New solid base catalysts for biodiesel synthesis

The application of heterogeneous catalysts for the manufacture of renewable biodiesel fuels offers an exciting, alternative clean chemical technology to current energy intensive processes employing soluble base catalysts. We recently synthesised tuneable MgO nanocrystals as efficent solid base catalysts for biodiesel synthesis, and have developed a simple X-ray spectroscopic method to quantitatively determine surface basicity, thereby providing a rapid screening tool for predicting the reactivity of new solid base catalysts. Promotion of these MgO nanocrystals through Cs doping dramatically enhances biodiesel production rates due to the formaion of a mixed Cs Mg(CO ) phase. These MgO derived nanocatalysts permit energy efficent, continuous processing of diverse, sustainable oil feedstocks in flow reactors.

In situ aberration corrected-transmission electron microscopy of magnesium oxide nanocatalysts for biodiesels

Biofuels are promising renewable energy sources and can be derived from vegetable oil feedstocks. Although solid catalysts show great promise in plant oil triglyceride transesterification to biodiesel, the identification of active sites and operating surface nanostructures created during their processing is essential for the development of efficient heterogeneous catalysts. Systematic, direct observations of dynamic MgO nanocatalysts from a magnesium hydroxide-methoxide precursor were performed under controlled calcination conditions using novel in situ aberration corrected-transmission electron microscopy at the 0.1 nm level and quantified with catalytic reactivity and physico-chemical studies. Surface structural modifications and the evolution of extended atomic scale glide defects implicate coplanar anion vacancies in active sites in the transesterification of triglycerides to biodiesel. The linear correlation between surface defect density (and therefore polarisability) and activity affords a simple means to fine tune new, energy efficient nanocatalysts for biofuel synthesis. © 2009 Springer Science+Business Media, LLC.

On the active site in heterogeneous palladium selox catalysts

The nature of the active site in the Pd-catalysed aerobic selective oxidation of cinnamyl and crotyl alcohols has been directly probed by bulk and surface X-ray techniques. The importance of high metal dispersions and the crucial role of surface palladium oxide have been identified. © The Royal Society of Chemistry 2006.

Rearrangement of α-pinene oxide using a surface catalysed spinning disc reactor (SDR)

Isomerisation of α-pinene oxide to campholenic aldehyde was performed by immobilising zinc triflate based catalysts on the surface of a spinning disc reactor (SDR). Two types of catalyst have been studied and the influence of operating parameters such as rotational speed, feed flow rate and reaction temperature on conversion and selectivity towards campholenic aldehyde has been investigated in considerable detail. The findings of the study suggest that immobilising the catalyst on the reactor surface and performing the reaction in continuous mode has potential for achieving benefits of Green Chemical Technology (GCT).

Promoter effects in the polymerisation of a mixed hydrocarbon feed with silica-supported BF3

The activity of a silica-supported BF3–methanol solid acid catalyst in the cationic polymerisation of an industrial aromatic C9 feedstock has been investigated. Reuse has been achieved under continuous conditions. Titration of the catalyst acid sites with triethylphosphine oxide (TEPO) in conjunction with 31P MAS NMR shows the catalyst to have two types of acid sites. Further analysis with 2,6 di-tert-butyl-4-methylpyridine (DBMP) has revealed the majority of these acid sites to be Brønsted in nature. The role of α-methylstyrene in promoting resin polymerisation via chain transfer is proposed.

Progress in the development of mesoporous solid acid and base catalysts for converting carbohydrates into platform chemicals

This chapter provides a general overview of recent studies on catalytic conversion of fructose, glucose, and cellulose to platform chemicals over porous solid acid and base catalysts, including zeolites, ion-exchange resins, heteropoly acids, as well as structured carbon, silica, and metal oxide materials. Attention is focused on the dehydration of glucose and fructose to HMF, isomerization of glucose to fructose, hydrolysis of cellulose to sugar, and glycosidation of cellulose to alkyl glucosides. The correlation of porous structure, surface properties, and the strength or types of acid or base with the catalyst activity in these reactions is discussed in detail in this chapter.

Pedagogical Perceptions of Classroom Performance in the Teacher Evaluative Process: A Mixed Methods Study

This sequential explanatory, mixed methods research design examines the role teachers should enact in the development process of the teacher evaluation system in Louisiana. These insights will ensure teachers are catalysts in the classroom to significantly increase student achievement and allow policymakers, practitioners, and instructional leaders to direct as learned decision makers.

Desenvolvimento de material BaCexPr1-xO3 (0 ≤ X ≤ 1) com estrutura perovskita para oxidação catalítica do CO a CO2 em reator de leito fixo

Barium Cerate (BaCeO3) is perovskite type structure of ABO3, wherein A and B are metal cations. These materials, or doped, have been studied by having characteristics that make them promising for the application in fuel cells solid oxide, hydrogen and oxygen permeation, as catalysts, etc .. However, as the ceramic materials mixed conductivity have been produced by different synthesis methods, some conditions directly influence the final properties, one of the most important doping Site B, which may have direct influence on the crystallite size, which in turn directly influences their catalytic activity. In this study, perovskite-type (BaCexO3) had cerium gradually replaced by praseodymium to obtain ternary type materials BaCexPr1-xO3 and BaPrO3 binaries. These materials were synthesized by EDTA/Citrate complexing method and the material characterized via XRD, SEM and BET for the identification of their structure, morphology and surface area. Moreover were performed on all materials, catalytic test in a fixed bed reactor for the identification of that person responsible for complete conversion of CO to CO2 at low operating temperature, which step can be used as the subsequent production of synthesis gas (CO + H2) from methane oxidation. In the present work the crystalline phase having the orthorhombic structure was obtained for all compositions, with a morphology consisting of agglomerated particles being more pronounced with increasing praseodymium in the crystal structure. The average crystal size was between 100 nm and 142,2 nm. The surface areas were 2,62 m²g-1 for the BaCeO3 composition, 3,03 m²g-1 to BaCe0,5Pr0,5O3 composition and 2,37 m²g-1 to BaPrO3 composition. Regarding the catalytic tests, we can conclude that the optimal flow reactor operation was 50 ml / min and the composition regarding the maximum rate of conversion to the lowest temperature was BaCeO3 to 400° C. Meanwhile, there was found that the partially replaced by praseodymium, cerium, there was a decrease in the catalytic activity of the material.

Development of the Oxide Ion Conductor Na0.5Bi0.5TiO3 (NBT) for Solid Oxide Cells

Na0.5Bi0.5TiO3 (NBT) is a well-known lead-free piezoelectric material with potential to replace lead zirconate titanate (PZT),1 however high leakage conductivity for the material has been widely reported.2 Through a combination of Impedance Spectroscopy (IS), O2- ion transference (EMF) number experiments and O18 tracer diffusion measurements, combined with Time-of-flight Secondary Ion Mass Spectrometry (TOFSIMS), it was identified that this leakage conductivity was due to oxygen ion conductivity. The volatilization of bismuth during synthesis, causing oxygen vacancies, is believed to be responsible for the leakage conductivity.3 The oxide-ion conductivity, when doped with magnesium, exceeds that of yttria-stabilized zirconia (YSZ) at ~500 °C,3 making it a potential electrolyte material for Intermediate Temperature Solid Oxide Cells (ITSOCs). Figure 1 shows the comparison of bulk oxide ion conductivity between 2 at.% Mg-doped NBT and other known oxide ion conductors.

As part of the UK wide £5.7m 4CU project, research has concentrated on trying to develop NBT for use in Intermediate Temperature Solid Oxide Cells (ITSOCS). With the aim of achieving mixed ionic and electronic conduction, transition metals were chemically doped on to the Ti-site. A range of experimental techniques was used to characterize the materials aimed at investigating both conductivity and material structure (Scanning Electron Microscopy (SEM), IS, X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS)). The potential for NBT as an ITSOC material, as well as the challenges of developing the material, will be discussed.

(1) Takenaka T. et al. Jpn. J. Appl. Phys 1999, 30, 2236.

(2) Hiruma Y. et al. J. Appl. Phys 2009, 105, 084112.

(3) Li. M. et al. Nature Materials 2013, 13, 31.

Evaluation of strontium-site-deficient Sr2Fe1.4Co0.1Mo0.5O6-δ-based perovskite oxides as intermediate temperature solid oxide fuel cell cathodes

In this paper strontium-site-deficient Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ-based perovskite oxides (S_xFCM) were prepared and evaluated as the cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). All samples exhibited a cubic phase structure and the lattice shrinked with increasing the Sr-deficiency as shown in XRD patterns. XPS results determined that the transition elements (Co/Fe/Mo) in S_xFCM oxides were in a mixed valence state, demonstrating the small polaron hopping conductivity mechanism existed. Among the samples, S_1.950FCM presented the lowest coefficient of thermal expansion of 15.62 × 10^-6 K^-1, the highest conductivity value of 28 S cm^-1 at 500 °C, and the lowest interfacial polarization resistance of 0.093 Ω cm² at 800 °C, respectively. Furthermore, an anode-supported single cell with a S_1.950FCM cathode was prepared, demonstrating a maximum power density of 1.16 W cm^-2 at 800 °C by using wet H₂ (3% H₂O) as the fuel and ambient air as the oxidant. These results indicate that the introduction of Sr-deficiency can dramatically improve the electrochemical performance of Sr₂Fe_1.4Co_0.1Mo_0.5O_6-δ, showing great promise as a novel cathode candidate material for IT-SOFCs.

High performance cobalt-free Cu1.4Mn1.6O4 spinel oxide as an intermediate temperature solid oxide fuel cell cathode

In this work Cu_1.4Mn_1.6O₄ (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu⁺/Cu²⁺ and Mn³⁺/Mn⁴⁺ couples exist in the CMO sample, and a maximum conductivity of 78 S cm⁻¹ is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc₂O₃ stabilized ZrO₂ (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm² at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm⁻² at 800 °C under H₂ (3% H₂O) as the fuel and ambient air as the oxidant. These results indicate that Cu_1.4Mn_1.6O₄ is a superior and promising cathode material for IT-SOFCs.

Investigations on the structural, optical and magnetic properties of nanostructured cerium oxide in pure and doped forms and its polymer nanocomposites

In recent years, nanoscience and nanotechnology has emerged as one of the most important and exciting frontier areas of research interest in almost all fields of science and technology. This technology provides the path of many breakthrough changes in the near future in many areas of advanced technological applications. Nanotechnology is an interdisciplinary area of research and development. The advent of nanotechnology in the modern times and the beginning of its systematic study can be thought of to have begun with a lecture by the famous physicist Richard Feynman. In 1960 he presented a visionary and prophetic lecture at the meeting of the American Physical Society entitled “there is plenty of room at the bottom” where he speculated on the possibility and potential of nanosized materials. Synthesis of nanomaterials and nanostructures are the essential aspects of nanotechnology. Studies on new physical properties and applications of nanomaterials are possible only when materials are made available with desired size, morphology, crystal structure and chemical composition. Cerium oxide (ceria) is one of the important functional materials with high mechanical strength, thermal stability, excellent optical properties, appreciable oxygen ion conductivity and oxygen storage capacity. Ceria finds a variety of applications in mechanical polishing of microelectronic devices, as catalysts for three-way automatic exhaust systems and as additives in ceramics and phosphors. The doped ceria usually has enhanced catalytic and electrical properties, which depend on a series of factors such as the particle size, the structural characteristics, morphology etc. Ceria based solid solutions have been widely identified as promising electrolytes for intermediate temperature solid oxide fuel cells (SOFC). The success of many promising device technologies depends on the suitable powder synthesis techniques. The challenge for introducing new nanopowder synthesis techniques is to preserve high material quality while attaining the desired composition. The method adopted should give reproducible powder properties, high yield and must be time and energy effective. The use of a variety of new materials in many technological applications has been realized through the use of thin films of these materials. Thus the development of any new material will have good application potential if it can be deposited in thin film form with the same properties. The advantageous properties of thin films include the possibility of tailoring the properties according to film thickness, small mass of the materials involved and high surface to volume ratio. The synthesis of polymer nanocomposites is an integral aspect of polymer nanotechnology. By inserting the nanometric inorganic compounds, the properties of polymers can be improved and this has a lot of applications depending upon the inorganic filler material present in the polymer.

Catalizzatori polifunzionali per la sintesi di Metil Isobutil Chetone

In this work, we have examined the activity and selectivity of new catalysts for the single-stage production of methyl isobutyl ketone (MIBK, 4- methyl-2-pentanone) from acetone (both in liquid and gas phase), using a fixed bed reactor operated in the temperature range between 373 and 473 K. The main reaction pathways for the synthesis of MIBK from acetone are given in Fig.1. The first step is the self condensation of acetone to diacetone alcohol (DAA, 4-hydroxy-4-methyl-2-pentanone); the second step is the dehydration of DAA to mesityl oxide (MO, 4-methyl-3-penten-2-one); the final step is the selective hydrogenation of the carbon–carbon double bond of MO to form MIBK. The most commonly observed side reactions are over-condensations and unselective hydrogenations (also shown in Fig.1). Two types of catalysts were studied: i)Pd supported on MgO-SiO2 mixed oxides with ratio of Mg to Si, synthetized using Ohnishi’s method and ii)Pd supported on alumina doped with 5% or 10% of MgO. The different Mg-Si and Mg-Al catalysts were characterized by different techniques (XRD, BET, SEM, NH3-TPD and CO2-TPD) and tested under different conditions in the condensation of acetone to diacetone alcohol and its dehydration to mesityl oxide to enhance the activity. Palladium was chosen as metal component, and its hydrogenation activity was studied. A low hydrogenation activity negatively affects the acetone conversion and promotes the production of mesityl oxide. Hydrogenation conditions being too severe may favor the unwanted hydrogenation of acetone to 2-propanol and of MIBK to methyl isobutyl carbinol (MIBC, 4-methyl-2-pentanol) but this effect is less detrimental to the MIBK selectivity than an unsufficient hydrogenation activity.

Nanostructured catalysts for the development of the hydrogen economy

La catalyse joue un rôle essentiel dans de nombreuses applications industrielles telles que les industries pétrochimique et biochimique, ainsi que dans la production de polymères et pour la protection de l’environnement. La conception et la fabrication de catalyseurs efficaces et rentables est une étape importante pour résoudre un certain nombre de problèmes des nouvelles technologies de conversion chimique et de stockage de l’énergie. L’objectif de cette thèse est le développement de voies de synthèse efficaces et simples pour fabriquer des catalyseurs performants à base de métaux non nobles et d’examiner les aspects fondamentaux concernant la relation entre structure/composition et performance catalytique, notamment dans des processus liés à la production et au stockage de l’hydrogène. Dans un premier temps, une série d’oxydes métalliques mixtes (Cu/CeO2, CuFe/CeO2, CuCo/CeO2, CuFe2O4, NiFe2O4) nanostructurés et poreux ont été synthétisés grâce à une méthode améliorée de nanocasting. Les matériaux Cu/CeO2 obtenus, dont la composition et la structure poreuse peuvent être contrôlées, ont ensuite été testés pour l’oxydation préférentielle du CO dans un flux d’hydrogène dans le but d’obtenir un combustible hydrogène de haute pureté. Les catalyseurs synthétisés présentent une activité et une sélectivité élevées lors de l’oxydation sélective du CO en CO2. Concernant la question du stockage d’hydrogène, une voie de synthèse a été trouvée pour le composét mixte CuO-NiO, démontrant une excellente performance catalytique comparable aux catalyseurs à base de métaux nobles pour la production d’hydrogène à partir de l’ammoniaborane (aussi appelé borazane). L’activité catalytique du catalyseur étudié dans cette réaction est fortement influencée par la nature des précurseurs métalliques, la composition et la température de traitement thermique utilisées pour la préparation du catalyseur. Enfin, des catalyseurs de Cu-Ni supportés sur silice colloïdale ou sur des particules de carbone, ayant une composition et une taille variable, ont été synthétisés par un simple procédé d’imprégnation. Les catalyseurs supportés sur carbone sont stables et très actifs à la fois dans l’hydrolyse du borazane et la décomposition de l’hydrazine aqueuse pour la production d’hydrogène. Il a été démontré qu’un catalyseur optimal peut être obtenu par le contrôle de l’effet bi-métallique, l’interaction métal-support, et la taille des particules de métal.