Sulfur and nitrogen oxides (SOX/NOX) are the primary air toxic gas pollutants emitted during fuel... more Sulfur and nitrogen oxides (SOX/NOX) are the primary air toxic gas pollutants emitted during fuel combustion, causing health and environmental concerns. Therefore, their emission in flue gases is strictly regulated. The existing technologies used to decrease SOX/NOX content are flue gas desulfurization, which necessitates high capital and operating costs, and selective catalytic reduction, which, in addition to these costs, requires expensive catalysts and high operating temperatures (350–400 °C). New wet scrubbing processes use O3 or H2O2 oxidants to produce (NH4)2SO4 and NH4NO3 fertilizers upon ammonia injection. However, these oxidants are expensive, corrosive, and hazardous. SiO2/Co(OH)2 nanocomposites are presented here as potential catalysts for SOX/NOX oxidation in wet scrubber reactors to scrub these toxic gases using atmospheric oxygen as the oxidant at relatively low temperatures of 60–90 °C. Several silica-cobalt-oxide-based nanocomposites were synthesized as potential ca...
EPR spectroscopy of pre-color treated natural diamonds – yellow and green: correlation between na... more EPR spectroscopy of pre-color treated natural diamonds – yellow and green: correlation between natural pre colored diamond paramagnetic centers and nitrogen concentration.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Unprecedented fused acceptor-donor-acceptor triad (Q-TTF-Q) incorporating the donor tetrathiafulv... more Unprecedented fused acceptor-donor-acceptor triad (Q-TTF-Q) incorporating the donor tetrathiafulvalene (TTF) and the acceptor p-benzoquinone (Q) has been synthesized. The solution UV-Vis spectrum displays a low energy absorption band which is attributed to an intramolecular charge transfer between both antagonistic units. The presence of reversible oxidation and reduction waves for the donor and acceptor moieties was in agreement with the ratio TTF/quinones units. The monoradical anion Q-TTF-Q-. was generated upon chemical reduction and monitored by ESR spectroscopy. This was demonstrated as a Class II mixed valence system with the existence of a temperature dependent intramolecular electron transfer.
Acta Crystallographica Section E Structure Reports Online, 2009
In the title compound, [Ni(SCN)(C16H32N4)]ClO4·H2O, the NiIIion is coordinated by the four N atom... more In the title compound, [Ni(SCN)(C16H32N4)]ClO4·H2O, the NiIIion is coordinated by the four N atoms of the tetraazacyclotetradeca-4,11-diene macrocyclic ligand and by the S atom of a thiocyanate anion. The perchlorate anion is rotationally disordered around one Cl—O bond between two orientations; the occupancies refined to 0.61 (4) and 0.39 (4). Intermolecular O—H...N, N—H...O and N—H...N hydrogen bonds link two cations, two anions and two solvent water molecules into a centrosymmetric cluster. The crystal packing is further stabilized by weak intermolecular C—H...O hydrogen bonds.
Coal is one of the major fuels for power generation, and it will continue in this capacity for th... more Coal is one of the major fuels for power generation, and it will continue in this capacity for the next several decades. Two types of coal are mainly used: lignite and bituminous coals. When exposed to air, post-mining, the coal surface undergoes LTO (low-temperature oxidation) at RT-150°C according to the atmospheric oxygen level. The LTO process decreases the calorific value of the coal, and consequently, different gases are released [mainly carbon oxides (CO, CO 2), water vapor, hydrogen (H 2), and also some low molecular-weight organic gases (C 1−5)]. Some of these gases are toxic and flammable. In extreme cases, fires erupt. The mechanism by which the molecular oxygen oxidizes the coal macromolecule at the temperature range of 30−150°C (LTO process) is complex and also involves a chain of radical reactions that take place; however, the exact underlying mechanism is not yet clear. The LTO process was studied in detail by simulating the processes occurring in the coal piles by using two coal types: an American Bailey coal, used in Israeli coal-fired utilities and a German Hambach lignite, used in German utilities. The mechanism underlying the LTO process and the radical reactions that are involved are discussed in detail.
A technique for evaluation of the diamond is a HPHT diamond presented using microwave spectroscop... more A technique for evaluation of the diamond is a HPHT diamond presented using microwave spectroscopy. This effect is most pronounced in a waveguide transmission measured by the S12 parameter at 12–12.7 GHz, 20.9–21 GHz, and 22.2–22.23 GHz.
We report the discovery that a flow of CO2, N2 or He can sufficiently reduce the spin-spin intera... more We report the discovery that a flow of CO2, N2 or He can sufficiently reduce the spin-spin interactions of specific stable carbon centered radicals by displacing the molecular oxygen in the atmosphere enabling their detection via electron paramagnetic resonance (EPR). This finding unlike other reported effects on carbon radicals occurs under STP conditions and is reversible.
Journal of Chemical Technology & Biotechnology, 2002
Abstract: Israeli ¯y ash is highly basic when exposed to water, due to the very low sulfur conten... more Abstract: Israeli ¯y ash is highly basic when exposed to water, due to the very low sulfur content allowed in coal imports because of the strict environmental regulations (with respect to SOx emissions). Thus, the ¯y ash is a potential chemical neutralization/fixation agent for acidic ...
The reactions of Å O 2 CH 3 radicals with Cu II (glycine) 2 and Cu II (GGG), GGG = glycylglycylgl... more The reactions of Å O 2 CH 3 radicals with Cu II (glycine) 2 and Cu II (GGG), GGG = glycylglycylglycine, in aqueous solutions were studied. The results demonstrate that the peroxyl radicals oxidize the copper complexes forming relatively stable intermediates of the type L m Cu III-OOCH 3. These intermediates decompose via oxidation of the ligands glycine and GGG, respectively. Substituents on the alkyl of the peroxyl radical affect somewhat the kinetics of reaction but not the mechanism of oxidation. It is suggested that analogous reactions are probably contributing to the radical-induced deleterious biological processes.
The reduced lacunary polyoxotungstate, [PW11O39]8−, reacts with the .CH2CH(OH)CH3 and .CH2C(CH3)2... more The reduced lacunary polyoxotungstate, [PW11O39]8−, reacts with the .CH2CH(OH)CH3 and .CH2C(CH3)2OH radicals via a mechanism involving β-hydroxide elimination to yield propene and 2-methyl propene respectively, and [PW11O39]7−. [PW11O39]8− is also oxidized by methyl radicals in a reaction which yields methane as the major product. It is proposed that the reactions proceed via the formation of short lived transients with W–C
While the formation of the peroxo dimer complex is common among sterically unhindered cobalt(II) ... more While the formation of the peroxo dimer complex is common among sterically unhindered cobalt(II) complexes, the tendency of cobalt(II) complexes to form 1:1 adducts with dioxygen increases in more polar solvents, at low temperatures, higher dioxygen pressure, low ...
The effects of N-alkylation on the redox potential of the couples NiU 2 +/NiL i 4, L = tetraaza-1... more The effects of N-alkylation on the redox potential of the couples NiU 2 +/NiL i 4, L = tetraaza-14-membered-macrocyclic ligands, and on the properties of the monovalent nickel complexes in aqueous solutions are reported for 14 complexes. The spectra and lifetimes of the NiU + complexes are reported. The self-exchange rates for the couples NiU 24/NiL i + were determined. Two of the ligands were synthesized for the first time for this study. Cyclic voltammetry and pulse radiolysis were used. The results point out that: (i) N-alkylation always shifts the redox potential to a less cathodic one; this effect stems to a large degree from the decrease in the solvation energy of the complex caused by the N-alkylation of the ligand. (ii) The lifetime of the monovalent complexes is not linearly related to the redox potential of the NiU 24 / NiU 4 couples. (iii) The NiU 4 complexes exist in several isomeric forms; the rate of the isomerization depends on the structure of the ligand. (iv) Different isomers of NiU + may be formed when the complex NiU 24 is reduced by different reagents; therefore, the pulseradiolytically formed NiU ÷ complexes might have different properties than those formed electrochemically.
The reactions of 'CH2C(CH,)2NH,t with Cut(aq) and Cr(H20)62t were studied using the pulse radioly... more The reactions of 'CH2C(CH,)2NH,t with Cut(aq) and Cr(H20)62t were studied using the pulse radiolysis technique. The formation of the unstable [Cu"-CH2C(CH3),(NH,+)1+ and [(H20)5Cr111-CH,C(CH3)2(NH3t)]2t ions was observed in these reactions. These complexes decompose via @ elimination of NH, to yield 2-methylpropene, ammonia, and Cu2+(aq) or Crft(aq). The rates of these @-elimination reactions are considerably slower than those of the analogous @-hydroxyl elination. It is suggested that the rates of the @elimination processes are correlated to the strengths of the CO and C-N bonds, which are cleaved in these reactions. A valence-bond analysis coupled with some ab-initio SCF-MO computations explains the effect of protonation on these bond strengths.
Sulfur and nitrogen oxides (SOX/NOX) are the primary air toxic gas pollutants emitted during fuel... more Sulfur and nitrogen oxides (SOX/NOX) are the primary air toxic gas pollutants emitted during fuel combustion, causing health and environmental concerns. Therefore, their emission in flue gases is strictly regulated. The existing technologies used to decrease SOX/NOX content are flue gas desulfurization, which necessitates high capital and operating costs, and selective catalytic reduction, which, in addition to these costs, requires expensive catalysts and high operating temperatures (350–400 °C). New wet scrubbing processes use O3 or H2O2 oxidants to produce (NH4)2SO4 and NH4NO3 fertilizers upon ammonia injection. However, these oxidants are expensive, corrosive, and hazardous. SiO2/Co(OH)2 nanocomposites are presented here as potential catalysts for SOX/NOX oxidation in wet scrubber reactors to scrub these toxic gases using atmospheric oxygen as the oxidant at relatively low temperatures of 60–90 °C. Several silica-cobalt-oxide-based nanocomposites were synthesized as potential ca...
EPR spectroscopy of pre-color treated natural diamonds – yellow and green: correlation between na... more EPR spectroscopy of pre-color treated natural diamonds – yellow and green: correlation between natural pre colored diamond paramagnetic centers and nitrogen concentration.
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Unprecedented fused acceptor-donor-acceptor triad (Q-TTF-Q) incorporating the donor tetrathiafulv... more Unprecedented fused acceptor-donor-acceptor triad (Q-TTF-Q) incorporating the donor tetrathiafulvalene (TTF) and the acceptor p-benzoquinone (Q) has been synthesized. The solution UV-Vis spectrum displays a low energy absorption band which is attributed to an intramolecular charge transfer between both antagonistic units. The presence of reversible oxidation and reduction waves for the donor and acceptor moieties was in agreement with the ratio TTF/quinones units. The monoradical anion Q-TTF-Q-. was generated upon chemical reduction and monitored by ESR spectroscopy. This was demonstrated as a Class II mixed valence system with the existence of a temperature dependent intramolecular electron transfer.
Acta Crystallographica Section E Structure Reports Online, 2009
In the title compound, [Ni(SCN)(C16H32N4)]ClO4·H2O, the NiIIion is coordinated by the four N atom... more In the title compound, [Ni(SCN)(C16H32N4)]ClO4·H2O, the NiIIion is coordinated by the four N atoms of the tetraazacyclotetradeca-4,11-diene macrocyclic ligand and by the S atom of a thiocyanate anion. The perchlorate anion is rotationally disordered around one Cl—O bond between two orientations; the occupancies refined to 0.61 (4) and 0.39 (4). Intermolecular O—H...N, N—H...O and N—H...N hydrogen bonds link two cations, two anions and two solvent water molecules into a centrosymmetric cluster. The crystal packing is further stabilized by weak intermolecular C—H...O hydrogen bonds.
Coal is one of the major fuels for power generation, and it will continue in this capacity for th... more Coal is one of the major fuels for power generation, and it will continue in this capacity for the next several decades. Two types of coal are mainly used: lignite and bituminous coals. When exposed to air, post-mining, the coal surface undergoes LTO (low-temperature oxidation) at RT-150°C according to the atmospheric oxygen level. The LTO process decreases the calorific value of the coal, and consequently, different gases are released [mainly carbon oxides (CO, CO 2), water vapor, hydrogen (H 2), and also some low molecular-weight organic gases (C 1−5)]. Some of these gases are toxic and flammable. In extreme cases, fires erupt. The mechanism by which the molecular oxygen oxidizes the coal macromolecule at the temperature range of 30−150°C (LTO process) is complex and also involves a chain of radical reactions that take place; however, the exact underlying mechanism is not yet clear. The LTO process was studied in detail by simulating the processes occurring in the coal piles by using two coal types: an American Bailey coal, used in Israeli coal-fired utilities and a German Hambach lignite, used in German utilities. The mechanism underlying the LTO process and the radical reactions that are involved are discussed in detail.
A technique for evaluation of the diamond is a HPHT diamond presented using microwave spectroscop... more A technique for evaluation of the diamond is a HPHT diamond presented using microwave spectroscopy. This effect is most pronounced in a waveguide transmission measured by the S12 parameter at 12–12.7 GHz, 20.9–21 GHz, and 22.2–22.23 GHz.
We report the discovery that a flow of CO2, N2 or He can sufficiently reduce the spin-spin intera... more We report the discovery that a flow of CO2, N2 or He can sufficiently reduce the spin-spin interactions of specific stable carbon centered radicals by displacing the molecular oxygen in the atmosphere enabling their detection via electron paramagnetic resonance (EPR). This finding unlike other reported effects on carbon radicals occurs under STP conditions and is reversible.
Journal of Chemical Technology & Biotechnology, 2002
Abstract: Israeli ¯y ash is highly basic when exposed to water, due to the very low sulfur conten... more Abstract: Israeli ¯y ash is highly basic when exposed to water, due to the very low sulfur content allowed in coal imports because of the strict environmental regulations (with respect to SOx emissions). Thus, the ¯y ash is a potential chemical neutralization/fixation agent for acidic ...
The reactions of Å O 2 CH 3 radicals with Cu II (glycine) 2 and Cu II (GGG), GGG = glycylglycylgl... more The reactions of Å O 2 CH 3 radicals with Cu II (glycine) 2 and Cu II (GGG), GGG = glycylglycylglycine, in aqueous solutions were studied. The results demonstrate that the peroxyl radicals oxidize the copper complexes forming relatively stable intermediates of the type L m Cu III-OOCH 3. These intermediates decompose via oxidation of the ligands glycine and GGG, respectively. Substituents on the alkyl of the peroxyl radical affect somewhat the kinetics of reaction but not the mechanism of oxidation. It is suggested that analogous reactions are probably contributing to the radical-induced deleterious biological processes.
The reduced lacunary polyoxotungstate, [PW11O39]8−, reacts with the .CH2CH(OH)CH3 and .CH2C(CH3)2... more The reduced lacunary polyoxotungstate, [PW11O39]8−, reacts with the .CH2CH(OH)CH3 and .CH2C(CH3)2OH radicals via a mechanism involving β-hydroxide elimination to yield propene and 2-methyl propene respectively, and [PW11O39]7−. [PW11O39]8− is also oxidized by methyl radicals in a reaction which yields methane as the major product. It is proposed that the reactions proceed via the formation of short lived transients with W–C
While the formation of the peroxo dimer complex is common among sterically unhindered cobalt(II) ... more While the formation of the peroxo dimer complex is common among sterically unhindered cobalt(II) complexes, the tendency of cobalt(II) complexes to form 1:1 adducts with dioxygen increases in more polar solvents, at low temperatures, higher dioxygen pressure, low ...
The effects of N-alkylation on the redox potential of the couples NiU 2 +/NiL i 4, L = tetraaza-1... more The effects of N-alkylation on the redox potential of the couples NiU 2 +/NiL i 4, L = tetraaza-14-membered-macrocyclic ligands, and on the properties of the monovalent nickel complexes in aqueous solutions are reported for 14 complexes. The spectra and lifetimes of the NiU + complexes are reported. The self-exchange rates for the couples NiU 24/NiL i + were determined. Two of the ligands were synthesized for the first time for this study. Cyclic voltammetry and pulse radiolysis were used. The results point out that: (i) N-alkylation always shifts the redox potential to a less cathodic one; this effect stems to a large degree from the decrease in the solvation energy of the complex caused by the N-alkylation of the ligand. (ii) The lifetime of the monovalent complexes is not linearly related to the redox potential of the NiU 24 / NiU 4 couples. (iii) The NiU 4 complexes exist in several isomeric forms; the rate of the isomerization depends on the structure of the ligand. (iv) Different isomers of NiU + may be formed when the complex NiU 24 is reduced by different reagents; therefore, the pulseradiolytically formed NiU ÷ complexes might have different properties than those formed electrochemically.
The reactions of 'CH2C(CH,)2NH,t with Cut(aq) and Cr(H20)62t were studied using the pulse radioly... more The reactions of 'CH2C(CH,)2NH,t with Cut(aq) and Cr(H20)62t were studied using the pulse radiolysis technique. The formation of the unstable [Cu"-CH2C(CH3),(NH,+)1+ and [(H20)5Cr111-CH,C(CH3)2(NH3t)]2t ions was observed in these reactions. These complexes decompose via @ elimination of NH, to yield 2-methylpropene, ammonia, and Cu2+(aq) or Crft(aq). The rates of these @-elimination reactions are considerably slower than those of the analogous @-hydroxyl elination. It is suggested that the rates of the @elimination processes are correlated to the strengths of the CO and C-N bonds, which are cleaved in these reactions. A valence-bond analysis coupled with some ab-initio SCF-MO computations explains the effect of protonation on these bond strengths.
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