Separation Of Propylene Research Articles

Tailor-Made Microporous Metal-Organic Frameworks for the Full Separation of Propane from Propylene Through Selective Size Exclusion.

Adsorptive separation of olefin/paraffin mixtures by porous solids can greatly reduce the energy consumption associated with the currently employed cryogenic distillation technique. Here, the complete separation of propane and propylene by a designer microporous metal-organic framework material is reported. The compound, Y6 (OH)8 (abtc)3 (H2 O)6 (DMA)2 (Y-abtc, abtc = 3,3',5,5'-azobenzene-tetracarboxylates; DMA = dimethylammonium), is rationally designed through topology-guided replacement of inorganic building units. Y-abtc is both thermally and hydrothermally robust, and possesses optimal pore window size for propane/propylene separation. It adsorbs propylene with fast kinetics under ambient temperature and pressure, but fully excludes propane, as a result of selective size exclusion. Multicomponent column breakthrough experiments confirm that polymer-grade propylene (99.5%) can be obtained by this process, demonstrating its true potential as an alternative sorbent for efficient separation of propane/propylene mixtures.

Adsorption Process Intensification through Structured Packing: A Modeling Study Using Zeolite 13X and a Mixture of Propylene and Propane in Hollow-Fiber and Packed Beds

There is scope to intensify the traditional adsorptive separation process which relies on packing a bed with adsorbent pellets. The hollow-fiber bed is one of the several structured configurations that have been proposed to overcome the high pressure drop and inefficient heat transfer of this random packing arrangement. While heat and mass transfer and pressure drop losses are improved in the hollow-fiber bed, the adsorbent packing density is reduced leading to a potential loss of capacity. In this computational study, we performed preliminary parametric comparisons of these bed properties, for equivalent cases in the packed bed and the hollow-fiber bed. Optimized five step single bed cycles for the separation of propylene and propane on zeolite 13X were also studied. For the same recovery and purity, the hollow-fiber bed was found to have a productivity that was five times higher than the packed bed. The hollow-fiber bed also showed higher productivity, when parameters such as the desorption pressure and...

Process intensification of distillation using a microwick technology to demonstrate separation of propane and propylene

Process intensification (PI) of distillation using a microchannel distillation (MCD) device successfully reduced the height of a theoretical plate (HETP) in separating propane and propylene to 1.2 cm, representing 10 theoretical stages. Mass transfer is enhanced using thin wicking structures that are 0.17 mm thick in counterflow with vapor. Liquid is segregated in the wicks by applying a siphon relative to the vapor phase, which also enables the device to operate horizontally. A scalable device containing 11 wicks was operated cryogenically in total reflux. The HETP varied between 1.2 and 4.5 cm, representing a dramatic reduction over commercial structured packings and comparable to other PI approaches. Significant improvements are expected with further development. Potential application for intensified distillation processes include distributed manufacturing and difficult separations involving close boiling compounds and meeting high purity specifications. The ultimate application is isotopic enrichment, where the number of stages required is typically multiple thousands. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3690–3699, 2018

Position-specific carbon and hydrogen isotopic compositions of propane from natural gases with quantitative NMR

Position-specific isotope compositions of light hydrocarbons are expected to provide valuable information on their formation and migration-degradation processes. Here we present a high-accuracy and high-precision (≤±10 and ≤±1‰ for 2H and 13C isotope compositions, respectively) method to determine position-specific hydrogen and carbon isotope compositions of propane from natural gases with quantitative NMR. Customized, light-weight high-pressure sapphire NMR cells were developed for liquefied propane samples. Precision and accuracy of our technique were demonstrated using 13C-labeled compounds, neat samples of C3-C5 with natural isotope abundances, and inter-laboratory comparison of a C7 sample. To determine position-specific isotope compositions of propane from natural gas samples, a method was developed to collect and purify large amount (~6.8 mmol) of propane, using a variable-temperature cold trap. A test with a synthetic sample of natural gas mixture indicates that little isotope fractionation occurred during the propane separation and purification from natural gas mixtures. For the first time, high-precision and high accuracy data are reported of position-specific carbon and hydrogen isotope compositions of propane from different sources, including conventional and unconventional petroleum reservoirs. Preliminary results show that position-specific isotope fractionations between the center and terminal sites of propane vary widely for the different sources. Position-specific isotope compositions of propane have the potential to improve our understanding on the origins, migration and degradation processes of natural gas and hydrocarbons in general.

Economic Estimation of Various Membranes and Distillation for Propylene and Propane Separation

The separation of propylene and propane is very costly due to similar physical-chemical properties. In this study, the effect of various membranes on the economic performance of the olefin unit was evaluated. The Robeson’s line cannot judge the economic performance of membrane separation systems. A precise model of cocurrent and counter-current hollow fiber membrane was developed and implemented in a commercial chemical engineering software to estimate the economics of the best inorganic (ZIF-8) and polymeric (6FDA-TrMPD) membranes compared with the existing distillation unit. At the same area, the cocurrent flows have higher recovery and the counter-current flows have higher purity. The use of the alternative polymer membrane results in a drastic increase in costs. The ZIF-8 membrane performance leads to a 30% increase in the total capital costs, while the annual cost considerably decreased by 46%. When the membrane performance is appropriate in terms of selectivity and permeability, the use of membrane ...

Poly urethane mixed matrix membranes for propylene and propane separation

In this study, a dense mixed matrix membrane based on polyether ester urethane was fabricated using solution casting and dry phase inversion method. The mixed matrix membranes containing non-porous silica mineral nanoparticles, 4A zeolite nanoparticles, and ZIF-8 MOF nanoparticles with different loading. After characterized by FTIR, DLS, and SEM analysis, the membranes were used to separate propylene and propane. The presence of silica particles increased the micro phase separation, slightly reduced permeability, and increased selectivity. The presence of 4A and ZIF-8 particles increased the micro phase combination and permeability, and selectivity increased with the proper distribution of the particles in the polymer. A good distribution and adaptability of ZIF-8 in the polymer was observed because of the presence of the organic imidazolate ligands. The 4A particle shows inadequate compatibility to PU, and it reduces the membrane performance under loadings over 5% due to the formation of nonselective surrounding pores. In the best case, the membrane selectivity increased by 30% and its permeability increased to 133 barrer by adding 15 wt % of the ZIF-8 particle in the polyester-polyether urethane matrix.

Recently developed heat pump assisted distillation configurations: A comparative study

Various configurations of vapor recompression (VRC), bottoms flashing (BF) and external heat pump (EHP) for energy and/or costs savings were proposed in literature. Based on published studies, the best configuration for having the highest performance among the proposed separation systems cannot be easily identified by process engineers as the basis for comparison were not the same. In this study, a comparative study was carried out among the most recent configurations of VRC, BF, EHP and two previously proposed ideas for thermal enhancement of VRC. Based on the schemes and ideas presented by previous researchers, 18 heat pump assisted configurations were designed for separation of propylene from a propylene-propane mixture. The highest total energy saving of 93.8% was identified upon application of a configuration, designed based on heat recuperation ideas. Based on the results of current research, the BF exhibited the best economic performance among the basic heat pump systems, while the external heat pump system exhibited the worst energy and economic performance compared to the other designs. The base conventional distillation column was found to have the lowest capital costs (15.6 mUSD), while a heat recuperated VRC system had the lowest annual operating costs (3.04 mUSD) and total annual costs (7.63 mUSD).

Diffusion phenomena of propane and propylene in colloidal zeolitic imidazolate Framework-8 particles

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

Techno-economic assessment of an energy self-sufficient process to produce biodiesel under supercritical conditions

This paper presents a conceptual design, simulation and techno-economic assessment of an energy self-sufficient process to produce 10,000t per year of biodiesel using supercritical methanol and propane as cosolvent. A suitable heat-integrated design of the process was performed using a part of the produced biodiesel (7.4wt.%) to achieve the energy self-sufficiency for the plant. The simulations were performed by Aspen Plus considering a continuous multitubular reactor operating at 280°C, 128bar, methanol-to-oil molar ratio of 24, propane-to-methanol molar ratio of 0.05, and a residence time of 9.7min. The use of flash separators instead of distillation columns for methanol and propane separation contribute significantly to reduce the energy requirement, with respect to other studies. Final products are high purity of methyl esters (99.8%) and glycerol (96.4%). The economic analysis of the biodiesel plant resulted in a break-even point for the biodiesel selling price of 0.479€/kg (at 10% rate of return), so the process can compete with the existing alkali and acid catalyzed processes.

Separation of propylene and propane by functional mixture of imidazolintum chloride ionic liquid – Organic solvent – Cuprous salt

Abstract To lower viscosity and possible negative effect on mass/heat transfer in industrial operation, we prepared a new absorption system to separate propylene from propane, i.e., ionic liquids (ILs)-organic solvent-cuprous salt. The absorption system is constructed by IL of 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]); organic solvent of pyridine, N,N-dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP); cuprous chloride (CuCl). We experimentally measured the absorption capability and selectivity of such a new system for pure propylene, propane or their mixture at 1–7 bar and 298–318 K. We investigated different factors such as temperature, pressure, species of organic solvent, Cu+ concentration and regeneration and recycling of absorbents. The addition of organic solvent significantly lowers the viscosity of absorption system (approximately one order of magnitude lower). Organic solvent interestingly enhances the absorption capability for propylene while suppresses the absorption selectivity slightly. Species of solvent has a huge effect on separation performance. [Bmim][Cl]-pyridine-CuCl gives the best separation performance, e.g., in the absorption of a mixture of 50 mol% propylene and 50 mol% propane, the solubility of propylene in [Bmim][Cl]-pyridine-CuCl-2M (mass ratio of [Bmim][Cl]:pyridine, 10:1) is 0.064 mol/L at 298 K/2 bar while that of propane is 0.0105 mol/L with absorption selectivity of 6.1, which is comparable to some other ILs-Ag+ or ILs-Cu+ absorption systems. Such an absorption system can be regenerated through temperature and pressure swing and recycled without remarkable activity loss. Therefore, this new system is a good potential absorbent for separating propylene and propane.

ZIF-8 Membranes via Interfacial Microfluidic Processing in Polymeric Hollow Fibers: Efficient Propylene Separation at Elevated Pressures.

Propylene/propane (C3H6/C3H8) separations are performed on a large scale by energy-intensive distillation processes. Membranes based on metal-organic framework (MOF) molecular sieves, such as zeolitic imidazolate framework-8 (ZIF-8), offer the potential to perform these separations at considerably lower cost. However, the fabrication of scalable ZIF-8 membranes with high performance at elevated pressures and temperatures is challenging. We report the fabrication of high-quality ZIF-8 hollow fiber membranes in engineered polymeric hollow fibers via the interfacial microfluidic membrane processing (IMMP) technique. Control of fiber microstructure, as well as optimization of IMMP conditions, allow us to achieve a C3H6/C3H8 separation factor of 180 (at 1 bar and 25 °C), which remains high (60) at 120 °C. Furthermore, high-pressure operation of these membranes was investigated. Detailed permeation measurements indicate excellent suppression of defects at higher pressures up to 9.5 bar, allowing a C3H6/C3H8 separation factor of 90 at 9.5 bar. The membranes also display a 4-fold increase in flux at 9.5 bar as compared to operation at 1 bar. The long-term stability of the ZIF-8 hollow fiber membranes is demonstrated by continuous operation over a month without loss of C3H6 permeance or selectivity.

Isomorphous Substitution of Copper in Nickel Phosphate and Their Separation of Propylene Over Propane

Isomorphous Substitution of Copper in Nickel Phosphate and Their Separation of Propylene Over Propane

Spirobisindane-based polyimide as efficient precursor of thermally-rearranged and carbon molecular sieve membranes for enhanced propylene/propane separation

High performance thermally-rearranged (TR) and carbon molecular sieve (CMS) membranes made from an intrinsically microporous polymer precursor PIM-6FDA-OH are reported for the separation of propylene from propane. Thermal rearrangement of PIM-6FDA-OH to the corresponding polybenzoxazole (PBO) membrane resulted in a pure-gas C3H6/C3H8 selectivity of 15 and C3H6 permeability of 14 Barrer, positioning it above the polymeric C3H6/C3H8 upper bound. For the first time, the C3H6/C3H8 mixed-gas properties of a TR polymer were investigated and showed a C3H6 permeability of 11 Barrer and C3H6/C3H8 selectivity of ~11, essentially independent of feed pressure up to 5bar. The CMS membrane made by treatment at 600°C showed further improvement in performance as demonstrated with a pure-gas C3H6/C3H8 selectivity of 33 and a C3H6 permeability of 45 Barrer. The mixed-gas C3H6/C3H8 selectivity dropped from 24 to 17 from 2 to 5bar feed pressure due to a decrease in C3H6 permeability most likely caused by competitive sorption without any evidence of plasticization.

Determination of position-specific carbon isotope ratios in propane from hydrocarbon gas mixtures

Position-specific isotope ratios (PSIRs), also termed intramolecular isotope ratios, provide novel information to probe molecular structure, reaction mechanics, and molecular signatures for gas to source correlation. Successful application of this technique to natural gas may provide key insights into gas origin and formation mechanisms, which often cannot be satisfactorily addressed using bulk or compound-specific isotope analyses (CSIA) alone. In this study, we present a method to determine the PSIR of propane from hydrocarbon gas mixtures at natural abundance using a step-wise quantification and compound-specific isotope monitoring approach. First, we purify/enrich propane using a proprietary cryogenic gas processing unit, and then convert it to acetic acid (AA) by both enzyme-catalyzed and chemical reactions. Our method of PSIR analysis makes progress in several regards, including efficient propane separation from low-propane concentration gas mixtures (0.5% v/v) using relatively small sample quantities (below 8mL propane). This advance in methodology enables more routine analysis and an optimized workflow for isotope analysis with strict quality control. Results obtained from oil-derived natural gas show that the center carbon in propane is more 13C-enriched than the terminal carbons by about 19.2‰. Our results are discussed in the context of previous efforts in propane intramolecular analysis and potential future uses of this novel technique to improve understanding of the origin of gases, their formation, and the isotope reversal phenomenon.

Permeability of C1–C3 hydrocarbons through MDK membranes under nonisothermal conditions at lower temperatures

The presented nonisothermal technique for investigation of membrane gas separation (using MDK-1 membrane as an example) demonstrates possibilities of rapid assessment of the separation power of commercial membranes for both individual components and various mixtures in the temperature range of‒20 to +40°C. The efficiency of the membrane process under these conditions (cross-flow membrane module model) for separation of propane–methane mixtures has been evaluated. It has been shown that the permeability of methane decreases with a decrease in temperature in the Arrhenius coordinates and the propane permeability increases. The separation selectivity in the mixture decreases by more than twofold in comparison with the ideal selectivity. Nevertheless, a significant improvement of separation has been observed at lower temperatures, with the recovery of the desired product and its purity being variable in a wide range depending on the practical goal. The nonisothermal technique is supposed to be useful for rapid selection of conditions (temperature, pressure, components to be separated) for efficient application of polymeric membranes for separation of hydrocarbon-containing mixtures that are close in composition to real gas sources.

Adsorption separation for high purity propane from liquefied petroleum gas in a fixed bed by removal of alkanes

Abstract The process for high purity propane production via adsorption separation of propane from liquefied petroleum gas (LPG) was investigated at ambient temperature and atmospheric pressure under dynamic conditions in a fixed bed. Breakthrough curves for LPG adsorption on 4A, 5A, 13X and NaY zeolite pellets and granular activated carbon were measured. The length of unused bed (LUB) values for isobutane and butane adsorption in fixed beds with different adsorbent samples were determined by analyzing breakthrough curves. Effects of bed height (5–10 cm) and flow rate (60–100 mL/min) on adsorption characteristics of propane, isobutane and butane onto activated carbon were also examined. Among all these five adsorbent samples, activated carbon exhibited the highest adsorption capacity and the best separation performance, and the concentration of propane in the outlet gas could reach as high as 99.7% (volume fraction). Besides, the LUB value of activated carbon fixed bed was the smallest, which indicated that activated carbon fixed bed was more suitable for adsorption separation of propane from LPG. Adsorption dynamics also showed that relatively lower flow rate and relatively longer bed length were favorable for removal of isobutane and butane from LPG. The Yoon–Nelson model provided a good fit to the experimental data and there was a nice agreement between the numerical simulations and the corresponding data obtained from experiments. All the correlation coefficients in fitted equations exceeded 0.98, indicating a good confidence level for the fit.

Adsorption and separation of propane and propylene by Cuban natural volcanic glass

As a previous study for higher applications, a natural volcanic glass of technological Type I material from Cuba (VVN) was used as adsorbent to separate propane and propylene under flow conditions at a temperature range of 328–343 K by using inverse gas chromatography (IGC). From chromatographic data, the involved differential adsorption heats and the corresponding separation coefficient were estimated. The experimental results showed the capacity of VVN material in the adsorption and separation of light hydrocarbon mixtures at relatively low temperatures due to the weak interaction of these molecules with the adsorbent surface, and therefore the observed low heat adsorption values. This material also presented high stability, since after 150 adsorption/desorption cycles, its properties were maintained.

Separation of propylene and propane by alkylimidazolium thiocyanate ionic liquids with Cu + salt

Abstract Ionic liquids (ILs) coupled with Ag + or Cu + salts to form a new kind of reactive absorbent have been studied to separate light olefin from paraffin recently. In this work, we prepared two halogen-free alkylimidazolium thiocyanate ILs with cheaper cuprous thiocyanate, i.e., [Bmim]SCN–CuSCN and [Emim]SCN–CuSCN (Bmim, 1-butyl-3-methylimidazolium; Emim, 1-ethyl-3-methylimidazolium) and investigated their absorption capability for propylene, propane and mixture of both at 1–7 bar and 298–318 K. The effects of operating parameter including cation nature, temperature, pressure, Cu + concentration and reuse of absorbent were investigated. Propylene shows a chemical absorption while propane does a physical one, and increasing Cu + concentration effectively improves the absorption capability for propylene and the selectivity of propylene/propane. [Bmim]SCN–CuSCN has higher absorption capability and selectivity for propylene than [Emim]SCN–CuSCN, e.g., [Bmim]SCN–CuSCN-1.5 M can absorb 0.12 mol of propylene per liter while 0.012 mol of propane per liter at 1 bar and 298 K, with a selectivity of 10, which is comparable to some other ILs-Ag + salts and better than pure ILs. Such absorbents can be regenerated through temperature and pressure swing without remarkable activity loss. This work shows that alkylimidazolium thiocyanate ILs with Cu + salts are promising reactive absorbents to separate propylene from propane.

Gas-phase simulated moving bed: Propane/propylene separation on 13X zeolite

In the last years several studies were carried out in order to separate gas mixtures by SMB technology; however, this technology has never been implemented on an industrial scale. In the present work, a gas phase SMB bench unit was built and tested for the separation of propane and propylene mixtures, using 13X zeolite extrudates as adsorbent and isobutane as desorbent. Three experiments were performed to separate propane/propylene by gas phase SMB in the bench scale unit with a 4-2-2 configuration, i.e., open loop circuit by suppressing section IV (desorbent regeneration followed by a recycle). Consequently, all the experiments were conducted using an external supply of pure isobutane as desorbent. Parameters such as switching time, extract and raffinate stream flow rates were changed to improve the efficiency of the process. Experimental results have shown that it is feasible to separate propylene from propane by gas phase SMB at a bench scale and that this process is a potential candidate to replace the conventional technologies for the propane/propylene separation. The performance parameters obtained are very promising for future development of this technology, since propylene was obtained in the extract stream with a purity of 99.93%, a recovery of 99.51%, and a productivity of 114.08 kgC3H6 h−1 madsorbent−3. Propane was obtained in the raffinate stream with a purity of 98.10%, a recovery of 99.73% and a productivity of 30.42 kgC3H8 h−1 madsorbent−3. The success of the above mentioned bench scale tests is a big step for the future implementation of this technology in a larger scale.

Functional Solution Composed of Cu(I) Salt and Ionic Liquids to Separate Propylene from Propane

We prepared a new class of functional solutions by dissolving CuCl or CuBr into 1-butyl-3-methylimidazolium bromide ([BMIM][Br]) or 1-ethyl-3-methylimidazolium bromide ([EMIM][Br]). We determined experimentally the solubility of propylene and propane in such solutions respectively at 1–8 bar and 298–313 K, and investigated the separation of propylene from propylene/propane mixture. The absorption capacity and selectivity for propylene were enhanced with the addition of Cu(I) salt and were affected by cationic side chain and anionic species following this order [EMIM][Br]-CuCl < [EMIM][Br]-CuBr < [BMIM][Br]-CuCl < [BMIM][Br]-CuBr. It was observed that this absorption was a chemical nature through π-interaction between Cu(I) cation and propylene. In a typical result, the absorption capacity for propylene of [BMIM][Br]-CuBr (Cu(I) cation, 1.5 M) is 0.13 mol/L at 298 K and 1 bar while it is 0.01 mol/L for propane with a selectivity of 13, which is comparable to those absorption systems with more expensive sil...