CN112495374B - Method for preparing supported noble metal catalyst by adopting low-temperature plasma modified graphene and application - Google Patents
Method for preparing supported noble metal catalyst by adopting low-temperature plasma modified graphene and application Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical class [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 73
- 239000003054 catalyst Substances 0.000 title claims abstract description 44
- 238000000034 method Methods 0.000 title claims abstract description 25
- 229910000510 noble metal Inorganic materials 0.000 title claims abstract description 20
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 43
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000012279 sodium borohydride Substances 0.000 claims abstract description 10
- 229910000033 sodium borohydride Inorganic materials 0.000 claims abstract description 10
- 238000005984 hydrogenation reaction Methods 0.000 claims abstract description 9
- 238000002360 preparation method Methods 0.000 claims abstract description 9
- 230000009467 reduction Effects 0.000 claims abstract description 5
- 239000008367 deionised water Substances 0.000 claims description 17
- 229910021641 deionized water Inorganic materials 0.000 claims description 17
- 239000006185 dispersion Substances 0.000 claims description 14
- KJPRLNWUNMBNBZ-QPJJXVBHSA-N (E)-cinnamaldehyde Chemical compound O=C\C=C\C1=CC=CC=C1 KJPRLNWUNMBNBZ-QPJJXVBHSA-N 0.000 claims description 12
- 239000007864 aqueous solution Substances 0.000 claims description 12
- 229940117916 cinnamic aldehyde Drugs 0.000 claims description 12
- KJPRLNWUNMBNBZ-UHFFFAOYSA-N cinnamic aldehyde Natural products O=CC=CC1=CC=CC=C1 KJPRLNWUNMBNBZ-UHFFFAOYSA-N 0.000 claims description 12
- 238000001291 vacuum drying Methods 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 9
- 239000001301 oxygen Substances 0.000 claims description 9
- 229910052760 oxygen Inorganic materials 0.000 claims description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 8
- 238000009832 plasma treatment Methods 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 6
- 238000005406 washing Methods 0.000 claims description 6
- 238000005303 weighing Methods 0.000 claims description 6
- 239000002253 acid Substances 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 5
- 239000000243 solution Substances 0.000 claims description 5
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 claims description 2
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 claims description 2
- 238000000926 separation method Methods 0.000 claims description 2
- 238000000967 suction filtration Methods 0.000 claims description 2
- 239000002082 metal nanoparticle Substances 0.000 abstract description 8
- 238000009903 catalytic hydrogenation reaction Methods 0.000 abstract description 5
- 238000006555 catalytic reaction Methods 0.000 abstract description 4
- 230000004048 modification Effects 0.000 abstract description 4
- 238000012986 modification Methods 0.000 abstract description 4
- 230000000694 effects Effects 0.000 abstract description 2
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 abstract 1
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 238000006243 chemical reaction Methods 0.000 description 27
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 25
- 239000000463 material Substances 0.000 description 20
- 208000028659 discharge Diseases 0.000 description 18
- 229910052751 metal Inorganic materials 0.000 description 17
- 239000002184 metal Substances 0.000 description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 239000008346 aqueous phase Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 230000003197 catalytic effect Effects 0.000 description 8
- 239000012071 phase Substances 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 5
- 238000001914 filtration Methods 0.000 description 5
- 239000001257 hydrogen Substances 0.000 description 5
- 229910052739 hydrogen Inorganic materials 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- 238000000643 oven drying Methods 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 238000006722 reduction reaction Methods 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 238000009210 therapy by ultrasound Methods 0.000 description 4
- 150000001299 aldehydes Chemical class 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- 239000002105 nanoparticle Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000001179 sorption measurement Methods 0.000 description 3
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- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000002134 carbon nanofiber Substances 0.000 description 2
- 239000002041 carbon nanotube Substances 0.000 description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 description 2
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical class C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000002086 nanomaterial Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- WTEVQBCEXWBHNA-UHFFFAOYSA-N Citral Natural products CC(C)=CCCC(C)=CC=O WTEVQBCEXWBHNA-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- XOJVVFBFDXDTEG-UHFFFAOYSA-N Norphytane Natural products CC(C)CCCC(C)CCCC(C)CCCC(C)C XOJVVFBFDXDTEG-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000007036 catalytic synthesis reaction Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 229940043350 citral Drugs 0.000 description 1
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- 238000010586 diagram Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- WTEVQBCEXWBHNA-JXMROGBWSA-N geranial Chemical compound CC(C)=CCC\C(C)=C\C=O WTEVQBCEXWBHNA-JXMROGBWSA-N 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000005660 hydrophilic surface Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000004530 micro-emulsion Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
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- 239000012074 organic phase Substances 0.000 description 1
- 238000006053 organic reaction Methods 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000027756 respiratory electron transport chain Effects 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/42—Platinum
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
- B01J37/349—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of flames, plasmas or lasers
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/132—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group
- C07C29/136—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH
- C07C29/14—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of a —CHO group
- C07C29/141—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by reduction of an oxygen containing functional group of >C=O containing groups, e.g. —COOH of a —CHO group with hydrogen or hydrogen-containing gases
Abstract
The invention belongs to the technical field of catalysts, and particularly relates to a method for preparing a supported noble metal catalyst by adopting low-temperature plasma modified graphene and an application thereof, wherein O 2 is taken as a plasma gas source, the discharge power of O 2 is regulated under a certain vacuum degree, O 2 high-energy plasma and vacuum ultraviolet photons are generated, the graphene surface is uniformly bombarded in a short time, the pretreatment effect is achieved, and then the low-temperature plasma modified graphene supported noble metal catalyst is prepared by a sodium borohydride reduction method. The catalyst can be used for the selective hydrogenation reaction of water phase alpha, beta-unsaturated aldehyde. The dispersibility of graphene in water is improved through low-temperature plasma controllable modification, the dispersity of metal nano particles on the surface of the graphene is improved, and finally the aim of improving water phase catalytic hydrogenation is fulfilled. The preparation process of the catalyst is simple and convenient, environment-friendly, high in treatment speed and simple in operation, and provides scientific basis and important thought for constructing an economic, green and sustainable catalytic reaction system.
Description
Technical Field
The invention belongs to the technical field of catalysts, and particularly relates to a method for preparing a supported noble metal catalyst by adopting low-temperature plasma modified graphene and application thereof.
Background
In recent years, some novel support materials have been developed for selective hydrogenation catalysis of unsaturated aldehyde/ketone conjugated molecules (e.g., citral, cinnamaldehyde, etc.). Among them, carbon nanomaterials, including Carbon Nanofibers (CNF), carbon Nanotubes (CNT), graphene (graphene), and Graphene Oxide (GO), have received attention due to their unique electronic structures and mechanical properties. They have proven to be excellent supports for developing supported metal catalysts for selective catalytic hydrogenation reactions.
The surface chemistry of the supported catalyst has a great impact on the selective catalytic hydrogenation performance. The catalytic reaction rate is influenced by changing the dispersibility of the active center on the surface of the catalyst and the adsorption performance of the catalyst surface on the reaction substrate; and the product selectivity is affected by changing the adsorption pattern to the substrate molecule. Graphene, which is a novel carbon nanomaterial, has excellent surface chemical properties such as hydrophobicity and good electron transfer performance besides excellent characteristics such as large surface area, high mechanical strength, acid and alkali resistance, small mass transfer resistance and the like, and is favorable for adsorbing a weak polar substrate and improving the reaction rate. In addition, by changing its surface chemistry, its adsorption pattern to the substrate will also change, thus achieving different product selectivities. Therefore, the graphene supported catalyst shows good catalytic performance in selective hydrogenation reaction.
In the preparation process of the metal catalyst, the hydrophobic property of the graphene surface is unfavorable for the dispersion of the metal nano particles on the surface, so that the size of the supported particles is larger, and the catalytic activity is lower. To solve this problem, the preparation of the supported metal catalyst is usually carried out in a two-step process. Firstly, oxidizing a graphene material by using a strong oxidant (such as concentrated sulfuric acid and concentrated nitric acid) for introducing some hydrophilic functional groups (such as carboxyl and hydroxyl) on the surface of the graphene material, increasing anchoring sites of metal nano particles and improving the dispersibility of the metal nano particles on the surface of the material; and then further removing the redundant hydrophilic groups on the catalyst through chemical reduction or inert gas heat treatment, and recovering the hydrophobic and oleophilic surface of the catalyst for subsequent organic reaction. However, the treatment process has complicated operation, high energy consumption and large pollution.
Water has received increasing attention in recent years as a green solvent in catalytic and organic synthesis. The hydrophobic character of the graphene material surface also makes its dispersibility in the aqueous phase poor. How to perform proper surface treatment on graphene to improve the water dispersibility of the graphene becomes a key to be solved for realizing the efficient water-phase reaction. The method provides scientific basis and important thought for constructing an economic, green and sustainable catalytic reaction system.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a method for preparing a supported noble metal catalyst by modifying graphene by low-temperature plasma and using the supported noble metal catalyst in an aqueous phase for alpha, beta-unsaturated aldehyde selective hydrogenation reaction.
According to the invention, a small amount of oxygen-containing functional groups are introduced into the surface of graphene by an oxygen plasma modification technology, so that the surface hydrophilicity of the graphene is improved. Then preparing the supported noble metal catalyst by a sodium borohydride (NaBH 4) aqueous phase reduction method. Due to the fact that the graphene surface is subjected to partial hydrophilic treatment, on one hand, the dispersibility of graphene in water is improved, and the dispersibility of metal nano particles on the surface of the graphene is improved in the process of preparing the noble metal catalyst through aqueous phase reduction (shown in figure 2); on the other hand, the surface of the graphene material is changed from hydrophobicity to amphiphilicity (as shown in figure 3) after being treated, so that emulsion can be formed in an aqueous phase and an organic phase (cinnamaldehyde), and the catalytic hydrogenation activity of the aqueous phase is improved. This work creates a simple and green selective hydrogenation catalytic system, further expanding its application in related academic and industrial fields.
The invention prepares the aqueous phase alpha, beta-unsaturated aldehyde hydrogenation catalyst with high conversion rate and selectivity by utilizing a low-temperature plasma modification technology, and the preparation method comprises the following steps:
(1) And placing graphene powder with certain mass into a culture dish, and placing the culture dish into low-temperature plasma equipment, wherein the culture dish is made of glass or quartz and the like.
(2) And adjusting parameters of the equipment, and selecting certain discharge power, vacuum degree, discharge time and discharge atmosphere of the equipment.
Wherein, the discharge power is 100-180W, the vacuum degree of the equipment is 10-30 Pa, the discharge duration is 1-10 min, and the discharge atmosphere can be oxygen, hydrogen, nitrogen and other atmosphere.
(3) And (3) weighing the modified graphene obtained in the step (2), dispersing in deionized water, and fully and uniformly stirring to obtain modified graphene dispersion liquid.
Wherein the mass concentration of the modified graphene dispersion liquid is 0.04-0.3%.
(4) Adding a certain mass of noble metal chloride aqueous solution into the modified graphene dispersion liquid in the step (3), stirring for a certain time, and then dropwise adding a sufficient amount of sodium borohydride (NaBH 4) aqueous solution under vigorous stirring to reduce the mixture at room temperature;
Wherein the noble metal chloride comprises one or more of chloroplatinic acid, chloroauric acid, palladium chloride and ruthenium chloride, and the concentration of the added chloride aqueous solution is 5-15 mg/mL; the mass ratio of the noble metal chloride to the modified graphene is 0.5-7.5:10; the mass ratio of sodium borohydride (NaBH 4) to modified graphene is (3-15) (10-30).
(5) After reduction at room temperature, carrying out suction filtration separation, washing with deionized water, and drying at 60-80 ℃ for 10-20 hours to obtain a plasma modified graphene loaded metal platinum catalyst;
wherein the drying mode is vacuum drying, the vacuum drying temperature is 60 ℃, and the drying time is 12 hours.
The invention has the advantages that:
(1) The invention adopts low-temperature plasma technology to modify graphene, is used for introducing some hydrophilic functional groups (such as carboxyl and hydroxyl) on the surface of the graphene, increases the anchoring sites of metal nano particles, and improves the dispersibility of the metal nano particles on the surface of a material. The method is simple and convenient to operate, low in energy consumption and environment-friendly.
(2) The catalyst obtained by modifying the carrier graphene and then loading the metal can react in a water phase at high temperature, so that the efficient hydrogenation of cinnamaldehyde can be realized, and the high catalytic activity can be obtained. The catalyst shows excellent selectivity in hydrogenation reaction of cinnamaldehyde.
(3) The preparation method of the catalyst has simple steps and low cost, can be suitable for aqueous phase reaction, and has higher catalytic activity in high-temperature aqueous phase.
Drawings
FIG. 1 is an X-ray powder diffraction analysis chart (XRD) of a graphene-supported metal Pt catalyst modified by a low-temperature plasma technique obtained in example 1 of the present invention;
FIG. 2 is a Transmission Electron Microscope (TEM) image of the original graphene of comparative example 1 and the graphene-supported metal Pt catalyst modified by the low temperature plasma technique of example 1 of the present invention;
Fig. 3 is a dispersion diagram of the original graphene-supported Pt catalyst of comparative example 1 and the graphene-supported Pt catalyst modified by the low-temperature plasma technology obtained in example 1 of the present invention in a water and oil phase system;
Fig. 4 is a graph showing the optical contact angle measurement of the graphene-supported Pt catalyst modified by the low-temperature plasma technique obtained in example 1 of the present invention and the original graphene in comparative example 1;
FIG. 5 is a graph showing the dispersion of an emulsion of the oxygen plasma treated graphene-supported Pt catalyst obtained in example 1 in a cinnamaldehyde and water two-phase system;
FIG. 6 is a graph showing the catalytic hydrogenation performance of graphene-supported metal Pt treated with oxygen plasma obtained in comparative example 1 and example 1 of the present invention;
FIG. 7 is a graph showing catalytic performance of the catalyst of example 1 for 3 cycles.
Detailed Description
The invention is illustrated below in connection with specific examples, which are given solely for the purpose of illustration and are not intended to limit the scope of the invention.
Unless otherwise defined, terms (including technical and scientific terms) used herein should be interpreted to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Example 1
0.6G of graphene is weighed and placed in plasma treatment equipment, and low-temperature plasma discharge treatment is carried out under the conditions of 20Pa of vacuum degree, 160W of discharge power, 3min of discharge time and oxygen of discharge atmosphere. 0.2g of the modified graphene sample is weighed and dispersed in 200mL of deionized water, and then is fully stirred, and 2.65mL of H 2PtCl6·6H2 O aqueous solution with the concentration of 10mg/mL is added and stirred for 30min. 20mL of an aqueous sodium borohydride solution having a concentration of 4mg/mL was added dropwise to the above dispersion with stirring at a rotation speed of 1000 r/min. And after the reaction is finished, filtering and washing the obtained product by deionized water, and finally placing the product into a vacuum drying oven, and vacuum drying at 60 ℃ for 12 hours to obtain the dried graphene-loaded metal Pt material modified by low-temperature plasma.
As shown in FIG. 1, the XRD pattern of graphene-supported noble metal Pt modified by the low-temperature plasma technology obtained in the embodiment 1 of the invention is shown, and from the graph, the prepared material is matched with standard cards (JCPDS (joint p-S) No.26-1079 and JCPDS (joint p-S) No. 04-0802) of graphene and Pt, so that the phase of the sample is a graphene-supported noble metal Pt catalyst, and the successful loading of Pt nano particles is confirmed by the TEM pattern.
Comparative example 1 TEM of pristine graphene and plasma-treated graphene-supported Pt metal catalyst is shown in fig. 2. From the graph, the Pt nanoparticles are more uniformly loaded on the surface of the Pt nanoparticles after plasma treatment, and the dispersibility is remarkably improved.
Experiments such as dispersibility and contact angle prove that the hydrophilicity after plasma modification is better, and the carrier at normal temperature shows hydrophilic surface, which is beneficial to the dispersion of metal nano particles on the carrier in the catalyst preparation process and promotes the improvement of reaction rate.
As can be seen from fig. 5, the graphene-supported Pt catalyst treated by oxygen plasma forms a microemulsion in a cinnamaldehyde and water two-phase system, and the dispersion is relatively uniform.
And weighing 0.02g of the obtained graphene loaded metal Pt material modified by the low-temperature plasma, placing the material in a sample bottle, adding 1g of cinnamaldehyde and 19g of deionized water, and performing ultrasonic treatment for 30min. Then put into a reactor, replaced three times with nitrogen and hydrogen respectively, the reaction conditions are as follows: the reaction pressure is 3MPa, the reaction temperature is 80 ℃, the reaction time is 4 hours, the rotating speed is 500r/min, and the performance analysis of the conversion rate and the selectivity is carried out.
Example 2
The specific procedure of this example was as in example 1, and only the plasma discharge power was changed to 100W.
Example 3
The specific procedure of this example was as in example 1, and only the plasma discharge power was changed to 120W.
Example 4
In this comparative example, as in example 1, only the plasma discharge power was changed to 140W.
Example 5
The specific procedure of this comparative example was as in example 1, changing only the plasma discharge power to 180W.
Example 6
0.6G of graphene is weighed and placed in plasma treatment equipment, and low-temperature plasma discharge treatment is carried out under the conditions of 30Pa vacuum degree, 160W discharge power, 3min discharge time and oxygen discharge atmosphere. 0.2g of the modified graphene sample is weighed and dispersed in 200mL of deionized water, and then is fully stirred, and 2.65mL of H 2PtCl6·6H2 O aqueous solution with the concentration of 10mg/mL is added and stirred for 30min. 20mL of an aqueous sodium borohydride solution having a concentration of 4mg/mL was added dropwise to the above dispersion with stirring at a rotation speed of 1000 r/min. And after the reaction is finished, filtering and washing the obtained product by deionized water, and finally placing the product into a vacuum drying oven, and vacuum drying at 60 ℃ for 12 hours to obtain the dried graphene-loaded metal Pt material modified by low-temperature plasma.
And weighing 0.02g of the obtained graphene loaded metal Pt material modified by the low-temperature plasma, placing the material in a sample bottle, adding 1g of cinnamaldehyde and 19g of deionized water, and performing ultrasonic treatment for 30min. Then put into a reactor, replaced three times with nitrogen and hydrogen respectively, the reaction conditions are as follows: the reaction pressure is 3MPa, the reaction temperature is 80 ℃, the reaction time is 4 hours, the rotating speed is 500r/min, and the performance analysis of the conversion rate and the selectivity is carried out.
Example 7
The procedure of this example was as in example 6, except that the vacuum degree of the plasma treatment was changed to 10Pa.
Example 8
The specific procedure of this comparative example was as in example 6, with only the plasma treatment time being changed to 1min.
Example 9
The procedure of this example was as in example 6, with only the plasma treatment time being changed to 5min.
Example 10
The preparation method of the modified graphene is the same as that of example 1. 0.2g of the modified graphene sample is weighed and dispersed in 100mL of deionized water, and then is fully stirred, and 2.65mL of H 2PtCl6·6H2 O aqueous solution with the concentration of 10mg/mL is added and stirred for 30min. 20mL of an aqueous sodium borohydride solution having a concentration of 4mg/mL was added dropwise to the above dispersion with stirring at a rotation speed of 1000 r/min. And after the reaction is finished, filtering and washing the obtained product by deionized water, and finally placing the product into a vacuum drying oven, and vacuum drying at 60 ℃ for 12 hours to obtain the dried graphene-loaded metal Pt material modified by low-temperature plasma.
And weighing 0.02g of the obtained graphene loaded metal Pt material modified by the low-temperature plasma, placing the material in a sample bottle, adding 1g of cinnamaldehyde and 19g of deionized water, and performing ultrasonic treatment for 30min. Then put into a reactor, replaced three times with nitrogen and hydrogen respectively, the reaction conditions are as follows: the reaction pressure is 3MPa, the reaction temperature is 80 ℃, the reaction time is 4 hours, the rotating speed is 500r/min, and the performance analysis of the conversion rate and the selectivity is carried out.
Example 11
The procedure of this example was as in example 10, except that the modified graphene sample was dispersed in 300mL deionized water.
Example 12
The procedure of this example was as in example 10, except that the volume of the aqueous solution of H 2PtCl6·6H2 O added at a concentration of 10mg/mL was changed to 1.325mL.
Example 13
The procedure of this example was as in example 1, except that the volume of the aqueous solution of H 2PtCl6·6H2 O added at a concentration of 10mg/mL was changed to 5.3mL.
Example 14
The catalyst in example 1 was recovered by centrifugal filtration after the end of the first reaction and recycled 3 times, and the operation was the same as in example 1, and the experimental results are shown in table 1 and fig. 7.
The result of the circulation experiment shows that the catalytic performance of the catalyst is not greatly reduced after 3 times of circulation use, which indicates that the prepared catalyst has better stability.
Comparative example 1
0.2G of the original graphene sample is weighed, dispersed in 200mL of deionized water, fully stirred, added with 2.65mL of aqueous solution of H 2PtCl6·6H2 O with the concentration of 10mg/mL, and stirred for 30min. 20mL of an aqueous sodium borohydride solution having a concentration of 4mg/mL was added dropwise to the above dispersion with stirring at a rotation speed of 1000 r/min. And after the reaction is finished, filtering and washing the obtained product by deionized water, and finally placing the product into a vacuum drying oven, and vacuum drying at 60 ℃ for 12 hours to obtain the dried graphene-loaded metal Pt material modified by low-temperature plasma.
And weighing 0.02g of the obtained graphene loaded metal Pt material modified by the low-temperature plasma, placing the material in a sample bottle, adding 1g of cinnamaldehyde and 19g of deionized water, and performing ultrasonic treatment for 30min. Then put into a reactor, replaced three times with nitrogen and hydrogen respectively, the reaction conditions are as follows: the reaction pressure is 3MPa, the reaction temperature is 80 ℃, the reaction time is 4 hours, the rotating speed is 500r/min, and the performance analysis of the conversion rate and the selectivity is carried out.
TABLE 1
TABLE 2
Claims (2)
1. A preparation method of a plasma modified graphene supported noble metal catalyst for selectively hydrogenating cinnamaldehyde in a high-temperature water phase is characterized by comprising the following steps of: the preparation method comprises the following specific steps:
(1) Placing graphene in a culture dish and placing the graphene in low-temperature plasma treatment equipment;
(2) Adjusting parameters of equipment, and performing plasma treatment on graphene in an oxygen atmosphere to obtain modified graphene;
The parameters of the device are: the discharge power is 140-180W, the vacuum degree is 20-30 Pa, and the discharge duration is 1-10 min;
(3) Weighing the modified graphene obtained in the step (2), dispersing in deionized water, and fully and uniformly stirring to obtain a modified graphene dispersion liquid with the mass concentration of 0.04-0.3%;
(4) Adding noble metal chloride aqueous solution into the modified graphene dispersion liquid in the step (3), uniformly stirring, and then dropwise adding sodium borohydride aqueous solution with the concentration of 3.0-5.0 mg/mL under vigorous stirring to reduce the solution at room temperature;
The noble metal chloride is one or more of chloroplatinic acid, chloroauric acid, palladium chloride and ruthenium chloride; the concentration of the added chloride aqueous solution is 5-15 mg/mL; the mass ratio of the noble metal chloride to the modified graphene is 1.325-7.5:10;
the mass ratio of the sodium borohydride to the modified graphene is 3-15:10-30;
(5) And (3) after reduction at room temperature, carrying out suction filtration separation, washing with deionized water and drying to obtain the plasma modified graphene supported noble metal catalyst.
2. The method for preparing the plasma modified graphene supported noble metal catalyst for selective hydrogenation of cinnamaldehyde in a high-temperature and water phase according to claim 1, wherein the drying in the step (5) is vacuum drying, the vacuum drying temperature is 60-80 ℃, and the drying time is 10-20 h.
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