Acidic Exchange Resin Research Articles

Di-d-fructose Dianhydride-Enriched Caramels: Effect on Colon Microbiota, Inflammation, and Tissue Damage in Trinitrobenzenesulfonic Acid-Induced Colitic Rats

In the present study we describe the preparation and chemical characterization of a caramel with a high (70%) content of difructose dianhydrides (DFAs) and glycosylated derivatives (DFAs). This product was obtained by thermal activation (90 degrees C) of highly concentrated (90% w/v) aqueous D-fructose solutions using the sulfonic acid ion-exchange resin Lewatit S2328 as caramelization catalyst. DFAs represent a unique family of cyclic fructans with prebiotic properties already present in low proportions (<15%) in commercial caramel. We report the antiinflammatory activity of the new DFA-enriched caramel in the trinitrobenzenesulfonic acid (TNBS) model of rat colitis, an experimental model that resembles human inflammatory bowel disease (IBD), and compare its effects with those obtained with a commercial sucrose caramel and with linear fructooligosaccharides (FOS). For this purpose, the effects on colon tissue damage, gut microbiota, short-chain fatty acid (SCFAs) production, and different inflammatory markers were evaluated. The administration of DFA-enriched caramel to colitic rats showed intestinal antiinflammatory effect, as evidenced macroscopically by a significant reduction in the extent of the colonic damage induced by TNBS. This effect was similar to that obtained with FOS in the same experimental settings, whereas commercial caramel was devoid of any significant antiinflammatory effect. The beneficial effect was associated with the inhibition of the colonic levels of the proinflammatory cytokines, tumor necrosis factor alpha (TNF alpha) and interleukin 1beta (IL-1beta), and the reduction in colonic myeloperoxidase (MPO) activity and inducible nitric oxide synthase (iNOS) expression. The DFA-enriched caramel also promoted a more favorable intestinal microbiota, increasing lactobacilli and bifidobacteria counts as well as inducing higher concentrations of SCFAs in the luminal colonic contents. These results reinforce the concept of DFAs and glycosyl-DFAs as dietary beneficial compounds with prebiotic properties and suggest that the novel DFA-enriched caramel here reported may be an interesting candidate to be explored for the dietary treatment of human IBD.

Efficient and stable solid acid catalysts synthesized from sulfonation of swelling mesoporous polydivinylbenzenes

Abstract Efficient and stable solid acid catalysts, sulfonic groups functional swelling mesoporous polydivinylbenzenes (PDVB- x -SO 3 Hs), were synthesized from sulfonation of swelling mesoporous polydivinylbenzenes (PDVB- x s) by chlorosulfonic acid in CH 2 Cl 2 . Nitrogen adsorption–desorption isotherms showed that PDVB- x -SO 3 Hs have high surface area and abundant mesoporosity. Elemental analysis and acid–base titration techniques showed that PDVB- x -SO 3 Hs have high concentration of sulfonic groups. Esterifications of acetic acid with cyclohexanol, hexanoic acid with ethanol, lauric acid with ethanol and acylation of anisole with acetyl chloride showed that PDVB- x -SO 3 Hs are more active than arenesulfonic, propyl-sulfonic groups functional mesoporous silicas (SBA-15-Ar-SO 3 H, SBA-15-Pr-SO 3 H) and strongly acidic ion-exchange resin (Amberlyst 15). The superior performance of PDVB- x -SO 3 Hs is attributed to their unique features including large surface area, abundance of mesoporosity as well as high content of sulfonic groups.

Acid exchange resins deactivation in the esterification of free fatty acids

In this work the deactivation of an ionic exchange resin, used as catalyst for promoting the esterification of fatty acids for producing biodiesel, has been studied. At this purpose, a dynamic mathematical model, suitable to describe the performances of a continuous tubular reactor containing the catalysts mixed with stainless steel springs as inert diluent, and its evolution with time due to the catalyst deactivation, has been developed. Experimental runs, performed in a pilot plant tubular reactor on fatty acid mixtures (oleins), are reported in the paper. The catalyst deactivation has been shown to depend mainly on the poisoning effect of iron that was present as impurity in the fatty acids used as feedstock. Some information about catalyst regeneration is also given at the end of the paper.

Isoamylene Trimerization in Liquid-Phase over Ion Exchange Resins and Zeolites

Liquid-phase trimerization of 2-methyl-1-butene and 2-methyl-2-butene mixtures over solid acid catalysts was carried out in a batch-stirred tank reactor in the temperature range 333−373 K. Diisoamylenes and triisoamylenes were the main products. Cracking products among C6−C9 and C11−C14 were also obtained under the assayed conditions. The catalityc performance of five different acidic ion exchange resins (Amberlyst 15, Amberlyst 35, Amberlyst 70, Purolite CT-252, Purolite CT-276) and four zeolites (H-BEA-25, H-FAU-30, H-FAU-6 and H-MOR-20) was assessed. Experimental results showed that Amberlyst 15 and H-FAU-30 were the best catalysts for isoamylene trimerization, with selectivities above 40% at 373 K. The most influencing physical properties of the catalysts on the selectivity toward dimers and trimers were acid capacity, acid strength, and specific surface area for resins, and microporous surface area for zeolites. Isoamylene trimerization extent was larger at higher temperature. The most probable mecha...

Conversion of Waste Cooking Oil to Biodiesel via Enzymatic Hydrolysis Followed by Chemical Esterification

Biodiesel (BD) is usually produced by alkali-catalyzed methanolysis of expensive edible oils. Although waste cooking oils (WCO) containing high free fatty acid (FFA) are inexpensive, they cannot be processed effectively by alkali catalysis because of the formation of soap, which reduces the BD yield and makes the downstream process complicated. A process consisting of enzymatic hydrolysis followed by chemical esterification was developed for the production of BD from WCO. The enzyme Candida rugosa lipase was used for the hydrolysis of WCO to fatty acid (FA). The complete conversion of WCO to FA was achieved after 10 h at a water to WCO ratio of 1:1 (v/v), 5 g of WCO, 5 mL of lipase−water solution (0.5 g/L), and temperature of 30 °C. After hydrolysis, FA was separated and converted to BD by chemical esterification using Amberlyst 15 (acidic styrene-divinylbenzene sulfonated ion-exchange resin) as a catalyst. The maximum BD yield of 99% was obtained after 2 h at a methanol to FA molar ratio of 4:1, 10 mL of FA−isooctane solution (0.35 M), 1 g of Amberlyst 15, and temperature of 60 °C. The activity of C. rugosa lipase slightly decreased with recycling, and FA yield after five cycles was 92%. Amberlyst 15 was repeatedly used for 100 cycles without loosing its activity. The developed two-step process has a potential to be used industrially as it can tolerate feedstocks containing a wide range of FFA and water.

Recovery of cellulases by adsorption/desorption using cation exchange resins

Cellulases from Trichoderma reesei were recovered by adsorption in sodium acetate buffer at lower pH using cation exchange resins followed by desorption at higher pH. The weakly acidic ion exchange resin WK10 was found to be the best among the six resins tested in terms of the enzyme activity recovery. The optimal pH values for the adsorption and desorption were 4.0 and 8.0, respectively, and the optimal adsorption and desorption times were both 5 h. Almost 100% of the initial cellulase activity was recovered under the optimal conditions with the supplement of β-glucosidase, which was unable to be efficiently recovered due to its strong adsorption (95.7%) but poor desorption (1.9%).

Kinetics and modeling of fatty acids esterification on acid exchange resins

Biodiesel, a renewable fuel of vegetal origin, has been an object of a rapidly growing interest, in the latest years, both as a pure fuel and as blending component to reduce exhaust pollutants of traditional diesel fuel. Biodiesel is conventionally produced through a well-established technology that involves the use of alkaline catalysts and is, therefore, not compatible with the presence of free fatty acids (FFAs) in the feedstock due to the formation of soaps. Also the presence of FFA in small amounts is detrimental, because, formed soaps strongly affect the successive glycerol separation giving place to a long settling time. Normally, highly refined vegetable oils are used as raw materials for biodiesel production. A preliminary stage of acidity reduction is necessary, when the starting material is characterized by a high free acidity (higher than 0.5% by weight). This pre-treatment can be pursued, as example, by means of an esterification reaction of the FFAs with methanol, catalyzed by sulphonic ionic exchange resins. In the present work, a batch reactor has been used for the study of the above-mentioned reaction and different acid ionic exchange resins have been tested as heterogeneous catalysts. Two kinds of substrates have been submitted for esterification with methanol: a model mixture of soybean oil artificially acidified with oleic acid and a commercial high-acidity mixture of waste fatty acids (oleins). A detailed kinetic model has been developed and tested in which the following key phenomena, characterizing the system, have been introduced: (i) the physical phase equilibrium (partitioning equilibrium) of the components between the resin-absorbed phase and the external liquid phase; (ii) the ionic exchange equilibria; (iii) an Eley–Rideal surface reaction mechanism. The developed kinetic model was able to correctly interpret all the experimental data collected, both as a function of the temperature and of the catalyst concentration.

Synthesis of Well-Defined Polystyrene-Block-Polyglycidol (PS-b-PG) Block Co-polymers by Anionic Polymerization

Well-defined polystyrene-block-polyglycidol (PS-b-PG) block co-polymers of various composition were prepared in two steps: (i) sequential anionic polymerization of styrene in benzene initiated with sec. butyl lithium followed by the polymerization of ethoxy ethyl glycidyl ether in the presence of the phosphazene base P4-t-Bu and (ii) deprotection of the corresponding polystyrene-block-poly(ethoxy ethyl glycidyl ether) block co-polymers with concentrated HCl or an acidic ion-exchange resin, respectively. The polymers were characterized by size-exclusion chromatography, nuclear magnetic resonance spectroscopy and differential scanning calorimetry, proving that narrow distributed block co-polymers of predetermined composition were obtained, which, based on their amphiphilic character, self-organize into hydrophilic and hydrophobic domains.

Cross-Contamination Test of an Enthalpy Wheel Loading a Strong Acidic Cation Ion-Exchange Resin or 3A Zeolite as a Desiccant Material

Enthalpy wheels have been widely used for achieving comfortable air-conditioning with low energy consumption. Desiccant materials such as silica gel and molecular sieves are used so as to give it a latent heat exchanging function. However, this important function has become the cause of cross-contamination because substances with offensive odors are also adsorbed onto desiccants. In this study, cross-contamination of an enthalpy wheel consisting of ion-exchange resin particles as a desiccant material is examined and compared with a commercialized 3A zeolite wheel. It is found that the ion-exchange resin type wheel shows a smaller cross-contamination ratio than the other for all contaminants tested in this study, i.e. ammonia, carbon dioxide, formaldehyde and propane, although water-soluble and smaller contaminants such as ammonia still indicated a higher contamination ratio.

Di-d-fructose Dianhydride-Enriched Products by Acid Ion-Exchange Resin-Promoted Caramelization of d-Fructose: Chemical Analyses

Caramelization commonly occurs when sugars, or products containing a high proportion of sugars, are heated either dry or in concentrated aqueous solutions, alone or in the presence of certain additives. Upon thermal treatment of sugars, dehydration and self-condensation reactions occur, giving rise to volatiles (principally 2-hydroxymethylfurfural, HMF), pigments (melanoidines) and oligosaccharidic material, among which di-D-fructose dianhydrides (DFAs) and glycosylated DFA derivatives of different degree of polymerization (DP) have been identified. This study reports a methodology to produce caramel-like products with a high content of DFAs and oligosaccharides thereof from commercial D-fructose based on the use of acid ion-exchange resins as caramelization promotors. The rate of formation of these compounds as a function of D-fructose concentration, catalyst proportion, temperature, catalyst nature and particle size has been investigated. The use of sulfonic acid resins allows conducting caramelization at remarkable low temperatures (70-90 degrees C) to reach conversions into DFA derivatives up to 70-80% in 1-2 h, with relative proportions of HMF < 2%.The relative abundance of individual DFA structures can be modulated by acting on the catalyst nature and reaction conditions, which offers a unique opportunity for nutritional studies of DFA-enriched products with well-defined compositions.

Experimental study and process simulation of n-butyl acetate produced by transesterification in a catalytic distillation column

The production of n-butyl acetate by transesterification of methyl acetate with n-butanol, catalyzed by acidic ion-exchange resin NKC-9, was experimentally investigated in a homemade catalytic distillation column with a diameter of 80 mm. A non-equilibrium stage model for describing the catalytic distillation process was established and solved with Newton-Homotopy method. The effect of feeding mode, reflux ratio, material molar ratio and number of reactive sections on the conversion of methyl acetate was investigated. The experimental results agree well with those obtained by the theoretical simulation calculations, indicating the accuracy and reliability of the non-equilibrium model. It can be concluded that the non-equilibrium model established in this paper can provide theoretical guidance for the further process design and optimization.

Low Temperature De-acidification Process of Animal Fat as a Pre-Step to Biodiesel Production

An esterification process is proposed to lower Free Fatty Acids (FFA) content in waste animal fat using solid acid ion exchange resins as catalysts. The final aim is to make this material a suitable feedstock for biodiesel production. Its exploitation does not interfere with the food chain, besides allowing to lower biodiesel production costs.

Kinetic Study of Esterification of Lactic Acid with Isobutanol and n-Butanol Catalyzed by Ion-exchange Resins

The esterification reactions of lactic acid with isobutanol and n-butanol have been studied in the presence of acid ion-exchange resin Weblyst D009. The influences of catalyst loading, stirrer speed, catalyst particle size, initial reactant molar ratio and temperature on the reaction rate have been examined. Experimental kinetic data were correlated by using the Pseudo-homogeneous, Langmuir-Hinshelwood and Eley-Rideal models. Nonideality of the liquid phase was taken into account by using activities instead of molar fractions. The activity coefficients were calculated according to the group contribution method UNIFAC. Provided that the nonideality of the liquid is taken into account, the esterification kinetics of lactic acid with isobutanol and n-butanol catalyzed by the acid ion-exchange resin can be described using all three models with reasonable errors.

One-pot synthesis of N-methylindoles from N-methylanilines and of benzofurans from phenols using transition-metal carbene X–H insertion reactions

Transition-metal carbene X–H insertion reactions (X=N or O) have been employed in the simple conversion of anilines and phenols into indoles and benzofurans, respectively. Thus copper(II) catalyzed N–H insertion reactions of α-diazo-β-ketoesters with N-methylanilines followed by treatment with acidic ion-exchange resin gives indoles. In a similar manner, dirhodium(II) catalyzed O–H insertion reactions of α-diazo-β-ketoesters with phenols followed by treatment with PPA gives benzofurans.

Catalytic etherification of glycerol by tert-butyl alcohol to produce oxygenated additives for diesel fuel

The heterogeneous catalytic etherification of glycerol with tert-butyl alcohol was investigated in presence of lab-made silica supported acid catalysts. As reference, two commercial acid ion-exchange resins were also used. Experiments were carried out in batch mode at T R ranging from 303 to 363 K. An increase in reaction temperature favors the formation of di-substituted ethers. The etherification reaction proceeds according to a consecutive path and the surface reaction between adsorbed glycerol and protonated tert-butanol (tertiary carbocation) can be considered as the rate determining step. Steric hindrance phenomena and water hinder the formation of tri-substituted ether (TBGE). As expected, water removal was necessary to allow the higher ethers formation. The specific activity (turnover frequency, TOF) of A-15 catalyst is significantly higher than that of the other studied acid systems, due to the wide pore diameter that allows an easier accessibility of the reagent molecules.

Selective recovery of Cr and Cu in leachate from chromated copper arsenate treated wood using chelating and acidic ion exchange resins

The purpose of this study was to selectively remove chromium and copper from CCA-treated wood acid leachates (initial concentrations of 447–651 mg As l −1, 374–453 mg Cu l −1 and 335–622 mg Cr l −1) using ion exchange resins and precipitation techniques. Batch experiments revealed that the chelating resin Dowex M4195 had a high copper selectivity in the presence of chromium while the Amberlite IR120 resin had a high chromium sorption capacity. Combining M4195 and IR120 resins in four successive columns, made with Plexiglas tube, led to 96% copper extraction and 68% chromium extraction. NH 4OH (4 M) efficiently eluted copper from the chelating resin while H 2SO 4 (10% v/v) was used for IR120 resin elution. Copper and chromium recovery by elution reached 94% and 81%, respectively. Successive sorption and elution steps using M4195 and IR120 ion exchange resins presented similar metal removal capacities over the five cycles. No resin deterioration was observed but the results suggested arsenic bulk diffusion into the M4195 resin. Successive treatments of CCA-treated wood leachate with M4195 and IR120 allowed for copper and chromium removal while arsenic could be extracted by coagulation treatment with ferric chloride and precipitation with Ca(OH) 2 at pH 5.7. This final process led to 99.9% arsenic removal. The final effluent contained less than 1 mg l −1 of arsenic, chromium and copper.

Liquid-phase synthesis of ethyl tert-butyl ether over acid cation-exchange inorganic–organic resins

In this study the possibility to increase the productivity of acid cation-exchange resin catalysts active sites in ETBE synthesis was elucidated. For this purpose the inorganic–organic sulfonated cation-exchange resins with different polymer loadings (1.5–9.2 wt.%) have been synthesized. Such polymer/carrier composites as well as commercial acidic microporous gel-type ion-exchange resin KU-2-8 and macroporous Amberlyst 15 have been studied in the ETBE synthesis. Acid properties of all solids were determined by quasi-equilibrium thermogravimetry of ammonia desorption. We have found out that polymer loading and acid capacity affect oppositely on the ETBE productivity. As a result, there is no direct correspondence between the ETBE productivity of the inorganic–organic sulfonated cation-exchange resins per gram of catalyst on their acidity. However, there is a linear relation between the productivity per gram of polymeric phase and acidity. It was established that due to a better accessibility of acid sites for reactants loaded sulfonated cation-exchange resins exceeds the commercial catalysts by the site time yield values.

New sulfonic acid ion-exchange resins for the preesterification of different oils and fats with high content of free fatty acids

The preesterification of free fatty acid (FFA) containing vegetable oils by strong acid ion-exchange resins was studied. The catalysts were characterized by scanning electron microscopy (SEM) and ion-exchange capacity. Based on a simple kinetic model the rate constants were determined. The effect of the catalyst structure, particle size, stirring speed, oil properties and water removal method on the reaction rate was investigated. Calculation of the turn over frequencies (TOFs) revealed high catalyst activities. Excellent conversions were obtained even without water removal, due to an extractive esterification. During recycling durability tests a catalyst activity loss occurred. The deactivation mechanism was investigated and the exhausted catalysts were successfully regenerated. A catalyst fouling was not observed. The presented preesterification process facilitates the processing of low quality, high FFA containing oils to biodiesel via basic transesterification and might help to reduce the production costs.

Ethyl acetate synthesis by coupling of fixed-bed reactor and reactive distillation column—Process integration aspects

Coupling of a fixed-bed reactor and a reactive distillation column was used for acetic acid and ethanol esterification utilizing strong acidic ion-exchange resin as catalyst. Laboratory experiments were focussed on the investigation of catalyst loading effect on reaction conversion in a fixed-bed reactor at the temperature interval between 60 and 120 °C with partial separation of products in the form of their azeotropic mixture by the flash distillation. This procedure increased the reaction conversion above chemical equilibrium. The experimental results achieved with a reactive distillation column of the overall efficiency of 14 theoretical stages (1 reaction stage) were successfully compared with numerical simulation by means of AspenPlus software.

Kinetics of free fatty acids esterification: Batch and loop reactor modeling

Biodiesel is a fuel derived from a renewable vegetable origin and is object of growing interest in recent years both as a pure fuel and as blending component to reduce exhaust pollutants of traditional diesel fuel. The conventional biodiesel production technology involves the use of alkaline catalysts and is therefore not compatible with large amounts of free fatty acids (FFAs) and moisture in the feedstock due to the formation of soaps that strongly affect the feasibility of glycerol separation by liquid–liquid splitting. A preliminary stage of acidity reduction is therefore necessary, for this process, if the starting material is characterized by a free acidity higher than 0.5% by weight often contained in cheaper feedstock which lowers the production costs. This can be pursued, for example, by means of an esterification reaction of the FFAs with methanol, catalyzed by ionic-exchange sulphonic acid resins. In the present work, the above-mentioned reaction has been studied in different reactor configurations on a model mixture composed by artificially acidified soybean oil with oleic acid using an acid exchange resin as catalyst. This work has been developed in two parts: (i) a kinetic study in batch conditions with the purpose of developing a suitable kinetic expression and determining the related parameters and (ii) a study of the FFAs esterification in a packed bed tubular reactor operated inside a circulation loop. The kinetic model that is developed on the basis of several batch runs is able to simulate also the behavior of dynamic tubular loop reactor, providing that the external mass transfer resistance is properly accounted for. The mass transfer coefficient is satisfactorily modeled using correlations available on literature.