Steam Reforming Of Ethanol Research Articles

Ethanol conversion at low temperature over CeO2—Supported Ni-based catalysts. Effect of Pt addition to Ni catalyst

The effect of Pt addition on the performance of Ni/CeO2 catalyst for the low temperature steam reforming of ethanol is investigated. The reaction mechanism was explored using diffuse reflectance infrared spectroscopy under reaction conditions and temperature-programmed surface reaction of ethanol. The addition of Pt to Ni/CeO2 catalyst promoted the decomposition of dehydrogenated and acetate species to hydrogen, methane, CO and carbonate species. Furthermore, the presence of Pt reduced the rate of catalyst deactivation. In situ X-ray absorption studies revealed the formation of a nickel carbide phase during steam reforming of ethanol over Ni/CeO2 catalyst, which was associated with amorphous carbon deposition and catalyst deactivation. X-ray photoelectron spectroscopy in combination with kinetic and structural data was consistent with a partial Pt monolayer on Ni in the bimetallic catalyst. The segregation of Pt on the surface of the Ni particles minimized the formation of nickel carbide and promoted catalyst stability.

Ethanol steam reforming over bimetallic coated ceramic foams: Effect of reactor configuration and catalytic support

In recent years, hydrogen production from renewable feed-stocks attracts particular attention. Specifically, the steam reforming of biomass-derived bioethanol could provide H2-rich effluent streams, representing an interesting research field. This study focuses on the development of bimetallic structured catalysts (containing Ni and Pt as active species and supported on ceria and ceria-zirconia) active in Ethanol Steam Reforming (ESR) reaction at low-temperature (300–600 °C) and characterized by improved heat transfer properties. ESR reaction was carried out on ceramic foams and, as a comparison, on powders catalysts. In particular, catalytic tests were carried out on two reactor configurations: catalytic powders were tested in both a tubular and annular reactor; in addition, the tubular configuration was also employed for the structured catalysts. Unsatisfactory results were observed for powders in the tubular reactor while the better thermal management of the annular configuration ensured significantly higher conversions. Moreover, the enhanced thermal conductivity of SiC foams catalysts, tested in the tubular reactor, allowed overcoming heat transfer limitations in an easy reactor geometry, resulting in very good performances. The catalytic behaviour of bimetallic CeO2 and CeO2–ZrO2 based catalysts was also compared and the effect of catalytic support on ethanol conversion and H2 yield at different space velocities (100,000–400,000 h−1) was investigated. Finally, Pt–Ni/CeO2–ZrO2 catalysts, which displayed a more interesting catalytic activity with respect to CeO2 based samples, were employed for stability tests at 100,000 h−1 and 450 °C: products gas distribution was not affected during TOS and total ethanol conversion was recorded for almost 5 h.

In situ photoelectron spectroscopy study of ethanol steam reforming over RhPd nanoparticles and RhPd/CeO2

In situ X-ray photoelectron spectroscopy (XPS) was carried out over model Rh0.5Pd0.5 nanoparticles and Rh0.5Pd0.5 nanoparticles supported on CeO2 following exposure to oxygen at 573–823K, to hydrogen at 573K (activation of the catalyst), to a mixture of ethanol and water at 823K simulating ethanol steam reforming (ESR) conditions, and to hydrogen at 823K. The presence of the CeO2 support had a strong influence on the atomic rearrangement and on the oxidation state of Rh0.5Pd0.5 nanoparticles. CeO2 exerted a quenching effect on the metal nanoparticles and limited atomic rearrangement under the different atmospheres tested except for ESR, where a partial segregation of Rh toward the surface of the nanoparticles was observed. When supported on CeO2, Rh0.5Pd0.5 nanoparticles were significantly more oxidized due to metal-support interaction. By comparing these in situ XPS results with a previous operando near-ambient pressure XPS study conducted in a synchrotron facility at 0.05 mbar over the same samples, it is concluded that the information obtained for the unsupported Rh0.5Pd0.5 nanoparticles is similar in both cases, whereas Rh0.5Pd0.5 nanoparticles supported on CeO2 are clearly more oxidized and enriched in Pd in the volume sampled under operando ESR conditions compared to that obtained in the in situ experiments. The study of catalytic systems under operando conditions appears essential to identify the active species at work during ESR, as the restructuring driven by the reforming environment induces strong changes in their architecture.

Kinetic and process study of ethanol steam reforming over Ni/Mg(Al)O catalysts: The initial steps

In this work, a 2 wt.% Ni/Mg(Al)O catalyst was subjected to kinetic studies for the ethanol steam reforming (ESR) reaction at 500°C, with space-time ranging from 0.03 to 0.50mgmin/ml and with PC2H5OH:PH2O:PInert=0.0163:0.0500:0.93 (atm) as standard conditions. The results indicate that dehydrogenation and dehydration of ethanol were the predominant reactions. CH3CHO and C2H4 were primary products and formed in parallel on different active sites. H2O and C2H5OH competed for the same active sites on the catalyst surface and the reaction order with respect to H2O was negative. The apparent activation energy for ethanol conversion was 110kJ/mol. Furthermore, temperature-programmed desorption experiments confirmed the competing adsorption of C2H5OH and H2O. Temperature-programmed deuteration of used catalyst showed that the catalyst contained C2H4, CHx, acetate and carbonate species during ESR reaction.

Efficient hydrogen production from ethanol steam reforming over La-modified ordered mesoporous Ni-based catalysts

This paper describes the synthesis of a group of meso-xLaNiAl catalysts with ordered mesostructure and La promoters, and their catalytic performance for hydrogen production from ethanol steam reforming. For comparison, the conventional 0LaNiAl catalyst was prepared by impregnation with γ-Al2O3. The characterization results exhibited that meso-xLaNiAl materials possessed excellent textural properties, such as high specific surface areas, large pore volumes and uniform pore sizes. The ordered mesostructure was beneficial to obtain and maintain the 4–6nm Ni nanoparticles, which were smaller than that of the conventional 0LaNiAl catalyst (∼10nm). Consequently, meso-xLaNiAl catalysts exhibited superior initial activity with respect to the reference 0LaNiAl catalyst, especially at higher temperatures (873 and 973K). Particularly, the meso-3LaNiAl catalyst gained the highest amount of easily reduced Ni species and then the highest active surface areas. In addition, the highest initial activity at 873K is exhibited over meso-3LaNiAl catalyst, which is mainly attributed to the highly dispersed nickel nanoparticles and abundant active surface areas. The meso-3LaNiAl catalyst also exhibited excellent long-term stability. Besides the excellent textural properties, the presence of La-modifiers enhanced the basicity of the catalyst, strengthened the metal-support interaction and cleaned the deposited carbon, resulting in the suppression of carbon deposition and the improvement of stability.

Hydrogen production by steam reforming of ethanol over dual-templated Ni–Al2O3 catalyst

A dual-templated Ni–Al2O3 catalyst (SINA) was prepared by a single-step evaporation-induced self-assembly (EISA) method using P123 and ionic liquid as templates. For comparison, a P123-templated Ni–Al2O3 catalyst (SNA) was also prepared by a single-step evaporation-induced self-assembly (EISA) method in the absence of ionic liquid. Both catalysts were applied to the hydrogen production by steam reforming of ethanol. The effect of ionic liquid addition on the physicochemical properties and catalytic activities of the catalysts was investigated. Although both catalysts exhibited a mesoporous structure, SINA catalyst retained higher surface area and larger pore volume than SNA catalyst. It was also revealed that SINA catalyst retained higher nickel surface area and higher ethanol adsorption capacity than SNA catalyst. In the hydrogen production by steam reforming of ethanol, both catalysts exhibited a stable catalytic performance with complete conversion of ethanol. However, SINA catalyst exhibited higher hydrogen yield than SNA catalyst. High surface area and high nickel dispersion of SINA catalyst were responsible for its high hydrogen yield. The addition of ionic liquid as a co-template in the preparation of mesoporous SINA catalyst increased surface area, nickel dispersion, and catalytic activity of the catalyst.

Improved ethanol steam reforming on Rh/Al2O3 catalysts doped with CeO2 or/and La2O3: Influence in reaction pathways including coke formation

In this paper, Rh catalysts supported over bare γ-Al2O3 and γ-Al2O3 modified with different promoters (15wt%La2O3 and/or 2.5wt%CeO2) were reported. The catalysts were prepared by successive impregnation: first the rare earth oxide promoter and then Rh. Hydrogen production by ethanol steam reforming (ESR) over these catalysts was investigated. Among the catalysts, Rh/La2O3–CeO2–γ-Al2O3 catalyst shows the highest hydrogen yield as well as the best stability during the reaction. Reaction pathways of the ESR over these Rh catalysts are investigated from the analysis of the adsorbed species and gas phase products formed during temperature programmed desorption of ethanol and ethanol steam reforming reaction. The differences in the reaction pathways and products distribution are as a result of the modification of the stability of some reaction intermediates caused by the presence of a small quantity of CeO2 and La2O3 on the support surfaces: in effect, acetaldehyde was formed as an intermediate over the modified-γ-Al2O3 supported catalysts while in the case of the bare Al2O3 support the main route of the steam reforming reaction is the direct ethanol decomposition. Analysis of the used catalysts by XPS, TGA and RAMAN showed that changes in reaction pathways associated to the presence of promoters in the Al2O3 support also modifies the extension and type of carbon deposited on catalyst surfaces.

Effect of potassium addition on a long term performance of Co–ZnO–Al2O3 catalysts in the low-temperature steam reforming of ethanol: Co-precipitation vs citrate method of catalysts synthesis

The promotion effect of potassium on Co–ZnO–Al2O3 catalysts in the steam reforming of ethanol has been studied with samples prepared by co-precipitation and citrate methods. Experimental results of catalytic activity, selectivity and coke deposition phenomena are reported. Potassium addition (1 and 2wt.%) had a significant influence on catalytic efficiency at various ethanol+water vapours streams (H2O:EtOH=21:1, 15:1, 12:1 molar ratios). It acts as a promoter improving catalyst stability, activity as well as marginalizing coke deposition on the catalyst surface. Catalysts prepared by the co-precipitation method, with smaller cobalt active phase crystallites and with potassium deposited on the catalyst surface are more stable in the steam reforming of ethanol than those with large crystallites prepared by citrate method, into which potassium was introduced together with all others components. The efficiency of the potassium promotion is higher when it is deposited on the catalyst surface with smaller cobalt active phase crystallites. The water excess equivalent to the H2O:EtOH molar ratio higher than 15:1 has been necessary for the stable SRE. Even potassium-promoted K–Co–ZnO–Al2O3 catalyst needs the ethanol–water feed with a large excess of water.

Steam Reforming of Ethanol over Manganese and Iron Oxides for Hydrogen Production

MnO, Mn2O3, Fe2O3 and Fe3O4 are catalytically active for the steam reforming of ethanol. The main reaction products were acetaldehyde, acetone, CO2 and H2 in the temperature range of 300–550 °C. At low temperatures, high selectivity for acetone (up to 75%) was observed for MnO. Based on the study results, the relation between product selectivity of the oxide catalysts and their acid–base/redox properties balance is suggested. The selectivity for hydrogen was about 80% for Fe2O3 at 550 °C with 100% ethanol conversion.

Total Energy Requirement for Hydrogen Production Reactor Using Various Porous Media Materials

In a hydrogen production reactor, combustion of LPG was used as a heat source for ethanol steam reforming. For such purpose, the operating temperature was required to be around 700-900°C along the entire height of the reactor. Various types of porous media materials were used as a heat transfer media, i.e. 25mm ceramic saddles, random size bio-filter media from MTEC, ceramic foam, and ceramic balls. The objective of this study was to obtain the practical amount of total energy input, and compare with theoretical calculation which can achieve the required temperature of ethanol steam reforming for the hydrogen production. From our experiments, 13.20 kW of energy was needed to fulfill the requirement of the reactor, while only 2.49 kW was expected from theoretical calculation. Most energy loss was due mainly to: 1) heat loss at the top of the reactor where the metal part was directly exposed to the environment, 2) a large amount of energy loss at the furnace stack and, 3) insufficient mixing at the early stage of combustion at the bottom of the furnace as noticed by high CO concentration in flue gas. The porous media material has a significant effect on temperature distribution and energy consumption. The results show that the use of ceramic saddles as porous media consume more energy than the ceramic foam and the bio-filter media mixed with ceramic saddles during the start-up period of the reactor.

Mechanistic Insights of Ethanol Steam Reforming over Ni–CeOx(111): The Importance of Hydroxyl Groups for Suppressing Coke Formation

We have studied the reaction of ethanol and water over Ni–CeO2-x(111) model surfaces to elucidate the mechanistic steps associated with the ethanol steam reforming (ESR) reaction. Our results provide insights about the importance of hydroxyl groups to the ESR reaction over Ni-based catalysts. Systematically, we have investigated the reaction of ethanol on Ni–CeO2-x(111) at varying Ce3+ concentrations (CeO1.8–2.0) with absence/presence of water using a combination of soft X-ray photoelectron spectroscopy (sXPS) and temperature-programmed desorption (TPD). Consistent with previous reports, upon annealing, metallic Ni formed on reduced ceria while NiO was the main component on fully oxidized ceria. Ni0 is the active phase leading to both the C–C and C–H cleavage of ethanol but is also responsible for carbon accumulation or coking. We have identified a Ni3C phase that formed prior to the formation of coke. At temperatures above 600 K, the lattice oxygen from ceria and the hydroxyl groups from water interact cooperatively in the removal of coke, likely through a strong metal–support interaction between nickel and ceria that facilitates oxygen transfer.

Catalytic behavior of Ru supported on Ce0.8Zr0.2O2 for hydrogen production

Ru (2wt.%) on Ce0.8Zr0.2O2 catalysts were investigated to test their ethanol steam reforming (ESR) performance. The supports were obtained through two different synthesis methods: co-precipitation (PI) and mechanochemical reaction (MR). Characterization of the catalysts, before and after ESR, were performed using X-ray powder diffraction (XRPD), nitrogen physisorption, CO chemisorption, temperature programmed reduction (TPR), high resolution transmission electron microscopy (HR-TEM), thermogravimetry, and X-ray photoelectron spectroscopy (XPS) measurements. The Ru (2wt.%) PI catalyst exhibited the highest activity and selectivity to hydrogen and no coke deposition was observed during catalytic operation, even when compared to Ni (8wt.%) PI catalyst. A possible reaction pathway is proposed. The remarkably good catalytic performance of Ru (2wt.%) PI is regarded as being due to a combination of factors: improved metal dispersion on Ce0.8Zr0.2O2, favorable metal-support interaction and water gas shift reaction promotion.

Hydrogen production from ethanol over Ir/CeO2 catalyst: Effect of the calcination temperature

The influence of calcination temperature on the structural property and catalytic behavior of Ir/CeO2 for oxidative steam reforming of ethanol (OSR) was extensively investigated. In order to elucidate the structure–performance relationship, the as-prepared catalysts were characterized before and after catalytic test by various techniques such as X-ray diffraction spectroscopy (XRD), Temperature programmed reduction (TPR), High resolution transmission electron microscopy (HRTEM), H2-chemisorption, Raman spectroscopy and Oxygen storage capacity (OSC), etc. The experimental results indicated that various calcination temperatures greatly affected catalyst activity and stability. The catalysts calcined below 550°C (400Ir–Ce, 550Ir–Ce) exhibited the higher values of ethanol conversion and hydrogen yield and the better performance was maintained for up to 60h, resulting from the highly dispersed Ir species and the less coke formation due to the strong metal–support interaction (MSI). On the contrary, the 850Ir–Ce sample, processing weaker MSI, presented a less catalytic behavior, the complete ethanol conversion being reached only at 650°C rather than 450°C compared to the other systems. Stability test of 850Ir–Ce catalyst also revealed that H2 concentration in the outlet gas continuously decreased from 41mol% to 33mol%, which was caused by the combination of deactivating coke formation and the serious sintering of active Ir particles. Such an original and quantified structure sensitivity analysis might shed light on the development of high efficient catalyst for hydrogen production from biomass-derived feedstocks.

Hydrogen production by conversion of ethanol using atmospheric pressure microwave plasmas

The efficiency of hydrogen production from ethanol in the atmospheric pressure plasma generated in waveguide-supplied metal-cylinder-based microwave plasma source (MPS) was investigated experimentally. The tested parameters of hydrogen production efficiency were: hydrogen production rate in NL(H2)/h, energy yield of hydrogen production in NL(H2)/kWh, ethanol conversion degree in % and volume concentration of hydrogen in the outlet gas in %. Two ethanol based methods of hydrogen production were performed, namely ethanol dry and steam reforming. The best achieved experimental results showed that the energy yield of hydrogen production was about 78 NL(H2) per kWh of absorbed microwave energy in the case of ethanol dry reforming and about 257 NL(H2)/kWh in the case of ethanol steam reforming. Presented microwave plasma method can be successfully used for hydrogen production not only from ethanol, but also from different liquid compounds like gasoline, heavy oils and biofuels.

Steam reforming and oxidative steam reforming of ethanol over La0.6Sr0.4CoO3−δ perovskite as catalyst precursor for hydrogen production

The catalytic activity and stability of the La0.6Sr0.4CoO3−δ perovskite, as a catalyst precursor, for the hydrogen production by steam reforming of ethanol (SRE) and oxidative steam reforming of ethanol (OSRE) were investigated. The resistance to sintering and carbon deposition of the catalyst for these reactions were explored. For this purpose, the catalytic activity of La0.6Sr0.4CoO3−δ was studied as a function of the temperature and the time-on-stream. Before and after testing, the catalyst precursor was characterized by temperature programed reduction (TPR), X-ray diffraction, SEM-EDX and specific surface area (BET). The results evidenced that the catalyst was highly selective to hydrogen with a good stability for OSRE reaction. The cobalt ions in the perovskite could be reduced to nanoparticles of metallic cobalt under reducing atmospheres. The precursor could be totally regenerated to the initial perovskite structure under a specific thermal treatment, leading to its high resistance to the sintering.

Toward Understanding Metal-Catalyzed Ethanol Reforming

Steam reforming of ethanol (SRE) is a strategic reaction for H2 production. However, despite considerable work, several aspects of the mechanism and catalytic system for this reaction are not fully understood. There have been many efforts to improve the understanding of the catalysts’ behavior during SRE, using both theoretical studies and experimental investigations based on operando characterization techniques. Even though cobalt and nickel are considered the most promising catalytically active metals for industrial SRE, acquiring further knowledge on the reaction mechanism, metal–support interactions, and catalyst deactivation (due to carbon accumulation, sintering, or metal oxidation) will enable the successful design of new and stable catalysts. In this review, we analyze the reaction pathways for metal-catalyzed SRE and discuss the available experimental and theoretical data to suggest alternatives to address three major issues: (i) the impact of particle size and metal oxidation state in the SRE pe...

Hydrogen generation over 30CoxVy/70SBA-15 mesoporous materials well-balanced by Co and V co-doping

This study examined hydrogen generation by ethanol steam reforming (ESR) over metal-doped SBA-15, Co/SBA-15, Co and V co-doped SBA-15, and V/SBA-15. The changes in the oxidation state of cobalt species during activation through a H2-TPR experiment before ESR were investigated. The materials were pre-reduced by a H2-treatment at 550 °C. A small quantity of cobalt oxide species remained in the reduced CoV (30 wt.%) co-doped SBA-15 (70 wt.%) but it was not observed in the 30Co/70SBA-15. The catalytic performance varied according to the molar ratio of the loaded metals, Co and V. The 30Co1V1/70SBA-15 showed a significantly higher reforming reactivity and the efficiencies decreased in the order of 30Co1V1/70SBA-15 > 30Co2V1/70SBA-15 > 30Co/70SBA-15 > 30Co1V2/70SBA-15 > 30V/70SBA-15 because of the synergy between cobalt and vanadium ions. H2 production was maximized to 95% over 30Co1V1/70SBA-15 at a reaction temperature of 700 °C, CH3CH2OH:H2O of 1:3 and GHSV (gas hourly space velocity) of 6000 h−1. At the end of activation, metallic cobalt was detected in all the materials. The cobalt oxide species might interact more strongly with the vanadium ions in the material, which results in the formation of a more cobalt vanadium composite and larger amount of Co2+. The presence of Co2+ in the reduced material might help equilibrate the steps of ethanol activation and carbon oxidation, resulting in stable materials. Moreover, vanadium oxides appear to provide oxygen to cobalt species, resulting in increases in hydrogen production and the suppression of CO generation.

Hydrogen production by ethanol steam reforming over Ni/SBA-15 mesoporous catalysts: Effect of Au addition

A series of Ni/SBA-15 and Ni-Au/SBA-15 mesoporous catalysts were synthesized by incipient wetness impregnation and tested in ethanol steam reforming for hydrogen production. ICP-OES, N2 adsorption–desorption, XRD, H2-TPR, TEM and TG-DTG were used to characterize these catalysts in detail. It was found that the incorporation of Au into Ni/SBA-15 catalysts not only improved the dispersion of the NiO phase to form the smaller nickel oxide particle, but also strengthened the interaction between the SBA-15 support and NiO phase, thus efficiently reducing the coke deposition on active sites. Due to these promoting effects, the Au promoted Ni/SBA-15 catalyst showed a high activity and excellent long-term stability for ethanol steam reforming.

Modification of Ni/γ-Al2O3 catalyst with plasma for steam reforming of ethanol to generate hydrogen

Hydrogen provides clean energy when combusted since it is carbon-free. Generation of hydrogen via reforming of hydrocarbons is of high potential to power the fuel cell. Reforming of ethanol with the help of catalyst is viable due to abundant sources of ethanol. In this study, Ni/γ-Al2O3 is evaluated for its catalytic activity on steam reforming of ethanol. In the meantime, a dielectric barrier discharge (DBD) is used to pretreat Ni/γ-Al2O3 catalyst to enhance the catalytic activity and the resistance of coke formation. Results show that at a temperature of 710 K, the ethanol conversions achieved with untreated and plasma-treated catalysts are 68.0 and 88.6%, respectively. Ethanol conversion achieved with plasma treated catalyst reaches 96.2% with the carbon balance of 97% at 810 K, indicating that plasma treatment is an effective approach to enhance the catalytic activity and durability. Moreover, hydrogen yield reaches 320 mg/h gcat for plasma-treated catalyst and is 10% higher than that achieved with the untreated one.

Corrigendum: Monometallic Carbonyl‐Derived CeO2‐Supported Rh and Co Bicomponent Catalysts for CO‐Free, High‐Yield H2 Generation from Low‐Temperature Ethanol Steam Reforming

Corrigendum: Monometallic Carbonyl‐Derived CeO₂‐Supported Rh and Co Bicomponent Catalysts for CO‐Free, High‐Yield H₂ Generation from Low‐Temperature Ethanol Steam Reforming