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Highly filled, high solids content, water-borne polymer–Gibbsite nanocomposites are prepared with Gibbsite contents as high as 35 wt%. The polymer–Gibbsite nanocomposites are synthesised via conventional starved feed emulsion polymerization using negatively charged butyl acrylate-co-acrylic acid oligomers, which functioned as electrosteric stabilizers for the initial platelets and the subsequently formed latex particles. A simple mathematical model describing the amount of cooligomer required for the colloidal stability of the initial Gibbsite platelets and the subsequently formed particles was derived. This model was used to determine the reaction conditions required for obtaining colloidally stable nanocomposites with a targeted filler content. Cryogenic transmission electron microscopy characterization of the resulting nanocomposites with filler contents up to 20 wt% revealed fully encapsulated Gibbsite platelets and a mixed morphology of “muffin-like” and encapsulated particles was obtained at higher filler contents.

This paper presents a novel, green Knoevenagel procedure for the chemical transformation of benzaldehydes into their corresponding α,β-unsaturated acids. The essential part of this procedure is a solvent-free condensation which uses environmentally benign amines or ammonium salts as catalysts instead of pyridine and piperidine as used in the traditional Knoevenagel condensation. The condensation step is followed by a decarboxylation in the solid phase, resulting in high overall yields and purity. The influence of temperature and catalyst type on the yield of sinapinic acid was monitored for the reaction between syringaldehyde and malonic acid. After optimization of this reaction, its scope was explored for various types of benzaldehydes demonstrating a broad applicability of this procedure. The developed method provides good to an excellent conversion of various benzaldehydes and high selectivity to the respective α,β-unsaturated acids in an environmentally friendly and efficient way.

Using ethylene glycol dimethacrylate (EGDMA) as a cross-linker Gibbsite platelets were successfully encapsulated fully using an ATRP-mediated emulsion polymerisation technique. Previously we reported a “muffin-like” morphology, which was obtained using the same approach without a cross-linker. This morphology was attributed to the mobility of the growing polymeric chains, allowing them to move one side of the platelet during the reaction. The addition of EGDMA reduces this mobility and it is shown that this approach indeed leads to encapsulated Gibbsite. A comprehensive study of the reaction conditions, in particular the cross-linker addition profile and concentration, was carried out in combination with cryo-TEM characterization of the final particle morphology.

Hydrogen is a promising renewable energy source that can be produced from biomass using aqueous-phase reforming (APR). Here, using data obtained from AspenPlus and the literature, we evaluated the phase state, temperature-dependent enthalpy, and Gibbs free energy for the APR of small biomass model substrates. Phase equilibrium studies reveal that, under typical APR reaction conditions, the reaction mixture is in the liquid phase. Therefore, we show for the first time that the water-gas shift reaction (WGSR), which is the second main reaction of APR, must be modeled in the liquid phase, resulting in an endothermic instead of an exothermic enthalpy of reaction. A significant implication of this finding is that, although APR has been introduced as more energy saving than conventional reforming methods, the WGSR in APR has a comparable energy demand to the WGSR in steam reforming (SR).

Successful miniemulsion polymerizations of very hydrophobic monomers, such as lauryl methacrylate and 4-tert-butyl styrene, initiated by very hydrophobic (i.e., completely water-insoluble) lauroyl peroxide, are reported. Conversion-time histories, as well as final latex properties, for example, the particle size distribution, are different from similar miniemulsion polymerizations in the presence of water-soluble initiators. The observed differences can be attributed to the average number of radicals inside a miniemulsion particle; the system obeys Smith-Ewart case I rather than Case II kinetics. Albeit the pairwise generation of radicals in the monomer droplets, substantial polymerization rates are observed. Water, present in the droplet interfacial layer, is supposed to act as chain transfer agent. The product of a chain transfer event is a hydroxyl radical, exit of this hydroxyl radical allows for the presence of single radicals in particles. The proposed mechanisms allow for agreement between initial droplet and final particle size distributions in miniemulsion polymerization initiated by lauroyl peroxide.

Sinapinic acid is a widespread compound in vegetable material and is as such common in the human diet. Recently it has drawn attention because of its biological activities. Sinapinic acid can be synthesized from syringaldehyde via the Knoevenagel- Doebner condensation. However this reaction is limited by the formation of 4-vi- nylsyringol after a second decarboxylation. To gain more detailed information about this reaction and to improve control over the formation of sinapinic acid, the concentration time history of syringaldehyde and the reaction products of this reaction have been monitored over time at different reaction temperatures. The formation of 4-vinylsyringol was found to be inhibited by performing the reaction at temperature below 80˚C. This allows the reaction to be optimized for the production of sinapinic acid, with an optimal yield of 78% after 2.5 hours at 70˚C.

In this paper, we present a series of amorphous non-isocyanate poly(hydroxy urethane)s (PHU) synthesized from diglycerol dicarbonate in bulk conditions at mild temperatures, without using a catalyst. Diglycerol dicarbonate has been synthesized from diglycerol and dimethyl carbonate and was subsequently reacted with various diamines to form PHUs. These fully bio-based PHUs were amorphous and displayed a broad range of Tg values i.e. from -7 to 66 °C. 1D and 2D NMR techniques were used to determine the ratio between primary and secondary hydroxyl groups formed along the PHU backbone, which was found to be 31:69 for all compositions. The number-average molecular weights were calculated from NMR data and range from 4100 to 9400 g/mol. In FTIR spectra, residual cyclic carbonate groups were observed, which is in agreement with the loss of diamine as detected by NMR. TGA analysis indicated that the polymers are stable up to 200 °C. The polymers synthesized are expected to perform well in e.g. coating applications, given their molecular and thermal properties as well as the abundance of reactive hydroxyl functionalities present along the PHU backbone, which can be used for curing purposes and/or further functionalization.

A novel procedure was developed to determine the direction of silica growth during the formation of a silica shell around aqueous microdroplets in water-in-oil Pickering emulsions. Two fluorescently labeled silica precursors were added consecutively and the resulting microcapsules were visualized via confocal fluorescence microscopy, allowing the conclusion that the locus of reaction moves in the positive radial direction, i.e. from the inside to the outside. A consequence of the growth direction is that water has to diffuse through the shell to participate in the reaction on the outer surface of the shell.

A new scale-up concept for microwave assisted flow processing is presented where modular scale-up is achieved by implementing microwave cavities in series. The scale-up concept is demonstrated for case studies of a packed-bed reactor and a wall-coated tubular reactor. With known kinetics and reaction temperature, a packed-bed reactor gave a conversion of 99% with the highest production rate of 170 kgprod/kgcat·h for esterification of acetic acid and ethanol catalyzed by ion-exchange resin in 18 cavities. A similar approach for a multicomponent reaction of benzaldehyde, piperidine, and phenylacetylene catalyzed by a thin Cu film in a wall-coated tubular reactor gave 99% conversion with the highest production rate of 7740 kgprod/kgcat·h in 28 cavities. In both cases, the pseudo first order reaction rate with respect to the limiting reactant yielded a typical rise in conversion and production rate. In a packed-bed reactor-heat exchanger operated at a temperature between 343 and 348 K, the conversion in the esterification reaction increased from 22% to 88% when the number of cavities was increased from one to eight. The experimental conversions matched the predictions of a packed bed reactor model within 5%. The production capacity in flow reactors, restricted to smaller sizes due to a limited microwave penetration depth and dominated mainly by the reaction kinetics, was increased by modular scale-up with implementation of the microwave multicavity assembly.

High pressure homogenization is at the heart of many emulsification processes in the food, personal care and pharmaceutical industry. The droplet size distribution is an important property for product quality and is aimed to be controlled in the process. Therefore a population balance model was built in order to predict the droplet size distribution subject to various hydrodynamic conditions found in a high pressure homogenizer. The hydrodynamics were simulated using Computational Fluid Dynamics and the turbulence was modeled with a RANS k–e model. The high energy zone in the high pressure homogenizer was divided into four compartments. The compartments had to be small enough to secure nearly homogeneous turbulent dissipation rates but large enough to hold a population of droplets. A population balance equation describing breakage and coalescence of oil droplets in turbulent flow was solved for every compartment. One set of parameters was found which could describe the development of the droplet size distribution in the high pressure homogenizer with varying pressure drop. An improvement of 65% was found compared to the same model containing just one compartment. The compartment approach may provide an alternative to direct coupling of CFD and population balances.

Colloid mills are the most common emulsification devices used in industry for products with high oil content. Drop breakage occurs when the emulsion is flowed through a small gap between rotor and stator under laminar shear conditions. In this paper, we have developed the first full population balance equation (PBE) model for colloid mills and used the model to better understand the relevant drop breakage mechanisms. The PBE model accounted for both drop breakage and coalescence and generated predictions of the drop size distribution after each pass of the emulsion through the colloid mill. Drops were assumed to break due to capillary instability with the distribution of drop sizes resulting from each breakage event studied in detail. A viscosity model was developed to predict the emulsion viscosity as function of the oil fraction and the high shear rates commonly used. Nonlinear optimization was used to estimate adjustable parameters in the breakage and coalescence functions to minimize the least-squares difference between predicted and measured drop size distributions for high oil-to-surfactant emulsions. We concluded that experimentally observed drop volume distributions could not be predicted with daughter drop distribution functions reported in the literature. Improved predictions were obtained using a new bimodal distribution function which captured drop breakage into multiple, nearly uniform daughter drops with a large number of small satellite drops. We also investigated model extensibility for changes in the oil fraction, emulsion flow rate and rotor speed.