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A new approach for the production of 2,5-furandicarboxylic acid by in situ oxidation of 5-hydroxymethylfurfural starting from fructose

The production of 2,5-furandicarboxylic acid (FDCA) starting with fructose as substrate via acid-catalyzed formation and subsequent oxidation of 5-hydroxymethylfurfural (HMF) was investigated. It was shown that an effective separation of the oxidation catalyst from fructose in combination with extraction and derivatization of formed HMF in methyl isobutyl ketone (MIBK) leads to formation of FDCA as final product. Two systems were developed to realize the concept, one by phase separation with a membrane, the other by encapsulating the oxidation catalyst in silicone beads.

Production of Spherical Beads by JetCutting

Until now, the production of spherical and monodisperse small beads from higher-viscosity fluids was hardly possible. JetCutting is a new, simple and efficient cutting technology for the production of monodisperse beads of small particle size from low- to high-viscosity fluids in large quantities. Since spherical beads are intermdiate or products in various industries, e.g., the pharmaceutical, chemical and food industries, manifold applications are possible. Offering further advantages, the JetCutter has a great potential to replace convential technologies for bead production.

Transformation of cinchonidine during the enantioselective hydrogenation of ethyl pyruvate to ethyl lactate

Abstract The transformation of cinchonidine (CIN) during the enantioselective hydrogenation of ethyl pyruvate on Pt/Al 2 O 3 was investigated. Under reaction conditions, cinchonidine was hydrogenated consecutively first at the quinuclidine part and then at the quinuline ring. However, the hydrogenation of the aromatic ring system, causing a drop in activity and enantioselectivity, did not begin until complete conversion of ethyl pyruvate occurred. By stopping the reaction at a conversion of approximately 70%, the activity and enantioselectivity of the catalyst could be maintained constant at high values for more than 10 repeated uses without the addition of fresh modifier at the beginning of each new hydrogenation cycle.

Improvement of the Jet Cutting Method for the Preparation of Spherical Particles from Viscous Polymer Solutions

Recently, we presented a new method for the production of uniform spherical particles (beads). This technology is based on cutting a solid liquid jet which is pressed out of a nozzle into cylindrical segments by means of a rotating cutting tool consisting of several wires. Due to the surface tension, the segments form spherical beads while falling which can then be collected. The diameter of the resulting beads is determined by the mass flow through the nozzle, the number of cutting wires, and the number of rotations of the cutting tool. In contrast to common techniques the high output production of small beads (<1 mm) is possible even from highly viscous fluids. In this article, we report about recent improvements of the jet cutting method with regard to the mathematical model and the reduction of losses by the application of diagonal cutting.

A novel strategy for heterogenisation of homogeneous and colloidal chiral catalysts and their application in enantioselective reactions

For the heterogenisation of chiral catalysts, a novel method has been developed and applied to different enantioselective reactions. The new heterogenisation method is based on the three-dimensional entrapment of catalysts by electrostatic attraction between a polyelectrolyte and an oppositely charged catalyst. An easy preparation procedure, a simple separation and a good retention of the active metal in the polymeric material and a high long-term stability of the entrapped catalyst are the significant features of this new heterogenisation method. Applying these entrapped catalysts in the hydroformylation of vinyl acetate, an enantiomeric excess (ee) of 39% could be obtained with a rhodium diphosphine complex. The activities and selectivities in the hydrogenation of dimethyl itaconate have been found to be competitive with homogeneous catalysts. A change in the direction of enantioselectivity has been observed by using entrapped Ru catalysts in different solvents. For the entrapment of chirally stabilised Pt-colloids used in the enantioselective hydrogenation of ethyl pyruvate, different polyanions have been found to be suitable. A constant enantioselectivity and a good activity during 25 hydrogenation cycles were obtained employing alginate-entrapped Pt-colloids.

Ceria supported gold–platinum catalysts for the selective oxidation of alkyl ethoxylates

This work covers the development of a ceria based AuPt catalyst for the selective aerobic oxidation of alkyl ethoxylates to their corresponding carboxylic acids. By optimizing metal loading and the Au to Pt ratio the activity of the catalyst could be increased significantly, while maintaining total selectivity. Although the choice of ceria as a support helped to suppress intermediate metal leaching, the catalyst still showed poor long-term stability in repeated batches. The cause for deactivation could finally be identified by TPR studies as over-oxidation. These suspicions were confirmed by a long-term stability study in continuous-mode. It proved to be possible to deactivate the catalyst on purpose by employing unfavourable oxidising reaction conditions, i.e. low substrate concentrations and excess oxygen. By avoiding such unfavourable conditions either in continuous-flow mode or in repeated batches, the long-term stability of the catalyst increased tremendously. A substrate screening of various ethoxylates showed that the catalyst was very well-suited to selectively oxidize a wide range of alkyl ethoxylates.

Nutritional requirements and the impact of yeast extract on the D-lactic acid production by Sporolactobacillus inulinus

This study provides detailed insight into the impact of complex nutrient sources on the fermentation of Sporolactobacillus inulinus, a highly productive D-lactic acid producing bacterium. The composition of various yeast extracts and peptones was analyzed and compared to the cultivation results of S. inulinus. Special attention was paid to the utilization of peptides and free amino acids. It turned out that free amino acids are the limiting factor for the lactic acid production. This limitation could be prevented in a fed-batch experiment, in which the product concentration was increased to 222 g L−1 by the addition of free amino acids and vitamins. Furthermore, a synthetic medium based on the analytical data of the reference yeast extract was developed to elucidate the nutritional requirements in detail.

Conversion of Fructose to HMF in a Continuous Fixed Bed Reactor with Outstanding Selectivity

5-Hydroxymethylfurfural (HMF) is a very promising component for bio-based plastics. Efficient synthesis of HMF from biomass is still challenging because of fast degradation of HMF to by-products under formation conditions. Therefore, different studies, conducted mainly in monophasic and biphasic batch systems with and without water addition have been published and are still under investigation. However, to produce HMF at a large scale, a continuous process is preferable. Until now, only a few studies have been published in this context. In this work, it is shown that fluorous alcohol hexafluoroisopropanol (HFIP) can act as superior reaction solvent for HMF synthesis from fructose in a fixed bed reactor. Very high yields of 76% HMF can be achieved in this system under optimized conditions, whilst the catalyst is very stable over several days. Such high yields are only described elsewhere with high boiling reaction solvents like dimethylsulfoxide (DMSO), whereas HFIP with a boiling point of 58 °C is very easy to separate from HMF.

Catalytic Dehydration of Fructose to 5-Hydroxymethylfurfural (HMF) in Low-Boiling Solvent Hexafluoroisopropanol (HFIP)

A mixture of hexafluoroisopropanol (HFIP) and water was used as a new and unknown monophasic reaction solvent for fructose dehydration in order to produce HMF. HFIP is a low-boiling fluorous alcohol (b.p. 58 °C). Hence, HFIP can be recovered cost efficiently by distillation. Different ion-exchange resins were screened for the HFIP/water system in batch experiments. The best results were obtained for acidic macroporous ion-exchange resins, and high HMF yields up to 70% were achieved. The effects of various reaction conditions like initial fructose concentration, catalyst concentration, water content in HFIP, temperature and influence of the catalyst particle size were evaluated. Up to 76% HMF yield was attained at optimized reaction conditions for high initial fructose concentration of 0.5 M (90 g/L). The ion-exchange resin can simply be recovered by filtration and reused several times. This reaction system with HFIP/water as solvent and the ion-exchange resin Lewatit K2420 as catalyst shows excellent performance for HMF synthesis.