Gas-phase Products Research Articles

Study of LPG steam reform using Ni/Mg/Al hydrotalcite-type precursors

Liquefied petroleum gas (LPG) is a mixture of hydrocarbons that has a broad distribution network in several countries. In this context, the objective of this study was to evaluate the steam reforming of LPG using catalysts derived from hydrotalcites. The precursors were characterized by X-ray fluorescence analysis, BET surface area, temperature programmed reduction, thermogravimetric analysis, in situ X-ray diffraction spectroscopy and X-ray absorption spectroscopy. Catalysts were synthesized with 47.5% Ni content without increasing the particle diameter. All catalysts showed the formation of the same gas phase products: H2, CO, CH4 and CO2. Ni1.64Mg1.36Al catalyst showed the highest conversion (about 70%) and lower deactivation by coke deposition after 24 h reaction. The use of higher reaction temperatures (1073 and 1173 K), for steam reforming process, resulted in higher conversions of LPG, increased formation of H2 and lowered the formation of carbon deposits.

Secondary organic aerosol formation from α-methylstyrene atmospheric degradation: Role of NOx level, relative humidity and inorganic seed aerosol

Secondary Organic Aerosol (SOA) formation during the photolysis and OH-photooxidation of α-methylstyrene was investigated using a simulation chamber at atmospheric pressure and room temperature (296 ± 1) K. α-Methylstyrene concentration was followed by gas chromatography with a mass spectrometric detector (GC–MS) and the aerosol production was monitored using a Fast Mobility Particle Sizer (FMPS). The effect of varying α-methylstyrene (0.5 ppm - 2 ppm) and NOx (0.5 ppm - 1.0 ppm) concentrations on SOA formation was explored, as was the effect of the relative humidity (RH) (5–50%) and the presence of inorganic seed particles. Results indicate that SOA yields increase at higher α-methylstyrene concentrations; low NOx and high RH conditions favour more rapid aerosol formation and a higher aerosol yield; SOA formation is independent of seed surface area, within the studied range, for both inorganic seed particles ((NH4)2SO4 and CaCl2). An off-line chemical analysis using a filter/denuder sampling system and GC–MS confirms acetophenone as the main gas phase product in both processes, photolysis and photooxidation. For the first time, SOA composition in α-methylstyrene degradation was analysed, observing acetophenone and acetol as products present in the formed aerosol in presence and absence of NOx.

Reduced Gas-Phase Kinetic Models for Burning of Douglas Fir

New skeletal chemical kinetic models have been obtained by reducing a detailed model for the gas-phase combustion of Douglas Fir pyrolysis products. The skeletal models are intended to reduce the cost of high-resolution wildland fire simulations, without substantially affecting accuracy. The reduction begins from a 137 species, 4533 reaction detailed model for combustion of gas-phase biomass pyrolysis products, and is performed using the directed relation graph with error propagation and sensitivity analysis method, followed by further reaction elimination. The reduction process tracks errors in the ignition delay time and peak temperature for combustion of gas-phase products resulting from the pyrolysis of Douglas Fir. Three skeletal models are produced as a result of this process, corresponding to a larger 71 species, 1179 reaction model with less than 1\% error in ignition delay time compared to the detailed model, an intermediate 54 species, 637 reaction model with 24\% error, and a smaller 54 species, 204 reaction model with 80\% error. Using the skeletal models, peak temperature, volumetric heat release rate, premixed laminar flame speed, and diffusion flame extinction temperatures are compared with the detailed model, revealing an average maximum error in these metrics across all conditions considered of less than 1\% for the larger skeletal model, 10\% for the intermediate model, and 24\% for the smaller model. All three skeletal models are thus sufficiently accurate and computationally efficient for implementation in high-resolution wildland fire simulations, where other model errors and parametric uncertainties are likely to be greater than the errors introduced by the reduced kinetic models presented here.

In Situ Investigation of the Thermal Decomposition of Cl4(CH3CN)W(NiPr) During Simulated Chemical Vapor Deposition

Design of precursors for thin film growth by chemical vapor deposition (CVD) can be informed by knowledge of the precursor decomposition mechanism. However, the vast majority of decomposition characterization is done by techniques that do not capture CVD conditions. This work used a custom CVD reactor with in situ Raman spectroscopy capabilities to investigate the gas phase thermal decomposition of the tungsten imido complex Cl4(CH3CN)WNiPr, a known precursor for the aerosol‐assisted (AA)CVD of tungsten carbonitride thin films. In combination with previous computational and ex situ data, we propose a decomposition mechanism for this precursor under CVD conditions, based on observation of gas phase products of N(imido)‐C bond homolysis and σ‐bond metathesis between the precursor W–Cl bond and H2.

Non-isothermal pyrolysis of grape marc

The non-isothermal decomposition behavior of grape marc (GM) residues from wine industry was investigated by using different thermal analysis techniques, including: (1) thermogravimetric analysis/differential thermogravimetry (TGA-DTG) to study the thermal decomposition kinetics; (2) thermogravimetry (TG-DTG) coupled with Fourier transform infrared spectroscopy (FTIR) to investigate the nature of the gas-phase products released during the pyrolytic breakdown; and (3) simultaneous thermogravimetry/differential scanning calorimetry (TGA–DSC) analysis to obtain information on the heat flows associated with the thermal decomposition of grape marc. Thermogravimetric measurements at five different heating rates (i.e., 2.5, 5, 10, 20, 40 K min−1) were performed for the kinetic computations, which were carried out by adopting a “model-free” approach based on the application of isoconversional methods. In more details, two different integral methods, i.e., the linear Ozawa–Flynn–Wall (OFW) method and the nonlinear Vyazovkin incremental method, were comparatively used in order to obtain a set of kinetic parameters useful for the conceptual design of thermochemical processes involving grape marc. The reliability of the obtained parameters was confirmed by the successful application of the same data to reproduce experimental TG curves not included in the kinetic computations. The effect of the heating rate on the nature of the gas-phase products arising from grape marc decomposition as well as on the heat flows associated with the pyrolytic process was also investigated. Finally, the study was complemented with an extensive investigation on chemical and physical properties of grape marc residues (i.e., ultimate analysis, proximate analysis, calorific values determination, FTIR analysis and cellulose, hemicellulose and lignin content determination), which provides useful input data for modeling grape march conversion processes.

Chemical characterization of nanoparticles and volatiles present in mainstream hookah smoke

Waterpipe smoking is becoming more popular worldwide and there is a pressing need to better characterize the exposure of smokers to chemical compounds present in the mainstream smoke. We report real-time measurements of mainstream smoke for carbon monoxide, volatile organic compounds and nanoparticle size distribution and chemical composition using a custom dilution flow tube. A conventional tobacco mixture, a dark leaf unwashed tobacco and a nicotine-free herbal tobacco were studied. Results show that carbon monoxide is present in the mainstream smoke and originates primarily from the charcoal used to heat the tobacco. Online measurements of volatile organic compounds in mainstream smoke showed an overwhelming contribution from glycerol. Gas phase analysis also showed that very little filtration of the gas phase products is provided by the percolation of mainstream smoke through water. Waterpipe smoking generated high concentrations of 4-100 nm nanoparticles, which were mainly composed of sugar derivatives and especially abundant in the first 10 min of the smoking session. These measured emissions of volatiles and particles are compared with those from a reference cigarette (3R4F) and represent the equivalent of the emission of one or more entire cigarettes for a single puff of hookah smoke. Considerations related to the health impacts of waterpipe smoking are discussed.

Insights into pyrolysis and co-pyrolysis of tobacco stalk and scrap tire: Thermochemical behaviors, kinetics, and evolved gas analysis

In this study, the co-pyrolysis kinetics of tobacco stalk and scrap tire were investigated via thermogravimetric analyzer, while Fourier transform infrared spectrometer was used for the analysis of gas-phase products transition. The pyrolysis of tobacco stalk could be divided into three stages: moisture removal, volatile removal, and slow decomposition of residues. And there was an additional stage of the decomposition of additives for scrap tire. The positive interaction between tobacco stalk and scrap tire occurred when their ratio is 2:8, at which both differential thermal gravity peak temperatures reached a minimum of 320.5 and 390.7 °C in their corresponding regions. The size of the tire particles (from 250 μm to 3 mm) appeared to have little effect on the differential thermal gravity peak temperature of the mixtures. From the results of the kinetic analysis, the synergistic effect at multiple mixing ratios made the energy required for the co-pyrolysis process significantly lower than that of the single pyrolysis. Under the mixed conditions, the formation of organic gases and CO2 was suppressed, the possible mechanism involved was discussed. The results obtained in this study can be used to understand the co-pyrolysis of tobacco stalk/scrap tire and provide a basis for further industrial applications.

To Boldly Look Where No One Has Looked Before: Identifying the Primary Photoproducts of Acetylacetone.

We investigate the gas-phase photochemistry of the enolone tautomer of acetylacetone (pentane-2,4-dione) following S2(ππ*) ← S0 excitation at λ = 266 and 248 nm, using three complementary time-resolved spectroscopic methods. Contrary to earlier reports, which claimed to study one-photon excitation of acetylacetone and found OH and CH3 as the only important gas-phase products, we detect 15 unique primary photoproducts and demonstrate that five of them, including OH and CH3, arise solely by multiphoton excitation. We assign the one-photon products to six photochemical channels and show that the most significant pathway is phototautomerization to the diketone form, which is likely an intermediate in several of the other product channels. Furthermore, we measure the equilibrium constant of the tautomerization of the enolone to diketone on S0 from 320 to 600 K and extract Δ H = 4.1 ± 0.3 kcal·mol-1 and Δ S = 6.8 ± 0.5 cal·mol-1·K-1 using a van't Hoff analysis. We correct the C-OH bond dissociation energy in acetylacetone, previously determined as 90 kcal·mol-1 by theory and experiment, to a new value of 121.7 kcal·mol-1. Our experiments and electronic structure calculations provide evidence that some of the product channels, including phototautomerization, occur on S0, while others likely occur on excited triplet surfaces. Although the large oscillator strength of the S2 ← S0 transition results from the (ππ*) excitation of the C═C-C═O backbone, similar to conjugated polyenes, the participation of triplets in the dissociation pathways of acetylacetone appears to have more in common with ketone photochemistry.

Chemical looping gasification of lignocellulosic biomass with iron-based oxygen carrier: Products distribution and kinetic analysis on gaseous products from cellulose

Product distribution and kinetics analysis of chemical looping gasification (CLG) of cellulose with Fe2O3 were investigated. Based on the thermodynamic simulation, the optimum vaporization temperature of the product H2 was 850 °C. The influence of reaction temperatures and oxygen carrier mixing ratios on product distribution were explored via tube furnace reactor combined with on-line mass spectrometry. When the Fe2O3 mixing ratio was 10%, the gas phase product content was the highest, which may be caused by the incomplete oxidation transition to complete oxidation. Kinetic parameters such as the activation energy of the gas phase product were obtained by an isoconversion method. The CLG process could reduce the activation energy of gaseous products of CO2, CH4, and H2, and the activation energy of CO2 (79.21 kJ/mol) was the highest. Characterization of solid phase products analyzes using SEM. The solid phase product content decreases slightly with increasing temperature because of the higher carbon conversion at elevated temperatures. As the Fe2O3 blending ratio increased, the surface morphology of CE changed from bulk to relatively loose structure, and the particles also aggregate, which may be beneficial to the reaction. This paper provides a reference for clarifying the thermodynamics and kinetics of chemical looping gasification of biomass organic components.

Impact of temperature and pressure on the characteristics of two-phase flow in coal

Temperature and pressure are key factors affecting gas–liquid two-phase flows in porous media. Although evidence supports the effect of temperature on coal-bed methane (CBM) exploration, the fluid production is, at present, not sufficiently understood. By conducting nitrogen and water two-phase displacement experiments under different temperatures and pressures and monitoring the production of fluids at different times, this study obtained quantitative experimental measures for investigating the multi-phase seepage properties. The results indicated that (1) in the temperature range of 30–180 °C, the liquid produced was mainly the free water in the coal, and heating a coal reservoir facilitated the desorption of the water; (2) experimental testing provided a novel characteristic curve for the entire two-phase displacement process, which could be separated into the liquid seepage stage, gas–liquid multi-phase seepage stage, and gas flow stage; (3) increasing the temperature affected the gas and liquid phase velocities, production, and saturations during displacement; (4) with an increase in pressure, the irreducible water increased, whereas the two-phase percolation area decreased. The experimental methodology and obtained results provided evidence that during heat injection enhanced CBM recovery, the gas production rate might increase after breakthrough, with a simultaneous increase in the liquid production. Heating coal seams can thus improve the gas production efficiency, but has disadvantages compared to the initial drainage.

Cu/Bi metal-organic framework-based systems for an enhanced electrochemical transformation of CO2 to alcohols

This work assesses the performance of Cu(II) and Bi(III)-based metal-organic framework (HKUST-1 and CAU-17, respectively) blends into the electroreduction of CO2 to alcohols in a filter-press electrochemical cell. The bimetallic materials are supported onto porous carbon paper to form gas diffusion electrodes with a favorable continuous electrochemical conversion of CO2 to methanol and ethanol, together with formic acid and gas-phase products (i.e. hydrogen, carbon monoxide and ethylene) in a 0.5 M KHCO3 aqueous solution. The maximum reaction rates and faradaic efficiencies for CO2 conversion to methanol and ethanol are rCH3OH=29.7 μmol·m−2·s-1 (FE = 8.6%) and rC2H5OH=48.8 μmol·m−2·s-1 (FE = 28.3%), respectively, at j = 20 mA·cm−2 which enhanced the values obtained at homometallic Cu and Bi-based materials independently. This denotes a synergic effect of Cu and Bi-based MOFs, associated with a favored interplay between the actives sites and reaction intermediates, prompting methanol formation and CC coupling reaction to ethanol. The results also show that reaction selectivity to produce alcohols can be controlled by Cu/Bi loading in the electrode surface and current density applied to the system. A 12% bismuth content seems to be the optimum for the production of alcohols (FEalcohols = 36.9%, Salcohols = 0.32). Regarding the current density, CO2 reduction is more selective to methanol with a j=10 mA·cm−2 (FECH3OH = 18.2%), while at j = 20 mA·cm−2, ethanol becomes the dominant CO2 reduction alcohol (FEC2H5OH = 28.3%). The performance of the Cu/Bi-MOFs remains also pseudo-stable after 5 h of operation denoting the potential of the mixed metal-organic systems for the utilization of CO2.

Heterogeneous photochemistry of dicarboxylic acids on mineral dust

Dicarboxylic acids have low volatilities and hence are present mostly in the particulate phase, including the surface of dust particles. Mineral dust, globally the most emitted aerosol, has photocatalytic properties that can initiate photo-induced heterogeneous chemistry of organic compounds, which is still poorly characterized. We investigated the photochemistry of five dicarboxylic acids (DCA) i.e., succinic (butanedioic) acid, glutaric (pentanedioic) acid, adipic (hexanedioic) acid, pimelic (heptanedioic) acid and suberic (octanedioic) acid on Arizona test dust (ATD) particles upon UV-A light irradiation (0–1.4 mW cm−2). Gas-phase products were monitored by a high-resolution proton-transfer-reaction mass spectrometer (PTR-ToF-MS), and surface sorbed products were extracted and analyzed by ultra-high-performance liquid chromatography coupled to a heated electrospray ionization high-resolution mass spectrometer (UHPLC-HESI-HRMS). Monoacids and aldehydes were the main observed and quantified gaseous products. In contrast, shorter chain DCA and highly oxygenated products were found at the surface of the dust particles. Interestingly, the photochemistry of these DCAs presented an even-odd alternation concerning their heterogeneous reactivity, with odd-numbered carbon diacids being more reactive than their even-numbered homologous ones. We present and discuss a reaction mechanism for the C4–C8 DCA heterogeneous photooxidation catalysed by TiO2/Fe2O3-rich dust particles. Our results suggest that photochemical processing on dust surfaces should be regarded as a possible efficient pathway for altering their surface properties impacting ice nucleation and cloud condensation properties.

Secondary organic aerosol formation from styrene photolysis and photooxidation with hydroxyl radicals

The formation of secondary organic aerosol (SOA) generated by irradiating styrene in the presence and/or absence of OH, NOx, H2O vapour and seed aerosol has been investigated for the first time. Experiments were conducted in a smog chamber at 298 K and atmospheric pressure. Styrene decay was measured by gas chromatography with a mass spectrometric detector (GC-MS), and the temporal evolution of the aerosol was monitored using a fast mobility particle sizer (FMPS). The SOA yield increases as the initial styrene concentration increases, leading to yields ranging from 1.8% to 3.5% for styrene photolysis, and from 2.4% to 5.0% for its photooxidation. In both cases, the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. The particle number concentration, mass and yield decrease in the presence of NOx and seed aerosol but increase at higher relative humidity (RH). The gas phase and SOA composition were analysed offline using a filter/denuder sampling system simultaneously collecting gas- and particle-phase products. Benzaldehyde was confirmed as the main gas-phase product of the reaction. However, although products in the particle phase were detected, they could not be identified. Moreover, the aqueous filter extracts were analysed using UV–Visible spectrophotometry to determine differences in the optical properties of SOA produced in the presence and absence of NOx. The results from this work may be used to discuss the implications of atmospheric SOA generation from styrene degradation.

Hydrogen production from sucrose via aqueous-phase reforming

Commercial sucrose was used to produce hydrogen in a combined approach of hydrogenation and aqueous phase reforming (APR). First a mixture of technical sorbitol/mannitol was produced by hydrogenating an aqueous solution of sucrose in a trickle bed reactor over 5 wt % Ru/C. The produced polyols were treated in a continuous reactor at 498 K and elevated pressure deploying a 2.5 wt % Pt/C catalyst to yield hydrogen. The highest hydrogen selectivity was 62%. No large differences were found when comparing a commercial available sorbitol to the technical sorbitol/mannitol mixture in terms of conversion levels and selectivity to the gas-phase products. This was accompanied by a similar distribution of products retained in the liquid phase. The efficiency of APR when utilizing Pt/C was found to be still insufficient for industrial implementation in terms of hydrogen production. Thus, additional efforts should be made to increase the obtained amounts of hydrogen per mole of converted sugar alcohols.

Effect of Ni incorporation in cobalt oxide lattice on carbon formation during ethanol decomposition reaction

In this work, we report the results of catalytic decomposition of ethanol over a porous mixed metal oxide of Ni-Co (NiCoO2) and analyze the effect of Ni incorporation in Co3O4 lattice on the activity and hydrogen selectivity from ethanol decomposition reaction. In-situ FTIR analysis was conducted between 50 °C to 400 °C for both, Co3O4 and NiCoO2, catalysts to understand the reaction mechanism leading to gas phase product distribution. On cobalt surface the reaction pathway proceeds via the formation of surface ethoxy intermediate that subsequently transforms to aldehyde and acetate intermediates before decomposing to release CO2, H2 and CH4 gases at high temperature. A similar pathway is followed on NiCoO2 surface, leading to aldehyde intermediate, which is relatively unstable and decomposes to release CO along with CH4 and H2 at 400 °C. The NiCoO2 catalyst shows relatively low selectivity for CO2, possibly due to the unstable aldehyde species providing little acetate intermediate that decomposes to release gaseous CO2. The addition of Ni improves the activity for ethanol decomposition by achieving a complete ethanol conversion at 350 °C as compared to 420 °C for cobalt alone. The crystallinity, morphology and particle analysis of the spent catalyst after the reaction was studied using XRD, SEM, and TEM respectively. The XRD shows a phase change of porous NiCoO2 to NiCo alloy, whereas SEM indicates the presence of fibrous structure on the surface with 91.7% of carbon while keeping 1:1 ratio of Ni and Co after the reaction. The detailed analysis of carbon structure using HRTEM-STEM shows the simultaneous growth of carbon nanofibers (CNFs) and multiwalled carbon nanotubes (MWCNTs) that were favored by larger and smaller crystallites respectively. A detailed mechanism of carbon deposition is also proposed.

Ethanol dehydration pathways in H-ZSM-5: Insights from temporal analysis of products

Abstract Ethanol dehydration to ethene via direct and ether mediated paths is mechanistically investigated via transient experiments in a Temporal analysis of products, TAP-3E reactor over a temperature range of 473–573 K in Knudsen regime conditions. Pulse experiments of ethanol over H-ZSM-5 do not yield diethyl ether as a gas phase product. Cofeed experiments with diethyl ether and C-13 labeled ethanol show that ethene formation from diethyl ether is the preferential route. Kinetic parameters from ab initio based microkinetic modelling of ethanol dehydration are compared to the experimental data of the TAP reactor by an in-house developed reactor model code TAPFIT. Rate coefficients in ethene adsorption are in agreement with the ab initio based microkinetic modelling parameters. The experimental data from a diethyl ether feed are compared to the simulated responses from the ab initio based kinetic parameters and further optimized by regression analysis. Reaction path analysis with the optimized kinetic parameters identifies the preference of an ether mediated path under the applied transient experimental conditions.

The Titan haze simulation experiment: Investigating Titan’s low-temperature atmospheric chemistry in a pulsed plasma jet expansion

AbstractThe Titan Haze Simulation (THS) experiment is a unique experimental platform that allows to simulate Titan’s complex atmospheric chemistry at low Titan-like temperature by generating a plasma discharge in the stream of a plasma jet expansion. Both gas and solid phase products are generated and can be analyzed using different in-situ and ex-situ diagnostics. Here, we present an overall description of the work accomplished with the THS in the last 10 years, our current research efforts, and the important implications for the analysis of Cassini’s returned data and preparation for future Titan missions.

DFT Studies on the Stereoselective Three-Component Ugi Reaction

Mechanism and stereochemistry of three component Ugi reaction (3C-Ugi) were studied theoretically based on DFT calculations. Structures of reagents, products, intermediates, and transition states were optimized at M062X/6-31+g(d,p) level of theory in gas phase and in methanol as a common solvent for this reaction. The reaction takes place through several processes, including atom inversion, bond rotation, acid-base, nucleophile-electrophile competitions. These diverse phenomena were studied to provide a clearer picture of the mechanism of this valuable reaction, especially in terms of stereochemistry considerations. According to the results, the enthalpy of the reaction was -45.9 and -41.2 kcal/mol for the dominant product in gas phase and in methanol. The stereoselectivity of the reaction was under the kinetic control of nucleophilic attack of isocyanide to less hindered si-face (E a = 4.1 compared to 7.4 kcal/mol for re-face) of more stable chiral (E)-iminium in methanol. DOI: http://dx.doi.org/10.17807/orbital.v11i1.1214

Formaldehyde Induces Mesenteric Artery Relaxation via a Sensitive Transient Receptor Potential Ankyrin-1 (TRPA1) and Endothelium-Dependent Mechanism: Potential Role in Postprandial Hyperemia.

Formaldehyde (FA), the smallest aldehyde, is generated endogenously, and is widespread in the environment in foods, beverages and as a gas phase product of incomplete combustion. The main metabolite of FA, formate, was increased significantly in murine urine (∼3×) after overnight feeding. Because feeding increases mesenteric blood flow, we explored the direct effects of FA in isolated murine superior mesenteric artery (SMA). Over the concentration range of 30–1,200 μM, FA strongly and reversibly relaxed contractions of SMA induced by three different agonists: phenylephrine (PE), thromboxane A2 analog (U46,619) and high potassium (60K, 60 mM K+). Formate (to 1.5 mM) induced a modest relaxation. FA (>1,500 μM) irreversibly depressed vascular function in SMA indicating vasotoxicity. The sensitivity (EC50) but not the efficacy (% relaxation) of FA-induced relaxations was dependent on blood vessel type (SMA << aorta) and contractile agonist (PE, EC50= 52 ± 14 μM; U46,619, EC50= 514 ± 129 μM; 60K, EC50= 1,093 ± 87 μM). The most sensitive component of FA vasorelaxation was within physiological levels (30–150 μM) and was inhibited significantly by: (1) mechanically impaired endothelium; (2) Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME); (3) transient receptor potential ankyrin-1 (TRPA1) antagonist (A967079); (4) guanylyl cyclase (GC) inhibitor (ODQ); and, (5) K+ channel inhibitor (BaCl2). A similar mechanism of SMA vasorelaxation was stimulated by the TRPA1 agonist cinnamaldehyde. Positive TRPA1 immunofluorescent staining and gene-specific sequence were present in SMA but not in aorta. These data indicate FA, but not formate, robustly relaxes SMA via a sensitive TRPA1- and endothelium-dependent mechanism that is absent in aorta. Thus, as FA levels increase with feeding, FA likely contributes to the physiological reflex of post-prandial hyperemia via SMA vasodilatation.

Kinetics and mechanisms of the gas-phase reactions of OH radicals with three C15 alkanes

The reaction constants and products for the reactions of OH radicals with different C15 alkanes, were determined by using Proton-Transfer-Reaction Mass Spectrum (PTR-MS) in the smog chamber. Rate coefficients (in units of 10−11 cm3 molecule−1 s−1) k1(pentadecane) = 1.72 ± 0.18,k2(2,6,10-trimethyldodecane) = 1.90 ± 0.20, k3(nonylcyclohexane) = 2.09 ± 0.22 were first obtained by the relative rate method using toluene and m-xylene as reference compounds at (298 ± 1)K and atmospheric pressure. In addition, the products of these reactions were measured by PTR-MS simultaneously. The results show that the major gas phase products observed in the OH radicals reactions were aldehydes and ketones for C15 alkanes. The possible reaction mechanisms were speculated and the atmospheric implications were also discussed.