Titanium dioxide nanotube confinement catalyst for methane dry reforming as well as preparation method and application of titanium dioxide nanotube confinement catalyst

Abstract

The invention discloses a titanium dioxide nanotube confinement catalyst for methane dry reforming and a preparation method and application thereof, a transition metal element is used as an active phase, the titanium dioxide nanotube confinement transition metal element catalyst is modified by a rare earth metal element, and the weight of the methane dry reforming catalyst is used as a reference. The content of the transition element is 1-10%, preferably 1-5%, and the content of the rare earth element is 1-5%, so that the problems of activity reduction and poor stability caused by easy generation of carbon deposition of the methane dry reforming catalyst in the prior art are solved.

Description

Technical field:

[0001] The present invention relates to the technical field of catalytic materials, and in particular to a titanium dioxide nanotube confined catalyst for methane dry reforming, and a preparation method and application thereof. Background technology:

[0002] Among the various schemes for the conversion and utilization of carbon dioxide, dry reforming of methane (DRM) to produce synthesis gas is one of the important means. However, due to the carbon deposition reaction during the reaction, a large amount of carbon deposition is generated on the catalyst surface, and the catalyst stability deteriorates or is deactivated due to carbon deposition. At the same time, studies have pointed out that the main reaction in the dry reforming process can only occur under high temperature conditions, and it is thermodynamically feasible only when the temperature is greater than 918K, so there are high requirements for the materials of the reaction device. Among non-precious metal catalysts, transition metals such as Ni and Co have shown catalytic performance comparable to that of precious metals, so they have been widely studied, but their resistance to carbon deposition is poor. Therefore, how to improve the resistance of non-precious metal catalysts to carbon deposition and reduce the reaction temperature has become the research focus of thermal catalytic methane dry reforming in recent years. Summary of the invention:

[0003] The purpose of the present invention is to provide a titanium dioxide nanotube confined catalyst for methane dry reforming and a preparation method and application thereof, which solves the problem of reduced activity and poor stability of methane dry reforming catalysts in the prior art due to easy carbon deposition.

[0004] The present invention is achieved through the following technical solutions:

[0005] A titanium dioxide nanotube confined catalyst for methane dry reforming uses transition metal elements as active phases, is a titanium dioxide nanotube confined transition metal element modified with a rare earth metal element, and has a transition element content of 1 to 10%, preferably 1 to 5%, based on the weight of the methane dry reforming catalyst, and a rare earth element content of 1 to 5%.

[0006] The transition metal is any one or more of Ni, Fe, Co, Ru or Cu; preferably, the transition metal is at least one of Ni and Co.

[0007] The rare earth metal includes any one or more of La, Ce, Y, Pr, and Nd; preferably, the rare earth metal is at least one of La and Ce.

[0008] The preparation method of the titanium dioxide nanotube confined catalyst for methane dry reforming comprises the following steps:

[0009] (a) dissolving a transition metal precursor and a rare earth metal precursor in a solvent to form a mixed solution, adding a titanium dioxide nanotube carrier, and confining the solution under vacuum at -0.01 to -0.5 MPa, and stirring the solution thoroughly;

[0010] (b) drying the solid mixture obtained in step (a), and then reducing it at 300-500° C. in a reducing atmosphere to obtain a sintering-resistant methane dry reforming catalyst.

[0011] In step (a), the transition metal precursor is at least one of the nitrate, sulfate, chloride or acetate of the transition metal; the rare earth metal precursor is at least one of the nitrate, sulfate, chloride or acetate of the rare earth metal; and the solvent includes any one or more of water, ethanol, acetone and isopropanol.

[0012] The reducing atmosphere in step (b) includes any one of H2 and CO, the gas flow rate is 10 to 100 mL / min, and the reduction time is 1 to 20 h.

[0013] The present invention also protects the use of the titanium dioxide nanotube confined catalyst for methane dry reforming in preparing synthesis gas by methane dry reforming, comprising the following steps: contacting methane and carbon dioxide with the catalyst, reacting in a fixed bed reactor, the reaction temperature being 600-700°C, the molar ratio of methane to carbon dioxide being 0.5-1.5:1, and the gas space velocity being 3000-400000 mL·g -1 ·h -1 .

[0014] The beneficial effects of the present invention are as follows:

[0015] 1) The addition of rare earth elements and the confinement effect of titanium dioxide nanotubes make the distribution of transition metal nanoparticles more uniform. The unique synergistic effect of the electron-deficient environment inside the titanium dioxide nanotubes and the electron-rich environment outside provides more active sites for CO2 activation and carbon oxidation. At the same time, the reaction shows good stability, overcoming the shortcomings of low activity and easy carbon deposition of non-precious metal catalysts.

[0016] 2) The catalyst preparation method described in this application has the advantages of simple process, easy operation and low cost. Description of the drawings:

[0017] Figure 1 These are the activity evaluation results of methane dry reforming of the catalysts used in Examples 1-3 and Comparative Examples 1-3.

[0018] Figure 2 These are the stability evaluation results of the catalysts used in Example 1 and Comparative Example 1 for methane dry reforming. Specific implementation method:

[0019] The following is a further description of the present invention, rather than a limitation of the present invention.

[0020] Example 1: A method for preparing a titanium dioxide nanotube confined catalyst for methane dry reforming

[0021] The specific steps are:

[0022] 0.14 g of nickel nitrate and 0.27 g of cerium nitrate were added to 10 mL of deionized water, stirred for 30 min, added to 1 g of titanium dioxide nanotube carrier, kept under -0.1 MPa vacuum for 2 h, then placed in a 120°C oven for 6 h, and reduced under H2 atmosphere at 400°C for 8 h to obtain Ce-modified titanium dioxide nanotube-confined Ni material F1.

[0023] The above catalyst is applied to methane dry reforming, and the specific application method is as follows:

[0024] The evaluation was conducted using a laboratory catalytic oxidation fixed bed reactor. 1g of material F1 was used as the catalyst. The gas CH4:CO2:Ar was 1:1:18 and the gas flow rate was 20ml / min. At 650°C and atmospheric pressure, a conversion rate of 93.3% was achieved. After 100h of reaction, the reaction showed good stability. Figure 2 , overcoming the shortcomings of low activity and easy carbon deposition of non-precious metal catalysts.

[0025] Example 2: A method for preparing a nanotube confined catalyst for methane dry reforming

[0026] The specific steps are:

[0027] 0.12 g of nickel chloride and 0.19 g of lanthanum chloride were added to 10 mL of anhydrous ethanol and stirred for 30 min. Then, the mixture was added to 1 g of titanium dioxide nanotube carrier and kept under a vacuum of -0.1 MPa for 2 h. The mixture was then placed in an oven at 120 °C for 6 h and reduced under a CO atmosphere at 500 °C for 8 h to obtain material F2 of La-modified titanium dioxide nanotube-confined Ni.

[0028] The above catalyst is applied to methane dry reforming, and the specific application method is as follows:

[0029] The evaluation was carried out using a catalytic oxidation fixed-bed reactor in the laboratory. 1 g of material F2 was used as a catalyst, the gas CH4:CO2:Ar=1:1:18, the gas flow rate was 20 ml / min, and at 650°C and normal pressure, a conversion rate of 89.7% was achieved. After 100 hours of reaction, the reaction showed good stability.

[0030] Example 3: A method for preparing a nanotube confined catalyst for methane dry reforming

[0031] The specific steps are:

[0032] 0.14 g of cobalt chloride and 0.23 g of cerium chloride were added to 10 mL of anhydrous ethanol, stirred for 30 min, added to 1 g of titanium dioxide nanotube carrier, kept at -0.1 MPa vacuum for 2 h, then placed in a 120°C oven for 6 h, and reduced at 500°C in a CO atmosphere for 8 h to obtain Ce-modified titanium dioxide nanotube-confined Co material F3.

[0033] The above catalyst is applied to methane dry reforming, and the specific application method is as follows:

[0034] The evaluation was carried out using a catalytic oxidation fixed-bed reactor in the laboratory. 1 g of material F3 was used as a catalyst, the gas CH4:CO2:Ar=1:1:18, the gas flow rate was 20 ml / min, and a conversion rate of 73.8% was achieved at 650°C and normal pressure. After 100 hours of reaction, the reaction showed good stability.

[0035] Comparative Example 1:

[0036] The specific steps are as follows: add 0.14g of nickel chloride to 10mL of anhydrous ethanol, stir for 30min, add to 1g of titanium dioxide nanotube carrier, keep under -0.1MPa vacuum for 2h, then put into a 120℃ oven for 6h, and reduce under CO atmosphere at 500℃ for 8h to obtain titanium dioxide nanotube confined Ni material F4. The specific steps are as follows:

[0037] The above catalyst is applied to methane dry reforming, and the specific application method is as follows:

[0038] The evaluation was carried out using a catalytic oxidation fixed-bed reactor in the laboratory. 1 g of material F3 was used as a catalyst, the gas CH4:CO2:Ar=1:1:18, the gas flow rate was 20 ml / min, and a conversion rate of 31.2% was achieved at 650°C and normal pressure. After 100 hours of reaction, the reaction stability was poor.

[0039] Comparative Example 2:

[0040] The specific steps are:

[0041] 0.14 g of cobalt chloride and 0.23 g of cerium chloride were added to 10 mL of anhydrous ethanol and stirred for 30 min. Then, the mixture was added to 1 g of titanium dioxide nanotube carrier and stirred at 80 °C for 12 h. The mixture was then placed in an oven at 120 °C for 6 h and reduced in a H2 atmosphere at 500 °C for 8 h to obtain the Ce-modified titanium dioxide nanotube Co-loaded material F5.

[0042] The above catalyst is applied to methane dry reforming, and the specific application method is as follows:

[0043] The evaluation was carried out using a catalytic oxidation fixed-bed reactor in the laboratory. 1 g of material F3 was used as a catalyst, the gas CH4:CO2:Ar=1:1:18, the gas flow rate was 20 ml / min, and a conversion rate of 16.6% was achieved at 650°C and normal pressure. After 100 hours of reaction, the reaction stability was poor.

[0044] Comparative Example 3:

[0045] 0.27 g of cerium nitrate was added to 10 mL of deionized water, stirred for 30 min, added to 1 g of titanium dioxide nanotube carrier, kept under -0.1 MPa vacuum for 2 h, then placed in a 120°C oven for 6 h, and reduced under H2 atmosphere at 400°C for 8 h to obtain Ce-modified titanium dioxide nanotube confined material F6.

[0046] The above catalyst is applied to methane dry reforming, and the specific application method is as follows:

[0047] The evaluation was carried out using a catalytic oxidation fixed-bed reactor in the laboratory. 1 g of material F6 was used as a catalyst, the gas CH4:CO2:Ar=1:1:18, the gas flow rate was 20 ml / min, and a conversion rate of 0.43% was achieved at 650°C and normal pressure. After 100 hours of reaction, the reaction stability was poor.

Claims

1. A titanium dioxide nanotube confined catalyst for methane dry reforming, characterized in that: The active phase is a transition metal element, which is a titanium dioxide nanotube modified with a rare earth metal element to confine the transition metal element. Based on the weight of the methane dry reforming catalyst, the transition element content is 1-10%, and the rare earth element content is 1-5%.

2. The titanium dioxide nanotube confined catalyst according to claim 1, characterized in that The content of transition elements is 1 to 5%.

3. The titanium dioxide nanotube confined catalyst according to claim 1 or 2, characterized in that: The transition metal is any one or more of Ni, Fe, Co, Ru or Cu.

4. The titanium dioxide nanotube confined catalyst according to claim 1, characterized in that The rare earth metal includes any one or more of La, Ce, Y, Pr, and Nd.

5. The method for preparing the titanium dioxide nanotube confined catalyst for methane dry reforming according to claim 1, characterized in that: The following steps are involved: (a) dissolving a transition metal precursor and a rare earth metal precursor in a solvent to form a mixed solution, adding a titanium dioxide nanotube carrier, and confining the mixture under vacuum at -0.01 to -0.5 MPa, and stirring the mixture thoroughly; (b) drying the solid mixture obtained in step (a), and then reducing it at 300-500° C. in a reducing atmosphere to obtain a sintering-resistant methane dry reforming catalyst.

6. The preparation method according to claim 5, characterized in that: In step (a), the transition metal precursor is at least one of the nitrate, sulfate, chloride or acetate of the transition metal; the rare earth metal precursor is at least one of the nitrate, sulfate, chloride or acetate of the rare earth metal; and the solvent includes any one or more of water, ethanol, acetone and isopropanol.

7. The preparation method according to claim 5, characterized in that: The reducing atmosphere in step (b) includes any one of H2 and CO, the gas flow rate is 10 to 100 mL / min, and the reduction time is 1 to 20 h.

8. Use of the titanium dioxide nanotube confined catalyst for methane dry reforming according to claim 1 in preparing synthesis gas by methane dry reforming, characterized in that: The method comprises the following steps: contacting methane and carbon dioxide with the catalyst, reacting in a fixed bed reactor, the reaction temperature being 600-700°C, the molar ratio of methane to carbon dioxide being 0.5-1.5:1, and the gas space velocity being 3000-400000 mL·g -1 ·h -1 .

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