Synthesis and Characterization of Ru-Loaded Anodized Aluminum Oxide for Hydrogenation Catalysis.

Anodized aluminum oxides (AAOs) are synthesized and used as catalyst support in combination with Ru as metal in hydrogenation catalysis. SEM and TEM analysis of the as-synthesized AAOs reveal uniform, ordered nanotubes with pore diameters of 18 nm, which are further characterized with Kr physisorption, XRD and FTIR spectroscopy. After impregnation of the AAOs with Ru, the presence of Ru nanoparticles inside the tubular pores is evidenced clearly for the first time via HAADF-STEM-EDX. The Ru-AAOs have been tested for catalytic activity, which showed high conversion and selectivity for the hydrogenation of toluene and butanal.

Cellulose amorphization by swelling in ionic liquid/water mixtures: a combined macroscopic and second-harmonic microscopy study.

Amorphization of cellulose by swelling in ionic liquid (IL)/water mixtures at room temperature is a suitable alternative to the dissolution-precipitation pretreatment known to facilitate enzymatic digestion. When soaking microcrystalline cellulose in the IL 1-ethyl-3-methylimidazolium acetate containing 20 wt % water, the crystallinity of the cellulose sample is strongly reduced. As less than 4 % of the cellulose dissolves in this mixture, this swelling method makes a precipitation step and subsequent energy-intensive IL purification redundant. Second-harmonic generation (SHG) microscopy is used as a structure-sensitive technique for in situ monitoring of the changes in cellulose crystallinity. Combined optical and SHG observations confirm that in the pure IL complete dissolution takes place, while swelling without dissolution in the optimal IL/water mixture yields a solid cellulose with a significantly reduced crystallinity in a single step.

End-of-life treatment of poly(vinyl chloride) and chlorinated polyethylene by dehydrochlorination in ionic liquids.

There is an urgent need for green technologies to remove halogens from halogenated polymers at the end of their lifetime. Ionic liquids (ILs) were used to dehydrochlorinate and/or dissolve the chlorinated polymers poly(vinyl chloride) (PVC) and chlorinated polyethylene (CPE). The dehydrochlorination activity of an IL depends mainly on its anion and is related to the high hydrogen-bond-accepting ability (ß value) of the anion. Different phosphonium ILs successfully dissolve and dehydrochlorinate PVC and CPE at temperatures from 80 °C. PVC is dehydrochlorinated up to 98 % after 60 min in tetrabutylphosphonium chloride ([P4444 ][Cl]) at 180 °C. PVC pieces stabilized by calcium stearate (4 mm(3) ) are dehydrochlorinated more slowly; conversions of 85 and 96 % are reached after 1 and 8 h, respectively. Smaller pieces are dehydrochlorinated faster. High loadings, for example, 0.3 g stabilized PVC in 0.5 g IL, can be applied with only a minor loss of conversion. [P4444 ][Cl] proved to be stable during several consecutive reactions; after each run more than 99 % of the IL can be recovered. The structure of the dehydrochlorinated PVC was studied by (13) C cross-polarization magic-angle spinning NMR and FTIR spectroscopy; the removal of Cl and the formation of double bonds were confirmed. Carefully dehydrochlorinated CPE was processed further by acyclic diene metathesis depolymerization with ethylene and the Hoveyda-Grubbs second-generation catalyst to yield α,ω-dienes such as 1,5-hexadiene and 1,6-heptadiene.