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This study investigated the effect of a mixed obstacle layout on the deflagration mechanism of propane--air premixed gases. Most previous studies focused on a single type of obstacle, changing the shape and number of the obstacles to observe the effect on the flame deflagration characteristics. However, in real explosion accident sites, obstacles are often a mixture of different types. Little literature exists on the deflagration characteristics of hybrid barriers in semiconfined spaces. In this paper, the deflagration characteristics of propane-air premixed gas with a mixed structure of hurdles and square obstacles was studied. First, the effectiveness of numerical simulations was demonstrated by comparing experimental and large eddy simulation (LES) results for the flame dynamics with a single flat plate obstacle. Based on this, the flame behavior for different layouts of square obstacles in a mixed obstacle configuration was further simulated using the large eddy simulation method, focusing on the flame behavior, overpressure characteristics, and flow field structure in the vicinity of the obstacle. The results showed that a mixed obstacle promoted flame evolution more than a single obstacle when the square obstacle was within a critical distance from the ignition source location at the same moment in time. When the flame front crossed the first hurdle-type obstacle, the flame pattern spread in a "cat's paw" pattern to the unburned portion of the tube. In addition, the increased distance of the square obstacle from the ignition source did not allow the peak overpressure and the peak rate of overpressure rise to show a positive feedback mechanism. Finally, the strength of the vorticity in the flow field was positively correlated with the distance of the square obstacle from the ignition source. The results of study provide theoretical for the prevention of explosions. [ABSTRACT FROM AUTHOR]

The present study investigates the chemical kinetics of low-temperature oxidation of propane activated by nanosecond pulsed dielectric barrier discharge in a flow reactor. Molecular beam mass spectrometry with tunable synchrotron vacuum ultraviolet photoionization (SVUV-PIMS) is employed for components identification and quantification. A series of hydrocarbons and oxygenated intermediates are observed, including fuel-specific species reported for the first time in this system like propyl hydroperoxide (C 3 H 7 OOH), acrolein (C 3 H 4 O 2), oxetane (-CH 2 CH 2 CH 2 O-), methyloxirane (-CH(CH 3)CH 2 O-), and propanol (n -/ i -C 3 H 7 OH), which provide original kinetic information in the plasma-assisted low-temperature oxidation of propane. The detection of alkyl hydroperoxide (ROOH) demonstrates the existence of alkyl peroxy (RO 2) formed through oxygen addition to alkyl (R) and the detection of cyclic ethers provides evidence for the presence of hydroperoxyl alkyl (QOOH). A kinetic model incorporating plasma chemistry and combustion chemistry is developed for plasma-assisted oxidation of propane. Path fluxes of fuel consumption and oxygenated intermediates formation are provided based on model analysis. Besides H abstractions by the OH radical, reactions activated by plasma involving electron impact dissociation, O(1D)/Ar* quenching dissociation, and ionization contribute much to fuel consumption. The formed propyl (n -/ i -C 3 H 7) are exclusively consumed through oxygen addition producing propyl peroxy (n -/ i -C 3 H 7 O 2). Propyl peroxy can participate in self- and cross-reactions yielding various oxygenated intermediates such as aldehydes, ketones, alcohols, and propoxy (n -/ i -C 3 H 7 O). Discrepancies between simulations and experiments suggest that further kinetic studies on low-temperature mechanisms, including propyl peroxy related reactions for plasma-assisted combustion modeling, are still desired. [ABSTRACT FROM AUTHOR]

Laminar flame speed (S L) measurements of stoichiometric propane in an oxygen-argon oxidizer were performed in a shock tube at unburned-gas temperatures of 296–1234 K and near-atmospheric pressures. Non-intrusive laser-induced breakdown is used to ignite expanding flames following the reflected-shock passage. Flame propagation is recorded using schlieren imaging in a recently implemented side-wall imaging flame test section (SWIFT). In a refined approach to account for flame distortion and the slight residual motion of the post-reflected-shock gas, an area-averaged formulation of the linear-curvature model (the AA-LC model) is derived for use extrapolating flame data to zero stretch. Measured S L values extracted using the AA-LC model closely agree with previous experimental measurements performed in a conventional kinetics shock tube (CKST) using much smaller flame kernels, providing evidence of the earlier data having been ignition affected. Below the chemistry-affected limit of 1050 K, experimental S L values fall in the range of values simulated with the detailed AramcoMech 3.0 kinetic mechanism and propane-specific mechanisms from NUIG and San Diego but exhibit a stronger temperature dependence than predicted by the mechanisms. Over the wide temperature range of the present data, the ubiquitous power-law form of empirical fit is shown to be inadequate for capturing the S L temperature dependence; a non-Arrhenius form is shown to perform favorably. The uncertainties of flame speed measurements performed in the SWIFT average 3.0% and 4.4% for experiments performed under static and post-reflected-shock conditions, respectively, a reduction from the 5.8% average uncertainty of CKST experiments. This work represents a significant step forward in the development of experimental capabilities for high-temperature flame speed measurements. The present results illustrate the potential value of the shock-tube flame speed method to provide measurements useful for informing kinetic model tuning and validation at conditions for which experimental data were not previously obtainable. [ABSTRACT FROM AUTHOR]

The low and intermediate temperature oxidation of propane has been investigated by using a novel supercritical pressure jet stirred reactor (SP-JSR) with and without 20% CO 2 additions at fuel lean and rich conditions at 10 and 100 atm and 500–1000 K. The mole fractions of C 3 H 8 , O 2 , CO, CO 2 , CH 2 O, C 2 H 4 , CH 3 CHO, and C 3 H 6 were quantified by using a micro-gas chromatograph (µ-GC). The experiment showed that different from that of 10 atm, at 100 atm only a weak negative temperature coefficient (NTC) behavior was observed because of the significant shift of the intermediate temperature HO 2 chemistry to lower temperature. In addition, at 100 atm, existing models in literatures could successfully capture the onset temperatures of the low and intermediate chemistry, while under-predict the fuel oxidation quantitatively and fail to capture the NTC behavior between 650 and 780 K at both fuel lean and rich conditions. Similar discrepancy was observed in studies of n-butane and dimethyl ether (DME) oxidations in literatures, implying that there existed large uncertainties in hierarchy model development of fuels with low temperature chemistries at extremely high pressures. Reaction pathways and sensitivity analyses showed that RO 2 competing reactions through (P1) RO 2 = QOOH, (P2) RO 2 = C 3 H 6 + HO 2 , (P3) RO 2 + CH 2 O/HO 2 = RO 2 H + HCO / O 2 dominated the low and intermediate temperature chemistries, followed by HO 2 / H 2 O 2 chemistry at 100 atm, which differed from the dominant pathway through QOOH consumption reactions at lower pressures. Especially, P3 is a new pathway of RO 2 consumption at high pressures, which was not observed in importance at low pressures. Special attention should be paid to the accurate computations of n-C 3 H 7 O 2 / i-C 3 H 7 O 2 + CH 2 O and n-C 3 H 7 O 2 / i-C 3 H 7 O 2 + in the P3 pathway and n-C 3 H 7 O 2 / i-C 3 H 7 O 2 decomposition reactions in the P2 pathway at high pressures. [ABSTRACT FROM AUTHOR]

The article focuses on a novel electrolyzer developed by researchers from the Illinois Institute of Technology that can convert carbon dioxide (CO2), a major greenhouse gas, into propane, a high-energy-density fuel source. It involves using a new catalytic system with modified surfaces and ionic liquids to efficiently and selectively produce propane from CO2, offering potential for sustainable and economically viable fuel production.

To extend the temperature for propane ignition to a lower region (< 680 K), ozone (O 3) was used as an ignition promoter to investigate the low-temperature chemistry of propane. Ignition delay times for propane containing varying concentrations of O 3 (0, 100, and 1000 ppm) were measured at 25 bar, 654–882 K, and equivalence ratios of 0.5 and 1.0 in a rapid compression machine (RCM). Species profiles during propane ignition with varying O 3 concentrations were recorded using a fast sampling system combined with a gas chromatograph (GC). A kinetic model for propane ignition with O 3 was developed. O 3 shortened ignition delay times of propane significantly, and the NTC behavior was weakened. O atoms released from O 3 reacted with propane through hydrogen abstraction reactions, which led to the fast production of OH radicals. The following oxidation of fuel radicals generated additional OH radicals. Consequently, the inhibition caused by the slow chemistry of hydrogen peroxide (H 2 O 2) in the NTC region was weakened in the presence of O 3. Experimental results with O 3 addition can provide extra constraints on the low-temperature chemistry of propane. Species profiles during propane ignition at 730 K with 1000 ppm O 3 addition showed the production of propanal (C 2 H 5 CHO), acetone (CH 3 COCH 3), and acetaldehyde (CH 3 CHO) was promoted significantly. Model analyses indicated that O 3 shifted the oxidation temperature of propane to a lower region, in which reactions of ROO radicals (NC 3 H 7 O 2 and IC 3 H 7 O 2) tend to generate RO radicals (NC 3 H 7 O and IC 3 H 7 O). The promotion of RO radicals led to the fast production of C 2 H 5 CHO, CH 3 COCH 3 , and CH 3 CHO. The corresponding species profile highlighted the reaction relevant to ROO and RO radicals (NC 3 H 7 O + O 2 = C 2 H 5 CHO + HO 2 and 2 IC 3 H 7 O 2 = 2 IC 3 H 7 O + O 2). Rate constants of these reactions were updated, which can potentially improve the performance of the core mechanism under lower temperatures and provide references for model development of larger hydrocarbons. [ABSTRACT FROM AUTHOR]

The influence of thermochemistry on the reactivity of fuels at low temperatures (600–1000 K) is studied here. Specifically, the effect of different sets of thermochemistry on chemical model predictions is explored, where various sets are calculated at different levels of theory in addition to recently updated group additivity values. Experimentally measured ignition delay times for propane, the pentane isomers and n -heptane are simulated using NUIGMech1.2 and replacing the thermochemistry of the low-temperature species with the calculated values. For propane, three different thermochemistry sets were calculated, namely CCSD(T)-F12/TZ-F12//B2PLYP-D3/TZ//B2PLYP-D3/TZ (QM1), CCSD(T)-F12/TZ-F12//B2PLYP-D3/TZ// ω B97X-D/TZ (QM2) and B2PLYP-D3/TZ/ ω B97X-D/6-31G*// ω B97X-D/6-31G* (QM3). The QM2 results provide parameters to optimize new group additivity (NGA) values which are used to calculate the fourth set of thermochemistry. The model predictions using these four sets are compared to those using NUIGMech1.2 for propane. As the QM1 and QM2 calculations are expensive, the thermochemistry calculated from the QM3 and NGA calculations are used in the pentane isomer and n -heptane models. For all of the models, it is found that the thermochemistry of the species involved in the low-temperature reaction sequence (RH, Ṙ, RO 2 H, RȮ 2 , Q ˙ OOH and Ȯ 2 QOOH species) significantly affect fuel reactivity. The NGA values were developed based on all of these species except Ȯ 2 QOOH radicals. The thermochemistry of Ȯ 2 QOOH species cannot be accurately calculated with the NGA representations due to the importance of non-next-nearest neighbor interactions of –OOH substitution. Further development of the NGA method to capture such interactions is in progress. Overall, the model developed using the NGA thermochemistry shows better agreement with experimental data than the model using thermochemistry from affordable and prominent QM methods, such as QM3. Based on the results presented for propane, the pentane isomers and n -heptane, the thermochemistry calculated using the NGA method can be used to model the oxidation of higher order hydrocarbons at low temperatures. [ABSTRACT FROM AUTHOR]

Within the range of temperatures suitable for CO 2 /CH 4 replacement, propane can form hydrates at widely milder conditions than those required for methane and carbon dioxide hydrates. Recent studies proved that the addition of minor quantities of propane to carbon dioxide strongly enhances replacement process, both in terms of methane recovery and carbon dioxide storage. At the same time, the capture of propane remains limited, even if the thermodynamic conditions are widely suitable for its capture. This study experimentally provided a coherent explanation of such a process. Hydrates were formed and dissociated on a lab-scale reactor with binary mixtures containing 90 vol% of CO 2 /CH 4 and 10 vol% of C 3 H 8 ; the results were compared with the phase equilibrium conditions of the pure species, obtained with the same procedure. The promoting/inhibiting effect of propane on the forming system was quantified and explained in terms of typology of hydrate structure formed and cage occupancy. Based on the results achieved in this study, the replacement mechanism, in presence of propane, was finally characterized and compared with the results obtained when replacement was carried out with the same procedure but with pure carbon dioxide and CO 2 /N 2 mixtures. • Hydrates were formed with binary CH 4 /C 3 H 8 and CO 2 /C 3 H 8 (90/10) vol% gas mixtures. • C 3 H 8 promoted only the capture of CH 4 , producing unit cells with both the species. • Self-preservation effect was observed: melting occurred at + 4.2 – 8.5 °C. • Additions of C 3 H 8 favour both CH 4 recovery (+73.5 %) and CO 2 storage (+78.6 %). • Also the preservation of solid structures was improved: + 74.4 % of new hydrates. [ABSTRACT FROM AUTHOR]

MnO 2 –based catalysts have been widely used in the removal of short–chain volatile organic compounds (VOCs), such as propane. In this study pre–synthesized shape and size selective silver nanoparticles (AgNPs) decorated on shape dependent MnO 2 nanorods (MnO 2 NR) and nanosphere (MnO 2 NS) supports to investigate the effect of MnO 2 morphology on the complete oxidation of propane. The introduction of well–defined AgNPs on MnO 2 is greatly enabled strong metal support interactions (SMSI), reducibility, creation of oxygen vacancies and higher propane adsorption binding energy (by DFT calculation). Various analysis including HRTEM–STEM, XPS, P–XRD, FT–IR, Raman, BET, O 2 –TPD, H 2 –TPR and in–situ DRIFT–IR has been carried out in an effort to establish the mechanistic pathway, and it could be concluded that the 1Ag/MnO 2 NS has substantiated impressive catalytic activity. Further, DFT calculations supported the propane adsorption is more favorable over Ag/MnO 2 than bare MnO 2 support. The propane oxidation performance over Ag/MnO 2 NS system is remarkably higher than bare MnO 2 NR support, probably due to SMSI effect, crystal defects, increased reducibility and oxygen vacancies. Overall, it was concluded that over 1Ag/MnO 2 NS has displayed excellent catalytic activity via Mars–van–Krevelen mechanism. [Display omitted] • Synthesized different MnO 2 nanocrystal shapes & the AgNPs loaded catalysts. • Shape dependent of MnO 2 crystals are correlated with total oxidation of propane. • MnO 2 nanospheres exhibited superior activity than nanorods in propane oxidation owing to its higher O ads , enhanced O v and surface O species. • Ag NPs incorporation over MnO 2 are active than bare support due to enhanced SMSI [ABSTRACT FROM AUTHOR]

Catalytic transformation of light alkanes to aromatic compounds which are feedstocks to petrochemical industries is an important process. Here, a simple method of co-impregnation was employed to synthesize Zn-Cu/ZSM-5 for propane aromatization. Copper of varying loading 1–3 wt% was co-impregnated with zinc to improve zinc stability at the reaction condition. Catalyst physicochemical properties were analyzed using XRD, BET, N 2 -adsorption, FTIR, FTIR-Pyridine, SEM, TEM, H 2 -TPR and XPS. The XRD and FTIR characterization showed that the modified catalysts retained their crystallinity after metal impregnation with the XPS confirming the metal species having oxidation state of 2+. Hydrogen-TPR and XPS change in reduction temperature and binding energy spectra showed stronger intermetallic interaction respectively. Incorporation of Cu with Zn on ZSM-5 reduced Bronsted acidity from the FTIR-Pyridine while N 2 -adsorption isotherms verified the catalyst are microporous. The performance tests for propane aromatization over synthesized catalysts were carried out in a fixed bed reactor using GHSV of 1200 ml/g-h at 540 °C and atmospheric pressure. Co-impregnation of Zn with Cu improved the catalytic activity and sustained aromatic selectivity at an average of 85% for 12 h' time on stream as compared to HZSM-5 (10%) and Zn/ZSM-5 (50%). Product distribution showed reduced light hydrocarbon formation and increased aromatic compounds with high selectivity towards toluene, m and o-xylene among the aromatic product distribution. The best aromatic selectivity product distribution was recorded for 2 wt% Cu with Zn, thus a more stable catalyst developed. XPS and H 2 -TPR analysis showed that the synergistic interaction between the two metals (Cu and Zn) improved the performance of bimetallic Zn-Cu/ZSM-5 catalyst by promoting zinc dispersion and stability during reaction. [ABSTRACT FROM AUTHOR]

The aromatization process of light alkanes is one of the major ways of adding value to the lower saturated hydrocarbons obtained from the refining process and Liquid Petroleum Gas, LPG. The thermodynamic analysis based on Gibbs free energy minimization subject to certain constraints was used to reduce the number of proposed species from thirty-six to thirteen at reaction conditions of 550 °C and 1 bar. The process of minimizing the Gibbs free energy equation was done using MATHCAD and Aspen Plus software in a carbon-free atmosphere. Influence of temperature (400 0C–1000 0C), pressure (1–10 bar), and flow rate (1 M of propane and molar fraction of products) was studied on product distribution in the form of selectivity, yield, and conversion of propane. It was observed that the formation of aromatics was least favored as seen from the yield at various temperatures. The hydrocarbon selectivity and yield were reported on a carbon basis. It was discovered that methane formation was most favored. The temperature which determines the maximum yield of the desired product was determined, yield and selectivity of aromatics were found to be independent of pressure at 1 to 10 bar, and m-xylene was found to be the most favored of the isomers of xylene. This work also presented the computational justification for assuming that isomers of products obtained from propane aromatization are in quasi-equilibrium. [ABSTRACT FROM AUTHOR]

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• A facile synthesis of GaN supported on SiO 2 as an active catalyst for the dehydrogenation of propane to propene with CO 2 was achieved. • It is found that CO 2 can not only enhance the catalytic conversion and selectivity but also influence the deposited carbon formation. • The 5-GaN/Q-3 catalyst shows a propane conversion of 31 % with a selectivity of 93 % for propene at 600 °C with the molar ratio of C 3 H 8 /CO 2 /N 2 = 1/2/7. • The small particle size and well dispersion of GaN and efficient affinity of Q-3 support to CO 2 contribute to the enhanced catalytic performances. GaN/Q-x catalysts (Q-x: SiO 2 support with varying pore size) were successfully prepared through an initial wetness impregnation of gallium nitrate hydrate and melamine, and subsequent a facile solid-phase reaction. The as-synthesized GaN nanoparticles could be well dispersed upon being loaded on Q-x support. It is found that GaN is an active phase for the dehydrogenation of propane to propene in CO 2 atmosphere, wherein CO 2 acts as a soft oxidant for not only promoting the activity and selectivity but also closely influencing the deposited carbon formation. In addition, the GaN/Q-3 catalyst with 5 wt % of GaN displays a propane conversion of 31 % with a selectivity of 93 % for propene at 600 °C in CO 2 atmosphere, which is obviously superior to bulk GaN under the same reaction conditions. This is due to the synergetic interaction of small particle size and well dispersion of GaN and efficient CO 2 adsorption in narrow-pore-rich Q-3 support. So, this finding not only extends the catalytic system of CO 2 oxidation dehydrogenation of propane to propene, but also promotes its progress towards potential industrial exploitation. [ABSTRACT FROM AUTHOR]

An experimental and computational investigation is carried out to characterize the influence of reactants on critical conditions for extinction and for autoignition of propane and n- heptane in nonpremixed counterflow configurations. Propane or vaporized n- heptane mixed with nitrogen is transported in one stream while the other stream is made up of air mixed with nitrogen. Measurements of the oxidizer stream temperature needed for autoignition are made at fixed values of the strain rate, either with the fuel mass fraction varied at a fixed oxygen mass fraction or with the oxygen mass fraction varied at a fixed fuel mass fraction. Extinction strain rates for propane are measured as a function of the oxygen mass fraction with room-temperature feed streams and the fuel mass fraction fixed and for n- heptane as a function of the fuel mass fraction with the oxygen mass fraction and feed-stream temperatures fixed. Predictions of critical conditions for extinction and autoignition are made employing detailed kinetic mechanisms. Predictions of critical conditions for extinction are in reasonable agreement with measurements, but there are significant discrepancies for autoignition. Measurements show that increasing the mass fraction of either fuel or oxygen increases the overall reactivity thereby reducing the autoignition temperature. The kinetic models predict the increase in reactivity of the mixing layer with increasing mass fraction of fuel but predict very little change in reactivity of the mixing layer with increasing mass fraction of oxygen, thus failing to predict the influence of oxygen on autoignition. It is concluded that there may exist kinetic pathways responsible for this disagreement that are yet to be discovered, and paths that fail to explain the results are identified. [ABSTRACT FROM AUTHOR]

• At a fixed T and P , the cloud-points were measured for PVS in several supercritical fluids. • The measured cloud-point pressures for all systems show a LCST-type phase behavior. • The PC-SAFT model is applied to correlate and predict the solubility of PVS. • The strong interactions between PVS and CO 2 leads to higher solubility of PVS in CO 2 /DME mixture. • The weak cross-interactions between CO 2 and co-solvent result in the increase of the solubility of PVS in their mixtures. The cloud-points (CPs) of poly(vinyl stearate) (PVS) in several fluids, such as carbon dioxide (CO 2), propane, butane, propylene, 1-butene, and dimethyl ether (DME), and in their mixtures are reported herein. A high-pressure apparatus with a variable-volume view cell was used to measure the CPs of the PVS mixtures. The measured CP pressures for all the systems exhibited a lower critical solution temperature (LCST) phase behavior. The CPs for ternary systems consisting of CO 2 , DME, propylene, 1-butene, and PVS were distributed over the temperature range of 333−453 K and the pressure range of 35−203 MPa. To understand the effect of interactions between the solvents, co-solvents, and PVS at a molecular level, the perturbed-chain statistical associating fluids theory (PC-SAFT) model was applied to the modeling of these systems, and the predicted results were observed to be consistent with the tendency of experimental data. A theoretical investigation using the PC-SAFT model revealed some important information. The strong interactions between PVS and CO 2 resulted in the high solubility of PVS in the CO 2 /DME mixture, while the weak interactions between CO 2 and the co-solvent (i.e., propylene, 1-butene) increased the solubility of PVS in their mixtures. [ABSTRACT FROM AUTHOR]

• dealumination with nitrate acid leads to significant change in acid-base properties of Beta. • dealumination improves catalytic activity and selectivity in propane dehydrogenation with CO 2. • activity rises with the surface concentration of dispersed and minly redox in origin Cr species. New active and selective catalysts for propane to propene dehydrogenation in assistance of CO 2 (CO 2 -PDH) were prepared by chromium incorporation in siliceous SiBeta. The Cr-containing SiBeta zeolite catalysts were obtained by two-step postsynthesis preparation procedure which consist, in the first step, removal of aluminum from TEABeta zeolite with Si/Al of 17 by treatment with nitric acid solution to obtain an aluminium-free SiBeta support with Si/Al ratio of 1000 and, in the second step, various amounts of Cr were introduced into the siliceous SiBeta zeolite structure by wet impregnation. The well correlation between the number of redox Cr sites and propene yield up to 2 wt % of Cr has been determined. Comparing of catalytic activity of Cr-containing Beta zeolite catalysts with the identical Cr content (2 wt % of Cr) supported on SiBeta and AlBeta revealed that the dealumination has great impact on catalytic properties. Low acidity of SiBeta is suitable for achieving high selectivity to propene (above 80 %) while high acidity of starting AlBeta promotes propane cracking to lighter hydrocarbons. Moreover, in switch operation mode between propane dehydrogenation in presence and absence of CO 2 the formation rate of propene raises in mode with CO 2 only over Cr-containing SiBeta zeolite catalyst, while over Cr-containing AlBeta zeolite catalyst a negative effect on the rate of propene formation was observed. [ABSTRACT FROM AUTHOR]

To evaluate the effects of Type I and Type II photoinitiator systems on curing efficiency, degree of conversion (DC) and chemico-physical properties of resin based materials. A comonomer base containing 50%wt 2.2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (bis-GMA) and 50%wt triethyleneglycol dimethacrylate (TEGDMA) was formulated with either 0.5 or 1mol% of Type II camphoroquinone (CQ), Type I monoacylphosphine oxide (MAPO) or bis-acylphosphine oxide (BAPO) photoinitiators. The Type II system was either a binary (1: 2 CQ:amine) or ternary system (1: 2 CQ:amine + 0.5 mol% DPI). Degree and rate of polymerization was measured by Fourier Transform Infrared Spectroscopy (FTIR). Knoop micro-hardness prior to and following ethanol immersion was assessed. Flexural strength and modulus was measured under three-point bend test. Water sorption and solubility was also evaluated. The photoinitiator absorption spectra and the total absorbed energy per unit volume (E abs) for 0.5mol% photoinitiator in each material was calculated. Despite the reduced total absorbed energy per unit volume for CQ based systems, ternary Type II system significantly improved curing efficiency (P < 0.05) compared to both Type I photoinitiators and degree of conversion compared to MAPO only, whilst exhibiting comparable mechanical and physical properties compared to both Type I based materials at equivalent molar concentrations of photoinitiator (P > 0.05). Ternary Type II systems is an efficient alternative to improve the polymerization of resin materials, promoting similar or even better properties than Type I initiators. DPI can increase the reactivity of CQ systems and promote polymerization rates superior than Type I photoinitiators. • CQ has lower total absorbed energy than MAPO/BAPO with similar DC in ternary system. • The use of DPI promote higher rate of curing despite low molar absorptivity of CQ. • Ternary systems are a viable way to increase the reactivity of dental resins. [ABSTRACT FROM AUTHOR]

• Selective CO2 adsorption over propane was significantly higher compared to toluene in pore sizes of 2–10 nm. • Polar and heavier oil constituents such as toluene diffuse slowly compared to propane. • Increasing pore size reduces the extent of CO2, propane and toluene adsorbed on the silica surfaces. The need to recover our energy resources in a sustainable manner necessitates the development of technological approaches to reduce water use and enhance the use and storage of alternative processing fluids such as CO 2. These societal and technological needs require a fundamental understanding of the pore-scale organization and transport behaviors of confined fluids. Therefore, the aim of this study is to establish a molecular-scale basis for evaluating CO 2 -induced selective adsorption and diffusive transport behavior of hydrocarbon fluids such as propane and toluene in silica nanopores with sizes in the range of 2–10 nm. The studied fluids are composed of CO 2 -propane, CO 2 -propane-toluene, and CO 2 -toluene. CO 2 was found to adsorb preferentially to the silica surfaces by forming hydrogen bonds with the surface hydroxyl (−OH) groups. The selective adsorption of CO 2 over propane was significantly higher compared to toluene at the pore sizes in the range of 2–10 nm. Increasing pore size reduces the extent of CO 2 , propane and toluene adsorbed on the silica surfaces while the corresponding diffusivities increased. Anisotropic diffusivities of the confined molecules were noted. More polar and higher molecular weight constituents of the oil such as toluene diffuse more slowly in confinement. These studies provide detailed scientific insights into the role of CO 2 in enhancing hydrocarbon recovery from unconventional and complex porous environments. These molecular-scale investigations suggest that CO 2 has a higher tendency to displace lighter aliphatic hydrocarbon molecules such as propane away from the surface as opposed to heavier hydrocarbon molecules such as toluene. [ABSTRACT FROM AUTHOR]

Abstract As the key component of the micro power system, the thermal performance of the micro combustor is crucial to the system efficiency. In this paper, the numerical simulation of a micro combustor partially filled with porous medium was conducted. The thermal non-equilibrium model was employed in to investigate the heat transfer between the gas and porous medium. The effect of wall thermal conductivity on thermal performance, chemical reactions in porous medium, and the heat recirculation through porous medium and wall was deeply analyzed. The results show that, in stable operation range, higher wall thermal conductivity or inlet velocity enhances the heat recirculation and reduces the heat loss ratio. The enhancement effect of wall thermal conductivity on reaction rate of R179 "i-C3H7+O2=C3H6+HO2" in porous medium zone is stronger for high inlet velocity and negligible for low inlet velocity. Increasing the wall thermal conductivity can promote the heat recirculation of the micro combustion mainly through gas-to-porous heat convection, while the gas-to-wall heat convection exchange can promote the flame moving upstream, extending the stable operation range of the micro porous combustor. [ABSTRACT FROM AUTHOR]

Abstract The oxidation properties of propane have been investigated by conducting experiments in a laminar flow reactor at a pressure of 100 bar and temperatures of 500–900 K. The onset temperature for reaction increased from 625 K under oxidizing conditions to 725 K under reducing conditions. A chemical kinetic model for high pressure propane oxidation was established, with particular emphasis on the peroxide chemistry. The rate constant for the important abstraction reaction C 3 H 8 + HO 2 was calculated theoretically. Modeling predictions were in satisfactory agreement with the present data as well as shock tube data (6–61 bar) and flame speeds (1–5 bar) from literature. [ABSTRACT FROM AUTHOR]

Abstract Wild poinsettia (Euphorbia heterophylla L.) is a troublesome weed in irrigated summer crops and orchards. Data regarding the optimal herbicide rates for control of this weed, the impact of phenology on control efficacy, and non-chemical control methods for this weed are scarce. The objectives of this study were to: conduct dose-response analyses for trifloxysulfuron at 0–11.2 g a. i. ha−1, glyphosate at 0–2880 g a. i. ha−1, glufosinate-ammonium at 0–1600 g a. i. ha−1 and propane flaming at 0–83 kg ha−1 on wild poinsettia at 4-leaf, 8-leaf and flowering stages; evaluate the long-term control efficacy of these treatments; and link these finding to physiological models. Petri dish and pot experiments examined the germination and phenology of wild poinsettia. The calculated base temperature was 11.4 °C, and physiological time and wild poinsettia fresh weight and leaf number were strongly correlated, with R2 values of 0.96 and 0.97, respectively. Wild poinsettia phenology had a crucial impact on herbicide efficacy. At the 4-leaf stage, all herbicide treatments were effective within the recommended rates with ED 90 values of 3.2, 698 and 206 g a. i. ha−1 for trifloxysulfuron, glyphosate and glufosinate-ammonium, respectively. As the weed matured, it was less susceptible to these treatments. At the 8-leaf stage, only glyphosate and glufosinate-ammonium achieved an ED 90 within their recommended rates. The efficacy of flaming on wild poinsettia control was high at the 4-leaf stage with a control level of 95%, compared to only 31% and 13% at the 8-leaf and flowering stages, respectively. The long-term study revealed that for the 8-leaf application, the high glyphosate rate (1440 g a. i. ha−1) was the only effective treatment, with 95% fresh weight reduction and complete flowering inhibition. This study promotes optimal herbicide applications and demonstrates the potential use of propane flaming for effective wild poinsettia control. The integration of data regarding optimal control with a phenology model offers an efficient tool to improve wild poinsettia management. Highlights • Wild poinsettia phenology stage had a crucial impact on control efficacy. • Propane flaming effectively controlled wild poinsettia at the 3–4 leaf stage. • Only Glyphosate controlled wild poinsettia effectively at later stage, 7–8 leaf. • Control data together with plant growth models offer efficient management tools. [ABSTRACT FROM AUTHOR]

Heading full speed towards the extensive use of H 2 for humanity's energy needs, blue hydrogen production from light hydrocarbons is one of the most promising alternatives. In this study the production of hydrogen through propane steam reforming (PSR) reaction is investigated over Rh nanoparticles dispersed on M x O y -Al 2 O 3 supports of variable M x O y (M: La, Gd) content towards optimizing catalytic performance. The intrinsic activity and the formation of intermediate CH 4 are markedly affected by varying M x O y content passing through a maximum for 10 wt% La 2 O 3 or Gd 2 O 3. Up to 8- and 3.5-fold increases in turnover frequency (TOF) at 400 °C are achieved on these optimally loaded with La 2 O 3 and Gd 2 O 3 catalysts, respectively, accompanied by more than two-fold higher H 2 yields. The reducibility of both rhodium species and the M x O y -Al 2 O 3 support strongly depends on the M x O y content, which then determines the catalytic activity. In situ diffuse reflectance infrared furrier transform spectroscopy (DRIFTS) experiments revealed that CH x species generated by the dissociative adsorption of propane interact either with H 2 yielding CH 4 and/or with hydroxyl groups producing formate species and eventually CO x and H 2 in a manner which depends on M x O y content. However, the latter path is over-favored for samples with 20 wt% M x O y possessing excessive reducibility, and in combination to an over-strengthening of formates adsorption, the conversion rate to CO x and H 2 is strongly inhibited. Scaling-up the fabrication of the most active Rh/10%La 2 O 3 -Al 2 O 3 catalyst at higher application readiness (structured as pellets) and testing under realistic conditions revealed its suitability for propane reformers. [Display omitted] • Catalytic activity of Rh/M x O y -Al 2 O 3 (M: La, Gd) depends on La 2 O 3 or Gd 2 O 3 loading. • The intrinsic reaction rate and H 2 yield are maximized for 10 wt% La 2 O 3 or Gd 2 O 3. • Methane selectivity follows the same trend with propane steam reforming activity. • Optimum catalysts are characterized by moderate reducibility (OSC). • The intermediate produced CH x species play a crucial role on the reaction pathway. [ABSTRACT FROM AUTHOR]

The present work evaluates the action of nitroreductase enzyme immobilized on Tosylactivated magnetic particles (MP-Tosyl) on three disperse dyes which contain nitro and azo groups. The dyes included Disperse Red 73 (DR 73), Disperse Red 78 (DR 78), and Disperse Red 167 (DR 167). The use of a magnet enabled the rapid and easy removal of the immobilized enzyme after biotransformation; this facilitated the identification of the products generated using high-performance liquid chromatography with diode array detector (HPLC-DAD) and mass spectrometry (LC-MS/MS). The main products formed by the in vitro biotransformation were identified as the product of nitro group reduction to the correspondent amine groups, which were denoted as follows: 50% of 2-(2-(4-((2-cyanoethyl)(ethyl)amino)phenyl)hydrazinyl)-5-nitrobenzonitrile, 98% of 3-((4-((4-amino-2-chlorophenyl) diazenyl)phenyl) (ethyl)amino)propanenitrile and 99% of (3-acetamido-4 - ((4-amino-2-chlorophenyl) diazenyl) phenyl) azanediyl) bis (ethane-2,1-diyl) for DR 73, DR 78 and DR 167, respectively. Based on the docking studies, the dyes investigated were found to be biotransformed by nitroreductase enzyme due to their favorable interaction with the active site of the enzyme. Theoretical results show that DR73 dye exhibits a relatively lower rate of degradation; this is attributed to the cyanide substituent which affects the electron density of the azo group. The docking studies also indicate that all the dyes presented significant reactivity towards DNA. However, Disperse Red 73 was found to exhibit a substantially higher reactivity compared to the other dyes; this implies that the dye possesses a relatively higher mutagenic power. The docking results also show that DR 73, DR 78 and DR 167 may be harmful to both humans and the environment, since the mutagenicity of nitro compounds is associated with the products formed during the reduction of nitro groups. These products can interact with biomolecules, including DNA, causing toxic and mutagenic effects. [ABSTRACT FROM AUTHOR]

Abstract Ionic liquid is promising solvent for capturing carbon dioxide (CO 2) from natural gas and separation of olefin/paraffin. In this work, the solubilities of propane (C 3 H 8) and propylene (C 3 H 6) in two ionic liquids 1-hexyl-3-methylimidazolium trifluoromethanesulfonate and 1-hexyl-3-methylimidazolium hexafluorophosphate from 293 K to 343 K at pressures up to 990 kPa were determined using the isochoric saturation method with relative expanded uncertainty of 4%. The experimental results were correlated successfully by the NRTL equation with AAD less than 1.35%. Based on the solubility data in this work and from literature, the Henry's constants and the ideal selectivities of CO 2 /C 3 H 8 and C 3 H 6 /C 3 H 8 in ionic liquids with different molar volumes were compared so as to investigate the effect of the free volume in ionic liquid. The results show that ionic liquid with very large molar volume (large free volume) has good separation performance for CO 2 /C 3 H 8 and C 3 H 6 /C 3 H 8. Highlights • Solubilities of C 3 H 6 and C 3 H 8 in [HMIM][TfO] and [HMIM][PF 6 ] were reported. • Effect of molar volume of IL on solubility and selectivity was studied. • IL with high molar volume has good separation performance for C 3 H 6 /C 3 H 8 and CO 2 /C 3 H 8. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate framework-8 (ZIF-8) enables a kinetic separation of propane and propylene with high efficiency, although the detailed mechanism has not yet been clarified. In the present study, we measure the adsorption rates of propane and propylene in ZIF-8 particles and in-situ X-ray diffraction patterns of ZIF-8 during the gas adsorption process to investigate the effect of the gas pressure and the flexibility of ZIF-8 framework on the diffusion process of propane and propylene in ZIF-8 particles. The adsorption rates of propane and propylene depend on the gas pressure, which would be due to the enlargement of the pore window diameter of the ZIF-8 framework during the gas adsorption as suggested by in-situ XRD measurements. This result is also supported by the calculation of interaction potential profiles between a gas molecule and the ZIF-8 framework, in which an energy barrier at the pore window limits the gas diffusion and the height of the barrier decreases with the increase in the pore window diameter. Furthermore, we find that the adsorption rates of propane and propylene depend on the particle size of ZIF-8, and the selectivity of propylene over propane increases with the particle size. [ABSTRACT FROM AUTHOR]

Microalgae are potential raw materials for biofuel applications. In this work, microbial lipids from Choricystis minor var. minor were extracted with conventional solvents in a Soxhlet apparatus and with compressed fluids with or without the use of a co-solvent (ethanol or hexane). Also, the total achievable yield of fatty acid methyl esters (FAME) was determined in both unextracted microalga, extraction residue and extracted lipids. Ethanol was the best solvent for conventional extraction but hexane was more selective for saponifiable lipids. Compressed propane was better than supercritical carbon dioxide (scCO 2 ) for the extraction of microbial lipids and the use of ethanol as co-solvent improved both extraction rates and yields. The best FAME yield was achieved with scCO 2 plus ethanol at 80 °C and 150 bar (FAME yield of 16.7 g 100 g −1 dry biomass for a mass extraction yield of 31.6%). Hexane was not advantageous as an extraction co-solvent. [ABSTRACT FROM AUTHOR]

Employing NPT molecular dynamics method with consistent valence force field, dissociation processes of propane hydrate with and without methanol additive are simulated at different temperatures and a constant pressure of 50 MPa. We analyze structural snapshots, radial distribution functions, density distributions, angle distributions, change of energies, mean square displacements and diffusion coefficients of two comparative models and find that encaging methanol molecules in the 5 12 cavities could enhance the diffusion behaviors of H 2 O and C 3 H 8 molecules and shorten the decomposition time of propane hydrate. The hydroxyl group of methanol could form hydrogen bonds with the water cage skeleton, and destroy the original hydrogen bond balance of the hydrate simultaneously. Our theoretical results could provide a useful guideline to understand gas hydrate blocking wellbore in the production and transportation of oil and gas. [ABSTRACT FROM AUTHOR]

Theoretical investigation on the stability of water cavities (5 12 , 5 12 6 2 , and 5 12 /5 12 6 2 ) with the incorporation of a series of molecules (CH 4 and C 3 H 8 ) is accomplished. Geometry optimization for the guest molecules, host cages, and their complexes was carried out at B3LYP/6-31+G(d) level, and on the basis of the optimized geometry, single-point energy calculation was performed at M06-2X/6-31++G(d) level to determine the interaction and stability energies. The relative energies of inclusion complexes were investigated to infer structural stability and occupancy of guest molecules. It is compared that the stabilization energy of double-cage encapsulated with CH 4 /C 3 H 8 guest molecule. It is found that fully occupied cages are more stable than partially occupied cages, and the stability of double-cage system in half full state gradually increases. For double-cage, CH 4 @5 12 /C 3 H 8 @5 12 6 2 cage is the most stable structure and the stability for the empty cage could be enhanced when water molecules number is increased. For CH 4 @5 12 /(guest)@5 12 6 2 and 5 12 /(guest)@5 12 6 2 , the interaction between guest molecule and host molecules enhances with the increase of molecular weight of the guest. Meanwhile, the formation of the CH 4 @5 12 cage is more favorable compared to the CH 4 @5 12 6 2 cage. [ABSTRACT FROM AUTHOR]

Emission of greenhouse gases like CO 2 is associated with global warming and ultimately climate change. Oxy-fuel combustion as a carbon capture technique is among the most widely recommended means of tackling CO 2 emission. The use of oxygen/carbon dioxide (O 2 /CO 2 ) mixture as oxidizer in place of air will result in distinct combustion characteristics. Flame blowout is one of such characteristics and is one of the critical operational issues in real combustion systems. In this study, blowout characteristics of air and oxyfuel combustion of propane in a non-premixed, swirl-stabilized combustor were studied. The effect of the equivalence ratio on flame blow off for three oxidizer mixtures (air, oxyfuel I, and oxyfuel II) was first studied. Furthermore, the effect of CO 2 addition and swirl number on oxyfuel flame blowout was also studied. Results show that the propane–air flame transits from: attached flame - lifted flame - no flame regimes with the lifted flame regime occurring at a critical velocity ratio (ratio of fuel velocity to oxidizer velocity). The oxyfuel I and oxyfuel II flames, however, transit directly from attached flame to no flame regime at all firing rates below 4.5MW/m 3 bar. This is due to the fact that oxyfuel I and oxyfuel II could not reach the critical velocity ratio for oxy-flames (Critical velocity ratio observed = 3) before flame blowout. We observed that the critical velocity ratio for propane oxyfuel combustion is six times more than that of propane–air combustion (about 0.5). At 5 MW firing rate, the amount of CO 2 required in the oxidizer at the attached flame - lifted flame transition point decreases from 76% to 74% as the equivalence ratio decreases from 1 to 0.9. The velocity ratios at this operating condition are 3.1 and 3.2, respectively and are more than critical velocity ratio for propane oxyfuel combustion. This indicated that attached flame - lifted flame transition is strongly dependent on the critical velocity ratio irrespective of the equivalence ratio. Further studies showed that oxyfuel flames are more stable at stoichiometry conditions and swirl number of unity. [ABSTRACT FROM AUTHOR]

Lean combustion is a very well-known technology for low carbon and NOx emissions and yet relatively high combustion efficiency. On the other hand, lean combustion flames may blow off in absence of well-designed flame stabilizers. This article presents an experimentally validated modelling approach to study lean premixed flames anchored on a conical bluff body. The structure of an unconfined premixed propane-air flame, stabilized on a conical bluff body, has been computationally examined for conditions of 0.8 to near blow off equivalence ratio (Ø). Reynolds number of about 30,600 is considered based on the conveying pipe’s diameter (10.4cm) and upstream velocity (4.5m/s). the effect of radiation heat losses on flame stability is examined as well as the flow and temperature profiles. Experiments were performed to measure the flame’s spatial temperature profile in order to validate the developed computational models. Our model’s result portrayed a good agreement with experimental measurements. As expected, calculated temperature profiles show that reduction in Ø reduces flame temperature. Results also show that the open-base cone generate a larger recirculation zone – which favours flame stability – than the closed-base cone. Overall, this article highlights the potential of computational models in providing greater insights in the study of flames sustainability nearby the lean combustion limit. [ABSTRACT FROM AUTHOR]

For designing LNG spiral wound heat exchangers (SWHE), the boiling heat transfer and pressure drop characteristics of two-phase hydrocarbon refrigerant flowing downward at shell side should be known. In this study, an explosion-proof experimental rig was established for observing flow patterns and measuring heat transfer coefficients and pressure drops. The test section contained three-layer tube bundles to emulate the actual structure and flow conditions of a SWHE. Propane as one main component of shell-side refrigerant was used as the tested fluid. Through the experimental analysis, the influence laws of vapor quality, mass flux on flow pattern, heat transfer and pressure drop of propane are obtained. As the vapour quality increases, the heat transfer coefficient in the shell side of LNG SWHE initially increases and then decreases, representing a maximum at a vapour quality of 0.8~0.9. The flow patterns in the shell side of LNG SWHE present to be the column falling film flow, droplet falling film flow, shear flow, mist flow and gas flow as the vapour quality increases from 0.2 to 1.0. [ABSTRACT FROM AUTHOR]

With the aim of investigating the solutions of ethane shortage in a commercial ethylene plant, addition of propane as supplementary feedstock and increasing steam to hydrocarbon ratio were proposed as possible strategies. These strategies were proposed to compensate for the ethane shortage in the thermal cracking unit of the commercial plant. Run length, ethylene yield, and propylene yield were considered as the determining factors to appraise the strategies. The major contribution of present work would be the investigation of effect of feed shift on the run length of the steam cracker. Regarding this, five different cases were investigated in real plant condition. To include all the aspects of process, a mathematical model with reasonable assumptions was developed and then validated against the real plant data. Based on the obtained results, increasing propane concentration leads to increase in propylene yield and decrease in ethylene yield. Besides, run length of process was obtained to be longer in the cases with higher propane content in the feed stream. [ABSTRACT FROM AUTHOR]

Al-Ti oxides supported noble-metal catalysts were prepared by combining the mechanical ball-milling method and incipient wetness impregnation method, in which the Al-Ti mixed oxides were etched by various concentrations of phosphoric acid for improving the performance of propane oxidation. Phosphate-modified Pd/Al 2 O 3 -TiO 2 catalyst with Al/P ratios of 3:1 showed high catalytic activity that more than 90 % C 3 H 8 was converted completely at 380 °C and GHSV of 100000 h−1, with 5 vol% H 2 O and 10 vol% CO 2. Characterization results revealed that the mixing of Al 2 O 3 and TiO 2 provided a high specific surface area and excellent pore structure, while the modification of phosphate supplied a stronger interaction between Pd species and supporter which is favorable to their dispersion and enhancing the catalytic stability in the tough conditions. The H 2 -TPR and O 2 -TPD results suggested that marked brilliant redox ability and abundant surface oxygen species of phosphate-modified Pd/Al 2 O 3 -TiO 2 catalysts are beneficial to the activation of O 2 and the increase of catalytic activity. Moreover, the XPS spectra indicated that phosphate induced some electromigration and made the content of Pd0 and Pd2+ in an appropriate ratio which enable the Pd species to display brilliant ability in supplying active oxygen species and breaking the C-H bond, which improved the C 3 H 8 catalytic activity of noble-metal catalyst greatly. [Display omitted] • P-doped Pd/Al 2 O 3 -TiO 2 catalyst was prepared for propane combustion by mechanical ball-milling and impregnation method • Catalyst with Al/P ratio of 3 exhibited 97 % propane conversion in humid condition at 400 °C and GHSV of 100,000 h−1 • The phosphorus doping made Pd particles more evenly-distributed • Enhanced activity of p-doped catalyst attributed to the brilliant redox ability and abundant surface oxygen species • The catalyst with Pd0/Pd2+ ratio of 3:2 was more beneficial for propane combustion [ABSTRACT FROM AUTHOR]