Johan Paul

Zeolite-catalysed conversion of C3 sugars to alkyl lactates

The direct conversion of C3 sugars (or trioses) to alkyl lactates was achieved using zeolite catalysts. This reaction represents a key step towards the efficient conversion of bio-glycerol or formaldehyde to added-value chemicals such as lactate derivatives. The highest yields and selectivities towards the desired lactate product were obtained with Ultrastable zeolite Y materials having a low Si/Al ratio and a high content of extra-framework aluminium. Correlating the types and amounts of acid sites present in the different zeolites reveals that two acid functions are required to achieve excellent catalysis. Bronsted acid sites catalyse the conversion of trioses to the reaction intermediate pyruvic aldehyde, while Lewis acid sites further assist in the intramolecular rearrangement of the aldehyde into the desired lactate ester product. The presence of strong zeolitic Bronsted acid sites should be avoided as much as possible, since they convert the intermediate pyruvic aldehyde into alkyl acetals instead of lactate esters. A tentative mechanism for the acid catalysis is proposed based on reference reactions and isotopically labelled experiments. Reusability of the USY catalyst is demonstrated for the title reaction.

Glyoxylase biomimics: zeolite catalyzed conversion of trioses

Direct conversion of biomass derived trioses such as dihydroxyacetone (DHA) and glyceraldehyde (GLA) to alkyl lactates was carried out using alcohols over various Y type zeolite materials. The conversion takes place through a pyruvic aldehyde intermediate which subsequently undergoes esterification. The screened catalysts can be grouped based on their ability to either form methylglyoxal dialkyl acetal or alkyl lactate. The discussed catalysis shows strong resemblance with the biological lactic acid synthesis routes where glyoxylases effect the reaction. Zeolites may therefore be considered as functional biomimics of these enzymes.

Spherical MCM-41 as support material in enantioselective HPLC

Abstract Spherical MCM-41 particles covalently linked with (R)-naphthylethylamine as selector are reported as a new chiral stationary phase for HPLC and show excellent resolution and efficiency in combination with low inlet pressures.

Combinatorial screening and conventional testing of antimony-rich selective oxidation catalysts

Abstract The use of high-throughput synthesis and screening techniques is demonstrated with the optimization of and the search for new antimony-rich mixed-metal oxide catalysts for the selective oxidation of isobutane to methacrolein. Three 207-member catalyst libraries have been prepared via a sol-gel synthesis procedure using design software and a synthesis robot. The catalyst libraries have been examined for catalytic activity and selectivity using spatially resolved mass spectrometry in an open-well reactor system. The reaction products have been detected by mass spectrometry and the massive data obtained have been analyzed with the help of dedicated software. Using a composition spread approach, an optimal composition of Mo–V–Sb catalysts has been identified. Screening of 68 combinations of other antimony-rich mixed oxides on libraries provides evidence that the Mo–V–Sb system is a unique ternary composition for selective oxidation of isobutane to methacrolein. Scale up of the combinatorially interesting compositions confirmed unequivocally their excellent catalytic behavior.

High-Throughput Platform for Synthesis of Melamine-Formaldehyde Microcapsules

The synthesis of microcapsules via in situ polymerization is a labor-intensive and time-consuming process, where many composition and process factors affect the microcapsule formation and its morphology. Herein, we report a novel combinatorial technique for the preparation of melamine-formaldehyde microcapsules, using a custom-made and automated high-throughput platform (HTP). After performing validation experiments for ensuring the accuracy and reproducibility of the novel platform, a design of experiment study was performed. The influence of different encapsulation parameters was investigated, such as the effect of the surfactant, surfactant type, surfactant concentration and core/shell ratio. As a result, this HTP-platform is suitable to be used for the synthesis of different types of microcapsules in an automated and controlled way, allowing the screening of different reaction parameters in a shorter time compared to the manual synthetic techniques.

Molecular designed vanadia-titania supported SBA-15 for the oxidative dehydrogenation of isobutane and propane

Vanadium and titanium oxide species were successfully deposited on a mesoporous SBA-15 support by the Molecular Designed Dispersion (MDD) method. A combination of different techniques (XRD, N 2 -soprtion, DRS, H 2 -TPR and Raman) was used to verify the nature of the vanadia on the various mesoporous catalysts. The catalytic performance for the oxidative dehydrogenation of isobutane was investigated by steady-state experiments in a fixed bed micro multi-tubular reactor. Catalysis was focused on the selective production of olefins such as isobutene and propene. The catalytic results are presented in varying process conditions and are discussed in terms of V loading, V dispersion and Ti promotion.