燃料重整制氢及应用的研究现状和展望

燃料重整制氢是应用催化剂使燃料经过复杂的化学反应生成氢气的制氢方法。本文介绍了氢燃料相对于其他燃料的优缺点及燃料重整制氢的研究现状,论述了混氢燃料发动机相对于传统发动机所具有的优势,指出了重整制氢是未来发动机发展的重要趋势。     

Efficient bimetallic catalysts for hydrogen generation from diesel fuel

Fuel cell requires hydrogen as its fuel source for generating power. Hydrogen for use in auxiliary power units is produced in a fuel processor by the catalytic reforming of hydrocarbons. Diesel, jet fuel, gasoline, as well as natural gas, are potential fuels that all have existing infrastructure of manufacture and distribution, for hydrogen production for fuel cell applications. It is well known that essentially all hydrocarbon feeds contain sulfur at different concentrations. In addition to coking, sulfur poisoning is the main force for deactivation of pre-reforming and reforming catalysts. The objective of this paper is to develop, test and characterize efficient catalysts for hydrogen generation from diesel autothermal reforming. Bimetallic catalysts exhibited superior performance compared to the commercial catalyst and the monometallic counterparts. BET, TPD, TPR, and XPS were utilized for surface analysis of these formulations, which showed that the enhanced stability is due to a strong metal–metal and metal–support interaction in the catalyst.     

JP-8 catalytic cracking for compact fuel processors

In processing heavier hydrocarbons such as military logistic fuels (JP-4, JP-5, JP-8, and JP-100), kerosene, gasoline, and diesel to produce hydrogen for fuel cell use, several issues arise. First, these fuels have high sulfur content, which can poison and deactivate components of the reforming process and the fuel cell stack; second, these fuels may contain non-volatile residue (NVR), up to 1.5 vol.%, which could potentially accumulate in a fuel processor; and third is the high coking potential of heavy hydrocarbons. Catalytic cracking of a distillate fuel prior to reforming can resolve these issues. Cracking using an appropriate catalyst can convert the various heavy organosulfur species in the fuel to lighter sulfur species such as hydrogen sulfide (H₂S), facilitating subsequent sulfur adsorption on zinc oxide (ZnO). Cracking followed by separation of light cracked gas from heavies effectively eliminates non-volatile aromatic species. Catalytic cracking can also convert heavier hydrocarbons to lights (C₁–C₃) at high conversion, which reduces the potential for coke formation in the reforming process. In this study, two types of catalysts were compared for JP-8 cracking performance: commercially-available zeolite materials similar to catalysts formulated for fluidized catalytic cracking (FCC) processes, and a novel manganese/alumina catalyst, which was previously reported to provide high selectivity to lights and low coke yield. Experiments were designed to test each catalyst’s effectiveness under the high space velocity conditions necessary for use in compact, lightweight fuel processor systems. Cracking conversion results, as well as sulfur and hydrocarbon distributions in the light cracked gas, are presented for the two catalysts to provide a performance comparison.     

Internal reforming of hydrocarbon fuels in tubular solid oxide fuel cells

The application of heterogeneous catalysis has an important role to play in the successful commercial development of solid oxide fuel cell (SOFC) technology. In this paper, we present an SOFC that combines a catalyst layer with a conventional anode, allowing internal reforming via partial oxidation (POX) of fuels such as methane, propane, butane, biomass gas, etc., without coking and yielding stable power output. The catalyst layer is fabricated on the anode simply by catalyst support coating and reforming catalyst impregnation. The composition and microstructure of catalyst support layer as well as the catalyst composition was easily tailored to meet the demand of in situ reforming. The usage of catalyst layer as an integrated part of the traditional SOFC will provide a simple low-cost power-generating system at substantially higher fuel efficiency and faster start-ups, and may accelerate the application of SOFCs through the direct use of hydrocarbon fuels.     

Plasma-assisted catalytic reforming of propane and an assessment of its applicability on vehicles

A plasma-catalyst hybrid converter operating under atmospheric pressure was developed and a series of experiments were carried out to investigate its hydrogen-rich gas production performance. The hydrocarbon fuel used was propane. In the converter, electrons were energized by an electric field to ionize the propane and air mixture. In addition, a catalyst was installed at the downstream of the reformer to enhance the production of hydrogen-rich gas. Firstly, a parametric study of the operating parameters was carried out to assess the reforming performance of the plasma-catalyst hybrid converter on producing hydrogen-rich gas. This was followed by a feasibility assessment with an engine supplemented by the hydrogen-rich gas produced by the hybrid converter. The ratio of combustion assisting and combustion impeding (A/I) composition was analyzed. It is anticipated that the results would serve as a good guideline for setting-up parameters when reforming hydrocarbon fuels onboard vehicles.     

Progress report on the catalyst layers for hydrocarbon-fueled SOFCs

Solid oxide fuel cell (SOFC) is an energy conversion device that can directly convert the chemical energy of carbonaceous fuels into electricity. Solving the problem of carbon deposition in the conventional nickel-based anode is essential to improving the performance of SOFC when operating on carbonaceous fuels. Although impressive progress has been made in the development of alternative anode materials, nickel-based anodes with superior catalytic activity for carbonaceous fuels are still the most promising anode for the commercialization of SOFCs. The deposition of a catalyst layer with high catalytic activity for carbonaceous fuels over the nickel-based anode has been demonstrated as an effective way to enhance the performance and long-term stability of hydrocarbon-based SOFC. This review introduces the working principles of the catalyst layers, discusses the recent progress of the catalyst layer materials for hydrocarbon-fueled SOFC and issues of the different catalyst layer materials. Finally, some of the future prospects and challenges of the catalyst layers are summarized in this review article.     

A review of biomass-derived fuel processors for fuel cell systems

Fuel cell coupled with biomass-derived fuel processor can convert renewable energy into a useful form in an environmental-friendly and CO₂-neutral manner. It is considered as one of the most promising energy supply systems in the future. Biomass-derived fuels, such as ethanol, methanol, biodiesel, glycerol, and biogas, can be fed to a fuel processor as a raw fuel for reforming by autothermal reforming, steam reforming, partial oxidation, or other reforming methods. Catalysts play an important role in the fuel processor to convert biomass fuels with high hydrogen selectivity. The processor configuration is another crucial factor determining the application and the performance of a biomass fuel processing system. The newly developed monolithic reactor, micro-reactor, and internal reforming technologies have demonstrated that they are robust in converting a wide range of biomass fuels with high efficiency. This paper provides a review of the biomass-derived fuel processing technologies from various perspectives including the feedstock, reforming mechanisms, catalysts, and processor configurations. The research challenges and future development of biomass fuel processor are also discussed.     

An alternative process for gasoline fuel processors

The article explores the thermodynamics of an alternate hydrogen generation process - dry autothermal reforming and its comparison to autothermal reforming process of isooctane for use in gasoline fuel processors for SOFC. A thermodynamic analysis of isooctane as feed hydrocarbon for autothermal reforming and dry autothermal reforming processes for feed OCIR (oxygen to carbon in isooctane ratio) from 0.5 to 0.7 at 1 bar pressure under analogous thermoneutral operating conditions was done using Gibbs free energy minimization algorithm in HSC Chemistry. The trends in thermoneutral points (TNP), important product gas compositions at TNPs and fuel processor energy requirements were compared and analyzed. Dry autothermal reforming was identified as a less energy consuming alternative to autothermal reforming as the syngas can be produced with lower energy requirements at thermoneutral temperatures, making it a promising candidate for use in gasoline fuel processors to power the solid oxide fuel cells. The dry autothermal reforming process for syngas production can also be used for different fuels.     

Characterization of kilowatt-scale autothermal reformer for production of hydrogen from heavy hydrocarbons

Catalytic autothermal reforming is considered one of the most effective methods of producing hydrogen from heavy hydrocarbon fuels, such as diesel fuel, for fuel cell or emissions reduction applications. This article describes an investigation of the reactor characteristics and catalytic efficiency of a kilowatt-scale catalytic autothermal reformer currently being developed at Argonne National Laboratory. Dodecane and hexadecane were used individually as surrogates for diesel fuels to simply the reaction study and the interpretation of the test results. The reforming of these hydrocarbon fuels was examined at a variety of oxygen-to-carbon and steam-to-carbon ratios at gas hourly space velocities ranging from 10,000 to 100,000 h⁻¹. At steady state, the product composition correlated well with that calculated from thermodynamic equilibrium at a representative equivalent temperature. The oxygen-to-carbon ratio was determined to be the most significant operating parameter that influenced the reforming efficiency; the reforming efficiency (and the selectivity to CO_x) increased with increasing oxygen-to-carbon ratio up to about 0.42, at which value the maximum efficiency was attained.     

An overview of the methanol reforming process: Comparison of fuels,catalysts, reformers,and systems

One of the main challenges facing power generation by fuel cells involves the difficulties related to hydrogen storage. Several methods have been suggested and studied by researchers to overcome this problem. Among these methods, using fuel reformers as a component of the fuel cell system is a practical and promising alternative to hydrogen storage. Among many hydrogen carrier fuels used in reformers, methanol is one of the most attractive ones because of its distinctive properties. To design and improve of the methanol reformate gas fuel cell systems, different aspects such as promising market applications for reformate gas–fueled fuel cell systems, and catalysts for methanol reforming should be considered. Therefore, our goal in this paper is to provide a comprehensive overview on the past and recent studies regarding methanol reforming technologies, while considering different aspects of this topic. Firstly, different fuel reforming processes are briefly explained in the first section of the paper. Then properties of various fuels and reforming of these fuels are compared, and the characteristics of commercial reformate gas–fueled systems are presented. The main objective of the first section of the paper is to give information about studies and market applications related to reformation of various fuels to understand advantages and disadvantages of using various fuels for different practical applications. In the next sections of the paper, advancements in the methanol reforming technology are explained. The methanol reforming catalysts and reaction kinetics studies by various researchers are reviewed, and the advantages and disadvantages of each catalyst are discussed, followed by presenting the studies accomplished on different types of reformers. The effects of operating parameters on methanol reforming are also discussed. In the last section of this paper, methanol reformate gas–fueled fuel cell systems are reviewed. Overall, this review paper provides insight to researchers on what has been accomplished so far in the field of methanol reforming for fuel cell power generation applications to better plan the next stage of studies in this field.     

Design and development of a diesel and JP-8 logistic fuel processor

The paper describes the design and performance of a breadboard prototype for a 5 kW fuel-processor for powering a solid oxide fuel cell (SOFC) stack. The system was based on a small, modular catalytic Microlith auto-thermal (ATR) reactor with the versatility of operating on diesel, Jet-A or JP-8 fuels. The reforming reactor utilized Microlith substrates and catalyst technology (patented and trademarked). These reactors have demonstrated the capability of efficiently reforming liquid and gaseous hydrocarbon fuels at exceptionally high power densities. The performance characteristics of the auto-thermal reactor (ATR) have been presented along with durability data. The fuel processor integrates fuel preparation, steam generation, sulfur removal, pumps, blowers and controls. The system design was developed via ASPEN^® Engineering Suite process simulation software and was analyzed with reference to system balance requirements. Since the fuel processor has not been integrated with a fuel cell, aspects of thermal integration with the stack have not been specifically addressed.     

Reforming options for hydrogen production from fossil fuels for PEM fuel cells

PEM fuel cell systems are considered as a sustainable option for the future transport sector in the future. There is great interest in converting current hydrocarbon based transportation fuels into hydrogen rich gases acceptable by PEM fuel cells on-board of vehicles. In this paper, we compare the results of our simulation studies for 100 kW PEM fuel cell systems utilizing three different major reforming technologies, namely steam reforming (SREF), partial oxidation (POX) and autothermal reforming (ATR). Natural gas, gasoline and diesel are the selected hydrocarbon fuels. It is desired to investigate the effect of the selected fuel reforming options on the overall fuel cell system efficiency, which depends on the fuel processing, PEM fuel cell and auxiliary system efficiencies. The Aspen-HYSYS 3.1 code has been used for simulation purposes. Process parameters of fuel preparation steps have been determined considering the limitations set by the catalysts and hydrocarbons involved. Results indicate that fuel properties, fuel processing system and its operation parameters, and PEM fuel cell characteristics all affect the overall system efficiencies. Steam reforming appears as the most efficient fuel preparation option for all investigated fuels. Natural gas with steam reforming shows the highest fuel cell system efficiency. Good heat integration within the fuel cell system is absolutely necessary to achieve acceptable overall system efficiencies.     

Autothermal reforming of n-dodecane and desulfurized Jet-A fuel for producing hydrogen-rich syngas

Catalytic reforming is a technology to produce hydrogen and syngas from heavy hydrocarbon fuels in order to supply hydrogen to fuel cells. A lab-scale 2.5 kW_t autothermal reforming (ATR) system with a specially designed reformer and combined analysis of balance-of-plant was studied and tested in the present study. NiO–Rh based bimetallic catalysts with promoters of Ce, K, and La were used in the reformer. The performance of the reformer was studied by checking the hydrogen selectivity, CO_x selectivity, and energy conversion efficiency at various operating temperatures, steam to carbon ratios, oxygen to carbon ratios, and reactants' inlet temperatures. The experimental work firstly tested n-dodecane as the surrogate of Jet-A fuel to optimize operating conditions. After that, desulfurized commercial Jet-A fuel was tested at the optimized operating conditions. The design of the reformer and the catalyst are recommended for high performance Jet-A fuel reforming and hydrogen-rich syngas production.     

Improvement of the internal reforming of metal-supported SOFC at low temperatures

Automotive Solid oxide fuel cells (SOFCs) require improvements in mechanical robustness, power generation at low temperatures, and system compactness. To address these issues, we attempt to improve the internal reformation of metal-supported SOFCs (MS-SOFCs) via catalyst infiltration. After introducing nickel/gadolinium-doped ceria (Ni/GDC) nanoparticles, power densities of 1.16 Wcm⁻² with hydrogen (3%H₂O) and 0.85 Wcm⁻² with methane (Steam-to-Carbon ratio, S/C = 1.0) are obtained at 600 °C, 0.7 V. This is the highest performance achieved in previous studies on MS-SOFCs. Internal reforming with various hydrocarbon is also demonstrated. In particular 0.64 Wcm⁻² at 600 °C, 0.7 V is obtained when the fuel is iso-octane. We develop a numerical model to separately analyze reforming and electrochemical reaction. Catalyst infiltration dramatically increases the number of active sites for steam reforming. In addition, ruthenium/gadolinium-doped ceria (Ru/GDC) should be suitable as a catalyst metal at low temperatures because of the lower activation energy of steam reforming.     

天然气水蒸气重整与SOFC耦合应用

固体氧化物燃料电池（SOFC）系统具有高能源效率和使用可再生燃料的可能性,将在未来的可持续能源系统中发挥重要作用。过去几年燃料电池的发展很快,但在成本、稳定性和市场份额方面,该技术仍处于早期发展阶段。在以天然气为燃料的SOFC系统中,燃料的重整过程和燃料利用水平都可能影响系统运行的稳定性、热量和能量平衡,从而影响系统的使用寿命、输出功率和效率。因此,对燃料重整过程的设计与控制对有效的SOFC电池运行具有重要意义。对天然气在SOFC系统中的重整器配置方式（包括外重整和内重整）、重整参数和重整燃料利用方式进行了详细的综述分析,并对未来天然气SOFC系统的发展进行了展望。     

Advanced tubular solid oxide fuel cells with high efficiency for internal reforming of hydrocarbon fuels

Solid oxide fuel cells (SOFCs) constitute an attractive power-generation technology that converts chemical energy directly into electricity while causing little pollution. NanoDynamics Energy (NDE) Inc. has developed micro-tubular SOFC-based portable power generation systems that run on both gaseous and liquid fuels. In this paper, we present our next generation solid oxide fuel cells that exhibit total efficiencies in excess of 60% running on hydrogen fuel and 40+% running on readily available gaseous hydrocarbon fuels such as propane, butane etc. The advanced fuel cell design enables power generation at very high power densities and efficiencies (lower heating value-based) while reforming different hydrocarbon fuels directly inside the tubular SOFC without the aid of fuel pre-processing/reforming. The integrated catalytic layered SOFC demonstrated stable performance for >1000 h at high efficiency while running on propane fuel at sub-stoichiometric oxygen-to-fuel ratios. This technology will facilitate the introduction of highly efficient, reliable, fuel flexible, and lightweight portable power generation systems.     

Cool flame partial oxidation and its role in combustion and reforming of fuels for fuel cell systems

The purpose of this review was to integrate the most recent and relevant investigations on the auto-oxidation of fuel oils and their reforming into hydrogen-rich gas that could serve as a feed for fuel cells and combustion systems. We consider the incorporation of partial oxidation under cool flame conditions to be a significant step in the reforming process for generation of hydrogen-rich gas. Therefore, we have paid particular attention to the partial oxidation of fuels at low temperature in the cool flame region. This is still not a well-understood feature in the oxidation of fuels and can potentially serve as a precursor to low NO_x emissions and low soot formation. Pretreatment, including atomization, vaporization and burner technology are also briefly reviewed. The oxidation of reference fuels (n-heptane C₇H₁₆, iso-octane C₈H₁₈ and to a lesser extent cetane C₁₆H₃₄) in the intermediate and high temperature ranges have been studied extensively and it is examined here to show the significant progress made in modeling the kinetics and mechanisms, and in the evaluation of ignition delay times. However, due to the complex nature of real fuels such as petroleum distillates (diesel and jet fuel) and biofuels, much less is known on the kinetics and mechanisms of their oxidation, as well as on the resulting reaction products formed during partial oxidation. The rich literature on the oxidation of fuels is, hence, limited to the cited main reference fuels. We have also covered recent developments in the catalytic reforming of fuels. In the presence of catalysts, the fuels can be reformed through partial oxidation, steam reforming and autothermal reforming (ATR) to generate hydrogen. But optimum routes to produce cost effective hydrogen fuel from conventional or derivative fuels are still debatable. It is suggested that the use of products emanating from partial oxidation of fuels under cool flame conditions could be attractive in such reforming processes, but this is as yet untested. The exploitation of developments in oxidation, combustion and reforming processes is always impacted by the resulting emission of pollutants, including NO_x, SO_x, CO and soot, which have an impact on the health of the fragile ecosystem. Attention is paid to the progress made in innovative techniques developed to reduce the level of pollutants resulting from oxidation and reforming processes. In the last part, we summarize the present status of the topics covered and present prospects for future research. This information forms the basis for recommended themes that are vital in developing the next generation energy-efficient combustion and fuel cell technologies.     

Comparative study of gasoline,diesel and biodiesel autothermal reforming over Rh-based FeCrAl-supported composite catalyst

Catalytic autothermal reforming (ATR) of a number of hydrocarbon fuels was studied over composite RhCZ-S catalyst (0.24 wt% Rh supported on structured Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl carrier). Iso-octane and n-hexadecane as model compounds of gasoline and diesel fuel, respectively, showed similar properties in ATR process, indicating weak influence of molecular weight and branching degree of liquid alkanes on catalyst performance. Biodiesel ATR characteristics were similar to those of n-hexadecane ATR, as the utilized biodiesel predominantly contained alkanes, being products of fatty acid tail fragments hydrogenation. Even in the case of gasoline ATR, sufficient amount of monoaromatics did not influence a lot on the catalyst performance. Diesel ATR showed rather different situation: the catalyst tended to lose activity due to coking, and incomplete fuel conversion was observed. Analysis of unreacted fuel revealed bi- and polyaromatic compounds (mainly naphtalenes and antracenes) were difficult to convert.     

High performance of direct methane-fuelled solid oxide fuel cell with samarium modified nickel-based anode

Natural gas is one of the most attractive fuels for solid oxide fuel cell (SOFC), while the anode activity for methane fuel has a great influence on the performance and stability of SOFC. Samarium is a good catalyst promoter for methane reforming. In this work, samarium is used to modify nickel catalyst, which results in small nickel oxide particles. The SmNi-YSZ (yttria-stabilized zirconia) anode has smaller particles and better interfacial contact between nickel and YSZ compared with conventional Ni-YSZ anode. The fine structure of SmNi-YSZ anode results in high activity for electrochemical oxidation of hydrogen and low polarization resistance of the cell. The performance of SmNi-YSZ anode cell with humidified methane as fuel is greatly improved, which is similar to that with hydrogen as fuel. The maximum power densities of SmNi-YSZ anode cell are 1.56 W cm⁻² for humidified hydrogen fuel and 1.54 W cm⁻² for humidified methane fuel at 800 °C. The maximum power density is increased by 221% when samarium is used to modify Ni-YSZ anode for humidified methane fuel at 650 °C. High cell performance results in good stability of SmNi-YSZ anode cell and the cell runs stably for more than 600 min for humidified methane fuel.     

Autothermal reforming of aliphatic and aromatic hydrocarbon liquids

The process of catalytic partial oxidation of hydrocarbon liquids in the presence of steam to generate a hydrogen-rich gas is called autothermal reforming (ATR), wherein no external heat source other than reactants preheat is required. As an alternative to conventional steam reforming, the ATR process, considered for use with fuel cell power plants, may expand the range of fuels that can be converted to hydrogen to include middle distillate fuels derived from petroleum or coal.Carbon formation constitutes the main problem in autothermal reforming of heavy fuels under conditions of high thermal and conversion efficiency. A better understanding of the parametric effects on carbon formation in ATR can be obtained by studying the basic types of components that occur in heavy fuels (paraffins, aromatics, olefins and sulfur compounds). Experimental results are presented here for the ATR of paraffins (n-hexane, n-tetradecane) and aromatics (benzene, naphthalene) over supported nickel catalysts. Under similar operating conditions, reaction temperatures and intermediates, and the propensity for carbon formation in the autothermal reformer have been found to be characteristic of the hydrocarbon type used. The effects of various operating parameters on carbon formation are illustrated for the different fuels used in ATR. In tests with aliphatic/aromatic mixtures, synergistic effects have been determined.