A method for producing n-butane by oxidative coupling of ethane based on hydrotalcite catalyst

Abstract

The present invention relates to the field of carbon resource conversion technology, and more specifically to a method for producing n-butane by oxidative coupling of ethane using a hydrotalcite catalyst. The method comprises the following steps: introducing carbon dioxide as a weak oxidant and ethane gas simultaneously into a reactor, and carrying out an oxidative coupling reaction in the presence of the hydrotalcite catalyst and under illumination to produce n-butane. By utilizing carbon dioxide as the oxidant and hydrotalcite as the catalyst under illumination to carry out the oxidative coupling of ethane, the present invention not only achieves the chemical utilization of carbon dioxide but also produces n-butane, an important basic raw material for organic chemical industry. Furthermore, the use of light as the driving force of the reaction helps reduce the energy consumption cost of the oxidative coupling reaction process for ethane, thus presenting a method with broad application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon resource conversion, and in particular to a method for preparing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst. Background Art

[0002] n-Butane is an important raw material for the organic chemical industry, widely used in fuels, solvents, aerosols, refrigerants, inflators, and in the preparation of high-value-added products such as maleic anhydride, acetic acid, and acetaldehyde. Currently, n-butane is primarily derived from the separation of oilfield gas, wet natural gas, and cracked gas. However, this process is complex, costly, and energy-intensive.

[0003] In recent years, with the large-scale exploitation of shale gas, the reaction of direct C-C coupling of ethane to produce n-butane has attracted widespread attention due to its high atomic utilization rate and economic feasibility. Due to thermodynamic limitations, the reaction temperature of ethane oxygen-free coupling to produce n-butane is generally high and is accompanied by carbon deposition. The use of ethane oxygen coupling reaction can overcome thermodynamic limitations and has a lower reaction temperature. Among them, carbon dioxide (CO2) is a mild oxidant. Its use in the oxidative dehydrogenation process of alkanes can not only appropriately reduce the reaction temperature, improve the equilibrium yield of the product, and extend the service life of the catalyst, but also reduce greenhouse gas emissions, with good social benefits. However, due to the stable molecular structure of ethane, it is difficult to activate. In addition, the bond energy of the C-C bond in the ethane molecule is lower than the bond energy of the C-H bond, so the breakage of the C-C bond is more likely to occur than the breakage of the C-H bond in thermodynamics. Therefore, how to inhibit the deep oxidation of low-carbon alkanes (efficiently breaking all C-H bonds and C-C bonds to produce CO2) is a hot topic. x ) However, improving the selectivity of the product n-butane is the difficulty of this reaction. Summary of the Invention

[0004] To solve the above problems, the present invention provides a method for preparing n-butane by oxidative coupling of ethane using a hydrotalcite catalyst.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst comprises the following steps:

[0007] Using CO2 as a weak oxidant, CO2 and ethane gas are introduced into the reactor at the same time, and an oxidative coupling reaction is carried out to prepare n-butane under the conditions of hydrotalcite catalyst and light.

[0008] Furthermore, the hydrotalcite catalyst is NiTiX-LDH (X=Al, Mg, Co, Zn, Fe, Cr, V, In, etc.), wherein the molar ratio of Ni:Ti:X is adjustable in the range of 1-8:1:0.005-7.

[0009] Furthermore, the carrier gas is one or both of nitrogen and argon.

[0010] Furthermore, the light source of the illumination includes at least one of the following: a xenon lamp, an LED lamp, a tungsten lamp, a mercury lamp or sunlight.

[0011] Furthermore, the light intensity is 10 to 1000 mW / cm 2 .

[0012] Furthermore, the ethane gas includes at least one of the following: shale gas, petroleum gas, natural gas, coke oven gas and petroleum cracking gas.

[0013] Furthermore, the molar ratio of the CO2 to the ethane gas is 0 / 100 to 100 / 1.

[0014] Furthermore, the total pressure of the CO2 and ethane gas is 0.001 to 10 MPa.

[0015] The present invention has the following beneficial effects:

[0016] The present invention reacts ethane and carbon dioxide over a hydrotalcite catalyst under illumination, directly undergoing CC coupling of ethane to high-value n-butane, thereby achieving extremely high n-butane selectivity. The reaction also produces a small amount of synthesis gas (CO and H2), which can be further produced through Fischer-Tropsch synthesis to produce other high-value chemicals, further improving economic efficiency and thus possessing broad application prospects.

[0017] The present invention utilizes carbon dioxide greenhouse gas as an oxidant for ethane oxidation, which can not only appropriately lower the reaction temperature, improve the equilibrium yield of the product, inhibit carbon deposition and extend the service life of the catalyst, but also reduce greenhouse gas emissions, thus having good social benefits.

[0018] The catalyst used in the present invention is hydrotalcite, which is simple to synthesize, easy to produce on a large scale and convenient to industrialize.

[0019] The present invention uses light energy as the driving force of the reaction, has a mild reaction, and is beneficial to reducing the energy consumption cost of the ethane oxidative coupling reaction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0021] Figure 1 This is the X-ray diffraction pattern of the NiTiAl-LDH catalyst in Example 1 of the present invention.

[0022] Figure 2This is a gas chromatographic analysis chart of the product in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0024] Example 1

[0025] 30 mg of NiTiAl-LDH was placed in the reactor, wherein Ni:Ti:Al=2:1:0.005;

[0026] A mixture of C2H6 and CO2 at 0.2 MPa was introduced, wherein C2H6:CO2=1:1 (v / v);

[0027] The reaction system was illuminated with a xenon lamp for 2 h, and the product was detected by gas chromatography. The chromatogram is shown in FIG. Figure 2 As shown, the products include n-butane and a small amount of synthesis gas (C0 and H2).

[0028] Example 2

[0029] 30 mg of NiTiV-LDH was placed in the reactor, wherein Ni:Ti:V=2:1:0.005;

[0030] A mixture of C2H6 and CO2 at 0.2 MPa was introduced, wherein C2H6:CO2=1:1 (v / v);

[0031] The reaction system was illuminated with a xenon lamp for 2 h, and the products were detected by gas phase detection. The results showed that the products included n-butane and a small amount of synthesis gas (C0 and H2).

[0032] Example 3

[0033] Place 30 mg of NiTiZn-LDH in the reactor, where Ni:Ti:Zn=2:1:0.005;

[0034] A mixture of C2H6 and CO2 at 0.2 MPa was introduced, wherein C2H6:CO2=1:1 (v / v);

[0035] The reaction system was illuminated with a xenon lamp for 2 h, and the products were detected by gas phase detection. The results showed that the products included n-butane and a small amount of synthesis gas (C0 and H2).

[0036] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for producing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst, characterized in that: The following steps are involved: Using CO2 as a weak oxidant, CO2 and ethane gas are introduced into the reactor simultaneously, and an oxidative coupling reaction is carried out to prepare n-butane under the conditions of hydrotalcite catalyst and light. The hydrotalcite catalyst is NiTiX-LDH, where X=Al, V, Zn, and the molar ratio of Ni:Ti:X is adjustable in the range of 1 to 8:1:0.

005.

2. The method for producing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst according to claim 1, wherein: The light source of the illumination includes at least one of the following: a xenon lamp, an LED lamp, a tungsten lamp, a mercury lamp or sunlight.

3. The method for producing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst according to claim 1, wherein: Light intensity is 10-1000 mW / cm 2 .

4. The method for producing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst according to claim 1, wherein: The ethane gas includes at least one of the following: shale gas, petroleum gas, natural gas, coke oven gas and petroleum cracking gas.

5. The method for producing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst according to claim 1, wherein: The molar ratio of the CO2 to the ethane gas is 0 / 100 to 100 / 1.

6. The method for producing n-butane by oxidative coupling of ethane based on a hydrotalcite catalyst according to claim 1, wherein: The total pressure of the CO2 and ethane gas is 0.001-10 MPa.

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