CN115722239B - Method for preparing vanadium phosphorus oxide catalyst with assistance of eutectic solvent and application of method - Google Patents
Method for preparing vanadium phosphorus oxide catalyst with assistance of eutectic solvent and application of method Download PDFInfo
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- CN115722239B CN115722239B CN202211561801.6A CN202211561801A CN115722239B CN 115722239 B CN115722239 B CN 115722239B CN 202211561801 A CN202211561801 A CN 202211561801A CN 115722239 B CN115722239 B CN 115722239B
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- oxide catalyst
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- vanadium
- vanadium phosphorus
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- 230000005496 eutectics Effects 0.000 title claims abstract description 71
- 239000002904 solvent Substances 0.000 title claims abstract description 71
- LJYCJDQBTIMDPJ-UHFFFAOYSA-N [P]=O.[V] Chemical compound [P]=O.[V] LJYCJDQBTIMDPJ-UHFFFAOYSA-N 0.000 title claims abstract description 61
- 239000003054 catalyst Substances 0.000 title claims abstract description 60
- 238000000034 method Methods 0.000 title claims abstract description 30
- 239000012018 catalyst precursor Substances 0.000 claims abstract description 104
- WVDDGKGOMKODPV-UHFFFAOYSA-N Benzyl alcohol Chemical compound OCC1=CC=CC=C1 WVDDGKGOMKODPV-UHFFFAOYSA-N 0.000 claims abstract description 81
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 60
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 claims abstract description 58
- 239000011541 reaction mixture Substances 0.000 claims abstract description 58
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 claims abstract description 54
- 238000006243 chemical reaction Methods 0.000 claims abstract description 49
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims abstract description 48
- 238000010438 heat treatment Methods 0.000 claims abstract description 47
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 30
- 229910052751 metal Inorganic materials 0.000 claims abstract description 29
- 239000002184 metal Substances 0.000 claims abstract description 29
- 235000019445 benzyl alcohol Nutrition 0.000 claims abstract description 27
- 238000001816 cooling Methods 0.000 claims abstract description 25
- 150000003839 salts Chemical class 0.000 claims abstract description 21
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 20
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 claims abstract description 14
- 230000003647 oxidation Effects 0.000 claims abstract description 12
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims abstract description 7
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 173
- 238000003756 stirring Methods 0.000 claims description 40
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 30
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 18
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 claims description 14
- 239000002243 precursor Substances 0.000 claims description 13
- 239000012298 atmosphere Substances 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 11
- TVXBFESIOXBWNM-UHFFFAOYSA-N Xylitol Natural products OCCC(O)C(O)C(O)CCO TVXBFESIOXBWNM-UHFFFAOYSA-N 0.000 claims description 9
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 9
- HEBKCHPVOIAQTA-UHFFFAOYSA-N meso ribitol Natural products OCC(O)C(O)C(O)CO HEBKCHPVOIAQTA-UHFFFAOYSA-N 0.000 claims description 9
- 239000000811 xylitol Substances 0.000 claims description 9
- HEBKCHPVOIAQTA-SCDXWVJYSA-N xylitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)CO HEBKCHPVOIAQTA-SCDXWVJYSA-N 0.000 claims description 9
- 235000010447 xylitol Nutrition 0.000 claims description 9
- 229960002675 xylitol Drugs 0.000 claims description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 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 6
- 230000035484 reaction time Effects 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 5
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 229910052720 vanadium Inorganic materials 0.000 claims description 4
- VYLVYHXQOHJDJL-UHFFFAOYSA-K cerium trichloride Chemical compound Cl[Ce](Cl)Cl VYLVYHXQOHJDJL-UHFFFAOYSA-K 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 3
- 238000011065 in-situ storage Methods 0.000 claims description 3
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 claims description 3
- 238000012216 screening Methods 0.000 claims description 3
- 230000003213 activating effect Effects 0.000 claims description 2
- 229910002651 NO3 Inorganic materials 0.000 claims 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 15
- 238000001994 activation Methods 0.000 description 45
- 230000004913 activation Effects 0.000 description 43
- LEABNKXSQUTCOW-UHFFFAOYSA-N [O].[P].[V] Chemical compound [O].[P].[V] LEABNKXSQUTCOW-UHFFFAOYSA-N 0.000 description 39
- 230000000052 comparative effect Effects 0.000 description 28
- 238000002360 preparation method Methods 0.000 description 25
- 238000011156 evaluation Methods 0.000 description 22
- 238000010992 reflux Methods 0.000 description 20
- 238000001035 drying Methods 0.000 description 19
- 238000012854 evaluation process Methods 0.000 description 19
- 238000001914 filtration Methods 0.000 description 19
- 238000005406 washing Methods 0.000 description 19
- 238000007792 addition Methods 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000012752 auxiliary agent Substances 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 239000011777 magnesium Substances 0.000 description 5
- 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 description 4
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- CDQSJQSWAWPGKG-UHFFFAOYSA-N butane-1,1-diol Chemical compound CCCC(O)O CDQSJQSWAWPGKG-UHFFFAOYSA-N 0.000 description 3
- 230000009466 transformation Effects 0.000 description 3
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 238000012512 characterization method Methods 0.000 description 2
- GDVKFRBCXAPAQJ-UHFFFAOYSA-A dialuminum;hexamagnesium;carbonate;hexadecahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Mg+2].[Al+3].[Al+3].[O-]C([O-])=O GDVKFRBCXAPAQJ-UHFFFAOYSA-A 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 229960001545 hydrotalcite Drugs 0.000 description 2
- 229910001701 hydrotalcite Inorganic materials 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910001510 metal chloride Inorganic materials 0.000 description 2
- 125000004437 phosphorous atom Chemical group 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- -1 vanadyl phosphate Chemical compound 0.000 description 2
- OHVLMTFVQDZYHP-UHFFFAOYSA-N 1-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)-2-[4-[2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidin-5-yl]piperazin-1-yl]ethanone Chemical compound N1N=NC=2CN(CCC=21)C(CN1CCN(CC1)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)=O OHVLMTFVQDZYHP-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 238000001069 Raman spectroscopy Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000008065 acid anhydrides Chemical group 0.000 description 1
- 230000009435 amidation Effects 0.000 description 1
- 238000007112 amidation reaction Methods 0.000 description 1
- HKVFISRIUUGTIB-UHFFFAOYSA-O azanium;cerium;nitrate Chemical compound [NH4+].[Ce].[O-][N+]([O-])=O HKVFISRIUUGTIB-UHFFFAOYSA-O 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- OEYIOHPDSNJKLS-UHFFFAOYSA-N choline Chemical compound C[N+](C)(C)CCO OEYIOHPDSNJKLS-UHFFFAOYSA-N 0.000 description 1
- 229960001231 choline Drugs 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000000386 donor Substances 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000032050 esterification Effects 0.000 description 1
- 238000005886 esterification reaction Methods 0.000 description 1
- 235000013373 food additive Nutrition 0.000 description 1
- 239000002778 food additive Substances 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 239000000852 hydrogen donor Substances 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- FQUPMIQUWINAGY-UHFFFAOYSA-L magnesium ethane-1,2-diol dichloride Chemical compound [Mg+2].[Cl-].[Cl-].OCCO FQUPMIQUWINAGY-UHFFFAOYSA-L 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 239000000575 pesticide Substances 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 150000003077 polyols Chemical class 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
- 238000000844 transformation Methods 0.000 description 1
- 229920006305 unsaturated polyester Polymers 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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
- Y02P20/584—Recycling of catalysts
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- Furan Compounds (AREA)
- Catalysts (AREA)
Abstract
The invention provides a method for preparing a vanadium phosphorus oxide catalyst with the assistance of a eutectic solvent, which comprises the following steps: mixing vanadium pentoxide, isobutanol and benzyl alcohol with a eutectic solvent, and then heating to react to obtain a reaction mixture; cooling the reaction mixture to a preset temperature, adding concentrated phosphoric acid into the reaction mixture, and heating again to react to obtain a vanadium phosphorus oxide catalyst precursor; roasting the vanadium phosphorus oxide catalyst precursor to obtain a vanadium phosphorus oxide catalyst; the eutectic solvent is formed from a metal salt and an organic alcohol. The invention also provides application of the vanadium phosphorus oxide catalyst obtained by the method in preparing maleic anhydride by selective oxidation of n-butane. The vanadium phosphorus oxide catalyst prepared by the method of the invention has higher activity in the reaction of preparing maleic anhydride by selective oxidation of n-butane.
Description
Technical Field
The invention belongs to the field of chemical catalysis, and particularly relates to a method for preparing a vanadium phosphorus oxide catalyst with the assistance of a eutectic solvent, and application of the vanadium phosphorus oxide catalyst.
Background
Maleic anhydride is one of world tri-large acid anhydrides, unsaturated carbon-carbon double bonds and carbon-oxygen double bonds exist in molecules, and can be subjected to various reactions such as polymerization, amidation, addition, esterification and the like, and is used as an important chemical raw material, and is mainly used for preparing unsaturated polyesters, food additives, coatings, pesticides, lubricating oil additives, surfactants and the like; in addition, maleic anhydride can be used for preparing tetrahydrofuran, 1-4 butanediol, etc. by hydrogenation. The vanadium phosphorus oxide catalyst is the only industrial catalyst for preparing maleic anhydride by selective oxidation of n-butane, but the catalyst has the problems of poor activity, low yield of target products and the like at present. Therefore, in order to improve the activity of the catalyst and the yield of the target product, a great deal of research on the preparation of the vanadium phosphorus oxide catalyst is carried out by a great deal of domestic and foreign scholars.
The patent application CN113058625A ball-mills the vanadium phosphorus oxide catalyst precursor and the choline chloride-alcohol eutectic solvent, so that the activity of the catalyst and the selectivity of target products are improved. Patent application CN111701608A proposes a preparation method for preparing a vanadium phosphorus oxide catalyst by using hydrotalcite as an auxiliary material, and the adjustment and control of the acidity and the alkalinity of the catalyst are realized by introducing hydrotalcite with different acidity and alkalinity, so that the activity of the vanadium phosphorus oxide catalyst and the selectivity of maleic anhydride are improved to a certain extent. Patent application CN104971750a uses alkali metal Na, K, rb, cs or a mixture thereof as an auxiliary agent to improve the catalytic performance of the vanadium phosphorus oxide catalyst, and researches show that the addition of a proper amount of alkali metal can improve the selectivity of maleic anhydride. However, although the activity of the catalyst and the selectivity of the target product are improved to some extent by modifying the vanadium phosphorus oxide catalyst in the prior art, the dual regulation and control of the structure and the electrons cannot be realized, and the regulation and control of the organic and the metal are required to be performed in two steps, so that the effect is not obvious and the steps are complicated.
Accordingly, there is an urgent need to provide a method for preparing a vanadium phosphorus oxide catalyst.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for preparing a vanadium phosphorus oxide catalyst by assistance of a eutectic solvent and also provides application of the vanadium phosphorus oxide catalyst.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a method for preparing a vanadium phosphorus oxide catalyst with the assistance of a eutectic solvent, which comprises the following steps:
(1) Mixing vanadium pentoxide, isobutanol and benzyl alcohol with a eutectic solvent, and then heating to react to obtain a reaction mixture;
(2) Cooling the reaction mixture to a preset temperature, adding concentrated phosphoric acid into the reaction mixture, and heating again to react to obtain a vanadium phosphorus oxide catalyst precursor;
(3) Roasting the vanadium phosphorus oxide catalyst precursor to obtain a vanadium phosphorus oxide catalyst;
wherein the eutectic solvent in step (1) is formed of a metal salt and an organic alcohol.
Further, the eutectic solvent is a uniform transparent mixture formed by mixing and stirring the metal salt and the organic alcohol and heating to 50-100 ℃, wherein the molar ratio of the metal salt to the organic alcohol is 1 (1-6).
Further, the metal salt is at least one of magnesium chloride, magnesium nitrate, cerium chloride, ammonium cerium nitrate, copper chloride and cerium nitrate, and the organic alcohol is at least one of ethylene glycol, glycerol and xylitol.
Further, the metal salt is at least one of magnesium chloride, magnesium nitrate and copper chloride.
Further, in step (1):
the reaction temperature is 100-180 ℃ and the reaction time is 1-6 h;
the volume ratio of the benzyl alcohol to the isobutanol is 1 (3-5);
the molar ratio of the metal in the metal salt to the vanadium in the vanadium pentoxide is (0.0001-0.02): 1.
Further, in step (2):
and cooling the reaction mixture to 60-100 ℃, wherein the reaction temperature of the reaction mixture and the concentrated phosphoric acid is 100-150 ℃, the reaction time is 8-16 h, and the mass concentration of the concentrated phosphoric acid is more than or equal to 80%.
Further, in step (3):
the roasting temperature of the vanadium phosphorus oxide catalyst precursor is 420-440 ℃, and the roasting time is 10-24 hours.
Further, in step (3):
the roasting atmosphere is nitrogen atmosphere, or mixed atmosphere of n-butane and air, or mixed atmosphere of n-butane, oxygen and nitrogen.
Further, in step (3):
before roasting, firstly tabletting and forming the vanadium phosphorus oxide catalyst precursor, grinding and screening to obtain precursor particles with the particle size of 10-50 meshes, and then placing the precursor particles into a fixed bed reactor, and activating at high temperature in situ in the roasting atmosphere to obtain the vanadium phosphorus oxide catalyst.
The invention also provides an application of the vanadium phosphorus oxide catalyst obtained by the method in preparing maleic anhydride by selective oxidation of n-butane, wherein,
the reaction conditions for preparing maleic anhydride by the selective oxidation of n-butane are as follows: the reaction temperature is 400-550 ℃, the reaction pressure is 0.1-0.3 MPa, and the space velocity of the n-butane mixed gas is 1000h -1 ～2500h -1 The concentration of the n-butane is 1.3 to 1.8 weight percent.
Compared with the prior art, the invention has the beneficial technical effects that:
(1) The synthesis of the metal-based alcohol eutectic solvent is simple, the cost is low, and compared with a vanadium phosphorus oxide catalyst without the addition of the eutectic solvent and the addition of the traditional auxiliary agent, the catalyst has higher activity in the reaction of preparing maleic anhydride by the selective oxidation of n-butane.
(2) The invention adopts the metal-based alcohol eutectic solvent to strengthen the preparation of the vanadium phosphorus oxide catalyst, and changes the oxidation-reduction characteristic, the surface acid-base property, the P/V and the like of the catalyst after the eutectic solvent is added, thereby effectively improving the activity of the catalyst.
(3) The eutectic solvent auxiliary agent disclosed by the invention consists of metal chloride and organic alcohol, and a stronger hydrogen bond effect exists between the metal chloride and the organic alcohol, so that compared with the traditional auxiliary agent, the eutectic solvent can induce the growth behavior of a precursor, and in the activation process of the precursor, the eutectic solvent is decomposed, so that the specific surface area of the catalyst is increased.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1A is a scanning electron microscope image of a vanadium phosphorus oxide catalyst precursor obtained in example 4 of the present invention;
FIG. 1B is a scanning electron microscope image of a vanadium phosphorus oxide catalyst precursor obtained in comparative example 10 of the present invention;
FIG. 2A is a scanning electron microscope image of the vanadium phosphorus oxide catalyst obtained in example 4 of the present invention;
FIG. 2B is a scanning electron microscope image of the vanadium phosphorus oxide catalyst obtained in comparative example 10 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
The invention provides a method for preparing a vanadium phosphorus oxide catalyst with the assistance of a eutectic solvent, which comprises the following steps:
(1) Mixing vanadium pentoxide, isobutanol and benzyl alcohol with a eutectic solvent, and then heating to react to obtain a reaction mixture, wherein the eutectic solvent is formed by metal salt and organic alcohol.
In the present invention, the method of forming the eutectic solvent by the metal salt and the organic polyol is the prior art, and the person skilled in the art can refer to the method disclosed in the prior art for preparation, for example, according to the following method: specifically, metal salt and organic alcohol are mixed and stirred and heated to 50-100 ℃ to form a uniform and transparent mixture, wherein the molar ratio of the metal salt (hydrogen bond acceptor) to the organic alcohol (hydrogen bond donor) is 1 (1-6). The metal salt is at least one of magnesium chloride, magnesium nitrate, cerium chloride, ceric ammonium nitrate, copper chloride and cerium nitrate, preferably at least one of magnesium chloride, magnesium nitrate and copper chloride. The organic alcohol is at least one of ethylene glycol, glycerol and xylitol.
The reaction temperature is 100-180 ℃, preferably 130-140 ℃, and the reaction time is 1-6 h, preferably 3-5 h. The volume ratio of benzyl alcohol to isobutanol is 1 (3-5), and the molar ratio of metal in the metal salt to vanadium in the vanadium pentoxide is (0.0001-0.02): 1, preferably (0.005-0.01): 1.
(2) And cooling the reaction mixture to a preset temperature, adding concentrated phosphoric acid into the reaction mixture, heating again, reacting, filtering, washing and drying the product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
Cooling the reaction mixture to 60-100 ℃, wherein the reaction temperature of the reaction mixture and the concentrated phosphoric acid is 100-150 ℃, the reaction time of heating reflux is 8-16 h, and the mass concentration of the concentrated phosphoric acid is more than or equal to 80%.
(3) Roasting the vanadium phosphorus oxide catalyst precursor to obtain the vanadium phosphorus oxide catalyst.
The roasting temperature of the vanadium phosphorus oxide catalyst precursor is 420-440 ℃ and the roasting time is 10-24 h. The roasting atmosphere is nitrogen atmosphere or mixed atmosphere of n-butane and air or mixed atmosphere of n-butane, oxygen and nitrogen, the volume ratio of n-butane to air is (0.8-1.8): 100, and the volume ratio of n-butane, oxygen and nitrogen is (0.8-1.8): 10-25): 75-85.
In order to facilitate the effect evaluation of the catalyst, the roasting step can be carried out after the vanadyl phosphate precursor is formed, and the roasting step is directly used for the effect evaluation of the catalyst; or roasting and then forming, and then evaluating the catalyst effect.
In a preferred embodiment, before roasting, the vanadium phosphorus oxide catalyst precursor is firstly pressed into tablets, then ground and sieved to obtain precursor particles with the size of 10-50 meshes, preferably 20-40 meshes, then the precursor particles with the volume of 1-5 ml, preferably 2-4 ml are measured and placed in a fixed bed reactor, and the vanadium phosphorus oxide catalyst is obtained by high-temperature in-situ activation in the roasting atmosphere.
The invention also provides an application of the vanadium phosphorus oxide catalyst obtained by the method in preparing maleic anhydride by selective oxidation of n-butane, wherein the reaction conditions for preparing maleic anhydride by selective oxidation of n-butane are as follows: the reaction temperature is 400-550 ℃, the reaction pressure is 0.1-0.3 MPa, and the space velocity of the n-butane mixed gas is 1000h -1 ～2500h -1 The concentration of the n-butane is 1.3 to 1.8 weight percent.
The method for preparing the vanadium phosphorus oxide catalyst with the assistance of the eutectic solvent is illustrated by a specific example. The compounds of the following examples can be prepared directly according to the existing methods, respectively, and of course, in other examples are also available directly from the market without being limited thereto.
Wherein the organic alcohol is Ethylene Glycol (EG), glycerol (GL) and Xylitol (XL), e.g., the eutectic solvent of magnesium chloride and ethylene glycol is denoted MgCl 2 EG, the eutectic solvent of magnesium chloride and xylitol is denoted MgCl 2 Eutectic solvents of/XL, magnesium nitrate and glycerol are denoted as Mg (NO 3 ) 2 Eutectic solvents of nitric acid, pel and ethylene glycol are denoted Ce (NO) 3 ) 3 EG, the eutectic solvent of chlorinated Pel and ethylene glycol is denoted CeCl 2 EG, the eutectic solvent of ceric ammonium nitrate and ethylene glycol is denoted Ce (NH) 4 ) 2 (NO 3 ) 6 /EG。
Example 1
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 3.5mmol of ethylene glycol are added to the mixture1.75mmol CeCl 2 The formed eutectic solvent (CeCl) 2 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
Tabletting and molding the vanadium phosphorus oxide catalyst precursor, grinding and screening to obtain particles with 20-40 meshes, weighing 3mL of catalyst precursor particles, and placing the particles in a fixed bed reactor. At a space velocity of 2000h -1 Raw gas (C) 4 H 10 /O 2 /N 2 Activation in =1.36/18.20/80.44 (v/v/v)), activation for 12h at 2 ℃/min to 430 ℃ from room temperature, and then reduction of the bed temperature to 420 ℃ for n-butane oxidation to prepare maleic anhydride.
The reaction tail gas is analyzed on line by gas chromatography, the conversion rate of n-butane is 88.7%, the selectivity of maleic anhydride is 65.5%, and the mass yield of maleic anhydride is 98%.
Example 2
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 3.5mmol of ethylene glycol are added together with 1.75mmol of Ce (NO) 3 ) 3 The eutectic solvent formed (Ce (NO 3 ) 3 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 86.2%, the selectivity of maleic anhydride was 64.8%, and the mass yield of maleic anhydride was 94.2%.
Example 3
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 3.5mmol of glycerol are added together with 1.75mmol of Mg (NO) 3 ) 2 The eutectic solvent formed (Mg (NO 3 ) 2 and/GL) and mechanically stirring at 135 ℃ for reaction for 3 hours to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12 hours under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 93.1%, the selectivity of maleic anhydride was 64.2%, and the mass yield of maleic anhydride was 101%.
Example 4
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 3.5mmol of ethylene glycol and 1.75mmol of MgCl are added 2 The eutectic solvent (MgCl) formed 2 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 87.6%, the selectivity of maleic anhydride was 68.0%, and the mass yield of maleic anhydride was 100.5%.
Example 5
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 、15ml benzyl alcohol and 60ml isobutanol were mixed and then 3.5mmol xylitol and 1.75mmol MgCl were added 2 The eutectic solvent (MgCl) formed 2 XL), mechanically stirring and reacting for 3 hours at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12 hours under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 86%, the selectivity of maleic anhydride was 70%, and the mass yield of maleic anhydride was 101%.
Example 6
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 3.5mmol of ethylene glycol are added together with 1.75mmol of Ce (NH) 4 ) 2 (NO 3 ) 6 The eutectic solvent formed (Ce (NH) 4 ) 2 (NO 3 ) 6 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 88%, the selectivity of maleic anhydride was 71%, and the mass yield of maleic anhydride was 105%.
Example 7
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 45ml of isobutanol are mixed and then 3.5mmol of ethylene glycol and 3.5mmol of MgCl are added 2 The eutectic solvent (MgCl) formed 2 EG), at 140 DEG CAnd (3) mechanically stirring and reacting for 5 hours to obtain a reaction mixture, cooling the reaction mixture to 100 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 150 ℃, heating and refluxing for 8 hours under continuous stirring, and filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 84%, the selectivity to maleic anhydride was 72%, and the mass yield of maleic anhydride was 102%.
Example 8
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 75ml of isobutanol are mixed and then 3.5mmol of ethylene glycol and 0.584mmol of Mg (NO) are added 3 ) 2 The eutectic solvent formed (Mg (NO 3 ) 2 (EG), mechanically stirring and reacting for 6 hours at 180 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 60 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 100 ℃, heating and refluxing for 16 hours under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 86%, the selectivity of maleic anhydride was 70%, and the mass yield of maleic anhydride was 102%.
Comparative example 1
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed, then 3.5mmol of ethylene glycol is added, the mixture is mechanically stirred at 135 ℃ for reaction for 3 hours to obtain a reaction mixture, then the reaction mixture is cooled to 80 ℃, 7.23ml of phosphoric acid with the mass fraction of 85% is added, the temperature is raised to 135 ℃, the mixture is heated to reflux for 12 hours under continuous stirring, and the obtained product is filtered, washed and dried to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 83.8%, the selectivity of maleic anhydride was 65.2%, and the mass yield of maleic anhydride was 92.2%.
Comparative example 2
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 0.8mmol of MgCl is added 2 Mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 81.6%, the selectivity of maleic anhydride was 66.7%, and the mass yield of maleic anhydride was 91.8%.
Comparative example 3
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 0.8mmol of MgCl are added in sequence respectively 2 And 3.5mmol of ethylene glycol, mechanically stirring and reacting for 3 hours at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12 hours under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 83.2%, the selectivity of maleic anhydride was 65.7%, and the mass yield of maleic anhydride was 92.2%.
Comparative example 4
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 Mixing 15ml of benzyl alcohol and 60ml of isobutanol, mechanically stirring at 135 ℃ for reaction for 3 hours to obtain a reaction mixture, cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12 hours under continuous stirring, and filtering, washing and drying the obtained product to obtain the vanadium phosphorus oxide catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 79.5%, the selectivity of maleic anhydride was 66.0%, and the mass yield of maleic anhydride was 88.4%.
Comparative example 5
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 0.9mmol of ethylene glycol and 0.9mmol of ErCl are added 3 The eutectic solvent formed (ErCl 3 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 50.6%, the selectivity of maleic anhydride was 66.4%, and the mass yield of maleic anhydride was 56.7%.
Comparative example 6
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 1.0mmol of ethylene glycol and 1.0mmol of SnCl are added 4 The formed eutectic solvent (SnCl) 4 EG), the reaction was mechanically stirred at 135℃for 3 hours to give a reaction mixture, and the reaction mixture was then reduced7.23ml of phosphoric acid with the mass fraction of 85% is added to the mixture until the temperature reaches 80 ℃, the mixture is heated to 135 ℃, and after the mixture is heated and refluxed for 12 hours under continuous stirring, the obtained product is filtered, washed and dried, and the vanadium-phosphorus-oxygen catalyst precursor is prepared.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 53.0%, the selectivity of maleic anhydride was 68.0%, and the mass yield of maleic anhydride was 60.7%.
Comparative example 7
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 1.1mmol of ethylene glycol and 1.1mmol of YCl are added 3 The eutectic solvent (YCl) formed 3 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 55.5%, the selectivity of maleic anhydride was 66.2%, and the mass yield of maleic anhydride was 62.0%.
Comparative example 8
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 1.3mmol of ethylene glycol and 1.3mmol of BaCl are added 2 The eutectic solvent formed (BaCl) 2 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 65.1%, the selectivity of maleic anhydride was 72.3%, and the mass yield of maleic anhydride was 79.5%.
Comparative example 9
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml benzyl alcohol and 60ml isobutanol were mixed and then 1.2mmol glycerol and 1.2mmol CoCl were added 2 The eutectic solvent formed (CoCl 2 and/GL) and mechanically stirring at 135 ℃ for reaction for 3 hours to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12 hours under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 61.3%, the selectivity of maleic anhydride was 66.2%, and the mass yield of maleic anhydride was 68.5%.
Comparative example 10
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 3.5mmol of 1-4 butanediol are added together with 1.75mmol of MgCl 2 The eutectic solvent (MgCl) formed 2 BDO), mechanically stirring and reacting for 3 hours at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12 hours under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium phosphorus oxide catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 66.50%, the selectivity of maleic anhydride was 63.45%, and the mass yield of maleic anhydride was 71.18%.
Comparative example 11
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml of benzyl alcohol and 60ml of isobutanol are mixed and then 1.3mmol of ethylene glycol and 1.1mmol of CoCl are added 2 The eutectic solvent formed (CoCl 2 (EG), mechanically stirring and reacting for 3h at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12h under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium-phosphorus-oxygen catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 71.7%, the selectivity of maleic anhydride was 66.7%, and the mass yield of maleic anhydride was 80.6%.
Comparative example 12
(1) Preparation of vanadium phosphorus oxygen catalyst precursor
Will 9.094g V 2 O 5 15ml benzyl alcohol and 60ml isobutanol were mixed and then 1.2mmol1-4 butanediol was added with 1.2mmol CoCl 2 The eutectic solvent formed (CoCl 2 BDO), mechanically stirring and reacting for 3 hours at 135 ℃ to obtain a reaction mixture, then cooling the reaction mixture to 80 ℃, adding 7.23ml of phosphoric acid with the mass fraction of 85%, heating to 135 ℃, heating and refluxing for 12 hours under continuous stirring, and then filtering, washing and drying the obtained product to obtain the vanadium phosphorus oxide catalyst precursor.
(2) Catalyst precursor activation and evaluation
The catalyst precursor activation and evaluation process was the same as in example 1. The conversion of n-butane was 66.5%, the selectivity of maleic anhydride was 64.5%, and the mass yield of maleic anhydride was 72.4%.
As can be seen from a comparison of example 4 and comparative examples 1, 2, 3, mgCl is used in example 4 2 Vanadium phosphorus oxygen catalyst (VPO-MgCl) obtained by using EG as eutectic solvent 2 EG) is about 3 to 6% higher than in comparative examples 1-3, mgCl 2 The addition of the/EG eutectic solvent facilitates the improvement of catalyst performance. This is because of MgCl 2 The EG eutectic solvent not only promotes the generation of the active crystal face of the catalyst, but also promotes the gamma-VOPO 4 Formation of a crystalline phase. Raman spectroscopy demonstrated this presumption, mgCl 2 beta-VOPO in the presence of EG eutectic solvent 4 And gamma-VOPO 4 The relative strength of the phases is higher than other catalysts, indicating that the eutectic solvent can modulate the composition of the crystalline phase. Notably, VPO-MgCl 2 EG (VO) 2 P 2 O 7 The characteristic peaks of the crystalline phase show split peaks, which indicate that the microstructure of the catalyst is different, and may be caused by v=o bonds with different angles.
TABLE 1 XRD characterization of the catalyst precursors in example 4 and comparative examples 1-3
XRD characterization results of the vanadium phosphorus oxide catalyst precursors of example 4 and comparative examples 1, 2, and 3 are shown in table 1. Wherein the vanadium phosphorus oxide catalyst precursors in example 4 and comparative examples 1-3 are represented as PVPO-MgCl, respectively 2 /EG、PVPO-EG、PVPO-MgCl 2 And PVPO-MgCl 2 EG. Example 4 use of the eutectic solvent MgCl of the present invention 2 And preparing vanadium phosphorus oxide catalyst precursor by EG. In comparative example 1, only the organic alcohol ethylene glycol was used, but no metal salt was used. In comparative example 2, only a metal salt was used, but no organic alcohol ethylene glycol was used. In example 3, although magnesium chloride and ethylene glycol were used simultaneously, they were added separately to the reactants, and they did not form the eutectic solvent MgCl 2 EG, that is to say both, do not participate in the reaction in the form of a eutectic solvent.
As can be seen from Table 1, the single hydrogen donor and eutectic solvent act as an additive to affect the precursor growth process, and the relative crystal plane content and grain size are changed, possibly due to the specific surface formation between the different additive molecules and the catalystAdsorption, regulating and controlling the growth process of the crystal. EG alone in comparative example 1, I (001) /I (130) With the highest ratio, probably an unstable complex with vanadium during the synthesis of the precursor, the growth of the (001) plane is promoted. PVPO-MgCl 2 EG and PVPO-MgCl 2 The former of the two precursors EG has smaller grain size, is more beneficial to the topological transformation of crystalline phases, and shows that the existence of hydrogen bond network in the eutectic solvent can enable crystals to grow in a preferred direction.
FIGS. 1A and 1B are illustrations of the preparation of example 4 and comparative example 10, respectively, with the addition of ethylene glycol magnesium chloride eutectic solvent (MgCl) 2 EG), 1-4 butanediol magnesium chloride eutectic solvent (MgCl) 2 BDO) to obtain a micro-topography of the catalyst precursor. As can be seen from FIG. 1A, PVPO-MgCl 2 EG presents a lamellar structure and has better dispersibility. Whereas the PVPO-MgCl of FIG. 1B 2 BDO exhibits a certain stacking structure and is poorly dispersible due to MgCl 2 The stability of/EG is stronger, and the hydrogen bond network and vanadium atoms act, so that the growth of crystal nucleus can be induced to a certain extent, and the precursor can keep a more regular lamellar structure. This is further demonstrated in FIG. 2A, PVPO-MgCl of lamellar structure 2 After activation of/EG, fine particles are more easily formed (FIG. 2A), which is advantageous in increasing the exposed specific surface area and thus the conversion of n-butane. VPO-MgCl in FIG. 2B 2 BDO has a more regular large plate-like structure, and the BDO has larger thickness and poor dispersibility, so that the BDO has reduced performance. Determination of VPO-MgCl by BET fully automatic specific surface and porosity Analyzer 2 EG and VPO-MgCl 2 BDO, 12.81 and 10.15 in order, is consistent with the topographical features presented by SEM as described above. The higher specific surface area facilitates the exposure of the catalyst active sites, thereby improving the catalytic performance.
The eutectic solvent of the present invention was not used in comparative example 4, but the eutectic solvents of comparative examples 5 to 12 were used to participate in the reaction, but the composition of the eutectic solvents of comparative examples 5 to 12 was quite different from that of the present invention, that is, the eutectic solvents of comparative examples 5 to 12 were used in a range different from that of the present invention. Comparing the data of the conversion rate of n-butane, the selectivity of maleic anhydride and the mass yield of maleic anhydride of examples 1 to 8 of the present invention with those of comparative examples 4 to 12, it is known that the vanadium phosphorus oxide catalyst prepared by using the eutectic solvent of the present invention shows higher activity in the reaction of preparing maleic anhydride by selective oxidation of n-butane.
The metal eutectic solvent can induce the formation of a catalyst precursor, and some eutectic solvents are unfavorable for topological transformation of crystalline phases in the activation process, and are also unfavorable for the increase of the number of active surfaces of the vanadium phosphorus oxide catalyst and the enrichment of surface P atoms, so that the performance of the vanadium phosphorus oxide catalyst is poor. The eutectic solvent protected by the invention is added in the preparation process, so that not only can the enrichment of metal auxiliary agents and P atoms to the surface of the catalyst be effectively doped, but also the catalyst precursor can be enabled to present fine particles after being activated, and the specific surface area of the vanadium phosphorus oxygen catalyst is improved. The addition of the eutectic solvent of the present invention induces V 5+ The formation of the crystalline phase and the highest acid amount on the surface of the catalyst, thereby remarkably improving the performance of the vanadium phosphorus oxide catalyst.
It should be noted that, each component or step in each embodiment may be intersected, replaced, added, and deleted, and therefore, the combination formed by these reasonable permutation and combination transformations shall also belong to the protection scope of the present invention, and shall not limit the protection scope of the present invention to the embodiments.
Those of ordinary skill in the art will appreciate that: the above discussion of any embodiment is merely exemplary and is not intended to imply that the scope of the disclosure of embodiments of the invention, including the claims, is limited to such examples; combinations of features of the above embodiments or in different embodiments are also possible within the idea of an embodiment of the invention, and there are many other variations of the different aspects of the embodiments of the invention as described above, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, and the like, which are made within the spirit and principles of the embodiments of the invention, are included within the scope of the embodiments of the invention.
Claims (9)
1. The method for preparing the vanadium phosphorus oxide catalyst with the assistance of the eutectic solvent is characterized by comprising the following steps of:
(1) Mixing vanadium pentoxide, isobutanol and benzyl alcohol with a eutectic solvent, and then heating to react to obtain a reaction mixture;
(2) Cooling the reaction mixture to a preset temperature, adding concentrated phosphoric acid into the reaction mixture, and heating again to react to obtain a vanadium phosphorus oxide catalyst precursor;
(3) Roasting the vanadium phosphorus oxide catalyst precursor to obtain a vanadium phosphorus oxide catalyst;
wherein the eutectic solvent in step (1) is formed of a metal salt and an organic alcohol;
the metal salt is at least one of magnesium chloride, magnesium nitrate, cerium chloride, ceric ammonium nitrate and ceric nitrate, and the organic alcohol is at least one of glycol, glycerol and xylitol.
2. The method according to claim 1, wherein the eutectic solvent is a homogeneous transparent mixture formed by mixing and stirring the metal salt and the organic alcohol and heating to 50-100 ℃, wherein the molar ratio of the metal salt to the organic alcohol is 1 (1-6).
3. The method according to claim 2, wherein the metal salt is at least one of magnesium chloride and magnesium nitrate.
4. The method according to claim 1, wherein in step (1):
the reaction temperature is 100-180 ℃ and the reaction time is 1-6 h;
the volume ratio of the benzyl alcohol to the isobutanol is 1 (3-5);
the molar ratio of the metal in the metal salt to the vanadium in the vanadium pentoxide is (0.0001-0.02): 1.
5. The method according to claim 1, wherein in step (2):
and cooling the reaction mixture to 60-100 ℃, wherein the reaction temperature of the reaction mixture and the concentrated phosphoric acid is 100-150 ℃, the reaction time is 8-16 h, and the mass concentration of the concentrated phosphoric acid is more than or equal to 80%.
6. The method according to claim 1, wherein in step (3):
the roasting temperature of the vanadium phosphorus oxide catalyst precursor is 420-440 ℃ and the roasting time is 10-24 hours.
7. The method according to claim 1, wherein in step (3):
the roasting atmosphere is nitrogen atmosphere, or mixed atmosphere of n-butane and air, or mixed atmosphere of n-butane, oxygen and nitrogen.
8. The method of claim 7, wherein in step (3):
before roasting, firstly tabletting and forming the vanadium phosphorus oxide catalyst precursor, grinding and screening to obtain precursor particles with the particle size of 10-50 meshes, and then placing the precursor particles into a fixed bed reactor, and activating at high temperature in situ in the roasting atmosphere to obtain the vanadium phosphorus oxide catalyst.
9. Use of a vanadium phosphorus oxide catalyst obtainable by a process according to any one of claims 1 to 8 for the selective oxidation of n-butane to maleic anhydride, wherein,
the reaction conditions for preparing maleic anhydride by the selective oxidation of n-butane are as follows: the reaction temperature is 400-550 ℃, the reaction pressure is 0.1-0.3 MPa, and the space velocity of the n-butane mixed gas is 1000h -1 ~2500 h -1 The concentration of the n-butane is 1.3-wt% -1.8-wt%.
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