CN112044434B - Single-atom noble metal/transition metal oxide composite material and preparation method and application thereof - Google Patents

Single-atom noble metal/transition metal oxide composite material and preparation method and application thereof Download PDF

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CN112044434B
CN112044434B CN202011121258.9A CN202011121258A CN112044434B CN 112044434 B CN112044434 B CN 112044434B CN 202011121258 A CN202011121258 A CN 202011121258A CN 112044434 B CN112044434 B CN 112044434B
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noble metal
composite material
metal oxide
acetone
transition metal
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CN112044434A (en
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连超
李杨
邓明亮
杨洪衬
王梦云
王敏朵
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Beijing Single Atom Catalysis Technology Co ltd
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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
    • 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
    • B01J35/394—
    • 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
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • 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
    • 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
    • C07C29/143—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 ketones
    • C07C29/145—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 ketones with hydrogen or hydrogen-containing gases
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention discloses a single-atom noble metal/transition metal oxide composite material and a preparation method and application thereof, wherein the composite material is prepared by loading noble metal on transition metal oxide in a single-atom form, and the single atom of the noble metal accounts for 0.01-1.0wt%. When the composite material is prepared, a dispersing agent, in particular a catalyst of polyamino acid, is added, so that the noble metal is more uniformly dispersed on the carrier. The monatomic noble metal/transition metal oxide composite material obtained by the invention can be used as a monatomic catalyst for preparing isopropanol by catalytic hydrogenation of acetone, and the catalyst is simple and convenient to prepare, easy to amplify, low in preparation cost, high in low-temperature activity, high in selectivity and good in stability; in addition, the monatomic catalyst has high activity, high efficiency, good selectivity and long service life in the reaction of preparing the isopropanol by the acetone gas phase selective catalytic hydrogenation.

Description

Single-atom noble metal/transition metal oxide composite material and preparation method and application thereof
Technical Field
The invention relates to the technical field of monatomic catalysts. More particularly, it relates to a monoatomic/transition metal oxide catalyst and its application in catalytic hydrogenation of acetone.
Technical Field
The catalytic hydrogenation of aldehydes and ketones to the corresponding alcohols is an important reaction for the production of fine chemicals. Taking acetone as an example, isopropanol which is a product of hydrogenation reaction of acetone is an important chemical and is widely applied to the fields of chemical engineering such as paint, medicine, pesticide and the like. In 2011 alone, the global usage of isopropanol reached 6.4 megatons. At present, isopropanol is obtained mainly through hydration reaction of propylene, and the process not only needs to use corrosive chemicals, but also needs to consume a lot of energy, and does not meet the requirement of green industry. In modern industry, a large amount of acetone is excessive, so that if acetone can be efficiently hydrogenated to isopropanol, the current situation of excessive acetone can be greatly relieved, and the isopropanol product with higher added value can be obtained; therefore, the method for preparing the isopropanol by efficiently hydrogenating the acetone has important social significance.
Acetone can be converted to isopropanol in liquid and vapor phase catalytic reactions. The gas phase route is more practical due to higher conversion efficiency and reaction continuity. In past research, a variety of heterogeneous catalysts have been used in acetone hydrogenation reactions. Most common such as raney nickel catalysts, copper-chromium oxide composite catalysts, and the like; however, these catalysts have significant disadvantages such as low catalytic performance and selectivity; in addition, the toxicity of the used medicines and the harsh reaction conditions (high temperature and high pressure) in the reaction process are not beneficial to wide industrial popularization. In the last two decades, nanoscience and catalysis technologies have been rapidly developed, and more research is focused on regulating and controlling the size, morphology, structure and composition of a nano catalyst, so as to improve catalytic activity, selectivity and stability. For example, ni nanoparticles synthesized by wet chemistry methods have higher catalytic performance than those synthesized by conventional impregnation and precipitation methods.
The prior art acetone hydrogenation mostly uses nickel-based or copper-based catalysts, or uses noble metals such as Pt, pd, ru, etc. Acetone and hydrogen are fed into a fixed bed reactor according to a certain proportion, and are hydrogenated at a proper temperature and hydrogen pressure to generate isopropanol.
CN103706377A discloses a platinum-based catalyst for catalytic hydrogenation of acetone, which is prepared by mixing octadecylamine and a carrier uniformly, and injecting acetylacetone platinum dissolved in oleylamine and a transition metal salt to obtain a supported platinum catalyst. The catalyst obtained in the patent is used for acetone hydrogenation, the selectivity of isopropanol is good, but the utilization efficiency of the catalyst is not high, the dosage of the catalyst is high, and the acetone conversion rate is greatly reduced at a high airspeed, and industrial production is not utilized.
CN101927168A discloses a nickel-based catalyst for preparing isopropanol by acetone hydrogenation, which is an alumina carrier loaded with Ni, mo and Zn. The acetone conversion rate and the isopropanol selectivity are high, but the space velocity of the acetone liquid is 0.5/h, and the production efficiency is very low. CN103030526A discloses a method for preparing isopropanol by gas-phase hydrogenation of acetone, wherein the catalyst is 10-40wt% of CuO,10-25wt% of NiO, and 25-70wt% of Al 2 O 3 And an auxiliary selected from MgO, znO or CaO. Similarly, the space velocity is increased but still in the lower range (below 5.0/h). CN104084209A discloses a MgO-supported high-activity nickel catalyst for preparing isopropanol by acetone hydrogenation, wherein the catalyst is a solution A prepared from nickel nitrate and magnesium nitrate, a sodium carbonate solution is added, the solution A is stirred at a high speed, and the obtained green precipitate is filtered, washed, calcined, and reduced by switching hydrogen atmosphere to obtain the catalyst. The catalyst is complicated to prepare, needs two-step roasting, and also needs to be in a hydrogen atmosphere. The catalyst has high acetone conversion rate of 1 and high isopropanol selectivity at a high space velocity.
One problem with the above prior art catalysts is that the utilization efficiency of the catalyst is low, a large amount of noble metal is required, and the cost is high; on the other hand, the catalyst has a short life and the activity of the catalyst gradually decreases after a certain period of use. This is one of the reasons that such catalysts have been difficult to be industrially applied. The monoatomic catalyst with the highest metal atom utilization rate, a definite active center structure and a low coordination number has become a new research hotspot in the field of materials. With the continuous reduction of the size of the metal, the coordination number of the metal is reduced, the surface free energy of metal atoms is increased sharply, the highly unsaturated characteristic is easier to adsorb reaction substrates and even change the path of catalytic reaction, and the corresponding catalytic activity is also improved. Monatomic catalysts have been used as heterogeneous catalysts, but monatomic catalysts for vapor phase hydrogenation of acetone to produce isopropanol have not been reported.
Disclosure of Invention
The first purpose of the invention is to provide a single-atom noble metal/transition metal oxide composite material, wherein noble metal is loaded on transition metal oxide in a single-atom form, and the single atom of the noble metal accounts for 0.01-1.0wt%.
Preferably, the noble metal is present in the monoatomic noble metal/transition metal oxide composite in an amount of 0.1 to 0.5wt%.
Preferably, the noble metal is at least one selected from gold, silver, platinum, palladium and nickel, and the transition metal oxide is at least one selected from iron oxide, manganese oxide, nickel oxide, cuprous oxide, cobalt oxide, cerium oxide, titanium oxide, silicon oxide and aluminum oxide.
More preferably, the noble metal is platinum and the transition metal compound is cerium oxide. Among noble metal materials, platinum (Pt) is widely used in the fields of energy conversion and environmental protection due to its excellent catalytic performance, however, its large-scale commercial application is hindered by the factors of platinum resource scarcity, high cost, low use efficiency, etc. CeO (CeO) 2 The catalyst material has excellent chemical properties, has abundant oxygen defects on the surface, can be used for anchoring noble metal atoms, and is often applied to heterogeneous catalytic reaction; with CeO 2 The synthesis of the carrier is simple, and the carrier is convenient for large-scale production and provides possibility for commercial application.
In a preferred embodiment of the invention, the monatomic/transition metal oxide is Pt/CeO 2 And the XRD has the following characteristic peaks: 28.6 +/-0.3 degrees, 33.8 +/-0.3 degrees, 47.5 +/-0.3 degrees and 52.1 +/-0.3 degrees.
The inventors found that Pt/CeO having the characteristic peaks of XRD as described above 2 The catalyst for preparing isopropanol by catalytic hydrogenation of acetone has high catalytic activity and good selectivity.
Preferably, the metal oxide is in the shape of a nanorod, a nanodisk, a nanoparticle, a nanocube; preferably, the nano-rod has the length of 20-100nm and the diameter of 3-10nm.
The second object of the present invention is to provide a method for preparing the above-mentioned monatomic noble metal/transition metal oxide composite material, comprising the steps of:
adding a precursor containing noble metal into an aqueous solution of a nanoscale transition metal oxide, adding a dispersing agent, stirring for 20-40h, washing, centrifuging, vacuum drying, heating the obtained sample to 150-200 ℃ in a mixed gas of hydrogen and an inert gas, and heating for 1-4h to obtain the monatomic noble metal/transition metal oxide composite material.
The dispersing agent is at least one selected from polyether polyol, long-chain alkyl sulfonate, polyamino acid, lauryl alcohol ether phosphate and potassium lauryl alcohol ether phosphate, preferably polyamino acid, and the polyamino acid is at least one selected from polyglutamic acid, polylysine and polyaspartic acid.
The inventor unexpectedly finds that the polyamino acid not only can disperse the precursor of the noble metal, but also has abundant groups on the polyamino acid, such as amino, carboxyl and carbonyl, which can play a chelating role with the noble metal to anchor the noble metal on the transition metal oxide carrier, and the obtained monoatomic noble metal/transition metal oxide composite material has the advantages of uniform distribution of the noble metal, narrow particle size distribution, stable activity and long catalytic life when used in a catalyst.
In a more preferred embodiment of the present invention, the polyamino acid is polylysine, which is more basic and facilitates the anchoring of the noble metal to the transition metal oxide support.
The precursor containing the noble metal is a salt of the noble metal, and preferably a salt of an acid group containing the noble metal. For example, when the noble metal is platinum, the precursor is at least one of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, platinum acetylacetonate and tetraammineplatinum nitrate, and preferably at least one of chloroplatinic acid, potassium chloroplatinate, sodium chloroplatinate, chloroplatinic acid, sodium chloroplatinate and potassium chloroplatinate.
The nanometer metal oxide can be in the shapes of nanorods, nanodiscs, nanoparticles and nanocubes, and is preferably the nanorods, and the nanorods have the length of 50-100nm and the diameter of 5-10nm.
Preferably, the mass ratio of the precursor containing noble metal, the nanoscale transition metal oxide and the dispersing agent is 1-5:50-300:5-30, preferably 1-2:50-200:10-20.
The concentration of the metal oxide in the aqueous solution of the nano-scale transition metal oxide is 0.3-1g/mL.
Preferably, the hydrogen gas is present in an amount of 5-10% by volume of the mixture of hydrogen gas and an inert gas, which is well known in the art, such as helium or argon.
The washing solvent is a mixed solvent of alcohol and water, and specifically is a mixed solvent of alcohol and water according to a volume ratio of 1-2; the alcohol is at least one of methanol, ethanol and propanol. The centrifugal speed of the centrifugation is 2000-3000r/min.
The third purpose of the invention is to provide the application of the single-atom precious metal/transition metal oxide composite material as a catalyst for preparing isopropanol by catalytic hydrogenation of acetone.
A fourth object of the present invention is to provide a method for preparing isopropanol by catalytic hydrogenation of acetone and hydrogen, which is characterized in that the above-mentioned monatomic noble metal/transition metal oxide composite is used as a catalyst.
Further, the method for preparing isopropanol by catalytic hydrogenation of acetone and hydrogen comprises the following steps: the method comprises the following steps of putting a single-atom noble metal/transition metal oxide composite material serving as a catalyst into a fixed bed reactor, and preparing isopropanol through catalytic reaction by using acetone and hydrogen as raw materials.
The reaction pressure is 0.1-1MPa, the reaction temperature is 50-100 ℃, the flow rate ratio of acetone to hydrogen is 1 -1 。
Preferably, the reaction pressure is 0.1-0.2MPa, the reaction temperature is 60-70 ℃, the flow rate ratio of acetone to hydrogen is 1 -1 。
By controlling the reaction conditions within the above range, the conversion of acetone and the selectivity of isopropanol can be both satisfactory. In the preferred technical scheme of the invention, the acetone conversion rate and the isopropanol selectivity are both more than 99 percent; in addition, the catalyst provided by the invention has the advantages that the noble metal active component is stably and lowly loaded on the transition metal oxide in a monoatomic state, the stability is good, the catalyst can be kept for 100 hours without being replaced, the acetone conversion rate is over 98 percent, and the isopropanol selectivity is over 99 percent.
The method for preparing isopropanol by catalytic hydrogenation of acetone provided by the invention has three main advantages: 1) The problem that noble metals in noble metal/transition metal oxide carrier materials are dispersed in the form of nano particles, the size of the nano particles is consistent, and the catalytic activity is high is solved; 2) Because the noble metal is dispersed in atomic level, the utilization efficiency of the metal is improved to the maximum extent, and the use cost of the catalyst is reduced; 3) The method has the advantages of improving the interaction between the catalyst and the carrier, solving the problem of poor material stability, prolonging the service life of the catalyst and solving the problem of high cost of the noble metal catalyst.
The invention has the advantages of
1) The noble metal in the composite material provided by the invention is dispersed in atomic level, and the composite material shows excellent catalytic activity and stability in the reaction of preparing isopropanol by acetone hydrogenation, so that the problem of obtaining isopropanol with higher added value while solving the problem of excess acetone is solved.
2) The method provided by the invention has wider modulation space, and the content of the noble metal and the content of the transition metal can be correspondingly increased or reduced (ensuring that the noble metal and the transition metal are monoatomic) within a certain range. Solves the problems of large size range, irregular shape and the like of products prepared by the prior art.
3) The method provided by the invention can prepare noble metal/transition metal oxide composite materials with dispersed atomic level on a large scale; the catalytic material with a definite structure lays a foundation for the correlation of the catalyst structure and the performance.
4) The invention creatively uses the polyamino acid as a stabilizer, so that the monoatomic acid is more uniformly and stably loaded on the transition metal oxide carrier. The prepared catalyst has more stable activity and longer service life.
Drawings
FIG. 1 shows Pt/CeO obtained in example 1 of the present invention 2 Electron micrograph (c).
FIG. 2 shows Pt/CeO obtained in comparative example 1 of the present invention 2 X-ray diffraction pattern of (a).
FIG. 3 shows an implementation of the inventionPt/CeO obtained in example 1 2 Electron microscopy images at atomic scale.
FIG. 4 shows Pt/CeO prepared in example 1 of the present invention 2 The dark field pattern of (a).
FIG. 5 shows Pt/CeO obtained in example 1 of the present invention 2 Pt element distribution diagram of (a).
FIG. 6 shows Pt/CeO obtained in example 1 of the present invention 2 Distribution diagram of Ce element.
FIG. 7 shows Pt/CeO obtained in example 1 of the present invention 2 Distribution diagram of the O element.
FIG. 8 shows Pt/CeO prepared in example 1 of the present invention 2 The conversion rate and selectivity of the catalytic hydrogenation of acetone at different temperatures.
FIG. 9 shows Pt/CeO obtained in example 1 of the present invention 2 Stability profile of (d).
FIG. 10 shows Pt/CeO obtained in example 1 of the present invention 2 Comparison of acetone hydrogenation catalytic performance with other materials.
Detailed Description
In order to more clearly illustrate the present invention, the present invention is further described below with reference to preferred embodiments and the accompanying drawings. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
In the present invention, the production method is a conventional method unless otherwise specified, and the raw materials used are commercially available from public or produced according to the prior art without specifically specified, and the percentages are mass percentages without specifically specified.
Polylysine used in the invention is purchased from Thermo Fisher and has a molecular weight of about 5300; polyglutamic acid used was purchased from Thermo Fisher and has a molecular weight of about 6800.
CeO for use in the invention 2 The nano-rod is self-made, and the specific method is that the hydrothermal method and the calcination method are combined, and Ce (NO) is used 3 ) 2 ·6H 2 O is cerium source, ce (NO) is slowly injected into NaOH solution 3 ) 2 ·6H 2 Stirring the O solution, transferring the O solution into a high-pressure reaction kettle, and reacting for 24 hours at the temperature of 100 ℃ to obtain the productThe material is deionized and washed by absolute ethyl alcohol, dried and calcined for 2 hours at 400 ℃ in air atmosphere to obtain CeO 2 The nanometer size is about 50-100nm in length and 5-10nm in diameter.
Preparation example 1
0.30g of CeO 2 The nanorods were dispersed in 50mL of aqueous solution, sonicated to a homogeneous solution, 3mg of potassium tetrachloroplatinate was added to the above solution, 30mg of polylysine was added, stirred for 12h, then centrifuged, washed 3 times with a mixed solution of water and ethanol (1, v/v), the unadsorbed metal precursor was removed, and the material was placed in a vacuum oven overnight at 70 ℃. The dried material is placed in a tube furnace in H 2 and/Ar (volume ratio is 5. After the reaction is finished, taking out the product to prepare Pt/CeO 2 . The loading capacity of the catalyst is 0.18 percent by a method for measuring the content of the catalyst by an inductively coupled plasma emission spectrometer.
For the prepared Pt/CeO 2 The characteristics are carried out by a spherical aberration electron microscope and a synchrotron radiation technology, and the result proves that the noble metal Pt is dispersed in CeO in a monoatomic form 2 In a carrier. FIG. 1 shows Pt/CeO obtained in this example 2 A Transmission Electron Microscope (TEM) photograph of (a). It can be observed that Pt/CeO 2 With CeO to which no noble metal precursor is added 2 Has the same appearance and is a nano rod. The obtained Pt/CeO 2 The X-ray diffraction of (2) is shown in FIG. 2.
Furthermore, the invention is also applicable to the prepared Pt/CeO 2 The electron microscope samples of (1) were observed at multiple angles and not at CeO 2 Pt or other nanoparticles were observed on the support surface. To further determine the Pt concentration in Pt/CeO 2 Distribution in the material, the invention is used for preparing Pt/CeO 2 Performing electron microscopy characterization for spherical aberration correction, as shown in FIG. 3, there are numerous "dots" with brighter colors dispersed in CeO 2 On the nanorods, it was demonstrated that Pt was dispersed in CeO in the form of a single atom 2 In a carrier material.
The element distribution characterization charts of FIGS. 4-7 further show that the Pt, ce and O are uniformly dispersed in the Pt/CeO 2 The above shows that the method can realize the dispersion of noble metal atoms on the carrierThe above.
Preparation example 2
The other conditions and procedures were the same as in preparation example 1 except that polylysine was replaced with polyglutamic acid of equal mass.
Preparation example 3
The other conditions and procedures were the same as in preparation example 1 except that polylysine was replaced with sodium dodecylsulfate of equal mass.
Preparation example 4
The other conditions and procedure were the same as in preparation example 1 except that the amount of polylysine was changed to 15mg.
Preparation example 5
The other conditions and procedures were the same as in preparation example 1 except that the amount of polylysine was changed to 60mg.
Preparation example 6
The other conditions and procedures were the same as in preparation example 1 except that the amount of polylysine was changed to 10mg.
Preparation example 7
The other conditions and procedure were the same as in preparation example 1 except that the amount of polylysine was changed to 100mg.
Comparative preparation example 1
The other conditions and procedures were the same as in preparation example 1 except that lysine was not added.
Application example 1
The catalytic hydrogenation of acetone involved in the present invention occurs in a continuous flow system. The catalyst can be directly tested without any pretreatment, 0.2g of the catalyst of preparation example 1 is packed in a quartz fixed bed reactor, and the mass ratio of hydrogen to acetone is 4:1, the reaction is carried out at 0.1 MPa.
The acetone hydrogenation catalysis is carried out under the conditions to prepare the isopropanol, the product is quantified by a gas chromatograph (SP-6890, an ion flame detector), and the following experiments are carried out on different reaction temperatures, different space velocities and the service life of the catalyst:
FIG. 8 shows that the space velocity of acetone is 50h -1 While, pt/CeO obtained in preparation example 1 2 Conversion and selectivity to catalytic hydrogenation of acetone at different temperatures.It can be seen that Pt/CeO 2 The catalyst shows conversion close to thermodynamic equilibrium at 60-120 ℃, wherein at 60 ℃, the conversion rate of acetone and the selectivity of isopropanol are high and close to 100%, so that 60 ℃ is selected as the reaction temperature in the later experiment. Interestingly, even when the reaction temperature dropped to 40 deg.C, pt/CeO was used 2 Still, 78% conversion of acetone was exhibited.
The reaction temperature of 60 ℃ is selected, the acetone conversion rate and the isopropanol selectivity are studied under different acetone space velocities, and the acetone conversion rate and the isopropanol selectivity are found to be even between 50 and 60 DEG C -1 The high acetone space velocity can still keep high acetone conversion rate and isopropanol selectivity.
The stability of the catalytic reaction is another important factor in evaluating the performance of the material. As shown in FIG. 9, pt/CeO obtained in example 1 2 In continuous operation for 100h, the catalyst maintains the acetone conversion efficiency of 98-99.6% and the isopropanol selectivity of 99.9%, and has excellent circulation stability.
The above results show that the Pt/CeO of our invention 2 The material shows excellent catalytic activity and circulation stability in the reaction of preparing isopropanol by acetone gas phase hydrogenation, and has good application potential.
Application example 2
The isopropanol is prepared by hydrogenating acetone under the same conditions as the application example 1, the reaction temperature is 60 ℃, and the airspeed of the acetone is 55h -1 The results of replacing the catalysts obtained in preparation examples 1 to 3 are shown in Table 1 below:
TABLE 1
Figure BDA0002732074720000071
Figure BDA0002732074720000081
Comparative example 1
Examination of the monatomic catalyst Pt/CeO obtained in preparation example 1 on a fixed-bed reactor 2 And conventional nano-catalyst Pt/Fe 3 O 4 ，Ni/MgO-Al 2 O 3 ，Cu/SiO 2 Performance for vapor phase conversion of acetone to isopropanol. The catalyst input was xxg, acetone was added to the reactor at a rate of 6g/h, the reaction temperature was 80 ℃ and the pressure was 1Mpa, and the final product was quantified by gas chromatography (SP-6890, ion flame detector). As shown in FIG. 10, the conversion frequency (calculation formula: conversion frequency = mole of acetone converted/(mole of platinum. Unit time)) of each catalyst was calculated as Pt/CeO obtained in preparation example 1 2 Shows extremely high activity in the acetone hydrogenation reaction, and the conversion frequency reaches 15372h -1 Is obviously higher than the conventional nano catalyst Pt/Fe 3 O 4 ，Ni/MgO-Al 2 O 3 ，Cu/SiO 2 。
The catalysts of preparation 2, preparation 3 and comparative preparation 1 each had a conversion frequency of 14791h under the same conditions -1 ，13837h -1 ，8674h -1 。
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.

Claims (8)

1. A single atom noble metal/transition metal oxide composite material is that noble metal is loaded on transition metal oxide in a single atom form, wherein the noble metal single atom accounts for 0.01 to 1.0wt percent; the noble metal is platinum, and the transition metal oxide is cerium oxide; the preparation method of the monatomic noble metal/transition metal oxide composite material comprises the following steps:
adding a precursor containing noble metal into an aqueous solution of a nanoscale transition metal oxide, adding a dispersing agent, stirring for 20-40h, washing, centrifuging, vacuum drying, heating the obtained sample to 150-200 ℃ in a mixed gas of hydrogen and an inert gas, and heating for 1-4h to obtain a monoatomic noble metal/transition metal oxide composite material;
the dispersant is selected from polylysine; the precursor containing the noble metal is a salt of the noble metal;
the mass ratio of the precursor containing noble metal, the nano-scale transition metal oxide and the dispersing agent is 1-2:50-200:10-20.
2. The composite material of claim 1, wherein the metal oxide is in the form of nanorods, nanodiscs, nanoparticles, nanocubes.
3. The composite material of claim 2, wherein the metal oxide is in the form of nanorods having a length of 50-100nm and a diameter of 5-10nm.
4. The composite material of claim 3, wherein the XRD of the composite material has the following characteristic peaks: 28.6 +/-0.3 degrees, 33.8 +/-0.3 degrees, 47.5 +/-0.3 degrees and 52.1 +/-0.3 degrees.
5. The composite material according to claim 1, wherein the noble metal-containing precursor is a salt of an acid group containing a noble metal.
6. A process for the preparation of isopropanol by the catalytic hydrogenation of acetone and hydrogen, characterized in that a monatomic noble metal/transition metal oxide composite material according to any one of claims 1 to 5 is used as catalyst.
7. The method of claim 6, comprising the steps of: placing a single-atom noble metal/transition metal oxide composite material serving as a catalyst in a fixed bed reactor, and preparing isopropanol by taking acetone and hydrogen as raw materials through catalytic reaction; the reaction pressure is 0.1-1MPa, the reaction temperature is 50-100 ℃, the flow rate ratio of acetone to hydrogen is 1 -1 。
8. The process according to claim 7, wherein the reaction pressure is 0.1 to 0.2MPa, the reaction temperature is 60 to 70 ℃, the ratio of the flow rates of acetone and hydrogen is 1 to 4 to 6, and the liquid space velocity of acetone is 50 to 65h -1 。
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