Recent Developments Towards Commercialization of Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFC) are receiving an increasing level of attention for both small- and large-scale applications due their high fuel flexibility compared to other types of fuel cells. This article reviews recent work in SOFC materials research, with an emphasis on anodes that can directly utilize hydrocarbon fuels

Choriented Maps: Visualizing SDG Data on Mobile Devices

Choropleth maps and graduated symbol maps are often used to visualize quantitative geographic data. However, as the number of classes grows, distinguishing between adjacent classes increasingly becomes challenging. To mitigate this issue, this work introduces two new visualization types: choriented maps (maps that use colour and orientation as variables to encode geographic information) and choriented mobile (an optimization of choriented maps for mobile devices). The maps were evaluated in a graphical perception study featuring the comparison of SDG (Sustainable Development Goal) data for several European countries. Choriented maps and choriented mobile visualizations resulted in comparable, sometimes better effectiveness and confidence scores than choropleth and graduated symbol maps. Choriented maps and choriented mobile visualizations also performed well regarding efficiency overall and performed worse only than graduated symbol maps. These results suggest that the use of colour and orientation as visual variables in combination can improve the selectivity of map symbols and user performance during the exploration of geographic data in some scenarios.Comment: Accepted for publication in the Cartographic Journa

The Activity of Fe-Pd Alloys for the Water-Gas Shift Reaction

The role of Fe promoters has been investigated on Pd/ceria, Pt/ceria and Rh/ceria catalysts for the water-gas shift (WGS) reaction in 25 Torr of CO and H2O, under differential reaction conditions. While no enhancement was observed with Pt and Rh, the activity of Pd/ceria increased by as much as an order of magnitude upon the addition of an optimal amount of Fe. Similarly, the addition of 1 wt% Pd to an Fe2O3 catalyst increased the WGS rate at 453 K by a factor of 10 over that measured on Fe2O3 alone, while the addition of Pt or Rh to Fe2O3 had no effect on rates. The amount of Fe that was necessary to optimize the rates increased with Pd loading but was independent of the order in which Fe and Pd were added to the ceria. Increased WGS activity was also observed upon the addition of Fe to Pd supported on Ce0.5Zr0.5O2. XRD measurements, performed after running the catalyst under WGS conditions, show the formation of a Fe-Pd alloy, even though similar measurements on an Fe/ceria catalyst showed that Fe3O4 was the stable phase for Fe in the absence of Pd. Possible implications of these results on the development of new WGS catalysts are discussed

The Effect of Oxide Dopants in Ceria on \u3cem\u3en\u3c/em\u3e-Butane Oxidation

Solid solutions of CeO2 with Yb2O3, Y2O3, Sm2O3, Gd2O3, La2O3, Nb2O5, Ta2O5, and Pr6O11 were prepared by sol-gel methods. All of the samples exhibited a single, cubic phase in x-ray diffraction and the lattice parameters were consistent with formation of the solid solutions. Surprisingly, all of the mixed oxides exhibited a much lower catalytic activity for n-butane oxidation than that of pure CeO2 at 650 K, with Sm0.2Ce0.8O1.9, Gd0.2Ce0.8O1.9, La0.2Ce0.8O1.9, Nb0.1Ce0.9O2.05, and Ta0.1Ce0.9O2.05 showing rates less than 10-2 that of pure ceria. Lower dopant levels with Sm+3 and Gd+3 affected the rates proportionately less. The implications of these results for use of ceria as an oxidation catalyst are discussed

A Comparison of Ceria and Sm-Doped Ceria for Hydrocarbon Oxidation Reactions

The oxidation of methane, ethane, propane, and n-butane has been studied over CeO2 and Ce0.8Sm0.2Ox (SDC) catalysts. The rates for methane and ethane were found to be indistinguishable over the two catalysts, while the rates for propane and n-butane were much higher on ceria compared to SDC. The difference between n-butane oxidation over ceria and SDC is shown to result from a low-temperature rate process on ceria that is not present on SDC. Measurements using CD4 and C4D10 show that both low- and high-temperature rates exhibit a similar kinetic-isotope effect; however, the low-temperature process is half-order in O2, while the high-temperature process is zeroth-order. Pulse studies demonstrate that oxygen from the bulk becomes accessible for reaction at approximately the same temperature as that at which the high-temperature rate process becomes important. The implications of these results for understanding the effect of doping on reactions over ceria, and for characterization of oxides using standard test reactions, are discussed

The Effect of Fe and Other Promoters on the Activity of Pd/Ceria for the Water-Gas Shift Reaction

The effect of adding oxide promoters, at monolayer coverages, to Pd/ceria catalysts was studied for the water-gas-shift reaction in 25 torr each of H2O and CO under differential conditions. Oxides of Fe, Tb, Gd, Y, Sn, Sm, Pr, Eu, Bi, Cr, V, Pb, and Mo were added to ceria by wet impregnation of aqueous salts and calcined to 873 K prior to addition of 1 wt% Pd. While most of the oxides had a negligible effect on the water-gas-shift rates, rates on the Fe-promoted sample were 8 times higher than on the unpromoted Pd/ceria at 473 K, while rates on the Mo- and Pb-promoted cerias were significantly lower than on pure Pd/ceria. By varying the Fe loading, it was found that the maximum catalytic activity was achieved at the monolayer coverage. Addition of Fe in bulk ceria through sol-gel and preparation of Fe2O3-CeO2 physical mixtures had no effect on the catalytic activity

Characterization of SO\u3csub\u3e2\u3c/sub\u3e-Poisoned Ceria-Zirconia Mixed Oxides

CeO2, ZrO2, and a series of CexZr1-xO2 catalysts with 1 wt% Pd were exposed to fixed exposures of SO2 under oxidizing environments and then characterized by FTIR, pulse-reactor studies with CO and O2, and temperature-programmed desorption (TPD). For exposures above 473 K, sulfates were formed on all of the materials; however, the results are consistent with the formation of bulk sulfates on CeO2 and only surface sulfates on ZrO2. For the mixed oxides, the quantity of sulfates formed at 673 K increased linearly with the Ce content. In TPD, the sulfates on ZrO2 were stable to higher temperatures than those formed on CeO2, which decomposed in a well-defined peak between 900 and 1050 K. The sulfates on both oxides were reduced by CO above 750 K. Even though XRD patterns for the mixed oxide were significantly different from that of the physical mixture, the TPD and pulse-reactor results were similar to what would be expected for physical mixtures of CeO2 and ZrO2, suggesting that sulfate species are associated with individual metal cations. Finally, pulse-reactor studies with CO and O2 at 873 K show that the sulfates can be reversibly reduced and oxidized on both CeO2 and ZrO2, so that sulfur poisoning gives rise to an apparent increase in oxygen storage, demonstrating that this method is not acceptable for measurement of this quantity

A Mechanistic Study of Sulfur Poisoning of the Water-Gas-Shift Reaction Over Pd/Ceria

The effect of sulfur on the water-gas-shift (WGS) activity of Pd/ceria catalysts has been studied using steady-state rate measurements, pulse-reactor studies, and FTIR. After exposing Pd/ceria to SO2 at 673 K in an oxidizing environment, the WGS rates dropped to a value close to that observed on Pd/alumina. Both pulse-reactor and FTIR measurements showed that cerium sulfates can be readily reduced by CO and re-oxidized by O2 at 723 K; however, unlike reduced ceria, the Ce2O2S formed by reduction of the sulfates cannot be re-oxidized by H2O or CO2. The implications of these measurements for understanding oxygen-storage capacity (OSC) of three-way catalysts are discussed

Optimization of carbon source efficiency for lipid production with the oleaginous yeast Saitozyma podzolica DSM 27192 applying automated continuous feeding

Background: Biotechnologically produced microbial lipids are of interest as potential alternatives for crude and plant oils. Their lipid profile is similar to plant oils and can therefore be a substitute for the production of biofuels, additives for food and cosmetics industry as well as building blocks for oleochemicals. Commercial microbial lipids production, however, is still not profitable and research on process optimization and cost reduction is required. This study reports on the process optimization using glucose or xylose with the unconventional oleaginous yeast Saitozyma podzolica DSM 27192 aiming to reduce the applied carbon source amount without sacrificing lipid productivity. Results: By optimizing the process parameters temperature and pH, lipid productivity was enhanced by 40%. Thereupon, by establishing a two-phase strategy with an initial batch phase and a subsequent fed-batch phase for lipid production in which a constant sugar concentration of about 10 g/L was maintained, resulted in saving of ~ 41% of total glucose and ~ 26% of total xylose. By performing the automated continuous sugar feed the total sugar uptake was improved to ~ 91% for glucose and ~ 92% for xylose and thus, prevented waste of unused carbon source in the cultivation medium. In addition, reduced glucose cultivation resulted in to 28% higher cell growth and 19% increase of lipid titer. By using xylose, the by-product xylonic acid was identified for the first time as by-product of S. podzolica. Conclusions: These findings provide a broad view of different cultivation process strategies with subsequent comparison and evaluation for lipid production with S. podzolica. Additionally, new biotechnological characteristics of this yeast were highlighted regarding the ability to produce valuable organic acids from sustainable and renewable sugars