A supported nickel-gallium-aluminum composite metal oxide catalyst, a preparation method and application thereof

Abstract

The application belongs to the technical field of catalyst preparation, and particularly relates to a supported nickel-gallium-aluminum composite metal oxide catalyst, a preparation method and application thereof. The supported nickel-gallium-aluminum composite metal oxide catalyst provided by the application comprises an Al2O3 carrier with a specific content, an active component Ni and a doping component Ga, has a suitable content of bonded NiO and isolated NiO species or pure bonded NiO species, so that the active component and the carrier have a suitable interaction, the selectivity to ethylene is improved, the catalytic activity is better, and excellent ODHE catalytic performance is obtained; and the application of Ni and Ga with a specific molar ratio can effectively regulate the Lewis acid active sites on the surface of the catalyst, and then improve the selectivity to ethylene in the ODHE reaction.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a supported nickel-gallium-aluminum composite metal oxide catalyst, its preparation method, and its application. Background Technology

[0002] The growing global demand for ethylene has prompted researchers to develop new process routes for ethylene production. Currently, the production of ethylene via the oxidative dehydrogenation of ethane (ODHE) is attracting increasing attention. The ODHE process requires relatively little external heat, significantly reducing energy consumption, and the coke deposits formed on the ODHE redox catalyst are easily removed by oxygen in the reactant feed. Therefore, the oxidative conditions not only lower the thermodynamic barrier to dehydrogenation and increase ethane conversion, but also minimize coke formation and extend catalyst lifespan. However, ethane combustion under oxidative conditions also readily generates CO. x Since it contains H2O, this reaction faces the problem of "high conversion rate and high selectivity cannot be achieved simultaneously".

[0003] Developing efficient ODHE catalysts is key to solving this problem. Under low-temperature conditions, the ODHE reaction can be activated by Ni-based metal oxides. Changes in the chemical properties of the Ni active sites on the catalyst surface significantly affect its catalytic performance. For example, Ni-based mesoporous alumina catalysts (NiAl catalysts) possess highly dispersed Ni active components, thus exhibiting high activity and improving the conversion rate of the ODHE reaction. However, existing NiAl catalysts suffer from weak interactions between the active components and the support, resulting in relatively poor ethylene selectivity. Summary of the Invention

[0004] The purpose of this invention is to provide a supported nickel-gallium-aluminum composite metal oxide catalyst, its preparation method and application. The supported nickel-gallium-aluminum composite metal oxide catalyst provided by this invention has a suitable interaction between the active component and the support, and exhibits high selectivity for ethylene in the ODHE reaction.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a supported nickel-gallium-aluminum composite metal oxide catalyst, with the general formula Ni a Ga b O / Al2O3; the Ni a Ga b O is dispersed on the surface and in the porous structure of the Al2O3; Ni in the supported nickel-gallium-aluminum composite metal oxide catalyst a Ga bThe content of O is 10-30 wt%; the ratio of a to b is 1-15:1; the content of Al2O3 in the supported nickel-gallium-aluminum composite metal oxide catalyst is 70-90 wt%.

[0007] Preferably, the ratio of a to b is 3 to 12:1.

[0008] This invention also provides a method for preparing the supported nickel-gallium-aluminum composite metal oxide catalyst described above, comprising the following steps:

[0009] After the first calcination of Al2O3, it is mixed with a precursor solution and then impregnated, dried, and calcined again to obtain a supported nickel-gallium-aluminum composite metal oxide catalyst; the precursor solution includes Ni precursor and Ga precursor.

[0010] Preferably, the temperature of the first roasting is 400-800℃, and the holding time is 2-6h.

[0011] Preferably, the Ni precursor includes one or more of inorganic nickel and organic nickel; the Ga precursor includes one or more of inorganic gallium and organic gallium.

[0012] Preferably, the mass concentration of Ni precursor in the precursor solution is 3.9-7.9%, and the mass concentration of Ga precursor is 0.4-3.5%; the mass ratio of the precursor solution to Al2O3 is 8.60-8.80:1.

[0013] Preferably, the impregnation is carried out under stirring conditions; the stirring speed is 200-500 rpm; and the impregnation time is 0.5-24 h.

[0014] Preferably, the drying is infrared drying or oven drying; the drying temperature is 100-200℃, and the holding time is 1-24h.

[0015] Preferably, the second calcination is carried out in air; the temperature of the second calcination is 450-600°C, and the holding time is 3-6 hours.

[0016] The present invention also provides the application of the supported nickel-gallium-aluminum composite metal oxide catalyst described in the above-described scheme or the supported nickel-gallium-aluminum composite metal oxide catalyst obtained by the preparation method described in the above-described scheme in the selective oxidative dehydrogenation of ethane to produce ethylene.

[0017] This invention provides a supported nickel-gallium-aluminum composite metal oxide catalyst. The supported nickel-gallium-aluminum composite metal oxide catalyst provided by this invention includes a specific amount of Al2O3 support, an active component Ni, and a dopant component Ga. It has suitable amounts of bonded NiO and isolated NiO species, or simply bonded NiO species. Isolated NiO refers to NiO that does not interact with the support, while bonded NiO refers to NiO that has a strong interaction with the support. This ensures suitable interaction between the active component and the support, improving the selectivity for ethylene and exhibiting good catalytic activity, thus achieving excellent ODHE catalytic performance. This invention uses a specific molar ratio of Ni to Ga, which can effectively control the Lewis acid active sites on the catalyst surface, thereby improving its selectivity for ethylene in the ODHE reaction.

[0018] This invention also provides a method for preparing the supported nickel-gallium-aluminum composite metal oxide catalyst described above. The preparation method provided by this invention uses a wet impregnation method to prepare the catalyst, which is simple and facilitates large-scale preparation.

[0019] This invention also provides the application of the supported nickel-gallium-aluminum composite metal oxide catalyst described in the above-described scheme or the supported nickel-gallium-aluminum composite metal oxide catalyst obtained by the preparation method described in the above-described scheme in the selective oxidative dehydrogenation of ethane to ethylene. The supported nickel-gallium-aluminum composite metal oxide catalyst provided by this invention is suitable for the selective oxidative dehydrogenation of ethane to ethylene reaction and can improve the selectivity of the target product ethylene. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The above are the H2-TPR spectra of the catalysts in Examples 1-4 and Comparative Examples 1-2 of this invention.

[0022] Figure 2 The images show the pyridine infrared spectra of the catalysts in Examples 1-4 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0023] This invention provides a supported nickel-gallium-aluminum composite metal oxide catalyst, with the general formula Ni a Ga b O / Al2O3; the Ni a Ga bO is dispersed on the surface and in the porous structure of the Al2O3; Ni in the supported nickel-gallium-aluminum composite metal oxide catalyst a Ga b The content of O is 10-30 wt%; the ratio of a to b is 1-15:1; the content of Al2O3 in the supported nickel-gallium-aluminum composite metal oxide catalyst is 70-90 wt%.

[0024] In this invention, the specific surface area of ​​the Al2O3 is preferably 152 m². 2 ·g -1 The average pore size is preferably 17.3 nm. In the supported nickel-gallium-aluminum composite metal oxide catalyst provided by this invention, when the active component is loaded onto the support, the specific surface area is between 128.8 and 138.4 m². 2 ·g -1 The pore size is between 13.7 and 17.5 nm.

[0025] In this invention, the Ni in the supported nickel-gallium-aluminum composite metal oxide catalyst a Ga b The content of O is preferably 12-27 wt%, more preferably 15-24 wt%, and even more preferably 18-21 wt%.

[0026] In this invention, the ratio of a (moles of metallic Ni) to b (moles of metallic Ga) is preferably 3 to 12:1, more preferably 5 to 10:1, and even more preferably 7 to 8:1. In a specific embodiment of this invention, a is preferably 1 to 15, more preferably 5 to 10; and b is preferably 1 to 15, more preferably 1.

[0027] In this invention, the content of Al2O3 in the supported nickel-gallium-aluminum composite metal oxide catalyst is preferably 73-88 wt%, more preferably 76-85 wt%, and even more preferably 79-82 wt%.

[0028] This invention also provides a method for preparing the supported nickel-gallium-aluminum composite metal oxide catalyst described above, comprising the following steps:

[0029] After the first calcination of Al2O3, it is mixed with a precursor solution and then impregnated, dried, and calcined again to obtain a supported nickel-gallium-aluminum composite metal oxide catalyst; the precursor solution includes Ni precursor and Ga precursor.

[0030] In this invention, the preferred temperature for the first calcination is 400–800°C, more preferably 500–700°C, and even more preferably 700°C; the preferred holding time is 2–6 hours, more preferably 2–4 hours, and even more preferably 2 hours; the first calcination is preferably carried out in air. This invention, through N2 adsorption-desorption experiments, determined that the specific surface area of ​​Al2O3 is 152 m². 2 ·g -1 The average pore size is 17.3 nm. This invention, through calcination of the support, not only obtains a rich pore structure but also removes impurities adsorbed on the support surface, which is beneficial for the subsequent loading of active components.

[0031] In this invention, the Ni precursor preferably includes one or more of inorganic nickel and organic nickel; the inorganic nickel preferably includes one or more of nickel nitrate and nickel chloride, more preferably nickel nitrate; the organic nickel preferably includes one or more of nickel citrate and nickel acetate; the Ga precursor preferably includes one or more of inorganic gallium and organic gallium; the inorganic gallium preferably includes one or more of gallium nitrate and gallium chloride, more preferably gallium nitrate; the organic gallium preferably includes one or more of gallium acetate and gallium citrate.

[0032] In this invention, the mass concentration of Ni precursor in the precursor solution is preferably 3.9-7.9%, more preferably 4.9-6.9%, and even more preferably 5.9%, and the mass concentration of Ga precursor is preferably 0.4-3.5%, more preferably 1.4-2.5%, and even more preferably 2%.

[0033] In this invention, the mass ratio of the precursor solution to Al2O3 is preferably 8.60 to 8.80:1, more preferably 8.65 to 8.75:1, and even more preferably 8.70:1.

[0034] In this invention, the impregnation is preferably carried out under stirring conditions; the stirring speed is preferably 200-500 rpm, more preferably 300 rpm; the impregnation time is preferably 0.5-24 h, more preferably 1-12 h.

[0035] In this invention, the drying is preferably infrared drying or oven drying, more preferably infrared drying; the drying temperature is preferably 100-200℃, more preferably 120℃, and the heat preservation time is preferably 1-24h, more preferably 12h.

[0036] In this invention, the second calcination is preferably carried out in air; the temperature of the second calcination is preferably 450–600°C, more preferably 500–550°C, and the holding time is preferably 3–6 h, more preferably 4–5 h. This invention calcines the impregnated support, allowing the active component to form oxides and creating an interaction between the active component and the support, thereby regulating the catalytic performance of the catalyst.

[0037] The present invention also provides the application of the supported nickel-gallium-aluminum composite metal oxide catalyst described in the above-described scheme or the supported nickel-gallium-aluminum composite metal oxide catalyst obtained by the preparation method described in the above-described scheme in the selective oxidative dehydrogenation of ethane to produce ethylene.

[0038] The supported nickel-gallium-aluminum composite metal oxide catalyst provided by this invention is suitable for the selective oxidative dehydrogenation of ethane to produce ethylene, and can improve the selectivity of the target product ethylene.

[0039] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.

[0040] Example 1

[0041] 10g of Al₂O₃ was calcined in air at 700℃ for 2h. In a beaker, 1.72g of Ni(NO₃)₂·6H₂O and 0.102g of Ga(NO₃)₃·xH₂O were dissolved in 20mL of water at 25℃ and stirred for 60min to obtain a precursor solution. 2.5g of the calcined Al₂O₃ was placed in the precursor solution, stirred for 60min, dried under infrared light at 120℃ for 12h, and then calcined at 550℃ for 5h to obtain Ni. 15 Ga1O / Al2O3 catalyst. H2-TPR spectroscopy analysis revealed that the relative content of isolated NiO species on the catalyst surface was 12%, while the relative content of bonded NiO species was 62%.

[0042] Example 2

[0043] 10g of Al₂O₃ was calcined in air at 700℃ for 2h. In a beaker, 1.64g of Ni(NO₃)₂·6H₂O and 0.164g of Ga(NO₃)₃·xH₂O were dissolved in 20mL of water at 25℃ and stirred for 60min to obtain a precursor solution. 2.5g of the calcined Al₂O₃ was placed in the precursor solution, stirred for 60min, and then dried under infrared light at 120℃ for 12h to obtain powder. The powder was then calcined at 550℃ for 4h to obtain Ni. 10 Ga1O / Al2O3 catalyst. H2-TPR spectroscopy analysis revealed that the relative content of isolated NiO species on the catalyst surface was 11%, while the relative content of bonded NiO species was 63%.

[0044] Example 3

[0045] 10 g of Al₂O₃ was calcined in air at 700 °C for 2 h. In a beaker, 1.50 g of Ni(NO₃)₂·6H₂O and 0.263 g of Ga(NO₃)₃·xH₂O were dissolved in 20 mL of water at 25 °C and stirred for 60 min to obtain a precursor solution. 2.5 g of the calcined Al₂O₃ was placed in the precursor solution, stirred for 60 min, and then dried at 120 °C for 12 h using infrared spectroscopy to obtain a powder. The powder was then calcined at 550 °C for 4 h to obtain the Ni₅Ga₁O / Al₂O₃ catalyst. H₂-TPR spectroscopy analysis showed that the relative content of isolated NiO species on the catalyst surface was 4%, and the relative content of bonded NiO species was 75%.

[0046] Example 4

[0047] 10g of Al₂O₃ was calcined in air at 700℃ for 2h. In a beaker, 0.849g of Ni(NO₃)₂·6H₂O and 0.747g of Ga(NO₃)₃·xH₂O were dissolved in 20mL of water at 25℃ and stirred for 60min to obtain a precursor solution. 2.5g of the calcined Al₂O₃ was placed in the precursor solution, stirred for 60min, and then dried at 120℃ for 12h using infrared spectroscopy to obtain a powder. The powder was then calcined at 550℃ for 4h to obtain the Ni₁Ga₁O / Al₂O₃ catalyst. H₂-TPR spectroscopy analysis showed that the relative content of isolated NiO species on the catalyst surface was 0%, and the relative content of bonded NiO species was 71%.

[0048] Comparative Example 1

[0049] The preparation method of this comparative example is the same as that of Example 1, except that the amount of Ni(NO3)2·6H2O added is 1.86 g, and Ga(NO3)3·xH2O is not added, resulting in the NiO / Al2O3 catalyst. H2-TPR spectroscopy analysis showed that the relative content of isolated NiO species on the catalyst surface was 14%, and the relative content of bonded NiO species was 61%.

[0050] Comparative Example 2

[0051] The preparation method of this comparative example is the same as that of Example 1, except that the amount of Ga(NO3)3·xH2O added is 1.375g, and Ni(NO3)2·6H2O is not added, so as to obtain the catalyst GaO / Al2O3, which does not contain NiO-related species.

[0052] Comparative Example 3

[0053] 10g of Al₂O₃ was calcined in air at 700℃ for 2 hours; 1.86g of Ni(NO₃)₂·6H₂O was calcined in a crucible at 550℃ for 4 hours to obtain NiO powder; 2.5g of the calcined Al₂O₃ was ground and mixed with the NiO powder to obtain a physically mixed NiO / Al₂O₃-mix. H₂-TPR spectroscopy analysis showed that the relative content of isolated NiO species on the catalyst surface was 100%, and the relative content of bonded NiO species was 0%.

[0054] Application Example 1

[0055] The catalysts from Examples 1-4 and Comparative Examples 1-3 were applied to the selective oxidative dehydrogenation of ethane to produce ethylene, and the specific steps were as follows:

[0056] 0.5g of quartz sand was laid in the lower layer of the reactor, and 1g of 40-60 mesh tableted catalyst was loaded. 0.3g of quartz sand was laid on top of the catalyst. The reaction temperature was 450-500℃, and the pressure was atmospheric pressure. The volume ratio of ethane, oxygen, and nitrogen in the feed gas was 6:6:88, and the total flow rate was 125mL / min. After the reactor temperature and gas flow rate stabilized (1h), samples were taken for analysis to determine the ethane conversion rate, ethylene selectivity, and yield. The performance evaluation results are shown in Table 1.

[0057] Table 1 Performance Evaluation Results

[0058] Example 1 <![CDATA[Ni 15 Ga1O / Al2O3]]> 450℃ 20.6％ 90.9％ 18.7％ Example 2 <![CDATA[Ni 10 Ga1O / Al2O3]]> 450℃ 16.3％ 94.8％ 15.5％ Example 3 <![CDATA[Ni5Ga1O / Al2O3]]> 400℃ 9.2％ 99.1％ 9.1％ Example 3 <![CDATA[Ni5Ga1O / Al2O3]]> 450℃ 16.2％ 97.4％ 15.8％ Example 4 <![CDATA[Ni1Ga1O / Al2O3]]> 450℃ 5.4％ 96.1％ 5.2％ Comparative Example 1 <![CDATA[NiO / Al2O3]]> 450℃ 22.5％ 90.5％ 20.4％ Comparative Example 2 <![CDATA[GaO / Al2O3]]> 450℃ 1.5％ 68.0％ 1.0％ Comparative Example 3 <![CDATA[NiO / Al2O3-mix]]> 450℃ 99.9％ 0％ 0％

[0059] As can be seen from Table 1, there are differences in conversion rate and selectivity when the catalysts of Examples 1-4 and Comparative Examples 1-3 are used to catalyze the selective oxidative dehydrogenation of ethane to prepare ethylene. However, the catalysts of Examples 1-4 have higher ethylene selectivity, indicating that the catalyst of the present invention can improve the ethylene selectivity in the ODHE reaction. Corresponding to the isolated NiO species and bonded NiO species on the catalyst surface, it can be found that the presence of bonded NiO species is more conducive to improving ethylene selectivity.

[0060] The pyridine infrared spectroscopy was performed on the catalysts of Examples 1-4 and Comparative Examples 1-2, and the results are as follows: Figure 2 As shown. According to Figure 2 It can be seen that Ni5Ga1O / Al2O3 has more Lewis acid sites, which is beneficial to the desorption of ethylene, thus exhibiting higher ethylene selectivity.

[0061] As can be seen from the above embodiments, the supported nickel-gallium-aluminum composite metal oxide catalyst provided by the present invention has higher ethylene selectivity.

[0062] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. The application of a supported nickel-gallium-aluminum composite metal oxide catalyst in the selective oxidative dehydrogenation of ethane to ethylene, characterized in that, The preparation method of the supported nickel-gallium-aluminum composite metal oxide catalyst is as follows: 10g of Al2O3 is calcined in air at 700℃ for 2h; in a beaker, 1.50g of Ni(NO3)2·6H2O and 0.263g of Ga(NO3)3·xH2O are dissolved in 20mL of water at 25℃ and stirred for 60min to obtain a precursor solution; 2.5g of calcined Al2O3 is placed in the precursor solution, stirred for 60min, and then dried in the infrared at 120℃ for 12h to obtain powder, and calcined at 550℃ for 4h to obtain Ni5Ga1O / Al2O3; 0.5g of quartz sand was laid in the lower layer of the reactor, and 1g of 40-60 mesh catalyst was packed in. 0.3g of quartz sand was laid on the upper layer of the catalyst. The reaction temperature was 450℃ and the pressure was atmospheric pressure. The volume ratio of ethane, oxygen and nitrogen in the feed gas was 6:6:88 and the total flow rate was 125mL / min.

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