Oxidative Steam Reforming Of Ethanol Research Articles

Influence of Ru-substitution on the performance of pyrochlore catalysts in oxidative steam reforming of ethanol

This study reveals that La2Zr2−xRuxO7−δ optimizes hydrogen production and ethanol conversion, particularly at a 2.66% Ru concentration, outperforming traditional 5 wt% Ru catalysts through superior long-term stability and efficiency.

Operando DRIFT-MS study of oxidative steam reforming of ethanol (OSRE) on Ni-Co mixed oxides under non-equilibrium conditions

The oxidative steam reforming of ethanol (OSRE) reaction to produce hydrogen under non-equilibrium conditions was successfully achieved using mixed oxides (MO) of Ni and Co. The catalysts were synthesized with hydrotalcite (HT) type as a precursor by simultaneous coprecipitation assisted by microwaves. The solids were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The OSRE reaction was also implemented under operando conditions by diffuse reflectance infrared spectroscopy with Fourier transform coupled to mass spectrometry (DRIFT-MS) to study the path of molecules on the surface of these solids. The results confirmed the presence of the reduced phases of Ni and Co for all the systems and revealed that the OII/OI ratio increased for the samples containing Co, indicating that the greatest number of oxygen vacancies is present in these solids, which explains their high capacity to oxidize CO to CO2 in the catalytic test. It was possible to show that the NiCo bimetallic phase presents better catalytic performance for the production of hydrogen by effectively breaking the C-C bond and oxidizing the CHx species on the surface, which is reflected in the complete conversion of ethanol and a high selectivity to CO2 and H2 over other products such as CO, CH4, and acetaldehyde.

Operando DRIFT-MS for studying the oxidative steam reforming of ethanol (OSRE) reaction

An operando DRIFT-MS system (Diffuse Reflectance Infrared Fourier Transform Spectroscopy coupled with Mass Spectrometry) was designed and set up to study the oxidative steam reforming of ethanol reaction (OSRE). This reaction involves the mixture of water, ethanol and oxygen to produce mainly hydrogen, which is a rather attractive energy carrier. Spectroscopic monitoring of the process is a key tool to contribute to the understanding of: i) the dynamics on the catalyst surface, ii) the reaction mechanism and iii) the effect of the solid's properties on the catalytic process. In this sense, this document sets forth the experimental design that allows to carry out the study under operando DRIFT-MS conditions through time for the OSRE reaction. Selection criteria for parameters, materials, configuration, and experimental conditions are included, particularly optimizing the parameters of particle size and the dilution factor with KBr as well as the temperature and flow conditions for carrying out the reaction.•Clear signals of the adsorbed species in IR that do not present interference by water in the reaction atmosphere.•Simple assembly and online product detection by MS that allow to follow the change in the products of the OSRE reaction according to the temperature.•Controlled entry of gases and quantification by loop injection.

Effect of support on the performance of PtRu-based catalysts in oxidative steam reforming of ethanol to produce hydrogen.

Oxidative steam reforming of ethanol (OSRE) to produce hydrogen has been investigated over a series of supported PtRu catalysts, with different supports. Bimetallic PtRu-based catalysts were prepared by the impregnation method using H2PtCl6 and RuCl3 as precursors. Six supports (reducible oxides of ZrO2, CeO2, and Co3O4, and irreducible oxides of ZnO, Al2O3, and NiO) were chosen to fabricate bimetallic catalysts. The catalytic performance of the OSRE reaction in the series of PtRu-based samples was evaluated using a fixed-bed flow reactor under atmospheric pressure. In front reaction, the catalyst was pre-activated by reduction under 200°C for 3h. The gas hourly space velocity was adjusted at 66,000 h-1, and the optimal molar ratios of the H2O/EtOH and O2/EtOH feeds were 4.9 and 0.44, respectively. The results indicated that the PtRu supported on the ZrO2 and CeO2 exhibited superior catalytic performance in the OSRE reaction under a low temperature (a TR of approximately 320°C) for producing the main products of H2 and CO2 with lower CO and CH4 by-products. Also, it was quite stable during a long time evaluation; the maximum YH2 maintained at 4.5-4.2, and the CO distribution approached 3.3-3.5mol% around 84h test at 340°C over the PtRu/ZrO2 catalyst.

Ruthenium substituted pyrochlore metal oxide catalysts Y2Ce2-xRuxO7-δ (x = 0–0.4) for oxidative steam reforming of ethanol

Metal oxides Y2Ce2-xRuxO7-δ (x = 0–0.4) with partial substitution of Run+ cations in the host structure were synthesized to study their catalytic activity on oxidative steam reforming of ethanol (OSRE). The samples were characterized using X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) and temperature-programmed reduction (TPR). The performances investigated by varied temperatures, Ru ion content, carbon-to-oxygen ratios and long-term stability. The lowest activation temperature on OSRE is 300 °C, which is significantly lower than that of La2Ce2-xRuxO7-δ (400 °C). The cell dimension of Y2Ce2-xRuxO7-δ was reduced compare to La2Ce2-xRuxO7-δ for the replacement of the Y3+ ion with La3+ ion. The reduced unit cell in the host structure not only increase the surface composition of the Ce4+ ions, but also induce the synergetic effect of Run+/Ru4+ (n > 4) and Ce4+/Ce3+, which lead to the enhanced OSRE activity. The optimized catalyst Y2Ce1.6Ru0.4O7-δ showed selectivity of hydrogen SH2 = 84(4)% (YH2 = 2.5(1) mol/mol EtOH) and carbon monoxide SCO = 48(1)% for long-term stability test at T = 300 °C, C/O = 0.5, and O2/C2H5OH = 1.5.

H2 production over Pt-Ni/CeO2-SiO2 via ethanol reforming in a fluidized bed

The aim of the present work is to study the application of a fluidized bed reactor for oxidative steam reforming of ethanol (OESR) over a bimetallic 3wt% Pt-10wt% Ni/CeO2-SiO2 catalyst. In particular, the effect of cerium salt precursor (nitrate (N), ammonium nitrate (AN) and acetylacetonate (AC)) on catalyst activity and stability was investigated. Three catalysts were synthetized. In all cases, the support was composed of a CeO2-SiO2 mixed oxide and the ceria content for all the catalysts was fixed to 30 wt%. The tests were carried out at a steam to ethanol ratio (f.r.) of 4 and oxygen to ethanol ratio (o.r.) of 0.5; temperature was fixed to 500°C and the weigh hourly space velocity (WHSV) to 12.3 h-1. All the samples displayed a partial deactivation with time-on-stream and ethanol was completely converted only for few hours. The initial H2 yield was very close to the predicted thermodynamic value (41.5%) and a gradual yield lowering was observed over the three catalysts. However, after 80 h of test, all the samples reached a plateau condition, with no more variation in selectivity. It is worthwhile noting that, for the sample AC, the final conversion was attested to 75%, while the other two catalysts displayed a similar behaviour with plateau conversion of almost 60%. In addition, a higher H2 yield (20%) was recorded after 100 h of test for the sample AC and the carbon formation rate measured after the test on the latter catalyst was almost 1 half of the values found for the catalysts N and AN: in the case of acetylacetonate, the organic group of the salt probably assures a templanting effect, which protects ceria molecules, improving their dispersion and increasing catalyst activity towards both reforming and carbon gasification reactions.

Kinetics of Oxidative Steam Reforming of Ethanol Over Bimetallic Catalysts Supported on CeO2–SiO2: A Comparative Study

The catalytic activity of M(Ag, Ru, Pt)–Ni/CeO2–SiO2 catalysts prepared by wet impregnation at different M loadings (0–3 wt%) for oxidative steam reforming of ethanol (OSR) was investigated at H2O/C2H5OH = 4, O2/C2H5OH = 0.5, T = 300–600 °C and WHSV = 61.7 h−1. Ag deposition on the Ni/CeO2–SiO2 sample resulted in lower H2 yields, whatever the silver content. Conversely, Ru and Pt addition improved the performances of the monometallic sample and catalyst activity was enhanced by the reduction of metals loading. Similar results were recorded over the catalysts prepared at the same metals content and a metal loading of 0.5 wt% was sufficient to reach the highest performance in the investigated temperature interval. The kinetic model able to predict the experimental results obtained over the most promising formulations includes ethanol decomposition, methane oxidation and steam reforming, water gas shift; Pt as well as Ru addition to the Ni/CeO2–SiO2 sample reduced the activation energy of the involved reactions and Ru was demonstrated to be a valid substitute of the Pt for OSR of ethanol. Thus, by employing smaller noble metal content and less expensive materials, it is possible to reduce the catalyst price.

Oxygen mobility and its relationship with the oxidative steam reforming of ethanol (OSRE)

This work focuses on the study of the relationship between oxygen mobility and catalytic activity in the oxidative steam reforming of ethanol (OSRE). The experimental strategy focused on the evaluation of redox properties using techniques such as isotopic oxygen exchange (IE 18O2), in addition to the partial oxygen storage capacity and oxygen storage complete capacity (OSC/OSCC) in mixed Ni and Co oxides. The effects of some synthesis parameters such as ultrasound and microwave assistance were also studied, as were the effects of incorporating promoters (Ce-Pr) on the oxygen mobility of the catalysts and their redox properties, establishing that the high mobility of oxygen is directly related to the performance of OSRE.

Hydrogen production by oxidative reforming of ethanol in a fluidized bed reactor using a Pt Ni/CeO2SiO2 catalyst

Abstract Oxidative steam reforming of ethanol (OESR) was investigated over Pt Ni/CeO2 SiO2 catalysts prepared from different cerium salt precursors. During stability tests performed at 500 °C, steam/ethanol ratio (S/E) of 4 and oxygen/ethanol ratio of 0.5 (O/E), the highest performance was recorded over the catalyst prepared form organic precursors. The most promising formulation was tested at different temperatures, S/E and O/E. Complete conversion was recorded during 100 h of the test at 600 °C, with a very low carbon formation rate (6.9·10−7 gcoke, oxidized·gcatalyst−1·gcarbon,fed−1·h−1). The increase of oxygen content in the reacting mixture from 5 to 7.5% had a beneficial effect on H2 yield, which rose of more than 20% after 100 h of test, and on the conversion of by-products. When steam/ethanol ratio grew from 4 to 6, a slightly lower performance improvement was observed. Therefore, the highest activity and stability during OESR over the Pt Ni/CeO2 SiO2 catalyst prepared from organic salts was achieved at 600 °C, O/E = 0.75 and S/E = 6.

Effects of Co Addition to Supported Ni Catalysts on Hydrogen Production from Oxidative Steam Reforming of Ethanol

The effects of adding Co to a Ni/MgAl2O4 catalyst on activity and stability in the oxidative steam reforming of ethanol (OSRE) were investigated. The catalysts were prepared by impregnation and cha...

Experimental and kinetic study of oxidative steam reforming of ethanol over fresh and spent bimetallic catalysts

Two bimetallic catalysts (Pt-Co and Ni-Co), supported on a CeO2-SiO2 mixed oxide and prepared by wet impregnation, were tested for oxidative steam reforming of ethanol in a fixed bed and compared with a previously investigated Pt-Ni sample. The Ni-Co catalyst displayed an improved performance compared to the Pt-Co one, in terms of both activity and stability: a mean conversion below 80% was reached over the noble metal-based catalyst after 70 h of time-on-stream at 500 °C while the same value, with a higher H2 yield, was recorded over the Ni-Co sample after 260 h. A kinetic investigation was also performed and the model assuring the best agreement with experimental data involved ethanol decomposition, methane oxidation, methane steam reforming and water gas shift reactions. The activation energies (Ea) of the above reactions over the Ni-Co catalyst were shown to be lower than those measured for the noble-metal based sample, demonstrating that a higher activity can be reached by combining nickel and cobalt: for example, in the case of methane reforming, Ea = 77.1 kJ·mol−1 was predicted against a value of 231.7 kJ·mol−1 found for the Pt-Co sample. A further kinetic study was performed over the spent catalysts and the extent of deactivation was found to be more pronounced over the Pt-Co/CeO2-SiO2 catalyst.

Oxidative steam reforming of ethanol in a fluidized bed over CeO2-SiO2 supported catalysts: effect of catalytic formulation

Abstract Pt-Ni/CeO2-SiO2, K-Pt-Ni/CeO2-SiO2 and Pt-Co/CeO2-SiO2 catalysts, prepared by wet impregnation, were reduced in situ and tested for the oxidative steam reforming of ethanol in a fluidized bed reactor at 500 °C, H2O/C2H5OH ratio of 4 and O2/C2H5OH ratio of 0.5. The results of physiochemical characterization revealed high surface area for all the catalysts, due to their deposition on silica, and considerable reducibility. However, K-addition to the Ni-based sample worsened the catalytic performance: during stability tests, a quite high carbon formation was observed upon potassium doping. Moreover, the K-containing catalyst displayed a not negligible by-products selectivity (i.e. acetaldehyde). On the other hand, Ni substitution by cobalt resulted in significantly lower ethanol conversions and hydrogen yields after 220 h of time-on-stream (TOS). However, all the catalysts at different times reached a plateau condition with no more deactivation. The best results were observed for the Pt-Ni/CeO2-SiO2 catalyst, which displayed a stable performance after 300 h of test, with a reduction in ethanol conversion of only 20%. Carbon formation was measured during the test, demonstrating that coke selectivity progressively decreased with TOS, until observing a net rate of coke formation equal to zero.

Highly active and stable Pt-Ni/CeO2-SiO2 catalysts for ethanol reforming

In this work, the Pt-Ni/CeO2-SiO2 catalyst was prepared by wet impregnation and tested for steam and oxidative steam reforming of ethanol at low-temperature (300–600 °C). The solids were characterized by X-ray fluorescence (XRF) and diffraction (XRD), nitrogen adsorption, Raman spectroscopy, temperature programmed reduction (TPR) and oxidation (TPO). Reforming tests were carried out between 10,000 and 30,000 h−1, recording total conversion at T > 450 °C, independently from the contact time and the feed composition; in addition, hydrogen yield was marginally affected by O2 co-feeding, especially in the mild-temperature range. During stability tests, carried out at 500 °C and 20,000 h−1 for at least 45 h, oxygen addition reduced carbon formation rate (CFR) of almost 30%, assuring a complete conversion for 55 h. Catalyst deposition on high surface area silica improved active species dispersion and metal-support interaction, preventing sintering phenomena and resulting in a much lesser coke selectivity than that observed for the silica-free sample.

Renewable Hydrogen from Ethanol Reforming over CeO2-SiO2 Based Catalysts

In this research, a bimetallic Pt-Ni/CeO2-SiO2 catalyst, synthetized via wet impregnation, was successfully employed for the oxidative steam reforming of ethanol between 300 and 600 °C. The reaction performance of the Pt-Ni catalyst was investigated and compared with the Ni/CeO2-SiO2, Pt/CeO2-SiO2 as well as CeO2-SiO2 sample. The bimetallic catalyst displayed the best results in terms of hydrogen yield and by-products selectivity, thus highlighting the crucial role of active species (Pt and Ni) in promoting ethanol conversion and reaching the products distribution predicted by thermodynamics. The most promising sample, tested at 500 °C for more than 120 h, assured total conversion and no apparent deactivation, demonstrating the stability of the selected formulation. By changing contact time, the dependence of carbon formation rate on space velocity was also investigated.

Oxidative steam reforming of ethanol (OSRE) over stable NiCo–MgAl catalysts by microwave or sonication assisted coprecipitation

The present paper reports the physicochemical and catalytic characterization of NiCo–MgAl mixed oxides prepared from hydrotalcite (HT) precursors using ultrasound (US) or microwave radiation (MW)-assisted coprecipitation. The US or MW use reduces the preparation time and enhance both basicity and redox properties of the material compared to the solid obtained by the conventional method (coprecipitation).The oxidative steam reforming of ethanol (OSRE) was performed during 100 h (stability test) with or without solid pre-reduction in order to understand some aspects of the OSRE mechanism when transition metal catalysts are used without activation. The results demonstrate the potential of using 1Ni1Co mixed oxides obtained by MW or US assistance which exhibited better properties and catalytic stability employing shorter synthesis times. Furthermore, experiments conducted without material pre-reduction indicate the sensitivity of OSRE to the basic strength of the surface. A marked increase in basicity decrease H2 yield because of the formation of C3 byproducts.

Oxidative steam reforming of ethanol on rhodium catalyst – I: Spatially resolved steady-state experiments and microkinetic modeling

Oxidative steam reforming of ethanol is an important process for on board production of hydrogen in fuel cell based auxiliary power systems. Although the process has been extensively studied from a catalyst perspective, accurate models that capture species and temperature information required by model-based control algorithms during operation have not yet been developed adequately. In this work, we develop a reduced micro-kinetic model for ethanol oxidative steam reforming, which can be used in computational fluid dynamics (CFD) studies and subsequently to develop model-based control strategies. We experimentally study cordierite monolith based reactors in which Rh/CeO2 catalysts are prepared by the solution-combustion method. The catalyst system is characterized by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), temperature programmed reduction and temperature programmed desorption analyses. The experimental reformer design enables measurement of species concentrations at various points along the reactor length, along with radial temperature profiles. A micro-kinetic model is adapted from the literature and validated against these experiments, with good agreement. The model results suggest a linear activation pathway for ethanol over rhodium catalysts by forming ethoxide, acetyl and acetate intermediates. After formation of single carbon species, the methane reforming pathway is followed. We expect that these studies, when coupled with transient studies will help in formulating model-based control strategies for ethanol reformers in complex fuel cell systems.

Hydrogen production from oxidative steam reforming of ethanol over Ir catalysts supported on Ce–La solid solution

The Ce1−xLaxO2−δ solid solution (CL) supported Ir (nIr/CL, n = 2, 5 and 10 wt.%) catalysts are studied for H2 production from ethanol oxidative steam reforming (OSR). The Ir dispersion, surface area, oxygen vacancy density and carbon deposition resistance of nIr/CL catalysts are greatly enhanced compared with Ir/CeO2. Among the tested catalysts, 5%Ir/CL shows the best catalytic performance, exhibiting >99.9% ethanol conversion at 400 °C with H2 yield rate of 323 μmol·gcata−1·s−1 and no obvious carbon deposition after used. The 5%Ir/CL catalyst contains the highest amount of reducible interface Ce4+, leading to a strong interaction with surface Ir species at the metal-support interface during the OSR reaction. The strong interaction induces Ir to be well dispersed on the CL support, and is associated with more redox-active sites (interface Ce4+/Ce3+), to guarantee high activity.

Hydrogen production from oxidative steam reforming of ethanol on nickel-substituted pyrochlore phase catalysts

A series of Ni-substituted pyrochlore oxides of La2Ce2−xNixO7−δ (x = 0.0–0.45) is prepared and their catalytic performance is studied. All compounds are characterized by X-ray powder diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR). Based on the XRD and XPS analyses, Ni is incorporated into the pyrochlore structure and induces the formation of Ce3+ ions. The reduction behavior and catalytic performance are directly related to the Ni content. The H2 consumption in the TPR and H2 production increases with the increased Ni content. The catalytic properties of these catalysts in the oxidative steam reforming of ethanol (OSRE) are investigated. The highest catalytic activity is obtained for the x = 0.45 sample, with a hydrogen selectivity of 82.60(5)% and the most stable catalyst is x = 0.2 with an average hydrogen selectivity of 79.0(4)%. The improved catalytic behavior can be attributed to the synergetic effect of cerium and nickel ions in the pyrochlore framework, which induces oxygen vacancies and reduces carbon formation.

Effects of the cobalt content of catalysts prepared from hydrotalcites synthesized by ultrasound-assisted coprecipitation on hydrogen production by oxidative steam reforming of ethanol (OSRE)

This paper reports a study of the catalytic performance of CoMgAl mixed oxides (with 5, 10, 15 and 20% Co content) in the oxidative steam reforming of ethanol (OSRE). The catalysts were produced by calcination of hydrotalcites prepared using the ultrasound-assisted coprecipitation method and were H2-activated before the catalytic reaction. The mixed oxides were extensively analyzed by X-ray diffraction (XRD), Raman spectroscopy, H2 temperature-programmed reduction (H2-TPR), N2 adsorption-desorption, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (SEM-EDX), finding significant differences in their structural, reduction–oxidation (redox), textural and morphological properties, which directly affect the H2 production from OSRE. Catalysts with 10 and 15% Co concentrations generate the highest H2 yields, which results from the formation of solids with an adequate active phase dispersion, an absence of agglomerates, a decreased content of Co3+ species and a high surface area.

Promoter effect of Ce and Pr on the catalytic stability of the Ni-Co system for the oxidative steam reforming of ethanol

This article presents a study of the catalytic stability of Ni and Co mixed oxides promoted with 5wt% Ce or Pr in the oxidative steam reforming of ethanol (OSRE). The catalysts were obtained by the calcination of hydrotalcite-type precursors (HT) prepared by the co-precipitation method and the reconstruction of the HT phase in the presence of aqueous (Ce/Pr-EDTA) complexes. The solids were characterized by X ray-diffraction (XRD), surface area (BET), X-ray fluorescence (XRF), temperature-programmed reduction (TPR-H2), and temperature-programmed desorption of CO2 (TPD-CO2) and O2 (TPD-O2), and they were additionally evaluated in the OSRE for 100h. The stability tests indicate that the presence of rare earths promotes a reduction of the precursors of coke. These results evidence the fundamental role of the lattice oxygen and the reducibility of the oxide phases.