化学链干重整联合制氢热力学分析及实验

提出了一种化学链甲烷干重整联合制氢工艺。该工艺由还原反应器、干重整反应器、蒸汽反应器和空气反应器组成，在实现制氢的同时获得可变H₂/CO比的合成气。借助ASPEN plus软件和小型流化床实验台，在等温条件下，温度900℃，采用Fe₂O₃/Al₂O₃载氧体，对该工艺进行热力学分析和实验验证。结果显示，当铁氧化物被还原至FeO/Fe时，干重整反应器内甲烷转化率可以达到98%，CO产率可以达到94%。干重整反应器中同时发生甲烷干重整和部分氧化反应，载氧体内部晶格氧可以有效降低积炭并提高合成气H₂/CO比。积炭发生于晶格氧消耗殆尽时。积炭进入蒸汽反应器，发生气化反应，降低氢气纯度。     

不同结构微反应器下甲烷水蒸气重整制氢性能对比

微通道反应器是便携式制氢领域目前最有发展前景的技术之一。为了提高甲烷水蒸气重整在微反应器内制氢的效果,设计了三种不同结构的微反应器几何模型,分别为直管(Pipe)模型、平板圆弧弯道(FCC)模型和三纹内螺旋枪管(Tri-g ISB)模型,利用Ansys Fluent流体仿真软件结合甲烷水蒸气重整制氢的CHEMKIN反应机理文件对三种不同结构的微反应器进行了数值模拟分析。通过研究不同条件下微反应器出口气体组分变化可知,入口速度越小,CH₄转化率和H₂体积分数越高;S/C>3时,CH₄转化率增大至80%以上、H₂含量增加至73vol%以上;壁面温度越大,CH₄转化率可稳定在99.9%,几乎完全转化,H₂含量增大到77vol%以上,但温度过高会降低H₂产量,增加CO含量。通过计算不同条件下微反应器达到稳定所需时间可知,随入口速度和S/C增加稳定时间均逐渐减小并趋于稳定,随壁面温度增加,稳定时间先减小后增加。通过对比三种微反应器可知,复...     

柴油自热重整制氢反应及反应器

设计了带预热段的绝热管式反应器(A型)和带喷嘴及预热段的绝热管式反应器(B型),设计了相应流程并组建了柴油自热重整制氢装置,以直馏柴油为原料,研究了2种反应器内的柴油自热重整制氢反应行为。研究结果表明:2种结构的反应器均能用于柴油自热重整制氢,采用带喷嘴的绝热管式反应器可以确保雾化及气化效果良好,柴油热裂解生成甲烷的反应有助于柴油制氢过程。     

化学链干重整联合制氢热力学分析及实验

提出了一种化学链甲烷干重整联合制氢工艺。该工艺由还原反应器、干重整反应器、蒸汽反应器和空气反应器组成,在实现制氢的同时获得可变H_2/CO比的合成气。借助ASPEN plus软件和小型流化床实验台,在等温条件下,温度900℃,采用Fe_2O_3/Al_2O_3载氧体,对该工艺进行热力学分析和实验验证。结果显示,当铁氧化物被还原至FeO/Fe时,干重整反应器内甲烷转化率可以达到98%,CO产率可以达到94%。干重整反应器中同时发生甲烷干重整和部分氧化反应,载氧体内部晶格氧可以有效降低积炭并提高合成气H_2/CO比。积炭发生于晶格氧消耗殆尽时。积炭进入蒸汽反应器,发生气化反应,降低氢气纯度。     

CuO/ZnO/CeO_2-ZrO_2催化甲醇水蒸气重整制氢性能

以液体燃料甲醇分布式现场重整制氢系统开发为研究目的,根据非对称耦合的思想,将Cu O/Zn O/Ce O2-Zr O2甲醇水蒸气重整催化剂和Pt/Al2O3催化燃烧催化剂应用于套筒式小型制氢反应器中,实现了甲醇水蒸气重整反应和燃烧反应的耦合。实验考察了Cu O/Zn O/Ce O2-Zr O2催化剂在套筒式小型制氢反应器中的性能。结果表明:在套筒式小型制氢反应器内,Cu O/Zn O/Ce O2-Zr O2催化剂的甲醇水蒸气重整活性比商业Cu O/Zn O/Al2O3催化剂高出30%左右;并且多次开停车和改变反应条件,均未对催化剂和反应器产生明显影响,150 h内催化剂和反应器稳定性良好。当反应温度为230~260℃,甲醇气体空速为300~1200 h-1,水醇物质的量比(S/M)为1.2时,最大氢产率达162.8 L/h,可为百瓦级质子交换膜燃料电池提供氢源。     

铁基氧载体化学链CO2重整CH4方法制备合成气

提出一种铁基氧载体（Fe₃O₄/FeO）化学链CO₂重整CH₄方法制备合成气。为评价该系统的性能,采用Aspen Plus软件对其进行过程模拟和热力学分析。以CH₄转化率、CO₂转化率、能源利用效率和产气氢碳比（H₂/CO）为评价指标,得到系统的优化运行条件,并研究各操作参数（包括各反应器的温度和压力、氧载体甲烷比和CO₂甲烷比）对系统性能的影响。结果表明：当系统处于优化工况时,得到CH₄转化率为97.91%、CO₂转化率为32.76%、能源利用效率为93.77%及产气氢碳比为0.93。该系统能有效利用CO₂和CH₄这两种温室气体获得较低氢碳比的合成气,利于二甲醚的高效合成。     

甲烷水蒸气重整与微管固体氧化物燃料电池电堆耦合性研究

目的：以甲烷水蒸气重整合成气为燃料，测试微管式固体氧化物燃料电池(MT-SOFC)电堆的电化学性能。方法：以活性氧化铝为载体，通过浸渍工艺制备出甲烷水蒸气重整催化剂，测试催化剂在不同反应温度、水碳比、体积空速下的反应活性。将甲烷水蒸气重整的合成气作为MT-SOFC电堆的燃料，测试电堆的发电性能。结果：在750℃，体积空速为550 h^-1时，甲烷转化率达99.5%。甲烷水蒸气重整耦合MT-SOFC电堆发电，其功率达43.5 W，功率密度达0.20 W/cm²。催化剂催化活性较高，电堆电化学性能平稳。结论：甲烷水蒸气重整耦合MT-SOFC电堆发电的工艺可提高燃料的利用效率，对发展新能源和保护环境具有现实意义。     

吸附强化焦油蒸汽重整制取氢气

分别采用固相反应法、溶胶凝胶法制备了Ni/Mg-Ca₁₂Al₁₄O₃₃催化剂、CaO-Ca₁₂Al₁₄O₃₃吸附剂,并将其作为重整催化剂、CO₂吸附剂应用在焦油蒸汽重整制取氢气的研究中,通过与普通蒸汽重整进行对比,系统地研究了重整温度、S/C比（反应体系中水蒸气与碳元素的摩尔比）、质量空速对焦油吸附强化蒸汽重整制氢特性的影响。结果表明,CO₂吸附剂的加入能够有效提升焦油重整效果,氢气产率、体积分数均得到显著提高,其中氢气体积分数达95%以上。随着S/C比的增加、质量空速的减小,普通蒸汽重整和吸附强化重整的制氢效果均是增强的,且均在S/C比、质量空速分别达到12：1、0.128 h⁻¹后增幅不再明显;尽管如此,相比普通重整,吸附强化重整降低了最佳重整制氢温度,在800℃时氢气产率能够达到87.35%。     

Investigation of mini-reformer for hydrogen production

以解决小功率燃料电池氢源问题为目的,研制了集原料预热、甲醇水蒸气重整（MSR）、催化燃烧、水汽变换（WGS）于一体的自热式重整制氢反应器。通过条件实验考察了操作温度、甲醇气体空速、水醇比（W/M）等操作条件对重整反应的影响,并在苛刻条件下进行了稳定性研究。实验证明,反应器最大净产氢量可达90 L/h,可为百瓦级质子交换膜燃料电池提供氢源。     

甲烷作为储氢介质产业模式下的关键技术分析

随着“双碳”目标的提出，氢能作为一种无碳能源，有望成为未来能源的重要形式。甲烷(CH₄)作为天然气的主要成分，质量含氢量高达25%,是烃类中质量含氢量最高的物质，基于天然气储运的完善基础设施，可有效避免氢气(H₂)难于储运的产业发展痛点。分析了甲烷作为储氢载体的氢能产业发展技术路径，从制氢端考虑，对甲烷重整制氢、甲烷裂解制氢技术的现状以及面临的挑战加以分析；从甲烷制取角度，介绍了甲烷化技术的动态和难点。     

High combustion activity of methane induced by reforming gas over Ni/Al2O3 catalysts

During the reactions related to oxidative steam reforming and combustion of methane over -alumina-supported Ni catalysts, the temperature profiles of the catalyst bed were studied using an infrared (IR) thermograph. IR thermographical images revealed an interesting result: that the temperature at the catalyst bed inlet is much higher under CH₄/H₂O/O₂/Ar = 20/10/20/50 than under CH₄/H₂O/O₂/Ar = 10/0/20/70; the former temperature is comparable to that over noble metal catalysts such as Pt and Pd. Based on the temperature-programmed reduction and oxidation measurements over fresh and used catalysts, the metallic Ni is recognized at the catalyst bed inlet under CH₄/H₂O/O₂/Ar = 20/10/20/50, although it is mainly oxidized to NiAl₂O₄ under CH₄/H₂O/O₂/Ar = 10/0/20/70. This result indicates that the addition of reforming gas (CH₄/H₂O = 10/10) to the combustion gas (CH₄/O₂ = 10/20) can stabilize Ni species in the metallic state even under the presence of oxygen in the gas phase. This would account for its extremely high combustion activity.     

褐煤热解-气化-制油系统的CO2减排策略

褐煤热解-气化-制油系统是现代煤化工发展的一个重要研究内容。来自系统多个单元产生的CH₄和CO₂如果发生重整反应,将重整得到H₂/CO比值较高的合成气添加到制油流程中,可实现更多的C被固定到产品中而减少CO₂的直接排放量。对CH₄-CO₂和CH₄-H₂O两种重整反应方式、来自煤热解和费托合成两股甲烷气和典型的干粉气化和水煤浆气化两种流程进行了组合研究。分析结果显示,来自热解和费托合成的甲烷重整后不足以提供调节合成气H₂/CO比例所需的氢气,水煤气变换反应对于褐煤制油系统来说是必需的。从C转化成油的角度来看,采用干粉气化和CH₄-H₂O重整的方案是较好的选择。     

REACTOR-MEMBRANE PERMEATOR CASCADE FOR ENHANCED PRODUCTION AND RECOVERY OF H2 AND CO2 FROM THE CATALYTIC METHANE-STEAM REFORMING REACTION

The catalytic reforming of methane by steam is an important industrial process that produces H₂, CO and CO₂, thus chemically transforming natural gas, coal gas and light hydrocarbon feedstocks to synthesis gas or hydrogen fuel. Methane-steam reforming may consist of a number of reactions depending on the reforming catalyst, operating conditions and feedstock composition, The typical industrially desirable reactions are the reverse of methanation (CH₄ + H₂O = CO + 3H₂) and the water-gas shift (CO + H₂O = CO₂ + H₂). Both reactions are equilibrium limited and the composition of the mixture that exits the reformer is in accordance with the one calculated thermodynarmically. Removal of reaction products at the reactor exit by means of selective membrane permeation can offer improved CH₄ conversions and CO₂ and H₂ yields, assuming the subsequent utilization of the reject streams by a second methane-steam reformer. We numerically investigated the feasibility of a system of two tubular methane-steam reformers, in series with an intermediate permselective polyimide membrane permeator, as means of improving the overall CH₄ conversion and the H₂, CO₂ yields over conventional methane-steam reforming equilibrium reaction-separation schemes that are currently in industrial practice. The unique feature of the permselective polyimide separator is the simultaneous removal of H₂ and CO₂ versus CH₄ and CO from the reformed streams. The utilized 6FDA-3,3', 5,5'-TMB aromatic polyimide was reportedly characterized [10] and found to exhibit superior permselective properties compared with other polyimides of the same or different dianhydride sequence. Conversion and yield of the designed reactor-membrane permeator reforming system can be maximized by optimizing the permselective properties of the membrane material and the design variables of the reactors and the permeator. Product recovery and purity in the permeate stream need to be compromised to overall enhance methane conversion and product yield. The operating variables that were varied to investigate their effect on the magnitude of conversion and yield included the inlet pressure of the first reformer, the temperature of both reformers, and the permeator dimensionless Pe' number (variation of the first two variables results to a drastic change in the composition of the reformed stream that enters into the permeator). The numerical results show that the new reformer-membrane permeator cascade process can be more effective (it can offer increased CH₄ conversions and H₂, CO₂ yields) than conventional equilibrium methane-steam reforming reaction-separation processes currently in practice.     

Effect of complex oxide promoters and Pd on activity and stability of Ni/YSZ (ScSZ) cermets as anode materials for IT SOFC

Effect of fluorite-like or perovskite-like complex oxide promoters, Pd and Cu on the performance of Ni/8YSZ and Ni/ScCeSZ anode materials in CH₄ steam reforming (SR) or selective oxidation (SO) by O₂ into syngas was studied. The spatial distribution of dopants in composites before and after contact with the reaction feed, features of components mutual interaction and forms of deposited coke were controlled by TEM combined with EDX analysis. The lattice oxygen mobility and reactivity were estimated by CH₄ and H₂ temperature-programmed reduction (TPR), and the amount of deposited carbon after operation in the feed with stoichiometric H₂O/CH₄ ratio was estimated by the temperature-programmed oxidation. Promoters decrease the amount of deposited coke, while doping by Pd or Cu ensures also a good and stable performance at moderate (550 °C) temperatures required for the intermediate-temperature solid oxide fuel cells (IT SOFC) operation.     

Ni-CeO2-K/γ-Al2O3催化剂上沼气联合重整制合成气

采用超声波辅助等体积浸渍法制备Ni-CeO₂-K/γ-Al₂O₃催化剂用于沼气联合重整反应,采用 BET、XRD、TG/DTG等技术对催化剂性质进行了表征,在微型固定床反应装置中研究了反应温度、体积空速、原料气组成等对沼气联合重整反应特性的影响,并对催化剂的稳定性进行了研究。结果表明,助剂CeO₂的加入,提高了催化剂中Ni的分散度,降低了催化剂还原温度。升高反应温度和减小体积空速,能够提高沼气中CH₄和CO₂的转化率;原料气中加入水蒸气,能够明显提高H₂/CO体积比;加入的O₂容易与H₂、CO发生反应,CH₄转化率稍有提高。在常压、反应温度850℃、体积空速为100000h^-1、摩尔比CH₄∶CO₂∶H₂O∶O₂∶Ar=1∶0.5∶0.5∶0.1∶0.01的优化条件下,沼气中CH₄转化率超过95%,CO₂转化率超过75%,生成合成气H₂/CO体积比约为1.6,反应48h后,催化剂未见积炭,保持稳定的活性。与沼气干重整相比,沼气联合重整不利于沼气中CO₂的转化。     

Methane steam reforming over Ni/Ce–ZrO2 catalyst: Influences of Ce–ZrO2 support on reactivity, resistance toward carbon formation, and intrinsic reaction kinetics

Ni/Ce–ZrO₂ showed good methane steam reforming performance in term of stability toward the deactivation by carbon deposition. It was first observed that the catalyst with Ce/Zr ratio of 3/1 showed the best activity among Ni/Ce–ZrO₂ samples with the Ce/Zr ratios of 1/0, 1/1, 1/3, and 3/1. Temperature-programmed oxidation (TPO) experiments indicated the excellent resistance toward carbon formation for this catalyst, compared to conventional Ni/Al₂O₃; the requirement of inlet H₂O/CH₄ to operate without the formation of carbon species is much lower. These benefits are related to the high oxygen storage capacity (OSC) of Ce–ZrO₂. During the steam reforming process, in addition to the reactions on Ni surface (*), the redox reactions between the gaseous components present in the system and the lattice oxygen (O_x) on Ce–ZrO₂ surface also take place. Among these reactions, the redox reactions between the high carbon formation potential compounds (CH₄, CH_x-*n and CO) and the lattice oxygen (O_x) can prevent the formation of carbon species from the methane decomposition and Boudard reactions, even at low inlet H₂O/CH₄ ratio (1.0/1.0).

Regarding the intrinsic kinetic studies in the present work, the reaction order in methane over Ni/Ce–ZrO₂ was observed to be approximately 1.0 in all conditions. The dependence of steam on the rate was non-monotonic, whereas addition of oxygen as an autothermal reforming promoted the rate but reduced CO and H₂ production selectivities. The addition of a small amount of hydrogen increased the conversion of methane, however, this positive effect became less pronounced and the methane conversion was eventually inhibited when high hydrogen concentration was added. Ni/Ce–ZrO₂ showed significantly stronger negative impact of hydrogen than Ni/Al₂O₃. The redox mechanism on ceria proposed by Otsuka et al. [K. Otsuka, T. Ushiyama, I. Yamanaka, Chem. Lett. (1993) 1517; K. Otsuka, M. Hatano, A. Morikawa, J. Catal. 79 (1983) 493; K. Otsuka, M. Hatano, A. Morikawa, Inorg. Chim. Acta 109 (1985) 193] can explain this high inhibition.     

Study of mixed steam and CO2 reforming of CH4 to syngas on MgO-supported metals

The activity of mixed steam and CO₂ reforming of CH₄ to produce synthesis gas was investigated and compared with those of steam reforming alone and CO₂ reforming alone at 600–900°C under atmosphere pressure on MgO-supported noble metals. Mixed reforming shows a far lower CH₄ conversion than the value for thermodynamic equilibrium. The activity decreases following the order Ru,Rh> Ir> Pt,Pd. Little deactivation was observed for Ru, Rh and Ir catalysts. An isotope labelled ¹³CO₂ experiment was carried out in situ for mixed reforming on Rh/MgO and the results suggest that CO₂ dissociates as CO-M and O-M. The results of the temperature program reaction (TPR) of mixed reforming shows that CH₄ adsorbs and dissociates before reaction starts and that CO₂ reforming and steam reforming start simultaneously. A possible reaction mechanism is discussed.     

Catalytic reduction of N2O over steam-activated FeZSM-5 zeolite: Comparison of CH4, CO, and their mixtures as reductants with or without excess O2

The catalytic reduction of N₂O by CH₄, CO, and their mixtures has been comparatively investigated over steam-activated FeZSM-5 zeolite. The influence of the molar feed ratio between N₂O and the reducing agents, the gas-hourly space velocity, and the presence of O₂ on the catalytic performance were studied in the temperature range of 475–850 K. The CH₄ is more efficient than CO for N₂O reduction, achieving the same degree of conversion at significantly lower temperatures. The apparent activation energy for N₂O reduction by CH₄ was very similar to that of direct N₂O decomposition (140 kJ mol⁻¹), being much lower for the N₂O reduction by CO (60 kJ mol⁻¹). This suggests that the reactions have a markedly different mechanism. Addition of CO using equimolar mixtures in the ternary N₂O + CH₄ + CO system did not affect the N₂O conversion with respect to the binary N₂O + CH₄ system, indicating that CO does not interfere in the low-temperature reduction of N₂O by CH₄. In the ternary system, CO contributed to N₂O reduction when methane was the limiting reactant. The conversion and selectivity of the reactions of N₂O with CH₄, CO, and their mixtures were not altered upon adding excess O₂ in the feed.     

Transient modeling of combined catalytic combustion/CH4 steam reforming

This paper presents an investigation into the complex interactions between catalytic combustion and CH₄ steam reforming in a co-flow heat exchanger where the surface combustion drives the endothermic steam reforming on opposite sides of separating plates in alternating channel flows. To this end, a simplified transient model was established to assess the stability of a system combining H₂ or CH₄ combustion over a supported Pd catalyst and CH₄ steam reforming over a supported Rh catalyst. The model uses previously reported detailed surface chemistry mechanisms, and results compared favorably with experiments using a flat-plate reactor with simultaneous H₂ combustion over a γ-Al₂O₃-supported Pd catalyst and CH₄ steam reforming over a γ-Al₂O₃-supported Rh catalyst. Results indicate that stable reactor operation is achievable at relatively low inlet temperatures (400 °C) with H₂ combustion. Model results for a reactor with CH₄ combustion indicated that stable reactor operation with reforming fuel conversion to H₂ requires higher inlet temperatures. The results indicate that slow transient decay of conversion, on the order of minutes, can arise due to loss of combustion activity from high-temperature reduction of the Pd catalyst near the reactor entrance. However, model results also show that under preferred conditions, the endothermic reforming can be sustained with adequate conversion to maintain combustion catalyst temperatures within the range where activity is high. A parametric study of combustion inlet stoichiometry, temperature, and velocity reveals that higher combustion fuel/air ratios are preferred with lower inlet temperatures (≤500 °C) while lower fuel/air ratios are necessary at higher inlet temperatures (600 °C).