scholarly journals Newly observed peroxides and the water effect on the formation and removal of hydroxyalkyl hydroperoxides in the ozonolysis of isoprene

2013 ◽  
Vol 13 (11) ◽  
pp. 5671-5683 ◽  
Author(s):  
D. Huang ◽  
Z. M. Chen ◽  
Y. Zhao ◽  
H. Liang
Keyword(s):  
Experimental Evidence ◽  
Gas Phase ◽  
Chemical Processes ◽  
Flow Tube ◽  
Tube Reactor ◽  
Criegee Intermediates ◽  
Long Lifetime ◽  
Laboratory Investigations ◽  
Range Of Values ◽  
Recent Laboratory

Abstract. The ozonolysis of alkenes is considered to be an important source of atmospheric peroxides, which serve as oxidants, reservoirs of HOx radicals, and components of secondary organic aerosols (SOAs). Recent laboratory investigations of this reaction identified hydrogen peroxide (H2O2) and hydroxymethyl hydroperoxide (HMHP) in ozonolysis of isoprene. Although larger hydroxyalkyl hydroperoxides (HAHPs) were also expected, their presence is not currently supported by experimental evidence. In the present study, we investigated the formation of peroxides in the gas phase ozonolysis of isoprene at various relative humidities on a time scale of tens of seconds, using a quartz flow tube reactor coupled with the online detection of peroxides. We detected a variety of conventional peroxides, including H2O2, HMHP, methyl hydroperoxide, bis-hydroxymethyl hydroperoxide, and ethyl hydroperoxide, and interestingly found three unknown peroxides. The molar yields of the conventional peroxides fell within the range of values provided in the literature. The three unknown peroxides had a combined molar yield of ~ 30% at 5% relative humidity (RH), which was comparable with that of the conventional peroxides. Unlike H2O2 and HMHP, the molar yields of these three unknown peroxides were inversely related to the RH. On the basis of experimental kinetic and box model analysis, we tentatively assigned these unknown peroxides to C2−C4 HAHPs, which are produced by the reactions of different Criegee intermediates with water. Our study provides experimental evidence for the formation of large HAHPs in the ozonolysis of isoprene (one of the alkenes). These large HAHPs have a sufficiently long lifetime, estimated as tens of minutes, which allows them to become involved in atmospheric chemical processes, e.g., SOA formation and radical recycling.

scholarly journals Newly observed peroxides and the water effect on the formation and removal of hydroxyalkyl hydroperoxides in the ozonolysis of isoprene

2013 ◽  
Vol 13 (2) ◽  
pp. 5279-5314
Author(s):  
D. Huang ◽  
Z. M. Chen ◽  
Y. Zhao ◽  
H. Liang
Keyword(s):  
Experimental Evidence ◽  
Gas Phase ◽  
Chemical Processes ◽  
Flow Tube ◽  
Tube Reactor ◽  
Criegee Intermediates ◽  
Long Lifetime ◽  
Laboratory Investigations ◽  
Range Of Values ◽  
Recent Laboratory

Abstract. The ozonolysis of alkenes is considered to be an important source of atmospheric peroxides, which serve as oxidants, reservoirs of HOx radicals, and components of secondary organic aerosols (SOAs). Recent laboratory investigations of this reaction identified hydrogen peroxide (H2O2) and hydroxymethyl hydroperoxide (HMHP). Although larger hydroxyalkyl hydroperoxides (HAHPs) were also expected, their presence is not currently supported by experimental evidence. In the present study, we investigated the formation of peroxides in the gas phase ozonolysis of isoprene at various relative humidities on a time scale of tens of seconds, using a quartz flow tube reactor coupled with the online detection of peroxides. We detected a variety of conventional peroxides, including H2O2, HMHP, methyl hydroperoxide, bis-hydroxymethyl hydroperoxide, and ethyl hydroperoxide, and interestingly found three unknown peroxides. The molar yields of the conventional peroxides fell within the range of values provided in the literature. The three unknown peroxides had a combined molar yield of ~30% at 5% relative humidity (RH), which was comparable with that of the conventional peroxides. Unlike H2O2 and HMHP, the molar yields of these three unknown peroxides were inversely related to the RH. On the basis of experimental kinetic and box model analysis, we tentatively assigned these unknown peroxides to C2–C4 HAHPs, which are produced by the reactions of different Criegee intermediates with water. Our study provides experimental evidence for the formation of large HAHPs in the ozonolysis of isoprene (one of the alkenes). These large HAHPs have a sufficiently long lifetime, estimated as tens of minutes, which allows them to become involved in atmospheric chemical processes, e.g. SOA formation and radical recycling. These standards are needed to accurately specify HAHPs, although their synthesis is a challenge.

A gas-phase synthesis of Ag-centered phenylenediamine clusters

2020 ◽  
Vol 8 (30) ◽  
pp. 10325-10332
Author(s):  
Mengdi Guo ◽  
Baoqi Yin ◽  
Benben Huang ◽  
Haiming Wu ◽  
Zhixun Luo
Keyword(s):  
Gas Phase ◽  
Soft Landing ◽  
Flow Tube ◽  
Phase Synthesis ◽  
Gas Phase Synthesis ◽  
Tube Reactor

Gas-phase synthesis of Ag-centered phenylenediamine clusters is achieved by dual sources combined with a flow tube reactor, producing Raman-active soft-landing deposits.

IR Diagnostics of MOCVD Reaction Chemistry

1992 ◽  
Vol 282 ◽  
Author(s):  
Bruce H. Weiller
Keyword(s):  
Reaction Time ◽  
Gas Phase ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Flow Tube ◽  
Tube Reactor ◽  
Ftir Spectrometer ◽  
Ir Diagnostics ◽  
Trimethyl Aluminum ◽  
Phase Chemical

ABSTRACTThe gas-phase chemical reactions in the Metallorganic Chemical Vapor Deposition (MOCVD) of A1N and TiN have been studied using IR spectroscopy. The products formed from the reaction of trimethyl aluminum (TMA) and NH3 were compared to those from the reaction of TMAwith NF3 using a static gas-phase IR cell. Reaction with NH3 is rapid at 25 °C, and the IR spectrum of the product is consistent with the acid-base adduct (CH3)3Al-NH3. At 25 °C, no reaction between TMA and NF3 was observed. However, at 58 °C a slow reaction occurredto give (CH3)2AlF. The reaction of Ti(N(CH3)2)4 with NH3 was also studied using a flow-tube reactor with a sliding injector port that provides control over the reaction time between two reactive flows. By monitoring the disappearance of Ti(N(CH3)2)4 as a function of NH3 partial pressure and reaction time, we have obtained a preliminary estimate of the rate constant as ∼ 10−16 cm3 molecule−1 s−1 at 25 °C. This result confirms that the reaction is rapid even at room temperature and demonstrates the utility of the flow-tube reactor and FTIR spectrometer for studies of MOCVD chemistry.

Gas Phase Adduct Reactions in MOCVD Growth of GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
A. Thon ◽  
T.F. Kuech
Keyword(s):  
Activation Energy ◽  
Gas Phase ◽  
Decomposition Temperature ◽  
Adduct Formation ◽  
Gas Phase Reactions ◽  
Flow Tube ◽  
Exponential Factor ◽  
First Order ◽  
Mocvd Growth ◽  
Tube Reactor

ABSTRACTGas phase reactions between trimethylgallium (TMG) and ammonia were studied at high temperatures, characteristic to MOCVD of GaN reactors, by means of insitu mass spectroscopy in a flow tube reactor. It is shown, that a very fast adduct formation followed by elimination of methane occurs. The decomposition of TMG and the adduct - derived compounds are both first order and have similar apparent activation energy. The pre-exponential factor of the adduct decomposition is smaller, and hence is responsible for the higher full decomposition temperature of the adduct relative to that of TMG.

scholarly journals The Caltech Photooxidation Flow Tube reactor: design, fluid dynamics and characterization

2017 ◽  
Vol 10 (3) ◽  
pp. 839-867 ◽  
Author(s):  
Yuanlong Huang ◽  
Matthew M. Coggon ◽  
Ran Zhao ◽  
Hanna Lignell ◽  
Michael U. Bauer ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Laminar Flow ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Reactor Design ◽  
Secondary Flows ◽  
Flow Profile ◽  
Flow Tube ◽  
Actual Performance ◽  
Tube Reactor

Abstract. Flow tube reactors are widely employed to study gas-phase atmospheric chemistry and secondary organic aerosol (SOA) formation. The development of a new laminar-flow tube reactor, the Caltech Photooxidation Flow Tube (CPOT), intended for the study of gas-phase atmospheric chemistry and SOA formation, is reported here. The present work addresses the reactor design based on fluid dynamical characterization and the fundamental behavior of vapor molecules and particles in the reactor. The design of the inlet to the reactor, based on computational fluid dynamics (CFD) simulations, comprises a static mixer and a conical diffuser to facilitate development of a characteristic laminar flow profile. To assess the extent to which the actual performance adheres to the theoretical CFD model, residence time distribution (RTD) experiments are reported with vapor molecules (O3) and submicrometer ammonium sulfate particles. As confirmed by the CFD prediction, the presence of a slight deviation from strictly isothermal conditions leads to secondary flows in the reactor that produce deviations from the ideal parabolic laminar flow. The characterization experiments, in conjunction with theory, provide a basis for interpretation of atmospheric chemistry and SOA studies to follow. A 1-D photochemical model within an axially dispersed plug flow reactor (AD-PFR) framework is formulated to evaluate the oxidation level in the reactor. The simulation indicates that the OH concentration is uniform along the reactor, and an OH exposure (OHexp) ranging from ∼ 109 to ∼ 1012 molecules cm−3 s can be achieved from photolysis of H2O2. A method to calculate OHexp with a consideration for the axial dispersion in the present photochemical system is developed.

scholarly journals Changing shapes and implied viscosities of suspended submicron particles

2015 ◽  
Vol 15 (14) ◽  
pp. 7819-7829 ◽  
Author(s):  
Y. Zhang ◽  
M. S. Sanchez ◽  
C. Douet ◽  
Y. Wang ◽  
A. P. Bateman ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Gas Phase ◽  
Shape Change ◽  
Particle Diameter ◽  
Submicron Particles ◽  
Flow Tube ◽  
Shape Factors ◽  
Tube Reactor ◽  
Organic Particles ◽  
Dynamic Shape

Abstract. The change in shape of atmospherically relevant organic particles is used to estimate the viscosity of the particle material without the need for removal from aerosol suspension. The dynamic shape factors χ of particles produced by α-pinene ozonolysis in a flow tube reactor, under conditions of particle coagulation, were measured while altering the relative humidity (RH) downstream of the flow tube. As relative humidity was increased, the results showed that χ could change from 1.27 to 1.02, corresponding to a transition from aspherical to nearly spherical shapes. The shape change could occur at elevated RH because the organic material had decreased viscosity and was therefore able to flow to form spherical shapes, as favored by the minimization of surface area. Numerical modeling was used to estimate the particle viscosity associated with this flow. Based on particle diameter and RH exposure time, the viscosity dropped from 10(8.7±2.0) to 10(7.0±2.0) Pa s (two sigma) for an increase in RH from < 5 to 58 % at 293 K. These results imply that the equilibration of the chemical composition of the particle phase with the gas phase can shift from hours at mid-range RH to days at low RH.

scholarly journals Kinetic and mechanistic study on gas phase reactions of ozone with a series ofcis-3-hexenyl esters

RSC Advances ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 4230-4238 ◽  
Author(s):  
Qilei Zhang ◽  
Xiaoxiao Lin ◽  
Yanbo Gai ◽  
Qiao Ma ◽  
Weixiong Zhao ◽  
...  
Keyword(s):  
Reaction Kinetics ◽  
Gas Phase ◽  
Experimental Methods ◽  
Mechanistic Study ◽  
Gas Phase Reactions ◽  
Flow Tube ◽  
Theoretical Methods ◽  
Tube Reactor ◽  
Kinetics Of

Reaction kinetics of O3with fourcis-3-hexenyl esters were studied using experimental methods in a flow tube reactor as well as using theoretical methods.

Flow Tube Kinetics of Gas-Phase Cvd Reactions

1993 ◽  
Vol 334 ◽  
Author(s):  
Bruce H. Weiller
Keyword(s):  
Ir Spectra ◽  
Gas Phase ◽  
Chemical Reactions ◽  
Rate Constant ◽  
Room Temperature ◽  
Flow Tube ◽  
Tube Reactor ◽  
Ftir Spectrometer ◽  
Kinetics Of ◽  
Phase Chemical

AbstractThis paper explores the use of a flow-tube reactor coupled to an FTIR spectrometer to study gas-phase chemical reactions in CVD systems. We show that our apparatus can generate reliable kinetics data by reproducing the literature rate constant for the reaction between O3 and isobutene. We present data from this apparatus on two technologically important systems: TiN from Ti(NMe2)4 (TDMAT) and NH3 and SiO2 from tetraethoxysilane (TEOS) and O3. The results presented include kinetics data for the reaction of Ti(NMe2)4 with NH3 and ND3 at room temperature and the IR spectra of the products from the reaction of TEOS with O3 at 175°C.

scholarly journals Kinetics of 1- and 2-methylallyl + O2 reaction, investigated by photoionisation using synchrotron radiation

2021 ◽  
Author(s):  
Domenik Schleier ◽  
Engelbert Reusch ◽  
Marius Gerlach ◽  
Tobias Preitschopf ◽  
Deb Pratim Mukhopadhyay ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Reaction Kinetics ◽  
Molecular Oxygen ◽  
Light Source ◽  
Storage Ring ◽  
Vacuum Ultraviolet ◽  
Flow Tube ◽  
Tube Reactor ◽  
Swiss Light Source ◽  
Kinetics Of

The reaction kinetics of the isomers of the methylallyl radical with molecular oxygen has been studied in a flow tube reactor at the vacuum ultraviolet (VUV) beamline of the Swiss Light Source storage ring.

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