Recycling of process streams in ethanol production from softwoods based on enzymatic hydrolysis

In ethanol production from lignocellulose by enzymatic hydrolysis and fermentation, it is desirable to minimize addition of fresh-water and waste-water streams, which leads to an accumulation of substances in the process. This study shows that the amount of fresh water used and the amount of waste water thereby produced in the production of fuel ethanol from softwood, can be reduced to a large extent by recycling of either the stillage stream or part of the liquid stream from the fermenter. A reduction in fresh-water demand of more than 50%, from 3 kg/kg dry raw material to 1.5 kg/kg dry raw material was obtained without any negative effects on either hydrolysis or fermentation. A further decrease in the amount of fresh water, to one-fourth of what was used without recycling of process streams, resulted in a considerable decrease in the ethanol productivity and a slight decrease in the ethanol yield     

Die ersten Fluorotrithiatetraphosphaheptane

The First Fluoro-trithiatetraphospha-heptanes Fluorinated α- and β-tetraphosphorus-trisulfur molecules were prepared by the reaction of α- or β-P₄S₃X₂ (X = Cl, Br, I) with (n-butyl)₃SnF. The substitution reaction of the α-isomers yields under retention of the configuration at the phosphorus atoms α-P₄S₃XF and α-P₄S₃F₂. In the reaction of the β-isomers more products were observed, because the configuration of the phosphorus atom can be retained or inversed in the first step of the substitution which yields β-P₄S₃X_exoF_exo or β-P₄S₃X_exoF_endo. The mass relation of the products depends on the halogen ligand. In the second substitution β-P₄S₃(F_exo)₂ or β-P₄S₃F_exoF_endo are formed. β-P₄S₃(F_endo)₂ was not observed. By the reaction of β-P₄S₃I₂ with BiX₃ (X = Cl, Br, I) we also were able to prepare small amounts of β-P₄S₃X_endoX_exo-molecules (X = I, Cl, Br) with an inversed configuration at one phosphorus atom. The ³¹P- and ¹⁹F-NMR parameter of all compounds are discussed.     

Reaktionen von P4S3I2 mit bifunktionellen Liganden

Reactions of P₄S₃I₂ with Bifunctional Ligands Nitrogen, oxygen, selenium or carbon atoms were introduced as bridges into the P₄S₃ skeleton by the reaction of α- or β-P₄S₃I₂ with bifunctional ligands. Among compounds in the series α-P₄S₃-α-E, the oxide μ-P₄SO was made for the first time. High concentrations of α-P₄S₄Se, made by a new route, allowed observation of ⁷⁷Se satellites in its ³¹P NMR spectrum and hence the assignment of ³¹P chemical shifts. Polymeric species were more stable than these monomers, leading to low yields in both reactions. α- and β-isomers of P₄S₃I₂ reacted with diethyl malonate. While β-P₄S₃I₂ gave traces of β-P₄S₃(CR₂)(R = C₂H₅CO₂) and of β-P₄S₃(CHR₂)_exo(CHR₂)_endo, along with insoluble products, α-P₄S₃I₂ yielded α-P₄S₃(CR₂), which could be isolated. P₄S₂(CR₂), a new skeleton similar to that of P₄S₃, was formed on storage of CS₂ solutions of a-P₄S₃(CR₂) for two days. The ³¹P NMR data of the molecules are given.     

Potentiometric stripping analysis for mercury after preconcentration in a potassium permanganate trap

Water samples of total volume 0.5–5 l, containing mercury in the range 0.05–5 μg l^-1 are oxidized with excess of potassium permanganate and then reduced with tin(II) chloride. The mercury is transferred to 5–10 ml of a dilute potassium permanganate trap solution by cycling air through the sample and the trap solution. The mercury(II) content of the trap solution is determined by potentiometric stripping analysis. The accuracy, precision and detection limit of the technique are discussed.     

Synthesis,crystal structure,and NMR spectroscopy of a 1,3,2λ5,4λ5-oxathiadiphosphetane

From the crude product of the synthesis of the dithiadiphosphetane [RP(S)S]₂ (with R = 2,4,6-iPr₃C₆H₂), the trans-oxathiadiphosphetane has been isolated, C₃₀H₄₀OP₂S₃. X-ray structure analysis and mass spectroscopic investigations give unequivocal evidence for this structure: monoclinic, C2/c (no. 15), a = 13.066(8), b = 21.726(8), c = 12.070(6) Å, β = 103.54(10)°, V = 3331 ų, Z = 4, and D_c = 1.158 g/cm³. The asymmetric unit consists of half the formula unit. Solid-state ³¹P NMR spectra give information about the chemical shift anisotropy. Results of IGLO calculations of the ³¹P nuclear magnetic shielding tensor agree satisfactorily with the experimental data. Monitoring the reaction of several dithiadiphosphetanes with benzophenone in solution by ³¹P NMR spectroscopy indicates that additional oxathiadiphosphetanes as well as thiotrimetaphosphonates are present. © 1996 John Wiley & Sons, Inc.     

Crosslinking of ethylene-vinyl alcohol copolymers via polymeranalogous reactions

A practical model for polymeranalogous reactions is ethylene-vinyl alcohol copolymer with a controllable amount of hydroxylic groups. The reaction of the hydroxyl groups with various compounds leads to further functionalized polymers. The functional groups introduced are useful for modification or crosslinking reactions. The modification of ethylene-vinyl alcohol copolymers with carboxylic anhydrides and hydroxy carboxylic acids is the main subject of this investigation. The crosslinking reaction of these products with bifunctional epoxies was followed by means of viscosimetric measurements. The dependence of the reaction behaviour on the structure of the functionalized polymers used is discussed.     

Inhibitory Effects by Antioxidants on the Oscillations of the Briggs‐Rauscher Reaction in Mixed EtOH/H2O Medium

The Briggs‐Rauscher (BR) oscillating reaction in mixed 20% EtOH/H₂O (v/v) medium is studied together with the inhibitory effects by the addition of hydroalcoholic solutions of antioxidants on its oscillatory regime. As in aqueous BR mixtures, the inhibitory effect consists of an immediate cessation of oscillations, an inhibitory time that linearly depends on the concentration of the antioxidant added, and subsequent regeneration of oscillations. The effects of several water‐insoluble and water‐soluble antioxidants were investigated: at a parity of concentration of antioxidant added, inhibition times in the mixed EtOH/H₂O medium are 2–3 times lower than those reported previously in aqueous solution. However, the mechanism of the BR reaction, as far as that of the inhibitory effect, seems to be the same in either aqueous or mixed medium. The findings reported and discussed here are an indication that the analytical procedure to assess the activity of free radical scavengers based on the BR reaction can be extended to lipophilic antioxidants.     

Synthesis and Structural Characterization of the Tetrakis(methimazolyl)borates Li[Bmt4] and [Ru(p‐cymene)(Bmt4)][PF6]

The lithium tetrakis(methimazolyl)borate, Li[Bmt₄], is accessible from the reaction of Li[BH₄] with four equivalents of methimazole. The crystal structure of Li[Bmt₄] supported by four water molecules is described. Reaction of Li[Bmt₄] with [Ru(p‐cymene)Cl₂]₂ and subsequent treatment with NH₄PF₆ in CH₃CN results in the formation of the complex [Ru(p‐cymene)(Bmt₄)][PF₆]. In addition, we report the result of the X‐ray structure analysis of the chiral Ru complex [Ru(p‐cymene)(Bmt₄)][PF₆].     

Pulse magnetoelectrolysis

We present a novel technique consisting in the combination of pulse plating and magnetoelectrolysis. This technique is applied to copper electrolysis between two vertical copper-electrodes. The modulation of the current inside an inhomogeneous magnetic field generates a modulated Lorentz force driving an oscillating convection studied using particle image velocimetry. The resulting changes in the concentration boundary layers are analysed by means of a Mach-Zehnder interferometer.