Hg(3P1) photosensitized decomposition of 2,5-dihydrofuran

1970 ◽  
Vol 48 (1) ◽  
pp. 25-32 ◽  
Author(s):  
B. Francis ◽  
A. G. Sherwood
Keyword(s):  
Nitric Oxide ◽  
Carbon Monoxide ◽  
Excited State ◽  
Free Radical ◽  
Vapor Phase ◽  
Quantum Yields ◽  
Low Pressures

The mercury photosensitized decomposition of 2,5-dihydrofuran was studied in the vapor phase at 25 ± 2 °C. Major products are carbon monoxide, propene, and hydrogen, while biallyl, allene, methylacetylene, furan, 2,3-dihydrofuran, tetrahydrofuran, and small amounts of three unidentified products are also produced. The quantum yields of all products are decreased by increasing substrate pressure, indicating collisional deactivation of an excited state precursor which, at low pressures, decomposes according to the scheme [Formula: see text]The product P is not furan and its possible identity is discussed. The free radical component of the reaction was further studied by carrying out the reaction in the presence of nitric oxide. The results are consistent with the above processes.

Evidence of a solvent-mediated barrier to radiationless decay in the state of thiophosgene in solution

1995 ◽  
Vol 73 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Jieming Li ◽  
Ronald P. Steer
Keyword(s):  
Excited State ◽  
Free Radical ◽  
The State ◽  
The Other ◽  
Solute Molecule ◽  
Quantum Yields ◽  
Excitation Wavelength ◽  
Barrier Crossing ◽  
Nonradiative Process ◽  
Nonradiative Processes

Thiophosgene, Cl2CS, has been excited in the near-uv and the resulting quantum yields of [Formula: see text] fluorescence and of Cl2CS consumption have been measured as a function of solvent composition (perfluoro-n-hexane, n-hexane, CCl4), temperature, and excitation wavelength. In agreement with previous work it is shown that (i) nonradiative processes dominate the decay of the [Formula: see text] state in solution, and (ii) perfluoroalkane solvents act as inert "heat baths". The process by which the [Formula: see text] state is apparently "quenched" by CCl4 and n-hexane has been discovered. The nonradiative process leading to [Formula: see text] decay involves activation and crossing a barrier, the height of which is a function of the nature and composition of the solvent. CCl4 and n-hexane do not quench the excited state, but instead accelerate its rate of relaxation by lowering the barrier between the bound, radiative portion of the surface and a dark, unbound region. There is evidence that CCl4 or n-hexane form clusters around a Cl2CS solute molecule in mixed perfluoroalkane–CCl4 or n-hexane solutions. Barrier crossing leads to photodecomposition via at least two parallel paths, one free radical (Cl + ClCS) and the other likely molecular (Cl2 + CS), the relative contributions of which are a function of excitation wavelength. Keywords: thiophosgene, photochemistry, solvent-mediated barrier crossing.

Ultra-Low Amounts of Palladium (0.005-0.05 Wt% Pd) Supported on Titania: Remarkable Low-Temperature Activity for NO Reduction with CO and Structure-Function Property Relationships in Methane Oxidation

2020 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Libor Kovarik ◽  
Nicholas R. Jaegers ◽  
János Szanyi ◽  
Yong Wang
Keyword(s):  
Nitric Oxide ◽  
Carbon Monoxide ◽  
Methane Oxidation ◽  
Steam Reforming ◽  
Methane Steam Reforming ◽  
Oxide Reduction ◽  
Water Steam ◽  
Methane Steam ◽  
Anatase Titania ◽  
Nitric Oxide Reduction

<p>Atomically dispersed Pd +2 cations with ultra-dilute loading of palladium (0.005-0.05 wt%) were anchored on anatase titania and characterized with FTIR, microscopy and catalytic tests. CO infrared adsorption produces a sharp, narrow mono-carbonyl Pd(II)-CO band at ~2,130 cm<sup>-1</sup> indicating formation of highly uniform and stable Pd+2 ions on anatase titania. The 0.05 wt% Pd/TiO<sub>2</sub> sample was evaluated for methane combustion under dry and wet (industrially relevant) conditions in the presence and absence of carbon monoxide. Notably, we find the isolated palladium atoms respond dynamically upon oxygen concentration modulation (switching-on and switching off). When oxygen is removed from the wet methane stream, palladium ions are reduced to metallic state by methane and catalyze methane steam reforming instead of complete methane oxidation. Re-admission of oxygen restores Pd<sup>+2</sup> cations and switches off methane steam reforming activity. Moreover, 0.05 wt% Pd/TiO<sub>2</sub> is a competent CO oxidation catalyst in the presence of water steam with 90% CO conversion and TOF ~ 4,000 hr<sup>-1</sup> at 260 ⁰C. </p><p>More importantly, we find that diluting 0.05 wt% Pd/titania sample with titania to ultra-low 0.005 wt% palladium loading produces a remarkably active material for nitric oxide reduction with carbon monoxide under industrially relevant conditions with >90% conversion of nitric oxide at 180 ⁰C (~460 ppm NO and 150 L/g*hr flow rate in the presence of >2% water steam) and TOF ~6,000 hr<sup>-1</sup>. Pd thus outperforms state-of-the-art rhodium containing catalysts with (15-20 times higher rhodium loading; rhodium is ~ 3 times more expensive than palladium). Furthermore, palladium catalysts are more selective towards nitrogen and produce significantly less ammonia relative to the more traditional rhodium catalysts due to lower Pd amount nd lower water-gas-shift activity. Our study is the first example of utilizing ultra-low (0.05 wt% and less) noble metal (Pd) amounts to produce heterogeneous catalysts with extraordinary activity for nitric oxide reduction. This opens up a pathway to study other Pd, Pt and Rh containing materials with ultra-low loadings of expensive noble metals dispersed on titania or titania-coated oxides for industrially relevant nitric oxide abatement.</p>

scholarly journals Cloned, expressed rat cerebellar nitric oxide synthase contains stoichiometric amounts of heme, which binds carbon monoxide.

1992 ◽  
Vol 89 (23) ◽  
pp. 11141-11145 ◽  
Author(s):  
K. McMillan ◽  
D. S. Bredt ◽  
D. J. Hirsch ◽  
S. H. Snyder ◽  
J. E. Clark ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Carbon Monoxide ◽  
Nitric Oxide Synthase ◽  
Oxide Synthase

Oxidation of Si(100) in nitric oxide at low pressures: An x-ray photoelectron spectroscopy study

1997 ◽  
Vol 70 (1) ◽  
pp. 63-65 ◽  
Author(s):  
A. Kamath ◽  
D. L. Kwong ◽  
Y. M. Sun ◽  
P. M. Blass ◽  
S. Whaley ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Photoelectron Spectroscopy ◽  
Spectroscopy Study ◽  
X Ray ◽  
Low Pressures
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