CN108855071A - A kind of preparation method and applications of cerium oxide support type high-dispersion nano catalyst - Google Patents
A kind of preparation method and applications of cerium oxide support type high-dispersion nano catalyst Download PDFInfo
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- CN108855071A CN108855071A CN201810764421.XA CN201810764421A CN108855071A CN 108855071 A CN108855071 A CN 108855071A CN 201810764421 A CN201810764421 A CN 201810764421A CN 108855071 A CN108855071 A CN 108855071A
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/56—Platinum group metals
- B01J23/63—Platinum group metals with rare earths or actinides
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- 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
- B01J37/08—Heat treatment
- B01J37/082—Decomposition and pyrolysis
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/16—Reducing
- B01J37/18—Reducing with gases containing free hydrogen
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- C07—ORGANIC CHEMISTRY
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Abstract
The invention discloses a kind of methods of high dispersive cerium oxide carrier nanometer catalyst, including：The cerium oxide powder of carried noble metal after air calcination, is placed under reducing atmosphere and is restored at a temperature of 100~900 DEG C, obtains the cerium oxide carrier nanometer catalyst of high dispersive.Method of the invention effectively improves active site utilization rate by air calcination redisperse metallic particles using the redox characteristic and vacancy position plasticity carried noble metal of ceria；It is at low cost, controllability is strong；Prepared high-dispersion nano catalyst shows good catalytic activity, selectivity and stability in all kinds of important Industrial Catalysis hydrogenation reactions.
Description
Technical field
The invention belongs to catalyst technical fields, and in particular to a kind of method system by efficient redisperse noble metal granule
Preparing cerium oxide support type high-dispersion nano catalyst.
Background technique
For high-dispersion nano catalyst because its active component atom utilization is high, catalytic performance is excellent, can reduce preparation cost
And it attracts attention.It is ground currently, preparing high-dispersion nano catalyst by oxide carrier oxygen vacancy position supported active metals and becoming
Study carefully hot spot.
Easily cause metal dispersion uneven using traditional preparation methods supported active metals component, and supported, heterogeneous is urged
Metallic particles is easy to reunite especially under hot environment during the reaction for agent, and catalytic performance is caused to decline.Cerium oxide is loaded
Type catalyst, metal ion and surface Lacking oxygen can produce stronger interaction and weaken particle migration, reunite, therefore manage
The dispersion degree of metal ion can be improved by upper raising cerium oxide carrier surface oxygen vacancy concentration.However cerium oxide surface Lacking oxygen
Exposure in air easily adsorption of oxygen and be oxidized, disappear.The patent application of Publication No. CN106824165A discloses one
The preparation method of kind CeO 2 supporting high-dispersion nano catalyst, this method are manufactured using reducibility gas reduction ceria
Surface Lacking oxygen utilizes the CeO 2 supporting type catalyst of metal ion and Lacking oxygen strong interaction preparation high dispersive.But
It is that this method needs to keep oxygen-free environment to protect Lacking oxygen, complicated for operation；Content of metal is limited by oxygen vacancy concentration；?
In catalysis reaction, metal can carry out or heat up with reaction and generate reunion, and performance is caused to decline.
In addition, in heterogeneous catalysis field, cerium oxide loaded catalyst is mainly used for catalytic oxidation, this is because two
Cerium oxide Lattice Oxygen rich in, can be used as the reservoir of oxygen, stores under suitable condition and release oxygen is used for
The reaction of catalytic surface.Compared to oxidation reaction, CeO 2 supporting type catalyst is in catalytic hydrogenation field using less, mechanism
It studies also few.
Summary of the invention
In view of the above-mentioned problems, the present invention provides a kind of method preparation high dispersive oxygen by efficient redisperse noble metal granule
Change cerium carrier nanometer catalyst, this method is easy to operate, and it is low in cost, it solves traditional preparation methods and easily causes metal point
Dissipate non-uniform problem.High-dispersion nano catalyst high temperature resistant, the stable structure being prepared by this method, are used for being catalyzed
Field of hydrogenation can get excellent catalytic activity, selectivity and stability.
A kind of preparation method of high dispersive cerium oxide carrier nanometer catalyst, including：
The cerium oxide powder of carried noble metal after air calcination, is placed in reducing atmosphere at a temperature of 100~900 DEG C
Under, restored the cerium oxide carrier nanometer catalyst for obtaining high dispersive.
The high temperature air calcining can operate in air furnace, and the air furnace is free-air furnace, crucible
It covers tightly and blow-by；The cerium oxide powder of carried noble metal is contained in the crucible of suitable capacity, is placed in air furnace
Calcining, as calcining carries out, small metallic particles tends to disappear molten and migrate in catalyst surface, in order to promote ceria table
The generation of face Lacking oxygen and the metallic particles for effectively capturing and fixing migration, and then make metallic particles redisperse, the calcining
Temperature is preferably 400~700 DEG C.
Guarantee that ceria cellular structure is stablized while in order to guarantee metallic particles dispersibility, the air calcination step
Rapid programmed rate is preferably 5~20 DEG C/min, further preferably 5~10 DEG C/min.
Under setting air calcination temperature, in general proper extension calcination time, precious metal dispersion can be correspondinglyd increase,
But when noble metal has reached optimum dispersion effect at the calcination temperature, extending calcination time will not work again substantially, phase
It answers, the calcination time is preferably 2~8h, further preferably 3~6h, is still more preferably 4h.
The reducibility gas is the one or more of hydrogen, carbon monoxide or low-carbon hydro carbons, the low-carbon hydro carbons
Carbon atom number is 1~4.
The reduction step programmed rate is 2~20 DEG C/min；Reduction temperature is 100~500 DEG C；Recovery time
For 1~6h；Reducing gas flow velocity is 30~80mL/min.
In order to make the noble metal of redisperse gradually revert to elemental without particle aggregation from oxidation state, gold is not influenced
Belong to the dispersion in carrier surface, the reduction step programmed rate is preferably 1~5 DEG C/min, and reduction temperature is preferably
150~300 DEG C, the recovery time is preferably 1~3h；In order to avoid too low flow velocity keeps catalyst reduction insufficient, excessively high stream
Speed can blow winged catalyst solid powder and influence reduction effect and hydrogen be caused to waste, and the hydrogen flow rate is preferably 40~
60mL/min。
Noble metal in the cerium oxide powder of the carried noble metal is Pd, Pt, Rh, Ru, Au, Ag or Ir.
The very few influence reactivity of noble-metal-supported amount, while being also unfavorable for high-volume industrial production application；Load capacity mistake
Can mostly metallic particles be made to assemble, dispersion degree decline can not obtain the nanocatalyst of high dispersive and increase production cost, described
Noble-metal-supported amount is 0.1~5.0wt%；Further preferably 0.4~2.0wt%.
Raw material-carried noble metal cerium oxide powder used in the present invention, using traditional infusion process by ceria powder
It is obtained after last carried noble metal.The cerium oxide powder is business or makes the one or more of cerium oxide by oneself, from oxygenerating
Cerium is prepared by two one-step hydrothermals of the prior art.
Preferably, pass through traditional infusion process carried noble metal by carrier of the reduction-state ceria rich in Lacking oxygen,
Its specific preparation method includes：
Cerium oxide powder is placed under reducing atmosphere and is restored, reduction-state ceria is obtained, is added into pre-
In the noble metal precursor liquid solution first prepared, stirs, is heated to solvent evaporated, obtained solid is polished, obtains carried noble metal
Cerium oxide powder.
The reduction temperature of the cerium oxide powder is 200~800 DEG C；Heating rate is 1~20 DEG C/min；Recovery time
For 2~8h；Reducing gas flow velocity is 30~80mL/min.
By reducing atmosphere, (reducibility gas for constructing reducing atmosphere is hydrogen, carbon monoxide or low-carbon hydro carbons to the step
It is one or more, the carbon atom number of the low-carbon hydro carbons is 1~4) under pyroreaction obtain the titanium dioxide rich in Lacking oxygen
Cerium carrier promotes metal ion to disperse using ceria surface vacancy.Rich content, the oxygen being evenly distributed are empty in order to obtain
Position, the programmed rate is preferably 1~10 DEG C/min, and reduction temperature is preferably 400~600 DEG C, and the recovery time is preferred
For 3~6h.In order to avoid too low flow velocity keeps catalyst reduction insufficient, excessively high flow velocity can blow winged catalyst solid powder shadow
It rings reduction effect and hydrogen is caused to waste, the reducing gas flow velocity is preferably 30~60mL/min.
The noble metal precursor liquid solution is that hydrochloride, nitrate, Acetate Solution or the acetylacetone,2,4-pentanedione of noble metal are molten
Liquid；The noble metal includes Pd, Pt, Rh, Ru, Au, Ag or Ir.
The stirring rate is 200~1000rpm；Mixing time be 8~for 24 hours；Heating temperature is 40~120 DEG C；Add
The hot time be 8~for 24 hours.
In order to make, reduction-state ceria supports sufficiently adsorb the metal ion in noble metal precursor liquid solution and dispersion is equal
Even, the stirring rate is preferably 400~800rpm；In order to reduce the hair of metallic particles agglomeration in solvent evaporation process
Raw, heating temperature is preferably 40~80 DEG C；In order to make solvent evaporation completely and guarantee metal ion and carrier in evaporation process
Uniformly contact, the mixing time is consistent with heating time maintenance, preferably 10~14h.
0.5~the 2h of milling time；Sieving and casing is≤200 mesh.
After heating solvent evaporated, the solidification of the ceria of carried noble metal on the wall, need before calcination by its into
Row grinding, makes even particle distribution, and the milling time is 0.5~2h；Preferably 0.5~1h；It, can to guarantee grinding effect
Solid powder after grinding is sieved, Sieving and casing is≤200 mesh.
The research of the invention finds that：The step for high temperature air is calcined is catalyzed the cerium oxide loaded nano of preparation high dispersive
Agent plays a decisive role, and ceria surface Lacking oxygen and other kinds of defect increase in calcination process；It is ripe according to Ostward
Change mechanism, loads to the metallic particles on cerium oxide and gradually disappear the small cluster of melt into ceria surface in calcining temperature-rise period
Migration, surface Lacking oxygen effectively captures and fixed metal cluster, and then achievees the effect that effective redisperse metallic site.Then,
Using subsequent low-temperature reduction, oxidation state metal ion is reduced into elemental, and the cerium oxide support type of high dispersive is prepared
Nanocatalyst.
High-dispersion nano catalyst high temperature resistant, the stable structure of the method preparation provided through the invention；It is used for urging
Change hydrogenation reaction, such as phenol selectivity adds hydrogen to cyclohexanone, nitrobenzene are selectively hydrogenated to aniline, trimethylbenzoquinone adds hydrogen to arrive
Quinhydrones etc. can obtain excellent catalytic activity, selectivity and stability.This is because the present invention utilizes the oxygen of ceria
After changing reduction characteristic and vacancy position plasticity carried noble metal, by air calcination redisperse noble metal granule, effectively improve
Active site dispersion degree, so in catalytic reaction process improve active site utilization rate.
The present invention can Effective Regulation metal redisperse degree and ceria table by control reducing condition and calcination condition
Face oxygen vacancy concentration.Metal redisperse degree can pass through high resolution electron microscopy (HRTEM), hydrogen heating reduction (H2- TPR), X-ray
The chemical characterizations means qualitative analyses such as diffraction (XRD) and CO chemisorption quantitative analysis；Ceria oxygen vacancy concentration can be with
By XRD, the chemical characterizations means quantitative analysis such as Raman spectrum and XPS.The cerium oxide loaded catalyst of this method preparation exists
Performance in catalytic hydrogenation reaction can be tested by feed stock conversion, target product selectivity and catalyst life to be commented
Valence.
Compared with prior art, the present invention has the following advantages that and beneficial achievement：
(1) at low cost, abundant raw material is easy to get, commercially with self-control cerium oxide；
(2) controllability is strong, and it is dense to prepare different metal dispersion degree, different Lacking oxygens by control reducing condition and calcination condition
The nanocatalyst of degree；
(3) the high-dispersion nano catalyst prepared by can be applied in all kinds of important Industrial Catalysis hydrogenation reactions, such as
Phenol hydrogenation, trimethylbenzoquinone add hydrogen, hydrogenation of chloronitrobenzene and hydrogenation on cinnamic aldehyde etc. to react, and have good catalytic activity and product
Selectivity, and show good heat-resistant stable.
Detailed description of the invention
Fig. 1 is the business CeO of the purchase of traditional Chinese medicines company used in the embodiment of the present invention 12Powder sample photo
Fig. 2 is that the CeO of two one-step hydrothermals preparation is utilized in the embodiment of the present invention 22Powder sample photo
Fig. 3 is the 5wt%Pd/CeO that the number prepared in the embodiment of the present invention 3 is A2Catalyst XRD diagram
Fig. 4 is the 5wt%Pd/CeO that the number prepared in the embodiment of the present invention 3 is B2Catalyst XRD diagram
Fig. 5 is the 5wt%Pd/CeO that the number prepared in the embodiment of the present invention 3 is A2Catalyst HRTEM figure
Fig. 6 is the 5wt%Pd/CeO that the number prepared in the embodiment of the present invention 3 is B2Catalyst HRTEM figure
Fig. 7 is the Pt/CeO prepared in the embodiment of the present invention 42Catalyst XRD diagram
Fig. 8 is the Pt/CeO prepared in the embodiment of the present invention 42Catalyst HRTEM figure
Fig. 9 is the comparative sample Pt/CeO prepared in comparative example 1 of the present invention2Catalyst HRTEM figure
Figure 10 is the Pd/CeO prepared in the embodiment of the present invention 52Catalyst XRD diagram
Figure 11 is the Pd/CeO prepared in the embodiment of the present invention 52Catalyst HRTEM figure
Figure 12 is the comparative sample Pd/CeO prepared in comparative example 2 of the present invention2Catalyst HRTEM figure
Figure 13 is the reduction-state ceria HRTEM figure prepared in the embodiment of the present invention 6
Figure 14 is business (traditional Chinese medicines) the ceria HRTEM figure prepared in comparative example 3 of the present invention
Specific embodiment
For a further understanding of the present invention, below with reference to embodiment to a kind of high-dispersion nano catalyst provided by the invention
And preparation method thereof be specifically described, however, the present invention is not limited to these examples.The skilled practitioner is according to upper
Summary of the invention made nonessential change lower to core concept of the present invention guidance is stated, protection scope of the present invention is still fallen within.
Embodiment 1：Serial dispersion degree Ru/CeO2The preparation of catalyst
Appropriate business ceria (traditional Chinese medicines) is taken, is warming up to 800 DEG C under carbon monoxide atmosphere with 10 DEG C/min, reduction
3h, gas flow rate 50mL/min.Reduction terminates to be down to room temperature, obtains reduction-state ceria.
20mg/mL chlorination ruthenium solution 210uL is taken, is dissolved in 10mL deionized water, the above-mentioned reduction-state titanium dioxide of 500mg is added
Cerium, 800rpm stir lower 60 DEG C of oil bath heatings for 24 hours, grinding screening.Above step is consistent, and prepares more parts.After screening
Solid powder is contained in 20mL crucible, is placed in air furnace and is calcined, and is warming up to different temperatures (200~900 with 10 DEG C/min
DEG C), calcine 4h.Calcining, which is placed under hydrogen atmosphere, is warming up to 300 DEG C with 5 DEG C/min, restores 1h, obtains serial Ru/CeO2It urges
Agent.
Above-mentioned business CeO2For the commercially available business CeO bought from traditional Chinese medicines company2, specific surface area 6.8m2/ g, such as Fig. 1 institute
Show, is in light yellow powder, without other specially treateds when use.
To the Ru/CeO of this method preparation2Carry out CO chemisorption characterization, the results showed that：
As calcination temperature increases, metal dispersity increases, 700 DEG C of calcinings be it is best, suitable calcination temperature range is 400
~700 DEG C.Result above is provable, and air furnace calcining can play the role of redisperse metal component, can be effective using this method
Prepare high dispersive cerium oxide carrier nanometer catalyst.
Table 1 is the Ru/CeO of serial calcination temperature preparation2The metal point that catalyst and its corresponding CO absorption test obtain
Divergence.
The Ru/CeO of the serial calcination temperature preparation of table 12Catalyst and its corresponding CO absorption test dispersion degree
Embodiment 2：Serial oxygen vacancy concentration Au/CeO2The preparation of catalyst
Appropriate self-control ceria is taken, 500 DEG C is warming up in a hydrogen atmosphere with 20 DEG C/min, restores 3h, gas flow rate
80mL/min.Reduction terminates to be down to room temperature, obtains reduction-state ceria.
10mg/mL chlorauric acid solution 500uL is taken, is dissolved in 10mL deionized water, the above-mentioned reduction-state titanium dioxide of 500mg is added
Cerium, 1000rpm stir lower 100 DEG C of oil bath heating 10h, grinding screening.Above step is consistent, and prepares more parts.After sieving
Solid powder be contained in 20mL crucible, be placed in air furnace and calcine, different temperatures (200~900 is warming up to 20 DEG C/min
DEG C), calcine 8h.Calcining, which is placed under hydrogen atmosphere, is warming up to 200 DEG C with 5 DEG C/min, restores 1h, obtains series A u/CeO2It urges
Agent.
Above-mentioned self-control CeO2To utilize the CeO of two one-step hydrothermals preparation2, specific surface area 138m2/ g, as shown in Fig. 2,
In yellow powder, without other specially treateds when use.
To the Au/CeO of this method preparation2XPS characterization has been carried out, O 1s track swarming has been fitted, the results showed that：With forging
Temperature is burnt to increase, ceria Lacking oxygen increases, 700 DEG C of calcinings be it is best, suitable calcination temperature range is 400~700 DEG C.
Result above is provable, and air furnace calcining can be played the role of increasing cerium oxide Lacking oxygen, this is because crucible cover
It covers tightly, air concentration is limited, and as the temperature rises, air is consumed, and ceria structure change leads to vacancy and surface pleat
Wrinkle increases, and equally distributed Lacking oxygen is conducive to the redisperse of active component, and then obtains high-dispersion nano catalyst.
Table 2 is the Au/CeO of serial calcination temperature preparation2Catalyst and its corresponding ceria Lacking oxygen percentage.
The Au/CeO of the serial calcination temperature preparation of table 22Catalyst and its corresponding ceria Lacking oxygen percentage
Embodiment 3：Redispersion performance verification
Appropriate business ceria (traditional Chinese medicines) is taken, is warming up to 600 DEG C in a hydrogen atmosphere with 10 DEG C/min, restores 4h, gas
Body flow velocity 60mL/min.Reduction terminates to be down to room temperature, obtains reduction-state ceria.
Appropriate 10mg/mL palladium nitrate solution is taken, control Pd load capacity is 5wt%, is dissolved in 10mL deionized water, is added
The above-mentioned reduction-state ceria of 500mg, 1000rpm stir lower 50 DEG C of oil bath heatings for 24 hours, are contained in 20mL crucible after grinding screening
In.Above-mentioned steps are consistent, and prepare two parts, a copy of it is placed in air furnace and calcines, and is warming up to 500 DEG C with 5 DEG C/min, forges
Burn 4h, number A；Another is not calcination processing, number B.Most latter two sample is placed under atmosphere of hydrogen with 5 DEG C/min
500 DEG C are warming up to, 1h is restored.
Two samples of above-mentioned preparation are subjected to XRD and HRTEM characterization, wherein Fig. 3 is the 5wt%Pd/ that number is A
CeO2Catalyst XRD diagram；Fig. 4 is the 5wt%Pd/CeO that number is B2Catalyst XRD diagram；Fig. 5 is the 5wt%Pd/ that number is A
CeO2Catalyst HRTEM figure；Fig. 6 is the 5wt%Pd/CeO that number is B2Catalyst HRTEM figure, the results showed that：
The peak intensity of Pd (111) is low in the sample XRD spectra that number is A, and the sample XRD spectrum of same load capacity number B
The peak intensity of Pd (111) is high in figure, illustrates that 500 degree of air furnace calcinings can play the role of redisperse metal.The sample that number is A
There is obvious metallic particles in HRTEM high power figure, partial size statistical result showed is 3~5nm；The sample HRTEM high power figure that number is B
In do not find obvious particle, this is because Pd is agglomerated into great metallic particles, therefore have obvious diffraction maximum in XRD spectra, and
High resolution electron microscopy characterization is local characterization, and there are sample preparation contingency, do not find that particle is since sample preparation is taken caused by sample.
Result above is provable, can effective redisperse metal active site using this method.
Embodiment 4：High dispersive Pt/CeO2The preparation of catalyst
Appropriate business ceria (traditional Chinese medicines) is taken, is warming up to 600 DEG C in a hydrogen atmosphere with 10 DEG C/min, restores 3h, gas
Body flow velocity 50mL/min.Reduction terminates to be down to room temperature, obtains reduction-state ceria.
10mg/mL acetylacetone,2,4-pentanedione platinum solution 200uL is taken, is dissolved in 10mL deionized water, the above-mentioned reduction dioxy of 200mg is added
Changing cerium, 500rpm stirs lower 60 DEG C of oil bath heating 14h, is contained in 20mL crucible after grinding screening, is placed in air furnace and calcines,
700 DEG C are warming up to 5 DEG C/min, calcines 8h.Calcining, which is placed under atmosphere of hydrogen, is warming up to 200 DEG C with 2 DEG C/min, restores 6h,
Obtain high dispersive Pt/CeO2Catalyst.
To the Pt/CeO of this method preparation2CO chemisorption, XRD and HRTEM characterization, XRD and HRTEM characterization knot are carried out
Fruit difference is as shown in Figure 7,8, the results showed that：
The prepared Pt/CeO of CO chemisorption test2Catalyst metals dispersion degree is up to 73%；Without the correlation of Pt in XRD
Peak, only the business CeO of cubic fluorite structure2Diffraction maximum；Without obvious metallic particles in HRTEM high power figure, region power spectrum is shown
Palladium content is 0.7wt%.Result above is provable, can effectively prepare high dispersive cerium oxide support type using the redisperse method and receive
Rice catalyst.
Comparative example 1：Comparative sample Pt/CeO2The preparation of catalyst
Appropriate business ceria (traditional Chinese medicines) is taken, is warming up to 600 DEG C in a hydrogen atmosphere with 10 DEG C/min, restores 3h, gas
Body flow velocity 50mL/min.Reduction terminates to be down to room temperature, obtains reduction ceria.
10mg/mL acetylacetone,2,4-pentanedione platinum solution 400uL is taken, is dissolved in 10mL deionized water, the above-mentioned reduction dioxy of 500mg is added
Change cerium, 500rpm stirs lower 60 DEG C of oil bath heating 14h, do not calcine, be placed directly under atmosphere of hydrogen with 2 DEG C/min after grinding screening
200 DEG C are warming up to, 6h is restored, obtains comparative sample Pt/CeO2Catalyst.
To the Pt/CeO without calcining preparation2Carry out CO chemisorption, XRD and HRTEM characterization, the results showed that：
The prepared comparative sample Pt/CeO of CO chemisorption test2Catalyst metals dispersion degree is only 23%；Without Pt in XRD
Relevant peaks, the only business CeO of cubic fluorite structure2Diffraction maximum, this is attributable to, and Pt load capacity is low, and not up to XRD is detected
Line；HRTEM characterization has an obvious metallic particles, grain diameter about 4.5nm and is unevenly distributed, as shown in Figure 9.Result above pair
Than provable, redisperse metal is played the role of in air furnace calcining.
Related catalytic performance test is done to embodiment 4 and 1 products obtained therefrom of comparative example below
Pt/CeO prepared by above-described embodiment 4 and comparative example 12Catalyst is used for liquid phase trimethylbenzoquinone hydrogenation reaction.
Evaluation condition：Trimethylbenzoquinone 2g；Catalyst 20mg；Hydrogen 0.5MPa；90 DEG C of reaction temperature；Isopropanol 20mL.According to above-mentioned
Catalyst, trimethylbenzoquinone precise are placed in 50mL reaction kettle by evaluation condition, are driven away with hydrogen purge reaction kettle 3 times
Residual air is filled with hydrogen to 0.5MPa again, is placed in 90 DEG C of oil bath pans and reacts, reaction terminates to use GC-2014 Shimadzu chromatography
Carrying out product analysis, it is as shown in table 3 that trimethylbenzoquinone convert the time used completely, as shown in Table 3, the Pt/ of the preparation of embodiment 4
CeO2It is 80min that catalysis trimethylbenzoquinone, which adds hydrogen convert the time used completely,；Under the conditions of rating peer, prepared by comparative example 1
Time used in catalyst is 130min.The experimental results showed that having preferable catalytic activity by catalyst prepared by this method.
The catalyst prepared in 3 embodiment 4 of table and comparative example 1 is to trimethylbenzoquinone catalytic hydrogenation result
Embodiment 5：High-dispersion Pd/CeO2The preparation of catalyst
It is derived from ceria processed (specific surface area 138m2/ g), 400 DEG C are warming up to 5 DEG C/min in a hydrogen atmosphere, reduction
4h, gas flow rate 60mL/min.Reduction terminates to be down to room temperature, obtains reduction ceria.
10mg/mL palladium acetylacetonate solution 500uL is taken, is dissolved in 10mL deionized water, the above-mentioned reduction dioxy of 500mg is added
Changing cerium, 800rpm stirs lower 70 DEG C of oil bath heating 12h, is contained in 20mL crucible after grinding screening, is placed in air furnace and calcines,
600 DEG C are warming up to 10 DEG C/min, calcines 4h.Calcining, which is placed under atmosphere of hydrogen, is warming up to 250 DEG C, reductase 12 h with 2 DEG C/min,
Obtain high-dispersion Pd/CeO2Catalyst.
To the Pd/CeO of this method preparation2CO chemisorption, XRD and HRTEM characterization, XRD and HRTEM characterization knot are carried out
Fruit is respectively as shown in Figure 10,11, the results showed that：
The prepared Pd/CeO of CO chemisorption test2Catalyst metals dispersion degree is up to 52%；Without the correlation of Pd in XRD
Peak, only the self-control CeO of cubic fluorite structure2Diffraction maximum；Without obvious metallic particles in HRTEM high power figure.Result above can be demonstrate,proved
It is bright, high dispersive cerium oxide carrier nanometer catalyst can be effectively prepared using the redisperse method.
Comparative example 2：Comparative sample Pd/CeO2The preparation of catalyst
It is derived from ceria processed (specific surface area 138m2/ g), 400 DEG C are warming up to 5 DEG C/min in a hydrogen atmosphere, reduction
4h, gas flow rate 60mL/min.Reduction terminates to be down to room temperature, obtains reduction ceria.
10mg/mL palladium acetylacetonate solution 500uL is taken, is dissolved in 10mL deionized water, the above-mentioned reduction dioxy of 500mg is added
Change cerium, 800rpm stirs lower 70 DEG C of oil bath heating 12h, do not calcine, be placed directly under atmosphere of hydrogen with 2 DEG C/min after grinding screening
250 DEG C are warming up to, reductase 12 h obtains comparative sample Pd/CeO2Catalyst.
To the Pd/CeO without calcining preparation2Carry out CO chemisorption, XRD and HRTEM characterization, the results showed that：
The prepared comparative sample Pd/CeO of CO chemisorption test2Catalyst metals dispersion degree is 19%；Without Pd's in XRD
Relevant peaks, only the self-control CeO of cubic fluorite structure2Diffraction maximum, it is low that this is attributable to Pd load capacity, not up to XRD detection line；
HRTEM characterization has an obvious metallic particles, grain diameter about 3.9nm and is unevenly distributed, as shown in figure 12.Result above comparison
Provable, air furnace calcining step plays the role of redisperse metal.
Related catalytic performance test is done to embodiment 5 and 2 products obtained therefrom of comparative example below
Pd/CeO prepared by above-described embodiment 5 and comparative example 22Catalyst is used for liquid phase phenol hydrogenation reaction.Evaluate item
Part：Phenol 0.5mmol；Pd/Phenol=0.5mol%；Hydrogen 0.1MPa；80 DEG C of reaction temperature；Water 5mL；T=4.5h.According to
Catalyst, phenol precise are placed in 20mL flask by above-mentioned evaluation condition, and it is empty to drive residual away with hydrogen purge flask 3 times
Gas is filled with hydrogen again and maintains 0.1MPa, is placed in 80 DEG C of oil bath pans and reacts, and reaction terminates to be carried out with GC-2014 Shimadzu chromatography
Product analysis, the conversion ratio of phenol hydrogenation, cyclohexanone selectivity and yield are as shown in table 4, as seen from table, prepared by embodiment 5
Pd/CeO2Phenol conversion is 98% in catalyst 4.5h, and selectivity is 99%；Under the conditions of rating peer, prepared by comparative example 2
Catalyst phenol conversion ratio be 24%, selectivity be 94%.The experimental results showed that being had preferably by catalyst prepared by this method
Catalytic activity and selectivity of product.When catalyst is reused 5 times, the Pd/CeO of the preparation of embodiment 52Catalyst can still be kept
94% phenol conversion and 97% cyclohexanone selectivity, and comparative example 2 prepare catalyst use 5 times when phenol conversion
It is 8.0%, selectivity is 90%.The result shows that having preferable recycling stability by catalyst prepared by this method.
The catalyst Pyrogentisinic Acid's catalytic hydrogenation result prepared in 4 embodiment 5 of table and comparative example 2
Embodiment 6：Reduction-state CeO2Preparation
Appropriate business ceria (traditional Chinese medicines) is taken, is warming up to 500 DEG C in a hydrogen atmosphere with 20 DEG C/min, restores 3h, gas
Body flow velocity 50mL/min.Reduction terminates to be down to room temperature, obtains reduction-state ceria.
To reduction-state CeO2HRTEM characterization is carried out, as shown in figure 13.
Comparative example 3：CeO without any processing2
Appropriate business ceria (traditional Chinese medicines) is taken, has carried out HRTEM characterization, as shown in figure 14.
Embodiment 6 and comparative example 3 compare provable ceria supports and increase through reduction treatment surface Lacking oxygen, theoretically
Be conducive to subsequent carried metal.
Claims (9)
1. a kind of preparation method of cerium oxide support type high-dispersion nano catalyst, including：
The cerium oxide powder of carried noble metal after air calcination, is placed under reducing atmosphere and carries out at a temperature of 100~900 DEG C
Reduction, obtains the cerium oxide carrier nanometer catalyst of high dispersive.
2. preparation method according to claim 1, which is characterized in that the air calcination temperature is 400~700 DEG C.
3. preparation method according to claim 1 or 2, which is characterized in that the heating rate of control air calcination step is 5
~20 DEG C/min.
4. preparation method according to claim 1, which is characterized in that the reduction temperature is 100~500 DEG C, heating speed
Rate is 2~20 DEG C/min, and the recovery time is 1~6h, and reducing gas flow velocity is 30~80mL/min.
5. preparation method according to claim 1, which is characterized in that the reducibility gas be hydrogen, carbon monoxide or
Low-carbon hydro carbons it is one or more, wherein the carbon atom number of low-carbon hydro carbons be 1~4.
6. preparation method according to claim 1, which is characterized in that in the cerium oxide powder of the carried noble metal
Noble metal is Pd, Pt, Rh, Ru, Au, Ag or Ir；Load capacity is 0.1~5.0wt%.
7. preparation method according to claim 1 or 6, which is characterized in that the cerium oxide powder of the carried noble metal
Preparation method, including：
After cerium oxide powder is reduced to reduction-state ceria, it is added into previously prepared noble metal precursor liquid solution
In, it stirs, be heated to solvent evaporated, obtained solid is polished, obtains the cerium oxide powder of carried noble metal；
Wherein, the reduction temperature of the cerium oxide powder is 200~800 DEG C；Heating rate is 1~20 DEG C/min；When reduction
Between be 2~8h；Reducing gas flow velocity is 30~80mL/min；The stirring rate is 200~1000rpm, heating temperature 40
~120 DEG C.
8. cerium oxide support type high-dispersion nano made from a kind of preparation method as described in any one of claims 1 to 6 is catalyzed
Agent.
9. a kind of preparation method of cerium oxide support type high-dispersion nano catalyst as claimed in claim 8 and its catalysis plus
Application in hydrogen reaction.
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