Working-state morphologies of ion exchange catalysts and their influence on reaction kinetics

Jeřábek, Karel; Hanková, Libuše; Holub, Ladislav

doi:10.1016/j.molcata.2010.10.004

Cited by 26 publications

(17 citation statements)

References 11 publications

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“…by contact with polar solvents and reactants, respectively, consequently changing the accessibility of the acidic sites (e.g. [30,31]). Another point is also the size of the reactants that might influence the molecular traffic inside such swelling resins.…”

Section: Reaction Progress Monitoringmentioning

confidence: 99%

Selective formation of triacetin by glycerol acetylation using acidic ion-exchange resins as catalyst and toluene as an entrainer

Kale

Umbarkar

Dongare

et al. 2015

Applied Catalysis A: General

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Section: Reaction Progress Monitoringmentioning

confidence: 99%

Selective formation of triacetin by glycerol acetylation using acidic ion-exchange resins as catalyst and toluene as an entrainer

Kale

Umbarkar

Dongare

et al. 2015

Applied Catalysis A: General

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“…Isobutene is slightly bigger than ethanol. To quantify the ease of penetration of a molecule into a porous domain of a certain density, in relation to its quantity in the free solution, the Ogston distribution coefficient, K O , estimated by [7,28] Table 2 agree with the fact that transport through gradually denser domains is more hindered for longer alcohols than for shorter ones. It is also noticeable that K O values for a given polymer density decrease progressively as the alcohol size increases.…”

Section: Fig1 Main Reactions Involved In the Present Studymentioning

confidence: 90%

“…Similarly, comparison between the random coil diameter and the equivalent pore size, of the different density domains of a swollen polymer [28], provides information on the spaces between polymer chains that a molecule would require to permeate through it without enthaplic interactions ( Table 2). The random coil diameter, Φ d , can be estimated by the equation [29,30] 0.5882…”

Section: Fig1 Main Reactions Involved In the Present Studymentioning

confidence: 99%

Catalytic Activity and Accessibility of Acidic Ion-Exchange Resins in Liquid Phase Etherification Reactions

et al. 2015

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Although macroreticular acidic ion-exchange resins have been widely used as catalysts in the industrial world for decades, their catalytic behavior is still far from being completely understood at a molecular level. Several characterization techniques coexist, which provide information about their properties. Only few of these techniques give an actual picture of their working-state features when swollen in anhydrous polar reactive media such as in etherification processes, where they are extensively used. The inverse steric exclusion chromatography technique, based on modeling the micropores structure, or gel-phase, as a set of discrete volume fractions with a characteristic polymer chain density, constitutes an appropriate procedure to assess the morphology of ion-exchangers in the swollen state. Present work proposes an empirical model to correlate the properties of the volume fractions with their catalytic activity in the etherification reaction rates of isobutene by addition of C1 to C4 linear primary alcohols. Sixteen different macroreticular acidic ion-exchange catalysts, both commercial and lab-made, have been used, which differ in acid capacity, sulfonation type, cross-linking degree and swollen-phase volume fractions distribution. Experimental reaction rates have been expressed as a sum of contributions of each individual volume fraction. The contribution of each polymer volume fraction corresponds to the product of the catalyst acidity, the characteristic volume fraction within the gel-phase of the catalyst, and a specific turnover frequency (TOF) of that fraction. Accessibility of the reacting alcohol, expressed in terms of the Ogston coefficient, has been also included in the empirical dependency equation presented in this work.

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“…These resins could be more advantageous materials than the most commonly employed materials used for the acid hydrolysis of lignocellulosic biomass (e.g., zeolites, carbon and hybrid materials), especially due to their structural and functional versatility and stability in reaction media. In fact, the morphology and chemical properties of these resins can be easily tuned by modifying the nature and amount of structural, cross-linking and functional monomers used [31][32][33].The presence of additional polar groups in combination with sulfonic groups in carbon-based materials clearly enhances the hydrolysis of cellulose [34][35][36][37] by favoring the adsorption of β-(1,4)-glucans. This effect was observed also in other supports, such as silica and resins [38][39][40].…”

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confidence: 99%

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confidence: 99%

Gel-Type and Macroporous Cross-Linked Copolymers Functionalized with Acid Groups for the Hydrolysis of Wheat Straw Pretreated with an Ionic Liquid

et al. 2019

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Several sulfonated cross-linked copolymers functionalized with hydroxyl and carboxylic groups have been synthesized. The amount of the cross-linking monomer was tailored (from 4% up to 40%) to tune the resulting micro-and nano-morphologies, and two types of catalysts, namely, gel-type and macroreticular catalysts, were obtained. These copolymers were employed in the catalytic hydrolysis of wheat straw pretreated in 1-ethyl-3-methylimidazolium acetate to obtain sugars. Remarkably, the presence of additional oxygenated groups enhances the catalytic performances of the polymers by favoring the adsorption of β-(1,4)-glucans and makes these materials significantly more active than an acidic resin bearing only sulfonic groups (i.e., Amberlyst 70). In addition, the structure of the catalyst (gel-type or macroreticular) appears to be a determining factor in the catalytic process. The gel-type structure provides higher glucose concentrations because the morphology in the swollen state is more favorable in terms of the accessibility of the catalytic centers. The observed catalytic behavior suggests that the substrate diffuses within the swollen polymer matrix and indirectly confirms that the pretreatment based on dissolution/precipitation in ionic liquids yields a substantial enhancement of the conversion of lignocellulosic biomass to glucose in the presence of heterogeneous catalysts.Catalysts 2019, 9, 675 2 of 18 substrate [5]. In this way, the particle size can be reduced, the porosity can be improved, and the crystallinity of the cellulose can be altered. After fractioning its main components, e.g., cellulose, hemicellulose and lignin, biomass can be converted into a wide variety of industrial products, such as biofuels, biomaterials, cellulose pulps, cellulose nanofibers, oligosaccharides and a large number of by-products, in addition to lignin derivatives.Numerous studies have shown ionic liquids (ILs) to be effective at solubilizing lignocellulosic biomass, allowing for subsequent regeneration by precipitation with anti-solvents. Depending on the anti-solvent used, it is possible to achieve selective precipitation and separate the lignocellulosic biomass into its main components [6][7][8][9][10][11][12][13][14]. Among the most commonly employed ILs, 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) holds a privileged position due to its physico-chemical properties.The acid hydrolysis of the polysaccharide fractions of lignocellulosic biomass, which leads to monosaccharides that can be converted into fine chemicals or platform molecules used for industrial applications, can be performed in the presence of enzymes, homogeneous catalysts or heterogeneous catalysts [15][16][17][18][19][20][21]. During the last few years, increasing attention has been focused on the heterogeneous approach, which leads to several advantages in terms of the process design and plant costs [22][23][24][25]. Some of us have investigated using resins as catalysts or scaffolds in material chemistry [26][27][28][29][30]. These resins could be more...

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Working-state morphologies of ion exchange catalysts and their influence on reaction kinetics

Cited by 26 publications

References 11 publications

Selective formation of triacetin by glycerol acetylation using acidic ion-exchange resins as catalyst and toluene as an entrainer

Selective formation of triacetin by glycerol acetylation using acidic ion-exchange resins as catalyst and toluene as an entrainer

Catalytic Activity and Accessibility of Acidic Ion-Exchange Resins in Liquid Phase Etherification Reactions

Gel-Type and Macroporous Cross-Linked Copolymers Functionalized with Acid Groups for the Hydrolysis of Wheat Straw Pretreated with an Ionic Liquid

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