a study of the reactions between halides of metalloids and phenylacetylenes

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Chemistry of potassium halides and their role in corrosion in biomass and waste firing

Compared to the use of traditional fossil fuels (coal, oil, natural gas), combustion of biomass and waste fuels has several environmental and economic advantages for heat and power generation. However, biomass and waste fuels might contain halogens (Cl, Br, F), alkali metals (Na, K) and heavy metals (Zn, Pb), which may cause harmful emissions and corrosion problems. Hightemperature corrosion occurs typically on furnace waterwalls and superheaters. The corrosion of the boiler tube materials limits the increase of thermal efficiency of steam boilers and leads to costly shutdowns and repairs. In recent years, some concerns have been raised about halogen (Cl, Br, and F)-related hightemperature corrosion in biomass- and waste-fired boilers. Chlorine-related high-temperature corrosion has been studied extensively. The presence of alkali chlorides in the deposits is believed to play a major role in the corrosion observed in biomass and waste fired boilers. However, there is much less information found in literature on the corrosion effect of bromine and fluorine. According to the literature, bromine is only assumed to play a role similar to chlorine; the role of fluorine is even less understood. In this work, a series of bubbling fluidized bed (BFB) bench-scale tests were carried out to characterize the formation and sulfation behaviors of KCl and KBr in BFB combustion conditions. Furthermore, a series of laboratory tests were carried out to investigate the hightemperature corrosion behaviors of three different superheater steels (10CrMo9-10, AISI 347 and Sanicro 28) exposed to potassium halides in ambient air and wet air (containing 30% H2O). The influence of H2O and O2 on the high-temperature corrosion of steels both with and without a salt (KCl) in three gas atmospheres (2% H2O-30% O2-N2, 2% H2O-2% O2-N2 and 30% H2O-2% O2-N2) was also studied. From the bench-scale BFB combustion tests, it was found that HBr has a clearly higher affinity for the available K forming KBr than HCl forming KCl. The tests also indicated that KCl has a higher tendency for sulfation than KBr. From the laboratory corrosion tests in ambient air (also called “dry air” in Paper III and Paper IV), it was found that at relatively low temperatures (≤ 550 °C) the corrosivity of KBr and KF are similar to KCl. At 600 °C, KF showed much stronger corrosivity than KBr and KCl, especially for 10CrMo9-10 and AISI 347. When exposed to KBr or KF, 10CrMo9-10 was durable at least up to 450 °C, while AISI 347 and Sanicro 28 were durable at least up to 550 °C. From the laboratory corrosion tests in wet air (30% H2O), no obvious effect of water vapor was detected at 450 °C. At 550 °C, the influence of water vapor became significant in some cases, but the trend was not consistent. At 550 °C, after exposure with KBr, 10CrMo9-10 suffered from extreme corrosion; after exposure with KF and KCl, the corrosion was less severe, but still high. At 550 °C, local deep pitting corrosion occurred on AISI 347 and Sanicro 28 after exposure with KF. Some formation of K2CrO4 was observed in the oxide layer. At 550 °C, AISI 347 and Sanicro 28 suffered from low corrosion (oxide layer thickness of < 10 μm) after exposure with KBr and KCl. No formation of K2CrO4 was observed. Internal oxidation occurred in the cases of AISI 347 with KBr and KCl. From the laboratory corrosion tests in three different gas atmospheres (2% H2O-30% O2-N2, 2% H2O-2% O2-N2 and 30% H2O-2% O2-N2), it was found that in tests with no salt, no corrosion occurred on AISI 347 and Sanicro 28 up to 600 °C in both the “O2-rich” (2% H2O-30% O2-N2) and “H2O-rich” (30% H2O-2% O2-N2) gas atmospheres; only 10CrMo9-10 showed increased corrosion with increasing temperature. For 10CrMo9-10 in the “O2-rich” atmosphere, the presence of KCl significantly increased the corrosion compared to the “no salt” cases. For 10CrMo9-10 in the “H2O-rich” atmosphere, the presence or absence of KCl did not show any big influence on corrosion. The formation of K2CrO4 was observed only in the case with the “O2-rich” atmosphere. Considering both the results from the BFB tests and the laboratory corrosion tests, if fuels containing Br were to be combusted, the corrosion damage of superheaters would be expected to be higher than if the fuels contain only Cl. Information generated from these studies can be used to help the boiler manufacturers in selecting materials for the most demanding combustion systems.

The biological application of cobalt

This review collects and summarises the biological applications of the element cobalt. Small amounts of the ferromagnetic metal can be found in rock, soil, plants and animals, but is mainly obtained as a by-product of nickel and copper mining, and is separated from the ores (mainly cobaltite, erythrite, glaucodot and skutterudite) using a variety of methods. Compounds of cobalt include several oxides, including: green cobalt(II) (CoO), blue cobalt(II,III) (Co3O4), and black cobalt(III) (Co2O3); four halides including pink cobalt(II) fluoride (CoF2), blue cobalt(II) chloride (CoCl2), green cobalt(II) bromide (CoBr2), and blue-black cobalt(II) iodide (CoI2). The main application of cobalt is in its metal form in cobalt-based super alloys, though other uses include lithium cobalt oxide batteries, chemical reaction catalyst, pigments and colouring, and radioisotopes in medicine. It is known to mimic hypoxia on the cellular level by stabilizing the α subunit of hypoxia inducing factor (HIF), when chemically applied as cobalt chloride (CoCl2). This is seen in many biological research applications, where it has shown to promote angiogenesis, erythropoiesis and anaerobic metabolism through the transcriptional activation of genes such as vascular endothelial growth factor (VEGF) and erythropoietin (EPO), contributing significantly to the pathophysiology of major categories of disease, such as myocardial, renal and cerebral ischaemia, high altitude related maladies and bone defects. As a necessary constituent for the formation of vitamin B12, it is essential to all animals, including humans, however excessive exposure can lead to tissue and cellular toxicity. Cobalt has been shown to provide promising potential in clinical applications, however further studies are necessary to clarify its role in hypoxia-responsive genes and the applications of cobalt-chloride treated tissues.

Intercalation of kaolins by alkaline earth metal salts

A suite of new materials, based on chemical modification of kaolins, has been successfully prepared via manipulation of the kaolin structure and subsequent intercalation by CaCl2 and MgCl2. A standard kaolinite(KGa-1)and a commercially available halloysite (New Zealand china clay) were used for this study. The kaolins are given several cycles of intercalation and deintercalation using a common intercalant such as potassium acetate. The number of cycles given depends on the type of kaolin. After this treatment, both kaolinite and halloysite hydrate show considerable broadening of the (00l) reflections which indicate extensive exfoliation of the layers. In the case of kaolinite, exfoliated layers roll to form tubes similar to proper halloysite. Kaolins modified by the above treatment readily intercalate MgCl2 and CaCl2 from saturated solutions of these salts. On intercalation with CaCl2 and MgCl2, kaolinite layers expand to 10A and 9.8A, and those of halloysite to 12.8A and 15.5A, respectively. To our knowledge, this is the first report of successful intercalation of alkaline-earth halides by kaolins.

Photocatalysis on supported gold and silver nanoparticles under ultraviolet and visible light irradiation

Studies of the optical properties and catalytic capabilities of noble metal nanoparticles (NPs), such as gold (Au) and silver (Ag), have formed the basis for the very recent fast expansion of the field of green photocatalysis: photocatalysis utilizing visible and ultraviolet light, a major part of the solar spectrum. The reason for this growth is the recognition that the localised surface plasmon resonance (LSPR) effect of Au NPs and Ag NPs can couple the light flux to the conduction electrons of metal NPs, and the excited electrons and enhanced electric fields in close proximity to the NPs can contribute to converting the solar energy to chemical energy by photon-driven photocatalytic reactions. Previously the LSPR effect of noble metal NPs was utilized almost exclusively to improve the performance of semiconductor photocatalysts (for example, TiO2 and Ag halides), but recently, a conceptual breakthrough was made: studies on light driven reactions catalysed by NPs of Au or Ag on photocatalytically inactive supports (insulating solids with a very wide band gap) have demonstrated that these materials are a class of efficient photocatalysts working by mechanisms distinct from those of semiconducting photocatalysts. There are several reasons for the significant photocatalytic activity of Au and Ag NPs. (1) The conduction electrons of the particles gain the irradiation energy, resulting in high energy electrons at the NP surface which is desirable for activating molecules on the particles for chemical reactions. (2) In such a photocatalysis system, both light harvesting and the catalysing reaction take place on the nanoparticle, and so charge transfer between the NPs and support is not a prerequisite. (3) The density of the conduction electrons at the NP surface is much higher than that at the surface of any semiconductor, and these electrons can drive the reactions on the catalysts. (4) The metal NPs have much better affinity than semiconductors to many reactants, especially organic molecules. Recent progress in photocatalysis using Au and Ag NPs on insulator supports is reviewed. We focus on the mechanism differences between insulator and semiconductor-supported Au and Ag NPs when applied in photocatalytic processes, and the influence of important factors, light intensity and wavelength, in particular estimations of light irradiation contribution, by calculating the apparent activation energies of photo reactions and thermal reactions.

UV Photodissociation Action Spectroscopy of Haloanilinium Ions in a Linear Quadrupole Ion Trap Mass Spectrometer

UV-vis photodissociation action spectroscopy is becoming increasingly prevalent because of advances in, and commercial availability of, ion trapping technologies and tunable laser sources. This study outlines in detail an instrumental arrangement, combining a commercial ion-trap mass spectrometer and tunable nanosecond pulsed laser source, for performing fully automated photodissociation action spectroscopy on gas-phase ions. The components of the instrumentation are outlined, including the optical and electronic interfacing, in addition to the control software for automating the experiment and performing online analysis of the spectra. To demonstrate the utility of this ensemble, the photodissociation action spectra of 4-chloroanilinium, 4-bromoanilinium, and 4-iodoanilinium cations are presented and discussed. Multiple photoproducts are detected in each case and the photoproduct yields are followed as a function of laser wavelength. It is shown that the wavelength-dependent partitioning of the halide loss, H loss, and NH3 loss channels can be broadly rationalized in terms of the relative carbon-halide bond dissociation energies and processes of energy redistribution. The photodissociation action spectrum of (phenyl)Ag-2 (+) is compared with a literature spectrum as a further benchmark.

Investigation of the gas phase reactivity of the 1-adamantyl radical using a distonic radical anion approach

The gas phase reactions of the bridgehead 3-carboxylato-1-adamantyl radical anion were observed with a series of neutral reagents using a modified electrospray ionisation linear ion trap mass spectrometer. This distonic radical anion was observed to undergo processes suggestive of radical reactivity including radical-radical combination reactions, substitution reactions and addition to carbon-carbon double bonds. The rate constants for reactions of the 3-carboxylato-1-adamantyl radical anion with the following reagents were measured ( in units 10(-12) cm(3) molecule(-1) s(-1)): O-18(2) ( 85 +/- 4), NO ( 38.4 +/- 0.4), I-2 ( 50 +/- 50), Br-2 ( 8 +/- 2), CH3SSCH3 ( 12 +/- 2), styrene ( 1.20 +/- 0.03), CHCl3 ( H abstraction 0.41 +/- 0.06, Cl abstraction 0.65 +/- 0.1), CDCl3 ( D abstraction 0.035 +/- 0.01, Cl abstraction 0.723 +/- 0.005), allyl bromide (Br abstraction 0.53 +/- 0.04, allylation 0.25 +/- 0.01). Collision rates were calculated and reaction efficiencies are also reported. This study represents the first quantitative measurement of the gas phase reactivity of a bridgehead radical and suggests that distonic radical anions are good models for the study of their elusive uncharged analogues.

Differential substrate behaviours of ethylene oxide and propylene oxide towards human glutathione transferase theta hGSTT1-1

The transformation of ethylene oxide (EO), propylene oxide (PO) and 1- butylene oxide (1-BuO) by human glutathione transferase theta (hGSTT1-1) was studied comparatively using 'conjugator' (GSTT1 + individuals) erythrocyte lysates. The relative sequence of velocity of enzymic transformation was PO > EO >> 1-BuO. The faster transformation of PO compared to EO was corroborated in studies with human and rat GSTT1-1 (hGSTT1-1 and rGSTT1-1, respectively) expressed by Salmonella typhimurium TA1535. This sequence of reactivities of homologous epoxides towards GSTT1-1 contrasts to the sequence observed in homologous alkyl halides (methyl bromide, MBr; ethyl bromide, EtBr; n-propyl bromide, PrBr) where the relative sequence MeBr >> EtBr > PrBr is observed. The higher reactivity towards GSTT1-1 of propylene oxide compared to ethylene oxide is consistent with a higher chemical reactivity. This is corroborated by experimental data of acid-catalysed hydrolysis of a number of aliphatic epoxides, including ethylene oxide and propylene oxide and consistent with semi-empirical molecular orbital modelings.

A 1h And 13c Magnetic Resonance And Infrared Spectroscopic Study Of Coordinated 2-Aminocyclopentene-1-Dithiocarboxylic Acid And Its S-Methyl Ester

The ligating properties of 2-aminocyclopentene-1-dithiocarboxylic acid and its S-methyl esters were investigated. Complexes with Zn(II), Cd(II) and Hg(II) halides were synthesized and characterized by infrared and proton and carbon-13 NMR studies. The results are concordant with a bidentate coordination of the -CS2 group to the metal ions

Complexes Of Imidazoline-2-Thione And Its 1-Methyl Analogue With Cu(Ii), Zn(Ii), Cd(Ii) And Hg(Ii) Salts

The reaction of Cu(II), Zn(II), Cd(II) and Hg(II) chlorides and bromides with imidazoline-2-thione (IZT) and its N-methyl derivative (NMIZT) yields complexes of stoichiometry ML3X2 and ML2X (IZT) and its N-methyl derivative (NMIZT) yields complexes of stoichiometry ML3X2 and ML2X (where M=Cu(I)); copper(II) halides yield Cu(I) complexes. On the basis of infrared and 13C n.m.r.