Photosensitization by Cd 3P1 atoms. I. Decomposition of acetone

1970 ◽  
Vol 48 (8) ◽  
pp. 1333-1334 ◽  
Author(s):  
B. L. Kalra ◽  
A. R. Knight
Keyword(s):  
Acetone Vapor ◽  
Direct Photolysis ◽  
Virtual Identity ◽  
Excited Species ◽  
Volatile Products ◽  
Acetone System

The photodecomposition of acetone vapor at 255 °C sensitized by Cd 3P1 atoms has been investigated. On irradiation of the Cd–acetone system at 3261 Å, both direct and sensitized reaction occur. CO and CH4 are the only significant volatile products, and their yield is decreased by addition of SF6 as inert quenching gas. The required participation of triplet acetone molecules in the sensitized reaction and the virtual identity of the direct and sensitized decompositions provide additional evidence for the importance of this excited species in direct photolysis.

scholarly journals Aqueous-phase photochemical oxidation and direct photolysis of vanillin – a model compound of methoxy-phenols from biomass burning

2013 ◽  
Vol 13 (10) ◽  
pp. 27641-27675
Author(s):  
Y. J. Li ◽  
D. D. Huang ◽  
H. Y. Cheung ◽  
A. K. Y. Lee ◽  
C. K. Chan
Keyword(s):  
Aqueous Phase ◽  
Biomass Burning ◽  
Model Compound ◽  
Photochemical Oxidation ◽  
Particle Phase ◽  
Organic Mass ◽  
Direct Photolysis ◽  
Volatile Products ◽  
Reacting Mixtures ◽  
Condition B

Abstract. We present here experimental results on aqueous-phase (A) photochemical oxidation (with UV and OH radicals generated from H2O2 photolysis) and (B) direct photolysis (with only UV irradiation) of a methoxy-phenol, vanillin (VL), as a model compound from biomass burning. Both on-line aerosol mass spectrometric (AMS) characterization and off-line chemical analyses were performed. AMS analyses of dried atomized droplets of the bulk reacting mixtures showed that VL almost entirely evaporates during the drying process. Large amounts of organic mass remained in the particle phase after reactions under both conditions. Under condition (A), AMS measured organic mass first increased rapidly and then decreased, attributable to the formation of non-volatile products and subsequent formation of smaller and volatile products, respectively. The oxygen-to-carbon (O:C) ratio of the products reached 1.5 after about 80 min, but dropped substantially thereafter. In contrast, organic mass increased slowly under condition (B). The O:C ratio reached 1.0 after 180 min. In off-line analyses, small oxygenates were detected under condition (A), while hydroxylated products and dimers of VL were detected under condition (B). Particle hygroscopic growth factor (GF) and cloud condensation nuclei (CCN) activity of the reacting mixtures were found to be dependent on both organic volume fraction and the degree of oxygenation of organics. Results show that (1) aqueous-phase processes can lead to the retention of a large portion of the organic mass in the particle phase; (2) once retained, this portion of organic mass significantly changes the hygroscopicity and CCN activity of the aerosol particles; (3) intensive photochemical oxidation gave rise to an O:C ratio as high as 1.5 but the ratio decreased as further oxidation led to smaller and more volatile products; and (4) polymerization occurred with direct photolysis, resulting in high-molecular-weight products of a yellowish color. This study demonstrates that aqueous-phase reactions of a methoxy-phenol can lead to substantial amount of secondary organic aerosol (SOA) formation. Given the vast amount of biomass burning input globally, model representation of either the SOA budget or their subsequent effects would not be adequate if the contribution of SOA formation from aqueous-phase reactions of methoxy-phenols is not considered.

scholarly journals Aqueous-phase photochemical oxidation and direct photolysis of vanillin – a model compound of methoxy phenols from biomass burning

2014 ◽  
Vol 14 (6) ◽  
pp. 2871-2885 ◽  
Author(s):  
Y. J. Li ◽  
D. D. Huang ◽  
H. Y. Cheung ◽  
A. K. Y. Lee ◽  
C. K. Chan
Keyword(s):  
Aqueous Phase ◽  
Biomass Burning ◽  
Model Compound ◽  
Photochemical Oxidation ◽  
Particle Phase ◽  
Organic Mass ◽  
Direct Photolysis ◽  
Volatile Products ◽  
Reacting Mixtures ◽  
Condition B

Abstract. We present here experimental results on aqueous-phase (A) photochemical oxidation (with UV and OH radicals generated from H2O2 photolysis) and (B) direct photolysis (with only UV irradiation) of a methoxy phenol, vanillin (VL), as a model compound from biomass burning. Both on-line aerosol mass spectrometric (AMS) characterization and off-line chemical analyses were performed. AMS analyses of dried atomized droplets of the bulk reacting mixtures showed that VL almost entirely evaporates during the drying process. Large amounts of organic mass remained in the particle phase after reactions under both conditions. Under condition (A), AMS measured organic mass first increased rapidly and then decreased, attributable to the formation of non-volatile products and subsequent formation of smaller and volatile products, respectively. The oxygen-to-carbon (O : C) ratio of the products reached 1.5 after about 80 min, but dropped substantially thereafter. In contrast, organic mass increased slowly under condition (B). The O : C ratio reached 1.0 after 180 min. In off-line analyses, small oxygenates were detected under condition (A), while hydroxylated products and dimers of VL were detected under condition (B). Particle hygroscopic growth factor (GF) and cloud condensation nuclei (CCN) activity of the reacting mixtures were found to depend on both organic volume fraction and the degree of oxygenation of organics. Results show that (1) aqueous-phase processes can lead to the retention of a large portion of the organic mass in the particle phase; (2) once retained, this portion of organic mass significantly changes the hygroscopicity and CCN activity of the aerosol particles; (3) intensive photochemical oxidation gave rise to an O : C ratio as high as 1.5 but the ratio decreased as further oxidation led to smaller and more volatile products; and (4) polymerization occurred with direct photolysis, resulting in high-molecular-weight products of a yellowish color. This study demonstrates that aqueous-phase reactions of a methoxy phenol can lead to substantial amount of secondary organic aerosol (SOA) formation. Given the vast amount of biomass burning input globally, model representation of either the SOA budget or their subsequent effects would not be adequate if the contribution of SOA formation from aqueous-phase reactions of methoxy phenols is not considered.

Direct Photolysis of 2-Propanol Vapor

1972 ◽  
Vol 50 (14) ◽  
pp. 2217-2223 ◽  
Author(s):  
O. S. Herasymowych ◽  
A. R. Knight
Keyword(s):  
Quantum Yield ◽  
Wavelength Range ◽  
Exposure Time ◽  
Yield Enhancement ◽  
Quantum Yields ◽  
Unimolecular Decomposition ◽  
Direct Photolysis ◽  
Volatile Products ◽  
Temperature And Pressure

The photolysis of 2-propanol vapor in the 1800–2000 Å wavelength range has been investigated. The volatile products of the reaction and their quantum yields at 80 °C and 200 Torr substrate pressure are H2 (0.64), CH3COCH3 (0.34), CH4 (0.39), CH3CHO (0.29), CO (0.15), and C2H6 (0.08). A mechanism is proposed that accounts for the observed rate variations with substrate pressure, exposure time, temperature, and pressure of inert addend. Acetone and acetaldehyde undergo significant secondary decomposition and this is the source of CO, CH4, and C2H6. Acetaldehyde is formed in the unimolecular decomposition of C3H7O radicals produced in the primary process.The effects of CO2 and CF4 as inert addends have been examined and it has been established that the quantum yield enhancement through collision induced predissociation that has been reported to occur in methanol is not a characteristic of the 2-propanol photolysis.

Effect of pyrolysis temperature on volatile products from hazelnut shells: products characteristics and antioxidant activity assessment of liquid products

2021 ◽  
Vol 19 (4) ◽  
pp. 383-391
Author(s):  
Chenxi Zhao ◽  
Yupeng Xing ◽  
Wei Lv ◽  
Juhui Chen ◽  
Xiaogang Liu ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Composition Analysis ◽  
Maximum Output ◽  
Activity Assessment ◽  
Volatile Products ◽  
Liquid Products ◽  
Fuels And Chemicals ◽  
Gas Products ◽  
Combustible Gases ◽  
Hazelnut Shells

Abstract It is being considered to pyrolyze lignin-rich biomass samples (hazelnut shells, HSs) into bio-fuels and chemicals to solve energy shortages and environmental concerns, volatile products (including liquid products and gas products) were produced and characterized from HSs pyrolysis at 400–1000 °C. With the temperature increases, the maximum output of liquid products was up to 35.79% produced at 700 °C, gas products yields increased from 21.82 to 55.46%. Gas chromatography and mass spectrometry (GC–MS) study indicated that liquid products from HSs riched in phenolic compounds, exceed 42% of liquid products and increased as the temperature rises. The application experiment showed that HSs liquid products had a significant role in antioxidant activity, and revealed that not limited to phenols, all compounds containing phenolic hydroxyl structure act as antioxidant. Composition analysis of gas products showed that more combustible gases were produced at the higher temperature, resulted in the significant increase in gas products higher heating value (HHV) from 6.21 to 24.36 MJ/kg.

scholarly journals Analysis of the Pyrolytic Behaviour of Birch, Maple, and Rowan Leaves

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2091
Author(s):  
Valentina Zubkova ◽  
Andrzej Strojwas ◽  
Marcin Bielecki
Keyword(s):  
Combustion Products ◽  
Carbonyl Groups ◽  
Chemical Parameters ◽  
Chemical Reagents ◽  
Urban Greenery ◽  
Volatile Products ◽  
Different Types ◽  
Ft Ir ◽  
Xrd Techniques ◽  
Lower Contribution

A research study was conducted on the thermal behaviour of leaves of urban greenery (birch, maple, and rowan) and the products of their pyrolysis and extraction as assisted by microwaves. The obtained products of pyrolysis and extraction were investigated with the use of FT-IR and UV spectroscopies and XRD techniques. A contractive analysis of samples of chars, condensates, after-extraction residue, and extracts showed that the changes in structural-chemical parameters of leaves of different types of trees during pyrolysis and extraction take place in distinct ways. About 22% of material was removed from birch leaves during extraction, and more than 17% of material was extracted from maple and rowan leaves. It was determined that, during pyrolysis of after-extraction residue of leaves, many fewer PAH compounds with carbonyl groups along with alcohols and phenols are emitted than during pyrolysis of non-extracted leaves. Taking into account that pyrolysis is the first stage of combustion, a decrease in the amount of dangerous compounds in the volatile products of pyrolysis leads to a lower contribution of such compounds in combustion products. This indicates that leaves of urban greenery can be subjected to combustion after extraction, and the obtained extracts can be used as a source of phytochemicals and chemical reagents.

scholarly journals UV/Vis-Based Persulphate Activation for p-Nitrophenol Degradation

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 480
Author(s):  
Valentin Dubois ◽  
Carmen S. D. Rodrigues ◽  
Ana S. P. Alves ◽  
Luis M. Madeira
Keyword(s):  
Reaction Time ◽  
Oxidation Process ◽  
Activation Process ◽  
Direct Photolysis ◽  
Simulated Solar Light ◽  
Uv Visible ◽  
Oxidation Efficiency ◽  
Nitrophenol Degradation ◽  
Persulphate Oxidation ◽  
Radiation Type

In the present work, the degradation of p-nitrophenol (PNP) and its mineralization by a UV/Vis-based persulphate activation process was investigated. Firstly, a screening of processes as direct photolysis, persulphate alone and persulphate activated by radiation was performed. The incidence of radiation demonstrated to have an important role in the oxidant activation, allowing to achieve the highest PNP and total organic carbon (TOC) removals. The maximum PNP oxidation (100%) and mineralization (61.6%)—both after 2 h of reaction time—were reached when using T = 70 °C, (S2O82−) = 6.4 g/L and I = 500 W/m2. The influence of radiation type (ultraviolet/visible, visible or simulated solar light) was also evaluated, being found that the source with the highest emission of ultraviolet radiation (UV/visible) allowed to achieve the best oxidation efficiency; however, solar radiation also reached very-good performance. According to quenching experiments, the sulphate radical is key in the activated persulphate oxidation process, but the hydroxyl radical also plays an important role.

scholarly journals Moisture Resistance, Thermal Stability and Fire Behavior of Unsaturated Polyester Resin Modified with L-histidinium Dihydrogen Phosphate-Phosphoric Acid

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 932
Author(s):  
Kamila Sałasińska ◽  
Maciej Celiński ◽  
Kamila Mizera ◽  
Mateusz Barczewski ◽  
Paweł Kozikowski ◽  
...  
Keyword(s):  
Phosphoric Acid ◽  
Polyester Resin ◽  
Unsaturated Polyester ◽  
Fire Behavior ◽  
Fire Retardant ◽  
Thermomechanical Properties ◽  
Unsaturated Polyester Resin ◽  
Dihydrogen Phosphate ◽  
Smoke Emission ◽  
Volatile Products

In this paper, the fire behavior of unsaturated polyester resin (UP) modified with L-histidinium dihydrogen phosphate-phosphoric acid (LHP), being a novel intumescent fire retardant (IFR), was investigated. Thermal and thermomechanical properties of the UP with different amounts of LHP (from 10 to 30 wt. %) were determined by thermogravimetric analysis (TG) as well as dynamic mechanical thermal analysis (DMTA). Reaction to small flames was studied by horizontal burning (HB) test, while fire behavior and smoke emission were investigated with the cone calorimeter (CC) and smoke density chamber. Further, the analysis of volatile products was conducted (TGA/FT-IR). It was observed that the addition of LHP resulted in the formation of carbonaceous char inhibiting the thermal decomposition, burning rate and smoke emission. The most promising results were obtained for the UP containing 30 wt. % of LHP, for which the highest reduction in maximum values of heat release rate (200 kW/m2) and total smoke release (3535 m2/m2) compared to unmodified polymer (792 kW/m2 and 6895 m2/m2) were recorded. However, some important disadvantage with respect to water resistance was observed.

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