基于3D打印技术的甲烷水蒸气重整研究

天然气(主要成分为甲烷)重整是天然气高效清洁利用的重要途径,重整获得富含氢气的重整气,可供固体氧化物燃料电池进行高效发电。甲烷水蒸气重整需要反应器以及负载其上的重整催化剂,基于3D打印技术的多孔结构具有良好的耐高温、抗氧化和结构稳定性等特点,负载Ni基催化剂用于甲烷催化重整可有效提升反应器稳定性,但相关研究较少。采用浸渍法将Ni-CeO₂/γ-Al₂O₃催化剂负载于3D打印制备的多孔结构和金属泡沫反应器,通过催化剂形貌、分布规律、相结构以及热稳定性的表征,研究了重整反应温度、浆料配比、反应器结构等因素对甲烷水蒸气重整效果的影响。结果显示,催化剂的最佳配比是PVA含量为3.5%(若无特殊说明,均为质量分数),Ni含量为19%,CeO₂和γ-Al₂O₃的含量分别为16%和2.5%。重整测试结果表明,负载催化剂前,重整反应温度低于700℃时,Inconel625和泡沫Ni多孔反应器重整得到的氢气浓度均低于13%(体积分数),而重整反应温度高于800℃时,Inco...     

光催化分解水制氢体系助催化剂研究进展

煤、石油、天然气等不可再生能源的消耗导致环境污染日益严重,开发和使用清洁的可再生能源迫在眉睫。利用太阳能光催化分解水制氢被认为是解决化石能源紧缺和环境污染问题的有效途径之一。光催化分解水制氢体系非常复杂,助催化剂是影响催化剂光催化效率的一个关键因素,它的引入可以有效提高催化剂的光催化活性和氢气产生速率,因此,开发廉价高效的助催化剂已逐渐成为本领域的研究热点。本文结合光催化分解水制氢原理,简要介绍了助催化剂的作用,对近年来光催化分解水产氢助催化剂的种类和研究内容进行了总结,分析和讨论了几类重要助催化剂的特点及作用机理,并对助催化剂的发展进行了展望,以期为新型高效光催化制氢材料的设计提供参考。     

应用市场

正上海华西与科莱恩催化剂签订制氢工艺战略合作伙伴1月31日,上海华西化工科技有限公司与科莱恩催化剂业务单元就中国制氢项目建立了战略联盟关系。根据协议,科莱恩的催化剂符合且适用于上海华西的中温变换(MTS)许可工艺。科莱恩将为重整、加氢脱硫和水煤气变换工艺提供多种催化剂。此项协议将上海华西的先进工艺技术与科莱恩一流的催化剂相结合,旨在为制氢生产商提供高效、经济的解决方案。     

甲醇重整制氢技术

本文简述了氢气用途,对工业上目前几种常用制氢方法做了概述,本文对甲醇重整制氢及净化工艺作了介绍,并比较了不同的重整净化方法主要技术指标。     

汽油氧化重整制氢反应镍催化剂的实验研究

在小型固定床反应器中,考察了汽油氧化重整制氢反应体系中镍催化剂 的催化性能。实验考察了镍/三氧化二铝催化剂,活性组分镍含量对汽油氧化重整制氢反应的影响,实验还考察了镍/三氧化二铝催化剂中加入贵金属助剂的催化性能。实验结果表明单组元镍/三氧化二铝催化剂对汽油氧化重整制氢反应在反应温度低于650℃时,其活性较低,生成氢气的选择性也不高;反应温度高于650℃时,其反应活性及生成氢的选择性有明显的提高。镍/三氧化二铝催化剂中加入贵金属组分作为助催化剂制成的双金属催化剂在汽油制氢反应中的催化活性及生成氢的选择性均有明显的提高。     

核能制氢与高温气冷堆

氢是环境友好的能源载体，利用核能制氢引起了广泛的研究兴趣。本文对核能制氢的工艺，包括甲烷蒸汽重整、高温电解和热化学循环进行了综述；提出了制氢过程对反应堆的要求，并介绍了高温气冷堆用于核能制氢的优势。     

Ni/Rh催化剂下微通道甲烷自热重整制氢特性研究

针对微细通道内甲烷自热重整反应,采用活性位浓度比为10∶1的Ni/Rh催化剂建立了数学物理模型,通过数值模拟方法研究了绝热工况下温度、流量、氧碳比及水碳比等因素对催化重整特性的影响规律。结果表明:催化反应的温度阈值为750K,当温度超过750K时甲烷转化率迅速升高;在纯氧条件下随着甲烷流量的增大,制氢功率增大,而在空气条件下制氢功率减小;随着氧碳比的增加,甲烷的转化率升高,制氢功率先增大后逐渐减小;随着水碳比的增加,甲烷转化率降低;当入口反应气中氧碳比控制在0.5以下、水碳比为3.5且入口温度为900K时,可实现微通道内甲烷催化重整的高效转化。     

混合导体透氧膜反应器中焦炉煤气重整制合成气的实验研究

研究了以焦炉煤气为原料在BaCo0.7Fe0.2Nb0.1O3-δ(BCFNO)透氧膜反应器中制合成气。实验结果表明,BCFNO膜反应器的自催化性能差。加入催化剂后,膜反应器的重整性能得到明显提高,在875℃,焦炉煤气中甲烷转化率为87.0%,产物中氢气和一氧化碳选择性分别为78.3%、105.6%,透氧量达到15.8ml/(cm2.min)。焦炉煤气中的甲烷在膜反应器中反应路径为首先焦炉煤气中的氢气与膜片透过去的氧反应生成水,然后甲烷再与水重整生成氢气和一氧化碳。实验过程中,透氧膜没有出现破裂,BCFNO透氧膜反应器在富氢的焦炉煤气下显示出很好的稳定性。     

小型天然气水蒸汽重整制氢系统的研发

为向北京市的氢燃料电池汽车提供氢气,在北京北部的永丰高科技园区建设了一座50Nm^3／hr天然气水蒸汽重整制氢装置。通过对工艺系统的优化,对关键设备的开发研究．及对控制系统的开发．完成了以天然气转化-变压吸附工艺净化制氢单元由脱盐水系统-空气压缩系统-循环冷却水系统组成的公用工程单元的撬装模块化设计．经过调试,所产出的氢气完全达到或超过德国奔驰汽车对燃料电池用氢气提出的要求、证明本装置向小气量、高纯度用户提供氢气是可行的。     

乙醇水蒸气重整制氢催化材料的制备及其性能研究

用浸渍法制备了以 CeO2 为助剂的镍基乙醇水蒸气重整制氢催化剂(Ni/CeO2/γ Al2O3)。该种催化剂在较低的温度下具有较高的氢气产率和较高的CO2 选择性,并使副产物 CH4 和 CO的选择性限制在较低水平。在 600℃,催化剂 16% Ni/CeO2/γ Al2O3的氢气产率可达4.8,生成 CO2、CO和 CH4 的选择性分别为70.7%、21%和7%。     

基于熔融盐加热的甲烷蒸汽重整制氢反应器的熵产生率和氢气产率分析

太阳能热化学储能能够有效解决太阳能时间和空间分布不均的问题。在工业甲烷蒸汽重整反应器模型的基础上,利用有限时间热力学理论建立了基于熔融盐加热的甲烷蒸汽重整反应器（steam methane reforming reactor heated by molten salt,MS-SMRR）模型,得到了MS-SMRR的设计参数,并分析了MS-SMRR的几何参数和操作参数对氢气产率和总熵产生率的影响规律。结果表明：在氢气产率一定时,逆流参考反应器比顺流参考反应器的总熵产生率低,且消耗的熔融盐少;增大熔融盐进口温度和减小反应混合物进口压力能够显著提高MS-SMRR的氢气产率。研究结果对实际MS-SMRR的优化设计具有一定的理论指导意义。     

Optimization of an experimental membrane reactor for low-temperature methane steam reforming

The systematic and rigorous model-based optimization of the configuration and operating conditions of a methane membrane steam reforming reactor for hydrogen production is performed. A permeable membrane with Pd–Ru deposited on a ceramic dense support is used to selectively remove the produced hydrogen from the reaction zone. The shifted chemical equilibrium towards hydrogen production enables the achievement of high methane conversion at relatively low reactor temperature levels. Steam reforming takes place over a Ni–Pt/CeZnLa ceramic foam-supported catalyst that ensures better thermal distribution, at an operating temperature of 773 K and a pressure of 10⁶ Pa. A nonlinear, two-dimensional, and pseudo-homogeneous mathematical model of the membrane fixed-bed reactor is developed and subsequently validated using experimental data. For model validation purposes, two sets of experiments have been performed at the experimental reactor installed at CPERI/CERTH. The first set of experiments aims to investigate membrane permeability in order to estimate the parameters involved in the applied Sieverts law. The second set of experiments explores the performance of the membrane reactor at different steam to carbon ratios and total inlet volumetric flowrates. The derived mathematical model, consisted of mass, energy, and momentum balances that consider both axial and radial gradients of temperature and concentration, is then utilized within a model-based optimization framework that calculates the optimal operating conditions for the highly interactive reactor system. The optimal steam to carbon ratio and sweep gas flow rate that minimize the overall methane utilization (i.e., reformed methane and equivalent methane for heating purposes) are calculated for a range of hydrogen production rates. Τhe optimal reactor design configuration described by the length of the catalyst zone is also obtained for a given pure hydrogen production rate.     

Using biomass as an energy source with low CO2 emissions

This work deals with the carbon dioxide cycle and emissions from biomass incineration under a hydrogen production context. It is proposed to use the thermal energy obtained by biomass combustion to produce water steam, which afterwards would be converted into hydrogen by high temperature electrolysis (HTE). In France, the thermal energy potential from nonvalorised biomass reaches almost 6.5 Mtep. In this study, the potential avoided carbon emissions are quantified as well as the feasible hydrogen production capacity based on the steam supplied by the incineration units. Results show that carbon consumption in hydrogen production by steam methane reforming (SMR) or biomass incineration–HTE process is almost equivalent between both processes. However, the hydrogen produced by the biomass incineration–HTE process used to fuel vehicles, would lead to a decrease of 135 Mt of carbon from fossil origins yearly, in contrast to SMR.     

Modelling and optimization of syngas production by methane dry reforming over samarium oxide supported cobalt catalyst: response surface methodology and artificial neural networks approach

The reforming of methane by carbon dioxide for the production of syngas is a potential technological route for the mitigation of greenhouse gases. However, the process is highly endothermic and often accompanied by catalyst deactivation from sintering and carbon deposition. Besides, the applications of dissimilar catalytic systems in methane dry reforming have made it difficult to obtain generalized optimum conditions for the desired products. Hence, optimization studies of any catalytic system often resulted in a unique optimum condition. The present study aimed to investigate optimum conditions of variables such as methane (CH₄) partial pressure, carbon dioxide (CO₂) partial pressure and reaction temperature that will maximize syngas yields from methane dry reforming over samarium oxide supported cobalt (Co/Sm₂O₃) catalyst. The Co/Sm₂O₃ catalyst was synthesized using wet-impregnation method and characterized by thermogravimetric analysis), field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray powder diffraction and nitrogen (N₂) physisorption. Syngas production by methane dry reforming over the synthesized Co/Sm₂O₃ catalyst was investigated in a stainless steel fixed-bed reactor. The process variables (CH₄ partial pressure, CO₂ partial pressure and reaction temperature) for the syngas production were optimized using response surface methodology (RSM). The RSM and artificial neural networks (ANNs) were used to predict the syngas production from the experimental data. The comparative analysis between the two models showed that the ANN model has better prediction of the syngas yields compared to the RSM model as evident from the good agreement between the observed and the predicted values. At maximum desirability value of 0.97, optimum CH₄ and CO₂ partial pressures of 47.9 and 48.9 kPa were obtained at reaction temperature of 735 °C resulting in syngas yield of ~79.4 and 79.0% for hydrogen (H₂) and carbon monoxide (CO), respectively.     

Hydrogen production from methane steam reforming: parametric and gradient based optimization of a Pd-based membrane reactor

In this work three mathematical models for methane steam reforming in membrane reactors were developed. The first one is a steady state, non isothermal, non isobaric and one dimensional model derived from material and energy balances and validated using experimental data from the literature. It is referred as full model. The influence of two different intrinsic kinetics available, as well as, the influence of five important parameters on methane conversion (X_CH4_{\mathrm{CH}_{4}}) and hydrogen recovery (Y_H2_{\mathrm{H}_{2}}) were parametrically evaluated through simulations. The second model, referred as meta-model, was obtained though the response surface technique. This meta-model was included into a constrained optimization problem solved using NPSOL. The third model, referred as a simplified model, takes into account only mass balances from the full model. Using this model, a gradient based method (DIRCOL) was used to perform the optimization of the sum of methane conversion and hydrogen recovery. High methane conversions and hydrogen recoveries were reached through these methodologies.     

Numerical study of hydrogen production by the sorption-enhanced steam methane reforming process with online CO<Subscript>2</Subscript> capture as operated in fluidized bed reactors

A three-dimensional (3D) Eulerian two-fluid model with an in-house code was developed to simulate the gas-particle two-phase flow in the fluidized bed reactors. The CO₂ capture with Ca-based sorbents in the steam methane reforming (SMR) process was studied with such model combined with the reaction kinetics. The sorption-enhanced steam methane reforming (SE-SMR) process, i.e., the integration of the process of SMR and the adsorption of CO₂, was carried out in a bubbling fluidized bed reactor. The very high production of hydrogen in SE-SMR was obtained compared with the standard SMR process. The hydrogen molar fraction in gas phase was near the equilibrium. The breakthrough of the sorbent and the variation of the composition in the breakthrough period were studied. The effects of inlet gas superficial velocity and steam-to-carbon ratio (mass ratio of steam to methane in the inlet gas phase) on the reactions were studied. The simulated results are in agreement with the experimental results presented by Johnsen et al. (2006a, Chem Eng Sci 61:1195–1202).     

Key Role of Lanthanum Oxychloride: Promotional Effects of Lanthanum in NiLaOy/NaCl for Hydrogen Production from Ethyl Acetate and Water

The hydrogen economy is accelerating technological evolutions toward highly efficient hydrogen production. In this work, the catalytic performance of NiO/NaCl for hydrogen production via autothermal reforming of ethyl acetate and water is further improved through lanthanum modification, and the resulted 3%‐NiLaO_y/NaCl catalyst achieves as high as 93% H₂ selectivity and long‐term stability at 600 °C. The promoting effect is caused by the strong interactions between lanthanum and NiO/NaCl, by which LaNiO₃ and a novel LaOCl phase are formed. The key role of LaOCl in promoting low‐temperature hydrogen production is highlighted, while effects of LaNiO₃ are well known. The LaOCl (010) facet possesses high adsorption capacity toward co‐chemisorbing ethyl acetate and water. LaOCl strongly interacts with ethyl acetate and H₂O in the form of hydrogen bonding and coordination effect. The interactions induce tensions inside ethyl acetate and H₂O, activate the molecules, and hence decrease the energy barrier for reaction. In situ Fourier transform infrared spectroscopy (FTIR) reveals that LaOCl along with NaCl enhances the adsorption ability of NiO/NaCl. Moreover, LaOCl improves the dispersion of Ni species in NiO–LaNiO₃–LaOCl nanosheets, which possess abundant active sites. The effects together promote hydrogen evolution. Furthermore, the NiLaO_y/NaCl catalyst can be easily reborn after deactivation due to the water solubility of NaCl.     

Exergy efficiency improvement in hydrogen production process by recovery of chemical energy versus thermal energy

Exergy analysis is recently being employed as one of the preferred methods to improve the design performance of a system and to achieve overall sustainability. Exergy is mainly composed of physical or thermo-mechanical and chemical components and a single stream can possess one or more forms of exergy. Where there is exergy lost in unused chemical streams or wasted energy, the recovery of exergy would reduce losses and increase the second law efficiency of the process. In many chemical process plants such as hydrogen (H₂), ammonia, nitric acid, etc., there is a potential to recover waste or excess heat by process heat exchange or by generating utilities. For a process like steam–methane (CH₄) reforming (SMR), exergy efficiency can be improved by recovering the available excess heat partially or fully in the form of chemical energy or thermal energy. This paper presents the generalised system analysis to show that the recovery of exergy in the form of chemical energy is better than in thermal energy form due to fewer losses and higher efficiency. The concept is illustrated with the example of a simple combustion system with excess heat in which saving fuel proves to be more exergy efficient than generating utility. The approach is applied to an industrial case study of H₂-producing SMR plant with two modified cases of steam generation and recycling portion of unconverted CH₄ as feed. In the case study, heat exchanger network is treated as a separate process component and a simple methodology is proposed to calculate the exergy losses for the same. The results of the case study prove that the recovery of chemical energy is more efficient than that of thermal energy from an exergy perspective.     

Graphene Nanoarchitectonics: Recent Advances in Graphene‐Based Electrocatalysts for Hydrogen Evolution Reaction

Under the double pressures of both the energy crisis and environmental pollution, the exploitation and utilization of hydrogen, a clean and renewable power resource, has become an important trend in the development of sustainable energy‐production and energy‐consumption systems. In this regard, the electrocatalytic hydrogen evolution reaction (HER) provides an efficient and clean pathway for the mass production of hydrogen fuel and has motivated the design and construction of highly active HER electrocatalysts of an acceptable cost. In particular, graphene‐based electrocatalysts commonly exhibit an enhanced HER performance owing to their distinctive structural merits, including a large surface area, high electrical conductivity, and good chemical stability. Considering the rapidly growing research enthusiasm for this topic over the last several years, herein, a panoramic review of recent advances in graphene‐based electrocatalysts is presented, covering various advanced synthetic strategies, microstructural characterizations, and the applications of such materials in HER electrocatalysis. Lastly, future perspectives on the challenges and opportunities awaiting this emerging field are proposed and discussed.