Separation Of Light Hydrocarbons Research Articles

Two isoreticular pillared-layer frameworks as stationary phases for gas chromatographic applications – Unusual peak broadening in size exclusion chromatography, determination of thermodynamic and kinetic data

Short GC capillary columns were coated with micro particles of the two isoreticular pillared-layer frameworks (PLFs) [Cu2(cam)2(dabco)] and [Cu2(cam)2(bipy)] (cam2− = (+)-camphoric acid, dabco = 1,4-diazabicyclo[2.2.2]octane, bipy = 4,4′-bipyridine) by the technique of the so called “Controlled SBU Approach”. It is demonstrated that the small pore openings of [Cu2(cam)2(dabco)] enable size dependent gas chromatographic separations which were not observed on [Cu2(cam)2(bipy)]. In some cases the interaction with the smaller pore system lead to unusual peak broadening. Both compounds offer excellent properties for the high resolution separation of light hydrocarbons including isomers. Chromatographic parameters, including resolution factors and selectivities, as well as thermodynamic data characterizing the interaction between the stationary phase and the analytes were determined from the temperature-dependent retentions times. Furthermore, isothermal measurements were used for the calculation of diffusion constants of selected analytes in the mobile phase and in the [Cu2(cam)2(dabco)] and [Cu2(cam)2(bipy)] structures.

Anionic metal-organic framework for adsorption and separation of light hydrocarbons.

The reaction of nickel(II) sulfate with 4,4',4"-s-triazine-2,4,6-triyltribenzoate in dimethyl sulfoxide afforded a hexanuclear nickel(II)-based anionic 2-fold interpenetrated metal-organic framework exhibiting the ability to adsorb and separate light hydrocarbons and canted antiferromagnetism.

Feasibility of the preparation of silica monoliths for gas chromatography: Fast separation of light hydrocarbons

The preparation conditions of silica monoliths for gas chromatography were investigated. Silica-based monolithic capillary columns based on sol–gel process were tested in the course of high-speed gas chromatographic separations of light hydrocarbons mixture (C1–C4). The impact of modifying the amount of porogen and/or catalyst on the monolith properties were studied. At the best precursor/catalyst/porogen ratio evaluated, a column efficiency of about 6500 theoretical plates per meter was reached with a very good resolution (4.3) for very light compounds (C1–C2). The test mixture was baseline separated on a 70cm column. To our knowledge for the first time a silica-based monolithic capillary column was able to separate light hydrocarbons from methane to n-butane at room temperature with a back pressure in the range of gas chromatography facilities (under 4.1bar).

A polyhedral metal–organic framework based on the supermolecular building block strategy exhibiting high performance for carbon dioxide capture and separation of light hydrocarbons

By using the supermolecular building block (SBB) strategy, a polyhedron-based metal-organic framework (PMOF), which features three types of cages with multiple sizes and shapes, has been synthesized. It exhibits high performance for CO2 capture (170 cm(3) g(-1) at 273 K under 1 bar) and selectivity of CO2/CH4 (9.4) and C3H8/CH4 (271.5).

Mathematical Modeling of the Process of Catalytic Hydrodewaxing of Atmospheric Gasoil Considering the Interconnection of the Technological Scheme Devices

The authors proposed a mathematical model of the reactor of hydrodewaxing process and methodology to address the relationship of processes and devices for predicting the hydrodewaxing reactor operation and the related apparatus - stabilization column of the gas-product mix in order to use them to predict resource-efficient modes of the equipment operation. The influence of the downstream stabilization column composition of raw materials and quality of stable hydrogenate in order to determine the optimal irrigation flow into the column to increase the separation of hydrogen sulfide and light hydrocarbons by the top of the column is shown.

The adsorption and simulated separation of light hydrocarbons in isoreticular metal-organic frameworks based on dendritic ligands with different aliphatic side chains.

Three isoreticular metal-organic frameworks, JUC-100, JUC-103 and JUC-106, were synthesized by connecting six-node dendritic ligands to a [Zn4O(CO2)6] cluster. JUC-103 and JUC-106 have additional methyl and ethyl groups, respectively, in the pores with respect to JUC-100. The uptake measurements of the three MOFs for CH4, C2H4, C2H6 and C3H8 were carried out. At 298 K, 1 atm, JUC-103 has relatively high CH4 uptake, but JUC-100 is the best at 273 K, 1 atm. JUC-100 and JUC-103 have similar C2H4 absorption ability. In addition, JUC-100 has the best absorption capacity for C2H6 and C3H8. These results suggest that high surface area and appropriate pore size are important factors for gas uptake. Furthermore, ideal adsorbed solution theory (IAST) analyses show that all three MOFs have good C3H8/CH4 and C2H6/CH4 selectivities for an equimolar quaternary CH4/C2H4/C2H6/C3H8 gas mixture maintained at isothermal conditions at 298 K, and JUC-106 has the best C2H6/CH4 selectivity. The breakthrough simulations indicate that all three MOFs have good capability for separating C2 hydrocarbons from C3 hydrocarbons. The pulse chromatographic simulations also indicate that all three MOFs are able to separate CH4/C2 H4/C2H6/C3H8 mixture into three different fractions of C1, C2 and C3 hydrocarbons.

A [Cu2(bdc)2(dabco)] coated GC capillary column for the separation of light hydrocarbons and the determination thermodynamic and kinetic data thereof

The unique properties of MOFs (MOF=metal–organic framework) such as their adjustable pore size, high intrinsic surface area and organic functionalizations make them a suitable class of materials for chromatographic separations. Micro particles of [Cu2(bdc)2(dabco)] (bdc2−=terephthalate, DABCO=1,4-diazabicyclo[2.2.2]octane) were prepared by a cyclic deposition method based on the technique of the so called “controlled SBU approach” and anchored via SAMs (SAM=self-assembled monolayer) in a short GC capillary column to generate a wall-bonded cross linked stationary phase. It could be demonstrated, that the fabricated column exhibits a high separation power for the light hydrocarbons C1–C7. Chromatographic parameters, including resolution factors and selectivity as well as thermodynamic data characterizing the interaction between the stationary phase and the analytes, were determined from the temperature-dependent measurements of the retentions times of these analytes. In addition, isothermal measurements were used for the calculation of diffusion constants in [Cu2(bdc)2(dabco)].

Tuning a layer to a pillared-layer metal–organic framework for adsorption and separation of light hydrocarbons

Rational assembly from a layer structure to a pillared-layer metal-organic framework affords an ideal microporous material with large Langmuir surface area for highly selective separation of hydrocarbons.

Selective adsorption of olefin–paraffin on diamond-like frameworks: diamondyne and PAF-302

Olefin–paraffin separation is one of the most significant processes in the petrochemical industry. An energy efficient method such as adsorption is considered to be a promising alternative to the traditional cryogenic distillation for the purification of olefins or paraffins. In this work, the grand canonical Monte Carlo (GCMC) method was used to study the adsorption and separation of light hydrocarbons (including ethylene, ethane, propylene and propane) by two diamond-like frameworks: diamondyne (originally named D-carbon in J. Mater. Chem. A, 2013, 1, 3851) and PAF-302, and further explore the mechanism for the adsorptive separation of olefins and paraffins. It is found that both diamondyne and PAF-302 show high uptake of hydrocarbons under ambient conditions, which greatly exceed those of MOFs and ZIFs. The saturation adsorption amounts of ethylene, ethane, propylene and propane on diamondyne are 14.5, 12.3, 10.3 and 8.9 mmol g−1, while they are 31.8, 28.0, 32.0, 30.3 mmol g−1 for PAF-302, which indicates that PAF-302 is an excellent candidate for hydrocarbon adsorption. In addition, it is also found that diamondyne shows preferential adsorption of olefins in the olefin–paraffin mixtures, like most commonly reported MOFs and ZIFs. However, interestingly, PAF-302 exhibits favorable adsorption for paraffins over olefins, which is an entirely different behavior to diamondyne, even though they have similar diamond-like structures.

Metal–organic frameworks with potential for energy-efficient adsorptive separation of light hydrocarbons

The separation of hydrocarbons with carbon numbers in the 1–3 range is of great significance in the purification of natural gas, production of ethylene and propylene with the required 99.5%+ purity levels as feeds to polymerization reactors, and separation of ethyne from mixtures with ethylene. In this study the performances of a total of 19 different MOFs, carefully selected to span a wide range of functionalities, were evaluated for a variety of separation tasks. For all separation tasks investigated, MOFs with high density of open metal sites, CoMOF-74, MgMOF-74, and FeMOF-74, have significantly better separation potential than other MOFs, ZIFs or zeolites that have been suggested in the literature. Of particular significance is the possibility offered by CoMOF-74, MgMOF-74, and FeMOF-74 for “fractionating” a 6-component CH4/C2H2/C2H4/C2H6/C3H6/C3H8 mixture to yield individual pure components. Such separations are likely to have a significant industrial impact, resulting in significant energy savings when compared to current technologies that rely on distillation.

A capillary gas chromatographic column with a porous layer based on the divinylbenzene-vinylimidazole copolymer

Capillary columns with a new sorbent based on the divinylbenzene-vinylimidazole organic copolymer are proposed. The properties of the prepared columns are discussed. It is demonstrated that columns based on the divinylbenzene-vinylimidazole polymer with different selectivities can be prepared by varying the relative amount of vinylimidazole in the initial polymerization mixture. The examples of separation of light hydrocarbons, permanent gases, and oxygen-containing compounds are given.

Improved processes of light hydrocarbon separation from LNG with its cryogenic energy utilized

Liquefied natural gas (LNG) often consists of some kinds of light hydrocarbons other than methane, such as ethane, propane and butane, which are of high additional value. By efficiently utilization of LNG cryogenic energy, these light hydrocarbons ( C 2 + ) can be separated from LNG with low power consumption and LNG is gasified meanwhile. Two novel light hydrocarbon separation processes are proposed in this paper. The first process uses a demethanizer working at higher pressure (about 4.5 MPa). The methane-riched natural gas from the demethanizer can be compressed to pipeline pressure with low power consumption. The other one uses a demethanizer working at lower pressure (about 2.4 MPa). By cascade utilization of LNG cryogenic energy, the methane-riched natural gas from the demethanizer is entirely re-liquefied. Then the liquid product is pressurized to pipeline pressure by pumps instead of compressors, reducing the power consumption greatly. By both of the two processes, liquefied ethane and LPG (liquefied petroleum gas, i.e. C 3 + ) at atmosphere pressure can be obtained directly, and high ethane recovery rate can be gained. On the basis of one typical feed gas composition, the effects of the ethane content and the ethane price to the economics of the light hydrocarbon separation plants are studied, and the economics are compared for these two processes. The results show that recovering light hydrocarbons from LNG can gain great profits by both of the two processes, and from the view of economics, the low pressure process is better than the high pressure process.

Silica sputtering as a novel collective stationary phase deposition for microelectromechanical system gas chromatography column: Feasibility and first separations

Since the late 1970s, approaches have been proposed to replace conventional gas chromatography apparatus with silicon-based microfabricated separation systems. Performances are expected to be improved with miniaturization owing to the reduction of diffusion distances and better thermal management. However, one of the main challenges consists in the collective and reproducible fabrication of efficient microelectromechanical system (MEMS) gas chromatography (GC) columns. Indeed, usual coating processes or classical packing with particulate matters are not compatible with the requirements of collective MEMS production in clean room facilities. A new strategy based on the rerouting of conventional microfabrication techniques and widely used in electronics for metals and dielectrics deposition is presented. The originality lies in the sputtering techniques employed for the deposition of the stationary phase. The potential of these novel sputtered stationary phases is demonstrated with silica sputtering applied to the separation of light hydrocarbons and natural gases. If kinetic characteristics of the sputtered open tubular columns were acceptable with 2500 theoretical plates per meter, the limited retention and resolution of light hydrocarbons led us to consider semipacked sputtered columns with rectangular pillars allowing also significant reduction of typical diffusion distances. In that case separations were greatly improved because retention increased and efficiency was close to 5000 theoretical plates per meter.

A capillary gas chromatographic column with a porous layer based on a mesoporous material

A procedure for synthesizing an MSM-41-type mesoporous mesophase material (MMM) layer, that is, a layer of a solid porous material with a regular arrangement of nanoscale calibrated pores and a unified geometry, on the inner wall of a capillary column was developed. Because of the high specific surface area of silica, capillary columns with a porous MMM layer on the basis of silica allow the amount of samples introduced to be increased by an order of magnitude compared with the known capillary porous-layer columns. An example of the separation of light hydrocarbons is described. The properties of columns with MMM porous layers are discussed.

Fast separation of light hydrocarbons by gas chromatography on monolithic capillary columns based on silica gel

Monolithic capillary columns based on silica gel were tested in the course of high-speed gas-chromatographic separations of a five-component mixture of C1–C4 hydrocarbons. It was found that short-length monolithic columns could be used because of their high specific efficiency; this allowed us to shorten the column dead time and the duration of analysis. The column performance of about 1000 theoretical plates per second was reached. The test sorbate mixture was completely separated on a 58.5-cm column with an efficiency of about 18 700 theoretical plates in a time shorter than 17 s. It was noted that CO2 and N2O should be predominantly used as carrier gases.

A multicapillary gas chromatographic column with a Sol-Gel sorbent based on aluminum oxide

A multicapillary gas chromatographic column with an adsorption layer based on alumina was prepared. The column allowed the high-speed separation of C1-C4 light hydrocarbons to be performed in 8–12 s. The possibility of creating columns with various selectivities was demonstrated.

Electrostatically Mediated Specific Adsorption of Small Molecules in Metallo-Organic Frameworks

We investigate the interaction of ethylene and ethane with a Cu-tricarboxylate complex and show that at low loadings the lighter molecule has a higher binding energy as a result of an increased interaction with the framework Cu and stronger hydrogen bonding with the basic framework oxygens. This leads to selective adsorption of ethylene by a factor of about 2 at low pressure, which is overcome by the stronger van der Waals interaction of ethane at high loadings, explaining recent literature data. The results suggest the possibility of separation of light hydrocarbons at low pressures or in trace amounts.

Defect formation and transport in SrFe1-xAlxO3-δ

Perovskite-related phases derived from SrFeO3-δ are among known mixed conductors with highest oxygen permeability and are thus of interest as the ceramic membrane materials for oxygen separation and partial oxidation of light hydrocarbons. Dense ceramics of SrFe1-xAlxO3-δ (x=0.1–0.5) were prepared via the glycine-nitrate process. The cubic solid solution formation was found to occur in the concentration range x=0–0.35. Increasing aluminum content leads to decreasing thermal expansion coefficients (TECs), relative fraction of Fe4+ under oxidizing conditions, and also the total conductivity, predominantly p-type electronic at oxygen pressures close to atmospheric. The TECs vary in the range (13.5–16.4)×10−6 K−1 at 373–923 K and increase up to (18.6–31.9)×10−6 K−1 at 923–1273 K. The oxygen permeation fluxes decrease moderately with aluminum additions. The Mossbauer spectroscopy data and p(O2) dependencies of electrical properties indicate a small-polaron mechanism of electronic transport in SrFe1-xAlxO3-δ. Reducing oxygen partial pressure results in transition from dominant p- to n-type electronic conduction. The low-p(O2) stability limit of SrFe1-xAlxO3-δ perovskites lies between that of LaFeO3-δ and Fe/Fe1-γO boundary.

Exploring the Potential of Mesoporous Silica, SBA-15, as an Adsorbent for Light Hydrocarbon Separation

Equilibrium adsorption isotherms for methane, ethane, ethylene, acetylene, propane, and propylene have been measured for the first time on mesoporous silica, SBA-15, and the data are analyzed by using the Langmuir−Freundlich adsorption isotherm model. The adsorption capacities for ethylene and propylene are found to be higher than those for corresponding alkanes. Likewise, adsorption of acetylene is more pronounced as compared to ethylene. The isosteric heats of adsorption for various adsorbates estimated by the Clausius−Clapeyron equation are higher for olefins and acetylene and are comparable with those reported for π-complexation based systems. Such a trend has in turn suggested a higher affinity of SBA-15 framework for alkenes over corresponding alkanes, which has been examined in terms of the textural characteristics of SBA-15. It is suggested that SBA-15 can potentially be a good adsorbent for separation of light hydrocarbons.

Evaluation of transition metal complexes of aminopropylsilyl-dithiooxamide bonded phases for gas chromatography

Copper(II) and cobalt(II) complexes of dithiooxamide chemisorbed on aminopropyl bonded silicas were prepared and evaluated for the separation of light hydrocarbons (C 4 and below) by microcolumn gas chromatography (GC). All the columns appeared to be effective for the separation of C 1–C 4 saturates with reproducible retention times. In general, the sample components were retained longer on the metal-containing packings presumably due to specific solute-metal interactions. The cobalt(II) complex of aminopropylsilyl-dithiooxamide bonded phase showed better selectivity for the test solutes, particularly the C 2 hydrocarbons. This result, which reflects the higher capability of cobalt(II) to form pi-complexes with electron donor compounds than copper(II), showed a significant improvement in the separation of the C 2 hydrocarbons over molecular sieve 5A, alkyl bonded silicas and copper(II) complexes of cyano- or mercaptopropyl bonded phase where ethane and ethylene eluted as a single peak. Thermal stability test showed that the columns could be operated at temperatures up to 200 °C without any appreciable change in retention properties.