直流电晕等离子体重整甲烷二氧化碳制取合成气的研究

为了探究线筒式直流电晕等离子重整CH_4和CO_2制合成气的效果,利用直流电晕放电装置对CH_4和CO_2进行了重整实验。考察了大气压下甲烷含量、放电电压和进气流量对反应物转化率、产物选择性和能量转化效率的影响。结果表明,随着进气中甲烷含量的增大,CH_4转化率下降,CO_2转化率上升,产物选择性和能量转化效率皆先上升后下降;随着电压的增大,原料转化率和选择性皆呈上升趋势,但都存在一个极限值,能量转化效率先上升后下降;随着进气流量的增大,原料转化率和产物选择性皆下降,能量转化效率先上升后下降。整体上,线筒式直流电晕等离子体重整甲烷和二氧化碳制取合成气具有设备简单、产物选择性高和能量转化效率高的优点。     

热等离子体重整二氧化碳和甲烷制合成气的研究进展

合成气是一种非常重要的化工原料,近年来利用甲烷和二氧化碳重整制合成气成为了一个研究热点。本文讨论了等离子体重整的机理,重点介绍了不同重整方式,包括射流法、电弧法以及两者结合的方法在二氧化碳和甲烷重整中的应用。相对于冷等离子体,热等离子体重整更适合应用于工业放大生产,有较好的应用前景。     

甲烷二氧化碳氧气氧化重整的研究

在镍基催化剂化的甲烷二氧化碳重整反应中加入氧气使得热性的甲烷选择性氧化与吸热的二氧化碳重整责任中反应能够同时进行。实验结果表明，氧气的加入降低了反应温度，同时还可以在一定程度上调节Ｈ２ＣＯ比。良好的催化剂稳定性可能是由于镍粒子在表面镧氧化物中的分布的结果。     

甲烷、二氧化碳重整反应中催化剂研究进展

对近年来甲烷、二氧化碳催化重整制合成气的重要用途进行了概述,综述了催化剂的活性组分、载体、助剂及催化剂的积碳失活的研究现状,并对催化剂的制备方法进行了介绍。     

甲烷—二氧化碳重整反应制取合成气的新进展

综述了９０年代以来ＣＨ４－ＣＯ２重整反应在改性镍基催化剂、贵金属负载型催化剂和分子筛催化材料研究方面的最新发展。     

二氧化碳重整甲烷制合成气研究进展

由于二氧化碳重整甲烷制合成气具有很多优点,因此引起了广泛的关注。本文综述了二氧化碳重整甲烷制取合成气的研究进展,介绍了二氧化碳重整甲烷热力学、甲烷和二氧化碳的活化、二氧化碳重整甲烷反应过程中的表面积碳和消碳和二氧化碳重整甲烷反应机理的研究现状,并进行了讨论和分析。     

甲烷的二氧化碳重整动力学研究

The kinetics of CO2 reforming of methane has been studied at 976-1033K on a commercial NiO/CaO/Al2O3 catalyst in a packed-bed continuous reactor. The reaction was carried out at atmospheric pressure and CO2/CH4 ratio > 2. The Hougen-Watson rate models were fitted to experimental data assuming the dissociative adsorption of methane as the rate-determining step. The reaction rate showed an effective reaction order of about unity for CH4. The apparent activity energy was found to be 104kJ·mol-1. Therefore the kinetic reaction parameters were determined and a possible reaction mechanism was proposed.     

甲烷与二氧化碳重整制合成气Ni与Co基催化剂的研究进展

综述了助剂、载体与催化剂制备方法对Ni基催化剂、Co基催化剂、Ni-Co基催化剂上甲烷与二氧化碳重整制合成气催化性能的影响,以及甲烷与二氧化碳重整催化反应机理的研究,展望了催化剂未来的发展方向。     

甲烷二氧化碳催化重整催化剂研究进展

甲烷二氧化碳催化重整反应由于对于环境保护与综合利用资源具有重大意义,近年来得到了研究者的广泛重视。本文参阅众多文献,概述了二氧化碳、甲烷催化重整反应的研究动态。着重介绍了催化剂活性组分的选取,载体影响和助剂作用等方面的最新进展。     

甲烷部分氧化及重整反应多相催化剂的研究进展

介绍国内外甲烷制合成气技术中多相催化剂的研究进展,包括催化剂在水蒸气重整、甲烷部分氧化和二氧化碳重整制合成气技术中的研究情况,重点评述了催化剂的活性组分、助剂和载体方面的研究进展及存在的问题。     

Carbon dioxide reforming of methane over lanthanum-modified catalysts in a fluidized-bed reactor

Nickel on lanthanum-modified aluminas were prepared and tested as catalysts for the CO₂ + CH₄ 2CO + 2H₂ reaction in a fluidized-bed reactor. Attrition tests show that lanthanum increases the strength of the carrier significantly. TPR and XRD results indicate that nickel enters into positions in the Al-O spinel blocks of the subsurface LaAl₁₂O₁₉ phase. This results in lower reducibility and thus lower activity for the reforming reaction as compared to nickel on unmodified alumina. While the unmodified catalyst deactivated rapidly under the chosen test conditions, the modified catalysts seem to be stable over several hours. However, the stability is sensitive to the pretreatment conditions of the catalysts.     

Carbon dioxide reforming of methane under periodic operation

The carbon dioxide reforming of methane under periodic operation over a commercial Ni/SiO₂·MgO catalyst was investigated at two different temperatures, 923 and 1,023 K. According to this operation, pure methane and carbon dioxide were alternately fed to the catalyst bed where methane cracking and the reverse Boudouard reaction took place, respectively. Therefore, hydrogen and carbon monoxide products appeared separately in different product streams. The performance of this operation was compared to that of the steady state operation with simultaneous feed of both carbon dioxide and methane. At 1,023 K, the methane conversion and hydrogen yield from the periodic operation initially decreased with time on stream and eventually leveled off at values about half of those obtained in the steady state operation with co-feed of both reactants. The decreased catalytic activity was due to the accumulation of carbonaceous deposit and loss of metal active sites. However, a different trend was observed at 923 K. The methane conversion and hydrogen yield were almost constant over the time on stream, although more carbonaceous deposit was progressively accumulated on the catalyst bed during the reaction course. At this temperature, the periodic operation offered the equivalent hydrogen yield to the steady state operation. The observed behavior could be due to the different mechanisms of carbon formation over the catalyst. Finally, it was found that cycle period and cycle split did not influence the reaction performance within the ranges of this study.     

Ni-Ce-ZrO2催化剂在二氧化碳甲烷重整制合成气中的研究

采用XRD、氢化学吸附作用、TPR和XPS等技术研究了共沉淀方法制备N i-Ce-ZrO2催化剂对二氧化碳甲烷重整的性能。N i的载入量和CeO2与ZrO2的比率系统地被改变将使N i-Ce-ZrO2催化剂最优化。发现15w t%N i与Ce0.8Zr0.2O2共沉淀有体相的状态,在800℃用CH4制合成气超过97%,并且经过100h的反应,活性被维持没有重大的损失。     

Carbon dioxide reforming of methane in kilohertz spark‐discharge plasma at atmospheric pressure

The spark‐discharge plasma, generated between tubular and rotary‐disc electrodes using a sine‐wave high voltage with 5 kHz frequency, was explored for CO₂ reforming of CH₄. Based upon the investigation on the effects of specific energy input and CO₂/CH₄ ratio, the energy costs (EC) and fuel‐production efficiencies (η) at various CO₂/CH₄ ratios (r) in the same conversion range were compared and accordingly their sequences were given: EC (r = 0.5) and EC (r = 3) are the lowest; η(r = 0.5) is the highest. Compared with other nonthermal discharge techniques, the kilohertz spark discharge exhibits low EC and high fuel‐production efficiency, especially at high total‐carbon conversions. Preliminary investigation on partial oxidation and CO₂ mixed reforming at (O₂ + CO₂)/CH₄ = 0.5 exhibited high H₂/CO ratio (nearly 2) and low total‐carbon EC (0.59–0.96 MJ/mol, 58–77% of total‐carbon conversion, and O₂/(CO₂ + O₂) = 0.8). © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Hydrogen from steam methane reforming by catalytic nonthermal plasma using a dielectric barrier discharge reactor

A scaled-up dielectric barrier discharge (DBD) reactor has been developed and demonstrated for the production of hydrogen from steam methane reforming (SMR) by catalytic nonthermal plasma (CNTP) technology. Compared to SMR, CNTP offers conversion at ambient pressure (101.325 kPa), low temperature with better efficiency, making it suitable for distributed hydrogen production with small footprint. There have been several lab-scale DBD reactors reported in the literature. Dimension of the scaled-up DBD reactor is about six times the lab-scale version and can produce 0.9 kg H₂/day. The scale-up is, however, nonlinear; several technical innovations were required including spray nozzle for homogeneous introduction of steam, perforated tube central electrodes for generation of homogeneous plasma. Conversion efficiency of the scaled-up DBD reactor is 70–80% at 550°C and 500 W. A continuous run of 8 hr was demonstrated with typical product gas composition of 69% H₂, 6% CO₂, 15% CO, 10% CH₄.     

Carbon dioxide reforming of methane with a free energy minimization approach

Carbon dioxide reforming of methane to syngas is one of the primary technologies of the new poly-generation energy system on the basis of gasification gas and coke oven gas. A free energy minimization is applied to study the influence of operating parameters (temperature, pressure and methane-to-carbon dioxide ratio) on methane conversion, products distribution, and energy coupling between methane oxidation and carbon dioxide reforming methane. The results show that the methane conversion increases with temperature and decreases with pressure. When the methane-to-carbon dioxide ratio increases, the methane conversion drops but the H₂/CO ratio increases. By the introduction of oxygen, an energy balance in the process of the carbon dioxide reforming methane and oxidation can be realized, and the CO/H₂ ratio can be adjusted as well without water-gas shift reaction for Fischer-Tropsch or methanol synthesis. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Carbon dioxide separation and dry reforming of methane for synthesis of syngas by a dual‐phase membrane reactor

High‐temperature CO₂ selective membranes offer potential for use to separate flue gas and produce a warm, pure CO₂ stream as a chemical feedstock. The coupling of separation of CO₂ by a ceramic–carbonate dual‐phase membrane with dry reforming of CH₄ to produce syngas is reported. CO₂ permeation and the dry reforming reaction performance of the membrane reactor were experimentally studied with a CO₂–N₂ mixture as the feed and CH₄ as the sweep gas passing through either an empty permeation chamber or one that was packed with a solid catalyst. CO₂ permeation flux through the membrane matches the rate of dry reforming of methane using a 10% Ni/γ‐alumina catalyst at temperatures above 750°C. At 850°C under the reaction conditions, the membrane reactor gives a CO₂ permeation flux of 0.17 mL min^?1 cm^?2, hydrogen production rate of 0.3 mL min^?1 cm^?2 with a H₂ to CO formation ratio of about 1, and conversion of CO₂ and CH₄, respectively, of 88.5 and 8.1%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2207–2218, 2013     

On a possible mechanism of the methane steam reforming in a gliding arc reactor

This work is dedicated to the study of methane steam reforming (SR) using a rotating discharge reactor. The process efficiency is described in terms of methane conversion, SR selectivity, energy input and hydrogen production cost. The experiments clearly demonstrated the ability of glidarc to accelerate chemical reactions at low temperatures and with very low energetic costs. A good approximation model describing the chemical processes on the basis of classical thermodynamics is also proposed. The analysis gives information on reactor design in order to improve its chemical performances.     

Carbon dioxide reforming of methane over nickel catalysts supported on mesoporous MgO

In this paper, ordered mesoporous MgO nanocrystals [MgO(M)] were synthesized, and the nickel catalysts supported on MgO(M) were facilely prepared by impregnation method. The obtained Ni/MgO(M) catalysts with advantageous textural properties were investigated as the catalysts for the carbon dioxide reforming of methane reaction. It was found that compared with the Ni/MgO(C) catalyst [MgO(C): commercial MgO], the mesoporous pore structure of MgO(M) could effectively limit the growth of the activity metal, and the Ni/MgO(M) catalysts showed high catalytic activities as well as long catalytic stabilities toward this reaction. The results showed that the conversions of CH₄ and CO₂ were only decreased <5 % after 100 h of reaction at 650 °C. The improved catalytic performance was suggested to be closely associated with both the advantageous structural properties, such as large specific surface area, uniform pore size, and the “confinement effect” of the mesoporous matrixes contributed to stabilize the Ni active sites during the reaction. The carbon species deposited on the spent Ni/MgO(M) catalyst were analysized by TG and Raman, and the results exhibited that the carbon species after 100 h of reaction were mainly active carbon species.     

Carbon dioxide reforming of methane to synthesis gas over supported Ni catalysts

Carbon dioxide reforming of methane to synthesis gas has been investigated over supported Ni catalysts in the temperature range of 500–850°C. Addition of CaO (10mol%) promoter to the Ni/γ-Al₂O₃ resulted in an increase of reaction rate and an improvement of catalyst stability, which may be related to enhanced reducibility of the promoted catalyst. The kinetic studies show that the overall reaction can be described by a Langmuir-Hinshelwood mechanistic scheme, assuming that methane dissociation is the rate determining step. In addition to adsorbed CO and formate species, three types of carbonaceous species, C, C_β and C_γ, were found to exist on the Ni catalyst. While the active C, species is suggested to be responsible for CO formation, the less active C_β and C_γ species are attributed to causing catalyst deactivation.