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1.
The kinetics of CO2 absorption into aqueous solutions of N,N‐diethylethanolamine (DEEA), and N,N‐dimethylethanolamine (DMEA), and their blends with monoethanolamine (MEA) have been studied in a stopped‐flow apparatus. The kinetics experiments were carried out at the concentrations of DEEA and DMEA varying from 0.075 to 0.175 kmol/m3, respectively, and that of MEA ranging between 0.0075 and 0.0175 kmol/m3, over the temperature range of 293–313 K. Two kinetics models are proposed to interpret the reaction in the blended amine systems and the results show that the model which incorporates the base‐catalyzed hydration mechanism and termolecular mechanism resulted in a better prediction. Furthermore, the kinetics behaviors of CO2 absorption into two blended systems are comprehensively discussed according to their molecular structures. It can be concluded that the interaction between tertiary amines and primary amines as well as the alkyl chain length of tertiary amines have a significant influence on the kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1350–1358, 2018  相似文献   

2.
CO2 solubility data are important for the efficient design and operation of the acid gas CO2 capture process using aqueous amine mixture. 2-(Diethylamino)ethanol (DEEA) solvent can be manufactured from renewable sources like agricultural products/residue, and 1,6-hexamethyldiamine (HMDA) solvents have higher absorption capacity as well as reaction rate with CO2 than conventional amine-based solvents. The equilibrium solubility of CO2 into aqueous binary mixture of DEEA and HMDA was investigated in the temperature range of 303.13-333.13 K and inlet CO2 partial pressure in the range of 10.133-20.265 kPa. Total concentration of aqueous amine mixtures in the range of 1.0-3.0 kmol/m3 and mole fraction of HMDA in total amine mixture in the range of 0.05-0.20 were taken in this work. CO2 absorption experiment was performed using semi-batch operated laboratory scale bubble column to measure equilibrium solubility of CO2 in amine mixture, and CO2 absorbed amount in saturated carbonated amine mixture was analyzed by precipitation-titration method using BaCl2. Maximum equilibrium CO2 solubility in aqueous amine mixture was observed at 0.2 of HMDA mole fraction in total amine mixture with 1.0 kmol/m3 total amine concentration. New solubility data of CO2 in DEEA+HMDA aqueous mixtures in the current study was compared with solubility data available in previous studies conducted by various researchers. The study shows that the new absorbent as a mixture of DEEA+HMDA is feasible for CO2 removal from coal-fired power plant stack gas streams.  相似文献   

3.
Aqueous solutions of MDEA, MDEA + DEA and MDEA + MEA containing 4.2 kmol/m3 total amine, were contacted with CO2 at a partial pressure of 2.58 MPa and temperatures ranging from 120 to 180°C, in a stainless steel batch reactor. The reaction products include the known degradation compounds of the amines as well as products formed from secondary interactions in the amine blends. The rate of degradation was first order in the amines and, in magnitude, followed the sequence MDEA < MEA < DEA. Furthermore, the rate constant for MDEA was independent of amine substitution level and blend constituents. From a practical standpoint, MDEA + DEA blends would require frequent DEA make-up to maintain treating efficiency.  相似文献   

4.
张瑞  李末霞  罗潇  梁志武 《化工学报》2015,66(9):3719-3725
利用13C NMR技术对CO2捕获叔胺溶剂进行了碳元素的定量研究,主要考察了对胺溶剂解吸热影响较大的HCO3-的生成规律。重点对叔胺分子结构中羟基官能团(-OH)、羟烷基数目、烷基支链及氮原子(N)所连接烷基链大小对胺溶剂生成HCO3-的影响。在20℃条件下分别对1 mol·L-1具有不同CO2负载的1-二甲基氨基-2-丙醇(1DMA2P)、N-甲基二乙醇胺(MDEA)、3-二甲氨基-1-丙醇(3DMA1P)、二乙氨基-2-丙醇(1DEA2P)、N,N-二乙基乙醇胺(DEEA)、N,N-二甲基乙醇胺(DMMEA)及三乙醇胺(TEA)溶液进行了13C NMR测试研究。实验结果显示:在相同浓度的叔胺水溶液中,同一CO2负载下的叔胺-CO2-水体系中HCO3-的含量顺序为:DMMEA > MDEA>3DMA1P > 1DMA2P > TEA > DEEA > 1DEA2P。通过对各叔胺分子结构中N原子的电子云密度大小及空间位阻效应分析,得出如下结论:3DMA1P分子中-OH官能团离N原子的距离大于其在DMMEA分子中的距离,导致其生成了较少的HCO3-;DMMEA分子中N原子上连接的烷基链小于DEEA分子中N原子上的烷基链,导致DMMEA溶液中生成了更多的HCO3-;MDEA分子中羟烷基数目少于TEA分子中的羟烷基数目,且MDEA比TEA多了一个甲基,导致MDEA溶液中含有更多的HCO3-;3DMA1P相比1DMA2P、DEEA相比1DEA2P分子中都少了一个甲基支链,导致3DMA1P溶液相比1DMA2P溶液、DEEA溶液相比1DEA2P溶液生成了更多的HCO3-。  相似文献   

5.
N‐Ethylethanolamine (EEA) and N,N‐diethylethanolamine (DEEA) represent promising candidate alkanolamines for CO2 removal from gaseous streams, as they can be prepared from renewable resources. In this work, the reaction rate constant for the reaction between CO2 and EEA was determined from the absorption rate measurements of CO2 in a blend comprising DEEA, EEA and H2O. A stirred‐cell reactor with a plane, horizontal gas‐liquid interface was used for the absorption studies. While the DEEA concentration in the formulated solution was varied in the range of 1.5–2.5 kmol/m3, the initial EEA concentration was 0.1 kmol/m3. A zwitterion mechanism for EEA and a base‐catalyzed hydration mechanism for DEEA were used to describe the reaction kinetics. At 303 K, the second‐order reaction rate constant for the CO2 reaction with EEA was found to be 8041 m3/(kmol s). The liquid‐side mass transfer coefficient was also estimated, and its value (0.004 cm/s) is in line with those typical of stirred‐cell reactors.  相似文献   

6.
The solubility of hydrogen sulfide and carbon dioxide in an aqueous solution containing 35 wt% methyldiethanolamine (MDEA) (3.04 kmol/m3, 4.52 mol/kg) has been measured at 40° and 100°C at partial pressures of the acid gas up to 530 kPa. Some data for hydrogen sulfide in a 50 wt% solution of MDEA (4.38 kmol/m3, 8.39 mol/kg) were also obtained. Also, densities of CO2-aqueous MDEA solutions were measured at 40°C.  相似文献   

7.
By mixing an aqueous solution of tertiary amine, N,N‐dimethylethanolamine (DMEA), with naphthenic acid (RCOOH) derived from heavy oil, a CO2 switchable zwitterionic surfactant (RCOO?DMEAH+) aqueous system was constructed. The CO2 switchability of this zwitterionic surfactant was confirmed by visual inspection, pH measurements, and conductivity tests, i.e., the RCOO?DMEAH+ decomposed into RCOOH, DMEAH+ and HCO3? after bubbling CO2 through but switched back to its original state by subsequent bubbling N2 through at 80 °C to remove the CO2. The interfacial tension tests of heavy oil in DMEA aqueous solutions indicated that the solution containing 0.5 wt% of DMEA and 0.2 wt% of NaCl resulted in the lowest interfacial tension. The O/W emulsion formed when aqueous solutions of DMEA were used to emulsify heavy oil exhibited the best performance when the oil/water volume ratio, DMEA concentration, and NaCl concentration were 65:35, 0.5 and 0.2 wt%, respectively. The feasibility of pipeline transport of the O/W heavy oil emulsion was evaluated. The results illustrated that the demulsification of the O/W emulsion after transport could be easily realized by bubbling CO2 through. Although demulsification efficiency still needs to be improved, the recycling of the aqueous phase after demulsification by removal of CO2 looks promising.  相似文献   

8.
2-Amino-2-methyl-1-propanol (AMP), which is the sterically hindered form of monoethanolamine (MEA), is a credible substitute to conventional CO2-capturing solvents. Its performance can be improved by blending with a highly reactive polyamine promoter. Two such aqueous blends of AMP/TETA and AMP/TEPA were chosen here (TETA = triethylenetetramine and TEPA = tetraethylenepentamine). The kinetics of CO2 absorption in the proposed blends was investigated at 308, 313, and 318 K using the stirred cell technique. The concentrations of AMP and polyamine were varied between 2 to 3 kmol/m3 and 0.1 to 0.5 kmol/m3, respectively. From the measured values of the fast pseudo-first order constants, the second-order rate constants for the reactions of CO2 with TETA (14 695 m3/(kmol s)) and TEPA (19 250 m3/(kmol s)) were determined at T = 313 K. Both TETA and TEPA react faster with CO2 than MEA. Further, the respective activation energy values were found (40 and 37 kJ/mol). Finally, the equilibrium solubility of CO2 for both blends was measured at T = 303 K. The loading capacity was higher than that for the aqueous blends of AMP/MEA, AMP/DEA, and AMP/MDEA (here, DEA and MDEA denote diethanolamine and N-methyldiethanolamine). The highest value of loading capacity (1.12 mol CO2/mol amine at 2.01 kPa equilibrium partial pressure of CO2) was noted in AMP/TEPA mixtures. The new findings on our proposed blends will strengthen the AMP/polyamine application in CO2 separation.  相似文献   

9.
Among numerous techniques existing for reducing CO2 emissions, CO2 capture by absorption in aqueous alkanolamine solutions was specifically studied in this work. For the choice of the adequate amine solution, two major criteria must be taken into account: absorption performances (higher with primary and secondary amines) and energy costs for solvent regeneration (more interesting with tertiary and sterically hindered amines). The different types of amines can also be mixed in order to combine the specific advantages of each type of amines, an activation phenomenon being observed. Aqueous solutions of (piperazinyl‐1)‐2‐ethylamine (PZEA, a polyamine known as absorption activator) and 1‐amino‐2‐propanol (AMP, a sterically hindered amine), pure or mixed with other amines, are experimentally compared with respect to CO2 removal performances by means of absorption test runs achieved in a special gas‐liquid contactor at 25 °C. The positive impact of addition of PZEA to monoethanolamine (MEA), N‐methyldiethanolamine (MDEA), and AMP solutions was clearly highlighted. The absorption performances have also been satisfactorily simulated with coherent physicochemical data.  相似文献   

10.
The mass transfer performance of CO2 absorption into blended N,N‐diethylethanolamine (DEEA)/ethanolamine (MEA) solutions was investigated using a lab‐scale absorber (H = 1.28 m, D = 28 mm) packed with Dixon ring random packing. The mass transfer coefficient KGav, the unit volume absorption rate Φ, outlet concentration of CO2 (yCO2), and the bottom temperature Tbot of CO2 in aqueous DEEA/MEA solutions were determined over the feed temperature range of 298.15–323.15 K, lean CO2 loading of 0.15–0.31 mol/mol, over a wide range of liquid flow rate of 3.90–9.75 m3/m2‐h, by using inert gas flow rate of 26.11–39.17 kmol/m2‐h and 6–18 kPa CO2 partial pressure. The results show that liquid feed temperature, lean CO2 loading, liquid flow rate, and CO2 partial pressure had significant effect on those parameters. However, the inert gas flow rate had little effect. To allow the mass transfer data to be really utilized, KGav and yout correlations for the prediction of mass transfer performance were proposed and discussed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3048–3057, 2017  相似文献   

11.
Absorption rates for CO2 into aqueous solutions of TEA, MDEA and blends of MEA with MDEA and TEA were measured in a stirred cell by a method similar to that used by Laddha and Danckwerts (1981). Second order rate constants for CO2-TEA and CO2-MDEA were obtained from the single amine data for temperatures in the range of 25-60°C. A modified pseudo first order model based on the film theory is used to predict the rate of absorption of CO2 into mixed amine solutions. This model accounts for the variation of amine concentration in the film and assumes a shuttle mechanism for rate enhancement. Bulk liquid concentrations of the various species present are obtained from a simplified thermodynamic model. The model predicts absorption rates that are in agreement with experimental measurements.  相似文献   

12.
Ternary diffusion coefficients of monoethanolamine (MEA) and N-methyldiethanolamine (MDEA) in aqueous solutions have been measured at 303.2, 313.2, and 323.2 K. The systems studied are aqueous solutions containing total amine concentrations of 2.5 and 4.0 kmol/m3 and each solution prepared with four different amine molar ratios. The main diffusion coefficients (D11 and D22) and cross-diffusion coefficients (D12 and D21) and the density and viscosity of the aqueous amine solutions are discussed and analyzed as a function of temperature and their concentration.  相似文献   

13.
Literature data on the rates of reaction between CO2 and alkanolamines (MEA, DEA, DIPA, TEA and MDEA) in aqueous solution are discussed. These data induced us to carry out absorption experiments of CO2 into aqueous DEA, DIPA, TEA and MDEA solutions from which the respective rate constantsThe results for DEA and DIPA were analysed by means of a zwitterion-mechanism which was derived from the mechanism originally proposed by Danckwerts [1The reaction rate of CO2 with aqueous TEA and MDEA solutions shows a significant base catalysis effect which is also reported by Donaldson and Nguy  相似文献   

14.
Literature data on the rates of reaction between CO2 and alkanolamines (MEA, DEA, DIPA, TEA and MDEA) in aqueous solution are discussed. These data induced us to carry out absorption experiments of CO2 into aqueous DEA, DIPA, TEA and MDEA solutions from which the respective rate constants were derived. The experimental technique was similar to that used by Laddha and Danckwerts[30].The results for DEA and DIPA were analysed by means of a zwitterion-mechanism which was derived from the mechanism originally proposed by Danckwerts[16The reaction rate of CO2 with aqueous TEA and MDEA solutions shows a significant base catalysis effect which is also reported by Donaldson and Nguy  相似文献   

15.
《Chemical engineering science》2001,56(21-22):6211-6216
Blends of ‘activating’ primary or secondary amines (diethanolamine, DEA) with tertiary amines, (methyldiethanolamine, MDEA) are commonly used for the removal of CO2 from gas mixtures. To avoid undesirable side-effects from these activators, such as increased corrosion or higher energy requirements for regeneration, we propose using immobilised primary or secondary amine groups on solid supports. In this manner the activating additives can be localised to those parts of the absorption column where the high absorption rates achieved are truly beneficial and excluded elsewhere.The studies presented were carried out to provide an initial evaluation of the feasibility of this novel concept. Preliminary experiments carried out in a discontinuously operated stirred tank reactor reveal similar enhancement of the CO2 absorption into ‘activated’ MDEA solution, when the soluble DEA additive is replaced by a suspended solid adsorbent, containing the equivalent quantity of immobilised amine groups. Further experiments examined the CO2 absorption in a three phase fluidised bed column. They demonstrated that the immobilised activator can be employed in a continuously operated process too.All experimental results support the basic feasibility of using immobilised primary amines in place of homogeneous additives to enhance CO2 absorption in tertiary amine solutions.  相似文献   

16.
The reaction kinetics and molecular mechanisms of CO2 absorption using nonaqueous and aqueous monoethanolamine (MEA)/methyldiethanolamine (MDEA)/2-amino-2-methy-1-propanol (AMP) solutions were analyzed by the stopped-flow technique and ab initio molecular dynamics (AIMD) simulations. Pseudo first-order rate constants (k0) of reactions between CO2 and amines were measured. A kinetic model was proposed to correlate the k0 to the amine concentration, and was proved to perform well for predicting the relationship between k0 and the amine concentration. The experimental results showed that AMP/MDEA only took part in the deprotonation of MEA-zwitterion in nonaqueous MEA + AMP/MEA + MDEA solutions. In aqueous solutions, AMP can also react with CO2 through base-catalyzed hydration mechanism beside the zwitterion mechanism. Molecular mechanisms of CO2 absorption were also explored by AIMD simulations coupled with metadynamics sampling. The predicted free-energy barriers of key elementary reactions verified the kinetic model and demonstrated the different molecular mechanisms for the reaction between CO2 and AMP.  相似文献   

17.
In the present work, a simple‐to‐use correlation is developed to predict the solubility of CO2 in aqueous solutions of DEA and MDEA as a function of the reduced partial pressure and temperature. Using the interaction parameters generated, the model is applied to correlate the CO2 loading in different amine solutions. The results from the proposed correlation have been compared with the reported experimental data and it was found that there is a good agreement between the observed data and the model predictions over a wide range of operating conditions in aqueous solutions of both diethanolamine (DEA) and methyldiethanolamine (MDEA).  相似文献   

18.
《分离科学与技术》2012,47(14):2167-2173
It has been reported that a basic aqueous solution was effective in extracting short chain C2–C6 fatty acids from noncatalytically cracked triacylglyceride oils. However, the extraction efficiency was not optimal over the entire range (C2–C12) of acids present in the cracking reactor organic liquid product (OLP). Therefore, an additional study was performed to explore the efficiency of solvent extraction using aqueous amines for this application. Based on the screening of several amines, two tertiary amines, trimethyl amine (TMA), and dimethyl ethanolamine (DMEA), were selected and evaluated. The extraction conditions were optimized with respect to several factors: temperature, amine concentration, and the amine-to-OLPratio (amine/OLP). Under optimal conditions, both TMA and DMEA were effective in extracting a wide range of organic acids, with TMA removing 93% of total acids and DMEA removing 100% of total acids. The amine/OLP was found to be a significant factor, as was the concentration of the amine solution. Temperature was not found to be a significant factor over the range studied. These results provide a basis for the development of a scalable, continuous process to produce a variety of C2–C12 fatty acids from biological sources.  相似文献   

19.
The objective of the present work was to find the accurate kinetic models and mechanism for CO2 absorption into tertiary amine solution, aiming at understanding the contribution of the CO2 reaction with H2O, OH, and tertiary amines on the overall reaction rate. First, the kinetics of CO2 absorption into water instead of a buffer solution were studied using the stopped-flow technique at 293–313 K, with initial CO2 molar concentration of 1.1–37.3 mM. The experimental first-order reaction rate constant () was determined to be about 1000 times larger than the value for CO2 absorption into buffer solution reported in the reference. The was then correlated by a proposed semiempirical model and a simplified theoretical model, giving the activation energy for CO2 reacting with H2O as fitted by the simplified theoretical model in good agreement with the value of previous research. Also, the pH values and hydroxyl ion concentrations of aqueous Diethylaminoethanol (DEEA) solutions were determined at 293–313 K, with DEEA molar concentration of 0.1–0.4 M and CO2 loading of 0–0.626 mol/mol. In addition, the observed first-order reaction rate constant ( k0_DEEA ) of binary DEEA-H2O solution with DEEA molar concentration of 0.1–0.4 M reacting with CO2 was determined at 293–313 K. It should be pointed out that the kinetic experiments of CO2 absorption into DEEA solution was done with the molar ratio of DEEA to CO2 fixed at 20. The values of k0_DEEA were then fitted and predicted by four models (i.e., termolecular model, base-catalyzed model, the improved model, and Khalifah model). The results show the improved model and Khalifah model can predict k0_DEEA well with an average absolute relative difference (AARD) <5%. The predicted results indicate that the contribution of OH to k0_DEEA cannot be ignored for the absorption of CO2 into tertiary amine solutions, and could be responsible for 50–70% of the total absorption reaction rate. Furthermore, the k0 value of CO2 absorption into aqueous triethanolamine and CO2-loaded DEEA solution were further investigated and comprehensively discussed, suggesting that both pK a and the CO2 solubility affect k0 , with pK a having a much more significant effect. © 2018 American Institute of Chemical Engineers AIChE J, 65: 652–661, 2019  相似文献   

20.
Alkanolamines are the most popular absorbents used to remove CO2 from process gas streams. Therefore, the CO2 reaction with alkanolamines is of considerable importance. The aim of this article is to provide an overview on the kinetics of the reaction of CO2 with aqueous solutions of alkanolamines. The various reaction mechanisms that are used to interpret experimental kinetic data – zwitterion, termolecular and base‐catalyzed hydration – are discussed in detail. Recently published data on reaction kinetics of individual amine systems and their mixtures are considered. In addition, the kinetic behavior of several novel amine‐based solvents that have been proposed in the literature is analyzed. Generally, the reaction of CO2 with primary, secondary and sterically hindered amines is governed by the zwitterion mechanism, whereas the reaction with tertiary amines is described by the base‐catalyzed hydration of CO2.  相似文献   

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