Preparation method of metal oxide catalyst based on plasma

Abstract

The invention belongs to the technical field of catalyst preparation, and discloses a plasma-based metal oxide catalyst preparation method, which comprises: S1, treating a metal organic framework MOFs material by using a low-temperature plasma technology to obtain a metal oxide having an organic framework structure; s2, doping the metal oxide obtained in the step S1 with metal elements through an impregnation-chemical reduction method to obtain a composite metal oxide CO2-CH4 reforming catalyst, wherein the metal elements comprise manganese, cobalt, iron, nickel, copper, silver and platinum; the problem that the application of the MOFs material in the field of catalytic reforming of CH4 / CO2 is restricted due to the fact that the MOFs material derivative prepared by an existing roasting method cannot keep the original frame structure is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a method for preparing a plasma-based metal oxide catalyst. Background Art

[0002] Carbon dioxide (CO 2 ) and methane (CH 4 ) and other greenhouse gas emissions are one of the main reasons. 2 Capture, utilization and storage technologies are critical to controlling emissions, capturing CO from industrial and energy processes. 2 and store or convert it into useful products such as chemicals, building materials, etc., reducing its negative impact on the atmosphere. 4 ) is the world's second largest greenhouse gas, with high warming potential and short lifespan. In recent years, my country has achieved certain results in the resource utilization of methane, but methane emission control still faces great challenges. 4 / CO 2 Preparation of synthesis gas (H2 / CO) to achieve CH 4 Emission Control and CO 2 The design and development of high-efficiency metal-supported catalysts is an important way to improve the catalytic reforming of CH 4 / CO 2 It is an important means to increase the yield of synthesis gas.

[0003] Metal-organic frameworks (MOFs) are often used as catalysts or support materials due to their rich structures and compositions, diverse heteroatom doping, adjustable unique morphology and pore structure, and large specific surface area. 4 and CO 2 The molecule has good affinity in CH 4 and CO 2 There is good application potential in catalytic conversion. MOFs contain catalytically active metals, but the metal sites in MOFs are usually combined with organic ligands, not exposed, and usually inactive.

[0004] At present, most of the research on the catalytic performance of MOFs focuses on the combination of MOFs and nano-metal particles. The MOFs derivatives prepared by the traditional calcination method have the problems of organic framework collapse and destruction, as well as metal oxide agglomeration, which restricts the application of MOFs materials in catalytic reforming of CH 4 / CO 2 Therefore, the present invention proposes a plasma-based preparation method of a metal oxide catalyst to solve this problem. Summary of the invention

[0005] The present invention is intended to provide a method for preparing a plasma-based metal oxide catalyst to solve the problem that the MOFs material derivatives prepared by the existing calcination method cannot maintain the original framework structure, thereby restricting the MOFs material in catalytic reforming of CH 4 / CO 2 Problems with application in the field.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a plasma-based metal oxide catalyst comprises the following steps:

[0008] S1. Using low-temperature plasma technology to process metal organic framework materials to obtain metal oxides with organic framework structures;

[0009] S2, doping the metal oxide obtained in step S1 with metal elements by impregnation-chemical reduction method to obtain a composite metal oxide CO 2 -CH 4 Reforming catalyst.

[0010] Further, in S1, the specific method of treating the metal organic framework material using low temperature plasma technology is:

[0011] A1. dissolving the metal organic framework material in a methanol solution, and using ultrasound to evenly disperse the metal organic framework material in the methanol solution to obtain a mixture A;

[0012] A2, moving the mixture A to a vacuum drying oven for drying through a low-temperature plasma flat-plate reactor;

[0013] A3, connect the flat plate reactor inlet to 2 The mixed gas of O / Ar is prepared, and the high voltage electrode and the ground electrode of the high voltage power supply are connected to the two ends of the flat-plate reactor respectively, and the voltage and frequency applied to the flat-plate reactor are adjusted to generate O 2 / Ar low temperature plasma;

[0014] A4. 2 A mixture B of / Ar low-temperature plasma and A is collected, cleaned, ultrasonically dispersed and dried in sequence to obtain a metal oxide C with an organic framework structure.

[0015] Furthermore, the metal elements in S2 include manganese, cobalt, iron, nickel, copper, silver and platinum.

[0016] Further, in S2, the specific method of doping the metal element by the impregnation-chemical reduction method is:

[0017] B1, dispersing the C obtained in step A4 in methanol using ultrasound to obtain a uniform emulsion D;

[0018] B2, dissolving the metal salt of the metal element in methanol to obtain solution E;

[0019] B3, take NaBH 4 Dissolve in methanol to obtain solution F;

[0020] B4, adding solution E to emulsion D, stirring to make it fully mixed to obtain emulsion G;

[0021] B5. Add solution F to emulsion G, and obtain emulsion H after sufficient reaction;

[0022] B6. The solid product obtained by centrifuging the emulsion H is fully washed and dried to obtain a Ni-CoO catalyst with an organic framework structure.

[0023] Beneficial effects of the technical solution:

[0024] The Ni-CoO catalyst prepared by the present invention has an organic framework structure and a large specific surface area, and has atomic-scale metal-metal oxide active sites, thereby effectively improving the catalytic reforming of CO 2 -CH 4 The catalytic activity and product selectivity of MOFs make them suitable for catalytic reforming of CH 4 / CO 2 There is sufficient application value in application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope (SEM) comparison diagram of the CoO-ZIF-67 prepared in Example 1 of the present invention and the original ZIF-67;

[0026] Figure 2 This is a comparison diagram of the X-ray diffraction of CoO-ZIF-67 prepared in Example 1 of the present invention and the original ZIF-67;

[0027] Figure 3 This is a comparison diagram of infrared spectra of CoO-ZIF-67 prepared in Example 1 of the present invention and original ZIF-67;

[0028] Figure 4 The composite material ZIF-67 / Al in Example 1 of the present invention 2 O 3 CO 2 / CH 4 Reforming efficiency graph;

[0029] Figure 5The composite material CoO-ZIF-67 / Al in Example 1 of the present invention 2 O 3 CO 2 / CH 4 Reforming efficiency graph;

[0030] Figure 6 The composite material Ni-CoO-ZIF-67 / Al in Example 1 of the present invention 2 O 3 CO 2 / CH 4 Reforming efficiency diagram. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0032] A method for preparing a plasma-based metal oxide catalyst comprises the following steps:

[0033] S1. Using low-temperature plasma technology to process metal organic framework materials to obtain metal oxides with organic framework structures;

[0034] Among them, the specific method of using low-temperature plasma technology to treat metal organic framework materials is:

[0035] A1. dissolving the metal organic framework material in a methanol solution, and using ultrasound to evenly disperse the metal organic framework material in the methanol solution to obtain a mixture A;

[0036] A2, moving the mixture A to a vacuum drying oven for drying through a low-temperature plasma flat-plate reactor;

[0037] A3, connect the flat plate reactor inlet to 2 The mixed gas of O / Ar is prepared, and the high voltage electrode and the ground electrode of the high voltage power supply are connected to the two ends of the flat-plate reactor respectively, and the voltage and frequency applied to the flat-plate reactor are adjusted to generate O 2 / Ar low temperature plasma;

[0038] A4. 2 A mixture B of / Ar low-temperature plasma and A is collected, cleaned, ultrasonically dispersed and dried in sequence to obtain a metal oxide C with an organic framework structure.

[0039] S2, doping the metal oxide obtained in step S1 with metal elements by impregnation-chemical reduction method to obtain a composite metal oxide CO 2 -CH 4 Reforming catalyst.

[0040] Among them, metal elements include manganese, cobalt, iron, nickel, copper, silver and platinum.

[0041] Among them, the specific method of doping metal elements by impregnation-chemical reduction method is:

[0042] B1, dispersing the C obtained in step A4 in methanol using ultrasound to obtain a uniform emulsion D;

[0043] B2, dissolving the metal salt of the metal element in methanol to obtain solution E;

[0044] B3, take NaBH 4 Dissolve in methanol to obtain solution F;

[0045] B4, adding solution E to emulsion D, stirring to make it fully mixed to obtain emulsion G;

[0046] B5. Add solution F to emulsion G, and obtain emulsion H after sufficient reaction;

[0047] B6. The solid product obtained by centrifuging the emulsion H is fully washed and dried to obtain a Ni-CoO catalyst with an organic framework structure.

[0048] Example 1

[0049] 1. Preparation of metal oxide CoO-ZIF-67.

[0050] Step 1: Weigh 500 mg of ZIF-67 and disperse it in 20 ml of methanol solution under ultrasonic conditions to obtain emulsion A';

[0051] Step 2: moving the emulsion A' to a low-temperature plasma flat-plate reactor;

[0052] Step 3: Move the flat-plate reactor containing emulsion A' to a vacuum drying oven and dry at 60°C for 12 hours;

[0053] Step 4: Connect the inlet of the flat-plate reactor to an oxygen-containing 20% ​​O 2 / Ar mixed gas, with a total gas flow rate of 50 ml / min;

[0054] Step 5: Connect the two ends of the flat-plate reactor to the high voltage pole and the ground pole of the high voltage power supply respectively, adjust the voltage and frequency applied to the flat-plate reactor, and run it for 3 hours under the condition of a discharge power of 10 watts;

[0055] Step 6: After the plasma discharge is completed, the substances in the flat-plate reactor are collected to obtain a mixture B';

[0056] Step 7: The mixture B' was washed three times with an ethanol solution, separated and dried at 100°C to obtain an atomic-sized metal oxide C' with an organic framework structure, which was defined as CoO-ZIF-67.

[0057] The obtained samples CoO-ZIF-67 and original ZIF-67 were analyzed by scanning electron microscopy (SEM). Figure 1 As shown, the microstructure of ZIF-67 after low-temperature plasma treatment does not change significantly from that of the original ZIF-67, the nanoparticle size is well developed, and no sintering occurs.

[0058] The obtained samples CoO-ZIF-67 and original ZIF-67 were subjected to X-ray diffraction (XRD) analysis. Figure 2 As shown, the diffraction angles at 7.9°, 10.6°, 12.9°, 14.7°, 16.5°, 18.4°, 22.0°, 24.6°, 26.4°, 29.6° and 32.3° represent the (011), (002), (112), (022), (013), (222), (114), (233), (134), (044) and (235) crystal planes, respectively. Figure 2 It can be seen that the intensity of the diffraction peak of the XRD spectrum of ZIF-67 becomes weaker after low-temperature plasma treatment, but the position of the diffraction peak remains consistent with the original ZIF-67, and no new diffraction peak appears, which indicates that the Co metal node in ZIF-67 is oxidized and the crystallinity of ZIF-67 is reduced.

[0059] The obtained sample CoO-ZIF-67 and the original ZIF-67 were analyzed by infrared spectroscopy (FT-IR). Figure 3 FT-IR spectra of ZIF-67 before and after low-temperature plasma treatment. Figure 3 It can be seen that a new characteristic peak appears at 664 cm-1 in ZIF-67 after low-temperature plasma treatment, which is due to the Co-O bond characteristic peak of CoO.

[0060] 2. The metal oxide CoO-ZIF-67 prepared by the above method is used to prepare the metal oxide catalyst Ni-CoO-ZIF-67.

[0061] Step 1: Weigh 200 mg of CoO-ZIF-67 and disperse it in 20 ml of methanol by ultrasonic to obtain a uniform emulsion D';

[0062] Step 2: Weigh 20 mg of nickel perchlorate and dissolve it in 10 ml of methanol to obtain a cyan solution E';

[0063] Step 3: Weigh 40 mg of NaBH 4 Dissolve in 10 ml of methanol by sonication to obtain solution F';

[0064] Step 4: Add solution E' into emulsion D', stir to mix thoroughly and evenly to obtain a turquoise emulsion G';

[0065] Step 5: Add solution F' dropwise to emulsion G'. When the cyan color fades, stop adding solution F'. After sufficient reaction, obtain emulsion H'.

[0066] Step 6: The solid product obtained by centrifuging the emulsion H' was fully washed with ethanol three times and dried at 60° C. for 12 h to obtain Ni-CoO with an organic framework structure, which was defined as Ni-CoO-ZIF-67.

[0067] 3. Activity test

[0068] Catalytic reforming of CO by ZIF-67, CoO-ZIF-67 and Ni-CoO-ZIF-67 2 / CH 4 Activity test, test conditions are: discharge power 2 ~ 12W, each discharge power test time is 1 hour, gas flow rate is 50mL / min, CH 4 The volume concentration is 20%, CO 2 The volume concentration is 10%, argon is used as the balance gas, and the space velocity is 5000h-1.

[0069] Preparation of catalyst:

[0070] (1) Weigh 200 mg ZIF-67 and 1800 mg Al 2 O 3 Physically mix thoroughly to obtain ZIF-67 / Al with a ZIF-67 mass content of 10%. 2 O 3 Composite catalyst;

[0071] (2) Weigh 200 mg CoO-ZIF-67 and 1800 mg Al 2 O 3 The CoO-ZIF-67 / Al2O3 mixture was fully physically mixed to obtain a CoO-ZIF-67 / Al2O3 mixture with a CoO-ZIF-67 mass content of 10%. 2 O 3 Composite catalyst;

[0072] (3) Weigh 200 mg Ni-CoO-ZIF-67 and 1800 mg Al 2 O 3 Physically mix thoroughly to obtain Ni-CoO-ZIF-67 / Al with a Ni-CoO-ZIF-67 mass content of 10%. 2 O 3 Composite catalyst.

[0073] ZIF-67 and Al 2 O 3 The catalytic effect of the composite catalyst is as follows Figure 4As shown in the figure, ZIF-67 as an active component has a CO 2 and CH 4 The conversion rate is less than 20%.

[0074] CoO-ZIF-67 and Al 2 O 3 The catalytic effect of the composite catalyst is as follows Figure 5 As shown in the figure, CoO-ZIF-67 as an active component has a CO 2 and CH 4 The conversion rates of catalytic reforming CO 2 / CH 4 The effect is significantly higher than that of ZIF-67.

[0075] Ni-CoO-ZIF-67 and Al 2 O 3 The catalytic effect of the composite catalyst is as follows Figure 6 As shown in the figure, Ni-CoO-ZIF-67 as the active component has a CO 2 and CH 4 The highest conversion rates of CO and H2 were 55% and 47%, respectively, and the yields of CO and H2 were 32% and 27.5%, respectively. 2 / CH 4 The effect is significantly higher than that of ZIF-67 and CoO-ZIF-67.

[0076] In summary, the atomic-sized metal oxide (CoO-ZIF-67) prepared in this embodiment can maintain the organic framework structure of its precursor ZIF-67, overcoming the disadvantage of the traditional high-temperature calcination treatment of ZIF-67 causing the collapse of the organic framework structure. The metal-metal oxide catalyst (Ni-CoO-ZIF-67) prepared based on CoO-ZIF-67 exhibits good CO 2 / CH 4 Restructuring effect.

[0077] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a plasma-based metal oxide catalyst, It is characterized in that The following steps are involved: S1. Using low-temperature plasma technology to process metal organic framework materials to obtain metal oxides with organic framework structures; S2, doping the metal oxide obtained in step S1 with metal elements by impregnation-chemical reduction method to obtain a composite metal oxide CO 2 -CH 4 Reforming catalyst.

2. The method for preparing a plasma-based metal oxide catalyst according to claim 1, It is characterized in that In S1, the specific method of treating metal organic framework materials using low temperature plasma technology is: A1. dissolving the metal organic framework material in a methanol solution, and using ultrasound to evenly disperse the metal organic framework material in the methanol solution to obtain a mixture A; A2, moving the mixture A to a vacuum drying oven for drying through a low-temperature plasma flat-plate reactor; A3, connect the flat plate reactor inlet to 2 The mixed gas of O / Ar is prepared, and the high voltage electrode and the ground electrode of the high voltage power supply are respectively connected to the two ends of the flat-plate reactor, and the voltage and frequency applied to the flat-plate reactor are adjusted to generate O 2 / Ar low temperature plasma; A4, O 2 A mixture B of / Ar low-temperature plasma and A is collected, cleaned, ultrasonically dispersed and dried in sequence to obtain a metal oxide C with an organic framework structure.

3. The method for preparing a plasma-based metal oxide catalyst according to claim 2, It is characterized in that The metal elements in S2 include manganese, cobalt, iron, nickel, copper, silver and platinum.

4. The method for preparing a plasma-based metal oxide catalyst according to claim 3, It is characterized in that In S2, the specific method of doping metal elements by impregnation-chemical reduction method is: B1, dispersing the C obtained in step A4 in methanol using ultrasound to obtain a uniform emulsion D; B2, dissolving the metal salt of the metal element in methanol to obtain solution E; B3, take NaBH 4 Dissolve in methanol to obtain solution F; B4, adding solution E to emulsion D, stirring to make it fully mixed to obtain emulsion G; B5. Add solution F to emulsion G, and obtain emulsion H after sufficient reaction; B6. The solid product obtained by centrifuging the emulsion H is fully washed and dried to obtain a Ni-CoO catalyst with an organic framework structure.

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