Selection and performance comparison of jet fuel surrogates for autothermal reforming

Three fuel mixtures were investigated as possible surrogates for low-sulfur JP-8. The selected fuel mixtures were chosen based on a desire to match hydrocarbon chemical composition classes found in real jet fuels. The surrogate fuels selected consisted of single, binary and tertiary-component mixtures of n-dodecane, decalin and toluene in liquid volume ratios of 10:0:0, 9:1:0 and 7:1:2. The hydrocarbon components selected represented the largest chemical classes within JP-8 of normal paraffin, cyclo-paraffin and aromatic. The surrogate fuels and individual surrogate fuel components were reacted in an atmospheric pressure autothermal reformer with noble metal catalysts under conditions of steam-to-carbon ratio of 2.0, fuel equivalency energy flow of 3.3 kW thermal, space velocities of 21,000-28,000 h⁻¹ and variable oxygen-to-carbon ratios of 0.8-1.2. For all fuels investigated fuel conversion of greater than 96% could be achieved. The single component n-dodecane proved to be the least reactive resulting in lower hydrogen yields, lower reforming efficiency and increased olefin products in the reformate. The binary mixture of n-dodecane and decalin resulted in a closer match with JP-8, but did not correlate well in terms of fuel conversion and hydrogen yield. Aliphatic mixtures also exhibited greater olefin production. The three-component mixture of n-dodecane/decalin/toluene provided the best correlation to JP-8 and appears to be a good three-component surrogate fuel, particularly over the operating range of oxygen to carbon ratio of 0.95-1.10.     

Mixed and autothermal reforming of methane with supported Ni catalysts with a core/shell structure

Supported nickel catalysts with a core/shell structure of Ni/Al₂O₃ and Ni/MgO-Al₂O₃ synthesized under multi-bubble sonoluminescence (MBSL) conditions were tested for mixed steam and dry (CO₂) reforming and autothermal reforming of methane. In the previous tests, the supported Ni catalysts made of 10% Ni loading on Al₂O₃ or MgO-Al₂O₃ had shown good performances in the steam reforming of methane (methane conversion of 97% at 750 °C), in the partial oxidation of methane (methane conversion of 96% at 800 °C) and in dry reforming of methane (methane conversion of 96% at 850 °C) and showed high thermal stability for the first 50-150 h. In this study, the supported Ni catalysts showed good performance in the mixed and autothermal reforming of methane with their excellent thermal stability for the first 50 h. In addition, very interestingly, there was no appreciable carbon deposition on the surface of the tested catalysts after the reforming reaction.     

Autothermal reforming of diesel fuel in a structured porous metal catalyst: Both kinetically and transport controlled reaction

Autothermal reforming (ATR) of diesel fuel into syngas was studied experimentally and theoretically. The experiments were performed in a reactor consisting of two cylindrically shaped monoliths 50 × 55 mm. Different catalytically active components and supports (Co, Mn, Rh, BaO, La₂O₃/Al₂O₃ and SiO₂) were tested. The reactor parameters were as follows: O₂/C = 0.5, S/C = 1.5–1.7, T_in = 350–400 °C. The regularly structured catalytic monoliths were prepared using various metal porous supports. The most active and coke resistant catalyst was determined. The original modeling approach was based on the assumption that ATR involves two parallel reaction routes: (1) complete hydrocarbon oxidation, (2) steam reforming of hydrocarbon. The experimental data and the results of reactor modeling agreed well and allowed a conclusion that the ATR rate is controlled by inter-phase mass transfer. However, the contribution of the reaction routes (1) and (2), i.e., the distribution of hydrocarbon flux between these reactions is determined by the ratio of the reaction rate constants and oxygen concentration near the surface.     

Development of iso-octane fuel processor system for fuel cell applications

An iso-octane fuel processor system with three different reaction stages, autothermal reforming (ATR) reaction of iso-octane, high temperature shift (HTS) and low temperature shift (LTS) reactions, was developed for applications in a fuel cell system. Catalytic properties of the prepared Ni/Fe/MgO/Al₂O₃ and Pt–Ni/CeO₂ or molybdenum carbide catalysts were compared to those of commercial NiO/CaO/Al₂O₃ and Cu/Zn/Al₂O₃ catalysts for ATR and LTS reaction, respectively. It was found that the prepared catalysts formulations in the fuel processor system were more active than those of the commercial catalysts. As the exit gas of iso-octane ATR over the Ni/Fe/MgO/Al₂O₃ catalyst was passed through Fe₃O₄–Cr₂O₃ catalyst for HTS and Mo₂C or Pt–Ni/CeO₂ catalyst for LTS reaction, the concentration of CO in hydrogen-rich stream was reduced to less than 2400 ppm. The results suggest that the iso-octane fuel processor system with prepared catalysts can be applied to PEMFC system when a preferential partial oxidation reaction is added to KIST iso-octane reformer system.     

Hydrogen production for fuel cell by oxidative reforming of diesel surrogate: Influence of ceria and/or lanthana over the activity of Pt/Al2O3 catalysts

A series of Pt catalysts supported on Al₂O₃ (Pt/A), Al₂O₃-CeO₂ (Pt/A-C), Al₂O₃-La₂O₃ (Pt/A-L) and Al₂O₃-La₂O₃-CeO₂ (Pt/A-L-C) have been prepared and tested in the oxidative reforming of diesel surrogate with the aim of studying the influence of ceria and lanthana additives over the activity and stability toward hydrogen production for fuel cell application. Several characterization techniques, such as adsorption-desorption of N₂, X-ray diffraction, X-ray photoelectron spectroscopy, temperature programmed reduction, H₂ chemisorption, and thermogravimetric analysis, have been used to define textural, structural, and surface properties of catalysts and to establish relationships with their behaviour in reaction. This physicochemical characterization has shown that lanthana inhibits the formation of α phase in alumina support and decreases ceria dispersion. Activity results show a better performance of ceria-loaded catalysts, being the Pt/A-C sample the system that offers higher H₂ yields after 8 h of reaction. The greater H₂ production for ceria-loaded catalysts, particularly in the case of the system Pt/A-C, is attributed to the Pt-Ce interaction that may change the electronic properties and/or the dispersion of active metal phase. Also, the Ce^III form of Ce^IV/Ce^III redox pair enhances the adsorption of oxygen and water molecules, thus increasing the catalytic activity and also decreasing coke deposition over surface active Pt phases. Stability tests showed that catalysts in which Pt crystallites are deposited on the alumina substrate covered by a lanthana monolayer, give rise to an increase in stability toward H₂ production.     

Critical solubility of dimethyl ether (DME)+diesel fuel and dimethyl carbonate (DMC)+diesel fuel

An experimental apparatus was developed for measuring the critical solubility. The critical solubilities were determined for binary mixtures of DME+diesel fuel and DMC+diesel fuel. For DME+diesel fuel their critical solubility temperatures ranged from 272.83 to 255.13 K while the mass fractions of DME varied from 3.44 to 95.8%; For DMC+diesel fuel, their critical solubility temperatures were between 273.58 and 302.72 K while the mass fractions of DMC varied from 1.22 to 89.6%.     

燃料电池用柴油重整制氢技术现状与展望

现有储氢技术在储氢密度、能耗及相应的基础设施建设等方面存在明显短板,难以满足燃料电池技术商业化发展需求,现场制氢技术得到了广泛关注。其中,柴油重整制氢技术以其理论产氢比率高、适用领域广、基础设施完善、安全性好、成本低等优点,可广泛应用于汽车、船舶、分布式发电等民用领域以及潜艇、舰船等军事领域,成为热点研究之一。本文综述了柴油重整制氢的分类,详细介绍了蒸汽重整、部分氧化重整和自热重整制氢的反应机理,并对三种重整反应的优缺点进行了对比分析;在此基础上,概述了三种重整反应国内外研究现状。总体而言,蒸汽重整产物中氢气浓度最高但系统质量较大,比较适用于固定制氢领域;自热重整技术系统结构较为紧凑,产物氢气浓度适中,比较适用于汽车等移动制氢领域;部分氧化重整技术由于产物H₂/CO比率较低,加之反应温度较高,容易发生结焦反应,目前其应用领域还相对有限。     

Role of zeolite structure on NO reduction with diesel fuel over Pt supported zeolite catalysts

A highly desirable selective catalytic reduction (SCR) of NO with real life diesel fuel over Pt supported zeolites with different topologies (Pt-ZSM-5, Pt-FER, Pt-MOR and Pt-BEA) is studied under simulated exhaust conditions. The catalysts are characterized by CO chemisorption, NH₃-TPD and TGA. The NO conversion ability of these catalysts has been correlated with zeolite structure and acidity. Pt-MOR is found to be the most active catalyst, 90% NO conversion at 300 °C, however Pt-FER showed highly desirable low temperature window, 77% NO conversion below 260 °C. Over ZSM-5, BEA and Y with three dimensional pore structures extensive carbonaceous deposits are observed by TGA which are detrimental to NO conversion. On the other hand, FER zeolite having one dimensional pore structure did not allow extensive coke formation resulting in a highly desired low temperature NO conversion. The results suggest that, NO reduction mainly take place near the zeolite pore opening, which is in reasonable agreement considering the long and bulky molecules in diesel fuel.     

Zirconia-supported LaCoO3 catalysts for hydrogen production by oxidative reforming of diesel: Optimization of preparation conditions

The influence of calcination temperature and precursor type used in the preparation of ZrO₂-supported LaCoO₃ catalyst on its behaviour for hydrogen production by oxidative reforming of diesel has been analyzed in terms of LaCoO₃ structure. Four samples have been prepared by wetness co-impregnation with cobalt and lanthanum salts and characterized by means of XRD, BET, SEM-EDX, TXRF and XPS. Physicochemical characterization shows a great influence of the nature of precursors and calcination temperature used in the synthesis on the textural, morphological, surface and structural properties of LaCoO₃ deposited over ZrO₂. The use of nitrate precursors and high calcination temperature leads to the formation of LaCoO₃ perovskite structures of high grain and crystallite size on ZrO₂ support. On the contrary, the catalyst prepared from acetate precursors and calcined at low temperature showed perovskite crystallites of lower size. For this sample, the smaller perovskite crystallites on the catalyst at the beginning of the reaction imply higher and more stable hydrogen production for short-term test aging test.     

Assessment of pyrolysis oil as an energy source for diesel engines

This paper describes an experimental study of using tyre pyrolysis oil (TPO) obtained from waste automobile tyres by vacuum pyrolysis method, as a fuel in diesel engine. In this work, performance and emission parameters of a single cylinder water cooled diesel engine running on TPO diesel reference fuel (RF) blends in steps of 20% on volume basis of TPO, viz. TPO20 up to TPO70 were used as fuels and the results compared with diesel operation. Results indicated that reliable operation can be achieved up to 70% of TPO diesel blends. Thermal efficiencies were lower compared to diesel operation. Higher smoke, HC and CO emissions were recorded in the experimentation. Oil sticking was occasionally found on the nozzle stem and sac. There was no corrosion in the injection system after running the engine with TPO–RF blends.     

Synthesis of alumina-nitrogen-doped carbon support for CoMo catalysts in hydrodesulfurization process

More stringent environmental legislation imposes severe requirements to reduce the sulfur content in diesel to ultra-low levels with high efficient catalysts.In this paper,a series of CoMo/NDC@alumina cat-alysts were synthesized by combination of the chemical vapor deposition of nitrogen-doped carbon(NDC) using 1,10-phenanthroline and co-impregnation of Mo and Co active components.The optimal cat-alyst with additive of 25％ 1,10-phenanthroline was screened by a series of property characterization and the hydrodesulfrization (HDS) active test.The amount of "CoMoS" active phase of the optimal CoMo/C3 catalyst increased 5.3％ as compared with the CoMo/γ-Al2O3.The introduction of NDC improved the sul-fidation degree of Mo by 21.8％ as compared to the CoMo/γ-Al2O3 catalyst,which was beneficial to form more active sites.The HDS conversion of the NDC supported catalysts are higher than CoMo/γ-Al2O3 whether for the dibenzothiophene (DBT) or 4,6-dimethyl dibenzothiophene (4,6-DMDBT).Further hydroprocessing evaluation with Dagang diesel revealed that the CoMo/C3 catalyst possessed higher HDS property and the removal rate of DBTs in the diesel increased by 4％-11％ as compared to the CoMo/γ-Al2O3 catalyst.     

Methane reforming of syngas produced by co-gasification of coal and wastes. Effect of catalysts and of experimental conditions

Syngas obtained by co-gasification of coal and wastes was hot cleaned in two catalytic reactors, which allowed destroying tar and gaseous hydrocarbons with more than one carbon atom. H₂S and NH₃ contents were also significantly reduced, but CH₄ concentrations varying between 2% and 10% and small amounts of H₂S (below 100 ppmv) were still found in syngas, depending on coal type and waste composition. This paper studies the effect of experimental conditions on CH₄ destruction by reforming reactions in absence and in presence of catalysts. The effect of experimental conditions (temperature, steam flow rate and syngas composition) on CH₄ destruction and on CO conversion into CO₂ in the absence of catalyst was studied first, using the Equilibrium Reactor model from CHEMKIN modelling software. The selected experimental conditions were then tested in a fixed bed reactor with and without catalyst and the results obtained were consistent with CHEMKIN Equilibrium Reactor model predictions. Commercial Ni-based catalysts were tested (G-90 B5 and G 56B from C&CS). These catalysts were capable of significantly reducing CH₄ content, by promoting reforming reactions. At the experimental conditions used and in absence of steam, G 56B seems to be more effective in CH₄ conversion, as lower CH₄ contents were obtained. In presence of steam both catalysts were capable of completely destroying CH₄. Both catalysts also promoted WGS (water gas shift) reaction to some extent, though they are not specific catalysts for this reaction. Thus, a high increase in H₂ content was observed, due to its formation by both reforming and WGS reactions. For a complete conversion of CO into CO₂ and H₂ a specific catalyst for WGS reaction is still needed.     

工艺条件对Ni/Al2O3和Ni/CeO2-Al2O3催化剂在甲烷自热重整制氢反应中催化性能的影响

采用共沉淀法制备γ-Al₂O₃载体和不同Ce添加量的CeO₂-Al₂O₃载体,然后用浸渍法制备Ni负载质量分数10%的Ni/γ-Al₂O₃和Ni/CeO₂-Al₂O₃催化剂。在固定床微反装置中考察了反应温度、原料气配比和CH₄空速等工艺条件对Ni/γ-Al₂O₃和Ni/Ce₃₀Al₇₀O_δ催化剂在甲烷自热重整制氢反应中催化性能的影响。结果表明,添加Ce的催化剂催化性能有较大提高,在Ni/Ce₃₀Al₇₀O_δ催化剂上,反应温度750 ℃时, CH₄转化率94.3％,与Ni/Al₂O₃催化剂相比,提高20％。Ni/γ-Al₂O₃和Ni/CeO₂-Al₂O₃催化剂的CH₄转化率均随反应温度的升高而增大。原料气中n(O₂)∶n(CH₄)和n(H₂O)∶n(CH₄)的增加均能提高各催化剂的CH₄转化率。但n(O₂)∶n(CH₄)和n(H₂O)∶n(CH₄)的变化对各催化剂的催化性能的影响不同。随着n(O₂)∶n(CH₄)的增大,产物中n（H₂）∶n（CO）降低,n（CO₂）∶n(CO＋CO₂)升高;而n(H₂O)∶n(CH₄)增大时,产物中n（H₂）∶n（CO）和n（CO₂）∶n(CO＋CO₂)均升高。随着CH₄空速的增加,Ni/Al₂O₃催化剂上CH₄转化率、n（H₂）∶n（CO）和n（CO₂）∶n(CO＋CO₂)均较大程度下降;而在Ni/Ce₃₀Al₇₀O_δ催化剂上,随着CH₄空速的增加,CH₄转化率、n（H₂）∶n（CO）和n(CO₂）∶n(CO＋CO₂)变化不大。     

Co/CeO2-ZrO2 catalysts prepared by impregnation and coprecipitation for ethanol steam reforming

Co/CeO₂-ZrO₂ catalysts for the ethanol steam reforming were prepared by wet incipient impregnation and coprecipitation methods. These catalysts were characterized by nitrogen adsorption, TEM-EDX, XRD, H₂-TPR, and CO chemisorption techniques. It was found that the catalyst reducibility was influenced by the preparation methods; catalysts with different reduction behaviors in the pre-reduction showed different catalytic activities toward hydrogen production. The H₂-TPR studies suggested the presence of metal–support interactions in Co/CeO₂-ZrO₂ catalysts during their hydrogen pre-reduction, a necessary treatment process for catalysts activation. These interactions were influenced by the preparation methods, and the impregnation method is a favorable method to induce a proper metal–support effect that allows only partial reduction of the cobalt species and leads to a superior catalytic activity for the hydrogen production through ethanol steam reforming. At 450 °C, the impregnated catalyst gives a hydrogen production rate of 147.3 mmol/g-s at a WHSV of 6.3 h⁻¹ (ethanol) and a steam-to-carbon ratio of 6.5.     

Structured silicalite-1 encapsulated Ni catalyst supported on SiC foam for dry reforming of methane

Structured silicalite-1 zeolite encapsulated Ni catalyst supported on silicon carbide foam (i.e., Ni@S1-SiC) was prepared using a new yet simple one-pot method, showing the significantly improved anti-sintering and anti-coking performance in comparison with the conventional supported and encapsulated Ni catalysts (i.e., Ni/S1, Ni/S1-SiC, and Ni@S1), in catalytic dry reforming of methane (DRM). The developed Ni_0.08@S1-SiC catalyst showed high CO₂/CH₄ conversions of >85% and H₂/CO molar ratio of >0.85 at 700°C, outperforming other control catalysts under investigation. Additionally, the Ni_0.08@S1-SiC catalyst demonstrated high turnover frequency (TOF) values of ~5.6 and ~2.1/s regarding to CO₂/CH₄ conversions at 400°C, exhibiting excellent stability and low pressure-drop during 100 hr on stream evaluation. Post-reaction characterization of the used catalysts demonstrated that the combination of zeolite encapsulated Ni catalysts and SiC foam enabled well-dispersed and ultrafine Ni nanoparticles, low pressure drop and intensified transfer steps, presented excellent anti-sintering and anti-coking abilities.     

Effect of piezo-driven injection system on the macroscopic and microscopic atomization characteristics of diesel fuel spray

This study was conducted to determine the macroscopic and fuel atomization characteristics of a piezo-driven injection system and to compare it with a solenoid-driven injection system in a common-rail diesel engine.In order to obtain the macroscopic characteristics of fuel spray, the spray development process was visualized using the spray visualization system composed of a Nd:YAG laser and an ICCD camera. The injection characteristics of the fuel spray such as injection rate and injection delay profile were investigated under the various injection conditions. The injection and atomization characteristics were investigated in terms of the droplet mean axial and radial velocities, droplet diameter, and droplet distributions obtained using a phase Doppler particle analyzer (PDPA) system.It was found that the piezo-driven injection system has a short injection delay and quickly reaches the maximum injection rate compared to the solenoid-driven injection system. Spray tip penetration makes little difference; however, the spray cone angle of the piezo-driven injector is larger than that of the solenoid-driven injector. The atomization performance of the piezo-driven injection system is superior to that of the solenoid-driven injection system due to a faster response time and higher injection rate.     

Emission characteristics of diesel, gas to liquid, and biodiesel-blended fuels in a diesel engine for passenger cars

The need for diversification of energy sources and reducing various emissions including CO₂ emission in diesel engine can be met with alternative diesel fuels such as gas to liquid (GTL) and GTL–biodiesel blends. But there should be a clear understanding of the combustion and engine-out emission characteristics for alternative fuels. In this respect, an experimental study was conducted on a 2.0 L 4 cylinders turbocharged diesel engine fuelled with those alternative diesel fuels to investigate the engine-out emission characteristics under various steady-state engine operating conditions. The results revealed that noticeable decreases in THC (22–56%) and CO (16–52%) emissions for GTL–biodiesel blends were observed, whereas NOx emissions for GTL–biodiesel blends increased by a maximum of 12% compared to diesel. With regard to particle size distributions (PSDs) for GTL–biodiesel blends, the particulate matter (PM) number concentration in accumulation mode decreased, as a result of the excess oxygen content in biodiesel. Contrary to the tendency in the accumulation mode, there was a slight increase in the PM number concentration in the nucleation mode under the operating conditions wherein the exhaust gas recirculation (EGR) strategy was applied. The total PM number concentration for G + BD40 decreased by a maximum of 46% compared to that for diesel. From these results of enhanced emission characteristics compared to diesel and GTL fuel, the potential for the use of GTL–biodiesel blends could be confirmed.     

Reduction behaviors and catalytic properties for methanol steam reforming of Cu-based spinel compounds CuX2O4 (X=Fe,Mn, Al,La)

In this study, various Cu-based spinel compounds, i.e., CuFe₂O₄, CuMn₂O₄, CuAl₂O₄ and CuLa₂O₄, were fabricated by a solid-state reaction method. Reduction behaviors and morphological changes of these materials have been characterized by H₂ temperature-programmed reduction (H₂-TPR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Moreover, the catalytic properties for steam reforming of methanol (SRM) of these Cu-based spinel compounds were investigated. H₂-TPR results indicated that the reducibility of Cu-based spinel compounds was strongly dependent on the B-site component while the CuFe₂O₄ catalyst revealed the lowest reduction temperature (190 °C), followed respectively by CuAl₂O₄ (267 °C), CuMn₂O₄ (270 °C), and CuLa₂O₄ (326 °C). The reduced CuAl₂O₄ catalyst demonstrated the best performance in terms of catalytic activity. Based on the SEM and XRD results, pulverization of the CuAl₂O₄ particles due to gas evolution and a high concentration of nanosized Cu particles (≈50.9 nm) precipitated on the surfaces of the Al₂O₃ support were observed after reduction at 360 °C in H₂. The BET surface area of the CuAl₂O₄ catalyst escalated from 5.5 to 13.2 m²/g. Reduction of Cu-based spinel ferrites appear to be a potential synthesis route for preparing a catalyst with high catalytic activity and thermal stability. The catalytic performance of these copper-oxide composites was superior to those of conventional copper catalysts.     

Study of the morphology and kinetics of novel Ziegler–Natta catalysts for propylene polymerization

The morphological and kinetic characteristics of novel Ziegler–Natta catalysts were studied. Catalysts were prepared by Borealis Polymers Oy using a new synthesis technique (emulsion technology). Video microscopy was used to study the growth of single catalyst particles during polymerization in the gas and liquid phases. The distribution of single particle activity was very narrow in the catalyst without external support and was rather broad in the the silica‐supported catalyst. Video microscopy of molten polymer particles allowed observation of the process and degree of fragmentation of the catalyst particles. A correlation between the activation period during the initial stage of polymerization and catalyst fragmentation was found. Fragmentation was faster and more uniform with the catalyst without external support than with the silica‐supported catalyst. Scanning electron microscopy provided information on morphology evolution and shape replication of the catalyst particles. With the catalyst without external support, good shape replication was observed, and compact and spherical particles were formed. With the silica‐supported catalyst, shape replication was poor, and nonspherical porous polymer particle were formed. Modeling of the kinetics of propylene polymerization was done using a simple three‐step reaction scheme neglecting mass and heat transport effects. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2191–2200, 2005