Supported, Alkali-Promoted Cobalt Oxide Catalysts for NOx Removal from Coal Combustion Flue Gases

A series of cobalt oxide catalysts supported on alumina ({gamma}-Al{sub 2}O{sub 3}) were synthesized with varying contents of cobalt and of added alkali metals, including lithium, sodium, potassium, rubidium, and cesium. Unsupported cobalt oxide catalysts and several cobalt oxide catalysts supported ceria (CeO{sub 2}) with varying contents of cobalt with added potassium were also prepared. The catalysts were characterized with UV-visible spectroscopy and were examined for NO{sub x} decomposition activity. The CoO{sub x}/Al{sub 2}O{sub 3} catalysts and particularly the CoO{sub x}/CeO{sub 2} catalysts show N{sub 2}O decomposition activity, but none of the catalysts (unsupported Co{sub 3}O{sub 4} or those supported on ceria or alumina) displayed significant, sustained NO decomposition activity. For the Al{sub 2}O{sub 3}-supported catalysts, N{sub 2}O decomposition activity was observed over a range of reaction temperatures beginning about 723 K, but significant (>50%) conversions of N{sub 2}O were observed only for reaction temperatures >900 K, which are too high for practical commercial use. However, the CeO{sub 2}-supported catalysts display N{sub 2}O decomposition rates similar to the Al{sub 2}O{sub 3}-supported catalysts at much lower reaction temperatures, with activity beginning at {approx}573 K. Conversions of >90% were achieved at 773 K for the best catalysts. Catalytic rates per cobalt atom increased with decreasing cobalt content, which corresponds to increasing edge energies obtained from the UV-visible spectra. The decrease in edge energies suggests that the size and dimensionality of the cobalt oxide surface domains increase with increasing cobalt oxide content. The rate data normalized per mass of catalyst that shows the activity of the CeO{sub 2}-supported catalysts increases with increasing cobalt oxide content. The combination of these data suggest that supported cobalt oxide species similar to bulk Co{sub 3}O{sub 4} are inherently more active than more dispersed cobalt oxide species, but this effect was only observed with the CeO{sub 2}-supported catalysts

Effect of catalyst structure on oxidative dehydrogenation of ethane and propane on alumina-supported vanadia

ABSTRACT The catalytic properties of Al 2 O 3 -supported vanadia with a wide range of VO x surface density (1.4-34.2 V/nm 2 ) and structure were examined for the oxidative dehydrogenation of ethane and propane. UV-visible and Raman spectra showed that vanadia is dispersed predominately as isolated monovanadate species below ~2.3 V/nm 2 . As surface densities increase, two-dimensional polyvanadates appear (2.3-7.0 V/nm 2 ) along with increasing amounts of V 2 O 5 crystallites at surface densities above 7.0 V/nm 2 . The rate constant for oxidative dehydrogenation (k 1 ) and its ratio with alkane and alkene combustion (k 2 /k 1 and k 3 /k 1 , respectively) were compared for both alkane reactants as a function of vanadia surface density. Propene formation rates (per V-atom) are ~8 times higher than ethene formation rates at a given reaction temperature, but the apparent ODH activation energies (E 1 ) are similar for the two reactants and relatively insensitive to vanadia surface density. Ethene and propene formation rates (per V-atom) are strongly influenced by vanadia surface density and reach a maximum value at intermediate surface densities (~8 V/nm 2 ). The ratio of k 2 /k 1 depends weakly on reaction temperature, indicating that activation energies for alkane combustion and ODH reactions are similar. The ratio of k 2 /k 1 is independent of surface density for ethane, but increase slightly with vanadia surface density for propane, suggesting that isolated structures prevalent at low surface densities are slightly more selective for alkane dehydrogenation reactions. The ratio of k 3 /k 1 decreases markedly with increasing reaction temperature for both ethane and propane ODH. Thus, the apparent activation energy for alkene combustion (E 3 ) is 16 much lower than that for alkane dehydrogenation (E 1 ) and the difference between these two activation energies decreases with increasing surface density. The lower alkene selectivities observed at high vanadia surface densities are attributed to an increase in alkene adsorption enthalpies with increasing vanadia surface density. The highest yield of alkene is obtained for catalysts containing predominantly isolated monovanadate species and operated at high temperatures (~800 K) with reactor designs that avoid homogeneous reactions by minimizing residence time in areas without catalyst. INTRODUCTION Low molecular weight alkenes, such as ethene and propene, can be formed via non-oxidative dehydrogenation of the corresponding alkane. Non-oxidative dehydrogenation reactions are endothermic and lead to the concurrent formation of carbon and of lower molecular weight alkanes, both of which decrease alkene yields. Oxidative dehydrogenation (ODH) of light alkanes offers a potentially attractive route to alkenes, since the reaction is exothermic and avoids the thermodynamic constraints of non-oxidative routes by forming water as a byproduct. In addition, carbon deposition during ODH is eliminated, leading to stable catalytic activity. However, the yield of alkenes obtained by ODH on most catalysts is limited by alkene combustion to CO and CO 2 (CO x ) (see Chapter 1). Previous studies have shown that supported vanadia is the most active and selective simple metal oxide for alkane ODH, because its reducible nature leads to rapid redox cycles required for a catalytic turnover [1] EXPERIMENTAL METHODS VO These data were used to calculate reaction rates from the reactant and product molar flow rates. The reaction rates and selectivities as a function of residence time were used to obtain initial alkane dehydrogenation and combustion reaction rates and the rate constants in the Scheme. The sequence in the Scheme can be used to obtain the k 1 and k 2 rate constants from the initial alkene selectivity: RESULTS AND DISCUSSION Catalyst Characterization BET surface areas and apparent VO x surface densities, estimated from the Vcontent and the BET surface areas, are shown in th

Novel Composite Hydrogen-Permeable Membranes for Non-Thermal Plasma Reactors for the Decomposition of Hydrogen Sulfide

The goal of this experimental project is to design and fabricate a reactor and membrane test cell to dissociate hydrogen sulfide (H{sub 2}S) in a non-thermal plasma and recover hydrogen (H{sub 2}) through a superpermeable multi-layer membrane. Superpermeability of hydrogen atoms (H) has been reported by some researchers using membranes made of Group V transition metals (niobium, tantalum, vanadium, and their alloys), although it has yet to be confirmed in this study. Several pulsed corona discharge (PCD) reactors have been fabricated and used to dissociate H{sub 2}S into hydrogen and sulfur. Visual observation shows that the corona is not uniform throughout the reactor. The corona is stronger near the top of the reactor in argon, while nitrogen and mixtures of argon or nitrogen with H{sub 2}S produce stronger coronas near the bottom of the reactor. Both of these effects appear to be explainable base on the different electron collision interactions with monatomic versus polyatomic gases. A series of experiments varying reactor operating parameters, including discharge capacitance, pulse frequency, and discharge voltage were performed while maintaining constant power input to the reactor. At constant reactor power input, low capacitance, high pulse frequency, and high voltage operation appear to provide the highest conversion and the highest energy efficiency for H{sub 2}S decomposition. Reaction rates and energy efficiency per H{sub 2}S molecule increase with increasing flow rate, although overall H{sub 2}S conversion decreases at constant power input. Voltage and current waveform analysis is ongoing to determine the fundamental operating characteristics of the reactors. A metal infiltrated porous ceramic membrane was prepared using vanadium as the metal and an alumina tube. Experiments with this type of membrane are continuing, but the results thus far have been consistent with those obtained in previous project years: plasma driven permeation or superpermeability has not been observed. A new test cell specially designed to test the membranes has been constructed to provide basic science data on superpermeability

Factors shaping prayer frequency among 9- to 11-year-olds

This paper begins by reviewing the evidence from international research concerning the personal and social correlates of prayer frequency during childhood and adolescence. Overall these data continue to support the view that young people who pray not only report higher levels of personal wellbeing but also report higher levels of pro-social attitudes. These findings raise a research question of particular relevance within church schools regarding the factors that predict higher levels of prayer activity among students. The Student Voice Project offers data that can illuminate this research question. Among the 3,101 9- to 11-year old students who participated in the project 11% prayed daily, 9% at least once a week, 32% sometimes, 11% once or twice a year, and 37% never. The present paper tests the power of four sets of predictor variables to account for individual differences in prayer frequency among these students: personal factors (age and sex), psychological factors (using the three dimensional model of personality proposed by Eysenck), church attendance (self, mother, and father), and family discussion about prayer (mother, father, and grandparents). Multiple regression analyses identified the discussion of prayer with the mother as the single most important predictor. These findings locate the development of the practice of prayer within the home, even more than within the church

Are Women Happier When Their Spouse is Teleworker?

© 2017 Springer Science+Business Media Dordrecht. This study explores the household production allocation and happiness of women when their spouse is teleworker using data from the British Household Panel Survey over the years 1991–2009. The study aims to answer whether the women spend additional time on housework and are happier when they or their partner is teleworker. Also, we explore whether are happier when they share the household–domestic production with their partners. Fixed effects estimates take place, and we consider a Bayesian Network framework and a directed acyclic graph for causal inference. The results show that women are more likely to state that the household allocation, such as cooking, cleaning, ironing and childcare is shared when their partner teleworks. Shopping is an exception which can be regarded as an outdoor activity while one partner may be mainly responsible for this chore. In addition, women are happier when they or their spouse is teleworker, and they report higher levels of happiness when the household production allocation is a shared process. This may indicate men teleworkers may contribute extra to the household production releasing a burden for the partners and improving their well-being

Commemorative Issue in Honor of Professor Calvin H. Bartholomew’s 75th Birthday

This editorial is written to recognize Professor Emeritus Calvin H. Bartholomew, who celebrated his 75th birthday in 2018, and to introduce the commemorative issue of Catalysts compiled in his honor. Following a brief biography that celebrates the career and contributions of Professor Bartholomew, the nine articles that make up the special issue are briefly reviewed. Dr. Bartholomew is an eminent researcher, an outstanding educator, mentor, and friend

Commemorative Issue in Honor of Professor Emeritus Calvin H. Bartholomew in Anticipation of His 75th Birthday

This book recognizes the career of Professor Emeritus Calvin H. Bartholomew, who celebrated his 75th birthday in 2018, and his contributions to the science and engineering of heterogeneous catalysis, a field which improves daily life in countless, but often unrecognized ways. Dr. Bartholomew is an eminent researcher, an outstanding educator, mentor, and friend. The nine chapters comprising the book were written by former students, collaborators, colleagues, and respected peers. Chapters cover supported iron Fischer–-Tropsch catalysts, a spectroscopic study of iron-based water gas shift catalysts, nickel catalysts both for (dry) methane reforming with associated carbon deactivation and carbon dioxide methanation, a methanol steam reforming catalyst, cobalt oxide on niobia catalysts for environmental applications, palladium catalysts supported on titania for hydrogen peroxide synthesis, methane combustion catalyst stability, and chiral catalyst deactivation. In summary, this book covers much of the breadth and points to the depth of Professor Bartholomew’s illustrious career. We thank him for his kind example and honor him for his lasting contributions

Advances in Catalyst Deactivation and Regeneration

Catalyst deactivation, the loss over time of catalytic activity and/or selectivity, is a problem of great and continuing concern in the practice of industrial catalytic processes. Costs to industry for catalyst replacement and process shutdown total tens of billions of dollars per year. [...

Heterogeneous Catalyst Deactivation and Regeneration: A Review

Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key features and considerations for each of these deactivation types is reviewed in detail with reference to the latest literature reports in these areas. Two case studies on the deactivation mechanisms of catalysts used for cobalt Fischer-Tropsch and selective catalytic reduction are considered to provide additional depth in the topics of sintering, coking, poisoning, and fouling. Regeneration considerations and options are also briefly discussed for each deactivation mechanism