A nickel-based amorphous aluminosilicate catalyst, its preparation method and use

Abstract

The application discloses a nickel-based amorphous silico-aluminate catalyst and a preparation method and application thereof, wherein a silicon source and a metal precursor are first added and ball-milled, then an aluminum source and an alkalinity regulator are added and ball-milled to obtain a catalyst initial gel; through hydrothermal reaction, centrifugal washing, calcination decomposition and reduction, a nickel-based amorphous silico-aluminate catalyst is finally obtained. The nickel-based amorphous silico-aluminate catalyst prepared by the application has high metal dispersity, an average particle size of about 3nm and strong metal-support interaction; when the catalyst is applied to a methane carbon dioxide reforming reaction, the initial carbon dioxide conversion rate is 91.8%, and the initial methane conversion rate is 86.4%; after 75h of reaction, the carbon dioxide conversion rate is 91.6%, the methane conversion rate is 86.5%, and the conversion rates do not change obviously, which indicates that the catalyst has excellent stability. The catalyst can effectively solve the bottleneck problems of metal sintering and carbon deposition of a CH4-CO2 reforming catalyst.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and relates to a nickel-based amorphous aluminosilicate catalyst for CH4-CO2 reforming and a preparation method and application thereof. BACKGROUND

[0002] The South China Sea is rich in oil and gas resources, and has large natural gas reserves. However, the CO2 content in typical gas fields is generally 20-80%, and the traditional process cannot be directly used. Through CH4-CO2 reforming technology, the high-energy process of gas separation can be avoided, and the resource utilization of two main greenhouse gases can be realized, which has both environmental protection and economic value. Since methane and carbon dioxide are both small molecules with stable thermodynamic properties, high temperatures above 700℃ are required to fully activate them. The CH4-CO2 reforming technology also has the bottleneck problems of high reaction temperature and serious carbon deposition of catalysts, and the research and development of new catalysts become the key to its industrial application.

[0003] At present, the catalysts for dry reforming of methane mainly include noble metal catalysts represented by Pt, Pd, Au, Ir, Ru, and non-noble metal catalysts represented by Ni, Fe, and Co. The noble metal catalysts have good reaction activity and carbon deposition resistance, but the limited resources and high prices greatly limit the industrial application of noble metal catalysts. Therefore, the research on CH4-CO2 reforming catalysts mainly focuses on non-noble metal catalysts. Among them, nickel-based catalysts have a catalytic activity comparable to noble metals, are widely available, and are inexpensive, becoming the main research direction at present. However, there are still two bottleneck problems: (1) carbon deposition. Since CH4-CO2 reforming reaction usually requires high temperatures above 700℃, carbon deposition is easily produced, covering active sites or even causing bed blockage, leading to catalyst deactivation; (2) sintering. Metal active phase migration and agglomeration occur in the reaction, leading to catalyst deactivation. These bottleneck problems limit the industrial application of nickel-based catalysts in CH4-CO2 reforming reaction.

[0004] Carbon deposition on CH4-CO2 reforming catalyst is mainly caused by deep cracking of methane on the metal surface, which can be reduced by "blocking" and "dissolving" strategies. "Blocking" inhibits the generation of carbon deposition by increasing metal dispersion and reducing the size of metal nickel, which can effectively inhibit the generation of carbon deposition. "Dissolving" promotes the digestion of carbon deposition by strengthening the activation ability of the catalyst to CO2, producing more surface oxygen species, and rapid conversion of carbon on the catalyst surface. Based on this, researchers at home and abroad have adopted various methods to improve the carbon deposition resistance and sintering resistance of nickel-based catalysts. Chinese Patent Publication No. CN114768859B, Wei Jin et al. prepared a silica-supported Ni-N-C material by introducing glucose and melamine into the impregnation system, which achieved high dispersion of metal Ni and improved the activity and stability of the catalyst. Chinese Patent Publication No. CN116786153A, He Binbin et al. prepared an encapsulated Ni@Silicalite-1 molecular sieve catalyst by ligand-assisted method, which achieved high dispersion of metal in the molecular sieve, and the catalyst did not show obvious deactivation after 50 h of reaction. Chinese Patent Publication No. CN114749182A, Zhao Huahua et al. prepared a Ni / La2O3 catalyst using La2O3 as the carrier, which strengthened the Ni-La interaction and promoted the activation of CO2. In addition, other researchers have also strengthened the carbon deposition resistance of CH4-CO2 reforming catalyst by introducing a second metal, adding alkaline additives, etc.

[0005] In summary, although certain progress has been made in the study of CH4-CO2 reforming catalysts, there are still deficiencies in catalyst reactivity, carbon deposition resistance and sintering resistance, which make it difficult to meet the industrial application of CH4-CO2 reforming. SUMMARY

[0006] The present application aims to solve the problem of severe carbon deposition and metal active phase sintering in the prior art CH4-CO2 reforming catalyst, and provides a nickel-based amorphous aluminosilicate catalyst, its preparation method and application. The nickel-based amorphous aluminosilicate catalyst prepared by ball milling uses amorphous aluminosilicate as a carrier to anchor metal nickel, which improves the CH4-CO2 reforming reaction activity and carbon deposition resistance and sintering resistance of the catalyst, and has important significance for promoting the industrialization of CH4-CO2 reforming reaction.

[0007] To achieve the above purpose, the present application provides a preparation method of a nickel-based amorphous aluminosilicate catalyst, comprising the following specific steps:

[0008] (1) First, the silicon source, aluminum source, metal precursor and alkalinity regulator are mixed by ball milling to obtain a catalyst initial gel;

[0009] (2) The initial catalyst gel is transferred to a polytetrafluoroethylene reactor for full reaction under a hydrothermal environment, and then the solid product is obtained by centrifugal washing and drying;

[0010] (3) The solid product is calcined to decompose the metal precursor, and then reduced in a hydrogen-argon mixed gas to obtain a nickel-based amorphous silico-aluminate catalyst.

[0011] In the present application, the silicon source is any one or a combination of two or more of white carbon black, alkaline silica sol, and water glass.

[0012] In the present application, the aluminum source is selected from any one or a combination of two of pseudoboehmite and sodium metaaluminate.

[0013] In the present application, the metal precursor is selected from any one or a combination of two or more of nickel nitrate hexahydrate, nickel sulfate heptahydrate, and nickel chloride.

[0014] In the present application, the alkalinity regulator is sodium hydroxide.

[0015] In step (1) of the present application, for the convenience of calculation, the silicon source, the aluminum source, and the metal precursor are replaced by equivalent oxides, the silicon source is calculated as silicon dioxide, the aluminum source is calculated as aluminum trioxide, and the metal precursor is calculated as nickel oxide, and the specific mass fractions are: silicon dioxide: 5-20%, aluminum trioxide: 1-10.0%, and nickel oxide: 1-10%. The alkalinity regulator is added according to the pH of the initial catalyst gel, and the synthesis pH range is controlled at 10-14.

[0016] In step (1) of the present application, the silicon source and the metal precursor are first ball milled, and then the aluminum source and the alkalinity regulator are added for continuous ball milling, and the single ball milling time ranges from 30-60 min, and the planetary disc rotation speed ranges from 500-600 rpm.

[0017] In the present application, the hydrothermal reaction temperature ranges from 100-200°C, the time ranges from 12-24 h, and the drying temperature ranges from 90-110°C.

[0018] In the present application, the calcination temperature ranges from 400-700°C.

[0019] In the present application, the metal species in the catalyst is controlled by adjusting the feeding sequence in the ball milling process, and the preferred feeding sequence is: the silicon source and the metal precursor are first ball milled, and then the aluminum source and the alkalinity regulator are added for continuous ball milling, and the metal dispersion of the catalyst synthesized by using this feeding sequence is higher, and the metal support interaction is stronger. In this process, the contact sequence of different raw materials is changed due to the change of the feeding sequence. Taking alkaline silica sol as an example, the highly dispersed silicon dioxide particles have rich surface silicon hydroxyl groups, which can coordinate with the metal precursor to generate NiSiO xThe species avoids the generation of nickel hydroxide precipitate from metal precursors, promotes the dispersion of nickel, and further converts into nickel silicate layer species in the subsequent hydrothermal reaction process. The nickel silicate layer has a unique "sandwich" sandwich structure, in which the internal nickel oxide is anchored by two layers of silicon oxygen tetrahedron, which can effectively inhibit the sintering and agglomeration of nickel in the high temperature process, so as to realize the regulation of metal-support interaction and the dispersion of nickel.

[0020] In the present application, the increase of metal loading can provide more active sites, which has a direct impact on the activity of the catalyst. However, too high metal loading not only increases the use of metal precursors and increases the cost of the catalyst, but also more easily leads to the agglomeration and sintering of metal during the reaction process, resulting in catalyst deactivation. In the present application, the mass fraction of nickel element in the nickel-based amorphous aluminosilicate catalyst is adjusted in the range of 1-7 wt%, preferably 5 wt%.

[0021] The second aspect of the present application provides a nickel-based amorphous aluminosilicate catalyst prepared by the above method.

[0022] The third aspect of the present application provides the application of the above nickel-based amorphous aluminosilicate catalyst in the methane carbon dioxide reforming reaction.

[0023] Through the above technical solution, the nickel-based amorphous aluminosilicate catalyst, its preparation method and application have the following beneficial effects:

[0024] (1) The synthesis process of the catalytic material is short, simple to operate, and beneficial to industrial production;

[0025] (2) No organic template agent, complexing agent or organic solvent is used in the synthesis system of the catalytic material, the preparation process is environmentally friendly and has little pollution;

[0026] (3) By adjusting the feeding sequence of the material, the nickel species in the catalyst can be simply and conveniently adjusted, the regulation of metal-support interaction is realized, the metal dispersion is improved, and the reaction activity of the catalyst is improved;

[0027] (4) The amorphous aluminosilicate has stable thermodynamic properties and does not decompose at high temperature, which avoids the sintering of the metal active phase and improves the sintering resistance of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 X-ray diffraction (XRD) characterization results of samples prepared by different feeding sequences.

[0029] Figure 2 (a) and (b) are transmission electron microscopy (TEM) characterization results of 5%Ni / ASA-1 and 5%Ni / ASA-2 samples after reduction, respectively.

[0030] Figure 3H2-TPR characterization results of samples prepared in different feeding sequences

[0031] Figure 4 (a) Initial catalytic activity test results of samples prepared in different feeding sequences; (b) 5% Ni / ASA-1 sample 75 h long period test. DETAILED DESCRIPTION

[0032] In the prior art, the synthesis of microporous or mesoporous materials often needs to use quaternary ammonium salt templates and various organic reagents such as organic ligands, causing environmental pollution. The synthesis process of microporous or mesoporous materials is complex and time-consuming, which is not conducive to industrial production. The skeleton of microporous or mesoporous materials is easy to collapse at high temperature, causing metal phase sintering, and the pore channel is easy to be blocked by carbon deposition during a long reaction process. Although the spinel-like carrier can strengthen the metal-support interaction, it is also easy to generate inert phases that are difficult to reduce, resulting in the loss of metal active phase. The use of noble metals or alkaline earth metals causes the cost of catalyst raw materials to rise.

[0033] Therefore, in the present application, the inventors first use a solid phase-like method to synthesize the nickel-based amorphous aluminosilicate catalyst. First, a metering ratio of silicon source, metal precursor, aluminum source and alkalinity regulator is sequentially added, and an initial catalyst gel is obtained by high-energy ball milling. The gel is transferred to a reaction kettle for sufficient reaction in a hydrothermal environment, and then a solid product is obtained by centrifugal washing and drying. The metal precursor is decomposed by calcination to obtain a nickel-based amorphous aluminosilicate catalyst. The inventors first discovered and experimentally verified that regulating the feeding sequence can change the metal species of the catalyst, thereby significantly improving the metal-support interaction of the catalyst and improving the metal dispersion. In the CH4-CO2 reforming reaction evaluation, the initial conversion rate of carbon dioxide is 91.8% and the initial conversion rate of methane is 86.4% for a sample with a metal loading of 5%. After 72 h of long period test, the reaction conversion rate does not decrease, and the amount of carbon deposition cannot be detected.

[0034] The present application will be described in detail below with specific examples. However, they should not be understood as limiting the scope of protection of the present application. The raw materials used in the following examples and comparative examples are commercially available.

[0035] Example 1

[0036] A preparation method of a nickel-based amorphous aluminosilicate catalyst, comprising the following specific steps:

[0037] (1) According to the feeding sequence of: silicon source + metal precursor → ball milling → aluminum source + alkalinity regulator, 60.04 g of basic silica sol (silicon source) and 5.34 g of nickel nitrate hexahydrate (metal precursor) are mixed in a ball milling tank, and a blue-green gel is obtained after ball milling for 30 min;

[0038] (2) 9.6 g of sodium hydroxide (alkalinity regulator) and 4.92 g of sodium metaaluminate were added into the blue-green colloidal substance obtained in step (1), and the mixture was ball-milled for another 30 min to obtain a light blue paste;

[0039] (3) The mixture after ball-milling was transferred into a polytetrafluoroethylene reactor, and hydrothermal reaction was carried out at 100°C for 24 h;

[0040] (4) The product after hydrothermal reaction was obtained in the form of a solid by centrifugal washing, and was repeatedly washed with deionized water until the pH of the washing liquid was less than 8;

[0041] (5) The product after washing was dried at 100-110°C overnight;

[0042] (6) The dried product was calcined at 550°C for 4-6 h, and then was reduced in a hydrogen-argon mixed gas to obtain a nickel-based amorphous aluminosilicate catalyst.

[0043] The mass fraction of nickel in the catalyst was 5 wt% by ICP-AES elemental analysis. The synthesized catalyst was named as 5%Ni / ASA-1.

[0044] Example 2

[0045] A preparation method of a nickel-based amorphous aluminosilicate catalyst was the same as that in Example 1, except that the amount of nickel nitrate hexahydrate was 1.07 g. The mass fraction of nickel in the catalyst was 1 wt% by ICP-AES elemental analysis.

[0046] Example 3

[0047] A preparation method of a nickel-based amorphous aluminosilicate catalyst was the same as that in Example 1, except that the amount of nickel nitrate hexahydrate was 3.20 g. The mass fraction of nickel in the catalyst was 3 wt% by ICP-AES elemental analysis.

[0048] Example 4

[0049] A preparation method of a nickel-based amorphous aluminosilicate catalyst was the same as that in Example 1, except that the amount of nickel nitrate hexahydrate was 7.48 g. The mass fraction of nickel in the catalyst was 7 wt% by ICP-AES elemental analysis.

[0050] Comparative Example 1

[0051] A preparation method of a nickel-based amorphous silico-aluminate catalyst, which is the same as that in Example 1, except that the feeding sequence in step (1) is changed to: silicon source + aluminum source → ball milling → metal precursor + alkalinity regulator, that is, the silicon source and the aluminum source are first added and ball milled for 30 min, and then the metal precursor and the alkalinity regulator are added and ball milled for another 30 min. The mass fraction of nickel in the catalyst is 5 wt% by ICP-AES elemental analysis. The synthesized catalyst is named as 5%Ni / ASA-2.

[0052] Comparative Example 2

[0053] A preparation method of a nickel-based amorphous silico-aluminate catalyst, which is the same as that in Example 1, except that the feeding sequence in step (1) is changed to: silicon source + alkalinity regulator → ball milling → aluminum source + metal precursor, that is, the silicon source and the alkalinity regulator are first added and ball milled for 30 min, and then the aluminum source and the metal precursor are added and ball milled for another 30 min. The mass fraction of nickel in the catalyst is 5 wt% by ICP-AES elemental analysis. The synthesized catalyst is named as 5%Ni / ASA-3.

[0054] Test Example 1: Analysis of structural properties of catalysts

[0055] The samples of Example 1 and Comparative Examples 1 and 2 were analyzed, and the results are as follows.

[0056] Figure 1 X-ray diffraction (XRD) patterns of samples prepared by different feeding sequences were obtained. Figure 1 It can be seen that the phase structure of the catalysts prepared by different feeding sequences in step (1) has obvious differences. The XRD spectra of the 5%Ni / ASA-1 and 5%Ni / ASA-2 samples show broad peaks without specific configurations, indicating that they are amorphous phase materials. The 5%Ni / ASA-3 sample shows obvious crystalline phase, and its configuration is similar to Y-type molecular sieve. Since the structure of Y-type molecular sieve is obviously different from that of amorphous silico-aluminate, and its thermal stability is poor, it is not suitable for this experimental system. Therefore, the 5%Ni / ASA-3 will not be analyzed in the following. In addition, no characteristic diffraction peaks belonging to NiO are found in the XRD spectra of all samples, which proves that this method has good dispersion effect on metals.

[0057] Figure 2 (a) and (b) are transmission electron microscopy (TEM) images of the 5%Ni / ASA-1 and 5%Ni / ASA-2 samples after reduction, respectively. Figure 2(a) It can be seen that after reduction, the metal particles of the 5%Ni / ASA-1 sample are uniformly distributed, and no obvious agglomeration phenomenon occurs, and the average particle size is about 3 nm. In comparison, the metal particles of the 5%Ni / ASA-2 sample are obviously agglomerated after reduction, and the average particle size is about 15 nm. The above results verify that the feeding sequence can change the metal dispersion of the catalyst, and the catalysts prepared in Examples 1-4 of the present application all have good metal dispersion.

[0058] Figure 3 The hydrogen temperature programmed reduction (H2-TPR) graphs of the 5%Ni / ASA-1 and 5%Ni / ASA-2 samples are shown in Figure 2. The H2-TPR technique can reflect the strength of the metal-support interaction by detecting the reduction temperature of the metal species in the catalyst. It can be seen from Figure 2 that the main reduction peak of the 5%Ni / ASA-1 sample is 630°C, and there is a weak reduction peak at 290°C. The main reduction peak of the 5%Ni / ASA-2 sample is 547°C. This indicates that the metal species in the 5%Ni / ASA-1 sample are mainly high-temperature species, and the metal and the support have a strong interaction. The above results verify that the feeding sequence can change the metal-support interaction of the catalyst, and the metal-support interaction of the catalyst prepared in the present application is strong. Figure 3

[0059] Test Example 2: Evaluation of the reaction performance of the catalyst

[0060] The samples of Example 1 and Comparative Example 1 were subjected to reaction evaluation, and the specific experimental conditions are as follows:

[0061] The above catalyst materials were pressed, crushed, and sieved to obtain 20-40 mesh catalyst particles, 0.4 g of catalyst was weighed and loaded into the middle of a fixed bed quartz reaction tube, and quartz wool was used as support below the catalyst bed. Then, a 10% volume fraction of H2 / Ar mixed gas was used as the reducing gas, and the flow rate was 100 mL / min. The reduction temperature was 650°C, the heating rate was 5°C / min, and the reduction time was 120 min.

[0062] The reaction evaluation was carried out in the above fixed bed reactor, and a methane / carbon dioxide / nitrogen mixed gas was introduced, with a volume ratio of 40% / 40% / 20%, a flow rate of 200 mL / min, a pressure of 0.1 MPa, and a reaction temperature of 750°C. The gas products after the reaction were analyzed online by an Agilent 8860 chromatograph.

[0063] Figure 4 ​(a) Initial activity tests for 5%Ni / ASA-1 and 5%Ni / ASA-2 samples. At 0 h, the catalytic activities of 5%Ni / ASA-1 and 5%Ni / ASA-2 samples were the same, with initial conversion rates of 91.8% for carbon dioxide and 86.4% for methane for 5%Ni / ASA-1, and 91.2% for carbon dioxide and 85.6% for methane for 5%Ni / ASA-2. After 5 h of reaction, the catalytic activity of 5%Ni / ASA-1 showed no significant change, while the catalytic activity of 5%Ni / ASA-2 showed a significant decrease.

[0064] Long-term testing was performed on the 5% Ni / ASA-1 sample, and the results are as follows: Figure 4 As shown in (b), the initial conversion rates were 91.8% for carbon dioxide and 86.4% for methane. After 75 h, the conversion rates were 91.6% for carbon dioxide and 86.5% for methane, with no significant change in the overall conversion rate. These results verify that the catalyst prepared in this invention possesses excellent stability.

Claims

1. A process for the preparation of a nickel-based amorphous aluminosilicate catalyst, characterized in that, The method comprises the following specific steps: (1) adding a silicon source and a metal precursor, then adding an aluminum source and an alkalinity regulator, and then continuously ball milling to obtain a catalyst initial gel; (2) transferring the catalyst initial gel to a polytetrafluoroethylene reactor, and fully reacting in a hydrothermal environment, and then obtaining a solid product through centrifugal washing and drying; (3) calcining the solid product to decompose the metal precursor, and then reducing in a hydrogen-argon mixed gas to obtain a nickel-based amorphous aluminosilicate catalyst.

2. The method for preparing the nickel-based amorphous aluminosilicate catalyst according to claim 1, characterized in that the silicon source is any one or a combination of two or more of white carbon black, alkaline silica sol, and water glass; the aluminum source is any one or a combination of two of pseudo-boehmite and sodium metaaluminate; the metal precursor is any one or a combination of two or more of nickel nitrate hexahydrate, nickel sulfate heptahydrate, and nickel chloride; and the alkalinity regulator is sodium hydroxide.

3. The method for preparing the nickel-based amorphous aluminosilicate catalyst according to claim 1, characterized in that in step (1), the silicon source, the aluminum source, and the metal precursor are replaced by equivalent oxides for convenience of calculation, the silicon source is calculated as silicon dioxide, the aluminum source is calculated as aluminum trioxide, and the metal precursor is calculated as nickel oxide, and the specific mass ratio is: 5-20% of silicon dioxide, 1-10.0% of aluminum trioxide, and 1-10% of nickel oxide; the alkalinity regulator is added according to the pH of the catalyst initial gel, and the synthesis pH range is controlled at 10-14; the hydrothermal reaction temperature range is 100-200 DEG C, the time range is 12-24 h, and the drying temperature range is 90-110 DEG C; and the calcination temperature range is 400-700 DEG C. In step (1), the single ball milling time range is 30-60 min, and the planetary disc rotation speed of the ball mill is 500-600 rpm.

7. The nickel-based amorphous aluminosilicate catalyst prepared by the method of any one of claims 1-6. The average metal particle size of the nickel-based amorphous aluminosilicate catalyst is 3 nm. The mass fraction of nickel in the nickel-based amorphous aluminosilicate catalyst is 1-7 wt%. The mass fraction of nickel in the nickel-based amorphous aluminosilicate catalyst is 5 wt%.

4. The process for the preparation of a nickel-based amorphous aluminosilicate catalyst according to claim 1, characterized in that, The carbon dioxide conversion rate is 91.8% and the methane conversion rate is 86.4% at the beginning of the reaction, and after 75 h of reaction, the carbon dioxide conversion rate is 91.6% and the methane conversion rate is 86.5%.

5. The method for preparing a nickel-based amorphous aluminosilicate catalyst according to claim 1, characterized in that, ​ 6. The process for the preparation of a nickel-based amorphous aluminosilicate catalyst according to claim 1, characterized in that, ​ ​ 8. The nickel-based amorphous aluminosilicate catalyst of claim 7, wherein, ​ 9. The nickel-based amorphous aluminosilicate catalyst of claim 7, wherein, ​ 10. The nickel-based amorphous aluminosilicate catalyst of claim 9, wherein, ​ 11. Use of the nickel-based amorphous aluminosilicate catalyst according to claim 7 in the reaction of carbon dioxide reforming of methane, characterized in that, ​

Images