Sorption Of Propane Research Articles

High Pressure In Situ Single-Crystal X-Ray Diffraction Reveals Turnstile Linker Rotation Upon Room-Temperature Stepped Uptake of Alkanes.

The rare availability of suitable single-crystal X-ray diffraction (SCXRD) structural data allows for the direct interpretation of the response of a framework to gas sorption and may lead to the development of improved functional porous materials. We report an in situ SCXRD structural investigation of a flexible MOF subjected to methane, ethane, propane, and butane gas pressures. Supporting theoretical investigations indicate weak host-guest interactions for the crystallographically modelled gaseous guests and, in addition, reveal that a turnstile mechanism facilitates the transport of alkanes through the seemingly nonporous system. Inflections present in the adsorption isotherms are furthermore rationalized as due to gate-opening, but without the expected creation of new accessible space.

High pressure sorption of various hydrocarbons and carbon dioxide in Kimmeridge Blackstone and isolated kerogen

We have measured adsorption and desorption of methane, ethane, propane, n-butane, iso-butane and carbon dioxide in Kimmeridge Blackstone at high pressures at temperatures of 60, 90 and 120 °C. Sorption of various light hydrocarbons and carbon dioxide in the isolated kerogen at 60 °C was also investigated. In our measurements, we used the gravimetric method. Physical and chemical properties of samples were measured to provide insight into sorption. Methane, ethane and carbon dioxide sorption was measured to 150 bar. Due to low vapor pressure of propane at 60 and 90 °C, the sorption was measured to 15 bar at 60 °C and 30 bar at 90 °C, respectively. At 120 °C, propane sorption was measured to 30 bar. Similarly, n-butane and iso-butane sorption was studied to 5, 9.5 and 15 bar at 60, 90 and 120 °C, respectively. Compared to sorption of these gases at moderate pressure in our recent work, high pressure sorption shows more pronounced hysteresis and non-monotonic excess sorption. In this work, we use the adsorbed layer density, estimated from grand canonical Monte Carlo (GCMC) simulations, and the liquid density to compute the absolute adsorption and examine the difference between the two. The results show that the absolute adsorption estimated with the two densities is significantly different in methane but similar in the other species. The butanes, n-butane and iso-butane, despite close bulk densities have very different adsorption. The adsorbed layer densities by GCMC simulations are different by about 10% which partly account for the adsorption difference. Other mechanisms may be at play due to different shape of the two molecules.

Equilibrium Sorption of Propane and 1-Hexene in Polyethylene: Experiments and Perturbed-Chain Statistical Associating Fluid Theory Simulations

The availability of sorption equilibrium data is important for the design and optimization of polymerization processes. In this work, we used a gravimetric apparatus based on a magnetic suspension balance and the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state to study the equilibrium sorption of propane and 1-hexene in polyethylene (PE). Propane is used as a diluent in the gas-phase catalytic polymerization of ethylene, while 1-hexene is a commonly used comonomer. Experiments were carried out at industrially relevant conditions using a large set of PE samples with densities from 902 to 967 kg m–3. The solubilities were rigorously evaluated using temperature-dependent crystallinities, and swelling corrections were considered. The solubilities of both penetrants increased with decreasing temperature and decreasing PE crystallinity. Additionally, the PC-SAFT binary interaction parameters did not depend on the temperature. Such dependencies are predicted by theory but are onl...

Propylene/propane plasticization in polyimide membranes

Polyimides have been considered as attractive polymers to be used in membrane based separation processes to separate propylene/propane mixtures. However, propane and propylene tend to plasticize polyimide membranes. In this study, we used molecular simulation techniques to gain insight on the relationship between molecular structure and plasticization of polyimides due to the sorption of propane and propylene molecules. Three fluorinated polyimides with different backbone rigidities were considered for this purpose: 6FDA–ODA, 6FDA–DPX and 6FDA–DAM (6FDA: 4,4-hexafluoroisopropylidene-diphthalic anhydride; DAM: 2,4,6-trimethyl-m-phenylene diamine; ODA: and 4,4-oxydianiline; DPX: 2,5-dimethyl-p-phenylenediamine). A combination of molecular dynamics and Monte Carlo methods was used to estimate sorption induced changes in the polymer matrices. Structural analyses such as radial distribution function, free volume, and local dynamics analyses were carried out to better understand the plasticization mechanism. Results showed that propane and propylene sorption capacities also depend on the polymer-penetrant interactions in addition to the fractional free volume of the polymer which has been shown as the dominant factor for CO2 sorption on the same polyimides in our previous work. The polymer-penetrant interactions are more dominant for propylene than propane due to high polarizability of propylene resulting from π-electron complexation. The analysis of preferential sorption sites in both single and binary gas adsorption reveals that site preferences are altered in binary gas adsorption due to the competition between propane and propylene molecules. The dianhydride structure contain the most preferential sorption site and hence is plasticized in the single gas adsorption case, whereas, the most preferential sorption site moves to the diamine structure in case of binary sorption, especially in more flexible polyimides such as 6FDA–ODA.

Ultraporous, Water Stable, and Breathing Zirconium-Based Metal-Organic Frameworks with ftw Topology.

"Breathing" metal-organic frameworks (MOFs) are an emerging class of soft porous crystals (SPCs) with potential for high working capacity for gas storage applications. However, most breathing MOFs have low stability and/or low surface area. Here we report a water-stable, high surface area, breathing MOF of ftw topology, NU-1105. While Zr6-oxo clusters as nodes introduce water stability in NU-1105, its high surface area and breathing character stem from its pyrene-based tetracarboxylate (Py-FP) linkers, in which the fluorene units (F) in the FP "arms" play a key role in promoting breathing behavior. During gas sorption studies, the "closed pore" (cp) ↔ "open pore" (op) transition of NU-1105 occurs at a propane pressure of ∼3 bar. At 1 bar, NU-1105 is in its cp form and adsorbs less propane than it would in its op form, highlighting improved working capacity. In situ powder X-ray diffraction during propane sorption was used to track the cp ↔ op transition, and molecular modeling was used to elucidate the structure of the op and cp forms of NU-1105. According to TD-DFT calculations, the proposed conformations of the Py-FP linkers in the op and cp forms are consistent with the measured excitation and emission spectra of the op and cp forms of NU-1105. Similar structural transitions are also observed in the porphyrinic MOF NU-1104 depending on the identity of the porphyrin core; we observed breathing behavior if the constituent Por-PTP linker is nonmetalated.

Sorption of propylene and propane in polyurethane membranes containing silver nanoparticles

ABSTRACTThe preparation of a facilitated transport membrane of polyurethane (PU) containing silver nanoparticles is reported. The propylene and propane sorption was investigated aiming at the selective separation from C3s mixtures. The silver particles were photogenerated in situ into the polyurethane matrix using UV light radiation and silver triflate (AgCF3SO3) as precursor. The morphological properties of these membranes (PUAg) reveled great dispersion of silver particles, which size was smaller than 110 nm. The propylene solubility in PUAg resulted more than four times superior to the one for the pure PU membrane, revealing the high affinity between silver and propylene. Flory–Huggins theory was more accurate to describe the propylene sorption behavior in PUAg than Henry's model. The ideal solubility selectivity of PUAg membrane resulted 24.4, indicating that there is a good potential for an industrial application aiming at the separation of propylene/propane. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42916.

Influence of The Metamorphism Grade and Porosity of Hard Coal on Sorption and Desorption of Propane / Wpływ Stopnia Metamorfizmu I Porowatości Węgli Kamiennych Na Sorpcję I Desorpcję Propanu

Abstract In this paper results of investigations of sorption of hard coal samples collected from the extracted coal seams of Polish coal mines are presented. As sorbate propane was used. Examinations were carried out in the temperature of 298 K by means of volumetric assessment with the use of apparatus ASAP 2010 of Micromeritics. On the basis of conducted examinations it has been found out that the amount of sorbed propane depend on a type of coal, its metamorphism grade, content of oxygen element, moisture and porosity of these coals. The greatest amounts of propane are sorbed by low carbonized, high-porosity coals of high content of oxygen and moisture. Sorption of relatively high amounts of propane by these coals (ca. 10 cm3/g) is a result of the influence of polar surface of coals with molecules of propane and good availability of internal microporous structure of these coals for molecules of examined sorbate. Medium and high carbonized coals sorb insignificant amounts of propane. These coals have compact structure and non-polar character of their surface, their internal porous structure is to a minor degree available for propane molecules in conditions of carried out research. Sorption of propane in this case, takes place mainly in surface pores and on the surface of coals. Moreover, measurements of desorption isotherms of propane showing irreversible character of sorption were made. Desorption isotherms do not come together with sorption isotherms forming open hysteresis loop. Amounts of non-desorbing propane remaining in the coal depend on the type of examined coal.

Tapered element oscillating microbalance (TEOM) studies of isobutane, n‐butane and propane sorption in β‐ and Y‐zeolites

AbstractA TEOM is used to elucidate the adsorption/desorption characteristics of alkylation reactants on USY‐ and β‐zeolites. Equilibrium adsorption isotherms were obtained on USY‐ and β‐zeolites using n‐butane, isobutane and propane as proxy reactant molecules (T = 303–398 K, adsorbate partial pressure 0–1.2 bar). Analysis of the transient adsorption/desorption profiles of these molecules from either a bed of the zeolite or pelletized particles of the crystals (with mean size < 1 μm) demonstrate that diffusion in the secondary meso‐/macroporous structure formed in the packing or the pellets controls the overall sorption rates. The experimental adsorption/desorption profiles from the pelletized zeolites were regressed with available mathematical models to obtain effective meso‐/macropore diffusivities for reactant molecules, and nearly perfect fits of the experimental and the modeled profiles. Taking into account the dead volume in the system, a criterion for reliable measurements of either micropore or mesopore diffusivities by the TEOM technique is derived. © 2009 American Institute of Chemical Engineers AIChE J, 2010

Enhanced propylene/propane separation by carbonaceous membrane derived from poly (aryl ether ketone)/2,6-bis(4-azidobenzylidene)-4-methyl-cyclohexanone interpenetrating network

An innovative combination of a photosensitive crosslinker, 2,6-bis(4-azidobenzylidene)-4-methyl-cyclohexanone (Azide) with poly (aryl ether ketone) (PAEK) is utilized to form a semi-interpenetrating network (IPN) as the precursor for carbon membranes. Low temperature pyrolysis (450–650 °C) of this precursor produces carbon membranes with excellent olefin/paraffin separation performance that surpasses the conventional trade-off line. The carbon membranes have reasonably good flexibility since excessive closure of the micropores is avoided. This is evident from the mechanical properties of the carbon membranes obtained from nanoindention to the pore size distribution derived from CO 2 adsorption. By varying the composition of Azide/PAEK and optimizing the low-temperature pyrolysis protocol, it was found that PAEK/Azide (80:20) pyrolysed at 550 °C exhibits the best propane/propylene separation performance with C 3H 6 permeability of 48 barrer and ideal C 3H 6/C 3H 8 selectivity of 44. Due to strong competitive sorption of propane and propylene molecules, the C 3H 6 permeability is lowered to 3.6 barrer and the C 3H 6/C 3H 8 selectivity to 32 in mixed gas experiments. However, this separation performance is still above the trade-off line. Even though both Azide and PAEK cannot form useful carbon membranes, their IPN is a unique precursor that can produce carbon membranes with comparable performance.

Influence of the sensitive zeolite material on the characteristics of a potentiometric hydrocarbon gas sensor

The voltage response of Na-ZSM-5 zeolite/Au electrodes with different Si/Al ratios is measured in dependence of propane partial pressure in O 2/CO 2/N 2 atmospheres at 723 K. A mixture of two Na x CoO 2 phases serves as a reference electrode. The zeolites with higher Si/Al ratios lead to higher sensitivities to propane at low concentrations (< 1000 ppm). It is shown that this is in accordance with the assumption of a sensor effect caused by changes of the Na + ion activity due to sorption of propane in the zeolite micropores. The response times to propane concentration steps decrease with increasing propane concentration.

Distribution of Platinum Particles in the Bimodal Micropore System of Activated Carbon

AbstractPlatinum (Pt)/activated‐carbon catalysts were prepared and characterized by pore‐size distribution (PSD), propane‐sorption dynamics, and activity of cyclohexane dehydrogenation to benzene. The batch‐type frequency‐response (FR) spectroscopic technique was applied to determine the mass‐transport rate of propane sorption. Two parallel sorption processes of different time constants were distinguished, suggesting that adsorption proceeds in smaller and larger micropores that are not interconnected. Increasing Pt loading affected the propane mobility, but increased the dehydrogenation activity only up to ca. 1 wt‐% of Pt content. It was concluded that clusters of metallic Pt‐atoms are located preferentially at the narrowest pores. Blocking these micropores, the Pt reduces the carbon surface available for sorption; also, a significant fraction of the metal becomes inaccessible for the reactant.

Simultaneous determination of diffusion and adsorption properties of microporous sorbents under continuous flow conditions by frequency response methods: propane in silicalite-1

Frequency response methods are applied in a novel manner to investigate the sorption dynamics of a bed of microporous sorbent under continuous flow conditions. It is demonstrated that the technique is capable of simultaneously determining the diffusion and sorption parameters controlling uptake into the sorbent independent of any parameters describing the sorbent bed. The system studied in this work is the sorption of propane into the zeolite silicalite 1. Diffusion parameters are obtained which are within the range of existing literature values.

Dynamic and catalytic studies of H-ferrierites made by hydrothermal and dry state syntheses

The activity and selectivity of skeletal isomerization of 1-butene and disproportionation of ethylbenzene on H-ferrierite catalysts prepared by dry state recrystallization of magadiite and conventional hydrothermal synthesis from an alkaline SiO 2/Al 2O 3 gel are compared. The isobutene yields of the samples were found to be similar even though the ferrierite crystals had quite different morphologies. Significant differences were observed in the isobutene selectivities which can be correlated with processes occurring inside the crystals. Ammonia, acetylene, methane and propane sorption and intracrystalline diffusion rate-spectra are reported using the frequency-response technique. The sorption properties of the acid sites and the diffusional resistances of the morphologically different ferrierite crystals are compared. It was found that by the dry state synthesis the quality of the ferrierite framework was similar to that obtained by the conventional hydrothermal synthesis. The channels of ferrierite recrystallized from magadiite, however, seem to have fewer barriers and, thus, show better kinetic properties, e.g., faster diffusion of propane and higher selectivity to the formation of isobutene.

Sorption of liquid propane in polyethylene

The kinetics of sorption and desorption of liquid propane in medium density polyethylene were studied by thermogravimetry as a function of temperature, pressure and time. Diffusion was mainly Fickian. Diffusion coefficients were of the order of 10 −7 to 10 −9 (cm 2 s −1) and the Arrhenius temperature dependence was obeyed with an activation energy of 52.2 kJ mol −1 in the temperature range between 0°C and 70°C. At 0°C gradual plastidsation led to non-Fickian diffusion in the case of sorption. The saturation concentrations of propane were typically 8 to 10% by mass in the temperature range 0–40°C calculated from boundary conditions fitted to a diffusion model. The sorption of propane led to an initial increase in oxidative induction time on exposure most probably due to solvation of precipitated antioxidant by the sorbed propane.

The effect of sorbed penetrants on the aging of previously dilated glassy polymer powders. II. n‐propane sorption in polystyrene

AbstractBoth the rate and apparent equilibrium of propane sorption in glassy polystyrene were increased after swelling the polymer by exposure to a highly sorbing vapor. Cyclic sorption experiments revealed that the increase in rate and apparent equilibrium of sorption due to the preswelling treatment decayed only during vacuum aging. The presence of low levels of propane in the polymer during aging, however, appeared to arrest the decay in sorption capacity. These composite results, taken in conjunction with the results of previous work in our laboratory, suggest that the component of the total sorption which resides in nonequilibrium, distended interchain gaps retards the chain motions which otherwise lead to consolidation of the dilated glass.

Sorption of propane in poly(ethyl methacrylate) near Tg

The sorption of propane in poly(ethyl methacrylate) was investigated above and below the polymer Tg and the dual-mode sorption model parameters were evaluated. The Langmuir capacity decreased as the temperature was raised to Tg and the apparent Henry's law constant exhibited a discontinuity at Tg. The enthalpy of microvoid filling ΔHH is more exothermic than the enthalpy of dissolution at T < Tg by about 8 kJ/mol.

Temperature dependence of sorption parameters near Tg for propane in a miscible blend of polystyrene and poly(vinyl methyl ether)

AbstractThe sorption of propane by 75:25% (w/w) miscible blends of polystyrene and poly(vinyl methyl ether) with different thermal histories was investigated near Tg. The dual‐mode sorption model was used to analyze the results. The evidence indicates that the Henry's law constant for states below Tg cannot be smoothly extrapolated from the rubbery state.

Effects of annealing on the sorption of propane in polycarbonate

Effects of annealing on the sorption of propane in polycarbonate

The sorption of propane in slurries of active carbon in water

Propane was adsorbed in a slurry of active carbon in water in a stirred cell. With the aid of a formal model the values of the transfer coefficients and mass transfer resistance can be obtained from experiments. Experiments were performed in which the stirrer speed, the weight fraction of active carbon in the slurry and the particle size were varied. Under the experimental conditions it was found that the particles did not interfere very much with the mass transfer across the gas—liquid interface. Intraparticle diffusion was important and was mainly caused by surface migration. It was observed that the capacity for adsorption was limited by the adsorption of water at the active sites on the carbon particle.

The sorption of propane in slurries of active carbon in water

Propane was adsorbed in a slurry of active carbon in water in a stirred cell. With the aid of a formal model the values of the transfer coefficients and mass transfer resistance can be obtained from experiments. Experiments were performed in which the stirrer speed, the weight fraction of active carbon in the slurry and the particle size were varied. Under the experimental conditions it was found that the particles did not interfere very much with the mass transfer across the gas—liquid interface. Intraparticle diffusion was important and was mainly caused by surface migration. It was observed that the capacity for adsorption was limited by the adsorption of water at the active sites on the carbon particle.