基于pH测量的CO2吸收到钠基溶液动态实验及模型

采用基于pH测量的CO₂吸收速率研究方法。将pH与溶液中的成分相关联,采用分段拟合获得CO₂吸收速率,获得溶液成分对吸收速率的影响规律。对于低浓度的NaOH来说,吸收速率一直保持不变直到CO₂物理吸收到NaHCO₃溶液中。对于高浓度的NaOH,NaOH完全转化成Na₂CO₃时,吸收速率降低。但在两个吸收阶段中,吸收速率不变,CO₂物理吸收到NaHCO₃中时,吸收速率随CO₂饱和度的增加而降低。对CO₂吸收到NaOH中,CO₂和钠离子浓度都促进吸收,钠离子浓度影响更大;对于CO₂吸收到Na₂CO₃中,当Na₂CO₃浓度大于0.05mol/L,吸收速率不随浓度增加;对于CO₂吸收到NaHCO₃中,低浓度的钠可以促进CO₂吸收,而高浓度的钠抑制CO₂吸收,这主要由于析盐的作用。为避免CO₂大量吸收,优先选择0.5mol/L以上浓度的NaHCO₃。     

填料吸收塔内乙醇胺溶液吸收CO2增强因子

醇胺溶液吸收CO₂是沼气提纯领域重要的研究课题。在实验填料吸收塔中,以NaOH水溶液吸收低浓度CO₂的实验结果估算了填料的有效相界面积,建立了乙醇胺（MEA）溶液吸收高浓度CO₂增强因子的数学模型,并从数学模型和实验的角度研究了MEA浓度、进气流率、CO₂浓度等工艺参数对MEA吸收CO₂增强因子的影响。结果表明,增强因子数学模型计算值与实验值能够良好吻合,MEA吸收CO₂化学反应增强因子随进气CO₂浓度增加而降低,随MEA浓度增加而增加,随进气流率增加而减小。     

富氧燃烧烟气冷凝塔钠碱法脱硫过程SO2和CO2共吸收建模与实验研究

建立SO₂与CO₂共吸收到钠基溶液中的吸收速率模型,假设该模型中SO₂的水解反应为瞬间反应;关于CO₂水解反应存在两种假设：有限动力学假设和瞬间反应假设。由这两种方法计算分别获得SO₂的吸收速率并与完全预混气液反应器中的的动态实验进行对比。采用瞬间反应假设可以预测反应速率的趋势,绝对反应速率误差仍然较大。而采用有限动力学假设的模拟值与实验值在pH>3吻合良好。CO₂对SO₂吸收速率的影响主要通过影响气相传质系数和相同pH下溶液总硫浓度产生。根据CO₂存在与否对SO₂吸收速率的影响,获得五个不同的相互作用pH的区间。pH>11.42时,SO₂/N₂吸收速率大于SO₂/CO₂,主要由于气相传质系数影响;7.8 < pH < 11.42时,SO₂/N₂的吸收速率和SO₂/CO₂吸收速率相似,主要由于气相传质系数和溶液总硫影响抵消;5.41 < pH < 7.8时,SO₂/CO₂的吸收速率相对较高,主要由于溶液总硫影响更大;2.8 < pH < 5.41时,SO₂/CO₂的吸收速率相对较低,主要由于气相传质系数影响;pH < 2.8时,SO₂/N₂和SO₂/CO₂吸收速率相似,主要受液相传质的控制。模拟同时获得不同pH下溶液中碳和硫相关离子的转化规律和SO₂吸收速率的控制步骤,为富氧燃烧冷却塔同时脱硫设备的设计和运行提供参考。     

均相体系中酸碱协同催化二氧化碳与环氧化物的环加成反应

基于“可持续发展”和“绿色化学”的概念,近年来CO₂的捕获、储存及资源化利用在工业上和学术上一直备受关注。通过具有100%原子经济性特点的CO₂与环氧化物环加成反应合成五元环状碳酸酯是最有前景的方法之一。基于均相催化剂的设计思想与方法,以CO₂和环氧化物的活化本质出发,从催化剂结构的角度综述了均相体系中酸碱协同催化CO₂与环氧化物环加成反应合成环状碳酸酯的研究进展,包括简单二元催化体系、功能型一元催化体系和金属配合物催化体系等。     

光催化还原CO2的机理与MgO在吸附转化方面的应用

由于CO₂的过量排放而引发的温室效应已成为当今世界面临的重要环境问题,将CO₂还原转化为高附加值化学品和燃料是解决这一问题的有效途径。其步骤包括吸收入射光子;电子-空穴对的产生、分离和转移;CO₂分子在表面上的吸附、活化和转化。基于MgO可增强CO₂在表面的吸附进而促进后续的光催化还原,介绍了光催化还原CO₂的机理以及MgO在CO₂还原与吸附等方面的应用研究。MgO表面化学吸附的CO₂分子变得不稳定,其反应活性高于线性CO₂分子,因此显著提高CO₂的转化效率,可见其在CO₂吸附与转化等方面具有良好的发展前景。     

氨基功能化介孔超分子聚合物的温和构筑及其CO2吸附性能

以3,3'-二硫代双(丙酰肼)和对苯二甲醛为组装基元,通过动态共价键采用界面组装法在常温常压下温和构筑了具有丰富CO₂吸附位点的介孔超分子聚合物PDP。利用动态共价键的动态可逆性,通过合成后修饰法将两种具有丰富氨基位点的化合物（聚乙烯亚胺及四乙烯五胺）组装于PDP结构上,构建了两种氨基功能化超分子聚合物材料PDPP和PDPT。相较于PDP,修饰后超分子聚合物CO₂吸附性能有了极大提升,PDPT在80℃下CO₂吸附量可达27.79cm³/g。动态亚胺组装策略具有制备条件温和、结构功能可控等特性,为开发CO₂高吸附性能材料提供了全新思路。     

CO2浓度对混溶态(CO2+正己烷)/盐水界面微观特性的影响

在CO₂以超临界状态封存于油气藏时,储层中流体间的界面性质是影响封存效率和封存量的重要因素。利用分子动力学模拟的方法,对330 K、20 MPa混溶条件下(CO₂+正己烷)/NaCl溶液系统的界面微观性质进行了研究,分析了混溶相中CO₂摩尔分数变化时,界面处CO₂和正己烷的亲水、疏水特性及其影响,为CO₂地质封存提供理论依据。研究发现,随着混溶相中CO₂摩尔分数的增加,界面厚度及粗糙度增大,分子渗透加深,热波动加剧。界面上CO₂与水之间更强的相互作用造成了CO₂注入过程中界面张力的降低。CO₂表现出类似于表面活性剂的性质,并在CO₂摩尔分数为65%(质量分数为50%)时,其界面累积量以及正己烷的驱离量最大。界面处存在特殊的分子微观结构,CO₂、水及正己烷分子呈现特殊的排布方式。     

超强碱离子液体-有机胺-水复配溶剂高效CO2捕集

CO₂捕集是实现碳减排的重要技术之一。其中，化学吸收法是一种有效的、适用于低CO₂分压的CO₂捕集技术。开发出一种高效、低能耗、环保的吸收剂是该领域的研究难点和热点。离子液体(ILs)作为一类绿色溶剂，在CO₂捕集中具有结构可调节、反应速率快、吸收量高等优势，但存在黏度大、价格昂贵等问题，本工作提出将超强碱离子液体1,8-二氮杂二环[5,4,0]十一碳-7-烯咪唑([HDBU][Im])与单乙醇胺(MEA)复配得到离子液体复配溶剂，来提高吸收剂的CO₂吸收量并降低吸收CO₂后溶剂的黏度。研究了离子液体浓度、吸收温度、CO₂分压等对离子液体复配溶剂捕集CO₂性能的影响，测定了离子液体复配溶剂在不同CO₂负荷下的密度和黏度等物性。结果表明，30wt%MEA+10wt%[HDBU][Im]具有较好的吸收能力，在40℃下，CO₂吸收量达到0.1453 g CO₂     

惰性气体对粉尘爆炸泄放特性影响的实验研究

爆炸泄放和爆炸抑制是工业上降低粉尘爆炸危害性的两个重要手段,同时实现粉尘爆炸抑制和泄放共同作用的效果值得关注。基于标准20 L球形粉尘爆炸装置侧向开泄放口,实验研究不同泄放口径和静态动作压力时CO₂/N₂对石松子粉泄放过程压力的影响,采用热重分析法分析了石松子粉尘分别在CO₂、N₂氛围的热重变化。结果表明,在20 mm泄放口径时,随着CO₂/N₂浓度的增加,泄放压力的降低幅值逐渐增大,且CO₂对粉尘爆炸泄放最大超压的减小效果要优于N₂。泄放压力值随着CO₂浓度的增加基本呈线性降低,当体系中的CO₂和N₂浓度增加到10%时对体系泄放压力值的降低效果开始趋于一致。对于40 mm泄放口径,添加相同浓度的CO₂体系泄放压力值要略低于N₂,降低幅值为6%~8%。对于60 mm泄放口径,CO₂/N₂两者抑制效果差别不大,且在添加浓度不超过8%时对体系泄放压力值的降低幅值影响较小。通过TGA曲线可以发现,在N₂气氛和CO₂气氛的热流条件中,石松子粉的热解过程在370℃左右开始出现明显的差异,CO₂气氛中石松子粉的热解速率要快于其在N₂气氛中的,因此在这个过程中CO₂的存在一定程度上会促进石松子粉的热解,随着热解温度进一步提升,CO₂对石松子粉热解的抑制效果开始逐渐体现。     

己二酸对MEA吸收-解吸CO2过程的影响<

实验研究了己二酸对MEA水溶液吸收-解吸CO₂的影响。在0.4 mol·L-1 MEA的CO₂吸收富液解吸过程加入一定量的己二酸并分析了其对CO₂解吸能耗和解吸速率的影响,发现解吸速率明显升高,析出单位体积CO₂的能耗显著降低;对解吸还原后的贫液进行了CO₂二次吸收的实验,发现因加酸引起的CO₂二次吸收量变化小于7%;为去除不确定因素对CO₂相似文献   

Free radical polymerizations of some vinyl monomers in carbon dioxide fluid

The effect of pressure ranging from ambient atmosphere to 28.5 MPa on the free radical polymerizations of methyl methacrylate (MMA) in carbon dioxide (CO₂) was investigated and discussed. The poly(methyl methacrylate) (PMMA) with high molecular weight was synthesized at quite high conversion of MMA in the polymerization at or below 9.2 MPa, as compared to those polymerized under 11.8–28.5 MPa. A phase transition behavior of MMA‐CO₂ binary mixture from homogeneous state to vapor‐liquid equilibrium (VLE) state was observed below 10.51 MPa. In such a VLE system, almost all MMA was found to exist in the liquid phase with higher concentration than that in homogenous system. Thus, the fast polymerization rate of MMA and high molecular weight of PMMA could be related to the VLE state of MMA/CO₂ under low pressure. Similar phenomena were also observed in the polymerization systems of styrene and vinyl acetate in CO₂, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Absorption of carbon dioxide in piperazine activated concentrated aqueous 2-amino-2-methyl-1-propanol solvent

In this work new experimental data on the rate of absorption of CO₂ into piperazine (PZ) activated concentrated aqueous solutions of 2-amino-2-methyl-1-propanol (AMP) over the temperature range 303–323 K are presented. The absorption experiments have been carried out in a wetted wall contactor over CO₂ partial pressure range of 5–15 kPa. PZ is used as a rate activator with a concentration ranging from 2 to 8 wt% keeping the total amine concentration in the solution at 40 wt%. The physical properties such as density and viscosity of concentrated aqueous AMP+PZ, as well as physical solubility of CO₂ in concentrated aqueous AMP+PZ, are also measured. New experimental data on vapor liquid equilibrium (VLE) of CO₂ in these concentrated aqueous solutions of AMP+PZ in the temperature range of 303–323 K have also been presented. The VLE measurements are carried out in an equilibrium cell in CO₂ pressure range of 0.1–140 kPa. A thermodynamic model based on electrolyte non-random two-liquid (eNRTL) theory is used to represent the VLE of CO₂ in aqueous AMP+PZ. Liquid phase speciations are estimated considering the nonideality of concentrated solutions of the amines and the calculated activity coefficients by eNRTL model. The CO₂ absorption in the aqueous amine solutions is described by a combined mass transfer-reaction kinetics model developed according to Higbie's penetration theory. The model predictions have been found to be in good agreement with the experimental results of the rates of absorptions of CO₂ into aqueous AMP+PZ.     

(CO2 + 2‐propanol) mixture as a foaming agent for polystyrene: A simple thermodynamic model for the high pressure VLE‐phase diagrams taking into account the foam vitrification

The equation of state model developed by Lacombe and Sanchez (J Phys Chem 1976, 80, 2352) is used in the form proposed later by Sanchez and Stone (Polymer Blends, Vol. 1: Formulation, 2000; Chapter 2) to correlate experimental vapor‐liquid equilibrium (VLE) data for the three binaries and the ternary systems. Experimental data from the binary systems carbon dioxide‐isopropyl alcohol (CO₂‐IPrOH), isopropyl alcohol‐polystyrene (IPrOH‐PS), and carbon dioxide‐polystyrene (CO₂‐PS) are used to calculate VLE properties for the ternary system CO₂‐IPrOH‐PS. Two‐dimensional VLE‐phase diagrams were calculated and used to describe from a thermodynamic point of view the pressure, volume, and temperature values that characterize a thermoplastic foam evolution process, from the extruder to the foaming die. For different initial mixture CO₂ + IPrOH concentrations, pressure reduction produces liquid foaming until the vitrification curve arrests the final foam volume expansion. The dependence of the vitreous transition with the system CO₂ + IPrOH concentration while foaming is represented by the Chow (Macromolecules 1980, 13, 362) equation. The calculation procedure is proposed as a design tool to reduce the amount of experimental data usually needed as a requirement previous to the design stage. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2663–2671, 2007     

A simplified model for the correlation of vapour-liquid equilibrium in the CO2-NH3-H2O system

A new simplified VLE model of the CO₂-NH₃-H₂O system under conditions of the distillation and absorption steps of the recycle urea process is developed. For the gaseous phase the virial state equation is adopted and the component activity coefficients are approximated by a simple linear expression. The resulting equations for the equilibrium constants of the physical and chemical equilibria are fitted to experimental values (in the literature) within the temperature range of 307 to 414 K and within the pressure range of 2 to 40 bar. Tests of the model on the experimental data are presented as well as the comparisons with other published simplified VLE models of the system.     

Modelling Vapour − Liquid Equilibrium of CO2 in Aqueous N‐Methyldiethanolamine through the Simulated Annealing Algorithm

The modified Clegg‐Pitzer equation is used to correlate and predict the vapor‐liquid equilibrium of the CO₂‐MDEA‐H₂O system. Simulated annealing (SA), a computational stochastic technique for finding near global minimum solutions to optimization problems, has been used for parameter estimation in the model to predict VLE of CO₂ in aqueous MDEA solution. The solubility of CO₂ in aqueous solutions of 23.8 wt % and 30.0 wt % of N‐methyldiethanolamine (MDEA) has been measured over the temperature range of 303‐323 K and CO₂ partial pressure range of 1 to 100 kPa. The model predicted equilibria have been found to be in good agreement with the experimental results of VLE measurement of this work as well as those in the open literature. In this work, the SA technique has been used as an alternative to the traditional Levenberg‐Marquardt (LM) technique, to predict the VLE data accurately.     

The decomposition of CO<Subscript>2</Subscript> in glow discharge

The energy of the first vibrational level of the N₂ molecule is quite close to the energy of the first level of the asymmetric mode of CO₂. Hence, fast resonance transfer of vibrational energy from N₂ molecules to CO₂, directly populating the necessary level, becomes feasible. As a result of CO₂-CO₂ collision, the population increase of higher vibrational levels of asymmetric mode of CO₂ takes place up to the decomposition of molecules.     

Analysis of the heat of reaction and regeneration in alkanolamine-CO<Subscript>2</Subscript> system

The estimation of regeneration heat of absorbent is important because it is a key factor that has an effect on the process efficiency. In this study, thermal stability and regeneration heat of aqueous amine solutions such as monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), N-methyldiethanolamine (MDEA), and 1,8-diamino-pmenthane (KIER-C3) were investigated by using TGA-DSC analysis. The thermal characteristics of the fresh and CO₂ rich amine solutions were estimated. The CO₂ rich amine solutions were obtained by VLE experiments at T=40 °C. The regeneration heat of aqueous MEA solution was 76.991–66.707 kJ/mol-CO₂, which is similar to heat of absorption. The reproducibility of the results was obtained. The regeneration heat of aqueous KIER-C3 20 wt% solution (1.68 M) was lower than that of aqueous MEA 30 wt% solution (4.91 M). Therefore, the KIER-C3 can be used as an effective absorbent for acid gas removal.     

A study of species formation of aqueous tertiary and hindered amines using quantitative 13C NMR spectroscopy

Tertiary and sterically hindered amines have been chosen as potential candidate absorbents, recommended for their high carbon dioxide (CO₂) loading capacity and easy regeneration. In this study, the CO₂ absorption characteristics of these amines were studied using ¹H nuclear magnetic resonance (NMR) and quantitative ¹³C NMR. The equilibrium experiments were conducted in the vapor–liquid equilibrium (VLE) apparatus, which was used to measure the CO₂ absorption capacities and relative absorption rates of aqueous solutions of methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP). The CO₂ loaded absorbents were used for NMR measurement to determine the distribution of species formed in the absorbents. This process confirmed the reaction mechanisms of the individual absorbents in relation to CO₂ absorption capacities.     

Solubility and absorption rate enhancement of CO2 in K2CO3

The influence of addition of 2-(1-piperazinyl)-ethylamine (as a promoter) on the solubility and absorption rate of carbon dioxide (CO₂) in aqueous potassium carbonate solution (as a main solvent) was investigated experimentally, using a vapor liquid equilibrium (VLE) equipment in temperatures from 303.15 to 323.15 K and CO₂ initial partial pressures between 25 and 75 kPa. The experimental data showed that the addition of 2-(1-piperazinyl)-ethylamine to potassium carbonate solution results in a significant enhancement in the solubility and absorption rate of CO₂. The response surface methodology was applied to explore the relationship between independent parameters on the CO₂ loading capacity of blended solution.