogenation reaction of dimethyl oxalate. The catalyst only uses metallic silver as an active center to catalyze the hydrogenation reaction of dimethyl oxalate, and compared with the silver load of more than 10wt.% in the prior art, the silver load in the invention is only 4wt.%, and the MG yield can reach more than 90%. In addition, the silver space time yield per unit mass of the silver-silicon catalyst reported in the prior art is less than 10 g.g Ag -1 ·h -1 The silver space-time yield per unit mass of the catalyst added with the cerium auxiliary agent is less than 1 g.g Ag -1 ·h -1 The space-time yield of silver per unit mass of the catalyst in the invention is up to 103 g.g Ag -1 ·h -1 . The catalyst has low silver loading capacity, greatly improves the silver utilization efficiency and greatly saves the catalyst production cost.
4. When the silver-based catalyst is used for preparing methyl glycolate through hydrogenation of dimethyl oxalate, the directional selectivity of methyl glycolate is high, and compared with a silver-silicon catalyst, the addition of cerium improves the selectivity from 84% to 93%, so that the energy consumption required by product separation is reduced.
5. Furthermore, the citric acid auxiliary agent is added in the preparation process of the difunctional carrier, the dispersity of the cerium oxide nanometer islands on silicon dioxide can be improved by adding the citric acid auxiliary agent, and the agglomeration of cerium oxide is avoided, so that the size of the cerium oxide nanometer islands is reduced, silver nanometer particles fall on the cerium oxide nanometer islands, the size of the silver nanometer particles is further reduced due to the reduction of the size of the cerium oxide nanometer islands, so that more active surfaces of silver species are exposed, and the catalytic activity of the catalyst is improved. The invention further controls the sizes of the silver species and the cerium oxide nanometer island by using the method, thereby obtaining the silver-based catalyst with the particle size of the silver species of 4-5nm and the cerium oxide nanometer island size of 4-6nm, and further improving the catalytic activity of the catalyst.
6. Furthermore, the invention increases the oxygen vacancy content on the cerium oxide by reducing the carrier, and the oxygen vacancy can form strong metal-carrier interaction with the metal silver, thereby improving the anchoring capability of the cerium oxide nanometer island to silver particles and enabling silver species to be selectively dispersed on the cerium oxide nanometer island.
7. Further, the silver precursor salt is selected from silver acetate, and the introduction of cerium can cause the valence state of silver to be increased to positive monovalent silver, and the adsorption and dissociation capability of the positive monovalent silver to hydrogen is weak, so that the activity of the catalyst is reduced sharply. The silver precursor salt is more beneficial to forming zero-valent silver and improving the stability of the catalyst. In the invention, the cerium source is selected from ammonium cerium nitrate, more gas is released in the roasting process of ammonium cerium nitrate relative to cerium nitrate, so that the dispersity of cerium oxide is improved, and compared with cerium sulfate, residual sulfate radical and silver species can generate silver sulfate due to the fact that the sulfate radical can not be removed, the valence state of silver is positive monovalent, and the activity of the silver-based catalyst is reduced. In the present invention, the silicon source is selected from hydrophilic fumed silica, which can improve the dispersity of cerium oxide relative to lipophilic fumed silica, alkaline silica sol or ammonification silica sol.
8. When the silver-based catalyst obtained by the invention is used for heterogeneous hydrogenation reaction of dimethyl oxalate, the catalyst has the characteristics of easily obtained raw materials, mild reaction conditions, simple and controllable process, stable structure, strong operability, good industrial application prospect and the like.
Drawings
FIG. 1 is a high resolution TEM image of the catalyst of comparative example 1 of the present invention;
FIG. 2 is a high resolution TEM image of the catalyst of example 1 of the present invention;
FIG. 3 is a high resolution TEM image of the catalyst of example 2 of the present invention;
FIG. 4 is a high resolution TEM image of the dual function carrier of example 2 of the present invention;
FIG. 5 is a high resolution TEM image of the dual function carrier of example 3 of the present invention;
FIG. 6 is a high resolution TEM image of the catalyst of example 10 of the present invention;
FIG. 7 shows the results of evaluation of the stability of the catalysts of comparative example 1 and examples 1 to 3 in the reaction for producing methyl glycolate by hydrogenating dimethyl oxalate according to the present invention.
Detailed Description
The present invention will be further described by way of examples, which are not intended to limit the scope of the invention. Experimental methods, in which specific conditions are not specified in examples, are generally available commercially according to conventional conditions as well as those described in handbooks, or according to general-purpose equipment, materials, reagents, etc. used under conditions suggested by manufacturers, unless otherwise specified.
The method for evaluating the on-line reduction and catalytic effect of the catalyst in this example and comparative example is as follows:
in the invention, the dimethyl oxalate hydrogenation reaction is carried out in a fixed bed reactor. Filling 1.0g of catalyst, reducing at 250 ℃ in a hydrogen atmosphere of 2.5MPa, keeping the gas flow at 100mL/min, cooling to the reaction temperature for 4 hours, gasifying dimethyl oxalate solution, mixing with hydrogen, entering a reaction system, enabling the hydrogen-ester ratio to be 80, and carrying out hydrogenation reaction at 2.5MPa and 225 ℃. The product after the reaction was analyzed by gas chromatography, and the conversion of dimethyl oxalate and the selectivity and yield of methyl glycolate were calculated. Because the dimethyl oxalate hydrogenation reaction is a continuous reaction, methyl glycolate is an intermediate hydrogenation product, and the difference of selectivity to the intermediate product can be reflected only when the conversion rate is not 100%, the reaction airspeed is regulated so that the reaction conversion rate is 98.5%; in the stability evaluation process, in order to make full use of all active sites to participate in the reaction, the occurrence of the condition that the catalyst is deactivated and the conversion rate is still 100% is prevented, and therefore, it is necessary to perform stability evaluation under the condition that the conversion rate is not 100%.
Specific experimental conditions for the comparative example and the catalysts of each example are shown in Table 1 below, and activity data are shown in Table 2 below.
Comparative example 1
Preparation of silver-silicon catalyst
The preparation of the silver-silicon catalyst comparative sample 1 with a single carrier is as follows:
0.1312g of silver nitrate was dissolved in 150ml of deionized water, stirred uniformly for 10min, and 2g of hydrophilic fumed silica powder from commercial purchase was added to the silver nitrate aqueous solution, stirred in the dark for 20h. The water was removed by rotary evaporation and the resulting catalyst precursor was placed in an oven at 110 ℃ overnight for drying to remove residual water. And finally, heating the catalyst precursor to 500 ℃ in an air atmosphere, and roasting for 4 hours to obtain the catalyst.
The catalyst of the comparative example was subjected to the above-mentioned on-line reduction conditions and catalyst evaluation method for 1.2 hours -1 The reaction was carried out under evaluation and the yield was reduced by 38.4% over 500 h.
Example 1
Preparation of silver cerium silicon catalyst (non-reducing, non-citric acid assisted)
The preparation of the silver cerium silicon catalyst sample 1 of the bifunctional carrier is as follows:
preparing a dual-function carrier:
0.2600g of ammonium cerium nitrate was dissolved in 150ml of deionized water, uniformly stirred for 10min, 4g of hydrophilic fumed silica powder from commercial purchase was added to the ammonium cerium nitrate aqueous solution, and stirred for 20h. The water was removed by rotary evaporation and the resulting bifunctional support precursor was placed in an oven at 110 ℃ for overnight drying to remove residual water. And finally, heating the catalyst precursor to 500 ℃ in an air atmosphere, and roasting for 4 hours to obtain the bifunctional carrier.
Preparation of silver-loaded bifunctional supported catalyst:
0.1289g of silver acetate was dissolved in 150ml of deionized water, stirred uniformly for 10min, 2.0g of the cerium oxide-silicon dioxide bifunctional support powder prepared above was added to an aqueous silver acetate solution, and stirred for 20h under a dark condition. The water was removed by rotary evaporation and the resulting catalyst precursor was placed in an oven at 110 ℃ overnight for drying to remove residual water. And finally, heating the catalyst precursor to 400 ℃ in an air atmosphere, and roasting for 4 hours to obtain the catalyst.
The catalyst of this example was subjected to the above-described on-line reduction conditions and catalyst evaluation method for 2.1 hours -1 The reaction was carried out under conditions that the catalyst remained stable for 100h and the yield was estimated to decrease by 15.7% over 500 h.
Example 2
Preparation of silver cerium silicon catalyst (reduction, non-citric acid assisted)
The example is the preparation of a silver cerium silicon catalyst sample 2 of a dual-function carrier, which is different from the preparation of a silver cerium silicon catalyst sample 1 of example 1 only in that the dual-function carrier prepared by the example is firstly reduced in reducing gas at high temperature, is transferred to inert gas for protection after being reduced, and is taken out when the silver cerium silicon catalyst is prepared. The reduction treatment is specifically as follows:
taking 2.5g of the difunctional carrier, uniformly spreading the difunctional carrier in a quartz boat, placing the quartz boat in the center of a tube furnace, vacuumizing and continuously introducing H 2 Heating to 500 ℃, reducing for 8h, and changing the gas into N after cooling to room temperature 2 After holding for 0.5h, the mixture was taken out and transferred into a glove box.
The catalyst of this example was subjected to the above-described on-line reduction conditions and catalyst evaluation method for 2.7 hours -1 The reaction was carried out under the condition that the catalyst remained stable for 100 hours and the yield was reduced by 6.5% in 500 hours.
Example 3
Preparation of silver cerium silicon catalyst (reduction, citric acid assisted)
This example is a preparation of a dual function carrier silver cerium silicon catalyst sample 3, which differs from the preparation of example 2 silver cerium silicon catalyst sample 2 only in that citric acid was added during the dual function carrier preparation of this example. The method comprises the following steps:
0.2600g of ammonium cerium nitrate was dissolved in 150ml of deionized water, 0.1823g of citric acid was added to the above solution, and uniformly stirred for 10 minutes, 4g of hydrophilic fumed silica powder from commercial purchase was added to an aqueous ammonium cerium nitrate solution, and stirred for 20 hours. The water was removed by rotary evaporation and the resulting bifunctional support precursor was placed in an oven at 110 ℃ for overnight drying to remove residual water. Finally, the catalyst precursor is heated to 500 ℃ under the air atmosphere, baked for 4 hours, the obtained dual-function carrier is taken 2.5g and evenly spread in a quartz boat, placed in the center of a tube furnace, and continuously introduced with H after vacuumizing 2 Heating to 500 ℃, reducing for 8 hours, changing the gas into argon after cooling to room temperature, keeping for 0.5 hour, taking out and transferring into a glove box.
The catalyst of this example was subjected to the above-described on-line reduction conditions and catalyst evaluation method for 3.6 hours -1 The reaction was carried out below and no significant deactivation was seen after 500h of evaluation.
Example 4
Preparation of silver cerium silicon catalyst (reduction, citric acid assisted), catalyst evaluation at different airspeeds
This example is a preparation of a dual function carrier silver cerium silicon catalyst sample 4, which is not different from the preparation of example 3 silver cerium silicon catalyst sample 3, and only the space velocity of the reaction evaluation is different, specifically as follows:
the catalyst of this example was subjected to the above-described on-line reduction conditions and catalyst evaluation method for 3.4 hours -1 The reaction was carried out as follows.
As is clear from comparative example 1 and example 1, the catalyst of comparative example 1 uses silica as a single carrier, and the catalyst activity is high, but the selectivity is only 84.1%, and the yield is only 82.8%. In example 1, the addition of cerium caused an increase in the valence of silver, a decrease in the activity of the catalyst, and a reaction conversion of 98.5%The space velocity at the time was reduced, but the selectivity was increased to 92.2%, the MG yield was increased to more than 90%, and the space-time yield per unit mass of silver was only 31.1 g.g Ag -1 ·h -1 The temperature is increased to 59.6 g.g Ag -1 ·h -1 The use efficiency of silver species is improved. Meanwhile, the addition of cerium also improved the stability of the catalyst, as shown in fig. 1, in which larger-sized silver particles (upper side) and smaller-sized silver particles (lower side) were simultaneously present, and the silver species of the catalyst of comparative example 1 were all distributed on silica, which is a weak interaction carrier of silver, and thus sintering agglomeration of silver particles could not be prevented, and thus small-sized silver particles were agglomerated to form large-sized silver particles. While the silver species in example 1 are partially distributed on the cerium oxide, as shown in fig. 2, the left small-sized silver particles are anchored on the cerium oxide, and the middle large-sized silver particles are not in direct contact with the cerium oxide, so that the silver particles are agglomerated and are larger in size. Cerium oxide is a strong interaction carrier of silver, and by the anchoring effect of cerium oxide on silver species, silver particles do not generate sintering growth to a large extent after the cerium oxide surface is enriched to a certain extent, so that the stability of the catalyst in comparative example 1 is greatly improved compared with that in example 1 as shown in fig. 7. Therefore, the cerium component is introduced into the silver-silicon catalyst, so that the partial activity is enhanced, the use efficiency of silver species is improved, the directional selectivity of methyl glycolate is improved, the stability of the catalyst is enhanced, and the separation cost and the catalyst replacement cost can be reduced in industrial application.
From examples 1 and 2, it is understood that example 2 is a hydrogen reduction treatment of a ceria-silica dual-function carrier. The silicon dioxide in the carrier is non-reducing oxide, the reduction process is not affected, the cerium oxide is reducible oxide, and after hydrogen treatment, part of oxygen atoms are H 2 The form of O is removed leaving an electron-rich oxygen vacancy. During the loading of metallic silver, these oxygen vacancies have an adsorption anchoring effect on silver ions, so that more silver species are distributed on the cerium oxide, as shown in fig. 3, where both silver particles are anchored on the cerium oxide. An improvement in the distribution of silver species,so that the dual function support structure fully exerts its stability enhancing effect, as shown in fig. 7, the stability of the catalyst of example 2 is higher than that of example 1. The redundant electrons are redistributed on the empty energy level of the cations, so that the valence state of silver and cerium is reduced, the activity of silver in a lower valence state is higher, the space-time yield of silver in unit mass of methyl glycolate is improved, and the use efficiency of silver atoms in unit is also enhanced. Therefore, the method of pre-reducing the carrier can improve the distribution of silver species, and the anchoring effect of cerium oxide on silver, so that the stability of the catalyst is improved, the activity of the catalyst is enhanced, and the silver space-time yield of methyl glycolate per unit mass is improved.
As is apparent from examples 2 and 3, in example 3, citric acid, which is an auxiliary agent, is added during the preparation of the dual-function carrier, and the citric acid can form coordination with the cerium part, so that the cerium part is not easy to aggregate, and is fully combusted during the calcination process to release a large amount of gas, so that the dispersity of cerium oxide is improved, and thus, the size of the cerium oxide nano islands is reduced, as shown in fig. 4 to 5, the cerium oxide size of the sample in example 2 is 6.9nm, and the cerium oxide single-oxide size of the sample in example 3 is 4.9nm. The size of the single cerium oxide nanometer island is reduced, the content of the adsorbed and anchored silver species is reduced, the size of silver particles is also reduced, the silver species is fully dispersed, the exposed specific surface area of silver is increased, the active sites are increased, and the space-time yield of the silver per unit mass of methyl glycolate is increased. Meanwhile, the oxygen vacancies exposed by the cerium oxide nano islands in the reduction process are increased, so that the anchoring effect of the cerium oxide nano islands on silver particles is enhanced, as shown in fig. 7, and the catalyst stability of example 3 is further improved compared with example 2. Therefore, the use of the citric acid auxiliary agent can improve the dispersity of cerium oxide and silver species, thereby improving the specific surface area of silver and the concentration of oxygen vacancies, and further improving the activity and stability of the catalyst
As is clear from examples 3 and 4, the catalyst in example 4 was evaluated at a conversion of 100%, the catalyst selectivity was 92.0%, and the space-time yield per unit mass of silver was 97.8 g.g Ag -1 ·h -1 Slightly lower than the silver per unit mass of the catalyst of example 3Air yield 103.1 g.g Ag -1 ·h -1 This suggests that properly reducing the space velocity can result in complete conversion of dimethyl oxalate, thereby reducing the cost of product separation.
Examples 5 to 6
The effect of different cerium sources on the particle size of silver cerium particles, as well as on the catalyst activity, was examined.
The cerium source and space velocity were different only compared to example 3.
Examples 7 to 9
The influence of different silver sources on the particle size of silver cerium particles and the influence of the activity of the catalyst are examined.
Only the silver source and space velocity were different compared to example 3.
Examples 10 to 12
The effect of different silver loadings on the particle size of the silver cerium particles, as well as the effect of catalyst activity, was examined.
Only the silver loading and space velocity were different compared to example 3.
Examples 13 to 15
The effect of different cerium loadings on the particle size of the silver cerium particles, as well as the effect of catalyst activity, was examined.
Only the silver cerium loading and space velocity were different compared to example 3.
Example 16
The influence of different silicon sources on the particle size of silver cerium particles and the influence of the activity of the catalyst are examined.
Only the silver cerium loading and space velocity were different compared to example 3.
TABLE 1 preparation conditions for each catalyst and particle diameters of silver and cerium oxide particles
TABLE 2 Activity data for the catalysts for heterogeneous hydrogenation of dimethyl oxalate
As is apparent from examples 3 and examples 5 to 6 in tables 1 to 2, ammonium cerium nitrate is more effective as a cerium source because ammonium cerium nitrate has a higher nitrogen content and a lower decomposition temperature, and thus the dispersibility of cerium oxide is higher than that of cerium nitrate as a cerium source. Cerium sulfate is not easy to decompose, a large amount of sulfate radicals remain, and the sulfate radicals anchor a large amount of silver ions, so that the valence state of silver particles is higher, and the activity of the catalyst is drastically reduced. Therefore, ceric ammonium nitrate works better as a cerium source.
As can be seen from examples 3 and examples 7-9 in tables 1-2, silver acetate works best as a silver source. The roasting of silver nitrate at 400 deg.c will have small amount of nitrogen and oxygen species remaining, and the decomposition temperature of silver phosphate is over 800 deg.c, so that these two matters have high silver valence and lowered activity. And silver acetate and silver lactate are used as silver sources, the decomposition temperature is low, a large amount of gas is released, the dispersion of silver is facilitated, the solubility of silver acetate is higher, and the stirring dispersion effect is good, so that the silver acetate is best used as the silver source.
It is seen from examples 3 and 10-12 in tables 1-2 that the silver loading was 4wt.% most effective. In example 10, the silver loading was too high and most of the silver was loaded on the silica support, however, the silica as a weak interaction support did not prevent agglomeration sintering of the silver particles, so that oversized silver particles were formed after reduction, the exposed silver specific surface area was reduced, and the activity was also reduced, as shown in fig. 6, the large-sized unanchored silver particles were present on the right side. While examples 11-12 have small silver particles, a higher silver valence and poor catalytic activity. Thus, a silver loading of 4wt.% works best.
From examples 3 and examples 13-15 in tables 1-2, it is seen that the cerium loading was 2wt.% most effective. With the increase of cerium content, cerium oxide nano-meterIsland size increases, silver particle dispersion increases, particle size decreases, silver valence increases, and thus activity decreases rapidly, as in example 15, at low space velocity of 0.3h, due to cerium oxide as a strongly interacting carrier -1 The conversion of the catalyst was only 27.3%. Meanwhile, the acid-base sites exposed on the cerium oxide are increased, the selectivity of byproducts is increased, and the directional selectivity of methyl glycolate is reduced. Thus, a cerium loading of 2wt.% works best.
As can be seen from examples 3 and 16 in tables 1-2, hydrophilic fumed silica works best as a silicon source. The hydrophilic fumed silica is not dissolved in the water phase, cerium oxide particles are larger, silver valence is slightly higher, and activity is slightly reduced in the process of preparing the difunctional carrier, so that the hydrophilic fumed silica has the best effect as a silicon source.
The preparation method of the bifunctional carrier catalyst has the characteristics of mild condition, simple preparation process, easily obtained raw materials, low cost, excellent catalytic performance and the like, can be singly used for producing methyl glycolate with high economic value and high requirement when being practically applied to industry, can still maintain the yield of more than 90 percent under higher airspeed, and has the space-time yield of silver per unit mass as high as 103.1 g.g Ag -1 ·h -1 . In addition, the stability of the catalyst is greatly improved, the service life of the catalyst is greatly prolonged, the loss caused by the industrial replacement of the catalyst is reduced, and the industrial cost is reduced.
The foregoing has described exemplary embodiments of the invention, it being understood that any simple variations, modifications, or other equivalent arrangements which would not unduly obscure the invention may be made by those skilled in the art without departing from the spirit of the invention.
Claims (10)
1. A silver-based catalyst, characterized in that the silver-based catalyst comprises a carrier and an active component, the active component is a silver species, and the carrier is a bifunctional carrier; the difunctional carrier comprises cerium oxide and silicon dioxide, and the silver-based catalyst has the structure that: the cerium oxide is dispersed on the surface of the silicon dioxide nano particles in the form of nano islands, and the silver species are located on the cerium oxide nano islands in the form of nano particles.
2. The silver-based catalyst according to claim 1, wherein the silver species comprises 1-20wt.% of the total mass of the silver-based catalyst, and the bifunctional support comprises 80-99wt.% of the total mass of the silver-based catalyst; the cerium oxide accounts for 1-40wt.% of the total mass of the dual-function carrier, and the silicon dioxide accounts for 60-99wt.% of the total mass of the dual-function carrier;
the specific surface area of the silver-based catalyst is 50-200m 2 Per gram, average pore volume of 0.7-1.4cm 3 And/g, the average pore diameter is 10-30nm.
3. The silver-based catalyst according to claim 1, wherein the particle size of the silver species is 1.0-20nm and the cerium oxide nano-islands are 2.0-30nm; further, the particle size of the silver species is 2-5nm, and the cerium oxide nano island size is 2-6nm; still further, the silver species has a particle size of 4-5nm and the cerium oxide nanoislands have a size of 4-6nm.
4. A method for preparing a silver-based catalyst according to any one of claims 1 to 3, characterized in that it comprises the steps of:
(1) Dissolving silver precursor salt in deionized water, and stirring to obtain silver precursor solution;
(2) Dispersing the difunctional carrier in the precursor solution obtained in the step (1), and stirring in a dark place;
(3) And (3) removing water in the mixture obtained in the step (2) through rotary evaporation to obtain a catalyst precursor precipitate, and drying and roasting the catalyst precursor to obtain the silver-based catalyst.
5. The method of preparing a silver-based catalyst according to claim 4, wherein the silver precursor salt is selected from any one of silver nitrate, silver phosphate, silver lactate or silver acetate, preferably from silver acetate;
the stirring time in the step (1) is 10-20min; stirring time in the step (2) is 10-40h; the drying conditions in the step (3) are as follows: the drying temperature is 80-130 ℃ and the drying time is 12-24 hours; the roasting temperature is 300-700 ℃ and the roasting time is 2-6h.
6. The method for preparing a silver-based catalyst according to claim 4, wherein the method for preparing a bifunctional support in step (2) comprises the steps of:
(a) Dissolving cerium precursor salt in deionized water, and stirring to obtain cerium precursor solution;
(b) Dispersing a silicon source in the cerium precursor solution obtained in the step (a), and stirring;
(c) Removing water in the mixture obtained in the step (b), performing rotary evaporation to obtain a difunctional carrier precursor precipitate, and drying and roasting the difunctional carrier precursor to obtain the difunctional carrier.
7. The method for preparing a silver-based catalyst according to claim 6, wherein in the preparation of the bifunctional support, the cerium precursor salt is any one of cerium nitrate, cerium sulfate or cerium ammonia nitrate, preferably selected from cerium ammonium nitrate; the silicon source is any one of hydrophilic fumed silica, lipophilic fumed silica, alkaline silica sol or ammonia silica sol, and is preferably selected from hydrophilic fumed silica;
the stirring time in the step (a) is 10-20min; stirring in the step (b) for 10-40h; the drying conditions in step (c) are: the drying temperature is 80-130 ℃ and the drying time is 12-24 hours; the roasting temperature is 300-700 ℃ and the roasting time is 2-6h.
8. The method of preparing a silver-based catalyst according to claim 6, wherein in the preparation of the dual-function carrier, the precursor solution in step (a) contains citric acid, specifically, cerium precursor salt and citric acid are dissolved in deionized water, and the mixture is stirred to obtain cerium precursor solution;
the molar ratio of the cerium precursor salt to the citric acid is 1:1.25-0.5.
9. The method for preparing a silver-based catalyst according to claim 6, wherein in the preparation of the bifunctional support, the bifunctional support is reduced and used for the preparation of the silver-based catalyst, specifically: reducing the difunctional carrier obtained in the step (c) in reducing gas at high temperature, transferring the reduced difunctional carrier into inert gas for protection, and taking out the difunctional carrier when the difunctional carrier is used in the step (2);
the reduction treatment conditions are as follows: the reduction temperature is 300-700 ℃, the reduction time is 2-10h, and the reducing gas is selected from hydrogen, carbon monoxide or ammonia, more preferably hydrogen;
the inert gas is selected from argon, nitrogen, helium or carbon dioxide, more preferably from argon.
10. Use of a silver-based catalyst according to any one of claims 1 to 3 for catalyzing the selective hydrogenation of dimethyl oxalate to methyl glycolate;
the method comprises the following steps: introducing mixed gasified dimethyl oxalate and hydrogen into a reactor packed with the silver-based catalyst for reaction;
the reaction pressure is 0.5-3.5MPa; the reaction temperature is 200-240 ℃; the mass airspeed of the dimethyl oxalate is 0.1-4.0h -1 The method comprises the steps of carrying out a first treatment on the surface of the The molar ratio of the hydrogen ester is 60-150.
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