甲烷催化裂解制氢技术研究进展

介绍了甲烷制氢的主要技术途径及甲烷裂解制氢的反应机理,综述了甲烷裂解制氢不同催化剂的研究进展,包括单金属催化剂、多金属催化剂、碳质催化剂及不同载体的研究进展和发展趋势,简述了微波辐射、等离子体等甲烷催化裂解制氢新技术,并对甲烷催化裂解制氢研究方向进行了展望。     

铁催化甲烷无氧裂解制氢和碳纳米材料研究进展

随着国家对空气质量和环保要求的日渐提高,能高效制氢且不会产生污染空气造成温室效应的制氢工艺是实现碳减排的有效手段。甲烷催化分解是一种无氧裂解制氢技术,也是甲烷的低温裂解。甲烷裂解的最终产物是氢和固体碳,能有效减少碳氢化合物的产生。在过渡金属催化剂中,铁能在高温下保持稳定,促使甲烷裂解朝正反应方向进行,并会产生高附加值的薄壁碳纳米管。综述了甲烷裂解制氢的优点、铁基催化剂类型、反应器类型以及催化剂再生方法。     

熔融金属法甲烷裂解制氢和碳材料研究进展

熔融金属法甲烷裂解技术作为近年来新兴的制氢技术，有效地解决了传统甲烷热裂解或催化裂解高能耗、低转化率以及催化剂失活等问题，避免了甲烷蒸汽重整制氢工艺高碳排放。在制氢的同时还能生产出具有附加值的碳产品，因而受到各方广泛关注。本文总结了熔融金属法甲烷裂解技术研究进展，并围绕工艺流程、反应机理、熔融介质的选择以及反应器设计等方面展开，给出了液相介质是否起催化作用的两类甲烷裂解反应机理，并详细阐述了熔融介质选择原则、发展趋势以及不同类型熔融介质的优缺点。再者，技术经济性以及温室气体减排量也在文中详细体现，进一步论证了该工艺的可行性和潜在效益。此外，文中还给出了未来技术发展趋势和建议，指出调控碳材料形貌，使之向高附加值碳材料转变应是未来重点发展方向之一。     

甲烷催化裂解制氢及碳纳米管的研究进展

介绍了甲烷催化裂解的反应机理,比较了催化剂3种再生方法,系统地阐述了催化剂组分和制备方法对甲烷催化裂解的影响,讨论了镍基催化剂催化产生碳纳米管的机理,列举了碳纳米管的应用。并结合现状提出了甲烷裂解制氢及碳纳米管在反应中存在的问题及应用前景。     

微波辐照下半焦催化甲烷裂解制氢研究

以未经任何活化的内蒙古煤热解半焦为催化剂,研究了甲烷在微波加热条件下裂解制氢的反应规律和催化剂失活机理,探讨了半焦的表面结构特征和含氧官能团,分析了反应条件对甲烷催化裂解过程的影响.研究表明,在650℃~850℃之间,内蒙古褐煤半焦是一种很好的甲烷裂解制氢催化剂,在半焦制备温度为850℃,反应温度为850℃,空速为600mL/(h·g)的条件下,半焦催化甲烷裂解的初始转化率最高达到了61.75%;升高半焦制备温度和催化反应温度以及降低空速有利于提高甲烷的转化率;半焦催化活性降低的主要原因是表面结构特性的改变和含氧官能团的减少.     

流化床与固定床中甲烷裂解制氢过程的比较

本文对流化床与固定床操作模式下的甲烷催化裂解制氢进行了比较研究。以纯甲烷为原料,分别考察了75Ni10Cu15Al和2Co1Al（原子比）催化剂上流化床与固定床操作模式下甲烷裂解制氢反应,结果表明流化床中的甲烷裂解反应速率较高。流化床操作的高表观速率主要是因为此模式下有效消除了外扩散,同时极大减少了内扩散阻力。同时不同温度下催化剂上生长的碳的TEM表征发现,金属颗粒尺寸随反应温度增加而增加,表明催化剂烧结是失活原因之一。但相同温度下固定床中催化剂金属颗粒尺寸明显大于流化床中的金属颗粒尺寸,且金属颗粒尺寸分布变宽,这说明流化床反应器有利于阻止金属颗粒的烧结。通过对甲烷裂解催化剂失活原因的分析发现流化床中催化剂颗粒的流态化有利于延长催化剂活性寿命。     

炭催化甲烷裂解制氢研究进展

综述了炭催化甲烷裂解制氢的研究进展,重点阐述了具有不同孔结构特征的微孔炭、介孔炭和金属负载型炭催化剂在甲烷催化裂解制氢过程中的催化性能和影响规律。与微孔炭具有较高初始活性、较低稳定性相比,介孔炭或具有微孔/介孔结构的多级孔结构炭材料表现出更高的催化活性和寿命;将金属负载于炭材料制得的金属负载型催化剂可同时利用金属的高活性和炭材料相对较高的稳定性提高催化裂解甲烷性能。该文还对炭催化甲烷裂解机理进行概述,指出通过调控炭材料结构与组成、提高甲烷催化裂解性能和加强对炭催化甲烷裂解机理研究是今后发展的方向。     

裂解碳五双烯烃选择加氢

通过对裂解碳五（C₅）馏分中双烯烃选择加氢催化剂的研制及其加氢工艺条件试验,考察了反应压力、空速、氢/双烯摩尔比和入口温度等主要工艺条件对催化性能的影响,得出裂解C₅双烯烃选择加氢的适宜工艺条件为：入口温度30～40 ℃、反应压力2.0～3.0 MPa、氢/双烯摩尔比1.5～2.5、体积时空速为2～4 h^-1。在上述条件下研制的催化剂可以使双烯烃转化率大于95％,生成单烯烃的选择性大于90％。稳定性试验结果表明研制的催化剂具有良好的稳定性。通过再生,催化剂可恢复原有的催化性能。     

专利信息

一种甲烷催化裂解制氢或氢烷的方法一种甲烷催化裂解制氢或氢烷的方法 ,其特征在于 :甲烷在非氧化条件下催化裂解来生产氢或氢烷 ,反应产品气中只含有甲烷和氢 ;反应条件为 :反应温度 4 0 0～ 70 0℃ ,反应压力为 0 .0 5～ 1ＭＰａ ,甲烷空速为 0 .5～ 5 0ｈ- 1;所用催化剂的主活性组分为Ｆｅ、Ｃｏ、Ｎｉ中的一种或几种。与传统的制氢方法相比 ,本发明所提供的甲烷制氢、氢烷的方法更经济 ,更方便。公开号　ＣＮ135 0 977Ａ　　公开日　 2 0 0 2 .5 .2 9高硅β沸石及其制备方法一种β沸石 ,ＳｉＯ2 /Ａｌ2 Ｏ3为 6 0～ 80 ,红外酸度 ,总酸…     

碳四烷烃催化裂解制低碳烯烃的研究进展

论述了碳四烷烃催化裂解制低碳烯烃的催化剂体系、影响因素及催化裂解方式。该催化剂体系包括硅铝酸盐及锆硫酸盐,氧化铝与碱金属或碱土金属的混合物,负载型催化剂等3种类型。其中分子筛(晶体硅铝酸盐)及其改性催化剂是研究开发的主要方向。除操作条件外,稀释剂、引发和抑制剂和裂解反应方式对催化裂解反应均有影响。催化裂解反应机理与催化剂的种类和反应条件相关。对于酸性分子筛催化剂有2种比较公认的机理:正碳离子机理,自由基与正碳离子机理两种形式。研究表明碳四烷烃,特别是正丁烷催化裂解制低碳烯烃具有良好的低碳烯烃收率,收率可达50%以上。     

Thermo-catalytic decomposition of waste lubricating oil over carbon catalyst

The thermo-catalytic decomposition of waste lubricating oil over a carbon catalyst was investigated in an I.D. of 14.5mm and length of 640mm quartz tube reactor. The carbon catalysts were activated carbon and rubber grade carbon blacks. The decomposition products of waste lubricating oil were hydrogen, methane, and ethylene in a gas phase, carbon in a solid phase and naphthalene in a liquid phase occurring within the temperature ranges of 700 °C-850 °C. The thermo-catalytic decomposition showed higher hydrogen yield and lower methane yield than that of a non-catalytic decomposition. The carbon black catalyst showed higher hydrogen yield than the activated carbon catalyst and maintained constant catalytic activity for hydrogen production, while activated carbon catalyst showed a deactivation in catalytic activity for hydrogen production. As the operating temperature increased from 700 °C to 800 °C, the hydrogen yield increased and was particularly higher with carbon black catalyst than activated carbon. As a result, carbon black catalyst was found to be an effective catalyst for the decomposition of waste lubricating oil into valuable chemicals such as hydrogen and methane.     

Nonoxidative Activation of Methane

Effective utilization of methane remains one of the long-standing problems in catalysis. Over the past several years, various routes, both direct and indirect, have been considered for the conversion of methane to value-added products such as higher hydrocarbons and oxygenates. This review will focus on the range of issues dealing with thermal and catalytic decomposition of methane that have been addressed in the last few years. Surface science studies (molecular beam methods and elevated-pressure reaction studies) involving methane activation on model catalyst systems are extensively reviewed. These studies have contributed significantly to our understanding of the fundamental dynamics of methane decomposition. Various aspects of the nonoxidative methane to higher hydrocarbon conversion processes such as high-temperature coupling and two-step low-temperature methane homologation have been discussed.

Decomposition of methane results in the production of CO_x-free hydrogen (which is of great interest to state-of-the-art low-temperature fuel cells) and various types of carbon (filamentous carbon, carbon black, diamond films, etc.) depending on the reaction conditions employed; these issues will be briefly addressed in this review.     

Decomposition of methane over Ni catalysts supported on carbon fibers formed from different hydrocarbons

In order to get pure hydrogen without CO and CO₂, the decomposition of methane into hydrogen and carbon fibers (CF) over Ni/carbon catalysts has been investigated. The reason for the use of carbon materials as supports is to avoid a costly elimination treatment of the catalyst from the formed CF. The Ni/carbon catalysts prepared by the impregnation of various carbon materials with Ni(NO₃)₂ dissolved in acetone, followed by reduction in hydrogen at 573 K, showed better catalytic performance in the decomposition of methane than those prepared by the impregnation with aqueous Ni(NO₃)₂. The Ni(40 wt%)/CF(from 1-C₄H₈) showed the highest catalytic performance giving a C/Ni value (moles of deposited carbon per mole of Ni on the catalyst) of 1920 until complete deactivation of the catalyst. SEM and TEM images of the CF formed from methane indicated their thickness to be ≈10-150 nm with the same size of Ni particles at their tips at the early stage of the decomposition of methane, but the thickness changed to ≈40-100 nm at the final stage of decomposition. An estimate of the average size of Ni crystallites from XRD measurement suggested that the carbons deposited from methane on various Ni/CF would modify the size of Ni crystallites during the reaction. It is suggested that ≈20 nm Ni crystallites are most active for the growth of carbon nanofibers.     

Study of Methane Decomposition on Fe/MgO-Based Catalyst Modified by Ni,Co, and Mn Additives

Catalytic decomposition of methane (CDM) generates clean hydrogen and carbon nanomaterials. In this study, methane decomposition to hydrogen and carbon was investigated over Ni-, Co-, or Mn-doped Fe/MgO catalysts. The doping effect of different metals, varying from 3 to 10?wt%, was investigated. The catalytic performance of the obtained materials (noted 15%Fe+x%metal/MgO) revealed that the doping effect of Ni, Co, and Mn significantly improved the activity of Fe/MgO. Among the Ni-doped catalyst series, the 15%Fe+3%Ni/MgO catalyst performed better than the rest of the Ni catalysts. The 6%Co-containing catalyst remained the best in terms of activity in the Co-doped catalyst series and the 15%Fe+6%Mn/MgO solid showed better methane conversion for the Mn-doped series. Overall, 3%Ni-containing catalyst displayed the best catalytic performance among all Ni-, Co-, and Mn-doped catalysts. XRD, N₂ sorption, and H₂ temperature-programmed reduction (TPR), Laser–Raman spectroscopy, thermogravimetric analysis (TGA) under air, and temperature-programmed oxidation (TPO) were used for catalyst characterization. The results revealed that all the doped catalysts exhibited better metallic active site distribution than 15%Fe/MgO and proved that metal doping played a crucial role in catalytic performance.     

掺杂型负载金属催化剂在甲烷裂解反应中的研究进展

甲烷催化裂解反应能够同时制取不含碳氧化物的高纯氢和纳米碳材料,引起研究界的广泛关注。Ni、Fe和Co是常用的甲烷裂解反应的催化剂的活性组分,但单活性组分的负载型金属催化剂往往存在转化率低和寿命短等缺点,通过催化剂的设计改进其性能是催化剂研究工作的重要方向之一。除了制备方法的选择和反应条件的优化,利用不同金属组分性质间的差异,在其中引入第二或第三组分,同样能够有效改善催化剂的性能。对掺杂型负载金属催化剂的研究进行了综述。概述了催化剂的失活机理及模型（活性位覆盖模型和孔道口堵塞模型）,以及如何从失活原因出发进行掺杂型负载金属催化剂的设计。根据掺杂元素作用方式不同,分类介绍了当前掺杂型负载金属催化剂的主要研究成果及其未来的发展方向。     

Hydrogen production by the thermocatalytic decomposition of methane in a fluidized bed reactor

CO₂-free production of hydrogen via thermocatalytic decomposition of methane in a fluidized bed reactor (FBR) was studied. The technical approach is based on a single-step decomposition of methane over carbon catalyst in air/water vapor free environment. The factors affecting Fe catalyst (Iron powder activity in methane decomposition reactions were examined. Carbon species produced in the process were characterized by SEM methods. The fluidization quality in a gas-fluidized bed of Fe (Iron powder) and Fe/Al₂O₃ catalyst was determined by the analysis of pressure fluctuation properties, and the results were confirmed with characteristics of methane decomposition. The effect of parameters on the H₂ yield was examined. Fibrous carbon formed over Fe catalyst surface. The hydrogen yield increased with increasing reactor temperature, and decreased with increasing superficial velocity of methane inlet stream. The conversion rate of methane is maintained by attrition of produced carbon on Fe catalyst surface in a FBR.     

Catalytic filamentous carbon as supports for nickel catalysts

Ni catalysts supported on catalytic filamentous carbon (CFC) were studied in the model reaction of methane decomposition at 525 °C. The supports (CFC) were synthesized by decomposition of methane over metal catalysts (Ni, Ni-Cu, Co and Fe-Co-alumina) at 500-675 °C. The yield of secondary carbon was shown to reach 224 g/g_Ni on the Ni/CFC (Ni-Cu, 625 °C) catalyst. The stability and activity of the Ni/CFC catalysts for deposition of the secondary carbon at 525 °C depend both on textural properties of the support and on the surface structure of the CFC filaments. It seems that highly porous carbon supports are more suitable for development of Ni/CFC catalyst for methane decomposition. The catalytic properties of the supported Ni/CFC systems may be accounted for by generation of weak dispersive interactions between specifically shaped Ni crystallites 30-70 nm in size and basal planes on the surface of the carbon filament.     

Hydrogen production by decomposition of ethane-containing methane over carbon black catalysts

Mixtures of methane and small amounts of ethane were decomposed in the presence of carbon black (CB) catalysts at 1,073–1,223 K for hydrogen production. Although most of the added ethane was first decomposed to ethylene and hydrogen predominantly by non-catalytic reaction, subsequent decomposition of ethylene was effectively facilitated by the CB catalysts. Because some methane was produced from ethane, the net methane conversion decreased as the added ethane increased. The rate of hydrogen production from methane was decreased by the added ethane. A reason for this is that adsorption of methane on the active sites is inhibited by more easily adsorbing ethylene. In spite of this, the hydrogen yield increased with an increase of the added ethane because the contribution of ethane and ethylene decomposition to the hydrogen production was dominant over methane decomposition. A higher hydrogen yield was obtained in the presence of a higher-surface-area CB catalyst.     

Hydrogen production by catalytic decomposition of methane over carbon catalysts in a fluidized bed

A fluidized bed reactor made of quartz tube with an I.D. of 0.055 m and a height of 1.0 m was employed for the thermocatalytic decomposition of methane to produce CO₂ — free hydrogen. The fluidized bed was used for continuous withdrawal of the carbon products from the reactor. Two kinds of carbon catalysts — activated carbon and carbon black — were employed in order to compare their catalytic activities for the decomposition of methane in the fluidized bed. The thermocatalytic decomposition of methane was carried out in a temperature range of 800–925°C, using a methane gas velocity of 1.0–3.0 U _mf and an operating pressure of 1.0 atm. Distinctive difference was observed in the catalytic activities of two carbon catalysts. The activated carbon catalyst exhibited higher initial activity which decreased significantly with time. However, the carbon black catalyst exhibited somewhat lower initial activity compared to the activated carbon catalyst, but its activity quickly reached a quasi-steady state and was sustained over time. Surfaces of the carbon catalysts before and after the reaction were observed by SEM. The effect of various operating parameters such as the reaction temperature and the gas velocity on the reaction rate was investigated.     

煤焦中灰成分对甲烷裂解的影响

利用煤焦作为催化剂,采用小型石英管固定床为反应装置,对甲烷在煤焦、脱灰煤焦、煤灰以及石英砂床层上在温度为1123 K下的裂解反应进行了较为详细的研究。甲烷在脱灰煤焦上和新鲜的褐煤焦上的转化率和氢气收率有一定的差别。煤灰作为催化剂时,甲烷初始转化率和氢气初始收率分别为9.81%和8.14%。表明煤焦中的灰成分对甲烷裂解有一定的影响。随着反应时间的增加,甲烷的转化率和氢气的收率都逐渐降低。通过扫描电子显微镜和比表面积测定仪对反应前后的褐煤焦、脱灰煤焦进行了表征。甲烷裂解后煤焦比表面积、微孔容都明显降低,平均孔径增大。说明甲烷裂解生成的积炭堵塞煤焦的微孔。SEM照片显示甲烷裂解后积炭覆盖在煤焦的表面,使煤焦的催化活性逐渐降低。