Hydrocarbons In Gas Phase Research Articles

Graphene oxide aerogels for adsorptive separation of aromatic hydrocarbons and cycloalkanes

Efficient separation of benzene and cyclohexane has critical importance for production of commodity chemicals, and is one of the most challenging separations in the industry. Physisorption by recyclable, porous solids has a significant potential in substituting energy-intensive azeotropic or extractive distillation methods. Reduced graphene oxide aerogels (rGOAs) are emerging materials holding great promise for connecting unique properties of 2D graphene with ordinary 3D materials. The benzene/cyclohexane separation on rGOAs self-assembled by the chemical reduction with l-ascorbic acid, sodium bisulphite and (for the first time) sodium dithionite was studied by dynamic gas adsorption methods, and the adsorption performance was analysed in relation to aerogels physicochemical properties. The aerogel reduced with sodium dithionite (rGOA_DTN) had the highest reduction degree and specific surface area (461.2 m2g-1), with the highest contribution of mesopores. It was also the sample with the uppermost uptake of benzene and cyclohexane. The binary component adsorption on rGOA_DTN resulted in the selectivity of the adsorption of benzene over cyclohexane of 2.1. Adsorption-desorption studies demonstrated the excellent thermal stability of the adsorbent in the long-run operation. Because the adsorption capacity did not correlate with the mesopores but with macropores surface area, the selectivity of the adsorption was attributed to the different physicochemical structure of aerogels surface. The benzene molecule interacted strongly by specific C-H···π interactions, while the cyclohexane molecule was excluded from the surface of aerogels because of its shape/size. Results demonstrated that rGOAs can be a versatile and flexible platform for adsorptive gas-phase hydrocarbons separation.

17O Labeling Reveals Paired Active Sites in Zeolite Catalysts

Current needs for extending zeolite catalysts beyond traditional gas-phase hydrocarbon chemistry demand detailed characterization of active site structures, distributions, and hydrothermal impacts. A broad suite of homonuclear and heteronuclear NMR correlation experiments on dehydrated H-ZSM-5 catalysts with isotopically enriched 17O frameworks reveals that at least two types of paired active sites exist, the amount of which depends on the population of fully framework-coordinated tetrahedral Al (Al(IV)-1) and partially framework-coordinated tetrahedral Al (Al(IV)-2) sites, both of which can be denoted as (SiO)4-n-Al(OH)n. The relative amounts of Al(IV)-1 and Al(IV)-2 sites, and subsequent pairing, cannot be inferred from the catalyst Si/Al ratio, but depend on synthetic and postsynthetic modifications. Correlation experiments demonstrate that, on average, acidic hydroxyl groups from Al(IV)-1/Al(IV)-2 pairs are closer to one another than those from Al(IV)-1/Al(IV)-1 pairs, as supported by computational DFT calculations. Through-bond and through-space polarization transfer experiments exploiting 17O nuclei reveal a number of different acidic hydroxyl groups in varying Si/Al catalysts, the relative amounts of which change following postsynthetic modifications. Using room-temperature isotopic exchange methods, it was determined that 17O was homogeneously incorporated into the zeolite framework, while 17O → 27Al polarization transfer experiments demonstrated that 17O incorporation does not occur for extra-framework AlnOm species. Data from samples exposed to controlled hydrolysis indicates that nearest neighbor Al pairs in the framework are more susceptible to hydrolytic attack. The data reported here suggest that Al(IV)-1/Al(IV)-2 paired sites are synergistic sites leading to increased reactivity in both low- and high-temperature reactions. No evidence was found for paired framework/nonframework sites.

CO2-mediated thermal treatment of disposable plastic food containers

In accordance with global economic prosperity, the frequencies of food delivery and takeout orders have been increasing. The pandemic life, specifically arising from COVID-19, rapidly expanded the food delivery service. Thus, the massive generation of disposable plastic food containers has become significant environmental problems. Establishing a sustainable disposal platform for plastic packaging waste (PPW) of food delivery containers has intrigued particular interest. To comprise this grand challenge, a reliable thermal disposable platform has been suggested in this study. From the pyrolysis process, a heterogeneous plastic mixture of PPW was converted into syngas and value-added hydrocarbons (HCs). PPW collected from five different restaurants consisted of polypropylene (36.9 wt%), polyethylene (10.5 wt%), polyethylene terephthalate (18.1 wt%), polystyrene (13.5 wt%), polyvinyl chloride (4.2 wt%), and other composites (16.8 wt%). Due to these compositional complexities, pyrolysis of PPW led to formations of a variety of benzene derivatives and aliphatic HCs. Adapting multi-stage pyrolysis, the different chemicals were converted into industrial chemicals (benzene, toluene, styrene, etc.). To selectively convert HCs into syngas (H2 and CO), catalytic pyrolysis was adapted using supported Ni catalyst (5 wt% Ni/SiO2). Over Ni catalyst, H2 was produced as a main product due to CH bond scission of HCs. When CO2 was used as a co-reactant, HCs were further transformed to H2 and CO through the chemical reactions of CO2 with gas phase HCs. CO2-assisted catalytic pyrolysis also retarded catalyst deactivation inhibiting coke deposition on Ni catalyst.

Anthropogenic Volatile Organic Compound (AVOC) Autoxidation as a Source of Highly Oxygenated Organic Molecules (HOM).

Gas-phase hydrocarbon autoxidation is a rapid pathway for the production of in situ aerosol precursor compounds. It is a highway to molecular growth and lowering of vapor pressure, and it produces hydrogen-bonding functional groups that allow a molecule to bind into a substrate. It is the crucial process in the formation and growth of atmospheric secondary organic aerosol (SOA). Recently, the rapid gas-phase autoxidation of several volatile organic compounds (VOC) has been shown to yield highly oxygenated organic molecules (HOM). Most of the details on HOM formation have been obtained from biogenic monoterpenes and their surrogates, with cyclic structures and double bonds both found to strongly facilitate HOM formation, especially in ozonolysis reactions. Similar structural features in common aromatic compounds have been observed to facilitate high HOM formation yields, despite the lack of appreciable O3 reaction rates. Similarly, the recently observed autoxidation and subsequent HOM formation in the oxidation of saturated hydrocarbons cannot be initiated by O3 and require different mechanistic steps for initiating and propagating the autoxidation sequence. This Perspective reflects on these recent findings in the context of the direct aerosol precursor formation in urban atmospheres.

The miscible behaviors and mechanism of CO2/CH4/C3H8/N2 and crude oil in nanoslits: A molecular dynamics simulation study

Using molecular dynamics simulations, we have investigated the miscible behaviors of different gas (CO2, N2, CH4, C3H8) and different crude oils in nanoslits at 413 K and 60 MPa. In this study, the effect of gas type, the polarity and the chain length of crude oil on the miscible process of gas and crude oil is explored. The simulation results show that CO2, CH4, C3H8 and N2 are more miscible with apolar crude oil than polar crude oil due to the stronger interaction between polar crude oil and silica surface. It is worth noting that the solubility of polar crude oil in CO2 phase is higher than that in hydrocarbon gas phase and N2 phase. In addition, it is found that the chain length of crude oil could affect the dissolution of crude oil in hydrocarbon gas and N2. In contrast, it has a negligible effect on the miscibility of crude oil and CO2. The simulation results could provide valuable guidance for enhancing oil recovery in the development of deep and ultra-deep reservoirs.

Comparison of ozone measurement methods in biomass burning smoke: an evaluation under field and laboratory conditions.

In recent years wildland fires in the United States have had significant impacts on local and regional air quality and negative human health outcomes. Although the primary health concerns from wildland fires come from fine particulate matter (PM2.5), large increases in ozone (O3) have been observed downwind of wildland fire plumes (DeBell et al., 2004; Bytnerowicz et al., 2010; Preisler et al., 2010; Jaffe et al., 2012; Bytnerowicz et al., 2013; Jaffe et al., 2013; Lu et al., 2016; Lindaas et al., 2017; McClure and Jaffe, 2018; Liu et al., 2018; Baylon et al., 2018; Buysse et al., 2019). Conditions generated in and around wildland fire plumes, including the presence of interfering chemical species, can make the accurate measurement of O3 concentrations using the ultraviolet (UV) photometric method challenging if not impossible. UV photometric method instruments are prone to interferences by volatile organic compounds (VOCs) that are present at high concentrations in wildland fire smoke. Four different O3 measurement methodologies were deployed in a mobile sampling platform downwind of active prescribed grassland fire lines in Kansas and Oregon and during controlled chamber burns at the United States Forest Service, Rocky Mountain Research Station Fire Sciences Laboratory in Missoula, Montana. We demonstrate that the Federal Reference Method (FRM) nitric oxide (NO) chemiluminescence monitors and Federal Equivalent Method (FEM) gas-phase (NO) chemical scrubber UV photometric O3 monitors are relatively interference-free, even in near-field combustion plumes. In contrast, FEM UV photometric O3 monitors using solid-phase catalytic scrubbers show positive artifacts that are positively correlated with carbon monoxide (CO) and total gas-phase hydrocarbon (THC), two indicator species of biomass burning. Of the two catalytic scrubber UV photometric methods evaluated, the instruments that included a Nafion® tube dryer in the sample introduction system had artifacts an order of magnitude smaller than the instrument with no humidity correction. We hypothesize that Nafion®-permeating VOCs (such as aromatic hydrocarbons) could be a significant source of interference for catalytic scrubber UV photometric O3 monitors and that the inclusion of a Nafion® tube dryer assists with the mitigation of these interferences. The chemiluminescence FRM method is highly recommended for accurate measurements of O3 in wildland fire plume studies and at regulatory ambient monitoring sites frequently impacted by wildland fire smoke.

Removal and transformation of unconventional air pollutants in flue gas in the cement kiln-end facilities

To understand the removal and transformation behaviors of unconventional air pollutants (polycyclic aromatic hydrocarbons, heavy metals and carbonyl compounds) in the flue gas in cement kiln-end facilities, including SP boiler, a slide stream SCR-DeNOx system, raw mill and baghouse filter, the gas and particle matter samples at the inlets and outlets of each kiln-end installation were collected and the contents of the unconventional air pollutants were measured. The results showed that the concentrations of the polycyclic aromatic hydrocarbons (PAHs) in particulate and gas-phase, heavy metals in the particulate matter were 17.5 μg m−3, 48.7 μg m−3 and 3113.1 μg m−3 at the inlet of the SP boiler, and decreased to 0.6 μg m−3, 17.7 μg m−3 and 39.7 μg m−3, respectively, while the concentrations of carbonyl compounds in gas-phase increased from 1988.5 μg m−3 to 2844.5 μg m−3 after flue gas successively passed through the kiln-end facilities. The cooling of flue gas and the precipitation of coarse particulate matter in the SP boiler resulted in a significant decrease of PAHs concentration in both gas-phase and particulate-phase, as well as the heavy metal concentration in the particulate-phase, while the SP boiler hardly had any influence on the removal and transformation of carbonyl compounds. Grinding and heat exchange in the raw mill accelerated the volatilization of compounds with the low boiling point in the raw meal, which increased concentrations of gas-phase PAHs and carbonyl compounds. When flue gas passed through the baghouse filter, almost all particulate-phase PAHs, heavy metals and most of the gas-phase PAHs, were removed while the carbonyl compounds concentration maintained unchanged. Furthermore, some portion of gas-phase PAHs and carbonyl compounds were removed by the SCR-DeNOx system.

Shipboard Acoustic Observations of Flow Rate From a Seafloor‐Sourced Oil Spill

AbstractIn 2004 a debris flow generated by Hurricane Ivan toppled an oil production platform in Mississippi Canyon lease block 20 (MC20). Between 2004 and the installation of a containment system in 2019 MC20 became an in situ laboratory for a wide range of hydrocarbon in the sea‐related research, including different methods of assessing the volumetric flow rate of hydrocarbons spanning different temporal scales. In 2017 a shipboard acoustic Doppler current profiler (ADCP) and high‐frequency (90 to 154 kHz) broadband echosounder were deployed to assess the flow rate of liquid and gas phase hydrocarbons. Measurements of horizontal currents were combined with acoustic mapping to determine the rise velocity of the seep as it moved downstream. Models of the rise velocity for fluid particles were used to predict the size of oil droplets and gas bubbles in the seep. The amplitude and shape of the broadband acoustic backscatter were then used to differentiate between, and determine the flow rate of, hydrocarbons. Oil flow rate in the seep was estimated to be 56 to 86 barrels/day (mean barrels/day) while the flow rate of gaseous hydrocarbons was estimated to be 98 to 359 m3/day (mean m3/day).

Evaluation of the Tenti S6 model for hydrocarbon fuels at elevated temperatures using filtered Rayleigh scattering measurements.

This Letter targets the assessment of the well-known Tenti S6 model for predicting the Rayleigh-Brillouin scattering (RBS) spectra of select gas-phase hydrocarbon fuels (CH4, C2H2, C2H4, C3H8, and C4H10) over a temperature range of 300 to 700 K. The Tenti S6 model is evaluated by comparing filtered Rayleigh scattering (FRS) measurements to synthetic FRS signals generated from the combination of the Tenti S6 output and an accurate iodine absorption filter model. The experimental and synthetic FRS results agree very well (<3% difference) over the full temperature range for CH4, C2H2, and C2H4, indicating accurate calculation of the RBS spectra. For C3H8 and C4H10, there are some large differences between the experimental and synthetic FRS results which cannot be resolved through tuning of bulk viscosity, internal heat capacity, or inclusion of vibrational degrees of freedom, suggesting the need for detailed measurements of the Rayleigh-Brillouin spectra.

Impact of in-situ gas liberation for enhanced oil recovery and CO2 storage in liquid-rich shale reservoirs

ABSTRACT Carbon dioxide injection in shale reservoirs can be beneficial for enhanced oil recovery and CO2 storage scenarios. CO2 mass transfer can be influenced strongly by the in-situ liberation of light oil components from live oil forming a distinct gas phase. This mechanism has been overlooked in the past for studying CO2 and oil interactions in tight formations. In this work, a series of analytical solutions and numerical simulations were developed to identify the effect on EOR by CO2 due to the liberation of a light hydrocarbon gas phase from live oil in shales. The analytical model demonstrated faster diffusion of CO2 in the two-phase system due to the presence of this gas phase. Using numerical approaches, laboratory-scale simulations indicated that in-situ gas formation can increase oil recovery by 35%. At the field-scale, an additional oil recovery of 9.8% could be attained. Also, the CO2 storage capacity of shale formations could be significantly enhanced due to capillary trapping of CO2 in the liberated gas. The results of this study could potentially be used to improve evaluations of the potential of CO2 EOR in shale reservoirs.

Eco-Friendly Usage of Aviation Gasoline; Benzene and Toluene Concentration Effect

Abstract The Clapeyron equation defines the relationship between temperature and vapor pressure. If the absolute temperature graph is plotted, a straight line is obtained on the y-axis of the graph against the logarithm of the vapor pressure. Each liquid and gas-phase hydrocarbon can be determined in the graph. While plotting this graph of the benzene-toluene mixture that affects fuel performance, the pressure values ​​of the mixture are determined by the separation of the mixture from the air. Usually, when drawing this graph, critical temperatures and pressures are essential and more pronounced in hydrocarbons where aromatic structures are rich. To determine the vapor pressure, the atmospheric pressure, such as the boiling range of the sample, must be determined depending on the liquid boiling temperature of a reflux condenser. This means that the temperature of the fuel at a vapor pressure exceeding 760 mmHg in the same graph, apart from this temperature, is estimated. The slopes of other petroleum products can determine the slope of the obtained temperature distribution. If the boiling point cannot be determined experimentally, the temperature value in the Engler distillation curve corresponding to 20 % distillation can be taken. A proposed solution of the McCabe-Thiele method as an alternative to other methods for the distillation properties of the benzene and toluene mixture that affect the fuel efficiency is described in this study.

Sources apportionment and carcinogenic risk of polycyclic aromatic hydrocarbons in gas phase of urban Shanghai: Based on high volume solid phase extraction (Hi-volume SPE).

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants, posing potentially serious threats to human health. This study analyzed compositional characteristics, sources, and carcinogenic risks of PAHs in the atmospheric gas phase at an urban site in Shanghai, East China. Seventy-four gas phase samples were collected during the warm months of May-October 2018 using a high-volume solid phase extraction (Hi-volume SPE) technique. The total concentration of sixteen priority PAHs (ΣPAHs) was in the range of 5.54-182.05ngm-3 (average 34.47ngm-3) and the total of seven carcinogenic PAHs (ΣCPAHs) was in range of 0.03-1.49ngm-3 (average 0.48ngm-3), accounting for 1.47% of ΣPAHs and indicating low carcinogenic potential. Redundancy analyses indicated positive correlations between ΣPAHs and air quality, and ΣCPAHs and average high temperature, and a negative correlation between ΣPAHs and wind speed. Four possible sources, namely petroleum and petrogenic sources, traffic emissions, coal combustion, and mixed gasoline and coal combustion sources, were identified by positive matrix factorization (PMF), accounting for 62.84%, 19.31%, 10.15%, and 7.69% of ΣPAHs, respectively. The overall lifetime lung cancer risk (LLCR) through inhalation of PAHs was estimated to be at a low risk level of 1.61×10-5. The LLCR based on PMF apportionment decreased in the order of mixed gasoline and coal combustion sources (47.07%)>traffic emissions (35.10%)>petroleum and petrogenic sources (11.06%)>coal combustion (6.74%). This study demonstrates the effectiveness of Hi-volume SPE in collecting and analyzing atmospheric gas phase PAHs.

Analysis of the Concentration of Gas-Phase and Solid-Phase Polyaromatic Hydrocarbons in Industrial Emissions from Aluminum Production

Aluminum production is one source of atmospheric polycyclic aromatic hydrocarbons (PAHs), of which benzo[a]pyrene is the best-studied representative. Other high-priority PAHs are attracting increasing attention for differentiation of PAH emissions and sources. Monitoring of these compounds is difficult because PAHs are present in both the solid-phase and gas-phase emissions (with the solid phase containing condensed PAHs); the gas-phase concentration of these substances depends on the manufacturing process temperature and the temperature of the environment. Atmospheric PAH emissions primarily originate from the pot-room ventilation skylights and gas-treatment-unit smokestacks. Low-molecularweight compounds dominate the gas emissions from the pot-room ventilation skylights and posttreatment emissions, while higher molecular weight compounds dominate the gas/dust/air mixture received for treatment. The gas/dust/air mixture received from the pot rooms for treatment by the gas treatment unit and discharged into the atmosphere through the smokestacks shifts the distribution of PAHs present in the atmosphere in favor of light, volatile compounds. The PAHs are close to uniformly distributed between the gas and solid phases of the gas/dust/air mixture emitted from the pot-room skylights. Over 70 wt.% of the PAHs in the emissions downstream of the gas treatment unit are in the gas phase, while the majority of the PAHs entering the gas treatment unit are in the solid phase. The resulting PAH distribution data for the gas/air mixture must be taken into account when developing the techniques for sampling the industrial emissions from the skylights and the atmospheric emissions downstream of the gas treatment unit during aluminum production.

Postsynthetic Modification of ZIF-8 Membranes via Membrane Surface Ligand Exchange for Light Hydrocarbon Gas Separation Enhancement.

The ability to tailor the pore structure of metal-organic framework (MOF) membranes enables synthesis of new or modified MOF membranes with enhanced separation characteristics. This work employs a modified version of solvent-assisted ligand exchange, termed membrane surface ligand exchange (MSLE), to modify the pore structure of zeolitic imidazolate framework-8 (ZIF-8) membranes. This paper is the first to perform a time-based, ex situ characterization and gas permeation study of ZIF-8 MSLE with 5,6-DBIM (DBIM, dimethylbenzimidazole) to effectively narrow the ZIF-8 pores, enhance light hydrocarbon gas-phase separations, and give insight into the exchange mechanism with respect to time and temperature. The results show that relatively fast exchange kinetics occur mainly at the outer surface of the ZIF-8 membrane during the initial 30 min of exchange and enables significant (40-70%) increases in propylene/propane selectivity with minimal (10-20%) propylene permeance losses for the modified ZIF-8 membranes. We postulate as the reaction time proceeds, the ligand-exchange rate slows as the DBIM linker diffuses into the ZIF-8 membrane beyond the external surface, exchanges with the original linker, disrupts the original framework's crystallinity, and then increases long-range order/crystallinity as the reaction proceeds. The H2/C2 separation factor increases with increased 5,6-DBIM content in the ZIF-8 framework which is facilitated by increased MSLE time and reaction temperature.

Prediction of methanol loss by hydrocarbon gas phase in hydrate inhibition unit by back propagation neural networks

Gas hydrate often occurs in natural gas pipelines and process equipment at high pressure and low temperature. Methanol as a hydrate inhibitor injects to the potential hydrate systems and then recovers from the gas phase and re-injects to the system. Since methanol loss imposes an extra cost on the gas processing plants, designing a process for its reduction is necessary. In this study, an accurate back propagation neural network (BPNN) is designed for the prediction of methanol loss by the gas phase as a function of temperature, pressure, and methanol composition in the aqueous phase. Different configurations of BPNN were trained, tested, and a configuration providing the smallest absolute average relative deviation (AARD%) was chosen as an optimum structure. Finally, comparisons made among the accuracy of the developed BPNN model, process simulators, and probabilistic neural network (PNN). Results confirm that the designed BPNN model is more accurate than the other considered predictive tools. The BPNN provided an AARD=5.75% for prediction of experimental data, while Aspen-HYSYS, Aspen-Plus, and PNN presented an AARD% of 9.71, 12.57, and 13.27, respectively.

Hydrothermal upgrading of heavy oil in the presence of water at sub-critical, near-critical and supercritical conditions

In this study, the hydrothermal upgrading (HTU) of high sulfur-content heavy oil was investigated at sub-critical (Sub-CW), near-critical (NCW) and supercritical water (SCW) conditions. Products obtained after HTU, including gases, liquid, and coke (if formed), were analyzed to understand the upgrading performance at different conditions. At Sub-CW (200, 250, and 300 °C), 250 °C is the optimum temperature where a viscosity reduction from 2073 to 1758 mPa s was achieved with a slight removal of sulfur (mainly sulfur) and the generation of a small amount of light and non-condensable hydrocarbons in gas phase (C1–C4, isoalkanes and alkenes, H2S, CO2 and H2, etc.). At NCW (350 °C) and SCW (400 °C), heavy oil was upgraded into light oil with a significant removal of heteroatoms, an increase of saturates content, a reduction of aromatics, resins and asphaltenes contents, and a high yield of light gaseous hydrocarbons (mainly methane). Simultaneously, each SARA fraction was also greatly ameliorated: the content of light alkanes with low molecular weight in saturates was increased, diaromatics content in aromatics was increased with a reduction of polyaromatics content, aromatics-type carbon atoms in resins was increased with a decrease in aliphatic hydrocarbons. Moreover, MALDI-TOF measurements of asphaltenes show that the molecular weights of asphaltenes were reduced. All these results indicated that HTU at Sub-CW can be used for heavy oil pre-treatment (in-situ or ex-situ upgrading) considering its main effect of viscosity reduction with a small removal of heteroatoms, while HTU at NCW and SWC has a great potential in in-situ and ex-situ upgrading and oil refining as it can convert heavy oil into light oil.

Nanoscale confined multicomponent hydrocarbon thermodynamic phase behavior and multiphase transport ability in nanoporous material

Abstracts Multicomponent hydrocarbon transport in nanoporous material is influenced by the nanoscale thermodynamic phase behavior, heterogeneous pore structure and hydrocarbon-molecules-pore wall interaction. Little is known about the multicomponent hydrocarbon transport mechanisms in realistic 3D nanoporous material. We here propose a nanoscale pore network multiphase multicomponent hydrocarbon transport model to study multicomponent hydrocarbon thermodynamic phase behavior and transport ability across a wide range of pressure and temperature. A novel thermodynamic phase equilibrium calculation model is proposed considering the multiphase interface curvature change and phase saturation in irregular pore cross-sections. The multicomponent gas slippage effect and liquid phase boundary slip length variation with pore size are incorporated into the mode. Study results find that for low liquid phase saturations with high capillary pressure, the liquid mainly resides in the pore corners, and for high saturations with low capillary pressure it forms liquid bridges. The formation of liquid bridges, and thus ultimately decrease in gas phase transport ability, depends on the interplay of multicomponent hydrocarbon composition, pressure, temperature, the local pore shape, pore size as well as three-phase contact angle. The multicomponent hydrocarbon gas phase permeability through 3D pore network is influenced by the composition and temperature when the pore pressure is less than 15 MPa, while multicomponent gas phase permeability is unaffected by the pore pressure and temperature change at relatively high pressure (>15 MPa). The liquid phase permeability increases with the increase of dense phase composition and the decrease of temperature at pressure less than 15 MPa. This work provides a new multicomponent hydrocarbon thermodynamic phase equilibrium model and a novel work flow of assessing multicomponent hydrocarbon multiphase transport ability in heterogeneous irregular nanoporous material.

Hydrogenation and hydrodesulfurization in gas phase of light hydrocarbons from hydrocracking, desulfurization and delayed coking. I catalyst deactivation

Hydrogenation and hydrodesulfurization reactions of hydrocarbons in gas phase was studied in a fluidized-bed reactor using PdNiW/TiO2-Al2O3 and NiMo/TiO2Al2O3 catalysts. Catalyst deactivation was performed at different temperatures and using hydrocracking product with and without delayed coking naphtha feeds. Delta of species and catalysts activities were measured, and catalyst characterized by physical and chemical properties, metals and carbon dispersion, acid sites content and benzene diffusivity in hydrogen. Coke was extracted by CS2 and analyzed by MAS 13C NMR. There are different rates of sites deactivation when processing gas feed with or without olefinic hydrocarbons on these catalysts. Olefins and diolefins produce carbon deposits fast; carbon distribution across the radius of particle depend on temperature and amounts of aromatics in the feed. Reaction and deactivation rates constants were obtained for each of catalysts. The simulation model used only predicted well products properties without olefins and diolefins. The mechanism of reaction are discusses based on solid characterizations.

Low-pressure gas chromatography with chemical ionization mass spectrometry for quantification of multifunctional organic compounds in the atmosphere

Abstract. Oxygenated volatile organic compounds (OVOCs) are formed during the oxidation of gas-phase hydrocarbons in the atmosphere. However, analytical challenges have hampered ambient measurements for many of these species, leaving unanswered questions regarding their atmospheric fate. We present the development of an in situ gas chromatography (GC) technique that, when combined with the sensitive and specific detection of chemical ionization mass spectrometry (CIMS), is capable of the isomer-resolved detection of a wide range of OVOCs. The instrument addresses many of the issues typically associated with chromatographic separation of such compounds (e.g., analyte degradation). The performance of the instrumentation is assessed through data obtained in the laboratory and during two field studies. We show that this instrument is able to successfully measure otherwise difficult-to-quantify compounds (e.g., organic hydroperoxides and organic nitrates) and observe the diurnal variations in a number of their isomers.

Sources of Particulate Matter Emissions Variability From a Gasoline Direct Injection Engine

Particulate matter (PM) emissions from gasoline direct injection (GDI) engines are a concern due to the health effects associated with ultrafine PM. This experimental study investigated sources of PM emissions measurement variability observed in previous tests and also examined the effect of ethanol content in gasoline on PM emissions. Some engine operating parameters (fuel and oil temperature, positive crankcase ventilation filtration) and test conditions (dilution air conditions) were studied and controlled but could not account for the level of measurement variability observed. Fourier transform infrared spectrometry (FTIR) measurements of gas phase hydrocarbon emissions provided evidence that changes in fuel composition were responsible for the variability. Exhaust emissions of toluene and ethanol were correlated positively with PM emissions, while emissions of isobutylene correlated negatively. Exhaust emissions of toluene and isobutylene were interpreted as markers of gasoline aromatic content and gasoline volatility, respectively. Tests conducted with gasoline containing added toluene (10% v/v) supported this hypothesis and led to the overall conclusion that the PM emissions variability observed can be attributed to changes in the composition of the pump gasoline being used. Tests conducted with gasoline containing added ethanol (10% and 30% v/v) found that increasing ethanol fuel content increased PM emissions at the steady-state operating condition utilized.