Liquid-liquid extraction of protactinium(V) using tri-iso-octylamine

Solvent extraction of protactinium with tri-iso-octyl-amine (TIOA) in xylene, benzene, carbon tetrachloride and chloroform from HCl, HF, HNO3, HClO4 and H2SO4 media was studied using Pa-233 as a radiotracer. The extraction efficiencies of protactinium were determined as a function of shaking time, concentrations of mineral acids in aqueous phase, extractant concentrations and diluents in organic phase. The extraction mechanism was discussed. The results show that the extracted species in the organic phase is [(R3N-H)(n)Pa(OH)(x)Cl-y(5-x-y)].

BTEX的环境行为与生态毒理

BTEX是苯(benzene)、甲苯(toluene)、乙苯(ethylbenzen)和二甲苯(xylene)的统称,存在于原油和石油产品中,同时作为化工原料应用于农药、塑料及合成纤维等制造业。BTEX广泛存在于大气、水体和土壤等环境介质,对相应的生态系统和人类健康产生严重危害。本文分析了各环境介质中BTEX的来源及分布特征,探讨了其在各种环境系统间的迁移和转化规律,重点从生殖发育毒性方面讨论了BTEX产生的人体健康效应,最后对今后研究重点进行了探讨。

Catalytic performance of MCM-22 zeolite for alkylation of toluene with methanol

MCM-22 zeolite with mid-strong acidity and openings of 10-membered ring channels may obtain a high catalytic activity and selectivity for alkylation of toluene with methanol. The acidic sites, for catalyzing alkylation of toluene with methanol, are weaker than that for catalyzing toluene disproportionation. Compared with silicon as a modifier, modification of MCM-22 with La(NO3)(3) is a promising way to improve the catalytic selectivity of para-xylene. In addition, the experimental results also clearly indicate the characteristics of MCM-22 structure consisting of large intracrystalline cages, some of which may locate on surface of MCM-22. (C) 2004 Elsevier B.V. All rights reserved.

Tridentate CCC-Pincer Bis(carbene)-Ligated Rare-Earth Metal Dibromides. Synthesis and Characterization

The first xylene-bridged bis(N-heterocyclic carbene) (bis(NHC))-ligated CCC-pincer rare-earth metal dibromides (PBNHC)LnBr(2)(THF) (PBNHC = 2,6-(2,4,6-Me3C6H2NCHCHNCCH2)(2)C6H3; 1: Ln = Sc; 2: Ln = Lu; 3: Lu = Sm) were prepared by in situ treatment of a THF suspension of 2,6-bis(1-mesitylimidazolium methyl)-1-bromobenzene dibromides ((PB-NHC-Br) center dot 2HBr) and lanthanide trichlorides (LnCl(3)) with dropwise addition of nBuLi at room temperature.

One-pot synthesis of polyimides via Ni-catalyzed coupling of bis(chlorophthalimide)s

A one-pot synthesis method for the preparation of polyimides containing biphenyl units was developed via nickel-catalyzed coupling reaction of bis(chlorophthalimide)s which were prepared from chloroplithalic anhydrides and diamines in xylene. The resulting polyimides had inherent viscosities of above 0.60dL g(-1). In the meantime, the copolymerizations from a mixture of three isomeric bis(chlorophthalimide)s gave the polymers with inherent viscosities of 0.36-0.55 gdL(-1). The solubility and film formability of the copolymers were better than those of homopolymers from bis(4-chlorophthalimide). The 10% weight loss of these polyimides was between 470 and 531 degrees C.

Functionalization of an ethylene-propylene copolymer with allyl (3-isocyanate-4-tolyl) carbamate

An ethylene-propylene copolymer (EPM) was functionalized with an iso cyanate-bearing unsaturated monomer, allyl(3-isocyanate-4-tolyl) carbamate (TAI), with dicumyl peroxide as an initiator in a xylene solution. Fourier transform infrared (FTIR) was used to confirm the formation of EPM-g-TAI. The peak at 2273 cm(-1), characteristic of -NCO groups in EPM-g-TAI, revealed evidence of grafting. The grafting degree was determined with both chemical titration and FTIR. The grafting degree could be adjusted, and the maximum was over 6 wt % without any gelation. The molar mass distribution of EPM-g-TAI was narrower than that of EPM. The rheological behavior of both EPM-g-TAI and EPM was investigated with a rotational rheometer. The apparent viscosity of EPM-g-TAI was higher than that of EPM and increased with an increasing grafting degree of TAI. Surface analysis by contact-angle measurements showed that contact angles of EPM-g-TAI samples to a given polar liquid decreased with an increasing grafting degree of TAI. We also obtained the dispersion component of the surface free energy (gamma(S)(d)), the polar component of the surface free energy (gamma(S)(d)), and the total surface free energy (gamma(S) = gamma(S)(d) + gamma(S)(p)) of the grafted EPM. These parameters increased with the enhancement of the grafting degree, which gave us a quantitative estimation of the polar contribution of the grafted TAI to the total surface free energy of EPM-g-TAI.

Synthesis and characterization of PCL/PEG/PCL triblock copolymers by using calcium catalyst

Triblock copolymer PCL-PEG-PCL was prepared by ring-opening polymerization of epsilon-caprolactone (CL) in the presence of poly(ethylene glycol) catalyzed by calcium ammoniate at 60 degreesC in xylene solution. The copolymer composition and triblock structure were confirmed by H-1 NMR and C-13 WR measurements. The differential scanning calorimetry and wide-angle X-ray diffraction analyses revealed the micro-domain structure in the copolymer. The melting temperature T-c and crystallization temperature T-c of the PEG domain were influenced by the relative length of the PCL blocks. This was caused by the strong covalent interconnection between the two domains. Aqueous micelles were prepared from the triblock copolymer. The critical micelle concentration was determined to be 0.4-1.2 mg/l by fluorescence technique using pyrene as probe, depending on the length of PCL blocks, and lower than that of corresponding PCL-PEG diblock copolymers. The H-1 NMR spectrum of the micelles in D2O demonstrated only the -CH2CH2O- signal and thus confirmed. the PCL-core/PEG-shell structure of the micelles.

Cationic cyclization of neoprene with a diethylaluminum chloride and organic chloride catalyst system

The cyclization of neoprene was achieved with the aid of a cationic catalyst system based on diethylaluminum chloride (Et2AlCl) and an organic chloride, allyl chloride (CH2=CHCH2Cl) or benzyl chloride (C6H5CH2Cl). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility and some gelling were obtained. Xylene was a good solvent for the cyclization process, which took place in a very short time (less than or equal to5 min). The products were characterized with IR, H-1-NMR, differential scanning calorimetry, and gel permeation chromatography. The polycyclic structure was determined. The degree of cyctization and the incorporated solvent content were estimated with a H-1-NMR method.

Study on the cyclization of cis-1,4 polybutadiene in various solvents and its mechanism

The cyclization of cis-1,4 polybutadiene in various solvents (mesitylene,xylene, toluene,benzene and cyclohexane) with the catalyst composed of CH2=CHCH2Cl-AlEt2Cl was studied. The infrared spectra of the cyclized products were investigated. It was shown that the products produced in cyclohexane and mesitylene have infrared spectra identical with those of the original cis-1,4-polybutadiene and the products obtained in other aromatics have infrared spectra different from each other and distinguishing with those of the parent cis-1,4 polybutadiene. The analyses of infrared spectra came to the conclusion that the molecules of aromatic solvent participate in cyclization of cis-1,4 polybutadiene at the given condition. A possible reaction scheme involving an electrophilic substitution of carbonium ions for Ar-H of aromatic solvents was proposed. Some experimental facts were explained with great satisfaction on the basis of the above mechanism.

Cationic cyclization of styrene-butadiene rubber

Controlled cyclization of styrene-butadiene rubber (SBR) was achieved with the aid of cationic catalyst system based on diethylaluminium chloride (AIEt(2)Cl) and benzyl chloride (C6H5CH2Cl) and by working in xylene solution at high temperature (T > 100 degreesC). The main parameters of the cyclization process were investigated. Elastomers with low intrinsic viscosity, ready solubility, free gel were obtained. The products were characterized with IR H-1-NMR, DSC, GPC. The polycyclic structure was determined. (C) 2001 Published by Elsevier Science Ltd.

Synthesis of a new kind of polyamide and polyester including aromatic spirodilactone

A new kind of monomers including aromatic spirodilactone-5, 5'-carboxy-7,7'-dioxo-2,2'-spirobi(benzo-[c]tetrahydrofuran) is synthesized from m-xylene and paraformaldehyde. It is converted to a series of polyamides and polyesters by means of low-temperature solution polycondensation and interfacial polycondensation. NMR and IR spectra, solubility, mechanical and thermal properties of all these polymers are investigated. The polymers have high glass transition temperatures and good thermal oxidative properties. All polyamides have high viscosity and good solubility in strong polar organic solvents such as DMSO, DMAc, DMF and NMP. All polyamides can be cast into transparent, flexible and tough films possessing good tensile properties.

Morphology and mechanical properties of PP/HMWPE blends

Mechanical properties and morphology of blends of polypropylene (PP) with high molecular weight polyethylene (HMWPE) prepared by coprecipitation from xylene solution are investigated. Compared to blends of PP with commercial high-density polyethylene (HDPE), the mechanical properties of the blends of PP/HMWPE are much superior to those of PP/HDPE blends. Not only is the tensile strength stronger, but also the elongation at break is much higher than that of the PP/HDPE blends of the same composition. These differences increase with increasing HMWPE and HDPE content. Scanning electron microscopy of the fracture surface resulting from the tensile tests shows that the compatibility in PP/HMWPE blends is much better than that in PP/HDPE blends. This is most likely attributable to the enhanced chain entanglement of HMWPE with the PP in the amorphous phase due to the lower crystallinity, owing to the high molecular weight of the HMWPE, and a much more flexible chain. The thermal behavior and spherulite morphology of both blends are also investigated.