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The hydrogen in the vent gas stream of the hydrocracker (used to produce bio-jet fuel) cannot be reused since it has many impurities. The metal membrane can be a potential candidate for recovering hydrogen from this vent gas. In this work, the authors report the development of a composite palladium membrane and its application, for the first time, in the recovery of hydrogen from a simulated vent gas environment. A dense thin film (thickness ~3 µm) of Pd metal was coated on a ceramic support tube by the sputter deposition technique. The hydrogen permeance of the Pd membrane was found to be 18.75 × 10-6 mol·m-2·h-1·Pa-1, which was reduced to 3.25 × 10-6 mol·m-2·h-1·Pa-1, with an exposure of 100 h in the simulated bio-jet fuel environment. To avoid the loss of permeability, a thin layer of Pt can be coated over the Pd membrane. The present study used MATLAB software to simulate the Pt-coated Pd composite membrane performance in the bio-jet fuel production environment. Simulation studies confirmed that a membrane area of ~95 cm² (250 mm length and 12 mm OD) is sufficient for the complete recovery of hydrogen from the vent gas stream of hydrocracker at a feed velocity of 0.075 m/s. [ABSTRACT FROM AUTHOR]

90Sr (T1/2 = 28 y) is always in equilibrium with 90Y in High Level Liquid waste (HLLW) and hence 90Sr is a suitable long lasting source of 90Y, if it is purified suitably for therapeutic applications. A combination of CMPO & TBP was found to be the most suitable solvent system for alpha activity removal. CMPO has high selectivity for alpha contaminants (Pu/Am) w.r.t. 90Sr. For regeneration of spent organic, 3 M Phosphoric acid was most suitable with the ability to strip back more than 98% of gross alpha activity in single contact and thus solvent system was qualified for recycling. [ABSTRACT FROM AUTHOR]

90Y, a beta emitting radionuclide (T1/2 ~ 64 h, Emax= 2.3 MeV), the daughter product of 90Sr is used for radio therapeutic applications. Non dispersive solvent extraction in hollow fibre membrane contactor (HFMC) with CMPO solvent studies were done to achieve the desired purification of 90Sr nitrate solution with respect to gross alpha activity. This purified solution is promising feed for 90Sr–90Y generator to achieve the clinical grade product of 90Y. In HFMC recirculations, around 99.97% alpha impurities were extracted in two recirculations from the feed solution with 0.2 M CMPO while only two recirculations were required with 0.4 M CMPO. A simplified mathematical model has also been developed to model the extraction of alpha impurities through the HFMC using CMPO as a solvent. [ABSTRACT FROM AUTHOR]

A Ranque-Hilsch Vortex Tube (RHVT) is a device that can cause simultaneous thermal and species separation in a compressible fluid mixture. The binary mixture is compressed and tangentially introduced into the vortex chamber of the RHVT, and two streams are withdrawn at opposite ends of the device. The RHVT acts as a centrifugal separator that separates the mixture into two streams, one enriched and the other depleted of the component with higher molecular weight. The extent of separation depends on the magnitude of swirl velocity of gas mixture inside the RHVT. Now a new combined heat and mass transfer model using heat and mass transfer analogy has been proposed by the authors to predict the species separation in a RHVT. The aim of this paper is to use this model to estimate the magnitude of swirl velocity of gas mixture inside the RHVT. The estimated values have been compared with range of experimentally as well as numerically obtained values reported in the literature. For a given configuration in published literature and values of cold mass fraction the average swirl velocity inside the RHVT was found to vary between 90 m/s and 130 m/s. It is found that for a fixed value of inlet pressure, average swirl velocity is a function of cold mass fraction. The value of average swirl velocity minimizes near cold mass fraction = 0.3 and maximizes near cold mass fraction = 0.8. Parametric studies have been carried out to understand the effect of important RHVT parameters on swirl velocity. Also relation between swirl velocity and species separation has been explored. [ABSTRACT FROM AUTHOR]

Ruthenium-palladium (Ru-Pd) and ruthenium-nickel (Ru-Ni) bimetallic nanoalloy particles with various metal compositions were synthesized by microwave irradiated (MWI) solvothermal technique using PVP (poly-N-vinyl-2-pyrrolidone) as capping agent and ethylene glycol as a solvent as well as reducing agent. Synthesized bimetallic nanoalloy particles were subsequently impregenated onto γ-Al2O3 support to obtain supported nanoalloy catalysts. Agglomeration of nanoalloyparticles were restricted by using excess solvent during synthesis, then distilled and recovered after completion of reaction. Hydrogenation of Dibenzo-18-crown-6 ether (DB18C6) was carried out at 9 MPa, 120°C and 3.5 h using synthesized bimetallic nanoalloy catalysts. It was observed that bimetallic nanolloycatalyst synthesized by MWI using Ru:Pd 3:1 % (w/w), exhibited higher catalytic activity and resulted 98.9 % conversion of DB18C6 with 100 % selectivity towards cis-syn-cis dicyclohexano-18-crown-6 ether (CSC DCH18C6). [ABSTRACT FROM AUTHOR]

Rh/γ-Al2O3 nanocatalysts with different metal loading were synthesized by two different techniques i. e. microemulsion and microwave irradiated solvothermal technique. Synthesized nanocatalysts were then successfully implemented for the hydrogenation of 4',4'(5')-di-tert-butyldibenzo-18-crown-6 ether (DTBuB18C6) at 70 bar, 353-393 K temperature and 5 h. It was observed that 3 wt% nanocatalyst obtained by microemulsion technique exhibited higher catalytic activity and resulted 40 % conversion with high selectivity towards cis-syn-cis di-tert-dicyclohexano-18-crown-6ether (CSC DTBuCH18C6). [ABSTRACT FROM AUTHOR]

Deuterium-labeled biologically active compounds are gaining importance because they can be utilized as tracers or surrogate compounds to understand the mechanism of action, absorption, distribution, metabolism, and excretion. Deuterated drug molecules (heavy drugs) become novel as well as popular because of better stability and bioavailability compared with their hydrogen analogs. Labeling of organic molecules with deuterium at specific positions is thus gaining popularity. In this work, we have exploited a highly regioselective and enantioselective direct Michael addition of methyl- d3 alkyl ketones to dimethyl(phenyl)silylmethylene malonate that was catalyzed by ( S)- N-(2-pyrrolidinylmethyl)pyrrolidine/trifluoroacetic acid/ D2O combination with high yield and isotopic purity. The 5,5-dideutero-4-dimethyl(phenyl)silyl-6-undecyl-tetrahydropyran-2-one was obtained from the adduct of methyl- d3 undecanyl ketone and dimethyl(phenyl)silylmethylene malonate by a silicon controlled diastereoselective ketone reduction, lactonization, and deethoxycarbonylation. The dideuterated silylated tetrahydropyran-2-one is the precursor for geminal 2H2-labeled (+)-4-hydroxy-6-undecyl-tetrahydropyran-2-one, an advanced intermediate for gem-dideutero (-)-tetrahydrolipstatin and (+)-δ-hexadecanolide syntheses. [ABSTRACT FROM AUTHOR]

Niobium and tantalum are valued for their uses in nuclear, steel, aviation and electronics industries. This paper elucidates the development of a multistage counter-current separation process for obtaining pure niobium and tantalum from the hydrofluoric acid solution of Coumbite-Tantalite ore (leach liquor), with trioctyl amine (TOA) as the extractant solvent. Contrary to the conventionally used multistage process this novel route does not use any other acid in addition to hydrofluoric acid, resulting in the elimination of the generation of mixed fluoride waste. Reaction equilibrium constants for the reactions involving the extraction of hydrofluoric acid, niobium and tantalum have been determined and were used to generate equilibrium distribution curve of niobium and tantalum in the organic and aqueous phase. The number of counter-current stages required for an appropriate organic to aqueous phase volume (O/A) ratio was determined using McCabe-Thiele calculations. Selective extraction of 99% of tantalum from the leach liquor was achieved using 5 v / v % TOA and two counter-current stages for an O/A ratio of four. The tantalum lean raffinate was treated with commercial grade hydrofluoric acid to form the niobium feed solution having 16 M free acidity. Near complete extraction of niobium was achieved using a three stage counter-current process with O/A ratio of two and 10 v /v% TOA as the organic extractant. The calculations for the stage-wise variation of concentrations were validated by batch experimental simulation of counter-current processes. • A trioctyl-amine based continuous multistage counter-current process for niobium-tantalum separation has been developed. • Multiple numbers of HF molecules combines with one molecule TOA depending on the free acidity of the aqueous phase. • Selective extraction of tantalum from the leach liquor is achieved with low TOA concentration in the organic phase. • The stage-wise variation of metal concentrations was elucidated by batch experimental studies. [ABSTRACT FROM AUTHOR]

Deuterium-labeled biologically active compounds are gaining importance because they can be utilized as tracers or surrogate compounds to understand the mechanism of action, absorption, distribution, metabolism, and excretion. Deuterated drug molecules (heavy drugs) become novel as well as popular because of better stability and bioavailability compared with their hydrogen analogs. Labeling of organic molecules with deuterium at specific positions is thus gaining popularity. In this work, we have exploited a highly regioselective and enantioselective direct Michael addition of methyl-d3 alkyl ketones to dimethyl(phenyl)silylmethylene malonate that was catalyzed by (S)-N-(2-pyrrolidinylmethyl)pyrrolidine/trifluoroacetic acid/ D2 O combination with high yield and isotopic purity. The 5,5-dideutero-4-dimethyl(phenyl)silyl-6-undecyl-tetrahydropyran-2-one was obtained from the adduct of methyl-d3 undecanyl ketone and dimethyl(phenyl)silylmethylene malonate by a silicon controlled diastereoselective ketone reduction, lactonization, and deethoxycarbonylation. The dideuterated silylated tetrahydropyran-2-one is the precursor for geminal (2) H2 -labeled (+)-4-hydroxy-6-undecyl-tetrahydropyran-2-one, an advanced intermediate for gem-dideutero (-)-tetrahydrolipstatin and (+)-δ-hexadecanolide syntheses., (Copyright © 2013 John Wiley & Sons, Ltd.)