Thin-layer chromatography of inorganic lons phosphate on cellulose in acetic acid and in acetic acid-ammonium acetate media

Summary Systematic study for the chromatographic behaviour of 49 inorganic ions has been carried out on cellulose phosphate layer in acetic acid and acetic acid — ammonium acetate media. Feasibilities for the effective separations of analytical interest are demonstrated on the 0.25 mm layer in both media.     

New process for producing cellulose acetate from wood in concentrated acetic acid

To explore further potential applications of acetic acid pulp, an investigation was conducted to develop a direct method for producing cellulose acetate from wood in combination with atmospheric acetic acid pulping. The process consists of delignification, totally chlorine-free bleaching, and esterification, with the concentrated acetic acid aqueous solution being used as only solvent throughout the process. The acetic acid pulp with kappa number of 30 and ISO brightness of 16 was bleached with 5% ozone on pulp to kappa number of 1.4 and brightness of 61. The resulting bleached pulp was further bleached with peracetic acid to kappa number of less than 1.0 and brightness of 68. The final bleached acetic acid pulp was acetylated with acetic anhydride in the concentrated acetic acid for 45 min to produce cellulose acetate with an apparent degree of substitution (DS) of 2.54. Although the product was lower grade compared with commercially available cellulose diacetate because it was prepared from the chemical pulp but not dissolving pulp, the product was almost soluble in acetone. Eventually, the DS of the acetone-soluble fraction was 2.62. The acetone solubility might be attributed to the original acetic acid pulp that had been partially acetylated during the pulping.     

Chitosan-cellulose sulfate acetate complexation in acetic acid solutions

Colloidal and optical properties of dispersions of chitosan-cellulose sulfate acetate interpolyelectrolyte complexes resultant from mixing dilute solutions of the polymers in acetic acid and in acetic acid-based buffer mixtures are investigated. It is established that, in acetic acid, an insoluble complex is formed whose composition corresponds to the unit ratio [chitosan]: [cellulose sulfate acetate] = 1: 1.5, mol/mol. Particle size and concentration are independent of the order of mixing of the solutions of the polymers. In buffer solvents, the particle size is larger and the particle concentration is lower than those in acetic acid. Excess chitosan causes the dissolution of the complex. The addition of low-molecular-weight electrolytes to ionic strengths of 0.2–0.3 also promotes the dissolution of the interpolyelectrolyte complex. The complex becomes completely soluble at ionic strengths of 1.5–2.0.     

COMMUNICATION: Mild reaction of ethyl cellulose and N- phenylmaleamic acid in acetic anhydride

The reaction at room temperature of ethyl cellulose (EC) and N-phenylmaleamic acid (NPMA) (maleanilic acid) in acetic anhydride with a catalytic amount of anhydrous sodium acetate resulted in a Michael type of product whereby a cellulose ether was formed. The cyclisation product N-phenylmaleimide was minor. This revised version was published online in August 2006 with corrections to the Cover Date.     

Improving fermentation performance of recombinant zymomonas in acetic acid-containing media

In the production of ethanol from lignocellulosic biomass, the hydrolysis of the acetylated pentosans in hemicellulose during pretreatment produces acetic acid in the prehydrolysate. The National Renewable Energy Laboratory (NREL) is currently investigating a simultaneous saccharification and cofermentation (SSCF) process that uses a proprietary metabolically engineered strain ofZymomonas mobilis that can coferment glucose and xylose. Acetic acid toxicity represents a major limitation to bioconversion, and cost-effective means of reducing the inhibitory effects of acetic acid represent an opportunity for significant increased productivity and reduced cost of producing fermentation fuel ethanol from biomass. In this study, the fermentation performance of recombinant Z.mobilis 39676:pZB4L, using a synthetic hardwood prehydrolysate containing 1% (w/v) yeast extract, 0.2% KH₂PO₄, 4% (w/v) xylose, and 0.8% (w/v) glucose, with varying amounts of acetic acid was examine. To minimize the concentration of the inhibitory undissociated form of acetic acid, the pH was controlled at 6.0. The final cell mass concentration decreased linearly with increasing level of acetic acid over the range 0-0.75% (w/v), with a 50% reduction at about 0.5% (w/v) acetic acid. The conversion efficiency was relatively unaffected, decreasing from 98 to 92%. In the absence of acetic acid, batch fermentations were complete at 24 h. In a batch fermentation with 0.75% (w/v) acetic acid, about two-thirds of the xylose was not metabolized after 48 h. In batch fermentations with 0.75% (w/v) acetic acid, increasing the initial glucose concentration did not have an enhancing effect on the rate of xylose fermentation. However, nearly complete xylose fermentation was achieved in 48 h when the bioreactor was fed glucose. In the fed-batch system, the rate of glucose feeding (0.5 g/h) was designed to simulate the rate of cellulolytic digestion that had been observed in a modeled SSCF process with recombinant Zymomonas. In the absence of acetic acid, this rate of glucose feeding did not inhibit xylose utilization. It is concluded that the inhibitory effect of acetic acid on xylose utilization in the SSCF biomass-to-ethanol process will be partially ameliorated because of the simultaneous saccharification of the cellulose.

     

Improved two-step hydrothermal process for acetic acid production from carbohydrate biomass

An improved two-step process for converting carbohydrate biomass to acetic acid under hydrothermal conditions is proposed. The first step consists of the production of lactic acid from carbohydrate biomass, and the second step consists of conversion of the lactic acid obtained in the first step to acetic acid using CuO as an oxidant. The results indicated that CuO as an oxidant in the second step can significantly improve the production of high-purity acetic acid from lactic acid, and the maximum yield of acetic acid was 61%, with a purity of 90%. The yield of acetic acid obtained using the improved two-step hydrothermal process from carbohydrate biomass, such as glucose, cellulose and starch, was greater than that obtained using traditional two-step process with H2O2 orO2. In addition, a proposed pathway for the production of acetic acid from lactic acid in the second step with CuO was also discussed. The present study provides a useful two-step process for the production of acetic acid from carbohydrate biomass.     

Anion-exchange behaviour of various metals on DEAE-cellulose in mixed acetic acid-nitric acid media

A number of nitrato complexes of metals have been found to be adsorbed on DEAE-cellulose from mixed acetic acid-nitric acid media, although none can be adsorbed from aqueous nitric acid solutions. The distribution coefficients of Sc, Mo, La, Sm, W, Re, Bi, Th and U are given as functions of acetic acid and nitric acid concentrations (sometimes in the presence of hydrogen peroxide to prevent hydrolytic precipitation). For 25 other metals column adsorption behaviour is described for a 90% acetic acid-10% 7.6M nitric acid mixture. Favourable differences in the distribution coefficients allow useful separations such as FeMoW and USmMoBiTh, to be achieved.     

Influence of UV pretreatment on the abies wood catalytic delignification in the medium “acetic acid–hydrogen peroxide–TiO2”

Some regularities of abies-wood oxidative delignification by acetic acid–hydrogen peroxide mixture under the action of suspended TiO₂ catalyst and UV pretreatment of wood pulp were studied. The combined action of TiO₂ catalyst and of UV-pretreatment of abies-wood allow to produce at optimal conditions of the delignification process the chemically pure cellulose containing no residual lignin. The major characteristics of cellulose product obtained from abies-wood correspond to the characteristics of microcrystalline cellulose.     

Coulometric generation of acetylions by oxidation of mercury in acetic anhydride and in acetic acid/acetic anhydride mixture

Coulometric generation of acetyl (CH₃CO⁺) ions by oxidation of mercury in acetic anhydride and in acetic acid/acetic anhydride (5:95, v/v) is described. Current/potential curves for solvents, titrated bases, indicator and mercury showed that in both these solvents mercury is oxidized at potentials which are much more negative than those for the titrated bases and other components present in the solution. Quinoline, triethanolamine, triethylamine, pyridine and quinolin-8-ol in acetic anhydride, as well as triethylamine, 2,2′-bipyridine, 2,4,6-collidine, pyridine and sodium acetate in acetic acid/acetic anhydride were titrated with acetyl ions generated by the oxidation of mercury. In this way, it was established that the oxidation of mercury to mercury (I) ions proceeds quantitatively with 100% current efficiency.     

Screened indicators in anhydrous acetic acid medium: Chromatic evaluation of their transitions

Three efficient indicators consisting of Malachite Green and a screening dye for use in anhydrous acetic acid media have been designed by use of complementary tristimulus data. The transition quality can be evaluated by plotting the relative greyness of the indicator against free perchloric acid concentration. Several bases have been successfully determined titrimetrically with use of these indicators.     

Reactions of the radial cattions of acetic acid and acetic anhydride in CFCl3

The ESR spectra of -irradiated, at –196 °C, solutions of acetic acid and acetic anhydride were studied depending on their concentrations in CFCl₃. The structure of thus produced radical cations is confirmed with the deuterium substituted analogues. It has been shown that the ion-molecular reaction of the radical cation CH₂COOH⁺ in the isolated dimer takes place for the dilute solutions of acetic acid in CFCl₃ resulting in the formation of CH₃COO follwed by its decomposition to CH₃+CO₂ while the radicals CH₂COOH are formed via secondary processes. The reactions of radical cations of acetic oxide have been also studied.     

Membrane extraction for removal of acetic acid from biomass hydrolysates

Production of bioethanol from lignocellulosic biomass requires pretreatment of the biomass in order to improve the susceptibility of the cellulose to enzymatic hydrolysis to glucose. When dilute acid is used to perform this process, the hemicellulose is also hydrolyzed to its component sugars while simultaneously releasing acetyl groups attached to the hemicellulose backbone. Other compounds from the lignin and sugar degradation products are also produced that inhibit subsequent bioconversion of the solubilized sugars to the desired products. In this work we focused on removal of acetic acid from a dilute sulphuric acid pretreated corn stover hydrolysate.Acetic acid has been extracted into an organic phase at pH values below its pK_a. The organic phase diluent consisted of octanol. Alamine 336, a tertiary amine and Aliquat 336 a quaternary amine were used as the aliphatic amine extractants. Our results indicate more than 60% removal of acetic acid using Alamine 336. Extraction rates were much slower for Aliquat 336 probably due to the higher viscosity of the Aliquat 336/octanol phase.The presence of sulphate anions, as a result of dilute sulphuric acid pretreatment, results in the co-extraction of bisulphate anion. Bisulphate anion is preferentially extracted at pH values below its pK_a. Consequently the pH of the hydrolysate increases from between 1 and 2 to above 4.0 during extraction. In addition, extraction of low molecular weight lignins and phenolics is also observed. Thus the membrane extraction process developed here may be used not only for removal of acetic acid but also to adjust the pH of the hydrolysate to values that are more compatible for fermentation and to remove other inhibitory compounds.     

Multiphase telomerisation of butadiene with acetic acid and acetic anhydride

Two different routes to acetoxyoctadiene are presented. The first one uses the well-known telomerisation of butadiene with acetic acid operating in a multiphase semi-batch mode. The second reaction involves the cleavage of acetic anhydride, hydrogen transfer via ketene formation and thus a telomerisation as well.     

Thermal evolution of acetic acid nanodeposits over 123-180 K on noncrystalline ice and polycrystalline ice studied by FTIR reflection-absorption spectroscopy: hydrogen-bonding interactions in acetic acid and between acetic acid and ice

Acetic acid vapor-deposited on ultrathin noncrystalline ice (NCI) and polycrystalline ice (PCI) films (less than 6 nm thick) under ultrahigh vacuum conditions has been investigated by using Fourier Transform Infrared Reflection-Absorption Spectroscopy. Pristine acetic acid deposited at 123 K (on a copper support) appears as an amorphous solid, which undergoes an irreversible phase transformation to a more structurally ordered (polycrystalline) form upon annealing to 153 K. Acetic acid is found to adsorb on NCI and PCI films initially through hydrogen bonding between C=O and dangling OH (of ice), followed by the formation of multilayers at 123 K. Thermal evolution studies of a low exposure of acetic acid on the ultrathin NCI and PCI films show that acetic acid undergoes coevaporation with water likely as an acetic acid hydrate at 155 K, which continues until the entire ice film has been exhausted at 165 K. Above 165 K, the remaining acetic acid solid appears to evaporate without undergoing the phase transformation, in contrast to the case of a high acetic acid exposure. Coevaporation of acetic acid with water is also found to proceed at a faster rate than the subsequent evaporation of acetic acid, which is consistent with the weaker interactions observed in the H-bonded acetic acid hydrate than that in acetic acid solid.     

The combined effects of acetic acid, formic acid, and hydroquinone on Debaryomyces hansenii physiology

The combined effects of inhibitors present in lignocellulosic hydrolysates was studied using a multivariate statistical approach. Acetic acid (0–6 g/L), formic acid (0–4.6 g/L) and hydroquinone (0–3 g/L) were tested as model inhibitors in synthetic media containing a mixture of glucose, xylose, and arabinose simulating concentrated hemicellulosic hydrolysates. Inhibitors were consumed sequentially (acetic acid, formic acid, and hydroquinone), alongside to the monosaccharides (glucose, xylose, and arabinose). Xylitol was always the main metabolic product. Additionally, glycerol, ethanol, and arabitol were also obtained. The inhibitory action of acetic acid on growth, on glucose consumption and on all product formation rates was found to be significant (p≤0.05), as well as formic acid inhibition on xylose consumption and biomass production. Hydroquinone negatively affected biomass productivity and yield, but it significantly increased xylose consumption and xylitol productivity. Hydroquinone interactions, either with acetic or formic acid or with both, are also statistically signficant. Hydroquinone seems to partially lessen the acetic acid and amplify formic acid effects. The results clearly indicate that the interaction effects play an important role on the xylitol bioprocess.     

Anion exchange of some elements in acetic acid-hydrochloric acid medium

A comparative study of the adsorbability of Cd(II), Ni(II), Mn(II), Ga(III), La(III), Mo(VI) and bromide from aqueous acetic acid solutions on' Dowex 1-X8, 100–200 mesh, in the acetate and chloride forms, proved that chloride ions are indispensable for high adsorption from concentrated acetic acid solutions. A study of the adsorption isotherms of Ni(II), Mn(II) and Cd(II) on the acetate-form resin from acetic acid-hydrochloric acid solutions, showed that these elements form anionic complexes. The K_d values on RCl-exchanger, for a given acetic acid concentration, were highly dependent on the total exchange capacity of the resin. A simplified anion-exchange separation procedure in aqueous acetic acid was developed, with an adsorption step from a mixture of acetic and hydrochloric acids.     

Refractometry of lyotropic mesophase systems: Ethyl cellulose/m-cresol and ethyl cellulose/acetic acid

An Abbé refractometer with a rotatable polarizer mounted on the eyepiece is used for determining the two principal refractive indices of birefringent concentrated solutions of ethyl cellulose in m-cresol and in acetic acid. At a certain concentration, birefringence appears for both systems, and the concentration agrees with that for the onset of iridescence (here defined as the critical concentration C_a for formation of the liquid-crystalline phase). The birefringence of concentrated solutions depends strongly on concentration and temperature and can be generalized by a master curve. The refractive index increments for both systems are almost independent of temperature at high concentrations.     

Dosage mercurimetrique des thioethers en milieu acetique anhydre: Titrimetric determination of thioethers with mercury(II) perchlorate in anhydrous acetic acid media

(Titrimetric determination of thioethers with mercury(II) perchlorate in anhydrous acetic acid media). Thioethers form mercury(II) complexes which are less stable than the thiol complexes. Potentiometric titrations at the millimolar level are possible with a silver amalgam indicating electrode if mercury(II) perchlorate is used as titrant and the medium is anhydrous acetic acid.     

Experimental and theoretical studies of the kinetics of the reactions of OH radicals with acetic acid, acetic acid-d3 and acetic acid-d4 at low pressure

The kinetics of the reactions of OH with acetic acid, acetic acid-d3 and acetic acid-d4 were studied from 2 to 5 Torr and 263-373 K using a discharge flow system with resonance fluorescence detection of the OH radical. The measured rate constants at 300 K for the reaction of OH with acetic acid and acetic acid-d4 (CD3C(O)OD) were (7.42+/-0.12)x10(-13) and (1.09+/-0.18)x10(-13) cm3 molecule-1 s-1 respectively, and the rate constant for the reaction of OH with acetic acid-d3 (CD3C(O)OH) was (7.79+/-0.16)x10(-13) cm3 molecule-1 s-1. These results suggest that the primary mechanism for this reaction involves abstraction of the acidic hydrogen. Theoretical calculations of the kinetic isotope effect as a function of temperature are in good agreement with the experimental measurements using a mechanism involving the abstraction of the acidic hydrogen through a hydrogen-bonded complex. The rate constants for the OH+acetic acid and OH+acetic acid-d4 reactions display a negative temperature dependence described by the Arrhenius equations kH(T)=(2.52+/-1.22)x10(-14) exp((1010+/-150)/T) and kD(T)=(4.62+/-1.33)x10(-16) exp((1640+/-160)/T) cm3 molecule-1 s-1 for acetic acid and acetic acid-d4, respectively, consistent with recent measurements that suggest that the lifetime of acetic acid at the low temperatures of the upper troposphere is shorter than previously believed.