Ethanol Steam Research Articles

Bioethanol to Hydrogen Membrane Surface Characteristics Change Study

The problem of the gradual transformation of the modern economy towards greater production and consumption of ‘green’ energy requires a significant revision of existing technologies. One of the possible ways to develop green energy is the use of hydrogen as the most environmentally friendly fuel. Hydrogen can be obtained both by electrolysis, using solar energy, and using biorenewable raw materials, which can be used as ethanol, biogas, peat, agricultural waste. At the same time, for regions with a low level of illumination, the production of hydrogen by electrolysis of water using electricity generated by solar panels is inaccessible, and therefore the processing of biorenewable raw materials can take a leading position. Bioethanol is a large-capacity product with a proven production technology that widely uses waste from agriculture and wood processing. Ethanol can be used as a feedstock for hydrogen generation by means of catalytic pyrolysis or catalytic steam reforming. Membrane-catalytic steam reforming of ethanol with the production of hydrogen makes it possible to obtain hydrogen without the use of an additional purification step, however, the efficiency and stability of the membrane becomes the determining parameter that ensures the efficiency of the entire process. The degradation of inorganic membranes during catalytic steam reforming is closely related to the change in porosity as a result of hydrolysis of the membrane surface. In this connection, the study of the physicochemical properties of membranes during operation can make a significant contribution to the development of stable catalytic membranes for hydrogen production. The article presents the results of studying the physicochemical properties of an inorganic membrane for ethanol steam reforming by the method of low-temperature nitrogen adsorption. The Langmuir, Brunauer-Emmett-Taylor, t-plot and Barrett-Joyner-Halenda models were used to estimate the surface change. An increase in the surface area of mesopores during the operation of the membrane was determined.

Multi-size distributed Ni catalyst embedded in SiCxOy film by inverse microemulsion-precipitation method for ethanol steam reforming

Ni/SiCxOy catalysts with multi-size distribution of Ni particles, were prepared and supported on porous SiC ceramics by a combination of inverse microemulsion and precipitation methods, as reaction microchannels for ethanol steam reforming (ESR). The microstructure, phase composition, reduction performance, hydrogen production performance of ESR, and the type and growth of carbon deposition were investigated for Ni/SiCxOy catalysts. The Ni catalysts embedded in SiCxOy film with the appropriate amount of precipitant exhibited multi-size distribution and minimal particle size. The initial ethanol conversion rate and H2 selectivity of Ni/SiCxOy catalysts during ESR reaction were 100% and 75%, respectively, remaining 95% and 69.2% after 20 h, respectively. Raman and SEM results indicate that Ni/SiCxOy catalysts with appropriate amounts of precipitant tended to grow more loosely arranged carbon nanowires. The combination of inverse microemulsion and precipitation methods produced smaller and multi-size distributed Ni/SiCxOy catalysts with superior durability and hydrogen production performance in ESR reaction.

Silicon Nitride Supported Cobalt Catalyst for Enhanced Hydrogen Production from Ethanol Steam Reforming

Silicon Nitride Supported Cobalt Catalyst for Enhanced Hydrogen Production from Ethanol Steam Reforming

Regulating cobalt chemical state by CeO2 facets preferred exposure for improved ethanol steam reforming

Regulating the chemical state of Co sites to develop high-performance Co-based catalysts for ethanol steam reforming reaction is desirable but challenging. Herein, we report an effective strategy of tuning chemical states of Co sites by preferred exposure of CeO2 facets. The as-prepared Co/CeO2-(M) and Co/CeO2-(U) catalysts have exposure preference of (111) facet and (100) facet of CeO2 supports, respectively. The results demonstrate that the Co/CeO2-(M) has Co sites in lower oxidation state and exhibits higher CC bond cleavage capability and more excellent catalytic performance for ethanol steam reforming reaction than Co/CeO2-(U), the hydrogen selectivity reaches as high as 97% at ethanol conversion of 100%. In situ synchrotron radiation photoionization mass spectrometry and density functional theory calculations reveal that Co site in low oxidation state has a significant preference for carbon chain shortening by CC cleavage over carbon chain lengthening by condensation reaction, thus improving the hydrogen production efficiency of ethanol steam reforming reaction. This work provides an effective strategy to enhance the catalytic performances of Co-based catalysts for ethanol steam reforming reaction and expands the understanding about ethanol steam reforming reaction mechanism.

Design and optimization of a crossflow tube reactor system for hydrogen production by combining ethanol steam reforming and water gas shift reaction

Crossflow tube reactors with crossflow configuration are considered a special design for hydrogen production via ethanol steam reforming with less catalyst than conventional packed bed reactors. However, the results showed that crossflow tube reactors would produce an elevated concentration of carbon monoxide, which has a detrimental effect on further applications of the product gas from steam reforming, such as hydrogen purification. This drawback can be diminished by integrating a water gas shift reaction unit into the steam reformer. This study's combined system is numerically investigated for hydrogen production and enrichment. The results show that low reaction temperatures are favorable for hydrogen production. The steam/ethanol (S/E) ratio of 3 is optimal for hydrogen production and CO reduction in the system combined with ethanol steam reforming and water gas shift reaction. Both variations in the catalytic tube diameter and the catalyst thickness positively affect hydrogen production. However, the effect of the tube diameter is higher than that of the catalyst thickness. This study also uses a parametric sweep associated with the evolutionary computation of bound optimization by quadratic approximation (BOBYQA) method to optimize the system’s tube arrangement. The optimized system intensifies H2 yield by 1.05 times and improves CO reduction by 37.71% compared to ethanol steam reforming alone.

The mechanism of ethanol steam reforming on Co10|α-Al2O3 (0001) surface: A DFT study

ESR (Ethanol steam reforming) seems to be a promising way to produce hydrogen which has been proposed as the most desirable energy carriers to overcome the problem of fossil fuels shortage. The ESR mechanism on the optimized Co10|α-Al2O3 (0001) surface is investigated by means of DFT calculations. The results show that oxidation state of Co cluster and micro-chemical environment play important roles in the ESR reaction. C-C bond scission is favored on the Co0 site while C-O bond scission is likely to happen on the Cox+ site, and the energy barrier is influenced by the number of hydrogen and oxygen atoms that are bonded with C/O atom. ESR reaction is initiated by the O-H bond scission of ethanol on the Cox+ site: CH3CH2OH*→ CH3CH2O*→CH3*+CH2O*→CH2O*+OH*→H2COOH*→COOH*+H2*→CO*+H2*with the dehydrogenation of H2COO* as the rate-determining step.

Investigating the influence of Ni-CexZr1−XO2 interaction on oxygen vacancy and catalytic behavior of Ni/CexZr1−XO2 catalysts for ethanol steam reforming

Ni/CexZr1−xO2 catalysts were synthesized with two types of CexZr1−xO2 solid solutions to understand the role of oxygen vacancy in ethanol steam reforming (ESR). The cubic Ce0.93Zr0.07O2 (CZ) contained more oxygen vacancies on the surface and in the lattice structure than the tetragonal Ce0.07Zr0.93O2 (ZC). Even though the Ni-CexZr1−xO2 interaction basically increased the surface oxygen vacancy (OVS) on the interfacial region, it also induced different bulk oxygen vacancy (OVb) behavior: no OVb over Ni/ZC and no change over Ni/CZ. In the ESR, active oxygen species (Ox) generated on the OVS simultaneously involved SR, and water gas shift reaction (WGS) to produce H2. Zero OVb over Ni/ZC influenced the Ox involving–reaction routes, resulting in the limitation of WGS and the high TOF values at 750 °C. Furthermore, since the OVb played a significant role as the Ox carrier, Ni/CZ showed the highest H2 production rate in the ESR at 750 °C.

Post treatment and properties of PVA/SS composite nanofibers

Using deionized water as a solvent, the polyvinyl alcohol/silk sericin (PVA/SS) mixed solution was prepared, and the PVA/SS composite nanofiber membrane was spun by the electrostatic spinning method. The characteristics and properties of the PVA/SS composite nanofiber membrane untreated and treated with methanol and ethanol steam were analyzed by scanning electron microscope, infrared spectrum and X-ray diffraction. The results showed that the morphology of the PVA/SS composite nanofibers was fine in this experiment. The average diameter and standard deviation of diameter first increased, then decreased and at last increased with the increase of the SS content. The average diameter of nanofibers treated with methanol and ethanol steam was smaller than that without treatment. The infrared spectrum showed that the peak value of SS in the PVA/SS composite nanofibers treated with methanol steam and ethanol steam for 3 d changed. X-ray diffraction showed that the crystallization of the PVA/SS composite nanofiber membrane after being treated with methanol and ethanol vapor was changed. The results provide theoretical support for biomedical materials and tissue engineering scaffolds.

A critical and systematic review of sustainable hydrogen production from ethanol/bioethanol: Steam reforming, partial oxidation, and autothermal reforming

The emerging study of hydrogen energy is receiving substantial attention in the scientific community due to its efficiency in approaching net zero and environmental sustainability. Meanwhile, bioethanol is a sustainable and carbon–neutral fuel for hydrogen production. This research aims to assess various ethanol reforming routes, including ethanol steam reforming, partial oxidation, and autothermal reforming, and evaluate the differences in hydrogen production as a function of catalyst physicochemistry and experimental parameters. For all three techniques, 75 % hydrogen selectivity is attained at 400 °C. In the ethanol steam reforming, non-noble metals (Co and Ni) are more reactive than noble metals (Rh and Ru). However, the sequence of hydrogen selectivity is featured by Rh > Ir > Ru > Pt > Ni > Co in autothermal reforming of ethanol. The partially filled d-orbitals of various transition metals can uptake or provide electrons to various reagents, thereby controlling reaction activity. Non-noble metals are inexpensive, making these catalysts appealing for a variety of reforming processes. The small crystal size <10 nm and the large Brunauer-Emmett-Teller surface area of the metal-support particles regulate the dispersion and reactivity of the catalyst. Hydrogen selectivity is lower in partial oxidation and autothermal reforming, while CO and CO2 exhibit no specific selectivity trend. The reactivity of intermediate reactions such as dehydrogenation and decarbonylation positively correlated with the reaction temperature and the steam/oxygen/ethanol ratio, which regulates syngas product distributions. Overall, this review provides a vision for sustainable hydrogen production and decarbonization to achieve the net zero target.

Hydrogen production from tar steam reforming over hydrangea-like Co-phyllosilicate catalyst derived from Co/Sepiolite

Co-phyllosilicate with structure flexibility is acknowledged as a promising catalyst for hydrogen production by steam reforming. In this work, a series of hydrangea-like Co-phyllosilicate catalysts were synthesized by a template-free urea hydrothermal method, where the silica source was supplied by amorphous sepiolite. Both the exsolution property of phyllosilicate and the hierarchical macro-/meso-pore architectures of hydrangea-like morphology were combined to improve the metal dispersion and reactant activation. The catalytic behaviors of as-synthesized xCo/SEP-PS catalysts were evaluated in simulated tar (phenol + ethanol) steam reforming. It was founded that 10Co/SEP-PS catalyst achieved an optimal conversion (89.3%) and H2 yield (67.4%) at 700 °C, as well as the lowest apparent activation energy of 35.5 kJ/mol. Various characterization results coupling with experimental investigations indicated that the fine Co particles implanted on Co-phyllosilicate lamella were highly stable and active for H2 production. Meanwhile, the hydrangea-like Co-phyllosilicate provided high Lewis acidity and developed pore structure, significantly facilitating the reactant adsorption and activation, especially for phenol dehydrogenation. The synergy between developed pore structure and enhanced metal-support interaction of Co-phyllosilicate conferred 10Co/SEP-PS with a robust durability in a 50 h stability test and effective resistance to metal sintering and coke deposition.

Numerical simulation of a combined system of ethanol steam reforming and HT-PEM fuel cell

ABSTRACT In the present study, the integrated system of ethanol steam reforming (ESR) and the high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) is simulated using ASPEN Plus™ and MATLABTM, respectively, in order to develop a clean energy technology. In ESR section, an ethanol steam reforming reactor (ESRR) is simulated using the R-Plug reactor based on a mechanistic kinetic model instead of a simple R-Gibbs reactor to consider the complexity of ESR reactions and a water gas shift reactor (WGSR) using the R-Equilibrium reactor modules of ASPEN Plus™ to obtain the optimal hydrogen production conditions. The simulated results show good agreement with the experimental observations for hydrogen yield, and it is found that the yield of hydrogen increases with increase in temperature and S/E ratio with minimal effect of pressure on it. Based on ESR section simulations, the optimal operating conditions of 923 K with S/E ratio of 4 under atmospheric condition are selected for ESRR and 423 K for WGSR to maximize hydrogen yield and minimize CO amount, respectively. The ESR section product is found to produce the fuel-cell-grade hydrogen [0.25 mole % of CO (dry, CO2-free basis) with the remaining as hydrogen] to be used in the HT-PEMFC section. The performance of HT-PEMFC section combined with ESR section is analyzed using MATLABTM, for the operating parameters like temperature, pressure, and feed CO concentration.

A comparative DFT study of ethanol steam reforming over Co(1 0 0) and CoO(1 0 0) surfaces: Molecular reaction mechanism

Unraveling the roles of cobalt sites with different oxidation states is crucial for understanding mechanism of cobalt-catalyzed ethanol steam reforming (ESR) reaction. In this work, the roles of Co(0) and Co(II) sites in ESR reaction are comparatively explored by DFT calculation studies about reaction pathways over Co(100) and CoO(100) surfaces, and a novel molecular reaction mechanism has been provided. The results demonstrate that the Co(II) site in Co-based catalyst exhibits distinct preference for dehydrogenation over dehydration of ethanol especially in the presence of H2O molecule. For the conversion of acetaldehyde, the Co(0) site exhibits significant preference for decomposition and water addition over aldol addition of acetaldehyde, thus facilitating the carbon chain shortening to improve ethanol steam reforming. Therefore, the Co(0) and Co(II) sites exhibit synergistic effects on ESR reaction, especially the role of Co(0) site in selective conversion of acetaldehyde is more crucial for high-efficiency reforming of ethanol.

Magnesium addition to Ni spinels and a composite as design strategy of catalysts for ethanol steam reforming

Two synthesis strategies were considered, by one side, spinel structures were studied as precursors of Ni based catalysts and by the other side a mixed oxide composite as support in order to achieve the necessary basic characteristics that could minimize carbon formation in ethanol steam reforming reaction (ESR). For this purpose, two spinels families, Ni1-xMgxAl2O4 and Mg1-xNixAl2O4 and a composite Ni/MgO–Al2O3 were successfully synthetized. Catalysts were characterized by XRD, SBET, TPR, XPS, CO2-TPD and evaluated in ESR. The best catalytic activity was observed for Ni0.99Mg0.01Al2O4 and Ni/MgO–Al2O3. These catalysts presented the highest values of H2 selectivity and the least values of CO selectivity with almost zero formation of methane. This excellent behavior was attributed to the higher reducibility and higher amount of available Ni° species at surface with a higher support interaction. Long term experiences were conducted in order to evaluate stability. Both catalysts remained stable with minimum carbon formation.

DBD plasma-assisted ethanol steam reforming for green H2 production: Process optimization through response surface methodology (RSM)

This work investigates ethanol steam reforming (ESR) to produce hydrogen (H2) in a dielectric barrier discharge (DBD) plasma reactor. A five-level, three-factor experiment design was performed using a response surface methodology (RSM) to evaluate the combined effects of the three process parameters, including discharge power, total flow rate, and ethanol-to-water (EtOH/H2O) molar ratio on the plasma-assisted ESR reaction. Quadratic regression models were employed in RSM to fit the experimental results and present the correlation between process parameters and targeted responses (EtOH conversion, H2 yield, H2 selectivity, and specific energy requirement (SER) for H2 production). The results suggested that the EtOH/H2O molar ratio is considered to have the most significant effect on the EtOH conversion and H2, H2 selectivity, while the total flow rate is the most significant parameter determining SER for H2 production. Process optimization demonstrated the optimal process conditions, including a discharge power of 55.9 W, a total flow rate of 26.7 ml/min, and an EtOH/H2O molar ratio equal to 0.34. A validation test was performed and confirmed the feasibility of the optimization process.

Appraisal of Ni Species Supported on Porous MgO during Ethanol Steam Reforming by XAS

AbstractOperando time‐resolved X‐ray absorption spectroscopy (XAS) was used to determine nickel species supported on porous MgO during the ethanol steam reforming reaction. The Principal Component Analysis (PCA) of the nickel K‐edge XAS spectra revealed Ni(OH)2, NiMgO, and metallic Ni during the activation and reaction of the catalysts. The Multivariate Curve Resolution‐Alternating Least Squares (MCR‐ALS) method for the time‐resolved XAS spectra data permitted to calculate the concentration of species during the activation and reaction steps and to determine the formation of NiMgO and nickel reduction degree. The samples prepared with surfactants, Ni10MgO‐F127 and Ni10MgO‐P123, showed less nickel reduction (less than 30 %) but were more active and stable than the reference Ni10MgO catalyst, which reduced 52 %. It happened due to the smaller particle size and a larger specific area of the porous supports. The samples synthesized without Pluronic deactivated, and ethanol dehydrogenation became predominant instead of the ethanol steam reforming.

Catalytic and electrocatalytic performance of Sr(Ti0.3Fe0.7Ru0.07)O3-δ for applications in solid oxide fuel cells supplied with ethanol steam reforming mixtures

Direct utilization of alcohols in Solid Oxide Fuel Cells (SOFCs) can improve the conversion efficiency by using excess heat for internal reforming and simplify the system balance of plant. Thanks to their scarce carbon-formation tendency, perovskite oxide anodes are promising alternatives to Ni-based cermets. Here we show that Sr(Ti0.3Fe0.7Ru0.07)O3-δ (STF-Ru) exsolution anodes provide both catalytic reforming activity and electrochemical activity with steam/ethanol (S/E) mixtures at 3:1 and 2:1 M ratio between 700 and 800 °C. Electrolyte-supported scandia stabilized zirconia SOFCs with STF-Ru anodes and Sr0.95Ti0.3Fe0.7O3-δ (STF) cathodes are reasonably stable in the 3:1 S/E mixture over 20 h at 800 °C, with maximum power density of 195 mW/cm2 and 140 mW/cm2 at 0.7 V. Deactivation instead occurs with the 2:1 S/E mixture. Comparatively, cells with Ni-YSZ anodes rapidly coke and fail under the same conditions. Ethanol steam reforming experiments in a fixed bed powder reactor reveal that, above 650 °C, gas phase reactions convert ethanol to CO, hydrogen, acetaldehyde and ethylene, while STF-Ru catalyzes steam reforming. Thermogravimetric and Raman characterizations show that a moderate amount of carbon is deposited on the STF-Ru surface, which is more amorphous than the disruptive carbon which degrades Ni-YSZ.

Hydrogen production from ethanol by combined microwave discharge plasma and Cu/Zn/Al catalyst

The ethanol solution was reformed by liquid-phase microwave discharge plasma to produce H2-rich syngas. In order to further improve the hydrogen production of syngas after discharge, the method of combining of microwave discharge plasma in liquid (MDPL) and catalyst was proposed for the first time in this paper. The catalyst was Cu/Zn/Al catalyst prepared by thecoprecipitation synthesis method. The catalytic system was placed at the outlet of discharge plasma system, and the hydrogen production of the syngas after Cu/Zn/Al catalysis was used as the catalyst activity evaluation. This study focused on the effect of Cu/Zn/Al catalyst on the syngas after microwave plasma discharge at different catalytic temperatures. The hydrogen production reached the maximum when the catalytic temperature reached 350 °C. At the same temperature, the mass of Cu/Zn/Al catalyst was 1.5 g, the hydrogen production of syngas reached 274.8 mL/min, and the hydrogen production after catalysis was 2.3 times of that before catalysis. The hydrogen production of Cu/Zn/Al catalyzed syngas without ethanol steam was 145.0 mL/min. The hydrogen production of Cu/Zn/Al alone catalyzed ethanol vapor was 14.1 mL/min. It was found that the Cu/Zn/Al catalyst could effectively utilize the excess ethanol vapor in the syngas to produce hydrogen, and no by-products were produced during the catalytic process. Meanwhile, the Cu/Zn/Al catalyst could also utilize other gaseous by-products in syngas to further enhance hydrogen production. Therefore, the combination of microwave discharge plasma and Cu/Zn/Al catalyst had a synergistic effect on hydrogen production from ethanol solution, and the synergistic efficiency was up to 72.7%. This method provides an effective solution to further improve the hydrogen production from microwave plasma.

Efficient Catalysts of Ethanol Steam Reforming Based on Perovskite-Fluorite Nanocomposites with Supported Ni: Effect of the Synthesis Methods on the Activity and Stability

Catalysts based on perovskite—fluorite nanocomposites with supported nickel 5%Ni/[Pr0.15Sm0.15Ce0.35Zr0.35O2 + LaMn0.9Ru0.1O3] were synthesized by three different methods. Structural and surface features of as-prepared samples were elucidated by N2 adsorption, XRD, HR TEM with EDX; reducibility and reactivity were estimated by H2-TPR, and catalytic properties were studied in ethanol steam reforming in the 500–700 °C temperature range. The best catalytic activity without coke accumulation was demonstrated for the 5%Ni/[Pr0.15Sm0.15Ce0.35Zr0.35O2+ LaMn0.9Ru0.1O3] catalyst with nanocomposite support obtained by a simple sequential polymeric preparation method. Highly dispersed particles of metallic nickel strongly fixed on the support after the reaction were shown by the HR-TEM and H2 –TPR data. The catalyst provides stable full conversion of ethanol and hydrogen yield above 60% at 600 °C for at least 6 h.

Electron density donation of concomitant peroxide anions in La0.25Ce0.75O1.88 boosting cobalt-catalyzed ethanol steam reforming for hydrogen production

Tuning the valence state and reducibility of Co active site in Co-based catalysts to improve catalytic performances is desirable for hydrogen production from ethanol steam reforming (ESR) reaction. In this work, we fabricate Co/LaxCe1−xO2−x/2 (x = 0.5, 0.25, 0.17) catalysts and investigate their catalytic performances for ESR reaction. Our studies manifest that the catalytic performances of Co-based catalysts have been effectively improved by La doping in CeO2. Among the investigated catalysts, Co/La0.25Ce0.75O1.88 exhibits the highest catalytic activity and durability, the hydrogen yield reaches as high as 80 % at ethanol conversion of 100 %, with an excellent durability during long-time (58 h) catalytic experiment. X-ray photoelectron spectroscopy (XPS) and hydrogen temperature programmed reduction (H2-TPR) studies demonstrate that the valence state and reducibility of the Co/La0.25Ce0.75O1.88 are effectively regulated via donation of electron density from the concomitant peroxide anions in La0.25Ce0.75O1.88 to the supported cobalt catalyst, the CC bond cleavage capability has been significantly enhanced to boost the hydrogen-production efficiency from ESR reaction. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies reveal that Co/La0.25Ce0.75O1.88 shows a remarkable preference for producing C1 products, the Co species in low valence state and with high reducibility result in highly efficient CC cleavage and excellent catalytic durability.

Effect of CeO2 on carbon deposition resistance of Ni/CeO2 catalyst supported on SiC porous ceramic for ethanol steam reforming

Ni/CeO2 catalysts (nCeO2:nNi = 0, 1, 4, 7, 10) supported on SiC porous ceramics for ethanol steam reforming (ESR) were investigated with respect to hydrogen production performance and growth of carbon deposition. The oxygen released from CeO2 enables the oxidation of CHx species to serve as carbon precursors, thus providing Ni/CeO2 catalysts with stronger resistance to carbon deposition compared with Ni catalysts. The Ni/CeO2 catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics. Under 500 °C for 25 h of ESR reaction, the ethanol conversion rate over Ni/CeO2 catalysts (nCeO2:nNi = 7) is sustained up to 100% and H2 selectivity is essentially kept at 74%. The by-product selectivity declines stepwise with increasing content of CeO2, which is attributed to the adsorption and oxidation of CO and of CHx species as CH4 precursor from CeO2. The scanning electron microscopy (SEM) and transform electron microscopy (TEM) results reveal that further loading of CeO2 on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles. Furthermore, carbon deposition on Ni/CeO2 catalysts preferentially outgrow filamentous rather than amorphous carbon, with a tendency for the latter to be more deactivated.