阅读说明：本技术 一种轻质烷烃的催化偶联方法 (Catalytic coupling method of light alkane ) 是由 刘丽娜 戴静 张芝昆 李原玲 于 2020-12-25 设计创作，主要内容包括：本发明涉及烷烃的催化偶联技术领域,具体涉及一种轻质烷烃的催化偶联方法。本发明提供的轻质烷烃的催化偶联方法,包括如下步骤：将轻质烷烃和惰性气体的混合原料气通入装有催化剂的低温等离子体反应器中,在催化剂存在的条件下进行催化偶联反应,制备得到轻质烷烃偶联产物；所述催化剂为单原子铂催化剂。本发明提供的轻质烷烃的催化偶联方法,其首次将单原子铂催化剂应用于等离子体催化甲烷无氧偶联反应中,实现了低温无氧条件下甲烷的高效定向C-2碳氢化合物的转化,能够有效提高C-2化合物的选择性和烷烃转化率。(The invention relates to the technical field of catalytic coupling of alkane, in particular to a catalytic coupling method of light alkane. The catalytic coupling method of light alkane provided by the invention comprises the following steps: introducing mixed raw material gas of light alkane and inert gas into a low-temperature plasma reactor filled with a catalyst, and performing catalytic coupling reaction in the presence of the catalyst to prepare a light alkane coupling product; the catalyst is a monatomic platinum catalyst. The catalytic coupling method of light alkane provided by the invention is used for applying a monatomic platinum catalyst to plasma catalysis methane anaerobic coupling reaction for the first timeIn the middle, the efficient orientation C of methane under the low-temperature anaerobic condition is realized 2 The conversion of hydrocarbon can effectively improve C 2 Selectivity of compound and alkane conversion.)

1. A catalytic coupling method of light alkane is characterized by comprising the following steps:

introducing mixed raw material gas of light alkane and inert gas into a low-temperature plasma reactor filled with a catalyst, and performing catalytic coupling reaction in the presence of the catalyst to prepare a light alkane coupling product;

the catalyst is a monatomic platinum catalyst.

2. The catalytic coupling method of light alkanes of claim 1, wherein the active component of said monatomic platinum catalyst is metallic platinum and the support is cerium dioxide.

3. The catalytic coupling method of light alkane according to claim 1 or 2, wherein the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 0.1% to 2%.

4. The catalytic coupling method of light alkanes according to any one of claims 1 to 3, wherein the catalytic coupling reaction temperature is 25 ℃ to 200 ℃, the reaction pressure is 0.1MPa to 0.3MPa, and the residence time of the mixed raw material gas in the dielectric barrier discharge region is 4 to 50 s.

5. The catalytic coupling method of light alkanes according to any of claims 1 to 4, wherein the power of said low temperature plasma reactor is 6-75w and the discharge frequency is 8-10 kHz.

6. The process for catalytic coupling of light alkanes according to any of claims 1 to 5, wherein the volume ratio of light alkanes to inert gases in the mixed feed gas is 1 (0.8-2);

the volume space velocity of the mixed raw material gas is 1400-14000h^-1。

7. The process for the catalytic coupling of light alkanes according to any one of claims 1 to 6, characterized in that said monatomic platinum catalyst is prepared by a process comprising the following steps:

1) calcining the metal cerium salt to obtain a cerium dioxide carrier;

2) mixing a chloroplatinic acid aqueous solution with a cerium dioxide carrier, and then drying the mixture to obtain a dried mixture;

3) and calcining the dried mixture in the air to obtain the monatomic platinum catalyst.

8. The process for the catalytic coupling of light alkanes according to any one of claims 1 to 7,

in the step 1), the calcining temperature is 330-370 ℃, and the calcining time is 3-5 h;

in the step 2), the mixing mode is that an aqueous solution of chloroplatinic acid is dripped on a cerium dioxide carrier; the mass ratio of the chloroplatinic acid to the cerium dioxide carrier in the chloroplatinic acid aqueous solution is (0.002-0.053) to 1, the drying temperature is 95-110 ℃, and the drying time is 10-14 h;

in the step 3), the air is flowing air, the calcining temperature is 750-850 ℃, and the calcining time is 8-12 h.

9. The method for catalytic coupling of light alkanes according to any of claims 1 to 8, wherein said low temperature plasma reactor is a dielectric barrier discharge plasma reactor.

10. The process for the catalytic coupling of light alkanes according to any of claims 1 to 9, wherein said light alkanes are methane and said light alkane coupling products comprise hydrogen, acetylene, ethylene and ethane;

the inert gas is selected from one or more of nitrogen, helium and argon;

the metal cerium salt is Ce (NO)₃)₃·6H₂O。

Technical Field

The invention relates to the technical field of catalytic coupling of alkane, in particular to a catalytic coupling method of light alkane.

Background

Methane, as a light alkane, has great potential in the future to become a hydrocarbon feedstock for the synthesis of petrochemical derivatives, and thus, the chemical conversion of methane into valuable chemicals has broad prospects. There are many existing methods for methane conversion, including indirect conversion of methane, mainly by steam reforming, and direct conversion of methane, CO₂Reforming or partial oxidation processes convert methane to synthesis gas (H)₂+ CO), and then converted to chemicals by Fischer-Tropsch synthesis; the direct conversion of methane is divided into oxidative coupling and non-oxidative coupling of methane, wherein the anaerobic coupling of methane (NCM) has good economy because it avoids the energy-intensive synthesis gas step, and the anaerobic coupling of methane is in the process of producing C₂Hydrocarbons and H₂No CO is generated_xHas unique advantages. However, because of the strong C-H bond energy of methane, the nonpolar structure and high ionization energy, the traditional methane thermal activation process usually needs extremely high temperature (more than 1000 ℃) to be carried out, and even if the catalyst exists, at least 800 ℃ is needed to promote the anaerobic coupling reaction of methane, which not only increases the production cost, but also reduces the C because the catalyst is inactivated due to carbon deposition and high-temperature sintering₂The selectivity of the hydrocarbon.

Low temperature (non-equilibrium) plasma technology (NTP) is a promising alternative to facilitate the occurrence and progression of thermodynamically unfavorable reactions at low temperatures, reducing energy input. NTP has a low overall temperature, up to room temperature, but electron temperatures as high as 20000K, and accelerated electrons, ions and radicals can directly activate C-H bonds without heating the reactor to a higher temperature. However, the NTP technique has a disadvantage in that it has a large number of side reactions, and produces a large amount of by-products, resulting in a low conversion rate of methane and a low selectivity of products. The combination of NTP technology and conventional supported metal catalyst can improve the conversion rate of methane and the selectivity of products to a certain extent, but the improvement range is limited, and the requirements of industrial production cannot be effectively met.

Disclosure of Invention

The invention aims to solve the problems that various side reactions are easy to generate when the existing low-temperature plasma technology is used for realizing light alkane coupling, and the conversion rate and the product selectivity of the light alkane are also improved to be limited even if the light alkane is combined with a conventional supported metal catalyst, and further provides a catalytic coupling method of the light alkane.

In order to achieve the purpose, the invention adopts the following technical scheme:

a catalytic coupling method of light alkane comprises the following steps:

introducing mixed raw material gas of light alkane and inert gas into a low-temperature plasma reactor filled with a catalyst, and performing catalytic coupling reaction in the presence of the catalyst to prepare a light alkane coupling product;

the catalyst is a monatomic platinum catalyst.

Preferably, the active component of the monatomic platinum catalyst is metal platinum, and the carrier is cerium dioxide.

Preferably, the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 0.1% -2%.

Preferably, the temperature of the catalytic coupling reaction is 25-200 ℃, the reaction pressure is 0.1-0.3MPa, and the retention time of the mixed raw material gas in the dielectric barrier discharge region is 4-50 s.

Preferably, the power of the low-temperature plasma reactor is 6-75w, and the discharge frequency is 8-10 kHz.

Preferably, the volume ratio of the light alkane to the inert gas in the mixed raw material gas is 1 (0.8-2);

the volume space velocity of the mixed raw material gas is 1400-14000h^-1。

Preferably, the preparation method of the monatomic platinum catalyst includes the steps of:

1) calcining the metal cerium salt to obtain a cerium dioxide carrier;

2) mixing a chloroplatinic acid aqueous solution with a cerium dioxide carrier, and then drying the mixture to obtain a dried mixture;

3) and calcining the dried mixture in the air to obtain the monatomic platinum catalyst.

Preferably, the first and second liquid crystal materials are,

in the step 1), the calcination temperature is 330-370 ℃, and the calcination time is 3-5 hours;

in the step 2), the mixing mode is that an aqueous solution of chloroplatinic acid is dripped on a cerium dioxide carrier; the mass ratio of the chloroplatinic acid to the cerium dioxide carrier in the chloroplatinic acid aqueous solution is (0.002-0.053) to 1, the drying temperature is 95-110 ℃, and the drying time is 10-14 hours; the concentration of the chloroplatinic acid aqueous solution is 50-55 g/L.

In the step 3), the air is flowing air, the calcination temperature is 750-850 ℃, and the calcination time is 8-12 hours. Optionally, the flow rate of the flowing air is 80-120 ml/min.

Preferably, the low-temperature plasma reactor is a Dielectric Barrier Discharge (DBD) plasma reactor.

Optionally, the low-temperature plasma reactor is a plasma-catalytic mixed fixed bed reactor.

Preferably, the light alkane is methane, and the light alkane coupling product comprises hydrogen, acetylene, ethylene and ethane;

the inert gas is selected from one or more of nitrogen, helium and argon;

the metal cerium salt is Ce (NO)₃)₃·6H₂And O. The molecular formula of the chloroplatinic acid is H₂PtCl₆·6H₂O。

The invention has the beneficial effects that:

1) the catalytic coupling method of light alkane provided by the invention applies a monatomic platinum catalyst to methane anaerobic coupling reaction catalyzed by plasma for the first time, and the catalytic coupling reaction is carried out by introducing mixed feed gas of light alkane and inert gas into a low-temperature plasma reactor filled with the catalyst, wherein the reaction is carried out under the low-temperature anaerobic condition, and energy-concentrated synthesis is not included in the reaction processNo CO generation in the gas forming process_xThe catalyst is economic and effective, and has good catalytic performance in a low-temperature plasma system by utilizing the metal active center of the atom distribution of the monatomic platinum catalyst in an unsaturated coordination environment, quantum constraint and strong metal-carrier interaction, so that the C can be effectively improved₂Selectivity and yield of the compound and alkane conversion.

The method realizes the catalytic coupling of light alkane, and the main product is a gaseous product C₂Compound and hydrogen, and C₂The selectivity of the compound is as high as 60%, a complex separation and purification process is not needed, and the invention can realize the efficient directional C of methane under the conditions of low temperature and no oxygen₂And (4) converting hydrocarbon.

2) The catalytic coupling method of light alkane provided by the invention further comprises the step of using metal platinum as an active component of the monatomic platinum catalyst and using cerium dioxide as a carrier. The invention can effectively improve C through the synergistic effect of the metal platinum and the cerium dioxide₂The selectivity of the compound and the conversion rate of alkane are high, and meanwhile, the catalyst has stronger Pt-O-Ce bonds due to atomic dispersion of metal platinum on a cerium dioxide carrier, has excellent thermal stability, overcomes the problem that a single-atom catalyst is easy to agglomerate and sinter at high temperature to be inactivated, and can stably run for more than 40 hours through research.

3) The invention provides a catalytic coupling method of light alkane, and further, the low-temperature plasma reactor is a dielectric barrier discharge plasma reactor. The invention is beneficial to improving C by adapting the monatomic platinum catalyst with the active component of metal platinum and the carrier of cerium dioxide to the dielectric barrier discharge plasma reactor₂Selectivity of compound and alkane conversion.

4) According to the catalytic coupling method of light alkane provided by the invention, further, the catalyst prepared by the preparation method of the specific monatomic platinum catalyst is beneficial to atomic dispersion on a cerium dioxide carrier, so that the catalytic activity of the catalyst is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is an SEM picture of a monatomic platinum catalyst prepared in example 1 of the present invention.

FIG. 2 is a graph showing the results of the stability test of the monatomic platinum catalyst of example 5 of the present invention.

Detailed Description

The following examples are provided to further understand the present invention, not to limit the scope of the present invention, but to provide the best mode, not to limit the content and the protection scope of the present invention, and any product similar or similar to the present invention, which is obtained by combining the present invention with other prior art features, falls within the protection scope of the present invention.

The examples do not show the specific experimental steps or conditions, and can be performed according to the conventional experimental steps described in the literature in the field. The reagents or instruments used are not indicated by manufacturers, and are all conventional reagent products which can be obtained commercially.

Example 1

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain a mixed raw material gas (the volume ratio of the methane to the helium in the mixed raw material gas is 1:1), and reacting the mixed raw material gas for 1400h^-1The catalyst is introduced into a DBD low-temperature plasma reactor (a discharge area of the DBD low-temperature plasma reactor is filled with 100mg of monatomic platinum catalyst, an active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, and the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 1 percent)And (2) carrying out coupling reaction, wherein the reaction temperature is 25 ℃, the reaction pressure is normal pressure, the mixed raw material gas passes through a dielectric barrier discharge area at the flow rate of 20ml/min, the power of the DBD low-temperature plasma reactor is 6.75w, the discharge frequency is 9kHz, and coupling products of hydrogen, acetylene, ethylene and ethane are prepared.

The DBD low-temperature plasma reactor comprises a cylindrical quartz tube with the outer diameter of 25mm, the inner diameter of 20mm and the length of 360mm, a threaded stainless steel rod with the outer diameter of 16mm is arranged on the long axis of the cylindrical quartz tube and serves as a high-voltage electrode, a discharge area is arranged between the stainless steel rod and the inner wall of the side face of the cylindrical quartz tube, a catalyst supported by an asbestos net is placed in the discharge area, the discharge length of the discharge area is 40mm, the discharge gap is 2mm, and the discharge volume is 4.52 ml; an aluminum foil with the length of 40mm is arranged on the outer wall of the side face of the cylindrical quartz tube and is used as a grounding electrode; the DBD low-temperature plasma reactor further comprises a CTP-2000K alternating-current high-voltage power supply (Coronalab, Nanjing, China) with the maximum peak voltage of 30KV and the frequency of 10kHz, wherein one end of the power supply is connected with the high-voltage electrode, the other end of the power supply is connected with a grounding electrode, discharge parameters are detected by an oscilloscope (DS2102A, Rigol Technologies, Beijing, China) connected with the DBD low-temperature plasma reactor, and the grounding electrode is further connected with a thermocouple for detecting the temperature in the DBD low-temperature plasma reactor.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 350 ℃ for 4 hours to prepare CeO₂A carrier;

2) dripping 2ml of chloroplatinic acid water solution with the concentration of 53g/L onto 4g of cerium dioxide carrier, and then drying the cerium dioxide carrier at 100 ℃ for 12 hours to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 800 ℃, and the calcining time is 10 hours, so as to obtain the monatomic platinum catalyst.

As shown in fig. 1, the platinum catalyst prepared in this example is a monatomic catalyst, wherein the monatomic platinum is shown in the circle.

Example 2

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain a mixed raw material gas (the volume ratio of the methane to the helium in the mixed raw material gas is 1:1), and reacting the mixed raw material gas for 1400h^-1The method comprises the steps of introducing a volume space velocity into a DBD low-temperature plasma reactor (a discharge area of the DBD low-temperature plasma reactor is filled with 100mg of a monatomic platinum catalyst, an active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 1 percent), carrying out catalytic coupling reaction, wherein the reaction temperature is 25 ℃, the reaction pressure is 0.1MPa, the retention time of a reaction raw material gas in a dielectric barrier discharge area is 4.42s, the power of the DBD low-temperature plasma reactor is 9.56w, the discharge frequency is 9kHz, and preparing coupling products of hydrogen, acetylene, ethylene and ethane.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 350 ℃ for 4 hours to prepare CeO₂A carrier;

2) dripping 2ml of chloroplatinic acid water solution with the concentration of 53g/L onto 4g of cerium dioxide carrier, and then drying the cerium dioxide carrier at 100 ℃ for 12 hours to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 800 ℃, and the calcining time is 10 hours, so as to obtain the monatomic platinum catalyst.

Example 3

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain a mixed raw material gas (the volume ratio of the methane to the helium in the mixed raw material gas is 1:1), and reacting the mixed raw material gas for 1400h^-1Is introduced into the DBD low-temperature plasma reactor (the DBD low temperatureThe method comprises the steps that 100mg of monatomic platinum catalyst is filled in a discharge area of a plasma reactor, the active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 1%), catalytic coupling reaction is carried out, the reaction temperature is 25 ℃, the reaction pressure is 0.1MPa, the retention time of reaction raw material gas in a medium barrier discharge area is 4.42s, the power of a DBD low-temperature plasma reactor is 22.6w, the discharge frequency is 9kHz, and coupling products of hydrogen, acetylene, ethylene and ethane are prepared.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 350 ℃ for 4 hours to prepare CeO₂A carrier;

2) dripping 2ml of chloroplatinic acid water solution with the concentration of 53g/L onto 4g of cerium dioxide carrier, and then drying the cerium dioxide carrier at 100 ℃ for 12 hours to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 800 ℃, and the calcining time is 10 hours, so as to obtain the monatomic platinum catalyst.

Example 4

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain a mixed raw material gas (the volume ratio of the methane to the helium in the mixed raw material gas is 1:1), and reacting the mixed raw material gas for 1400h^-1The method comprises the following steps of (1) introducing a volume space velocity into a DBD low-temperature plasma reactor (a discharge area of the DBD low-temperature plasma reactor is filled with 100mg of a monatomic platinum catalyst, an active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 1%), carrying out catalytic coupling reaction, wherein the reaction temperature is 25 ℃, the reaction pressure is 0.1MPa, the residence time of a reaction raw material gas in a dielectric barrier discharge area is 4.42s, the power of the DBD low-temperature plasma reactor is 36w, and the discharge is carried outThe frequency is 9kHz, and coupling products of hydrogen, acetylene, ethylene and ethane are prepared.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 350 ℃ for 4 hours to prepare CeO₂A carrier;

2) dripping 2ml of chloroplatinic acid water solution with the concentration of 53g/L onto 4g of cerium dioxide carrier, and then drying the cerium dioxide carrier at 100 ℃ for 12 hours to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 800 ℃, and the calcining time is 10 hours, so as to obtain the monatomic platinum catalyst.

Example 5

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain a mixed raw material gas (the volume ratio of the methane to the helium in the mixed raw material gas is 1:1), and reacting the mixed raw material gas for 1400h^-1The method comprises the steps of introducing a volume space velocity into a DBD low-temperature plasma reactor (a discharge area of the DBD low-temperature plasma reactor is filled with 100mg of a monatomic platinum catalyst, an active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 1 percent), carrying out catalytic coupling reaction, wherein the reaction temperature is 25 ℃, the reaction pressure is 0.1MPa, the residence time of a reaction raw material gas in a dielectric barrier discharge area is 4.42s, the power of the DBD low-temperature plasma reactor is 54w, the discharge frequency is 9kHz, and preparing coupling products of hydrogen, acetylene, ethylene and ethane.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 350 ℃ for 4 hours to prepare CeO₂A carrier;

2) dripping 2ml of chloroplatinic acid water solution with the concentration of 53g/L onto 4g of cerium dioxide carrier, and then drying the cerium dioxide carrier at 100 ℃ for 12 hours to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 800 ℃, and the calcining time is 10 hours, so as to obtain the monatomic platinum catalyst.

Example 6

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain a mixed raw material gas (the volume ratio of the methane to the helium in the mixed raw material gas is 1:1), and reacting the mixed raw material gas for 1400h^-1The method comprises the steps of introducing a volume space velocity into a DBD low-temperature plasma reactor (a discharge area of the DBD low-temperature plasma reactor is filled with 100mg of a monatomic platinum catalyst, an active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 1 percent), carrying out catalytic coupling reaction, wherein the reaction temperature is 25 ℃, the reaction pressure is 0.1MPa, the retention time of a reaction raw material gas in a dielectric barrier discharge area is 4.42s, the power of the DBD low-temperature plasma reactor is 72.45w, the discharge frequency is 9kHz, and preparing coupling products of hydrogen, acetylene, ethylene and ethane.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 350 ℃ for 4 hours to prepare CeO₂A carrier;

2) dripping 2ml of chloroplatinic acid water solution with the concentration of 53g/L onto 4g of cerium dioxide carrier, and then drying the cerium dioxide carrier at 100 ℃ for 12 hours to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 800 ℃, and the calcining time is 10 hours, so as to obtain the monatomic platinum catalyst.

Example 7

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain mixed raw material gas (the volume ratio of methane to helium in the mixed raw material gas is 1:0.8), and mixing the mixed raw material gas for 1500h^-1The method comprises the steps of introducing a volume space velocity into a DBD low-temperature plasma reactor (a discharge area of the DBD low-temperature plasma reactor is filled with 100mg of monatomic platinum catalyst, an active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, the mass percentage of the metal platinum in the monatomic platinum catalyst in the catalyst is 0.8%), carrying out catalytic coupling reaction, wherein the reaction temperature is 25 ℃, the reaction pressure is 0.3MPa, the residence time of a reaction raw material gas in a dielectric barrier discharge area is 5s, the power of the DBD low-temperature plasma reactor is 60w, the discharge frequency is 8kHz, and preparing coupling products of hydrogen, acetylene, ethylene and ethane.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 330 ℃ for 5 hours to prepare CeO₂A carrier;

2) dripping 1.6ml of chloroplatinic acid water solution with the concentration of 53g/L onto 4g of cerium dioxide carrier, and then drying the chloroplatinic acid water solution for 14 hours at the temperature of 95 ℃ to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 750 ℃, and the calcining time is 12 hours, so as to obtain the monatomic platinum catalyst.

Example 8

This example provides a method for catalytic coupling of methane, comprising the steps of:

mixing methane and helium to obtain a mixed raw material gas (the volume ratio of the methane to the helium in the mixed raw material gas is 1:2), and keeping the mixed raw material gas at 14000h^-1The volume space velocity of the catalyst is introduced into a DBD low-temperature plasma reactor (a discharge area of the DBD low-temperature plasma reactor is filled with 100mg of monatomic platinum catalyst, an active component of the monatomic platinum catalyst is metal platinum, a carrier is cerium dioxide, and the metal platinum in the monatomic platinum catalyst is in the catalystAccounting for 2 percent of the mass percent) is performed with a catalytic coupling reaction, the reaction temperature is 200 ℃, the reaction pressure is 0.1MPa, the residence time of the reaction raw material gas in a dielectric barrier discharge area is 4s, the power of the DBD low-temperature plasma reactor is 63w, the discharge frequency is 10kHz, and the coupling products of hydrogen, acetylene, ethylene and ethane are prepared.

The preparation method of the monatomic platinum catalyst comprises the following steps:

1) adding Ce (NO)₃)₃·6H₂Calcining O at 370 ℃ for 3 hours to prepare CeO₂A carrier;

2) 4ml of chloroplatinic acid water solution with the concentration of 53g/L is dripped on 4g of cerium dioxide carrier, and then the cerium dioxide carrier is dried for 10 hours at the temperature of 110 ℃ to obtain a dried mixture;

3) and calcining the dried mixture in flowing air (the flow rate of the flowing air is 100mL/min), wherein the calcining temperature is 850 ℃, and the calcining time is 8 hours, so as to obtain the monatomic platinum catalyst.

Comparative example 1

This comparative example provides a process for the catalytic coupling of methane, which differs from the present example 1 in that the discharge region of the DBD low temperature plasma reactor is not loaded with catalyst.

Comparative example 2

This comparative example provides a process for the catalytic coupling of methane, which differs from the present example 2 in that the DBD low temperature plasma reactor does not contain a catalyst in the discharge region.

Comparative example 3

This comparative example provides a process for the catalytic coupling of methane, which differs from the present example 3 in that the discharge zone of the DBD low temperature plasma reactor is not loaded with catalyst.

Comparative example 4

This comparative example provides a process for the catalytic coupling of methane, which differs from the present example 4 in that the discharge region of the DBD low temperature plasma reactor is not loaded with catalyst.

Comparative example 5

This comparative example provides a process for the catalytic coupling of methane, which differs from the present example 5 in that the discharge region of the DBD low temperature plasma reactor is not loaded with catalyst.

Comparative example 6

This comparative example provides a process for the catalytic coupling of methane, which differs from the present example 6 in that the discharge region of the DBD low temperature plasma reactor is not loaded with catalyst.

Comparative example 7

This comparative example provides a catalytic coupling method of methane, which is different from example 1 of the present application in that a monatomic platinum catalyst contained in a discharge region of a DBD low-temperature plasma reactor is replaced with cerium oxide.

Comparative example 8

This comparative example provides a catalytic coupling method of methane, which is different from example 2 of the present application in that a monatomic platinum catalyst contained in a discharge region of a DBD low-temperature plasma reactor is replaced with cerium oxide.

Comparative example 9

This comparative example provides a catalytic coupling method of methane, which is different from example 3 of the present application in that a monatomic platinum catalyst contained in a discharge region of a DBD low-temperature plasma reactor is replaced with cerium oxide.

Comparative example 10

This comparative example provides a catalytic coupling method of methane, which is different from example 4 of the present application in that a monatomic platinum catalyst contained in a discharge region of a DBD low-temperature plasma reactor is replaced with cerium oxide.

Comparative example 11

This comparative example provides a catalytic coupling method of methane, which is different from example 5 of the present application in that a monatomic platinum catalyst contained in a discharge region of a DBD low-temperature plasma reactor is replaced with cerium oxide.

Comparative example 12

This comparative example provides a catalytic coupling method of methane, which is different from example 6 of the present application in that a monatomic platinum catalyst contained in a discharge region of a DBD low-temperature plasma reactor is replaced with cerium oxide.

Comparative example 13

This comparative example provides a catalytic coupling method of methane, which is different from example 5 of the present application in that a monatomic platinum catalyst contained in a discharge region of a DBD low-temperature plasma reactor is replaced with a non-monatomic ceria-supported metal platinum catalyst.

Test example 1: the coupling products obtained in examples 1 to 8 and comparative examples 1 to 13 were analyzed by an online gas chromatograph (GC,6890A, Agilent Technologies, USA) equipped with a Carboxen 1000 packed column, and the conversion of methane, C, was calculated according to the following formula₂Selectivity for the compound, selectivity for hydrogen, C₂Yield of the compound wherein C₂The compound refers to acetylene, ethylene, ethane, C₂The overall selectivity of the compound refers to the overall selectivity of acetylene, ethylene and ethane, C₂The total yield of the compound refers to the total yield of acetylene, ethylene and ethane. The results are shown in Table 1.

Conversion (%) of methane ═ amount of converted methane mass/total methane feed gas × 100%

C₂Selectivity (%) of compound 2 xc₂The amount of substance of the compound/the amount of substance of converted methane × the selectivity (%) of 100% hydrogen gas is the amount of substance of hydrogen gas/(the amount of substance of converted methane × 2) × 100%.

TABLE 1

Test example 2: according to the method for catalytically coupling the methane, provided by the example 5, the mixed raw material gas is 1400h^-1The volume airspeed of the reactor is continuously led into the DBD low-temperature plasma reactor for catalytic coupling reaction, and the reaction is continuously carried outThe time is 40h, and then the conversion of methane, C, is measured₂Selectivity of the compound and selectivity of hydrogen to verify the thermal stability of the monatomic platinum catalyst. The test result is shown in fig. 2, and fig. 2 shows that after the monatomic platinum catalyst provided by the invention is continuously operated for 40 hours, the conversion rate of methane can still be stabilized between 38% and 39%, the selectivity of ethane is stabilized at about 40%, the selectivity of hydrogen is stabilized at about 30%, the selectivity of ethylene and acetylene is stabilized at about 5%, and the monatomic platinum catalyst has excellent thermal stability.

It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.