Preparation of higher flux NaA zeolite membrane on asymmetric porous support and permeation behavior at higher temperatures up to 145 °C in vapor permeation

NaA zeolite membranes were synthesized on an asymmetric porous alumina support with a lower mass-flow resistance for development of more economically feasible membranes with higher permeation performance. The support influence on permeation fluxes through the membrane using asymmetric support was investigated by vapor permeation at 100–145 °C in a mixture of water (10 wt.%)/ethanol (90 wt.%) in which the higher permeation fluxes up to 37 kg m⁻² h⁻¹ or water permeances up to 3.2 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹at 145 °C were observed. The performance was higher than those in the previously reported NaA membrane on a monolayer porous alumina support of 31 kg m⁻² h⁻¹ or water permeances of 2.5 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹at 145 °C. These results are experimental evidence to show the effect of asymmetric support utilization in membrane preparation on the higher membrane performance. The estimate of the pressure drop over the both types of support indicates that the improvement of higher permeation fluxes in the asymmetric type membrane could be attributed to the suppression of pressure drop in the support layer due to lower mass-flow resistance there.     

Synthesis of industrial scale NaY zeolite membranes and ethanol permeating performance in pervaporation and vapor permeation up to 130 °C and 570 kPa

NaY zeolite tubular membranes in an industrial scale of 80 cm long were synthesized on monolayer and asymmetric porous supports. The quality of synthesized membranes were evaluated by pervaporation (PV) experiments in 80 cm long at 75 °C in a mixture of water (10 wt.%)/ethanol (90 wt.%), resulting in higher permeation fluxes of 5.1 kg m⁻² h⁻¹ in the monolayer type membrane and of 9.1–10.1 kg m⁻² h⁻¹ in the asymmetric-type membranes, respectively. The uniformity with small performance fluctuation in longitudinal direction of the membranes were observed by PV for 10–12 cm long samples at 50 °C in a mixture of methanol (10 wt.%)/MTBE (90 wt.%). The ethanol single component permeation experiments in PV and vapor permeation (VP) up to 130 °C and 570 kPa were performed to determine the relations between the ethanol flux and the ethanol pressure difference across the membrane which is represented by permeance (Π, mol m⁻² s⁻¹ Pa⁻¹) for estimate of potential of ethanol extraction through the present NaY zeolite membranes applying feasible studies. Results indicate that (1) the permeation fluxes are linearly proportional to the driving force of vapor pressure for each sample in VP and PV. The permeances through an asymmetric support type membrane were rather constant of 0.6–1.2 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ in the wide temperature range of 90–130 °C in PV and VP, indicating that the ethanol permeances have weak temperature dependency with the feed at the saturated vapor pressure.

The results of superheating VP experiments showed that ethanol permeation fluxes are increased with increasing of the degree of superheating at a given constant feed vapor pressure. The ethanol permeances are increased with increasing of temperature at a given feed vapor pressure. The superheating VP could be a feasible process in industry.     

Development of a membrane reactor for decomposing hydrogen sulfide into hydrogen using a high-performance amorphous silica membrane

We have successfully developed a membrane reactor for decomposing hydrogen sulfide into hydrogen using an amorphous silica membrane for the first time. The membrane was prepared by the CVD method with tetramethoxysilane and oxygen, and showed excellent hydrogen permeance at 873 K of the order of 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ and high hydrogen/nitrogen permselectivity of 10⁴. The membrane reactor constructed with our membrane and a commercially available catalyst decomposed hydrogen sulfide into hydrogen with higher conversion than the equilibrium conversion. This conversion enhancement was because of the selective extraction of hydrogen from the reaction side to the permeate side by the silica membrane.     

Improvement of neutron detection efficiency with high sensitive CR-39 track detector

Two subjects have been studied for establishing an efficient detection technique applicable to neutrons with an energy higher than 20 MeV, for which personnel dosimetry becomes more important especially in space activities and radiation protection around high-energy accelerators.

A performance of a new sensitive detector, recently developed copolymer of CR-39 and N-isopropylacrylamide, was checked in a D–T neutron field. It was confirmed experimentally that its sensitivity was several times as high as a pure CR-39 in the radiator effect and more than twice in the total efficiency. In the other experiment, CR-39 samples were exposed to 65 MeV quasi-monoenergetic neutrons, and the registration characteristics have been investigated from a fundamental point of view. The particles recorded were divided into three groups of proton relatives, -particles and heavy ions by applying the growth curve method and the multi-step etching technique. The measured fractions were in good agreement with the values calculated by SSNERS code previously developed.     

Practical synthesis of thiirene 1‐oxides that possess two bulky alkyl substituents

Acetylenes that possess two bulky alkyl substituents reacted with sulfur dichloride to furnish the corresponding 2,3‐dialkyl‐2,3‐dichlorothiiranes ( 5 ) nearly quantitatively. The alkaline hydrolysis of 5 afforded 2,3‐dialkylthiirene 1‐oxides ( 10 ) in high yields. These two reactions could be successively carried out in one flask, and 2,3‐di‐tert‐butyl‐, 2,3‐di‐(1‐adamantyl)‐, and 2‐(1‐adamantyl)‐3‐tert‐butylthiirene 1‐oxides ( 10a–c ) were obtained in 70, 80, and 90% yields, respectively, based on the starting acetylenes, thus providing the most convenient synthesis of thiirene 1‐oxides. Disulfur dichloride also reacted with acetylenes to give 5 in good yields with the elimination of one sulfur atom. Although the alkaline hydrolysis of 5 provided 10 exclusively, acid hydrolysis gave a mixture of α‐oxothioketone 9 and thiirene 1‐oxide 10 in modest yields. All thiirene 1‐oxides 10a–c isomerized to produce α‐oxothioketones 9 in high yields when heated in boiling toluene. Reactions of a bis‐acetylene ( 18 ) with disulfur dichloride and with sulfur dichloride gave a dihydropentathiepin ( 19 ) in high yields. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:424–430, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10070     

Synthesis and thermal dissociation of polymers having hemiacetal ester moieties

Polymers having hemiacetal ester moieties in the side chain were synthesized and their thermal dissociation was examined. 1‐Alkoxyethyl methacrylates (1) were synthesized from methacrylic acid with alkyl vinyl ethers and their radical copolymerizations with butyl methacrylate were carried out at 80°C for 6.5 h using AIBN as an initiator to afford the corresponding copolymers having the hemiacetal ester moieties in the side chain. The hemiacetal ester moieties in the copolymers thermally converted to carboxyl groups with elimination of the corresponding vinyl ethers. The thermal dissociation of the hemiacetal ester moieties in the side chain obeyed first‐order kinetics at 140°C, and their reactivities were in the following order: 1‐(tert‐butoxy)ethyl > 1‐isopropoxyethyl > 1‐ethoxyethyl > 1‐butoxyethyl ester. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 609–614, 1999     

Organocatalytic Enantioselective Decarboxylative Reaction of Malonic Acid Half Thioesters with Cyclic N‐Sulfonyl Ketimines by Using N‐Heteroarenesulfonyl Cinchona Alkaloid Amides

The organocatalytic enantioselective decarboxylative Mannich reaction of malonic acid half thioesters (MAHTs) with cyclic N‐sulfonyl ketimines by using N‐heteroarenesulfonyl cinchona alkaloid amides afforded products with high enantioselectivity. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. The reaction proceeds through a nucleophilic addition of the MAHTs to the ketimines prior to decarboxylation.     

Improvement of ethanol selectivity of silicalite membrane in pervaporation by silicone rubber coating

In order to improve the pervaporation performance of silicalite membrane, two types of silicone rubber, KE45 and KE108, were coated on the membrane surface. The initial molecular weight of KE108 is high and vulcanizing starts when it comes into contact with moisture in air, whereas the initial molecular weight of KE45 is low and vulcanizing starts when it is mixed with a catalyst. KE108 was found to be more effective than KE45 in enhancing the ethanol selectivity of silicalite membranes. A membrane coated using a 3 wt.% KE108 hexane solution showed separation factor of =125 with a total flux of 0.14 kg/m² h.     

Creation of a type 1 blue copper site within a de novo coiled-coil protein scaffold

Type 1 blue copper proteins uniquely coordinate Cu(2+) in a trigonal planar geometry, formed by three strong equatorial ligands, His, His, and Cys, in the protein. We designed a stable Cu(2+) coordination scaffold composed of a four-stranded α-helical coiled-coil structure. Two His residues and one Cys residue were situated to form the trigonal planar geometry and to coordinate the Cu(2+) in the hydrophobic core of the scaffold. The protein bound Cu(2+), displayed a blue color, and exhibited UV-vis spectra with a maximum of 602-616 nm, arising from the thiolate-Cu(2+) ligand to metal charge transfer, depending on the exogenous axial ligand, Cl(-) or HPO(4)(2-). The protein-Cu(2+) complex also showed unresolved small A(∥) values in the electron paramagnetic resonance (EPR) spectral analysis and a 328 mV (vs normal hydrogen electrode, NHE) redox potential with a fast electron reaction rate. The X-ray absorption spectrum revealed that the Cu(2+) coordination environment was identical to that found in natural type 1 blue copper proteins. The extended X-ray absorption fine structure (EXAFS) analysis of the protein showed two typical Cu-N(His) at around 1.9-2.0 ?, Cu-S(Cys) at 2.3 ?, and a long Cu-Cl at a 2.66 ?, which are also characteristic of the natural type 1 blue copper proteins.     

Simultaneous quantitation of sphingoid bases and their phosphates in biological samples by liquid chromatography/electrospray ionization tandem mass spectrometry

We developed a liquid chromatography/electrospray ionization tandem mass spectrometry method for the simultaneous quantitative determination of C18 sphingosine (Sph), C18 dihydrosphingosine (dhSph), C18 phytosphingosine (pSph), C18 sphingosine-1-phosphate (S1P), C18 dihydrosphingosine-1-phosphate (dhS1P), and C18 phytosphingosine-1-phosphate (pS1P). Samples were prepared by simple methanol deproteinization and analyzed in selected reaction monitoring modes. No peak tailing was observed on the chromatograms using a Capcell Pak ACR column (1.5 mm i.d. × 250 mm, 3 μm, Shiseido). The calibration curves of the sphingoids showed good linearity (r > 0.996) over the range of 0.050-5.00 pmol per injection. The accuracy and precision of this method were demonstrated using four representative biological samples (serum, brain, liver, and spleen) from mice that contained known amounts of the sphingoids. Samples of mice tissue such as plasma, brain, eye, testis, liver, kidney, lung, spleen, lymph node, and thymus were examined for their Sph, dhSph, pSph, S1P, dhS1P, and pS1P composition. The results confirmed the usefulness of this method for the physiological and pathological analysis of the composition of important sphingoids.