Jürgen Ortner

Catalytic Thermochemical Reactor/Receiver for Solar Reforming of Natural Gas: Design and Performance

The advantages of thermochemical conversion of concentrated solar energy using catalytic processes are discussed. The design of a solar volumetric thermochemical reactor/receiver (TCRR) with catalytic absorber, method for synthesis of catalytically activated ceramics, and preparation of catalytic absorber have been described. The prototype TCRR was tested in the high flux solar furnace at the DAC, Cologne by using the dioxide reforming of methane. The tests were performed to check the main concept of the TCRR design and catalytic absorber, to study the influence of solar flux distribution, the reagent flows and their ratio on the productivity or conversion, determine the reagents conversion depending on the focal point disposition with respect to the absorber, and to study the efficiency of the thermochemical conversion. The chemical and total efficiencies of the CO2–methane conversion were calculated using the experimentally measured concentrations of the reaction products. The highest overall efficiency achieved in these experiments was 30% with the Ni–Cr catalytic absorber.

Green photochemistry: solar photooxygenations with medium concentrated sunlight

The rose bengal sensitized photooxygenations of citronellol and 1,5-dihydroxynaphthalene were performed successfully under solar irradiation conditions, and complete conversions (>95%) were achieved in almost all cases in relatively short illumination times. The selected reactions were easily performed on multigram to kilogram scales using cheap and commercially available starting materials, and yielded important key-intermediates for industrial applications.

Green photochemistry: the solar-chemical Photo-Friedel-Crafts acylation of quinones

The photoreactions between 1,4-quinones (1 and 4) and aldehydes (2 and 5), yielding acylated hydroquinones as sole products, were investigated under artificial and solar irradiation conditions. Three different solar reactors were used for the photochemical syntheses with sunlight (PROPHIS, CPC and a flat bed reactor), and the CPC system was found to be the most robust one in terms of weather dependence. The solar reactions can be easily performed on a half-kilogram scale using cheap and commercially available starting materials.

IMMOBILIZED PHOTOSENSITIZERS FOR SOLAR PHOTOCHEMICAL APPLICATIONS

New hydrophilic immobilized photosensitizers (heterogeneous phase) were synthesized that overcome some disadvantages of the use of homogeneous phase sensitizers for detoxification and disinfection of water. The chosen sensitizers, based on porphyrin moieties, were bound on poly(methyl methacrylate) (PMMA). The measured production rate of singlet oxygen is significantly higher than that of the well-known rose bengal immobilized on Merrifield polymer. The sensitive polymer can be used for detoxification and disinfection of polluted water.

Solar collectors versus lamps—a comparison of the energy demand of industrial photochemical processes as exemplified by the production of ε-caprolactam

The energy demand of photochemical synthesis of e-caprolactam was compared for two plant concepts. The conventional lamp-driven concept followed the process as realized on an industrial scale by Toray Ltd, Japan and a solar concept was designed at identical yearly output. The aim of the comparison was to determine the savings of fossil fuels that could be achieved if photochemistry could make use of solar radiation instead of artificial light. The use of solar radiation for the photochemical production of e-caprolactam has a 4-fold lower demand for electric current and an 8-fold lower demand for cooling energy as compared to an equivalent conventionally operated route. Furthermore, due to avoided conversion of fossil fuel to electric current, a solar process would allow specific emissions of 1.5–2.5tons of CO2 per ton e-caprolactam to be avoided, depending on the primary energy carrier used.

Technologies for the solar photochemical and photocatalytic manufacture of specialities and commodities: A review.

Solar radiation and solar technology substitute for electricity, cooling energy and expensive equipment that are required for the conventional lamp-operated photochemical techniques. The maturity of the techniques would allow commercial-scale applications. In the meantime numerous reaction classes have been proved to be feasible for synthetic solar photochemical technology, including photooximations, sensitized photoisomerizations, photooxygenations and photocycloadditions, photorearrangements, photoinduced alkylations, and catalyzed heterocyclizations and photooxidations. A wide variety of valuable products could be manufactured that way.

Back to the roofs – the solarchemical production of fine chemicals with sunlight

Three photochemical reactions were performed successfully under solar irradiation conditions: the photoacylation of quinones with aldehydes and the rose bengal sensitized photooxygenations of citronellol or 1,5-dihydroxynaphthalene. All reactions were easily performed on multigram to kilogram scales using cheap and commercially available starting materials, and yielded important key-intermediates for industrial applications.