Performance of Ni catalyst supported on La-hexaaluminate in CO<Subscript>2</Subscript> reforming of CH<Subscript>4</Subscript>

CO₂ reforming of CH₄ was performed using Ni catalyst supported on La-hexaaluminate which has been an well-known material for high-temperature combustion. La-hexaaluminate was synthesized by sol-gel method at various conditions where different amount of Ni (5–20 wt%) was loaded. Ni/La-hexaaluminate experienced 72 h reaction and its catalytic activity was compared with that of Ni/Al₂O₃, Ni/La-hexaaluminate shows higher reforming activity and resistance to coke deposition compared to the Ni/Al₂O₃ model catalyst. Coke deposition increases proportionally to Ni content. Consequently, Ni(5)/La-hexaaluminate(700) is the most efficient catalyst among various Ni/La-hexaaluminate catalysts regarding the cost of Ni in Ni(X)/La-hexaaluminate catalysts. BET surface area, XRD, EA, TGA and TPO were performed for surface characterization. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Effect of CeO<Subscript>2</Subscript>-addition sequence on the performance of CeO<Subscript>2</Subscript>-modified Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst in autothermal reforming of iso-octane

Two types of CeO₂-modified Ni/Al₂O₃ catalysts were prepared by a consecutive impregnation method with different sequences in the impregnation of Ni and CeO₂, and their performance in autothermal reforming (ATR) of isooctane was investigated. Catalysts prepared by adding CeO₂ prior to the addition of Ni, Ni/CeO₂-Al₂O₃, produced larger amounts of hydrogen than those obtained using catalysts prepared by adding the two components in an opposite sequence, Ni-CeO₂/Al₂O₃. The results of H₂ chemisorption and temperature-programmed reduction revealed that added CeO₂ increased the dispersion of the Ni species on Al₂O₃ and suppressed the formation of NiAl₂O₄ in the catalyst such that large amounts of Ni species were present as NiO, the active species for the ATR. The elemental and thermogravimetric analyses of deactivated catalysts indicated that Ni/CeO₂-Al₂O₃, which showed a longer lifetime than Ni-CeO₂/Al₂O₃, contained lesser amounts and different types of coke on the surface.     

Oxidative reforming of methane on structured Ni-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/cordierite catalysts

The catalytic properties of Ni/Al₂O₃ composites supported on ceramic cordierite honeycomb monoliths in oxidative methane reforming are reported. The prereduced catalyst has been tested in a flow reactor using reaction mixtures of the following compositions: in methane oxidation, 2–6% CH₄, 2–9% O₂, Ar; in carbon dioxide and oxidative carbon dioxide reforming of methane, 2–6% CH₄, 6–12% CO₂, and 0–4% O₂, and Ar. Physicochemical studies include the monitoring of the formation and oxidation of carbon, the strength of the Ni-O bond, and the phase composition of the catalyst. The structured Ni-Al₂O₃ catalysts are much more productive in the carbon dioxide reforming of methane than conventional granular catalysts. The catalysts performance is made more stable by regulating the acid-base properties of their surface via the introduction of alkali metal (Na, K) oxides to retard the coking of the surface. Rare-earth metal oxides with a low redox potential (La₂O₃, CeO₂) enhance the activity and stability of Ni-Al₂O₃/cordierite catalysts in the deep and partial oxidation and carbon dioxide reforming of methane. The carbon dioxide reforming of methane on the (NiO + La₂O₃ + Al₂O₃)/cordierite catalyst can be intensified by adding oxygen to the gas feed. This reduces the temperature necessary to reach a high methane conversion and does not exert any significant effect on the selectivity with respect to H₂.     

Effect of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> xerogel support on hydrogen production by steam reforming of LNG over Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> catalyst

An Al₂O₃-ZrO₂ xerogel (AZ-SG) was prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/AZ-SG catalyst was then prepared by an impregnation method, and was applied to hydrogen production by steam reforming of LNG. A nickel catalyst supported on commercial alumina (A-C) was also prepared (Ni/A-C) for comparison. The hydroxyl-rich surface of the AZ-SG support increased the dispersion of nickel species on the support during the calcination step. The formation of a surface nickel aluminate-like phase in the Ni/AZ-SG catalyst greatly enhanced the reducibility of the Ni/AZ-SG catalyst. The ZrO₂ in the AZ-SG support increased the adsorption of steam onto the support and the subsequent spillover of steam from the support to the active nickel sites in the Ni/AZ-SG catalyst. Both the high surface area and the well-developed mesoporosity of the Ni/AZ-SG catalyst improved the gasification of adsorbed surface hydrocarbons in the reaction. In the steam reforming of LNG, the Ni/AZ-SG catalyst showed a better catalytic performance than the Ni/A-C catalyst. Moreover, the Ni/AZ-SG catalyst showed strong resistance toward catalyst deactivation.     

Effect of Nickel as Dopant in Mn/TiO<Subscript>2</Subscript> Catalysts for the Low-Temperature Selective Reduction of NO with NH<Subscript>3</Subscript>

Nickel doped manganese oxide supported on titania materials were investigated for the low-temperature NH₃-SCR. For this purpose, a series of Ni modified Mn/TiO₂ catalysts were prepared and evaluated for the low-temperature SCR of NO with ammonia in the presence of excess oxygen. The catalytic performance of these materials was compared with respect to the nickel weight percentage in order to examine the correlation between physicochemical characteristics and reactivity of optimized materials. It was found that the 5% Mn–2% Ni/TiO₂ catalyst showed the highest activity and yielded 100% NO conversion at 200 °C. XRD results reveal highly dispersed manganese–nickel species on TiO₂ support for the Mn–Ni/TiO₂ catalysts. Our TPR data results suggested an increase in reducibility of manganese species in Mn–Ni/TiO₂ catalysts. The absence of the high-temperature (736 K) peak indicates that the dominant phase is MnO₂. This increase of reducibility and dominant MnO₂ phase seems to be the reason for the enhanced activity and time on stream patterns of nickel-promoted titania-supported manganese catalysts. BET results illustrate that the high NO conversion is strongly dependant on the specific surface area and pore volume of this catalyst. All the physicochemical techniques we used suggested that the composition of manganese and nickel oxides on the support surface is playing an important role for the enhancement of NO conversion and the prominent time on stream stability.     

Partial oxidation of methane over Ni/Ce-Zro<Subscript>2</Subscript>/θ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>

The catalytic behavior of Ni/Ce-ZrO₂/θ-Al₂O₃ has been investigated in the partial oxidation of methane (POM) toward synthesis gas. The catalyst showed high activity and selectivity due to the heat treatment of the support and the promotional effect of Ce-ZrO₂. It is suggested that the support was stabilized through the heat treatment of γ-Al₂O₃ and the precoating of Ce-ZrO₂, on which a protective layer was formed. Moreover, sintering of the catalyst was greatly suppressed for 24 h test. Pulse experiments of CH₄, O₂ and/or CH₄/O₂ with a molar ratio of 2 were systematically performed over fresh, partially reduced and well reduced catalyst. Results indicate that CH₄ can be partially oxidized to CO and H₂ by the reactive oxygen in complex NiO_x species existing over the fresh catalyst. It is demonstrated that POM over Ni/Ce-ZrO₂/θ-Al₂O₃ follows the pyrolysis mechanism, and both the carbonaceous materials from CH₄ decomposition over metallic nickel and the reactive oxygen species present on NiO_x and Ce-ZrO₂ are intermediates for POM.     

The promotional effect of K on the catalytic activity of Ni/MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> for the combined H<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> reforming of coke oven gas for syngas production

A K-promoted 10Ni-(x)K/MgAl₂O₄ catalyst was investigated for the combined H₂O and CO₂ reforming (CSCR) of coke oven gas (COG) for syngas production. The 10Ni-(x)K/MgAl₂O₄ catalyst was prepared by co-impregnation, and the K content was varied from 0 to 5 wt%. The BET, XRD, H₂-chemisorption, H₂-TPR, and CO₂-TPD were performed for determining the physicochemical properties of prepared catalysts. Except under the condition of a K/Ni=0.1 (wt%/wt%), the Ni crystal size and dispersion decreased with increasing K/Ni. The coke resistance of the catalyst was investigated under conditions of CH₄: CO₂: H₂: CO:N₂=1 : 1 : 2 : 0.3 : 0.3, 800 °C, 5 atm. The coke formation on the used catalyst was examined by SEM and TG analysis. As compared to the 10Ni/MgAl₂O₄ catalyst, the Kpromoted catalyst exhibited superior activity and coke resistance, attributed to its strong interaction with Ni and support, and the improved CO₂ adsorption characteristic. The 10Ni-1K/MgAl₂O₄ catalyst exhibited optimum activity and coke resistance with only 1wt% of K.     

Ni-Co bimetallic catalyst for CH<Subscript>4</Subscript> reforming with CO<Subscript>2</Subscript>

A co-precipitation method was employed to prepare Ni/Al₂O₃-ZrO₂, Co/Al₂ O₃-ZrO₂ and Ni-Co/Al₂O₃-ZrO₂ catalysts. Their properties were characterized by N₂ adsorption (BET), thermogravimetric analysis (TGA), temperature-programmed reduction (TPR), temperature-programmed desorption (CO₂-TPD), and temperature-programmed surface reaction (CH₄-TPSR and CO₂-TPSR). Ni-Co/Al₂O₃-ZrO₂ bimetallic catalyst has good performance in the reduction of active components Ni, Co and CO₂ adsorption. Compared with mono-metallic catalyst, bimetallic catalyst could provide more active sites and CO₂ adsorption sites (C + CO₂ = 2CO) for the methane-reforming reaction, and a more appropriate force formed between active components and composite support (SMSI) for the catalytic reaction. According to the CH₄-CO₂-TPSR, there were 80.9% and 81.5% higher CH₄ and CO₂ conversion over Ni-Co/Al₂O₃-ZrO₂ catalyst, and its better resistance to carbon deposition, less than 0.5% of coke after 4 h reaction, was found by TGA. The high activity and excellent anti-coking of the Ni-Co/Al₂O₃-ZrO₂ catalyst were closely related to the synergy between Ni and Co active metal, the strong metal-support interaction and the use of composite support.     

Catalytic Steam Reforming of Propane over Ni/LaAlO<Subscript>3</Subscript> Catalysts: Influence of Preparation Methods and OSC on Activity and Stability

Abstract  

To develop an efficient catalyst for steam reforming of propane, Ni/LaAlO₃ catalysts were prepared by deposition precipitation, impregnation, and solvo-thermal methods, and characterized by XRD, BET, H₂-TPR, elemental analyses, and TEM. Ni/Al₂O₃ and Ni/CeO₂ catalysts were also synthesized by the solvo-thermal method for comparison. The Ni/LaAlO₃ catalysts exhibited better catalytic performance than both Ni/Al₂O₃ and Ni/CeO₂ catalysts, and activities with Ni/LaAlO₃ were found to be dependent upon the preparation methods. In particular, the Ni/LaAlO₃ catalyst synthesized by the solvo-thermal method exhibited the highest activity presumably because tetrahydrofuran helps distribute generated Ni nanoparticles onto the catalyst surface in a uniform fashion. In addition, the solvo-thermally prepared Ni/LaAlO₃ catalyst was found to be highly stable, with its activity being maintained at least during 100 h. The observed high stability is attributed to the excellent oxygen storage capacity of LaAlO₃, which was first determined by thermogravimetric methods as well as by soot oxidations in the presence of Al₂O₃, CeO₂, and LaAlO₃. Compared to the Ni/Al₂O₃ and Ni/CeO₂ catalysts, Ni/LaAlO₃ exhibited suppressed carbon formation even at lower S/C ratios due to the superior oxygen transport ability of the LaAlO₃ support.     

Influence of Calcination Temperature on Activity and Selectivity of Ni–CeO<Subscript>2</Subscript> and Ni–Ce<Subscript>0.8</Subscript>Zr<Subscript>0.2</Subscript>O<Subscript>2</Subscript> Catalysts for CO<Subscript>2</Subscript> Methanation

Herein, we studied the influence of calcination temperature (500–800 °C) of Ni/CeO₂ and Ni/Ce_0.8Zr_0.2O₂ catalysts on the specific surface area, pore volume, crystalline size, lattice parameter, chemical bonding and oxidation states, nickel dispersion and CH₄/CO production rate in CO₂ methanation. In general, the catalytic performance revealed that Zr doping catalysts could increase the CH₄ production rate. Combined with the production rate and the characterizations results, we found that the combination of nickel dispersion, peak area of CO₂–TPD and O_II/(O_II + O_I)) play the critical role in increasing the CH₄ production rate. It is well to be mentioned that the CO production rate is strongly influenced by the nickel dispersion. Furthermore, the in-situ DRIFTS confirmed that the CO originates from the decomposition of H-assisted formate species.     

Reductive amination of ethanol to ethylamines over Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

Ni(x)/Al₂O₃ (x=wt%) catalysts with Ni loadings of 5–25 wt% were prepared via a wet impregnation method on an γ-Al₂O₃ support and subsequently applied in the reductive amination of ethanol to ethylamines. Among the various catalysts prepared, Ni(10)/Al₂O₃ exhibited the highest metal dispersion and the smallest Ni particle size, resulting in the highest catalytic performance. To reveal the effects of reaction parameters, a reductive amination process was performed by varying the reaction temperature (T), weight hourly space velocity (WHSV), and NH₃ and H₂ partial pressures in the reactions. In addition, on/off experiments for NH₃ and H₂ were also carried out. In the absence of NH₃ in the reactant stream, the ethanol conversion and selectivities towards the different ethylamine products were significantly reduced, while the selectivity to ethylene was dominant due to the dehydration of ethanol. In contrast, in the absence of H₂, the selectivity to acetonitrile significantly increased due to dehydrogenation of the imine intermediate. Although a small amount of catalyst deactivation was observed in the conversion of ethanol up to 10 h on stream due to the formation of nickel nitride, the Ni(10)/Al₂O₃ catalyst exhibited stable catalytic performance over 90 h under the optimized reaction conditions (i.e., T=190 °C, WHSV=0.9 h^?1, and EtOH/NH₃/H₂ molar ratio=1/1/6).     

V-promoted Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst for synthetic natural gas (SNG) production: Catalyst preparation methodologies

The effect of preparation method on the catalytic performance of V-promoted Ni/Al₂O₃ catalysts for synthetic natural gas (SNG) production via CO methanation has been investigated. The Ni-V/Al₂O₃ catalysts were prepared by co-impregnation (CI) method, deposition precipitation (DP) method as well as two sequential impregnation (SI) methods with different impregnation sequence. Among the prepared catalysts, the one prepared by CI method exhibited the best catalytic performance due to its largest H₂ uptake and highest metallic Ni dispersion. In a 91h-lifetime test, this catalyst showed high stability at high temperature and weight hourly space velocity. This work demonstrates that the catalytic performance of the V-promoted Ni/Al₂O₃ catalysts can be improved by carefully controlling the preparation method/conditions.     

CO<Subscript>2</Subscript> methanation and co-methanation of CO and CO<Subscript>2</Subscript> over Mn-promoted Ni/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

A series of Mn-promoted 15 wt-% Ni/Al₂O₃ catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al₂O₃ catalysts for CO₂ methanation and the comethanation of CO and CO₂ in a fixed-bed reactor was investigated. The catalysts were characterized by N2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and highresolution transmission electron microscopy. The presence of Mn increased the number of CO₂ adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al₂O₃ catalysts had improved CO₂ methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO₂ conversion was achieved with the 1.71Mn-Ni/Al₂O₃ catalyst. The co-methanation tests on the 1.71Mn-Ni/Al₂O₃ catalyst indicated that adding Mn markedly enhanced the CO₂ methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO₂ methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.

Open image in new window

     

Synthesis of nickel catalysts supported on Zr-doped ordered mesoporous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and their catalytic performance for low-temperature CO<Subscript>2</Subscript> reforming of CH<Subscript>4</Subscript>

A series of Zr-doped ordered mesoporous Al₂O₃ with various Zr contents were synthesized by evaporation-induced self-assembly strategy and the Ni-based catalysts supported on these Al₂O₃ materials were prepared by impregnation method. These catalysts with large specific surface area, big pore volume, uniform pore size possess excellent catalytic performance for the low-temperature carbon dioxide reforming of methane. The activities of these catalysts were tested in carbon dioxide reforming of methane reaction with temperature increasing from 500 to 650?°C and the stabilities of these catalysts were evaluated for long time reaction at 650?°C. It was found that when Zr/(Zr?+?Al) molar ratio?=?0.5%, the Ni/0.5ZrO₂–Al₂O₃ catalyst showed the highest activity, and exhibited superior stabilization compared to the Ni-based catalyst supported on traditional ordered mesoporous Al₂O₃. The “confinement effect” from mesoporous channels of alumina matrix is helpful to stabilize the Ni nanoparticles. As a promoter, Zr could stabilize the ordered mesoporous framework by reacting with Al₂O₃ to form ZrO₂–Al₂O₃ solid solution. Since ZrO₂ enhances the dissociation of carbon dioxide, more oxygen intermediates are given to remove the carbon formed during the reaction.     

Hydrogen Production from Glycerol Over Nickel Catalysts Supported on Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Modified by Mg,Zr, Ce or La

Hydrogen production from glycerol reforming in liquid (aqueous phase reforming, APR) and vapor (steam reforming SR) phase over alumina-supported nickel catalysts modified with Ce, Mg, Zr and La was studied. Characterization of catalysts by temperature programmed reduction and XPS analyses revealed important structural effects: (i) the intercalation of Mg between nickel and alumina that inhibited the alumina incorporation to nickel phases, (ii) the close contact between Ni and Zr phases and, (iii) the close surface interaction of La and Ce ions with NiO phases. The catalytic activity of the samples studied in this work clearly indicated the different catalyst functionalities necessary to carry out aqueous-phase and vapor-phase steam reforming of glycerol. For aqueous phase reforming of glycerol, the addition of Ce, La and Zr to Ni/Al₂O₃ improves the initial glycerol conversions obtained over the Ni/Al₂O₃ supported catalyst. It is suggested that the differences in catalytic activities are related with geometric effects caused by the decoration of Ni phases by Ce and La or by the close interaction between Ni and Zr. In spite that nickel catalysts showed high APR activities at initial times on stream, all samples showed, independently of support, important deactivation rates that deactivate the catalysts after few hours under operation. Catalysts characterization after APR showed the oxidation of the active metallic Ni during reaction as the main cause of the observed deactivation. In the case of the glycerol steam reforming in vapor phase, the use of Ce, La, Mg and Zr as promoters of Ni based catalysts increases the hydrogen selectivity. Differences in activity were explained in terms of enhancement in: surface nickel concentration (Mg), capacity to activate steam (Zr) and stability of nickel phases under reaction conditions (Ce and La).     

CeO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> catalyst prepared by physical mixing for NH<Subscript>3</Subscript> selective catalytic reduction: Evidence about the migration of sulfates from TiO<Subscript>2</Subscript> to CeO<Subscript>2</Subscript> via simple calcination

A mechanical mixture of CeO₂ and TiO₂ powder with a small amount of sulfate was applied for the selective catalytic reduction (SCR) of NO with NH₃. After calcination at 500 oC, the mixed sample showed significantly enhanced activity and selectivity compared to the uncalcined one and, moreover, demonstrated even higher activity than the conventional V₂O₅/TiO₂ catalyst above 300 °C. Combined characterization results revealed that the main active sites were newly formed sulfate species on CeO₂, the number of which increased with calcination. Temperatureresolved DRIFT spectra provided convincing evidence about the migration of sulfate species from TiO₂ to CeO₂, as confirmed from the shift of v(S=O) band as a result of the mechanical mixing and the subsequent calcination.     

Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and CeO<Subscript>2</Subscript>-promoted MgO sorbents for CO<Subscript>2</Subscript> capture at moderate temperatures

A series of Al₂O₃ and CeO₂ modified MgO sorbents was prepared and studied for CO₂ sorption at moderate temperatures. The CO₂ sorption capacity of MgO was enhanced with the addition of either Al₂O₃ or CeO₂. Over Al₂O₃-MgO sorbents, the best capacity of 24.6 mg- CO₂/g-sorbent was attained at 100 °C, which was 61% higher than that of MgO (15.3 mg-CO₂/g-sorbent). The highest capacity of 35.3 mg-CO₂/g-sorbent was obtained over the CeO₂-MgO sorbents at the optimal temperature of 200 °C. Combining with the characterization results, we conclude that the promotion effect on CO₂ sorption with the addition of Al₂O₃ and CeO₂ can be attributed to the increased surface area with reduced MgO crystallite size. Moreover, the addition of CeO₂ increased the basicity of MgO phase, resulting in more increase in the CO₂ capacity than Al₂O₃ promoter. Both the Al₂O₃-MgO and CeO₂-MgO sorbents exhibited better cyclic stability than MgO over the course of fifteen CO₂ sorption-desorption cycles. Compared to Al₂O₃, CeO₂ is more effective for promoting the CO₂ capacity of MgO. To enhance the CO₂ capacity of MgO sorbent, increasing the basicity is more effective than the increase in the surface area.

Open image in new window

     

Effects of MgO promoter on properties of Ni/Al2O3 catalysts for partial oxidation of methane to syngas

The effects of MgO promoter on the physicochemical properties and catalytic performance of Ni/Al₂O₃ catalysts for the partial oxidation of methane to syngas were studied by means of BET, XRD, H₂-TPR, TEM and performance evaluation. It was found that the MgO promoter benefited from the uniformity of nickel species in the catalysts, inhibited the formation of NiAl₂O₄ spinel and improved the interaction between nickel species and support. These results were related to the formation of NiO-MgO solid solution and MgAl₂O₄ spinel. Moreover, for the catalysts with a proper amount of MgO promoter, the nickel dispersiveness was enhanced, therefore making their catalytic performance in methane partial oxidation improved. However, the excessive MgO promoter exerted a negative effect on the catalytic performance. Meanwhile, the basicity of MgO promoted the reversed water-gas shift reaction, which led to an increase in CO selectivity and a decrease in H₂ selectivity. The suitable content of MgO promoter in Ni/Al₂O₃ catalyst was ∼7 wt-%. Translated from Journal of Fuel Chemistry and Technology, 2006, 34(4): 450–455 [译自: 燃料化学学报]     

Ni/La<Subscript>2</Subscript>O<Subscript>3</Subscript>-ZrO<Subscript>2</Subscript> catalyst for hydrogen production from steam reforming of acetic acid as a model compound of bio-oil

Hydrogen production from steam reforming of acetic acid was investigated over Ni/La₂O₃-ZrO₂ catalyst. A series of Ni/La₂O₃-ZrO₂ catalysts were synthesized by sol-gel method coupled with wet impregnation, which was characterized by XRD, BET, TEM, EDS, TG, SEM and TPR. Catalytic activity of Ni/La₂O₃-ZrO₂ was evaluated by steam reforming of acetic acid at the temperature range of 550-750 °C. The tetragonal phase La_0.1Zr_0.9O_1.95 is formed through the doping of La₂O₃ into the ZrO₂ lattice and nickel species are highly dispersed on the support with high specific surface area. H₂ yield and CO₂ yield of Ni/La₂O₃-ZrO₂ catalyst with 15%wt Ni reaches 89.27% and 80.41% at 600 °C, respectively, which is attributed to high BET surface area and sufficient Ni active sites in strong interaction with the support. 15%wt Ni supported on La₂O₃-ZrO₂ catalyst maintains relatively stable catalytic activities for a period of 20 h.     

Synthesis and properties of flux-cast refractories in the Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-MgO-B<Subscript>2</Subscript>O<Subscript>3</Subscript> system

Details are given of the synthesis and testing of flux-cast refractory materials in the alumina-rich region of the Al₂O₃-MgO-B₂O₃ system; XRD and petrography indicate that the main structure-forming phases are corundum and magnesian spinel. In subordinate amounts there are the boroaluminate 9Al₂O₃·2B₂O₃ and the previously unknown compound 4Al₂O₃·MgO·2B₂O₃, whose composition has been established by microprobe analysis. Corrosion tests showed that three-component systems containing magnesium and boron oxides at levels of 5–10% do not increase the corrosion resistance of refractories in molten sodium-calcium-silicate glass and electrovacuum borosilicate glass. __________ Translated from Novye Ogneupory, No. 3, pp. 161–163, March, 2008.