Catalysts For Autothermal Reforming Research Articles

Influence of Ba on Co-Al-Ba composite oxide catalysts in auto-thermal reforming of acetic acid for hydrogen production

Influence of Ba on Co-Al-Ba composite oxide catalysts in auto-thermal reforming of acetic acid for hydrogen production

Temperature and hydrogen flow rate controls of diesel autothermal reformer for 3.6 kW PEM fuel cell system with autoignition delay time analysis

In this paper catalyst temperature and hydrogen flow rate controls are an area of interest for autothermal reforming (ATR) of diesel fuel to provide continuous and necessary hydrogen flow to the on-board fuel cell vehicle system. ATR control system design is important to ensure proper and stable performance of fuel processor and fuel cell stack. Fast system response is required for varying load changes in the on-board fuel cell system. To cope with control objectives, a combination of PI and PID controllers are proposed to keep the controlled variables on their setpoints. ATR catalyst temperature is controlled with feedback PID controller through variable OCR (oxygen to carbon ratio) manipulation and kept to the setpoint value of 900 °C. Additionally diesel auto-ignition delay time is implemented through fuel flow rate delay to avoid complete oxidation of fuel. Hydrogen flow rate to the fuel cell stack is kept to setpoint of required hydrogen flow rate according to fuel cell load current using PI controller. An integrated dynamic model of fuel processor and fuel cell stack is also developed to check the fuel cell voltage. Product gas composition of 35, 18 and 4% is achieved for hydrogen, nitrogen, and carbon dioxide, respectively. The results show fast response capabilities of fuel processor following the fuel cell load change and successfully fulfills the control objectives.

Development of Supported Ni Catalysts for Autothermal Reforming of Methane

Development of Supported Ni Catalysts for Autothermal Reforming of Methane

Start-up strategy of a diesel reformer using the decomposition heat of hydrogen peroxide for subsea applications

A diesel reformer start-up strategy using hydrogen peroxide (H2O2) decomposition heat is first proposed for subsea applications such as submarines and unmanned underwater vehicles (UUVs), requiring no oxygen. H2O2 can supply not only both the oxygen and steam required for the diesel autothermal reforming (ATR) reaction but also heat via the catalytic H2O2 decomposition reaction. We utilize the high-quality heat from H2O2 for the reformer start-up by evaporating and chemically decomposing the 50 wt% concentration H2O2. A comparative reformer start-up strategy study is performed between conventional diesel ATR and diesel-H2O2 ATR using a 1 kWe-class diesel reformer. For the conventional start-up, three steps of partial oxidation, partial load ATR, and full load ATR are required to heat the ATR reformer after electrically preheating the ATR catalyst. However, the proposed strategy requires only one full load ATR step after preheating the ATR catalyst using H2O2 decomposition heat. With the suggested start-up strategy, a simplified sequence with negligible temperature fluctuations and a 57% start-up time reduction are achieved. We find it significant that the full load flowrate of superheated steam generation from the H2O2 decomposer is a critical factor in simplifying and shortening the start-up procedure.

Zn‐Al hydrotalcite‐derived Co x Zn y AlO z catalysts for hydrogen generation by auto‐thermal reforming of acetic acid

Auto-thermal reforming (ATR) of acetic acid (HAc) is considered as a promising route for hydrogen generation from renewable resources, while oxidation, coking, and sintering need to be addressed for durable catalysts in ATR. In the current work, Zn-Al hydrotalcite-derived CoxZnyAlOz catalysts were prepared by co-precipitation and evaluated in a fixed-bed tubular quartz continuous-flow reactor. The Co0.70Zn3.30AlO5.5 ± δ catalyst presented a HAc conversation near 100% and a stable hydrogen yield near 3.01 mol-H2/mol-HAc. The characterization results of XRD, H2-TPR, BET, SEM, XPS, and TG indicated that the hydrotalcite structure was obtained via co-precipitation method; over the hydrotalcite-derived mixed oxides, (a) the specific surface area was increased with high dispersion of Co, (b) the phases of ZnO with spinel of ZnAl2O4,CoAl2O4, Co3O4, and ZnCo2O4 were beneficial to improve resistance to coking and oxidation, and (c) the relative stability of Co species over ZnO and spinel phases helps to suppress sintering. Meanwhile, ratio of O/C and temperatures near 0.28 and 650 °C, respectively, were also evaluated and proposed as optimized conditions for hydrogen generation, and the durable Co0.70Zn3.30AlO5.5 ± δ catalyst produced a rate of 114.9 mmol-H2/s/g-catalyst in a 15-hour ATR test, showing promising potential for hydrogen generation.

Electrodeposition of NiPd Alloy in Alkaline Ni2+ – Pd2+ – Cl– – NH3 – H2O System

Synthesis of NiPd alloy is investigated in many research centers in the world mainly due to its interesting properties making possible its application as magnetic and catalytic materials. NiPd alloys were investigated also as catalysts in autothermal reforming of methane (1), counter electrode electrocatalyst in liquid-junction solar cells (2), utilization of CO2 and methane in dry reforming process (3), anodes in methanol oxidation (4) and toluene hydrogenation (5). Exchange current density versus the enthalpy of hydrogen adsorption (Log(i0)-dGMe-H) dependence allows on assumption that material composed of Ni and Pd will exhibit high catalytic properties towards hydrogen evolution reaction (HER). Previously we reported studies on electrochemical co-deposition of nickel with palladium from acidic solutions containing aquachloro- complexes of both elements (6) as well as palladium with cobalt (7, 8) and nickel with molybdenum (9). In literature, in spite of its wide application range, few reports exist concerning electrodeposition of NiPd alloys. Existing reports are focused on synthesis of NiPd alloys from suplphate-chloride (5), ethylenediamine (4) and chloride (6) based baths. In present work authors reported studies focused on electrochemical deposition in alkaline ammonia based system for first time. Described studies were started from thermodynamic and UV-Vis analysis enabling qualitative description of analysed system. Electrochemistry of Ni2+ – Pd2+ – Cl– – NH3 – H2O system was analyzed based on results of cyclic voltammetry combined with electrochemical quartz crystal microbalance (EQCM). In further step synthesized alloys were characterized towards their compositions (WD-XRF), morphology (SEM, AFM), structure (XRD) and catalytic properties towards HER.

Hydrogen production from bio-fuels using precious metal catalysts

Fuel cell systems with integrated autothermal reforming unit require active and robust catalysts for H2 production. Thus, an experimental screening of catalysts for autothermal reforming of commercial biodiesel fuel was performed. Catalysts consisted of a monolithic cordierite substrate, an oxide support (γ-Al2 O3 ) and Pt, Ru, Ni, PtRh and PtRu as active phase. Experiments were run by widely varying the O2 /C and H2 O/C molar ratios at different gas hourly space velocities. Fresh and aged catalysts were characterized by temperature programmed methods and thermogravimetry to find correlations with catalytic activity and stability.

Ni 담지 CexZr1-xO2촉매상에서 프로판의 자열개질반응

본 연구는 <TEX>$Ni/Ce_xZr_{1-x}O_2$</TEX> 촉매를 이용하여 프로판의 자열개질반응을 통한 수소제조에 관한 것이다. <TEX>$Ni/Ce_xZr_{1-x}O_2$</TEX> 촉매는 용매로서 물을 사용한 방법(CZ-W), 우레아와 물을 사용한 방법(CZ-UW), 우레아, 에탄올 및 물을 사용한 방법(CZ-UWA)으로 각각 제조하였다. 반응물질의 조성은 <TEX>$Steam/C_3H_8$</TEX>=3, <TEX>$C_3H_8/O_2$</TEX>=2.70 이었고, 반응은 상압 고정층 유통식 반응기에서 <TEX>$300{\sim}700^{\circ}C$</TEX> 온도범위에서 진행하였다. 촉매제조시 용매에 우레아 및 에탄올을 첨가할 경우 촉매의 활성이 증가하였다. CZ-UW 촉매의 경우 클러스터형태의 탄소생성에 기인한 활성점 피막으로 인해 쉽게 비활성화가 초래됐다. 하지만 CZ-UWA 촉매의 경우 반응 후 탄소가 활성에 영향을 미치지 않는 나노파이버형태로 존재하여 활성저하가 발생되지 않음을 SEM을 통해 확인했다. 또한 <TEX>$Ni/Ce_{0.75}Zr_{0.25}O_2$</TEX> 촉매의 전환율 및 수율이 더 좋게 나타났으며 또한 소량의 Cobalt를 첨가했을 때 탄소에 대한 저항성이 크게 향상됨을 TGA로 확인하였다. In this study, the catalytic performance and characterization of <TEX>$Ni/Ce_xZr_{1-x}O_2$</TEX> were investigated using an autothermal reforming (ATR) process for hydrogen production. The <TEX>$Ni/Ce_xZr_{1-x}O_2$</TEX> catalysts were prepared using the following methods: the water method (CZ-W), urea water method (CZ-UW) and urea, water and ethanol method (CZ-UWA). The performance of <TEX>$Ni/Ce_xZr_{1-x}O_2$</TEX> catalysts in autothermal reforming of propane for hydrogen production was studied in a fixed-bed flow reactor. Reaction tests were conducted by using a feed of <TEX>$H_2O/C_3H_8/O_2$</TEX>=3/1/0.37 and <TEX>$300{\sim}700^{\circ}C$</TEX>. The CZ-UW and CZ-UWA catalysts showed higher propane conversion and hydrogen yield than the CZ-W catalyst. The activity test confirmed that the improvement in the water-ethanol catalyst was due to the low level of carbon deposition. SEM showed that the surface carbon consisted of clusters on the used CZ-UW catalyst, which is incontrast to the nano-fiber morphology observed on the used CZ-UWA catalyst. It was found that the amount of carbon deposition depends on the preparation method. Especially the <TEX>$Ni/Ce_{0.75}Zr_{0.25}O_2$</TEX> was showed higher propane conversion and hydrogen yield than the other catalysts. Also TGA showed that the resistance of carbon deposition increase to Co addition.

High-Throughput Screening for the Promoters of Alumina Supported Ni Catalysts in Autothermal Reforming of Methane

The conversion of natural gas(methane) to syngas (reforming reaction) is regarded as alternative routes for production of great value compounds, such as synthetic liquid fuels and oxygenated compounds. The aim of this work is to investigate the highest activity catalyst among 30 catalyst candidates which consists of Ni-M [M (promoter) = Co, Fe, Ce] on γ-Al2O3, by combinatorial method for autothermal reforming. The catalyst candidates with different M/Ni molar ratio were prepared by the impregnation method. The consistent results were found between 32 channel reactors and single fixed bed reactor. It was found that the best catalyst is 5.54 wt%Ni-13.3wt% Ce/γ-Al2O3.

Effect of different promoters on Ni/CeZrO 2 catalyst for autothermal reforming and partial oxidation of methane

Ni/CeZrO 2 catalysts promoted by Ag, Fe, Pt and Pd were investigated for methane autothermal reforming and partial oxidation of methane. The catalysts properties were determined by BET surface area, X-ray diffraction (XRD), H 2 temperature-programmed reduction (TPR), temperature-programmed desorption of CO 2 (CO 2-TPD) and UV–vis diffuse reflectance spectroscopy (DRS). Nickel dispersions were evaluated using a model reaction, the dehydrogenation of cyclohexane. BET surface area results showed that the catalysts prepared by successive impregnation presented lower surface area which favored the smaller nickel dispersion. XRD analysis showed the formation of a ceria–zirconia solid solution. TPR experiments revealed that the addition of Pt and Pd as promoters increased the reducibility of nickel. CO 2-TPD results indicated that the AgNiCZ catalysts presented the best redox properties among all catalysts. The autothermal reforming of methane showed that, among different promoters, the sample modified with silver, AgNiCZ, presented higher methane conversion and better stability during the reaction. These results are related to the good reducibility and to the higher redox capacity observed in TPR and CO 2-TPD analysis. Samples prepared by successive impregnation technique resulted in a smaller catalytic activity. For partial oxidation of methane, just as happened in autothermal reforming, AgNiCZ also presented the best performance during the 24 h of reaction and the addition of silver by successive impregnation resulted in a lower methane conversion, probably, due to the smaller metal dispersion.

The effects of CeO 2 on the activity and stability of Pt supported catalysts for methane reforming, as addressed by in situ temperature resolved XAFS and TEM analysis

The effects of Ce as a promoter on the activity and stability of Pt/Al 2O 3 and Pt/CeO 2–Al 2O 3 catalysts for autothermal reforming and partial oxidation of methane (POM) were investigated. The Pt/CeO 2–Al 2O 3 catalyst exhibited higher activity and stability than the Pt/Al 2O 3 catalyst. Analysis by in situ X-ray absorption spectroscopy under POM conditions reveals that Pt is reduced by heating the catalysts to about 730 K. The overall first-shell coordination numbers suggest changes in Pt cluster morphology with increasing temperature. Transmission electron microscopy showed strong Pt agglomeration with time on stream for the Pt/Al 2O 3 catalyst. The higher stability of the Pt/CeO 2–Al 2O 3 catalyst was attributed to a combination of different properties: (i) hindrance of carbon deposition on the Pt surface for a reactor fed with low H 2O/CH 4 ratio; (ii) interaction of Pt O Ce species in the presence of oxygen, inhibiting vapor and diffusion transport of PtO 2 and mainly, (iii) thermal stability of the support, which prevents the loss of surface area, and consequently the sintering of the Pt.

Sulfur-tolerant Pt/Gd 2O 3–CeO 2–Al 2O 3 catalyst for high efficiency H 2 production from autothermal reforming of retail gasoline

Pt/CeO 2–Al 2O 3 catalysts with and without Gd 2O 3 additive were prepared by stepwise incipient wetness impregnation (IWI) method. The catalysts were tested for autothermal reforming (ATR) of retail gasoline containing 158–500 ppm sulfur under the optimal reaction conditions: 800 °C, gasoline WHSV of 0.9 h −1 and a H 2O/O 2/C molar ratio of 5/0.35/1. It is found that the content of Gd 2O 3 and impregnation procedure for catalyst preparation significantly affected the catalyst performance. Pt catalyst supported on the Al 2O 3 that was pre-impregnated with Ce and Gd nitrates orderly to 15 wt% CeO 2 and 1.6 wt% Gd 2O 3 was the best catalyst for ATR of gasoline with high reactivity and excellent stability. Within 1000-h ATR of retail gasoline over this catalyst, gasoline conversion was slowly decreased to 95% after 300-h run and then remained at ∼95% throughout the test, while H 2 fraction in reformate remained at ∼67% with a CH 4 fraction less than 0.6%. It is revealed that modification of Al 2O 3 with CeO 2 first and Gd 2O 3 then endowed the produced Pt catalyst with many advantageous effects such as significantly improved and stabilized Pt–CeO 2 interaction, greatly attenuated Pt-sintering, and enhanced oxygen ion conductivity of bulk CeO 2.

Effect of iron on durability of nickel-based catalysts in auto-thermal reforming of ethanol for hydrogen production

Iron-promoted nickel-based catalysts were prepared by impregnation, tested in auto-thermal reforming (ATR) of ethanol for hydrogen production, and characterized by TPR, XRD, BET, TEM, and XPS. With the introduction of iron, mixed crystals of NiAl 2O 4–FeAl 2O 4 spinel phase are formed, which results in modifications of its structural and electronic properties. The reaction results show a remarkable improvement on durability in catalytic activity as well as selectivity to hydrogen in ATR: over the 10 wt.% iron-loading nickel catalyst, conversion of ethanol at 99.61% and selectivity of hydrogen around 115% are kept at 600 °C during a 30-h test, while that of iron-free sample decreases sharply from 85.10% to 19.71% on hydrogen selectivity within a 26-h test. The improved durability is attributed to the synergistic effect of the NiAl 2O 4–FeAl 2O 4 mixed crystals that are more resistant to sintering and oxidation in the oxidative atmosphere of ATR.

Production of synthesis gas by autothermal reforming of iso-octane and toluene over metal modified Ni-based catalyst

The reforming process of gasoline is an attractive technique for fuel processor or hydrogen station applications. We investigated catalytic autothermal reforming (ATR) of iso-octane and toluene over transition metal supported catalysts. The catalysts were prepared by an incipient wetness impregnation method and characterized by N 2 physisorption, XRD, and TEM techniques before and after the reaction. Many of the tested catalysts displayed reasonably good activity towards the reforming reactions of iso-octane. Especially, Ni/Fe/MgO/Al 2O 3 catalyst showed more activity than the other catalysts tested in this study including commercial HT catalyst. Ni/Fe/MgO/Al 2O 3 catalyst showed good stability for 700 h in the ATR of iso-octane. No major change was observed in catalytic activity in ATR of iso-octane or in the structure of catalyst. Since iso-octane, toluene are surrogates of gasoline, Ni/Fe/MgO/Al 2O 3 catalyst can be considered as ATR catalyst for gasoline fuel processor and hydrogen station systems.

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/Al 2O 3 and Pt–Ni/CeO 2 or molybdenum carbide catalysts were compared to those of commercial NiO/CaO/Al 2O 3 and Cu/Zn/Al 2O 3 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/Al 2O 3 catalyst was passed through Fe 3O 4–Cr 2O 3 catalyst for HTS and Mo 2C or Pt–Ni/CeO 2 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.

Experimental studies of pure hydrogen production in a commercialized fluidized-bed membrane reactor with SMR and ATR catalysts

The operating performance of a bubbling fluidized-bed membrane reactor for generating hydrogen was investigated using Pd–Ag planar membranes and both a steam methane reforming (SMR) catalyst and an autothermal reforming (ATR) catalyst. The reactor was mostly operated at 500– 600 ∘ C and 1500–2600 kPa. A detailed parametric study showed improved overall membrane effectiveness factors and hydrogen permeation fluxes compared with previous tests. Hydrogen permeation fluxes were 4.8– 12 Nm 3 / m 2 h for SMR catalyst operations and 9– 18 Nm 3 / m 2 h for ATR catalyst operations, significantly higher than previous hydrogen permeation fluxes reported in the literature. The ATR catalyst led to better performance than the SMR catalyst. Some catalyst particles were lost during operation with both catalysts, while the catalyst activity was stable.

Perovskite catalysts for the auto-reforming of sulfur containing fuels

The ideal fuel for PEMs and SOFC fuel cells is pure hydrogen, which is not available in nature and thus needs to be produced from other resources. It is a special task to make hydrogen from JP-8 (kerosene-based jet propulsion fuel), which consists of high hydrocarbon and aromatic compounds, as well as contains a significant amount of sulfur (up to 3000 ppm). The auto-thermal reforming (ATR) process is externally energy-intensive and cost-effective method for hydrogen generation. However, it is critical to develop highly efficient, low-cost catalyst. This paper presents a detailed description of a novel combustion approach for synthesis of complex LaFeO 3-based catalysts. The activities of these catalysts for ATR of JP-8 fuel were also tested in unique Micro-Scale Bench-Top Reactor System. Several non-noble (Me = K, Na, Li, Cs, Co, Mo) and noble metals additives (Me = Pt, Pd, Ru, Re) were tested as B-site substitution in La 0.6Ce 0.4Fe 0.8− Z Ni 0.2Me Z O 3− δ perovskite to find the compositions that possess stable and effective performance under severe sulfur containing environment. It was shown that small amounts of potassium (2 wt.%) or ruthenium (1 wt.%) doped to above perovskite structure significantly increase catalysts activity and lead to their stable performance during reforming of JP-8 fuel with up to 220 ppm of sulfur.

Integration of gasoline prereforming into autothermal reforming for hydrogen production

An integrated process for hydrogen production which couples gasoline prereforming and autothermal reforming (ATR) over nickel-based catalysts was investigated using stainless steel fixed-bed reactors. Meanwhile the integrated process was compared with the gasoline ATR process without prereforming. The results indicate that in the gasoline ATR process without prereforming, the nickel-based ATR catalyst deposited with coke after short reaction time-on-stream under the following working conditions ( T = 770 °C, P = 5.0 bar, steam-to-carbon feed ratio (S/C, mol/mol) of 2.7, oxygen-to-carbon feed ratio (O 2/C) of 0.5 and gas hourly space velocity (GHSV) of 28,000 ml g −1 h −1). Quite the contrary, in the integrated process, almost 100% gasoline conversion and 99.4% selectivity to hydrogen were obtained and maintained well under similar working conditions during 100 h reaction time-on-stream. Actually, almost coke-free operation of the process was achieved, which was confirmed by scanning electron microscopy (SEM) and O 2-TPSR characterizations of the used ATR catalyst. Reformate that contains no light alkenes or other higher hydrocarbons could be obtained from the ATR reactor. In addition, the nickel-based prereforming catalyst prepared by a coprecipitation method had high catalytic activity and promising stability.

Activity and Structure of Perovskites as Diesel‐Reforming Catalysts for Solid Oxide Fuel Cell

Recent progress in developing perovskite materials as more cost‐effective catalysts in autothermal reforming (ATR) of diesel fuel to hydrogen‐rich reformate for solid oxide fuel cell (SOFC) application is reported. Perovskite‐type metal oxides with B sites partially exchanged by ruthenium were prepared and evaluated under ATR reaction conditions. The hydrogen yield, reforming efficiency, and COx selectivity of these catalysts were investigated using diesel surrogate fuel with 50 ppm sulfur. The catalyst performances have approached or exceeded a benchmark, high‐cost rhodium‐based material. In parallel with the reactivity study, we also investigated the physical properties of B‐site doped perovskites and their impact on the reforming performance using various characterization techniques such as BET, X‐ray powder diffraction, temperature programmable reduction, scanning electron microscopy, and synchrotron X‐ray absorption spectroscopy. We found that ruthenium is highly dispersed into perovskite lattice and its redox behavior is directly associated with reforming activity.

La–Ce–Ni–O monolithic perovskite catalysts potential for gasoline autothermal reforming system

Hydrogen generation from gasoline is essentially one of the critical technologies for the commercialization of small-scale fuel cells auxiliary/backup power systems, so catalysts suitable for autothermal reforming (ATR) of gasoline are desperately needed. La 0.8Ce 0.2NiO 3 with a crystal structure of perovskite was developed both in pellet and on cordierite substrate by citrate method. Autothermal reforming of gasoline or its surrogates, n-octane with or without thiophene additive, was carried out on either bulk perovskite pellet or monolithic perovskite catalyst. During the 220-h long-term test, the pellet catalyst exhibited high thermal stability and activity with hydrogen yield approaching to the theoretical maximum value and only minor amount of CH 4 slipping through. It possessed fairly good sulfur tolerance, almost immune to 5 ppmw sulfur although could still be seriously poisoned when subjected to high concentration of sulfur or gasoline. The monolithic perovskite catalysts were developed by screening slurries, binders as well as substrates with or without pre-washcoating CeZrO 2. The monolithic La 0.8Ce 0.2NiO 3 formed in situ on the raw cordierite monolith could be an effective catalyst for ATR of gasoline, exhibiting superior performance to the catalyst of 0.3 wt.%Rh/CeO 2–ZrO 2/cordierite at a temperature range 650–800 °C. On whatever the pellet or monolithic catalysts, the active sites were presumably the in situ reduced Ni 0 which were well dispersed and stabilized by the perovskite crystal structure. The good performances of La 0.8Ce 0.2NiO 3, better thermal stability and immunity to carbon foul and sulfur poison than LaNiO 3 could be ascribed to the increased oxygen mobility with the presence of sesquioxide of cerium.