Catalytic ammonia oxidation on platinum: mechanism and catalyst restructuring at high and low pressure

This research examines the influence of ammonia photo-oxidation on the reduction of the water contaminant, bromate (BrO3-) as a potential removal strategy. It has long been recognized that aqueous ammonia (NH3) has the potential to accelerate the photodecomposition of bromate. This phenomenon has never been studied in dilute solutions whereby its impact during water treatment with UV low-pressure lamps may be used advantageously. It is hypothesized that the accelerated rate of BrO3- photodecomposition in the presence of NH3 is attributed to the generation of an additional supply of electrons as ammonia photo-oxidation occurs. The findings revealed that the rate of bromate photo-decay is increased in the presence of ammonia even in dilute ammonia and BrO3- solutions and the reaction is further accelerated in basic solutions and solutions containing chloride ions. Nitrate is the final stable reaction product formed with prolonged irradiation, followed by a depression of pH. Hypobromous acid was undetected at these concentrations. It was also found that ammonia oxidation occurred in the presence of bromide ions even in acidic solution. The hypothesis that electrons are made available for electron scavengers when ammonia oxidation occurs was verified using sulphur hexafluoride as an electron scavenger.

Download Full-text

Characterization of catalyst and catchment gauzes used in medium- and low-pressure ammonia oxidation plants

Journal of Materials Science ◽

10.1007/bf02403880 ◽

1992 ◽

Vol 27 (3) ◽

pp. 685-691 ◽

Cited By ~ 7

Author(s):

J. L. G. Fierro ◽

J. M. Palacios ◽

F. Tomas

Keyword(s):

Ammonia Oxidation ◽

Low Pressure

Download Full-text

KINETICS OF LOW PRESSURE AMMONIA OXIDATION OVER RH(111)

Latin American Applied Research - An international journal ◽

10.52292/j.laar.2018.253 ◽

2018 ◽

Vol 48 (1) ◽

pp. 27-30

Author(s):

U. N. FAGIOLI ◽

B. V. BOEHN ◽

M. RAFTI ◽

R. IMBIHL

Keyword(s):

Single Crystal ◽

Mass Spectroscopy ◽

Pressure Range ◽

Ammonia Oxidation ◽

Low Pressure ◽

Quadrupole Mass ◽

Catalytic Surface ◽

Sticking Coefficients ◽

Kinetics Of

The kinetics of the NH3 + O2 reaction over a Rh(111) single crystal catalytic surface was explored in the 10-6 mbar pressure range at temperatures between 300-900 K. Selectivity towards N2 and NO products, and reactive sticking coefficients were monitored in situ using differentially pumped quadrupole mass spectroscopy (QMS).

Download Full-text

Effects of Electrical Discharges in Low Pressure Gases on the Morphology of Polyethylene Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052730 ◽

1974 ◽

Vol 32 ◽

pp. 544-545

Author(s):

L.H. Bolz ◽

D.H. Reneker

Keyword(s):

Power Distribution ◽

Electrical Discharge ◽

Dielectric Breakdown ◽

Ionic Species ◽

Low Pressure ◽

Polymer Surfaces ◽

Electrical Discharges ◽

Adhesive Bonds ◽

Power Distribution Lines ◽

Modification Of The Surface

The attack, on the surface of a polymer, by the atomic, molecular and ionic species that are created in a low pressure electrical discharge in a gas is interesting because: 1) significant interior morphological features may be revealed, 2) dielectric breakdown of polymeric insulation on high voltage power distribution lines involves the attack on the polymer of such species created in a corona discharge, 3) adhesive bonds formed between polymer surfaces subjected to such SDecies are much stronger than bonds between untreated surfaces, 4) the chemical modification of the surface creates a reactive surface to which a thin layer of another polymer may be bonded by glow discharge polymerization.

Download Full-text

Field ion microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104236 ◽

1988 ◽

Vol 46 ◽

pp. 434-435

Author(s):

Gert Ehrlich

Keyword(s):

Low Temperature ◽

Sample Surface ◽

Low Pressure ◽

Radius Of Curvature ◽

Field Ion Microscopy ◽

Phosphor Screen ◽

Ion Microscopy ◽

Field Ion Microscope

The field ion microscope, devised by Erwin Muller in the 1950's, was the first instrument to depict the structure of surfaces in atomic detail. An FIM image of a (111) plane of tungsten (Fig.l) is typical of what can be done by this microscope: for this small plane, every atom, at a separation of 4.48Å from its neighbors in the plane, is revealed. The image of the plane is highly enlarged, as it is projected on a phosphor screen with a radius of curvature more than a million times that of the sample. Müller achieved the resolution necessary to reveal individual atoms by imaging with ions, accommodated to the object at a low temperature. The ions are created at the sample surface by ionization of an inert image gas (usually helium), present at a low pressure (< 1 mTorr). at fields on the order of 4V/Å.

Download Full-text