CN111250080A - Pd/MgO-Al2O3Catalyst, preparation method and application thereof - Google Patents

Pd/MgO-Al2O3Catalyst, preparation method and application thereof Download PDF

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CN111250080A
CN111250080A CN201811458857.2A CN201811458857A CN111250080A CN 111250080 A CN111250080 A CN 111250080A CN 201811458857 A CN201811458857 A CN 201811458857A CN 111250080 A CN111250080 A CN 111250080A
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salt
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mgo
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田志坚
杨林
潘振栋
马怀军
曲炜
李鹏
王小平
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Dalian Institute of Chemical Physics of CAS
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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
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
    • 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
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
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    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
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    • C07C67/36—Preparation of carboxylic acid esters by reaction with carbon monoxide or formates

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Abstract

The application discloses a preparation method of a catalyst, which is characterized by comprising the following steps: (1) dipping the first carrier in a solution containing a second carrier precursor salt, and roasting to obtain a composite carrier; (2) and (3) dipping the composite carrier in a solution containing active metal salt, and reducing to obtain the catalyst. The catalyst provided by the invention is gamma-Al2O3A carrier of composite structure composed of MgO and optionally gamma-Al2O3The large specific surface area and the weak alkaline property of the MgO surface; with gamma-Al2O3Compared with the carrier, the dispersity of palladium in the catalyst is obviously improved to 77.2 percent. Catalyst Performance evaluation results TableObviously, the Pd/MgO-Al prepared by the invention2O3The catalyst shows good catalytic activity in the reaction of synthesizing dimethyl oxalate by CO gas-phase coupling, and has industrial application prospect.

Description

Pd/MgO-Al2O3Catalyst, preparation method and application thereof
Technical Field
The application relates to a preparation method and application of a catalyst for synthesizing dimethyl oxalate by CO gas-phase coupling, belonging to the field of chemical catalysis.
Background
Dimethyl oxalate is an important organic chemical raw material and is commonly used for the preparation of various medicines, dyes, extracting agents, solvents and other chemical intermediates and the like. For example, hydrolysis of dimethyl oxalate can yield oxalic acid, which is aminated to form oxamide, a particularly important application being hydrogenation to ethylene glycol. At present, domestic ethylene glycol depends heavily on import, so that dimethyl oxalate is generated by coupling carbon monoxide, and then ethylene glycol is obtained by hydrogenation, and the C1 route for preparing ethylene glycol has important strategic significance and economic significance.
The traditional production method of dimethyl oxalate is esterification synthesis, a large amount of caustic soda, sulfuric acid and the like are consumed in the process, the problems of energy consumption and pollution are prominent, the production period is long, and the method is not suitable for the development of modern industry any more. The synthesis of dimethyl oxalate by carbon monoxide coupling is mainly divided into a liquid phase method and a gas phase method according to a reaction system. The gas phase method has the advantages of rich raw material sources, low price, mild reaction conditions, low energy consumption, simple equipment, environmental friendliness, high selectivity and the like. However, further improvement is required in terms of reduction in catalyst cost, improvement in catalyst activity, and the like.
Among the catalysts for synthesizing dimethyl oxalate by carbon monoxide gas-phase coupling, most of the currently reported catalysts use palladium as an active component and alumina as a carrier, and the catalysts in Chinese patents CN105381799A, CN105903466A, CN1059797717A and CN108246289A all use α -Al2O3The alumina is used as a carrier and is roasted at a high temperature of more than 1000 ℃ to obtain α -Al2O3The carrier can remove most surface acid centers, but causes the defects of low specific surface area of the carrier, easy agglomeration of active component palladium and low dispersion degree of palladium, Linqian et Al (α -Al)2O3The influence of the property of (2) on the catalysis of the CO coupling reaction by the supported palladium catalyst, published by catalysis 2006,27(10):911-]α -Al from different sources2O3Pd/α -Al used for catalyzing the reaction of preparing dimethyl oxalate by CO coupling is prepared for the carrier2O3Catalyst, wherein the dispersion degree of Pd metal is between 1.09 and 28.16 percent. Peng siyan et al [ MgO: an excellent catalyst support for CO oxidizing CO-catalytic oxygenate, Catal. Sci. Technol.,2014,4,1925]The Pd/MgO catalyst for catalyzing the reaction of preparing dimethyl oxalate by CO coupling is prepared by taking MgO as a carrier, and the catalytic activity of the weakly alkaline catalyst on the surface of the MgO is obviously improved, but the problem that the MgO as the carrier has low specific surface area and the catalyst is formed in the industrial application of a fixed bed reactor exists.
Other forms of carriers have been reported successively, and Chinese patent CN101993361B reports a kind of layered composite carrier, which is made of α -Al2O3At least one inert carrier selected from SiC, spinel, mullite and cordierite as core, and is prepared from α -Al2O3、θ-Al2O3、δ-Al2O3、γ-Al2O3Or at least one porous coating material in the molecular sieve is used as the shell, wherein the weight ratio of the shell to the inner core is 0.005-0.6: 1. The preparation of the layered composite carrier is complex, which is not beneficial to large-scale production and catalyst cost reduction. Chinese patent CN108187691 reports a carrier with a filled composite structure, the precursor of the carrier with a filled composite structure needs to be etched and fixed to obtain the carrier with a filled composite structure, Pd is used as an active component and Fe and Cu are used as additives to prepare a catalyst with a filled composite structure, and the preparation process is complex; . Chinese patent CN106745212A reports MTiO3The carrier (M represents any one of magnesium, calcium, zinc, cobalt and nickel), the carrier needs to be prepared by gel, dried, roasted and extruded into strips, and the preparation process is complicated. Chinese patent CN107456999A reports that the catalyst impregnated with palladium is reduced in situ by a porous manganese organic framework carrier, the carrier can be obtained only by reacting for 2-5 days by a solvothermal method, and the preparation process is complex and long in time. Some patents report nano-carriers, as reported in Chinese patent CN103055851AThe nano-magnesia is used as a carrier, and the CN104174393A carrier is ZnO of nano flowers (the average size is 2-4 mu m and the thickness of the nano sheets is about 30nm) assembled by porous nano sheets, but the problem of catalyst molding can exist in the industrial application of a fixed bed reactor.
Therefore, a new carrier is developed, the advantages of large specific surface area and weak alkalinity of the surface can be achieved, high dispersion of active components on the carrier can be realized, the catalyst cost is further reduced, the catalyst activity is improved, and the method has important significance for industrial application.
Disclosure of Invention
According to one aspect of the present application, there is provided a method of preparing a catalyst comprising a catalyst consisting of gamma-Al2O3And alkaline earth metal oxide, and active component Pd loaded on the surface of the composite structure carrier; the catalyst provided by the invention is gamma-Al2O3A carrier of composite structure composed of MgO and optionally gamma-Al2O3The large specific surface area and the weak alkaline property of the MgO surface; with gamma-Al2O3Compared with the carrier, the dispersity of palladium in the catalyst is obviously improved to 77.2 percent. The evaluation result of the catalyst performance shows that the Pd/MgO-Al prepared by the invention2O3The catalyst shows good catalytic activity in the reaction of synthesizing dimethyl oxalate by CO gas-phase coupling, and has industrial application prospect.
The preparation method of the catalyst is characterized by comprising the following steps:
(1) dipping the first carrier in a solution containing a second carrier precursor salt, and roasting to obtain a composite carrier; the solution containing the second carrier precursor salt comprises a Mg salt;
(2) and (3) dipping the composite carrier in a solution containing active metal salt, and reducing to obtain the catalyst.
Optionally, the first support is selected from γ -Al2O3、θ-Al2O3At least one of (1).
Optionally, the specific surface area of the first support is greater than 50m2/g。
Optionally, the specific surface area of the first support is 128.3m2/g、167.7m2/g、185.3m2/g、189.1m2/g、190.3m2(iv) g and any two values in the range between the specific surface areas thereof.
Alternatively,
the Mg salt is at least one selected from halide, nitrate, nitrite, sulfate, sulfite, phosphate and acetate of Mg.
Optionally, the concentration of the solution containing the second carrier precursor salt is 0.1-5 mol/L.
Optionally, the concentration of the solution containing the second carrier precursor salt is 1-3 mol/L.
Alternatively, the impregnation in step (1), the equivalent-volume impregnation, the excess impregnation, the multiple impregnation and the like of conventional impregnation methods are applicable.
Optionally, the first support comprises γ -Al2O3(ii) a The second carrier comprises MgO;
the molar weight of MgO and gamma-Al in the composite carrier2O3The specific surface area ratio of (A) is 3.12-11.7mmol/100m2Al2O3。
Optionally, the molar amount of MgO in the composite carrier is related to γ -Al2O3The specific surface area ratio of (A) is 3.90-7.80mmol/100m2Al2O3。
Optionally, the roasting conditions in step (1) are as follows: the temperature is 300-600 ℃, preferably 400-600 ℃;
the heating rate is 0.1-20 ℃/min, preferably 0.5-10 ℃/min;
the time is 1 to 24 hours, preferably 4 to 12 hours.
Optionally, the upper limit of the temperature of the calcination is selected from 400 ℃, 500 ℃, or 600 ℃; the lower limit is selected from 300 deg.C, 400 deg.C or 500 deg.C.
Optionally, the upper limit of the temperature rise rate of the roasting is selected from 0.5 ℃/min, 1 ℃/min, 5 ℃/min, 10 ℃/min, 15 ℃/min or 20 ℃/min; the lower limit is selected from 0.1 deg.C/min, 0.5 deg.C/min, 1 deg.C/min, 5 deg.C/min, 10 deg.C/min or 15 deg.C/min.
Alternatively, the upper limit of the time of calcination is selected from 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 18 hours, 20 hours, or 24 hours; the lower limit is selected from 1 hour, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 18 hours, or 20 hours.
Optionally, the solution containing the active metal salt in step (2) comprises a Pd salt;
the Pd salt is at least one selected from palladium chloride, palladium acetate and palladium nitrate;
preferably, the solution containing the active metal salt includes a solvent;
the solvent is at least one selected from deionized water, acetone, benzene and toluene.
Optionally, the reducing conditions in step (2) are: the temperature is 200-600 ℃, and the time is 2-6 hours.
Optionally, the reduction comprises hydrogen atmosphere reduction, hydrazine reduction, ethylene glycol reduction.
Optionally, in the reduction process of the catalyst in the step (2), conventional reduction methods such as hydrazine reduction, ethylene glycol reduction, reduction atmosphere reduction and the like are all applicable, preferably hydrogen atmosphere reduction, preferably the reduction temperature is 200-600 ℃; preferably, the reduction time is 2 to 6 hours.
Optionally, the catalyst comprises a composite support and an active metal; the active metal comprises Pd;
the active metal accounts for 0.01-0.5% of the composite structure carrier by mass.
Optionally, the dispersion of the active metal is 45.3% to 77.2%.
Optionally, the upper limit of the mass fraction of the active metal in the composite structure carrier is selected from 0.05%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%; the lower limit is selected from 0.01%, 0.05%, 0.1%, 0.2%, 0.3% or 0.4%.
Optionally, the upper limit of the dispersion of the active metal is selected from 58.3%, 60.4%, 75.1%, or 77.2%; the lower limit is selected from 45.3%, 58.3%, 60.4% or 75.1%.
Specifically, the application aims at the problems and provides a preparation method of a catalyst for synthesizing dimethyl oxalate by CO gas phase coupling, which is prepared from gamma-Al2O3And MgO, and a catalyst composed of active components loaded on the surface of the composite structure carrier, comprising the following preparation steps:
(1) mixing gamma-Al2O3Putting the mixture into one or more than two salt solutions of magnesium, calcium or barium, dipping, drying and roasting to obtain a composite structure carrier;
(2) and adding the composite structure carrier into a salt solution containing an active component Pd for dipping, drying and reducing after dipping to prepare the composite structure carrier supported active component palladium catalyst.
Al in the composite Carrier as described above2O3Has a specific surface area of more than 50m2/g，γ-Al2O3、θ-Al2O3Etc. can provide a large specific surface area, but α -Al2O3Too small a specific surface area is not suitable for this.
The amount of MgO in the composite carrier is 3.12-11.7mmol/100m2Al2O3Preferably 3.90 to 7.80mmol/100m2Al2O3At this time, the magnesia covers 1-2 layers on the surface of the alumina, which can cover the acid center on the surface of the alumina to provide a weakly alkaline carrier, but if the magnesia content is too high, the part of the channels of the carrier are blocked, the specific surface area is reduced, and the dispersion of palladium is not facilitated.
The active component is noble metal Pd, and the mass fraction of the active component in the composite structure carrier is 0.01-0.5%.
In the step (1), the magnesium salt is one or more soluble salts selected from halides, nitrates, nitrites, sulfates, sulfites, phosphates and acetates, the concentration of the salt solution is 0.1-3mol/L, preferably 1-3mol/L, and the conventional impregnation methods such as equal-volume impregnation, excess impregnation and multiple impregnation are all applicable.
The calcination temperature in the step (1) is 300-600 ℃, preferably 400-500 ℃, and the excessive calcination temperature can cause the reduction of the specific surface area of the carrier; the heating rate is 0.1-20 ℃/min, preferably 0.5-10 ℃/min; the calcination time is from 1 to 24 hours, preferably from 4 to 12 hours.
The Pd salt precursor in step (2) as described above is selected from any one of palladium chloride, palladium acetate, and palladium nitrate, preferably palladium acetate; the solvent is selected from any one of deionized water, acetone, benzene or toluene, and acetone is preferred.
In the reduction process of the catalyst in the step (2), conventional reduction methods such as hydrazine reduction, ethylene glycol reduction, reduction atmosphere reduction and the like are all suitable, preferably hydrogen atmosphere reduction, and the preferred reduction temperature is 200-600 ℃; preferably, the reduction time is 2 to 6 hours.
According to another aspect of the application, a method for synthesizing dimethyl oxalate by CO gas phase coupling is provided, which is characterized in that raw gas is introduced into a reactor filled with a catalyst and reacts with the catalyst in a contact way to obtain a product containing dimethyl oxalate; the feed gas comprises CO and methyl nitrite;
the catalyst is selected from at least one of the catalysts prepared according to the method.
Optionally, the reaction conditions are: the gas volume space velocity is 1000-8000 h-1(ii) a The reaction temperature is 80-200 ℃; the reaction pressure is 0.001-2 MPa.
Optionally, the reaction conditions are: gas volume space velocity 4000h-1(ii) a The reaction temperature is 125 ℃; the reaction pressure was 0.1 MPa.
The beneficial effects that this application can produce include:
1) the catalyst provided by the application can have gamma-Al2O3The catalyst has the advantages of large specific surface area and weak alkalinity of MgO surface, and can realize high dispersion of an active component Pd on a carrier, thereby reducing the cost of the catalyst and improving the activity of the catalyst, and has important significance for industrial application.
2) The catalyst provided by the application, and gamma-Al2O3Compared with the carrier, the dispersion degree of palladium in the catalyst is obviously improved and reaches as high as77.2 percent. The evaluation result of the catalyst performance shows that the Pd/MgO-Al prepared by the invention2O3The catalyst shows good catalytic activity in the reaction of synthesizing dimethyl oxalate by CO gas-phase coupling, and has industrial application prospect.
Drawings
FIG. 1 is a transmission electron micrograph of the catalyst obtained in example 2.
Fig. 2 is a transmission electron micrograph of the catalyst obtained in comparative example 1.
Detailed Description
The present application will be described in detail with reference to examples, but the present application is not limited to these examples.
The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.
The analysis method in the examples of the present application is as follows:
and carrying out morphology analysis by using a JEM-2100 transmission electron microscope.
The conversion, selectivity, in the examples of the present application were calculated as follows:
in the examples of the present application, the CO conversion and the dimethyl oxalate selectivity were calculated on the basis of carbon moles.
Example 1
5g of a specific surface area of 167.7m2G spherical gamma-Al2O3Soaking in 9.8ml magnesium nitrate solution for 8 hours, wherein the concentration of magnesium ions is 2.0mol/L, drying at 120 ℃, and then roasting at 550 ℃ for 4 hours in air atmosphere to obtain the magnesia-alumina composite structure carrier, wherein magnesia covers 1.5 layers of the surface of alumina.
0.5319g of palladium acetate was added to 50ml of acetone and then subjected to ultrasonic treatment to obtain a palladium acetate/acetone impregnation solution. Then, 5g of the magnesia-alumina composite carrier was impregnated in 4ml of the solution in a sealed state, and after 6 hours of the impregnation, acetone was distilled off. Finally reducing for 2 hours at 400 ℃ in hydrogen atmosphere to obtain 0.4 percent Pd/MgO-Al2O3A catalyst.
Example 2
5g of a specific surface area of 128.3m2(g) commercially available spherical Al2O3Soaking in 5ml magnesium nitrate solution for 8 hours, wherein the concentration of magnesium ions is 1.0mol/L, drying at 120 ℃, and then roasting at 400 ℃ for 12 hours in air atmosphere to obtain the magnesia-alumina composite structure carrier, wherein magnesia covers 1 layer of the surface of alumina.
0.1330g of palladium acetate was added to 50ml of acetone and then subjected to ultrasonic treatment to obtain a palladium acetate/acetone impregnation solution. Then, 5g of the magnesia-alumina composite carrier was impregnated in 4ml of the solution in a sealed state, and after 6 hours of the impregnation, acetone was distilled off. Finally reducing for 6 hours at 200 ℃ in hydrogen atmosphere to obtain 0.1 percent Pd/MgO-Al2O3A catalyst.
Example 3
5g of a specific surface area of 189.1m2G spherical gamma-Al2O3Soaking in 7.4ml magnesium nitrate solution for 8 hours, wherein the concentration of magnesium ions is 1.0mol/L, drying at 120 ℃, and then roasting at 600 ℃ for 4 hours in air atmosphere to obtain the magnesia-alumina composite structure carrier, wherein magnesia covers 1 layer of the surface of alumina.
0.6650g of palladium acetate was added to 50ml of acetone and then subjected to ultrasonic treatment to obtain a palladium acetate/acetone impregnation solution. Then, 5g of the magnesia-alumina composite carrier was impregnated in 4ml of the solution in a sealed state, and after 6 hours of the impregnation, acetone was distilled off. Finally reducing for 2 hours at 600 ℃ in hydrogen atmosphere to obtain 0.5 percent Pd/MgO-Al2O3A catalyst.
Example 4
5g of a specific surface area of 190.3m2G spherical gamma-Al2O3Soaking in 4.9ml magnesium acetate solution for 8 hours, wherein the concentration of magnesium ions is 3.0mol/L, drying at 120 ℃, and then roasting at 600 ℃ for 4 hours in air atmosphere to obtain the magnesia-alumina composite structure carrier, wherein magnesia covers 2 layers of the surface of alumina.
0.1330g of palladium acetate was added to 50ml of acetone and then subjected to ultrasonic treatment to obtain a palladium acetate/acetone impregnation solution. Then, 5g of the magnesia-alumina composite carrier was impregnated in 4ml of the solution in a sealed state, and after 6 hours of the impregnation, acetone was distilled off. Finally reducing for 4 hours at 400 ℃ in hydrogen atmosphere to obtain 0.1 percent Pd/MgO-Al2O3A catalyst.
Example 5
5g of a specific surface area of 185.3m2G spherical gamma-Al2O3Soaking in 4.9ml magnesium sulfate solution for 8 hours, wherein the concentration of magnesium ions is 3.0mol/L, drying at 120 ℃, and then roasting at 400 ℃ for 8 hours in air atmosphere to obtain the magnesia-alumina composite structure carrier, wherein magnesia covers 2 layers on the surface of alumina.
0.6650g of palladium acetate was added to 50ml of acetone and then subjected to ultrasonic treatment to obtain a palladium acetate/acetone impregnation solution. Then, 5g of the magnesia-alumina composite carrier was impregnated in 4ml of the solution in a sealed state, and after 6 hours of the impregnation, acetone was distilled off. Finally, hydrazine hydrate is used for reduction to prepare 0.5 percent Pd/MgO-Al2O3A catalyst.
Comparative example 1
0.5319g of palladium acetate was added to 50ml of acetone and then subjected to ultrasonic treatment to obtain a palladium acetate/acetone impregnation solution. Then, 5g of the solution was hermetically immersed in 4ml of the solution to have a specific surface area of 167.7m2A spherical alumina carrier, impregnated for 6 hours and then distilled to remove acetone. Finally reducing for 2 hours at 400 ℃ in hydrogen atmosphere to obtain 0.4 percent Pd/Al2O3A catalyst.
The catalysts prepared in examples 1-5 and comparative example 1 were tested for dispersion of Pd by CO pulse adsorption, the dispersion results are shown in table 1.
The catalysts prepared in examples 1-5 and comparative example 1 were applied to the reaction of synthesizing dimethyl oxalate by gas phase coupling of CO. The performance evaluation of the catalyst adopts a fixed bed reactor, the inner diameter of the fixed bed reactor is 12mm, the length of the fixed bed reactor is 600mm, 4mL of catalyst samples are filled, a small amount of quartz sand is filled at the upper part and the lower part of the fixed bed reactor, the composition (volume ratio) of raw material gas is 21% CO, 16% MN (methyl nitrite), the rest is nitrogen, and the gas airspeed is 4000h-1The reaction pressure was 0.1MPa, and the catalyst performance was examined at a reaction temperature of 125 ℃. The reaction results are shown in Table 1.
TABLE 1 test results of dispersion of metallic Pd in catalyst and evaluation results of catalyst performance
Figure BDA0001888256930000091
The morphology characterization of the catalysts prepared in examples 1 to 5 and comparative example 1 is performed, fig. 1 is the morphology of the catalyst prepared in example 1, and as can be seen from fig. 1, the particle size distribution of the active component is uniform between 1 nm and 3nm and is uniformly dispersed on the carrier. The morphology of the catalysts prepared in examples 2 to 5 was similar to that of example 1.
The morphology of the catalyst prepared in comparative example 1 is shown in fig. 2, and fig. 2 shows that the active component has non-uniform particle size distribution and particle aggregation phenomenon.
Although the present application has been described with reference to a few embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

Claims (10)

1. A preparation method of a catalyst is characterized by comprising the following steps:
(1) dipping the first carrier in a solution containing a second carrier precursor salt, and roasting to obtain a composite carrier; the solution containing the second carrier precursor salt comprises a Mg salt;
(2) and (3) dipping the composite carrier in a solution containing active metal salt, and reducing to obtain the catalyst.
2. The method of claim 1, wherein the first support is selected from γ -Al2O3、θ-Al2O3At least one of;
preferably, the specific surface area of the first support is greater than 50m2/g。
3. The method of claim 1,
the Mg salt is selected from at least one of halide, nitrate, nitrite, sulfate, sulfite, phosphate and acetate of Mg;
preferably, the concentration of the solution containing the second carrier precursor salt is 0.1-5 mol/L;
preferably, the concentration of the solution containing the second carrier precursor salt is 1-3 mol/L.
4. The method of claim 1, wherein the first support comprises γ -Al2O3(ii) a The second carrier comprises MgO;
the molar weight of MgO and gamma-Al in the composite carrier2O3The specific surface area ratio of (A) is 3.12-11.7mmol/100m2Al2O3；
Preferably, the molar amount of MgO in the composite carrier is equal to that of gamma-Al2O3The specific surface area ratio of (A) is 3.90-7.80mmol/100m2Al2O3。
5. The method of claim 1, wherein the firing conditions in step (1) are: the temperature is 300-600 ℃, preferably 400-600 ℃;
the heating rate is 0.1-20 ℃/min, preferably 0.5-10 ℃/min;
the time is 1 to 24 hours, preferably 4 to 12 hours.
6. The method of claim 1, wherein the solution containing an active metal salt in step (2) comprises a Pd salt;
the Pd salt is at least one selected from palladium chloride, palladium acetate and palladium nitrate;
preferably, the solution containing the active metal salt includes a solvent;
the solvent is at least one selected from deionized water, acetone, benzene and toluene.
7. The method according to claim 1, wherein the reducing conditions in step (2) are: the temperature is 200-600 ℃, and the time is 2-6 hours;
preferably, the reduction comprises hydrogen atmosphere reduction, hydrazine reduction, ethylene glycol reduction.
8. The method of claim 1, wherein the catalyst comprises a composite support and an active metal; the active metal comprises Pd;
the active metal accounts for 0.01 to 0.5 percent of the mass fraction of the composite structure carrier;
preferably, the dispersion degree of the active metal is 45.3% to 77.2%.
9. A method for synthesizing dimethyl oxalate by CO gas phase coupling is characterized in that raw gas is introduced into a reactor filled with a catalyst and contacts with the catalyst for reaction to obtain a product containing dimethyl oxalate; the feed gas comprises CO and methyl nitrite;
the catalyst is selected from at least one of the catalysts prepared according to the process of any one of claims 1 to 8.
10. The process according to claim 9, characterized in that the reaction conditions are: the gas volume space velocity is 1000-8000 h-1(ii) a The reaction temperature is 80-200 ℃; the reaction pressure is 0.001-2 MPa.
CN201811458857.2A 2018-11-30 2018-11-30 Pd/MgO-Al2O3Catalyst, preparation method and application thereof Pending CN111250080A (en)

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CN111939929A (en) * 2020-09-08 2020-11-17 安徽师范大学 Binary metal nano Pd/alumina catalyst and preparation method thereof, and method for preparing dimethyl oxalate through CO coupling oxidation
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CN111939929A (en) * 2020-09-08 2020-11-17 安徽师范大学 Binary metal nano Pd/alumina catalyst and preparation method thereof, and method for preparing dimethyl oxalate through CO coupling oxidation
CN112121793A (en) * 2020-09-17 2020-12-25 万华化学集团股份有限公司 Catalyst for preparing citronellal by citral hydrogenation, preparation method of catalyst, and method for preparing citronellal by citral hydrogenation
CN113750993A (en) * 2021-10-15 2021-12-07 中国科学院大连化学物理研究所 Palladium monoatomic catalyst, preparation method thereof and application thereof in Suzuki coupling reaction

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