The solubility of mixtures of carbon dioxide and hydrogen sulphide in an aqueous dipa solution

The solubility of mixtures of carbon dioxide and hydrogen sulphide in an aqueous solution of di-isopropanolamine (2.5 kmol m^?3 DIPA) has been measured at temperatures of 40 °C and 100°C. Partial pressures of CO₂ ranged from 2.0 to 5991 kPa, while partial pressures of H₂S ranged from 1.3 to 4126 kPa.     

New AMP/polyamine blends for improved CO2 capture: Study of kinetic and equilibrium features

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.     

The solubility of mixtures of H2S and CO2 in an mdea solution

The solubility of mixtures of hydrogen sulfide and carbon dioxide in a 50 mass per cent aqueous solution of methyldiethanolamine (MDEA) solution has been measured at 40°, 70° and 100°C. Partial pressures of the acid gases ranged from 0.08 to 10 450 kPa.     

Equilibrium solubility of H2S and CO2 and their mixtures in a mixed solvent

The solubility of hydrogen sulphide, carbon dioxide, and their mixtures has been measured at 40° and 100°C in a mixed solvent consisting of 20.9 wt% MDEA (methyldiethanolamine), 30.5 wt% sulfolane (tetrahydrothiophene-1, 1-dioxide), and 48.6 wt% water. The results have been compared with those for aqueous 2.0 mol/dm³ MDEA and an analogous mixed solvent, containing AMP (2-amino-2-methyl-1-propanol), which are available in the literature. These data were used to modify the solubility model of Deshmukh and Mather (1981) to account for the mixed solvent effects on the system thermodynamics. Results show that the model is useful as a first approximation in predicting acid gas solubilities; agreement with experiment was generally found to be within £15%.     

The development of kinetics model for CO2 absorption into tertiary amines containing carbonic anhydrase

CO₂ absorption into aqueous solutions of two tertiary alkanolamines, namely, MDEA and DMEA with and without carbonic anhydrase (CA) was investigated with the use of the stopped‐flow technique at temperatures in the range of 293–313 K, CA concentration varying from 0 to 100 g/m³ in aqueous MDEA solution with the amine concentration ranging from 0.1 to 0.5 kmol/m³, and CA concentration varying from 0 to 40 g/m³ in aqueous DMEA solution with the amine concentration ranging from 0.05 to 0.25 kmol/m³. The results show that the pseudofirst‐order reaction rate (k_{0, amine}; s^?1) is significantly enhanced in the presence of CA as compared with that without CA. The enhanced values of the kinetic constant in the presence of CA has been calculated and a new kinetics model for reaction of CO₂ absorption into aqueous tertiary alkanolamine solutions catalyzed by CA has been established and used to make comparisons of experimental and calculated pseudo first‐order reaction rate constant (k_{0, with CA}) in CO₂‐MDEA‐H₂O and CO₂‐DMEA‐H₂O solutions. The AADs were 15.21 and 15.17%, respectively. The effect of pKa on the CA activities has also been studied by comparison of CA activities in different tertiary amine solutions, namely, TEA, MDEA, DMEA, and DEEA. The pKa trend for amines were: DEEA > DMEA > MDEA > TEA. In contrast, the catalyst enhancement in amines was in the order: TEA> MDEA> DMEA> DEEA. Therefore, it can be seen that the catalyst enhancement in the amines decreased with their increasing pKa values. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Measurement of heat of mixing for ammonium chloride + ammonia system at 25 °c

Heat of mixing for ammonium chloride in liquid ammonia at 25°C was determined in the concentration range 0-50 wt% NH₄Cl. It was calculated from the differential heat of solution observed in this work and the differential heat of dilution estimated from activities of solvent. A twin isoperibol calorimeter consisting of two stainless Dewar vessels was used at a relatively high pressure (up to 1.5 MPa). The accuracy of this calorimetry was examined by measuring the heat of solution for tris-(hydroxymethyl)aminomethane(THAM) in 0.1 kmol/m³ HCl at 25°C, and satisfactory agreement within 1.1% between experimental and literature value was obtained. The reproducibility for the experiment was within 2.8%.     

The solubility of H2S and CO2 in a diethanolamine solution at low partial pressures

The solubility of H₂S, CO₂ and their mixtures in a 2.0 kmol m^?3 aqueous solution of diethanolamine has been determined at 40°C and 100°C at partial pressures of the acid gases between 0.003 and 6.5 kPa. The results have been compared with values calculated by a method of prediction.     

Chemical Absorption of Carbon Dioxide into Aqueous Colloidal Silica Solution with Diethanolamine

Abstract

The chemical absorption rate (R_A) of CO₂ was measured into the aqueous nanometer sized colloidal silica solution of 0–31 wt% and diethanoleamine of 0–2 kmol/m³ in the flat‐stirred vessel with the impeller size of 0.034 m and its agitation speed of 50 rev/min at 25°C and 0.101 MPa, and compared with the values estimated from the model based on the film theory accompanied by chemical reaction. The value of the volumetric liquid‐side mass transfer coefficient (k_La) of CO₂, which was used to estimate the value of R_A, was obtained by the empirical correlation formula presenting the relationship between k_La and the rheological behavior of the aqueous colloidal silica solution. The value of R_A in the aqueous colloidal silica solution was decreased by the reduction of k_La due to the elasticity of the solution.     

Degradation of alkanolamine blends by carbon dioxide

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.     

The oxidation of aqueous sodium sulphite solutions

In this paper new experimental work on the kinetics of the absorption of oxygen in an aqueous solution of sodium sulphite with cobaltous sulphate as a catalyst, has been presented and compared with already published data. It is shown that the reaction of oxygen with sodium sulphite is zero order in sulphite, first order in cobalt and second order in oxygen for 2 × 10⁴ N/m² <p_O2 < 10⁵ N/m², 150°C <T < 60°C, 3 × 10^?6 kmol/m³ <c_Co⁺⁺ < 3 × 10^?3 kmol/m 7.50 < pH < 8.50 and 0.4 kmol/m² <c_SO2-- < 0.8 kmol/m³. The reaction rate constant can be varied by more than two decades by changing the cobalt concentration, pH and temperature.The specific interfacial areas, a, and mass transfer coefficients, k_L, measured by DeWaal and Beek [14, 15] using an incorrect kinetic model of this reaction, are reinterpreted with the results of the present kinetic investigation. It is shown that their values of a and k_L are a factor 2.2 too low and too high, respectively, but that their values of k_La are correct.     

The kinetics of dissolved oxygen reaction in aqueous sodium dithionite solutions

The kinetics of the reaction between dissolved oxygen and sodium dithionite in alkaline aqueous solution was investigated in a stirred cell. For dithionite concentrations below 0.08 kmol/m³ and sodium hydroxide concentrations from 0.044 to 0.27 kmol/m³, the results show the reaction to be first order in dithionite and zero order in oxygen. The Arrhenius activation energy was determined to be 76.2 MJ/kmol in the temperature range 15 to 34°C. Addition of other electrolytes (sodium sulphate or potassium chloride) had no effect on the kinetics.     

Characterizations of composite cathodes with La0.6Sr0.4Co0.2Fe0.8O3?δ and Ce0.9Gd0.1O1.95 for solid oxide fuel cells

Composite cathodes with La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ (LSCF) and Ce_0.9Gd_0.1O_1.95 (GDC) are investigated to assess for solid oxide fuel cell (SOFC) applications at relatively low operating temperatures (650–800 °C). LSCF with a high surface area of 55 m²g⁻¹ is synthesized via a complex method involving inorganic nano-dispersants. The fuel cell performances of anode-supported SOFCs are characterized as a function of compositions of GDC with a surface area of 5 m²g⁻¹. The SOFCs consist of the following: LSCF-GDC composites as a cathode, GDC as an interlayer, yttrium stabilized zirconia (YSZ) as an electrolyte, Ni-YSZ (50: 50 wt%) as an anode functional layer, and Ni-YSZ (50: 50 wt%) for support. The cathodes are prepared for 6LSCF-4GDC (60: 40 wt%), 5LSCF-5GDC (50: 50 wt%), and 4LSCF-6GDC (40: 60 wt%). The 5LSCF-5GDC cathode shows 1.29 Wcm⁻², 0.97 Wcm⁻², and 0.47 Wcm⁻² at 780 °C, 730 °C, and 680 °C, respectively. The 6LSCF-4GDC shows 0.92 Wcm⁻², 0.71 Wcm⁻², and 0.54 Wcm⁻² at 780 °C, 730 °C, and 680 °C, respectively. At 780 °C, the highest fuel cell performance is achieved by the 5LSCF-5GDC, while at 680 °C the 6LSCF-4GDC shows the highest performance. The best composition of the porous composite cathodes with LSCF (55 m²g⁻¹) and GDC (5 m²g⁻¹) needs to be considered with a function of temperature.     

Vapor pressure and heat of solution of sulfur dioxide in 1-methyl-2-pyrrolidone and its aqueous solution

A new method was developed to measure the vapor pressure of sulfur dioxide above various liquid absorbents. It was applied to pure 1-methyl-2-pyrrolidone and its aqueous solution at 50°C to 91°C for SO₂ loadings of 3.73 × 10 ⁴ kg/kg to 2.16 × 10 ⁻² kg/kg. A chemical model was developed. The heat of solution was calculated from the dependence of the vapor pressure on temperature and was 3.98 × 10⁷ J/kmol (exothermic) for pure 1-methyl-2-pyrrolidone. The vapor pressures disagreed with the only previously published set of results but were confirmed by independent measurements with a gas chromatograph.     

Increasing the performance of asymmetric pervaporation membranes for the separation of methanol/methyl-tert-butyl ether mixtures by the introduction of sulfonated polyimide into the poly(amide-imide) matrix

A series of novel asymmetric membranes from polymer composites of poly(amide-imide) with various content of sulfonated polyimide (1–6 wt%) was obtained through the nonsolvent-induced phase separation process. Selective transport properties of the obtained materials were investigated in terms of pervaporation separation of methanol/methyl-tert-butyl ether mixtures at different temperatures. The introduction of the sulfonated polyimide to the poly(amide-imide) matrix leads to a significant increase in membrane flux and an overall decrease in the process selectivity. Composite membranes having 1 wt% sulfonated polyimide in the matrix showed increased values of membrane flux (0.960 kg m⁻² h⁻¹ in comparison with 0.682 kg m⁻² h⁻¹ for unmodified membranes at 40°C, 10 wt% methanol), while having similar selectivity values (79.2 wt% methanol in permeate in comparison with 82 wt% for unmodified membranes at 40°C, 10 wt% methanol). Modified membrane showed the highest separation factor of 147 while separating methanol from its 3 wt% mixture with methyl-tert butyl ether at 52°C with the overall flux of 1.01 kg m⁻² h⁻¹. A semiempirical mathematical model was developed and applied to test the efficiency of obtained membranes in the hybrid process of methanol/methyl-tert-butyl ether mixtures separation.     

Studies on the potential of coal fly ash as a heterogeneous catalyst in oxidation of aqueous sodium sulfide solutions with hydrogen peroxide

The potential of fly ash procured form coal-fired thermal power plants was studied as a heterogeneous catalyst in the oxidation of aqueous sodium sulfide solutions with hydrogen peroxide in the temperature range of 303–323 K. The effects of various parameters (source of fly ash, fly ash loading, initial concentrations of sodium sulfide and hydrogen peroxide, electrolyte and deactivation of catalytic effect of fly ash) were studied. For an initial sodium sulfide and hydrogen peroxide concentration of 26·98×10⁻² kmol m⁻³ and 24·28×10⁻² kmol m⁻³ respectively, only 4% (w/v) fly ash loading intensified the rate of oxidation by a factor of 4·52 over that without fly ash at 303 K. The deactivation of the catalytic effect of fly ash was found to be less than 20% even after six repeated uses. The kinetics of aqueous phase decomposition of hydrogen peroxide was also studied in the presence of fly ash in alkaline medium. ©1997 SCI     

Integral conversion of SO2: Hysteresis and rate discontinuities

The oxidation of SO₂ was carried out over an American Cyanamid V₂O₅ catalyst in an insulated integral reactor without significant interparticle resistances under the following conditions: 10 percent SO₂-air feed, feed temperatures in the range of 430°C to 590°C, 108 kPa pressure, and entrance temperatures of the gases in the annular heat exchanger from 400°C to 450°C, with one set of conversions being obtained without annular air flow. Gas analysis was accomplished by the oxidation of SO₂ to SO₃ with potassium permanganate. The method was fully tested before adoption. Final conversions in the range of 5 to 60 percent were observed. A hysteresis loop was found in the plane of outlet conversion versus the average feed temperature. The multiplicity is possibly stable but probably decays with the time constants in the order of days which is evident from the transient data that were obtained. A one dimensional model was able to correlate the conversion data through the Arrhenius rate parameters in the Boreskov-Sokolova⁽⁸⁾ rate expression which changed from A = 1.92 × 10⁷ m³/(s·kg) and E = 151 MJ/kmol to A = 0.344 m³/(s·kg) and E = 33.5 MJ/kmol at a calculated temperature at the surface of the catalyst of 517°C. Similar behavior has been observed in other studies concerned with basic kinetic studies over catalyst pellets. The analogy between the behavior of the catalyst pellets and the behavior of the integral reactor can thus be fully drawn with respect to hysteresis and rate discontinuities.     

Surface Energetics of Nanoscale LaMnO3+δ Perovskite

Perovskite type LaMnO₃ and related materials are important compounds with many useful and unique physical and chemical properties. There is a lack of experimental thermochemical data on the energetics of LaMnO₃ nanoparticles. In this work, a series of LaMnO_3+δ samples were synthesized via the citrate method and calcined at 700°C–1050°C. All samples displayed rhombohedral structure (X‐ray diffraction) with similar oxygen stoichiometry 3+δ = 3.16–3.18 (iodometric titration coupled with gravimetric analysis). The BET surface area varied from null for bulk sample to 6.88 ± 0.08 × 10³ m²/mol for the sample calcined at 700°C. The water content varied linearly with the surface area with the highest value being 2.34 wt%. The chemisorbed water adsorption enthalpy was ?63.0 ± 4.1 kJ/mol with the chemisorbed water coverage of 8 H₂O/nm². High‐temperature oxide melt drop solution calorimetry, performed in sodium molybdate at 702°C, yielded enthalpy of formation from La₂O₃, Mn₂O₃, and O₂ of bulk LaMnO_3.16 of ?77.85 ± 1.94 kJ/mol. After correction of drop solution enthalpies of nanometric samples for water content, the calorimetric data were used to calculate the surface energy of LaMnO_3+δ. The energy of the anhydrous surface was 2.27 ± 0.29 J/m², and that of the hydrous surface was 2.02 ± 0.27 J/m². These values are higher than the surface energies of LaMnO_3.00 predicted elsewhere by theoretical methods, probably due to the different oxygen content and possibly more complex surface structure and exposed surface planes. The measured surface energy of LaMnO_3+δ lies between the values reported recently for BaTiO₃ and PbTiO₃ and close to the reported values for MnO₂. This suggests that LaMnO_3+δ surface is predominantly MnO₂‐terminated, in line with the trends predicted by theoretical calculations.     

Absorption of carbon dioxide in aqueous colloidal silica solution with NaOH

The absorption rate (R _A ) of carbon dioxide was measured into an aqueous nanometer-sized colloidal silica solution of 0–31 wt% and NaOH of 0–2 kmol/m³ in a flat-stirred vessel for various sizes and speeds of 25 °C and 101.3 N/m² to obtain the volumetric liquid-side mass transfer coefficient (k _L a _L ) of CO₂. The film theory accompanied by chemical reaction between CO₂ and NaOH was used to estimate the theoretical value of absorption rate of CO₂. The empirical correlation formula containing the relationship between k _L a _L and rheological property of the aqueous colloidal silica solution was presented. The value of R _A in the aqueous colloidal silica solution was decreased by the reduction of k _L a _L due to elasticity of the solution.     

Absorption of Carbon Dioxide into Aqueous Xanthan Gum Solution Containing Monoethanolamine

Abstract

Carbon dioxide was absorbed into the aqueous xanthan gum (XG) solution in the range of 0–0.151 wt% containing monoethanolamine (MEA) of 0–2 kmol/m³ in a flat‐stirred vessel with the impeller of 0.05 m and agitation speed of 50 rpm at 25°C and 0.101 MPa to measure the absorption rate of CO₂. The volumetric liquid‐side mass transfer coefficient (k_La_L) of CO₂ decreased with increasing XG concentration, and was correlated with the empirical formula having the rheological behavior of XG solution. The chemical absorption rate of CO₂ was estimated by the film theory using the values of k_La_L and physicochemical properties of CO₂ and MEA. The aqueous XG solutions made the rate of absorption of CO₂ accelerated compared with the Newtonian liquid based on the same viscosity of the solution.     

THE DIFFUSION COEFFlCIENT OF HEHEHP IN HEPTANE MEASURED BY THE MODIFIED STOKES CELL TECHNIQUE AT TEMPERATURES BETWEEN 25 AND 55°C.

The diffusion coefficient of HEHEHP in heptane has been measured by the modified Stokes cell technique at temperatures between 25 and 55^°C. The Stokes cell was calibrated by measuring acetic acid diffusion with the pH-stat technique. The average diffusion coefficient of HEHEHP in heptane was determined to be 0.97 × 10 ^?9 m²/s at 25 ^°C for HEHEHP concentrations of 0 - 0.1 kmol/m³. The diffusion coefficient did not vary significantly with HEHEHP concentration. The Wilke-Chane relationship was used to predict D values of 1.53 × lO^?9m²/s and 1.01 × 10 ^?9m²/s for the monomelic and dimeric species respectively. Comparison of the measured and predicted diffusion coefficients led to the conclusion that the HEHEHP was substantially dimenzed over the concentration range studied

An activation energy of 6.90 kJ/mol was calculated from the diffusion coefficient measurements at elevated temperature.