CN107715877B

CN107715877B - Hollow mesoporous carbon microsphere shell confinement copper catalyst and preparation method and application thereof

Info

Publication number: CN107715877B
Application number: CN201710958424.2A
Authority: CN
Inventors: 李忠; 张国强; 贾东森; 闫俊芬; 王佳君
Original assignee: Taiyuan University of Technology; Shanxi Luan Mining Group Co Ltd
Current assignee: Taiyuan University of Technology; Shanxi Luan Mining Group Co Ltd
Priority date: 2017-10-16
Filing date: 2017-10-16
Publication date: 2021-02-19
Anticipated expiration: 2037-10-16
Also published as: CN107715877A

Abstract

A hollow mesoporous carbon microsphere shell confinement copper catalyst is characterized in that the catalyst consists of carrier hollow mesoporous shell carbon spheres and an active component copper, wherein the weight percentage of copper is 7.0-11.5 wt%, and the weight percentage of carbon is 88.5-93.0 wt%; the specific surface area is 480-1240 m²A pore volume of 1.7-2.3 cm³The most probable pore diameter of the shell layer is 3.5-8.5 nm; the average cavity size of the carbon spheres is 160-200 nm, the average thickness of the shell layer is 60-180 nm, and the average particle size is 280-560 nm. The invention has the advantages of high activity and stability.

Description

Hollow mesoporous carbon microsphere shell confinement copper catalyst and preparation method and application thereof

Technical Field

The invention relates to a hollow mesoporous carbon microsphere shell confinement copper catalyst, a preparation method and application thereof.

Background

Dimethyl carbonate (DMC), a non-toxic, environmentally friendly, and versatile chemical feedstock. The molecular structure of the compound contains functional groups such as carbonyl, methyl, methoxyl and the like, has various reaction performances, and is an important organic synthesis intermediate; the electrolyte can also be used as the electrolyte of a lithium ion battery, a gasoline additive for reducing pollutant emission and the like, so the electrolyte has good development prospect and market potential.

The current DMC production methods include phosgene, transesterification, methanol oxidative carbonylation, methanol direct, and urea alcoholysis. The methanol oxidation carbonylation method has good application prospect due to the advantages of high selectivity, high atom utilization rate, low production cost, good activity, environmental protection and the like.

Research shows that Cu in copper species loaded in molecular sieve or carbon material carrier^ⅠAre the major active species. The density functional theory calculation shows that Cu₂The O (111) crystal face is favorable for the decomposition of methanol to generate methoxyl, and the oxygen defect site is favorable for O₂The adsorption and desorption of (b) promotes the formation of DMC.

Patent CN102600843A, CN102872879A reports that the activated carbon supported nano copper catalyst has higher catalytic activity in the synthesis of dimethyl carbonate by methanol gas phase oxidation and carbonylation. However, the activated carbon mainly has a microporous structure, a large number of active nano copper species are mainly dispersed on the surface of the carrier, the surface energy is high, and the active carbon is easy to agglomerate and grow in the reaction process, so that the catalytic activity is reduced, and the stability of the catalyst is reduced.

Patent CN103599781A, CN104324757A reports that nano-copper particles are located in a hollow carbon sphere cavity structure to construct a core-shell structure, and a core-shell carbon-coated nano-copper catalyst is prepared, so as to improve catalytic activity and stability of the catalyst. But since the copper species in the catalyst is mainly Cu⁰Instead of Cu^ⅠResulting in lower catalytic activity; and the volume of the carbon sphere cavity is too large, nano copper species can still agglomerate in the reaction process, so that the stability of the catalyst is reduced.

Disclosure of Invention

The invention aims to provide a hollow mesoporous carbon microsphere shell confinement copper catalyst with high activity and stability, a preparation method and application in synthesis of dimethyl carbonate.

In view of the defect that copper nanoparticles are easy to agglomerate in the active carbon loaded nano copper catalyst and the core-shell carbon coated nano copper catalyst, the invention takes tetraethoxysilane, resorcinol and formaldehyde as main raw materials, prepares hollow carbon spheres with shell layers rich in a large number of mesopores by solution preparation, hydrothermal synthesis and carbonization etching, uses the hollow carbon spheres as a carrier of the catalyst, and then uses an ultrasonic-assisted isometric immersion method to load copper species into the shell mesopores to prepare the shell-layer limited copper catalyst of the hollow mesoporous carbon microsphere, which is used for the reaction of synthesizing dimethyl carbonate by methanol gas phase oxidation and carbonylation. The catalyst prepared by the method has the characteristics of adjustable carbon sphere particle size and shell mesoporous aperture, and active species nano copper particles are uniformly dispersed in shell mesoporous, and have small particle size, strong anti-agglomeration capability, high catalytic activity and good stability.

The catalyst consists of a carrier hollow mesoporous shell carbon sphere and an active component copper, wherein the weight percentage of the copper is 7.0-11.5 percent, and the weight percentage of the carbon is 88.5-93.0 percent; the specific surface area is 480-1240 m²A pore volume of 1.7-2.3 cm³The most probable pore diameter of the shell layer is 3.5-8.5 nm; the average cavity size of the carbon spheres is 160-200 nm, the average thickness of the shell layer is 60-180 nm, and the average particle size is 280-560 nm.

The preparation method of the catalyst comprises the following steps:

(1) stirring absolute ethyl alcohol, deionized water and 25wt% ammonia water at 25-30 ℃ for 5-10 min, adding tetraethoxysilane, and continuously stirring for 6-8 h to form a solid silicon ball template agent; wherein the weight ratio of absolute ethyl alcohol: deionized water: ammonia water: the volume ratio of the ethyl orthosilicate is 80-100: 16-20: 2.1-2.3: 3-4;

(2) adding deionized water according to the mass ratio of the deionized water to the CTAC of 2-4: 1, stirring to prepare a CTAC aqueous solution, adding the deionized water and the absolute ethyl alcohol into the solid silica sphere sol according to the volume ratio of the deionized water to the absolute ethyl alcohol of 4-6: 1, stirring to obtain a mixed solution, then adding the CTAC aqueous solution into the mixed solution dropwise under a violent stirring state, adding resorcinol, finally adding formaldehyde and ethyl orthosilicate, stirring at 25-30 ℃ for 10-12 hours to obtain a carbon-silicon polymer mixed solution, wherein the CTAC: anhydrous ethanol: solid silica sphere sol: resorcinol: formaldehyde: the molar ratio of the ethyl orthosilicate is 3.5-10.5: 110-120: 2-2.5: 1-3: 4-12: 2-6.

(3) Heating the carbon-silicon polymer mixed solution at 100-200 ℃ for 18-30 h to form a carbon-silicon polymer microsphere precursor, then carrying out centrifugal separation, centrifugally washing the precipitate with deionized water for 2-5 times, and drying at 40-60 ℃ for 18-24 h to obtain carbon-silicon polymer microsphere precursor powder;

(4) placing the precursor powder in a tubular high-temperature furnace, and inputting nitrogen gas with the volume of 20-30 mL/(g)_catMin), heating at the rate of 4-6 ℃/min, heating at the temperature of 700-800 ℃, keeping at a constant temperature for 3-5 h, then naturally cooling to room temperature to complete the carbonization process to generate carbon-silicon polymer microspheres, adding carbon-silicon polymer microsphere powder into a hydrofluoric acid aqueous solution with the weight of 5-10 wt%, standing for 18-24 h to remove silicon dioxide, centrifugally washing the precipitate with deionized water for 2-5 times, drying the precipitate at the temperature of 70-90 ℃ for 10-14 h, and drying to obtain the mesoporous shell layer carbon spheres;

(5) weighing Cu (NO)₃)₂·3H₂And O, adding deionized water, stirring to obtain a copper nitrate solution with the concentration of 0.176-0.310 mol/L, weighing hollow mesoporous shell carbon spheres according to the composition of the catalyst, adding the hollow mesoporous shell carbon spheres into the solution, uniformly stirring, and placing the solution in an ultrasonic reactor for ultrasonic treatment for 50-70 min, wherein the ultrasonic frequency is 80-100 KHz. Drying the mixture subjected to ultrasonic treatment at the temperature of 30-50 ℃ for 18-24 h to obtain a catalyst precursor;

(6) putting the catalyst precursor into a tubular high-temperature furnace, and inputting nitrogen gas by 20-30 mL/(g)_catMin), the heating rate is 2-4 ℃/min, the heating temperature is 300-400 ℃, the constant temperature is kept for 3-5 h, so that copper species in the precursor react with the carbon carrier at high temperature in a nitrogen atmosphere, and Cu reacts^ⅡReduction to Cu^ⅠAnd naturally cooling the product to room temperature to obtain the hollow mesoporous carbon microsphere shell confinement copper catalyst.

The catalyst of the invention is used for the reaction of synthesizing dimethyl carbonate by methanol gas phase oxidation carbonylation, and the reaction steps and the process conditions are as follows:

(1) weighing quartz sand according to the mass ratio of the catalyst to the quartz sand of 1: 5-10, uniformly mixing the two, putting the mixture into a fixed bed tubular reactor, and heating a catalyst bed layer in the reactor to 120-140 ℃ in a nitrogen atmosphere.

(2) The raw materials are CH according to the molar ratio₃OH∶CO∶O₂The components of 2-6: 6-18: 1-3 enter a preheating furnace, are heated to 110-130 ℃ by the preheating furnace and then enter a reactor, and the volume space velocity of a feeding gas phase is 5840-17520 h^-1The reaction is carried out at the reaction temperature of 120-140 ℃ and under the pressure of normal pressure-1.0 MPa.

Product storage

The catalyst of the invention should be stored in a closed and light-proof way, and should be waterproof, sun-proof and acid, alkali and salt corrosion resistant, the storage temperature is 15-25 ℃, and the relative humidity is less than or equal to 10%.

Detection, analysis, characterization

The morphology, the chemical and physical properties and the catalytic activity of the prepared hollow mesoporous carbon microsphere shell confinement copper catalyst are detected, analyzed and characterized. Analyzing the element composition of the catalyst by using an Atomic Absorption Spectrometer (AAS); detecting the texture property and the pore structure of the catalyst by using a physical adsorption instrument; the morphology of the catalyst and the degree of dispersion of the active species were observed with a transmission electron microscope, TEM.

Compared with the prior art, the invention has the following advantages:

the invention aims at the defect of preparation of a copper-supported catalyst of a carbon material synthesized by dimethyl carbonate, adopts hollow carbon spheres with shells rich in a large number of mesopores as a carrier of the catalyst, and uses an ultrasonic-assisted isometric impregnation method to load copper species into the mesopores of the shells to prepare the limited-area copper-based catalyst. The preparation method is simple to operate, advanced in process and capable of adjusting the particle size of the carbon spheres and the mesoporous aperture of the shell layer, the confinement effect of the mesoporous shell layer of the carbon spheres enables the active species nano copper particles to be uniformly dispersed in the mesoporous of the shell layer, the particle size is small, the agglomeration resistance is high, and compared with the traditional active carbon loaded nano copper catalyst and the core-shell carbon coated nano copper catalyst, the agglomeration of copper species can be effectively avoided, so that the catalytic activity and the stability are obviously improved. The methanol conversion rate is 12-20%, the DMC selectivity is 85-93%, and the space-time yield of DMC reaches 350-600 mg g^-1·h^-1The catalytic activity can be stably maintained for 80-120 h.

Drawings

FIG. 1 is a nitrogen adsorption and desorption isotherm diagram of a copper catalyst in a shell confinement of a hollow mesoporous carbon microsphere prepared in examples 2, 4 and 5 of the present invention.

Fig. 2 is a pore size distribution diagram of the hollow mesoporous carbon microsphere shell confinement copper catalyst prepared in the

embodiments

2, 4 and 5 of the present invention.

Detailed Description

The invention is further illustrated but not limited by the following specific examples.

Comparative example 1

The method comprises the following specific steps of catalyzing methanol oxidative carbonylation to synthesize dimethyl carbonate by using a core-shell carbon-coated nano copper catalyst I:

(1) preparation of copper oleate complex

Weighing 2.42g of copper nitrate and 6.09g of sodium oleate, weighing 20mL of absolute ethyl alcohol, 15mL of deionized water and 35mL of hexane, adding into a three-neck flask, heating the three-neck flask to 70 ℃, and stirring for 2 hours to form a complex liquid. Adding the complexing solution into a separating funnel, separating, standing for 10min, and keeping an upper organic layer after separating; and adding the organic layer into a beaker, adding 100mL of deionized water, stirring and washing for 10min, adding the washing solution into a separating funnel, separating, standing for 10min, and remaining the upper organic layer after separating. Drying the organic layer in an oven at 50 deg.C for 5 hr to obtain copper oleate complex (C)₁₈H₃₃O₂)₂Cu。

(2) Preparing copper oleate emulsion

Weighing 0.12g of copper oleate complex, weighing 5mL of deionized water, adding into a beaker, and stirring for 5min to obtain copper oleate emulsion.

(3) Preparing an aqueous glucose solution

Weighing 0.9g of glucose, weighing 100mL of deionized water, adding into a beaker, and stirring for 5min to obtain a 0.05mol/L glucose aqueous solution.

(4) Preparing mixed solution

Placing the prepared glucose aqueous solution and copper oleate emulsion in a beaker, then placing in a water bath kettle for heating, wherein the heating temperature is 30 ℃, and stirring is carried out for 40min at the rotating speed of 150r/min, thus obtaining the mixed emulsion.

(6) Hydrothermal synthesis

And transferring the mixed emulsion into a polytetrafluoroethylene container, placing the container into a reaction kettle, sealing the reaction kettle, placing the reaction kettle into an oven, heating the reaction kettle at 180 ℃ for 4 hours, and carrying out hydro-thermal synthesis to form a carbon-coated copper precursor. After hydrothermal synthesis, stopping heating, and cooling the reaction kettle to room temperature along with the furnace.

(7) Centrifugal separation

Opening the kettle, transferring the suspension in the polytetrafluoroethylene container into a centrifugal tube, performing centrifugal separation at a separation rotation number of 8000r/min for 10min, retaining the precipitate after separation, and discarding the supernatant.

(8) Washing and suction filtering

Placing the precipitate in a beaker, adding 100mL of deionized water, stirring and washing for 5min, and then performing suction filtration by using three layers of medium-speed qualitative filter paper to obtain a product filter cake; and placing the product filter cake in a beaker, adding 100mL of absolute ethyl alcohol, stirring and washing for 5min, and performing suction filtration by using three layers of medium-speed qualitative filter paper to obtain the product filter cake.

(9) Drying

And (3) drying the product filter cake in an oven at the drying temperature of 50 ℃ for 6h to obtain carbon-coated copper precursor powder.

(10) Carbonization and reduction

Placing the carbon-coated copper precursor powder in a quartz boat, then placing the quartz boat in a quartz heating tube of a tube type high-temperature furnace, inputting nitrogen at a nitrogen input speed of 20mL/min, starting the tube type high-temperature furnace to heat at a constant temperature of 500 ℃ for 2h at a temperature rise rate of 10 ℃/min, and carrying out carbonization and reduction on the product. Carbonizing the carbon-coated copper precursor powder at high temperature in nitrogen atmosphere to obtain Cu in the carbon spheres^ⅡIs reduced to Cu⁰The oleic acid complex decomposes at high temperature to form a hollow structure and is in a carbon sphere coating shape. And after the reaction is finished, stopping heating, and naturally cooling to room temperature along with the furnace under the protection of nitrogen to obtain the core-shell carbon-coated nano copper catalyst I. The catalyst composition was 14.3 wt% copper and 85.7 wt% carbon.

(11) Catalytic methanol oxidative carbonylation reaction for synthesizing dimethyl carbonate

Weighing 0.3g of catalyst and 2.1g of quartz sand, uniformly mixing the catalyst and the quartz sand, filling the mixture into a fixed bed tubular reactor, and introducing N₂，N₂The flow rate was 20 mL/min. Starting the preheating furnace and the reaction furnace to heat, heating the preheating furnace to 130 ℃, and heating the catalyst bed layer in the reactor to 140 ℃.

② closing N₂Introducing CO and O₂And methanol. CO and O₂The input of the mass flow meter is used, the CO flow is 40mL/min, O₂The flow rate is 5 mL/min; methanol is input by Series III type micro-sampling pump, the flow rate of the methanol is 0.05mL/min, and the methanol is gasified in a preheating furnace and is mixed with CO and O₂Mixed well and then entered the reactor. The volume space velocity of the feed gas phase is 29200h^-1。

Thirdly, the reaction is carried out under the conditions that the temperature is 140 ℃ and the pressure is normal pressure, and products discharged from the reactor are condensed by a condenser and then are recovered.

Comparative example 2

The method comprises the following specific steps of catalyzing methanol oxidative carbonylation to synthesize dimethyl carbonate by using a core-shell carbon-coated nano copper catalyst II:

(1) preparing solution

Weighing 8g of copper acetate, weighing 40mL of absolute ethyl alcohol and 3mL of formaldehyde, adding into a stainless steel container, and stirring for 4 hours on a magnetic stirrer to obtain a mixed solution.

(2) Solvothermal synthesis

And (3) placing the stainless steel container containing the mixed solution into a reaction kettle, sealing, then placing the reaction kettle into a resistance heating furnace, heating at the temperature of 400 ℃ for 8 hours at the temperature rising rate of 10 ℃/min, and carrying out solvothermal synthesis. When the temperature is raised to 100 ℃, the copper acetate is dehydrated; when the temperature is increased to 300 ℃, under the auxiliary condition of absolute ethyl alcohol, the copper acetate is thermally decomposed to generate Cu₂O; when the temperature is increased to 300-400 ℃, Cu₂Reducing O in situ to Cu under the action of formaldehyde; and carbonizing the organic precursor to generate carbon, and depositing the carbon on the surface of the copper nanoparticle to form the core-shell carbon-coated nano copper. After the solvent is thermally synthesized, the heating is stopped, and the reaction kettle is cooled to room temperature along with the furnace.

(3) Centrifugal separation

Opening the kettle, transferring the mixed solution in the stainless steel container into a centrifugal tube, performing centrifugal separation at a separation rotation number of 8000r/min for 10min, retaining precipitate after separation, and discarding supernatant.

(4) Washing and centrifugal separation

And (3) placing the precipitate in a beaker, adding 100mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation, wherein the separation revolution number is 8000r/min, the separation time is 10min, retaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 3 times.

(5) Preparing hydrochloric acid aqueous solution

25mL of hydrochloric acid and 50mL of deionized water are weighed and added into a beaker, and stirred for 5min to obtain 6mol/L of hydrochloric acid aqueous solution.

(6) Etching with hydrochloric acid

Adding the washed and centrifugally separated precipitate into a hydrochloric acid aqueous solution, stirring for 5min to obtain a mixed solution, and then placing the mixed solution in an ultrasonic reactor for ultrasonic treatment for 3min at the ultrasonic frequency of 40 kHz. And in the ultrasonic dispersion process, the hydrochloric acid etches the copper in the carbon-coated nano copper particles to obtain a core-shell carbon-coated nano copper particle mixed solution with a cavity structure.

(7) Centrifugal separation

And transferring the core-shell carbon-coated nano copper particle mixed solution into a centrifugal tube, performing centrifugal separation, wherein the separation revolution number is 8000r/min, the separation time is 10min, retaining the precipitate after separation, and discarding the supernatant.

(8) Washing and centrifugal separation

(9) Drying

And (3) drying the precipitate after washing and centrifugal separation in an oven at the drying temperature of 60 ℃ for 6h to obtain the core-shell carbon-coated nano copper catalyst II. The catalyst composition was 17.7 wt% copper, 82.3 wt% carbon

(10) Catalytic methanol oxidative carbonylation reaction for synthesizing dimethyl carbonate

Example 1

(1) Preparation of solid silicon ball template agent

80mL of absolute ethyl alcohol, 16mL of deionized water and 2.15mL (25 wt%) of ammonia water are weighed, added into a beaker, then placed into a water bath kettle with magnetic stirring, and stirred for 5min at 25 ℃.

② measuring 3.1mL of tetraethoxysilane, adding the tetraethoxysilane into the beaker, and continuously stirring the mixture for 6 hours at the temperature of 25 ℃ to form sol, namely the solid silicon ball template agent.

(2) Preparation of hollow mesoporous shell carbon spheres

Preparing a CTAC aqueous solution: weighing CTAC2.319g, adding into a beaker, adding 4.638g of deionized water, and stirring for 10min to obtain a CTAC aqueous solution.

② 52mL of absolute ethyl alcohol and 208mL of deionized water are weighed and added into the solid silica sol, and the mixture is stirred for 10min at 25 ℃ to form a mixed solution.

③ keeping the mixed solution in a violent stirring state, then dropwise adding CTAC aqueous solution, and stirring for 30min at 25 ℃ after the addition is finished.

And fourthly, weighing 0.93g of resorcinol, adding the resorcinol into the mixed solution, and continuously stirring the mixed solution for 30min at the temperature of 25 ℃.

Measuring 1.26mL (37 wt%) of formaldehyde and 3.75mL of ethyl orthosilicate, simultaneously adding the mixed solution, and stirring at 25 ℃ for 10 h.

Sixthly, transferring the mixed solution into a polytetrafluoroethylene container, placing the container into a reaction kettle, sealing the reaction kettle, placing the reaction kettle into an oven, heating the reaction kettle at the temperature of 100 ℃ for 18 hours, and carrying out hydro-thermal synthesis to form the carbon-silicon polymer microsphere precursor. And after hydrothermal synthesis, closing the oven, taking out the reaction kettle, and naturally cooling the reaction kettle to room temperature in the air.

Seventhly, opening the kettle, transferring the suspension in the polytetrafluoroethylene container into a centrifugal tube, performing centrifugal separation at a separation speed of 8000r/min for 2min, retaining the precipitate after separation, and discarding the supernatant.

Eighthly, placing the precipitate in a beaker, adding 200mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, remaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 2 times.

Ninthly, placing the precipitate in an oven for drying at the drying temperature of 40 ℃ for 24h to obtain the carbon-silicon polymer microsphere precursor powder.

Placing precursor powder into quartz boat, then placing into quartz heating tube of tube-type high-temperature furnace, and inputting nitrogen gas, wherein nitrogen gas input speed is 20 mL/(g)_catMin). And starting the tubular high-temperature furnace to heat, wherein the heating rate is 4 ℃/min, the heating temperature is 700 ℃, and the constant temperature is kept for 3h, so that the precursor is carbonized at high temperature in a nitrogen atmosphere to generate the carbon-silicon polymer microspheres. After the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen.

Preparing a hydrofluoric acid aqueous solution: measuring 150mL of deionized water, adding the deionized water into a plastic beaker, measuring 22.4mL (40 wt%) of hydrofluoric acid, adding the hydrofluoric acid into the plastic beaker, stirring the mixture while adding the deionized water, and fixing the volumeTo 200mL, a 5wt% hydrofluoric acid aqueous solution was prepared.

Adding the carbon-silicon polymer microsphere powder into the hydrofluoric acid aqueous solution, and standing for 24h to remove silicon dioxide.

And (3) pouring the supernatant in the beaker, adding 200mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, retaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 2 times.

And (3) drying the washed and centrifugally separated precipitate in an oven at the drying temperature of 70 ℃ for 14h to obtain the hollow mesoporous shell carbon spheres.

(3) Preparation of hollow mesoporous carbon microsphere shell confinement copper catalyst

Weighing Cu (NO)₃)₂·3H₂O0.085 g, weighing 2mL of deionized water, adding into a beaker, and stirring for 5min to obtain a copper nitrate aqueous solution.

② 0.3g of hollow mesoporous shell carbon spheres are weighed and added into the solution, stirred for 10 minutes and then placed into an ultrasonic reactor for ultrasonic treatment for 50 minutes, and the ultrasonic frequency is 80 KHz.

Thirdly, the mixture after ultrasonic treatment is placed in an oven to be dried, the drying temperature is 30 ℃, the drying time is 24 hours, and the precursor of the hollow mesoporous carbon microsphere shell layer confinement copper catalyst is obtained after drying.

Fourthly, the dried precursor powder is placed in a quartz boat and then in a quartz heating tube of a tube type high temperature furnace, and nitrogen is input at the nitrogen input speed of 20 mL/(g)_catMin). Starting the tubular high-temperature furnace to heat at a heating rate of 2 ℃/min and a heating temperature of 300 ℃ for 3h at a constant temperatureReacting copper species in the precursor with the carbon carrier at high temperature in nitrogen atmosphere to obtain Cu^ⅡReduction to Cu^Ⅰ. And after the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen to obtain the hollow mesoporous carbon microsphere shell layer confined copper catalyst. The catalyst composition was copper 7.0 wt%, carbon 93.0 wt%; specific surface area of 720m²Per g, pore volume of 2.1cm³The most probable pore diameter of the shell is 3.5 nm; the average cavity size of the carbon sphere is 160nm, the average thickness of the shell layer is 60nm, and the average particle size is 280 nm.

(4) Catalytic methanol oxidative carbonylation reaction for synthesizing dimethyl carbonate

Weighing 0.15g of catalyst and 0.75g of quartz sand, uniformly mixing the catalyst and the quartz sand, filling the mixture into a fixed bed tubular reactor, and introducing N₂，N₂The flow rate was 20 mL/min. Starting the preheating furnace and the reaction furnace to heat, heating the preheating furnace to 110 ℃, and heating the catalyst bed layer in the reactor to 120 ℃.

② closing N₂Introducing CO and O₂And methanol. CO and O₂The input of the mass flow meter is used, the CO flow is 6mL/min, O₂The flow rate is 1 mL/min; methanol is input by Series III type micro-sampling pump, the flow rate of the methanol is 0.01mL/min, and the methanol is gasified in a preheating furnace and is mixed with CO and O₂Mixed well and then entered the reactor. The space velocity of the gas phase volume of the feeding is 5840h^-1。

Thirdly, the reaction is carried out under the conditions of 120 ℃ and normal pressure, and products from the reactor are condensed by a condenser and then recovered.

Example 2

(1) Preparation of solid silicon ball template agent

Weighing 90mL of absolute ethyl alcohol, 18mL of deionized water and 2.22mL (25 wt%) of ammonia water, adding the absolute ethyl alcohol, the deionized water and the ammonia water into a beaker, then placing the beaker into a water bath kettle with magnetic stirring, and stirring the beaker at 25 ℃ for 10 min.

② measuring 3.6mL of tetraethoxysilane, adding the tetraethoxysilane into the beaker, and continuously stirring for 7 hours at the temperature of 25 ℃ to form sol, namely the solid silicon ball template agent.

(2) Preparation of hollow mesoporous shell carbon spheres

Preparing a CTAC aqueous solution: CTAC4.638g is weighed and added into a beaker, and then 13.914g of deionized water is added, and stirring is carried out for 15min to obtain a CTAC aqueous solution.

Measuring 55mL of absolute ethyl alcohol and 275mL of deionized water, adding the absolute ethyl alcohol and the 275mL of deionized water into the solid silica sol, and stirring the mixture for 15min at 25 ℃ to obtain a mixed solution.

And fourthly, weighing 1.86g of resorcinol, adding the resorcinol into the mixed solution, and continuously stirring the mixed solution for 30min at the temperature of 25 ℃.

Taking 2.52mL (37 wt%) of formaldehyde and 7.50mL of ethyl orthosilicate, simultaneously adding the mixed solution, and stirring for 11h at 28 ℃.

Sixthly, transferring the mixed solution into a polytetrafluoroethylene container, placing the container into a reaction kettle, sealing the reaction kettle, placing the reaction kettle into an oven, heating the reaction kettle at the temperature of 100 ℃ for 24 hours, and carrying out hydro-thermal synthesis to form the carbon-silicon polymer microsphere precursor. And after hydrothermal synthesis, closing the oven, taking out the reaction kettle, and naturally cooling the reaction kettle to room temperature in the air.

Eighthly, placing the precipitate in a beaker, adding 200mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, remaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 3 times.

Ninthly, placing the precipitate in a drying oven for drying at the drying temperature of 50 ℃ for 20h to obtain the carbon-silicon polymer microsphere precursor powder.

Placing precursor powder into quartz boat, then placing into quartz heating tube of tube-type high-temperature furnace, and inputting nitrogen gas, wherein nitrogen gas input speed is 25 mL/(g)_catMin). Starting a tubular high-temperature furnace to heat, wherein the heating rate is 5 ℃/min, the heating temperature is 750 ℃, and the constant temperature is kept for 4h to ensure that the precursor is heatedThe body is carbonized at high temperature and in nitrogen atmosphere to generate the carbon-silicon polymer microspheres. After the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen.

Preparing a hydrofluoric acid aqueous solution: weighing 150mL of deionized water, adding the deionized water into a plastic beaker, weighing 35.8mL (40 wt%) of hydrofluoric acid, adding the hydrofluoric acid into the plastic beaker, stirring the mixture while adding the deionized water, and fixing the volume to 200mL to obtain an 8 wt% hydrofluoric acid aqueous solution.

Adding the carbon-silicon polymer microsphere powder into the hydrofluoric acid aqueous solution, and standing for 20 hours to remove silicon dioxide.

And (3) pouring the supernatant in the beaker, adding 200mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, retaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 3 times.

And (3) drying the precipitate after washing and centrifugal separation in an oven at the drying temperature of 80 ℃ for 12h to obtain the hollow mesoporous shell carbon spheres.

Weighing Cu (NO)₃)₂·3H₂O0.118 g, weighing 2mL of deionized water, adding into a beaker, and stirring for 5min to obtain a copper nitrate aqueous solution.

② 0.3g of hollow mesoporous shell carbon spheres are weighed and added into the solution, stirred for 10 minutes and then placed into an ultrasonic reactor for ultrasonic treatment for 60 minutes, and the ultrasonic frequency is 90 KHz.

Thirdly, the mixture after ultrasonic treatment is placed in an oven to be dried, the drying temperature is 40 ℃, the drying time is 20 hours, and the precursor of the hollow mesoporous carbon microsphere shell layer confinement copper catalyst is obtained after drying.

Fourthly, the dried precursor powder is placed in a quartz boat and then in a quartz heating tube of a tube type high temperature furnace, and nitrogen is input with the input speed of 25 mL/(g)_catMin). Starting a tubular high-temperature furnace to heat, wherein the heating rate is 3 ℃/min, the heating temperature is 350 ℃, and the constant temperature is kept for 4h, so that copper species in the precursor react with the carbon carrier at high temperature in a nitrogen atmosphere, and Cu reacts^ⅡReduction to Cu^Ⅰ. And after the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen to obtain the hollow mesoporous carbon microsphere shell layer confined copper catalyst. The catalyst composition was 9.7 wt% copper, 90.3 wt% carbon; specific surface area of 980m²G, pore volume of 2.2cm³The most probable pore diameter of the shell is 3.5 nm; the average cavity size of the carbon spheres is 180nm, the average thickness of the shell layer is 120nm, and the average particle size is 420 nm.

Weighing 0.22g of catalyst and 1.76g of quartz sand, uniformly mixing the catalyst and the quartz sand, filling the mixture into a fixed bed tubular reactor, and introducing N₂，N₂The flow rate was 20 mL/min. Starting the preheating furnace and the reaction furnace to heat, heating the preheating furnace to 120 ℃, and heating the catalyst bed layer in the reactor to 130 ℃.

② closing N₂Introducing CO and O₂And methanol. CO and O₂The input of the mass flow meter is used, the CO flow is 12mL/min, O₂The flow rate is 2 mL/min; methanol is input by Series III type micro-sampling pump, the flow rate of the methanol is 0.02mL/min, and the methanol is gasified in a preheating furnace and is mixed with CO and O₂Mixed well and then entered the reactor. The volume space velocity of the feed gas phase is 11680h^-1。

Thirdly, the reaction is carried out at the temperature of 130 ℃ and the pressure of 1.0MPa, and the product from the reactor is condensed by a condenser and then recovered.

Example 3

(1) Preparation of solid silicon ball template agent

Weighing 100mL of absolute ethyl alcohol, 20mL of deionized water and 2.30mL (25 wt%) of ammonia water, adding the absolute ethyl alcohol, the deionized water and the ammonia water into a beaker, then placing the beaker into a water bath kettle with magnetic stirring, and stirring the beaker for 5min at 25 ℃.

② measuring 4.0mL of tetraethoxysilane, adding the tetraethoxysilane into the beaker, and continuously stirring for 8 hours at the temperature of 25 ℃ to form sol, namely the solid silicon ball template agent.

(2) Preparation of hollow mesoporous shell carbon spheres

Preparing a CTAC aqueous solution: CTAC6.957g is weighed and added into a beaker, and 27.828g of deionized water is added and stirred for 20min to obtain CTAC water solution.

Measuring 58mL of absolute ethyl alcohol and 348mL of deionized water, adding the absolute ethyl alcohol and the deionized water into the solid silica sol, and stirring the mixture for 20min at 25 ℃ to obtain a mixed solution.

And fourthly, weighing 2.79g of resorcinol, adding the resorcinol into the mixed solution, and continuously stirring the mixed solution for 30min at the temperature of 25 ℃.

Measuring 3.78mL (37 wt%) of formaldehyde and 11.25mL of ethyl orthosilicate, simultaneously adding the mixed solution, and stirring at 30 ℃ for 12 h.

Sixthly, transferring the mixed solution into a polytetrafluoroethylene container, placing the container into a reaction kettle, sealing the reaction kettle, placing the reaction kettle into an oven, heating the reaction kettle at the temperature of 100 ℃ for 30 hours, and carrying out hydro-thermal synthesis to form the carbon-silicon polymer microsphere precursor. And after hydrothermal synthesis, closing the oven, taking out the reaction kettle, and naturally cooling the reaction kettle to room temperature in the air.

Eighthly, placing the precipitate in a beaker, adding 200mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, remaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 4 times.

Ninthly, placing the precipitate in a drying oven for drying at the drying temperature of 60 ℃ for 18h to obtain the carbon-silicon polymer microsphere precursor powder.

Placing precursor powder into quartz boat, then placing into quartz heating tube of tube-type high-temperature furnace, and inputting nitrogen gas, its nitrogen gas input speed is 30 mL/(g)_catMin). And starting the tubular high-temperature furnace to heat, wherein the heating rate is 6 ℃/min, the heating temperature is 800 ℃, and the constant temperature is kept for 5h, so that the precursor is carbonized at high temperature in a nitrogen atmosphere to generate the carbon-silicon polymer microspheres. After the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen.

Preparing a hydrofluoric acid aqueous solution: weighing 150mL of deionized water, adding the deionized water into a plastic beaker, weighing 44.7mL (40 wt%) of hydrofluoric acid, adding the hydrofluoric acid into the plastic beaker, stirring the mixture while adding the deionized water, and fixing the volume to 200mL to obtain 10wt% hydrofluoric acid aqueous solution.

Adding the carbon-silicon polymer microsphere powder into the hydrofluoric acid aqueous solution, and standing for 18h to remove silicon dioxide.

And (3) pouring the supernatant in the beaker, adding 200mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, retaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 4 times.

Drying the precipitate in oven at 90 deg.C for 10 hrAnd obtaining the hollow mesoporous shell carbon spheres.

Weighing Cu (NO)₃)₂·3H₂O0.150 g, weighing 2mL of deionized water, adding into a beaker, and stirring for 5min to obtain a copper nitrate aqueous solution.

② 0.3g of hollow mesoporous shell carbon spheres are weighed and added into the solution, stirred for 10 minutes and then placed into an ultrasonic reactor for ultrasonic treatment for 70 minutes, and the ultrasonic frequency is 100 KHz.

Thirdly, the mixture after ultrasonic treatment is placed in an oven to be dried, the drying temperature is 50 ℃, the drying time is 18 hours, and the precursor of the hollow mesoporous carbon microsphere shell layer confinement copper catalyst is obtained after drying.

Fourthly, the dried precursor powder is placed in a quartz boat and then in a quartz heating tube of a tube type high temperature furnace, and nitrogen is input with the input speed of 30 mL/(g)_catMin). Starting a tubular high-temperature furnace to heat, wherein the heating rate is 4 ℃/min, the heating temperature is 400 ℃, and the constant temperature is kept for 5h, so that copper species in the precursor react with the carbon carrier at high temperature in a nitrogen atmosphere, and Cu reacts^ⅡReduction to Cu^Ⅰ. And after the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen to obtain the hollow mesoporous carbon microsphere shell layer confined copper catalyst. The catalyst composition was 11.5wt% copper, 88.5 wt% carbon; specific surface area of 1240m²Per g, pore volume of 2.3cm³The most probable pore diameter of the shell is 3.5 nm; the average cavity size of the carbon spheres is 200nm, the average thickness of the shell layer is 180nm, and the average particle size is 560 nm.

Weighing 0.30g of catalyst and 3.00g of quartz sand, uniformly mixing the catalyst and the quartz sand, filling the mixture into a fixed bed tubular reactor, and introducing N₂，N₂The flow rate was 20 mL/min. Starting the preheating furnace and the reaction furnace to heat, heating the preheating furnace to 130 ℃, and heating the catalyst bed layer in the reactor to 140 ℃.

② closing N₂Introducing CO and O₂And methanol. CO and O₂The input of the mass flow meter is used, the CO flow is 18mL/min, O₂The flow rate is 3 mL/min; methanol is input by Series III type micro-sampling pump, the flow rate of the methanol is 0.03mL/min, and the methanol is gasified in a preheating furnace and is mixed with CO and O₂Mixed well and then entered the reactor. The space velocity of the gas phase volume of the feeding is 17520h^-1。

Thirdly, the reaction is carried out at the temperature of 140 ℃ and the pressure of 0.5MPa, and the product from the reactor is condensed by a condenser and then recovered.

Example 4

(1) Preparation of solid silicon ball template agent

Weighing 85mL of absolute ethyl alcohol, 17mL of deionized water and 2.18mL (25 wt%) of ammonia water, adding the absolute ethyl alcohol, the deionized water and the ammonia water into a beaker, then placing the beaker into a water bath kettle with magnetic stirring, and stirring the beaker for 8min at 25 ℃.

② measuring 3.3mL of tetraethoxysilane, adding the tetraethoxysilane into the beaker, and continuously stirring the mixture for 6 hours at the temperature of 25 ℃ to form sol, namely the solid silicon ball template agent.

(2) Preparation of hollow mesoporous shell carbon spheres

Preparing a CTAC aqueous solution: CTAC3.478g is weighed and added into a beaker, and then 8.695g of deionized water is added, and stirring is carried out for 10min to obtain a CTAC aqueous solution.

② 53mL of absolute ethyl alcohol and 238mL of deionized water are weighed, added into the solid silica sol and stirred for 10min at 25 ℃ to obtain a mixed solution.

And fourthly, weighing 1.39g of resorcinol, adding the resorcinol into the mixed solution, and continuously stirring the mixed solution for 30min at the temperature of 25 ℃.

Measuring 1.89mL (37 wt%) of formaldehyde and 5.62mL of ethyl orthosilicate, simultaneously adding the mixed solution, and stirring at 26 ℃ for 10 h.

Sixthly, transferring the mixed solution into a polytetrafluoroethylene container, placing the container into a reaction kettle, sealing the reaction kettle, placing the reaction kettle into an oven, heating the reaction kettle at the temperature of 150 ℃ for 21 hours, and carrying out hydro-thermal synthesis to form the carbon-silicon polymer microsphere precursor. And after hydrothermal synthesis, closing the oven, taking out the reaction kettle, and naturally cooling the reaction kettle to room temperature in the air.

Eighthly, placing the precipitate in a beaker, adding 200mL of deionized water, stirring and washing for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, remaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 5 times.

Ninthly, placing the precipitate in an oven for drying at the drying temperature of 45 ℃ for 22h to obtain the carbon-silicon polymer microsphere precursor powder.

Placing precursor powder into quartz boat, then placing into quartz heating tube of tube-type high-temperature furnace, and inputting nitrogen gas, its nitrogen gas input speed is 22 mL/(g)_catMin). And starting the tubular high-temperature furnace to heat, wherein the heating rate is 4 ℃/min, the heating temperature is 720 ℃, and the constant temperature is kept for 3.5h, so that the precursor is carbonized at high temperature in a nitrogen atmosphere to generate the carbon-silicon polymer microspheres. After the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen.

Preparing a hydrofluoric acid aqueous solution: weighing 150mL of deionized water, adding the deionized water into a plastic beaker, weighing 26.9mL (40 wt%) of hydrofluoric acid, adding the hydrofluoric acid into the plastic beaker, stirring the mixture while adding the deionized water, and fixing the volume to 200mL to obtain a 6 wt% hydrofluoric acid aqueous solution.

Adding the carbon-silicon polymer microsphere powder into the hydrofluoric acid aqueous solution, and standing for 22h to remove silicon dioxide.

The supernatant in the beaker was decanted and deionised by additionStirring and washing 200mL of water for 5min, then transferring the washing liquid into a centrifugal tube, carrying out centrifugal separation at a separation speed of 8000r/min for 2min, retaining the precipitate after separation, and discarding the supernatant. Washing and centrifugal separation were repeated 5 times.

And (3) drying the washed and centrifugally separated precipitate in an oven at 75 ℃ for 13h to obtain the hollow mesoporous shell carbon spheres.

Weighing Cu (NO)₃)₂·3H₂O0.102 g, weighing 2mL of deionized water, adding into a beaker, and stirring for 5min to obtain a copper nitrate aqueous solution.

② 0.3g of hollow mesoporous shell carbon spheres are weighed and added into the solution, stirred for 10 minutes and then placed into an ultrasonic reactor for ultrasonic treatment for 55 minutes, and the ultrasonic frequency is 85 KHz.

Thirdly, the mixture after ultrasonic treatment is placed in an oven to be dried, the drying temperature is 35 ℃, the drying time is 22 hours, and the precursor of the hollow mesoporous carbon microsphere shell layer confinement copper catalyst is obtained after drying.

Fourthly, the dried precursor powder is placed in a quartz boat and then in a quartz heating tube of a tube type high temperature furnace, and nitrogen is input with the input speed of 22 mL/(g)_catMin). Starting the tubular high-temperature furnace to heat, wherein the heating rate is 2 ℃/min, the heating temperature is 320 ℃, and the constant temperature is kept for 3.5h, so that copper species in the precursor react with the carbon carrier at high temperature in a nitrogen atmosphere, and Cu reacts^ⅡReduction to Cu^Ⅰ. And after the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen to obtain the hollow mesoporous carbon microsphere shell layer confined copper catalyst. The catalyst composition was 8.3 wt% copper, 91.7 wt% carbon; specific surface area is 660m²G, pore volume of 1.9cm³The most probable pore diameter of the shell layer is 5.9 nm; the average cavity size of the carbon spheres is 170nm, the average thickness of the shell layer is 90nm, and the average particle size is 350 nm.

Weighing 0.18g of catalyst and 1.08g of quartz sand, uniformly mixing the catalyst and the quartz sand, filling the mixture into a fixed bed tubular reactor, and introducing N₂，N₂The flow rate was 20 mL/min. Starting the preheating furnace and the reaction furnace to heat, heating the preheating furnace to 115 ℃, and heating the catalyst bed layer in the reactor to 125 ℃.

② closing N₂Introducing CO and O₂And methanol. CO and O₂The input of the mass flow meter is used, the CO flow is 9mL/min, O₂The flow rate is 1.5 mL/min; methanol is input by Series III type micro-sampling pump, the flow rate of the methanol is 0.02mL/min, and the methanol is gasified in a preheating furnace and is mixed with CO and O₂Mixed well and then entered the reactor. The space velocity of the volume of the gas phase of the feeding is 8760h^-1。

Thirdly, the reaction is carried out at the temperature of 125 ℃ and the pressure of 0.7MPa, and the product from the reactor is condensed by a condenser and then recovered.

Example 5

(1) Preparation of solid silicon ball template agent

Firstly, measuring 95mL of absolute ethyl alcohol, 19mL of deionized water and 2.26mL (25 wt%) of ammonia water, adding the absolute ethyl alcohol, the deionized water and the ammonia water into a beaker, then placing the beaker into a water bath kettle with magnetic stirring, and stirring the beaker at 25 ℃ for 5 min.

② measuring 3.8mL of tetraethoxysilane, adding the tetraethoxysilane into the beaker, and continuously stirring for 7.5 hours at the temperature of 25 ℃ to form sol, namely the solid silicon ball template agent.

(2) Preparation of hollow mesoporous shell carbon spheres

Preparing a CTAC aqueous solution: CTAC5.797g is weighed and added into a beaker, and 20.289g of deionized water is added and stirred for 15min to obtain CTAC aqueous solution.

Measuring 56mL of absolute ethyl alcohol and 308mL of deionized water, adding the absolute ethyl alcohol and the deionized water into the solid silica sol, and stirring the mixture for 10min at 25 ℃ to obtain a mixed solution.

And fourthly, weighing 2.32g of resorcinol, adding the resorcinol into the mixed solution, and continuously stirring the mixed solution for 30min at the temperature of 25 ℃.

Measuring 3.15mL (37 wt%) of formaldehyde and 9.37mL of ethyl orthosilicate, simultaneously adding the mixed solution, and stirring at 29 ℃ for 12 h.

Sixthly, transferring the mixed solution into a polytetrafluoroethylene container, placing the container into a reaction kettle, sealing the reaction kettle, placing the reaction kettle into an oven, heating the reaction kettle at the temperature of 200 ℃ for 27 hours, and carrying out hydro-thermal synthesis to form the carbon-silicon polymer microsphere precursor. And after hydrothermal synthesis, closing the oven, taking out the reaction kettle, and naturally cooling the reaction kettle to room temperature in the air.

Ninthly, placing the precipitate in an oven for drying at the drying temperature of 55 ℃ for 19h to obtain the carbon-silicon polymer microsphere precursor powder.

Placing precursor powder into quartz boat, then placing into quartz heating tube of tube-type high-temperature furnace, and inputting nitrogen gas, wherein nitrogen gas input speed is 28 mL/(g)_catMin). And opening the tubular high-temperature furnace to heat, wherein the heating rate is 6 ℃/min, the heating temperature is 780 ℃, and the constant temperature is kept for 4.5h, so that the precursor is carbonized at high temperature in a nitrogen atmosphere to generate the carbon-silicon polymer microspheres. After the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen.

Preparing a hydrofluoric acid aqueous solution: measuring 150mL of deionized water, adding the deionized water into a plastic beaker, measuring 40.2mL (40 wt%) of hydrofluoric acid, adding the hydrofluoric acid into the plastic beaker, stirring the mixture while adding the deionized water, and carrying out constant volume to 200mL to obtain 9 wt% of hydrofluoric acidAn aqueous acid solution.

Adding the carbon-silicon polymer microsphere powder into the hydrofluoric acid aqueous solution, and standing for 19h to remove silicon dioxide.

And (3) drying the washed and centrifugally separated precipitate in an oven at the drying temperature of 85 ℃ for 11h to obtain the hollow mesoporous shell carbon spheres.

Weighing Cu (NO)₃)₂·3H₂O0.134 g, weighing 2mL of deionized water, adding into a beaker, and stirring for 5min to obtain a copper nitrate aqueous solution.

② 0.3g of hollow mesoporous shell carbon spheres are weighed and added into the solution, stirred for 10 minutes and then placed into an ultrasonic reactor for ultrasonic treatment for 65 minutes, and the ultrasonic frequency is 95 KHz.

Thirdly, the mixture after ultrasonic treatment is placed in an oven to be dried, the drying temperature is 45 ℃, the drying time is 19 hours, and the precursor of the hollow mesoporous carbon microsphere shell layer confinement copper catalyst is obtained after drying.

Fourthly, the dried precursor powder is placed in a quartz boat and then in a quartz heating tube of a tube type high temperature furnace, and nitrogen is input with the input speed of 28 mL/(g)_catMin). Starting the tubular high-temperature furnace to heat, wherein the heating rate is 4 ℃/min, the heating temperature is 380 ℃, and the constant temperature is kept for 4.5h to ensure that the copper in the precursor isThe seed reacts with carbon carrier at high temperature and in nitrogen atmosphere, and is composed of Cu^ⅡReduction to Cu^Ⅰ. And after the reaction is finished, stopping heating, and naturally cooling the product to room temperature along with the furnace under the protection of nitrogen to obtain the hollow mesoporous carbon microsphere shell layer confined copper catalyst. The catalyst composition was copper 10.6 wt%, carbon 89.4 wt%; specific surface area of 480m²G, pore volume of 1.7cm³The most probable pore diameter of the shell layer is 8.5 nm; the average cavity size of the carbon spheres is 190nm, the average thickness of the shell layer is 150nm, and the average particle size is 490 nm.

Weighing 0.26g of catalyst and 2.34g of quartz sand, uniformly mixing the catalyst and the quartz sand, filling the mixture into a fixed bed tubular reactor, and introducing N₂，N₂The flow rate was 20 mL/min. Starting the preheating furnace and the reaction furnace to heat, heating the preheating furnace to 125 ℃, and heating the catalyst bed layer in the reactor to 135 ℃.

② closing N₂Introducing CO and O₂And methanol. CO and O₂The input of the mass flow meter is used, the CO flow is 15mL/min, O₂The flow rate is 2.5 mL/min; methanol is input by Series III type micro-sampling pump, the flow rate of the methanol is 0.02mL/min, and the methanol is gasified in a preheating furnace and is mixed with CO and O₂Mixed well and then entered the reactor. The volume space velocity of the feeding gas phase is 14600h^-1。

Thirdly, the reaction is carried out at the temperature of 135 ℃ and the pressure of 0.3MPa, and the product from the reactor is condensed by a condenser and then recovered.

The reaction performance obtained using methanol conversion, selectivity of methanol to DMC and DMC space-time yield as indices is shown in table 1:

TABLE 1

The present invention is not limited to the above embodiments, and various changes and modifications may be made by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A hollow mesoporous carbon microsphere shell confinement copper catalyst is characterized in that the catalyst consists of carrier hollow mesoporous shell carbon spheres and an active component copper, wherein the weight percentage of copper is 7.0-11.5 wt%, and the weight percentage of carbon is 88.5-93.0 wt%; the specific surface area is 480-1240 m²A pore volume of 1.7-2.3 cm³The most probable pore diameter of the shell layer is 3.5-8.5 nm; the average cavity size of the carbon spheres is 160-200 nm, the average thickness of the shell layer is 60-180 nm, and the average particle size is 280-560 nm;

the catalyst is prepared by taking ethyl orthosilicate, resorcinol and formaldehyde as main raw materials, preparing a solution, performing hydro-thermal synthesis and carbonization etching to prepare hollow carbon spheres with shells rich in a large number of mesopores, using the hollow carbon spheres as a carrier of the catalyst, and loading copper species into the shell mesopores by using an ultrasonic-assisted isometric immersion method;

the preparation method of the hollow mesoporous carbon microsphere shell confinement copper catalyst comprises the following steps:

(1) stirring absolute ethyl alcohol, deionized water and 25wt% ammonia water at 25-30 ℃ for 5-10 min, adding tetraethoxysilane, and continuously stirring for 6-8 h to form solid silica sphere sol; wherein the weight ratio of absolute ethyl alcohol: deionized water: ammonia water: the volume ratio of the ethyl orthosilicate is 80-100: 16-20: 2.1-2.3: 3-4;

(2) adding deionized water according to the mass ratio of the deionized water to the CTAC of 2-4: 1, stirring to prepare a CTAC aqueous solution, adding the deionized water and the absolute ethyl alcohol into the solid silica sphere sol according to the volume ratio of the deionized water to the absolute ethyl alcohol of 4-6: 1, stirring to obtain a mixed solution, then adding the CTAC aqueous solution into the mixed solution dropwise under a violent stirring state, adding resorcinol, finally adding formaldehyde and ethyl orthosilicate, stirring at 25-30 ℃ for 10-12 hours to obtain a carbon-silicon polymer mixed solution, wherein the CTAC: anhydrous ethanol: solid silica sphere sol: resorcinol: formaldehyde: the molar ratio of the ethyl orthosilicate is = 3.5-10.5: 110-120: 2-2.5: 1-3: 4-12: 2-6;

(4) placing the precursor powder in a tubular high-temperature furnace, and inputting nitrogen gas with the volume of 20-30 mL/(g)_catMin), heating at the rate of 4-6 ℃/min, heating at the temperature of 700-800 ℃, keeping at a constant temperature for 3-5 h, then naturally cooling to room temperature to generate carbon-silicon polymer microspheres, adding carbon-silicon polymer microsphere powder into a hydrofluoric acid aqueous solution with the concentration of 5-10 wt%, standing for 18-24 h, centrifugally washing the precipitate for 2-5 times by using deionized water, drying the precipitate at the temperature of 70-90 ℃ for 10-14 h, and drying to obtain hollow mesoporous shell carbon spheres;

(5) weighing Cu (NO)₃)₂·3H₂Adding deionized water, stirring to obtain a copper nitrate solution with the concentration of 0.176-0.310 mol/L, weighing hollow mesoporous shell carbon spheres according to the composition of a catalyst, adding the hollow mesoporous shell carbon spheres into the solution, uniformly stirring, and placing the solution in an ultrasonic reactor for ultrasonic treatment for 50-70 min, wherein the ultrasonic frequency is 80-100 KHz; drying the mixture subjected to ultrasonic treatment at the temperature of 30-50 ℃ for 18-24 h to obtain a catalyst precursor;

(6) putting the catalyst precursor into a tubular high-temperature furnace, and inputting nitrogen gas by 20-30 mL/(g)_catMin), heating at the rate of 2-4 ℃/min, heating at the temperature of 300-400 ℃, keeping the constant temperature for 3-5 h, and naturally cooling the product to room temperature to obtain the hollow mesoporous carbon microsphere shell confinement copper catalyst.

2. The application of the hollow mesoporous carbon microsphere shell confinement copper catalyst as claimed in claim 1, wherein the catalyst is used for the reaction of synthesizing dimethyl carbonate by methanol gas phase oxidation carbonylation, and the reaction steps and the process conditions are as follows:

(1) weighing quartz sand according to the mass ratio of the catalyst to the quartz sand of 1: 5-10, uniformly mixing the two, putting the mixture into a fixed bed tubular reactor, and heating a catalyst bed layer in the reactor to 120-140 ℃ under the nitrogen atmosphere;

(2) raw materials are according to moleMole ratio of CH₃OH∶CO∶O₂The components with the mass ratio of = 2-6: 6-18: 1-3 enter a preheating furnace, are heated to 110-130 ℃ by the preheating furnace and then enter a reactor, and the volume space velocity of a feeding gas phase is 5840-17520 h^-1The reaction is carried out at the reaction temperature of 120-140 ℃ and under the pressure of normal pressure-1.0 MPa.