CN111672518B - Porous titanium oxide shell assembled single-atom bimetallic magnetic catalyst, preparation and application - Google Patents

Porous titanium oxide shell assembled single-atom bimetallic magnetic catalyst, preparation and application Download PDF

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CN111672518B
CN111672518B CN201911283228.5A CN201911283228A CN111672518B CN 111672518 B CN111672518 B CN 111672518B CN 201911283228 A CN201911283228 A CN 201911283228A CN 111672518 B CN111672518 B CN 111672518B
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季生福
冉真真
刘建芳
王辰
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Beijing University of Chemical Technology
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Abstract

A magnetic catalyst of single-atom bimetal assembled by porous titanium oxide shells, preparation and application belong to the technical field of catalysts. In magnetic Fe 3 O 4 The surface of the nucleus is synthesized into a layer with hanging-NH 2 NH of (C) 2 -MILs-125 (Ti) shell layer, thereby bringing M metal ions into contact with shell NH 2 suspension-NH in MIL-125 (Ti) 2 Complexing to prepare M- & gt NH 2 ‑MIL‑125(Ti)@Fe 3 O 4 A nanosphere; drying and roasting to obtain M- & gt NH 2 MILs-125 (Ti) decomposes into porous titania shells, while the complexed metal M forms monoatoms confined in the porous titania shells. Has good methanol conversion rate and methyl formate selectivity, and the catalyst after reaction can be separated and recovered by using an external magnetic field.

Description

Porous titanium oxide shell assembled single-atom bimetallic magnetic catalyst, preparation and application
Technical Field
The invention relates to a porous titanium oxide shell assembled single-atom bimetallic magnetic catalyst, preparation and catalytic reaction for preparing methyl formate by one step from liquid-phase methanol, belonging to the technical field of single-atom metal magnetic catalysts and fine chemical engineering.
Background
Methanol is an important basic chemical raw material, and along with the surplus production capacity of methanol, the development of a methanol downstream product with high added value has important significance. Among the numerous downstream methanol products, methyl formate is an attractive green chemical product for high value-added downstream methanol. Methyl formate is an important organic synthesis intermediate and has been widely used in the fields of acetate fiber synthesis, medicine, pesticide and the like.
Recent studies have found that supported catalysts having catalytic activities such as Au and Pd can convert methanol in a liquid phase into methyl formate in one step. As found by Da Shi et al, au-Pd/TiO was used 2 The double-function catalyst takes liquid-phase methanol as raw material, and can generate methyl formate in one step under the condition of oxygen(Da Shi,Jianfang Liu,Rui Sun,Shengfu Ji,Scott M.Rogers,Bethany M.Connolly,Nikolaos Dimitratos,Andrew E.H.Wheatley.Preparation of bifunctional Au-Pd/TiO 2 catalysts and research on methanol liquid phase one-step oxidation to methyl format.catalysis today.2018,316, 206-213). Jianfang Liu et Al found that the use of a bifunctional catalyst with MIL-53 (Al) assembled Pd as the active component allowed the liquid phase methanol to be catalytically converted in one step in the presence of oxygen to methyl formate (Jian-Fang Liu, jin-Cheng Mu, rong-Xian Qin, formation-Fu Ji.Pd nanoparticles immobilized on MIL-53 (Al) as highly effective bifunctional catalysts for oxidation of liquid methanol to methyl format. Petroleum science 2019,16, 901-911). Compared with the traditional two-step method for producing methyl formate by using methanol, the method has the advantages of simple process flow, less waste liquid, low production cost and the like, but the content of noble metal catalytic active components is generally higher.
Recent researches show that the single-atom catalyst has extremely low loading of the metal active component, can greatly improve the utilization efficiency of metal Atoms, and the single-atom catalyst active component loaded on the metal oxide carrier is quite stable in the reaction, such as Xiong Zhou and the like on a single-layer CuO film carrier grown on the surface of a Cu (110) monocrystal, so that the high-dispersion Au single-atom catalyst is prepared, has extremely high stability in CO oxidation reaction (Xiong Zhou, qian Shen, kaidi Yuan, wenshao Yang, qiani Chen, zhenhua Geng, jialin Zhang, xiang Shao, wei Chen, guoqin Xu, xueming Yang, kai wu. Unlaveling Charge State of Supported Au Single-atom CO oxidation reduction J. Am. Soc.2018,140, 554-557), and provides a new idea for reducing the cost of the noble metal catalyst.
The MIL-125 (Ti) series of metal-organic framework materials are porous crystal materials which are produced by self-assembly of titanium metal ions and polybasic organic acid ligands, and have the characteristics of nanoscale framework-type regular pore channel structures, large specific surface area, porosity and the like. If titanium metal ions and containing-NH 2 Self-assembling the multi-element organic acid ligand of (C) can generate the ligand with suspension-NH 2 NH of (C) 2 MIL-125 (Ti) metal-organic framework materialWhich hangs-NH 2 Can also be coordinated and complexed with other metal ions to form NH 2 -MILs-125 (Ti) porous cavities form uniform metal-amino coordination complex metal ion nodes and when such NH with metal-amino coordination complex metal ion nodes 2 When MIL-125 (Ti) is pyrolyzed in air, the organic acid ligand is decomposed to release gases such as carbon dioxide, water and the like; NH (NH) 2 The metal ions of MILs-125 (Ti) can form an ordered porous network oxide; and the metal-amino coordination complex metal ion node can form high-dispersion monoatomic metal.
With superparamagnetism Fe 3 O 4 The magnetic catalyst is nuclear, and can be easily separated and recovered by using an external magnetic field after the liquid phase catalytic reaction is completed. We use superparamagnetism Fe 3 O 4 MIL-53 (Al) @ SiO prepared for cores 2 @Fe 3 O 4 The magnetic catalyst can be easily recovered and reused by adopting an external magnetic field in the Friedel-Crafts acylation reaction process, and has good performance after being repeatedly used for 5 times (Sai Jiang, junlei Yan, fabien Habimana, shengfu Ji.preparation of magnetically recyclable MIL-53 (Al) @ SiO) 2 @Fe 3 O 4 catalysts and their catalytic performance for Friedel-Crafts acylation reaction.Catalysis Today,2016,264,83-90)。
Based on these studies, the idea of the present invention is to first prepare Fe with superparamagnetism 3 O 4 A core; then at magnetic Fe 3 O 4 The surface of the nucleus is synthesized into a layer with hanging-NH 2 NH of (C) 2 -MIL-125 (Ti) shell layer to prepare magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere. Due to NH 2 MIL-125 (Ti) is a porous crystalline material produced by self-assembly of titanium metal ions and 2-aminoterephthalic acid, containing dangling-NH 2 Can be coordinated and complexed with metal ions such as Au, pd, pt, ag and the like, and is formed by NH 2 The porous cavity of MIL-125 (Ti) forms uniform Au-amino coordination, pd-amino coordination, pt-amino coordination, ag-amino coordination and other nodes, thereby preparing the magnetic Au (Pd, pt, ag) →NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere. Roasting under air atmosphere to make NH 2 MIL-125 (Ti) is decomposed into porous titanium oxide shell layers, and Au-amino coordination, pd-amino coordination, pt-amino coordination, ag-amino coordination and other nodes are limited in the porous titanium oxide shell layers to form highly dispersed monoatoms Au, pd, pt, ag, so that the magnetic Au (Pd, pt, ag) -TiO of methyl formate prepared by liquid-phase methanol catalytic conversion of the assembled monoatoms Au, pd, pt, ag of the porous titanium oxide shell layers 2 @Fe 3 O 4 Catalyst, and single-atom Au and single-atom bimetallic Au-Pd (Au-Pt, au-Ag) composed of single-atom Pd, pt and Ag 2 @Fe 3 O 4 The magnetic catalyst has better catalytic performance.
In the invention, due to the adoption of NH 2 suspension-NH in MIL-125 (Ti) 2 Preparing Au (Pd, pt, ag) to NH by adopting a method of complexing with Au, pd, pt, ag plasma 2 MIL-125 (Ti), thus Au (Pd, pt, ag). Fwdarw.NH during firing 2 While MILs-125 (Ti) is decomposed into ordered porous titania shells, the complexed Au, pd, pt, ag forms a single atom confined within the porous titania shells, such single-atom bimetallic Au-Pd, au-Pt, au-Ag have very good methanol selective oxidation properties, while porous titania rich acid centers have good catalytic condensation (or esterification) properties. Therefore, the magnetic Au-Pd (Au-Pt, au-Ag) →TiO prepared by the invention 2 @Fe 3 O 4 The catalyst has good catalytic action on formaldehyde (formic acid) generated by liquid phase selective oxidation of methanol, and also has good catalytic action on further condensation (esterification) of formaldehyde (formic acid) generated in the reaction process and methanol, and is a double-function catalyst for synthesizing methyl formate by one step of methanol, wherein the catalytic selective oxidation and the catalytic condensation (or esterification) reactions are coupled together.
The novel magnetic Au-Pd (Au-Pt, au-Ag) -TiO prepared by the method of the invention 2 @Fe 3 O 4 The double-function catalyst not only has good catalytic reaction performance of one-step catalytic conversion of liquid-phase methanol into methyl formate, but also can be easily separated from reactants by utilizing an external magnetic field, and isThe operation such as recovery and repeated recycling is relatively simple, so that the method has important industrial application value.
Disclosure of Invention
The invention aims to provide a difunctional catalyst for one-step catalytic conversion of methanol into methyl formate, a preparation method and application thereof.
The invention firstly prepares Fe with superparamagnetism 3 O 4 A core; then at magnetic Fe 3 O 4 The surface of the nucleus is synthesized into a layer with hanging-NH 2 NH of (C) 2 -MIL-125 (Ti) shell layer to prepare NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres; further, M (selected from Au, pd, pt, ag, etc.) metal ions and shell NH 2 suspension-NH in MIL-125 (Ti) 2 Complexing to prepare M- & gt NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere; drying and roasting to obtain M- & gt NH 2 MIL-125 (Ti) is decomposed into a porous titanium oxide shell layer, and simultaneously, the complexed metal M forms a monoatomic confined domain in the porous titanium oxide shell layer to prepare the magnetic M-TiO of methyl formate prepared by methanol liquid phase catalytic conversion of the monoatomic bimetallic M such as Au-Pd, au-Pt and Au-Ag assembled on the porous titanium oxide shell layer 2 @Fe 3 O 4 Such as Au-Pd (Au-Pt, au-Ag) →TiO 2 @Fe 3 O 4 A catalyst.
Further preferably, the magnetic Au-Pd (Au-Pt, au-Ag) →TiO of the present invention 2 @Fe 3 O 4 The preparation of the bifunctional catalyst specifically comprises the following steps:
(1) Magnetic Fe 3 O 4 Preparing particles:
preferably: feCl is added 3 ·6H 2 O is dissolved in deionized water to prepare FeCl 3 10 to 15 mass percent of solution. Sodium acetate is dissolved in glycol to prepare glycol solution with the mass content of 5-10% of sodium acetate. At 30 ℃ with N 2 Under the protection and stirring condition, feCl is added 3 Dropwise adding the solution into ethylene glycol solution of sodium acetate, wherein FeCl 3 And sodium acetate in a mass ratio of 3:1, after the dripping is finished, the mixed solution is put into an autoclave at 180 DEG CCrystallizing for 8 hours, naturally cooling, washing with deionized water and ethanol respectively, and vacuum drying at 60deg.C to obtain magnetic Fe 3 O 4 Particles;
(2) Magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 Preparing nanospheres: weighing a certain amount of prepared magnetic Fe 3 O 4 Adding the particles into ethanol to prepare Fe 3 O 4 Is denoted as A solution, fe 3 O 4 The mass concentration of (2) is 5% -10%; weighing a certain amount of isopropyl titanate (TPOT), dissolving in Dimethylformamide (DMF), and preparing a solution of the isopropyl titanate, namely a solution B, wherein the mass concentration of the isopropyl titanate is 5-10%; weighing a certain amount of 2-amino terephthalic acid (NH) 2 -H 2 BDC) is dissolved in Dimethylformamide (DMF) to prepare a solution of 2-amino terephthalic acid, which is marked as C solution, wherein the mass concentration of the 2-amino terephthalic acid is 5% -10%; adding liquid B and liquid C into liquid A at 30-60deg.C under stirring, wherein the amount of added liquid is Fe 3 O 4 : isopropyl titanate: the mass ratio of the 2-amino terephthalic acid is 1: (0.3-0.8): (0.2-0.6), stirring thoroughly, ultrasonic treating with 160-200W ultrasonic power for 30-50 min, placing the mixed solution into an autoclave, hydrothermal crystallizing at 130-150deg.C for 68-72 hr, naturally cooling, washing with DMF and methanol respectively, and vacuum drying at 60deg.C for 12 hr to obtain magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere;
(3) Magnetism M- & gtNH 2 -MIL-125(Ti)@Fe 3 O 4 Preparing nanospheres: weighing a certain amount of magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 Dispersing the nanospheres in deionized water to prepare NH 2 -MIL-125(Ti)@Fe 3 O 4 Dispersion, NH 2 -MIL-125(Ti)@Fe 3 O 4 The mass concentration is 20% -30%; weighing a certain amount of metal M salt, dissolving in deionized water to prepare a solution, wherein the mass percentage concentration of the metal M is preferably 0.1-0.5%; dropwise adding the metal M salt solution into the magnetic NH under stirring 2 -MIL-125(Ti)@Fe 3 O 4 Filling the nanosphere dispersionStirring separately, and then performing ultrasonic treatment for 30-50 min under the ultrasonic power of 60-100W to finish the metal M ions and the shell NH 2 suspension-NH in MIL-125 (Ti) 2 Is washed by deionized water and ethanol respectively, and is dried in vacuum, such as at 50 ℃ for 8 hours, thus obtaining the magnetic M- & gt NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere.
Weighing a certain amount of M metal salt, dissolving in deionized water, and preparing into one or more of the following solutions: weighing a certain amount of chloroauric acid (HAuCl) 4 ) Dissolving in deionized water to prepare a solution with the mass concentration of gold of 0.1% -0.5%; weighing a certain amount of palladium chloride (PdCl) 2 ) Dissolving in deionized water to prepare a palladium solution with the mass concentration of 0.1-0.5%; a certain amount of chloroplatinic acid (H) is weighed 2 PtCl 6 ·6H 2 O) is dissolved in deionized water to prepare a solution with the mass concentration of platinum of 0.1-0.5%; weighing a certain amount of silver nitrate (AgNO) 3 ) Dissolving in deionized water to prepare a solution with the mass concentration of silver of 0.1-0.5%.
(4) Magnetic M.fwdarw.TiO 2 @Fe 3 O 4 And (3) preparing a catalyst: weighing a certain amount of magnetism M-NH 2 -MIL-125(Ti)@Fe 3 O 4 The nanospheres are put into a tubular reactor, are subjected to temperature programming roasting from room temperature to (320 ℃ to 380 ℃) in an air atmosphere with certain flow, and are kept to be roasted for 4 to 6 hours at 320 ℃ to 380 ℃ to obtain the prepared magnetic M- & gt TiO 2 @Fe 3 O 4 A catalyst.
Wherein the metal M element is selected from at least one of Au, pd, pt, ag, preferably two, more preferably Au and any one of the other three, and the mass content of each metal can reach 0.1-0.5 wt% respectively.
The invention adopts the prepared magnetic M-TiO 2 @Fe 3 O 4 Such as Au-Pd (Au-Pt, au-Ag) →TiO 2 @Fe 3 O 4 The catalyst double-function catalyst is applied to the liquid phase selective oxidation coupling catalytic condensation (esterification) reaction of methanol, and methyl formate is synthesized by methanol in one step; the catalytic reaction is carried out in a kettle type stirring reactor, and the liquidMethanol is used as raw material, and magnetic M- & gt TiO is added 2 @Fe 3 O 4 Such as Au-Pd (Au-Pt, au-Ag) →TiO 2 @Fe 3 O 4 Double-function catalyst, and H which is equimolar with methanol is added 2 O 2 Catalytic reaction is carried out, the reaction temperature is preferably 70-80 ℃, and the product methyl formate is obtained in one step. The result shows that the prepared magnetic M-TiO 2 @Fe 3 O 4 Such as Au-Pd (Au-Pt, au-Ag) →TiO 2 @Fe 3 O 4 The bifunctional catalyst has good methanol conversion rate and methyl formate selectivity, and the catalyst after reaction can be separated and recovered by using an external magnetic field, so that the catalyst has good repeated recycling performance.
The magnetic M-TiO prepared by the invention 2 @Fe 3 O 4 Such as Au-Pd (Au-Pt, au-Ag) →TiO 2 @Fe 3 O 4 The bifunctional catalyst has the following remarkable advantages:
(1) In the magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 Shell layer NH of nanospheres 2 suspension-NH of MIL-125 (Ti) 2 In the coordination complexing process with Au, pd, pt, ag plasma, the Au, pd, pt, ag plasma and the suspension-NH are realized due to the adoption of an ultrasonic method 2 Is fast, coordination bond and stable, thereby being Au (Pd, pt, ag) to NH 2 When MIL-125 (Ti) is decomposed into porous titanium oxide, the formation of high-dispersion single-atom bimetallic Au-Pd, au-Pt, au-Ag and other catalytic active sites provides guarantee.
(2) Prepared magnetic M- & gtTiO 2 @Fe 3 O 4 Such as Au-Pd (Au-Pt, au-Ag) →TiO 2 @Fe 3 O 4 In the bifunctional catalyst, the catalytic active component is a high-dispersion single-atom bimetallic M such as Au-Pd, au-Pt and Au-Ag assembled in a porous titanium oxide shell layer, so that aggregation and loss of the catalytic active component in the reaction process can be avoided, the stability of the catalyst is greatly improved, the content of the catalytic active component Au, pd, pt, ag and the like is extremely low, and the utilization efficiency of the noble metal Au, pd, pt, ag is greatly improved.
(3) Prepared magnetic Au-Pd (Au-Pt, au-Ag) →TiO 2 @Fe 3 O 4 The double-function catalyst can couple the selective oxidation, condensation and esterification of methanol, so that the methanol is catalytically converted into methyl formate in one step, the conversion rate and the selectivity are good, the catalyst after the reaction can be separated, recovered and recycled by using an external magnetic field, and the separation cost of the liquid phase catalytic reaction is reduced, so that the catalyst has important industrial application value.
Detailed Description
The present invention is further described below with reference to examples, but the present invention is not limited thereto.
Example 1
(1) Weigh 17.6g FeCl 3 ·6H 2 O was dissolved in 82.4g deionized water to prepare a solution (FeCl) 3 Concentration of 10.5%), 3.5g of sodium acetate was weighed and dissolved in 46.5g of ethylene glycol to prepare a solution (concentration of 7.0%), and N was added dropwise at the same time with stirring at a water bath temperature of 30 ℃ 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, then naturally cooling, respectively washing three times with deionized water and ethanol, and drying for 8 hours at 60 ℃ in vacuum to obtain the magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.5g of particles are added into 91.5g of ethanol to prepare solution A (the concentration is 8.5 percent); 3.4g of isopropyl titanate (TPOT) was weighed and dissolved in 46.6g of Dimethylformamide (DMF) to prepare solution B (TPOT concentration 6.8%); 3.2g of 2-aminoterephthalic acid was dissolved in 46.8g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 6.4%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 160W ultrasonic power for 50min, placing the mixed solution into autoclave, hydrothermal crystallizing at 130deg.C for 72 hr, naturally cooling, washing with DMF and methanol for 3 times respectively, and vacuum drying at 60deg.C for 12 hr to obtain the final product (denoted 3.8 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weighing 0.34g of HAuCl 4 Dissolved in 99.66g deionized water to make 0.20wt% AuA solution; weigh 0.53g PdCl 2 Dissolving in 99.47g deionized water to prepare 0.32wt% Pd solution; 12.3g of the prepared 3.8NH were weighed out 2 -MIL-125(Ti)@Fe 3 O 4 Nanospheres are added into 50.0g of deionized water, then 10.0g of 0.20wt% Au solution is added, then 10.0g of 0.32wt% Pd solution is added, after full stirring, ultrasonic treatment is carried out for 45min under 60W ultrasonic power, so as to lead the shell layer NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinates and complexes with Au ions and Pd ions. Then washing with deionized water and ethanol, filtering, vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.20Au-0.32Pd→3.8NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of prepared 0.20Au-0.32 Pd-3.8 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 5 hours, and naturally cooling to room temperature to obtain the catalyst, namely the catalyst which is recorded as 0.20wt% Au-0.32wt% Pd- & gtTiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol was added followed by 0.20wt% Au-0.32wt% Pd.fwdarw.TiO 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 75 ℃. After completion of the reaction, the conversion to methanol was 60.6% and the selectivity to methyl formate was 92.3% as determined by chromatographic analysis. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 2
(1) Weigh 17.6g FeCl 3 ·6H 2 O was dissolved in 82.4g deionized water to prepare a solution (FeCl) 3 Concentration of 10.5%), 3.5g of sodium acetate was weighed and dissolved in 46.5g of ethylene glycol to prepare a solution (concentration of 7.0%), and N was added dropwise at the same time with stirring at a water bath temperature of 30 ℃ 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, and then naturallyCooling, washing with deionized water and ethanol for three times, vacuum drying at 60deg.C for 8 hr to obtain magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.3g of particles are added into 91.7g of ethanol to prepare solution A (the concentration is 8.3 percent); 3.7g of isopropyl titanate (TPOT) was weighed and dissolved in 46.3g of Dimethylformamide (DMF) to prepare a solution B (TPOT concentration 7.4%); 3.6g of 2-aminoterephthalic acid was dissolved in 46.4g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 7.2%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating under 180W ultrasonic power for 40min, placing the mixed solution into autoclave, hydrothermal crystallizing at 140deg.C for 70 hr, naturally cooling, washing with DMF and methanol for 3 times respectively, and vacuum drying at 60deg.C for 12 hr to obtain the final product (denoted 4.2 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weigh 0.68g of HAuCl 4 Dissolving in 99.32g deionized water to prepare 0.39wt% Au solution; weigh 0.35g PdCl 2 Dissolving in 99.65g deionized water to prepare 0.21wt% Pd solution; weigh 12.5g of the 4.2NH produced 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.39wt% Au solution, adding 10.0g of 0.21wt% Pd solution, stirring thoroughly, and performing ultrasonic treatment under 70W ultrasonic power for 45min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinates and complexes with Au ions and Pd ions. Then washing with deionized water and ethanol, filtering, vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.39Au-0.21Pd→4.2NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of the prepared 0.39Au-0.21 Pd-4.2 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 4 hours, and naturally cooling to room temperature to obtain the Au-0 with the concentration of 0.39wt%.21wt％Pd→TiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol was added followed by 0.39wt% Au-0.21wt% Pd.fwdarw.TiO 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 80 ℃. After completion of the reaction, the conversion to methanol was 62.2% and the selectivity to methyl formate was 93.6% as determined by chromatographic analysis. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 3
(1) 21.6g of FeCl was weighed out 3 ·6H 2 O was dissolved in 78.4g deionized water to prepare a solution (FeCl) 3 12.9% of concentration), 4.3g of sodium acetate was weighed and dissolved in 45.7g of ethylene glycol to prepare a solution (8.6% of concentration), and N was added dropwise at the same time under stirring at a water bath temperature of 30 ℃ 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, then naturally cooling, respectively washing three times with deionized water and ethanol, and drying for 8 hours at 60 ℃ in vacuum to obtain the magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.3g of particles are added into 91.7g of ethanol to prepare solution A (the concentration is 8.3 percent); 3.9g of isopropyl titanate (TPOT) was weighed and dissolved in 46.1g of Dimethylformamide (DMF) to prepare a solution B (TPOT concentration 7.8%); 3.7g of 2-aminoterephthalic acid was dissolved in 46.3g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 7.4%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 200W ultrasonic power for 30min, placing the mixed solution into autoclave, hydrothermal crystallizing at 150deg.C for 68 hr, naturally cooling, washing with DMF and methanol for 3 times respectively, and vacuum drying at 60deg.C for 12 hr to obtain the final product (denoted 4.4 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weighing 0.82g of HAuCl 4 Dissolving in 99.18g deionized water to prepare 0.47wt% Au solution; weigh 0.18g PdCl 2 Dissolving in 99.82g deionized water to prepare 0.11wt% Pd solution; weigh 12.7g of the 4.4NH produced 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.47wt% Au solution, adding 10.0g of 0.11wt% Pd solution, fully stirring, and performing ultrasonic treatment under 80W ultrasonic power for 40min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinates and complexes with Au ions and Pd ions. Then washing with deionized water and ethanol, filtering, vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.47Au-0.11Pd→4.4NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of prepared 0.47Au-0.11 Pd-4.4 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 4 hours, and naturally cooling to room temperature to obtain the catalyst, namely the catalyst which is recorded as 0.47wt% Au-0.11wt% Pd- & gtTiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol was added followed by 0.47wt% Au-0.11wt% Pd.fwdarw.TiO 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 70 ℃. After completion of the reaction, the conversion to methanol was 60.1% and the selectivity to methyl formate was 94.2% as determined by chromatographic analysis. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 4
(1) 21.6g of FeCl was weighed out 3 ·6H 2 O was dissolved in 78.4g deionized water to prepare a solution (FeCl) 3 12.9% of concentration), 4.3g of sodium acetate was weighed and dissolved in 45.7g of ethylene glycol to prepare a solution (8.6% of concentration), and N was added dropwise at the same time under stirring at a water bath temperature of 30 ℃ 2 In the protected reactor, after the dripping is finishedPlacing the mixed solution into an autoclave, crystallizing at 180deg.C for 8 hr, naturally cooling, washing with deionized water and ethanol respectively for three times, and vacuum drying at 60deg.C for 8 hr to obtain magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.2g of particles are added into 91.8g of ethanol to prepare solution A (the concentration is 8.2 percent); 4.1g of isopropyl titanate (TPOT) was weighed and dissolved in 45.9g of Dimethylformamide (DMF) to prepare solution B (TPOT concentration 8.2%); 3.9g of 2-aminoterephthalic acid was dissolved in 46.1g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 7.8%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 170W ultrasonic power for 40min, placing the mixed solution into autoclave, hydrothermal crystallizing at 140deg.C for 70 hr, naturally cooling, washing with DMF and methanol for 3 times respectively, and vacuum drying at 60deg.C for 12 hr to obtain the final product (denoted 4.6 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weighing 0.32g of HAuCl 4 Dissolving in 99.68g deionized water to prepare 0.18wt% Au solution; 1.13g of H was weighed out 2 PtCl 6 ·6H 2 O was dissolved in 98.87g deionized water to make a 0.42wt% Pt solution; weigh 12.8g of the prepared 4.6NH 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.18wt% Au solution, adding 10.0g of 0.42wt% Pt solution, fully stirring, and performing ultrasonic treatment under 100W ultrasonic power for 30min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinates and complexes with Au ions and Pt ions. Then washing with deionized water and ethanol, filtering, vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.18Au-0.42Pt→4.6NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of prepared 0.18Au-0.42 Pt-4.6 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, and heating to 350 ℃ at a speed of 1 ℃/min under an air flow of 1ml/minAt the temperature of 350 ℃ and kept for roasting for 5 hours, naturally cooling to the room temperature, namely the prepared catalyst is recorded as 0.18wt% Au-0.42wt% Pt-TiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol was added followed by 0.18wt% Au-0.42wt% Pt.fwdarw.TiO 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 75 ℃. After completion of the reaction, the conversion to methanol was determined by chromatographic analysis to be 61.8% and the selectivity to methyl formate was 93.5%. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 5
(1) Weigh 24.3g FeCl 3 ·6H 2 O is dissolved in 75.7g deionized water to prepare solution FeCl 3 Concentration of 14.6%), 4.9g of sodium acetate was weighed and dissolved in 45.1g of ethylene glycol to prepare a solution (concentration of 9.8%), and N was added dropwise at the same time with stirring at a water bath temperature of 30 ℃ 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, then naturally cooling, respectively washing three times with deionized water and ethanol, and drying for 8 hours at 60 ℃ in vacuum to obtain the magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.0g of particles are added into 92.0g of ethanol to prepare solution A (the concentration is 8.0 percent); 4.4g of isopropyl titanate (TPOT) is weighed and dissolved in 45.6g of Dimethylformamide (DMF) to prepare a solution B (the concentration of TPOT is 8.8%); 4.2g of 2-aminoterephthalic acid was dissolved in 45.8g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 8.4%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 190W ultrasonic power for 30min, placing the mixed solution into autoclave, hydrothermal crystallizing at 135deg.C for 72 hr, naturally cooling, washing with DMF and methanol for 3 times respectively, and vacuum drying at 60deg.C for 12 hr to obtain the final product (denoted 4.9 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weighing 0.61g of HAuCl 4 Dissolving in 99.39g deionized water to prepare 0.35wt% Au solution; 0.62g of H is weighed 2 PtCl 6 ·6H 2 O was dissolved in 99.38g deionized water to make a 0.23wt% Pt solution; weigh 12.9g of the prepared 4.9NH 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.35wt% Au solution, adding 10.0g of 0.23wt% Pt solution, stirring thoroughly, and performing ultrasonic treatment under 90W ultrasonic power for 35min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinates and complexes with Au ions and Pt ions. Then washing with deionized water and ethanol, filtering, vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.35Au-0.23Pt→4.9NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of the prepared 0.35Au-0.23 Pt-4.9 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 6 hours, and naturally cooling to room temperature to obtain the catalyst, namely the catalyst which is recorded as 0.35wt% Au-0.23wt% Pt-TiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol is added first, and then 0.35wt% Au-0.23wt% Pt- & gtTiO is added 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 80 ℃. After completion of the reaction, the conversion to methanol was 63.7% and the selectivity to methyl formate was 93.1% as determined by chromatographic analysis. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 6
(1) Weigh 24.3g FeCl 3 ·6H 2 O was dissolved in 75.7g deionized water to prepare a solution (FeCl) 3 Concentration 14.6%) was prepared by dissolving 4.9g of sodium acetate in 45.1g of ethylene glycol to give a solution (concentrate)9.8% of the temperature of the water bath at 30 ℃ and under stirring, N is added dropwise at the same time 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, then naturally cooling, respectively washing three times with deionized water and ethanol, and drying for 8 hours at 60 ℃ in vacuum to obtain the magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.4g of particles are added into 91.6g of ethanol to prepare solution A (the concentration is 8.4 percent); 3.5g of isopropyl titanate (TPOT) was weighed and dissolved in 46.5g of Dimethylformamide (DMF) to prepare a solution B (TPOT concentration 7.0%); 3.4g of 2-aminoterephthalic acid was dissolved in 46.6g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 6.8%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 180W ultrasonic power for 45min, placing the mixed solution into autoclave, hydrothermal crystallizing at 130deg.C for 68 hr, naturally cooling, washing with DMF and methanol for 3 times respectively, and vacuum drying at 60deg.C for 12 hr to obtain the final product (denoted 4.0 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weighing 0.71g of HAuCl 4 Dissolving in 99.29g deionized water to prepare 0.41wt% Au solution; 0.46g of H is weighed out 2 PtCl 6 ·6H 2 O was dissolved in 99.54g deionized water to make a solution of 0.17wt% Pt; weigh 12.4g of the prepared 4.0NH 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.41wt% Au solution, adding 10.0g of 0.17wt% Pt solution, stirring thoroughly, and performing ultrasonic treatment under 80W ultrasonic power for 50min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinates and complexes with Au ions and Pt ions. Then washing with deionized water and ethanol, filtering, vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.41Au-0.17Pt→4.0NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of the prepared 0.41Au-0.17 Pt-4.0 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 5 hours, and naturally cooling to room temperature to obtain the catalyst, namely the catalyst which is recorded as 0.41-0.17 wt% of Au, 0.17wt% of Pt and TiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol was added followed by 0.41wt% Au to 0.17wt% Pt.fwdarw.TiO 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 70 ℃. After completion of the reaction, the conversion to methanol was 62.5% and the selectivity to methyl formate was 92.8% as determined by chromatographic analysis. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 7
(1) Weigh 17.6g FeCl 3 ·6H 2 O was dissolved in 82.4g deionized water to prepare a solution (FeCl) 3 Concentration of 10.5%), 3.5g of sodium acetate was weighed and dissolved in 46.5g of ethylene glycol to prepare a solution (concentration of 7.0%), and N was added dropwise at the same time with stirring at a water bath temperature of 30 ℃ 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, then naturally cooling, respectively washing three times with deionized water and ethanol, and drying for 8 hours at 60 ℃ in vacuum to obtain the magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.3g of particles are added into 91.7g of ethanol to prepare solution A (the concentration is 8.3 percent); 3.8g of isopropyl titanate (TPOT) was weighed and dissolved in 46.2g of Dimethylformamide (DMF) to prepare a solution B (TPOT concentration 7.6%); 3.7g of 2-aminoterephthalic acid was dissolved in 46.3g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 7.4%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 160W ultrasonic power for 50min, placing the mixed solution into autoclave, hydrothermal crystallizing at 135deg.C for 70 hr, and naturallyCooling, washing with DMF and methanol for 3 times, vacuum drying at 60deg.C for 12 hr to obtain 4.3NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weigh 0.38g of HAuCl 4 Dissolving in 99.62g deionized water to prepare 0.22wt% Au solution; weigh 0.51g of AgNO 3 Dissolving in 99.49g deionized water to prepare 0.32wt% Ag solution; 12.6g of the prepared 4.3NH was weighed out 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.22wt% Au solution, adding 10.0g of 0.32wt% Ag solution, stirring thoroughly, and performing ultrasonic treatment under 70W ultrasonic power for 50min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinate and complex with Au ions and Ag ions. Washing with deionized water and ethanol, filtering, and vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.22Au-0.32Ag→4.3NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of the prepared 0.22Au-0.32 Ag-4.3 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 4 hours, and naturally cooling to room temperature to obtain the catalyst, namely the catalyst which is recorded as 0.22wt% Au-0.32wt% Ag- & gtTiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a kettle-type stirring reactor, methanol is added firstly, and then 0.22wt% of Au-0.32wt% of Ag-TiO is added 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 80 ℃. After completion of the reaction, the conversion to methanol was 62.9% and the selectivity to methyl formate was 93.1% as determined by chromatographic analysis. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 8
(1) 21.6g of FeCl was weighed out 3 ·6H 2 O was dissolved in 78.4g deionized water to prepare a solution(FeCl 3 12.9% of concentration), 4.3g of sodium acetate was weighed and dissolved in 45.7g of ethylene glycol to prepare a solution (8.6% of concentration), and N was added dropwise at the same time under stirring at a water bath temperature of 30 ℃ 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, then naturally cooling, respectively washing three times with deionized water and ethanol, and drying for 8 hours at 60 ℃ in vacuum to obtain the magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.2g of particles are added into 91.8g of ethanol to prepare solution A (the concentration is 8.2 percent); 4.0g of isopropyl titanate (TPOT) is weighed and dissolved in 46.0g of Dimethylformamide (DMF) to prepare a solution B (the concentration of TPOT is 8.0%); 3.9g of 2-aminoterephthalic acid was dissolved in 46.1g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 7.8%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 200W ultrasonic power for 30min, placing the mixed solution into autoclave, hydrothermal crystallizing at 160deg.C for 68 hr, naturally cooling, washing with DMF and methanol for 3 times respectively, and vacuum drying at 60deg.C for 12 hr to obtain the final product (denoted 4.5 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weighing 0.58g of HAuCl 4 Dissolving in 99.42g deionized water to prepare 0.33wt% Au solution; weigh 0.40g of AgNO 3 Dissolving in 99.60g deionized water to prepare 0.25wt% Ag solution; weigh 12.7g of the 4.5NH produced 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.33wt% Au solution, adding 10.0g of 0.25wt% Ag solution, stirring thoroughly, and performing ultrasonic treatment under 90W ultrasonic power for 35min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinate and complex with Au ions and Ag ions. Washing with deionized water and ethanol, filtering, and vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.33Au-0.25Ag→4.5NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4)Weighing 5.0g of the prepared 0.33Au-0.25 Ag-4.5 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 6 hours, and naturally cooling to room temperature to obtain the gold-silver alloy nano-powder which is recorded as 0.33wt% Au-0.25wt% Ag- & gtTiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol is added first, and then 0.33wt% Au-0.25wt% Ag- & gtTiO is added 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 75 ℃. After completion of the reaction, the conversion to methanol was determined by chromatography to be 61.7% and the selectivity to methyl formate was 93.3%. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.
Example 9
(1) Weigh 24.3g FeCl 3 ·6H 2 O was dissolved in 75.7g deionized water to prepare a solution (FeCl) 3 Concentration of 14.6%), 4.9g of sodium acetate was weighed and dissolved in 45.1g of ethylene glycol to prepare a solution (concentration of 9.8%), and N was added dropwise at the same time with stirring at a water bath temperature of 30 ℃ 2 Placing the mixed solution into an autoclave after the dripping is finished in a protected reactor, crystallizing for 8 hours at 180 ℃, then naturally cooling, respectively washing three times with deionized water and ethanol, and drying for 8 hours at 60 ℃ in vacuum to obtain the magnetic Fe 3 O 4 And (3) particles.
(2) Weighing the prepared magnetic Fe 3 O 4 8.1g of particles are added into 91.9g of ethanol to prepare solution A (the concentration is 8.1 percent); 4.3g of isopropyl titanate (TPOT) was weighed and dissolved in 45.7g of Dimethylformamide (DMF) to prepare solution B (TPOT concentration 8.6%); 4.1g of 2-aminoterephthalic acid was dissolved in 45.9g of Dimethylformamide (DMF) to prepare a solution C (NH) 2 -H 2 BDC concentration 8.2%). Adding liquid B and liquid C into liquid A at 40deg.C under stirring, stirring thoroughly, ultrasonic treating with 170W ultrasonic power for 50min, and mixingPlacing the solution into an autoclave, performing hydrothermal crystallization at 150deg.C for 70 hr, naturally cooling, washing with DMF and methanol respectively for 3 times, and vacuum drying at 60deg.C for 12 hr to obtain the product (denoted 4.8 NH) 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(3) Weighing 0.65g of HAuCl 4 Dissolving in 99.35g deionized water to prepare 0.37wt% Au solution; weigh 0.31g of AgNO 3 Dissolving in 99.69g deionized water to prepare 0.19wt% Ag solution; weigh 12.9g of the prepared 4.8NH 2 -MIL-125(Ti)@Fe 3 O 4 Adding magnetic nanospheres into 50.0g deionized water, adding 10.0g of 0.37wt% Au solution, adding 10.0g of 0.25wt% Ag solution, stirring thoroughly, and performing ultrasonic treatment under 100W ultrasonic power for 30min to obtain shell NH 2 suspension-NH of MIL-125 (Ti) 2 Fully coordinate and complex with Au ions and Ag ions. Washing with deionized water and ethanol, filtering, and vacuum drying at 50deg.C for 8 hr to obtain powder material of 0.33Au-0.25Ag→4.8NH 2 -MIL-125(Ti)@Fe 3 O 4 Magnetic nanospheres.
(4) Weighing 5.0g of the prepared 0.33Au-0.25 Ag-4.8 NH 2 -MIL-125(Ti)@Fe 3 O 4 Placing the magnetic nanospheres into a tubular reactor, heating to 350 ℃ at a speed of 1 ℃/min under the air flow of 1ml/min, keeping roasting at 350 ℃ for 5 hours, and naturally cooling to room temperature to obtain the catalyst, namely the catalyst which is recorded as 0.33wt% Au-0.25wt% Ag- & gtTiO 2 @Fe 3 O 4 Magnetic bifunctional catalysts.
In a stirred tank reactor, methanol is added first, and then 0.33wt% Au-0.25wt% Ag- & gtTiO is added 2 @Fe 3 O 4 Magnetic bifunctional catalyst, and H which is equimolar with methanol is added 2 O 2 The catalytic reaction was carried out at 80 ℃. After completion of the reaction, the conversion to methanol was 63.3% and the selectivity to methyl formate was 94.1% as determined by chromatographic analysis. The catalyst is recycled for 5 times, and the conversion rate of methanol and the selectivity of products are not obviously reduced.

Claims (4)

1. The method comprises the following steps ofThe application of the porous titanium oxide shell assembled single-atom bimetallic magnetic catalyst is characterized in that the application is applied to the one-step preparation of methyl formate from liquid-phase methanol; the catalytic reaction is carried out in a kettle type stirring reactor, liquid methanol is taken as a raw material, and magnetic M- & gt TiO is added 2 @Fe 3 O 4 Double-function catalyst, and H which is equimolar with methanol is added 2 O 2 Carrying out catalytic reaction to obtain a product methyl formate in one step; the preparation method of the catalyst comprises the following steps: in magnetic Fe 3 O 4 The surface of the nucleus is synthesized into a layer with hanging-NH 2 NH of (C) 2 -MIL-125 (Ti) shell layer to prepare magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere; thereby M metal ions and NH 2 suspension-NH in MIL-125 (Ti) shell 2 Complexing to prepare magnetic M- & gt NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere; drying and roasting to obtain M- & gt NH 2 MIL-125 (Ti) is decomposed into a porous titanium oxide shell layer, and simultaneously, the complexed metal M forms a single atom limited domain in the porous titanium oxide shell layer to prepare the magnetic M-TiO of methyl formate prepared by methanol liquid phase catalytic conversion of single atom bimetal assembled by the porous titanium oxide shell layer 2 @Fe 3 O 4 The catalyst, wherein M is Au-Pd, au-Pt or Au-Ag, and the mass content of each metal is 0.1wt% to 0.5wt% respectively; the method specifically comprises the following steps:
(1) Magnetic Fe 3 O 4 Preparing particles;
(2) Magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 Preparing nanospheres: weighing a certain amount of prepared magnetic Fe 3 O 4 Adding the particles into ethanol to prepare Fe 3 O 4 Is marked as A solution; weighing a certain amount of isopropyl titanate TPOT, dissolving in dimethylformamide DMF to prepare an isopropyl titanate solution, and marking the solution as solution B; weighing a certain amount of 2-amino terephthalic acid NH 2 -H 2 BDC is dissolved in dimethylformamide DMF to prepare a solution of 2-amino terephthalic acid, which is marked as solution C; adding liquid B and liquid C into liquid A at 30-60deg.C under stirring, wherein the amount of added liquid is Fe 3 O 4 : isopropyl titanate: 2-amino terephthalic acidThe mass ratio of (2) is 1: (0.3-0.8): (0.2-0.6), stirring thoroughly, ultrasonic treating with 160-200W ultrasonic power for 30-50 min, placing the mixed solution into an autoclave, hydrothermal crystallizing at 130-150deg.C for 68-72 hr, naturally cooling, washing with DMF and methanol respectively, and vacuum drying to obtain magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere;
(3) Magnetism M- & gtNH 2 -MIL-125(Ti)@Fe 3 O 4 Preparing nanospheres: weighing a certain amount of magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 Dispersing the nanospheres in deionized water to prepare magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere dispersion; weighing a certain amount of metal M salt, and dissolving the metal M salt in deionized water to prepare a metal M salt solution; dropwise adding the metal M salt solution into the magnetic NH under stirring 2 -MIL-125(Ti)@Fe 3 O 4 Stirring fully in the nanosphere dispersion, and then performing ultrasonic treatment for 30-50 min under the ultrasonic power of 60-100W to finish the metal M ions and NH 2 suspension-NH in MIL-125 (Ti) shell 2 Is subjected to coordination complexing, is respectively washed by deionized water and ethanol, and is dried in vacuum at 50 ℃ for 8 hours, thus obtaining the prepared magnetic M- & gt NH 2 -MIL-125(Ti)@Fe 3 O 4 A nanosphere;
(4) Magnetic M.fwdarw.TiO 2 @Fe 3 O 4 And (3) preparing a catalyst: weighing a certain amount of magnetism M-NH 2 -MIL-125(Ti)@Fe 3 O 4 The nanospheres are put into a tubular reactor, are subjected to temperature programming roasting from room temperature to 350 ℃ in an air atmosphere with certain flow, and are kept to be roasted for 4 to 6 hours at 350 ℃ to obtain the prepared magnetic M-TiO 2 @Fe 3 O 4 A catalyst.
2. The use according to claim 1, wherein in step (2), fe in solution a 3 O 4 The mass concentration of (2) is 5% -10%; the mass concentration of isopropyl titanate in the solution B is 5-10%; the mass concentration of the 2-amino terephthalic acid in the solution C is 5-10%.
3. The use according to claim 1, wherein step (3) is magnetic NH 2 -MIL-125(Ti)@Fe 3 O 4 NH in nanosphere Dispersion 2 -MIL-125(Ti)@Fe 3 O 4 The mass concentration is 20% -30%; the mass percentage concentration of the metal M in the metal M salt solution is 0.1-0.5%.
4. The use according to claim 1, wherein step (1) is magnetic Fe 3 O 4 Preparing particles: feCl is added 3 ·6H 2 O is dissolved in deionized water to prepare FeCl 3 A solution with the mass content of 10-15%; dissolving sodium acetate into ethylene glycol to prepare an ethylene glycol solution with the mass content of 5-10% of sodium acetate; at 30 ℃ with N 2 Under the protection and stirring condition, feCl is added 3 Dropwise adding the solution into ethylene glycol solution of sodium acetate, wherein FeCl 3 And sodium acetate in a mass ratio of 3:1, after the dripping is finished, the mixed solution is put into an autoclave, crystallized for 8 hours at 180 ℃, then naturally cooled, respectively washed by deionized water and ethanol, and dried in vacuum at 60 ℃ to obtain the prepared magnetic Fe 3 O 4 And (3) particles.
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