Effect of ionic liquid treatment on the structures of lignins in solutions: molecular subunits released from lignin

The solution structures of three types of isolated lignin-organosolv (OS), Kraft (K), and low sulfonate (LS)-before and after treatment with 1-ethyl-3-methylimidazolium acetate were studied using small-angle neutron scattering (SANS) and dynamic light scattering (DLS) over a concentration range of 0.3-2.4 wt %. The results indicate that each of these lignins is comprised of aggregates of well-defined basal subunits, the shapes and sizes of which, in D(2)O and DMSO-d(6), are revealed using these techniques. LS lignin contains a substantial amount of nanometer-scale individual subunits. In aqueous solution these subunits have a well-defined elongated shape described well by ellipsoidal and cylindrical models. At low concentration the subunits are highly expanded in alkaline solution, and the effect is screened with increasing concentration. OS lignin dissolved in DMSO was found to consist of a narrow distribution of aggregates with average radius 200 ± 30 nm. K lignin in DMSO consists of aggregates with a very broad size distribution. After ionic liquid (IL) treatment, LS lignin subunits in alkaline solution maintained the elongated shape but were reduced in size. IL treatment of OS and K lignins led to the release of nanometer-scale subunits with well-defined size and shape.     

Operation of industrial-scale electron beam wastewater treatment plant

Textile dyeing processes consume large amount of water, steam and discharge filthy and colored wastewater. A pilot scale e-beam plant with an electron accelerator of 1 MeV, 40 kW had constructed at Daegu Dyeing Industrial Complex (DDIC) in 1997 for treating 1,000 m³ per day. Continuous operation of this plant showed the preliminary e-beam treatment reduced bio-treatment time and resulted in more significant decreasing TOC, COD_Cr, and BOD₅. Convinced of the economics and efficiency of the process, a commercial plant with 1 MeV, 400 kW electron accelerator has constructed in 2005. This plant improves the removal efficiency of wastewater with decreasing the retention time in bio-treatment at around 1 kGy. This plant is located on the area of existing wastewater treatment facility in DDIC and the treatment capacity is 10,000 m³ of wastewater per day. The total construction cost for this plant was USD 4 M and the operation cost has been obtained was not more than USD 1 M per year and about USD 0.3 per each m³ of wastewater.     

Predicting the Change of MWD Caused by Interchange Reactions During Melt‐Mixing of Linear and Branched Polycondensates (AB2)

During mix melting of hyperbranched AB₂‐ and linear CD‐polycondensates distributive properties are changing by interchange reactions. Two mathematical modeling approaches are presented: (i) Simplified approach of monodisperse population of three‐arm stars undergoing interchange reactions, both analytical and by Monte Carlo simulations, assuming interchange as subsequent scission and recombination of fragments. (ii) Full system of interchange and polycondensation/hydrolysis reactions with Monte Carlo simulations and kinetic model describing reactions of free groups (A, B, C, D) and bonds (AB, CD, BC, AD). MC simulations show that the final molecular weight and branching distribution is attained after 10% of reaction time. The change of structure, from few large fragments to more, smaller ones, is slower.

     

Enantioselective addition of diethyl malonate to ω-nitrostyrenes in the presence of cobalt and manganese complexes with N,N′-dibenzyl-(1S,2S)-cyclohexane-1,2-diamine

Enantioselective addition of diethyl malonate to nitrostyrene and para-chloronitrostyrene is catalyzed by cobalt and manganese complexes with N,N??-dibenzyl-(1S,2S)-cyclohexane-1,2-diamine generated in situ. Enantiomeric excess of the (R)-isomers in the reaction products is 66?C87%.     

Effect of the matrix composition on the activity of metal oxide catalysts in CVD synthesis of carbon nanotubes

Citrate-nitrate method was used to synthesize (Fe,Co)/MgO-Al₂O₃, (Fe,Mo)/MgO-Al₂O₃, and (CoMo)/MgO-Al₂O₃ catalysts for production of carbon nanotubes. Multi-walled nanotubes were formed on these catalysts by catalytic pyrolysis of a propane-butane mixture.     

Alkoxyamine re-formation reaction. Effects of the nitroxide fragment: a multiparameter analysis

A few years ago, Studer and co-workers (Macromolecules 2006, 39, 1347-1352) reported the dramatic effect of the reaction of re-formation of alkoxyamines on the fate of the nitroxide-mediated polymerization (NMP) of styrene. This prompted us to investigate more carefully the effects of the nitroxide structure on the re-formation rate constant k(c). Ten new values of k(c) were obtained for the reaction of imidozalidine nitroxide and the phenethyl radical. These values were combined with the 21 values of k(c) reported in the literature for a multiparameter analysis (log(k(c)/M(-1) s(-1)) = (10.22 ± 0.10) + (0.46 ± 0.02)E(s) + (0.41 ± 0.17)σ(I)) using the electrical Hammett constant σ(I) to describe both the stabilization and polar effects as well as the modified Taft steric constant E(s) of the nitroxide. The same analysis was performed for the k(c) values of the cross-coupling reaction of nitroxides with tert-butoxylcarbonyl-2-prop-2-yl radical (log(k(c)/M(-1) s(-1)) = (11.10 ± 0.25) + (0.57 ± 0.05)E(s) + (1.42 ± 0.18)σ(I)) and tert-butoxycarbonylethyl radical (log(k(c)/M(-1) s(-1)) = (10.23 ± 0.16) + (0.35 ± 0.03)E(s) + (0.93 ± 0.25)σ(I)). These correlations were applied for the analysis of the NMP of styrene controlled by 6π(?), 6θ(?), and 6ρ(?) using a Fischer phase diagram.     

Thermal stability of organoclays with mono- and di-alkyl cationic surfactants

In this study, mono- and di-alkyl cationic surfactants were used to prepare organoclays through ion exchange and the prepared organoclays were characterised by X-ray diffraction (XRD) and thermogravimetric analysis (TG). Larger basal spacings were observed in the interlayer of the organoclays intercalated with DDDMA than organoclays intercalated with DDTMA. The DTG curves identify the thermal stability of organoclays intercalated with two different types of surfactants (DDTMA and DDDMA) and the different arrangements of the surfactant molecules intercalated in the montmorillonite. Both organoclays intercalated with organic surfactant molecules proved to be thermally stable at high temperature. This study provides an understanding of the structure and properties of organoclays, which will enhance the potential applications of organoclays in environmental remediation.     

Base-induced transformations of ortho-nitrobenzylketones: intramolecular displacement of nitro group versus nitro-nitrite rearrangement

Reactions of 4-bromo-5-nitrophthalonitrile (BNPN) with enolates of alkyl 4-R-2,4-dioxobutanoates gave alkyl 3-acyl-5,6-dicyanobenzofuran-2-carboxylates, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles, or 3-acyl-1,2-benzoxazole-5,6-dicarbonitriles. With a base, 4-(2-R-2-oxoethyl)-5-nitrophthalonitriles either undergo nitro-nitrite rearrangement resulting in 3-acyl-1,2-benzoxazole-5,6-dicarbonitriles or yield 2-R-benzofuran-5,6-dicarbonitriles with a nitro group displacement.     

A new synthesis of 5-hydroxy-6-methyluracil

Dehydration of 5,6-dihydro-5,6-dihydroxy-6-methyl- and 5,6-dihydro-5,6-dihydroxy-1,3,6-trimethyl-uracil in 0.4 M aqueous sulfuric acid gives 5-hydroxy-6-methyl- and 5-hydroxy-1,3,6-trimethyluracil in quantitative yields. Two possible mechanisms have been examined using the mPW1k/6-311+G(2df,2pd)//mPW1k/6-31+G(d,p) method for the transformation of methylated and non-methylated 5,6-dihydro-5,6-dihydroxy-6-methyluracils into the corresponding 5-hydroxy-6-methyluracils. The first is a hydride C5-C6 shift occurring in concert with the loss of a water molecule and formation of the corresponding protonated 5,6-dihydro-5-oxo-6-methyluracils. The second is an acid-catalyzed dehydration reaction to yield 5-hydroxy-6-methyluracils. The calculations demonstrated that the second pathway was energetically most favorable.     

Phase range of the type-I clathrate Sr8Al(x)Si(46-x) and crystal structure of Sr8Al10Si36

Samples of the type-I clathrate Sr(8)Al(x)Si(46-x) have been prepared by direct reaction of the elements. The type-I clathrate structure (cubic space group Pm3n) which has an Al-Si framework with Sr(2+) guest atoms forms with a narrow composition range of 9.54(6) ≤ x ≤ 10.30(8). Single crystals with composition A(8)Al(10)Si(36) (A = Sr, Ba) have been synthesized. Differential scanning calorimetry (DSC) measurements provide evidence for a peritectic reaction and melting point at ～1268 and ～1421 K for Sr(8)Al(10)Si(36) and Ba(8)Al(10)Si(36), respectively. Comparison of the structures reveals a strong correlation between the 24k-24k framework sites distances and the size of the guest cation. Electronic structure calculation and bonding analysis were carried out for the ordered models with the compositions A(8)Al(6)Si(40) (6c site occupied completely by Al) and A(8)Al(16)Si(30) (16i site occupied completely with Al). Analysis of the distribution of the electron localizability indicator (ELI) confirms that the Si-Si bonds are covalent, the Al-Si bonds are polar covalent, and the guest and the framework bonds are ionic in nature. The Sr(8)Al(6)Si(40) phase has a very small band gap that is closed upon additional Al, as observed in Sr(8)Al(16)Si(30). An explanation for the absence of a semiconducting "Sr(8)Al(16)Si(30)" phase is suggested in light of these findings.