CN114524450B - Preparation method of nano cerium oxide ultraviolet absorbent - Google Patents
Preparation method of nano cerium oxide ultraviolet absorbent Download PDFInfo
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- 229910000420 cerium oxide Inorganic materials 0.000 title claims abstract description 28
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 title claims abstract description 26
- 230000002745 absorbent Effects 0.000 title claims abstract description 17
- 239000002250 absorbent Substances 0.000 title claims abstract description 17
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 238000006243 chemical reaction Methods 0.000 claims abstract description 50
- 238000001556 precipitation Methods 0.000 claims abstract description 48
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 33
- 239000004202 carbamide Substances 0.000 claims abstract description 33
- 239000002994 raw material Substances 0.000 claims abstract description 15
- 150000000703 Cerium Chemical class 0.000 claims abstract description 8
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 41
- 239000000463 material Substances 0.000 claims description 38
- 238000007254 oxidation reaction Methods 0.000 claims description 35
- 230000003647 oxidation Effects 0.000 claims description 19
- -1 cerium ions Chemical class 0.000 claims description 18
- 229910052684 Cerium Inorganic materials 0.000 claims description 17
- 230000032683 aging Effects 0.000 claims description 14
- 239000011259 mixed solution Substances 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 11
- 238000005086 pumping Methods 0.000 claims description 10
- 238000001816 cooling Methods 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 5
- 238000001914 filtration Methods 0.000 claims description 5
- 238000005406 washing Methods 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 abstract description 9
- 239000000126 substance Substances 0.000 abstract description 6
- 239000007788 liquid Substances 0.000 abstract description 5
- 238000006460 hydrolysis reaction Methods 0.000 abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 abstract description 4
- 238000010924 continuous production Methods 0.000 abstract description 3
- 230000008021 deposition Effects 0.000 abstract description 3
- 238000010438 heat treatment Methods 0.000 abstract description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 abstract description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 abstract description 2
- 230000007062 hydrolysis Effects 0.000 abstract description 2
- 239000002244 precipitate Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 9
- 229910000422 cerium(IV) oxide Inorganic materials 0.000 description 7
- 239000000843 powder Substances 0.000 description 7
- 239000011324 bead Substances 0.000 description 6
- CETPSERCERDGAM-UHFFFAOYSA-N ceric oxide Chemical compound O=[Ce]=O CETPSERCERDGAM-UHFFFAOYSA-N 0.000 description 6
- VGBWDOLBWVJTRZ-UHFFFAOYSA-K cerium(3+);triacetate Chemical compound [Ce+3].CC([O-])=O.CC([O-])=O.CC([O-])=O VGBWDOLBWVJTRZ-UHFFFAOYSA-K 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 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
- 238000004519 manufacturing process Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 239000005022 packaging material Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 230000003321 amplification Effects 0.000 description 2
- RWCCWEUUXYIKHB-UHFFFAOYSA-N benzophenone Chemical compound C=1C=CC=CC=1C(=O)C1=CC=CC=C1 RWCCWEUUXYIKHB-UHFFFAOYSA-N 0.000 description 2
- 239000012965 benzophenone Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000012847 fine chemical Substances 0.000 description 2
- 230000004907 flux Effects 0.000 description 2
- 238000003199 nucleic acid amplification method Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 230000035484 reaction time Effects 0.000 description 2
- 239000006097 ultraviolet radiation absorber Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 238000003917 TEM image Methods 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 238000000635 electron micrograph Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- VYKXQOYUCMREIS-UHFFFAOYSA-N methylhexahydrophthalic anhydride Chemical compound C1CCCC2C(=O)OC(=O)C21C VYKXQOYUCMREIS-UHFFFAOYSA-N 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 239000012716 precipitator Substances 0.000 description 1
- 238000011165 process development Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000011550 stock solution Substances 0.000 description 1
- JRMUNVKIHCOMHV-UHFFFAOYSA-M tetrabutylammonium bromide Chemical compound [Br-].CCCC[N+](CCCC)(CCCC)CCCC JRMUNVKIHCOMHV-UHFFFAOYSA-M 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000004383 yellowing Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/10—Preparation or treatment, e.g. separation or purification
-
- 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
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0006—Controlling or regulating processes
-
- 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
- B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
- B01J19/0093—Microreactors, e.g. miniaturised or microfabricated reactors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
- C01F17/224—Oxides or hydroxides of lanthanides
- C01F17/235—Cerium oxides or hydroxides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Nanotechnology (AREA)
- Inorganic Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Geology (AREA)
- Materials Engineering (AREA)
- Composite Materials (AREA)
- Analytical Chemistry (AREA)
- Manufacturing & Machinery (AREA)
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Abstract
The invention discloses a preparation method of a nano cerium oxide ultraviolet absorbent, which is prepared by taking cerium salt and urea as raw materials through a microchannel reactor; the pressure of the system in the micro-channel reactor is controlled to be 10-15 atm in the preparation process. The invention takes urea as precipitant, generates NH by hydrolysis reaction of urea in aqueous solution under heating 3 And CO 2 Cerium salt and ammonia water react to generate hydroxide precipitate; meanwhile, gas generated by urea hydrolysis forms bubbles, and impact and disturbance are formed on hydroxide precipitation generated by reaction, so that continuous driving force on insoluble substances is maintained along with liquid flow of a reaction system, and blockage of a reactor pipeline and deposition of insoluble substances are avoided; on the other hand, by controlling the pressure of the reaction system, intermittent gushing of liquid flow caused by rapid increase of the volume of the reaction system due to generation of bubbles is avoided, and stable and continuous production is ensured.
Description
Technical Field
The invention belongs to the field of anti-ultraviolet additives, and particularly relates to a preparation method of nano cerium dioxide by adopting a microchannel reactor.
Background
Under the action of ultraviolet rays, plastics and other high polymer materials can generate oxidation reaction, so that the polymers are degraded, and the problems of yellowing, reduced mechanical properties and the like occur. At present, a benzophenone organic ultraviolet absorber is commonly adopted as an LED packaging material (subdivided into an epoxy resin system and an organic silicon resin system), and the disadvantage of the benzophenone organic ultraviolet absorber is poor thermal stability and reduced ultraviolet shielding performance after long-time use. Nano cerium dioxide due to its internal O 2p In the state of Ce 4f The charge transfer between states can be strongly absorbed by ultraviolet light with the wavelength less than 400nm, has good low-toxicity heat stability and wide prospect in the field of ultraviolet shielding. At present, although the application of the nano cerium oxide ultraviolet absorbent in the field of different fine chemicals is reported, most of the preparation experiments are complex in process, in the research stage, the commercial application prospect of the amplified production is insufficient.
The microchannel reactor has the advantages of stable process, good product batch stability and no amplification effect as an advanced reactor device, so that the microchannel reactor has rapid development in the process development and amplification production of medicines and fine chemicals in recent years.
However, in the process of preparing nano cerium oxide by adopting cerium salt precipitation reaction, solid insoluble substances are generated, and pipeline blockage problems can occur when the nano cerium oxide is performed in a micro-channel reactor, so that process stability and product batch stability are affected.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provides a preparation method of nano cerium oxide which has simple and stable process and is easy to realize large-scale production.
In order to achieve the above purpose, the invention provides a preparation method of a nano cerium oxide ultraviolet absorbent, which is prepared by taking cerium salt and urea as raw materials through a micro-channel reactor; the pressure of the system in the micro-channel reactor is controlled to be 10-15 atm in the preparation process.
The invention takes urea as precipitant, generates NH by hydrolysis reaction of urea in aqueous solution under heating 3 And CO 2 Cerium salt and ammonia water react to generate hydroxide precipitate; meanwhile, gas generated by urea hydrolysis forms bubbles, and impact and disturbance are formed on hydroxide precipitation generated by reaction, so that continuous driving force on insoluble substances is maintained along with liquid flow of a reaction system, and blockage of a reactor pipeline and deposition of insoluble substances are avoided; on the other hand, by controlling the pressure of the reaction system, intermittent gushing of liquid flow caused by rapid increase of the volume of the reaction system due to generation of bubbles is avoided, and stable and continuous production is ensured.
Specifically, the preparation method of the nano cerium oxide ultraviolet absorbent comprises the following steps:
(1) Precipitation: pumping the mixed solution of cerium salt and urea into a micro-channel reactor at a constant flow rate to perform precipitation reaction; the concentration of cerium ions in the mixed solution is 0.1-0.2 mol/L, and the molar ratio of urea to cerium ions is 1.5-2.0; the reaction temperature in the precipitation stage is 80-90 ℃ and the residence time is 15-30 s;
(2) Oxidation stage: continuously flowing the mixed material subjected to the precipitation reaction in the step (1) in a microchannel reactor, cooling to 10-25 ℃ through heat exchange, and pumping hydrogen peroxide solution into the mixed material at a constant flow rate for oxidation reaction; the concentration of the pumped hydrogen peroxide solution is 0.2 to 0.4mol/L, and H is controlled 2 O 2 The molar ratio of the cerium ions to the cerium ions is 0.5 to 0.8; the reaction temperature in the oxidation stage is 10-25 ℃, and the residence time is 8-15 s;
(3) And (5) aging and roasting: and aging, filtering, washing, drying and roasting the materials obtained by the reaction in the microchannel reactor to obtain the nano cerium oxide ultraviolet absorbent.
The invention reasonably regulates and controls the reaction parameters of the microchannel reactor, further shortens the reaction time, improves the production efficiency and ensures the stable quality of the product.
In some examples, as a preferable mode, the concentration of cerium ions in the mixed solution of the step (1) is 0.15mol/L, and the molar ratio of urea to cerium ions is 1.9; the reaction temperature in the precipitation stage is 85 ℃, and the residence time is 24s; the concentration of the hydrogen peroxide solution pumped in the step (2) is 0.2mol/L, and H is controlled 2 O 2 The molar ratio of cerium ions is 0.6; the reaction temperature in the oxidation stage was 20℃and the residence time was 11s.
In some embodiments, the specific process of aging and roasting in the step (3) is preferably as follows: aging the materials obtained by the reaction of the microchannel reactor for 6 hours, filtering and washing, drying at 110 ℃, and roasting at 300 ℃ for 2 hours to obtain the nano cerium oxide ultraviolet absorbent.
Compared with the prior art, the invention has the following advantages:
the invention adopts the micro-channel reactor to control the reaction, realizes continuous production, has stable product quality, shortens the reaction time, improves the production efficiency and reduces the cost.
The invention adopts urea as a precipitator, and bubbles generated after thermal decomposition form impact and disturbance on a material system, so that the blockage of a reactor pipeline and the deposition of insoluble substances at a pipeline joint are avoided, and the process stability is improved.
Drawings
FIG. 1 is a flow chart of the preparation of the nano-cerium oxide ultraviolet absorbent of the present invention;
FIG. 2 is a diagram of an LED lamp bead obtained by sample preparation according to various embodiments of the present invention after an ultraviolet aging test;
in fig. 2, the lamp beads prepared in reference example, examples 1 to 5, comparative example 1 and comparative example 3 in table 1 of the specific embodiment are shown in order from left to right;
FIG. 3 is a TEM image of the sample obtained in example 1 of the present invention;
FIG. 4 is an XRD spectrum of a sample obtained in example 1 of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples.
The smallest diameter of the microchannel reactor channels used in the examples below was 1mm.
Example 1
As shown in fig. 1, the preparation method of the nano cerium oxide ultraviolet absorbent of the invention is as follows:
a precipitation step: cerium acetate (Ce) 3+ A concentration of 0.15 mol/L) and urea (0.285 mol/L)Stock solution (molar ratio of urea to cerium ions n) Urea /n Ce3+ =1.9) was pumped into the microchannel reactor at a constant flow rate of 60ml/min for precipitation reactions. The precipitation reaction stage temperature was 85℃and the residence time (precipitation step reactor volume/flow rate of mixed solution) was 24s.
An oxidation step: continuously flowing the material after precipitation reaction in a microchannel reactor, cooling to 20 ℃ through heat exchange, pumping 0.2mol/L hydrogen peroxide aqueous solution into the material at a constant flow rate of 27ml/min for oxidation reaction, and controlling H 2 O 2 And Ce (Ce) 3+ Molar ratio n of (2) H2O2 /n Ce3+ =0.6. The temperature of the oxidation reaction stage is 20 ℃, and the residence time (volume of the oxidation step reactor/total flow rate of the mixed raw material solution and hydrogen peroxide) is 11s.
The materials continuously flow in the whole microchannel reactor, and the pressure of the system is controlled to be 14atm by adopting a back pressure valve at the tail. Finally, the obtained material is aged for 6 hours, filtered, washed, dried at 110 ℃, and roasted for 2 hours at 300 ℃ to obtain cerium oxide sample powder.
From the electron micrograph (shown in FIG. 3) of the obtained ceria sample, it can be seen that the sample has a uniform particle size, and the particle size is less than 10nm. The apparent broadening of the XRD patterns (as shown in fig. 4) further demonstrates that the resulting ceria samples of the invention are nanoscale materials.
Example 2
A precipitation step: cerium nitrate (Ce) 3+ Mixed raw material solution (n) of urea (0.18 mol/L) and 0.1mol/L Urea /n Ce3+ =1.8) was pumped into the microchannel reactor at a constant flow rate of 50ml/min for precipitation reactions. The precipitation reaction stage temperature was 80℃and the residence time (precipitation step reactor volume/flow rate of mixed solution) was 29s.
An oxidation step: continuously flowing the material after precipitation reaction in a microchannel reactor, cooling to 12 ℃ through heat exchange, pumping 0.2mol/L hydrogen peroxide aqueous solution into the material at a flow rate of 15ml/min for oxidation reaction, and controlling H 2 O 2 And Ce (Ce) 3+ Molar ratio n of (2) H2O2 /n Ce3+ =0.6. The temperature of the oxidation reaction stage is 12 ℃, and the residence time (oxidation step reactor volume/mixed raw material dissolutionTotal flow rate of liquid and hydrogen peroxide) for 15s.
The materials continuously flow in the whole microchannel reactor, and the pressure of the system is controlled to be 13atm by adopting a back pressure valve at the tail. Finally, the obtained material is aged for 6 hours, filtered, washed, dried at 110 ℃ and roasted for 2 hours at 300 ℃ to obtain nano cerium oxide powder.
Example 3
A precipitation step: cerium nitrate (Ce) 3+ Mixed raw material solution (n) of urea (0.38 mol/L) and 0.2mol/L Urea /n Ce3+ =1.9) was pumped into the microchannel reactor at a constant flow rate of 85ml/min for precipitation reactions. The precipitation reaction stage temperature was 90℃and the residence time (precipitation step reactor volume/flow rate of the mixed solution) was 17s.
An oxidation step: continuously flowing the material after precipitation reaction in a microchannel reactor, cooling to 17 ℃ through heat exchange, pumping 0.3mol/L hydrogen peroxide aqueous solution into the material at a flow rate of 34ml/min for oxidation reaction, and controlling H 2 O 2 And Ce (Ce) 3+ Molar ratio n of (2) H2O2 /n Ce3+ =0.6. The temperature of the oxidation reaction stage is 17 ℃, and the residence time (volume of the oxidation step reactor/total flow rate of the mixed raw material solution and hydrogen peroxide) is 8s.
The materials continuously flow in the whole microchannel reactor, and the pressure of the system is controlled to be 14atm by adopting a back pressure valve at the tail. Finally, the obtained material is aged for 6 hours, filtered, washed, dried at 110 ℃ and roasted for 2 hours at 300 ℃ to obtain nano cerium oxide powder.
Example 4
A precipitation step: cerium acetate (Ce) 3+ Mixed raw material solution (n) of urea (0.22 mol/L) and 0.13mol/L Urea /n Ce3+ =1.7) was pumped into the microchannel reactor at a constant flow rate of 65ml/min for precipitation reactions. The precipitation reaction stage temperature was 82℃and the residence time (precipitation step reactor volume/flow rate of the mixed solution) was 22s.
An oxidation step: continuously flowing the material after precipitation reaction in a microchannel reactor, cooling to 15 ℃ through heat exchange, pumping 0.35mol/L hydrogen peroxide aqueous solution into the material at a flow rate of 16.9ml/min for oxidation reaction, and controlling H 2 O 2 And Ce (Ce) 3+ Molar ratio n of (2) H2O2 /n Ce3+ =0.7. The temperature of the oxidation reaction stage is 15 ℃, and the residence time (volume of the oxidation step reactor/total flow rate of the mixed raw material solution and hydrogen peroxide) is 12s.
The materials continuously flow in the whole microchannel reactor, and the pressure of the system is controlled to be 12atm by adopting a back pressure valve at the tail. Finally, the obtained material is aged for 6 hours, filtered, washed, dried at 110 ℃ and roasted for 2 hours at 300 ℃ to obtain nano cerium oxide powder.
Example 5
A precipitation step: cerium acetate (Ce) 3+ Mixed raw material solution (n) of urea (0.27 mol/L) and 0.17mol/L Urea /n Ce3+ =1.6) was pumped into the microchannel reactor at a constant flow rate of 70ml/min for precipitation reactions. The precipitation reaction stage temperature was 87℃and the residence time (precipitation step reactor volume/flow rate of the mixed solution) was 21s.
An oxidation step: continuously flowing the material after precipitation reaction in a microchannel reactor, cooling to 23 ℃ through heat exchange, pumping 0.4mol/L hydrogen peroxide aqueous solution into the material at a flow rate of 20.8ml/min for oxidation reaction, and controlling H 2 O 2 And Ce (Ce) 3 + Molar ratio n of (2) H2O2 /n Ce3+ =0.7. The temperature of the oxidation reaction stage is 23 ℃, and the residence time (volume of the oxidation step reactor/total flow rate of the mixed raw material solution and hydrogen peroxide) is 11s.
The materials continuously flow in the whole microchannel reactor, and the pressure of the system is controlled to be 11atm by adopting a back pressure valve at the tail. Finally, the obtained material is aged for 6 hours, filtered, washed, dried at 110 ℃ and roasted for 2 hours at 300 ℃ to obtain nano cerium oxide powder.
Comparative example 1
A precipitation step: cerium acetate (Ce) 3+ Mixed raw material solution (molar ratio of urea to cerium ion n) of 0.15mol/L and 0.18mol/L Urea /n Ce3+ =1.2) was pumped into the microchannel reactor at a constant flow rate of 50ml/min for precipitation reactions. The precipitation reaction stage temperature was 75℃and the residence time (precipitation step reactor volume/flow rate of the mixed solution) was 10s.
An oxidation step: after precipitation reactionContinuously flowing the materials in a microchannel reactor, cooling to 5 ℃ through heat exchange, pumping 0.25mol/L hydrogen peroxide aqueous solution into the materials at a flow rate of 18ml/min for oxidation reaction, and controlling H 2 O 2 And Ce (Ce) 3+ Molar ratio n of (2) H2O2 /n Ce3+ =0.6. The temperature of the oxidation reaction stage is 5 ℃, and the residence time (volume of the oxidation step reactor/total flow rate of the mixed raw material solution and hydrogen peroxide) is 14s.
The materials continuously flow in the whole microchannel reactor, and the pressure of the system is controlled to be 14atm by adopting a back pressure valve at the tail. Finally, the obtained material is aged for 6 hours, filtered, washed, dried at 110 ℃ and roasted for 2 hours at 300 ℃ to obtain nano cerium oxide powder.
Comparative example 2
A precipitation step: cerium acetate (Ce) 3+ Mixed raw material solution (molar ratio of urea to cerium ion n) of 0.15mol/L and 0.285mol/L Urea /n Ce3+ =1.9) was pumped into the microchannel reactor at a constant flow rate of 60ml/min for precipitation reaction at a stage temperature of 85 ℃.
An oxidation step: the temperature of the material is reduced to 20 ℃ through heat exchange, 0.2mol/L hydrogen peroxide aqueous solution is pumped into the material at a constant flow rate of 27ml/min for oxidation reaction, and H is controlled 2 O 2 And Ce (Ce) 3+ Molar ratio n of (2) H2O2 /n Ce3+ ＝0.6。
Before the experiment was started, the reaction system pressure was controlled to 9atm using a back pressure valve. In the experimental process, under the pressure condition, the mixed material has obvious gushing in the reaction device, the pressure of the device fluctuates, and the operation cannot be stably maintained.
Comparative example 3: the reaction vessel is a flask
100ml of cerium acetate (Ce 3+ Heating the mixed solution of urea and urea (2 mol/L) with water bath to 85 ℃, stirring for precipitation reaction for 3h, cooling to 20 ℃, and adding 45ml (n) of 0.2mol hydrogen peroxide solution H2O2 /n Ce3+ =0.6), stirring for 30min, aging the finally obtained material for 6h, filtering, washing, drying at 110 ℃, and roasting at 300 ℃ for 2h to obtain nano cerium oxide powder.
Effect examples
The samples obtained in the above examples were used to prepare LED beads according to the following methods:
100g of E51 epoxy resin, 100g of methyl hexahydrophthalic anhydride, 1.4g of tetrabutylammonium bromide and 1g of nano cerium dioxide sample, uniformly stirring at 70 ℃ for 30min, vacuum defoaming for 20min, and packaging to obtain the nano cerium dioxideThe LED lamp beads (cured at 130 ℃ for 1h and 135 ℃ for 5 h) are subjected to ultraviolet aging test (standard GB/T16422.3, wavelength 280-315 nm, 0.68W/m) 2 60 ℃,1000 h), remote 626 lumen tester (test conditions 3.5v,20 ma). After the ultraviolet irradiation aging test, the pearlescent flux test data of the LED lamp are shown in table 1, and the physical diagram of the LED lamp beads is shown in fig. 2 (the reference example, the examples 1-5, the comparative example 1 and the comparative example 3 in table 1 are sequentially from left to right).
The nano cerium dioxide obtained by the technical scheme of the invention can be applied to LED packaging materials, can still keep higher light transmittance after ultraviolet irradiation, and has obviously better ultraviolet irradiation aging resistance than a sample of a conventional precipitation method (comparative example 3).
When the micro-channel reactor is adopted for preparation, when the temperature in the precipitation reaction stage is reduced to 75 ℃, the ultraviolet radiation aging resistance of the LED packaging material prepared from the obtained nano cerium oxide is obviously reduced (comparative example 1).
TABLE 1 LED Lamp bead ultraviolet irradiation front and rear luminous flux test Using ultraviolet absorbers of various examples
Claims (3)
1. The preparation method of the nano cerium oxide ultraviolet absorbent is characterized in that the nano cerium oxide ultraviolet absorbent is prepared by taking cerium salt and urea as raw materials through a microchannel reactor; controlling the system pressure in the micro-channel reactor to be 10-15 atm in the preparation process;
the preparation method of the nano cerium oxide ultraviolet absorbent comprises the following steps:
(1) Precipitation: pumping the mixed solution of cerium salt and urea into a micro-channel reactor at a constant flow rate to perform precipitation reaction; the concentration of cerium ions in the mixed solution is 0.1-0.2 mol/L, and the molar ratio of urea to cerium ions is 1.5-2.0; the reaction temperature in the precipitation stage is 80-90 ℃ and the residence time is 15-30 s;
(2) Oxidation stage: continuously flowing the mixed material subjected to the precipitation reaction in the step (1) in a microchannel reactor, cooling to 10-25 ℃ through heat exchange, and pumping hydrogen peroxide solution into the mixed material at a constant flow rate for oxidation reaction; the concentration of the pumped hydrogen peroxide solution is 0.2 to 0.4mol/L, and H is controlled 2 O 2 The molar ratio of the cerium ions to the cerium ions is 0.5 to 0.8; the reaction temperature in the oxidation stage is 10-25 ℃, and the residence time is 8-15 s;
(3) And (5) aging and roasting: and aging, filtering, washing, drying and roasting the materials obtained by the reaction in the microchannel reactor to obtain the nano cerium oxide ultraviolet absorbent.
2. The method for preparing the nano-cerium oxide ultraviolet absorbent according to claim 1, wherein the concentration of cerium ions in the mixed solution in the step (1) is 0.15mol/L, and the molar ratio of urea to cerium ions is 1.9; the reaction temperature in the precipitation stage is 85 ℃, and the residence time is 24s; the concentration of the hydrogen peroxide solution pumped in the step (2) is 0.2mol/L, and H is controlled 2 O 2 The molar ratio of cerium ions is 0.6; the reaction temperature in the oxidation stage was 20℃and the residence time was 11s.
3. The method for preparing the nano cerium oxide ultraviolet absorbent according to claim 1, wherein the specific process of aging and roasting in the step (3) is as follows: aging the materials obtained by the reaction of the microchannel reactor for 6 hours, filtering and washing, drying at 110 ℃, and roasting at 300 ℃ for 2 hours to obtain the nano cerium oxide ultraviolet absorbent.
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