Methane Oxyforming for Synthesis Gas Production

This article is concerned with the reforming of methane to synthesis gas; a review of the steam reforming Rxn is presented, and the dry reforming and partial oxidation Rxns introduced. Collectively, these processes are known as “oxyforming.” A background to oxyforming, industrial practice, and some of the most important latest developments will be presented, along with a section on the uses of synthesis gas. The current understanding of the Rxn mechanisms for the three processes and the problem of deactivation by carbon deposition will be discussed in detail. Finally, the economics of synfuel production will be addressed and compared with the production of other fuels, and the future directions and outlook for oxyforming will be forwarded. This article should allow the reader to make comparisons between these three important industrial reactions.     

Methane Oxyforming for Synthesis Gas Production

This article is concerned with the reforming of methane to synthesis gas; a review of the steam reforming Rxn is presented, and the dry reforming and partial oxidation Rxns introduced. Collectively, these processes are known as “oxyforming.” A background to oxyforming, industrial practice, and some of the most important latest developments will be presented, along with a section on the uses of synthesis gas. The current understanding of the Rxn mechanisms for the three processes and the problem of deactivation by carbon deposition will be discussed in detail. Finally, the economics of synfuel production will be addressed and compared with the production of other fuels, and the future directions and outlook for oxyforming will be forwarded. This article should allow the reader to make comparisons between these three important industrial reactions.     

Catalytic Performance of Monolithic Foam Ni/SiC Catalyst in Carbon dioxide Reforming of Methane to Synthesis Gas

Carbon dioxide reforming of methane to synthesis gas has been investigated with Ni catalysts supported on monolithic foam SiC, which were prepared by the initial wetness impregnation method. The catalyst of 7 wt%Ni/SiC was verified to be the best one in different Ni content catalysts. Compared with other catalysts such as 7 wt%Ni/SiO₂ and 7 wt%Ni/Al₂O₃, the 7 wt%Ni/SiC catalyst exhibited not only the highest activity but also remarkable stability and excellent coke resistance during 100 h reaction. Furthermore, the conversion of CO₂ and CH₄ remained at about 96% and 94%, respectively in 100 h reaction time. The structure and properties of the catalysts were characterized by BET, XRD, H₂-TPR, XPS and TEM techniques.     

Experimental Investigations of Catalytic Partial Oxidation of Methane to Synthesis Gas in Various Types of Fluidized‐Bed Reactors

The partial oxidation of methane to synthesis gas over Ni/α‐Al₂O₃ catalysts (1 and 5 wt.‐% Ni loading, 71–160 and 250–355 μm particle diameter) was investigated in different types of fluidized‐bed reactors, i.e., the bubbling fluidized bed (FlB), the spout fluid bed (SFB) and the internally circulating fluidized bed (ICFB). A methane‐to‐oxygen ratio of 2:1 was used in all experiments and the temperature was varied between 700 and 800 °C. Gas velocities and catalyst masses were adjusted to assure a stable and controllable reactor operation. A nearly isothermal operation was established in all reactors. The thermodynamic equilibrium values were achieved in the FlB and SFB reactor whereas in the ICFB reactor slightly lower conversions and selectivities were obtained. Taking the direct scale‐up concept of the ICFB reactor into account, significant higher space‐time yields were obtained in this reactor than in the industrial‐scale bubbling fluidized‐bed reactor. No increase of the space‐time yield in comparison to the FlB was obtained in the SFB reactor.     

甲烷二氧化碳催化重整制取合成气的研究进展

近几十年来,甲烷二氧化碳催化重整反应引起了广泛的关注。综述了甲烷二氧化碳催化重整制取合成气的研究进展,介绍了催化剂的活性组分、载体、助催化剂及制备方法的研究现状和它们对催化剂活性和稳定性的影响情况,并对催化剂积炭的形成和消除、重整反应机理进行了讨论和分析。     

基于Fluent的微通道天然气废气重整的数值模拟

利用Fluent软件对微通道反应器中天然气废气重整进行数值模拟。利用甲烷来代替天然气进行模拟。多通道反应器由具有平行通道的堇青石块组成,每个平行通道用Rh/Al_2O_3催化剂洗涂。由于堇青石的低热导率,通道之间的热传递被忽略。研究了进料温度,燃料组成和天然气中存在的丙烷对温度和产物分布的影响。通过模拟结果可得出:开始温度沿着通道良好地分布,并且没有形成明显的热点;增加进料温度有利于甲烷转化和氢气生产,但会导致温度分布不均;提高进料中蒸汽的量有助于增加氢气形成,但轻微地减弱了甲烷转化;提高入口处的O_2/C比值可导致甲烷转化率和温度成比例地增加。     

Characterization of CeO2 Promoter of a Nanocrystalline Ni/MgO Catalyst in Dry Reforming of Methane

Ceria‐promoted nickel catalysts supported on nanocrystalline MgO were prepared and employed in methane reforming with CO₂. Their characterization was accomplished by X‐ray diffraction, BET, temperature‐programmed oxidation, and temperature‐programmed reduction (TPR) techniques. Cerium oxide (CeO₂) proved to have a positive effect on catalytic activity, stability, and carbon suppression in methane reforming with CO₂. A higher CeO₂ content increased the catalyst activity and decreased the amount of deposited carbon over the spent catalysts. The suppression of carbon was related to the high oxygen storage capacity of CeO₂. In addition, TPR analysis revealed that the CeO₂ promoter reduced the chemical interaction between nickel and support, resulting in an increase in reducibility and higher dispersion of nickel.     

Heat Exchangeability of a Catalytic Plate Reactor and Analysis of the Reactivity of Steam and CO2 in Methane Reforming

An assemble‐type plate reactor was developed and its intensified heat transfer compared to that of a conventional tubular reactor in methane reforming was confirmed. This characteristic enables accurate reaction kinetic analysis because of quasi‐isothermal operation with mild pressure loss. Reduced experiment cost is one of the features of the assemble‐type reactor. Simple thermal design equations applicable to plate reactors were also assessed. From experiments and accurate reaction analysis using the plate reactor it is suggested that H₂O and CO₂ have similar reactivity for a commercial Ni/α‐Al₂O₃ catalyst. The partial pressure of the oxidizing agent had much more influence on the reactivity of methane reforming than the species of this agent.     

Modeling of synthesis gas and hydrogen production in a thermally coupling of steam and tri-reforming of methane with membranes

In this novel study, tri-reforming process was used as a heat source to proceed steam reforming of methane in a two membrane hydrogen perm-selective Pd/Ag thermally coupled reactor. Results illustrated that H₂/CO ratio at the output of steam and tri-reforming sides reached to 6.1 and 0.9, respectively. Additionally the results showed that methane conversion at the output of steam and tri-reforming sides reached to 31% and 96%, respectively. By increasing the feed flow rate of tri-reforming side from 28,120 to 140,600 kmol h⁻¹, methane conversion and H₂ molar flow rate enhanced 40% and 28.64%, respectively.     

Preparation of a LaNiO3/γ‐Al2O3 Catalyst and its Performance in Dry Reforming of Methane

LaNiO₃/γ‐Al₂O₃ catalysts containing 10, 15, 20, and 25 wt % Ni were prepared by a combination of sol gel with propionic acid as solvent and an impregnation method (LNA‐acid) as well as with ethanol as solvent and addition of acetic acid (LNA‐eth). Catalytic activities towards CO₂ reforming of CH₄ were tested in a fixed‐bed reactor at 700 °C, 750 °C, and 800 °C. LNA‐eth with 20 wt % Ni exhibited the best activities in dry reforming of methane and a good activity and stability, when it was tested at 800 °C during 75 h time‐on‐stream.     

Techno‐Economic Analysis of Methane Pyrolysis in Molten Metals: Decarbonizing Natural Gas

Methane pyrolysis using a molten metal process to produce hydrogen is compared to steam methane reforming (SMR) for the industrial production of hydrogen. Capital and operating cost models for pyrolysis and SMR were used to generate cash‐flow and production costs for several different molten pyrolysis systems. The economics were most sensitive to the methane conversion and the value obtained for the solid carbon by‐product. The pyrolysis system at 1500 °C is competitive with a carbon tax of $78 t^?1; however, if a catalytic process at 1000 °C were developed using a conventional fired heater, it would be competitive with SMR without a carbon dioxide cost penalty. Several pyrolysis alternatives become competitive with increasing carbon dioxide taxes.     

Optimization of a Process Synthesis Superstructure Using an Ant Colony Algorithm

The optimization of chemical syntheses based on superstructure modeling is a perfect way for achieving the optimal plant design. However, the combinatorial optimization problem arising from this method is very difficult to solve, particularly for the entire plant. Relevant literature has focused on the use of mathematical programming approaches. Some research has also been conducted based on meta‐heuristic algorithms. In this paper, two approaches are presented to optimize process synthesis superstructure. Firstly, mathematical formulation of a superstructure model is presented. Then, an ant colony algorithm is proposed for solving this nonlinear combinatorial problem. In order to ensure that all the constraints are satisfied, an adaptive, feasible bound for each variable is defined to limit the search space. Adaptation of these bounds is executed by the suggested bound updating rule. Finally, the capability of the proposed algorithm is compared with the conventional Branch and Bound method by a case study.     

Kinetic and CFD Modeling of Exhaust Gas Reforming of Natural Gas in a Catalytic Fixed-Bed Reactor for Spark Ignition Engines

Fuel reforming is an attractive method for performance enhancement of internal combustion engines fueled by natural gas, since the syngas can be generated inline from the reforming process. In this study, 1D and 2D steady-state modeling of exhaust gas reforming of natural gas in a catalytic fixed-bed reactor were conducted under different conditions. With increasing engine speed, methane conversion and hydrogen production increased. Similarly, increasing the fraction of recirculated exhaust gas resulted in higher consumption of methane and generation of H₂ and CO. Steam addition enhanced methane conversion. However, when the amount of steam exceeded that of methane, less hydrogen was produced. Increasing the wall temperature increased the methane conversion and reduced the H₂/CO ratio.     

Production of Synthesis Gas via Dry Reforming of Methane over Co‐Based Catalysts: Effect on H2/CO Ratio and Carbon Deposition

The effect of support type on synthesis gas production using Co‐based catalysts supported over TiO₂‐P25, Al₂O₃, SiO₂, and CeO₂ was investigated. The catalysts were prepared by the incipient wet impregnation method and characterized by various techniques for comparison. Experiments were performed in a micro tubular reactor. The results revealed that all Co‐supported catalysts produced synthesis gas ratios of 1 and below and, thus, proved to be well‐suited for methanol and Fischer‐Tropsch syntheses. Co catalysts supported over TiO₂‐P25 and Al₂O₃ provided better synthesis gas ratios and stability performances. The promotion of a Co/TiO₂‐P25 catalyst with Ce had a substantial influence on its catalytic activity and the amount of carbon deposit. A Ce‐promoted catalyst diminished markedly the extent of carbon deposition and thus boosted the performance towards better activity and stability.     

Methane partial oxidation to synthesis gas over bimetallic cobalt/tungsten carbide catalysts and integration with a Mn substituted hexaaluminate combustion catalyst

Co_0.2W_0.8C_x and supported Co_0.2W_0.8C_x catalysts are shown to be active for the partial oxidation of methane to synthesis gas. The catalyst stability is improved by operating at elevated pressure, or in the presence of excess methane. At atmospheric pressure the Co_0.2W_0.8C_x catalysts deactivate by oxidation, as seen by X-ray diffraction. Manganese substituted hexaaluminate catalysts with different Mn contents have been tested as catalysts for the total combustion of methane. In particular BaMn₂Al₁₀O₁₉ is active and stable for the combustion reaction. The temperature rise observed in the reactor was up to 300 K, depending on the reaction conditions, and complete conversion of oxygen in the feed was achieved. A process for stabilising the carbide catalysts is demonstrated, combining the manganese substituted hexaaluminate total oxidation catalyst, in series before the carbide reforming catalyst: this process leads to stable operation, with no carbon formation in the reactor and no carbide catalyst oxidation observed.     

A Novel Technology for Natural Gas Conversion by Means of Integrated Oxidative Coupling and Dry Reforming of Methane

A novel process concept for the oxidative coupling of methane followed by the oligomerization to liquids has been developed within the frame of the EU integrated project OCMOL. This technology is based on process intensification principles via cutting‐edge structured microreactor technology. It is also a fully integrated industrial process through the re‐use and the recycling of by‐products, in particular CO₂, at every process stage. The focus of this contribution is on the reaction engineering aspects of the core steps, i.e., catalysts, kinetics and reactor design for the methane coupling and reforming.     

Partial Oxidation and Dry Reforming of Methane Over Ca/Ni/K(Na) Catalysts

Partial oxidation and dry reforming of methane to synthesis gas over Ca/Ni/K(Na) catalysts have been studied. Effects of temperature, pressure, and oxygen/methane ratios on catalytic activity, selectivity, and carbon formation have been determined. Also reforming of ¹³CH₄ in the presence of CO₂ and Temperature-Programmed Oxidation (TPO) of deposited carbon after the reaction indicated that both methane and CO₂ contribute to carbon formation. The TPO of deposited carbon on Ca/Ni/K catalyst showed that the catalyst consumed a significant amount of oxygen, only a fraction of which was consumed by carbon species on the surface, indicating that the surface oxygen plays a significant role in oxidizing and removing carbon species from the catalyst surfaces     

Structure and Catalytic Performance of Mg‐SBA‐15‐Supported Nickel Catalysts for CO2 Reforming of Methane to Syngas

A series of Mg‐modified SBA‐15 mesoporous silicas with different MgO contents were successfully synthesized by a simple one‐pot synthesis method and further impregnated with Ni. The Mg‐modified SBA‐15 materials and supported Ni catalysts were characterized by N₂ physisorption (BET), X‐ray diffraction (XRD), temperature‐programmed desorption of CO₂ (CO₂‐TPD), temperature‐programmed H₂ reduction (H₂‐TPR), and temperature‐programmed hydrogenation (TPH) techniques and used for methane dry reforming with CO₂. CO₂‐TPD results proved that the addition of Mg increased the total amount of basic sites which was responsible for the enhanced catalytic activity over the Mg‐modified Ni catalyst. The excellent catalytic stability of Ni/8Mg‐SBA‐15 was ascribed to less coking and higher stability of the Ni particle size due to the introduction of Mg.     

Brief Overview of the Partial Oxidation of Methane to Synthesis Gas

A review of the main developments in the partial oxidation of methane to synthesis gas since the first paper in 1929 to the present day is given. The reaction is discussed from the view of the thermodynamics; the main catalysts studied for the reaction are summarised, and the reaction mechanism is discussed. The review is not comprehensive, but it is designed to provide a general background to the most important developments in the field.     

苯乙烯装置中脱氢尾气吸收系统的建立与优化

阐述了苯乙烯的现状并分析装置脱氢尾气的价值。重点对绝热脱氢法中粗苯乙烯塔进行了模拟设计和优化。通过Aspen Plus软件的模拟,建立了一套脱氢尾气吸收系统,并且探讨了吸收塔的影响因素,确立了最优工况,对实际工业生产起到一定的指导作用。