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.     

Development of highly efficient methanol steam reforming system for hydrogen production and supply for a low temperature proton exchange membrane fuel cell

Methanol steam reforming (MSR) has been regarded as a promising hydrogen supply method for proton exchange membrane fuel cell (PEMFC), while the efficiency for hydrogen production and integration method of MSR with PEMFC are two major challenges for commercial applications. Here, we present a highly efficient MSR system for hydrogen production and supply for low temperature PEMFC (LT-PEMFC). The MSR system has a highly compact microreactor, wherein MSR, methanol combustion, and CO selective methanation reactions occur. The CO selective methanation is used to reduce the content of CO concentration to remit the CO poison, then the reformate of MSR system is mixed with air and supply for the LT-PEMFC. Then, experimental tests are conducted to investigate the effects of operating parameters on hydrogen production. A staged supply strategy is proposed, it enables to startup the system within 11.2 min and with methanol consumption of 34.72 g. Results show that the methanol conversion can reach up to 93.0% and system's energy efficiency of 76.2%. After integration with a LT-PEMFC, a maximum 160 W electricity can be generated. The results obtained in this study demonstrated that the developed MSR system can be used to supply hydrogen for LT-PEMFC and able to power mobile device requiring hundreds of watts power consumption.     

Methanation of CO on Ru/graphitized-carbon catalysts: Effects of the preparation method and the carbon support structure

Two kinds of Ru/C catalysts prepared by two different methods and supported on two graphitized carbons differing in their surface area were studied in CO methanation in the H₂-rich gas. The textural parameters of the support materials were characterized by means of N₂ physisorption. XRPD, XPS, TEM and CO- chemisorption studies indicate that the application of wet impregnation leads to more homogeneous composition of the Ru/carbon system and higher Ru dispersion than dry impregnation for both supports. The activity of the Ru/carbon samples in CO methanation in a H₂-rich gas stream depends on the structure and average size of the active phase crystallites. The combination of wet impregnation and the use of graphitized carbon of appropriate structure in the preparation of the Ru/C catalyst lead to a complete conversion of CO at 240 °C.     

CO2 methanation over Ni and Rh based catalysts: Process optimization at moderate temperature

H₂ was produced from aluminum/water reaction and reacted with CO₂ over Ni and Rh based catalysts to optimize the process conditions for CO₂ methanation at moderate temperature. Monometallic catalysts were prepared by incorporating Ni and Rh using nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and rhodium(III) chloride trihydrate (RhCl₃·3H₂O)as a precursor chemical. The preliminary study of the catalysts revealed higher activity and CH₄ selectivity for Rh based catalyst compared to that of Ni based catalyst. Further, Rh based catalyst was investigated using response surface methodology (RSM) involving central composite design. The quadratic model was employed to correlate the effects of variable parameters including methanation temperature, %humidity, and catalyst weight with the %CO₂ conversion, %CH₄ selectivity, and CH₄ production capacity. Analysis of variance revealed that methanation temperature and humidity play an important role in CO₂ methanation. Higher response values of CO₂ conversion (54.4%), CH₄ selectivity (73.5%) and CH₄ production capacity (8.4 μmol g^?1 min^?1) were noted at optimum conditions of 206.7°C of methanation temperature, 12.5% humidity and 100 mg of the catalyst. The results demonstrated the ability of Rh catalyst supported on palm shell activated carbon (PSAC) for CO₂ methanation at low temperature and atmospheric pressure.     

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。     

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。