Oxy‐fuel combustion for CO2 capture using a CO2‐tolerant oxygen transporting membrane

CO₂ capture via an oxy‐fuel route through the U‐shaped (Pr_0.9La_0.1)₂(Ni_0.74Cu_0.21Ga_0.05)O_4+δ (PLNCG) hollow fiber membrane with 100% CH₄ conversion and 100% CO₂ selectivity for 450 h has been explored for the first time. X‐ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy characterizations of the spent hollow fiber membrane have also been investigated. All these results indicate that PLNCG hollow fiber membrane shows excellent reaction performance and good stability under oxy‐fuel reaction conditions, which will be a potential rounte for reducing CO₂ emissions worldwide. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3856–3862, 2013     

Rate‐based‐Modellierung von CO2‐Absorptionskolonnen mit Anstaupackungen

The efficiency of columns for fluid separation can be increased by the application of sandwich packings. During the operation, different load‐dependent regimes with peculiar separation performance arise. In order to account for the effects of the individual flow regimes in a single model, both separation performance measurements and tomographic imaging are applied. A rate‐based model is presented, which takes the heterogeneous regimes in sandwich packings into account by means of appropriate correlations. The model is tested with experimental data for CO₂ absorption.     

Caged CO2 for the Direct Observation of CO2‐Consuming Reactions

CO₂‐consuming reactions, in particular carboxylations, play important roles in technical processes and in nature. Their kinetic behavior and the reaction mechanisms of carboxylating enzymes are difficult to study because CO₂ is inconvenient to handle as a gas, exists in equilibrium with bicarbonate in aqueous solution, and typically yields products that show no significant spectroscopic differences from the reactants in the UV/Vis range. Here we demonstrate the utility of 3‐nitrophenylacetic acid and related compounds (caged CO₂) in conjunction with infrared spectroscopy as widely applicable tools for the investigation of such reactions, permitting convenient measurement of the kinetics of CO₂ consumption. The use of isotopically labeled caged CO₂ provides a tool for the assignment of infrared absorption bands, thus aiding insight into reaction intermediates and mechanisms.     

Molecular‐based virial coefficients of CO2‐H2O mixtures

We report second and third virial coefficients for the system CO₂‐H₂O, calculated via cluster integrals using quantitative molecular models taken from the literature. Considered models include (1) fits to highly accurate ab initio calculations of the potential energy surfaces, and (2) semiempirical Gaussian Charge Polarizable Models (GCPM). Three‐body effects are found to be essential for obtaining quantitative results. Good agreement with experiment is obtained for the pure‐component coefficients, and for the cross second virial coefficient. For the two cross third virial coefficients, the few experimental data available do not agree well with the calculations; it is not clear whether this is due to problems with the data or deficiencies in the three‐body potentials. The uncertain state of the experimental data, and the relative mutual consistency of values computed from ab initio and GCPM models, suggest that calculated mixture third virial coefficients could be more accurate than values from experiment. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3029–3037, 2015     

Formation of poly‐vinyl‐alcohol structures by supercritical CO2

Poly‐vinyl‐alcohol (PVA) porous structures have been prepared using a supercritical phase inversion process in which supercritical carbon dioxide (SC‐CO₂) acts as the nonsolvent. First, we tested the versatility of the SC‐CO₂ phase inversion process, forming PVA/dimethylsulfoxide (DMSO) solutions with polymer concentrations ranging from 1 to 35% (w/w) and changing the process parameters. We worked at temperatures from 35 to 55°C and pressures from 100 to 200 bar obtaining different membranes morphologies: dense films, membranes with coexisting morphologies, and microparticles. However, we did not produce symmetric or asymmetric porous membranes. To obtain this result, we used casting solutions formed by adding acetone to DMSO with the aim of modifying the affinity between SC‐CO₂ and the liquid solvent. In this series of experiments, we obtained asymmetric membranes with skin layer thicknesses lower than 10 μm. The results obtained in this work have been explained considering that the membranes formation mechanism is related to the kinetics of the process; i.e. the affinity between the solvent (mixture of solvents) and SC‐CO₂. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Vapour–liquid equilibrium of CO2 in aqueous solutions of N‐methyl‐2‐ethanolamine

The equilibrium solubility of CO₂ into aqueous solution of sterically hindered N‐methyl‐2‐ethanolamine or methyl amino ethanol (MAE) was investigated in the temperature range of 303.1–323.1 K and total CO₂ pressure in the range of 1–350 kPa. The N‐methyl‐2‐ethanolamine aqueous solutions studied were 0.968, 1.574, 2.240 and 3.125 mol kg^?1 of solvent. © 2011 Canadian Society for Chemical Engineering     

Novel fixed‐carrier membranes for CO2 separation

A new membrane material having two kinds of CO₂ carriers was obtained. Composite membranes were prepared with the material and support membranes. The facilitated transport of CO₂ through these membranes was performed with pure CH₄ and CO₂ as well as CH₄/CO₂ mixtures containing 50 vol % CO₂. The results show that the membranes possess better CO₂ permeance than that of other fixed carrier membranes reported in the literature. In the measurements with pure gases, at 26°C, 0.013 atm of CO₂ pressure, the membrane with polysulfone support displays a CO₂ permeance of 7.93 × 10^?4 cm³ /cm² s cmHg and CO₂/CH₄ ideal selectivity of 212.1. In the measurements with mixed gases, at 26°C, 0.016 atm of CO₂ partial pressure, the membrane displays a CO₂ permeance of 1.69 × 10^?4 cm³ /cm² s cmHg and CO₂/CH₄ selectivity of 48.1. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2222–2226, 2002     

CO2‐Induced Mechanical Reinforcement of Polyolefin‐Based Nanocellular Foams

The effect of CO₂‐induced crystallization on the mechanical properties, in particular the yield and the ultimate stresses, of polyolefins is studied. PP and SEBS copolymer blends are used as examples and foamed after sorption of CO₂ at temperatures below T_m. CO₂ sorption thickens the crystalline lamellae and consequently increases T_m from 160 to 178 °C for both pure PP and PP/SEBS blend systems. Foams with an average cell size smaller than 250 nm retain the ultimate stress at the level of the polymer before foaming, even without the effect of CO₂‐induced crystallization. Including CO₂‐induced crystallization, the yield and the ultimate stresses of the foam can be improved by 30 and 50% over solid PP and by 22 and 40%, for solid PP/SEBS blends, respectively.

     

UNIFAC model for ionic liquid‐CO2 systems

The new group binary interaction parameters of UNIFAC model (a_nm and a_mn) between CO₂ and 22 ionic liquid (IL) groups were obtained by means of correlating the solubility data of CO₂ in pure ILs at different temperatures (>273.2 K). We measured the CO₂ solubility at low temperatures down to 243.2 K in pure ILs, i.e., [OMIM]⁺[BF₄]^? and [OMIM]⁺[Tf₂N]^?, and their equimolar amount of mixture, in order to fill the blank of solubility data at low temperatures and also to justify the applicability of UNIFAC model over a wider temperature range. It was verified that UNIFAC model can be used for predicting the CO₂ solubility in pure ILs and in the binary mixture of ILs both at high (>273.2 K) and low temperatures (<273.2 K) effectively, as well as identifying the new structure–property relation. This is the first work to extend the UNIFAC model to IL‐CO₂ systems. © 2013 American Institute of Chemical Engineers AIChE J 60: 716–729, 2014     

Modeling of CO2 equilibrium solubility in a novel 1‐Diethylamino‐2‐Propanol Solvent

In this work, the equilibrium solubility of CO₂ in a 1‐diethylamino‐2‐propanol (1DEA2P) solution was determined as a function of 1DEA2P concentration (over the range of 1–2 M), temperature (in the range of 298–333 K), and CO₂ partial pressure (in the range of 8–101 kPa). These experimental results were used to fit the present correlation for K₂ (Kent‐Eisenberg model, Austgen model, and Li‐Shen model). It was found that all of the models could represent the CO₂ equilibrium solubility in 1DEA2P solution with ADDs for Kent‐Eisenberg model, Austgen model, and Li‐Shen model of 6.3, 7.3, and 12.2%, respectively. A new K₂ correlation model, the Liu‐Helei model, was also developed to predict the CO₂ equilibrium solubility in 1DEA2P solution with an excellent ADD of 3.4%. In addition, the heat of absorption of CO₂ in 1DEA2P solution estimated by using the Gibbs‐Helmholtz equation was found to be ?45.7 ± 3.7 kJ/mol. Information and guidelines about effectively using data for screened solvents is also provided based on the three absorption parameters: CO₂ equilibrium solubility, second order reaction constant (k₂), and CO₂ absorption heat. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4465–4475, 2017     

CO2‐Abtrennung für fossil befeuerte Kraftwerke

An overview of technologies for fossil fuel power plants with drastically reduced CO₂ emissions is given. Post combustion capture, Pre combustion capture, and Oxyfuel technology are introduced and compared. Current research results indicate that Post combustion capture may lead to slightly higher losses in power plant efficiency than the two other technologies. However, retrofitting of existing plants with Oxyfuel technology is complex and costly, and retrofitting of Pre combustion capture is not possible. On the other hand, Post combustion capture is suited for retrofitting. Based on the mature technology of reactive absorption, it can be implemented on a large scale in the near future. Therefore, Post combustion capture using reactive absorption is discussed here in some detail.     

Simultaneous Adsorption of SO2, NO,and CO2 by K2CO3‐Modified γ‐Alumina

The simultaneous adsorption of SO₂, NO, and CO₂ on K₂CO₃‐modified γ‐alumina under different operating conditions was studied in a fixed‐bed reactor. The experimental results showed that the influence of a temperature increase on the simultaneous adsorption of the three gases was complex and different from the effects seen when both chemical adsorption and competitive adsorption existed. An increase in O₂ concentration and small amounts of water could enhance the adsorption of SO₂ and NO while the adsorption of CO₂ was not influenced. The breakthrough curves of the simultaneous adsorption experiments suggested that the investigated adsorbent may be a good candidate for the simultaneous adsorption of SO₂, NO, and part of the CO₂ while the adsorption capacity for CO₂ still needs to be enhanced.     

One‐step production of CO‐ and CO2‐free hydrogen from biomass

The reaction between a biomass (cellulose, sucrose, glucose, starch, cotton, or Japanese paper) and NaOH in the presence of water vapor produced pure hydrogen without CO and CO₂ at temperatures in the range 473–623K. The addition of Ni/Al₂O₃ or Rh/Al₂O₃ catalyst to cellulose enhanced the production of hydrogen at <573 K. The reaction between cellulose and NaOH can be written as: C₆H₁₀O₅ + 12NaOH + H₂O = 6Na₂CO₃ + 12H₂. The reactivities of alkali metal hydroxides were: KOH > NaOH ? LiOH. Copyright © 2004 Society of Chemical Industry