Magnetically separable Pt catalyst for asymmetric hydrogenation

A magnetic Pt/SiO₂/Fe₃O₄ catalyst consisting of chirally modified platinum supported on silica coated magnetite nanoparticles was prepared using an easy synthetic route and successfully applied for the enantioselective hydrogenation of various activated ketones. The magnetic catalyst modified with cinchonidine showed a catalytic performance (activity, enantioselectivity) in the asymmetric hydrogenation of various activated ketones in toluene comparable to the best known Pt/alumina catalyst used for these reactions. The novel catalyst can be easily separated from the reaction solution by applying an external magnetic field and recycled several times with almost complete retention of activity and enantioselectivity.     

Feststoffbildung durch Kristallisation und Fällung

Formation of solids by crystallization and precipitation. Formation of solids from solutions can take place by crystallization or precipitation. The principal factor is the relationship between solubility and supersaturation. In crystallization, the solubility of the crystallising substance is so high that the formation of solids occurs largely in the metastable zone in the immediate vicinity of the solubility limits. Crystal growth and nucleation are functions of supersaturation. If a high supersaturation is required at low substance-specific growth rates for an adequate crystal growth, high nucleation rates and hence small crystals will result. On this basis, the authors present information for the specific design of crystallization processes. In contrast, the solubility of the precipitated product must be very low for precipitation. Direct crystal formation is possible only for substance systems of high solubility. As a rule, however, the precipitated substance is so insoluble that solids are formed via amorphous intermediates. The results of a large number of experiments show the influence of various parameters of the precipitation process on the filtrability of the precipitated product.     

Gewinnung von Öl durch Schwelen von Ölschiefer und Teersand als Beitrag zur Energieversorgung

The contribution to energy supply of oil recovered by distillation of oil shale and tar sands . Following a world-wide survey of the most important deposits of oil shale and tar sands, the current activities in the USSR, China and Canada in the field of the industrial recovery of shale oil and bitumen from tar sand are described in broad terms. Thereafter, the current large-scale projects for the production of synthesis oil from these feedstocks are dealt with. The operating method and development status of modern processes for distilling oil shale are covered, as is the working principle of the hot water extraction of tar sand which is already commercially in application. The LR-Process method of operation and its especial feature of circulating the distilled residue as solid heat carrier are discussed in more detail. This is followed by information on the throughput potential of this process. The characteristic reactions influencing the quality of the LR products (oil, gas, residue, flue gas) are handled. Typical quality data for oil and gas obtained from oil shale and tar sands are given. A route is indicated for further processing of the condensate streams from the Lurgi-Ruhrgas Process. This consists of precipitation of solids, distillative separations and one hydrogenation step for the naphtha and oil fraction. These process steps produce a ?syncrude”? which can be further processed together with crude oil in conventional refineries. Examples are given for the independent further processing of syncrude to end-products customary on the market.