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This work studied the performance of Pt/Al2O3 and Pt/CexGd1-xO2/Al2O3 catalysts for the dry reforming of methane at 1073 K. Pt/Al2O3 catalyst underwent severe deactivation at the beginning of reaction, whereas the deactivation of Pt/Ce0.8Gd0.2/Al2O3 and Pt/Ce0.5Gd0.5/Al2O3 catalysts was less significant. Pt/36Ce0.8Gd0.2/Al2O3 catalyst remained quite stable during reaction. in situ XRD and XANES experiments showed the formation of oxygen vacancies and Ce3+ species during the reduction of the mixed oxide, which promoted the mechanism of carbon removal from the Pt particle. In the absence of mixed oxide, carbon deposition led to the deactivation of Pt/Al2O3 catalyst. The cyclohexane dehydrogenation reaction revealed that Pt sintering is responsible for the deactivation of Pt/Ce0.8Gd0.2/Al2O3 and Pt/Ce0.5Gd0.5/Al2O3 catalysts. The stability of Pt/36Ce0.8Gd0.2/Al2O3 catalyst is likely due to the close contact between Pt and the CeGd mixed oxide because of the higher extent of alumina coverage by the mixed oxide. This promotes the mechanism of carbon removal from the surface of Pt particles and inhibits Pt particle size growth.

This work investigated the effect of the nature of dopant (Pr, Nb and Zr) on the performance of Pt supported on cerium-based oxides deposited on alumina for dry reforming of methane. in situ XRD and XANES analyses showed that the sample doped with Pr exhibited the highest redutibility of ceria (23%). Furthermore, the cyclohexane dehydrogenation reaction revealed that the addition of Pr improved the resistance to metal sintering during the dry reforming reaction. In the absence of doped-ceria oxide, a strong deactivation took place on Pt/Al2O3 catalyst during reaction, which was due to the absence of support reducibility and the highest Pt sintering. Among the doped-ceria samples, Pt/CePr/Al2O3 exhibited the highest activity and stability. These results were attributed to: (i) the oxygen mobility of the supports containing ceria, mainly for the sample doped with Pr, which favors the carbon removal mechanism; and (ii) the absence of Pt sintering during the reaction.

The techno-economic analysis of a process to convert ethanol into H2 to be used as a fuel for PEM fuel cells of H2-powered cars was done. A plant for H2 production was simulated using experimental results obtained on monolith reactors for ethanol steam reforming and WGS steps. The steam reforming (Rh/CeSiO2) and WGS (Pt/ZrO2) monolith catalysts remained quite stable during long-term startup/shut down cycles, with no carbon deposition. The H2 production cost was significantly affected by the ethanol price. The monolith catalyst costs contribution was lower than that of conventional reactors. The H2 production cost obtained using the expensive Brazilian ethanol price (0.81 US$/L ethanol) was US$ 8.87/kg H2, which is lower than the current market prices (US$ 13.44/kg H2) practiced at H2 refueling stations in California. This result showed that this process is economically feasible to provide H2 as a fuel for H2-powered cars at competitive costs in refueling stations.

The effect of ceria dopant aiming at stability in Ni/doped-ceria anodic layers for direct ethanol solid oxide fuel cells (SOFC) was studied. Solid solutions of ceria doped with Y, Gd, Zr, or Nb (10 mol%) impregnated with NiO were tested in a fixed bed reactor for ethanol conversion reactions and for direct (dry) ethanol SOFC. The ceria dopant showed a marked effect on both the catalytic and the electrical transport properties of the ceramic support. Catalytic activity data revealed that the studied materials deactivate in ethanol decomposition reaction but are stable for ethanol steam reforming. Thus, feeding dry ethanol to the SOFC with a Ni/doped-ceria anodic catalytic layer evidenced that water produced from the electrochemical hydrogen oxidation provides steam for the internal reforming resulting in great stability of the fuel cells tested during ~100 h. The combined catalysis and SOFC results demonstrate Ni/doped-ceria is as candidate anode layer for stable SOFC running on bioethanol.

The development of more efficient processes for energy generation and the use of renewable energy sources, such as biogas, can promote the sustainable use of natural resources as well as the reduction of greenhouse gases emissions. The H2 production through biogas reforming for energy generation by fuel cells has been considered as an interesting alternative, since fuel cell systems exhibit higher energy efficiency than combustion engines. Thus, the aim of this work is to perform a techno-economic evaluation of a process for energy production by proton exchange membrane fuel cell using biogas reforming. For this, a plant for energy production was simulated. Next, the effect of important parameters such as composition of inlet stream of reforming reactor and biogas flow rate on the technical performance of the process, on cost of H2 production and on the selling price of energy generated was evaluated. The Jardim Gramacho landfill, located in the city of Rio de Janeiro/Brazil was used as a representative model of other landfills in Brazilian cities. The sensitivity analysis showed that the biogas flow rate had the greatest influence on the price of H2 produced and on the selling price of energy generated. The use of the highest biogas flow rate with a plant life of 14 y resulted in a high H2 production, a lower amount of H2O consumed and lower energy selling prices than the market selling prices. Moreover, these conditions made possible the supply of energy for 36,000 houses. These results showed that this technology is sustainable and economically feasible under these operating conditions. It may promote the widespread use of H2 and fuel cell technologies, which could ensure environmental sustainability.

This work investigated the performance of supported LaNiO3 perovskite-type oxides for the CO2 reforming of methane. The methane and CO2 conversion increased at the beginning of reaction for LaNiO3 and LaNiO3/Al2O3 catalysts. On the other hand, conversion remained quite constant for LaNiO3/CeSiO2. in situ XPS experiments under reaction conditions revealed that the metallic Ni particles were oxidized by CO2 from the feed for LaNiO3 and LaNiO3/Al2O3 catalysts. Ceria support was preferentially oxidized, limiting the oxidation of the metallic phase. Raman spectroscopy and thermogravimetric analysis showed that carbon was formed mainly over LaNiO3 and LaNiO3/Al2O3 catalysts. Supporting LaNiO3 over CeSiO2 almost completely suppressed carbon deposition. in situ XPS experiments showed a continuous change of ceria oxidation states between Ce4+ and Ce3+ under reaction conditions. This result in a high oxygen mobility of ceria support that reacts with carbon, inhibiting the formation of nickel carbide and consequently the nucleation and growth of carbon filaments.

Zirconia was used to support Ru, Ni, and Ru-Ni bimetallic nanoparticles for CO2 methanation. The formation of an alloy was detected in Ru K-edge spectra. The Ru/ZrO2 exhibited the highest CO2 reaction rate (1.35 mol/molmetal.s) with a CH4 selectivity of 97.3%. The diffuse reflectance infrared fourier transform spectroscopy experiments suggest that formates serve as intermediates in converting CO2 to CO via reverse water–gas shift at the interface between Ru and defect-sites on zirconia, while Ru metal intercepts CO, further hydrogenating it to CH4. The better performance of Ru/ZrO2 could be related to the Ru-zirconia interface and Ru on-top atoms, which promote the reverse water gas shift and the CO hydrogenation reactions. Thus, this work provided important information about the effect of alloying Ru with Ni on the performance of the catalyst for the CO2 methanation, as well as the mechanism of this reaction for the best catalyst, Ru/ZrO2.

A series of Pt/CeO2 catalysts with different support morphologies was studied for the low temperature ethanol steam reforming. Different ceria nanostructures (nanocube_NC, nanorod_NR and flower-like_FL) were prepared by the hydrothermal method and are compared with CeO2 obtained by precipitation. Support morphology was found to influence certain reaction routes, even though the reaction scheme was the same regardless of the support. Concerning catalyst stability at 573 K, Pt/CeO2- PPT exhibited rapid deactivation, whereas Pt/CeO2- NR remained rather stable. XPS surface analysis before and after reaction at 573 K revealed significant degree of Pt reduction on CeO2 nanorods, directly related to the reduction of Ce4+ into Ce3+. DRIFTS experiments under reaction conditions for 5 h, revealed an accumulation of acetates on the Pt/CeO2- PPT catalyst, likely due to the imbalance between the rate of acetate species decomposition to CHx (not facilitated over Ptδ+ of the catalyst with the lower Pt dispersion), and their desorption as CH4.

Different metals supported on SiO2 were tested for the hydrodeoxygenation of phenol. For Pt/SiO2, Pd/SiO2 and Rh/SiO2 catalysts, phenol is mainly tautomerized, followed by hydrogenation of the aromatic ring. The direct dehydroxylation of phenol followed by hydrogenolysis is favored over more oxophilic metals (Ru, Co and Ni).

This work studied the performance of Ni-based catalysts derived from LaNiO3 and CeSiO2 supported LaNiO3 perovskite-type oxides for the steam reforming of ethanol. In situ XRD and TPR revealed the presence of different Ni species on both calcined samples: LaNiO3, La2NiO4 and NiO phases. Both catalysts deactivated during the reaction. Ni sintering was ruled out based on the in situ XRD experiments under reaction conditions. For LaNiO3, metallic Ni particles were partially oxidized by the water present in the feed at the beginning of the reaction. Then, NiO particles formed were reduced again by the syngas produced during the reaction. TG analysis showed significant carbon formation on LaNiO3 catalyst. However, carbon formation was significantly decreased over LaNiO3/CeSiO2 catalyst, which was due to the important role of the support on the mechanism of carbon removal for steam reforming of ethanol.

A detailed investigation of the effect of Zn on the performance of supported Ni-based catalysts for steam reforming of ethanol is presented in this paper. A Ni/Al 2 O 3 and two ZnO/Al 2 O 3 supported Ni catalysts with different Zn/Al ratio were prepared. For the Ni/Al 2 O 3 and Ni/ZnAl 2 O 4 (Zn/Al = 0.5) catalysts, only metallic Ni particles were identified after reduction. Under ethanol steam reforming conditions, carbon filaments were formed during the reaction, which led to deactivation of the catalyst. It was shown that Zn present in excess (Ni/ZnO-Al 2 O 3 ) may form an alloy with compositions ranging from Zn-rich tetragonal NiZn and Ni-rich cubic Ni 4 Zn. The formation of NiZn alloy with different compositions plays a key role in catalyst performance, improving resistance to coke formation and its stability.

This work studied the effect of preparation method of MgO on the performance of Ni/MgO catalysts for steam reforming of ethanol. Three different MgO were prepared by precipitation and aging, precipitation and decomposition of precursor salt. Depending on the synthesis conditions, the basicity and the type of Ni species significantly varied. TPD of adsorbed CO 2 showed that the MgO prepared by precipitation and aging possess the highest amount of basic sites. TPR and XANES revealed the presence of two different Ni species: NiO particles and Ni 2+ inserted in the lattice of a NiO–MgO solid solution, which is hardly reducible. Ni supported on MgO obtained by precipitation and aging exhibited the highest reduction degree. The preparation method of MgO also affected the amount of carbon formed during SR of ethanol at 773 K under H 2 O/ethanol molar ratio of 3.0. Increasing basicity decreased the amount of carbon deposits, which was attributed to the increase of carbon gasification rate.

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.

The partial oxidation of methane was studied on Pt/Al2O3, Pt/ZrO2, Pt/CeO2 and Pt/Y2O3 catalysts. For Pt/Al2O3, Pt/ZrO2 and Pt/CeO2, temperature programmed surface reaction (TPSR) studies showed partial oxidation of methane comprehends two steps: combustion of methane followed by CO2, and steam reforming of unreacted methane, while for Pt/Y2O3 a direct mechanism was observed. Oxygen Storage Capacity (OSC) evaluated the reducibility and oxygen transfer capacity of the catalysts. Pt/CeO2 catalyst showed the highest stability on partial oxidation. The results were explained by the higher reducibility and oxygen storage/release capacity which allowed a continuous removal of carbonaceous deposits from the active sites, favoring the stability of the catalyst, For Pt/Al2O3 and Pt/ZrO2 catalysts the increase of carbon deposits around or near the metal particle inhibits the CO2 dissociation on CO2 reforming of methane. Pt/Y2O3 was active and stable for partial oxidation of methane, and its behavior was explained by a change in the reaction mechanism.

O biogás apresenta como vantagens, por exemplo, a redução da emissão de gases de efeito estufa e a redução de resíduos utilizados como matérias-primas. O objetivo deste trabalho foi realizar um estudo prospectivo, através da análise de artigos científicos e documentos patentários sobre osprocessos de aproveitamento do biogás como fonte de energia renovável, visando acompanhar o desenvolvimento tecnológico neste setor. Observou-se que, de maneira geral, o número de artigos científicos e de depósito de pedidos de patentes nesta áreaaumentou ao longo dos últimos dez anos.Os Estados Unidos se destacaram, sendo o país com maior número de publicações de artigos científicos e depósitos de pedidos de patentes nesse setor.

The effects of ceria morphology on catalytic performance of Ni/CeO2 catalysts for low temperature steam reforming of ethanol are investigated. XRD analyses showed that Ni supported on CeO2 nanostructures (nanocube, nanorod and flower-like) exhibited a smaller Ni0 crystallite size, which favoured ethanol decomposition at low temperatures as revealed by TPSR experiments. Moreover, regardless of ceria morphology, all catalysts deactivate during reaction at 300 °C. However, the amount of carbon formed is higher over Ni supported on CeO2 nanocubes, which exhibited a higher formation of nickel carbide phase, as detected by XANES analyses. The nature and the amount of carbon formed depends on reaction temperature. Increasing reaction temperature increases the amount of carbon deposited and favores the formation of carbon filaments.

Promotion of Ni/CeO 2 -nanocube with small amounts of Pt was shown to significantly enhance catalyst stability for steam reforming of ethanol. The main reaction pathway appeared to be essentially ethanol decomposition toward carbon oxides (CO/CO 2 ), H 2 and CH 4 . Further investigation of the stabilizing effect brought about by the presence of the noble metal by different techniques (XPS, TPSR, ethanol TPD, in-situ XAFS) revealed that Pt segregation toward the surface of the Ni particles minimized the formation of nickel carbide phase and consequently decreased catalyst deactivation. Pt addition promotes the hydrogenation of highly active carbon species adsorbed at the surface at a higher rate than carbon diffusion into bulk nickel. These findings points to an alternative way for minimizing the problem of carbon buildup on Ni-based catalysts for steam reforming of ethanol.

© 2017 Elsevier Ltd. Sustainability concerns have increasingly gained importance among organizations and their stakeholders around the world. In this context, eco-efficiency has become a consistent tool towards the transition to sustainable development and the efforts of eco-efficiency indicators have been used for comparative studies and decision-making tasks, providing better financial, environmental, and social performance. The aim of this paper is to provide a systematic literature review on the theme of sustainable development from the perspective of eco-efficiency, with the adaptation of the Knowledge Development Process intervention instrument - constructivist (ProKnow-C). The paper identifies and structures the state-of-the-art between Eco-Efficiency and Sustainable Development with a view to: (i) selecting a Bibliographic Portfolio (BP) that is aligned with the perception of the researchers on the theme; (ii) performing a bibliometric analysis of the selected BP; (iii) performing a thematic synthesis; (iv) finding the integration of eco-efficiency and sustainable development with other approaches; (v) proposing an innovative framework to achieve sustainable development through eco-efficiency indicators; and (vi) finding paths for further research. This research makes multiple new contributions, providing both academics and practitioners a better panorama to achieve sustainable development through eco-efficiency by expanding the literature review, highlighting the synergies and barriers between eco-efficiency and sustainable development and by comparing and analysing them, showing its relevant features. In addition, we synthesized the contributions of the BP according to the BASF indicators, sustainable dimensions and four measurement levels: industry, organization, project and process to better describe the current academic scenario on the subject.

This work studied the effect of the type of ceria dopant on the performance of Ni/CeO2 SOFC anode for ethanol conversion reaction. Ni-based catalysts supported on CeO2 doped with different cations (Gd, Y, Pr, Zr, Nb) were prepared by the hydrothermal method. The addition of dopant to ceria led to the formation of the solid solutions during calcination for all samples, except for CeNb sample due to the low solubility limit. In spite of the high oxygen mobility of ceria-based supports, all catalysts deactivated for ethanol decomposition reaction at 1123 K due to carbon deposition. The large Ni0 and CeO2 crystallites formed during calcination at high temperature reduced the effectiveness of the mechanism of carbon removal because of the low metal-support interfacial area. The lowest formation of carbon on Ni/CeNb catalyst was attributed to the presence of NiNb2O6 phase. The reduction of this phase leads to the formation of Ni particles covered by NbOx species, which inhibits carbon formation.

The catalytic activity of high specific area CeO2·SiO2 was investigated under a flowing ethanol/steam mixture at 773 K. An attempt was made to tune the oxygen mobility of the catalyst further by doping it with small amounts of certain early transition metal oxides (V, Cr, Mn, Nb, Mo, W). Among the dopants studied, Mn, Cr, and, to a lesser extent, W drive the reaction pathway toward acetone synthesis. These dopants likely promote acetone synthesis by (i) enhancing oxygen mobility and thereby accelerating the oxidation of ethanol derived adsorbed species toward acetates, (ii) limiting the buildup of carbonate species, and (iii) suppressing the ethanol dehydration pathway.

This report investigates the properties of nickel/gadolinium-doped ceria (Ni/GDC) as anode material for bio-ethanol fueled SOFC. The Ni/GDC cermets with 18 and 44 wt.% Ni were prepared by a hydrothermal method. Ethanol decomposition, steam reforming, and partial oxidation of ethanol were studied using a fixed-bed reactor at 1123 K. Carbon was formed only under dry ethanol for both catalysts. The addition of water or oxygen to the feed inhibited the formation of carbon. Ni/GDC was used as the anode current collector layer and as a catalytic layer in single cells tests. No deposits of carbon were detected in single cells with Ni/GDC catalytic layer after 50 h of continuous operation under direct (dry) ethanol. This result was attributed to the catalytic properties of the Ni/GDC layer and the operation mechanism of gradual internal reforming, in which the oxidation of hydrogen provides the steam for ethanol reforming, thus avoiding carbon deposition.

The performance of catalysts derived from LaCo1−xCuxO3 (x = 0.0 or 0.2) perovskite-type oxides for steam reforming (SR) and oxidative SR of ethanol at 773 K was evaluated. All catalysts deactivated during SR of ethanol. In the absence of Cu, the increase of calcination temperature from 873 to 1,073 K did not affect the stability of the samples. On the other hand, for the samples containing Cu, it was detected a higher rate of deactivation when the calcination temperature was increased. The loss of activity of LaCoO3 was attributed to the oxidation of Co metallic particles and amorphous carbon formation as revealed by in situ XAFS and thermogravimetric analyses. The addition of Cu favored the formation of carbon filaments. Moreover, the presence of oxygen in the feed decreased the carbon formation, improving the stability of the catalysts.

The performance of Ni-based catalysts synthesized by the combustion method, using different fuel-to-oxidizers ratios ( φ ), for ethanol conversion reactions was investigated. All catalysts were selective to hydrogen for steam reforming (SR) of ethanol. Regardless of the φ value, all catalysts deactivated during SR of ethanol at 773 K. Scanning electron microscopy and thermogravimetric analyses showed that the loss of activity was due to carbon deposition. However, decreasing φ reduced the amount of carbon formed. This was related to the smaller crystallite size of metallic Ni obtained for the sample with lower φ , as revealed by X-ray diffraction experiments. On the other hand, the catalysts were very stable at high reaction temperature (1073 K). The occurrence of the reverse of Boudouard reaction and the carbon gasification reaction inhibited carbon deposition. Furthermore, the presence of water or oxygen in the feed promoted the mechanism of carbon removal and catalyst stability.

The catalytic performance of Ni/CeGd SOFC anodes with low Ni content (18%wt) prepared by a hydrothermal method for ethanol conversion reactions was evaluated. Calcination temperature and reaction conditions significantly affected the activity and stability of the samples. Increasing calcination temperature decreased ethanol conversion. This was likely due to the larger CeGd crystallite size. All samples deactivated during reaction under pure ethanol at 773 K. The addition of water or oxygen to the feed and the increase of reaction temperature improved catalyst stability. Scanning electron microscopy and thermogravimetric analysis showed that the deactivation was due to carbon formation. In the presence of oxygen or water, the mechanism of carbon removal was favored. Moreover, carbon formation was not favored at high reaction temperature due to the reverse of the Boudouard reaction as well as the promoting effect of the support on the carbon gasification reaction.

This paper investigates the effect of lanthanum substitution by cerium oxide on the performance of La 1− x Ce x NiO 3 ( x = 0, 0.05, 0.1, 0.4, 0.7 and 1.0) perovskite-type oxide precursor for the oxidative steam reforming of ethanol. All catalysts are active and selective to hydrogen but carbon deposition occurs except for La 0.90 Ce 0.10 NiO 3 . Increasing the Ce content decreases the amount of carbon deposited, which passes through a minimum at around 10 wt% of Ce and then increases. The higher resistance to carbon formation on La 0.90 Ce 0.10 NiO 3 catalyst is due to the smaller Ni crystallite size. Furthermore, the support also plays an important role on catalyst stability during ethanol conversion reaction. The reduced La 0.9 Ce 0.1 NiO 3 sample exhibits the highest amount of oxygen vacancies, which decreases as ceria content increases. This highly mobile oxygen reacts with carbon species as soon as it forms, and thus keeps the metal surface free of carbon, inhibiting deactivation.

The catalytic performance of Ni/CeGd SOFC anodes prepared by co-precipitation for steam reforming of ethanol at different reaction temperatures was evaluated. The Ni/CeGd SOFC anode calcined at 1073 K exhibited the highest activity and the lowest by-products formation rates during SR at 773 K. The TG and SEM analyses of the used catalysts showed that the deactivation observed for SR at 773 K was associated with the formation of carbon filaments. It was also observed that the increase of reaction temperature from 773 to 1073 K decreased coke formation, which was no longer detected at 1073 K. This result was attributed to the reverse of the Boudouard reaction and the promoting effect of the support on carbon gasification.

In this study, we evaluated the effect of ceria–zirconia content on the performance of Pt/x%CeZrO2/Al2O3 (x = 0–40 wt.%) during partial oxidation of methane. X-ray diffraction results indicated that, for samples containing 10 and 20 wt.% of CeZrO2, there was the formation of a homogeneous solid solution between ceria and zirconia. On the other hand, for Pt/30%CeZrO2/Al2O3, there was the formation of a ceria rich phase and a zirconia rich phase whereas a ceria rich phase and an isolated zirconia phase were detected for Pt/40%CeZrO2/Al2O3. Catalytic tests showed that Pt/Al2O3 exhibited a significant deactivation, while Pt/10%CeZrO2/Al2O3 and Pt/20%CeZrO2/Al2O3 practically did not loose their activity after 24 h. A deactivation was detected for Pt/30%CeZrO2/Al2O3 and Pt/40%CeZrO2/Al2O3. The higher stability of the Pt/10%CeZrO2/Al2O3 and Pt/20%CeZrO2/Al2O3 catalysts was attributed to the high reducibility and consequently the high oxygen mobility of the homogeneous solid solution formed, which promoted the mechanism of carbon removal from the metallic particle.

Ceria plays an active catalytic role in removing carbon from the catalyst by a support-mediated cleaning mechanism. Increasing the support surface area using a novel preparation method led to improved catalyst stability and a lower coking rate. DRIFTS of adsorbed ethanol shows that oxygen from the support facilitates the formation of acetate intermediate species, thus demonstrating the ability of the support to donate oxygen. This oxygen may come from either O adatoms by adsorption of O2 at vacancies, whereby the cerium atoms involved are Ce4+. Or, it may come from vacancy-associated Type II bridging OH groups, where the cerium atoms involved are Ce3+. The higher oxygen/OH group mobility of high ceria surface area promotes the mechanism of carbon removal, which in turn contributes to the high stability of Co/CeO2 catalyst.

To promote long-term stability of Pt/CeO2 catalyst for ethanol steam reforming, two approaches were examined. Sn was added to Pt to suppress carbon formation. Although the catalyst with high Sn content exhibited improved stability, acetaldehyde selectivity was prohibitive. DRIFTS experiments revealed that Sn inhibited the ability of Pt to facilitate steam-assisted forward acetate decomposition reaction to carbonate, the precursor to CO2 formation. However, CO2 co-feeding was more effective, not only in promoting long-term catalyst stability, but also in maintaining high H2 selectivity. DRIFTS experiments indicate that the kinetic influence of CO2 can be explained as a competition with ethanol for adsorption sites, leading to a suppression in the rate of formation of coke precursors.

This paper studies the performance of LaNiO3 perovskite-type oxide precursor as a catalyst for both steam reforming and oxidative steam reforming of ethanol. According to results of temperature-programmed desorption of adsorbed ethanol and by carrying out diffuse reflectance infrared Fourier transform spectroscopy analyses of ethanol steam reforming, ethanol decomposes to dehydrogenated species like acetaldehyde and acetyl, which at moderate temperatures, convert to acetate by the addition of hydroxyl groups. Demethanation of acetate occurs at higher temperatures, leading to a steady state coverage of carbonate. Catalyst deactivation occurs from the deposition of carbon on the surface of the catalyst. Both thermogravimetric and scanning electron microscopy analyses of postreaction samples indicate that lower reaction temperatures and lower H2O/EtOH ratios favor the deposition of filamentous carbon. However, less carbon formation occurs when the H2O/EtOH ratio is increased. Increasing reaction temperature or including O2 in the feed suppresses filamentous carbon formation.

This paper studies the effect of space time on the deactivation of a Co/CeO2 catalyst during oxidative steam reforming of ethanol. Increasing space time increased the ethanol conversion and hydrogen selectivity whereas acetaldehyde formation decreased. Both thermogravimetric and scanning electron microscopy analyses of post-reaction samples indicate that higher space times favor the deposition of filamentous carbon. However, the amount of carbon formed passes through a maximum and then decreases at high space time. Higher space times appear to allow the support, based on its oxygen mobility property, enough contact time to supply O needed to clean the carbon.

The mechanisms of Co/ceria catalyst deactivation during steam reforming, oxidative steam reforming, and partial oxidation of ethanol were explored by comparing the results from different characterization techniques with those obtained from catalytic testing in a fixed-bed reactor. The nature of carbon deposition and the reaction conditions played critical roles in determining the extent of a catalyst deactivation. To shed light on the modes of carbon deposition under different reaction conditions, the mechanisms by which the adsorbed surface species turned over on the catalyst surface were evaluated using diffuse reflectance infrared spectroscopy under reaction conditions and temperature-programed desorption of adsorbed ethanol. In steam reforming, ethoxy species were converted to acetate and steam promoted forward acetate demethanation. The resulting methane decomposed on Co metal particles. In this case, carbon diffused through the Co particle, nucleating growth sites for filamentous carbon behind it, with the resulting filaments lifting Co from the support. High H2O/ethanol ratios and oxygen promoted cleaning of the cobalt surface.

The aim of the work was to study the performance of ceria catalysts to convert ethanol to hydrogen in a combined system including ethanol steam reforming and PROX. The roles of the active oxide component, partially reduced ceria, and the metal component, Pt, in the ethanol steam reforming mechanism were investigated by diffuse reflectance infrared spectroscopy (DRIFTS) carried out under steady state reaction conditions. The main mechanism was found to proceed by (1) dissociative adsorption of ethanol to ethoxy species; (2) dehydrogenation of ethoxy species to adsorbed acetaldehyde; (3) oxidation of acetaldehyde species by ceria OH groups to acetate; (4) acetate demethanation to CH4 and carbonate species; (5) carbonate decomposition to CO2; and presumably (6) CH4 decomposition steps. Though Pt improved the initial ethanol conversion rate by facilitating hydrogen transfer and demethanation steps, the Pt–ceria interface was quickly lost to the buildup of carbon-containing species, thus hindering the Pt from effectively demethanating the acetate intermediate. Unpromoted ceria, though less active, was a significantly more stable catalyst. The steps for the PROX reaction in the presence of acetaldehyde were found to include: (1) decomposition of acetaldehyde leading to CO and methane; (2) hydrogenation of acetaldehyde producing ethanol; and (3) oxidation of the CO.

The objective of this work was to study the effects of different noble metal loadings on Pt/CeZrO2/Al2O3 catalysts for the partial oxidation of methane. For both Al and CeZrAl series of samples, the decrease of platinum loading resulted in a significant increase of metallic dispersion. Temperature-programmed reduction and oxygen storage capacity analyses revealed that the sample containing 1.5% Pt presented superior redox properties when compared to the other samples. The catalytic tests showed that the use of smaller Pt contents lead to deactivation. X-ray absorption near edge structure experiments showed that all Pt is in the reduced form above 600 °C. In addition, there is evidence that the partial oxidation of methane proceeds through a two-step mechanism. The best performance was obtained for the 1.5Pt/CeZr/Al catalyst that has the largest platinum content, the presence of a homogeneous solid solution, good metal dispersion and high BET surface area.

The catalyst performance and the deactivation profiles of CeZrO 2 and Pt/CeZrO 2 were evaluated for the ethanol decomposition and steam reforming of ethanol reactions at 773 K. Unpromoted CeZrO 2 was quite stable whereas Pt/CeZrO 2 catalyst deactivated for all feed compositions studied. A reaction mechanism was proposed based on diffuse reflectance infrared spectroscopy analyses carried out under reaction conditions. The decomposition of the dehydrogenated and the acetate species is facilitated by the presence of the metal and resulted in high selectivity to hydrogen, methane, CO and CO 2 over Pt/CeZrO 2 . Diffuse reflectance infrared spectroscopy, transmission electron microscopy and temperature programmed oxidation and desorption analyses indicate that the loss of the Pt-support synergy leads to a buildup of carbonaceous residue, which is the likely reason of the deactivation of Pt/CeZrO 2 . In addition, once the interfacial boundary is lost, the demethanation of acetate becomes hindered, resulting in an increase in acetaldehyde selectivity with time onstream.

The effect of the support nature on the performance of Pd catalysts during partial oxidation of ethanol was studied. H 2 , CO 2 and acetaldehyde formation was favored on Pd/CeO 2 , whereas CO production was facilitated over Pd/Y 2 O 3 catalyst. According to the reaction mechanism, determined by DRIFTS analyses, some reaction pathways are favored depending on the support nature, which can explain the differences observed on products distribution. On Pd/Y 2 O 3 catalyst, the production of acetate species was promoted, which explain the higher CO formation, since acetate species can be decomposed to CH 4 and CO at high temperatures. On Pd/CeO 2 catalyst, the acetaldehyde preferentially desorbs and/or decomposes to H 2 , CH 4 and CO. The CO formed is further oxidized to CO 2 , which seems to be promoted on Pd/CeO 2 catalyst.

The effect of the support nature and metal dispersion on the performance of Pt catalysts during steam reforming of ethanol was studied. H2 and CO production was facilitated over Pt/CeO2 and Pt/CeZrO2, whereas the acetaldehyde and ethene formation was favored on Pt/ZrO2. According to the reaction mechanism, determined by temperature-programmed desorption (TPD) and Diffuse Reflectance Infrared Spectroscopy (DRIFTS) analysis, some reaction pathways are favored depending on the support nature, which can explain the differences observed on the resulting product distribution.

The surface properties and catalytic behavior of Pd/ x CeO 2 –Al 2 O 3 catalysts in partial oxidation of methane and autothermal reforming of methane were investigated. There was an increase on ceria's apparent crystallite sizes with the increase of CeO 2 loadings and with the rise of the calcination temperatures of the supports from 500 to 900 °C. A decrease on the density of Pd sites was observed with the use of supports calcined at lower temperature and with the increase of CeO 2 loadings. However, CO linearly bonded/CO bridged bonded intensity ratios showed an opposite trend. This apparent disagreement could be due to the partial coverage of Pd sites by CeO x species. Pd/Al 2 O 3 catalyst was strongly deactivated during partial oxidation or autothermal reforming of methane, while catalysts with higher ceria loadings exhibited superior stability. Pd/ x CeO 2 –Al 2 O 3 catalysts show an increase of activity for autothermal reforming of methane with the increase of CeO 2 loading. Therefore, the activity and stability apparently decrease with Pd dispersion. This fact was ascribed to partial coverage of Pd by [CePd x O]Pd 0 species, which show high ability to promote the gasification of coke. The formation of [CePd x O]Pd 0 species results in a decrease of the density of Pd sites but led to higher accessibility of the active sites to methane.

The catalytic performance of a Pt/CeZrO 2 catalyst was tested for ethanol decomposition, steam reforming, partial oxidation, and oxidative steam reforming. At low temperature, the catalyst underwent significant deactivation during ethanol decomposition and steam reforming reactions. Co-feeding oxygen decreased the deactivation rate of the catalyst but adversely affected the selectivity to hydrogen. Increasing the reaction temperature greatly improved the stability of the catalyst. A reaction mechanism was proposed based on results obtained from in situ diffuse reflectance infrared spectroscopy analyses carried out under reaction conditions. Ethanol adsorbs as ethoxy species, which may follow one of two distinct pathways: (i) decomposition and production of CO, CH 4 , and H 2 or (ii) dehydrogenation to acetaldehyde and acetyl species. The dehydrogenated species may undergo oxidation to acetate species. The addition of water to the feed promoted the formation of acetate species. Water also facilitated the decomposition of acetaldehyde and acetate reactions, resulting in the formation of methane, CO, and carbonate.

In this work, the effect of the thermal treatment temperature of the support on the behavior of Pt/CeZrO 2 /Al 2 O 3 catalysts on the methane partial oxidation was evaluated. BET surface area, metal dispersion and oxygen storage capacities and hydrogen consumption during TPR decreased with the increase of the thermal aging temperature. During the reaction of partial oxidation of methane, Pt/CeZrO 2 /Al 2 O 3 aged at 1073 and 1173 K presented the best performance. This result was attributed to the higher reducibility of the support and to the larger metal dispersion presented by these materials. These properties favor the carbon removal mechanism from the metal surface, avoiding deactivation.

In this work, the effect of the metal nature on the reaction mechanism of the partial oxidation of ethanol on Pt/CeO2 and Rh/CeO2 catalysts was studied by using diffuse reflectance infrared spectroscopy (DRIFTS) analyses. The results showed that the nature of the metal affected the reaction mechanism. On Pt/CeO2 catalyst, adsorption of ethanol gives rise to ethoxy species, which can be decomposed, producing CH4, H2 and CO, and dehydrogenated, forming acetaldehyde. The acetaldehyde species are dehydrogenated to acetyl species or may desorb. The acetyl species can be oxidized to acetate species or can be decomposed, forming CH4, H2 and CO. Furthermore, the acetate species previously formed can be decomposed to CH4, CO and/or oxidized to CO2 via carbonate species. On the other hand, for Rh-based catalyst, the ethoxy species can be also dehydrogenated to a cyclic compound (oxametallacycle). This intermediate is dissociated to CO, CHx and Cx, which are oxidized to CO2. Furthermore, it was observed that the oxidation of acetyl species to acetate species and the formation of CO2 are favored depending on the presence of the O2 in the feed on Pt/CeO2 and Rh/CeO2 catalysts, respectively.

The effect of the use of cerium (1 wt%)-doped alumina on the performance of Pt/Al2O3, Pt/CeO2/Al2O3 and Pt/CeZrO2/Al2O3 catalysts on the partial oxidation of methane (POM) was evaluated. The catalysts were characterized by X-ray diffraction (XRD), BET surface area and temperature-programmed reduction (TPR). Platinum dispersion was estimated through cyclohexane dehydrogenation. Pt/CeZrO2/Al-doped catalyst showed the best performance on the POM. XRD analysis revealed that the previous addition of ceria to alumina led to the formation of a homogeneous solid solution, which exhibited a high-oxygen storage capacity. The good activity and stability of this material was associated to its higher metal dispersion, higher oxygen storage capacity and larger degree of coverage of alumina by CeZrO2 oxide, which increase the effectiveness of the carbon cleaning mechanism.

The performance of supported platinum catalysts on the autothermal reforming of methane was evaluated. The effect of the calcination temperature of the CeZrO 2 support and of the reaction conditions (reaction temperature, presence of CO 2 in the feedstock, and H 2 O/CH 4 molar ratio) was studied. The catalysts were characterized by BET, XRD, and OSC analyses and the reaction mechanism was determined by TPSR experiments. The TPSR analyses indicate that autothermal reforming of methane proceeds through a two-step mechanism (indirect mechanism) over all catalysts studied. The Pt/Ce 0.75 Zr 0.25 O 2 catalyst presented the best stability, which depends not only on the amount of oxygen vacancies of the support but also on the metal particle size. The higher reducibility and oxygen storage/release capacity of Pt/Ce 0.75 Zr 0.25 O 2 catalyst promote the mechanism of continuous removal of carbonaceous deposits from the active sites, which takes place at the metal-support interfacial perimeter. The water also participates in this mechanism, favouring the carbon removal of metal particle. Furthermore, the reaction conditions influenced significantly the behaviour of Pt/Ce 0.75 Zr 0.25 O 2 catalysts. The increase of H 2 O/CH 4 molar ratio had a beneficial effect on the methane conversion and on the H 2 /CO molar ratio. However, the increase of the reaction temperature had an opposite effect. Both the methane conversion and H 2 /CO molar ratio decreased with the increasing of reaction temperature. Moreover, the addition of CO 2 to feedstock increased the initial methane conversion, but decreased the stability of the catalyst.

A fuel processing system using ethanol as a renewable feedstock is proposed to produce highly pure hydrogen to feed a fuel cell for power generation. Hydrogen production was accomplished through partial oxidation of ethanol over Rh/CeO2 catalyst. The reformate was admitted into a water–gas shift reactor for primary CO clean-up. In this purification stage two different CeO2-supported catalysts were investigated. The results from partial oxidation reaction revealed that hydrogen production is strongly affected by the reaction temperature. Therefore, it was clear that the operating condition must be adjusted to reach a more efficient process focused on maximizing the hydrogen production and deplete the CO formation. The catalyst behavior and infrared analyses showed that the mechanism of ethanol partial oxidation follows a different pathway over Rh-based catalysts. Regarding the water–gas shift step, it was seen that higher catalytic activities were reached over the vanadium-modified Pt/CeO2 catalyst within a wide range of temperature. Such improvement was suggested to be related to the presence of a V2O5 phase, much probably due to its redox properties. The results suggest that the catalysts presented in this contribution may be used as a fuel processor system for fuel cell applications.

The partial oxidation of ethanol was investigated over Ru and Pd catalysts supported onto yttria over a wide range of temperatures (473–1073 K). The product distributions obtained over these catalytic systems were correlated with diffuse reflectance infrared spectroscopy analyses (DRIFTS). Results showed that reaction route depended strongly on the type of metal. The decomposition of ethoxy species to CH4 and CO or oxidation to CO2 was promoted by Pd, and the acetaldehyde desorption was predominant over Ru in the low temperature region. Furthermore, the acetate and carbonate formation prevailed over Pd, which explained the lower acetaldehyde selectivity. The presence of CH4 and CO2 at high temperature is assigned to the decomposition of acetate species via carbonates over Pd-based catalysts. Ru was more suitable system for H2 production than Pd by achieving a selectivity of about 59%.

Hydrogen production for fuel cells from ethanol partial oxidation was evaluated on 1% Rh/CeO2 catalyst. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) were used to analyze carbon formation and the possible sintering of the metallic phase. X-ray fluorescence (XRF), nitrogen adsorption, and temperature-programmed reduction (TPR) were also used for catalyst characterization. Two groups of rhodium particles of different sizes were observed. By SEM/EDS analysis, no residual chloride was identified. TEM made it possible to identify the presence of rhodium in small clusters. On the other hand, products distribution was affected by reaction temperature. At 473 K, only traces of acetaldehyde were detected for the Rh/CeO2 catalyst. In the reaction conditions, no deactivation of the catalyst due to carbon deposition or sintering of the metal was observed. Overall, our results show that the performance of Rh/CeO2 catalyst points to promising applications in terms of H2 production for fuel cells technology by ethanol partial oxidation.