Dowex 50W-X8 Research Articles

An Investigation of Lanthanum Recovery from an Aqueous Solution by Adsorption (Ion Exchange)

Lanthanum (La(III)) is one of the high-demand rare earth elements with applications in various products. However, La(III) in mining waste streams and electronic waste also poses environmental and health concerns. Therefore, the recovery of La(III) in the waste is needed. In the present study, the adsorption of La(III) with Dowex 50W-X8, Amberchrom50WX4, Amberlyst 15, and Amberchrom 50WX2 was evaluated using a shaker water bath. Dowex 50W-X8 was found to be the best adsorbent and was used to investigate the effect of the shaker speed (RPM = 50–150), adsorbent dosage (1.0–4.0 g), pH (2.0–7.0), and temperature (20–40 °C) on adsorption. La(III) adsorption was found to increase with the shaker speed, as expected. On the other hand, the adsorption capacity decreased with the adsorbent amount. Also, the highest La(III) adsorption was observed at pH = 6.0. La(III) percentage removal did not vary significantly with a temperature from 20 °C to 40 °C. However, the first-order kinetic rate constant decreased moderately with increases in temperature. The adsorption of La(III) by Dowex 50-X8 followed the Freundlich isotherm model better than the Langmuir model. In addition, the adsorption kinetics were represented well by the pseudo-first-order kinetic model. Moreover, enthalpy and Gibbs free energy changes were found to be negative, indicating an exothermic and thermodynamically favorable adsorption process.

Pseudo-ternary chromatographic separation of dihydroxyacetone from the glycerol oxidation byproducts on a simulated moving bed cascade

The goal of this work was to experimentally separate dihydroxyacetone from glycerol oxidation products obtained over a Pt-Bi/AC catalyst, using a cascade of two simulated moving bed (SMB) units. For that, the lab-scale FlexSMB-LSRE® unit was used with six columns packed with a strong cationic exchange resin, the DOWEX 50WX-2, in acidic and calcium form. An SMB model was implemented in the gPROMS model builder software and used to design the separation regions, considering kinetic and equilibrium data previously obtained by frontal analysis on a fixed-bed column. Dihydroxyacetone was separated from the organic acids on the SMB packed with the resin in H+ form, being collected in the extract stream with 96.8 % purity on a glycerol-free basis and 87.0 % recovery. This stream was fed to a second unit packed with the resin in Ca2+ form, separating dihydroxyacetone from glycerol with 98.6 % purity and 89.0 % recovery. The SMB cascade showed a productivity of 21.7 kgDHA (m3adsorbent·day)−1, and an eluent consumption of 5.7 m3eluent kgDHA−1. The SMB model described accurately the experimental data.

Sorption and leaching of lithium ions from aqueous nitrate/ascorbate solution using Dowex 50WX8 sodium form

ABSTRACT In this work, Green and sustainable sorption method for Li(I) from nitrate medium using a solid functionalised Na+ form of Dowex 50WX8 resin was developed. Scanning electron microscope (SEM), Fourier transform infrared (FT-IR), and energy-dispersive X-ray (EDX) techniques were used for characterisations of Dowex resin before and after the loading of Li ions. The batch technique describes the effects of the different parameters affecting the sorption process was carried out. The batch experiments were studied using 100 mg/L Li(I) at the selected sorption conditions (shaking time = 30 min, adsorbent weight = 0.125 g, temperature= 25°C, and pH = 1) which give sorption efficiency = 60%. The experimental maximum sorption capacity of Dowex 50WX8-Na+ after one sorption cycle was found to be 15 mg/g . Thermodynamic studies indicated that the sorption of the Li(I) on Dowex 50WX8-Na+ resin is physical and exothermic adsorption with spontaneous nature. The maximum desorption efficiency of 85% and 70% was achieved with 1.0 M phosphoric acid and oxalic acid, respectively. An industrial application for green recycling and recovery of Li(I) from spent Li-ion batteries (LIBs) through its leaching with ascorbic acid (1.25 M) and H2O2 (10%) was performed. Lithium ions were selectively recovered (uptake %= 96%) from the spent Li-ions batteries leachate which contains associated metal ions (Co, Ni, and Mn) with Dowex 50Wx8-Na+ sorbent. A flow sheet that presents the performance of industrial method developed for the recycling and separation of Li(I) from (LIBs) under optimum sorption conditions is also provided.

ЦИТОТОКСИЧНА / ЦИТОСТАТИЧНА ДІЯ НА ПУХЛИННІ КЛІТИНИ ЛІНІЇ HELA КУЛЬТИВОВАНИХ ГРИБІВ FLAMMULINA VELUTIPES, CYCLOCYBE AEGERITA ТА HERICIUM ERINACEUS

The use in clinical and pharmaceutical practice of biological preparations obtained from natural raw materials, in particular from mushrooms, is of urgent importance. Currently, the cultivation technologies of medicinal mushrooms are widely used, the mycelium of which contains a significant amount of cytokinins – stimulators of proliferation and differentiation of various types of plant cells, which also exhibit an immunomodulatory and oncostatic effects in the organism of animals and humans. Therefore, the aim of this work was to determine the cytotoxic/cytostatic effect of cultivated mushrooms Flammulina velutipes, Cyclocybe aegerita and Hericium erinaceus. Purification of cytokinins was carried out in stages, using methods of centrifugation, fractionation with n-butanol, ion exchange chromatography on Dowex 50Wx8 columns and thin-layer chromatography on Silicagel 60 F254. Identification and quantification of cytokinins was performed by by liquid chromatography in the reverse phase of MS (Agilent 1200 LC, USA) on an Agilent Zorbax Eclipse XDB-C18 column. Cytotoxic/cytostatic screening was performed on HeLa cells derived from human cervical cancer tumors using the MTT assay and routine counting of the ratio of live to dead cells. The results of the research showed that the highest content of cytokinins per 1 g of dry weight was characteristic of cultivated mushrooms of the species H. erinaceus. Also, H. erinaceus has the highest toxicity against human cervical cancer cells of the HeLa line, while the mushrooms F. velutipes and C. aegerita showed a cytostatic (antiproliferative) effect.

Oxidation of benzyl alcohol catalyzed by ligand-stabilized Au nanoparticles in the presence of weak bases

Ligand-stabilized gold nanoparticles (tetrakis(hydroxymethyl)phosphonium chloride-Au, citrate-Au, cetrimonium bromide-Au) were synthesized and mixed with several weak-base solids (barium carbonate, Amberlite IRA-900) and acidic solid (Dowex 50WX2 resin). Those catalysts were applied for the oxidation of benzyl alcohol in water at 80 oC. Almost ligand-stabilized Au nanoparticles/weak-base solids showed good conversion of benzyl alcohol and high selectivity of benzoic acid, whereas ligand-stabilized Au nanoparticles/acidic solid were catalytically inactive. Nanoparticles were characterized by transmission electron microscopy, zetapotential measurement, and dynamic light scattering. The catalytic activity and product selectivity were determined by using a gas chromatography coupled with a mass selective detector. Our study suggests that the oxidation reaction in water could be catalyzed by gold with the presence of weak-base solids.

Modeling and equilibrium studies on the recovery of praseodymium (III), dysprosium (III) and yttrium (III) using acidic cation exchange resin

In this research, the possibility of using hydrogenated Dowex 50WX8 resin for the recovery and separation of Pr(III), Dy(III) and Y(III) from aqueous nitrate solutions were carried out. Dowex 50WX8 adsorbent was characterized before and after sorption of metal ions using Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (EDX) techniques. Sorption parameters were studied which included contact time, initial metal ion concentration, nitric acid concentration and adsorbent dose. The equilibrium time has been set at about 15.0 min. The experimental results showed that the sorption efficiency of metal ions under the investigated conditions decreased with increasing nitric acid concentration from 0.50 to 3.0 M. The maximum sorption capacity was found to be 30.0, 50.0 and 60.0 mg/g for Pr(III), DY(III) and Y(III), respectively. The desorption of Pr(III) from the loaded resin was achieved with 1.0 M citric acid at pH = 3 and found to be 58.0%. On the other hand, the maximum desorption of Dy(III) and Y(III) were achieved with 1.0 M nitric acid and 1.0 M ammonium carbonate, respectively. The sorption isotherm results indicated that Pr(III) and Y(II) fitted with nonlinear Langmuir isotherm model with regression factors 0.995 and 0.978, respectively; while, Dy(III) fitted with nonlinear Toth isotherm model with R2 = 0.966. A Flow sheet which summarizes the sorption and desorption processes of Pr(III), DY(III) and Y(III) using Dowex 50WX8 from nitric acid solution under the optimum conditions is also given.

Size Selectivity in the Hydroxylation of Esters of Unsaturated Fatty Acids

AbstractThe one‐pot two‐steps hydroxylation of fatty acid esters with H2O2 and acetic acid catalyzed by acidic ion exchange resins is reinvestigated aiming to shed light on the relationship between the structure of different substrates and the efficiency of different resins in promoting the hydrolysis of the intermediate epoxides to the corresponding diols. 1H‐NMR analysis of crude reaction mixtures highlight a correlation between the drying process of the resins, their cross‐linking degree, and their effectiveness in promoting such a hydrolysis. Employing dry Dowex 50WX2 as a catalyst, a close relationship is found between the steric hindrance of the substrates and the recovered diol/epoxide ratio, with less hindered substrates preferentially leading to the formation of high diol/epoxide ratios. Accordingly, this procedure is successfully applied to the valorization of the methyl ester of a waste cooking oil. Conversions and selectivity kinetics increase significantly when the amount of the catalyst is increased leading to successfully apply this one‐pot two‐steps hydroxylation reaction to esters of unsaturated fatty acids sterically bulkier than methyl oleate. Spectroscopic and morphological characterization of Dowex 50WX2 shows that the drying process and the interaction with the reagents affect the morphology of the catalyst and promotes the hydrolysis of the intermediate epoxides.Practical applications: Hydroxylated fatty acids are valuable intermediates in the synthesis of a variety of useful biochemicals, including mono‐ and di‐carboxylic acids, biolubricants, and cosmetics. Their work describes the successful application to a variety of esters of unsaturated fatty acids and to the methyl esters of a vegetable oil and a waste cooking oil, of a straightforward hydroxylation procedure, catalysed by commercially available acidic ion exchange resins and occurring under mild and easy to set‐up conditions. The evidence reported on the different catalytic activities and on the structural characterization of the as‐received and dried acidic ion exchange resins are of practical importance in their employment as acidic catalysts.

Advancement of the Cleavage Methods of Carbohydrate-derived Isopropylidene and Cyclohexylidene Ketals

Abstract:Carbohydrates, amino acids, and nucleosides, the fundamental building blocks of complex biomolecules in nature, are essential starting materials for the fabrication of natural and unnatural structural entities, which necessitate the masking and demasking of various functional groups with the utmost chemoselectivity, mildness, and efficiency to avoid unintended bond breaking and formation, as well as associated reactions. Ketals, benzylidene, methoxymethyl, p-methoxybenzyl, silyl ethers, trityl, tert-butyl carbamate, and other functional groups are widely used in modern organic synthesis. In carbohydrate chemistry, the commonly used protecting functionality of isopropylidene and cyclohexylidene ketals necessitates effective methods for selective cleavage. This review summarises different methods for deblocking isopropylidene and cyclohexylidene ketals using inorganic acids, Lewis acid, silica- supported inorganic acids, Amberlite-120 (H+) resin, phosphotungstic acid, Nafion-H, NaBArF4.2H2O, montmorillonite clay, Dowex 50W-X8, camphorsulphonic acid (CSA), ceric ammonium nitrate, molecular iodine, ionic liquids, zeolites and so on.

Identification of the best medium for experiments on chemical computation with Belousov–Zhabotinsky reaction and ferroin-loaded Dowex beads

Our study is focused on identification of the best medium for future experiments on information processing with Belousov–Zhabotinsky reaction proceeding in Dowex beads with immobilized catalyst inside. The optimum medium should be characterized by long and stable nonlinear behavior, mechanical stability and should allow for control with electric potential. We considered different types of Dowex ion-exchange resins, bead distributions and various initial concentrations of substrates: malonic acid and 1,4-cyclohexanedione. The electric potential on platinum electrodes, stabilized by a potentiostat is used to control medium evolution. A negative electric potential generates activator species HBrO2 on the working electrode according to the reaction: BrO3− + 2e− + 3H+ → HBrO2 + H2O, while positive electric potential attracts inhibitor species Br− to the proximity of it. We study oscillation amplitude and period stability in systems with ferroin loaded Dowex 50W-X2 and Dowex 50W-X8 beads during experiments exceeding 16 h. It has been observed, that the above mentioned resins generate a smaller number of CO2 bubbles close to the beads than Dowex 50W-X4, which makes Dowex 50W-X2 and Dowex 50W-X8 more suitable for applications in chemical computing. We report amplitude stability, oscillation frequency, merging and annihilation of travelling waves in a lattice of Dowex 50W-X8 beads (mesh size 50–100) in over 19 h long experiments with equimolar solution of malonic acid and 1,4-cyclohexanedione. This system looks as a promising candidate for chemical computing devices that can operate for a day.

Separation of Lignocellulose and Preparation of Xylose from Miscanthus lutarioriparius with a Formic Acid Method

Efficient component separation technology is one of the key ways to improve the efficiency of lignocellulose bioconversion. In this study, the formic acid method was used to separate the components of lignocellulose from Miscanthus lutarioriparius, hemicellulose was degraded into xylose simultaneously, and the composition and structure of the separated components were analyzed. Then, xylose was further purified with activated carbon for decolorization and resins for the removal of formic acid and other monosaccharide impurities. The results showed that formic acid could effectively separate the cellulose, hemicellulose, and lignin of lignocellulose with recoveries of 91.7%, 80.2%, and 85.3%, respectively. Structural analyses revealed that the cellulose and lignin underwent different degrees of formylation during the formic acid treatment, yet their primary structures remained intact, and the crystallinity of cellulose increased significantly. By GC–MS and HPLC analysis, xylose was the main component of hemicellulose extract, accounting for 74.90%. The activated carbon treatment decolorized the xylose extract more than 93.66% and gave a xylose recovery of 88.58%. D301 resin could effectively remove more than 99% of the formic acid residue in xylose. The xylose extract was further purified by removing arabinose and other monosaccharide impurities with Dowex 50wx4 resin, which increased the purity to 95%. The results demonstrated that the formic acid method is an effective method to separate lignocellulose and prepare xylose, and it has broad application prospects in the field of bio-refining lignocellulose resources such as Miscanthus lutarioriparius

The role of pH in the separation of Lu and Yb by ion-exchange explained by novel chemical structures of lanthanide complexes

The individual separation of lanthanides is very complex due to the similarities between these elements. Ion-exchange separations with carboxylic acids are widely studied, but the importance of pH is overlooked. This study used citric acid to evaluate Lu and Yb separation with Dowex 50W-X8. The separation was monitored by X-ray fluorescence. Five new structures of Lu and Yb citrates are proposed. Better separation occurs when the pH of the ligand is pH 4.5, where a mononuclear structure is formed. Conversely, polynuclear structures are formed at higher pH, and separation fails. X-ray diffraction reveals different phases at each pH value, and FTIR results support the proposed structures.

Improved separation scheme for 44Sc produced by irradiation of natCa targets with 12.8 MeV protons

Introduction44Sc is of great interest as a positron emission tomography (PET) radionuclide due to its suitable nuclear characteristics: Eβ+max = 1.47 MeV, branching ratio 94.3% and convenient half-life of 3.97 h. Here, 44Sc was produced via the widely used reaction 44Ca (p,n)44Sc using natural calcium as a target. MethodsThe irradiation was performed at TRIUMF using the 13 MeV cyclotron. The separation consisted of a combination of DGA branched resin and Dowex 50Wx8 (200–400 mesh). The distribution coefficients of Sc3+ on Dowex 50Wx8 (NH4+ form, 200–400 mesh) with ammonium α-hydroxyisobutyrate (pH = 4.8) medium were determined in this study. Results and conclusionThe tested scheme allows both a reliable separation of 44Sc from the target material as well as from the other competitive metals and a final fraction with high specific activity. The achieved radiochemical yield was 95 ± 3%.

Silver Nanoparticles and Ionic Silver Separation Using a Cation-Exchange Resin. Variables Affecting Their Separation and Improvements of AgNP Characterization by SP-ICPMS.

Silver nanoparticles (AgNPs) are frequently found in everyday products and, as a consequence, their release into the environment cannot be avoided. Once in aquatic systems, AgNPs interact with natural constituents and undergo different transformation processes. Therefore, it is important to characterize and quantify AgNPs in environmental waters in order to understand their behavior, their transformation, and their associated toxicological risks. However, the coexistence of ionic silver (Ag+) with AgNPs in aquatic systems is one of the greatest challenges for the determination of nanosilver. Ion-exchange resins can be used to separate Ag+ from AgNPs, taking advantage of the different charges of the species. In this work, Dowex 50W-X8 was used to separate Ag+ and AgNPs in order to easily determine AgNP concentrations using inductively coupled plasma optical emission spectroscopy. The separation methodology was successfully applied to river water samples with different ratios of Ag+ and AgNPs. However, the methodology is not useful for wastewater samples. The described methodology also demonstrated an improvement in the determination of the particle size of AgNPs present in river waters by single particle inductively coupled plasma mass spectrometry when a significant amount of Ag+ is also present.

Removal of impurities from solution containing rare earth elements by precipitation and rare earth elements recovery using ion exchange

Rare earth elements are generally separated from the leaching solution by concentration as a by-product of the processing plants. Among the main problems of their separation and extraction is the low level of them in the leaching stage. This study aimed to recover available rare earth elements from leaching solution of the non-magnetic sample of the Gazestan iron ore. The solution under investigation contained low concentrations of the rare elements cerium, lanthanum, neodymium, and yttrium, along with significant impurities including ferric ions, calcium, and phosphorus. Therefore, the removal of impurities, especially iron, were investigated. In this regard, it was tried to precipitate rare earth elements as fractional. The two main methods examined, 1) fractional precipitation of rare elements, iron and phosphate, and 2) precipitation of rare elements and calcium while increasing the solution temperature and remaining iron in the solution. Finally, the results of the two methods showed that rare earth elements were concentrated effectively. The REEs concentrated around two to three times higher than their initial level in the concentration step. After that, the adsorption experiments were performed on a batch scale by the Dowex50 WX4 cationic resin. Some experiments were also considered to investigate the effect of temperature enhancement on the adsorption of REEs on resin from the concentrated solution. As the temperature increased, the adsorption of the REEs from the solution increased significantly. In this case, the removal of iron was around 98%. The maximum adsorption of cerium, lanthanum, neodymium, and yttrium on the resin was, 99.11%, 98.67%, 99.0%, and 97.27%, respectively.

Reactive Chromatography Applied to Ethyl Levulinate Synthesis: A Proof of Concept

Levulinic acid (LA) has been highlighted as one of the most promising platform chemicals, providing a wide range of possible derivatizations to value-added chemicals as the ethyl levulinate obtained through an acid catalyzed esterification reaction with ethanol that has found application in the bio-fuel market. Being a reversible reaction, the main drawback is the production of water that does not allow full conversion of levulinic acid. The aim of this work was to prove that the chromatographic reactor technology, in which the solid material of the packed bed acts both as stationary phase and catalyst, is surely a valid option to overcome such an issue by overcoming the thermodynamic equilibrium. The experiments were conducted in a fixed-bed chromatographic reactor, packed with Dowex 50WX-8 as ion exchange resin. Different operational conditions were varied (e.g., temperature and flow rate), pulsing levulinic acid to the ethanol stream, to investigate the main effects on the final conversion and separation efficiency of the system. The effects were described qualitatively, demonstrating that working at sufficiently low flow rates, LA was completely converted, while at moderate flow rates, only a partial conversion was achieved. The system worked properly even at room temperature (303 K), where LA was completely converted, an encouraging result as esterification reactions are normally performed at higher temperatures.

Recovery of Uranium and Rare Earth Elements from Western Desert Phosphate Rocks with EDTA and Nitric Acid Solutions

Dissolution of uranium and rare earth elements from the Abu-Tartur phosphate rocks, Egypt using a mixed EDTA + nitric acid solution was studied. The effect of factors such as particle size, EDTA and nitric acid concentrations, agitation time, solid to liquid ratio, and dissolution temperature was studied, and the dissolution conditions were optimized. The optimized dissolution conditions were applied to a representative sample of the weathered rock assaying 1067 ppm rare earth elements. Before being processed, the representative sample was completely characterized using mineralogical and chemical analyses. From the obtained leach liquor, uranium was recovered by anion exchange with Duolite A 101D resin, and after uranium adsorption the rare elements were recovered by cation exchange with Dowex 50W-X8 resin.

Radiochemical separation of 224Ra from 232U and 228Th sources for 224Ra/212Pb/212Bi generator

The application of diagnostic and therapeutic radionuclides in nuclear medicine has grown significantly and has translated into the increased interest in radionuclide generators and their development. 224Ra and its shorter-lived daughters, 212Pb and 212Bi, are very interesting radionuclides from Targeted Alpha Therapy point of view for treatment of small cancers or metastatic forms. The purpose of the present work was to develop a simple generator for rapid elution of carrier-free 224Ra from 232U or 228Th sources by radiochemical separation based on extraction chromatography with the utilization of a home-made material. The bis(2-ethylhexyl) hydrogen phosphate (HDEHP) extractant was immobilized on polytetrafluroethylene (PTFE) grains and its ability to selectively adsorb 232U and 228Th, with simultaneous high elution recovery of 224Ra, was checked over few years. The 224Ra was quantitatively eluted with small volume (3–5 mL) of 0.1 M HNO3 with low breakthrough (<0.005%) and was used for further milking of 212Bi and 212Pb from DOWEX 50WX12 by 0.75 M and 2.0 M HCl, respectively. The elaborated here methods allowed high recovery of 224Ra, 212Pb and 212Bi radionuclides and their application in radiolabeling of various biomolecules.

Cadmium in Water Samples determined by Atomic Absorption Spectrometry after Solid Phase Extraction using DOWEX 50WX2 resin

The Pre-concentration of Cd(II) in water samples was carried out by using column solid phase extraction DOWEX 50WX2 prior to flame atomic absorption spectrometry analyzed. The analytical parameters consist of pH, flow rate, volume of eluent and volume of sample were determined.The optimum conditions were obtained pH was 5, sample flow rate was 1 mL min−1, volume of eluent nitric acid 1N was 10 mL and sample volume was 50 mL. The optimum conditions obtained were used to determine the detection limit and the accuracy of the method using tap water samples. Determination of detection limit used tap water which contain Cd 0.001 mg L-1 and the accuracy (recovery,%R) with concentration of Cd 0.01 mg L-1. The detection limit was found 0.2697±0.0899 µg L− 1 (n=7) and accuracy (n=7) was 93±6%. The result showed the accuracy still meets the acceptance criteria for accuracy (70%-125%) and the RSD 6% is smaller than the Horwitz value of 20.8%. Based on the accuracy (R%) and % RSD values obtained, it can be concluded that this method provides effective results for pre-concentration to increase the detection limit of Cd (II)in clean water using SSA-flame.

Biocatalytic Decarboxylation of Aromatic l-Amino Acids with In Situ Removal of Both Products for Enhanced Production of Biogenic Amines

Biogenic amines are important messengers in neurotransmission, drawing attention to pharmaceutical applications. Here, we developed a novel biocatalytic process for the preparation of biogenic amines using aromatic l-amino acid decarboxylase (AADC) under an in situ product removal (ISPR) condition. The AADC from Bacillus atrophaeus (AADC-BA) showed broad substrate specificity for aromatic amino acids, affording > 90% conversions of 10 mM substrates to corresponding products: 2-phenylethylamine (2-PEA), tryptamine, serotonin, and dopamine. Owing to enzyme inhibitions by the reaction products, we implemented an ISPR strategy using a cation exchange resin and an open reactor system for removal of amine and CO2, respectively. Under the open-air conditions, the addition of Dowex 50WX8 afforded 81% conversion of 100 mM l-phenylalanine to 2-PEA within 1 h, whereas 56% conversion was obtained without the resin. The ISPR strategy enabled the preparative-scale production of serotonin from 5-hydroxy-l-tryptophan (405 mg), yielding > 99% conversion within 40 min.

Assessment of ion exchange resins as catalysts for the direct transformation of fructose into butyl levulinate

The transformation of fructose into butyl levulinate in aqueous 1-butanol (initial molar ratio 1-butanol/fructose 79, and butanol/water 1.19) has been studied in a discontinuous reactor at 80−120 °C and 2.0 MPa over 8 sulfonic polystyrene-DVB ion exchange resins as catalysts (catalyst loading 0.85–3.4 %). Resins swell greatly in the reaction medium and the reaction takes place mainly in the swollen gel-phase. Swollen resins in water have been characterized by analysis of ISEC data, and spaces originated in the gel phase upon swelling are described in terms of zones of different polymer density. A relationship has been found between the morphology of swollen resins and ester production. Swollen resins with low polymer density show the highest butyl levulinate yield. Dowex 50Wx2 was the most effective because it creates the largest and widest spaces in the gel-phase when swelling. Consequently, it better accommodates the proton-transfer-reaction mechanisms.