Reforming Of Iso-octane Research Articles

Efficiency estimation of solid oxide fuel cell integrated with iso-octane pretreating system

The effect of iso-octane pretreatment on the efficiency of solid oxide fuel cell (SOFC) is important for selecting suitable pretreating technology. In this work, oxidation index and equivalent fuel utilization for SOFC with pure iso-octane as fuel and pre-treated iso-octane as fuel are designed in a novel way, and then the stable operating condition and efficiency of SOFC integrated with iso-octane pretreating system are investigated based on the fuel composition and anode gas characteristics. At low temperatures, solid carbon and methane are easy to be formed for iso-octane pretreatment, while H2 and CO are easy to be produced at high temperatures from thermodynamics. Steam reforming of 1 mol of iso-octane can produce 17 mol of H2 and 8 mol of CO, and thus steam reforming of iso-octane has little effect on the efficiency of SOFC. When the O/C ratio is 1.5 and the equivalent fuel utilization is 90%, the electrical efficiency of SOFC is 64.6% for steam reforming of iso-octane if the heat is provided by anode off-gas, which is 10.9% higher than that with the fuel from autothermal reforming of iso-octane and 32.6% higher than that with the fuel from catalytic partial oxidation of iso-octane. Through investigating the effect of iso-octane pretreating technology on the oxidation index of anode gas and real fuel utilizations of SOFC at different equivalent fuel utilizations, the accurate effect of iso-octane pretreatment on the efficiency of SOFC can be calculated and analyzed for iso-octane-fuelled SOFC, which can provide good guidance for the experimental process and practical application of iso-octane-fuelled SOFC.

Numerical Modeling of Hydrogen-Rich Gas Production From Gasoline Autothermal Reforming in a Plug Flow Reactor for Electric Vehicles

Abstract Due to the increase in the greenhouse effect, lowering emissions is becoming a certain issue all over the world. It is a concern to develop alternative options to minimize the spread of exhaust gases. For this purpose, in this study, the plug flow reactor in the system consisting of solid oxide fuel cell, reactor, electric motor, battery, burner, and the heat exchanger is considered. Numerical modeling of hydrogen gas generation in a plug flow reactor is studied. The reactor indicated on-board hydrogen gas generation for an electric motor automobile has not been modeled in the literature yet. Autothermal reforming of isooctane is simulated in the comsol multiphysics software program in the reactor particularly. Conversion of isooctane and H2O is examined at different overall heat transfer coefficients, input temperatures, and steam/carbon ratios. Also, there are certain differences between adiabatic and non-adiabatic conditions. The produced synthesis gas of hydrogen drastically increases in the non-adiabatic case. The obtained results from the model are compared with experimental data obtained from the literature. H2 production at the end of the autothermal reforming process indicates that the power provided from the reactor can operate a motor of an automobile. In this study, the achieved power is 65.8 kW (88 HP) and is sufficient for an automobile. Simulation results show that the reactor volume of 75 L supplies 0.18 mol−1 of H2 and 0.08 mol−1 of CO in the non-adiabatic case.

High-purity hydrogen production by sorption-enhanced steam reforming of iso-octane over a Pd-promoted Ni-Ca-Al-O bi-functional catalyst

Liquid hydrocarbon fuels produced from fossil resources are potential portable hydrogen carriers given their sufficient supply and extensively available infrastructures. However, effective approaches to hydrogen production from liquid hydrocarbons fuels are still insufficient, especially in the context of carbon emission control. Here, we report that high-purity hydrogen is produced with minimized CO2 emissions via the sorption enhanced steam reforming of iso-octane (SESRI), a model compound of gasoline. With a Pd-promoted Ni-CaO-Ca12Al14O33 bi-functional catalyst, 98.0% purity of hydrogen with 90% hydrogen yield was obtained for 10 consecutive SESRI-decarbonation cycles. XRD, SEM, and TEM techniques revealed that structural and morphological properties of the bi-functional catalyst were preserved after 10 cycles. Raman spectroscopy, CO2-TPO and TGA further demonstrated that coke formation was substantially suppressed in the presence of Pd, which played a key role in maintaining stable SESRI performance in terms of hydrogen production. Our results provide a feasible alternative for production of high-purity hydrogen from liquid fossil fuels, thereby being prospective in meeting the demand of portable hydrogen on short to medium term basis.

Hydrodynamic Effect on the Iso-octane Steam-Reforming in a Monolithic Reactor Channel

The production process of clean hydrogen by iso-octane steam reforming in a micro-reactor under atmospheric pressure, and the high temperature was investigated. The simulation is done using momentum conservation, mass conservation, and convection-diffusion equations, represented by the Navier-Stocks equations, the continuity equation, and the Steffan-Maxwell equation respectively. The resolution was performed using a differential equations discretization into their conservative by the finite element method with an unconditionally stable scheme. An analysis of the hydrodynamics of the flow effect shows that the hydrogen produced by iso-octane reforming is proportional to the mixed flow Reynolds number.

Oxidative Steam Reforming and Steam Reforming of Methane, Isooctane, and N-Tetradecane over an Alumina Supported Spinel-Derived Nickel Catalyst

The present work is focused on analyzing the potential of an alumina-supported spinel-derived nickel catalyst for oxidative steam reforming and steam reforming of model hydrocarbons present in gasoline and diesel, namely, isooctane and n-tetradecane, respectively. For comparative purposes these reforming processes have also been investigated for methane, and the catalytic behavior of a commercial rhodium catalyst has been evaluated as well. When operating with a relatively high volume hourly space velocity (equivalent to 60 000 cm3 C g–1 h–1) at a low temperature (600 °C) for 31 h time on stream, the activity of the investigated nickel catalyst is high and, more importantly, stable in the reforming of methane (by either steam reforming or oxidative steam reforming) and the oxidative steam reforming of isooctane. As for n-tetradecane a significant loss of activity with time on line is found, more pronounced under steam reforming conditions. Although the presence of oxygen helps in controlling coking, the r...

Hydrogen production from hydrocarbons over Rh supported on Ce-based oxides for automotive applications

On-board hydrogen production by reforming of fuel in the exhaust gas recirculation loop allows increasing the engine yield, thus decreasing the fuel consumption, and the formation of pollutants such as NOx. Various catalysts based on Rh supported on cerium-based oxides with alumina were prepared and characterized. Their catalytic performances were evaluated in the reforming of isooctane, chosen as model molecule, in the presence of a gas mixture of composition representative of the exhaust gas, i.e. H2O, CO2, O2 and N2. It was shown that the best performances in terms of hydrogen yield were obtained with the supports containing both ceria, in high amounts, and alumina, due to the high thermal stability of the support, the high metal dispersion and the limited sintering.

Cracking Reaction of Octane Fuel and Electrochemical Reaction on Ni-YSZ Cermet Anode of Internal Steam Reforming Solid Oxide Fuel Cell

A porous cermet of Ni and yttria stabilized zirconia (Ni-YSZ) cermet was used as an anode electrode for the octane-direct use SOFC. Influences of operating conditions, steam/carbon ratio and cell temperature on the steam internal reforming reaction and electrochemical reaction on the anode electrode were investigated. In order to understand the influence of difference in branching of carbon chain, n-octane (linear alkane) and iso-octane (branched chain alkane) were used. By the internal steam reforming of n-octane, H2, CO, CO2, CH4, and C2H6 are generated. The reforming rate of n-octane is large, while the reforming of iso-octane is slow reaction. When the fuel utilization is low, H2 and CO preferentially contribute for the power generation. The carbon deposition rate is quite large, although the initial power generation performance is high. Especially, the carbon deposition is remarkable when iso-octane is used as the fuel.

Electro-Catalytic and Fuel Cell Studies in an Internal Reforming Iso-Octane Fed SOFC Using Cu/CeO2 Composites As Anodic Electrodes

The internal reforming of iso-octane is examined in a solid oxide fuel cell of the type Cu-CeO2/YSZ/Pt. The results show that i-C8H18 is efficiently reformed by H2O to syngas over Cu/CeO2 composites, free of carbon deposits. Apart from iso-octane reforming, the products distribution at open circuit conditions is also influenced by the associated i-C8H18 thermal cracking and catalytic decomposition reactions as well as by the reverse water gas shift and methanation reactions. At closed circuit operation, the prevailing reactions are related to the electro-oxidation of H2 and CO and the co-electrolysis of H2O and CO2, at anodic and cathodic polarization conditions, respectively. AC impedance spectroscopy studies revealed that the cell and electrode resistances are substantially decreased with increasing temperature leading consequently to higher maximum power densities (12.6 mW/cm2, 850oC). The diffusion of charged and/or neutral species at the electrode surface is possibly the rate limiting step during fuel cell operation.

Behaviour of nickel–alumina spinel (NiAl2O4) catalysts for isooctane steam reforming

The suitability of NiAl2O4-based catalysts for steam reforming of isooctane, which is used here as a surrogate for gasoline, was examined at moderate temperatures (600–700 °C) during a relatively prolonged time on stream (about 30 h). A series of catalysts with a varying nickel loading in the 10–33 wt.% range were prepared by co-precipitation. This synthesis route was shown to be adequate to produce nickel/alumina catalysts with a small Ni particle size (8–10 nm). The catalytic behaviour and the extent of the observed loss of conversion were mainly controlled by the available metallic surface area. Coke formation in the form of both amorphous and graphitic filamentous carbon was identified as the main reason for deactivation. Thus, the best catalytic results corresponded to a 17 wt.Ni% loading since it showed the lowest specific carbon deposition per surface area of metallic sites. At elevated reforming temperatures (650 and 700 °C) noticeably higher conversion values were obtained and the stability was enhanced, which suggested that coking did not induce a marked effect on the catalytic behaviour.

Effect of Operating Conditions on the Electrochemical Performance of Ni-YSZ Cermet Anode for Solid Oxide Fuel Cells Using Octane Fuel

Ni-yttria stabilized zirconia (YSZ) cermet is evaluated as anode material for the solid oxide fuel cells operated by the direct internal steam reforming of iso-octane. Effect of the cell temperature and the steam/carbon ratio in the fuel was examined from the point of view of the cracking reaction performance, identification of the elementary process which governs power generation and durability. When both steam/carbon ratio and cell temperature are high enough, iso-octane is cracked to generate H2 and CO. The cracking reaction of iso-octane on the surface of the Ni-YSZ anode governs the reaction rate of the anode electrode. Outlet gas composition from the cell was analyzed by gas chromatography, and the single cell property was measured by the electrochemical method.

Autothermal reforming of iso-octane and gasoline over Rh-based catalysts: Influence of CeO2/γ-Al2O3-based mixed oxides on hydrogen production

Autothermal reforming (ATR) of iso-octane in the presence of Rh-based catalysts (0.5 wt% of Rh) supported onto γ-Al2O3, CeO2, and ZrO2 were initially carried out at 700 °C with a S/C ratio of 2.0, an O/C ratio of 0.84, and a gas hourly space velocity (GHSV) of 20,000 h−1. The activity of Rh/γ-Al2O3 was found to be higher than Rh/CeO2 and Rh/ZrO2, with H2 and (H2 + CO) yields of 1.98 and 2.48 mol/mol C, respectively, after 10 h. This Rh/γ-Al2O3 material, however, was potentially susceptible to carbon coking and produced 3.5 wt% of carbon deposits following the reforming reaction, as evidenced by C, H, N, and S elemental analysis. In contrast, Rh/CeO2 catalyst exhibited lower activity but higher stability than Rh/γ-Al2O3, with nearly no carbon being formed within 10 h. To combine the superior activity originated from Rh/γ-Al2O3 with high stability from Rh/CeO2, Rh/CeO2/γ-Al2O3 catalysts with different CeO2 contents were synthesized and examined for the ATR reactions of iso-octane. Compared to Rh/γ-Al2O3, the newly prepared Rh/CeO2/γ-Al2O3 catalysts (0.5 wt% of Rh and 20 wt% of CeO2) showed even enhanced activity during 10 h, and H2 and (H2 + CO) yields were calculated to be 2.08 and 2.62 mol/mol C, respectively. In addition, as observed with Rh/CeO2, the catalyst was further found to be stable with less than 0.3 wt% of carbon deposition after 10 h. The Rh/γ-Al2O3 and Rh/CeO2/γ-Al2O3 catalysts were eventually tested for ATR reactions using commercial gasoline that contained sulfur, aromatics, and other impurities. The Rh/γ-Al2O3 catalyst was significantly deactivated, showing decreased activity after 4 h, while the Rh/CeO2/γ-Al2O3 catalyst proved to be excellent in terms of stability against coke formation as well as activity towards the desired reforming reaction, maintaining its ability for H2 production for 100 h.

Effect of metal particle size on sulfur tolerance of Ni catalysts during autothermal reforming of isooctane

This paper describes to what extent Ni particle size affects the sulfur-tolerance of ceria-zirconia supported Ni catalysts during autothermal reforming (ATR) of isooctane. Particle size was isolated as an experimental variable by preparing catalysts with a range of Ni loadings that had nearly identical Ni surface areas. Under sulfur-free conditions, isooctane conversion and synthesis gas yield increased as the Ni particle size increased, contrary to the expectation that smaller particle sizes with lower Ni coordination would be more active. However, larger Ni particles proved to be more vulnerable to sulfur poisoning. The poor ATR activity of small Ni particles can be attributed either to a lack of sufficiently large nickel surface ensembles, or to their higher propensity to form nickel oxides under reaction conditions. This contribution suggests that, under typical ATR conditions, more highly dispersed Ni catalysts will not result in elevated sulfur tolerance.

Microchannel reactor modeling for combustion driven reforming of iso-octane

Coupling of exothermic and endothermic reactions in parallel microchannels is investigated through parametric variation of geometric and material properties in the context of hydrogen production by steam reforming of iso-octane, the surrogate for gasoline. Heat required for the endothermic reforming reaction is provided by the catalytic combustion of methane, the model compound for natural gas. The combination of steam reforming and combustion is modeled for a microchannel reactor configuration in which reactions and heat transfer take place in parallel, micro-sized, square-shaped flow paths with wall-coated catalysts. Thickness of the wall between microchannels, side-length of the microchannels and channel texture (straight-through vs. micro-baffled) are the geometric parameters being studied, while the use of different materials of construction – α-alumina, AISI-steel and iron – is also investigated. Instead of a fully-fledged 3-D mathematical model, the parametric runs are performed on a 2-D unit cell model which is justified to give results close to that of the former. When the wall thickness is increased from 1 × 10 −4 to 4 × 10 −4 m, the hydrogen yield, defined as moles of hydrogen produced per mole of iso-octane fed, increases by 42% because axial heat conduction in the wall becomes more pronounced and spreads the energy released by combustion into the reforming channel more effectively. Increase in the yield is more remarkable (110%) when the channel side-length is doubled from 2.8 × 10 −4 to 5.6 × 10 −4 m. Use of micro-baffles also enhances the hydrogen yield: in the 1–4 × 10 −4 m wall thickness range, the average increase is 16.5%, which is attributed both to the enhancement in heat transfer coefficients and axial conduction in the wall. As for the material property parameter, due to having the highest thermal conductivity, hence the ability of conducting heat axially, iron serves as the best wall material on the basis of highest hydrogen yield, compared with alumina and steel.

Hydrogen Production by Catalytic Reforming of Liquid Hydrocarbons

In this review, we are reporting the catalytic reforming of liquid hydrocarbon fuels carried out in our research group, covering the catalytic reforming of iso-octane and toluene as surrogate of gasoline, gasoline fuel processor system and steam reforming of n-hexadecane and decahydronaphthalene, main constituents of diesel. The commercial ICI reforming catalyst is prone to be poisoned by sulfur contained in iso-octane. We investigated various supported transition metal formulations and developed Ni/Fe/MgO/Al2O3 (KIST-5) catalyst with prolonged catalytic stability (>760 h), higher activity and sulfur tolerance ability over commercial ICI and HT catalysts for ATR reaction of iso-octane. We found that the concentration of CO can be reduced to <1,800 ppm by the gasoline fuel processor system charged with KIST-5 reforming catalyst, commercial HTS catalyst and KIST Pt–Ni/CeO2 LTS catalyst. The addition of Rh metal to spc-Ni/MgAl catalyst as promoter was found to be very effective in inhibiting the deactivation of spc-Ni/MgAl catalyst by sintering of reduced Ni metal at high temperature during steam reforming of n-hexadecane. A 0.3 wt% Rh loading on spc-Ni/MgAl catalyst was optimized to have the best performance for steam reforming of n-hexadecane among the prepared catalysts. The addition of Rh to spc-Ni/MgAl catalyst also restricted the deactivation of the catalyst due to carbon formation at high reaction temperature. In view point of prolonged stability and higher activity, these developed reforming catalysts have a good scope in the reforming process of gasoline and diesel for hydrogen station and fuel processor system applications.

Influence of gas-phase reactions on catalytic reforming of isooctane

The significance of gas-phase reactions in catalytic partial oxidation (CPOX) of isooctane at short contact times and high temperatures is studied experimentally and numerically to gain further understanding of hydrogen production by CPOX of logistic fuels for on-board applications. Special attention is given to the formation of coke precursors. CPOX of isooctane over a rhodium coated monolith with a molar inlet C/O ratio of 1.1 is used as reference case for a two-dimensional flow field description coupled with detailed surface and gas-phase reaction mechanisms. The results reveal catalyst coking and formation of coke precursors in the oxygen-free catalyst zone. Taking the product composition of the rich operated CPOX reactors (C/O = 1.0−1.6) as inlet composition, homogeneous conversion in the gas-phase is studied in the temperature range from 873 to 1173 K in a plug flow reactor. Conversion in the gas-phase is modeled by two detailed reaction mechanisms. Results show that most of the by-products and soot precursor species arise from unconverted fuel and not from additionally added hydrocarbons like ethylene. Both mechanisms well-predict all experimentally observed trends in gas-phase composition, both in axial reactor profiles and for different inlet compositions. The amount of soot precursors raises with increasing fuel feed corresponding to an increasing C/O ratio in CPOX experiments.

Influence of thiophene on the isooctane reforming activity of Ni-based catalysts

Influence of thiophene on the isooctane reforming activity of Ni-based catalysts

Influence of thiophene on the isooctane reforming activity of Ni-based catalysts

Abstract Catalytic reforming of liquid hydrocarbon fuels is challenging due to potential deactivation via carbon deposition and sulfur poisoning. To gain a better understanding of the effect of sulfur on the deactivation of Ni/Ce0.75Zr0.25O2 catalysts, isooctane conversion to syngas was studied in the presence of small amounts of thiophene under various O/C and H2O/C ratios representing steam reforming, partial oxidation, and autothermal reforming conditions. It was found that depending on the reaction conditions, thiophene underwent different degrees of desulfurization, leading to the formation of H2S. Under reaction conditions leading to nearly complete conversion of thiophene to H2S, the nickel catalyst lost only a small amount of its initial activity, but then maintained stable performance over longer times on stream. In contrast, reaction conditions under which thiophene emerged unconverted from the reactor led to severe and continued deactivation of the catalysts. Furthermore, co-feeding thiophene with isooctane caused significant increases in the temperature profile of the reactor and an increased amount of olefins were seen as products of the reaction, indicating that sulfur deactivated primarily catalyst sites responsible for endothermic steam reforming reactions, while having less impact on exothermic partial oxidation reactions. Controlling the reaction conditions in such a way as to generate sufficient hydrogen concentrations in the catalyst bed for effectively desulfurizing thiophene to H2S appears to be the key to maintain stable catalytic activities in the presence of sulfur compounds.

Influence of thiophene on the isooctane reforming activity of Ni-based catalysts

Catalytic reforming of liquid hydrocarbon fuels is challenging due to potential deactivation via carbon deposition and sulfur poisoning. To gain a better understanding of the effect of sulfur on the deactivation of Ni/Ce 0.75Zr 0.25O 2 catalysts, isooctane conversion to syngas was studied in the presence of small amounts of thiophene under various O/C and H 2O/C ratios representing steam reforming, partial oxidation, and autothermal reforming conditions. It was found that depending on the reaction conditions, thiophene underwent different degrees of desulfurization, leading to the formation of H 2S. Under reaction conditions leading to nearly complete conversion of thiophene to H 2S, the nickel catalyst lost only a small amount of its initial activity, but then maintained stable performance over longer times on stream. In contrast, reaction conditions under which thiophene emerged unconverted from the reactor led to severe and continued deactivation of the catalysts. Furthermore, co-feeding thiophene with isooctane caused significant increases in the temperature profile of the reactor and an increased amount of olefins were seen as products of the reaction, indicating that sulfur deactivated primarily catalyst sites responsible for endothermic steam reforming reactions, while having less impact on exothermic partial oxidation reactions. Controlling the reaction conditions in such a way as to generate sufficient hydrogen concentrations in the catalyst bed for effectively desulfurizing thiophene to H 2S appears to be the key to maintain stable catalytic activities in the presence of sulfur compounds.

Exhaust gas recirculation for on-board hydrogen production by isooctane reforming: Comparison of performances of metal/ceria–zirconia based catalysts prepared through pseudo sol–gel or impregnation methods

Isooctane reforming under conditions which are set by exhaust gas can be used to generate hydrogen on-board. Isooctane reforming reactivity tests have been performed with bimetallic catalysts Co-noble metal/ceria–zirconia, prepared either by insertion of transition metal in a ceria–zirconia matrix, either by their impregnation on ceria–zirconia. The influence of the preparation procedure on the activity of the noble metal-doped catalysts is discussed.

Neutron Diffraction Studies of Nickel-Containing Perovskite Oxide Catalysts Exposed to Autothermal Reforming Environments

Six nickel-containing perovskite oxides (La1−xSrx)M0.9Ni0.1O3±δ, where x = 0 or 0.2 and M = Cr, Fe, or Mn) were used to catalyze the autothermal reforming of isooctane (C8H18) into a hydrogen-rich gas during short-term tests at 700 °C. To determine the phase stability of the samples in the reducing environment of the reforming reactor, characterization studies of the as-prepared and tested perovskite samples were conducted using powder X-ray diffraction, powder neutron diffraction, transmission electron microscopy, and scanning electron microscopy. We determined that the reducing conditions of the microreactor caused metallic nickel to form in all six compositions. However, the extent of the nickel loss from the perovskite lattices varied: the chromium-containing compositions lost the least nickel, compared to the manganese- and iron-containing compositions, and the strontium-free compositions lost more nickel than their strontium-containing analogs. Five of the six perovskite compositions tested showed no breakdown of the perovskite lattice despite the loss of nickel from the B-sites, producing only the third example of a B-cation-deficient, 3d transition-metal-containing perovskite.