Reforming Of Diesel Research Articles

Exhaust Gas Fuel Reforming of Diesel Fuel by Nonthermal Arc Discharge for NOx Trap Regeneration Application

The present study is dedicated to the reforming of diesel fuel with diesel engine exhaust gas (i.e., air, CO2, and H2O mixture) using a nonthermal plasma torch for a NOx trap regeneration application. The plasma technology developed is based on a high voltage/low current nonthermal plasma torch. In the first part of the paper, experimental results on synthesis gas production from exhaust gas fuel reforming of diesel fuel are reported. In the second part of the paper, these experimental results are compared with a 1D multistage model using n-heptane as a surrogate molecule for diesel fuel. Two compositions of synthetic diesel engine exhaust gas, corresponding to high and low engine loads, have been studied. It has been demonstrated that the oxygen from CO2 and H2O hardly ever intervenes in the reforming reactions. In the most favorable condition corresponding to a higher O2 rate, a production of 7 × 10−3 mol·s−1 of syngas has been reached, corresponding to an energy efficiency and a conversion rate of 40% ...

Hydrogen production by reforming of diesel fuel over catalysts derived from LaCo 1− xRu xO 3 perovskites: Effect of the partial substitution of Co by Ru ( x = 0.01–0.1)

LaCo 1− x Ru x O 3 perovskites with different substitutions of Co by Ru ( x = 0.01–0.1) have been investigated as precursors of catalysts for the oxidative reforming of diesel for hydrogen production. The physicochemical characterization of LaCo 1− x Ru x O 3 perovskites revealed modifications in their structure, crystalline size and surface area with the incorporation of ruthenium into the perovskite lattice. The modifications in the perovskites affect the structure and morphology of the catalysts obtained by reduction of perovskites prior the reaction. In the catalysts derived from ruthenium-containing perovskites it is observed a better reducibility, smaller particle size of La 2O 3 and Co 0 phases and better surface concentration of Ru 0 particles with the increase in the degree of Co substitution in the perovskite. The modifications in the characteristics of the catalysts induced by the Co substitution in perovskite directly affect their catalytic behaviour in the oxidative reforming of diesel. It is found that the greater Co 0 + Ru 0 exposition and the higher extension of the La 2O 2CO 3 phase achieved in catalysts derived from perovskites with higher cobalt degree of substitution produces an increase in the activity and stability of the catalysts derived.

Zone-coated Rh-based monolithic catalyst for autothermal reforming of diesel

In this work we present results of hydrogen generation from diesel via autothermal reforming (ATR) obtained with monolithic catalysts consisting of either one or two layers of monometallic Rh and bimetallic RhPt washcoats. The Rh metal loading of the monometallic washcoats was varied between 0.5, 1.0 and 3.0wt%, while the weight ratio of Rh:Pt in the bimetallic washcoats was kept constant at 1:1. Furthermore, non-doped and CeLa-doped catalysts were also tested to detect differences in catalyst activity. The catalysts consisting of two layers of washcoats were termed zoned catalysts and each layer was applied to some given length in the axial direction of the monolith. All catalysts were prepared by impregnation using the incipient wetness technique with δ-Al2O3 as support and deposited onto 400cpsi cordierite monoliths. A total of eight catalysts, including both single layered and zone-coated, were tested in a bench-scale reactor using low-sulfur diesel as fuel at operating conditions H2O/C=2.5, O2/C=0.49 (λ=0.33), GHSV=17,000h−1 and P=1atm. The results showed that the zoned catalyst, covered with the two washcoats Rh1.0Pt1.0–Ce10La5.0/δ-Al2O3 and Rh3.0–Ce10La10/δ-Al2O3, respectively, was most active in terms of fuel conversion and hydrogen production. The zoned catalyst's long-term performance and stability was also evaluated in a full-scale reactor using low-sulfur and Fischer–Tropsch diesels at operating conditions H2O/C=2.5, O2/C=0.49 (λ=0.33), GHSV=10,800h−1, P=1atm, and at H2O/C=2.4, O2/C=0.39 (λ=0.26), GHSV=10,200h−1, P=1atm, respectively. The results showed that high fuel conversion and hydrogen production were obtained from both fuels. In addition, partial oxidation and steam reforming reactions were identified by closely studying the distribution of the analyzed product gas composition and the temperature measurements. Fresh and aged samples of the catalysts were characterized by N2-BET, H2 chemisorption, XRD, H2-TPR, O2-TPO and XPS analyses.

Effect of Hydrogen-Enriched Gas as a Reductant on the Performance of a Lean NOx Trap Catalyst for a Light-Duty Diesel Engine

Direct-injection diesel engines have become prime candidates for future transportation needs owing to their high thermal efficiency. However, the increase in nitrogen oxides (NO x) within local high-temperature regions and the increase in particulate matter within the diffusion flame region during diesel combustion are problematic and must be resolved. The utilization of NO x-absorbing catalysts, based on the concept of NO x storage and release, is one of the most promising techniques able to reduce NO x emissions within net oxidizing gas conditions. This type of NO x removal system, called the lean NO x trap (LNT) catalyst, absorbs NO x under lean exhaust gas conditions and releases NO x under rich conditions. This technology provides the advantage of high NO x conversion efficiency; however, the correct amount of reducing agent must be supplied within the catalytic converter under appropriate conditions in order to guarantee a high NO x reduction efficiency. In this research, the performance characteristics of an LNT, using a hydrogen-enriched gas as a reductant, were examined via various injection strategies and rich exhaust gas conditions. Although the hydrogen concentration of hydrogen-enriched gas also affects the LNT performance, the composition of hydrogen-enriched gas was fixed as a similar composition to that for the ideal re-forming of diesel fuel. The NO x reduction efficiency is closely connected to the injection timing and duration of reductant flow. When the injection was introduced 1.5 s after throttling, the LNT NO x conversion was maximized. However, the LNT NO x conversion decreased when the injection timing was earlier or later than 1.5 s. Because the actual rich duration of the exhaust gas is limited at a specific point during the rich operation for 3 s, the LNT NO x conversion was maximized when the hydrogen-enriched gas was injected at the minimum air-to-fuel ratio observed at the LNT inlet. By optimizing the control of this flow, the system encounters only a 1.9 per cent fuel penalty while maintaining a 90 per cent NO x reduction efficiency.

Effect of excess oxygen in plasma reforming of diesel fuel

This study investigated the plasma reforming process for diesel focusing on the relative ratio of oxygen to fuel. Excess O 2 in the partial oxidation process is known to increase the combustion portion, resulting in a decreased yield of H 2 and CO. However, in this parametric investigation, there was no apparent decrease in the H 2 and CO selectivity. Adding O 2 did not increase the portion of combustion in the overall reaction. Rather, an excess O 2 supply from partial oxidation stoichiometry resulted in an increase in CO 2 selectivity without a reduction in CO selectivity. Heavy hydrocarbon species were identified as a source of CO 2 in excess O 2 conditions due to preferential oxidative cracking. The additional oxidation of C 1–C 4 species by excess O 2 provided a minor contribution to CO 2. Excess O 2 affects soot generation characteristics by suppressing the agglomeration of soot particles, resulting in smaller particle generation. However, the oxidation of soot particles does not provide a major contribution to increasing the CO 2 selectivity. The results show that in a real reforming process, controlling the O 2 supply does not have a strong effect on the process selectivity of hydrogen.

Metal-supported Solid Oxide Fuel Cell with Diesel Reformer

1 kWe Diesel reforming sub-system was successfully developed and has been operated for 1000 hours without significant degradations. Metal-supported solid oxide fuel cell (SOFC) was also fabricated up to 10x10 cm2 scale avoiding expansive manufacturing process. Our metal-supported SOFC shows several critical and significant milestones to solve the crucial problems of ceramic-supported SOFC such as sealing and mechanical strength. In this paper performance of Diesel reformer with sulfur and low hydrocarbon remover (i.e. post-reformer) is discussed. Fabrication process of metal-supported cell developed by our group is introduced and critical issues to fabricate are discussed.

Reforming of Diesel Fuel for Hydrogen Production over Catalysts Derived from LaCo1−x M x O3 (M = Ru, Fe)

Catalysts derived from perovskite type oxides LaCo1−xMxO3 (M = Ru or Fe, x = 0.2) synthesized by a modified citrate sol–gel method were tested in the oxidative reforming of diesel for hydrogen production. Physicochemical characterization of the samples revealed differences in the surface area, crystalline size, reducibility and relative distribution of the cobalt active phase on the surface of catalyst. These properties have important implications in the catalytic behaviour of the samples in the oxidative reforming of diesel. The increase in reducibility and metal exposition implies higher reforming activity as it was observed for the catalyst derived from LaCo0.8Ru0.2O3.

Preparation of Perovskite-Based Catalysts for Diesel Reforming

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Development and evaluation of a microreactor for the reforming of diesel fuel in the kW range

Abstract The development and evaluation of a reactor based on microchannel technology for the reforming of diesel fuel is reported. The reactor itself was based on an integrated reformer/burner heat exchange reactor concept. 38 h of diesel reforming was performed at temperatures above 750 °C and at various S/C ratios, down to a minimum of 3.17, up to an electrical power equivalent of 5 kW. Over 98% total diesel conversion was observed at all times over the testing period. Variation of experimental parameters such as O/C and S/C ratios are critical for optimum operation of the reformer.

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, La 2O 3/Al 2O 3 and SiO 2) were tested. The reactor parameters were as follows: O 2/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.

Suppression of ethylene-induced carbon deposition in diesel autothermal reforming

Diesel has high-hydrogen density and well-developed infrastructure, which are beneficial properties for fuel cell commercialization. However, diesel reforming poses several technical difficulties, including carbon deposition, sulfur poisoning, and fuel delivery. Specifically, carbon deposition can cause catastrophic failures in diesel reformers. In diesel reformate gas, the concentration of ethylene, a carbon precursor, is higher than other shorter hydrocarbons (C 2–C 4). In this study, we examine the cause of ethylene formation in diesel reforming. Ethylene formation can be closely related to paraffins' decomposition from homogeneous reaction. A portion of the catalyst active sites can become occupied with aromatic compounds, degrading the activity of the catalyst. Thus, a portion of the paraffins is decomposed via non-catalytic, homogeneous reactions, accounting for much of the observed ethylene formation. In this study, reforming conditions and fuel delivery method are investigated with respect to ethylene formation. By using a diesel ultrasonic injector, reactant mixing was enhanced, resulting in suppression of ethylene formation. This subsequently inhibited the ethylene-induced carbon deposition and improved the long-term performance of diesel ATR (autothermal reforming).

Fuel constituent effects on fuel reforming properties for fuel cell applications

The effect of different types of compounds commonly found in diesel fuel (e.g., paraffins, naphthenes, and aromatics), as well as their chemical structure (e.g., branched versus linear paraffins) on fuel reforming has been investigated. Diesel reforming is very complicated because diesel is a complex mixture of hundreds of compounds with greatly different reactivities. The syngas production rates at the same conditions were observed in this order: paraffins > naphthenes ≫ aromatics. Additionally, the type of reforming performed (OSR, CPOX, or SR) as well as the process parameters (space velocity and reaction temperature) significantly affected the syngas production rates as well as carbon formation. The reactivity of one fuel component can affect the conversion pattern of others, e.g., overall yields from the reforming of a fuel mixture are not additive of yields from individual fuel components, rather the more reactive component is consumed first. Furthermore, the type of substituent in aromatics and naphthenes, the carbon chain length in n-paraffins, branching in paraffins, and degree of aromatic saturation affect the overall hydrocarbon conversion, syngas selectivity, and carbon formation. The presence of sulfur compounds in the fuel caused significant drops in H 2 yields compared to CO yields.

Hydrogen Production by Catalytic Reforming of Gaseous Hydrocarbons (Methane & LPG)

Hydrogen has been attracting great interest as a major energy source in near future. The lack of an infrastructure has led to a research effort to develop fuel processing technology for production of hydrogen. In this review, we are reporting the catalytic reforming of gaseous hydrocarbons carried out in our research group, covering dry-reforming of CH4, tri-reforming of CH4, the electrocatalytic reforming of CH4 by CO2 in the SOFC (solid oxide fuel cell) system and steam reforming of LPG. Especially, we have focused on our work, though the related work from other researchers is also discussed wherever necessary. It was found that tri-reforming of CH4 over NiO–YSZ–CeO2 catalyst was more desirable than dry-reforming of CH4 due to higher reforming activity and less carbon formation. The synthesis gas produced by tri-reforming of CH4 can be used for the production of dimethyl ether, Fischer–Tropsch synthesis fuels and high valued chemicals. To improve the problem of deactivation of catalyst due to carbon formation in the dry reforming of CH4, the internal reforming of CH4 by CO2 in SOFC system with NiO–YSZ–CeO2 anode catalyst was suggested for cogeneration of a syngas and electricity. It was found that Rh-spc-Ni/MgAl catalyst showed long term stability for 1,100 h in the steam reforming of LPG under the tested conditions. The addition of Rh to spc-Ni/MgAl catalyst restricted the deactivation of catalyst due to carbon formation in the steam reforming of LPG and diesel under the tested conditions. The result suggested that the developed reforming catalysts can be used in the reforming process of CH4, LNG and LPG for application to hydrogen station and fuel processor system.

Effects of ethylene on carbon formation in diesel autothermal reforming

In contrast to reforming of light hydrocarbons, diesel reforming has a few fundamental problems, such as coke formation in the reactor, which results in catastrophic failure of the reformer. Olefinic and aromatic hydrocarbons in diesel are known to be precursors of coke formation. Ethylene (C 2H 4) is reported to cause rapid coke formation in the reforming process. In our research, we have also found that C 2H 4 is clearly associated with carbon deposition. In addition, we revealed how C 2H 4 is produced and then converted to carbon. During this decomposition process of longer-chain paraffinic hydrocarbons, if a homogeneous mixture of fuel and oxidants (O 2 and/or H 2O) was not attained, a large quantity of C 2H 4 was produced by pyrolysis of heavier hydrocarbons at local fuel-rich areas. Thereafter C 2H 4 is transformed into carbon, in the absence of oxygen and water, through a pyrolytic process. Therefore, long-term reforming performance can be achieved by controlling the amount of C 2H 4.

Zirconia-supported LaCoO 3 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 ZrO 2-supported LaCoO 3 catalyst on its behaviour for hydrogen production by oxidative reforming of diesel has been analyzed in terms of LaCoO 3 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 LaCoO 3 deposited over ZrO 2. The use of nitrate precursors and high calcination temperature leads to the formation of LaCoO 3 perovskite structures of high grain and crystallite size on ZrO 2 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.

고체산화물 연료전지 시스템을 위한 kW급 마이크로채널 촉매 디젤 자열 개질기

Solid oxide fuel cell(SOFC) has a higher fuel flexibility than low temperature fuel cells, such as polymer electrolyte fuel cell(PEMFC) and phosphoric acid fuel cell(PAFC). SOFCs also use CO and CH₄ as a fuel, because SOFCs are hot enough to allow the CH₄ steam reformation(SR) reaction and water-gas shift(WGS) reaction occur within the SOFC stack itself. Diesel is a good candidate for SOFC system fuel because diesel reformate gas include a higher degree of CO and CH₄ concentration than other hydrocarbon(methane, butane, etc.) reformate gas. Selection of catalyst for autothermalr reforming of diesel was performed in this paper, and characteristics of reforming performance between packed-bed and microchannel catalyst are compared for SOFC system. The mesh-typed microchannel catalyst also investigated for diesel ATR operation for 1㎾-class SOFC system. 1㎾-class diesel microchannel ATR was continuously operated about 30 hours and its reforming efficiency was achieved nearly 55%.

Autothermal reforming of simulated and commercial diesel: The performance of zirconia-supported RhPt catalyst in the presence of sulfur

Simulated and commercial low-sulfur diesel fuels (S<10ppm) were studied in autothermal reforming (ATR) on Rh and Pt and bimetallic RhPt catalysts supported on ZrO2 with the aim of obtaining fuel gas suitable for solid oxide fuel cell applications.In ATR of the simulated fuels, the catalysts deactivated markedly in the presence of H2S, whereas in ATR of simulated fuels in the presence of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and in ATR of commercial diesel the catalyst deactivated only slightly over several hours. In view of its different effect, H2S cannot be considered a suitable model compound for heterocyclic sulfur compounds present in commercial low-sulfur fuels.In ATR of commercial low-sulfur diesel, carbon formation increased with the Pt loading, whereas sulfur deposition on the catalyst was strongest on the monometallic Rh/ZrO2. Furthermore, less carbon was deposited on the RhPt catalyst in the presence than absence of H2S, as sulfur blocked the catalyst active sites. The catalyst could be reactivated by stopping the H2S flow.

Reforming of Diesel Fuel in a Micro Reactor

Reforming of diesel fuel is challenging but very attractive for hydrogen production. It can facilitate the market entrance of fuel cells due to the existing infrastructure for distribution of diesel fuel. Reforming in micro reactors enables good heat transfer and therefore small and compact fuel processing systems e.g. for electrical energy generation in auxiliary power units.Due to the complexity of diesel, reforming of different diesel components and conversion intermediates in a micro reactor is investigated systematically within this work. Methane and propane were applied as conversion intermediates and hexadecane as a diesel surrogate. All experiments were conducted over a rhodium catalyst on Al2O3 or CeO2.For evaporation of the higher boiling hydrocarbons a micro structured injection nozzle was fabricated to create a fine hydrocarbon spray which evaporates in water vapour. Furthermore a complex gas chromatographic method to analyse hydrocarbons up to C16 and the permanent gases in one analysis run was developed.Experimental results show that the turnover frequency of the fuel molecules in the feed decreases linearly for straight chain hydrocarbons with an increasing number of carbon atoms. Calculations show that the observed conversions and product gas compositions are close to the thermodynamic equilibrium. The catalyst system Rh/CeO2 offers better reforming performance and higher resistance to coking apparently due to less acidic sites compared to Al2O3 and the oxygen storage capacity of CeO2.The ongoing work will examine the reforming behaviour of more model diesel fuel components e.g. mixtures of hexadecane and methylnaphthalene or synthetic diesel fuel. Experiments will be conducted in an optimised micro reformer, which disposes the heating energy by burning e.g. fuel cell off-gases. This also offers the consideration of start up and load changing behaviour.

Reforming of diesel fuel in a micro reactor for APU systems

Reforming of diesel fuel in micro reactors is a challenging but very attractive way for converting conventional fuel in a hydrogen rich gas for fuel cells applied for electrical energy generation, e.g. in auxiliary power units. To understand diesel reforming and to compare the process with reforming of other substances, the reforming of possible diesel conversion intermediates (methane and propane) and of a first diesel surrogate, hexadecane, was examined isothermally in a microchannel reactor in this study using rhodium as catalyst. The product analysis was established with a special method on a gas chromatograph to analyse all substances in one run. It was observed that branched feed molecules are converted faster on the rhodium catalyst than the unbranched molecules, latter ones exhibiting a reciprocal dependency of turnover frequency on carbon atoms per molecule. These observations are a first hint for the kinetics of the reforming. In higher hydrocarbons the CH groups seem to be converted more easily than CH2. CC bonds seem to be converted in an adsorbed state of both C due to the reciprocal dependency and due to negligible byproduct formation. Moreover, the negligible byproduct formation and the reciprocal dependency lead to the assumption that most of the conversion in the microchannels is performed on the catalyst surface and not in the gas phase.

Diesel evaporation as the first step of hydrogen production

Diesel constitutes the major fuel utilized in ships. Hence, diesel reforming is foreseen as one of the options for marine fuel cell applications. Evaporation of diesel fuel is an important stage in the diesel reforming processes. Thermal decomposition of the heavy feedstock that occurs primarily in the high temperature domain of the evaporation process leads to carboneous material formation and may plug the evaporator. Carboneous materials can also accumulate on the catalyst surface and cause serious problems in desulfurization and pre-reformer units. The diesel evaporator design is one of the key parameters to minimize carbon formation. The operating conditions must be optimized as well. In this study, the evaporation heat was supplied by two different ways. In the first evaporation system, the evaporation heat of the diesel fuel was supplied by an electrical furnace. In the second system, diesel was evaporated in a tube-and-tube heat exchanger via indirect heat supplied by hot nitrogen gas. The latter case was chosen to simulate the utilization of fuel reforming off-gases. Results indicate that evaporation by the hot gases results in much lower thermal decomposition of the diesel fuel compared to the utilization of the electrical energy.