Erkki Paatero

Determination of acid value, hydroxyl value and water content in reactions between dicarboxylic acids and diols using near-infrared spectroscopy and non-linear partial least squares regression

Abstract A predictive calibration model based on non-linear partial least squares (PLS) regression was developed to describe the relationship between the near-infrared (NIR) reflectance spectra and the acid value, hydroxyl value and water, content in polyesterification of dicarboxylic acids with diols. Two dicarboxylic acids and six diols were tested in different combinations with one dicarboxylic acid and one diol at a time. The polyesterifications were carried out isothermally in a laboratory scale semi-batch reactor at temperatures between 140–190 °C. NIR spectrometry offers a fast in-line method for monitoring and controlling the polyesterification reaction. A predictive model which relates all the NIR spectra and the measured acid values was developed. The calibration of the NIR spectra and the hydroxyl value succeeded in experiments where the hydroxyl value was determined. The measured water content and the NIR spectra could not be calibrated with the same model for different dicarboxylic acid and diol combinations. Principal component analysis (PCA) was used to classify the NIR spectra. The spectra could be classified according to the dicarboxylic acid and diol used in the experiment.

Effect of reversed micelles in Co/Ni separation by Cyanex 272

Abstract The extraction and separation of cobalt and nickel from aqueous sulphate solutions using Cyanex 272 reagent (Cytec Industries) in isooctane and D-70 (Shell Chemicals) was studied. The extractant was pre-neutralised with concentrated ammonia water, which forms a one-phase solution at an ammonia/reagent molar ratio of 1:1. The extraction experiments were carried out in a vigorously agitated co-current column reactor with fast phase separation in which the contact time could be varied between 2 and 90 s. The extraction kinetics of Co and Ni are very fast. During the first 10 s of phase contact about 90% of the metals are extracted into the organic phase. At the shortest contact time, when a small amount of cobalt and nickel had been extracted, the organic phase contained reversed micelles enclosing water, metal ions and ammonia. With increasing cobalt loading, the reversed micelles broke up and the concentration of water and nickel decreased in the organic phase. To achieve a high cobalt/nickel separation, the cobalt/extractant molar ratio should be 1 to 4 when the degree of neutralisation of the Cyanex 272 is equal to about 50%. In a system with 10 wt.% Cyanex 272 in D-70 diluent and 3.5 g/L Co and 30 g/L Ni in the aqueous feed, the highest separation factor (5000) was obtained when the feed phase volume ratio was 1:1 and the degree of neutralisation ( N ) was 45%. The pre-neutralised reagent was in that case in the form of a two-phase (liquid–liquid) solution.

Nanoporous manganese oxides as environmental protective materials-effect of Ca and Mg on metals sorption.

The selectivity of nanoporous manganese oxides for some alkali and transition metals over calcium and magnesium was studied. Two tunnel-structured oxides (OMS-1 and OMS-2) were synthesized by means of a hydrothermal route. Competitive uptake of metals and acid was studied using batch kinetic measurements at different metal ion concentrations. The experimental data were correlated with a dynamic model. The results show that the studied OMS materials selectively adsorb Cu, Ni and Cd in the presence of Ca and Mg. It was also found that the exchange rates were reasonably high due to the small particle dimensions. Both materials are stable in the studied conditions and their maximum Cu uptake capacity was 0.9-1.3 mmol/g. The results indicate that both materials have potential for environmental applications involving the uptake of harmful metal ions.

Kinetics of melt polymerization of maleic acid phthalic acids with propylene glycol

Abstract The kinetics of melt polymerization of maleic anhydride and phthalic anhydride with propylene glycol was studied in a laboratory-scale batch reactor operating at 160–220°C and at atmospheric pressure. Phthalic and maleic anhydrides are suitable model molecules for the polyesterification studies, since in the polymerization of phthalic anhydride only the esterification reaction takes place, but in the polymerization of maleic anhydride the double bonds isomerize and become partially saturated by the alcohol. A kinetic model was developed which included the polyesterification, isomerization and double bond saturation during the polymerization. The kinetic model was based on the principle of equal reactivities of the functional groups. The rate equations were coupled to the reactor mass balances, in which the change of the reaction mass due to water evaporation was included. The rate parameters for esterification, isomerization and double bond saturation were estimated from the experimental data by using nonlinear regression analysis. The kinetic model described well the polymerization data of maleic and phthalic anhydrides.

Monitoring the kinetics of the ion-exchange resin catalysed esterification of acetic acid with ethanol using near infrared spectroscopy with partial least squares (PLS) model

Abstract The esterification of acetic acid with ethanol in the presence of a heterogeneous acid catalyst was monitored by near infrared (NIR) spectroscopy. A strong acid macroporous poly(styrene- co -divinylbenzene) based ion-exchange resin was used as catalyst. The liquid phase esterification was carried out in a stirred batch laboratory reactor at 60°C. Samples taken from the reaction mixture were analysed both by NIR spectroscopy and by gas chromatography (GC). The concentration of the reactants acetic acid and ethanol as well as the reaction products water and ethyl acetate were predicted from NIR spectra by multivariate PLS calibration model and compared to concentrations obtained by GC. The results of the PLS predictions showed that the spectral range from 7600 to 3800 cm −1 is well suited for concentration measurements. The concentrations of acetic acid, ethanol, ethyl acetate and water were successfully predicted from the NIR spectra. Reaction monitoring is simpler and faster by NIR than by GC. NIR spectroscopy enables simultaneous on-line monitoring of all reaction components with an accuracy better than that obtained in this work by using GC.

Kinetic model for main and side reactions in the polyesterification of dicarboxylic acids with diols

A rate model based on a reaction mechanism was proposed for the melt polyesterification of dicarboxylic acids with diols for the case that no catalyst is added. The model includes the esterification, the cis-trans isomerization and the double bond saturation reactions. All three reactions are acid catalyzed. The overall reaction order of the main reaction increases with conversion due to a shift of the ionic equilibria in the liquid phase. This increase of the reaction order was described with a semi-empirical function. Experiments were carried out for the esterification of maleic acid with propylene glycol at 160–220°C in a laboratory scale batch reactor. The derived rate model successfully described the isomerization of maleic acid to fumaric acid, the saturation of the double bonds, and the polyesterification of maleic and fumaric acids. The model included two parameters for each of the three types of reactions taking place simultaneously.

Complex stability of sugars and sugar alcohols with NA + , CA 2+ , and LA 3+ in chromatographic separations using poly(styrene- CO -divinylbenzene) resins and aqueous organic eluents

The complex formation between metal ions and carbohydrates in solvent mixtures has been studied by chromatographic measurements. The effect of noncomplexing partition was decreased by attaching the active groups only on the shell of the stationary phase particles. Poly(styrene- co -divinylbenzene) resin beads were surface-sulfonated for that purpose. Thus the inner part of the sulfonated bead remained inactive and nonswellable. The counter-ions examined were Na + , Ca 2+ , and La 3+ , and the organic cosolvents were ethanol and acetonitrile. The stability constants of the very weakly complexing D -glucose, D -xylose, and L -rhamnose, the weakly complexing D -fructose and L -arabinose, and the strongly complexing xylitol and D -sorbitol were determined. The increasing organic cosolvent content increased the retention times, which is explained by the increased complex stability between the complexing solute and the counter-ion. The effect was greatest for the complex-forming sugars in the Ca 2+ form and for the sugar alcohols in the La 3+ form. The organic cosolvent had only a minor effect on the weakly complexing components, whereas the complex stability of the strongly complexing xylitol and sorbitol in 50 wt% ethanol solution in the La 3+ resin was more than five times higher compared to the stability measured in pure water.

Properties of the ammonium form of Versatic 10 in a liquid-liquid extraction system

Abstract The commercial reagent Versatic 10 (Shell Chemical) based on a mixture of highly branched isomers of C10 monocarboxylic acids is used to study the ammonium salt form of an acidic liquid cation exchanger for metal extraction. The degree of neutralisation is varied and the neutralisation process is considered by determining the phase equilibria and analyzing the distribution of components between phases as a function of pH. When gradually neutralising Versatic 10 with aqueous ammonia, first an ammonium carboxylate complex is formed in the organic phase with a stoichiometry of NH4A⋅4HA⋅qH2O where q=1.0–2.5. When the amount of ammonia is further increased a phase inversion is observed at about pH 8.4 as the concentration of Versatic 10 in the aqueous phase dramatically increases and the amounts of water and ammonia dramatically decrease in the organic phase. When concentrated ammonia (>about 2 M) in water is used for neutralisation a one-phase microemulsion is observed at the phase inversion pH. The one-phase region where maximal solubilization takes place is at 50% degree of neutralisation. Compared to normal organic phase this microemulsion solution has higher electrical conductivity and viscosity.

Polyesterification kinetics of complex mixtures in semibatch reactors

Abstract A systematic stoichiometric and kinetic model was developed for the acid-catalysed polyesterification of unsaturated dicarboxylic acids and mixtures of dicarboxylic acids. The model was based on a rigorous treatment of the functional groups and their reactions: esterification, cis–trans isomerization and double-bond saturation through Ordelt reaction. The model was applied on the polyesterification of maleic and phthalic acids with ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol in a semi-batch reactor at 160–195°C. Kinetic and thermodynamic parameters included in the model were estimated with non-linear regression. It was found that important simplifications can be introduced: the rate constants of the different esterification and isomerization reactions can be set equal, whereas it was necessary to treat the different double-bond saturation reactions with individual rate constants. A comparison of model predictions with experimental data revealed that the proposed kinetic treatment is relevant for polyesterification of complex mixtures.

Co-eluent effect in partition chromatography. Rhamnose-xylose separation with strong and weak cation-exchangers in aqueous ethanol.

The effect of ethanol in aqueous eluent on the chromatographic separation was studied at 298 K. Two sugars, L-rhamnose and D-xylose, were separated by using strong and weak cation-exchangers as a stationary phase. The ionic form of the resins was Na+ or Ca2+. The separations were carried out with sugar feed concentrations up to 35 wt% and with both low (about 1%) and high (about 10%) feed volume to bed volume ratios. The separation of the sugars was improved by adding ethanol into the eluent. The separation was also significantly enhanced when the weak cation-exchangers with the greatest affinity for water were used instead of strong cation-exchangers as a separation medium for the sugars having different hydrophilicities. The experimental data were successfully explained with a rate-based column model, which accounted for the volume changes of the stationary phase. A thermodynamic sorption model was utilized in column calculations.