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In this study, we made an effort to modify the Co/Al 2 O 3 , a typical catalyst for various steam reforming reactions, with Na, Mg, Zr, La, Ce and the elements from K to Zn in the periodic table of elements, in order to obtain a whole picture of impacts of these commonly used additives on catalytic behaviors of cobalt-based catalyst on one basis. The results showed Na, Mg, Zr, Sc, K and Cr addition increased specific area of the catalysts by creating new mesopores or decreasing pore radius while Ca filled the pores. The additives could also react with either cobalt species or alumina. CoV 2 O 6 , MgAl 2 O 4 , MnAl 2 O 4 NiAl 2 O 4 and ZnAl 2 O 4 and Co 7 Fe 3 alloy were formed during calcination/reduction of the catalysts. Na, K, Cu, Ni or Ce addition promoted the catalytic activity, while Mg, Ca, Sc, Ti, V, Cr, Mn suppressed. As for coking, Na, K, Ca, Fe, Zn, La helped to suppress coking while Cu or Zr enhanced. The coke became more aromatic over the modified catalysts. V or La promoted formation of the coke with graphite structure, while Cu or Fe was the opposite. The additives also affected the morphology of the coke or diameter of the carbon nanotubes formed. The in-situ DRIFTS studies showed that ethanol could be dehydrated to form C=C and dehydrogenated to form acetyl species at 100 °C. The addition of Na suppressed the formation of the acetyl species, while Cu addition promoted the acetyl species, C=O and C=C formation, leading to the high tendencies of Cu–Co/Al 2 O 3 towards coking. Image 1 • Na, K, Cu, Ni or Ce addition promoted catalysis, while Mg, Ca, Sc, Ti, V, Cr or Mn suppressed. • V or La promoted graphitic coke formation, while Cu or Fe produced amorphous coke. • Additives affected morphology of the coke or diameter of carbon nanotubes formed. • In-situ DRIFTS studies showed that ethanol degrade to C=C and acetyl species at 100 °C. • Cu promoted acetyl, C=O and coking formation, while Na addition suppressed acetyl. [ABSTRACT FROM AUTHOR]

This paper studied the effects of the additives including Zr, Mg and K on the catalytic behaviors of Co/Al 2 O 3 during the steam reforming of acetic acid. It was found that Zr additive had negligible effect on the performance of the cobalt catalyst, while Mg additive could markedly lower the activity and selectivity of the catalyst. In comparison, K showed remarkable positive effects on the cobalt catalyst. The additives affect the physiochemical properties of the catalyst in varied ways, imposing distinct effects on the performance of the catalysts. Zr additive did not affect reduction behaviors of cobalt oxides or distribution of metallic cobalt sites, thus the effects of Zr additive on performances of the catalyst was insignificant. Mg additive, in converse, led to reduction temperature of cobalt oxides shifting upwards, which negatively affected the formation of metallic cobalt sites on surface of the catalyst and consequently on the catalytic activity and stability. K additive could drastically promote the reduction of cobalt oxides, significantly promoting the catalytic activity and stability. Further to this, K additive could also effectively reduce methane formation during steam reforming of acetic acid through suppressing the methanation reactions. In addition, K additive could enhance the resistance of metallic cobalt towards oxidation, enhancing the catalytic stability, while Zr or Mg additive did not have such an effect. [ABSTRACT FROM AUTHOR]

This study investigated the distinct catalytic behaviors of mono Mn, Fe, Co, Ni, Cu and Zn catalysts in the reforming of the small organics including methanol, acetic acid and acetone. The results showed that Mn, Fe or Zn-based catalysts showed almost no activity for steam reforming of either methanol, acetic acid or acetone, due to their low capacity to break the chemical bonds of the organics or to activate steam. Co and Cu-based catalysts were generally active for steam reforming of methanol. Nevertheless, Co-based catalysts promoted methanol decomposition to form a substantial amount of CO. Alumina as a support remarkably influenced catalytic stability of the catalyst. The unsupported Cu catalyst showed a much lower stability than Cu/Al 2 O 3. Nevertheless, the unsupported Ni was more stable than Ni/Al 2 O 3 catalyst, due to its high resistivity towards coking. The unsupported Co, however, was prone to coking. The C/H ratios in the coke formed over the unsupported and alumina-supported Ni or Co catalysts were distinct, indicating the involvement of alumina in the coking process. In addition, Ni and Co catalysts behaved differently. Ni/Al 2 O 3 showed a superior stability than Co/Al 2 O 3 in steam reforming of acetone. The coke formed on Ni/Al 2 O 3 was more aromatic than that over Co/Al 2 O 3 catalysts while morphologies of coke (nanotubes over Ni/Al 2 O 3 versus fibrous coke over Co/Al 2 O 3) were also different. • Ni and Co catalysts showed superior activity for reforming than Mn, Fe or Zn. • Unsupported Ni was more stable than Ni/Al 2 O 3 , due to high resistivity to coking. • Coke formed in acetone reforming was less aromatic than that of acetic acid. • Coke formed in Ni and in Ni/Al 2 O 3 was different due to the effects of alumina. • The coke on Ni/Al 2 O 3 was less aliphatic than on Co/Al 2 O 3 in acetone reforming. [ABSTRACT FROM AUTHOR]

• Interaction between Ni and Al 2 O 3 impacts more on catalytic activity than Ni dispersion. • Weak interaction between Ni and Al 2 O 3 help to free Ni for catalytic reactions. • Weak interaction between Ni and Al 2 O 3 facilitates migration and sintering of nickel. • DRIFTS study show the interaction affects formation of the reaction intermediates. • The interaction affects thermal stability, structures and forms of the coke deposit. This study focused on the impacts of the varied extent of interaction between nickel and alumina in Ni/Al 2 O 3 on the catalytic behaviors and reaction intermediates formed in methanation of CO 2 and steam reforming of acetic acid. The calcination of alumina at high temperature eliminated some "reactive sites", alleviating the interaction between nickel species and alumina and significantly impacting the catalytic activities. The interaction between nickel and alumina was much stronger and the nickel dispersion was also higher over the 5% Ni/Al 2 O 3 -600 °C than over 5% Ni/Al 2 O 3 -1000 °C. However, the activities of the former catalyst was remarkably lower. The interaction between nickel and alumina played more profound influence than nickel dispersion on the catalytic activity. The weak interaction between nickel and alumina would help to "release" or "free" the nickel species for catalytic reactions, which, however, facilitated the migration and sintering of nickel. The in situ DRIFTS studies of methanation showed that the weaker interaction between alumina and nickel promoted the conversion of HCOO*, a key intermediate from methanation of CO 2 , to CH 4. The properties of coke formed in steam reforming was also affected by the interaction between nickel and alumina. Fibrous form and amorphous form of coke tended to form over the catalyst with stronger interaction, while carbon nanotube tended to form over the catalyst with weaker interaction. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the effects of strong base (KOH) addition on the catalytic performances of Ni/Al 2 O 3 catalysts in acetic acid steam reforming for hydrogen generation was investigated. The addition of KOH drastically changed the physiochemical property and catalytic performances of the nickel–based catalysts. KOH reacted with γ–Al 2 O 3 during calcination, forming ɑ–Al 2 O 3 with Al(OH) 3 as a reaction intermediate, which led to reconstruction of the porous structure, merge of small pores, decreased specific area and sintering of nickel. Most importantly, the catalytic activity of nickel–based catalysts were significantly enhanced by the addition KOH, especially the ones with low nickel loading. There are almost no active of 1 wt% Ni/Al 2 O 3 catalyst for steam reforming of acetic acid, while, with adding 5 wt % KOH, activity of the catalyst matched that of 20 wt% Ni/Al 2 O 3. In–situ DRIFTS study showed the involvement of the reactive intermediates including CH 3 , CH 2 , C O, COO, C O C, C C and absorbed CO 2 in acetic acid steam reforming. The Ni/Al 2 O 3 catalyst with low nickel loading had insufficient metallic nickel to gasify these reactive intermediates. The presence KOH effectively aided gasification of the reactive intermediates, and thus significantly promoted the catalytic activity. In addition, the KOH with varied loading significantly affect formation of catalytic coke and polymeric coke formed during the reforming reaction. Graphical abstract Image 1 Highlights • Adding KOH to Ni/Al 2 O 3 led to transformation of γ–Al 2 O 3 to ɑ–Al 2 O 3 and sintering of nickel. • KOH addition significantly enhances activity of Ni/Al 2 O 3 catalysts with low nickel loading. • DRIFTS study showed the reforming involved CH 3 , CH 2 , C O, COO, C O C, C C and *CO 2 species. • KOH presence effectively gasify the reactive intermediates and promote catalytic activity. • KOH loading significantly affect the formation of catalytic coke and polymeric coke. [ABSTRACT FROM AUTHOR]

The paper investigated the effects of various nickel precursors (Ni(NO 3 ) 2 , NiCl 2 , NiSO 4 , Ni(CH 3 COO) 2 , Ni(NH 2 SO 3 ) 2 ) on the catalytic behaviors of Ni/Al 2 O 3 catalysts in steam reforming of acetic acid, aiming to understand the fundamental influences of nickel metal precursors. The catalysts were characterized with TPR, TPO, TPR-MS, TPO-MS, XRD, TG-MS, FT-IR, FT-Raman, BET method, element analysis, TEM and SEM. The results revealed the substantial influence of the nickel precursors on properties of Ni/Al 2 O 3 catalysts. The use of NiSO 4 and Ni(NH 2 SO 3 ) 2 as nickel precursors led to the low activities of the catalysts, due to the formation of Ni 3 S 2 during reduction of the catalysts with hydrogen. The sulfur species were removed in the form of SO 2 during the calcination of the catalysts precursors in air and in the form of H 2 S during the reduction of the calcined catalyst in hydrogen. NiCl 2 /Al 2 O 3 catalyst showed a negligible activity as the chlorine poisoned the catalyst and was difficult to be removed via calcination. Furthermore, chlorine could accelerate sintering of alumina. In comparison, Ni(CH 3 COO) 2 as nickel precursor could effectively suppress the formation of NiAl 2 O 4 . Ni(CH 3 COO) 2 /Al 2 O 3 catalyst showed comparable activity to that of Ni(NO 3 ) 2 /Al 2 O 3 , but the resistivity towards coking was higher. In addition, the coke species produced over the catalysts have both large and small aromatic ring systems with the morphology of both amorphous and fibrous structures. [ABSTRACT FROM AUTHOR]

This study investigated the interaction of nickel species with alumina versus calcination temperature and nickel loading. A total of 22 Ni/Al 2 O 3 catalysts, calcined at the temperature from 500 to 1000 °C at a 50 °C increment, were employed for the study. High calcination temperature led to the formation of nickel–alumina spinel via the solid phase reaction, which shifted the reduction temperature to higher ranges. The catalyst, however, still achieved good activity after full reduction of the nickel–alumina spinel. Nevertheless, the high calcination temperature led to the collapse of the small pores and the formation of the big one, resulting in the significant decrease of specific surface area. At higher nickel loadings, more nickel species weakly interacted with alumina formed as the reactive center of alumina was saturated. With the increase of nickel loading, the catalytic activities were not varied much but the catalytic stability and the resistivity towards coking enhanced. The coke produced over the catalyst at low nickel loading tended to be amorphous, while the coke produced at the high nickel loading was more fibrous. Furthermore, the coke produced at the low loading contained more small aromatic rings and more oxygen-containing functional groups. The higher nickel loading possibly promoted the catalytic cracking reactions to form more catalytic coke while the low nickel loading probably favored the polymerization reactions to form the polymeric coke. In addition, the calcination at the higher temperature could enhance the stability of the catalysts, which might be related to the enlarged pore sizes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Molecular structure of the acids determines their behaviors in steam reforming. • Formic acid was more active in homogenous decomposition than acid with C C bond(s). • Number of C C bonds in the acids affects their reactivity and tendency to coking. • The coke formed during steam reforming of the acid has large aromatic ring systems. • The coke formed in reforming of the heavier carboxylic acids was fibrous. The paper investigated the effects of molecular structures on the conversion of the carboxylic acids (formic acid, acetic acid, propionic acid and butyric acid) during the steam reforming reactions. In essence, molecular structures determined catalytic behaviors of the organics during the reforming reactions. The acids with a C C bond were more stable than formic acid during the homogenous decomposition reactions. However, the steam reforming of formic acid was much easier than that of the heavier acids due to the absence of cracking of the C C bond during reforming. The difficulty for reforming of the carboxylic acids increased with the increase of the length of the aliphatic carbon chain (from acetic acid to butyric acid). The carboxylic acids with a longer aliphatic carbon chain (propionic acid and butyric acid) also had a higher tendency towards coking than acetic acid and formic acid. The coke formed in steam reforming of formic acid was the lowest compared with other acids. The C C bond and the number of C C bond in the carboxylic acids affected the reactivity of the carboxylic acids, their tendencies towards the formation of coke and the properties of the coke. The coke had larger aromatic ring systems and oxygen–containing functionalities during steam reforming of acetic acid. The amorphous coke formed in reforming of acetic acid, while the fibrous coke formed during the reforming of the heavier carboxylic acids. [ABSTRACT FROM AUTHOR]

In this study, steam reforming of acetic acid over the Ni/γ-Al 2 O 3 catalysts with varied nickel contents (from 2.5 to 40 wt%) was performed, aiming to investigate the effects of nickel loading on properties and catalytic behaviors of the catalysts. The results show that the interaction of nickel species with alumina varies with varied nickel loading. At lower nickel loadings, the nickel strongly interacting with alumina are the main species, while with the saturation of the reactive sites of alumina via loading more nickel, the proportion of the nickel species weakly interacting with alumina increased remarkably. Excess nickel on alumina can fill the pores, decreasing the reduction degree of nickel oxides, the specific area (from ca. 277 to 132 m 2  g −1 with the increase of nickel loading to 40 wt%), the pore volume, and the pore diameters. Nickel loading also significantly affects the catalytic activity, stability of the catalyst and the resistivity towards coking. With the increase of nickel loading to 10 wt%, the activity of the catalyst reached a plateau. The further increase of nickel loading did not further increase the activity, but increased the stability and the tolerance towards the deactivation induced by coking. In addition, with higher nickel loadings, the coke formed has more large aromatic ring system. [ABSTRACT FROM AUTHOR]

Highlights: [•] Eggshell membrane-templated nanocatalyst with a hierarchical structure. [•] The effects of immersion time and calcination temperature on the catalyst microstructure. [•] Both particle size and the interaction between the catalyst and the support affect the performance of methane steam reforming. [Copyright &y& Elsevier]

[Display omitted] • Ethanol-assisted water electrolysis via SOECs realizes one-step hydrogen production. • Integrating anode with an electrochemical oxidation reaction brings beneficial effects. • SOEC operated at an ultrahigh current density of 3.0 A cm−2 with superior stability. Steam electrolysis over solid oxide electrolysis cells (SOECs) is a promising technique to store renewable power (such as solar and wind power) into hydrogen, and bio-ethanol-assisted steam electrolysis not only increases energy conversion efficiency but also store bio-mass energy into valuable fuels. This study developed SOEC-type reactors for conducting ethanol-assisted water electrolysis for the first time. Conventional catalytic steam reforming of ethanol for hydrogen production consumes a lot of heat and includes a complicated process, while the ethanol-assisted water electrolysis can achieve thermoneutral operation at the electrolysis potential of 0.36 V and generate heat at the electrolysis potentials of above 0.36 V, simultaneously obtaining pure hydrogen from cathode chamber by one step. Micro-reformer constructed by loading fibrous catalysts within channeled anode supports performed efficient ethanol reforming to facilitate fuel oxidation on anode and hence promote steam electrolysis on cathode. Employing Ni-based materials for both anode and cathode enables the co-sintering of three layers of SOEC components, resulting in low cell resistances and stable electrolysis at a record high current density of 3.0 A cm−2 under a low overall cell voltage of less than 1.3 V. Therefore, this study has demonstrated an efficient way to generate green hydrogen energy from renewables. [ABSTRACT FROM AUTHOR]

Autothermal reforming of methane couples exothermal partial oxidation of methane and endothermal steam or dry reforming of methane to achieve high energy efficiency, which can be operated through solid oxide fuel cells (SOFCs) so that expensive oxygen is not required and safety issue caused by CH 4 /O 2 mixture is avoided. In addition, electric power is simultaneously generated. This study has demonstrated the efficient electrochemical autothermal reforming of methane over a SOFC reactor integrated with catalyst beds within anode channel structure. The catalyst bed reformer increases syngas yield by a factor of about 6 owing to the increased methane conversion and syngas selectivity. By numerical assessment, enhanced mass transportation is well validated by high fuel accessibility at the electrode-electrolyte interface benefiting from the integrated catalyst beds. Compared with conventional catalyst layer on anode surface, the catalyst beds are more efficient for conducting methane reforming. After the initial stabilization of cell microstructure, the SOFC reactor has demonstrated stable cell performance and syngas yield during the test for 120 h. The integrated SOFC reactor has demonstrated a promising application in performing catalytic reforming reactions. [Display omitted] • Electrochemical autothermal reforming of methane is performed on SOFCs. • Electrochemical autothermal reforming generates syngas as well as electric power. • Channeled anode supports are integrated with catalyst bed micro-reformer. • Integrated SOFC reactors improve cell performance and syngas yields. [ABSTRACT FROM AUTHOR]

This study aims to investigate La 2 Zr 2 O 7 pyrochlore-supported Ni nanocatalysts prepared by electrospinning and subsequent heat treatment. The solid solubility of Ni in La 2 Zr 2 O 7 forms an interaction between NiO and La 2 Zr 2 O 7 supports, which improves Ni dispersion and therefore increases catalytic activity during methane partial oxidation. The catalyst activity increased with Ni content up to 7 wt%. A further increase of the Ni content decreased the activity due to the limited solubility. The catalyst calcination temperature affected the interaction and hence the catalytic activity, and the optimal calcination temperature was 1000 °C. The Ni/La 2 Zr 2 O 7 catalyst was compared with a conventional Ni/Al 2 O 3 catalyst in term of the interaction. NiAl 2 O 4 formation caused a strong interaction between Ni and Al 2 O 3 supports, resulting in high reduction temperatures and low reducibility. In contrast, the limited solubility of Ni in La 2 Zr 2 O 7 supports formed a more effective interaction, demonstrating the higher reducibility and catalytic performance. Therefore, an effective interaction between active catalyst and support is crucial to achieve high catalytic performance. Image 1 • Limited solid solubility of Ni in La 2 Zr 2 O 7 forms an effective interaction. • The effective interaction improves Ni catalyst dispersion and reducibility. • Catalyst calcination temperature affects the interaction and hence catalytic activity. • Catalytic stability of the nanofibrous catalysts was confirmed. [ABSTRACT FROM AUTHOR]