Hydrogen production by catalytic partial oxidation of methane and propane on Ni and Pt catalysts

In recent years the catalytic partial oxidation has been taken into consideration as a suitable process for hydrogen production, because of its exothermic nature which makes the process less energy and capital cost intensive with respect to steam reforming. In this paper the behaviour of three different catalyst typologies, two based on Ni–_Al2O3${\mathrm{Al}}_2{\mathrm{O}}_3$ (different in active phase composition) and one constituted by Pt supported on _CeO2${\mathrm{CeO}}_2$, is studied for partial oxidation of propane (as representative of liquefied petroleum gas). For comparison the same catalysts have been tested also in methane partial oxidation.     

Reactivity of Ce-ZrO2 (doped with La-, Gd-, Nb-, and Sm-) toward partial oxidation of liquefied petroleum gas: Its application for sequential partial oxidation/steam reforming

Ce-ZrO₂ was found to have useful partial oxidation activity under moderate temperatures. It converted liquefied petroleum gas (LPG) to H₂, CH₄, CO and CO₂ with small amounts of C₂H₆ and C₂H₄ formations depending on the operating temperature and provided significantly greater resistance toward carbon deposition compared to conventional Ni/Al₂O₃. The doping of La, Sm and Gd over Ce-ZrO₂ considerably improved catalytic reactivity, whereas Nb-doping reduced its reactivity. It was found that the impact of doping element is strongly related to the degrees of oxygen storage capacity (OSC) and/or lattice oxygen (O_O^x) of materials. Among all catalysts, La-doped Ce-ZrO₂ was observed to have highest OSC value and was the most active catalyst. Above 850 °C with inlet LPG/O₂ molar ratio of 1.0/1.0, the main products from the reaction over La-doped Ce-ZrO₂ were H₂, CH₄, CO, and CO₂.     

On-board LPG reforming system for an LPG · hydrogen mixed combustion engine

In this study, we evaluated the properties of a reforming catalyst system for generating hydrogen from liquified petroleum gas (LPG) fuel and supplying hydrogen to an LPG engine. The fuel supply system of the LPG engine was modified in order to supply LPG to a reforming catalyst prior to combustion. A test apparatus was also built to evaluate the performance of a reforming catalyst system. Gas chromatography was used to measure H₂, N₂, O₂, CH₄, and CO emissions, while CO₂ emissions were measured using an exhaust gas analyzer. The products concentration of the reforming reactions according to reforming fuel quantity and air flow was analyzed. In actual engine operating conditions, H₂ yield and air flow were proportional, whereas H₂ yield and fuel reforming fuel quantity were inversely proportional. The experimental results of the reforming reaction under various conditions will be used as the basic data for integrating the reforming catalyst system into an actual operating engine.     

Partial oxidation of dimethyl ether by air into synthesis gas over Pt- and Rh/Ce0.75Zr0.25O2–δ catalysts

Dimethyl ether partial oxidation (DME PO) by air was studied over composite oxide Ce_0.75Zr_0.25O₂ supported Pt and Rh catalysts at temperatures 300–650 °C under atmospheric pressure, WHSV = 10 L·g_cat⁻¹·h⁻¹ and DME/O₂ molar ratio of 2. The BET, XRD, TEM and TPO techniques were used for catalyst characterization. Thermodynamic equilibrium product distribution of DME PO was calculated and used as reference data for interpreting the experimental results. Both catalysts demonstrated stable performance and coking resistance at DME PO. At 650 °C the catalysts provided complete conversion of DME and О₂ into a gas mixture of composition close to the thermodynamic equilibrium one. Synthesis gas productivity was >10 L·g_cat⁻¹·h⁻¹, its concentration in the outlet gas mixture exceeded 50 vol % that is quite suitable for solid oxide fuel cell feeding applications.     

DME/LPG燃料比例实时优化的HCCI燃烧控制新方法

根据燃料设计的思想,提出了混合燃料比例实时优化的HCCI燃烧控制新方法。在一台2135柴油机上,通过燃料成分设计（DME／LPG混合燃料）、混合气成分设计（进气添加二氧化碳）、发动机参数调整（改变压缩比）等多种模式对二甲醚HCCI燃烧进行了研究和比较。试验结果表明,在不同工况下实时进行DME／LPG比例优化,通过改变燃料的理化特性和可燃混合气的成分,实现了HCCI着火与燃烧的有效控制,能够显著拓展二甲醚HCCI燃烧的运行负荷范围,并且各个工况下热效率最高、HC和CO排放最低。     

用气相色谱法测定钢瓶内液化石油气中二甲醚含量

为了解决快速、准确测定液化石油气中二甲醚含量的问题,本文旨在提出用气相色谱法测定液化石油气中二甲醚含量的方法。用填充柱气相色谱法测定液化石油气中二甲醚的添加量。柱长10m×4mm,热导池检测器,氢气做载气,归一法计算样品中二甲醚含量。样品五次测定的相对标准偏差在1．3％～8．0％之间,检出限0．1％。     

Cermets Ni/(Ce0.9Ln0.1O1.95) (Ln = Gd,La, Nd and Sm) prepared by solution combustion method as catalysts for hydrogen production by partial oxidation of methane

Catalysts based on Ni/(Ce_0.9Ln_0.1O_1.95) (Ln = Gd, La, Nd and Sm) have been developed and tested for hydrogen production by partial oxidation of methane. The synthesis method (SCS, solution combustion synthesis) produces macroporous composite materials composed of ceramic (cer, Ce_0.9Ln_0.1O_1.95) and metallic (met, Ni) phases, without the need of an activation stage prior to the catalytic reaction. The catalysts have been characterized by different techniques: X-ray diffraction, N₂ adsorption-desorption, Hg porosimetry, Scanning Electron Microscopy, Temperature Programmed Reduction, H₂ and O₂ pulse chemisorption, X-ray photoelectron spectroscopy and Raman spectroscopy. With the exception of the lanthanum-loaded catalyst, the catalysts are highly active, selective and stable; being the one doped with gadolinium the most efficient. Correlations structure-activity point out that the excellent catalytic performance is related to the high catalytic surface area per unit mass of catalyst and to an appropriate balance of nickel dispersion to oxygen vacancies of the support.     

Hydrogen production by thermal partial oxidation of hydrocarbon fuels in porous media based reformer

The thermal partial oxidation process of methane was investigated numerically and experimentally. Thermodynamic calculations and kinetic simulation were performed using CHEMKIN tools to determine the practical operating conditions. Experimentally, a porous material-based reactor was built to perform the partial oxidation process. Temperature profiles along the reactor central axis and concentration profiles of CO, H₂, CO₂, C₂H₂ and CH₄ were measured. Two different porous structures were installed in the reaction zone: Al₂O₃ fiber static mixer structures and SiC foams. The effects of air preheating temperature, thermal load and air ratio on the reforming process were investigated for both structures. The numerical calculation showed that an air ratio down to 0.4 is a practical limit to perform the partial oxidation process. Experimentally, it was found that the air preheating temperature has no significant influence on the syngas composition; however, it does affect the soot point (λ_c). Higher heat recuperation was detected in the case of SiC foam based reformer than in the case of the Al₂O₃ mixer one. The SiC foam based reactor showed also a better performance than the Al₂O₃ regarding the soot point. For air preheating temperature of 700 °C, the current soot point for the SiC foam based reformer was 0.42, while it was 0.45 for the Al₂O₃ mixer one.     

Evaluation of the thermodynamic equilibrium of the autothermal reforming of dimethyl ether

In the present study, a thermodynamic analysis of the autothermal reforming of dimethyl ether (DME) for the production of hydrogen was carried out. The results clearly indicated that the carbon formation behavior, the boundary conditions between coke-free and coking regions, and the equilibrium composition of the reformate were dependent on the steam/DME ratio, O₂/DME ratio, temperature, and pressure of the system. For instance, carbon formation was effectively suppressed as the steam/DME ratio increased from 0 to 5, the O₂/DME ratio increased from 0 to 3, or the temperature rose from 100 to 1000 °C. In contrast, carbon formation was enhanced as the pressure was increased from 0.5 to 10 atm. The boundary temperature of coke-free operation decreased with an increase in the steam/DME and O₂/DME ratios. More specifically, at a steam/DME ratio of 3-5 and an O₂/DME ratio of 0-3, the boundary temperature ranged from 50 to 280 °C (when CH₄ formation was promoted) and 380 to 670 °C (when CH₄ formation was suppressed), respectively. Furthermore, at elevated temperatures, H₂ and CO formations were enhanced, and CH₄ formation was inhibited. The addition of steam enhanced H₂ production while reducing CO formation. On the contrary, an increase in the O₂/DME ratio reduced H₂ production while enhancing CO formation. Interestingly, the desired temperature for thermo-neutral condition, in which energy consumption was zero, can be achieved by correctly controlling the O₂/DME and steam/DME ratios.     

Yttrium-stabilized zirconia-promoted metallic nickel catalysts for the partial oxidation of methane to hydrogen

A metallic Ni catalyst has been prepared with nickel sponge and further promoted with YSZ (yttrium-stabilized zirconia) by an impregnation method. The catalysts are characterized by ICP, BET, SEM, XRD and H₂-TPR, and then studied for the partial oxidation of methane to hydrogen. The influences of reaction temperature, CH₄/O₂ ratios and gas hourly space velocity on the reaction rate are investigated. The catalyst characterization results show that the YSZ-promoted metallic Ni catalysts have high specific surface area; there is more NiO phase in the YSZ-promoted catalysts than in the metallic Ni catalyst; a mutual diffusion of Ni²⁺ and Zr⁴⁺ ions might happen between the NiO and YSZ phases. The reaction results show that the YSZ promotion increases the CH₄ conversion and the selectivities to H₂ and CO.     

Stability of Ni and Rh–Ni catalysts derived from hydrotalcite-like precursors for the partial oxidation of methane

In this work, NiMgAl and RhNiMgAl catalysts prepared from HTLCs precursors were investigated for the Partial Oxidation of Methane (POM) at 550 and 750 °C. Samples have been characterized by XRD, TPR, H₂ chemisorption, TPSR analyses, XPS, field emission scanning electron microscopy and Raman spectroscopy. NiMgAl catalysts with high Ni content (40 and 16 wt%) showed high stability and high methane conversion for POM. On the other hand those with lower Ni content (NiHT15 and NiHT25, with 6 and 4 wt%) exhibited low catalytic activity with low H₂/CO ratio (<2) and fast deactivation. In RhNiHT25 (0.6 wt. % Rh), the Ni reducibility was improved, increasing the methane conversion and hydrogen selectivity. In addition, the noticeable increase in stability was related to the absence of carbon deposition after 30 h on stream at 550 °C. These results show that RhNiHT25 is promising for application in membrane reactors to produce high purity hydrogen.     

Design of a methane processing system producing high-purity hydrogen

Design of a catalytic methane-to-proton exchange membrane fuel cell (PEMFC) grade hydrogen conversion system consisting of indirect partial oxidation (IPOX), water–gas shift (WGS) and preferential carbon monoxide oxidation (PROX) reactors is investigated using modeling and simulation techniques. Steady-state simulation, design and sizing of reactors, which are considered to be packed-bed tubular type, are carried out for twelve different feed composition and PEMFC power output configurations, namely (CH₄/O₂, H₂O/CH₄) = (2.24, 1.17), (1.89, 1.56) and (10, 50, 100, 500, 1000, 1500 W). For every configuration, material balance calculations are executed to obtain the flow rates of each species at each stream. These results are then used as boundary conditions to estimate the catalyst weights in each reactor via simulations conducted using a one-dimensional pseudo-homogeneous reactor model. Finally, reactor and catalyst particle dimensions are estimated by considering pressure drop and a set of criteria to quantify interfacial heat and intraparticle mass transfer resistances and fluid flow characteristics in packed beds. The total catalyst quantity is found to increase almost linearly with the PEMFC power output at both feed compositions. Total system volume, excluding piping, pumping, heat exchange and other peripheral units, is estimated to be 6.3, 40.3, 83.4, 488, 985 and 1527 cm³ for 10, 50, 100, 500, 1000 and 1500 W operations, respectively. WGS unit requires the highest space corresponding to ca. 50% of the total reactor volume, followed by IPOX (ca. 39%) and PROX (ca. 11%) reactors. Power densities, based on the weight and volume of the reactors are estimated as 1.1 kW/kg and 1.2 kW/l, respectively.     

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.     

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.     

Effective suppression of deactivation by utilizing Ni-doped ordered mesoporous alumina-supported catalysts for the production of hydrogen and CO gas mixture from methane

Several different kinds of ordered mesoporous alumina (OMA)-supported and Ni-doped OMA-supported Ni catalysts have been prepared for catalytic partial oxidation of methane (CPOM) to produce hydrogen and CO gas mixture. The Ni metal was incorporated in various ways of the impregnation, the doping, and the partial doping followed by impregnation. The prepared OMA-supported catalysts showed a wormhole-like, pseudo-hexagonal structure. By incorporating Ni in the OMA matrix during synthesis of supports, the resulting catalysts showed better-distributed and less-sintered nanocrystals even after CPOM at elevated temperature for over 100 h. By employing the partial doping of Ni followed by impregnation of Ni, the prepared CPOM catalyst was found more productive due to the well-distributed and well-anchored Ni nanocrystals inside the OMA matrix and the confined ordered mesopores as well. Through the test under non-stoichiometric feed ratio, the catalyst prepared only by impregnation was found vulnerable to carbon deposition and deactivated more rapidly. Even worse, the formation rate of carbon deposition was so fast that the test could not be conducted due to the increased pressure difference. In contrast, the highly distributed Ni nanocrystals partially or fully utilizing doping were found to have stronger resistance to carbon deposition.     

Reducing the operation temperature of a solid oxide fuel cell using a conventional nickel-based cermet anode on dimethyl ether fuel through internal partial oxidation

Dimethyl ether (DME)-oxygen mixture as the fuel of an anode-supported SOFC with a conventional nickel-cermet anode for operating at reduced temperatures is systematically investigated. The results of the catalytic tests indicate that sintered Ni-YSZ has high activity for DME partial oxidation, and DME conversion exceeds 90% at temperatures higher than 700 °C. Maximum methane selectivity is reached at 700 °C. Cell performance is observed between 600 and 800 °C. Peak power densities of approximately 400 and 1400 mW cm⁻² at 600 and 800 °C, respectively, are reached for the cell operating on DME-O₂ mixture. These values are comparable to those obtained using hydrogen as a fuel, and cell performance is reasonably stable at 700 °C for a test period of 340 min. SEM results demonstrate that the cell maintains good geometric integrity without any delimitation of respective layer after the stability test, and EDX results show that carbon deposition occurrs only at the outer surface of the anode. O₂-TPO analysis shows that carbon deposition over the Ni-YSZ operating on DME is greatly suppressed in the presence of oxygen. Internal partial oxidation may be a practical way to achieve high cell performance at intermediate-temperatures for SOFCs operating on DME fuel.     

一种用于液化燃料的电控共轨式喷射系统

介绍了一种新的电控共轨式燃油喷射系统。该系统根据各种液化代用燃料的特殊性质,采用电子控制技术和共轨式喷射原理,能够满足多种液化代用燃料在发动机上应用的要求。同时研究了这种系统的喷射特性,并以柴油为燃料进行了发动机台架试验,验证了系统的可行性。     

Further performance enhancement of a DME-fueled solid oxide fuel cell by applying anode functional catalyst

In order to increase the coking resistance of SOFCs operating on DME fuel, a Pt/Al₂O₃–Ni/MgO mixture catalyst was investigated for internal partial oxidation of DME. Catalytic test demonstrated the mixture catalyst has higher activity for DME partial oxidation and lower CH₄ selectivity than the individual Pt/Al₂O₃ and Ni/MgO catalysts. O₂-TPO analysis demonstrated that the mixture catalyst also had much higher coke resistance than sintered Ni-YSZ anode, especially at high O₂ to DME ratio. Raman spectroscopy of the carbon-deposited catalysts demonstrates that the graphitization degree of carbon is reduced with introducing O₂ into DME, and the carbon deposited on the mixture catalyst is almost in amorphous structure. Two operation modes of the mixture catalyst for indirect internal partial oxidation of DME, i.e, directly depositing on the anode surface and locating in the anode chamber were tried. The performance of the cells operating on DME fuel through both operation modes was studied by I–V polarization test and EIS characterization. The cells delivered attractive peak power density of around 750 mW cm⁻² by operating on DME-O₂ mixture gas, modestly lower than 1012–1065 mW cm⁻² operating on pure hydrogen fuel at 700 °C. The direct deposition of Pt/Al₂O₃–Ni/MgO onto anode surface to perform as a functional layer and a DME to O₂ ratio of 2:1 in the mixture gas is preferred to minimize coke formation and maximize power output for the cell to operate on DME fuel.