CN115382572A - Palladium catalyst with stable double sites and preparation method and application thereof - Google Patents
Palladium catalyst with stable double sites and preparation method and application thereof Download PDFInfo
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- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 title claims abstract description 443
- 229910052763 palladium Inorganic materials 0.000 title claims abstract description 166
- 239000003054 catalyst Substances 0.000 title claims abstract description 112
- 238000002360 preparation method Methods 0.000 title abstract description 17
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 30
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 27
- 230000003647 oxidation Effects 0.000 claims abstract description 14
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 claims abstract description 11
- 238000000151 deposition Methods 0.000 claims description 69
- 230000008021 deposition Effects 0.000 claims description 65
- 238000000034 method Methods 0.000 claims description 57
- 238000011282 treatment Methods 0.000 claims description 50
- QAMFBRUWYYMMGJ-UHFFFAOYSA-N hexafluoroacetylacetone Chemical compound FC(F)(F)C(=O)CC(=O)C(F)(F)F QAMFBRUWYYMMGJ-UHFFFAOYSA-N 0.000 claims description 34
- 239000003638 chemical reducing agent Substances 0.000 claims description 22
- 238000000231 atomic layer deposition Methods 0.000 claims description 21
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 13
- 239000008098 formaldehyde solution Substances 0.000 claims description 13
- 239000002808 molecular sieve Substances 0.000 claims description 10
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 9
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 8
- KBPLFHHGFOOTCA-UHFFFAOYSA-N 1-Octanol Chemical compound CCCCCCCCO KBPLFHHGFOOTCA-UHFFFAOYSA-N 0.000 claims description 6
- WRMNZCZEMHIOCP-UHFFFAOYSA-N 2-phenylethanol Chemical compound OCCC1=CC=CC=C1 WRMNZCZEMHIOCP-UHFFFAOYSA-N 0.000 claims description 6
- 238000005137 deposition process Methods 0.000 claims description 6
- WVDDGKGOMKODPV-ZQBYOMGUSA-N phenyl(114C)methanol Chemical compound O[14CH2]C1=CC=CC=C1 WVDDGKGOMKODPV-ZQBYOMGUSA-N 0.000 claims description 4
- KMTDMTZBNYGUNX-UHFFFAOYSA-N 4-methylbenzyl alcohol Chemical compound CC1=CC=C(CO)C=C1 KMTDMTZBNYGUNX-UHFFFAOYSA-N 0.000 claims description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 2
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 claims description 2
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 2
- 230000003197 catalytic effect Effects 0.000 abstract description 17
- 239000012298 atmosphere Substances 0.000 abstract description 7
- 238000006243 chemical reaction Methods 0.000 description 38
- 229910000420 cerium oxide Inorganic materials 0.000 description 37
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 37
- WVDDGKGOMKODPV-UHFFFAOYSA-N Benzyl alcohol Chemical compound OCC1=CC=CC=C1 WVDDGKGOMKODPV-UHFFFAOYSA-N 0.000 description 21
- 230000008569 process Effects 0.000 description 18
- 239000000758 substrate Substances 0.000 description 16
- 241000894007 species Species 0.000 description 14
- 206010006322 Breath holding Diseases 0.000 description 11
- 238000000605 extraction Methods 0.000 description 11
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- 101150003085 Pdcl gene Proteins 0.000 description 8
- 238000001035 drying Methods 0.000 description 8
- 229910052760 oxygen Inorganic materials 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 235000019445 benzyl alcohol Nutrition 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- 239000007789 gas Substances 0.000 description 7
- 239000007791 liquid phase Substances 0.000 description 7
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 239000001301 oxygen Substances 0.000 description 6
- 238000003756 stirring Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
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- 239000010453 quartz Substances 0.000 description 5
- 238000000952 abberration-corrected high angular annular dark-field scanning transmission electron microscopy Methods 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
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- 230000009467 reduction Effects 0.000 description 4
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- 239000007800 oxidant agent Substances 0.000 description 3
- 150000002940 palladium Chemical class 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 2
- 238000004998 X ray absorption near edge structure spectroscopy Methods 0.000 description 2
- 238000005034 decoration Methods 0.000 description 2
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- 239000004408 titanium dioxide Substances 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000008365 aqueous carrier Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical class [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
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- 239000012847 fine chemical Substances 0.000 description 1
- 239000003205 fragrance Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- -1 hexafluoroacetylacetone modified palladium Chemical class 0.000 description 1
- 238000000024 high-resolution transmission electron micrograph Methods 0.000 description 1
- 238000002173 high-resolution transmission electron microscopy Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000002779 inactivation Effects 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 229910052573 porcelain Inorganic materials 0.000 description 1
- 239000000843 powder Substances 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
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
- B01J31/0201—Oxygen-containing compounds
- B01J31/0205—Oxygen-containing compounds comprising carbonyl groups or oxygen-containing derivatives, e.g. acetals, ketals, cyclic peroxides
- B01J31/0208—Ketones or ketals
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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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
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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
- 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
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/44—Palladium
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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
- 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
- B01J23/56—Platinum group metals
- B01J23/63—Platinum group metals with rare earths or actinides
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/03—Catalysts comprising molecular sieves not having base-exchange properties
- B01J29/0308—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41
- B01J29/0316—Mesoporous materials not having base exchange properties, e.g. Si-MCM-41 containing iron group metals, noble metals or copper
- B01J29/0325—Noble metals
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- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
- B01J29/44—Noble metals
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
- C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
- C07C45/37—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups
- C07C45/38—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen of >C—O—functional groups to >C=O groups being a primary hydroxyl group
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- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/18—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself
- B01J2229/186—After treatment, characterised by the effect to be obtained to introduce other elements into or onto the molecular sieve itself not in framework positions
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- B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
- B01J2231/70—Oxidation reactions, e.g. epoxidation, (di)hydroxylation, dehydrogenation and analogues
- B01J2231/76—Dehydrogenation
- B01J2231/763—Dehydrogenation of -CH-XH (X= O, NH/N, S) to -C=X or -CX triple bond species
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Abstract
The invention provides a stable double-site palladium catalyst and a preparation method and application thereof, belonging to the technical field of catalytic chemistry. The invention provides a palladium catalyst with stable double sites, which comprises a carrier and palladium species dispersed on the surface of the carrier, wherein the palladium species comprises Pd 0 And Pd 2+ Said Pd 2+ Is Pd 0 And Pd 2+ 60-75% of the total amount, pd after the palladium catalyst is used 2+ Is Pd 0 And Pd 2+ 70 to 85 percent of the total amount. The palladium catalyst provided by the invention has stable double sites, and is used for catalyzing alcohol oxidation to prepare aldehyde, so that the catalytic efficiency and selectivity are high; and the palladium catalyst provided by the invention is not easy to deactivate after being stored in the air atmosphere for a long time.
Description
Technical Field
The invention relates to the technical field of catalytic chemistry, in particular to a palladium catalyst with stable double sites, a preparation method and application thereof.
Background
Aldehydes are precursors or intermediates for fine chemical synthesis of drugs, fragrances, pesticides, dyes, etc., and are one of the most basic and useful chemical products, and are generally produced industrially by oxidation of alcohols. Conventional benzyl alcohol oxidation processes typically use inorganic oxidants such as chromates and permanganates, but these inorganic oxidants are highly corrosive, highly toxic as by-products after alcohol oxidation, and high as by-products of the oxidation process with low aldehyde selectivity. Compared with the traditional method, the method for preparing aldehyde by utilizing alcohol solvent-free liquid phase catalytic oxidation uses a supported metal catalyst, takes oxygen molecules as an oxidant, takes a byproduct as water, and has the advantages of mild conditions, environmental protection and high economic value.
The supported metal catalyst used in the above method is generally a palladium-based catalyst, and the active site of palladium-catalyzed alcohol liquid phase oxidation is generally considered to be Pd 0 . Such as Mori et al by comparing single valence catalyst-PdHAP-0 (Pd) 0 ) And PdHAP-1 (Pd) 2+ ) The catalyst performance shows that the active center of the catalyst is Pd at the corner of the nanoparticle with the particle size of 3.8nm 0 Generated in situ (J.Am.chem.Soc., 2004,126, 10657-10666). Grunwaldt also indicates that the metallic palladium species is more active (j. Phys. Chem.b,2006,110, 25586-25589).
But using only Pd 0 The palladium-based catalyst serving as an active site catalyzes alcohol oxidation to prepare aldehyde, palladium species are unstable in the reaction process and need to be converted in situ, oxidation and reduction occur at a single site, and the catalytic efficiency and selectivity are still to be improved. The palladium-based catalyst is easy to deactivate after being stored in the air atmosphere for a long time, and needs to be subjected to reduction treatment before use.
Disclosure of Invention
The invention aims to provide a palladium catalyst with stable double sites, a preparation method and application thereof, the palladium catalyst provided by the invention has the stable double sites, and the palladium catalyst is used for catalyzing alcohol oxidation to prepare aldehyde, and has good stability, high catalytic efficiency and high selectivity in the reaction process; the palladium catalyst provided by the invention is not easy to deactivate after being stored for a long time in the air atmosphere.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a palladium catalyst with stable double sites, which comprises a carrier and palladium species dispersed on the surface of the carrier, wherein the palladium species comprises Pd 0 And Pd 2+ Said Pd 2+ Is Pd 0 And Pd 2+ 60-75% of the total amount, pd after the palladium catalyst is used 2+ Is Pd 0 And Pd 2+ 70 to 85 percent of the total amount.
Preferably, the palladium in the palladium catalyst is present in the form of clusters.
Preferably, the palladium element content in the palladium catalyst is 0.1 to 2wt%.
Preferably, the support comprises an oxide support or a molecular sieve support.
Preferably, the oxide support comprises titania, ceria or alumina and the molecular sieve support comprises an SBA-15 molecular sieve or a ZSM-5 molecular sieve.
The invention provides a preparation method of the palladium catalyst in the technical scheme, which comprises the following steps:
(1) Based on an atomic layer deposition method, carrying out deposition treatment on the surface of a carrier by sequentially pulsing gaseous hexafluoroacetylacetone palladium and a gaseous reducing agent to obtain a palladium catalyst; wherein, during the deposition treatment, the pulse time of the palladium hexafluoroacetylacetonate is not greater than the pulse time of the reducing agent;
or (2) performing deposition treatment on the surface of the carrier loaded with palladium by pulse gaseous hexafluoroacetylacetone based on an atomic layer deposition method to obtain the palladium catalyst.
Preferably, the reducing agent comprises hydrogen or formaldehyde solution.
Preferably, the number of deposition treatments in (1) and (2) is independently 1 to 100.
The invention provides application of the palladium catalyst in the technical scheme or the palladium catalyst prepared by the preparation method in the technical scheme in catalyzing alcohol to prepare aldehyde through oxidation reaction.
Preferably, the alcohol comprises benzyl alcohol, 4-methylbenzyl alcohol, 2-phenyl ethanol or 1-octanol.
The invention provides a palladium catalyst with stable double sites, which comprises a carrier and palladium species dispersed on the surface of the carrier, wherein the palladium species comprises Pd 0 And Pd 2+ Said Pd 2+ Is Pd 0 And Pd 2+ 60-75% of the total amount, pd after the palladium catalyst is used 2+ Is Pd 0 And Pd 2+ 70 to 85 percent of the total amount. The palladium catalyst provided by the invention has higher Pd 2+ /(Pd 0 +Pd 2+ ) The Pd catalyst is used for catalyzing alcohol oxidation to prepare aldehyde, and stable Pd can be maintained in the reaction process 2+ /(Pd 0 +Pd 2+ ) Ratio, pd 0 And Pd 2+ Can respectively play the roles of alcohol dehydrogenation and oxygen activation, and has high catalytic efficiency and high selectivity. Meanwhile, the palladium catalyst provided by the invention is not easy to inactivate after being stored in the air atmosphere for a long time.
The invention provides a preparation method of the palladium catalyst, which comprises the following steps: (1) Based on an atomic layer deposition method, carrying out deposition treatment on the surface of a carrier by sequentially pulsing gaseous hexafluoroacetylacetone palladium and a gaseous reducing agent to obtain a palladium catalyst; wherein, during the deposition treatment, the pulse time of the palladium hexafluoroacetylacetonate is not greater than the pulse time of the reducing agent; or (2) performing deposition treatment on the surface of the carrier loaded with palladium by pulse gaseous hexafluoroacetylacetone based on an atomic layer deposition method to obtain the palladium catalyst. The invention can prepare the stable double-site Pd with high Pd based on the atomic layer deposition method 2+ /(Pd 0 +Pd 2+ ) A proportion of a palladium catalyst to a palladium-containing catalyst,in particular, due to Pd in the oxidized state 2+ Species are usually present at the metal-oxide interface or generated by in situ oxidation, so for larger size palladium nanoparticles, pd 2+ The content is low. The invention prepares the palladium catalyst based on the atomic layer deposition method, can accurately control and stabilize the size, the position and the valence state of the catalytic center, has stable double sites compared with the traditional palladium supported catalyst prepared by the wet chemical method, and can keep higher and stable Pd in the alcohol oxidation reaction process 2+ /(Pd 0 +Pd 2+ ) The ratio, in turn, can promote the efficient coupling of alcohol dehydrogenation and oxidation reactions, and has catalytic activity far higher than that of palladium supported catalysts prepared by traditional wet chemistry methods. In addition, the palladium catalyst prepared by the atomic layer deposition method can stabilize the position and valence of Pd species in the deposition treatment process by pulsing proper amount of hexafluoroacetylacetone palladium or hexafluoroacetylacetone, so that the palladium catalyst can be stored for a long time in the air atmosphere without inactivation and can also keep better stability when being applied to the alcohol oxidation reaction process; the palladium catalyst prepared by the traditional wet chemical method usually needs roasting or reduction treatment to improve the catalytic activity, but the palladium catalyst prepared by the method is easy to inactivate in the storage process due to unstable palladium valence state, and is also easy to inactivate under the comprehensive action of a heat source, oxygen and alcohol reactants when being applied to the alcohol oxidation reaction process.
Furthermore, the invention can control the pulse amount of the hexafluoroacetylacetone palladium or hexafluoroacetylacetone by controlling the deposition treatment times in the atomic layer deposition method, thereby controlling the Pd gradient 0 And Pd 2+ Regulating and controlling the catalytic performance of the target catalyst.
Drawings
FIG. 1 shows 20Pd/CeO prepared in example 1 2 HRTEM image of (A);
FIG. 2 shows 20Pd/CeO prepared in example 1 2 The graph of AC-HAADF-STEM and the corresponding EDS graph in FIG. 2, a is 20Pd/CeO 2 The AC-HAADF-STEM of (A), (B), (c) and (d) are 20Pd/CeO 2 EDS plot of Ce, O and Pd as medium elements;
FIG. 3 is a preparation of example 1Prepared 20Pd/CeO 2 Pd K-edge XANES diagram.
Detailed Description
The invention provides a palladium catalyst with stable double sites, which comprises a carrier and palladium species dispersed on the surface of the carrier, wherein the palladium species comprises Pd 0 And Pd 2+ Said Pd 2+ Is Pd 0 And Pd 2+ 60-75% of the total amount, pd after the palladium catalyst is used 2+ Is Pd 0 And Pd 2+ 70 to 85 percent of the total amount.
The palladium catalyst provided by the invention comprises a carrier. In the present invention, the support preferably comprises an oxide support or a molecular sieve support; the oxide support preferably comprises titanium dioxide (TiO) 2 ) Cerium oxide (CeO) 2 ) Or aluminum oxide (Al) 2 O 3 ) Preferably, the molecular sieve support comprises an SBA-15 molecular sieve or a ZSM-5 molecular sieve. In the present invention, the carrier is in the form of powder, and the particle size of the carrier is not particularly limited in the present invention, and carriers having a particle size well known to those skilled in the art may be used. In the present invention, the carrier is preferably dispersed on the surface of a substrate, the substrate is preferably a quartz plate, and the size of the substrate is preferably 80mm × 80mm × 2mm; the amount of the carrier supported on the surface of the substrate is preferably 15 to 25mg, more preferably 20mg, in terms of the substrate having the size of 80mm × 80mm × 2 mm.
The palladium catalyst provided by the invention comprises palladium species dispersed on the surface of the carrier, wherein the palladium species comprises Pd 0 And Pd 2+ Said Pd 2+ Is Pd 0 And Pd 2+ 60 to 75% of the total amount, specifically 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, or 75%; pd after use of the palladium catalyst 2+ Is Pd 0 And Pd 2+ 70 to 85% of the total amount, specifically 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84% or 85%. In the invention, the palladium in the palladium catalyst exists in a cluster form; in the invention, the palladium active center in the palladium catalyst hasThe body is PdO cluster (coated with a small amount of Pd) 0 ) Rather than Pd clusters. In the present invention, the content of the palladium element in the palladium catalyst is preferably 0.1 to 2wt%, more preferably 0.2 to 1.8wt%, further preferably 0.4 to 0.8wt%, and further preferably 0.5 to 0.7wt%.
The invention provides a preparation method of the palladium catalyst in the technical scheme, which comprises the following steps:
(1) Based on an atomic layer deposition method, sequentially pulsing gaseous hexafluoroacetylacetone palladium and gaseous reducing agent to carry out deposition treatment on the surface of the carrier to obtain a palladium catalyst; wherein, in the deposition process, the pulse time of the palladium hexafluoroacetylacetonate is not more than the pulse time of the reducing agent;
or (2) performing deposition treatment on the surface of the carrier loaded with palladium by pulse gaseous hexafluoroacetylacetone based on an atomic layer deposition method to obtain the palladium catalyst.
In the present invention, unless otherwise specified, all the starting materials for the preparation are commercially available products well known to those skilled in the art. Two methods for preparing the palladium catalyst are described in detail below.
The method is based on an atomic layer deposition method, and comprises the steps of depositing on the surface of a carrier by sequentially pulsing gaseous hexafluoroacetylacetone palladium and a gaseous reducing agent to obtain a palladium catalyst; in the deposition treatment process, the pulse time of the hexafluoroacetylacetonatopalladium is not more than the pulse time of the reducing agent, and the breath holding time of the hexafluoroacetylacetonatopalladium is not less than the breath holding time of the reducing agent.
In the present invention, the reducing agent preferably includes hydrogen gas or a formaldehyde solution; the concentration of the formaldehyde solution is preferably 37wt%; the solvent of the formaldehyde solution is preferably water. In an embodiment of the present invention, the deposition process is preferably performed in a vacuum reaction chamber of an atomic layer deposition apparatus. The invention preferably disperses the carrier on the surface of the substrate, and then the substrate with the dispersed carrier on the surface is placed in a vacuum reaction chamber of the atomic layer deposition equipment for deposition treatment. In the present invention, the method of dispersing the carrier on the surface of the substrate preferably includes: mixing a carrier with ethanol, coating the obtained carrier liquid on the surface of a substrate, and drying to form a carrier layer on the surface of the substrate. The concentration of the carrier liquid is not particularly limited, and the carrier can be dispersed so as to facilitate subsequent coating. The present invention is not particularly limited to specific conditions for the coating and drying, and conditions well known to those skilled in the art may be used.
After the substrate with the carrier dispersed on the surface is placed in a vacuum reaction chamber, the present invention preferably sets deposition parameters, and the deposition parameters preferably include: the temperature of the vacuum reaction cavity is preferably 140-180 ℃, and more preferably 150-160 ℃; the pressure is preferably 10 to 70MPa, more preferably 20 to 50MPa; the temperature of the palladium hexafluoroacetylacetonate is preferably 55-70 ℃, and more preferably 60-65 ℃; the temperature of the reducing agent is preferably 20-30 ℃, and more preferably 25 ℃; the ratio of the flow rate of the carrier gas to the volume of the vacuum reaction chamber is preferably 1: (12 to 20), more preferably 1: (15-20); the carrier gas is preferably nitrogen, argon or helium.
After setting deposition parameters, the method preferably performs deposition treatment on the surface of the carrier, wherein the deposition treatment preferably comprises sequentially pulsing gaseous palladium hexafluoroacetylacetonate and gaseous reducing agent; wherein, in the deposition process, the pulse time of the palladium hexafluoroacetylacetonate is not more than the pulse time of the reducing agent. In the present invention, the pulse time of the palladium hexafluoroacetylacetonate is preferably 0.01 to 2s, more preferably 0.5 to 1s; the breath holding time is preferably 2 to 30s, and more preferably 2.2 to 8s; the evacuation time is preferably 3 to 70 seconds, more preferably 20 to 35 seconds. In the present invention, the pulse time of the reducing agent is preferably 0.01 to 2s, more preferably 0.6 to 1s; the breath holding time is preferably 2 to 30s, and more preferably 8 to 28s; the evacuation time is preferably 3 to 70 seconds, more preferably 5 to 25 seconds. In the present invention, the pulsed once gaseous palladium hexafluoroacetylacetonate and the pulsed once gaseous reducing agent are referred to as a single deposition cycle, and the number of deposition cycles in the deposition treatment process is preferably 1 to 100, more preferably 5 to 60, further more preferably 10 to 50, further more preferably 15 to 40, and further more preferably 20 to 30. In the present inventionDuring the deposition treatment, the palladium hexafluoroacetylacetonate reacts with the reducing agent to change the palladium valence state in the palladium hexafluoroacetylacetonate and form a palladium cluster (specifically, the palladium cluster is Pd-containing 0 And PdO double sites, and PdO clusters mainly based on PdO species) are obtained, and finally specific and stable Pd is obtained 2+ /(Pd 0 +Pd 2+ ) A proportion of a palladium catalyst. The invention preferably adjusts the pulse quantity of the palladium hexafluoroacetylacetonate and the reducing agent by controlling the deposition parameters and the cycle number, thereby being capable of controlling Pd in a gradient way 0 And Pd 2+ The ratio of (a) to (b).
Or, the invention is based on an atomic layer deposition method, and the palladium catalyst is obtained by depositing the pulse gaseous hexafluoroacetylacetone on the surface of the carrier loaded with palladium.
In the present invention, the carrier loaded with palladium is preferably prepared by a wet chemical method, that is, palladium is loaded on the surface of the carrier by a wet chemical method. In the present invention, the wet chemical method preferably includes a dipping method, a sol-gel method, or a deposition-precipitation method. Taking an immersion method as an example, the preparation method of the palladium-loaded carrier of the present invention preferably includes the following steps: adding carrier in PdCl 2 Dipping treatment is carried out in the solution, and then the carrier loaded with palladium is obtained after drying. In the invention, the carrier is preferably dispersed in water, and then the obtained carrier water dispersion liquid and the PdCl are mixed 2 Mixing the solutions; the concentration of the carrier in the aqueous carrier dispersion is preferably 250 to 400mg/mL, more preferably 300 to 350g/mL; the PdCl 2 The concentration of the solution is preferably 7-8 mg/mL, and more preferably 7.4mg/mL; the carrier and PdCl 2 The dosage ratio of the solution is preferably 1000mg: (500-1200) mL, more preferably 1000mg: (600-1000) mL. In the present invention, the immersion treatment is preferably performed at room temperature, and the immersion treatment time is preferably 20 to 30 hours, and more preferably 24 hours; the impregnation treatment is preferably carried out under stirring conditions. In the present invention, the temperature of the drying is preferably 65 to 75 ℃, more preferably 70 ℃; the time is preferably 10 to 15 hours, more preferably 12 hours. In the present invention, the content of the palladium element in the palladium-supporting carrier is preferably 0.1 to 2wt%, and specifically may be 0.1 wt%%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.8wt%, or 2wt%.
After the carrier loaded with palladium is obtained, the carrier loaded with palladium is preferably dispersed on the surface of a substrate, and then the substrate with the carrier dispersed on the surface is placed in a vacuum reaction cavity of atomic layer deposition equipment for deposition treatment; in the present invention, the method for dispersing the carrier loaded with palladium on the surface of the substrate is preferably the same as the method for dispersing the carrier on the surface of the substrate in the above technical solution, and details are not repeated herein.
After the substrate with the carrier dispersed on the surface is placed in a vacuum reaction chamber, the invention preferably sets deposition parameters, and the deposition parameters preferably include: the temperature of the hexafluoroacetylacetone is preferably 20-55 ℃, and more preferably 45-50 ℃; the selectable ranges of other deposition parameters are preferably consistent with the selectable ranges of deposition parameters of the above-described embodiments, and are not described herein.
After setting the deposition parameters, the present invention preferably performs a deposition process on the surface of the support, the deposition process preferably comprising pulsed gaseous hexafluoroacetylacetone. In the present invention, the pulse time of hexafluoroacetylacetone is preferably 0.01 to 2s, and more preferably 0.5 to 1s; the breath holding time is preferably 2 to 60s, and more preferably 3 to 10s; the evacuation time is preferably 3 to 70 seconds, more preferably 4 to 10 seconds. In the present invention, the pulsed once gaseous hexafluoroacetylacetone is referred to as a single deposition cycle, and the number of deposition cycles in the deposition treatment is preferably 1 to 100, more preferably 5 to 60, even more preferably 10 to 50, and even more preferably 15 to 40. In the invention, during the deposition treatment, hexafluoroacetylacetone can redisperse palladium in the carrier loaded with palladium to form small clusters, regulate the size and valence ratio of hexafluoroacetylacetone by regulating the cycle number of hexafluoroacetylacetone, and redisperse to form palladium clusters (specifically, the palladium clusters are Pd-bearing clusters) 0 PdO double sites and PdO clusters mainly containing PdO species) are obtained, and the specific and stable Pd is finally obtained 2+ /(Pd 0 +Pd 2+ ) A palladium catalyst in a proportion. The invention is preferably controlled by depositing ginsengThe pulse amount of hexafluoroacetylacetone is adjusted by the number and the cycle number, so that Pd can be controlled in a gradient manner 0 And Pd 2+ The ratio of (a) to (b).
The invention provides application of the palladium catalyst in the technical scheme or the palladium catalyst prepared by the preparation method in the technical scheme in catalyzing alcohol to prepare aldehyde through oxidation reaction. In the present invention, the alcohol preferably includes benzyl alcohol, 4-methylbenzyl alcohol, 2-phenylethanol or 1-octanol. In the present invention, the conditions of the oxidation reaction preferably include: the temperature is preferably 100 to 160 ℃, and more preferably 120 ℃; the oxygen pressure is preferably 0.2 to 0.4MPa, more preferably 0.3MPa; the ratio of the amount of palladium catalyst to the amount of alcohol is preferably 20mg: (8 to 12) mL, more preferably 20mg:10mL; the oxidation reaction is preferably carried out in the absence of a solvent; the oxidation reaction is preferably carried out under stirring conditions, preferably at a rate of 800 to 1200rpm, more preferably 1000rpm.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be apparent that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
20mg of CeO was taken 2 Mixing with ethanol as carrier, and mixing the obtained CeO 2 Coating the feed liquid on the surface of a quartz plate with the size of 80mm multiplied by 2mm, and forming CeO on the surface of the quartz plate after drying 2 A layer arranged in a vacuum reaction chamber of the atomic layer deposition equipment and formed on the CeO by utilizing an atomic layer deposition method 2 Depositing the surface of the layer, wherein the precursor is palladium hexafluoroacetylacetonate, and the reducing agent is formaldehyde solution (with the concentration of 37wt%, and the solvent is water);
the deposition parameters were set as: the temperature of the vacuum reaction cavity is 150 ℃, and the pressure is 50MPa; the temperature of the palladium hexafluoroacetylacetonate is 65 ℃, the temperature of the formaldehyde solution is 25 ℃, and the volume ratio of the flow of the carrier gas (argon) to the volume of the vacuum reaction cavity is 1:20;
the deposition treatment specifically comprises: firstly, pulse hexafluoroacetylacetone palladium vapor enters the vacuum reaction cavity, the pulse time is 0.5s, the gas holding time is 8s, and the air extraction time is 20s; then, the steam of the formaldehyde solution is pulsed into the vacuum reaction cavity, the pulse time is 0.6s, the gas holding time is 8s, and the air pumping time is 25s; completing one deposition cycle, repeating the operation for 20 cycles in total to obtain the hexafluoroacetylacetone modified palladium catalyst, and marking as 20Pd/CeO 2 The mass percentage of the Pd element is 0.42 percent.
FIG. 1 shows 20Pd/CeO prepared in example 1 2 HRTEM of (g); FIG. 2 shows 20Pd/CeO prepared in example 1 2 The AC-HAADF-STEM map and the corresponding EDS map of (A) in FIG. 2 is 20Pd/CeO 2 The AC-HAADF-STEM of (A), (B), (c) and (d) are 20Pd/CeO 2 EDS plot of Ce, O and Pd as medium elements; FIG. 3 shows 20Pd/CeO prepared in example 1 2 Pdk-edge XANES diagram of (A). The carrier CeO can be seen from a in FIGS. 1 and 2 2 But on a carrier CeO 2 No palladium particles were observed; meanwhile, as can be seen from a to d in FIG. 2, the palladium element is uniformly distributed in CeO 2 The above step (1); FIG. 3 shows 20Pd/CeO 2 The medium palladium is present in the form of PdO clusters.
Example 2
1000mg of CeO 2 Uniformly dispersed in 3mL of water, and then 600mL of PdCl with a concentration of 7.4mg/mL was added 2 Stirring the solution for 24 hours at room temperature at a stirring speed of 500rpm, and then drying the solution in an oven at 70 ℃ for 12 hours to obtain a carrier loaded with palladium (the mass fraction of Pd is 0.43 wt%);
mixing 20mg of the carrier loaded with palladium with ethanol, coating the obtained feed liquid on the surface of a quartz plate with the size of 80mm multiplied by 2mm, obtaining a carrier layer formed by the carrier loaded with palladium on the surface of the quartz plate after drying, placing the carrier layer in a vacuum reaction cavity of atomic layer deposition equipment, and performing deposition treatment on the surface of the carrier layer by utilizing an atomic layer deposition method, wherein the precursor is hexafluoroacetylacetone;
the deposition parameters were set as: the temperature of the vacuum reaction cavity is 160 ℃, and the pressure is 50MPa; the temperature of the hexafluoroacetylacetone is 50 ℃; the volume ratio of the flow of the carrier gas (argon) to the volume of the vacuum reaction cavity is 1:12;
the deposition treatment specifically comprises: introducing hexafluoroacetylacetone vapor into the vacuum reaction chamber in a pulse mode for 0.5s, a gas holding time of 10s and an air extraction time of 10s, completing one deposition cycle, repeating the operation for 20 cycles to obtain a hexafluoroacetylacetone-modified palladium catalyst, which is recorded as 20hacacPd/CeO 2 。
Examples 3 to 4
The palladium catalyst in examples 3 to 4 was prepared in substantially the same manner as in example 1 except that:
the deposition parameters were adjusted as: the temperature of the vacuum reaction cavity is 150 ℃, and the pressure is 70MPa;
the deposition treatment was adjusted to: firstly, pulse hexafluoroacetylacetone palladium vapor enters a vacuum reaction cavity, wherein the pulse time is 0.5s, the breath holding time is 8s, and the air extraction time is 20s; then, the steam of the formaldehyde solution is pulsed into the vacuum reaction cavity, the pulse time is 0.6s, the gas holding time is 8s, and the air pumping time is 25s; and the cycle numbers of the deposition treatment in examples 3 to 4 were 10 times and 15 times, respectively;
the final palladium catalysts obtained in examples 3 to 4 were respectively designated as 10Pd/CeO 2 And 15Pd/CeO 2 Wherein the mass percentage of the Pd element is 0.22 percent and 0.28 percent respectively.
Examples 5 to 6
The palladium catalysts of examples 5 to 6 were prepared in substantially the same manner as in example 1 except that:
adding CeO 2 Substituted by TiO 2 ；
The deposition parameters were adjusted as follows: the temperature of the vacuum reaction cavity is 180 ℃, and the pressure is 20MPa;
the deposition treatment was adjusted to: firstly, pulse hexafluoroacetylacetone palladium vapor enters a vacuum reaction cavity, wherein the pulse time is 2s, the breath holding time is 30s, and the air extraction time is 70s; then, the steam of the formaldehyde solution is pulsed into the vacuum reaction cavity, the pulse time is 2s, the gas holding time is 28s, and the air extraction time is 70s; the cycle times in the deposition treatment process are respectively 30 times and 50 times;
the finally obtained palladium catalysts in examples 5 to 6 were each noted as 30Pd/TiO 2 And 50Pd/TiO 2 Wherein the mass percentage of the Pd element is 1.1 percent and 1.8 percent respectively.
Example 7
The preparation of the palladium catalyst in example 7 is substantially the same as in example 1 except that:
CeO is added 2 Substitution with Al 2 O 3 ；
The deposition parameters were adjusted as: the temperature of the vacuum reaction cavity is 140 ℃, and the pressure is 10MPa;
the deposition treatment was adjusted to: firstly, pulse hexafluoroacetylacetone palladium vapor enters a vacuum reaction cavity, the pulse time is 0.01s, the breath holding time is 2.2s, and the air extraction time is 3s; then, the steam of the formaldehyde solution is pulsed into the vacuum reaction cavity, the pulse time is 0.01s, the gas holding time is 2s, and the air extraction time is 5s; and the cycle number in the deposition treatment process is 100;
the mass percentage of the Pd element in the finally obtained palladium catalyst is 0.1 percent.
Examples 8 to 9
The palladium catalyst of examples 8 to 9 was prepared in the same manner as in example 1 except that:
adding CeO 2 Replacing with SBA-15 molecular sieve;
the deposition treatment was adjusted to: firstly, pulse hexafluoroacetylacetone palladium vapor enters a vacuum reaction cavity, the pulse time is 0.6s, the breath holding time is 10s, and the air extraction time is 35s; then, the steam of the formaldehyde solution is pulsed into the vacuum reaction cavity, the pulse time is 1s, the gas holding time is 7s, and the air extraction time is 35s; and the cycle times in the deposition treatment processes in examples 8 to 9 were 10 times and 40 times, respectively;
the mass percentage of Pd element in the finally obtained palladium catalyst is 0.21% and 0.75%, respectively.
Example 10
The preparation method of the palladium catalyst in example 10 is substantially the same as that of example 1 except that:
CeO is added 2 Replacement ofIs ZSM-5 molecular sieve;
the deposition treatment was adjusted to: firstly, pulse hexafluoroacetylacetone palladium vapor enters a vacuum reaction cavity, the pulse time is 0.6s, the breath holding time is 10s, and the air extraction time is 35s; then, the steam of the formaldehyde solution is pulsed into the vacuum reaction cavity, the pulse time is 1s, the breath holding time is 7s, and the air extraction time is 35s; and the cycle number in the deposition treatment process is 20 times;
the mass percentage of the Pd element in the finally obtained palladium catalyst is 0.4%.
Example 11
The preparation method of the palladium catalyst in example 11 is substantially the same as that of example 2 except that:
the deposition parameters were adjusted as follows: the temperature of hexafluoroacetylacetone is 55 ℃;
the deposition treatment was adjusted to: the cycle number in the deposition treatment process is 40;
the final palladium catalyst obtained was recorded as 40hacacPd/CeO 2 。
Example 12
The palladium catalyst in example 12 was prepared in substantially the same manner as in example 2 except that:
adding CeO 2 Substituted by TiO 2 ；
The deposition parameters were adjusted as follows: the temperature of the vacuum reaction cavity is 140 ℃, and the pressure is 50MPa; the temperature of hexafluoroacetylacetone is 55 ℃; the volume ratio of the flow of the carrier gas (argon) to the volume of the vacuum reaction cavity is 1:15;
the deposition treatment was adjusted to: the cycle number in the deposition treatment process is 40 times;
the final palladium catalyst was recorded as 40hacacPd/TiO 2 。
Example 13
The palladium catalyst in example 14 was prepared in substantially the same manner as in example 2 except that:
PdCl 2 the volume of the solution was 1000mL, and the mass fraction of Pd in the finally obtained palladium-loaded support was 0.73wt%;
the deposition parameters were adjusted as: the temperature of hexafluoroacetylacetone is 55 ℃;
the deposition treatment was adjusted to: the cycle number in the deposition treatment process is 100 times;
the final palladium catalyst obtained was recorded as 100hacacPd/CeO 2 。
Comparative example 1
1000mg of CeO 2 Uniformly dispersed in 3mL of water, and then 600mL of PdCl with a concentration of 7.4mg/mL was added 2 The solution was stirred at 500rpm for 24h at room temperature and then dried in an oven at 70 ℃ for 12h to give a palladium-loaded support (mass fraction of Pd: 0.43 wt%).
Comparative example 2
1000mg of CeO 2 Dispersed homogeneously in 3mL of water, followed by the addition of 600mL of PdCl at a concentration of 7.4mg/mL 2 Stirring the solution at room temperature for 24h at a stirring speed of 500rpm, and then drying the solution in an oven at 70 ℃ for 12h to obtain a carrier loaded with palladium (the mass fraction of Pd is 0.43 wt%);
placing 20mg of the carrier loaded with palladium in a porcelain boat, and placing in a tube furnace H 2 -Ar mixed atmosphere (H) 2 The volume fraction is 5 percent), the temperature is raised to 250 ℃ at the heating rate of 5 ℃/min, the temperature is preserved for reduction treatment for 3 hours, and the obtained catalyst is marked as H-Pd/CeO 2 。
Test example 1
The palladium catalyst prepared by the embodiment of the invention is used for catalyzing the solvent-free liquid phase oxidation reaction of benzyl alcohol, and the specific method comprises the following steps: placing 20mg of the palladium catalyst prepared by the embodiment of the invention and 10mL of benzyl alcohol into a three-neck flask, and carrying out oxidation reaction for 15min under the conditions of 120 ℃, 1000rpm and 0.3MPa of oxygen pressure; a similar method is used for carrying out comparison by utilizing a catalyst in the literature to catalyze the solvent-free liquid-phase oxidation reaction of the benzyl alcohol. Specific results are shown in table 1. As can be seen from Table 1, the 20Pd/CeO prepared in example 1 2 The activity (TOF value) and selectivity of catalyzing the solvent-free liquid-phase oxidation reaction of the benzyl alcohol are the best, and the conversion rate is higher. In addition, 20Pd/CeO is adopted in the catalytic benzyl alcohol solvent-free liquid phase oxidation reaction process 2 With stable Pd 2+ /(Pd 0 +Pd 2+ ) In proportion and Pd during the reaction 2+ /(Pd 0 +Pd 2+ ) Is maintained at 75～85％。
TABLE 1 results of comparing catalytic performances of catalysts in examples and documents
The references referred to in table 1 are specifically as follows:
[1]J.Yang,K.Cao,M.Gong,B.Shan,R.Chen,Atomically decorating of MnO x on palladium nanoparticles towards selective oxidation of benzyl alcohol withhigh yield,J Catal,386(2020)60-69.
[2]P.Zhang,Y.Gong,H.Li,Z.Chen,Y.Wang,Solvent-free aerobic oxidation of hydrocarbons and alcohols with Pd@N-doped carbon from glucose,Nat.Commun.,4(2013)1593.
[3]Q.He,P.J.Miedziak,L.Kesavan,N.Dimitratos,M.Sankar,J.A.Lopez-Sanchez,M.M.Forde,J.K.Edwards,D.W.Knight,S.H.Taylor,C.J.Kiely,G.J.Hutchings,Switching-off toluene formation in the solvent-free oxidation of benzyl alcohol using supported trimetallic Au-Pd-Pt nanoparticles,Faraday Discuss.,162(2013)365-378.
[4]J.Pritchard,M.Piccinini,R.Tiruvalam,Q.He,N.Dimitratos,J.A.Lopez-Sanchez,D.J.Morgan,A.F.Carley,J.K.Edwards,C.J.Kiely,G.J.Hutchings,Effect of heat treatment on Au–Pd catalysts synthesized by sol immobilisation for the direct synthesis of hydrogen peroxide and benzyl alcoholoxidation,Catal.Sci.Technol.,3(2013)308-317.
[5]J.Wang,S.A.Kondrat,Y.Wang,G.L.Brett,C.Giles,J.K.Bartley,L.Lu,Q.Liu,C.J.Kiely,G.J.Hutchings,Au-Pd nanoparticles dispersed on composite titania/graphene oxide-supports as a highly active oxidation catalyst,ACS Catal.,5(2015)3575-3587.
[6]Y.-M.Lu,H.-Z.Zhu,J.-W.Liu,S.-H.Yu,Palladium nanoparticles supported on titanate nanobelts for solvent-free aerobic oxidation of alcohols,ChemCatChem,7(2015)4131-4136.
[7]H.Wang,X.-K.Gu,X.Zheng,H.Pan,J.Zhu,S.Chen,L.Cao,W.-X.Li,J.Lu,Disentangling the size-dependent geometric and electronic effects of palladium nanocatalysts beyond selectivity,Sci.Adv.,5(2019)6413.
test example 2
The catalysts prepared in examples 1-2 and comparative examples 1-2 (fresh catalyst and left in air atmosphere for 1 month or 3 months) were subjected to a catalytic performance test by the following specific method: 20mg of the catalyst and 10mL of benzyl alcohol were placed in a three-necked flask, and oxidation reaction was carried out at 120 ℃ and 1000rpm under an oxygen pressure of 0.3MPa for 1 hour, and the results of the performance test were shown in Table 2. It can be seen from table 2 that the catalysts prepared in examples 1 and 2 have high catalytic activity, and the catalysts can be stored for a long time and are not easily deactivated.
Table 2 results of performance test of catalysts prepared in examples 1 to 2 and comparative examples 1 to 2
Test example 3
The catalysts of examples and comparative examples were subjected to the catalytic performance test in accordance with the method of test example 2, and Pd was measured for each catalyst 2+ /(Pd 0 +Pd 2+ ) The ratio, specific results are shown in table 3. As shown in Table 3, the palladium catalysts provided by the embodiments of the present invention all have stable Pd in the process of catalyzing the solvent-free liquid phase oxidation of benzyl alcohol 2+ /(Pd 0 +Pd 2+ ) In proportion and Pd during the reaction 2+ /(Pd 0 +Pd 2+ ) Are all larger than 71 percent.
Table 3 results of performance testing of the catalysts of the examples and comparative preparations
From the above examples and comparative examples, it can be seen that the palladium catalyst with stable double sites provided by the present invention has much higher catalytic activity than the conventional palladium catalyst in the alcohol oxidation reaction, the selectivity of the generated aldehyde is higher (greater than 93%), and the palladium-based catalyst after the reaction is easy to separate and can be reused without performing regeneration treatment, etc., and has higher practical value.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A palladium catalyst with stable double sites comprises a carrier and palladium species dispersed on the surface of the carrier, wherein the palladium species comprises Pd 0 And Pd 2+ Said Pd 2+ Is Pd 0 And Pd 2+ 60-75% of the total amount, pd after the palladium catalyst is used 2+ Is Pd 0 And Pd 2+ 70-85% of the total weight.
2. The palladium catalyst of claim 1 wherein the palladium is present in the form of clusters.
3. The palladium catalyst according to claim 1 or 2, wherein the palladium element content in the palladium catalyst is 0.1 to 2wt%.
4. The palladium catalyst of claim 1 wherein the support comprises an oxide support or a molecular sieve support.
5. The palladium catalyst of claim 4 wherein the oxide support comprises titania, ceria or alumina and the molecular sieve support comprises an SBA-15 molecular sieve or a ZSM-5 molecular sieve.
6. A process for preparing a palladium catalyst as claimed in any one of claims 1 to 5 comprising the steps of:
(1) Based on an atomic layer deposition method, carrying out deposition treatment on the surface of a carrier by sequentially pulsing gaseous hexafluoroacetylacetone palladium and a gaseous reducing agent to obtain a palladium catalyst; wherein, in the deposition process, the pulse time of the palladium hexafluoroacetylacetonate is not more than the pulse time of the reducing agent;
or (2) performing deposition treatment on the surface of the carrier loaded with palladium by pulse gaseous hexafluoroacetylacetone based on an atomic layer deposition method to obtain the palladium catalyst.
7. The method according to claim 6, wherein the reducing agent comprises hydrogen gas or a formaldehyde solution.
8. The production method according to claim 6, wherein the number of deposition treatments in (1) and (2) is independently 1 to 100.
9. Use of a palladium catalyst as defined in any one of claims 1 to 5 or prepared by the method of any one of claims 6 to 8 for catalyzing the oxidation of an alcohol to produce an aldehyde.
10. Use according to claim 9, wherein the alcohol comprises benzyl alcohol, 4-methylbenzyl alcohol, 2-phenyl ethanol or 1-octanol.
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