Green Exfoliation of Graphite Flakes to Efficiently Synthesize Biographene

A new simple, rapid, and efficient methodology to produce undamaged graphene sheets from graphite flakes in water by a bio-exfoliation technology is described. The methodology consists in the application of a lipase, with a very exclusive mechanism of interaction with hydrophobic surfaces, combined with a previous mechanical sonication, to selectively generate biographene in water. The adsorption of the lipase on the graphene sheets permits to keep the sheets separated in comparison with other methods. It is possible to obtain more than 80% of graphene (in the form of Few Layer Graphene) from low-cost graphite and with less damage compared to commercial graphene oxide (GO) or reduced GO. Experimental analysis demonstrated the formation of bilayer graphene mainly using lipase from Thermomyces lanuginosus (TLL).</p

Zeolite LTA/Carbon membranes for air separation

Zeolite LTA membranes with few defects have been successfully synthesized on a carbon support by the secondary growth method, in which hydrothermal synthesis is preceded by the seeding of the carbon support with colloidal LTA zeolite crystals (about 100 nm) by means of the ElectroPhoretic Deposition (EPD) method. The effect of different synthesis parameters, such as pre-treatments of the carbon support, and different synthesis times and temperatures, on the quality of the zeolite LTA/carbon composite, were analysed by means of XRD, SEM, EDS, and TG–DTA–MS. In addition, in order to analyse the permeation characteristics of the composite materials, they were mounted in a permeation cell, and single gas components or binary mixtures of N2/O2 (in a ratio of 79:21) were fed to the zeolite side. The best zeolite LTA/carbon membrane was obtained using a pre-oxidised and EPD seeded support which then underwent hydrothermal treatment at 373 K for 4.5 h. This final composite, upon reaching the steady state, separates air with a high permeance (about 2.7 x 10-7 mol s-1 Pa-1 m-2) and possesses a good separation factor (about 2.7).Spanish Ministerio de Educación y Ciencia (Project CTQ2006-08958/PPQ) and the EU (FEDER program)

Selective hydrogenation of phenylacetylene to styrene on a Pd/TiO 2 coating in a microreactor

The selective hydrogenation of phenylacetylene to styrene by hydrogen was studied in the 25-50°C temperature range in a continuous flow microchannel of 250 μm i.d. with a Pd supported on mesoporous TiO2 catalyst. The inner wall of the microreactor was dip-coated with a prehydrolyzed titania precursor solution containing an EOxPOyEOx amphiphilic triblock copolymer (EO = ethylene oxide, PO = propylene oxide, x = 106, y = 70) and suspended palladium nanoparticles with an average diameter of 4 nm. Solvent was withdrawn from the channel at a rate of 1 cm/s yielding a 120 nm continuous titania layer with a cubic mesostructure after drying and calcination. The organic copolymer was removed by calcination at 300°C under a residual pressure of 15 mbar. The coating porosity was 0.4, resulting in overall coating mass of 1.32 mg with a 1 wt.% Pd content. The liquid flow was varied between 1 and 10 μL/min and the hydrogen flow between 250 and 550 μL/min (STP). This corresponds to superficial velocities of 0.034-0.34 cm/s and 8-18 cm/s for liquid and gas, respectively. The maximum selectivity to styrene of 95 % was observed at a phenylacetylene conversion of 88%. The reaction rate in terms of TOF was found to be up to 2 s-1

Selective hydrogenation of phenylacetylene to styrene on a Pd/TiO ₂ coating in a microreactor

The selective hydrogenation of phenylacetylene to styrene by hydrogen was studied in the 25-50°C temperature range in a continuous flow microchannel of 250 μm i.d. with a Pd supported on mesoporous TiO2 catalyst. The inner wall of the microreactor was dip-coated with a prehydrolyzed titania precursor solution containing an EOxPOyEOx amphiphilic triblock copolymer (EO = ethylene oxide, PO = propylene oxide, x = 106, y = 70) and suspended palladium nanoparticles with an average diameter of 4 nm. Solvent was withdrawn from the channel at a rate of 1 cm/s yielding a 120 nm continuous titania layer with a cubic mesostructure after drying and calcination. The organic copolymer was removed by calcination at 300°C under a residual pressure of 15 mbar. The coating porosity was 0.4, resulting in overall coating mass of 1.32 mg with a 1 wt.% Pd content. The liquid flow was varied between 1 and 10 μL/min and the hydrogen flow between 250 and 550 μL/min (STP). This corresponds to superficial velocities of 0.034-0.34 cm/s and 8-18 cm/s for liquid and gas, respectively. The maximum selectivity to styrene of 95 % was observed at a phenylacetylene conversion of 88%. The reaction rate in terms of TOF was found to be up to 2 s-1.</p