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121.
Development of liquid biofuels has entered a new phase of large scale pilot demonstration. A number of plants that are in
operation or under construction face the task of addressing the engineering challenges of creating a viable plant design,
scaling up and optimizing various unit operations. It is well-known that separation technologies account for 50–70% of both
capital and operating cost. Additionally, reduction of environmental impact creates technological challenges that increase
project cost without adding to the bottom line. Different technologies vary in terms of selection of unit operations; however,
solid–liquid separations are likely to be a major contributor to the overall project cost. Despite the differences in pretreatment
approaches, similar challenges arise for solid–liquid separation unit operations. A typical process for ethanol production
from biomass includes several solid–liquid separation steps, depending on which particular stream is targeted for downstream
processing. The nature of biomass-derived materials makes it either difficult or uneconomical to accomplish complete separation
in a single step. Therefore, setting realistic efficiency targets for solid–liquid separations is an important task that influences
overall process recovery and economics. Experimental data will be presented showing typical characteristics for pretreated
cane bagasse at various stages of processing into cellulosic ethanol. Results of generic material balance calculations will
be presented to illustrate the influence of separation target efficiencies on overall process recoveries and characteristics
of waste streams. 相似文献
122.
Snégaroff K Nguyen TT Marquise N Halauko YS Harford PJ Roisnel T Matulis VE Ivashkevich OA Chevallier F Wheatley AE Gros PC Mongin F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13284-13297
A series of chloro- and bromopyridines have been deprotometalated by using a range of 2,2,6,6-tetramethylpiperidino-based mixed lithium-metal combinations. Whereas lithium-zinc and lithium-cadmium bases afforded different mono- and diiodides after subsequent interception with iodine, complete regioselectivities were observed with the corresponding lithium-copper combination, as demonstrated by subsequent trapping with benzoyl chlorides. The obtained selectivities have been discussed in light of the CH acidities of the substrates, determined both in the gas phase and as a solution in THF by using the DFT B3LYP method. 相似文献
123.
124.
Vadim Mogilevskii 《Journal of Functional Analysis》2011,261(7):1955-1968
Let H be a Hilbert space and let A be a simple symmetric operator in H with equal deficiency indices d:=n±(A)<∞. We show that if, for all λ in an open interval I⊂R, the dimension of defect subspaces Nλ(A) (=Ker(A?−λ)) coincides with d, then every self-adjoint extension has no continuous spectrum in I and the point spectrum of is nowhere dense in I. Application of this statement to differential operators makes it possible to generalize the known results by Weidmann to the case of an ordinary differential expression with both singular endpoints and arbitrary equal deficiency indices of the minimal operator. 相似文献
125.
The LaXO(3):Tb(3+) (X = Al(3+), Ga(3+), In(3+)) perovskite nanoparticles were obtained using the nonhydrolytic treatment (Bradley reaction) of the molecular precursors of the La(O(i)Pr)(3), Al(O(i)Pr)(3), Ga(O(i)Pr)(3), In(5)O(O(i)Pr)(13), and Tb(acac)(3), respectively. It was shown that crystal structure and morphology evolution in the LaXO(3), X = Al, Ga, In nano-oxide series depended on the size and chemical properties of the X-metal atom. Formation of the LaInO(3):Tb(3+) nanoparticles is distinctly less thermodynamically demanding on contrary to the LaAlO(3):Tb(3+) and LaGaO(3):Tb(3+) since it provided crystalline product directly in the solution synthesis at 202 °C, which is the lowest reported synthesis temperature for this compound up-to-date. This behavior was ascribed to the effects directly connected with the dopant substitution (exchange of bigger La(3+) cation with smaller Tb(3+)) as well as reduction of the particle size. The size effects are mostly reflected in the expansion of the cell volume, changes of the cell parameters as well as shifting and broadening of the Raman bands. Indirectly, size reduction has also an effect on the luminescence properties through the higher probability of presence of surface and net defects as well as heterogeneous distribution of the Tb(3+) ions caused by high surface-to-volume ratio. The prepared nanophosphors show basically green emission with exception of white-green in case of the LaInO(3):Tb(3+). Strong emission quenching was found in the latter case being most likely a consequence of the nonradiative energy transfer between Tb(3+) and In(3+) as well as the presence of defects. In comparison to the Pechini's method, the LaXO(3) nanoparticles required significantly lower annealing temperature (700 °C) necessary for complete crystallization. Generally the resulting particles are distinctly smaller (5 to 25 nm) and less agglomerated (50-100 nm) depending on the reaction conditions as well as thermal treatment. For the first time, it was shown that the LaGaO(3):Tb(3+) nanopowder has crystallized in the high-temperature rhombohedral R3c phase. 相似文献
126.
Nakhjavan B Tahir MN Panthöfer M Gao H Gasi T Ksenofontov V Branscheid R Weber S Kolb U Schreiber LM Tremel W 《Chemical communications (Cambridge, England)》2011,47(31):8898-8900
A wet chemical approach from organometallic reactants allowed the targeted synthesis of Co@Fe(2)O(3) heterodimer and CoFe(2)O(4) ferrite nanoparticles. They display magnetic properties that are useful for magnetic MRI detection. 相似文献
127.
A Raman microprobe study of melt inclusions in kimberlites from Siberia, Canada, SW Greenland and South Africa 总被引:1,自引:0,他引:1
Mernagh TP Kamenetsky VS Kamenetsky MB 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,83(1):82-87
The geometries, energies and vibrational frequencies of various polyborates in both gaseous and aqueous phase were calculated at the B3LYP/aug-cc-pVDZ level. The calculated total symmetrical stretching Raman shifts of B(OH)(3), B(OH)(4)(-), B(2)O(OH)(4), B(2)O(OH)(5)(-), B(2)O(OH)(6)(2-), B(3)O(3)(OH)(3), B(3)O(3)(OH)(4)(-), B(3)O(3)(OH)(5)(2-), B(3)O(3)(OH)(6)(3-), B(4)O(5)(OH)(4)(2-) and B(5)O(6)(OH)(4)(-) were assigned to 877.40, 735.33, 785.22, 792.90, 696.79, 587.72, 599.06, 740.16, 705.01, 551.67 and 521.04cm(-1), respectively. The results can be used as the characteristic frequency for polyborates in aqueous phase at room temperature. At least six types of polyborates B(OH)(3), B(OH)(4)(-), B(3)O(3)(OH)(4)(-), B(3)O(3)(OH)(5)(2-), B(4)O(5)(OH)(4)(2-) and B(5)O(6)(OH)(4)(-), occur in aqueous solutions at ambient temperature. The chemical species distribution and the relevant interaction mechanisms among polyborates in the solutions were also suggested. 相似文献
128.
Theoretical investigations into the enantiomeric and racemic forms of α-(trifluoromethyl)lactic acid
Tonner R Soloshonok VA Schwerdtfeger P 《Physical chemistry chemical physics : PCCP》2011,13(3):811-817
There are many different hypotheses on the origin of biomolecular homochirality. One possible scenario concerns the enantiomeric enrichment of a nearly racemic solid via self-disproportionation of enantiomers. In particular, in a recent paper Soloshonok and co-workers showed a first example of optical self-purification of α-(trifluoromethyl)lactic acid by sublimation [V. A. Soloshonok et al., J. Am. Chem. Soc. 2007, 129, 12112]. Here we present detailed theoretical studies of α-(trifluoromethyl)lactic acid in the solid state as well as in the gas-phase dimeric form. The calculations of energy differences between dimers show that in the solid state the enantiomeric pure compound is energetically preferred, while in the gas phase the equilibrium shifts towards the racemic mixture although thermodynamic corrections cannot be neglected, thus providing a detailed microscopic explanation for the enantio-purification process for the first time. 相似文献
129.
The Ramanujan Journal - We construct polynomial solutions of the KZ differential equations over a finite field $${\mathbb F}_p$$ as analogs of hypergeometric solutions. 相似文献
130.
We consider random permutations which are spherically symmetric with respect to a metric on the symmetric group Sn and are consistent as n varies. The extreme infinitely spherically symmetric permutation‐valued processes are identified for the Hamming, Kendall‐tau and Cayley metrics. The proofs in all three cases are based on a unified approach through stochastic monotonicity. 相似文献