Methane steam reforming in an annular microchannel with Rh/Al2O3 catalyst

Regularities of methane conversion in the presence of water steam were obtained experimentally while activating chemical conversions on the inner convex wall of an annular microchannel. The steam methane reforming was done on the Rh/Al₂O₃ nanocatalyst with the heat applied through the microchannel gap from the outer wall. Concentrations of the products of chemical reactions in the outlet gas mixture are measured at different temperatures of the outer microchannel wall. The range of channel wall temperatures at which the ratio of hydrogen and carbon oxide in the outlet mixture grows substantially is determined. Data on the composition of methane conversion products for the ratio H₂O/CH₄ = 1.77 and the activation energy of methane steam reforming at reactor outer wall temperatures of up to 880°C are obtained. The effect of the radiation heat exchange and the external diffuse limitation on the rate of chemical conversions in methane steam reforming in an annular microchannel with external heat supply is determined.     

在Ni/HZSM-5催化剂上低温水蒸汽重整生物油制氢

利用浸渍方法制备的Ni/HZSM-5催化剂在生物油低温水蒸汽重整合成中表现了较高的催化活性． 探讨了催化剂的组成、重整温度、水碳比例对重整过程的影响．在电催化重整研究中,发现催化剂上通过的电流可以显著地促进生物油水蒸汽重整．通过对不同负载量的Ni/HZSM-5催化剂和Ni₂₀/Al₂O₃催化剂的催化活性的比较,NiO在催化剂中负载量为20%(Ni₂₀/ZSM)时表现出了最高的催化活性; 即使在450 oC时, 在Ni₂₀/ZSM催化剂上也可以达到碳转化率接近完全, 氢气产率约为90%的效果． 利用XRD、ICP/AES、H₂-TPR、BET等表征手段对Ni/HZSM-5催化剂的形态和结构进行了表征.     

Experimental study of incomplete oxidation of methane in a ring channel

Chemical transformations at incomplete methane oxidation in the air medium were studied experimentally at reaction activation on the wall of an annular microchannel. Methane was oxidized incompletely on a rhodium catalyst deposited on an inner wall of the channel. Concentrations of the products of chemical transformations were measured in the outlet gas mixture for different reactor temperatures and stay times. We have determined the range of channel wall temperatures and stay times of the mixture corresponding to an increase in the portion of hydrogen and carbon dioxide indicating transition from predominant methane combustion to cascade chemical reactions with activation of steam and carbon dioxide methane conversions. It is shown that the kinetic model of chemical transformations of methane in the air medium depends significantly on the temperature of channel walls and stay time of the mixture. The effect of outer diffusion deceleration on the rate of chemical transformations at incomplete methane oxidation under the strained conditions is determined. The work was financially supported by the Russian Foundation for Basic Research (Grant No. 05-08-65526).     

利用双段床反应器从生物油重整合成气合成甲醇

一种组合了合成气在线调整和甲醇合成的双段床反应器,成功应用于由生物油重整得到的富CO₂合成气的高效合成甲醇．在前段催化床反应器内,富含CO2的原始生物质合成气在CuZnAlZr催化剂的催化作用下可以有效地转化为含CO的合成气．经过450 oC的合成气在线调整之后,CO₂/CO的比率由6.3大幅降至1.2．经过调整后的生物质基合成气在后段催化床反应器内由工业CuZnAl催化剂催化合成甲醇,当反应条件为260 oC 和5.5 MPa时得到每小时每kg催化剂的最大甲醇     

XPS of a steam reforming NiAl2O4 catalyst

An XPS study of the behaviour of a Ni-αAl₂O₃ catalyst for a methane—steam reforming reaction was undertaken. The combined information from binding energy shifts and intensities is discussed in terms of the oxidation state of the Ni atoms in the fresh, used and reduced catalyst. Accumulations of Si and Pb were detected on the surface of the used catalyst, Si originating from the packing in the preheating zone in the reactor and Pb from the corrosion of a lead-containing valve by distilled water used to produce steam.     

Internal reforming in intermediate temperature solid oxide fuel cells running on natural gas

Methane steam reforming has been studied over a range of nickel/ceria-gadolinia cermet anodes, over the temperature range 500–700 °C appropriate for intermediate temperature ceriagadolinia based SOFCs. The influence of operating temperature and methane/steam ratio on the reforming characteristics, methane conversion and product selectivity, and the carbon deposition on the anode during reforming, has been determined for each anode. Nickel/ceria powders made from gas atomised intermetallic precursors have been studied as potential anode materials for intermediate temperature ceria-gadolinia based SOFCs running on natural gas. The powders have been characterised structurally and evaluated for their methane reforming characteristics and their resistance to carbon deposition during internal reforming, especially at low steam/methane ratios, over the relevant operating temperature ranges of ceriagadolinia based SOFCs. Their performance has been compared to conventionally prepared anodes and anodes generated from cast alloys, with very favourable results. Paper presented at the 9th EuroConference on Ionics, Ixia, Rhodes, Greece, Sept. 15 – 21, 2002.     

煤与天然气适度转化的甲醇-动力联产系统

本文开拓性地提出了一个新型煤和天然气综合利用、甲醇和电力联产的能源动力系统。新系统采用了燃料化学能适度转化的方法,煤先和纯氧与蒸汽发生部分气化反应,适度转化成合成气和半焦,碳转化率约为50%;半焦在天然气/水蒸气重整反应器中燃烧,为重整反应提供反应热;将甲醇生产系统与联合循环发电系统有机整合,来自煤和天然气的合成气先用于甲醇生产,未反应合成气用作发电燃料。研究表明在相同产出条件下,多功能系统比分产系统少消耗10%左右的化石燃料。本文工作为煤和天然气综合高效利用提供了新途径。     

Modelling of methanol-to-hydrogen steam reforming with a heat flux distributed along a microchannel

The flow of reacting mixture of methanol and steam in a 2D microslot was studied numerically at activation of the reactions on the channel wall. This modelling was carried out in the framework of Navier — Stokes equations for a laminar flow of multicomponent compressible gas. Correlations between thermal, diffusion, and physical-chemical processes were studied under the conditions of intense endothermic reaction and external heat supply distributed along the channel. It is shown that not only the amount of heat supplied to the reaction zone is essential, but also the mode of heat supply along the channel length is important, which allows optimization of the compact reactor for hydrogen production.     

温度对微通道CH4/O2/H2O自热重整暂态特性的影响

利用计算流体力学软件CFD和化学反应动力学软件CHEMKIN研究了微通道内催化壁面温度、反应混合气体初始温度对镍基催化剂上CH₄/O₂/H₂O自热重整反应暂态特性的影响。结果表明,微通道内的甲烷自热重整反应暂态特性与温度关系密切。温度越高,反应趋于平衡所需的时间越短;当反应器壁面温度较高时,提高反应混合气入口温度对反应影响不大;在相同的温升下,提高反应器壁面温度比提高反应混合气体初始温度对反应过程中氢气的产生和甲烷的转化更有利。     

Modeling of methane steam reforming in a microchannel with a heat flow distributed in length

Numerical modeling of a flow of a high-temperature mixture of methane with water vapors in a two-dimensional plane microchannel with activation of chemical conversions on the channel wall has been performed. The modeling was performed within the framework of Navier-Stokes equations for a laminar flow of a multicomponent compressible gas. The influence of the external heat flux supplied to the gas mixture and its distribution along the channel length on the properties of the methane steam reforming have been investigated. It has been shown that not only the amount of heat supplied to the reaction zone but also the method of heat supply along the channel length are important. All the reactions with the residence time of the mixture on the order of tens of milliseconds terminate several centimeters downstream from the channel inlet, which makes it possible to optimize a compact reactor for obtaining a synthesis gas.     

用NiCuZnAl催化剂最大化生物油自热水蒸汽重整制氢

在较低的温度下,通过将放热的部分氧化反应和吸热的水蒸汽重整反应耦合起来的自热方式实现了高效的制氢过程. 在氧碳比(O/C)为0.34,水碳比(S/C)为3,温度为600 oC时生物油接近完全转化,得到最高氢产率为64.3%. 自热水蒸汽重整反应条件温度、O/C、S/C、质量空速等可以用来控制反应氢产率和气体产物分布. 对自热过程和普通水蒸汽重整过程做了比较,并对反应机理进行了探讨.     

Characterization of ZrO2-promoted Cu/ZnO/nano-Al2O3 methanol steam reforming catalysts

Three Cu/ZnO/ZrO₂/Al₂O₃ methanol reforming catalysts were investigated using X-ray photoelectron spectroscopy (XPS). The catalysts which contained ZrO₂ from a monoclinic nanoparticle ZrO₂ precursor exhibit both a higher activity toward the methanol steam reforming reaction and a lower CO production rate compared to catalysts composed of an XRD-amorphous ZrO₂ produced by impregnation using a Zr(NO₃)₂ precursor. The presence of a monoclinic phase appears to result in an increased charge transfer between the Zr and Cu species, as evidenced by a relatively electron-rich ZrO₂ phase and a partially oxidized Cu species on reduced catalysts. This electron deficient Cu species is more reactive toward the methanol reforming reaction and partially suppresses CO formation through the reverse water gas shift or methanol decomposition reactions.     

Oxidation states of Cu in the CuO/CeO2/Al2O3 catalyst in the methanol steam reforming process

The biomorphic CuO/CeO₂/Al₂O₃ was used as a catalyst in methanol steam reforming (SRMe), and the reaction mechanism was studied. It was found that the oxidation states of Cu in the biomorphic sample would vary with the reaction temperature and they also affected the rate of the reaction. Below 200 °C, SRMe would not occur, and the X-ray diffractometry study indicated that the CuO/CeO₂/Al₂O₃ sample remained unchanged. Above 200 °C, the SRMe occurred when CuO started to be reduced to Cu. As the reaction temperature increased, Cu reacted with CO₂ and led to the formation of Cu₂O during the reversed water gas shift reaction. Above 250 °C, the conversion of MeOH to CO₂ and H₂ reached to a saturation of 95% even if the amount of metallic Cu was reduced to half of its original portion. This confirmed that both Cu and Cu₂O were active components for promoting SRMe.     

Continuous catalytic pyrolysis of oily sludge using U-shape reactor for producing saturates-enriched light oil

Continuous catalytic pyrolysis of oily sludge was carried out in a special U-shape reactor for producing saturates-enriched light oil. The sludge underwent thermal pyrolysis first and then catalytic pyrolysis. During the thermal pyrolysis, chain hydrocarbons were first cracked and further polymerized into aromatics. The effect of temperatures (400–800 °C) on the products was investigated and the maximum liquid yield (67.7%) was obtained at 500 °C. High temperature promoted polymerization, thus the distribution of aromatics in the liquid product was increased and was more concentrated in polyaromatics at 800 °C. In the catalytic upgrading stage, dolomite was used as catalyst and aromatics were adsorbed on it, either aggregated or decomposed. As a result, a light oil product with 57.0% saturates was obtained at the residence time of 8.9?s due to the conversion of aromatics and heavy hydrocarbons into light aliphatic hydrocarbons such as straight chain hydrocarbons. Compared with the oil phase in the raw sludge sample, the content of saturates was increased by 45.0% and that of the asphaltenes was reduced by 88.5%. Meanwhile, the inherent moisture in the oily sludge could participate in the steam reforming reaction, promoting the decomposition of aromatics and leading to an increase in the H₂ generation. Moreover, the release of H₂S was reduced from 0.132 to 0.005?mol per kg sludge and the sulfur content of the oil product was also decreased in the presence of dolomite. The deactivation of dolomite can be attributed to the carbonization of CaO and deposition of polyaromatic coke on the catalyst surface.     

用低温电催化重整方法和CoZnAl催化剂进行低温生物油重整制氢

利用电化学催化重整方法和CoZnAl催化剂实现了高效的生物油重整制氢过程．研究了电流强度对氢气产率、碳转化率以及产物分布的影响．结果表明,通过催化剂的电流对氢气产量和碳转化率都有明显的促进作用,在500 oC低温重整条件下氢气产率和碳转化率分别达到大约70%和85%．此外,用XRD、XPS、TGA和BET研究了电流对催化剂的结构和性能的影响．结果表明,通电催化床中热电子对生物油中含氧有机物的重整反应起着重要的促进作用．     

含氧有机物催化重整制备纯氢

研究了一种新的利用含氧化合物制备纯氢的催化变换过程,该过程耦合了含氧化合物的催化重整、水煤气变换反应和CO₂去除步骤. 详细研究了重整催化剂的筛选、反应条件以及不同的含氧化合物催化重整行为. 利用所述集成方法获得的最高氢气浓度为99.96vol%和最大转化率为97.1mol%. 此外,通过含氧化合物的解离、催化重整和水煤气变换反应研究,探讨了含氧化合物制备纯氢的相关反应路径.     

生物油及生物质炭电催化制氢

报道了以生物质热裂解产物-生物油和生物质炭为原料,利用双固定床反应器和电催化水蒸气重整方法高效制氢过程研究．获得的最大绝对氢产率达到110.9 g H₂/1 kg干生物质,气相产物包括72%H₂、26%CO₂、1.9%CO和痕量的CH₄．研究了添加生物质炭对生物油制氢效果的影响,以及重整反应温度、通入催化床的电流等反应条件对生物油和生物质炭制氢效果的影响．结果表明,生物质炭的添加使绝对氢产率增加了大约20%～45%,提     

原位核磁共振技术研究反应环境对光催化甲醇重整过程的影响

本文利用原位核磁共振技术，系统研究了在真实反应体系中反应环境（气氛、压强、气体量等）对甲醇光催化重整反应产物的影响.发现不同气氛对甲醇光催化重整的反应产物有着不同的抑制作用，而环境压强及气体量对于甲醇光催化重整反应产物产率的影响较小.在此基础上，本文进一步讨论了气体在催化剂表面的吸附方式和环境气氛影响甲醇光催化重整反应产物的机理.     

原位核磁共振技术研究光催化甲醇重整过程中甲醇与水的相互作用

本文利用原位液体核磁共振技术对真实固液体系光催化甲醇重整过程中水与甲醇之间的相互作用进行了系统性研究,证实了甲醇+水体系中氢键及质子交换相互作用的存在,并且发现催化剂的种类（包括不同晶型,以及同一晶型、不同形貌的TiO₂）、体系温度、光照反应条件都会影响甲醇与水之间的相互作用,进而影响到甲醇重整的效率．这表明催化剂及温度的合适选择对于提升甲醇重整效率起到非常重要的作用．     

电流对苯甲醚电催化重整过程的影响

用电催化重整方法和NiCuZn-Al₂O₃催化剂进行生物油模型化合物苯甲醚的水蒸气重整制氢研究,结果表明,在700 oC和4 A条件下,获得的最高碳转化率和氢产率分别为98.3%和88.7%,电催化重整过程中发现的电流促进效应主要归结于重整反应床中温度分布的改变和电阻丝发射的热电子影响. 利用X射线衍射方法分析了反应前后的NiCuZn-Al₂O₃催化剂结构变化. 实验导出的苯甲醚重整反应表观活化能为99.54 kJ/mol,明显高于乙醇、乙酸和生物油轻质组分的重整反应表观活化能.