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.

Carbon species removal was studied from a Fe–Ni catalyst supported on MgAl2O4 after methane dry reforming at 1023 K, atmospheric pressure and a CH4/CO2 molar ratio of 1:1. The deactivated and regenerated catalysts were characterized using X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and energy-dispersive X-ray spectroscopy (EDX)-STEM mapping. The catalyst regeneration was studied by CO2 and O2 temperature programmed oxidation (TPO) and by operando time-resolved X-ray diffraction (XRD). A transient response technique, Temporal analysis of products (TAP), was applied to investigate the isothermal carbon species gasification. Two different types of carbon species, graphitic and amorphous, were present after reaction. CO2 oxidation could remove part of the carbon species, although EDX-STEM mapping showed the presence of carbon species located far from active metals phase even after CO2–TPO at 1123 K. Carbon species removal by CO2 involves two contributions: (1) the dissociation of CO2 over Ni followed by the oxidation of carbon species by surface oxygen; (2) Fe oxidation by CO2 and subsequent carbon species oxidation by Fe oxide lattice oxygen. The oxidation of carbon species by O2 was identified from temperature programmed and isothermal experiments as a process including two processes: (1) oxidation of surface carbon by lattice oxygen and (2) particles migration to carbon species deposited far from active metals and subsequent oxidation through lattice oxygen of the iron and/or nickel oxides. The contribution of oxygen spillover in carbon gasification was considered to be negligible.

Carbon gasification from Fe–Ni catalysts after methane dry reforming

Both pure and mixed CeO2–Fe2O3 were prepared for CO2 reduction to CO by chemical looping. The crystallographic structure of the investigated materials was monitored in situ during H2 reduction and CO2 oxidation. A solid solution of iron in ceria was identified. Up to 70 wt % CeO2, a distinct Fe2O3 hematite phase occurred next to the solid solution. At higher CeO2 content, no diffraction patterns corresponding to iron oxide phases were present, but upon H2 temperature programmed reduction, a metal iron phase appeared. The Fe2O3 phase at lower CeO2 content, during H2 temperature programmed reduction, completely reduced at 700 °C while the solid solution was only partially reduced. For all investigated samples, CO2 reoxidized iron in one-step to Fe3O4 from 500 °C during temperature programmed oxidation. Adding CeO2 to Fe2O3 was beneficial for the materials activity and stability. Isothermal redox cycles were performed without significant loss of CO2 conversion. The highest CO yield was obtained for 20 wt % C...

CeO2-modified Fe2O3 for CO2 utilization via chemical looping

A two-layer fixed-bed catalytic reactor for syngas production by steam reforming of ethanol has been proposed. In the reactor, ethanol is first converted to a mixture of methane, carbon oxides and hydrogen over a Pd-based catalyst and then this mixture is converted to syngas over a Ni-based catalyst for methane steam reforming. It has been shown that the use of the two-layer fixed-bed reactor prevents coke formation and provides the syngas yield closed to equilibrium.

Synthesis gas production by steam reforming of ethanol

A bifunctional 5% Ni/CeO2–Fe2O3 (1:1) sample was prepared for the transformation of CO2 to CO by catalyst-assisted chemical looping. Generation of CO from CO2 through CH4 + CO2/CO2 redox cycles was investigated between 873 K and 973 K. In the reduction step, CH4 + CO2 is converted over Ni into syngas, which then reduces the CeO2–Fe2O3 oxygen storage material, yielding CO2 and H2O. CO is produced upon re-oxidation of the oxygen storage material by CO2. The addition of Ni to CeO2–Fe2O3 has a beneficial effect upon the activity of the material during periodic cycling. The crystallographic structure of the sample was examined using time-resolved in situ X-ray diffraction under H2 reduction and CO2 oxidation. H2-TPR reduced the Fe2O3 phase to Fe3O4, FeO and Fe. From 600 K onwards NiO reduction is initiated. Interaction between Ni and Fe leads to Ni3Fe alloy formation from 850 K onwards. This alloy remains stable up to 873 K during CO2 re-oxidation but is completely decomposed into Ni and Fe3O4 at 973 K. This re-oxidation of iron follows a one-step pathway to Fe3O4 between 773 K and 873 K, but a two-step pathway above 873 K. The methane reforming on the Ni-based catalyst is accompanied with formation and accumulation of surface carbon. This carbon is removed by oxidation with lattice oxygen from CeO2–Fe3O4 during or after re-oxidation with CO2.

Vladimir Galvita

Papers

Carbon gasification from Fe–Ni catalysts after methane dry reforming

CeO2-modified Fe2O3 for CO2 utilization via chemical looping

Synthesis gas production by steam reforming of ethanol

Catalyst-assisted chemical looping for CO2 conversion to CO

Carbon gasification from Fe-Ni catalysts for methane dry reforming