Hydrotalcite-like compounds and their preparation methods and applications, catalysts for autothermal reforming of small molecule alcohols to produce hydrogen and their preparation methods, and methods for producing hydrogen

Abstract

The present invention relates to the field of catalysts, and specifically relates to a hydrotalcite-like material, a preparation method and application thereof, a small molecule alcohol autothermal reforming hydrogen production catalyst, a preparation method thereof, and a hydrogen production method. The hydrotalcite-like material comprises metallic copper, nickel, aluminum and calcium, and characteristic peaks with 2θ being 11.688°±0.01, 23.205°±0.01 and 35.022°±0.01 exist in the XRD spectrum of the hydrotalcite-like material. The calcium-modified hydrotalcite-like material of the present invention has uniform particles, high purity, high specific surface area and porosity, and has a unique XRD spectrum. The corresponding unique structure is beneficial to the dispersion of metal components.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and particularly relates to a hydrotalcite-like material, a preparation method and application thereof, a small molecule alcohol autothermal reforming hydrogen production catalyst, a preparation method thereof, and a hydrogen production method. Background Art

[0002] With the current situation of global warming and the gradual depletion of fossil energy, people are urgently seeking a new type of renewable green energy to replace the application of fossil energy in industrial, living and other fields. Hydrogen energy, as a new type of renewable secondary energy, has a wide source, a large energy density, and is green and pollution-free. Only water is emitted during the use process, making it an ideal alternative to fossil energy. The traditional hydrogen production process is mainly based on methane steam reforming (MSR). Although MSR has the advantages of a mature hydrogen production process and a large production scale, its raw materials are non-renewable, the reaction temperature is high, and the reaction process is accompanied by strong endothermic heat. Therefore, there is an urgent need for a cleaner and more efficient hydrogen production process to replace the traditional MSR. Compared with the traditional hydrogen production process, in the autothermal reforming process (ATR), an air stream is additionally added to the raw material stream of steam reforming. Oxygen undergoes a partial reforming reaction with the reactants, thereby releasing a large amount of heat to supply heat for the steam reforming occurring simultaneously in the system. In actual production, the thermal neutral process of the system can usually be achieved by adjusting the temperature of the preheater and the flow rate of the air stream. Methanol, as a raw material for hydrogen production, has the advantages of a low decomposition temperature, a high hydrogen-carbon ratio, low toxicity, and convenient transportation. In addition, in addition to preparing methanol through the traditional Fischer-Tropsch synthesis method, in recent years, scientists have used carbon capture technology to convert CO in the air 2 into bio-methanol. Using bio-methanol as a raw material to produce hydrogen through an autothermal reforming reaction is a sustainable and efficient hydrogen production process. In addition to the hydrogen production process and reaction raw materials, an efficient catalyst is also a key factor affecting the hydrogen yield.

[0003] In industrial production of hydrogen by methanol reforming, noble metal platinum-based catalysts and non-noble metal copper-based catalysts are often used. Platinum-based catalysts cannot be mass-produced because of the scarcity of platinum reserves, high prices, and high hydrogen production costs. Non-noble metal copper-based catalysts are prone to sintering and deactivation at higher temperatures. Introducing a second metal into traditional copper-based catalysts to form an alloy with copper metal is beneficial to improving the stability of copper and also to enhancing the catalytic activity of the catalyst. In addition, after determining the active metal, finding a suitable catalyst support is also an important factor affecting the catalyst activity. Hydrotalcite (layered double metal hydroxide, LDHs) is often used in sewage adsorption treatment and drug targeted transportation, and is an efficient ion adsorption material and transportation material. In recent years, scientists have begun to use hydrotalcite as a catalyst precursor, which has the following advantages: ① high specific surface area, which is beneficial to the uniform distribution of the active metal on the surface of the support; ② high Lewis basicity, which is beneficial to the adsorption of CO 2 on the surface of the support, inhibits the formation of carbon deposition precursors, and improves the stability of the catalyst; ③ enhances the interaction between the metal and the support. The improvement of the interaction between the metal and the support is beneficial to the embedding of the active metal on the surface of the support, reduces the migration rate of the active metal at high temperatures, and inhibits the sintering of the active metal. ④ wide range of applications, and hydrotalcite derivatives of target elements can be obtained by controlling the preparation process. In summary, using hydrotalcite as a catalyst precursor is beneficial to improving the overall performance of the catalyst.

[0004] However, the hydrotalcite prepared by traditional hydrotalcite and traditional preparation methods has uneven particles, low purity, and the catalyst prepared from the existing hydrotalcite has poor anti-sintering ability, poor high-temperature stability, and low reaction activity.

[0005] For example, the traditional co-precipitation method requires the preparation of two or more raw material solutions, the addition rate and pH value of the raw material solutions need to be controlled during the reaction process, and there are disadvantages such as uneven component concentrations during the crystallization process, resulting in inconsistent composition and size of the formed hydrotalcite. The overall operation process is complex and time-consuming. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems existing in the prior art, such as the hydrotalcite prepared by traditional hydrotalcite and traditional preparation methods having uneven particles, low purity, and the catalyst prepared from the existing hydrotalcite having poor anti-sintering ability, poor high-temperature stability, and low reaction activity. The present invention provides a hydrotalcite-like material, its preparation method and application, a catalyst for autothermal reforming of small molecule alcohols to produce hydrogen, its preparation method, and a method for producing hydrogen. The hydrotalcite has uniform particles and high purity, and the prepared catalyst has good anti-sintering ability, good high-temperature stability, and high reaction activity.

[0007] To achieve the above object, a first aspect of the present invention provides a hydrotalcite-like material, which comprises metallic copper, nickel, aluminum and calcium, and the XRD pattern of the hydrotalcite-like material has characteristic peaks at 2θ = 11.688° ± 0.01, 23.205° ± 0.01 and 35.022° ± 0.01.

[0008] A second aspect of the present invention provides a preparation method of the hydrotalcite-like material described in the first aspect, which comprises: adding copper salt, nickel salt, aluminum salt and calcium salt into an aqueous alcohol solution, then adding urea for hydrothermal treatment, and after the hydrothermal treatment, filtering and freeze-drying.

[0009] A third aspect of the present invention provides an application of the hydrotalcite-like material described in the first aspect and / or the hydrotalcite-like material prepared by the preparation method described in the second aspect in the preparation of adsorbents and / or catalysts.

[0010] A fourth aspect of the present invention provides a preparation method of a small molecule alcohol autothermal reforming hydrogen production catalyst, which comprises: calcining the hydrotalcite-like material described in the first aspect and / or the hydrotalcite-like material prepared by the preparation method described in the second aspect under an inert atmosphere, and then reducing it under a reducing atmosphere.

[0011] A fifth aspect of the present invention provides a small molecule alcohol autothermal reforming hydrogen production catalyst obtained by the preparation method described in the fourth aspect, and the XRD pattern of the catalyst has characteristic peaks at 2θ = 31.408° ± 0.01, 38.009° ± 0.01, 44.996° ± 0.01 and 65.535° ± 0.01.

[0012] A sixth aspect of the present invention provides a method for producing hydrogen by autothermal reforming of methanol. Under the conditions of the catalyst described in the fifth aspect, methanol, water and oxygen are brought into contact for reaction.

[0013] The conditions of the contact reaction include: the gas hourly space velocity of the gaseous raw materials is 8000 - 15000 h -1 ; and / or methanol: water = (0.8 - 1.2):(0.5 - 4) in terms of moles; and / or methanol: oxygen = (0.8 - 1.2):(0 - 1) in terms of moles; and / or the reaction temperature is 300 - 600 °C, and / or the reaction pressure is 0.01 - 0.5 MPa.

[0014] By the above technical solutions, the present invention has the following beneficial effects:

[0015] The calcium-modified hydrotalcite-like material of the present invention has uniform particles, high purity, high specific surface area and porosity, and has a unique XRD pattern, and the corresponding unique structure is beneficial to the dispersion of metal components.

[0016] In particular, the supported catalyst obtained by heat-treating the calcium-modified hydrotalcite-like material of the present invention has metal particles with a small particle size and good dispersion, providing more adsorption sites and active sites for the catalytic reaction, increasing the contact area between the reactants and the active metal, and having higher catalytic activity and conversion rate. At the same time, calcium oxide with uniform dispersion will be formed on the surface of the support. Calcium oxide can act as an inert component to effectively isolate the metal nanoparticles, significantly improving the anti-sintering ability and high-temperature stability of the catalyst. In addition, the modification of calcium can increase the Lewis basicity of the support surface and also act as a CO 2 adsorbent, reducing the concentration of CO 2 during the reaction process, promoting the reaction to occur, enhancing the catalytic activity, and being particularly suitable for the autothermal reforming of small molecule alcohols such as methanol to produce hydrogen, with high conversion rate of small molecule alcohols, high hydrogen production rate, and high hydrogen selectivity. Description of the Drawings

[0017] Figure 1 XRD pattern of the hydrotalcite precursor prepared in the examples and comparative examples of the present invention;

[0018] Figure 2 XRD pattern of the catalysts prepared in the examples and comparative examples of the present invention;

[0019] Figure 3 SEM image of the sample morphology structure of Example 1 observed by scanning electron microscope;

[0020] Figure 4 SEM image of the sample morphology structure of Comparative Example 5 observed by scanning electron microscope;

[0021] Figure 5 TEM image of Example 1 observed by transmission electron microscope;

[0022] Figure 6 Temperature gradient curve of the catalytic activity of the sample of Example 3. Detailed Description of the Invention

[0023] The endpoints and any values within the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values within each range, between the endpoint values of each range, between the endpoint values and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0024] The present invention provides a hydrotalcite-like material, which includes metal copper, nickel, aluminum, and calcium. The XRD pattern of the hydrotalcite-like material has characteristic peaks at 2θ of 11.688°±0.01, 23.205°±0.01, and 35.022°±0.01.

[0025] The calcium-modified hydrotalcite-like particles of the present invention are uniform and have high purity, with a unique XRD pattern, and the corresponding unique structure is beneficial to the dispersion of metal components.

[0026] In the present invention, as long as the object of the present invention can be achieved, there is no special requirement for the molar ratio of copper, nickel, aluminum and calcium in the hydrotalcite-like. According to a preferred embodiment of the present invention, the molar ratio of copper, nickel, calcium and aluminum in the hydrotalcite-like is (1-10):(1-10):(60-70):30.

[0027] According to a preferred embodiment of the present invention, the molar ratio of copper, nickel, aluminum and calcium in the hydrotalcite-like is (1-10):(2-4):(65-70):30. By adopting the foregoing preference, the uniformity, purity, specific surface area and porosity of the hydrotalcite-like particles can be further improved.

[0028] According to a preferred embodiment of the present invention, in terms of moles, aluminum / (copper, nickel, aluminum and calcium) in the hydrotalcite-like is 0.01-0.6; aluminum / (copper, nickel and calcium) is 1-7.

[0029] According to a preferred embodiment of the present invention, in terms of moles, aluminum / (copper, nickel, aluminum and calcium) in the hydrotalcite-like is 0.17-0.33; aluminum / (copper, nickel and calcium) is 1-4. By adopting the foregoing preference, the uniformity and purity of the hydrotalcite-like particles can be further improved.

[0030] In the present invention, the particle size of the Cu-Ni alloy metal in the hydrotalcite-like is 6.8±1.5 nm.

[0031] In the present invention, the porosity of the hydrotalcite-like is 20-40%, preferably 25%-40%.

[0032] In the present invention, the specific surface area of the hydrotalcite-like is 65-140 m 2 g -1 ; preferably 80-140 m 2 g -1 ; preferably 85-120 m 2 g -1 .

[0033] The present invention provides a method for preparing the hydrotalcite-like, which includes: adding copper salt, nickel salt, aluminum salt and calcium salt into an alcohol aqueous solution, then adding urea for hydrothermal treatment, and filtering and freeze-drying after the hydrothermal treatment.

[0034] The method of the present invention combines the urea hydrolysis process and the hydrothermal process, omits the condensation reflux process of the conventional urea hydrolysis method, and by mixing urea in the salt solution, utilizes the slow decomposition of urea under high temperature and high pressure to release OH -The characteristics enable the precipitation process to proceed slowly, which is conducive to improving the uniformity of the solution concentration and obtaining hydrotalcite-like compounds with uniform particles and components. The high-temperature and high-pressure environment of the hydrothermal process can effectively control the crystal growth. In addition, an alcohol mixture is added as a dispersant during the hydrothermal process, which further avoids the agglomeration of the precipitate during the hydrolysis of urea, is conducive to controlling the particle size of the precipitate, and obtains a uniform and fine precipitate, that is, a hydrotalcite-like compound with uniform and pure particles of the present invention can be prepared.

[0035] In the present invention, as long as the object of the present invention can be achieved, there is no special requirement for the volume ratio of alcohol to water in the aqueous alcohol solution. According to a preferred embodiment of the present invention, the volume ratio of alcohol to water in the aqueous alcohol solution is (1-3):10.

[0036] According to a preferred embodiment of the present invention, the volume ratio of alcohol to water in the aqueous alcohol solution is (1-2):10. By adopting the foregoing preference, the uniformity and purity of the hydrotalcite-like particles can be further improved.

[0037] In the present invention, the type of alcohol in the aqueous alcohol solution can be a conventional choice in the art. According to a preferred embodiment of the present invention, the alcohol in the aqueous alcohol solution is a lower alcohol with 1-3 carbon atoms.

[0038] According to a preferred embodiment of the present invention, the alcohol in the aqueous alcohol solution is selected from at least one of ethanol, ethylene glycol, and propanol.

[0039] According to a preferred embodiment of the present invention, the alcohol in the aqueous alcohol solution is a mixed alcohol with a volume ratio of ethanol, ethylene glycol, and propanol of (0-3):(0.5-2):(0-1). By adopting the foregoing preference, the uniformity and purity of the hydrotalcite-like particles can be further improved.

[0040] In the present invention, the types of the copper salt, nickel salt, aluminum salt, and calcium salt can be a conventional choice in the art. According to a preferred embodiment of the present invention, the copper salt, nickel salt, aluminum salt, and calcium salt are nitrate and / or chloride hydrates.

[0041] According to a preferred embodiment of the present invention, the copper salt, nickel salt, aluminum salt, and calcium salt are nitrate hydrates. The inventors found that when nitrates are selected, nitrate radicals exist in the obtained hydrotalcite-like compounds. The nitrogen oxides and instantaneous strong pressure generated during the calcination treatment are conducive to pore formation and improve the porosity of the carrier.

[0042] In the present invention, a low pH during hydrothermal treatment is not conducive to the precipitation of metal cations and it is difficult to form the hydrotalcite-like structure of the present invention. While an excessively high pH will cause the collapse of the hydrotalcite-like structure of the present invention, reducing the porosity and specific surface area of the hydrotalcite-like structure of the present invention. According to a preferred embodiment of the present invention, the pH of the system environment is 7-11 after adding urea. By adjusting the pH value during the hydrothermal treatment process, it is beneficial to form the hydrotalcite-like morphology of the present invention, improve the specific surface area and pore volume, and increase the dispersion degree of active metals.

[0043] According to a preferred embodiment of the present invention, the pH of the system environment is 9-11 after adding urea.

[0044] In the present invention, the conditions of the hydrothermal treatment can be a conventional choice in the art. According to a preferred embodiment of the present invention, the conditions of the hydrothermal treatment include: the hydrothermal temperature is 80-170 °C, preferably 100-130 °C, for example, it can be 80 °C, 90 °C, 100 °C, 110 °C, 120 °C, 130 °C; the hydrothermal time is 12-48 h. By adopting the foregoing preferences, the particle uniformity and purity of the hydrotalcite-like can be further improved.

[0045] In the present invention, the conditions of the freeze-drying can be a conventional choice in the art. According to a preferred embodiment of the present invention, the conditions of the freeze-drying include: -60 °C to -40 °C, preferably -55 °C to -45 °C, the vacuum degree is 5-30 Pa, and the drying time is 12-24 h. By adopting the foregoing preferences, it is beneficial to preserve the hydrotalcite-like structure and make the active metals uniformly dispersed.

[0046] The present invention provides an application of the hydrotalcite-like in the preparation of an adsorbent and / or a catalyst, preferably in the preparation of a catalyst for the autothermal reforming of small molecule alcohols to produce hydrogen.

[0047] The present invention provides a preparation method of a catalyst for the autothermal reforming of small molecule alcohols to produce hydrogen. The preparation method includes: calcining the hydrotalcite-like and / or the hydrotalcite-like prepared by the preparation method under an inert atmosphere, and then reducing it under a reducing atmosphere.

[0048] For the supported catalyst obtained by heat-treating the calcium-modified hydrotalcite-like of the present invention, the metal particles have a smaller particle size and good dispersion degree, providing more adsorption sites and active sites for the catalytic reaction, increasing the contact area between the reactants and the active metals, having higher catalytic activity and conversion rate. At the same time, calcium oxide will be formed on the surface of the carrier in a uniformly dispersed manner. Calcium oxide can act as an inert component to effectively isolate the metal nanoparticles, significantly improving the anti-sintering ability and high-temperature stability of the catalyst. In addition, the modification of calcium can improve the Lewis basicity on the surface of the carrier and can also act as a CO 2 adsorbent, reducing CO during the reaction process2 The concentration promotes the reaction to occur, improves the catalytic activity, and is applicable to the autothermal reforming of small molecule alcohols such as methanol to produce hydrogen, with high conversion rate of small molecule alcohols, high hydrogen yield, and high hydrogen selectivity.

[0049] In the present invention, the conditions for roasting can be a conventional selection in the art. According to a preferred embodiment of the present invention, the conditions for roasting include: the temperature is 500 - 900 °C, preferably 600 - 900 °C; for example, it can be 600 °C, 800 °C; the heating rate is 1 - 10 °C / min, and the time is 1 - 10 h. By adopting the foregoing preferred scheme, the catalyst metal particles have a smaller particle size and good dispersion, providing more active sites for the catalytic reaction.

[0050] In the present invention, the conditions for roasting can be a conventional selection in the art. According to a preferred embodiment of the present invention, the conditions for reduction include: the temperature is 500 - 800 °C, preferably 600 - 800 °C, for example, it can be 600 °C, 700 °C; the time is 1 - 10 h.

[0051] In the present invention, the inert atmosphere can be a conventional selection in the art. According to a preferred embodiment of the present invention, the inert atmosphere is selected from at least one of a carbon dioxide atmosphere, a nitrogen atmosphere, a helium atmosphere, and an argon atmosphere.

[0052] According to a preferred embodiment of the present invention, the flow rate of the inert gas is 50 - 200 mL / min.

[0053] In the present invention, the reducing atmosphere can be a conventional selection in the art. According to a preferred embodiment of the present invention, the reducing atmosphere contains a hydrogen atmosphere and can also contain a diluent gas such as nitrogen.

[0054] According to a preferred embodiment of the present invention, the flow rate of the reducing gas is 20 - 100 mL / min, preferably 20 - 50 mL / min.

[0055] The present invention provides a catalyst for autothermal reforming of small molecule alcohols to produce hydrogen obtained by the described preparation method. In the XRD pattern of this catalyst, characteristic peaks exist at 2θ of 31.408° ± 0.01, 38.009° ± 0.01, 44.996° ± 0.01, and 65.535° ± 0.01.

[0056] The catalyst of the present invention has strong anti-sintering ability, high temperature stability, and high activity.

[0057] The present invention provides a method for autothermal reforming of methanol to produce hydrogen. Under the conditions of the described catalyst, methanol, water, and oxygen are brought into contact for reaction. The conditions for the contact reaction include: the gas-phase feed space velocity is 8000 - 15000 h -1; and / or methanol:water = (0.8 - 1.2):(0.5 - 4) in terms of moles; and / or methanol:oxygen = (0.8 - 1.2):(0 - 1) in terms of moles; and / or the reaction temperature is 300 - 600 °C, and / or the reaction pressure is 0.1 - 0.5 MPa.

[0058] By adopting the foregoing scheme of the present invention for hydrogen production by methanol autothermal reforming, the methanol conversion rate is high, the hydrogen production rate is high, and the hydrogen selectivity is high.

[0059] The reaction formula for hydrogen production by methanol autothermal reforming:

[0060]

[0061] In the formula, δ is the oxygen-carbon ratio in the reaction system.

[0062] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are commercially available products. The gas-phase products are analyzed for their composition by Agilent chromatography, and the reaction residual liquid is analyzed and detected by Shimadzu chromatography; the XRD spectrum is obtained by a Rigaku X-ray diffractometer Miniflex 600 (Cu Kα1 radiation); the SEM image is taken by a Hitachi cold field emission scanning electron microscope Regulus8100; the TEM image is taken by a Tecnai-G2-F30 FEI transmission electron microscope, and the specific surface area and porosity of the material are tested by a TriStar II 3020 automatic specific surface area and porosity analyzer.

[0063] Methanol conversion rate % = (mole percentage of methanol in raw materials - mole percentage of methanol in products) / mole percentage of methanol in raw materials * 100

[0064] Hydrogen yield % = 2 * hydrogen production rate / (4 * methanol feed rate + 2 * water feed rate) * 100%

[0065] Example 1

[0066] Mix 10 mL of ethylene glycol with 70 mL of deionized water to obtain solution A; weigh 0.6 g of Ni(NO 3 ) 2 ·6H 2 O, 0.125 g of Cu(NO 3 ) 2 ·3H 2 O, 3.7 g of Ca(NO 3 ) 2 ·4H 2 O and 2.8 g of Al(NO 3 ) 3 ·9H 2O is gradually dissolved in solution A, and after complete dissolution, a metal salt solution B is obtained; urea is added to solution B until it is completely dissolved to obtain solution C, and the pH of solution C is 10; solution C is transferred to a polytetrafluoroethylene high-pressure hydrothermal autoclave and hydrothermally treated at 110 °C for 24 h. After filtration and freeze-drying at -50 °C and a vacuum of 10 Pa for 24 h, a copper-nickel hydrotalcite precursor D is obtained; the XRD pattern of the copper-nickel hydrotalcite precursor D (sample denoted as CuNi-U-LDHs) is shown in Figure 1 , and characteristic peaks exist at 2θ of 11.688° ± 0.01, 23.205° ± 0.01, and 35.022° ± 0.01. The specific surface area is 112.36 m 2 g -1 cat ; the porosity is 37%, and its SEM is shown in Figure 3 . The copper-nickel hydrotalcite precursor synthesized by the present invention has a good flaky structure and is evenly dispersed.

[0067] The copper-nickel hydrotalcite precursor D is calcined at 800 °C for 3 h, with a nitrogen gas flow rate of 100 mL / min and a heating rate of 5 °C / min, to obtain a metal oxide mixture powder E (sample denoted as CuNi-U-MMO), and its XRD pattern is shown in Figure 2 , and characteristic peaks exist at 2θ of 31.408° ± 0.01, 38.009° ± 0.01, 44.996° ± 0.01, and 65.535° ± 0.01. The powder E is reduced at 800 °C and a hydrogen gas flow rate of 50 ml / min for 1 h to prepare a copper-nickel bimetal-supported catalyst, and its TEM is shown in Figure 5 . The CuNi alloy is evenly distributed on the surface of the support, and the metal particle size is 6.8 ± 1.5 nm, confirming the successful synthesis of the nanoscale catalyst.

[0068] The above catalyst is used for the autothermal reforming of methanol to produce hydrogen in an atmospheric-pressure fixed bed, where the reaction conditions are: GHSV = 10000 h -1 , S:C = 2, O 2 / C = 0.2, and the reaction temperature T = 600 °C. After the reaction products are cooled, gaseous products (H 2 , CH 4 , CO, and CO 2 ) and reaction residue liquid (CH 3 OH and H 2 O) are obtained. The gaseous products are analyzed for their composition by Agilent chromatography, while the reaction residue liquid is analyzed and detected by Shimadzu chromatography. The experimental results are shown in Table 1.

[0069] Example 2

[0070] Same as Example 1, except that 21 mL of ethanol was mixed with 70 mL of deionized water;

[0071] The pH of the system environment was 11 after adding urea;

[0072] The hydrothermal temperature was 100 °C; the calcination and reduction temperatures were 700 °C;

[0073] Cu(NO 3 ) 2 ·3H 2 O was used in an amount of 2.5 g. The experimental results are shown in Table 1.

[0074] The XRD pattern of the copper-nickel hydrotalcite precursor D was similar to that of Figure 1 The specific surface area was 86.24 m 2 g -1 cat ; the porosity was 26%.

[0075] The XRD pattern of the copper-nickel bimetal-loaded catalyst was similar to that of Figure 2 Similar.

[0076] Example 3

[0077] Same as Example 1, except that 14 mL of propanol was mixed with 70 mL of deionized water;

[0078] The pH of the system environment was 9 after adding urea;

[0079] The hydrothermal temperature was 130 °C; the calcination and reduction temperatures were 600 °C;

[0080] Cu(NO 3 ) 2 ·3H 2 O was used in an amount of 1.5 g. The experimental results are shown in Table 1.

[0081] The XRD pattern of the copper-nickel hydrotalcite precursor D was similar to that of Figure 1 Similar, with a specific surface area of 102.79 m 2 g -1 cat ; the porosity was 34%; the XRD pattern of the copper-nickel bimetal-loaded catalyst was similar to that of Figure 2 Similar,.

[0082] Example 4

[0083] Same as Example 1, except that the amount of Cu(NO 3 ) 2 ·3H 2 O was 5 g.

[0084] The specific surface area of the hydrotalcite-like material was 94.17 m 2 g-1 cat ; The porosity is 31%.

[0085] The experimental results are shown in Table 1.

[0086] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to Figure 1 ; The XRD pattern of the copper-nickel bimetal supported catalyst is similar to Figure 2 ;

[0087] Example 5

[0088] Same as Example 1, except that the addition amount of metal elements is adjusted so that the aluminum ratio (copper, nickel, aluminum, and calcium) is 0.21; aluminum / (copper, nickel, and calcium) is 0.27.

[0089] The specific surface area of the hydrotalcite-like material is 91.28 m 2 g -1 cat ; The porosity is 29%.

[0090] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to Figure 1 ; The XRD pattern of the copper-nickel bimetal supported catalyst is similar to Figure 2 ;

[0091] Example 6

[0092] Same as Example 1, except that the nitrate is directly added to deionized water instead of an alcohol solution.

[0093] The specific surface area of the hydrotalcite-like material is 70.47 m 2 g -1 cat ; The porosity is 25%.

[0094] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to Figure 1 ; The XRD pattern of the copper-nickel bimetal supported catalyst is similar to Figure 2 ;

[0095] Example 7

[0096] Same as Example 1, except that the added ethylene glycol solution is replaced with a mixed alcohol solution of the same volume of ethanol, ethylene glycol, and propanol, where the volume ratio of ethanol, ethylene glycol, and propanol added is 1.5:2:0.5.

[0097] The specific surface area of the hydrotalcite-like material is 106.77 m 2 g -1 cat ; The porosity is 38%.

[0098] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to Figure 1Similar; the XRD pattern of the copper-nickel bimetal supported catalyst is similar to that of Figure 2 Similar.

[0099] Example 8

[0100] Same as Example 1, except that the metal precursor is a chloride hydrate.

[0101] The specific surface area of the hydrotalcite-like material is 83.73 m 2 g -1 cat ; the porosity is 21%.

[0102] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to that of Figure 1 Similar; the XRD pattern of the copper-nickel bimetal supported catalyst is similar to that of Figure 2 Similar.

[0103] Example 9

[0104] Same as Example 1, except that the amount of urea added is adjusted so that the pH of the solution during the hydrothermal process is 7.

[0105] The specific surface area of the hydrotalcite-like material is 92.97 m 2 g -1 cat ; the porosity is 28%.

[0106] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to that of Figure 1 Similar; the XRD pattern of the copper-nickel bimetal supported catalyst is similar to that of Figure 2 Similar.

[0107] Example 10

[0108] Same as Example 1, except that the hydrothermal treatment temperature is 80 °C and the treatment time is 24 h.

[0109] The specific surface area of the hydrotalcite-like material is 88.65 m 2 g -1 cat ; the porosity is 26%.

[0110] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to that of Figure 1 Similar; the XRD pattern of the copper-nickel bimetal supported catalyst is similar to that of Figure 2 Similar.

[0111] Example 11

[0112] Same as Example 1, except that drying is carried out in an oven at 110 °C for 12 h.

[0113] The specific surface area of the hydrotalcite-like material is 66.21 m 2 g -1cat ; The porosity is 17%.

[0114] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to that of Figure 1 ; The XRD pattern of the copper-nickel bimetal supported catalyst is similar to that of Figure 2 similar.

[0115] Example 12

[0116] Same as Example 1, except that the calcination temperature is 500 °C and the calcination time is 4 h.

[0117] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to that of Figure 1 ; The XRD pattern of the copper-nickel bimetal supported catalyst is similar to that of Figure 2 similar.

[0118] Example 13

[0119] Same as Example 1, except that the reduction temperature is 500 °C and the reduction time is 1 h.

[0120] The XRD pattern of the copper-nickel hydrotalcite precursor D is similar to that of Figure 1 ; The XRD pattern of the copper-nickel bimetal supported catalyst is similar to that of Figure 2 similar.

[0121] Example 14

[0122] Same as Example 3, except that the temperature for the steam reforming of methanol for hydrogen production is 300 - 600 °C. Within the test range, the catalyst activity was tested at a temperature gradient of 50 °C. The test results are as shown in Figure 6 shown. It can be seen from Figure 6 that both the hydrogen yield and the methanol conversion rate are functions of temperature. Among them, methanol is completely converted at 450 °C, while the hydrogen yield reaches the highest value at 550 °C. Further increasing the temperature does not further increase the hydrogen yield, indicating that the reaction reaches equilibrium at 550 °C and this catalyst has excellent high-temperature stability.

[0123] Comparative Example 1

[0124] Same as Example 1, except that the copper salt was replaced with an equimolar amount of nickel salt. The experimental results are shown in Table 1. The XRD pattern is shown in Figure 1 (labeled as Ni-U-LDHs), and its XRD pattern is similar to that of Example 1. There are hydrotalcite-like characteristic peaks at 2θ of 11.688° ± 0.01, 23.205° ± 0.01, and 35.022° ± 0.01, indicating the successful synthesis of the hydrotalcite-like compound. The specific surface area of the hydrotalcite-like is 98.72 m 2 g -1 cat; The porosity is 23%. The XRD pattern of its calcined sample is shown in Figure 2 (The sample is labeled as Ni-U-MMO), and the characteristic peaks at 2θ of 37.248° ± 0.01 and 43.275° ± 0.01 correspond to the (200) and (220) crystal planes of NiO, respectively.

[0125] Comparative Example 2

[0126] Same as Example 1, except that the nickel salt is changed to an equimolar copper salt. The experimental results are shown in Table 1. The XRD pattern is shown in Figure 1 (The sample is labeled as Cu-U-LDHs), and its XRD pattern is similar to that of Example 1. The characteristic peaks of hydrotalcite-like compounds exist at 2θ of 11.688° ± 0.01, 23.205° ± 0.01, and 35.022° ± 0.01, indicating the successful synthesis of hydrotalcite-like compounds. The specific surface area of the hydrotalcite-like compound is 77.89 m 2 g -1 cat ; The porosity is 17%. The XRD pattern of its calcined sample is shown in Figure 2 (The sample is labeled as Cu-U-MMO), and the characteristic peaks at 2θ of 35.417° ± 0.01 and 35.453° ± 0.01 correspond to the (002) and (11-1) crystal planes of CuO, respectively.

[0127] Comparative Example 3

[0128] Same as Example 1, except that no calcium salt is added to the metal salt solution. The experimental results are shown in Table 1. NiCu-Al 2 O 3 The XRD pattern of its calcined sample is shown in Figure 2 (The sample is labeled as CuNi / γ-Al 2 O 3 )), and the characteristic peaks at 2θ of 35.417° ± 0.01 and 35.453° ± 0.01 correspond to the (002) and (11-1) crystal planes of CuO, respectively. The characteristic peaks at 2θ of 37.21° ± 0.01, 44.30° ± 0.01, and 62.9° ± 0.01 are the characteristic peaks of NiO.

[0129] Comparative Example 4

[0130] Preparation method of Ni-CeO 2 catalyst by sol-gel method. The specific preparation steps are as follows:

[0131] S1. Weigh 5 g of chitosan with an electronic balance, add it to 100 mL of deionized water, and stir evenly with a magnetic stirrer to obtain solution A; weigh 0.2 g of Ni(NO 3 ) 2 ·6H2 O and 2 g of Ce(NO 3 ) 2 ·6H 2 O were completely dissolved in solution A to obtain solution B; ammonia water was used as the alkaline solution to adjust the pH of the solution to 6 to obtain solution C. Finally, solution C was stirred at a constant temperature on a magnetic stirrer at a temperature of 80 °C and a stirring rate of 100 rpm / min until a gel was formed. The obtained gel was placed in an oven at 100 °C and dried for 24 h to obtain the precursor of the catalyst.

[0132] S2. After grinding the precursor of the catalyst into powder, it was pyrolyzed under a nitrogen flow of 10 mL / min at 400 °C for 3 h, and the heating rate was 5 °C / min. Subsequently, the nitrogen flow was changed to an air flow and pyrolyzed at the same temperature for 4 h. After cooling to room temperature, a nickel-based cerium oxide catalyst (the sample was denoted as Ni-CeO 2 ) was obtained, and its XRD pattern was as Figure 2 shown. Characteristic peaks of CeO 2 existed at 2θ of 28.554° ± 0.01, 33.081° ± 0.01, 47.478° ± 0.01, and 56.334° ± 0.01, which corresponded to the (111), (200), (220), and (311) crystal planes of CeO 2 respectively.

[0133] The autothermal reforming of methanol to produce hydrogen reaction was carried out under the same conditions as in Example 1.

[0134] Comparative Example 5

[0135] A copper-nickel bimetal-supported catalyst was prepared by the precipitation method. The specific preparation steps were as follows:

[0136] S1. Weigh 0.6 g of Ni(NO 3 ) 2 ·6H 2 O, 1.5 g of Cu(NO 3 ) 2 ·3H 2 O, 3.7 g of Ca(NO 3 ) 2 ·4H 2 O, and 2.8 g of Al(NO 3 ) 3 ·9H 2 O with an electronic balance and gradually dissolve them in 100 mL of deionized water A. After complete dissolution, a metal salt solution A was obtained; prepare 1 M NaOH and 0.015 M Na 2 CO 3 alkali solution: Weigh 10 g of NaOH and 4 g of Na 2 CO 3Dissolve it in 250 mL of deionized water to obtain Solution B; measure 100 mL of deionized water, and add Solution A and Solution B dropwise into the deionized water while maintaining the pH of the solution at 10. The precipitation process takes about 1 h to obtain Suspension C; transfer Solution C to a polytetrafluoroethylene high-pressure hydrothermal reactor, perform hydrothermal treatment at 110 °C for 24 h, and obtain a copper-nickel hydrotalcite precursor prepared by the coprecipitation method after filtration and freeze-drying for 24 h; the XRD pattern is shown in Figure 1 (The sample is labeled as CuNi-B-LDHs), and characteristic peaks of Ca-Al hydrotalcite exist at 2θ of 10.0139° ± 0.01, 20.611° ± 0.01, and 32.841° ± 0.01; the scanning electron micrograph is shown in Figure 4 , compared with Example 3, the copper-nickel bimetallic catalyst prepared by the precipitation method shows obvious agglomeration. The formation of agglomeration reduces the specific surface area and porosity of the hydrotalcite, which is not conducive to the uniform distribution of the active metal on the surface of the support. Its specific surface area is 70.48 m 2 g -1 cat ; the porosity is 18%.

[0137] S2. Place the copper-nickel hydrotalcite precursor D in a pyrolysis furnace at 800 °C for 3 h, with a nitrogen gas flow rate of 100 mL / min and a heating rate of 5 °C / min to obtain a metal oxide mixture powder E; place the powder E under the conditions of 800 °C and a hydrogen gas flow rate of 50 mL / min and reduce it for 1 h to prepare a copper-nickel bimetallic supported catalyst. The XRD pattern is shown in Figure 2 (The sample is labeled as CuNi-B-MMO), and the characteristic peaks at 2θ of 43.275° ± 0.01 and 37.248° ± 0.01 correspond to the (200) and (220) crystal planes of NiO respectively, and the characteristic peaks at 2θ of 35.417° ± 0.01 and 35.453° ± 0.01 correspond to the (002) and (11-1) crystal planes of CuO respectively.

[0138] Its SEM image is as shown in Figure 4 , indicating that the hydrotalcite particles are significantly agglomerated, showing that the method of the present invention helps to synthesize hydrotalcite with a high specific surface area and a complete flaky morphology.

[0139] Comparative Example 6

[0140] Purchase the SCST-201 primary reforming catalyst from Sichuan Shutai Chemical Technology Co., Ltd. The main components of this catalyst are NiO-Al 2 O 3 -K 2 O, and the active metal loading of this catalyst is the same as that in Comparative Example 1. Before use, grind this catalyst into particles with a mesh size of 40-60, and carry out activation and the natural reforming of methanol to produce hydrogen reaction under the same conditions as in Example 1.

[0141] Table 1

[0142]

[0143]

[0144] As can be seen from the results in Table 1, the technical solution of the present invention has a high methanol conversion rate and a high hydrogen yield, and has high application potential in the field of autothermal reforming of small molecule alcohols to produce hydrogen.

[0145] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for hydrogen production by autothermal reforming of methanol, in which methanol, water and oxygen are brought into contact and reacted under the condition of a catalyst, and the conditions for the contact reaction include: The gas-phase feed space velocity is 8000 - 15000 h -1 ; in terms of molar ratio, methanol∶water = (0.8 - 1.2)∶(0.5 - 4); in terms of molar ratio, methanol∶oxygen = (0.8 - 1.2)∶(0 - 1); the reaction temperature is 300 - 600 °C, and the reaction pressure is 0.1 - 0.5 MPa; The preparation method of the catalyst includes: calcining the hydrotalcite-like material in an inert atmosphere and then reducing it in a reducing atmosphere; the hydrotalcite-like material includes metals copper, nickel, aluminum and calcium, and characteristic peaks with 2θ of 11.688°±0.01, 23.205°±0.01, and 35.022°±0.01 exist in the XRD pattern of the hydrotalcite-like material, and the molar ratio of copper, nickel, calcium and aluminum in the hydrotalcite-like material is (1 - 10)∶(1 - 10)∶(60 - 70)∶30.

2. The method according to claim 1, wherein, the molar ratio of copper, nickel, calcium and aluminum in the hydrotalcite-like material is (5 - 10)∶(5 - 10)∶(65 - 70)∶30.

3. The method according to claim 2, wherein, in terms of molar ratio, the aluminum in the hydrotalcite-like material to (copper, nickel, aluminum and calcium) is 0.01 - 0.6; aluminum / (copper, nickel and calcium) is 1 - 7.

4. The method according to claim 3, wherein, in terms of molar ratio, the aluminum in the hydrotalcite-like material to (copper, nickel, aluminum and calcium) is 0.017 - 0.33; aluminum / (copper, nickel and calcium) is 1 - 4.

5. The method according to any one of claims 1 - 4, wherein, the particle size of the Cu-Ni alloy metal in the hydrotalcite-like material is 6.8±1.5 nm; and / or the porosity of the pores in the hydrotalcite-like material is 20 - 40%; and / or The specific surface area of the hydrotalcite-like material is 65-140 m 2 g -1 .

6. The method according to claim 5, wherein, the porosity of the pores in the hydrotalcite-like material is 25% - 40%; and / or The specific surface area of the hydrotalcite-like material is 80 - 140 m 2 g -1 .

7. The method according to claim 6, wherein, The specific surface area of the hydrotalcite-like material is 85 - 120 m 2 g -1 .

8. The method according to any one of claims 1 - 4, wherein, the preparation method of the hydrotalcite-like material includes: dissolving copper salt, nickel salt, aluminum salt and calcium salt, and then adding urea for hydrothermal treatment, filtering and freeze-drying after hydrothermal treatment.

9. The method according to claim 8, wherein, dissolve copper salt, nickel salt, aluminum salt and calcium salt in an alcohol aqueous solution.

10. The method according to claim 9, wherein, the volume ratio of alcohol to water in the alcohol aqueous solution is (1 - 3)∶10; and / or the alcohol in the alcohol aqueous solution is an alcohol with C1 - C3.

11. The method according to claim 10, wherein, the volume ratio of alcohol to water in the alcohol aqueous solution is (1 - 2)∶10; and / or the alcohol in the alcohol aqueous solution is selected from at least one of ethanol, ethylene glycol and propanol.

12. The method according to claim 11, wherein, the alcohol in the alcohol aqueous solution is a mixed alcohol with a volume ratio of (0 - 3)∶(0.5 - 2)∶(0 - 1) of ethanol, ethylene glycol and propanol.

13. The method according to claim 8, wherein, the copper salt, nickel salt, aluminum salt and calcium salt are nitrates and / or chloride hydrates; and / or The pH of the system environment is 7 - 11 after adding urea.

14. The method according to claim 13, wherein, the copper salt, nickel salt, aluminum salt and calcium salt are nitrate hydrates; and / or the pH of the system environment is 9 - 11 after adding urea.

15. The method according to claim 8, wherein, the conditions of the hydrothermal treatment include: the hydrothermal temperature is 80 - 170 °C; the hydrothermal time is 12 - 48 h; and / or the conditions of the freeze-drying include: the freezing temperature is -60 °C to -40 °C; the vacuum degree is 5 - 30 Pa, and the drying time is 12 - 24 h.

16. The method according to claim 15, wherein, the conditions of the hydrothermal treatment include: the hydrothermal temperature is 100 - 130 °C; and / or the conditions of the freeze-drying include: the freezing temperature is -55 °C to -45 °C.

17. The method according to claim 1, wherein, the conditions of the calcination include: the temperature is 500 - 900 °C, the heating rate is 1 - 10 °C / min, and the time is 1 - 10 h; and / or the conditions of the reduction include: the temperature is 500 - 800 °C, and the time is 1 - 10 h.

18. The method according to claim 17, wherein, the conditions of the calcination include: the temperature is 600 - 900 °C; and / or the conditions of the reduction include: the temperature is 600 - 800 °C.

19. The method according to claim 1, wherein, the inert atmosphere is selected from at least one of a carbon dioxide atmosphere, a nitrogen atmosphere, a helium atmosphere, and an argon atmosphere; and / or the reduction atmosphere contains a hydrogen atmosphere; The XRD pattern of the catalyst has characteristic peaks at 2θ of 31.408° ± 0.01, 38.009° ± 0.01, 44.996° ± 0.01, and 65.535° ± 0.

01.

20. The method according to claim 19, wherein, the flow rate of the inert atmosphere is 50 - 200 mL / min; and / or the flow rate of the reduction atmosphere is 20 - 100 mL / min.

Images