ABSTRACT
A thirst for water: Organic-inorganic hybrid silica nanosieve membranes with narrow pore size distributions were developed for the separation of binary (bio)alcohol/water mixtures, for example, to remove water from wet biofuels during production. These membranes dehydrate lower alcohols and show a stable performance in the presence of significant amounts of acetic acid.
Subject(s)
Alcohols/isolation & purification , Membranes, Artificial , Acetic Acid , Energy-Generating Resources , Porosity , Silicon Dioxide , WaterABSTRACT
Unprecedented hydrothermal stability in functional membranes has been obtained with hybrid organic-inorganic nanoporous materials, enabling long-term application in energy-efficient molecular separation, including dehydration up to at least 150 degrees C.
ABSTRACT
The incorporation of methyl groups in microporous silica membranes was proven to enhance the service time in the dehydration of a butanol-water mixture at 95 degrees C from a few weeks to more than 18 months with a water flux of about 4 kg m(-2) h(-1) and a selectivity between 500 and 20 000.
ABSTRACT
A polycrystalline sample of a new phase in the Sr-Fe-Mn-O system has been prepared by standard solid-state techniques. Characterization at room temperature by X-ray diffraction, high-resolution electron microscopy, Mössbauer spectroscopy and neutron diffraction has led to it being described as a 15-layered, rhombohedral (15R) perovskite [space group R&thremacr;m: a = 5.4489(1) Å, c = 33.8036(7) Å] with a previously unobserved structure. The pseudo close-packed SrO(3) layers have a (cchch)(3) stacking sequence such that the occupation of the interstitial 6-coordinate sites by Mn (or Fe) leads to the formation of Mn(2)O(9) units which are linked to each other either directly by a common vertex, or indirectly via a single, vertex-sharing MnO(6) octahedron. The stoichiometry of the compound was determined to be SrMn(0.915(5))Fe(0.085(5))O(2.979(3)). The face-sharing sites are occupied by 0.957(3)Mn/0.043(3)Fe while the exclusively corner-linked sites show a higher Fe occupation; 0.745(4)Mn/ 0.255(4)Fe. A neutron diffraction experiment carried out at 3 K indicated the presence of long-range magnetic order with the Mn(4+) cations aligned antiferromagnetically with an ordered moment of 2.26(3)&mgr;(B)/Mn(4+). Both the neutron and the susceptibility data are consistent with the Fe cations remaining magnetically disordered to 3 K. The latter data show T(N) = 220 K, and suggest that some spin frustration is present at low temperatures.
