Nano-copper oxide catalyst, its preparation method and application

Abstract

The application provides a preparation method of a nano copper oxide catalyst, which comprises the following steps: mixing nano copper oxide particles and a soluble cerium salt in water, and then performing a hydrothermal reaction under vacuum or a protective atmosphere, so that copper oxide on the surface of the nano copper oxide particles is partially reduced into cuprous oxide while including oxidized cerium oxide, and high cerium ions and cerium ions enter the crystal lattice of the copper oxide; then hydrazine is added to perform further reaction, so that the high cerium ions in the crystal lattice of the copper oxide are partially reduced into cerium ions, thereby realizing multiple lattice distortions of the copper oxide crystal lattice and obtaining a nano copper oxide catalyst rich in oxygen vacancies. The application also provides the nano copper oxide catalyst prepared by the method and a preparation method of the nano copper oxide catalyst.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a nano copper oxide catalyst and a preparation method and application thereof. BACKGROUND

[0002] Hydrogen, as a clean energy to replace fossil energy, has great potential in promoting the development of fuel cells. However, due to the physical and chemical limitations of hydrogen, the problem of safe storage and transportation of hydrogen is challenging to this major issue. Compared with gaseous hydrogen storage, in-situ hydrogen production using liquid fuels such as methanol (CH3OH, an ideal hydrogen carrier) with high hydrogen storage capacity not only realizes the safe storage and transportation of hydrogen, but also provides an alternative solution for the application of fuel cell systems. In addition, methanol can be obtained from various sources such as fossil fuels, renewable biomass and carbon dioxide hydrogenation. Notably, methanol steam reforming (MSR) is an economical and effective method because of its reasonable energy utilization, simple process control, and high hydrogen production rate under relatively mild reaction conditions, thus attracting wide interest in the field of energy chemistry and heterogeneous catalysis.

[0003] In the MSR reaction, it is crucial to evaluate the activity and product selectivity of the catalyst. Among various catalysts used in MSR, Cu-based catalysts are more attractive with the advantages of low cost, satisfactory low-temperature activity, and high H2 selectivity. However, due to the low Tamman temperature of Cu (407℃), Cu nanoparticles as a suitable active ingredient are prone to agglomeration and sintering. Therefore, an effective solution to this problem is to select appropriate additives (such as SiO2, Al2O3, ZnO and CeO2) to improve the catalytic performance and thermal stability of Cu in Cu-based catalysts. In particular, ceria, due to its special redox properties, has the functions of inhibiting carbon deposition and reducing by-product CO in the MSR reaction. There are various methods for preparing copper-based catalysts, such as CVD, sol-gel and co-precipitation. However, these methods involve multiple processing steps, and the synthesis of catalysts is quite complex (such as adding specific additives). Therefore, it is more attractive to prepare a new efficient copper-based catalyst for MSR reaction by a simple and easy method. In the prior art, Ce-based nanomaterials can be grown in situ on the surface of the support in Ce(NO3)3 solution through hydrothermal reaction, which not only increases the specific surface area, but also improves the catalytic performance.

[0004] However, the improved catalytic performance of the Ce-based nanomaterials loaded on the surface of the support is still limited, and there may also be durability problems. SUMMARY

[0005] The present application aims to provide a preparation method of an efficient catalyst for hydrogen production by reforming.

[0006] The present application is realized by the following technical solutions:

[0007] A preparation method of a reforming hydrogen production catalyst, comprising the following steps:

[0008] The nano copper oxide particles and the soluble cerium salt are mixed in water, and then a hydrothermal reaction is carried out under vacuum or a protective atmosphere, so that the copper oxide on the surface of the nano copper oxide particles is partially reduced to cuprous oxide, and high cerium ions and cerium ions are introduced into the crystal lattice of the copper oxide; then hydrazine is added for further reaction, so that the high cerium ions in the crystal lattice of the copper oxide are partially reduced to cerium ions, thereby realizing multiple lattice distortions of the copper oxide crystal lattice and obtaining a nano copper oxide catalyst rich in oxygen vacancies.

[0009] The ratio of the nano copper oxide, the soluble cerium salt and the hydrazine is 0.8-1.2g: 0.08-0.12mol: 0.04mol.

[0010] The protective atmosphere comprises an inert gas or nitrogen.

[0011] The temperature of the hydrothermal reaction is 160-200℃.

[0012] The ratio of the nano copper oxide and water is 0.8-1.2g: 25mL.

[0013] The time of the hydrothermal reaction is 25-35min;

[0014] The time of the further reaction is 25-35min.

[0015] The preparation method of the reforming hydrogen production catalyst further comprises a drying step.

[0016] The temperature of the drying is 55-65℃, and the time of the drying is 20-28h.

[0017] The preparation method of the reforming hydrogen production catalyst prepares a nano copper oxide catalyst.

[0018] The application of the nano copper oxide catalyst is applied to reforming hydrogen production.

[0019] The temperature of the reforming hydrogen production is 260-280℃.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application uses a hydrothermal method to prepare a CeO2 modified nano CuO catalyst, and the Cu 2+ on the surface of the catalyst is reduced to Cu +Afterwards, the cerium ions are oxidized to high cerium ions, so that the surface of the nano CuO particles is coated with CeO2. At the same time, in this reaction process, the high cerium ions also enter the crystal lattice of copper oxide. Then hydrazine is added for further reaction, so that the high cerium ions entering the crystal lattice of copper oxide are reduced, thereby realizing multiple lattice distortions of the crystal lattice of copper oxide, thereby generating a large number of oxygen vacancies. CeO2 is also partially reduced to Ce2O3. The coexistence of CeO2 and Ce2O3 improves the oxygen vacancies on the surface of copper oxide. Ce 4+ and Ce 3+ entering the crystal lattice of CuO adjusts the electronic structure of copper oxide and promotes the stability of Cu + in the reforming reaction. In addition, after loading high cerium oxide, the specific surface area of the nano copper oxide particles is also increased. In addition, CeO2 not only acts as a physical spacer to prevent the agglomeration and sintering of Cu elements during the reaction process, but also can form an interaction with Cu elements to promote the MSR reaction. The CuO-CeO2 catalyst prepared by this method can generate an interaction and abundant interfaces and oxygen vacancies between CuO and CeO2, thereby improving the performance of the MSR reaction. Therefore, the nano CuO catalyst prepared by the present application can achieve a methanol conversion rate close to 100% and a CO selectivity of 0.045%, and also has good stability. In comparison, the nano CuO catalyst obtained by hydrothermal treatment without using hydrazine has a low methanol conversion rate and poor CO selectivity at 270°C. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 XRD patterns of the catalysts prepared in Examples 1-4 and Comparative Example 1 are shown;

[0023] Figure 2 Raman spectra of the catalysts prepared in Examples 1-4 and Comparative Example 1 are shown;

[0024] Figure 3 H2-TPR patterns of the catalysts prepared in Example 2 and Comparative Example 1 are shown;

[0025] Figure 4 Cu 2p spectra in the XPS patterns of SCuO and CuO-Ce3 are shown;

[0026] Figure 5 Ce3d spectra in the XPS patterns of SCuO and CuO-Ce3 are shown; 5 / 2

[0027] Figure 6 O 1s spectra in the XPS patterns of SCuO and CuO-Ce3 are shown;

[0028] Figure 7 ​(a) FE-SEM, (b-c) HRTEM and (d-g) EDS mapping of CuO-Ce3 catalysts are shown;

[0029] Figure 8 HRTEM mapping of CuO-Ce3 catalysts are shown;

[0030] Figure 9 FT-IR spectra of CuO-Ce3 catalysts at different reforming reaction time are shown;

[0031] Figure 10 The experimental apparatus is shown schematically;

[0032] Figure 11 EPR spectra of oxygen vacancies of catalysts are shown;

[0033] Figure 12 (a) Catalytic performance of structured catalysts at different temperatures; (b) Steady-state performance of structured catalysts. Reaction conditions: 4 mL / h, H2O / CH3OH = 1.05 molar ratio.

[0034] Figure 13 a XRD patterns of RSCuO and RCuO-Ce2 are shown;

[0035] Figure 13 b XPS patterns of RSCuO and RCuO-Ce2 are shown;

[0036] Figure 13 a LLM patterns of RSCuO and RCuO-Ce2 are shown

[0037] Figure 14 a SEM of CuO-Ce3 before reaction is shown;

[0038] Figure 14 b SEM of CuO-Ce3 after reaction is shown;

[0039] Figure 14 c Raman spectra of CuO-Ce3 before and after reaction are shown.

[0040] Figure 15 a Relationship between methanol conversion and conversion temperature of catalysts is shown:

[0041] Figure 15 b Relationship between CO selectivity and conversion temperature of catalysts is shown;

[0042] Figure 15 c Relationship between H2 selectivity and conversion temperature of catalysts is shown;

[0043] Figure 15d shows the relationship between the steady-state performance of the catalyst and the conversion temperature; Figure 15 Conversion conditions of a-b: methanol water gas flow rate of 4 mL / h, wherein the molar ratio of H2O / CH3OH is 1.05. DETAILED DESCRIPTION

[0044] The present application is further described below in conjunction with specific examples.

[0045] The raw materials involved in the specific embodiments of the present application are as follows:

[0046] Copper oxide nanoparticles (CuO, 20 nm) were purchased from China Metallurgical New Materials Co., Ltd. Cerium nitrate hexahydrate (Ce(NO3)3·6H2O, purity ≥ 99.5%) was sourced from Macklin. Silica powder (SiO2), methanol (CH3OH) and ethanol were purchased from Shanghai Chemical Reagent Co., Ltd. Cordierite honeycomb ceramics (Φ20×50 mm, 400 cpsi) were purchased from Jiangxi Tianma Industrial Ceramics Co., Ltd. Aluminum sol (20 wt%, binder) was obtained from Suzhou Beller New Material Technology Co., Ltd. Hydrazine hydrate was purchased from Sigma-Aldrich. All reagents do not need further purification.

[0047] The characterization methods of the catalysts involved in the specific embodiments of the present application are as follows:

[0048] An inductively coupled plasma optical emission spectrometer (ICP-OES, PerkinElmer Avio500, USA) was used to determine the elemental composition of the catalysts. The crystalline phase of the catalysts was detected by an X-ray diffractometer (XRD, SmartLab SE, Rigaku, Japan) with a scanning range of 10° to 80° (2q, scan speed: 5° / min). The structure and chemical properties of the prepared catalysts were detected by Raman spectroscopy (Thermo Scientific DXR3, USA). The interaction of the catalysts was measured by hydrogen temperature programmed reduction (H2-TPR, Microtrac BELCat II, Japan). The surface chemical state of the catalysts was studied by X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha, USA) and Auger electron spectroscopy (XAES, Thermo Science K-Alpha, USA). Electron paramagnetic resonance spectroscopy (EPR, Bruker A300, Germany) was performed to examine the oxygen vacancies in the catalysts. The morphology of the catalysts was determined by field emission scanning electron microscopy (FE-SEM, Igmahd, Zeiss, UK). The lattice spacing and elemental distribution of the catalysts were examined by transmission electron microscopy (TEM, Themis Z, Netherlands) equipped with EDAX energy dispersive X-ray spectroscopy (EDS). Nitrogen adsorption-desorption experiments (ASAP 2460, Micromeritics, USA) were performed to measure the catalysts before and after the reaction, and the specific surface area and pore size distribution of the catalysts were obtained by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analysis. Fourier transform infrared spectroscopy (FTIR, Thermo Scientific Nicolet iN10, USA) was used to characterize the MSR reaction mechanism on the surface of the catalysts at 270°C, and the background of potassium bromide and the catalyst was deducted.

[0049] Example 1

[0050] Preparation of catalysts

[0051] CuO nanoparticles were added to the solution and stirred for 30 minutes. Then, the CuO containing solution was transferred to a 100 mL Teflon lined stainless steel autoclave and reacted in a forced draft oven at 180 °C for 12 hours. After cooling to room temperature, 0.01 mol of hydrazine hydrate was added to the stainless steel autoclave and then reacted in a forced draft oven at 180 °C for 5 hours. After repeated centrifugation of the nanoparticles with deionized water and ethanol, and then drying at 60 °C for 24 hours, the catalyst was obtained. Hereinafter, the catalyst prepared in Example 1 is noted as CuO-Cel.

[0052] Example 2

[0053] Preparation of the catalyst

[0054] CuO nanoparticles were added to the solution and stirred for 30 minutes. Then, the CuO containing solution was transferred to a 100 mL Teflon lined stainless steel autoclave and reacted in a forced draft oven at 180 °C for 12 hours. After cooling to room temperature, 0.01 mol of hydrazine hydrate was added to the stainless steel autoclave and then reacted in a forced draft oven at 180 °C for 5 hours. After repeated centrifugation of the nanoparticles with deionized water and ethanol, and then drying at 60 °C for 24 hours, the catalyst was obtained. Hereinafter, the catalyst prepared in Example 2 is noted as CuO-Ce2.

[0055] Example 3

[0056] Preparation of the catalyst

[0057] CuO nanoparticles were added to the solution and stirred for 30 minutes. Then, the CuO containing solution was transferred to a 100 mL Teflon lined stainless steel autoclave and reacted in a forced draft oven at 180 °C for 12 hours. After cooling to room temperature, 0.01 mol of hydrazine hydrate was added to the stainless steel autoclave and then reacted in a forced draft oven at 180 °C for 5 hours. After repeated centrifugation of the nanoparticles with deionized water and ethanol, and then drying at 60 °C for 24 hours, the catalyst was obtained. Hereinafter, the catalyst prepared in Example 3 is noted as CuO-Ce3.

[0058] Example 4

[0059] Preparation of the catalyst

[0060] 0.16 mol of Ce(NO3)3·6H2O was dissolved in deionized water, and then 1 gram of CuO nanoparticles were added to the solution and stirred for 30 minutes. The CuO-containing solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave and reacted in a forced-air drying oven at 180 °C for 12 hours. After cooling to room temperature, 0.01 mol of hydrazine hydrate was added to the stainless steel autoclave, and the reaction was carried out in a forced-air drying oven at 180 °C for 5 hours. The nanoparticles were repeatedly centrifuged with deionized water and ethanol, and then dried at 60 °C for 24 hours to obtain the catalyst. In the following text, the catalyst prepared in Example 4 is referred to as CuO-Ce4.

[0061] Comparative Example 1

[0062] Catalyst preparation

[0063] 0.08 mol of Ce(NO3)3·6H2O was dissolved in 25 mL of deionized water, followed by the addition of 1 g of CuO nanoparticles and stirring for 30 minutes. The CuO-containing solution was then transferred to a 100 mL Teflon-lined stainless steel autoclave and reacted in a forced-air drying oven at 180 °C for 12 hours. After cooling to room temperature, the hydrothermally treated nanoparticles were repeatedly centrifuged with deionized water and ethanol, and then dried at 60 °C for 24 hours. In the following text, the catalyst prepared in Comparative Example 1 is designated as SCuO. Furthermore, SCuO and CuO-Ce3 after 10 hours of reforming reaction are designated as RSCuO and RCuO-Ce3, respectively.

[0064] The characterization results of the catalysts prepared in the embodiments of the present invention are as follows:

[0065] The elemental composition of the catalysts prepared in Examples 1-5 and Comparative Example 1 was characterized by ICP-OES in this invention. The results are shown in the table below:

[0066] Table 1. Elemental composition of the catalysts prepared in each example

[0067]

[0068] As can be seen from the table above, the mass ratio of Cu / (Cu+Ce) decreases with increasing Ce(NO3)3·6H2O concentration in the hydrothermal reaction. Figure 1 As shown, the crystalline phases of the catalysts prepared in Examples 1-4 and Comparative Example 1 were characterized by XRD. The CuO phase (PDF#80-1917) was observed in all catalysts. With increasing Ce content, the peak values ​​of the CeO2 phase (PDF#75-0120) and CuO gradually decreased.

[0069] The present application used Raman spectroscopy to study the structure and chemical properties of the catalysts prepared in Examples 1-4 and Comparative Example 1. It can be seen from Figure 2 that the two peaks near 223 and 274 cm -1 correspond to the A1g and Eg modes of CuO, respectively. The peak centered at 453 cm -1 is attributed to the triply degenerate F2g vibration mode of CeO2crystals, while the peak near 600 cm -1 is related to oxygen defects (D band). The appearance of the D band is due to the formation of defects in the Ce-O coordination, which causes the vibration signal of Ce-O to not cancel out in all directions. This indicates that there may be a Cu-O-Ce coordination structure in the prepared catalyst, due to the unequal interaction between Cu-O and Ce-O, which causes the vibration of Ce-O in different directions to be different. In addition, as the Ce concentration increases, the F2g peak of CeO2red-shifts, indicating that there is a strong interaction between CuO and CeO2, which will lead to changes in the electronic structure and coordination environment of the catalyst.

[0070] In order to further characterize the interaction of CuO-CeO2, the present application examined the catalyst powders prepared in Example 2 and Comparative Example 1 by H2-TPR. Since CeO2cannot be reduced below 300°C, the H2reduction peak of the catalyst is related to CuO. Obviously, due to the addition of Ce element and hydrazine, the reduction peak narrows and moves to lower temperature, which indicates that the interaction of CeO2and CuO promotes the reduction of CuO at low temperature, thus being beneficial to the improvement of catalytic performance (as shown in Figure 3 ).

[0071] The present application used XPS analysis to characterize the surface chemical state of SCuO and CuO-Ce3. As shown in Figure 4 , in the Cu 2p spectrum, the peaks around 933.8 and 953.4 eV correspond to the 2p 2+ and 2p 3 / 2 orbital peaks of Cu 1 / 2 , respectively, and the remaining peaks belong to the satellite peaks of Cu 2+ . In addition, after the introduction of CeO2, the peaks of Cu2p 3 / 2 and Cu2p 1 / 2 move to lower binding energy, which indicates that the interaction between Cu and Ce can adjust the electronic structure. In the Ce3d 5 / 2 spectrum of the catalyst (as shown in Figure 5 ), it can be seen that there is also Ce 3+ in the catalyst.

[0072] In the MSR reaction, the oxygen vacancy of the catalyst plays an important role in the effective activation of H2O and the rapid conversion of C-containing intermediates, thereby increasing the conversion of methanol and reducing the selectivity of CO. The present invention uses XPS and EPR spectra to confirm the changes in the oxygen vacancy concentration of the catalysts of Example 2 and Comparative Example 1. As shown in Figure 6 , the O1s spectrum is decomposed into three contribution peaks, which are related to lattice oxygen (about 529.4 eV, OL), oxygen vacancy (about 531.2 eV, OV) and surface chemisorbed oxygen (about 532.3 eV, OC), respectively. Compared with SCuO, the OV peak area ratio (OV / (OL+OV+OC) of CuO-Ce3 increases from 29.5% to 37.2%. SCuO and CuO-Ce3 appear resonance signals at g = 2.003 (EPR signal) Figure 11 ), which is due to the presence of oxygen vacancies. Obviously, the EPR signal of CuO-Ce3 is higher. The stronger the EPR signal, the higher the oxygen vacancy concentration. In addition, the D band appearing on CuO-Ce2 indicates that more oxygen vacancies are formed on CuO-Ce2 compared with SCuO. These results collectively indicate that the oxygen vacancy concentration in the catalyst increases with the addition of hydrothermally formed CeO2.

[0073] The particle morphology of the catalyst was detected by SEM and TEM. The SCuO catalyst presents a spherical shape with a particle size of about 20.3 nm (Figure 7). Notably, during the hydrothermal reaction, CeO2 nanoparticles grow on the surface of CuO (red circles in Figure 7 b). The lattice spacings of 0.275 nm and 0.312 nm are related to CuO (1 1 0) and CeO2 (1 1 1), respectively, which is consistent with the XRD and Raman results. The EDS spectrum further studies the element distribution of CuO-Ce2. As shown in the spectra (Figures Figure 7 d-g), the Ce element is distributed on the surface of CuO, which indicates that there may be an interaction between CuO and CeO2 due to the obvious contact between the two oxides. In addition, the specific surface area, pore volume and average pore diameter of the catalyst were determined by N2 adsorption-desorption method (see Table 2). With the introduction of CeO2, the specific surface area of the SCuO catalyst increases from 19.9 m 2 / g to 31.1 m 2 / g, because smaller CeO2 nanoparticles are generated during the hydrothermal reaction. This result is consistent with the above TEM results.

[0074] Table 2

[0075]

[0076] Fourier transform infrared spectroscopy (FTIR) Figure 9The MSR reaction mechanism on the surface of CuO-Ce2 catalyst at 270℃ was investigated. The peaks at 3850-3650 cm -1 and 1456 cm -1 correspond to the stretching and symmetric bending of O-H bond from methanol. The strong absorption peaks of H2O are located at 3430 cm -1 and 1634 cm -1 . The peaks at 2919 cm -1 , 2848 cm -1 and 1100-1000 cm -1 are assigned to methoxy species (CH3O*), from the stretching of C-H and C-O bond. The C-H stretching, OCO asymmetric and symmetric stretching peaks of formate species (HCOO*) are located at 2958 cm -1 , 1560 cm -1 and 1390 cm -1 , respectively. The peaks near 2400-2300 cm -1 and 1730 cm -1 are related to the absorption of CO2 and the C=O vibration peak of aldehyde species (CH2O*). In addition, the peaks near 1650 cm -1 and 1210 cm -1 are assigned to bicarbonate. For CuO-Ce3 catalyst, the peak intensities near 3850-3650 cm -1 , 2919 cm -1 , 2400-2300 cm -1 , 1730 cm -1 and 1560 cm -1 increase with the reaction time, indicating that methanol, CH3O*, CO2, CH2O* and HCOO* are gradually accumulated on the catalyst surface. However, the peak signals of methanol, CH3O*, CO2, CH2O* and HCOO* will remain stable after 6 min, indicating that the adsorption of reactants and intermediates on the catalyst surface reaches saturation. These results reveal the reaction pathway of MSR as follows: (1) methanol is first dehydrogenated to CH3O*; (2) CH3O* is further dehydrogenated to CH2O*; (3) CH2O* reacts with OH* or O* dissociated from H2O to form HCOO*; (4) HCOO* is finally converted to CO2 and H2.

[0077] The present application adopts as Figure 10The device shown to carry out the reforming hydrogen. Specifically, first, 300 milligrams of catalyst mixed with an appropriate amount of SiO2, and compressed into a sheet. Then, the sheet-shaped catalyst is transferred to the reforming chamber of a tube furnace (OTF-1200X, China high frequency - Nanjing). Using a peristaltic pump (CT1000, China Crea) to deliver the aqueous methanol solution (H2O / CH3OH = 1.05 molar ratio) to the evaporation chamber. Unreacted reactants are collected by the condensing device, and then the gas products (i.e. H2, CO and CO2) are detected by gas chromatography (GC, SP-7890, China) equipped with TCD and FID. In addition, the electronic soap bubble flow meter (SCalPlus, China) is also used to determine the gas flow rate. The formula for calculating the conversion of methanol and the selectivity of the gas product is as follows:

[0078]

[0079] Before loading the catalyst, the cordierite honeycomb ceramic was pretreated. Specifically, washed with deionized water and ethanol several times, then dried at 100°C for 12 hours, and finally calcined at 800°C for 4 hours to remove residual organic matter. Then, CuO-Ce3 catalyst, deionized water and aluminum sol were added to a nylon tank, then ball milled for 2 hours (speed: 200 rpm / min). Next, the slurry formed by ball milling was repeatedly impregnated into the honeycomb ceramic, and then dried at 80°C. After each impregnation, the excess slurry in the honeycomb ceramic was removed by blowing. The catalyst loading was kept at ~300mg.

[0080] The catalytic performance of the catalyst was then evaluated when the MSR reaction was carried out in a quartz tube reactor at 210-290°C, H2O / CH3OH molar ratio of 1.05. As an endothermic reaction (in which), the conversion of methanol and CO selectivity both increased with the increase of reaction temperature ( Figure 15 a-b). The H2 selectivity of the catalyst was about 75% ( Figure 15c), thus providing sufficient H2 for the fuel cell system. Furthermore, under the same reaction conditions, CO selectivity decreases with increasing Ce content, possibly because the increased oxygen vacancy concentration promotes H2O dissociation, thereby accelerating the conversion of CO to CO2 in the water-gas shift reaction (WGSR). However, when the Ce content is too high, the methanol conversion rate decreases because the active sites of Cu species are blocked by CeO2, reducing the contact between Cu species and reactants. Therefore, among these catalysts, the CuO-Ce3 catalyst exhibits the best catalytic performance at 270 °C, with a methanol conversion rate of 100% and a CO selectivity of 0.045%. Since reaction stability is an important indicator for evaluating MSR catalysts, the steady-state performance of the CuO-Ce2 catalyst was investigated. After 100 hours of reaction, the methanol conversion rate decreased (from 100% to 92.3%), while the CO selectivity remained within the range of 0.036%–0.049%. Figure 15 (d) This indicates that the catalyst has good durability. To eliminate the influence of silica on catalytic performance, a blank test was conducted on pure silica flakes under the same reaction conditions, and the results showed no catalytic activity.

[0081] Methanol conversion and gas selectivity of catalyst powder. Reaction conditions: 270 ℃, 4 mL / h, H2O / CH3OH = 1.05 molar ratio.

[0082] Table 3

[0083]

[0084] In practical applications, structural catalysts are increasingly favored for large-scale catalytic reactions due to their low pressure drop and high utilization rate. Therefore, a structural catalyst was formed by coating CuO-Ce2 catalyst onto cordierite, and its catalytic activity and durability in the MSR reaction were investigated. This structural catalyst achieved 100% methanol conversion and 0.050% CO selectivity at 270℃. Figure 12 a). After 100 hours of reaction, the methanol conversion rate decreased from 100% to 92.0%, while the CO selectivity remained within the range of 0.043%-0.051% at 270℃. Figure 12 (b) This indicates that the catalyst exhibits good stability during long-term reactions. Furthermore, Table 4 summarizes the catalytic performance of various copper-based catalysts in the MSR reaction over the past few years. Compared to these copper-based catalysts, the copper-based catalyst prepared in this invention exhibits higher activity and lower CO selectivity at 270 °C.

[0085] Table 4

[0086] Catalyst Reaction temperature (℃) Methanol conversion (%) CO selectivity (%) Ref. Cu-In / SiO2 300 96.1 0.02 [1] CuO-CeO2 270 80 0.13 [2] CuO-ZnO-CeO2-ZrO2 280 99.9 0.29 [3] CeCuZn / CNTs 325 98.3 1.3 [4] (Ni0.2Cu0.8) / BN 320 100 0

[35] CuCeO2 260 100 0.6 [6] Cu-Ce / SBA-15 290 98.5 0.6 [7] CuO-ZnO-ZrO2 / Al2O3 / SiC 280 79.75 -- [8] CuZn / MCM-41 300 88 0.45 [9] 3D structured Cu-based catalyst 280 93.6 0.07

[10] Cu / SiC 280 82.9 --

[11] Cu / ZnO 275 94 3

[12] CuO-Ce3 270 100 ~0.045 This work

[0087] The documents referred to in the above table are as follows:

[0088] 1. F. Bossola, T. Roongcharoen, M. Coduri, C. Evangelisti, F. Somodi, L. Sementa, A. Fortunelli, V. Dal Santo, Discovering indium as hydrogen production booster for a Cu / SiO2 catalyst in steam reforming of methanol, Applied Catalysis B: Environmental 297 (2021) 120398. https: / / doi.org / 10.1016 / j.apcatb.2021.120398.

[0089] 2. Y. Chen, S. Li, S. Lv, Y. Huang, A novel synthetic route for MOF-derived CuO-CeO2 catalyst with remarkable methanol steam reforming performance, Catalysis Communications 149 (2021) 106215. https: / / doi.org / 10.1016 / j.catcom.2020.106215.

[0090] 3. X. Jia, H. Zhang, B. Ren, J. Xie, P. Ge, B. Zhang, Fe–Ni–Ce–Zr-modified CuO–ZnO catalyst for methanol steam reforming, Journal of the Energy Institute 110 (2023) 101316. https: / / doi.org / 10.1016 / j.joei.2023.101316.

[0091] 4H. Shahsavar, M. Taghizadeh, A.D. Kiadehi, Effects of catalyst preparation route and promoters (Ce and Zr) on catalytic activity of CuZn / CNTs catalysts for hydrogen production from methanol steam reforming, International Journal of Hydrogen Energy 46(13) (2021) 8906-8921. https: / / doi.org / 10.1016 / j.ijhydene.2021.01.010.

[0092] 5A.M. Kovalskii, A.T. Matveev, Z.I. Popov, I.N. Volkov, E.V. Sukhanova, A.A. Lytkina, A.B. Yaroslavtsev, A.S. Konopatsky, D.V. Leybo, A.V. Bondarev, I.V. Shchetinin, K.L. Firestein, D.V. Shtansky, D.V. Golberg, (Ni,Cu) / hexagonal BN nanohybrids - New efficient catalysts for methanol steam reforming and carbon monoxide oxidation, Chemical Engineering Journal 395 (2020) 125109.

[0093] https: / / doi.org / 10.1016 / j.cej.2020.125109.

[0094] 6. S. Yang, F. Zhou, Y. Liu, L. Zhang, Y. Chen, H. Wang, Y. Tian, C. Zhang, D. Liu, Morphology effect of ceria on the performance of CuO / CeO2 catalysts for hydrogen production by methanol steam reforming, International Journal of Hydrogen Energy 44(14) (2019) 7252-7261. https: / / doi.org / 10.1016 / j.ijhydene.2019.01.254.

[0095] 7. Y. Chen, Y. Huang, Influence of ceria existence form on deactivation behavior of Cu-Ce / SBA-15 catalysts for methanol steam reforming, International Journal of Hydrogen Energy 48(4) (2023) 1323-1336.

[0096] https: / / doi.org / 10.1016 / j.ijhydene.2022.10.046.

[0097] 8. S. Qian, H. Liu, Y. Wang, D. Mei, Structural optimization of 3D printed SiC scaffold with gradient pore size distribution as catalyst support for methanol steam reforming, Fuel 341 (2023) 127612. https: / / doi.org / 10.1016 / j.fuel.2023.127612.

[0098] 9 O.O. Fasanya, A.Y. Atta, M.T.Z. Myint, J. Dutta, B.Y. Jibril, Effects of synthesis methods on performance of CuZn / MCM-41 catalysts in methanol steam reforming, International Journal of Hydrogen Energy 46(5) (2021) 3539-3553.

[0099] https: / / doi.org / 10.1016 / j.ijhydene.2020.10.181.

[0100] 10 C. Li, S. Yuan, X. Yao, X. Yu, B. Li, S.-T. Tu, Structured nanoporous copper catalysts prepared by laser powder bed fusion and dealloying for on-board methanol steam reforming, Fuel 347 (2023) 128367. https: / / doi.org / 10.1016 / j.fuel.2023.128367.

[0101] 11 Y. Wang, H. Liu, D. Mei, S. Yu, Direct ink writing of 3D SiC scaffold as catalyst support for thermally autonomous methanol steam reforming microreactor, Renewable Energy 187 (2022) 923-932. https: / / doi.org / 10.1016 / j.renene.2022.02.004.

[0102] 12. E. Baydir, Ö. Aras, Methanol steam reforming in a microchannelreactor coated with spray pyrolysis method for durable Cu / ZnO nanocatalyst, Journal of Analytical and Applied Pyrolysis 158 (2021) 105278. https: / / doi.org / 10.1016 / j.jaap.2021.105278.

[0103] The phase composition of RSCuO and RCuO-Ce2 catalysts was determined by XRD. Figure 13 a) After 10 hours of reforming, all CuO in the sample was reduced to metallic Cu. However, CeO2 in the RCuO-Ce3 catalyst was not reduced, consistent with the H2-TPR results. No Cu was found on the catalyst surface after the reaction. 2+ Because of Cu 2+ The relevant satellite peaks (945-940 eV) in the Cu2p spectrum ( Figure 13 The presence of Cu in b) indicates that Cu on the catalyst surface is not present. 2+ Completely reduced to Cu0 or Cu + Due to Cu0 and Cu + The difference in binding energy between them in the Cu2p spectrum is not significant, and further analysis using the Cu LMM spectrum of the catalyst ( Figure 13 c) Used to confirm Cu 0 and Cu + The CuLMM spectrum of the catalyst was convolved into four peaks, with the two peaks near 916.2 and 918.7 eV corresponding to Cu. + and Cu 0 However, no Cu2O diffraction peaks were detected in the XRD pattern of the catalyst after 10 hours of reaction due to slight oxidation of the catalyst surface during the test. After the introduction of CeO2, Cu in the RCuO-Ce3 catalyst... + / (Cu + +Cu 0 The proportion increased from 26.5% to 41.0%. The results indicate that CeO2 and Ce... 3+ The interaction with Cu facilitates the formation of the Cu-O-Ce interface, thereby promoting Cu... + Stability of Cu + Increasing the ratio can enhance the synergistic effect between Cu and CeO2, thereby promoting the MSR reaction.

[0104] Sintering and carbon deposition are closely related to the deactivation of copper-based catalysts in the MSR reaction. To investigate the deactivation factors, the catalysts before and after the reaction were characterized by BET, SEM, and Raman. The CuO-Ce3 catalyst after 100 hours of reforming was named UCuO-Ce3. As can be seen from Table 2, the specific surface area of ​​CuO-Ce3 increased from 31.1 m² / s². 2 / g decreased to 13.2m 2 / g. After 100 hours of reaction, the catalyst particles significantly increased in size ( Figure 14 ab). Furthermore, no carbon D-band (approximately 1360 cm⁻¹) was observed. -1 (disordered and defective carbon) or G band (approximately 1580cm) -1 The signal peak of well-structured coke or graphite ( Figure 14 c). Therefore, sintering and growth can lead to the deactivation of the CuO-Ce3 catalyst, which may be due to the migration, aggregation, and Ostwald ripening of nanoparticles during the reaction.

[0105] The introduction of Ce species altered the electronic structure of the catalyst, promoting Cu in the reforming reaction. + The stability of the catalyst is attributed to the interaction between CuO and CeO2. Furthermore, the oxygen vacancy concentration of the catalyst increases (from 29.5% to 37.2%), and the specific surface area increases (from 19.9 to 31.1 m²). 2 / g). The results showed that the addition of Ce species could improve the catalytic activity of the MSR reaction and reduce the CO selectivity. Therefore, among these catalysts, the CuO-Ce3 catalyst exhibited the best catalytic performance, achieving 100% methanol conversion and 0.045% CO selectivity at 270 °C. After 100 hours of reaction, the methanol conversion decreased (from 100% to 92.3%), while the CO selectivity remained within the range of 0.036% to 0.049%, indicating excellent catalyst stability. In contrast, the SCuO catalyst achieved 78.1% methanol conversion and 0.118% CO selectivity at 270 °C. In practical applications, structural catalysts are increasingly favored for large-scale catalytic reactions due to their low pressure drop and high utilization rate. Therefore, the structural catalyst formed by coating CuO-Ce3 catalyst onto cordierite honeycomb ceramics achieved 100% methanol conversion and 0.050% CO selectivity at 270 °C. After 100 hours of reaction, the methanol conversion rate decreased from 100% to 92.0%, and the CO selectivity ranged from 0.043% to 0.051%. Fourier transform infrared spectroscopy further elucidated the evolution of reactants and intermediates on the catalyst surface. Furthermore, sintering and agglomeration were identified as causes of catalyst deactivation during the MSR reaction.

Claims

1. A method for preparing a nano-copper oxide catalyst, characterized in that: Includes the following steps: Nano-sized copper oxide particles and soluble cerium salts are mixed in water and then subjected to a hydrothermal reaction under vacuum or a protective atmosphere. This process partially reduces the copper oxide on the surface of the nano-sized copper oxide particles to cuprous oxide while simultaneously coating them with cerium oxide. Cerium oxide ions and cerium ions are then introduced into the copper oxide lattice. Hydrazine is then added for further reaction, which partially reduces the cerium oxide ions in the copper oxide lattice to cerium ions. This process achieves multiple lattice distortions in the copper oxide lattice, resulting in a nano-sized copper oxide catalyst rich in oxygen vacancies. The ratio of the nano-copper oxide particles, soluble cerium salt, and hydrazine is 0.8-1.2 g : 0.08-0.12 mol : 0.04 mol; The temperature of the hydrothermal reaction is 160-200℃; The ratio of the nano-copper oxide to water is 0.8-1.2 g: 25 mL.

2. The preparation method of the nano-copper oxide catalyst according to claim 1, characterized in that: The protective atmosphere includes an inert gas or nitrogen.

3. The method for preparing the nano-copper oxide catalyst as described in claim 1, characterized in that: The hydrothermal reaction time is 25-35 minutes.

4. The preparation method of the nano-copper oxide catalyst according to claim 1, characterized in that: It also includes a drying step; The drying temperature is 55-65℃, and the drying time is 20-28h.

5. The nano-copper oxide catalyst prepared by the method according to any one of claims 1-4.

6. The application of the nano-copper oxide catalyst as described in claim 5, characterized in that: It is applied to the reforming of alcohols to produce hydrogen.

7. The application of the nano-copper oxide catalyst as described in claim 6, characterized in that: The temperature for hydrogen production via reforming is 260-280℃; The alcohols include C1-C5 alcohols.

Images