Chemical absorption of carbon dioxide with triethanolamine in non-aqueous solutions

Carbon dioxide was absorbed into non-aqueous solvents such as methanol, ethanol, n-propanol, n-butanol, ethylene glycol, propylene glycol, and propylene carbonate, and into water in a stirred semi-batch tank with a planar gas-liquid interface at 298 K and 101.3 kPa. Triethanoamine (TEA) was used as a reactant with carbon dioxide. The reaction rate constants of the reaction between carbon dioxide and TEA were estimated by the mass transfer mechanism, which was accompanied by a fast pseudo-first-order reaction. An empirical correlation between the reaction rate constants and the solubility parameter of the solvent is presented. In non-aqueous solutions of TEA, dissolved carbon dioxide is expected to react with solvated TEA to produce an ion pair.     

Absorption of carbon dioxide into aqueous methyldiethanolamine

Gas absorption rates in a laminar liquid jet were measured for carbon dioxide in methyl- diethanolamine (MDEA) solutions. It was found that for the short contact times (<0.012s) of these absorption experiments there is only a small effect of any reaction between carbon dioxide and MDEA. Solubilities and molecular diffusivities for carbon dioxide in aqueous MDEA are estimated from measurements with nitrous oxide. The absorption rate data are described well using the solubilities and diffusivities measured in this work. Solubilities were measured over the temperature range 15 to 35°C and for MDEA concentrations up to 40%. Diffusion coefficients and viscosities were measured over the same temperature range and MDEA concentrations up to 20%.     

伴有二级不可逆反应的非牛顿幂律流体薄膜流中化学吸收的研究

本文对伴有二级不可逆反应的非牛顿幂律流体降膜流中的吸收过程进行了研究,提出扩散反应方程和它的解,并得到实验验证.     

Influence of polyethylene oxide on absorption of carbon dioxide into aqueous <Emphasis Type="Italic">N</Emphasis>-methyldiethanolamine solution

Carbon dioxide was absorbed into aqueous polyethylene oxide (PEO) solution containing N-methyldiethanolamine (MDEA) in a flat-stirred vessel to investigate the effect of non-Newtonian rheological behavior of PEO on the chemical absorption rate of CO₂, where the reaction between CO₂ and MDEA was assumed to be a first-order reaction with respect to the concentration of CO₂ and MDEA, respectively. A unified correlation equation containing the Deborah number, which reflects the viscoelastic properties of a non-Newtonian liquid, was used to obtain the volumetric liquid-side mass transfer coefficient of carbon dioxide in aqueous PEO solution. The elastic properties of PEO accelerated the absorption rate of CO₂ compared with that of a Newtonian liquid based on the same values of viscosity.     

Kinetics of the reaction between carbon dioxide and methyldiethanolamine

A stirred cell gas-liquid contactor was used to investigate the kinetics of the reaction between carbon dioxide and methyldiethanolamine (MDEA) in aqueous solutions. Experiments were conducted over the temperature range 15–35°C and for MDEA concentrations from 0.85 to 1.70 g mol/l. The kinetic data support a previously proposed mechanism in which MDEA acts as a homogeneous catalyst for CO₂ hydrolysis. The second-order rate constant was found to have a value of 2/47 l/g mols at 25°C, in good agreement with existing literature values. The second-order rate constant is correlated well by the Arrhenius expression

     

Simultaneous Absorption of H2S and Co2 Into Aqueous Methyldiethanolamine

Abstract

The tertiary araine methyldiethanolamine (MDEA) is finding increasing application as a chemical solvent for selective absorption of hydrogen sulfide from gases containing hydrogen sulfide and carbon dioxide. Gas streams of this type include some natural gases, synthetic gases from coal and heavy oil gasification and tail gases from sulfur plants. Selectivity for H2S is needed either to enrich Glaus sulfur plant feed in H2S or to remove only H₂S when CO₂ removal is not necessary or economic. For the absorption of hydrogen sulfide into MDEA, the reaction which occurs can be considered to be instantaneous while carbon dioxide undergoes a second-order reaction with MDEA.

In this work, the simultaneous absorption of two gases into a liquid containing a reactant with which both gases react is modelled using the film theory. Physical properties and kinetic rate parameters used in the model have been measured in our laboratory. The model is used to study the effect of process variables on the selectivity of MDEA for H₂S over C0₂. The simultaneous absorption of H₂S and CO₂ gases into aqueous MDEA is studied experimentally using a continuous stirred tank absorber. Experimental absorption rates are compared to predictions based on a multicomponent mass transfer model. The average deviations of the theoretical calculations from the experimental results are 10.2% and 12.9% for C0₂ and H₂S, respectively.     

MDEA溶液吸收CO_2动力学研究

采用圆盘塔,在常压、温度30～70℃、MDEA浓度1.75～4.28kmol/m~3条件下,以流动循环法测定了MDEA水溶液吸收CO_2的速率.利用自吸式搅拌鼓泡反应器测得的气液平衡关系整理数据,所有吸收速率数据均可用假一级快速可逆反应的吸收速率表达式来描述,即N_(co_2)=H_(co_2)(D_(co_2l)k_2c°_(Am)(1-a)~(1/2)(p_(co_2)-p_(co_2l)~*)式中k_2=5.86×10~6exp(-3984/T)并由此求得表观活化能为33.13kJ/mol.本文还讨论了温度、转化度和MDEA浓度对CO_2吸收速率的影响.     

A RIGOROUS MODEL FOR ABSORPTION OF CARBON DIOXIDE INTO AQUEOUS N-METHYLDIETHANOLAMINE SOLUTION

A rigorous model for absorption of carbon dioxide into aqueous N-methyldiethanolamine (MDEA) based on the assumption of reversible reactions and the simplified model with a pseudo-first order irreversible reaction hypothesis were employed to compare with experimental data. The experimental absorption rates were obtained from a characterized double stirred-cell absorber with a planar gas-liquid interface. It was demonstrated that the numerical solution of the rigorous model provides a better prediction for the absorption rate of carbon dioxide into aqueous MDEA solution than that of the simplified model. Only in the case of absorption experiments carried out at a low carbon dioxide partial pressure (p < 20 kpa) and low amine concentration (MDEA_total < 1000 mol/m³), the assumption of pseudo-first order irreversible reaction is reasonable.     

The effect of [bmim][Br] on the solubility of carbon dioxide and methane in glycols at pressures up to 14 MPa and temperatures ranging from 303 to 423 K

Solubility data of methane in ethylene glycol and 1-4 butylene glycol and carbon dioxide in ethylene glycol and 1-2 propylene glycol in the presence of the ionic liquid 1-butyl-3-methylimidazolium bromide have been measured in the temperature range (303–423) K at pressures up to 14 MPa. Henry's law constant of each solute in the studied solvent at saturation pressure is given. The experiments were performed in an autoclave type phase equilibrium apparatus using the total pressure method. For mixtures containing carbon dioxide and ethylene glycol no influence was observed. For mixtures containing carbon dioxide and 1-2 propylene glycol it was observed salting-out effect at 303.2 K and 323.2 K and salting-in effect at the remaining temperatures. For mixtures containing methane and ethylene glycol or 1-4 butylene glycol salting-in effect was observed.     

New systems and methods for the measurement of effective interfacial area and mass transfer coefficients in gas—liquid contactors

New systems have been developed for the measurement of effective interfacial area, a, by the chemical method which allow the use of hydrocarbon solvents, such as toluene, xylene, etc; polar solvents, such as benzyl alcohol, cyclohexanol, etc; and highly viscous solvents, such as diethylene glycol, polyethylene glycol, etc. In all the above cases, the reaction between carbon dioxide and selected amines is employed.Effective interfacial area and liquid-side mass transfer coefficient have been measured by the absorption of lean carbon dioxide and pure carbon monoxide/propylene, respectively, into cuprousamine solutions. Here, both water and polar substances, such as, pyridines, benzyl alcohol, isopropanol, etc. can be used.     

Absorption Rate of CO_2 into MDEA Aqueous Solution Blended with Piperazine and Diethanolanline

Absorption rate of CO2 into aqueous solution of N-methyldiethanolamine (MDEA) blended with di-ethanolamine (DEA) and piperazine (PZ) was studied and a kinetic model was established. It is shown that homogeneous activation mechanism could explain this absorption process. The absorption rate coefficients of carbon dioxide into MDEA aqueous solution blended with DEA, PZ or DEA+PZ were compared with each other. The results demonstrated that the different activation effect of DEA, PZ and DEA+PZ on the carbon dioxide absorption comes from the difference in CO2 combination rate, transport of PZ and DEA to MDEA and the regeneration rate of PZ and DEA.     

ABSORPTION OF H2S INTO AQUEOUS METHYLDIETHANOLAMINE

The absorption of H₂S into aqueous methyldiethanolamine (MDEA) was studied experimentally over the temperature range 15 to 35°C and for MDEA concentrations from 10 to 25 wt% using a laminar liquid jet device and a stirred-cell absorber. The contact times ranged from 2 × 10^-3 to 1 × 10^-2 seconds for the jet absorber and from 6 to 38 seconds for the stirred-cell absorber. It was found that the absorption rate data for both devices could be modelled assuming an instantaneous reaction regime for the reaction between H₂S and MDEA. The experimental results were interpreted to give an estimate for the diffusion coefficient of MDEA in water. Diffusion coefficient results are consistent for the two apparatuses. A lower bound for the second-order rate constant for the reaction between H₂S and MDEA is estimated from the experimental data to be 1.4 × 10¹⁰cm³/g mole s at 25°C     

酸性废气脱硫工艺中N-甲基二乙醇胺降解反应产物的研究

对用MDEA从甲醇酸性尾气中回收H2S装置中出现的胺液降解的现象进行了研究,通过气相色谱－质谱对降角产物结构进行了表征,提出了MDEA的降解反应机一。结果表明MDEA的降解主要为MDEA与CO2与H2O的反应,由于甲醇、氧和HCN等的存在,更加剧了MDEA降解发生,文中提出了相应的抑制措施。     

MEA—MDEA复合胺溶液吸收烟气中二氧化碳实验研究

采用搅拌实验装置,对MEA-MDEA不同配比的复合胺溶液吸收和解吸模拟烟道气中二氧化碳特性进行研究,揭示了吸收速率、吸收容量和酸碱度与时间之间的内在联系,并与目前工业应用较广的MEA、DEA溶液进行了对比分析;对CO2初始逸出温度,试液再生温度,试液再生率,再生pH值下降率进行了细致记录分析。实验结果表明,0．5mol／LMEA-0．5mol／LMDEA是MEA—MDEA复合胺体系中最佳配比溶液。     

MEA-MDEA复合胺溶液吸收烟气中二氧化碳实验研究

采用搅拌实验装置,对MEA-MDEA不同配比的复合胺溶液吸收和解吸模拟烟道气中二氧化碳特性进行研究,揭示了吸收速率、吸收容量和酸碱度与时间之间的内在联系,并与目前工业应用较广的MEA、DEA溶液进行了对比分析;对CO2初始逸出温度,试液再生温度,试液再生率,再生pH值下降率进行了细致记录分析。实验结果表明,0.5 mol/L MEA-0.5 mol/L MDEA是MEA-MDEA复合胺体系中最佳配比溶液。     

Investigation on kinetics of carbon dioxide absorption in aqueous solutions of monoethanolamine + 1, 3-diaminopropane

ABSTRACT

Environmental concerns from global warming and climate change demand carbon dioxide separation from post-combustion gases. Important parameters are involved in choosing the suitable solvent for carbon dioxide separation, including the reaction rate of carbon dioxide and the solvent. In this paper, the kinetics of carbon dioxide (CO₂) absorption in aqueous solutions of Monoethanolamine (MEA) + 1,3-Diaminopropane (DAP), a diamine containing two primary amino group, was developed. The measurements were performed in a stirred cell with a horizontal gas-liquid interface in the temperature range of 313.15–333.15 K and aqueous solutions of 10 wt% MEA + 5 wt% DAP and 12.5 wt% MEA + 2.5 wt% DAP. Experiments were conducted in an isothermal batch reactor with a horizontal gas-liquid interface under pseudo-first-order conditions, enabling the determination of the overall kinetic rate constant from the pressure drop method. Second-order reaction rate constants of CO₂ absorption in amine solutions were estimated using the calculated initial absorption rate. It was found that the rate constants in MEA+ DAP solutions were greater than in MEA solutions which means that DAP increases the reaction rate.     

Absorption of carbon dioxide in ethylenediamine solutions i. absorption kinetics and equilibrium

The chemical absorption of carbon dioxide by a laminar jet of ethylenediamine has been studied at 25.5°C under pseudo-first-order kinetic conditions. The reaction was found to be second-order with a rate constant of 1.0 x 10⁵ 1/g. mole sec. Equilibrium calculations at 18°C indicate that the partial pressure of carbon dioxide is very low, even over highly carbonated ethylenediamine solutions. The effects of amine concentration and carbonation ratio on the physical solubility and diffusivity of carbon dioxide in solution were inferred from corresponding results for nitrous oxide     

填料塔中混合胺吸收二氧化碳的研究

在填料塔中考察了常压下混合胺吸收剂[20%乙醇胺(MEA)+2% N-甲基二乙醇胺(MDEA),20%羟乙基乙二胺(AEE)+2% MDEA]对CO_2的吸收与解吸效果.同时测得了AEE+MDEA混合胺体系吸收剂脱除空气中体积分数约10%的CO_2的体积总传质系数K_Ga_v的近似值,并考察了进口气体中CO_2摩尔流量、气体流量、液体流量等因素对K_Ga_v的影响.实验结果表明,AEE+MDEA吸收效果明显好于MEA+MDEA,并且二者解吸效果相同;K_Ga_v随CO_2摩尔流量、气体流量、液体流量增大而增大.     

Mass transfer of carbon dioxide in aqueous polyacrylamide solution with methyldiethanolamine

Carbon dioxide was absorbed into aqueous polyacrylamide (PAA) solution containing methyl-diethanolamine (MDEA) in a flat-stirred vessel to investigate the effect of non-Newtonian rheological behavior of PAA on the rate of chemical absorption of CO₂, where the reaction between CO₂ and MDEA was assumed to be a first-order reaction with respect to the molar concentration of CO₂ and MDEA, respectively. The liquid-side mass transfer coefficient (k_L), which was obtained from the dimensionless empirical equation containing the viscoelasticity properties of a non-Newtonian liquid, was used to estimate the enhancement factor due to chemical reaction. PAA with elastic property of non-Newtonian liquid made the rate of chemical absorption of CO₂ accelerate compared with a Newtonian liquid     

Modified Zinc Oxide for the Direct Synthesis of Propylene Carbonate from Propylene Glycol and Carbon dioxide

A series of modified zinc oxide catalysts were prepared and their catalytic activities were evaluated by the direct synthesis of propylene carbonate from propylene glycol and carbon dioxide in the presence of acetonitrile, which acted as not only the solvent but also the dehydrating reagent in the reaction. The reusability test indicated that the modified catalysts had the high stability. Ammonium carbonate was added into the reaction to significantly elevate the selectivity of propylene carbonate.