A non-thermal, atmospheric pressure packed-bed plasma reactor has been used to study the effect o... more A non-thermal, atmospheric pressure packed-bed plasma reactor has been used to study the effect of temperature on the catalysis alone and plasma-assisted catalytic destruction of toluene and benzene in air, in both a one and two-stage configuration. For the one-stage configuration the plasma bed was packed with BaTiO3 beads, to which the catalyst was added; it was heated using thermocoax heating wire wrapped around the quartz tube reactor. For the two-stage configuration the catalyst was placed downstream of the plasma reactor, which is packed with BaTiO3 beads; the catalyst is placed in a purpose built heater. TiO2,�� -Al2O3, and Ag (0.5% weight) impregnated catalysts of both TiO2 and �� -Al2O3, were packed in the reactor to determine their effects. The reactor was heated up to ~ 500 °C and the destruction efficiencies for toluene and benzene were determined for a plasma alone, catalyst alone and the combined plasma-catalyst configuration; the levels of NOx were also discussed.
ABSTRACT A nonthermal, atmospheric pressure, packed-bed plasma reactor has been used to study the... more ABSTRACT A nonthermal, atmospheric pressure, packed-bed plasma reactor has been used to study the effect of temperature on the plasma−catalytic destruction of toluene and benzene in air. The plasma reactor was packed with BaTiO3 beads to which TiO2, γ-Al2O3, and Ag, Pt, or Pd impregnated catalysts were added. The reactor can be heated up to 500 °C, and the destruction efficiencies for toluene and benzene were determined for plasma alone, catalyst alone, and the combined plasma−catalyst configuration. Comparisons have been made to determine the relative contributions of the catalyst and plasma and to discover any synergistic effects. Plasma−catalysis shows greater destruction than catalysis alone with increasing temperature for both benzene and toluene. Catalysis alone has a threshold temperature of 300 °C for the destruction of toluene and benzene, but plasma−catalysis with Pd- and Pt-impregnated alumina achieves >95% destruction at this temperature and has a threshold of 100 °C. Toluene is more easily destroyed than benzene at all temperatures, by all catalysts.
A nonthermal, atmospheric pressure plasma, made-up of a BaTiO3 packed-bed reactor, has been used ... more A nonthermal, atmospheric pressure plasma, made-up of a BaTiO3 packed-bed reactor, has been used to study the formation of NOx and N2O during the plasma destruction of a range of volatile organic compounds (VOCs) and hazardous air pollutants, including chlorinated, brominated, fluorinated, and iodinated methane species, in a carrier gas of air. Using the plasma destruction of pure air as a baseline, it is found that the amount of NOx formed is unaffected by the addition of a few hundred parts per million of a simple hydrocarbon (e.g. methane). In the case of the fluorinated, chlorinated, and brominated methanes, we find enhanced production of NOx and a marked increase in the ratio of NO2 to NO formed, from approximately 1.1 in air and methane to approximately 2.3 in halogenated species. However, iodinated additives (specifically methyl iodide and diiodomethane) have remarkably different results compared to the other halogenated additives; they show enhanced increases in the NO2 to NO ratio ( approximately 6-13) and reduced NOx production. The enhanced conversion of NO to NO2 is attributed to reactions involving halogen oxides, e.g. ClO and IO.
ABSTRACT A non-thermal, atmospheric-pressure plasma has been used to study the effect of temperat... more ABSTRACT A non-thermal, atmospheric-pressure plasma has been used to study the effect of temperature on the plasma destruction of DCM in an air stream using a BaTiO3-packed-bedreactor, co-filled with TiO2 and gamma-Al2O3 catalysts. Comparisons have been made with plasma alone, catalysis alone and combined plasma/catalysis to determine any synergistic effects of combininig plasma and catalysis. Plasma/catalysis is the most successful method for destroying DCM over 125-400 degrees C. TiO2 was more effective than gamma-Al2O3 for plasma/catalysis. The energy efficiency of plasma/catalysis processing compared to catalysis alone is considered by examining the input power required to achieve equivalent destructions, finding that an energy reduction of approximate to 30% can be achieved by plasma activation of the catalyst.
This key comparison was performed to demonstrate the capability of NMIs to analyse the purity of ... more This key comparison was performed to demonstrate the capability of NMIs to analyse the purity of methane for use as a source gas in the preparation of standard gas mixtures. This capability is an essential requirement for the preparation of accurate standards of natural ...
We report the development of a microfabricated gas chromatography system suitable for the separat... more We report the development of a microfabricated gas chromatography system suitable for the separation of volatile organic compounds (VOCs) and compatible with use as a portable measurement device. Hydrofluoric acid etching of 95x95mm Schott B270 wafers has been used to give symmetrical hemi-spherical channels within a glass substrate. Two matching glass plates were subsequently cold bonded with the channels aligned; the flatness of the glass surfaces resulted in strong bonding through van der Waals forces. The device comprised gas fluidic interconnections, injection zone and 7.5 and 1.4m long, 320microm internal diameter capillaries. Optical microscopy confirmed the capillaries to have fully circular channel profiles. Direct column heating and cooling could be achieved using a combination of resistive heaters and Peltier devices. The low thermal conductivity of glass allowed for multiple uniform temperature zones to be achieved within a single glass chip. Temperature control over the range 10-200 degrees C was achieved with peak power demand of approximately 25W. The 7.5m capillary column was static coated with a 2microm film of non-polar dimethylpolysiloxane stationary phase. A standard FID and a modified lightweight 100mW photoionization detector (PID) were coupled to the column and performance tested with gas mixtures of monoaromatic and monoterpene species at the parts per million concentration level. The low power GC-PID device showed good performance for a small set of VOCs and sub ng detection sensitivity to monoaromatics.
ABSTRACT Results for the destruction of environmental pollutants, using a novel multistage dielec... more ABSTRACT Results for the destruction of environmental pollutants, using a novel multistage dielectric packed bed discharge plasma reactor (DPBD), carried out at an industrial scale flow rate of 300 L min(-1) are presented. Some initial results on the combination of a MnO(2) catalyst with the system are also given. Complete destruction of toluene is seen for an initial concentration of 10 ppm at a deposited energy density of 23 J L(-1) (0.006 kW h Nm(3-)). This is an order of magnitude better than previous values indicating high energy efficiency. No NOx, a previously common byproduct in plasma processing, can be detected.
Studies of climate change increasingly recognize the diverse influences of hydrocarbons in the at... more Studies of climate change increasingly recognize the diverse influences of hydrocarbons in the atmosphere, including roles in particulates and ozone formation. Measurements of key nonmethane hydrocarbons (NMHCs) suggest atmospheric mole fractions ranging from low picomoles per mol (ppt) to nanomoles per mol (ppb), depending on location and compound. To accurately establish mole fraction trends and to relate measurement records from many laboratories and researchers, it is essential to have accurate, stable, calibration standards. In February of 2008, the National Institute of Standards and Technology (NIST) developed and reported on picomoles per mol standards containing 18 nonmethane hydrocarbon compounds covering the mole fraction range of 60 picomoles per mol to 230 picomoles per mol. The stability of these gas mixtures was only characterized over a short time period (2 to 3 months). NIST recently prepared a suite of primary standard gas mixtures by gravimetric dilution to ascertain the stability of the 2008 picomoles per mol NMHC standards suite. The data from this recent chromatographic intercomparison of the 2008 to the 2011 suites confirm a much longer stability of almost 5 years for 15 of the 18 hydrocarbons; the double-bonded alkenes of propene, isobutene, and 1-pentene showed instability, in line with previous publications. The agreement between the gravimetric values from preparation and the analytical mole fractions determined from regression illustrate the internal consistency of the suite within ±2 pmol/mol. However, results for several of the compounds reflect stability problems for the three double-bonded hydrocarbons. An international intercomparison on one of the 2008 standards has also been completed. Participants included National Metrology Institutes, United States government laboratories, and academic laboratories. In general, results for this intercomparison agree to within about ±5% with the gravimetric mole fractions of the hydrocarbons.
A non-thermal, atmospheric pressure packed-bed plasma reactor has been used to study the effect o... more A non-thermal, atmospheric pressure packed-bed plasma reactor has been used to study the effect of temperature on the catalysis alone and plasma-assisted catalytic destruction of toluene and benzene in air, in both a one and two-stage configuration. For the one-stage configuration the plasma bed was packed with BaTiO3 beads, to which the catalyst was added; it was heated using thermocoax heating wire wrapped around the quartz tube reactor. For the two-stage configuration the catalyst was placed downstream of the plasma reactor, which is packed with BaTiO3 beads; the catalyst is placed in a purpose built heater. TiO2,�� -Al2O3, and Ag (0.5% weight) impregnated catalysts of both TiO2 and �� -Al2O3, were packed in the reactor to determine their effects. The reactor was heated up to ~ 500 °C and the destruction efficiencies for toluene and benzene were determined for a plasma alone, catalyst alone and the combined plasma-catalyst configuration; the levels of NOx were also discussed.
ABSTRACT A nonthermal, atmospheric pressure, packed-bed plasma reactor has been used to study the... more ABSTRACT A nonthermal, atmospheric pressure, packed-bed plasma reactor has been used to study the effect of temperature on the plasma−catalytic destruction of toluene and benzene in air. The plasma reactor was packed with BaTiO3 beads to which TiO2, γ-Al2O3, and Ag, Pt, or Pd impregnated catalysts were added. The reactor can be heated up to 500 °C, and the destruction efficiencies for toluene and benzene were determined for plasma alone, catalyst alone, and the combined plasma−catalyst configuration. Comparisons have been made to determine the relative contributions of the catalyst and plasma and to discover any synergistic effects. Plasma−catalysis shows greater destruction than catalysis alone with increasing temperature for both benzene and toluene. Catalysis alone has a threshold temperature of 300 °C for the destruction of toluene and benzene, but plasma−catalysis with Pd- and Pt-impregnated alumina achieves >95% destruction at this temperature and has a threshold of 100 °C. Toluene is more easily destroyed than benzene at all temperatures, by all catalysts.
A nonthermal, atmospheric pressure plasma, made-up of a BaTiO3 packed-bed reactor, has been used ... more A nonthermal, atmospheric pressure plasma, made-up of a BaTiO3 packed-bed reactor, has been used to study the formation of NOx and N2O during the plasma destruction of a range of volatile organic compounds (VOCs) and hazardous air pollutants, including chlorinated, brominated, fluorinated, and iodinated methane species, in a carrier gas of air. Using the plasma destruction of pure air as a baseline, it is found that the amount of NOx formed is unaffected by the addition of a few hundred parts per million of a simple hydrocarbon (e.g. methane). In the case of the fluorinated, chlorinated, and brominated methanes, we find enhanced production of NOx and a marked increase in the ratio of NO2 to NO formed, from approximately 1.1 in air and methane to approximately 2.3 in halogenated species. However, iodinated additives (specifically methyl iodide and diiodomethane) have remarkably different results compared to the other halogenated additives; they show enhanced increases in the NO2 to NO ratio ( approximately 6-13) and reduced NOx production. The enhanced conversion of NO to NO2 is attributed to reactions involving halogen oxides, e.g. ClO and IO.
ABSTRACT A non-thermal, atmospheric-pressure plasma has been used to study the effect of temperat... more ABSTRACT A non-thermal, atmospheric-pressure plasma has been used to study the effect of temperature on the plasma destruction of DCM in an air stream using a BaTiO3-packed-bedreactor, co-filled with TiO2 and gamma-Al2O3 catalysts. Comparisons have been made with plasma alone, catalysis alone and combined plasma/catalysis to determine any synergistic effects of combininig plasma and catalysis. Plasma/catalysis is the most successful method for destroying DCM over 125-400 degrees C. TiO2 was more effective than gamma-Al2O3 for plasma/catalysis. The energy efficiency of plasma/catalysis processing compared to catalysis alone is considered by examining the input power required to achieve equivalent destructions, finding that an energy reduction of approximate to 30% can be achieved by plasma activation of the catalyst.
This key comparison was performed to demonstrate the capability of NMIs to analyse the purity of ... more This key comparison was performed to demonstrate the capability of NMIs to analyse the purity of methane for use as a source gas in the preparation of standard gas mixtures. This capability is an essential requirement for the preparation of accurate standards of natural ...
We report the development of a microfabricated gas chromatography system suitable for the separat... more We report the development of a microfabricated gas chromatography system suitable for the separation of volatile organic compounds (VOCs) and compatible with use as a portable measurement device. Hydrofluoric acid etching of 95x95mm Schott B270 wafers has been used to give symmetrical hemi-spherical channels within a glass substrate. Two matching glass plates were subsequently cold bonded with the channels aligned; the flatness of the glass surfaces resulted in strong bonding through van der Waals forces. The device comprised gas fluidic interconnections, injection zone and 7.5 and 1.4m long, 320microm internal diameter capillaries. Optical microscopy confirmed the capillaries to have fully circular channel profiles. Direct column heating and cooling could be achieved using a combination of resistive heaters and Peltier devices. The low thermal conductivity of glass allowed for multiple uniform temperature zones to be achieved within a single glass chip. Temperature control over the range 10-200 degrees C was achieved with peak power demand of approximately 25W. The 7.5m capillary column was static coated with a 2microm film of non-polar dimethylpolysiloxane stationary phase. A standard FID and a modified lightweight 100mW photoionization detector (PID) were coupled to the column and performance tested with gas mixtures of monoaromatic and monoterpene species at the parts per million concentration level. The low power GC-PID device showed good performance for a small set of VOCs and sub ng detection sensitivity to monoaromatics.
ABSTRACT Results for the destruction of environmental pollutants, using a novel multistage dielec... more ABSTRACT Results for the destruction of environmental pollutants, using a novel multistage dielectric packed bed discharge plasma reactor (DPBD), carried out at an industrial scale flow rate of 300 L min(-1) are presented. Some initial results on the combination of a MnO(2) catalyst with the system are also given. Complete destruction of toluene is seen for an initial concentration of 10 ppm at a deposited energy density of 23 J L(-1) (0.006 kW h Nm(3-)). This is an order of magnitude better than previous values indicating high energy efficiency. No NOx, a previously common byproduct in plasma processing, can be detected.
Studies of climate change increasingly recognize the diverse influences of hydrocarbons in the at... more Studies of climate change increasingly recognize the diverse influences of hydrocarbons in the atmosphere, including roles in particulates and ozone formation. Measurements of key nonmethane hydrocarbons (NMHCs) suggest atmospheric mole fractions ranging from low picomoles per mol (ppt) to nanomoles per mol (ppb), depending on location and compound. To accurately establish mole fraction trends and to relate measurement records from many laboratories and researchers, it is essential to have accurate, stable, calibration standards. In February of 2008, the National Institute of Standards and Technology (NIST) developed and reported on picomoles per mol standards containing 18 nonmethane hydrocarbon compounds covering the mole fraction range of 60 picomoles per mol to 230 picomoles per mol. The stability of these gas mixtures was only characterized over a short time period (2 to 3 months). NIST recently prepared a suite of primary standard gas mixtures by gravimetric dilution to ascertain the stability of the 2008 picomoles per mol NMHC standards suite. The data from this recent chromatographic intercomparison of the 2008 to the 2011 suites confirm a much longer stability of almost 5 years for 15 of the 18 hydrocarbons; the double-bonded alkenes of propene, isobutene, and 1-pentene showed instability, in line with previous publications. The agreement between the gravimetric values from preparation and the analytical mole fractions determined from regression illustrate the internal consistency of the suite within ±2 pmol/mol. However, results for several of the compounds reflect stability problems for the three double-bonded hydrocarbons. An international intercomparison on one of the 2008 standards has also been completed. Participants included National Metrology Institutes, United States government laboratories, and academic laboratories. In general, results for this intercomparison agree to within about ±5% with the gravimetric mole fractions of the hydrocarbons.
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Papers by Alice Harling