Lesley Smart

Microwave heating during catalyst preparation : influence on the hydrodechlorination activity of alumina-supported palladium-iron bimetallic catalysts

Abstract Alumina-supported Pd–Fe mono- and bimetallic catalysts have been prepared by microwave irradiation and by conventional calcination methods. The catalysts were characterised by powder X-ray diffraction (XRD), temperature-programmed reduction (TPR) and nitrogen adsorption measurements. Hydrogen chemisorption measurements were performed after low- and high-temperature reduction (LTR and HTR) of the catalyst. Hydrodechlorination of chlorobenzene was carried out on the reduced catalysts. Microwave heating changed the crystallite size and the susceptibility of the catalysts to alloy formation, with a resultant increase in the activity of the reduced catalysts for the hydrodechlorination of chlorobenzene.

Synthesis of chromium-containing pigments from chromium recovered from leather waste.

Cobalt-chromite green and chrome-tin pink pigments have been prepared from chromium extracted from leather shavings produced as a waste product of the leather-tanning industry. The alkaline agent (NaOH, CaO, MgO, NH4OH) used in the extraction process influences the nature of the final product. The effect of the NH4OH:CaO ratio on the final product in the case of cobalt-chromite green was examined. The pigments obtained were characterized by FT-IR and X-ray diffraction (XRD). Colour measurements were compared with those recorded from materials prepared from pure Cr2O3. The leaching of Cr(VI) from the materials was examined by UV spectroscopy.

Studies on magnesia supported mono- and bimetallic Pd-Fe catalysts prepared by microwave irradiation method

Magnesia supported mono- and bimetallic Pd-Fe catalysts were prepared by conventional and microwave irradiation method. The prepared catalysts were characterised by N2 adsorption, temperature programmed reduction, selective hydrogen chemisorption and X-ray diffraction (XRD). The conventionally prepared catalysts after high temperature reduction (HTR) showed the formation of Pd-Fe alloy. In the case of microwave irradiated catalysts the formation of Pd-Fe alloy is limited during HTR reduction. These catalysts activity was tested in hydrodechlorination (HDC) of chlorobenzene. The catalysts prepared by microwave irradiation method are more active compared to conventionally prepared ones. The microwave irradiation leads to different morphology of the bimetallic catalysts. The HDC activity results are discussed in terms of structural differences between the catalysts prepared by conventional and microwave irradiation.

Solid State Chemistry: An Introduction, Fourth Edition

Provides a solid background to a fast-changing field, and also covers areas of new innovation Uses interesting applications to put the topics presented in context Incorporates a two-color layout and a four-color section to facilitate understanding of crystal structures Contains an extensive bibliography and suggestions for further reading to expedite searching for other relevant literature Includes question and answer sets, and an accompanying solutions manual Intended for first- and second-year undergraduates, this introduction to solid state chemistry includes practical examples of applications and modern developments to offer students the opportunity to apply their knowledge in real-life situations. The third edition of Solid State Chemistry: An Introduction has been comprehensively revised and updated. Building a foundation with a thorough description of crystalline structures, the book presents a wide range of the synthetic and physical techniques used to prepare and characterize solids. Other fundamental discussions include: bonding, superconductivity, and electrochemical, magnetic, optical, and conductive properties. The authors have added sections on fuel cells and electrochromic materials; conducting organic polymers, organic superconductors, and fullerenes; mesoporous solids and ALPOs; photonics; giant magnetoresistance (GMR) and colossal magnetoresistance (CMR); and p-wave (triplet) superconductors. The book also includes a completely new chapter, which examines the solid state chemical aspects of nanoscience. Each chapter contains a set of review questions and an accompanying solutions manual is available. Solid State Chemistry: An Introduction, Third Edition is written in a clear, approachable style that enhances the material by integrating its concepts in the context of current applications and areas of promising research.

Structure and activity of microwave irradiated silica supported Pd-Fe bimetallic catalysts in the hydrodechlorination of chlorobenzene

A series of silica supported Pd–Fe bimetallic catalysts were prepared by conventional as well as microwave heating methods. The catalysts were characterised by nitrogen adsorption (for BET surface area), X-ray diffraction (XRD), temperature-programmed reduction (TPR) and hydrogen chemisorption for their physico-chemical properties and were evaluated for chlorobenzene (CB) hydrodechlorination (HDC) activity. The catalysts prepared with microwave irradiation resulted into higher hydrodechlorination activity compared to their conventionally prepared analogues. These results are explained in terms of differences in the Pd morphology observed during the microwave irradiation.

Iron-doped zircon: the mechanism of formation

Iron-doped zircon (zirconium silicate) has been prepared from silica, zirconia and iron(II) sulphate heptahydrate using a mixture of sodium halides and alkali metal nitrates as mineralisers to lower the temperature of reaction. The formation of a silicon- and fluorine-containing glassy phase in the reaction vessel, together with evidence for a SiF3 breakdown product and the analysis of solid phases formed at intermediate temperatures, implicate the participation of a volatile silicon fluoride intermediate, probably SiF4, in the formation of the iron-doped zircon.

The influence of microwave heating on the morphology and benzene hydrogenation activity of alumina- and silica-supported palladium catalysts

Alumina- and silica-supported palladium catalysts were prepared by conventional and microwave heating. The catalysts have been characterized by nitrogen adsorption, hydrogen chemisorption, X-ray powder diffraction and temperature-programmed reduction and tested for benzene hydrogenation activity. The results show that preparation of samples by microwave heating leads to enhanced crystallite size and increased hydrogenation activity.

Microwave irradiation: an effective method for the preparation of low dispersed Pd/Al2O3 catalysts used in the hydrodechlorination of CCl2F2 to CH2F2

Microwave irradiation is found to be a faster method for the preparation of low dispersed Pd/Al2O3 catalysts with higher activity and selectivity to CH2F2 in the hydrodechlorination of CCl2F2.

Iron-doped zirconium silicate. Part 1.—The location of iron

Iron-doped zirconium silicate (zircon) has been shown by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDX) and 57Fe Mossbauer spectroscopy to consist of inclusions of α-Fe2O3 together with discrete paramagnetic Fe3+ species within the zircon structure. Electron paramagnetic resonance (EPR) spectra show that the Fe3+ species in the samples containing less than 0.2 mass% Fe occupies low-symmetry rhombic sites, but that in materials with higher concentrations of iron the Fe3+ also occupies other locations, including sites with axial symmetry. The colour of the iron-doped zircon is due to both the low symmetry Fe3+ species and the inclusions of α-Fe2O3.

To alloy or not to alloy

The cathode electrocatalysts for proton exchange membrane (PEM) fuel cells are commonly platinum and platinum based alloy nanoparticles dispersed on a carbon support. Control over the particle size and composition has, historically, been attained empirically, making systematic studies of the effects of various structural parameters difficult. The controlled surface modification methodology used in this work has enabled the controlled modification of carbon supported Pt nanoparticles by Cr so as to yield nanoalloy particles with defined compositions. Subsequent heat treatment in 5% H2 in N2 resulted in the formation of a distinct Pt3Cr alloy phase which was either restricted to the surface of the particles or present throughout the bulk of the particle structure. Measurement of the oxygen reduction activity of the catalysts was accomplished using the rotating thin film electrode method and the activities obtained were related to the structure of the nanoalloy catalyst particles, largely determined using Cr K edge and Pt L3 edge XAS.