Piperazine Solution Research Articles

Rapid in-situ covalent crosslinking to construct a novel azo-based interlayer for high-performance nanofiltration membrane

The strategy of introducing a hydrophilic interlayer (IL) on the substrate has been widely used in the preparation of nanofiltration (NF) membranes. In this paper, we perform a rapid in-situ coupling reaction of tannic acid (TA) and a dual diazonium salt (DDS) to construct a novel stable azo-based interlayer on the polysulfone (PSf) ultrafiltration membrane. Through exploring the concentration and the deposition time of TA, the protocol of fabricating the interlayer with the optimal hydrophilicity is determined. Relevant characterizations indicate that the thickness of the interlayer is quite thin, and the defects at the surface of the pristine substrates disappear after modification. Interestingly, the color of the substrate with interlayer changes dramatically after pouring piperazine (PIP) solution thereon, implying that there is considerable interaction between the phenolic hydroxyl groups at the interlayer and the PIP molecules in aqueous phase. By further reducing the PIP concentration, an active layer of which thickness is only about 35 nm was obtained. The separation performance evaluation suggests that the optimized novel NF membrane exhibits a 2.71-fold increase in water permeance (17.40 ± 1.09 L m−2h−1 bar−1) compared with the conventional one. Moreover, the discussion about the role of the interlayer on interfacial polymerization (IP) is also provided with advanced significance.

Integration of CO2 capture unit with membrane distillation technology: CO2 mitigation and freshwater production

The severe consequences of carbon dioxide (CO2) emissions into the atmosphere and a dire need for freshwater are among the biggest global challenges. The desire to meet these challenges has given rise to the motivation of proposing a direct contact membrane distillation (DCMD) technology integrated with the CO2 capture unit to mitigate CO2 and simultaneously produce freshwater. The CO2 capture unit has been modeled with Aspen Plus® V.10 and for the DCMD system, MATLAB software was adopted. MATLAB software was not linked to the Aspen Plus®. Thermal heat contained in both the purged gas and leanout stream was recovered by using a DCMD unit. A blended solution of methyldiethanolamine (MDEA) and piperazine (PZ) was considered as an absorbent to remove CO2 from the flue gas of a large-scale coal-fired power plant (650 MWe). About 85 % of the CO2 in the flue gas has been captured from the top of the stripper column. At MDEA/PZ (concentration ratio of MDEA and PZ in the aqueous solution) concentration of 30/20 wt.%, a reboiler duty of 3.27 MJ/kg CO2 was obtained. Freshwater was produced at a rate of 25.43 m3/day from DCMD unit 1 and 1428.19 m3/day from unit 2.

Vacuum-assisted diamine monomer distribution for synthesizing polyamide composite membranes by interfacial polymerization

Polyamide composite membranes are still required to promote their structure uniformity and desalination performance. Herein, a vacuum-assisted strategy was used to deal with this challenge by improving the distribution homogeneity of diamine monomer in porous substrates for typical interfacial polymerization. Laser scanning confocal microscope analyses demonstrate that the piperazine solution can be adsorbed in the microporous substrates with a very homogeneous and stable way. This uniform diamine distribution shows great advantages for synthesizing the selective layers of polyamide on the substrate surfaces via the interfacial polymerization of piperazine and trimesoyl chloride. The as-prepared polyamide layers with a circular size of 30 cm exhibit uniform structures including thickness less than 20 nm, cross-linking degree up to 100%, surface roughness lower than 20 nm and pore diameter about 0.41 nm. Therefore, the polyamide composite membranes present nanofiltration performances of ultrahigh rejection above 99.6% to Na2SO4 and high water permeability of 20 L/m2 h bar. These membranes also show a promising selectivity for NaCl/Na2SO4 up to 196, which is higher than most of the commercial and the reported nanofiltration membranes in recent years.

Prediction of CO2 Mass Transfer Flux in Aqueous Amine Solutions Using Artificial Neural Networks

In the present research, neural networks were applied to predict mass transfer flux of CO2 in aqueous amine solutions. Buckingham π theorem was used to determine the effective dimensionless parameters on CO2 mass transfer flux in reactive separation processes. The dimensionless parameters including CO2 loading, the ratio of CO2 diffusion coefficient of gas to a liquid, the ratio of the CO2 partial pressure to the total pressure, the ratio of film thickness of gas to liquid and film parameter as input variables and mass transfer flux of CO2 as output variables were in the modeling. A multilayer perceptron network was used in the prediction of CO2 mass transfer flux.As a case study, experimental data of CO2 absorption into Piperazine solutions were used in the learning, testing, and evaluating steps of the multilayer perceptron. The optimal structure of the multilayer perceptron contains 21 and 17 neurons in two hidden layers. The predicting results of the network indicated that the mean square error for mass transfer flux was 4.48%. In addition, the results of the multilayer perceptron were compared with the predictions of other researchers’ results. The findings revealed that the artificial neural network computes the mass transfer flux of CO2 more accurately and more quickly.

Chemical Absorption of Carbon Dioxide into Aqueous Piperazine Solutions Using a Stirred Reactor

In this work, the absorption of CO2 using aqueous piperazine (PZ) solution have been investigated both experimentally and theoretically. The absorption experiments were carried out in a stirred batch contactor with two flat blades. The experimental data are obtained over the temperature range of 298–338 K and for the PZ concentration, CO2 partial pressure, and the stirrer speed in the range of 0.5–1.5 kmol/m3, 2.5-7.5 bar, and 0-300 rpm, respectively. The influences of each variable upon the absorption flux, removal efficiency, and loading of CO2 have been investigated. In addition, a model based on chemical equilibrium in the liquid phase is employed to evaluate the concentration of chemical species in the liquid phase. Evidence suggests that CO2 absorption flux, removal efficiency, and the loading increase with decreasing the temperature and increasing the stirrer speed. When PZ concentration is increased, the absorption flux and removal efficiency increase and CO2 loading reduce. Also by increasing PZ concentration from 0.5 to 1.5 M at a temperature of 388 K, absorption efficiency is increased from 70 % to 95 %. CO2 absorption flux was decreased from about 0.0175 to 0.01 mol/m2 s when CO2 loading was increased from 0.32 to 0.51.

Mass Transfer Modeling of CO2 Absorption into Blended Aqueous MDEA–PZ Solution

In this research, the rate of CO2 absorption into methyl diethanolamine–piperazine (MDEA–PZ) solution was investigated. To model the mass transfer flux in the reactive absorption processes, the dimensionless parameters of the process were obtained using the Buckingham Pi theorem and considering the effective parameters in mass transfer. The CO2 mass transfer flux in the reactive absorption process depends on the mass transfer parameters of both the liquid and gas phases. Based on the dimensionless parameters obtained, a correlation is proposed to calculate the mass transfer flux of acidic gases in MDEA–PZ solutions. The mass transfer flux in the reactive absorption process is modeled based on the four laws of chemical equilibrium, phase equilibrium, mass balance, and charge balance. Experimental data from the literature were used to determine the constants of the derived correlation as a function of dimensionless parameters. In the provided correlation, the effects of dimensionless parameters including film parameter, CO2 loading, ratio of diffusion coefficients in the gas–liquid phase, CO2 partial to total pressure, and film thickness ratio as well as factors such as temperature, the number of free amines in the solution, the partial pressure of CO2, on the CO2 mass transfer flux were investigated. According to the results, the absorption rate decreases with increasing CO2 loading and film parameter, and the mean absolute deviation is about 3.6%, which indicates the high accuracy of the correlation.

Numerical simulation of CO2 chemical absorption in a gas-liquid bubble column using the space-time CESE method

Abstract In this study, numerical simulation of the removal process of CO2 using aqueous solutions of piperazine (PZ) in a bubble column has been done. The main focus of this work is to investigate the applicability of the space-time conservation element and solution element (CESE) method for the numerical solution of the coupling of hydrodynamics, mass transfer and chemical reactions. The reactive absorption process has been investigated by means of experiments and numerical simulation. A two-dimensional computational fluid dynamics (CFD) model in the Eulerian framework has been used to describe the gas-liquid system. To obtain the numerical solution, the CESE method based on a uniform rectangular mesh has been implemented by developing a computer code. Experimental study and CFD simulations have been carried out at different conditions of CO2 partial pressure (20 and 36 kPa) and solution concentration (0.1, 0.3 and 0.5 M). The simulation results were in reasonable agreement of 5.226 % and 4.575 % with the experimental values for gas holdup and mass transfer flux, respectively. The comparisons prove that the CESE method can be considered as a proper numerical method for the simulation of complex multiphase flows due to its simplicity, accuracy and low computational costs.

Modeling and validation of carbon dioxide absorption in aqueous solution of piperazine + methyldiethanolamine by PC-SAFT and E-NRTL models in a packed bed pilot plant: Study of kinetics and thermodynamics

A pilot plant with a closed cycle of the absorption/desorption process has been taken into account for the simulation of carbon dioxide (CO2) capture by piperazine (PZ) + methyldiethanolamine (MDEA) solution using Aspen Plus rate-based model with all design and operational parameters such as the hydraulic specifications of absorber and stripper as well as inlet flue gas conditions which are present in a commercial gas-fired burner for heating houses. Metal FLEXIPAC 250Y has been considered as the packing type to apply the model to the proposed correlations on Aspen Plus for calculation of flooding and pressure drop. In order to simulate the process, a new property package has been developed by electrolyte non-random two-liquid (E-NRTL) model and perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state which are used for the calculation of activity and fugacity coefficients respectively. The model has been compared with some experimental data e.g. CO2 absorption efficiency and CO2 loading and demonstrated good agreement with them.

Volumetric and viscometric properties of ternary solution of (piperazine +2-Amino-2-methyl-1-propanol + H2O) at T = (303.15–343.15) K

The densities and viscosities of ternary solution of piperazine (PZ) + 2-Amino-2-methyl-1-propanol (AMP) + H2O were measured at P = 101 kPa and T = (303.15–343.15) K. The effects of temperature and concentration on the density and viscosity of ternary solution were investigated. The apparent molar volume (Vφ), the limiting partial molar volume (Vφ0), viscosity B-coefficient, Helper's constant and the free energies of activation per mole of solvent (Δμ10≠) and solute (Δμ20≠) were calculated from the density and viscosity, respectively. The solute-solute and solvent-solute interactions were analyzed from the volumetric and viscometric properties. The results show that the PZ has a destructive effect on the structure of mixed solvent.

Experimental Modeling and Optimization of CO2 Absorption into Piperazine Solutions Using RSM-CCD Methodology.

The present work evaluates and optimizes CO2 absorption in a bubble column for the Pz-H2O–CO2 system. We analyzed the impact of the different operating conditions on the hydrodynamic and mass-transfer performance. For the optimization of the process, variable conditions were used in the multivariate statistical method of response surface methodology. The central composite design is used to characterize the operating condition to fit the models by the least-squares method. The experimental data were fitted to quadratic equations using multiple regressions and analyzed using analysis of variance (ANOVA). An approved experiment was carried out to analyze the correctness of the optimization method, and a maximum CO2 removal efficiency of 97.9%, an absorption rate of 3.12 g/min, an NCO2 of 0.0164 mol/m2·s, and a CO2 loading of 0.258 mol/mol were obtained under the optimized conditions. Our results suggest that Pz concentration, solution flow rate, CO2 flow rate, and speed of stirrer were obtained to be 0.162 M, 0.502 l/h, 2.199 l/min, and 68.89 rpm, respectively, based on the optimal conditions. The p-value for all dependent variables was less than 0.05, and that points that all three models were remarkable. In addition, the experiment values acquired for the CO2 capture were found to agree satisfactorily with the model values (R2 = 0.944–0.999).

Simultaneous Absorption of H2S and CO2 into the MDEA + PZ Aqueous Solution in a Rotating Packed Bed

This work presented experimental and modeling studies on the simultaneous absorption of H2S and CO2 into the N-methyldiethanolamine (MDEA) and piperazine (PZ) solution in a rotating packed bed (RPB...

Piperazine impregnation on Zeolite 13X as a novel adsorbent for CO2 capture: experimental and modeling

Zeolite 13X was modified using a piperazine solution for CO2 adsorption purposes. The operating parameters including temperature, pressure, piperazine concentration, adsorbent amount, and particle size are investigated experimentally to examine adsorption capacity. The maximum adsorption capacity was obtained at temperature of 25°C, pressure of 8 bar, piperazine concentration 2 wt.%, adsorbent amount of 1 g, and particle size of 200 µm. The adsorption capacity for Zeolite 13X is increased from 193.844 to 242.084 mg g−1 after modification. The empirical isotherm data are more consistent with Freundlich model. The best adsorption kinetic model was Elovich model. The thermodynamic parameters represent the spontaneous and exothermic of the process.

Monitoring the Interfacial Polymerization of Piperazine and Trimesoyl Chloride with Hydrophilic Interlayer or Macromolecular Additive by In Situ FT-IR Spectroscopy.

The interfacial polymerization (IP) of piperazine (PIP) and trimesoyl chloride (TMC) has been extensively utilized to synthesize nanofiltration (NF) membranes. However, it is still a huge challenge to monitor the IP reaction, because of the fast reaction rate and the formed ultra-thin film. Herein, two effective strategies were applied to reduce the IP reaction rate: (1) the introduction of hydrophilic interlayers between the porous substrate and the formed polyamide layer, and (2) the addition of macromolecular additives in the aqueous solution of PIP. As a result, in situ Fourier transform infrared (FT-IR) spectroscopy was firstly used to monitor the IP reaction of PIP/TMC with hydrophilic interlayers or macromolecular additives in the aqueous solution of PIP. Moreover, the formed polyamide layer growth on the substrate was studied in a real-time manner. The in situ FT-IR experimental results confirmed that the IP reaction rates were effectively suppressed and that the formed polyamide thickness was reduced from 138 ± 24 nm to 46 ± 2 nm according to TEM observation. Furthermore, an optimized NF membrane with excellent performance was consequently obtained, which included boosted water permeation of about 141–238 (L/m2·h·MPa) and superior salt rejection of Na2SO4 > 98.4%.

An Integrated Methodology towards Mitigation of Global Warming and Biomass Production for Biodiesel using Chlorella sorokiniana BTA 9031

The rise of atmospheric carbon dioxide (CO2)concentration as well as depletion of fossil fuel reserves calls for the development of clean and ecofriendly alternative fuel source. Recently, lipid rich microalgal biomass is being extensively studied for generation of biodiesel however, the expensesincurred on production of microalgal biomassis a significant hurdle. Almost 80 % of the production costis generated from the cultivation medium which majorly comprise of carbon, nitrogen and phosphate. If the microalgal cultivation could be linked to a CO2 capturing unit than the cost of production could be reduced to a large extent. CO2 absorption by means of aqueous amine solvents is known to be a mature technology and could be integrated with microalgal cultivation unit for efficient utilization of the captured CO2. In this present research work, blended solution of piperazine (PZ) and2-amino-2-methyl-1-propanol (AMP) (5/25 wt. %) was used to capture CO2 and then the captured CO2 was utilized as an inorganic carbon stream for growing Chlorella sorokiniana BTA 9031 for biodiesel production. The CO2rate absorption was governed by series of process variablesviz.solvent flow rate ranges (1.5 to 3) ×10⁻4 m3 min-1, absorption temperature (298 to 313) K,concentration of CO2 (10 to 15) kPa and gas flow rate(5 to 8) ×10⁻3 m3 min-1. The detected final biomass strengthofChlorella sorokiniana BTA 9031 was0.955g L-1. The fatty acid methyl esters (FAME) determinedsubsequentlyacid transesterification was observed to contain fatty acids suitable for biodiesel production.

Experimental study of carbon dioxide absorption by mixed aqueous solutions of methyl diethanolamine (MDEA) and piperazine (PZ) in a microreactor

In this study, chemical absorption of carbon dioxide (CO2) was performed by using MDEA+PZ (aMDEA) solvent. A T-shaped microreactor mixer was used as the mass transfer device to improve the absorption rate. Operating conditions used in this study were operating temperature (15–55°C), input solvent flow rate (0–0.4lmin−1), inlet gas flow rate (1-9lmin−1), and amine concentration in the solvent (0–40 weight percent). All the experiments were carried out at atmospheric pressure and CO2 concentration of 10% in the feed gas. The central composite design method was used to set an experimental design. The results of optimization showed that the use of a microreactor for CO2 adsorption using aMDEA solvent significantly increased the total coefficient of mass transfer in the gas phase, as compared with other mass transfer devices. The maximum value obtained through the model within the range of operating variables for the response (total mass transfer coefficient in the gas phase) was 1769kmolm−3h−1kPa−1.

P-Phenylenediamine-grafted multi-walled carbon nanotubes as a hydrophilic modifier in thin-film nanocomposite membrane

In this paper, an efficient thin-film nanocomposite (TFN) membrane was synthesized by interfacial polymerization and used for water desalination. Piperazine (PIP) and trimesoyl chloride were used as monomers, and p-phenylenediamine-grafted multi-walled carbon nanotube (p-PDA-MWCNT) was used as a hydrophilic modifier to enhance the performance of the polysulfone nanofiltration membrane. In order to characterize the synthesized p-PDA-MWCNTs, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and electron-dispersive spectroscopy were used. In order to enhance the performance of the membrane, different concentrations of p-PDA-MWCNTs (0.01, 0.02, 0.04, 0.05 and 0.075 wt%) were added to the PIP solution to prepare p-PDA-MWCNTs-embedded membranes. To check the performance of the modified membrane, solutions of 1000 mg L−1 Na2SO4, MgSO4, NaCl and CaCl2 were tested. The results show that TFN-modified membrane provides excellent water permeability and also salt rejection in the presence of 0.02 wt% p-PDA-MWCNTs which shows superior improvement in TFN membrane.

Evaluation of a modified spray‐applied interfacial polymerization method for preparation of nanofiltration membranes

ABSTRACTNanofiltration (NF) membranes were fabricated by using piperazine (PIP) and trimesoyl chloride (TMC) by conventional and spray‐applied interfacial polymerization methods, studying the effect of the application method for both phases, the number of applied layers, and the displacement speed for the spray application. A polysulfone ultrafiltration membrane was used as support. NF membranes were characterized by different spectroscopic, microscopic, and physicochemical techniques. Rejection capacity was evaluated for sodium chloride (NaCl), sodium sulfate (Na2SO4), and magnesium sulfate (MgSO4) salts; the decreasing rejection order was Na2SO4 > MgSO4 > NaCl for each NF membrane. NF membrane prepared with one layer of the sprayed out TMC solution and conventional application of PIP solution exhibited the highest salt rejection (99% for 1000 ppm Na2SO4) and a permeated flux of 10.28 L m−2 h−1 at 0.55 MPa. The modified method is a facile‐reproducible preparation methodology that reduces the consumption of time, effort, and reagents leading to a scalable manufacturing process for separation technology. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48129.

Effect of adding a smart potassium ion-responsive copolymer into polysulfone support membrane on the performance of thin-film composite nanofiltration membrane

Thin-film composite (TFC) nanofiltration (NF) membranes were fabricated via the interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride on polysulfone (PSf) support membranes blended with K+-responsive poly(N-isopropylacryamideco-acryloylamidobenzo-15-crown-5) (P(NIPAM-co-AAB15C5)). Membranes were characterized by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscope, scanning electron microscope, contact angle, and filtration tests. The results showed that: (1) Under K+-free conditions, the blended P(NIPAM-co-AAB15C5)/PSf supports had porous and hydrophilic surfaces, thereby producing NF membranes with smooth surfaces and low MgSO4 rejections; (2) With K+ in the PIP solution, the surface roughness and water permeability of the resultant NF membrane were increased due to the K+-induced transition of low-content P(NIPAM-co-AAB15C5) from hydrophilic to hydrophobic; (3) After a curing treatment at 95 °C, the improved NF membrane achieved an even higher pure water permeability of 10.97 L⋅m-2⋅h-1⋅bar-1 under 200 psi. Overall, this study provides a novel method to improve the performance of NF membranes and helps understand the influence of supports on TFC membranes.

Thermodynamic modelling of CO2 absorption into aqueous solutions of 2-diethylaminoethanol, piperazine, and blended diethylaminoethanol with piperazine

In this study, the Deshmukh–Mather (D-M) model was used to evaluate the equilibrium behaviour of CO2 + diethylaminoethanol (DEAE) + H2O, CO2 + piperazine (PZ) + H2O, and CO2 + DEAE + PZ + H2O systems. The binary interaction parameters of the model for mentioned systems were obtained by using experimental solubility data from the literature. The ability of the model to predict the concentration profiles for all chemical species present in the liquid phase at different concentrations of amine solution was tested. The excess properties such as Gibbs energy, enthalpy, and heat capacity as a function of the CO2 loading of the amine were obtained. The solution pH and activity coefficients were also investigated. The results of thermodynamic modelling indicated that the D-M model predicted the experimental data with average absolute relative deviations (AARDs) of 7.15%, 11.3%, and 8.65%, respectively, for the CO2 + DEAE + PZ + H2O, CO2 + PZ + H2O, and CO2 + DEAE + H2O systems. The model applied in this study can be used for process simulation based on the rate-based or equilibrium-stage models of CO2 absorption with DEAE + PZ solutions.

Efficient hybrid modeling of CO2 absorption in aqueous solution of piperazine: Applications to energy and environment

Carbon dioxide (CO2) considerably contributes to the greenhouse effects and consequently, to the global warming. Thus, reduction of CO2 emissions/concentration in the atmosphere is an important goal for various industrial and environmental sectors. In this research work, we study CO2 capture by its absorption in mixtures of water and piperazine (PZ). Experimental techniques to obtain the equilibrium data are usually costly and time consuming. Thermodynamic modeling by Equations of State (EOSs) and connectionist tools leads to more reliable and accurate results, compared to the empirical models and analytical modeling strategies. This research work utilizes Genetic Programming (GP) and Genetic Algorithm-Adaptive Neuro Fuzzy Inference System (GA-ANFIS) to estimate the solubility of CO2 in mixtures of water and piperazine (PZ). In both methods, the input parameters are temperature, partial pressure of CO2, and concentration of PZ in the solution. A total number of 390 data points is collected from the literature and used to develop GP and GA-ANFIS models. Assessing the models by the statistical methods, both models are found to acceptably predict the CO2 solubility in water/PZ mixtures. However, the GP exhibits a superior performance, compared to GA-ANFIS; the values of Average Absolute Relative Error (AARD) are 5.3213% and 9.7143% for the GP and GA-ANFIS models, respectively. Such reliable predictive tools can assist engineers and researchers to effectively determine the key thermodynamic properties (e.g., solubility, vapor pressure, and compressibility factor) which are central to design and operation of the carbon capture processes in a variety of chemical plants such as power plants and refineries.