Evaluation of the impact of H2O, O2, and SO2 on postcombustion CO2 capture in metal-organic frameworks

Molecular modeling methods are used to estimate the influence of impurity species: water, O(2), and SO(2) in flue gas mixtures present in postcombustion CO(2) capture using a metal organic framework, HKUST-1, as a model sorbent material. Coordinated and uncoordinated water effects on CO(2) capture are analyzed. Increase of CO(2) adsorption is observed for both cases, which can be attributed to the enhanced binding energy between CO(2) and HKUST-1 due to the introduction of a small amount of water. Density functional theory calculations indicate that the binding energy between CO(2) and HKUST-1 with coordinated water is ~1 kcal/mol higher than that without coordinated water. It is found that the improvement of CO(2)/N(2) selectivity induced by coordinated water may mainly be attributed to the increased CO(2) adsorption on the hydrated HKUST-1. On the other hand, the enhanced selectivity induced by uncoordinated water in the flue gas mixture can be explained on the basis of the competition of adsorption sites between water and CO(2) (N(2)). At low pressures, a significant CO(2)/N(2) selectivity increase is due to the increase of CO(2) adsorption and decrease of N(2) adsorption as a consequence of competition of adsorption sites between water and N(2). However, with more water molecules adsorbed at higher pressures, the competition between water and CO(2) leads to the decrease of CO(2) adsorption capacity. Therefore, high pressure operation should be avoided in HKUST-1 sorbents for CO(2) capture. In addition, the effects of O(2) and SO(2) on CO(2) capture in HKUST-1 are investigated: The CO(2)/N(2) selectivity does not change much even with relatively high concentrations of O(2) in the flue gas (up to 8%). A slightly lower CO(2)/N(2) selectivity of a CO(2)/N(2)/H(2)O/SO(2) mixture is observed compared with that in a CO(2)/N(2)/H(2)O mixture, especially at high pressures, due to the strong SO(2) binding with HKUST-1.     

Effect of background electrolytes and pH on the adsorption of Cu(II)/EDTA onto TiO2

Cu(II)/EDTA adsorption onto TiO2 has been studied with a variation of pH, ionic strength, and type of background electrolytes. Cu(II) adsorption onto TiO2 increased as ionic strength increased when NaClO4 was used as a background electrolyte. This can be explained by the increase of exp(-FPsi/RT) as a part of the electrostatic correction within a surface complexation model. Model predictions described experimental adsorption trends. Types of background anions (ClO4, Cl, NO2, NO3, SO3, and PO4) did not affect adsorption trends and adsorption amounts of Cu(II) onto TiO2. However, different trends were observed with various types of background ions used as ionic strength in EDTA and Cu(II)-EDTA adsorption. EDTA adsorption was decreased by using Na2SO3 and Na3PO4 as background ions, while NaClO4, NaCl, NaNO2, and NaNO3 showed negligible interference on the EDTA adsorption, which matched well with model predictions. The presence Na2SO3 and Na3PO4 also interfered with Cu(II)-EDTA adsorption, to a somewhat greater extent compared to EDTA adsorption, especially at lower pH. This interference was also noted in Cu(II)-EDTA adsorption with a variation of Cu(II)-EDTA concentration at constant ionic strength (3 x 10(-3) M) by using Na2SO3 and Na3PO4, especially at lower ratios of Cu(II)-EDTA to Na2SO3 and Na3PO4. These results suggest that the ratio of Cu(II)-EDTA to Na2SO3 and Na3PO4 is an important factor for the controlling of competition between these background ions and Cu(II)-EDTA onto TiO2. Model prediction generally matched well with experimental adsorption using NaClO4, NaCl, NaNO2, and NaNO3 as backgrounds ions, while a severe deviation was observed in the presence of Na2SO3 and Na3PO4. These results suggest that the mobility of copper ions as Cu(II)-EDTA can be increased from polluted area in the presence of multivalent background ions, especially as the ratio of adsorbates/background ions decreased.     

阳离子表面活性剂存在下水/有机两相体系中双环戊二烯氢甲酰化

研究了在阳离子表面活性剂存在下水/有机两相中水溶性铑配合物RhCI(CO)(TPPTS)2(TPPTS:P(m-C6H4SO3Na)3)催化双环戊二烯氢甲酰化反应,考察了反应温度、催化剂浓度、不同水溶性膦配体TPPTS和TPPDS(C5H5P(m-C6H4SO3Na)2),以及表面活性剂结构对催化反应的影响.结果表明,...     

273 K下Na2CO3-Na2SO4-Na2B4O7-H2O四元体系介稳相平衡的实验研究

采用等温蒸发法研究了四元体系Na2CO3-Na2SO4-Na2B4O7-H2O在273 K时的介稳相平衡及平衡液相的密度. 利用溶解度数据绘制了该四元体系273 K下的相图. 研究结果表明, 该四元体系有异成分复盐2Na2SO4·Na2CO3形成. 相图中有2个共饱点、5条单变量曲线和4个结晶相区. 4个结晶相区分别为盐Na2CO3·10H2O, Na2SO4·10H2O, Na2B4O7·10H2O和2Na2SO4·Na2CO3的结晶区. 复盐2Na2SO4·Na2CO3同时存在于包含Na2CO3-Na2SO4-H2O三元体系的其它四元体系或高元体系中. 在273 K介稳平衡相图中, 碳酸钠以Na2CO3·10H2O形式析出; 硫酸钠以Na2SO4·10H2O的形式析出; 硼酸钠的完整分子式为Na2B4O5(OH)4·8H2O. Na2CO3对Na2B4O7有盐析作用.     

Carbonate adsorption on goethite in competition with phosphate

Competitive interaction of carbonate and phosphate on goethite has been studied quantitatively. Both anions are omnipresent in soils, sediments, and other natural systems. The PO4-CO3 interaction has been studied in binary goethite systems containing 0-0.5 M (bi)carbonate, showing the change in the phosphate concentration as a function of pH, goethite concentration, and carbonate loading. In addition, single ion systems have been used to study carbonate adsorption as a function of pH and initial (H)CO3 concentration. The experimental data have been described with the charge distribution (CD) model. The charge distributions of the inner-sphere surface complexes of phosphate and carbonate have been calculated separately using the equilibrium geometries of the surface complexes, which have been optimized with molecular orbital calculations applying density functional theory (MO/DFT). In the CD modeling, we rely for phosphate on recent parameters from the literature. For carbonate, the surface speciation and affinity constants have been found by modeling the competitive effect of CO3 on the phosphate concentration in CO3-PO4 systems. The CO3 constants obtained can also predict the carbonate adsorption in the absence of phosphate very well. A combination of inner- and outer-sphere CO3 complexation is found. The carbonate adsorption is dominated by a bidentate inner-sphere complex, (FeO)2CO. This binuclear bidentate complex can be present in two different geometries that may have a different IR behavior. At a high PO(4) and CO3 loading and a high Na+ concentration, the inner-sphere carbonate complex interacts with a Na+ ion, probably in an outer-sphere fashion. The Na+ binding constant obtained is representative of Na-carbonate complexation in solution. Outer-sphere complex formation is found to be unimportant. The binding constant is comparable with the outer-sphere complexation constants of, e.g., SO(2-)4 and SeO(2-)4.     

Aqueous and gaseous adsorption from montmorillonite-carbon composites and from derived carbons

Clay-carbon composites and the carbons derived from demineralization of the clay template were examined for their aqueous adsorption properties (2,4,6-trichlorophenol and methylene blue) and for their gas adsorption/separation abilities regarding CO(2), CH(4), and N(2) gases. The sorption results are discussed in relation with their structural properties (surface area, pore width and volume, and surface chemistry). It was found that the properties of the adsorbents depend highly on the synthetic route, for instance, on the use of clay or H(2)SO(4) as structure mediating and activating agents, respectively. Particularly, the simultaneous use of clay and H(2)SO(4) leads to a synergistic action, which imparts to the final solids the highest sorption capacity and the best potential for separation of CO(2) from gaseous mixtures of CH(4) and N(2).     

Surface tensions of inorganic multicomponent aqueous electrolyte solutions and melts

A semiempirical model is presented that predicts surface tensions (σ) of aqueous electrolyte solutions and their mixtures, for concentrations ranging from infinitely dilute solution to molten salt. The model requires, at most, only two temperature-dependent terms to represent surface tensions of either pure aqueous solutions, or aqueous or molten mixtures, over the entire composition range. A relationship was found for the coefficients of the equation σ = c(1) + c(2)T (where T (K) is temperature) for molten salts in terms of ion valency and radius, melting temperature, and salt molar volume. Hypothetical liquid surface tensions can thus be estimated for electrolytes for which there are no data, or which do not exist in molten form. Surface tensions of molten (single) salts, when extrapolated to normal temperatures, were found to be consistent with data for aqueous solutions. This allowed surface tensions of very concentrated, supersaturated, aqueous solutions to be estimated. The model has been applied to the following single electrolytes over the entire concentration range, using data for aqueous solutions over the temperature range 233-523 K, and extrapolated surface tensions of molten salts and pure liquid electrolytes: HCl, HNO(3), H(2)SO(4), NaCl, NaNO(3), Na(2)SO(4), NaHSO(4), Na(2)CO(3), NaHCO(3), NaOH, NH(4)Cl, NH(4)NO(3), (NH(4))(2)SO(4), NH(4)HCO(3), NH(4)OH, KCl, KNO(3), K(2)SO(4), K(2)CO(3), KHCO(3), KOH, CaCl(2), Ca(NO(3))(2), MgCl(2), Mg(NO(3))(2), and MgSO(4). The average absolute percentage error between calculated and experimental surface tensions is 0.80% (for 2389 data points). The model extrapolates smoothly to temperatures as low as 150 K. Also, the model successfully predicts surface tensions of ternary aqueous mixtures; the effect of salt-salt interactions in these calculations was explored.     

Effects of atmospherically important solvated ions on organic acid adsorption at the surface of aqueous solutions

The effects of salts on the solubility of amphiphilic organic molecules are of importance to numerous atmospheric, environmental, and biological systems. A detailed picture of the influence of dissolved atmospheric salts, NaCl and Na(2)SO(4), on the adsorption of hexanoic acid at the vapor/water interface is developed using vibrational sum-frequency spectroscopy and surface tension measurements as a function of time, organic concentration, and solution pH. We have found that for hexanoic acid adsorption at the vapor/water interface, a fast initial adsorption is followed by two considerably slower processes: a reorientation of the polar headgroup and a restructuring of the headgroup solvation shell. The addition of salts affects this restructuring by reducing the range of water--headgroup interactions immediately upon surface adsorption for ion containing solutions. Reorientation of the organic headgroup with time occurs at the surface of both salt-containing and salt-free solutions, but the most stable orientation differs with the added ions. The dissolved salts also enhance the interfacial concentration of hexanoic acid, consistent with the known salting-out behavior of Cl(-) and SO(4)(2-) anions.     

Uptake of CO2, SO2, HNO3 and HCl on calcite (CaCO3) at 300 K: mechanism and the role of adsorbed water

All experimental observations of the uptake of the four title compounds on calcite are consistent with the presence of a reactive bifunctional surface intermediate Ca(OH)(HCO3) that has been proposed in the literature. The uptake of CO2 and SO2 occurs on specific adsorption sites of crystalline CaCO3(s) rather than by dissolution in adsorbed water, H2O(ads). SO2 primarily interacts with the bicarbonate moiety whereas CO2, HNO3 and HCl all react first with the hydroxyl group of the surface intermediate. Subsequently, the latter two react with the bicarbonate group to presumably form Ca(NO3)2 and CaCl2.2H2O. The effective equilibrium constant of the interaction of CO2 with calcite in the presence of H2O(ads) is kappa = deltaCO2/(H2O(ads)[CO2]) = 1.62 x 10(3) bar(-1), where CO2 is the quantity of CO2 adsorbed on CaCO3. The reaction mechanism involves a weakly bound precursor species that is reversibly adsorbed and undergoes rate-controlling concurrent reactions with both functionalities of the surface intermediate. The initial uptake coefficients gamma0 on calcite powder depend on the abundance of H2O(ads) under the present experimental conditions and are on the order of 10(-4) for CO2 and 0.1 for SO2, HNO3 and HCl, with gamma(ss) being significantly smaller than gamma0 for HNO3 and HCl, thus indicating partial saturation of the uptake. At 33% relative humidity and 300 K there are 3.5 layers of H2O adsorbed on calcite that reduce to a fraction of a monolayer of weakly and strongly bound water upon pumping and/or heating.     

磺化纤维素纳米纤维多孔膜支撑的高通量纳滤膜的制备及脱盐性能

以细菌纤维素为原材料, 先后通过NaIO₄和NaHSO₃氧化还原反应制备了表面部分磺酸化的细菌纤维素(SBC)纳米纤维. 利用SBC纳米纤维多孔膜替代传统的超滤膜作为支撑底膜, 结合界面聚合反应调控制得复合纳滤膜, 并对其纳滤性能进行研究. 结果表明, 制备得到了对Na₂SO₄和MgSO₄具有高截留率(>96%)和超高分离通量(>320 L·m ^-2·h ^-1·MPa ^-1)的新型纳滤膜.     

The interaction of CO2 with sodium-promoted W(011)

The activation of CO2 by interaction with Na atoms on tungsten was studied in a joint experimental/theoretical effort combining MIES, UPS (HeII) and first principles calculations. Experimentally, both the adsorption of Na on tungsten, followed by CO2 exposure to the Na-modified surface at 80 K, and the adsorption of CO2 on tungsten, followed by Na exposure to the CO2 covered substrate, were studied. Below about 120 K CO2 physisorbs on pure W(011), and the distance between the three main spectral features is as for gas phase CO2 (E(B) = 8.4, 12.1, 14.1 eV). When offered to a Na monolayer (ML) deposited onto W, CO2 is converted into a chemisorbed species. The spectral pattern is different from physisorbed CO2, and the three spectral features are shifted towards lower binding energies (E(B) = 6.3, 10.7, 13.9 eV). The chemisorption continues until all available Na species are converted into Na+ species. Additional CO2 offered to the system becomes physisorbed on top of the chemisorbed species. When a CO2 monolayer, physisorbed on tungsten at 80 K, is exposed to Na, the interaction leads initially to a decrease of the surface work function and to a rigid, global shift of all CO2 induced features towards larger binding energies by about 2 eV. Only beyond a minimum Na coverage of about 0.5 ML, chemisorbed species can be detected. We conclude that, initially, transfer of the Na(3s) electron to the tungsten substrate takes place. Above 0.5 ML Na coverage, back donation of charge to CO2 takes place whereby the physisorbed carbon dioxide species become converted into chemisorbed ones. The experimental results are interpreted with the help of first principle calculations carried out on suitable slab models. The structures and surface binding mode of the chemisorbed CO2 species are described. The calculated density of states for the most stable situations is in qualitative agreement with experimental data.     

Adsorption of NH3 onto activated carbon prepared from palm shells impregnated with H2SO4

Adsorption of ammonia (NH3) onto activated carbons prepared from palm shells impregnated with sulfuric acid (H2SO4) was investigated. The effects of activation temperature and acid concentration on pore surface area development were studied. The relatively large micropore surface areas of the palm-shell activated carbons prepared by H2SO4 activation suggest their potential applications in gas adsorption. Adsorption experiments at a fixed temperature showed that the amounts of NH3 adsorbed onto the chemically activated carbons, unlike those prepared by CO2 thermal activation, were not solely dependent on the specific pore surface areas of the adsorbents. Further adsorption tests for a wide range of temperatures suggested combined physisorption and chemisorption of NH3. Desorption tests at the same temperature as adsorption and at an elevated temperature were carried out to confirm the occurrence of chemisorption due to the interaction between NH3 and some oxygen functional groups via hydrogen bonding. The surface functional groups on the adsorbent surface were detected by Fourier transform infrared spectroscopy. The amounts of NH3 adsorbed by chemisorption were correlated with the contents of elemental oxygen present in the adsorbents. Mechanisms for chemical activation and adsorption processes are proposed based on the observed phenomena.     

Effect of dissolved CO2 on the potential stability of all-solid-state ion-selective electrodes.

The influence of dissolved CO2 on the potentiometric responses of all-solid-state ion-selective electrodes (ISEs) was systematically examined with four different types of electrodes fabricated by pairing pH-sensitive and pH-insensitive metal electrodes (Pt and Ag/AgCl, respectively) with pH-sensitive and pH-insensitive ion-selective membranes (H+-selective membrane based on tridodecylamine and Na+-selective membrane based on tetraethyl calix[4]arenetetraacetate, respectively). The experimental results clearly showed that the carbonic acid formed by the diffused CO2 and water vapor at the membrane/metal electrode interface varies the phase boundary potentials both at the inner side of the H+-selective membrane (deltaE(in)mem) and at the metal electrode surface (deltaEelec). The potential changes, deltaE(in)mem and deltaEelec, occurring at the facing boundaries, are opposite in their sign and result in a canceling effect if both the membrane and metal surface are pH-sensitive. Consequently, the H+-selective membrane coated on a pH-sensitive electrode (Pt) tends to exhibit a smaller CO2 interference than that on a pH-insensitive electrode (Ag/AgCl). When the all-solid-state Na+ and K+ ISEs were fabricated with both pH-insensitive metal electrode and ion-selective membrane, they did not suffer from CO2 interference. It was also confirmed that plasticization of the PVC leads to increased CO2 permeation. Various types of intermediate layers were examined to reduce the CO2 interference problem in the fabrication of H+-selective all-solid-state ISEs. The results indicated that the H+-selective electrode needs an intermediate layer that maintains a constant pH unless the carbonic acid formation at the interfacial area is effectively quenched.     

Design and interfacial behavior of two series of gemini amphiphiles with different charge positions based on imidazole moiety

Two series of gemini amphiphiles based on 2-heptadecylimidazole were designed. One is exo-BisImC17Cn (n=2, 4, 6, 8, 10), in which the positive charges are positioned on the outsides of the headgroups. The other is endo-BisImC17Cn (n = 2, 4, 6, 8, 10), whose positive charges are localized on the insides of the headgroups. The interfacial behavior at the air/water interface of these gemini amphiphiles was investigated in relation to the effect of the charge position and the spacer length. Monolayers of exo-BisImC17Cn show small differences in interfacial behavior when spread on water and aqueous Na2SO4 subphases. In contrast, significant distinctions were observed for molecules of endo-BisImC17Cn. The limiting areas of endo-BisImC17Cn monolayers on water are obviously larger than those on the aqueous Na2SO4 solution. While the limiting areas of the exo-BisImC17Cn monolayers increased monotonically with the spacer length, those of the endo-BisImC17C10 monolayer on Na2SO4 solution is obviously smaller than those of endo-BisImC17C6 and endo-BisImC17C8 monolayers, suggesting the wicket conformation of the alkyl chain in endo-BisImC17C10. On the other hand, both of the gemini amphiphiles could form complex monolayers with negatively charged TPPS at the air/water interface. The transferred complex multilayer films of the gemini amphiphiles/TPPS showed supramolecular chirality, although both of the gemini amphiphiles and TPPS are achiral. The exciton couplet was observed for the endo-BisImC17Cn/TPPS films, while no couplet was detected for the exo-BisImC17Cn/TPPS films. A reasonable comparison between the two series of geminis in relation to the effect of charge positions and the spacer lengths on the interfacial behavior and the supramolecular chirality was performed.     

Sulfate-enhanced catalytic destruction of 1,1,1-trichlorethane over Pt(111)

The catalytic destruction of 1,1,1-trichloroethane (TCA) over model sulfated Pt(111) surfaces has been investigated by fast X-ray photoelectron spectroscopy and mass spectrometry. TCA adsorbs molecularly over SO4 precovered Pt(111) at 100 K, with a saturation coverage of 0.4 monolayer (ML) comparable to that on the bare surface. Surface crowding perturbs both TCA and SO4 species within the mixed adlayer, evidenced by strong, coverage-dependent C 1s and Cl and S 2p core-level shifts. TCA undergoes complete dechlorination above 170 K, accompanied by C-C bond cleavage to form surface CH3, CO, and Cl moieties. These in turn react between 170 and 350 K to evolve gaseous CO2, C2H6, and H2O. Subsequent CH3 dehydrogenation and combustion occurs between 350 and 450 K, again liberating CO2 and water. Combustion is accompanied by SO4 reduction, with the coincident evolution of gas phase SO2 and CO2 suggesting the formation of a CO-SOx surface complex. Reactively formed HCl desorbs in a single state at 400 K. Only trace (<0.06 ML) residual atomic carbon and chlorine remain on the surface by 500 K.     

CXN天然沸石的研究2: 吸附性质

采用N~2,NH~3,CO~2,乙烯,丙烯,水,甲醇,乙醇,丙醇等作为吸附剂,研究了由我国CXN天然沸石改性制得的H-STI和Na-STI沸石的吸附性质,H-STI和Na-STI沸石的BET表面积及微孔孔体积约为420m^2/g和0.20m^3/g。根据NH~3和CO~2在H-STI沸石上的吸附等温线计算得到它们的吸附热分别为44.8和26.5kJ/mol。乙烯,丙烯,甲醇,乙醇,丙醇等在Na-STI沸石上的吸附等温线表明该沸石对有机分子的吸附具有链长选择性。在低分压下水相对于甲醇的吸附量表明沸石具有一定的疏水性质。     

Specific ion effects on interfacial water structure near macromolecules

We investigated specific ion effects on interfacial water structure next to macromolecules with vibrational sum frequency spectroscopy (VSFS). Poly-(N-isopropylacrylamide) was adsorbed at the air/water interface for this purpose. It was found that the presence of salt in the subphase could induce the reorganization of water adjacent to the macromolecule and that the changes depended greatly on the specific identity and concentration of the salt employed. Ranked by their propensity to orient interfacial water molecules, sodium salts could be placed in the following order: NaSCN > NaClO4 > NaI > NaNO3 approximately NaBr > NaCl > pure water approximately NaF approximately Na2SO4. This ordering is a Hofmeister series. On the other hand, varying the identity of the cation exhibited virtually no effect. We also showed that the oscillator strength in the OH stretch region was linearly related to changes in the surface potential caused by anion adsorption. This fact allowed binding isotherms to be abstracted from the VSFS data. Such results offer direct evidence that interfacial water structure can be predominantly the consequence of macromolecule-ion interactions.     

A Novel Biomass Supported Na2CO3 System for Flue Gas Desulfurization

The breakthrough and stoichiometric SO2 adsorption efficiencies of a biomass supported Na2CO3 system (80 wt %Na2CO3/straw) have reached 48.9% and 80.6% respectively at a desulfurization temperature of 80℃.     

两相催化体系中辛烯的氢甲酰化反应研究

考察了反应温度、膦／铑化、表面活性剂种类及浓度、CO／H2压力比等因素对水溶性铑－膦配合物RhCI(CO)(TPPTS)2催化剂催化1－辛烯、2－辛烯氢甲酰化反应活性的影响,并选择出了优化的反应条件。研究结果表明,在该体系中表面活性剂的结果是影响RhCI(CO)(TPPTS)2催化2－辛烯转化率和选择性的重要原因,并对在两相体系2－辛烯氢甲酰化反应中表面活性剂十四烷基二甲基苄基氯化铵（BDAC）明显优于十六烷基三甲基溴化铵（CTAB）的原因进行了探讨。     

氧杂氟表面活性剂及其与同电性碳氢表面活性剂混合溶液的表面吸附和胶团形成

研究了四种氧杂氟表面活性及其与同电性直链碳氢表面活性剂混合体系的表面活性;考察了混合体系中的表面吸附和胶团形成现象.在吸附层中分子间有明显的互疏作用,在溶液中倾向于各自形成胶团.还讨论了反离子结合度不同对理想混合胶团的组成CMC的计算的影响,提出了一般的计算式,实验测得这些氧杂氟表面活性剂有较低的胶团反离子结合度.