An Al-NiFe composite material for ethane reforming to produce synthesis gas with high selectivity and its application

Abstract

The present invention discloses an Al-NiFe composite material for producing synthesis gas through high selectivity through ethane reforming and its application. The preparation method comprises: using ethanol as a dispersant, fully dispersing aluminum salt and nickel ferrite, and heating at high temperature. The resulting product after self-propagating combustion is an aluminum oxide-nickel ferrite composite material, which is then reduced at high temperature to obtain the Al-NiFe composite material. The Al-NiFe composite material is composed of a nickel aluminate-nickel iron alloy, wherein the mass ratio of aluminum oxide to nickel ferrite is 1:10 to 1:5. The Al-NiFe composite material prepared by the present invention has a high ethane to CO2 conversion rate, thereby achieving efficient conversion of ethane to high-value-added CO, while consuming greenhouse gases. While achieving effective utilization of the ethane component in shale gas, it promotes carbon dioxide emission reduction and economic utilization.

Description

Technical Field

[0001] The present invention belongs to the technical field of iron-nickel alloy applications, and in particular relates to an Al-NiFe composite material for producing synthesis gas through ethane reforming with high selectivity and an application thereof. Background Art

[0002] Shale gas contains 3-16 vol.% ethane, which is cheap and available in large quantities and can be used as a raw material for industrial production of organic products such as ethylene and synthesis gas.

[0003] At present, the ethane dry reforming reaction using ethane and CO2 as raw materials can produce high-value-added synthesis gas, which can be used to synthesize chemical products such as ammonia, methanol, and acetic acid. At the same time, it consumes greenhouse gas CO2 and reduces carbon emissions. Therefore, it has received widespread attention in recent years.

[0004] At high temperatures, CO2-assisted ethane dry reforming involves a variety of side reactions, including the reverse water-gas shift and Boudouard reaction. Therefore, catalysts for ethane dry reforming should possess excellent catalytic selectivity, capable of selectively cleaving C-C bonds to achieve directional and stable conversion.

[0005] Generally speaking, noble metal catalysts, including Rh, Ru, and Pd, possess high catalytic activity and stability. Transition metals, such as Ni, Co, Cu, and Fe, are widely used due to their abundance and low cost. Catalysts containing Ni as the active component are particularly popular in ethane dry reforming reactions due to their high activity, low cost, and availability. However, Ni-based catalysts still suffer from poor resistance to carbon deposition and sintering, as well as low CO selectivity.

[0006] Compared to single metal catalysts, multimetallic alloys formed by combining two or more active components generally exhibit better catalytic performance than single metal oxides. Nickel ferrite, due to its unique crystal structure, exhibits excellent electrochemical, magnetic, and catalytic properties and is widely used in various fields. Nickel ferrite samples are easily reduced to form NiFe alloys in a high-temperature reducing atmosphere, which exhibits high-temperature activity. However, NiFe alloys are prone to sintering and high-temperature carbon deposition at high temperatures, leading to catalyst deactivation. Therefore, it is necessary to modify the nickel ferrite catalyst to improve its CO selectivity during the catalytic ethane dry reforming reaction. Summary of the Invention

[0007] Purpose of the invention: The present invention provides an Al-NiFe composite material for producing synthesis gas with high selectivity through ethane reforming and its application, so as to solve the problems of poor product stability and selectivity in the dry reforming of ethane catalyzed by existing nickel ferrite catalysts.

[0008] Summary of the invention: To achieve the above objectives, the present invention provides an Al-NiFe composite material for producing synthesis gas with high selectivity through ethane reforming. The preparation method of the Al-NiFe composite material comprises:

[0009] Aluminum salt and nickel ferrite are fully dispersed in ethanol as a dispersant and heated to high temperature. The resulting product after self-propagating combustion is an aluminum oxide-nickel ferrite composite material. This is then reduced at high temperature to obtain an Al-NiFe composite material. The Al-NiFe composite material is composed of a nickel aluminate-nickel iron alloy. The mass ratio of aluminum oxide to nickel ferrite is preferably 1:10 to 1:5.

[0010] Generally, Al-NiFe composite materials are brown solids.

[0011] In the present invention, ethanol serves as a dispersant for the aluminum salt and nickel ferrite, and is also a solvent for self-propagating combustion. The combustion temperature can reach above 1000°C, causing the aluminum element in the aluminum salt to form aluminum oxide on the surface of the nickel ferrite, forming an aluminum oxide-nickel ferrite structure, which is then reduced at high temperature to form a nickel aluminate-nickel-iron alloy structure.

[0012] Nickel ferrite has attracted widespread attention for its high catalytic activity in CO2 reduction due to its numerous surface oxygen vacancies and excellent reducibility. However, it tends to break C-H bonds during ethane dry reforming, resulting in the formation of byproducts and reduced product selectivity. High-temperature reduction of alumina-nickel ferrite to form an Al-NiFe composite can modulate the surface acidic sites, thereby improving CO selectivity, while also dispersing the Fe-Ni active sites and enhancing the catalytic activity of the catalyst.

[0013] The purpose of limiting the mass ratio of alumina to nickel ferrite is to regulate the surface formation and surface acidity and alkalinity of the catalytic material. If the mass ratio is too high, the excess alumina will promote ethane cracking and produce carbon deposits, leading to catalyst deactivation. If the mass ratio is too low, it can easily lead to reduced CO selectivity in the ethane reforming product.

[0014] Optionally, the aluminum salt is aluminum nitrate nonahydrate. The reason for selecting aluminum nitrate is that the Al-NiFe composite material formed using this precursor has the best catalytic performance.

[0015] Optionally, the mass volume ratio of the aluminum salt, nickel ferrite and ethanol is 0.367g:1g:10ml to 0.735g:1g:10ml.

[0016] The purpose of limiting the mass-to-volume ratio is to ensure that the aluminum salt and nickel ferrite are fully dispersed in ethanol. When this mass-to-volume ratio is too large, it indicates that the amount of ethanol added is relatively small, resulting in poor dispersion of the nickel ferrite, leaving some nickel ferrite unencapsulated by the alumina. When this mass-to-volume ratio is too small, it indicates that the amount of aluminum salt or nickel ferrite added is small, resulting in a relatively long combustion time, causing the alumina to sinter and agglomerate, and affecting activity.

[0017] Optionally, the calcination temperature is 600-800° C., the time is 30-60 min, and the reducing atmosphere is 10% hydrogen + 90% argon.

[0018] The purpose of limiting the calcination temperature and time is to ensure that the aluminum oxide present on the surface of the nickel ferrite forms a nickel aluminate-nickel-iron alloy structure with the nickel ferrite. When the calcination temperature is too high or the time is too long, the adverse effect is that the nickel-iron alloy agglomerates and sinters, thus affecting the catalytic sites. When the calcination temperature is too low or the time is too short, the adverse effect is that the nickel-iron alloy forms slowly, and the aluminum oxide in contact with the nickel-iron alloy cannot be completely converted into nickel aluminate, which in turn affects the formation of the catalytic interface, thereby affecting the catalytic stability and selectivity.

[0019] In addition, the Al-NiFe composite material prepared by the above method can be applied to the CO2 participation in ethane conversion reaction, specifically in the ethane dry reforming reaction, to achieve high selective conversion of ethane to CO.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0021] The present invention disperses aluminum salt and nickel ferrite in ethanol, fully mixes and disperses them, and then ignites them, so that the aluminum salt can form aluminum oxide that wraps around the nickel ferrite particles. The Al-NiFe composite material is then obtained through high-temperature reduction. Through the synergistic effect of nickel aluminate and iron-nickel alloy, high stability under high temperature conditions and selective breaking of the C-C bond in ethane molecules are achieved.

[0022] The Al-NiFe composite material prepared by the present invention has a high ethane and CO2 conversion rate, thereby realizing the efficient conversion of ethane into high-value-added CO, while consuming greenhouse gases. While realizing the effective utilization of the ethane component in shale gas, it promotes carbon dioxide emission reduction and economic utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Flow chart of preparation of Al-NiFe composite material according to an embodiment of the present invention;

[0024] Figure 2 XRD patterns of the reduced Al-NiFe composite material, the unreduced 10% Al2O3-NiFe2O4, and the original nickel ferrite in Example 1 of the present invention;

[0025] Figure 3 Graph showing the catalytic activity test results of the Al-NiFe composite materials in Examples 1-3 of the present invention. DETAILED DESCRIPTION

[0026] To make the technical solutions of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0027] This embodiment provides an Al-NiFe composite material for ethane reforming to produce synthesis gas with high selectivity, such as Figure 1 As shown, the preparation method of the Al-NiFe composite material includes:

[0028] Aluminum salt, nickel ferrite, and ethanol are uniformly mixed and ignited. The self-propagating combustion product is an aluminum oxide-nickel ferrite composite material, which is then reduced at high temperature to obtain an Al-NiFe composite material. The Al-NiFe composite material is composed of a nickel aluminate-nickel iron alloy. The mass ratio of aluminum oxide to nickel ferrite is preferably 1:10 to 1:5.

[0029] The Al-NiFe composite material prepared by the above method can be applied to the CO2 conversion reaction of ethane, specifically to the ethane dry reforming reaction, to achieve highly selective conversion of ethane to CO.

[0030] Example 1:

[0031] The mass volume ratio of aluminum nitrate nonahydrate, nickel ferrite and ethanol is 0.367g:1g:10ml;

[0032] Aluminum nitrate nonahydrate, nickel ferrite and ethanol were mixed and stirred for 10 minutes until uniform, and then subjected to high-temperature self-propagating combustion. The mixture was then calcined in an atmosphere with a volume ratio of H2:Ar = 10%:90% at a temperature of 600°C for 30 minutes. Finally, the Al-NiFe composite material was ground to obtain the composite material, which was recorded as 10% Al-NiFe.

[0033] Example 2:

[0034] The mass volume ratio of aluminum nitrate nonahydrate, nickel ferrite and ethanol is 0.735g:1g:10ml;

[0035] Aluminum nitrate nonahydrate, nickel ferrite and ethanol were mixed and stirred for 10 minutes until uniform, and then subjected to high-temperature self-propagating combustion. The mixture was then calcined in an atmosphere with a volume ratio of H2:Ar = 10%:90% at a temperature of 600°C for 30 minutes. Finally, the mixture was ground to obtain an Al-NiFe composite material, which was recorded as 20% Al-NiFe.

[0036] Example 3:

[0037] The mass volume ratio of aluminum nitrate nonahydrate, nickel ferrite and ethanol is 1.471 g:1 g:10 ml;

[0038] Aluminum nitrate nonahydrate, nickel ferrite and ethanol were mixed and stirred for 10 minutes until uniform, and then subjected to high-temperature self-propagating combustion. The mixture was then calcined in an atmosphere with a volume ratio of H2:Ar = 10%:90% at a temperature of 600°C for 30 minutes. Finally, the mixture was ground to obtain an Al-NiFe composite material, which was recorded as 40% Al-NiFe.

[0039] Comparative Example 1:

[0040] The mass volume ratio of nickel ferrite and ethanol is 1g:10ml;

[0041] Nickel ferrite and ethanol were mixed and stirred for 10 minutes until uniform, and then subjected to high-temperature self-propagating combustion. The mixture was then calcined in an atmosphere with a volume ratio of H2:Ar = 10%:90% at a temperature of 600°C for 30 minutes. Finally, the mixture was ground to obtain a NiFe composite material, which was recorded as NiFe.

[0042] Comparative Example 2:

[0043] Untreated pure nickel ferrite sample.

[0044] Comparative experiment:

[0045] The Al-NiFe composite materials prepared in Examples 1-3 and the sample materials prepared in Comparative Examples 1-2 were selected for catalytic activity testing. The testing method included: performing an ethane dry reforming reaction on the prepared Al-NiFe composite materials and the sample materials at 800° C. under normal pressure. The specific steps are as follows:

[0046] A catalytic experiment was carried out using a U-tube reaction heater in an air flow with a volume ratio of C2H6 / CO2 / Ar of 5%:5%:90% at a flow rate of 20 ml / min. The product was detected by a gas chromatograph FID detector. The experimental results are shown in Table 1.

[0047] Calculation formula: C2H6 conversion rate = (nC2H6 in -nC2H6 out ) / nC2H6 in*100%, of which:

[0048] nC2H6 in Indicates the ethane content in the reaction gas,

[0049] nC2H6 out Indicates the ethane content in the product gas.

[0050] CO selectivity = nCO / (nCO+nCH 4+ nC2H4) *100%, where:

[0051] nCO represents the CO content in the product,

[0052] nCH4 represents the methane content in the product,

[0053] nC2H4 represents the ethylene content in the product.

[0054] Table 1

[0055]

[0056] From the above experimental data, we can know that:

[0057] An Al-NiFe composite material prepared using aluminum nitrate nonahydrate as the aluminum salt and ethanol as the organic solvent significantly improved ethane conversion and CO selectivity during ethane dry reforming compared to NiFe catalysts without Al addition and pure nickel ferrite samples. The Al-NiFe composite material exhibited the highest CO selectivity during ethane dry reforming when the mass-to-volume ratio of aluminum nitrate nonahydrate: nickel ferrite: ethanol was 0.367g:1g:10ml.

[0058] Figure 2 The XRD patterns of the reduced Al-NiFe composite material, the unreduced 10% Al2O3-NiFe2O4, and the original nickel ferrite sample from Example 1 of the present invention are shown, with the abscissa representing the position of characteristic peaks and the ordinate representing the intensity of characteristic peaks. As can be seen from the figure, the unreduced 10% Al2O3-NiFe2O4 contains a nickel ferrite phase peak; after reduction, peaks of the nickel-iron alloy phase and the nickel aluminate phase peak appear, indicating the formation of a nickel aluminate-nickel-iron alloy.

[0059] Figure 3 This figure shows the catalytic activity test results of the Al-NiFe composite materials in Examples 1-3 of the present invention at 800°C, with time plotted on the abscissa and ethane conversion on the ordinate. As can be seen from the figure, at 800°C, the Al-NiFe composite material prepared in Example 1 achieves relatively stable ethane conversion, with a conversion exceeding 99%. The Al-NiFe composite materials prepared in Examples 2 and 3 exhibit poor catalytic stability and rapid deactivation.

[0060] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments shown herein, but is intended to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An Al-NiFe composite material for ethane reforming to produce synthesis gas with high selectivity, characterized in that: The preparation method of the Al-NiFe composite material comprises: Using ethanol as a dispersant, aluminum salt and nickel ferrite are fully dispersed and heated at high temperature. The product obtained after self-propagating combustion is an aluminum oxide-nickel ferrite composite material, which is then reduced at high temperature to obtain an Al-NiFe composite material. The composition of the Al-NiFe composite material is nickel aluminate-nickel iron alloy, wherein the mass ratio of aluminum oxide to nickel ferrite is 1:10 to 1:

5.

2. The Al-NiFe composite material according to claim 1, characterized in that The aluminum salt is aluminum nitrate nonahydrate.

3. The Al-NiFe composite material according to claim 2, characterized in that The mass volume ratio of the aluminum salt, nickel ferrite and ethanol is 0.367g:1g:10ml to 0.735g:1g:10ml.

4. The Al-NiFe composite material according to claim 3, characterized in that The reduction temperature is 600-800° C., the time is 30-60 min, and the reduction atmosphere is 10% hydrogen + 90% argon.

5. An application of the Al-NiFe composite material according to any one of claims 1 to 4, characterized in that: The Al-NiFe composite material is applied to the CO2-ethane conversion reaction.

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