Nickel-zirconium-based low-temperature methane carbon dioxide reforming catalyst

Abstract

The invention discloses a nickel-zirconium-based low-temperature methane carbon dioxide reforming catalyst, which is prepared by the following method: adding nickel salt, zirconium salt and a complexing agent into a container, adding water for dissolving, then adding carrier silicon dioxide powder, uniformly mixing to obtain a precursor liquid, heating and evaporating the precursor liquid to dryness to obtain solid powder, and then calcining to obtain a Ni-ZrO2 / SiO2 catalyst. The low-temperature methane and carbon dioxide reforming catalyst has good low-temperature methane and carbon dioxide reforming activity and stability under the low-temperature condition of 600 DEG C or below, and also has good carbon deposition resistance.

Description

Technical Field

[0001] This invention relates to the field of catalyst production technology, and in particular to a nickel-zirconium-based low-temperature methane-carbon dioxide reforming catalyst. Background Technology

[0002] The methane-carbon dioxide reforming reaction (also known as dry reforming, DRM, CO2 + CH4 → 2CO + 2H2) can directly convert two major greenhouse gases—methane and carbon dioxide—into high-value-added syngas (a mixture of CO and H2). This reaction not only provides a promising pathway for the high-value utilization of methane resources from natural gas, biogas, shale gas, and landfill gas, but also opens up new directions for the large-scale chemical fixation and resource conversion of carbon dioxide. The resulting syngas is a feedstock for many important chemical processes such as Fischer-Tropsch synthesis, methanol synthesis, and dimethyl ether synthesis, and its hydrogen-to-carbon ratio (H2 / CO ≈ 1) is particularly suitable for direct use in carbonyl synthesis and the production of liquid hydrocarbons. Therefore, the development of efficient and stable DRM catalysts is of great strategic significance for energy transition and environmental protection under the "dual carbon" target.

[0003] Among numerous DRM catalyst systems, nickel (Ni)-based catalysts are considered the most industrially promising non-precious metal catalysts due to their relatively high catalytic activity and significant cost advantages. However, nickel-based catalysts face severe challenges in DRM reactions, especially under low-temperature (typically 600°C and below) reaction conditions aimed at reducing energy consumption. The core issues are severe carbon deposition on the catalyst and sintering of the active component, nickel. These two factors are key reasons for rapid catalyst deactivation, increased pressure drop in the reaction bed, and even reactor blockage.

[0004] First, carbon deposition is particularly prominent at low temperatures. Carbon deposition can occur during the DRM reaction through various pathways, primarily including methane cracking (CH4 → C + 2H2) and carbon monoxide dismutation (i.e., the Boudouard reaction, 2CO → C + CO2). Thermodynamic analysis shows that the Boudouard reaction is more likely to occur than methane cracking in the temperature range below 700℃. This means that under the target low-temperature reaction conditions, the reaction product CO is highly susceptible to dismutation, generating solid carbon deposits on the catalyst surface and within the pores. These carbon species may encapsulate active sites in the form of relatively inert graphitic carbon, hindering contact between reactants and active centers; or they may grow into mechanically strong filamentous carbon (carbon nanotubes or carbon fibers), physically damaging the catalyst particle structure and even penetrating the catalyst, leading to pulverization. Therefore, suppressing carbon deposition induced by low-temperature CO dismutation is the primary challenge that must be overcome in developing low-temperature DRM catalysts.

[0005] Secondly, sintering of nickel particles is another major deactivation mechanism. Low-temperature reactions typically require smaller nickel particles (high dispersion) to provide sufficient active surface area to compensate for the decrease in intrinsic reaction rate. However, small-sized nickel nanoparticles possess high surface energy and mobility. Under the long-term high-temperature (even relatively low-temperature, such as 500-600℃) environment of DRM reactions, these tiny nickel particles tend to aggregate and grow into larger particles through surface migration, particle collision coalescence, or Ostwald ripening. Particle sintering not only directly reduces the number of active sites and lowers catalytic activity, but larger nickel particles are also more likely to catalyze the formation of amorphous carbon or graphitic carbon, which exacerbates the carbon deposition problem and creates a vicious cycle of deactivation.

[0006] Current research strategies primarily focus on improving catalyst preparation methods to obtain highly dispersed, small-sized nickel nanoparticles and stabilizing them on suitable supports to enhance their resistance to carbon deposition. Commonly used methods include impregnation, co-precipitation, sol-gel methods, and combustion synthesis. These methods aim to construct strong metal-support interactions (SMSI), utilizing the confinement effect or anchoring points of the support to immobilize nickel particles and inhibit their migration and growth.

[0007] However, existing technologies have an inherent contradiction and limitation: the excessive pursuit of nano-sized and highly dispersed nickel particles in pursuit of low-temperature activity often sacrifices thermal stability. As mentioned earlier, the thermodynamic instability of ultrafine nickel particles is amplified under reaction conditions, and even with certain metal-support interactions, sintering is still difficult to completely avoid in long-term harsh reaction environments. Once sintering occurs, the catalyst rapidly deactivates. Furthermore, relying solely on support modification or process optimization to control nickel particle size often faces problems such as complex processes, poor reproducibility, high costs, or insufficient catalyst mechanical strength. More importantly, many catalysts reported in studies have performed poorly in long-term stability tests below 600°C, making it difficult to simultaneously achieve anti-carbon deposition and anti-sintering, which is the core bottleneck for the practical application of low-temperature DRM technology.

[0008] In summary, developing a novel catalyst suitable for low-temperature (≤600℃) methane-carbon dioxide reforming reaction, which effectively coordinates and resolves the contradictions between "high activity," "strong resistance to carbon deposition," and "high resistance to sintering stability," is a key issue that urgently needs to be addressed in this technical field. Summary of the Invention

[0009] The purpose of this invention is to provide a nickel-zirconium-based low-temperature methane-carbon dioxide reforming catalyst, which exhibits good low-temperature methane-carbon dioxide reforming activity and stability at temperatures of 600°C and below, and also has good resistance to carbon deposition.

[0010] The design concept of this invention stems from an in-depth analysis of the bottlenecks in low-temperature methane-carbon dioxide reforming (DRM) reactions. Although ZrO2 is considered a potential additive or support due to its dual acid-base surface properties, conventionally prepared Ni-ZrO2 systems struggle to simultaneously achieve high activity, resistance to carbon deposition, and resistance to sintering at low temperatures. The fundamental reason is that conventional methods cannot precisely construct and stabilize a tight, uniform, and highly synergistic interfacial structure between Ni and ZrO2 at the microscale.

[0011] The technical solution adopted by this invention to solve its technical problem is: A nickel-zirconium-based low-temperature methane-carbon dioxide reforming catalyst is prepared by the following method: Nickel salt, zirconium salt and complexing agent are added to a container, dissolved in water, and then silicon dioxide powder is added as a support. The mixture is stirred to obtain a precursor liquid. The precursor liquid is heated and evaporated to dryness to obtain a solid powder, which is then calcined to obtain a Ni-ZrO2 / SiO2 catalyst.

[0012] In the preparation process, this invention utilizes the dual functions of glycine: as a strong complexing agent at low temperatures to ensure atomic-level uniform mixing of metal ions; and as a highly efficient fuel at high temperatures to instantaneously synthesize the target oxide through a self-propagating combustion reaction.

[0013] Ni(NO3)2·6H2O, Zr(NO3)4·5H2O, and glycine (NH2CH2COOH) were dissolved together in deionized water. At this stage, the complexation effect of glycine begins to play a crucial role. Glycine is an amphoteric amino acid whose molecule contains both amino and carboxyl groups, enabling it to form stable water-soluble complexes with various metal ions. 2+ and Zr 4+ The ions coordinate with glycine molecules to form complexes. This achieves uniform mixing of Ni and Zr ions at the molecular / atomic scale and effectively prevents segregation or precipitation caused by different degrees of hydrolysis during subsequent evaporation.

[0014] The solution is heated to dryness. This process is not only physical dehydration but also a sol-gel transformation. As the water evaporates, the solution concentration increases dramatically. The metal-glycine complexes cross-link through hydrogen bonds, coordination bonds, and the interactions of the remaining carboxyl and amino groups, forming a precursor layer with a three-dimensional network structure on the surface and within the pores of the SiO2 particles. This gel network "freezes" the Ni, Zr, C, N, and O elements in a highly uniform and dispersed state, preparing an ideal, microscopically uniform oxidant-fuel mixture for the subsequent combustion reaction.

[0015] High-temperature calcination: decomposition of complexes and combustion reaction in solution: The dried powder is heated in a muffle furnace. This process consists of two continuous and partially overlapping stages: Stage 1: Thermal decomposition of the complex and formation of the oxidant / fuel system. When the temperature rises to 200-300℃, the metal-glycine complex begins to thermally decompose, releasing coordinated glycine or its decomposition products (such as glycine esters), while nitrate also begins to decompose. However, at this point, the system has not yet undergone vigorous combustion.

[0016] Stage Two: Self-propagating solution combustion reaction. When the temperature rises to a certain critical point (ignition temperature, usually between 300-500℃), carbon and hydrogen (reducing fuel) from glycine and its decomposition products, which are uniformly dispersed in the gel network, undergo a violent redox reaction with nitrogen oxides from the decomposition of nitrate and oxygen from the atmosphere (oxidizing agent).

[0017] The combustion reaction directly generates highly dispersed NiO and ZrO2 nanoparticles. In the final catalyst, Ni is supported in the form of NiO, and Zr exists in the form of ZrO2, both highly dispersed on SiO2.

[0018] The high temperature and rapid cooling characteristics of combustion synthesis favor the formation of metastable, oxygen-vacancy-rich tetragonal zirconium oxide (t-ZrO2). Compared to the monoclinic phase, t-ZrO2 exhibits higher surface energy, more surface active sites, and better oxygen ion mobility. At the Ni-ZrO2 interface, these oxygen vacancies serve as active sites for activating CO2 molecules, efficiently gasifying carbon species deposited on Ni. This significantly enhances the catalyst's resistance to carbon deposition from the source, which is crucial for the low-temperature DRM process, which is prone to CO disproportionation.

[0019] The essence of this invention is a solution combustion method using glycine as a complexing agent-fuel dual-functional additive. It involves "pre-assembling" a molecularly uniform Ni-Zr precursor through complexation and then "instantly solidifying" this uniform structure into a nanocomposite oxide with strong interactions through a combustion reaction.

[0020] In the initial solution stage, Ni 2+ and Zr 4+ Bound together by glycine in the same complex system, a microscopically uniform "Ni-Zr-Gly" composite precursor is formed. This molecular-level mixing ensures that the generated NiO and ZrO2 can nucleate and grow at extremely close distances during subsequent combustion and calcination, greatly promoting the formation of a tight interface or even an amorphous interface layer or limited solid solution between the two. This structure is key to high-performance DRM catalysts, effectively promoting synergistic effects between active components.

[0021] Preferably, the nickel salt is Ni(NO3)2·6H2O.

[0022] Preferably, the zirconium salt is Zr(NO3)4·5H2O.

[0023] Preferably, the complexing agent is glycine.

[0024] Preferably, the heating and drying temperature is 50-150°C.

[0025] Preferably, the calcination temperature is 350-900℃ and the calcination time is 3-5 hours.

[0026] Preferably, in the Ni-ZrO2 / SiO2 catalyst, the Ni content is 1-10 wt%, the ZrO2 content is 1-30 wt%, and the balance is SiO2. More preferably, the Ni content is 5 wt%.

[0027] Preferably, the molar ratio of the complexing agent to the total amount of nickel and zirconium is 0.5-2:1. This ratio ensures sufficient complexation and provides an appropriate amount of fuel to maintain an effective combustion reaction.

[0028] The beneficial effects of this invention are: 1. An ideal microstructure for the active center was created: The catalyst prepared in this invention successfully achieved an ideal three-in-one structure of "high dispersion at the nanoscale," "high integration of the Ni-ZrO2 interface," and "ZrO2 crystal phase activation." The highly dispersed Ni particles provide abundant methane activation sites, ensuring high initial activity of the catalyst. The tight interface formed between Ni and ZrO2 through the combustion reaction generates strong metal-support interactions, allowing ZrO2 to effectively anchor Ni particles, significantly inhibiting their migration and aggregation during the reaction process. This endows the catalyst with excellent long-term thermal stability, resolving the contradiction between high dispersion and anti-sintering in low-temperature DRM.

[0029] 2. Significantly Enhanced Catalyst Resistance to Carbon Deposition: The unique preparation method of this invention ensures that ZrO2 in the catalyst primarily exists as a tetragonal phase (t-ZrO2) rich in oxygen vacancies. At the Ni-ZrO2 interface, these oxygen vacancies are highly efficient active sites for activating CO2 molecules (converting them into reactive oxygen species). During the reaction, the carbon precursors generated on the Ni surface can be promptly vaporized by the reactive oxygen species activated by ZrO2 at the interface, thus achieving "instantaneous generation and elimination." This interfacial synergistic carbon removal mechanism significantly inhibits carbon deposition at its source, and is particularly beneficial for combating carbon deposition problems caused by CO disproportionation reactions that easily occur at low temperatures (≤600℃).

[0030] 3. Simple, efficient, and highly reproducible process: This invention simplifies the complex structure regulation process into a one-step combustion synthesis, eliminating the need for complex subsequent processing steps. The molecular-level homogeneity of the precursor ensures the uniformity of the final catalyst composition and structure, giving the preparation method excellent reproducibility and controllability, which is beneficial for large-scale production. Attached Figure Description

[0031] Figure 1 This is a comparison chart of the conversion rates of methane catalyzed by different catalysts. Detailed Implementation

[0032] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0033] In this invention, unless otherwise specified, all raw materials and equipment used are commercially available or commonly used in the field. The methods described in the following embodiments are conventional methods in the field, unless otherwise specified.

[0034] Example 1: 0.246 g Ni(NO3)2·6H2O, 0.236 g Zr(NO3)4·5H2O, and 0.105 g glycine were placed in a beaker, and 1.5 mL of deionized water was added, followed by 0.9 g SiO2. The mixture was then heated to dryness in an oven at 90 °C. The resulting solid powder was calcined in a muffle furnace at 600 °C for 4 h to obtain a 5% Ni-ZrO2 / SiO2-G catalyst prepared by solution combustion. Here, G represents the addition of glycine during preparation, and 5% represents the Ni content in the catalyst as approximately 5% (mass percentage).

[0035] Comparative Example 1: Glycine was not added during the preparation process, but everything else was the same as in Example 1. A 5% Ni-ZrO2 / SiO2-N catalyst was used. Here, N represents that glycine was not added during the preparation process.

[0036] Example 2: The difference between this embodiment and Embodiment 1 is that: The solid powder was then dried in an oven at 50°C, and calcined in a muffle furnace at 350°C for 5 hours to obtain a 1% Ni-ZrO2 (30%) / SiO2-G catalyst prepared by solution combustion. Here, 1% represents the Ni content in the catalyst as 1% (mass percentage).

[0037] Example 3: The difference between this embodiment and Embodiment 1 is that: The solid powder was then dried in an oven at 150°C, and calcined in a muffle furnace at 900°C for 3 hours to obtain a 10% Ni-ZrO2 (1%) / SiO2-G catalyst prepared by solution combustion. Here, 10% represents the Ni content in the catalyst as 10% (mass percentage).

[0038] Catalyst performance test conditions (1) Weigh 20 mg of the 5% Ni-CeO2 / SiO2-G catalyst prepared in Example 1, Comparative Example 1, and CN112387285A and load it into a quartz tube reactor. Before the reaction, the catalyst was reduced with a 20% H2 / Ar mixed gas at 700℃ for 40 minutes. Then, the reaction gas (CO2: 15 ml / min, CH4: 15 ml / min, Ar: 70 ml / min) was introduced to start the reaction, and the reaction test temperature was 600℃. The composition of the gas generated in the reaction was detected by gas chromatography, and the methane conversion rate of each catalyst was calculated.

[0039] Table 1. Carbon deposition on the catalyst after the reaction

[0040] Depend on Figure 1 It can be seen that the methane conversion rate of the 5% Ni-ZrO2 / SiO2-G catalyst is significantly higher than that of the 5% Ni-ZrO2 / SiO2-N and 5% Ni-CeO2 / SiO2-G catalysts. Furthermore, the performance of the Ni-ZrO2 / SiO2-G catalyst remains relatively stable within 6 hours, indicating that the 5% Ni-ZrO2 / SiO2-G catalyst possesses high activity and stability in the methane-carbon dioxide reforming reaction. Thermogravimetric analysis (TGA) results show the amount of carbon deposits on the catalyst, as shown in Table 1. Table 1 shows that the carbon deposits after the reaction of the 5% Ni-ZrO2 / SiO2-G catalyst are significantly less than those of the 5% Ni-ZrO2 / SiO2-N and 5% Ni-CeO2 / SiO2-G catalysts, indicating that the 5% Ni-ZrO2 / SiO2-G catalyst has good anti-carbon deposition performance. These results indicate that the 5% Ni-ZrO2 / SiO2-G catalyst exhibits good low-temperature methane-carbon dioxide reforming activity and stability, while also demonstrating strong resistance to carbon deposition.

[0041] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A nickel-zirconium-based low-temperature methane carbon dioxide reforming catalyst, characterized by, Prepared by the following method: The nickel salt, zirconium salt and complexing agent are added into a container, dissolved with water, then the carrier silica powder is added, mixed to obtain a precursor solution, the precursor solution is heated to dryness to obtain a solid powder, then calcination to obtain a Ni-ZrO2 / SiO2 catalyst.

2. The Ni-Zr-based catalyst for low-temperature reforming of carbon dioxide and methane according to claim 1, characterized in that, The nickel salt is Ni(NO3)2·6H2O.

3. The Ni-Zr-based catalyst for low-temperature reforming of CH4 and CO2 according to claim 1, characterized in that, The zirconium salt is Zr(NO3)4·5H2O.

4. The Ni-Zr-based catalyst for low-temperature reforming of carbon dioxide and methane according to claim 1, wherein The complexing agent is glycine.

5. The Ni-Zr-based catalyst for low-temperature reforming of CH4 and CO2 according to claim 1, characterized in that, The temperature of heating to dryness is 50-150℃.

6. The Ni-Zr-based catalyst for low-temperature reforming of CH4 and CO2 according to claim 1, characterized in that, The calcination temperature is 350-900℃, and the calcination time is 3-5 hours.

7. The Ni-Zr-based catalyst for low-temperature reforming of CH4 and CO2 according to claim 1, characterized in that, In the Ni-ZrO2 / SiO2 catalyst, the content of Ni is 1-10wt%, the content of ZrO2 is 1-30wt%, and the balance is SiO2.

8. The Ni-Zr-based catalyst for low-temperature reforming of CH4 and CO2 according to claim 1, characterized in that, The molar ratio of the total amount of the complexing agent to nickel+zirconium = 0.5-2:1.

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