There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

CO2 conversion covers a wide range of possible application areas from fuels to bulk and commodity chemicals and even to specialty products with biological activity such as pharmaceuticals. In the present review, we discuss selected examples in these areas in a combined analysis of the state-of-the-art of synthetic methodologies and processes with their life cycle assessment. Thereby, we attempted to assess the potential to reduce the environmental footprint in these application fields relative to the current petrochemical value chain. This analysis and discussion differs significantly from a viewpoint on CO2 utilization as a measure for global CO2 mitigation. Whereas the latter focuses on reducing the end-of-pipe problem “CO2 emissions” from todays’ industries, the approach taken here tries to identify opportunities by exploiting a novel feedstock that avoids the utilization of fossil resource in transition toward more sustainable future production. Thus, the motivation to develop CO2-based chemistry does...

Sustainable Conversion of Carbon Dioxide: An Integrated Review of Catalysis and Life Cycle Assessment

Despite being first demonstrated over 160 years ago, and offering significant environmental benefits and high electrical efficiency, it is only in the last two decades that fuel cells have offered a realistic prospect of being commercially viable. The solid oxide fuel cell (SOFC) offers great promise and is presently the subject of intense research activity. Unlike other fuel cells the SOFC is a solid-state device which operates at elevated temperatures. This review discusses the particular issues facing the development of a high temperature solid-state fuel cell and the inorganic materials currently used and under investigation for such cells, together with the problems associated with operating SOFCs on practical hydrocarbon fuels.

/pdf/solid-oxide-fuel-cells-2vfiwiriu1.pdf

Solid oxide fuel cells

A study is conducted to demonstrate catalytic dehydrogenation of light alkanes on metals and metal oxides. The study provides a complete overview of the materials used to catalyze this reaction, as dehydrogenation for the production of light olefins has become extremely relevant. Relevant factors, such as the specific nature of the active sites, as well as the effect of support, promoters, and reaction feed on catalyst performance and lifetime, are discussed for each catalytic Material. The study compares different catalysts in terms of the reaction mechanism and deactivation pathways and catalytic performance. The duration of the dehydrogenation step depends on the heat content of the catalyst bed, which decreases rapidly due to the endothermic nature of the reaction. Part of the heat required for the reaction is introduced to the reactors by preheating the reaction feed, additional heat being provided by adjacent reactors that are regenerating the coked catalysts.

Catalytic dehydrogenation of light alkanes on metals and metal oxides.

The kinetics of reduction of a 10 wt %Fe2O3-MgAl2O4 spinel were investigated using XRD and time resolved Fe-K QXANES. The Rietveld refinement of the XRD pattern showed the replacement of Al with Fe in the spinel structure and the formation of MgFeAlOx. The XANES pre-edge feature was employed to study the reduction kinetics during H2-TPR (Temperature Programmed Reduction) up to 730°C. About 55% of the Fe3+ in MgFeAlOx was reduced to Fe2+. A shrinking core model, which takes into account both solid-state diffusion via an oxygen diffusion coefficient, and gas-solid reaction through a reaction rate coefficient, was applied. The activation energy for chemical reaction showed a linear dependence on the conversion, increasing from 104 to 126 kJ/mol over the course of material reduction. The good accordance between the shrinking core model description and the experimental data indicates that XANES pre-edge features can be used to correlate changes in material structure and reaction kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1339–1349, 2018

Insight in kinetics from pre-edge features using time resolved in situ XAS

The application of a CO2 sorbent which releases CO2 at a lower temperature than calcium oxide is of interest in view of reducing the operating temperature or increasing the operating pressure of the super-dry reforming process. To this end, three different CO2 sorbents based on lithium orthosilicate (Li4SiO4) were prepared and characterized: (i) Li4SiO4 as such; (ii) zirconia coated Li4SiO4, denoted Li4SiO4@ZrO2; (iii) Li4SiO4, coated with lithium metazirconate and denoted as Li4SiO4@Li2ZrO3. While the carbonation properties of Li4SiO4 were found satisfactory, its decarbonation was incomplete. Li4SiO4@ZrO2 on the other hand, was found to contain Li2SiO3 and Li2ZrO3 rather than the anticipated Li4SiO4 and showed fast carbonation and decarbonation of Li2ZrO3. The best performing material in terms of CO2 sorption capacity, stability and rate of carbonation-decarbonation was Li4SiO4@Li2ZrO3. Its superior performance is ensured by the core-shell structure saturated with Li, allowing for easy restructuring during carbonation and fast regeneration upon decarbonation.

CO2 sorption properties of Li4SiO4 with a Li2ZrO3 coating

Two hydrotalcite-based catalysts have been prepared to investigate the effect of synthesis methods on the catalyst behavior in ethanol dehydrogenation to acetaldehyde. On the first one, PdZn/Mg(Al)Ox, Pd and Zn were impregnated on the hydrotalcite support while on the second one, PdZn/Mg(Al)(Pd)(Zn)Ox, Pd and Zn were both incorporated during the support synthesis. Extensive catalyst characterization such as EXAFS, XPS, STEM, XRD,… allowed concluding that impregnation of the active metals gives rise to larger nanoparticles compared to incorporation. Impregnation provokes incomplete reduction, yielding nanoparticles with a PdZn shell and a Pd core. More homogeneously alloyed nanoparticles were obtained after incorporation. The higher methane selectivity on the impregnated catalyst is in agreement with the less uniformly alloyed nanoparticles, which more likely exhibit adjacent Pd-sites promoting product acetaldehyde decomposition. Overall, incorporation gave rise to the most active and selective catalyst to acetaldehyde for ethanol dehydrogenation to acetaldehyde.

https://biblio.ugent.be/publication/8556827/file/8556832.pdf

PdZn nanoparticle catalyst formation for ethanol dehydrogenation: Active metal impregnation vs incorporation

Fe2O3/MgFeAlOx materials are promising oxygen storage candidates for chemical looping CO2 conversion. In this work, the cyclic stability of a 50Fe(2)O(3)/MgFeAlOx (containing 50 wt % Fe2O3 and 50 wt % MgAl2O4) oxygen storage material is investigated. The evolution of its bulk properties over the course of 1000 H-2/CO2 redox cycles has been studied by means of( 57)Fe Mossbauer spectroscopy and in situ X-ray diffraction. As expected, all iron in the as-prepared oxygen storage material was present as Fe3+, 64% of which in iron-rich phases alpha-Fe2O3 and alpha-FeOOH and 36% in the form of a MgFeAlOx spinel. In contrast, after 1000 redox cycles, only 19% of iron was present in an iron-rich spinel such as Fe3O4, gamma-Fe2O3, and MgFe2O4. The remaining 81% was present in the form of Mg-Fe-Al-O, including Mg-x Fe1-xO. ILEEMS measurements showed surface enrichment of Fe3+ in 50Fe(2)O(3)/MgFeAlOx after 1000 redox cycles, with 36% of all surface Fe present as Fe3+ in iron-rich spinel phases such as gamma-Fe2O3 and/or MgFe2O4.

Fe2O3–MgAl2O4 for CO Production from CO2: Mössbauer Spectroscopy and in Situ X-ray Diffraction

The evolution of the constituents of an 8 wt%Ni-5 wt%Fe/MgAl2O4 catalyst for dry reforming of methane (DRM) is monitored by in situ quick X-ray absorption spectroscopy (QXAS) and 57Fe Mossbauer spectroscopy. In as prepared state, Fe is present as NiFe2O4 at the surface and as MgFe3+xAl2−xO4 within the support, whereas Ni is mainly present as NiO. During H2-TPR, NiFe2O4 and NiO form an alloy from 500 °C on and MgFe3+xAl2−xO4 is partially reduced to MgFe2+xAl2−xO4, such that Ni-Fe alloy, MgFe2+xAl2−xO4 and MgFe3+xAl2−xO4 are the prevalent phases in the reduced catalyst. During DRM, dominantly oxidizing environments (CH4/CO2 = 1/2, 1/1.5) lead to formation of FeOx nanoparticles at the surface of the Ni-Fe alloy, thereby affecting the DRM activity, and possibly to some reincorporation of Fe into the support. For CH4/CO2 = 1/1, no significant changes occur in the catalyst’s activated state, as a consequence of reduction by CH4 dissociation species counteracting oxidation by CO2. However, Mossbauer analysis detects continued extraction of Fe from the support, sustaining ongoing Ni-Fe alloying.

Vladimir Galvita

Papers

Insight in kinetics from pre-edge features using time resolved in situ XAS

CO2 sorption properties of Li4SiO4 with a Li2ZrO3 coating

PdZn nanoparticle catalyst formation for ethanol dehydrogenation: Active metal impregnation vs incorporation

Fe2O3–MgAl2O4 for CO Production from CO2: Mössbauer Spectroscopy and in Situ X-ray Diffraction

Looking inside a Ni-Fe/MgAl2O4 catalyst for methane dry reforming via Mössbauer spectroscopy and in situ QXAS