Based on a survey of the literature on pretreatment of fused silica capillaries, 3 etching procedures and 11 silanization protocols based on the vinylic silane 3-((trimethoxysilyl)propyl) methacrylate (gamma-MAPS) were found to be most representative as a means of ensuring attachment of in situ prepared vinylic polymers. These techniques were applied to fused silica capillaries and the success in establishing the intended surface modification was assessed. X-ray photoelectron spectroscopy (XPS) was used to characterize the chemical state of the surface, providing information regarding presence of the reagent bound to the capillary. Wetting angles were measured and correlated with the XPS results. An adherence test was done by photopolymerization of a 2 mm long plug of 1,6-butanediol dimethacrylate in the prepared capillaries and evaluation of its ability to withstand applied hydraulic pressure. SEM was also performed in cases where the plug was released or other irregularities were observed. Finally, the roughness of the etched surface, considered to be of importance, was assessed by atomic force microscopy. Alkaline etching at elevated temperature provided a surface roughness promoting adhesion. The commonly used silanization protocols involving water in the silanization or washing steps gave inadequate surface treatment. The best silanization procedure was based on toluene as a solvent.
The chambers of Trivial Pursuit: Locking immobilized enzymes or encapsulated whole cells into a compartment that is connected to the stirrer enables efficient reactions and facilitates the reuse of biocatalysts by using this SpinChem system. R‐ATA=(R)‐amine transaminase.
5‐hydroxymethylfurfural (HMF) is produced upon dehydration of C6 sugars in biorefineries. As the product, it remains either in aqueous solutions, or is in situ extracted to an organic medium (biphasic system). For the subsequent oxidation of HMF to 2,5‐furandicarboxylic acid (FDCA), ‘media‐agnostic’ catalysts that can be efficiently used in different conditions, from aqueous to biphasic, and to organic (microaqueous) media, are of interest. Here, the concept of a one‐pot biocatalytic cascade for production of FDCA from HMF was reported, using galactose oxidase (GalOx) for the formation of 2,5‐diformylfuran (DFF), followed by the lipase‐mediated peracid oxidation of DFF to FDCA. GalOx maintained its catalytic activity upon exposure to a range of organic solvents with only 1 % (v/v) of water. The oxidation of HMF to 2,5‐diformylfuran (DFF) was successfully established in ethyl acetate‐based biphasic or microaqueous systems. To validate the concept, the reaction was conducted at 5 % (v/v) water, and integrated in a cascade where DFF was subsequently oxidized to FDCA in a reaction catalyzed by Candida antarctica lipase B.
A rotating
bed reactor (RBR) has been modeled using computational
fluid dynamics (CFD). The flow pattern in the RBR was investigated
and the flow through the porous material in it was quantified. A simplified
geometry representing the more complex RBR geometry was introduced
and the simplified model was able to reproduce the main characteristics
of the flow. Alternating reactor shapes were investigated, and it
was concluded that the use of baffles has a very large impact on the
flows through the porous material. The simulations suggested, therefore,
that even faster reaction rates could be achieved by making the baffles
deeper. Two-phase simulations were performed, which managed to reproduce
the deflection of the gas–liquid interface in an unbaffled
system. A chemical reaction was implemented in the model, describing
the ion-exchange phenomena in the porous material using four different
Sherwood number correlations. The simulations were overall in good
agreement with experimental data.
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