Linear Paraffins Research Articles

Benzene reduction in gasoline range streams by adsorption processes using a PVDC–PVC carbon molecular sieve

A PVDC–PVC derived carbon molecular sieve (CMS-IMP12) was used for adsorbing the benzene contained in a sample of reforming gasoline from a Mexican Refinery. First an olefin free benzene enriched fraction (H-BHC) was obtained by distillation-hydrogenation. The adsorption process may be carried out in one and two-steps. In the one-step procedure, benzene was adsorbed along other hydrocarbons in a 28mL/100gads yield. The benzene enriched fraction (BEF) contained linear and branched paraffins and cycloparaffins (56%) and benzene (43%). In the two-step procedure, linear paraffins (PEF) were selectively separated from the H-BHC by 5A molecular sieve (7mL/100gads). Then, the paraffins free fraction (PFF, 30mL/100gads) was submitted to a further separation using the CMS material. The resulted adsorbed product (BEF, 42mL/100gads) was formed mainly by iso- and cycloparaffins (50%) and benzene (48%). The octane number of the one-step was lower than the two-steps benzene free fraction (BFF) (67 and 76, respectively) due to the presence of paraffins in the first one. In any case, the benzene may be recuperated from the BEF by distillation and the octane number of the recovered PEF and BFF may be improved by any commercial isomerization process.

Colonization and Biodegradation of Photo-Oxidized Low-Density Polyethylene (LDPE) by New Strains of Aspergillus sp. and Lysinibacillus sp.

ABSTRACTThe primary objective of this study was the isolation of low-density polyethylene (LDPE)-degrading microorganisms. Soil samples were obtained from an aged municipal landfill in Tehran, Iran, and enrichment culture procedures were performed using LDPE films and powder. Screening steps were conducted using linear paraffin, liquid ethylene oligomer, and LDPE powder as the sole source of carbon. Two landfill-source isolates, identified as Lysinibacillus xylanilyticus XDB9 (T) strain S7-10F and Aspergillus niger strain F1-16S, were selected as super strains. Photo-oxidation (25 days under ultraviolet [UV] irradiation) was used as a pretreatment of the LDPE samples without pro-oxidant additives. The PE biodegradation process was performed for 56 days in a liquid mineral medium using UV-irradiated pure LDPE films without pro-oxidant additives in the presence of the bacterial isolate, the fungal isolate, and the mixture of the two isolates. The process was monitored by measuring the fungal biomass, the bacterial growth, and the pH of the medium. During the process, the fungal biomass and the bacterial growth increased, and the pH of the medium decreased, which suggests the utilization of the preoxidized PE by the selected isolates as the sole source of carbon. Carbonyl and double bond indices exhibited the highest amount of decrement and increment, respectively, in the presence of the fungal isolate, and the lowest indices were obtained from the treatment of a mixture of both fungal and bacterial isolates. Fourier transform infrared (FT-IR), x-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses showed that the selected isolates modified and colonized preoxidized pure LDPE films without pro-oxidant additives.

Hydrothermal Deoxygenation of Triglycerides over Pd/C aided by In Situ Hydrogen Production from Glycerol Reforming

A one-pot catalytic hydrolysis-deoxygenation reaction for the conversion of unsaturated triglycerides and free fatty acids to linear paraffins and olefins is reported. The hydrothermal deoxygenation reactions are performed in hot compressed water at 250 °C over a Pd/C catalyst in the absence of external H2 . We show that aqueous-phase reforming (APR) of glycerol and subsequent water-gas-shift reaction result in the in situ formation of H2 . While this has a significant positive effect on the deoxygenation activity, the product selectivity towards high-value, long-chain olefins remains high.

Application of quasi-equilibrated thermodesorption of linear and di-branched paraffin molecules for detailed porosity characterization of the mono-layered zeolite MCM-56, in comparison with MCM-22 and ZSM-5.

The pore characteristics of zeolite samples including two kinds of ZSM-5 crystals as a base case and the unique mono-layered MCM-56 in different structural forms have been studied by the new method QE-TPDA (quasi-equilibrated temperature-programmed desorption and adsorption) in comparison with the standard nitrogen adsorption. Both approaches produce consistent results in terms of micro- and meso-porous features as well as quantitative pore volume values. The benefits of QE-TPDA include fast data acquisition (hours) and small sample size (milligrams). It is very flexible in using various hydrocarbons as probe molecules, which may reveal additional details associated with pores, their internal environment and dimensions/shape of the sorbate molecules. Hence, QE-TPDA is a valuable complementary tool for porosity characterization of the ever increasing diversity of porous materials and their pore structures. This was demonstrated by the results for the desorption of nonane and 2,2-dimethyloctane (DMO). The latter showed an additional maximum in the intermediate temperature range (between 'micro-' and 'mesopore' regions) which could be attributed to adsorption in the subsurface micropores (i.e. the pore mouths) where DMO could be partially adsorbed with t-butyl groups remaining on the outside. This was also reflected in the discrepancy between apparent volumes of micro- and mesopores calculated from the nonane and DMO experiments. Pillared MCM-56 revealed visibly enhanced subsurface micropore adsorption compared to the parent (mono-layer MWW) and MCM-22 (multi-layered MWW) consistent with the expected increase in the content of external 12 ring surface cups.

A study of Fe(III)TPPCl encapsulated in zeolite NaY and Fe(III)NaY in the oxidation of n-octane, cyclohexane, 1-octene and 4-octene

The Fe(III)TPPCl (Fe(III)tetraphenylporphyrin chloride) complex was immobilized using the encapsulation method in order to entrap the complex inside the faujasite NaY zeolite to obtain FeTPP–NaY. This was achieved by adding the FeTPP as a template during the synthesis of NaY. The ICP results show that a 0.3 wt% loading of Fe was achieved and the XRD confirmed the faujasite Y structure. Further to this, a Fe–NaY zeolite was synthesized for the purpose of comparing it with FeTPP–NaY. The synthesized FeTPP–NaY and Fe–NaY were tested in the oxidation of n-octane, 1-octene, 4-octene and cyclohexane to oxygenates in the liquid phase using acetonitrile as a solvent, H2O2 and tert-butyl hydroperoxide in water as oxidants at 80 °C. Conversions of n-octane of 1.8 and 2.9 % and selectivities to terminal products of 13 and 8.8 % were achieved using FeTPP–NaY and Fe–NaY, respectively. Conversions of 1.4 and 1.8 % were achieved for 1-octene and 4-octene, respectively. A higher conversion of 18 % for cyclohexane was observed. These results show that cyclohexane is most reactive under these conditions and that the NaY matrix is not suitable for selective linear paraffin oxidation. Furthermore, leaching of Fe from the Fe–NaY was observed, even though the faujasite NaY structure was maintained as confirmed by XRD, while for FeTPP–NaY, the leaching of Fe was not observed.

Octane enhancement by the selective separation of branched and linear paraffins in naphthas using a PVDC-PVC carbon molecular sieve

Silicalite-1 samples and PVDC based Carbon Molecular Sieve (CMS-IMP12) material were compared in the separation of linear and multi-branched paraffins present in a real feedstock by fixed bed adsorption experiments. The CMS-IMP12 material was obtained from the pyrolysis of a poly-(vinylidene choride-co-vinyl chloride) (PVDC-PVC) polymer commercially known as Saran™. Material balances of the breakthrough experiments showed higher adsorption capacities for the CMS-IMP12 (5.4–8.8g/100g-adsorbent) than for silicalite-1 (1.2–3.4g/100g-adsorbent) at the temperature range studied (175–325°C). Additionally, the octane number increment for the CMS-IMP12 was at least 4 units higher for the same amount of recovered non-adsorbed fraction (1.5g/100g-adsorbent). In order to simplify the description of the hydrocarbon mixture, the alkanes were classified according to their degree of branching as: linear, monomethyl, dimethyl (non-gem), dimethyl (gem) and trimethyl alkanes. Similarly, cycloalkanes as: non-branched (cyclopentane and cyclohexane), monomethyl, dimethyl (non-gem), dimethyl (gem) and trimethyl cycloalkanes, where gem refers to the relationship between two methyl groups that are attached to the same carbon atom. The CMS-IMP12 was able to separate gem-dimethylalkanes, gem-dimethylcycloalkanes and trimethylalkanes, while silicalite-1 was less selective.

Inspection and Determination of a Vehicle Arson Case According to Diesel Fuel and Gasoline

From a vehicle arson case, it briefly introduced the basic situation and investigation of fire, particularly discussed the inspection process of samples, even compared some main components with suspected criminal tool at length. The results showed that it was deteced gasoline composition in extracted material evidence of vehicle combustion residue,but the vehicle were diesel fuel car. Then it analysed in detail the difference of gasoline, diesel oil and mixture of gasoline and diesel oil on composition. Their composition characteristics were both have aromatic hydrocarbons, such as dimethylbenzene series, trimethylbenzene series, tetramethylbenzeneseries, methylindane, naphthalene series, But alkane composition and distribution was not the same, as diesel contained C11-C20 linear paraffin and branched paraffin which obviously normal distribution, even the content of alkanes was significantly higher than aromatic hydrocarbon.but gasoline was different , not only the alkane characteristics is not obvious, but also aromatic hydrocarbons high content; While the content of alkanes and aromatic hydrocarbon were similar in mixture. By comparing the plastic drum left on scene with inspected samples, their gasoline characteristics were the same, Thus we can determine the plastic drum was criminal tool of setting fire, it could provide powerful evidence to solve cases for fire investigators and criminal investigators.

Identification and quantification of (alkyl)benzenes in hydrocracked products of light cycle oil by GC–AED

GC–AED analysis was applied for detailed identification and quantification of (alkyl)benzenes in the hydrocracked light cycle oil (LCO) over alumina coated USY zeolite (ACZ) supported NiMoS catalyst. The specified AED peaks of C and H in the separated hydrocarbon species provide their H/C ratios. Several standard chemicals such as linear paraffins, (alkyl)cycloalkanes, (alkyl)benzenes, (alkyl)naphthalenes, and 3-ring compounds were examined to calibrate the area of their relative carbon and hydrogen peaks in the chromatogram to their atomic ratios. According to the combination of H/C ratio and carbon number, the series of (alkyl)benzenes from the hydrocracked products of LCO detected in the chromatograms were successfully identified and quantified. The methodology of GC–AED application developed in this study can be applied to identify the hydrocracked product from light, middle, as well as heavy oils.

Chevron's gas conversion catalysis-hybrid catalysts for wax-free Fischer–Tropsch synthesis

Syngas conversion offers a potential alternative to flaring or reinjection for monetization of associated gas. However, certain deployment applications disfavor the hydroprocessing infrastructure required to upgrade the linear paraffin wax product for blending or transport. We describe here Chevron's Gas Conversion Catalysis (GCC™) technology, a commercially viable hybrid syngas conversion catalyst comprising both a Fischer–Tropsch active metal and a zeolite component that truncates the Anderson–Schultz–Flory (ASF) distribution to provide a liquid hydrocarbon product without the need for downstream hydroprocessing at high pressure. This paper will focus on catalyst and process development including a discussion on the effect of zeolite properties on product specifications.

Optimized Utilization of Naphtha: Liquid Adsorption Separation of Linear Paraffins in Naphtha with n-Pentane as the Desorbent

The liquid adsorption separation of n-paraffins in naphtha with n-pentane as the desorbent was investigated and the subsequent recycle of n-pentane was simulated by Aspen Plus. The optimal operation conditions for both the adsorption and desorption processes were studied. Then n-pentane was recycled by simulated rectification; the raffinate bottom oil rich in non-normal hydrocarbons and the desorption bottom oil rich in normal hydrocarbons were obtained. As compared to the naphtha before the adsorption-recycle process, the ethylene yield would rise by 15.76% by employing the desorption bottom oil as the feed for the ethylene cracking process and the octane number of the raffinate bottom oil would rise by 20 units.

Isomerization of n-hexane on Pt–Ni catalysts supported on nanocrystalline H-BEA zeolite

The zeolite Beta used in this work consists of nanosized crystallites (20–30nm) aggregates, determined by HRTEM analysis. The influence of the zeolite structure and crystallite size on the desorption rates of linear paraffins was determined by ZLC chromatography. Desorption from Beta zeolite was faster than from USY zeolite. IR acidity analysis by adsorption and desorption of pyridine showed that Beta zeolite has a smaller number of Brønsted acid sites than USY zeolite, but that they are a little stronger. Pt–Ni/H-BEA catalysts showed higher activity than Pt–Ni/H-USY ones. This behavior can be attributed to the very small crystallites of Beta zeolite, which enable faster diffusion of the reactant and products molecules. Among bimetallic catalysts, the highest activity was observed with that containing 60% Pt. This result is very interesting in view of the cost reduction, relative to 100% Pt catalyst.

Octane Upgrading of C5/C6 Light Naphtha by Layered Pressure Swing Adsorption

The performance of a layered pressure swing adsorption (PSA) process for the separation of high research octane number (HRON) paraffins from a C5/C6 light naphtha fraction is simulated with a detailed, adiabatic single column PSA model. A zeolite 5A layer is used for selective adsorption of the low RON linear paraffins, while a zeolite beta-layer is used to separate the intermediate RON 3MP from the HRON fraction. The effects of various independent process variables (zeolite 5A to zeolite beta ratio, purge to feed ratio, cycle time, operating temperature, and depressurization mode) on the key dependent process variables (product RON, HRON species recovery, HRON purity, and adsorbent productivity) are evaluated. It is demonstrated that an optimal zeolite 5A to zeolite beta ratio can improve the product average RON up to 1.0 point as compared to existing processes using zeolite 5A only. Moreover, process simulations demonstrated that increasing the operating temperature from 523 to 543 K results in an octan...

Competitive Adsorption of C20−C36 Linear Paraffins on the Amorphous Microporous Silica−Alumina ERS-8 in Vapor Phase and Liquid Phase

Adsorption of C20−C36 linear paraffins on the amorphous microporous silica−alumina ERS-8 was studied at vapor phase and liquid phase conditions. Henry adsorption constants and low coverage adsorption enthalpies were determined using the pulse chromatographic method at temperatures between 90 and 370 °C in gas phase. The low coverage adsorption enthalpy increases linearly with carbon number with 5.5 kJ/mol per additional methyl group. Competitive adsorption in liquid and dense vapor phase conditions was studied by performing column breakthrough experiments with various binary C20−C36 n-paraffin mixtures diluted in short chain length alkane solvents or undiluted as bulk mixture, at temperatures ranging from 25 to 300 °C and pressures from 3 to 110 bar. Both the adsorption capacity and the selectivity are strongly temperature and pressure dependent. At low temperature and high pressure, all n-paraffins are adsorbed equally and no separation is possible. With increasing temperature and decreasing pressure, the density of the bulk phase decreases, and a transition from a pure liquid paraffin stream to a dense vapor stream occurs. In such conditions, longer n-paraffins are adsorbed preferentially compared to the shorter n-paraffins. The selectivity increases with increasing difference in chain length between the adsorbing n-paraffins.

Expanded fluid-based viscosity correlation for hydrocarbons using an equation of state

A previously developed correlation of viscosity to measured density was modified for use with densities calculated using a cubic equation of state. The correlation has two adjustable parameters per component, a compressed state density, ρ s o and an empirical parameter, c 2, that scales the viscosity response to fluid expansion. The inputs to the correlation are the fluid density and molecular weight, pressure, and the low pressure gas viscosity. In this study, gas or liquid densities were determined using the Advanced Peng–Robinson equation of state and therefore the critical properties, acentric factor, and volume translation factor of the component are required as input instead of the density. The modified correlation fit experimental viscosities for 39 pure hydrocarbons including n-alkanes, branched alkanes, alkenes, cyclics, and aromatics comprising 8337 experimental liquid and fluid phase data points, over a broad range of temperatures and pressures with an average absolute error under 6.0%. The method was also tested against experimental binary viscosity data that include linear paraffins, branched paraffins, naphthenes and aromatics with an average absolute error under 6% at 25 °C without the use of a binary interaction parameter for the compressed state density. If adjustable interaction parameters are used then the average absolute error is under 1%. The method was also applied to as well as a sweet natural gas mixture with an average absolute error under 2% and to mixtures of heavy oil and n-decane as well as Cold Lake bitumen and toluene with average absolute errors under 16%. The method was implemented in a commercial simulator proving to be simple, consistent across the critical point, and very fast from a computational point of view, running approximately twice as fast as a corresponding states method.

Diffusion of linear paraffins in silicalite studied by the ZLC method in the presence of CO2

The diffusion behavior of C4–C10n-alkanes in silicalite-1 has been investigated by using the Zero Length Column method. The diffusivities derived from measurements at different purge rates with different purge gases confirming intracrystalline diffusion control. Data are compared with results reported in the literature for MFI zeolites. The diffusivities were found to be consistent and agree well with data previous obtained by ZLC. However, these data showed a remarkable disagreement with other reported techniques (PFG-NMR, QENS and Permeation). The eventual influence of carbon dioxide (CO2) adsorption on diffusion properties of n-alkanes in silicalite was also investigated. For this purpose, a series of experiments was performed involving hydrocarbons mixed with CO2. Data were obtained at 303 K and flow rates between 20 and 80 mL/min. The presence of CO2 does not seem to influence the intracrystalline transport rate of the investigated light hydrocarbons (n-C4 and n-C6). On the other hand, the situation for n-C8 and n-C10 is more complex. The diffusivity values are higher compared to the previously reported values.

The crucial role of chemical detail for slip-boundary conditions: molecular dynamics simulations of linear oligomers between sliding aluminum surfaces

We study the slip-boundary conditions of short, linear paraffins and olefins confined between two sliding aluminum surfaces with molecular dynamics. Our simulations are based on a recently developed force field for the interaction between organic molecules and bulk aluminum. The lubricant molecules investigated all consist of six monomers but differ in the existence or location of merely one double bond. It turns out that this small change in the chemistry of the lubricant molecules can alter slip lengths quite dramatically, and is not strongly correlated with surface energies and bulk viscosity of the lubricant. For example, α and β-hexene have similar large negative slip length of Λ ≈ −8 Å, even though α-hexene adheres twice as strongly to the surface as β-hexene. Eliminating the double bond in β-hexene reduces the surface energy by another factor of two, but increases Λ from −8 to 120 Å. These results and those of additional simulations based on unrealistic, albeit occasionally used model potentials, make us conclude that surface energies and/or molecular geometries alone are not reliable indicators for slip-boundary conditions. Instead, it is necessary to consider the full chemical detail. As a more encouraging result, we find that the bulk viscosity appears to describe the dissipation within the sheared fluid close to the wall quite well, despite significant ordering near the boundaries. Moreover, all our systems show a relatively weak dependence of the slip length on the normal pressure.

Characterization of two diesel fuel degrading microbial consortia enriched from a non acclimated, complex source of microorganisms

BackgroundThe bioremediation of soils impacted by diesel fuels is very often limited by the lack of indigenous microflora with the required broad substrate specificity. In such cases, the soil inoculation with cultures with the desired catabolic capabilities (bioaugmentation) is an essential option. The use of consortia of microorganisms obtained from rich sources of microbes (e.g., sludges, composts, manure) via enrichment (i.e., serial growth transfers) on the polluting hydrocarbons would provide bioremediation enhancements more robust and reproducible than those achieved with specialized pure cultures or tailored combinations (co-cultures) of them, together with none or minor risks of soil loading with unrelated or pathogenic allocthonous microorganisms.ResultsIn this work, two microbial consortia, i.e., ENZ-G1 and ENZ-G2, were enriched from ENZYVEBA (a complex commercial source of microorganisms) on Diesel (G1) and HiQ Diesel (G2), respectively, and characterized in terms of microbial composition and hydrocarbon biodegradation capability and specificity.ENZ-G1 and ENZ-G2 exhibited a comparable and remarkable biodegradation capability and specificity towards n-C10 to n-C24 linear paraffins by removing about 90% of 1 g l-1 of diesel fuel applied after 10 days of aerobic shaken flask batch culture incubation at 30°C. Cultivation dependent and independent approaches evidenced that both consortia consist of bacteria belonging to the genera Chryseobacterium, Acinetobacter, Psudomonas, Stenotrophomonas, Alcaligenes and Gordonia along with the fungus Trametes gibbosa. However, only the fungus was found to grow and remarkably biodegrade G1 and G2 hydrocarbons under the same conditions. The biodegradation activity and specificity and the microbial composition of ENZ-G1 and ENZ-G2 did not significantly change after cryopreservation and storage at -20°C for several months.ConclusionsENZ-G1 and ENZ-G2 are very similar highly enriched consortia of bacteria and a fungus capable of extensively degrading a broad range of the hydrocarbons mainly composing diesel fuels. Given their remarkable biodegradation potential, stability and resistance to cryopreservation, both consortia appear very interesting candidates for bioaugmentation operations on Diesel fuel impacted soils and sites.

Design Challenges for Wax in a Fast-Track Deepwater Project

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper OTC 19160, "Design Challenges Due to Wax on a Fast- Track Deepwater Project," by Amir Alwazzan, SPE, and Mark Utgard, SPE, AMEC Paragon, and Dalmo Barros, Petrobras America, prepared for the 2008 Offshore Technology Conference, Houston, 5-8 May. The paper has not been peer reviewed. Flow-assurance threats, such as hydrates, waxes, and asphaltenes, can be identified and controlled if oil and gas production and transportation systems are designed accordingly and proper operating procedures are implemented. Therefore, prevention of wax deposition is key for good subsea deepwater-system design. Wax deposition can form a blockage and impede flow, causing weeks of lost production and operating difficulties. Introduction Flow assurance in subsea systems is an issue in the design of deepwater-field developments. Flow-assurance efforts focus on preventing solid deposits from blocking or restricting the rate of flow from the well. The principal solids of concern are wax and hydrates. For a given reservoir fluid, these solids precipitate at certain combinations of pressure and temperature. Precipitated solids often are carried downstream, slurried in the fluid, but precipitated solids also can deposit on the walls of the production equipment, which ultimately causes high pressure drops, plugging, and flow stoppage. Control of this deposition by prevention and/or mitigation is the essence of flow assurance. Wax in hydrocarbons is primarily paraffin, which is a white, odorless, tasteless, chemically inert compound composed of saturated hydrocarbons. The linear paraffins are easily measured by high-temperature gas chromatograph (HTGC). Two critical issues require special attention: gel formation (precipitation) and deposition. A hydrocarbon gel forms when wax precipitates from the oil and forms a 3D structure spanning the pipe. This condition does not occur while the fluid is flowing because the intermolecular structure is destroyed by shear forces as soon it is able to form. However, when the fluid stops flowing, wax particles will interact and join together, potentially forming a network resulting in a gel structure if enough wax comes out of solution. In a pipe, wax deposition results in flow restrictions. Slow buildup of wax layers in pipelines and flowlines is caused by the solidification of the paraffinic fractions on the cold inner surface of the pipe wall. Wax deposition is expected during steady-state operation in the flowline where the production-stream temperature is below the wax-appearance temperature (WAT). The deposition rate depends mainly on the fluid characteristics, flowing and pipe-wall temperatures, heat flux through the pipeline, and the shear stress at the wall.

Reactor Modeling of a Slurry Bubble Column for Fischer-Tropsch Synthesis

A complete reactor model was developed for a slurry bubble column for Fischer-Tropsch synthesis in taking into account the hydrodynamic features of the three phases (syngas, liquid mixture of linear paraffins and solid catalyst) and including thermodynamics and heat and mass transfers. This model was also able to take into account the gas recycle after condensation steps. Simulation results were compared with industrial data coming from a demonstration unit.

Fuel constituent effects on fuel reforming properties for fuel cell applications

The effect of different types of compounds commonly found in diesel fuel (e.g., paraffins, naphthenes, and aromatics), as well as their chemical structure (e.g., branched versus linear paraffins) on fuel reforming has been investigated. Diesel reforming is very complicated because diesel is a complex mixture of hundreds of compounds with greatly different reactivities. The syngas production rates at the same conditions were observed in this order: paraffins > naphthenes ≫ aromatics. Additionally, the type of reforming performed (OSR, CPOX, or SR) as well as the process parameters (space velocity and reaction temperature) significantly affected the syngas production rates as well as carbon formation. The reactivity of one fuel component can affect the conversion pattern of others, e.g., overall yields from the reforming of a fuel mixture are not additive of yields from individual fuel components, rather the more reactive component is consumed first. Furthermore, the type of substituent in aromatics and naphthenes, the carbon chain length in n-paraffins, branching in paraffins, and degree of aromatic saturation affect the overall hydrocarbon conversion, syngas selectivity, and carbon formation. The presence of sulfur compounds in the fuel caused significant drops in H 2 yields compared to CO yields.