Gas desulfurization with ferric chelates of EDTA and HEDTA: New model for the oxidative absorption of hydrogen sulfide: New model for the oxidative absorption of hydrogen sulfide

The experimental data of Wubs and Beenackers (AIChE J.1994, 40 (3), 433−444) on the oxidative absorption of H2S into aqueous solutions of ferric chelates of ethylenediaminetetraacetic acid (EDTA) and hydroxyethylethylenediaminetriacetic acid (HEDTA) were reinterpreted using a new penetration model for mass transfer parallel to chemical reaction. Different from the discussion by Wubs and Beenackers (1994), which was based on general, approximate models for the reactive absorption of gases into liquids, it now appears that the diffusivity of ferric chelates of EDTA and HEDTA are in good agreement with the values determined from the reactive absorption of molecular oxygen into aqueous solutions of ferrous EDTA and HEDTA (Wubs and Beenackers, Ind. Eng. Chem. Res.1993, 32, 2580−2594). Also, it now appears that the data from Wubs and Beenackers (1994) are compatible with ferric chelate complex equilibrium constants, reported elsewhere (for instance, Martell and Smith, Critical StabilityConstants, 1982). Reinterpretation of the absorption data from Wubs and Beenackers (1994) resulted in the following kinetic rate constants (T = 293 K, CFe(III) = 78 mol/m3 and 2 ≤ pH ≤ 9):  EDTA, monohydroxylated complex, 250 ≤ k1,1 ≤ 300 m3/(mol s); HEDTA, monohydroxylated complex, 1.4 ≤ k1,1 ≤ 1.6 m3/(mol s); HEDTA, dihydroxylated complex, 550 ≤ k1,1 ≤ 650 m3/(mol s); for the reaction rate expressed by −RH2S = k1,1CH2SCFe(III)

Onderzoek en veredeling op het gebied van Fusarium resistentie bij de anjer in Frankrijk en Italie ; (reisverslag maart 1986

In het bezochte gebied bevinden zich de belangrijkste centra voor onderzoek- en veredeling aan anjer in Europ

Oxidation of ferrous nitrilotriacetic acid with oxygen: A model for oxygen mass transfer parallel to reaction kinetics

The kinetics of the reaction of ferrous chelate of nitrilotriacetic acid (NTA) and gaseous oxygen were studied in a stirred-cell reactor. The initial concentration of ferrous chelate was 0.100 kmol/m(3). Other reaction conditions include 293 <T <333 K, 2 <pH <10, and 20 <p(O2) <90 kPa. The structure of ferrous chelates as a function of temperature and pH was studied by potentiometric titrations. Under the conditions applied, the reaction rate appeared to proceed according to R-O2 = k(1,2)C(O2)C(Fe(II))(2) with k(1,2)(infinity) = (1.4 +/- 0.35) x 10(7) m(6)/mol(2) s and E-a = 52.5 +/- 1.4 kJ/mol for no excess NTA. In the presence of excess NTA, a double-coordinated ferrous species is produced, whose reactivity appears to depend on pH and NTA concentration. Due to undesired side reactions with ligand NTA, more oxygen disappears than expected from the conversion of ferrous chelate. If no excess ligand is present, the gas absorption rate is pH-dependent for pH less than or equal to 4. Excess ligand results in a pH-dependence over the entire pH-range studied. The observed regeneration rate as a function of pH can be explained from a more comprehensive model, accounting for complex chemical reaction, in parallel with interfacial mass-transfer limitations