Entrapping Ru nanoparticles into TiO2 nanotube: Insight into the confinement synergy on boosting pho-thermal CO2 methanation activity

CO₂ methanation is a significant route to decrease carbon emission as well as realize carbon neutrality and has gained considerable concerns from experts in the environment and energy field currently. Herein, highly dispersed ruthenium nanoparticles entrapped in TiO₂ nanotubes, labeled as Ru-in/TNT, were constructed and adopted for photo-thermal driven CO₂ methanation. The Ru nanoparticles confined in the nanotube exhibited an enhanced CO₂ methanation activity, especially under light irradiation. Multiple characterization techniques (XRD, XPS, UV–vis DRS, HRTEM, Raman, etc.) were conducted to reveal the effect of confinement synergy on photo-thermal catalytic performance. A boosted photo-generated electron-hole separation efficiency is achieved as a result of the confinement effect, yielding more hot electrons to accelerate methanation activity. This photo-assisted confinement synergy can be expected for constructing an efficient photo-thermal catalytic system.     

Understanding the correlation between calcination temperature and performance in low-temperature methanation over Ni-Zr/Al2O3 catalysts

Low-temperature methanation of CO in the continuous stirred tank reactor (CSTR) over Zr doped Ni/Al₂O₃ catalyst calcined at different temperatures (673, 723, and 823 K) was investigated. XRD, TPR, XPS, ICP, SEM, and S-TPR techniques were employed to characterize the fresh and spent catalysts. Based on the characterization results, it was found that low-temperature (673 K) calcination could effectively prohibit the formation of NiAl₂O₄ spinel, thereby resulting in more reducible NiO particles, which were the essential precursor of methanation active sites over the catalyst surface. Thus, the highest CO conversion of 93.6% was achieved over the 25N3ZA-673 catalyst. In addition, the deactivation rate of 25N3ZA-673 was relatively slow in comparison to 25N3ZA-823 due to the presence of more reducible NiO. The formed nickel carbonyl species (Ni[CO]_x), which quickly decomposed at a higher reaction temperature, was closely related to the catalyst deactivation. Therefore, 25N3ZA-673 possessed much better stability at 593 K than that at 553 K.     

焦炉气甲烷化制LNG工业化装置运行技术分析

简述了国内首套焦炉气甲烷化制LNG的工艺原理、工艺流程,介绍了其重点工艺单元和催化剂:焦炉煤气净化、甲烷合成催化剂、甲烷合成工艺、合成气低温液化等。利用自主研发的预还原催化剂以及绝热型反应器和换热型反应器组合形成的焦炉煤气甲烷合成新工艺,可保证合成气中CO2体积分数小于50×10-6,甲烷合成反应更完全。工业运行结果表明,该装置具有工艺简单、操作平稳、设备投资少、能耗低等特点。     

基于催化剂防护及SNG品质的甲烷化工艺设计

描述了甲烷化过程中发生的主要反应,指出多级循环绝热固定床是适合完全甲烷化的成熟工艺。着重分析了甲烷化催化剂4种失活模式:高温烧结、硫中毒、析碳及羰基镍形成带来的活性流失,指出有效的应对措施是:循环气稀释进气CO反应浓度、进一步深度脱硫、保持高温水汽比及开停车过程N2置换。基于煤基合成气甲烷化过程中所有耗氢反应物质的量的配比平衡,推导了进气组分配比模数公式,提出了以平衡模值为基点建立模数调节区间的方法,端点模值对应SNG最低的质量保证值。实例证明以此方法可得到预期的SNG组分,并验证了所得SNG是一种优质清洁的替代性天然气。     

焦炉气甲烷化过程模拟计算顺序的确定

序贯模块法广泛应用于化工过程流程模拟。对于具有回路的化工过程,其计算顺序的确定是很重要的问题。本文针对有回路的焦炉气甲烷化流程进行了分析,确定了其模拟计算时的计算顺序,对焦炉气甲烷化流程的研究具有很好的参考价值。     

可用于富氢重整气中CO消除的负载型Ni基甲烷化催化剂研究进展

富氢重整气中微量CO会引起燃料电池中Pt电极的永久性中毒而影响燃料电池的性能,通过CO甲烷化反应是消除富氢重整气中微量CO的有效方法。介绍了近年来在CO甲烷化Ni基催化剂组成、制备方法和催化机理等方面的研究进展。阐述了载体的性质、稀土和贵金属助剂以及制备方法对CO甲烷化Ni基催化剂性能的影响。研究重点通过优化载体、组成和制备方法制备新型Ni基催化剂,使其在低温下对CO甲烷化反应有着很好的催化活性、选择性和稳定性,同时抑制高温下CO2甲烷化反应和逆水煤气反应的发生。     

焙烧温度对共沉淀法合成Ni/Al_2O_3甲烷化催化剂性能的影响

采用并流共沉淀法制备Ni负载质量分数为15%的Ni/Al2O3催化剂,用于CO加氢甲烷化反应。结合紫外可见光漫反射、氢气程序升温还原、N2物理吸附-脱附和X射线粉末衍射等技术,考察焙烧温度对催化剂结构、活性与稳定性的影响。结果表明,低温[(350-500)℃]焙烧的样品中活性组分Ni主要以孤立的Ni O物种和高分散的无定形Ni O物种存在,相应的还原态样品中Ni粒子尺寸较小,是其新鲜态样品低温活性较高的主要原因。800℃焙烧的样品中活性组分Ni主要以高分散的无定形Ni O物种和Ni Al2O4尖晶石微晶形式存在于催化剂表面,活性组分Ni与载体Al2O3间的作用力较强,稳定性较高,且经过800℃水热老化处理10 h后仍具有较大的比表面积(125 m2·g-1),是其具有较佳低温活性同时突显良好水热稳定性的主要原因。     

Ni‐Al2O3/Ni‐foam catalyst with enhanced heat transfer for hydrogenation of CO2 to methane

Monolithic Ni‐Al₂O₃/Ni‐foam catalyst is developed by modified wet chemical etching of Ni‐foam, being highly active/selective and stable in strongly exothermic CO₂ methanation process. The as‐prepared catalysts are characterized by x‐ray diffraction scanning electron microscopy, inductively coupled plasma atomic emission spectrometry, and H₂‐temperature programmed reduction‐mass spectrometry. The results indicate that modified wet chemical etching method is working efficiently for one‐step creating and firmly embedding NiO‐Al₂O₃ composite catalyst layer (～2 μm) into the Ni‐foam struts. High CO₂ conversion of 90% and high CH₄ selectivity of >99.9% can be obtained and maintained for a feed of H₂/CO₂ (molar ratio of 4/1) at 320°C and 0.1 MPa with a gas hourly space velocity of 5000 h^?1, throughout entire 1200 h test over 10.2 mL such monolithic catalysts. Computational fluid dynamics calculation and experimental measurement consistently confirm a dramatic reduction of “hotspot” temperature due to enhanced heat transfer. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4323–4331, 2015     

焙烧条件对镍基甲烷化催化剂性能的影响

考察了焙烧条件对工业甲烷合成催化剂Ni-MgO-Al2O3的性能的影响,采用X射线衍射、低温氮物理吸附、程序升温还原、CO脉冲吸附等手段对反应后的催化剂进行了表征。结果表明,随着焙烧温度的升高和焙烧时间的延长,催化剂活性金属组分分散效果更好,与载体的结合作用更强,催化剂还原的耗氢量变小。焙烧后有MgAl2O4和NiAl2O4等晶相结构形成,加强了催化剂的机械强度,同时提高了催化剂热稳定性能。在温度750℃、压力2 MPa、空速8 000h-1条件下,950℃焙烧3h的催化剂的活性最好。