CN1269599C - Prepn of nano noble metal particle easily to separate and reuse - Google Patents
Prepn of nano noble metal particle easily to separate and reuse Download PDFInfo
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- CN1269599C CN1269599C CN 03119843 CN03119843A CN1269599C CN 1269599 C CN1269599 C CN 1269599C CN 03119843 CN03119843 CN 03119843 CN 03119843 A CN03119843 A CN 03119843A CN 1269599 C CN1269599 C CN 1269599C
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Abstract
The present invention relates to a preparation method of nanometer noble metal particles, which is convenient for separation and recycling. Alcohol is added to a water phase as reducing agents, and polyvinyl alcohol or polyacrylamide is used as stabilizing agents, wherein the weight percentage of the water phase, the reducing agents and the stabilizing agents is 100: (5 to 45): 0, a reaction solution is stirred for 10 to 120 minutes at room temperature or when heated and is centrifugally separated at room temperature, and precipitates are dried to obtain nanometer noble metal. The reducing agents are monohydric alcohol or polyalcohol whose carbon chains is shorter than 5, the average molecular weight of the polyvinyl alcohol is from 5000 to 100000, and the average molecular weight of the polyacrylamide is more than 500000.
Description
Technical field
The present invention relates to a kind of preparation method of the easy easily separated and noble metal nano particles that reclaims.
Technical background
Noble metal catalyst uses in chemical engineering industry and scientific research extensively.Traditional catalyst is for the decentralization that improves noble metal and strengthen the catalysis of noble metal and noble metal is carried on inorganic material surface such as SiO
2, Al
2O
3And various material with carbon elements, and the report that loads on micropore and the mesopore molecular sieve is more arranged recently.This no doubt also has the theory of considering product and catalyst separation and catalyst recovery, but the recovery of noble metal thereafter (because of noble metal content in catalyst lower) become a stubborn problem.Though the nano-noble metal catalyst research more and more (Chem.Lett., 1974,645 that have stabilizing agent to exist in recent years; Chem.Lett., 1976,1197; H.Hirai, J.Macromol.Sci.-Chem., 1979, A 13 (5), and 633; T.Teranishi, M.Hosoe, and M.Miyake, Adv.Mater., 1997,9 (1), 65; J.Alvarez, J.Liu, E.Roman and A.E.Kaifer, Chem.Commun., 2000,1151; C-W Chen and M.Akashi, Langmuir, 1997,13,6465; A.B.R.Mayer, J.E.Mark, ColloidPoly.Sci., 1997,275,333), but the separation of nano-noble metal catalyst and loss are insoluble problems always.Took into account catalyst and separate with product and both taken into account Preparation of catalysts, the work that the catalyst noble metal reclaims does not appear in the newspapers as yet.
Summary of the invention
The objective of the invention is to use the stabilizing agent of easily removing to stablize nano metal platinum, make the function of stabilizing agent performance carrier again, be convenient to catalytic reaction and finish separating of afterproduct and catalyst, and the recycling use that when catalyst need reclaim, makes things convenient for metal platinum.
Have now found that, medium or ultra high molecular weight polyethylene is pure (PVA) and the polyacrylamide of HMW (PAA) partial hydrolysate can both be at solid-state down stabilized nanoscale noble metal.The noble metal particle diameter of in-situ reducing preparation is less than 5nm when the aforementioned stable agent is scattered in the noble metal reduction system, and significant change does not take place the noble metal particle diameter when solid-state when being transformed into, thereby can effectively bring into play the effect of noble metal catalyst; Catalyst has certain dilation but does not reduce activity of such catalysts in suitable solvent simultaneously.The former is neutral solid network inclusion noble metal catalyst, and the latter is poly-polyion type solid network inclusion noble metal catalyst.
According to the present invention, with the chloroplatinic acid is the platinum source, adding alcohols at aqueous phase is reducing agent, polyvinyl alcohol or polyacrylamide are stabilizing agent, wherein, water: reducing agent: the percentage by weight of stabilizing agent=100: 5-45: 0.1-10 (percentage by weight), the chloroplatinic acid addition is the 10-20mg/100ml water; Stirring reaction liquid 10-120 minute, centrifugation reactant liquor under the room temperature, dry sediment gets nano metal platinum.
According to the present invention, the reducing agent of employing is a carbon chain lengths less than 5 monohydric alcohol or polyalcohol.
According to the present invention, the mean molecule quantity of the polyvinyl alcohol of employing is 5000-100000.
According to the present invention, the polyacrylamide mean molecule quantity of employing is more than 500000.
According to the present invention, stirring is to carry out between room temperature to 100 ℃.
According to the present invention, the nano-noble metal of employing is Pd, Pt, Ir or Rh nano particle.
According to the present invention, the polyacrylamide of employing is a stabilizing agent when preparing metal platinum nano-particle, also adds the pH=1.0-4.0 that 0.05-0.2M hydrochloric acid makes reactant liquor, stirs the back and transfers to pH=3-5 with acetate.
According to the present invention, the polyacrylamide of employing is a stabilizing agent when preparing metal platinum nano-particle, and the sodium hydrate aqueous solution that also adds 0.05-0.2M makes the pH=8.0-10.0 of reactant liquor, and reaction finishes the back and transfers to pH=3-5 with acetate.
At aqueous phase, be that reducing agent, PVA are that stabilizing agent or the noble metal, especially the nano metal platinum that obtain for the precursor stabilizing agent with PAA can stable existences and can further not reunite with the alcohols.The precious metals pt colloid that with PVA is the stabilizing agent preparation in liquid phase concentrates through the heating decompression, and solidifies the metal Pt that obtains after 3 hours still remain on below the 5nm the intrinsic catalytic activity of tool in 100-130 ℃ of baking oven.This solid can absorb the water of 8 times of own wts and realize limited expansion in water, but does not have considerable expansion in other polarity or non-polar solven.And be stabiliser precursor with PAA, with the alcohols reducing agent at aqueous phase, hydrochloric acid or NaOH are hydrolyst, reach the purpose of reducing metal and in-situ preparing nano-noble metal simultaneously; The nano noble metal particles for preparing in this liquid-phase system under higher temperature is dispersed into colloidal state, after being cooled to room temperature, stabilizing agent carries noble metal sedimentation together, reach the effect of separate precious metal particle, and, this colloid further is hardened to solid in the presence of ethanol etc., the solid that can grind to form certain particle size after the drying is made catalyst and used.
Agents useful for same of the present invention is easy to get, and simple operating conditions is convenient to the mass preparation noble metal catalyst.
Dispersion by the Pickering agent is solidification process again, and the precious metal colloids such as platinum of in-situ reducing are stable at through in the stabilizing agent network that solidifies again, makes noble metal be not easy to reunite, and is convenient to the recovery of product and catalyst separation and noble metal catalyst.
Description of drawings
Fig. 1 is a PVA stabilized nano precious metals pt solid catalyst transmission electron microscope picture;
Fig. 2 is a PVA stabilized nano precious metals pt solid catalyst infrared spectrogram;
Fig. 3 is a polyacrylamide partial hydrolysate stabilized nano precious metals pt transmission electron microscope picture;
Fig. 4 is a polyacrylamide partial hydrolysate stabilized nano precious metals pt infrared spectrogram.
The specific embodiment
The following stated embodiment describes the present invention in detail, and in these examples of implementation, unless specified otherwise, the solid measurement unit is g (gram), and liquid meter units such as water, alcohol are mL (milliliter).
Embodiment 1 preferred PVA 124 (polyvinyl alcohol, the degree of polymerization 124) is a stabilizing agent stabilized nanoscale precious metals pt:
Taking by weighing 0.10g PVA adds in the 100mL single port bottle, add 25mL methyl alcohol and 25mL secondary water successively, be warming up to 60 ℃ under stirring, after treating the PVA dissolving, add 0.5mL chloroplatinic acid aqueous solution (platiniferous 7.4mg), continue to stir and be warming up to backflow, solution colour is by the faint yellow dark-brown that changes into after 40 minutes.After decompression distillation steamed unnecessary liquid (steaming 2/3 volume of liquid), remaining liq was cooled to room temperature.Layer precipitation taken off in centrifugation (4000r/min), and baking got the drying solid material in 3 hours in 110 ℃ of baking ovens.It is standby to be ground into the 100-120 order.Its Electronic Speculum figure sees accompanying drawing 1, and infrared spectrogram is seen accompanying drawing 2.
Embodiment 2PAA partial hydrolystate stabilized nano precious metals pt:
Taking by weighing the 0.15g mean molecule quantity and be 3000000 PAA adds in the 100mL single port bottle, add 25mL methyl alcohol and 25mL secondary water and 0.25mL chloroplatinic acid aqueous solution (platiniferous 3.7mg) successively, add the 0.1M hydrochloric acid solution and be adjusted to pH=2.0, be heated to 70 ℃ under stirring, continue to be stirred to polyacrylamide and all be warming up to that solution is little to boil after the dissolving, kept this state 4 hours.This moment solution color by faint yellow become brown.Solution is adjusted to pH=4.0 with acetate while hot.Solution is naturally cooled to room temperature, have black precipitate to separate out, precipitation discards washings to wash (25mL * 3) three times, and with 10mL ethanol displacement adsorbed water, precipitation is sclerosis progressively.Migrate out the precipitation and 50 ℃ of following vacuum drying 12 hours.Take out the gained solid, grind to form less than 200 order powder standby.Its Electronic Speculum figure sees accompanying drawing 3, and infrared spectrogram is seen accompanying drawing 4.
Embodiment 3PAA partial hydrolystate stabilized nano precious metals pt:
Taking by weighing the 0.15g mean molecule quantity and be 3000000 PAA adds in the 100mL single port bottle, add 25mL methyl alcohol and 25mL secondary water and 0.25mL chloroplatinic acid aqueous solution (platiniferous 3.7mg) successively, add the 0.1M hydrochloric acid solution and be adjusted to pH=4.0, be heated to 70 ℃ under stirring, continue to be stirred to polyacrylamide and all be warming up to that solution is little to boil after the dissolving, kept this state 4 hours.This moment solution color by faint yellow become brown.Solution is adjusted to pH=4.0 with acetate while hot.Solution is naturally cooled to room temperature, have black precipitate to separate out, precipitation discards washings to wash (25mL * 3) three times, and with 10mL ethanol displacement adsorbed water, precipitation is sclerosis progressively.Migrate out the precipitation and 50 ℃ of following vacuum drying 12 hours.Take out the gained solid, it is standby to grind to form 200 order powder.
Embodiment 4PAA partial hydrolystate stabilized nano precious metals pt:
Taking by weighing the 0.15g mean molecule quantity and be 3000000 PAA adds in the 100mL single port bottle, add 25mL methyl alcohol and 25mL secondary water and 0.25mL chloroplatinic acid aqueous solution (platiniferous 3.7mg) successively, add the 0.1M NaOH aqueous solution and be adjusted to pH=8.0, be heated to 70 ℃ under stirring, continue to be stirred to polyacrylamide and all be warming up to that solution is little to boil after the dissolving, kept this state 4 hours.This moment solution color by faint yellow become brown.Solution is adjusted to pH=4.0 with acetate while hot.Solution is naturally cooled to room temperature, have black precipitate to separate out, precipitation discards washings to wash (25mL * 3) three times, and with 10mL ethanol displacement adsorbed water, precipitation is sclerosis progressively.Migrate out the precipitation and 50 ℃ of following vacuum drying 12 hours.Take out the gained solid, it is standby to grind to form 200 order powder.
Embodiment 5 gained catalyst are catalysis ethyl pyruvate asymmetric hydrogenation after cinchonidine is modified.With embodiment 1 and embodiment 2 gained Pt catalyst, add a certain amount of cinchonidine, in suitable solvent, stirred 4-6 hour under the room temperature, aforesaid liquid is transferred in the autoclave, add ethyl pyruvate, logical hydrogen reducing, reactant liquor is with gas chromatographic analysis.Experimental result sees attached list 1.
Subordinate list 1, PVA stabilized nano precious metals pt (1) and polyacrylamide partial hydrolysate stabilized nano precious metals pt (2) are as catalyst catalysis ethyl pyruvate asymmetric hydrogenation result (cinchonidine 20mg, room temperature) after cinchonidine is modified
| Catalyst | Solvent | Hydrogen initial pressure (atm.) | r 0 (mmolg -1h -1) | e.e ％ |
| 1 2 1 2 1 1 2 2 1 2 | Ethanol/acetic acid ethanol/acetic acid toluene toluene ethanol/water ethanol/water ethanol/water ethanol/water ethanol ethanol | 5.0 50.0 5.0 5.0 5.0 50.0 5.0 52.9 5.0 5.0 | 37.1 55.9 52.6 27.0 111.7 90.1 241.3 56.3 242.1 386.9 | 51.1 15.5 46.4 19.4 35.4 33.1 25.8 45.0 50.5 44.6 |
Claims (7)
1, a kind of preparation method of the metal platinum nano-particle of being convenient to separate and recycling, with the chloroplatinic acid is the platinum source, adding alcohols at aqueous phase is reducing agent, polyvinyl alcohol or polyacrylamide are stabilizing agent, wherein, water: reducing agent: the percentage by weight of stabilizing agent=100: 5-45: 0.1-10, the chloroplatinic acid addition is the 10-20mg/100ml water; Stirring reaction liquid 10-120 minute, centrifugation reactant liquor under the room temperature, dry sediment gets nano metal platinum.
2, in accordance with the method for claim 1, it is characterized in that described reducing agent is a carbon chain lengths less than 5 monohydric alcohol or polyalcohol.
3, in accordance with the method for claim 1, it is characterized in that the mean molecule quantity of described polyvinyl alcohol is 5000-100000.
4, in accordance with the method for claim 1, it is characterized in that described polyacrylamide mean molecule quantity is more than 500000.
5, in accordance with the method for claim 1, it is characterized in that described stirring is to carry out between room temperature to 100 ℃.
6, in accordance with the method for claim 1, it is characterized in that described polyacrylamide is a stabilizing agent when preparing metal platinum nano-particle, also adds the pH=1.0-4.0 that 0.05-0.2M hydrochloric acid makes reactant liquor, stirs the back and transfers to pH=3-5 with acetate.
7, in accordance with the method for claim 1, it is characterized in that, described polyacrylamide is a stabilizing agent when preparing metal platinum nano-particle, and the sodium hydrate aqueous solution that also adds 0.05-0.2M makes the pH=8.0-10.0 of reactant liquor, and reaction finishes the back and transfers to pH=3-5 with acetate.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100409943C (en) * | 2005-07-28 | 2008-08-13 | 大连理工大学 | Method for preparing nano noble metal hydrogenation catalyst by substitution method and its use |
| CN106607180B (en) * | 2016-12-30 | 2019-02-22 | 广东工业大学 | A kind of separation method of nano particle |
| CN108414423A (en) * | 2018-04-27 | 2018-08-17 | 成都理工大学 | The scanning electron microscope imaging method of the micro-nano hole of rock |
| CN114700090A (en) * | 2021-12-03 | 2022-07-05 | 中北大学 | Stable-salt recycled nano noble metal solution, preparation method and application |
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