Two sets of new azobenzene-based bromide salts are synthesized, and their thermal photochromic properties are studied. Both sets are based on the imidazolium cation. The first set (1) features a symmetric biscation where two imidazolium head groups (Im) with different alkyl chains (Cn) are connected to a central azobenzene unit (Azo): [Azo(C1-Im-Cn) 2 ]; n = 6, 8, 10, 12, 14. The other one contains an n-alkylimidazolium cation (Cn-Im) bearing a terminal azobenzene unit (C1-Azo) substituted with an alkoxy chain (O-Cm) of either two (2) or six (3) carbon atoms: [C1-Azo-O-Cm-Im-Cn]; m = 2, n = 8, 10, 12 and m = 6, n = 8, 10, 12, 14, 16. For both cation classes, the influence of alkyl chains of varying length on the thermal phase behavior was investigated by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). For five compounds (Azo(-C1-Im-C12) 2 (1d), Azo(-C1-Im-C12) 2 (1e), C1-Azo-O-C2-Im-C10 (2b), C1-Azo-O-C2-Im-C12 (2c), and C1-Azo-O-C6-Im-C16 (3e)), the formation of a liquid crystalline phase was observed. The biscationic salts (1) are all comparatively high melting organic salts (180-240 °C), and only the two representatives with long alkylchains (C12 and C14) exhibit liquid crystallinity. The monocationic salts with an O-C2 bridge (2) melt between 140 and 170 °C depending on the alkyl chain length, but from an alkyl chain of 10 and more carbon atoms on they form a smectic A liquid crystalline phase. The representatives of the third set with a O-C6 bridge qualify as ionic liquids with melting points less than 100 °C. However, only the representative with a hexadecyl chain forms a liquid crystalline phase. Representative single crystals for all sets of cations could be grown that allowed for single crystal structure analysis. Together with small-angle X-ray scattering experiments they allow for a more detailed understanding of the thermal properties. Through irradiation with UV-light (320-366 nm) all compounds undergo trans-cis isomerization, which reverses under visible light (440 nm). Disciplines Ceramic Materials | Complex Fluids | Other Materials Science and Engineering CommentsReprinted (adapted) with permission from Cryst. Growth Des., 2015, 15 (9) (2c), and C1-Azo-O-C6-Im-C16 (3e)), the formation of a liquid crystalline phase was observed. The biscationic salts (1) are all comparatively high melting organic salts (180−240°C), and only the two representatives with long alkylchains (C12 and C14) exhibit liquid crystallinity. The monocationic salts with an O−C2 bridge (2) melt between 140 and 170°C depending on the alkyl chain length, but from an alkyl chain of 10 and more carbon atoms on they form a smectic A liquid crystalline phase. The representatives of the third set with a O−C6 bridge qualify as ionic liquids with melting points less than 100°C. However, only the representative with a hexadecyl chain forms a liquid crystalline phase. Representative single crystals for all sets of cations could be grown that allowed for single crystal structure analysis. Together ...

Activated carbons are widely used as commercial adsorbents. Thermal or chemical activation creates a pore system and functional groups on the inner surface which may significantly change adsorption properties. Therefore, in addition to knowledge of the structural properties, a sound understanding of surface chemistry is indispensable. This paper summarizes the state of art as well as new developments in both fields. Standardized methods for characterizing structural properties are volumetric measurements and mercury porosimetry. To get a more detailed insight into the region of micropores, a probe molecule method was developed. For characterization of surface chemistry, methods such as IR spectroscopy, temperature-programmed desorption, and Boehm titration are subject of research. Novel methods were developed such as measuring of excess isotherms and calorimetric measurement of heat of adsorption, which are presented and discussed in greater detail in this paper. As each single method can only provide limited information, a better description of surface chemistry requires combination and careful interpretation of complementary information from different methods. Property Standard Limitation Apparent density ASTM D 2854-09 Total ash content ASTM D 2866-11 Moisture ASTM D 2867-17 Ball-pan hardness ASTM D 3802-16 pH-value ASTM D 3838-05 Electrical conductivity ASTM D 1125-14 Water soluble components ASTM D 5029-98 Volatile matter content ASTM D 5832-98 Acid extractable content ASTM D 6385-99 Particle size distribution ASTM D 2862-16 granular activated carbon ASTM D 5158-98 powdered activated carbon Ignition temperature ASTM D 3466-06 granular activated carbon Dusting attrition ASTM D 5159-04 granular activated carbon www.ChemBioEngRev.de

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Auf der ACHEMA 2018 stellten sich 24 Firmen mit Bezug zum Themenfeld Adsorption vor. Das weit gefächerte Ausstellerfeld reichte von Adsorbentienherstellern über Messgeräteentwickler bis hin zu Anlagenbauern. Aufgrund der zeitlichen Nähe zur Fachmesse IFAT/Entsorga waren in diesem Jahr etwas weniger Aussteller vertreten als in den vorausgehenden Jahren. Der Bericht umreißt die wichtigsten Trends und Neuerungen aus der Adsorptionstechnik, die auf den Ständen präsentiert und in Gesprächen von den Ausstellern thematisiert wurden.

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