Pepijn Prinsen

Macroporous materials: microfluidic fabrication, functionalization and applications

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields.

Continuous-Flow Synthesis of Supported Magnetic Iron Oxide Nanoparticles for Efficient Isoeugenol Conversion into Vanillin

This work presents the synthesis of iron oxide nanocatalysts supported on mesoporous Al-SBA-15 by using a continuous-flow setup. The magnetic nanomaterials were tested as catalysts in the oxidative disruption of isoeugenol by using hydrogen peroxide as a green oxidant, featuring high activities (63-88 % conversion) and good selectivities to vanillin (44-68 %). The catalytic systems exhibited good magnetic properties when synthesized under continuous-flow conditions at temperatures not exceeding 190 °C. The use of microwave irradiation significantly reduced times of reaction drastically but exerted negative effects on catalyst reusability.

BPPO-Based Anion Exchange Membranes for Acid Recovery via Diffusion Dialysis

To reduce the environmental impact of acids present in various industrial wastes, improved and robust anion exchange membranes (AEMs) are highly desired. Moreover, they should exhibit high retention of salts, fast acid permeation and they should be able to operate with low energy input. In this work, AEMs are prepared using a facile solution-casting from brominated poly-(2,6-dimethyl-1,4-phenylene oxide) (BPPO) and increasing amounts of 2-phenylimidazole (PI). Neither quaternary ammonium salts, nor ionic liquids and silica-containing compounds are involved in the synthesis. The prepared membranes showed an ion exchange capacity of 1.1–1.8 mmol/g, a water uptake of 22%–47%, a linear expansion ratio of 1%–6% and a tensile strength of 0.83–10.20 MPa. These membranes have potential for recovering waste acid via diffusion dialysis, as the acid dialysis coefficient (UH) at room temperature for HCl is in the range of 0.006–0.018 m/h while the separation factor (S) is in the range of 16–28, which are higher than commercial DF-120B membranes (UH = 0.004 m/h, S = 24).

Electroconductive Composites from Polystyrene Block Copolymers and Cu–Alumina Filler

Technological advancements and development of new materials may lead to the manufacture of sustainable energy-conducting devices used in the energy sector. This research attempts to fabricate novel electroconductive and mechanically stable nanocomposites via an electroless deposition (ELD) technique using electrically insulating materials. Metallic Cu is coated onto Al2O3 by ELD, and the prepared filler is then integrated (2–14 wt %) into a matrix of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene-graft-maleic anhydride (PS-b-(PE-r-B)-b-PS-g-MA). Considerable variations in composite phases with filler inclusion exist. The Cu crystallite growth onto Al2O3 was evaluated by X-ray diffraction (XRD) analysis and energy dispersive spectrometry (EDS). Scanning electron microscopy (SEM) depicts a uniform Cu coating on Al2O3, while homogeneous filler dispersion is exhibited in the case of composites. The electrical behavior of composites is enhanced drastically (7.7 × 10−5 S/cm) upon incorporation of Cu–Al2O3 into an insulating polymer matrix (4.4 × 10−16 S/cm). Moreover, mechanical (Young’s modulus, tensile strength and % elongation at break) and thermal (thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC)) properties of the nanocomposites also improve substantially. These composites are likely to meet the demands of modern high-strength electroconductive devices.

Selective heavy metal removal and water purification by microfluidically-generated chitosan microspheres: Characteristics, modeling and application

Many industrial wastewater streams contain heavy metals, posing serious and irreversible damage to humans and living organisms, even at low concentrations due to their high toxicity and persistence in the environment. In this study, high-performance monodispersed chitosan (CS) microspheres were prepared using a simple microfluidic method and evaluated for metal removal from contaminated water. Batch experiments were carried out to evaluate the adsorption characteristics for the removal of copper ions, one representative heavy metal, from aqueous solutions. The inherent advantages of microfluidics enabled a precise control of particle size (CV = 2.3%), while exhibiting outstanding selectivity towards target ions (adsorption capacity 75.52 mg g-1) and fair regeneration (re-adsorption efficiency 74% after 5 cycles). An integrated adsorption mechanism analytic system was developed based on different adsorption kinetics and isotherms models, providing an excellent adsorption prediction model with pseudo-second order kinetics (R2 = 0.999), while the isotherm was fitted best to the Langmuir model (R2 = 0.998). The multi-step adsorption process was revealed via quantitative measurements and schematically described. Selective adsorption performance of CS microspheres in the present of other competitive metal ions with different valence states has been demonstrated and studied by both experimental and density functional theory (DFT) analysis.

A comprehensive study on the continuous flow synthesis of supported iron oxide nanoparticles on porous silicates and their catalytic applications

The present work demonstrates an efficient continuous flow methodology for the preparation of iron oxide nanoparticles supported on porous silicates. The effect of the iron precursor solution feed rate, the synthesis temperature and time and the support type on the catalyst characteristics were studied, as well on the catalytic activity in the microwave-assisted oxidation of benzyl alcohol with hydrogen peroxide and in the alkylation of toluene with benzyl chloride and with benzyl alcohol. The method appeared to deposit more α-Fe2O3 (hematite) on the support surface compared to similar catalyst materials synthesized using other methods. The catalyst deactivation observed in consecutive reaction cycles was mostly due to the blocking of active sites rather than metal leaching from the catalyst framework.

Batch versus Continuous Flow Performance of Supported Mono- and Bimetallic Nickel Catalysts for Catalytic Transfer Hydrogenation of Furfural in Isopropanol

Furfural takes an important position in hemicelluloses biorefinery platforms. It can be converted into a wide range of chemicals. One important valorization route is the catalytic hydrogenation. Whereas molecular hydrogen is mostly used in industrial hydrogenation processes, recent studies also showed that alcohols can be used as reductants from which hydrides can be transferred catalytically to furfural. This process is often assisted by the formation of significant amounts of side products, in despite of high yields to the hydrogenolysis product 2‐methylfuran. The present work explores the catalytic behavior in batch and continuous flow of mono‐ and bimetallic nickel catalysts supported on activated carbon for the catalytic transfer hydrogenation of furfural in isopropanol.