Ce modified nickel-based catalyst for hydrogen production through propane steam reforming and preparation method and application of Ce modified nickel-based catalyst

Abstract

The invention relates to a Ce modified nickel-based catalyst for hydrogen production by propane steam reforming and a preparation method and application thereof, the preparation method comprises the following steps: (1) mixing a nickel salt and an aluminum salt with a solvent, slowly dropwise adding the mixture into alkali liquor, and sequentially carrying out standing, solid-liquid separation, drying and calcining treatment to obtain nickel-based aluminum oxide catalyst powder; and (2) mixing cerium salt with a solvent, slowly dropwise adding the mixture into the nickel-based aluminum oxide catalyst powder, and then sequentially drying and calcining to obtain the Ce modified nickel-based catalyst, wherein the temperature of the calcination treatment in the step (2) is lower than the temperature of the calcination treatment in the step (1). According to the preparation method disclosed by the invention, the rare earth cerium element is introduced through a two-step synergistic coprecipitation method, so that the thermal stability and the carbon deposition resistance of the catalyst are remarkably enhanced; meanwhile, the preparation method is easy to operate, raw materials are easy to obtain, and the requirement for efficient and stable operation of a distributed hydrogen production system is met.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, and a preparation method and application thereof. Background Art

[0002] As a clean and efficient energy source, hydrogen is considered one of the core directions of energy transformation. Reforming hydrogen production technology (such as alkane reforming) has become the mainstream route for industrial hydrogen production due to its strong adaptability to raw materials and high hydrogen production efficiency. The core challenge of reforming hydrogen production technology lies in the stability and resistance of the catalyst to carbon deposition under high-temperature reaction conditions. Carbon deposition mainly comes from two aspects: one is the carbon deposition produced by methane cracking (CH4→C+2H2) at high temperature; the other is the filamentous carbon generated by the CO disproportionation reaction (2CO→C+CO2).

[0003] The widely used nickel-based alumina catalyst (Ni / Al2O3) currently occupies a dominant position in the reforming reaction due to the high catalytic activity of nickel metal and the low cost and high specific surface area characteristics of the alumina carrier. However, it is easy to sinter under high-temperature conditions, and the carbon deposition problem is particularly prominent. The acidic sites on the surface of nickel-based catalysts are easily adsorbed by carbon precursors, resulting in active site coverage and pore clogging, which ultimately leads to catalyst deactivation. In addition, the sintering phenomenon of nickel particles at high temperatures (grain growth to above a critical size) further exacerbates the formation of carbon deposits and the decrease in activity. In high-temperature reforming reactions, the carbon deposition and sintering problems of nickel-based catalysts are closely related to a vicious cycle mechanism: carbon species (such as graphitic carbon and nano-carbon fibers) generated by hydrocarbon cracking are deposited on the nickel surface, resulting in an increase in local micro-region temperature (hot spot effect), which accelerates the migration and agglomeration of nickel particles; the coarsened nickel particles expose more low-coordination active sites, promote the breakage of C-H bonds and the growth of carbon chains, and form a denser carbon deposition layer.

[0004] Propane steam reforming (SHR) to produce hydrogen demonstrates significant advantages in terms of raw materials, process, efficiency, and environmental friendliness, making it a key method for industrial hydrogen production. Propane is the primary component of liquefied petroleum gas (LPG), with an annual global production exceeding 300 million tons and a mature supply chain. As a high-carbon fuel, it has a high energy density. Furthermore, propane can be liquefied at room temperature and low pressure, making it easy to transport and store. The steam reforming reaction produces 10 moles of hydrogen per mole of propane, significantly exceeding the hydrogen production of methane, methanol, and other reforming reactions.

[0005] In the field of reforming hydrogen production technology, how to maintain the low-cost characteristics of nickel-based catalysts while simultaneously improving their carbon deposition suppression ability and high-temperature sintering resistance through structural innovation has become the core research direction for breaking through the bottleneck of cost reduction and efficiency improvement in this field.

[0006] CN110026199A proposes a lanthanum carbonate-modified alumina-supported nickel-based catalyst and a preparation method thereof. The catalyst is calcined in a CO2 atmosphere to obtain a La2O2CO3-modified Al2O3 carrier. The catalyst is then calcined in a CO2 atmosphere to obtain a La2O2CO3-modified Ni / Al2O3 catalyst. The catalyst demonstrates that La2O2CO3 can improve the reducing ability of Ni by regulating the interaction between Ni and Al2O3, thereby increasing the degree of reduction and active surface area of ​​Ni, and thus improving catalytic activity and stability. However, La2O2CO3 may decompose (La2O2CO3→La2O3+CO2↑) during high-temperature reactions (>800°C), resulting in degradation of the carrier structure. Furthermore, the high-temperature decomposition reaction inhibits the generation of oxygen vacancies in La2O2CO3.

[0007] CN117960177A discloses a carbon-modified alumina-supported nickel-based catalyst, its preparation method, and its application. The catalyst has the advantages of relatively simple preparation and high hydrodeoxygenation efficiency. The carbon component improves the dispersion and particle size distribution of the surface-supported metallic nickel, resulting in high conversion and target product yield. However, due to the stability deficiencies of the carbon component, the catalyst is prone to gasification in the high temperature and hydrogen-rich environment of the hydrodeoxygenation reaction, leading to collapse of the support structure. While the introduced carbon improves nickel dispersion, it itself may act as a carbon source and participate in side reactions.

[0008] All of the above existing technologies suffer from structural instability and poor stability at high temperatures. Furthermore, the catalysts have difficulty removing carbon deposit precursors at high temperatures due to low oxygen vacancy density and the occurrence of side reactions. Therefore, there is an urgent need for a new catalyst for propane steam reforming hydrogen production that can effectively address these challenges. Summary of the Invention

[0009] To address the above technical issues, the present invention provides a Ce-modified nickel-based catalyst for hydrogen production from propane steam reforming, as well as its preparation method and application. The Ce-modified nickel-based catalyst of the present invention effectively suppresses the high-temperature migration of nickel particles through the doping of CeO2, significantly improving catalyst stability and hydrogen production efficiency. Furthermore, the preparation method is simple, allowing for independent optimization of process parameters, facilitating industrial scale-up, and allowing for flexible regulation of the catalyst's composition and performance to meet the needs of diverse application scenarios, thereby enhancing process flexibility and scalability.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, the preparation method comprising the following steps:

[0012] (1) mixing nickel salt and aluminum salt with a solvent, slowly adding the mixture dropwise to an alkaline solution, and sequentially subjecting the mixture to standing, solid-liquid separation, drying, and calcination to obtain a nickel-based alumina catalyst powder;

[0013] (2) mixing the cerium salt with a solvent, slowly adding the mixture dropwise to the nickel-based alumina catalyst powder, and then drying and calcining the mixture in sequence to obtain the Ce-modified nickel-based catalyst;

[0014] Wherein, the temperature of the calcination treatment in step (2) is lower than the temperature of the calcination treatment in step (1).

[0015] The present invention achieves uniform co-precipitation of NiO and Al2O3 by precisely proportioning the nickel source and the aluminum source, combined with the process of slowly adding alkali solution, ensuring the high dispersibility and stability of the carrier; and introduces the CeO2 precursor through the impregnation co-precipitation method and calcines it under mild conditions, avoiding the destruction of CeO2 activity by high temperature and achieving uniform distribution of CeO2 on the NiO-Al2O3 carrier.

[0016] In the present invention, CeO2 is formed by Ce 3+ / Ce 4+ The redox cycle forms reversible oxygen vacancies, promoting CO2 dissociation and achieving in-situ carbon removal (reducing carbon deposits by 30%). CeO2 and Al2O3 form a Ce-Al-O interface, which enhances the anchoring effect on Ni particles and controls the particle size of Ni particles. At the same time, electronic modulation reduces the d-band center of Ni, inhibiting excessive cracking of alkanes. The price of rare earth Ce is cheaper than precious metals, only 1 / 50 of that of Ir, and CeO2-doped Ni / Al2O3 still maintains 90% of its initial activity after operating at 800°C for 100 hours, combining economy and durability.

[0017] As a preferred technical solution of the present invention, the nickel salt in step (1) includes nickel nitrate; and the aluminum salt includes aluminum nitrate.

[0018] Preferably, the molar ratio of nickel element to aluminum element in the nickel salt and aluminum salt is 1:(1-3), for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0019] Preferably, the solvent comprises deionized water and / or ethanol.

[0020] Preferably, the alkali solution comprises any one of sodium carbonate, sodium hydroxide, and aqueous ammonia, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of sodium carbonate and sodium hydroxide, a combination of sodium carbonate and aqueous ammonia, and a combination of sodium hydroxide and aqueous ammonia.

[0021] Preferably, the rate of slow dripping in step (1) is 2-3 s / drop, for example, 2 s / drop, 2.2 s / drop, 2.4 s / drop, 2.6 s / drop, 2.8 s / drop, 3 s / drop, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0022] As a preferred technical solution of the present invention, the mixing time in step (1) is 2-5h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0023] Preferably, the standing time in step (1) is 12-24 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0024] Preferably, the time for solid-liquid separation in step (1) is 12-20 h, for example, 12 h, 14 h, 16 h, 18 h, 20 h, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0025] Preferably, the drying temperature in step (1) is 120-150°C, for example, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0026] The drying time is 3-5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0027] As a preferred technical solution of the present invention, the temperature of the calcination treatment in step (1) is 600-700°C, for example, 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0028] The heating rate of the calcination treatment is 10-15°C / min, for example, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0029] The calcination treatment time is 4 hours to 6 hours, such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0030] As a preferred technical solution of the present invention, the cerium salt in step (2) includes cerium nitrate.

[0031] Preferably, the mixing in step (2) is carried out by ultrasonic dispersion; the time of the ultrasonic dispersion is 5-10 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0032] As a preferred technical solution of the present invention, after the slow dropwise addition to the nickel-based alumina catalyst powder in step (2), ultrasonic dispersion treatment is further performed; the time of the ultrasonic dispersion treatment is 15-20 minutes, for example, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0033] Preferably, the drying temperature in step (2) is 100-120°C, for example, 100°C, 105°C, 110°C, 115°C, 120°C, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0034] The drying time is 12-16 hours, for example, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0035] As a preferred technical solution of the present invention, the temperature of the calcination treatment in step (2) is 450-550°C, for example, 450°C, 470°C, 490°C, 510°C, 530°C, 550°C, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0036] The heating rate of the calcination treatment is 5-8°C / min, for example, 5°C / min, 5.5°C / min, 6°C / min, 6.5°C / min, 7°C / min, 7.5°C / min, 8°C / min, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0037] The calcination treatment time is 4-8 hours, for example, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0038] The present invention avoids the adverse effects of high temperature on the performance of CeO2 and enhances the synergistic effect of the carrier and the active component through the differentiated design of the first step calcination temperature (600-700°C) and the second step calcination temperature (450-550°C).

[0039] In a second aspect, the present invention provides a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, wherein the Ce-modified nickel-based catalyst is prepared by the preparation method described in the first aspect.

[0040] As a preferred technical solution of the present invention, the loading amount of cerium oxide in the Ce-modified nickel-based catalyst is 1-20wt%, for example, 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, 13wt%, 15wt%, 18wt%, 20wt%, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0041] The loading amount of nickel oxide in the Ce-modified nickel-based catalyst is 10-20wt%, for example, 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0042] In a third aspect, the present invention provides a method for preparing hydrogen by steam reforming of propane, wherein the method is carried out using the Ce-modified nickel-based catalyst as described in the second aspect.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] (1) The present invention can inhibit the growth of NiO grains, promote the dispersion of Ni particles, and delay the growth of nickel crystals by doping with CeO2; 3+ Electron transfer via oxygen vacancies inhibits Ni 0+ Over-oxidation significantly improves the catalyst's resistance to carbon deposition and hydrogen production rate.

[0045] (2) The present invention adopts a two-step collaborative co-precipitation method, which can accurately control the material composition and structure, optimize the process conditions in stages, and independently optimize and adjust the precursor concentration and impregnation time in each stage, flexibly control the composition and performance of the catalyst, and facilitate industrial scale-up production. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a scanning electron microscope (SEM) image of the catalyst prepared in Example 1.

[0047] Figure 2 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 1.

[0048] Figure 3 This is the X-ray diffraction (XRD) spectrum of the catalyst prepared in Example 1.

[0049] Figure 4 shows (a) O 1s and (b) Ni 2p of the catalyst prepared in Example 1 3 / 2 X-ray photon spectroscopy (XPS) spectrum.

[0050] Figure 5 It is the temperature programmed reduction (TPR) spectrum of the catalyst prepared in Example 1 and Comparative Example 1.

[0051] FIG6 is a thermogravimetric analysis (TG) spectrum of the catalysts prepared in Example 1(a) and Comparative Example 1(b).

[0052] Figure 7 It is a graph of hydrogen yield of the catalysts prepared in Example 1 and Comparative Example 1.

[0053] Figure 8 This is a graph showing the carbon monoxide yields of the catalysts prepared in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0055] Example 1

[0056] This embodiment provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, the preparation method comprising the following steps:

[0057] (1) 19.46 g of Ni(NO3)2·6H2O and 73.5 g of Al(NO3)3·9H2O were dissolved in 200 mL of deionized water, stirred magnetically for 2 h, and then slowly added dropwise to 25% ammonia water at a rate of 2 s / drop. After standing for 12 h, the solid-liquid separation was performed for 12 h, and then the mixture was dried at 120°C for 5 h. The mixture was calcined at 700°C for 4 h in a muffle furnace at a heating rate of 10°C / min and naturally cooled to obtain a nickel-based alumina catalyst powder.

[0058] (2) 6.3052 g of Ce(NO3)3·6H2O was dissolved in deionized water and ultrasonically dispersed for 5 minutes. The mixture was then slowly added dropwise to 22.5 g of nickel-based alumina catalyst powder and ultrasonically dispersed for 15 minutes. The mixture was dried at 100°C for 12 hours. The mixture was then calcined at 550°C in a muffle furnace at a heating rate of 5°C / min for 4 hours and naturally cooled to obtain the Ce-modified nickel-based catalyst.

[0059] The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) spectra, O 1s and Ni 2p 3 / 2 X-ray photon spectroscopy (XPS) spectra, such as Figure 1 -4 shown.

[0060] Example 2

[0061] This embodiment provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, the preparation method comprising the following steps:

[0062] (1) 19.46 g of Ni(NO3)2·6H2O and 73.5 g of Al(NO3)3·9H2O were dissolved in 200 mL of deionized water, stirred magnetically for 5 h, and then slowly added dropwise to 25% ammonia water at a rate of 3 s / drop. After standing for 24 h, the solid-liquid separation was performed for 20 h, and then the mixture was dried at 150°C for 3 h. The mixture was calcined at 600°C for 6 h in a muffle furnace at a heating rate of 15°C / min and naturally cooled to obtain a nickel-based alumina catalyst powder.

[0063] (2) 6.3052 g of Ce(NO3)3·6H2O was dissolved in deionized water and ultrasonically dispersed for 10 min. The mixture was then slowly added dropwise to 22.5 g of nickel-based alumina catalyst powder and ultrasonically dispersed for 20 min. The mixture was dried at 120°C for 16 h. The mixture was then calcined at 450°C in a muffle furnace at a heating rate of 8°C / min for 8 h and naturally cooled to obtain the Ce-modified nickel-based catalyst.

[0064] Example 3

[0065] This embodiment provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming. The only difference from Example 1 is that the temperature of the calcination treatment in step (1) is adjusted to 800°C, and the conditions of the other steps are the same as those in Example 1.

[0066] Example 4

[0067] This embodiment provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming. The only difference from Example 1 is that the temperature of the calcination treatment in step (2) is adjusted to 600°C, and the remaining step conditions are the same as those in Example 1.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming. The only difference from Example 1 is that the doping of Ce element in step (2) is omitted, and the remaining steps and conditions are the same as those in Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming. The only difference from Example 1 is that the mass of the Ce element in step (2) is replaced by the La element, and the remaining step conditions are the same as those in Example 1.

[0072] Comparative Example 3

[0073] This comparative example provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming. The only difference from Example 1 is that the mass of the Ce element in step (2) is replaced by the Ir element, and the remaining step conditions are the same as those in Example 1.

[0074] Comparative Example 4

[0075] This comparative example provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming. The only difference from Example 1 is that the temperature of the calcination treatment in step (2) is adjusted to 700°C, and the remaining step conditions are the same as those in Example 1.

[0076] Comparative Example 5

[0077] This comparative example provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming. The only difference from Example 1 is that the temperature of the calcination treatment in step (2) is adjusted to 800°C, and the remaining step conditions are the same as those in Example 1.

[0078] Comparative Example 6

[0079] This comparative example provides a method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, the preparation method comprising the following steps:

[0080] 19.46 g of Ni(NO3)2·6H2O, 73.5 g of Al(NO3)3·9H2O, and 6.3052 g of Ce(NO3)3·6H2O were dissolved in 200 mL of deionized water, magnetically stirred for 2 h, and then slowly added dropwise to 25% ammonia water at a rate of 2 s / drop; after standing for 12 h, the solid-liquid separation was carried out for 12 h, and then dried at 120°C for 5 h; the mixture was calcined at 700°C for 4 h in a muffle furnace at a heating rate of 10°C / min and naturally cooled to obtain the Ce-modified nickel-based catalyst.

[0081] Performance Testing

[0082] The catalysts prepared in Examples 1-4 and Comparative Examples 1-6 were tested for hydrogen yields from propane steam reforming at 950°C, as well as the total amount of carbon deposits on the catalysts after 100 hours of continuous operation. The test results are shown in Table 1. The temperature programmed reduction (TPR) spectra, thermogravimetric analysis (TG) spectra, hydrogen yield graphs, and carbon monoxide yield graphs of the catalysts prepared in Example 1 and Comparative Example 1 were tested, as shown in Table 1. Figure 5-8 shown.

[0083] Table 1

[0084]

[0085]

[0086] The test results show that:

[0087] (1) From Figure 1 As can be seen, the SEM image of the catalyst prepared in Example 1 shows that the material is composed of micron-sized particles (1-3 μm) with a rough surface and a porous structure. This morphology indicates that the material has a high specific surface area, which is conducive to reactant mass transfer and active site exposure;

[0088] from Figure 2 It can be seen that the TEM image of the catalyst prepared in Example 1 shows that the Ni-CeO2 particles (dark area) are uniformly embedded in the Al2O3 matrix, with an average particle size of about 8-10 nm. The interface coupling between Ni-CeO2 and Al2O3 can be observed to form a stable Ce-Al-O solid solution structure;

[0089] from Figure 3 It can be seen that the catalyst prepared in Example 1 shows a broadened Ni peak, which indicates that the presence of Ce in the catalyst helps to form a smaller Ni matrix, indicating that CeO2 can inhibit the growth of NiO grains, promote the dispersion of Ni particles, and delay the growth of nickel crystals during the reduction process;

[0090] As shown in Figure 4(a), the XPS spectrum of the O1S region of the catalyst prepared in Example 1 is assigned to lattice oxygen at 529.1EV, which is the main contribution peak of CeO2 intrinsic oxygen. It can give the material excellent redox performance and adaptability by dynamically storing and releasing oxygen. At the same time, the peak at 530.9EV is assigned to oxygen vacancies. These oxygen vacancies can serve as active sites to improve the catalytic activity of the material. 3 / 2 XPS spectrum of the region shows the presence of Ni in the catalyst 0+ The peak is symmetrical and has no satellite peaks, indicating that there are unoxidized nickel particles in the system; Ce 3+ Oxygen vacancies provide electrons to Ni, promoting the partial reduction of NiO (Ni 2+ →Ni 0 ), which means that CeO2 can dynamically compensate Ni 0+ The partial oxidation of Ni maintains the stability of the active site, and the oxygen vacancies inhibit the 0 Over-oxidation of ions maintains the balance of active species in the catalytic cycle;

[0091] from Figure 5 It can be seen that after the catalyst is doped with CeO2, the TPR test intersects with the high-temperature region of the unmodified catalyst and a weak reduction peak of CeO2 bulk oxygen is detected, which contributes to the additional hydrogen consumption value, indicating that the modification improves the reduction ability of the catalyst.

[0092] As shown in Figures 6(a) and (b), after 100 hours of continuous operation, the total amount of carbon deposits on the catalyst of Comparative Example 1 was high (weight loss of 80%), which was significantly lower than the total amount of carbon deposits on the catalyst prepared in Example 1 (weight loss <10%). The carbon deposits on the catalyst were reduced by 90%. The weight loss between 600 and 800°C indicated that the Ni particles sintered and deactivated at high temperatures. The addition of CeO2, by anchoring the Ni particles and inhibiting their reduction, enhanced the high-temperature sintering resistance of the Ni particles, making them suitable for high-temperature catalytic reactions. Furthermore, CeO2 dynamically stores and releases oxygen as an active site, reacting with the generated carbon deposits to improve the material's resistance to carbon deposition.

[0093] from Figure 7 It can be seen that the hydrogen yield under the conditions of no catalyst, comparative example 1 catalyst and embodiment 1 catalyst all increases with increasing temperature, which is consistent with the thermodynamic characteristics of endothermic reaction (ΔH>0); the yield under the catalyst-free system is below 10% throughout the process, and the efficiency is extremely low; at the same temperature, the yield of the comparative example 1 catalyst system is significantly higher than that without catalyst, and the growth rate of the comparative example 1 catalyst slows down at 850°C, and even the hydrogen yield decreases. This may be because the Ni particles sinter or the high-temperature phase change of the carrier (Al2O3) leads to a reduction in active sites; the yield of the embodiment 1 catalyst is higher than that of the comparative example 1 catalyst at all temperature points, especially in the high temperature zone (800-1000°C), the advantage expands, and the yield is still on an upward trend at 850°C; on the other hand, the hydrogen yield of the comparative example 1 catalyst begins to decrease, and the gap is more obvious at 950°C. The hydrogen production efficiency of the embodiment 1 catalyst is as high as nearly 55%, which indicates that the addition of CeO2 promotes the dispersion of Ni particles and slows down the sintering of nickel-based particles at high temperature.

[0094] from Figure 8 It can be seen that the CO yield of the catalyst in Example 1 is lower than that of the catalyst in Comparative Example 1 at all temperature points, and the difference is more obvious at 950°C. This is because the oxygen vacancies in CeO2 deeply oxidize CO to CO2 and release lattice oxygen at the same time. The CeO2 modification effectively inhibits CO generation while improving the propane conversion rate through the dynamic regulation mechanism of oxygen vacancies. The catalyst prepared in Example 1 significantly improves the catalyst's resistance to carbon deposition, especially its resistance to carbon deposition in high-temperature areas.

[0095] (2) By comparing Examples 1 and 2, it can be seen that the catalyst prepared in the present invention has excellent high-temperature carbon deposition resistance, and has a high hydrogen yield and good stability at 950°C.

[0096] (3) By comparing Example 1 with Examples 3-4, it can be seen that increasing the calcination temperature of the catalyst in step (1) has little effect on the thermal stability and anti-carbon deposition ability of the catalyst; however, increasing the calcination temperature of the catalyst in step (2) destroys the activity of cerium oxide, thereby affecting the thermal stability and anti-carbon deposition ability of the catalyst.

[0097] (4) By comparing Example 1 with Comparative Examples 1-3, it can be seen that whether the doping of cerium is omitted or cerium is replaced by lanthanum or iridium, the thermal stability and anti-carbon deposition ability of the catalyst will be affected. Therefore, the doping of cerium in the present invention can not only improve the thermal stability of the catalyst, but also reduce the cost, which is conducive to large-scale industrial production.

[0098] (5) By comparing Example 1 with Comparative Examples 4-5, it can be seen that adjusting the calcination temperature of step (2) to be greater than or equal to the calcination temperature of step (1) will destroy the activity of cerium oxide, thereby significantly reducing the catalyst's anti-carbon deposition ability and hydrogen production rate.

[0099] (6) From the comparison between Example 1 and Comparative Example 6, it can be seen that the present invention adopts a two-step collaborative co-precipitation method to prepare the Ce-modified catalyst, which significantly enhances the thermal stability and anti-carbon deposition ability of the catalyst. At the same time, the composition and performance of the catalyst can be flexibly regulated to meet the needs of different application scenarios, thereby improving the process flexibility and scalability.

[0100] In summary, the present invention provides a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, and its preparation method and application. Reversible oxygen vacancies are formed by doping with cerium oxide, which promotes CO2 dissociation, achieves in-situ carbon removal, and significantly improves the catalyst's ability to resist carbon deposition. At the same time, a Ce-Al-O interface is formed by cerium oxide and alumina, which enhances the anchoring effect on Ni particles and controls the particle size of Ni particles, further improving the catalyst's activity and ability to resist carbon deposition. The present invention prepares a cerium oxide-doped nickel-based alumina catalyst through a simple two-step collaborative co-precipitation method. The preparation process is simple, and the composition and performance of the catalyst can be flexibly regulated to meet the needs of different application scenarios, thereby improving process flexibility and scalability and facilitating industrial scale-up production.

[0101] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, characterized in that: The preparation method comprises the following steps: (1) mixing nickel salt and aluminum salt with a solvent, slowly adding the mixture dropwise to an alkaline solution, and sequentially subjecting the mixture to standing, solid-liquid separation, drying, and calcination to obtain a nickel-based alumina catalyst powder; (2) mixing the cerium salt with a solvent, slowly adding the mixture dropwise to the nickel-based alumina catalyst powder, and then drying and calcining the mixture in sequence to obtain the Ce-modified nickel-based catalyst; Wherein, the temperature of the calcination treatment in step (2) is lower than the temperature of the calcination treatment in step (1).

2. The preparation method according to claim 1, characterized in that The nickel salt in step (1) comprises nickel nitrate; the aluminum salt comprises aluminum nitrate; Preferably, the molar ratio of nickel element to aluminum element in the nickel salt and aluminum salt is 1:(1-3); Preferably, the solvent comprises deionized water and / or ethanol; Preferably, the alkali solution comprises any one of sodium carbonate, sodium hydroxide, and ammonia water, or a combination of at least two thereof; Preferably, the rate of slow dripping in step (1) is 2-3 s / drop.

3. The preparation method according to claim 1 or 2, characterized in that The mixing time in step (1) is 2-5 hours; Preferably, the standing time in step (1) is 12-24 hours; Preferably, the solid-liquid separation time in step (1) is 12-20 hours; Preferably, the drying temperature in step (1) is 120-150° C., and the drying time is 3-5 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that The temperature of the calcination treatment in step (1) is 600-700°C; the heating rate of the calcination treatment is 10-15°C / min; and the time of the calcination treatment is 4h-6h.

5. The preparation method according to any one of claims 1 to 4, characterized in that The cerium salt in step (2) includes cerium nitrate; Preferably, the mixing in step (2) is performed by ultrasonic dispersion; the ultrasonic dispersion time is 5-10 minutes.

6. The preparation method according to any one of claims 1 to 5, characterized in that After the step (2) is slowly added dropwise to the nickel-based alumina catalyst powder, an ultrasonic dispersion treatment is further performed; the ultrasonic dispersion treatment time is 15-20 minutes; Preferably, the drying temperature in step (2) is 100-120° C., and the drying time is 12-16 hours.

7. The preparation method according to any one of claims 1 to 6, characterized in that The temperature of the calcination treatment in step (2) is 450-550°C; the heating rate of the calcination treatment is 5-8°C / min; and the time of the calcination treatment is 4-8h.

8. A Ce-modified nickel-based catalyst for hydrogen production by propane steam reforming, characterized in that: The Ce-modified nickel-based catalyst is prepared by the preparation method according to any one of claims 1 to 7.

9. The Ce-modified nickel-based catalyst according to claim 8, characterized in that The loading amount of cerium oxide in the Ce-modified nickel-based catalyst is 1-20 wt %; the loading amount of nickel oxide in the Ce-modified nickel-based catalyst is 10-20 wt %.

10. A method for producing hydrogen by steam reforming of propane, characterized in that: The method is carried out using the Ce-modified nickel-based catalyst as claimed in claim 8 or 9.

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