Industrial Separation Processes Research Articles

Ultramicroporous Hydrogen-Bonded Organic Framework Material with a Thermoregulatory Gating Effect for Record Propylene Separation.

Propane/propylene separation is one of the most challenging and energy-consuming but most important tasks in the petrochemical industry. Herein, a stable hydrogen-bonded organic framework (HOF-FJU-1) was tailor-made for highly efficient propylene separation from binary C3H6/C3H8 and even seven component CH4/C2H4/C2H6/C3H6/C3H8/CO2/H2 mixtures. The temperature-controllable diffusion channels in HOF-FJU-1 have enabled the porous material to completely exclude propane to reach high-performance propylene purification under energy-efficient operation conditions. Single-crystal structural analysis revealed that the well-matched pore aperture of HOF-FJU-1 can exactly accommodate propylene molecules via multiple intermolecular interactions, exhibiting a very high propylene/propane selectivity of 616 at 333 K. The propylene purity and productivity are over 99.5% and 30.2 L kg-1 from the binary C3H6/C3H8 (50/50) mixture at 333 K. Through a follow-up column separation of C3H6/C2H4 at 353 K, not only high-purity propylene (99.5%) but also ethylene (98.3%) can be readily collected from the seven component CH4/C2H4/C2H6/C3H6/C3H8/CO2/H2 (31/10/25/10/10/1/13) cracking gas mixtures. The great potential of HOF-FJU-1 for the industrial propylene separation process has been further supported by the high stability of this porous material under different environments and straightforward processibility and regeneration feasibility.

Discrimination of xylene isomers in a stacked coordination polymer.

The separation and purification of xylene isomers is an industrially important but challenging process. Developing highly efficient adsorbents is crucial for the implementation of simulated moving bed technology for industrial separation of these isomers. Herein, we report a stacked one-dimensional coordination polymer {[Mn(dhbq)(H2O)2], H2dhbq = 2,5-dihydroxy-1,4-benzoquinone} that exhibits an ideal molecular recognition and sieving of xylene isomers. Its distinct temperature-adsorbate-dependent adsorption behavior enables full separation of p-, m-, and o-xylene isomers in both vapor and liquid phases. The delicate stimuli-responsive swelling of the structure imparts this porous material with exceptionally high flexibility and stability, well-balanced adsorption capacity, high selectivity, and fast kinetics at conditions mimicking industrial settings. This study may offer an alternative approach for energy-efficient and adsorption-based industrial xylene separation and purification processes.

Improving CH4 uptake and CH4/N2 separation in pillar‐layered metal–organic frameworks using a regulating strategy of interlayer channels

AbstractA pore engineering strategy involving the regulation of pillars in a series of pillar‐layered metal–organic frameworks was presented to promote pore size adjustment and pore environment optimization for efficient separation of CH4 from coal‐mine methane. Compared with the original Ni(BTC)(BPY) and Ni(BTC)(TED), the suitable pore size and rich supply of carboxylate oxygens in the newly constructed Ni(BTC)(PIZ) resulted in the strongest recognition of CH4, leading to both high CH4 uptake (1.62 mmol/g) and CH4/N2 (50/50) selectivity (7.32) at 298 K and 1 bar. Its optimal balance performance between uptake and selectivity was better than most reported adsorbents, which further led to the most efficient separation of CH4 from CH4/N2 mixtures. The stability of the structure and performance was verified by repeated cycle tests. Overall, it is believed the structure constructed based on the regulation strategy of the interlayer channel would enable the application of promising metal–organic frameworks in industrial gas separation processes.

Mixed (Ag+, Ca2+)-LTA zeolite with suitable pore feature for effective separation of C3H6/C3H8

Separating C3H6/C3H8 is a challenging task owing to their similar sizes and boiling points. In this study, we report a sequential and partial Ag+/Ca2+ ion-exchanged zeolite that exhibits ideal C3H6/C3H8 molecular sieving. Moreover, the zeolite exhibited superior C3H6 uptake of 2.37 mmol/g and molecular packing density (∼77% packing of liquid C3H6) at an extremely high C3H6: Ag+ ratio of 21.5 with Ag content as low as 1.18 wt%. The (Ag+, Ca2+) cations were sequentially exchanged into LTAs by comprehensively considering the extra-framework cation distribution and site preferences for different cations. By exchanging Ag+ with Na+ in the extra-framework of LTA, C3H6 can be admitted even at the average LTA apertures of sizes < 4 Å. Meanwhile, exchanged Ag+ also increased the adsorption kinetics of C3H6 by an order of magnitude. Hydrophobic modification on Ca-Ag-LTA was successfully achieved to significantly suppress the competition from water while retaining excellent regenerability in multiple cycles. The strategy of binary ion exchange to delicately tune the pore channels and chemistry and selectively admit molecules with beneficial kinetics might potentially be broadened to other industrial separation processes.

Ultra-permeable intercalated metal-induced microporous polymer nano-dots rooted smart membrane for environmental remediation

Energy efficient CO2 separation using ultrathin smart membranes must possess efficient permeation performance, higher surface area and hydrostatic stability at industrially relevant high pressures. However, ultrathin membranes are susceptible to lower surface area, plasticization and swelling which reduces the performance at higher pressure under humidified conditions. This paper evaluates the routes for the potential intercalated effect of metal-induced microporous polymers (MMPs) dots into a cellulose-based polymer matrix to enhance promising properties, including the surface area, CO2 permeation performance, plasticization resistance and hydrostatic stability of ultrathin smart membranes at high pressure. The MMP dots-rooted smart membrane demonstrated 55 nm thickness of ultrathin selective layer with a higher surface of 220 cm2. The enhancement of CO2 permeability from 14.1 to 108.9 Barrer and CO2/CH4 ideal selectivity from 11.8 to 31.1 was observed due to the integration of MMP dots into the cellulose polymer. This result could be due to enhancement of nitrogen lone pair electron interactions with CO2 followed by amines group which improved the CO2 adsorption on the membrane surface. The MMP dots-rooted membrane demonstrated plasticization resistance up to 26 bar pressure, as compared to a pristine polymer membrane which is a percentage increase of 160% under humidified conditions. The resulting ultrathin smart membrane exhibited stable performance for a duration of 200 h under humidified conditions which confirmed the higher hydrostatic stability of the membrane. These findings confirmed the potential of MMP dots materials for the development of an industrial scale CO2 separation process using intercalated membranes.

Construction of PPSU-MoS2/PA-MIL-101(Cr) Membrane with Highly Enhanced Permeance and Stability for Organic Solvent Nanofiltration.

Membranes with excellent separation performance and stability are needed for organic solvent nanofiltration in industrial separation and purification processes. Here we reported a newly PPSU-MoS2/PA-MIL-101(Cr) composite membrane with high permeance, good selectivity and stability. The MIL-101(Cr) was introduced in the polyamide (PA) layer via the PIP/TMC interfacial polymerization process on a microporous PPSU-MoS2 substrate. At a small doping amount of 0.005 wt% MIL-101(Cr), the PPSU-MoS2/PA-MIL-101(Cr) composite membrane exhibited a high methanol permeance of 12.03 L m−2 h−1 bar−1, twice higher than that of the pristine membrane without sacrificing selectivity. Furthermore, embedding MIL-101(Cr) notably enhanced the stability of the composite membrane, with permeance only decreasing by 8% after a long time operation of 80 h (pristine membrane decreased by 25%). This work demonstrated a composite membrane modified by MIL-101(Cr) with superior separation performance, which provides potential application of MOF materials for high-performance membranes in organic solvent nanofiltration and a theoretical foundation for future research in studying MOF’s influence on membrane properties.

EVALUATION OF DRAW SOLUTIONS FOR FORWARD OSMOSIS USING A SODIUM ALGINATE-BACTERIAL CELLULOSE MEMBRANE FOR WATER RECOVERY

Forward osmosis (FO) is an emerging membrane technology that is comparable with existing industrial membrane separation processes. Several studies have shown the potential of bacterial cellulose-alginate (BCA) as membrane material for FO system. An ideal draw solution (DS) compatible with this material was investigated. The three solutions used in the study include NaCl, MgCl2, and fructose. A simulated dirty water was used as the feed solution (FS) and a BCA as the membrane. An optimization study was conducted using central composite design (CCD) with the aid of Design Expert 7.0.0. The optimization was based on a fitted linear model analyzed through ANOVA with the normalized water flux maximized. The optimal solution was determined to be fructose with operating conditions at an osmotic pressure of 70 bar and a flow rate of 300 mL/min. The normalized water flux given these optimal conditions is predicted to be 1.437 LMH∙mm with a desirability of 0.768.

Assessment of bio-ionic liquids as promising solvents in industrial separation processes: Computational screening using COSMO-RS method

The use of organic solvents in the chemical industry for gas-liquid absorption or liquid-liquid extraction operations is still unavoidable. The search of “greener” solvents to replace fossil-based counterparts is a challenge for the scientific community. Biocompatible ionic liquids (bio-ILs) emerged as a sustainable approach for the development of greener processes. In this work, bio-ILs based on choline as common cation are evaluated as promising solvents in typical industrial separation processes such as gas absorption (refrigerants, CO2, H2S, NH3, or acetone) and liquid-liquid extraction (hydrocarbon separations, denitrogenation, desulfurization, and recovery of value-added compounds and/or contaminants from aqueous streams) by means of COSMO-RS method. Some bio-ILs show competitive behavior compared to the benchmark common ILs solvents for all the solutes evaluated. None of the solvents evaluated is predicted to form two liquid phases in aqueous solutions, so future work should be conducted on finding hydrophobic bio-ILs to perform these separations. On the other hand, bio-ILs in hydrocarbon separations by means of liquid-liquid extraction show competitive results in terms of selectivities (benzoate-based) and partition coefficients (bicarbonate-based) compared to benchmark sulfolane and common ILs previously tested.

Micro- and mesoporous metal-organic frameworks for hydrocarbon separation

The review presents data on the use of porous metal-organic frameworks for the separation of some industrially important hydrocarbon mixtures, such as ethane and ethylene, propane and propylene, benzene and cyclohexane, and xylene isomers. It is shown that enhancing the efficiency of materials based on porous metal-organic frameworks relies on understanding the nature of adsorption sites in their structures, the specifics of interactions between the framework and a particular substrate, and the structural response of the framework (host) as it is filled with guest molecules. The achievements of fundamental studies and unresolved problems related to the use of porous metal-organic frameworks in industrial hydrocarbon separation processes are critically analyzed.&lt;br&gt; The bibliography includes 183 references.

An Adaptive Hydrogen-Bonded Organic Framework for the Exclusive Recognition of p-Xylene.

Separation of xylene isomers is one of the most important but most challenging and energy-intensive separation processes in the petrochemical industry. Here, we report an adaptive hydrogen-bonded organic framework (HOF-29) constructed from a porphyrin based organic building block 4,4',4'',4'''-(porphyrin-5,10,15,20-tetrayl) tetrabenzonitrile (PTTBN), exhibiting the exclusive molecular recognition of p-xylene (pX) over its isomers of o-xylene (oX) and m-xylene (mX), as clearly demonstrated in the single crystal structure transformation and 1 H NMR studies. Single crystal structure studies show that single-crystal-to-single-crystal transformation from the as-synthesized HOF-29 to the pX exclusively included HOF-29⊃pX is triggered by the encapsulation of pX molecules, accompanied by sliding of the 2D layers and local distortion of the ligand, which provides multiple C-H⋅⋅⋅π interactions.

Efficient separation of 1,3‐butadiene fromC4hydrocarbons by flexible metal–organic framework with gate‐opening effect

AbstractEfficient and economical separation of 1,3‐butadiene (C4H6) from C4hydrocarbons is imperative yet challenging in industrial separation processes. Herein, a guest‐induced flexible Mn‐bpdc metal–organic framework (MOF) has been employed to separate C4H6from C4hydrocarbons, includingn‐butene (n‐C4H8),iso‐butene (iso‐C4H8),n‐butane (n‐C4H10), and iso‐butane (iso‐C4H10). Significantly, C4H6can instantaneously induce gate‐opening of Mn‐bpdc MOF at 0.13 bar and 298 K, thus significant amounts of C4H6can be adsorbed, while other C4hydrocarbons cannot induce the gate‐opening even at 1 bar. The uptake selectivities of Mn‐bpdc MOF for C4H6/n‐C4H8and C4H6/iso‐C4H8are up to 40.0 and 45.0 at 298 K and 1 bar, respectively, both surpassing all the reported adsorbents. In addition, breakthrough experiments verify that C4H6/n‐C4H8, C4H6/iso‐C4H8, C4H6/n‐C4H10, C4H6/iso‐C4H10, C4H6/n‐C4H8/n‐C4H10, and C4H6/iso‐C4H8/iso‐C4H10mixtures can be efficiently separated. More importantly, Mn‐bpdc possesses excellent water stability and outstanding regeneration ability for C4H6separation, making it a new benchmark for C4H6purification.

The scientific principles and technological determinants of haemodialysis membranes.

ABSTRACTIn most biological or industrial (including medical) separation processes, a membrane is a semipermeable barrier that allows or achieves selective transport between given compartments. In haemodialysis (HD), the semipermeable membrane is in a tubular geometry in the form of miniscule pipes (hollow fibres) and separation processes between compartments involve a complex array of scientific principles and factors that influence the quality of therapy a patient receives. Several conditions need to be met to accomplish the selective and desired removal of substances from blood in the inner cavity (lumen) of the hollow fibres and across the membrane wall into the larger open space surrounding each fibre. Current HD membranes have evolved and improved beyond measure from the experimental membranes available in the early developmental periods of dialysis. Today, the key functional determinants of dialysis membranes have been identified both in terms of their potential to remove uraemic retention solutes (termed ‘uraemic toxins’) as well subsidiary criteria they must additionally fulfill to avoid undesirable patient reactions or to ensure safety. The production of hundreds of millions of kilometres of hollow fibre membranes is truly a technological achievement to marvel, particularly in ensuring that the fibre dimensions of wall thickness and inner lumen diameter and controlled porosity—all so vital to core solute removal and detoxification functions of dialysis—are maintained for every centimetre length of the fragile fibres. Production of membranes will increase in parallel with the increase in the number of chronic kidney disease (CKD) patients expected to require HD therapies in the future. The provision of high-quality care entails detailed consideration of all aspects of dialysis membranes, as quality cannot in any way be compromised for the life-sustaining—like the natural membranes within all living organisms—function artificial dialysis membranes serve.

Selective Reduction of Niobium(V) Species to Promote Molecular Niobium/Tantalum Separation

The critical metals niobium (Nb) and tantalum (Ta) coexist in mineral sources, requiring a separation step to purify the elements from one another. The industrial separation process by solvent extraction uses stoichiometric hydrofluoric acid to manifest differences in the speciation of these otherwise chemically similar elements. The identification of alternative methods to separate Nb/Ta is desirable for fluoride waste reduction. In pursuit of this goal, the novel complexes [Na(CH3CN)3(Et2O)][M((S)-BINOLate)3] [M = Nb (1-Nb), Ta (1-Ta)] were synthesized and characterized. In electrochemical studies, a reduction event at the potential -2.04 V versus ferrocene/ferrocenium was observed for 1-Nb, whereas 1-Ta exhibited no metal-based waves in the electrochemical window. In addition to the inherent 4d/5d orbital energy differences between Nb/Ta, density functional theory calculations suggest a larger degree of π donation from the ligands to the metal cation in 1-Ta compared to 1-Nb, destabilizing the lowest unoccupied molecular orbital. This phenomenon contributes to a calculated reduction potential difference of ca. 0.75 V, allowing for the selective reduction of 1-Nb and separation of the reduction product through leaching with diethyl ether for a separation factor of 6 ± 2.

Polybenzoxazines in fabrication of separation membranes: A review

• Polybenzoxazine (PBz) use in fabrication of high-performance membranes is reviewed. • PBz is a high thermal, chemical and physical resistance polymer. • Properties and synthesis methods of PBz is introduced and reviewed. • Different types of PBz-based membranes are reviewed. • PBz-based membranes are used in harsh, strong acidic conditions or solvent filtration. The demand on developing new materials for fabricating polymeric membranes is growing progressively in membrane science. Since, novel materials with high chemical, mechanical and thermal resistance are needed to improve membrane separation performance. Low thermal resistance of membrane materials restricts application of polymeric membranes in many industrial separation processes such as membrane distillation or gas separation. Polybenzoxazines (PBzs) could be promising alternatives to fabricate high performance membranes due to outstanding temperature, chemical and physical stability of the resulted membranes. The properties of PBz systems could be easily modified by altering monomers and synthesizing main, side and end chain PBz precursors. In this review, the properties and synthesis methods of PBz is introduced and different types of PBz-based membranes such as ion exchange, electrospun nanofiber, pervaporation, gas separation, solvent resistance and antifouling membranes are reviewed. Most of PBz-based membranes are used in high temperature, harsh, and strong acidic conditions or solvent filtration successfully, approving high performance of these membrane materials. Moreover, the presence of phenolic groups could inherently grant antifouling capacity to these membranes. In addition, the relationship between structure and property of PBZs membranes is surveyed. This review will be beneficial for designing and fabricating membranes from PBz with specific characteristics for applications in harsh conditions.

ILC-based two-layer strategy for economic performance improvement in industrial MPC systems

The conventional LQG based economic performance design has found its difficulty in industrial application and so far, there is still no systematic and effective way to improve economic performance. As learned from the LQG benchmark performance assessment method, the economic performance improvement in MPC systems can be realized through adjusting controller parameters in addition to the well-known setpoints change approach. Therefore, we take advantage of LQG and iterative learning control (ILC) to propose a new two-layer periodical economic performance improvement strategy applicable in industrial MPC systems. By dividing the whole time into multiple intervals called periods and optimize the performance periodically, the economics finally reach its optimal. Promoted twice in a certain period, the performance acquires its first promotion through fixed variance obtained from the lower MPC layer, which transforms the nonlinear economic performance function (EPF) of LQG into a linear one. The ILC-based weight coefficients adjustment algorithm then provides the parameters to the MPC controller in the next period with the updating principle based on the idea of minimizing the tracking error between the current controller economic performance and an optimal one, which realizes the second performance improvement. Room for the second promotion is analyzed and convergence of the algorithm is proved. Finally, the effectiveness and applicability of the strategy are verified via a typical industrial separation process.

Determination and modeling of binary solid-liquid equilibria of para-xylene/meta-xylene, para-xylene/ortho-xylene by DSC method

Solid-liquid equilibria of three binary mixtures consisting of para-xylene, ortho-xylene, meta-xylene and ethylbenzene were investigated in this study using differential scanning calorimetry (DSC) method, the mixtures were cooled to -120 °C and then heated to 20 °C at different heating rates, eutectic phase diagrams were observed for para-xylene/ortho-xylene and para-xylene/meta-xylene binary systems. The freezing point of pure ethylbenzene at atmospheric pressure is around -95 °C, but due to the effect of induction time, the observed freezing temperature is lower than -120 °C, the operation temperature of industrial xylene crystallization separation process is higher than -80 °C traditionally, therefore ethylbenzene will not crystallize in practical process, the phase diagram for para-xylene/ethylbenzene was not achieved. The experimental data were compared with data from other literatures and new features were found. The data were well correlated by Apelblat equation and λH equation, it is significative to provide important engineering data for the separation and purification of xylene mixtures.

Application of a synthesized ionic liquid for possible use in industrial separation problems: A useful tool for solvent selection

A novel ionic liquid (2′,3′-epoxypropyl-N-methyl-2-oxopyrrolidinium salicylate) was assessed for possible use in industrial separation problems. This was conducted using a gas liquid chromatography technique at different temperatures, T = (313.15 – 343.15) K and at atmospheric pressure. The molecular interactions within the ionic liquid were determined for 34 solutes (alkanes, alkenes, alkynes, alcohols, ketones, aromatic compounds, sulphur compound, THF, acetonitrile) and water. Excess thermodynamic properties (enthalpies, ΔH1E,∞, Gibbs free energy, ΔG1E,∞ as well as the entropy term, TrefΔS1E,∞) at infinite dilution were calculated to further elucidate the intermolecular interactions occurring within the ionic liquid and solutes. The separation parameters (selectivity and capacity) values were computed from the activity coefficients at infinite dilution using the retention data obtained utilizing g.l.c to determine the feasibility of the ionic liquid for industrial separation processes. From the calculated selectivities and capacities, the presented ionic liquid can be suitable for the separation of industrial close boiling points mixtures. For the petrochemical separation problems, the investigated ionic liquids showed that large quantities would be required. The influence of cation and anion in the ionic liquid has been discussed. The investigated ionic liquid may be proposed for the separation of azeotropic mixtures such as alkane/alcohols, THF or acetone/alcohols.

Deep eutectic solvent as a possible entrainer for industrial separation problems: Pre-screening tool for solvent selection

Deep eutectic solvents, as a new type of nature-welcoming solvents, have shown a great interest in different areas of science and in solvent extraction for industrial separation processes. In this present study, the infinite dilution activity coefficients γ13∞, have been measured for 31 volatile organic solvents (alkanes, alkenes, alkynes, aromatics, cycloalkanes, cycloalkenes, alcohols, ketones, and thiophene) in the deep eutectic solvent (1-ethyl-1-methylpyrrolidinium bromide + glycerol) prepared at (1:2 molar ratio) measured at temperature ranging from T = (313.15 to 343.15) K and at atmospheric pressure using gas liquid chromatography coupled with thermal conductivity detector (GC-TCD). The values of the partial molar excess enthalpies (ΔH1E,∞), entropies (TrefΔS1E,∞), and Gibbs free energy (ΔG1E,∞) at infinite dilution were calculated from the experimental data of γ13∞ attained over the temperature range mentioned above. Selectivities and capacities for two separation problems (cyclohexane/benzene and acetone/ethanol) were calculated fromγ13∞ and compared to the other investigated DESs, ILs as well as the currently used traditional solvents found from the literature. Furthermore, the selectivity and capacity results proved that the examined DES cannot be utilized in separation of (acetone/ethanol) but can be utilized for cyclohexane/benzene separation.

Maximizing the freeze-dried extract yield by considering the solvent retention index: Extraction kinetics and characterization of Moringa oleifera leaves extracts

A complete chemical characterization of Moringa oleifera leaves was carried out showing a high content of extractives. Extraction kinetics of bioactive compounds present in this fraction were performed by conventional and ultrasound assisted extraction (UAE). A 50% (v/v) hydroalcoholic mixture led to the highest total phenolic compounds yield by conventional solvent extraction, 29.5 ± 0.3 mg per gram of moringa leaves. UAE did not bring any improvement when using hydroalcoholic mixtures probably due to the physical properties of the ethanol aqueous mixtures that affect the UAE performance, such as viscosity and vapor pressure of the mixture. The retention index of the different solvents in the raffinate phase was determined revealing the highest retention index for water, 9.5, and a continuous decrease by increasing ethanol concentration. Retention index is a key parameter in a solvent extraction process since it determines the number of stages in an industrial separation process and it is not usually reported in bioactive compounds extraction. Solvent extraction capacity and the retention index determined the final freeze-dried extract yield.

Monitoring of Groundwater Quality With Cokriging of Geochemical and Geoelectrical Measurements

Abstract The study presents the possibility of using geostatistical methods for monitoring groundwater quality. Poland is one of the largest copper producers in the world. However, the extraction and production of copper requires constant care for the natural environment. Reservoir Żelazny Most which is situated in South – Western Poland was designed to store flotation tailings out of nearby copper mines. It is one of the biggest industrial dumps in the world. The reservoir stores huge amounts of tailings and industrial water. Water migrating from dump to groundwater could be a potential source of contamination with chlorides, sulphates, heavy metals, and other hazardous substances used in ore separation process in the copper mining industry, like detergent and phenols. Monitoring system around Żelazny Most dump, which was designed to track harmful substances concentrations in groundwater, contains measuring wells and piezometers. They are used to collect groundwater samples for chemical analyses. The idea of the study was to integrate information provided by chemical analyses and geoelectrical measurements by cokriging method, utilizing correlation between electrical resistance of the soil solution and total dissolved solids concentration in groundwater. This enabled to obtain spatial distribution of total dissolved solids concentrations in groundwater at the part of eastern foreground of Żelazny Most dump.