Leibniz University of Hanover

About: Leibniz University of Hanover is a education organization based out in Hanover, Niedersachsen, Germany. It is known for research contribution in the topics: Finite element method & Population. The organization has 14283 authors who have published 29845 publications receiving 682152 citations.

Continuous Flow Techniques in Organic Synthesis

Abstract: As part of the dramatic changes associated with the need for preparing compound libraries in pharmaceutical and agrochemical research laboratories, the search for new technologies that allow automation of synthetic processes has become one of the main topics. Despite this strong trend for automation high-throughput chemistry is still carried out in batches, whereas flow-through processes are rather restricted to production processes. This is far from understandable because the main advantages of that approach are facile automation, reproducibility, safety, and process reliability, because constant reaction parameters can be assured. Indeed, methods and technologies are missing that allow rapid transfer from the research level to process development without time-consuming adaptation and optimization of methods from the laboratory scale to production plant scale. Continuous-flow processes are considered as a universal lever to overcome these restrictions and, only recently, joint efforts between synthetic and polymer chemists and chemical engineers have resulted in the first continuous-flow devices and microreactors; these allow rapid preparation of compounds with minimum workup. Many of these approaches use immobilized reagents and catalysts, which are embedded in a structured flow-through reactor. It is generally accepted, that for achieving best reaction and kinetic parameters for convective-flow processes monolithic materials are ideally suited as solid phases or polymer supports. In addition, immobilization techniques have to be developed that allow facile regeneration of the active species in the reactor.

Classical simulation of commuting quantum computations implies collapse of the polynomial hierarchy

Abstract: We consider quantum computations comprising only commuting gates, known as IQP computations, and provide compelling evidence that the task of sampling their output probability distributions is unli...

Bio-inspired polydopamine: a versatile and powerful platform for covalent synthesis of molecular sieve membranes.

Abstract: Inspired by the bioadhesive ability of the marine mussel, a simple, versatile, and powerful synthesis strategy was developed to prepare highly reproducible and permselective molecular sieve membranes by using polydopamine as a novel covalent linker. Attributing to the formation of strong covalent and noncovalent bonds, ZIF-8 nutrients are attracted and bound to the support surface, thus promoting the ZIF-8 nucleation and the growth of uniform, well intergrown, and phase-pure ZIF-8 molecular sieve membranes. The developed ZIF-8 membranes show high hydrogen selectivity and thermal stability. At 150 °C and 1 bar, the mixture separation factors of H2/CO2, H2/N2, H2/CH4, and H2/C3H8 are 8.9, 16.2, 31.5 and 712.6, with H2 permeances higher than 1.8 × 10–7 mol·m–2·s–1·Pa–1, which is promising for hydrogen separation and purification.

Mesoporous titania photocatalysts: preparation, characterization and reaction mechanisms

Abstract: Titanium dioxide is a very important semiconductor with a high potential for applications in photocatalysis, solar cells, photochromism, sensoring, and various other areas of nanotechnology. Increasing attention has recently been focused on the simultaneous achievement of high bulk crystallinity and the formation of ordered mesoporous TiO2 frameworks with high thermal stability. Mesoporous TiO2 has continued to be highly active in photocatalytic applications because it is beneficial for promoting the diffusion of reactants and products, as well as for enhancing the photocatalytic activity by facilitating access to the reactive sites on the surface of photocatalyst. This steady progress has demonstrated that mesoporous TiO2 nanoparticles are playing and will continue to play an important role in the protection of the environment and in the search for renewable and clean energy technologies. This review focuses on the preparation and characterisation of mesoporous titania, noble metals nanoparticles, transition metal ions, non-metal/doped mesoporous titania networks. The photocatalytic activity of mesoporous titania materials upon visible and UV illumination will be reviewed, summarized and discussed, in particular, concerning the influence of preparation and solid-state properties of the materials. Reaction mechanisms that are being discussed to explain these effects will be presented and critically evaluated.