Controlling chemical reactions in
porous heterogeneous catalysts
is a tremendous challenge because of the difficulty in producing uniform
active sites that can be tuned with precision. However, analogous
to enzymes, when a catalytic pocket provides complementary close contacts
and favorable intermolecular interactions with the reaction participants,
the reaction efficiency and selectivity may be tuned. Here, we report
an isoreticular family of catalysts based on the multicomponent metal–organic
framework MUF-77. The microenvironment around the site of catalysis
was successfully programmed by introducing functional groups (modulators)
to the organic linkers at sites remote from the catalytic unit. The
framework catalysts produced in this way exhibit several unique features,
including the simultaneous enhancement of both reactivity and stereochemical
selectivity in aldol reactions, the ability to catalyze Henry reactions
that cannot be accomplished by homogeneous analogs, and discrimination
between different reaction pathways (Henry versus aldol) that compete
for a common substrate.
The application of heat storage systems in households or the industry is one possibility to optimize the degree of heat utilization and to reduce greenhouse gas emissions. In contrast to established heat storage systems based on water, zeolitic systems reach energy densities of 150-200 kWh m-3 and allow for seasonal storage with almost no heat loss. However, a commercial breakthrough was not yet successful. Given this background, it is the aim of the present study to identify appropriate operational parameters for a zeolite heat storage system in the laboratory and to prepare an upscaling to demonstration scale. To this end, the pressure drop of the zeolite bed, the cycle time, and the optimal process parameters during thermal loading and deloading were determined.
While renewable heat makes up only 13 % of overall German heat consumption, the share of renewable electricity produced from wind, solar, water, and geothermal power already reached 36 % of overall electricity consumption in 2017. One measure to support the integration of renewable heat in the German energy system is the use of heat storage systems. Although water‐based heat storage systems for temperatures up to 100 °C are state of the art, systems for temperatures up to several hundred degrees Celsius are still under investigation or in the demonstration phase. Therefore, this work focuses on the development of a simulation model for analyzing and engineering fixed‐bed thermal storage systems that are filled with an inert bulk material such as stone fragments.
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