From fundamental insights to economic viability: recovering natural products from deodorizer distillates

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Experimental and kinetic study of (trans)esterification reactions on Lewatit K1221

(Trans)esterification reactions play a key role in today’s biorefineries. Conventionally, these reactions are performed using an acid and a base homogeneous catalyst, respectively for esterification and transesterification. Heterogeneous catalysis offers a competitive alternative for these reactions by not requiring dedicated catalyst separation and purification. A single, fixed bed catalytic reactor, comprising a top layer of acid catalyst for esterification of free fatty acids followed by a base catalyst bed for triglyceride transesterification, would allow intensifying present-day biorefinery conversion processes. In the present work, the attention is focused on the acid top layer, for which an acid ion-exchange resin has been considered. Apart from esterification, also acid catalyzed transesterification has been investigated on this resin. A fundamental kinetic model has been constructed to gain detailed insight in the (trans)esterification reactions that will be essential in the intensification of the corresponding biorefinery processes. Acid ion exchange resins have been selected as they are ecofriendly, noncorrosive and have a good stability and reusability. The investigated resin consists of a cross-linked polystyrene matrix with sulfonic acid groups as active sites. Due to its particular structure, the resin exhibits a remarkable swelling phenomenon when in contact with a polar solvent. Since an excess of methanol is used as (trans)esterification agent and water is formed by esterification, the resin is swollen during the reaction. The resin’s swelling determines the accessibility of its active sites and, hence, plays a critical role in the finally observed reaction kinetics. An experimental investigation of the temperature effect and that of the initial molar ratio of acetic acid and methanol for esterification and of ethyl acetate and methanol for transesterification, both catalyzed by Lewatit K1221, was performed. The experimental data have been adequately modelled using an Eley-Rideal reaction mechanism. Exchange between protonated methanol, which was assumed to, initially, occupy all active sites, and the acid or ester in esterification and transesterification, respectively, was explicitly accounted for. While the activation energy was determined at 49 kJ mol-1, irrespective of the reaction type, the difference in catalytic activity, is found back in the value for the rate coefficient, which is about 1 order of magnitude higher for esterification than for transesterification. A unique set of exchange coefficients was obtained, irrespective of the considered reaction, which indicates the model’s adequacy. Throughout the experimentation at 333 K and using an initial molar ratio 10:1, the catalyst’s active sites were found to be occupied by methanol for at least 60%

Experimental kinetic study of transesterification of ethyl acetate with methanol catalyzed by gel and macroporous acidic ion exchange resins

The reaction kinetics of the liquid-phase transesterification of ethyl acetate with methanol have been investigated over a series of commercially available ion-exchange resins. Two morphology types of cross-linked polymer resins have been considered, i.e., a gel type (Lewatit K1221) and a macroporous type (Lewatit K2640, Lewatit K2629 and Amberlyst 15). The effect of the swelling of the resin, the initial reactant molar ratio (1:1 – 10:1) and the temperature (303.15 – 333.15 K) on the reaction kinetics was experimentally assessed. Lewatit K1221, the gel-type resin, outperformed the macroporous-type resins, despite its similar number of sulfonic acid sites. The resin’s swelling behavior, which can be related to its degree of cross-linking with divinylbenzene, was identified as the key parameter to explain differences in acid site accessibility between the considered resins and, hence, the observed transesterification kinetics. A fundamental kinetic model, accounting for the chemical elementary steps as well as for the physical swelling due to solvent absorption, was constructed to quantitatively assess the experimental observations. According to this model (1) all active sites are occupied by methanol in protonated form, (2) the esters undergo a proton exchange with the protonated methanol and (3) the reaction occurs through an Eley-Rideal mechanism with the surface reaction of protonated ethyl acetate with methanol from the bulk as the rate-determining step. The kinetic model was able to adequately describe the entire experimental data set. An activation energy amounting to 49 kJ mol-1 was obtained, irrespective of the resin. Also the affinity of each of the resins for the esters was found to be similar. The differences in catalytic activity between the considered resins are found back in the values for the rate coefficients and, hence, can be brought into relation with the active site accessibility. The latter is a factor 3 to 4 higher for gel-type resins compared to macroporous-type resins. An independent experimental assessment of the resins’ swelling behavior confirmed the more pronounced swelling of the gel-type compared to the macroporous-type resins

Verwijdering van kwik uit waterige oplossingen : vergelijking van een nieuw ultrastabiel mesoporeus adsorbens met een commercieel ionenwisselaarshars

The performance of a new ultra stable, regenerable adsorbent SH-ePMO for the removal of mercury from aqueous solutions was compared with that of a commercial ion exchange resin TP-214. The operating variables studied were initial mercury concentration and contact time. The adsorption isotherms showed favourable adsorption. The adsorption isotherms were analyzed using Langmuir and Freundlich models. The Langmuir model yielded the best fit for the SH-ePMO, whereas the Freundlich model fitted best the adsorption on TP-214. The maximum adsorption capacities were 66, resp. 456 mg/g for SH-ePMO, resp. TP-214. TP-214 is capable of purifying water to ppt-levels. The adsorption kinetics showed a fast adsorption for both adsorbents. The kinetics were analyzed using Lagergren’s pseudo-first-order and pseudo-second-order kinetic models. The pseudo-first-order kinetic model showed a good agreement of the experimental data of both adsorbents. This study clearly shows the potential of the ultra stable, regenerable SH-ePMO for removing mercury from aqueous solutions and confirms the performance of the ion exchanger resin TP-214

Tuning component enrichment in amino acid functionalized (organo)silicas

A straightforward procedure to synthesize cysteine functionalized materials with tailored support properties has been developed. It allows tuning the hydrophobicity of the material via the incorporation of aliphatics, aromatics or silica in the framework structure. The aldol condensation of 4-nitrobenzaldehyde and acetone, as a probe reaction for the catalytic activity of the produced materials, exhibited a remarkable interplay between the reactant, solvent, traces of water and support hydrophobicity. A selective enrichment in the catalyst pores of specific bulk phase molecules is believed to be the key to achieve the targeted catalyst performance

A novel Malonamide Periodic Mesoporous Organosilica (PMO) for controlled Ibuprofen release

Controlled drug release gained a sharply increasing interest over recent years. Multiple materials have been screened as possible drug carriers, ranging from biodegradable polymers to hydroxyapatite[1]. Periodic Mesoporous Organosilicas are valuable alternatives as they possess a high chemical and thermal stability combined with a biocompatible nature[2]. Furthermore, their large internal surface area permits a high drug loading. Careful selection of the organic ‘bridged’ functionality allows a controlled release with respect to external stimuli, such as pH or temperature, of the drugs which are adsorbed via weak and reversible interactions, e.g. H-bonding, ionic and hydrophobic-phobic interaction[3]. In this contribution a novel malonamide (MA-PMO) and a methyl-malonamide PMO (mMA-PMO) bearing a high amount of functionalities, capable of multiple intramolecular interactions, are developed and thoroughly characterized[4]. Subsequently, these hybrid materials are evaluated in the controlled drug release of Ibuprofen

Nanotechnology in catalysis: the force awakens

Nanotechnology - defined as Key Enabling Technology in Europe - plays an important role in our society, e.g., in medicine, in sports, in water treatment applications, in energy devices and is now also emerging in the field of catalysis. It strongly encompasses research and development to synthesize, control, and manipulate catalytic systems of enhanced or even novel properties. These properties can be attributed to the size of the nanomaterial which is ranged in one or more external dimensions from approximately 1 to 100 nm