The effect of pH on the decomposition of peracetic acid in an aqueous solution was studied. It was found that three potential reactions, namely i) the spontaneous decomposition, ii) the hydrolysis and iii) the transition metal catalysed decomposition, are responsible for the consumption of peracetic acid. The spontaneous decomposition reaches its maximum at pH 8.2, while both the hydrolysis and metal ion catalysed decomposition increase as the pH increases. At pH 10.5 and higher, the hydrolysis becomes dominant when the metal ion catalysed decomposition is minimized by the addition of DTMPA. The kinetics of the peracetic acid hydrolysis was developed, which can very well predict the development of peracetic acid and hydrogen peroxide during the decomposition reaction.On a etudie l'effet du pH sur la dbomposition de l'acide peracetique dans une solution aqueuse. On a trouve que trois reactions potentielles, a savoir (1) la decomposition spontanee, (2) I'hydrolyse et (3) la decomposition catalysee par des metaux de transition, etaient responsables de la consommation de I'acide peracetique. La decomposition spontanee atteint son maximum a un pH de 8,2, tandis que I'hydrolyse et la decomposition catalysee aux ions metalliques augmentent toutes deux avec le pH. A partir d'un pH de 10,5, I'hydrolyse devient dominante lorsque la decomposition catalysee par les ions metalliques est minimisee par l'addition de DTMPA. La cinetique de l'hydrolyse de l'acide peracetique a ete etablie, et elle permet de bien predire le developpement de I'acide peracetique et du peroxyde d'hydrogene lors de la reaction de decomposition.

Peracetic acid may become one of alternative non-chlorine bleaching chemicals in the production of fully bleached chemical pulps. In this paper, the stability of peracetic acid was studied in an aqueous solution under conditions most likely encountered in the industrial processes. It was found that three potential reactions, namely i) the spontaneous decomposition, ii) the hydrolysis and iii) the transition metal catalyzed decomposition, are responsible for the consumption of peracetic acid. Furthermore, the kinetics of the spontaneous decomposition was developed. It was found that the reaction follows a second-order kinetics with the maximum rate at pH 8.2, which is the pK, of peracetic acid. Finally, the developed kinetic equation can describe very well the experimental results obtained in this study as well as the earlier data from Koubek (1964).L'acide peracetique pourrait Ctre une des substances de blanchiment sans chlore possible pour produire des pites chimiques completement blanchies. Dans cet article, on a etudie la stabilite de I'acide peracetique dans une solution aqueuse, dans les conditions les plus souvent rencontrees dans les procedes industriels. On a trouve que les trois reactions potentielles, soient la decomposition spontanee, I'hydrolyse et la decomposition catalysee des metaux de transition, etaient responsables de la consommation de l'acide peracetique. En outre, on a etabli la cinidique de la decomposition spontanee. On a trouve que la reaction suivait une cinetique du second ordre avec une vitesse maximale a un pH de 8,2, qui est le pK de I'acide peracetique. Enfin, I'equation cinetique etablie peut decrire parfaitement les resultats experimentaux obtenus dans cette etude ainsi que les anciennes donnees de Koubek (1964).Keywords: kinetics, peracetic acid, spontaneous decomposition, hydrolysis, pulp bleaching.Environmental concerns and market pressure are forcing the pulp and paper industry to explore alternatives to conventional chlorine containing bleaching chemicals. Recent results have shown that peracetic acid is a less capital intensive, easily retrofit and highly selective TCF bleaching agent when it is being used under the optimum conditions (Troughton et al., 1994).Peracetic acid is the mono-acetyl derivative of hydrogen peroxide and has a single acidic proton with a pK, of 8.2 at 25OC (Koubek et al., 1963). It is usually prepared by mixing acetic acid and hydrogen peroxide with sulfuric acid as a catalyst (Swern, 1970). This manufacturing process is reversible and thus an equilibrium mixture of reactants and products is normally obtained. The high purity peracetic acid can be obtained by distillation.Peracetic acid decomposes spontaneously in aqueous solution to give acetic acid and oxygen (Swern, 1970). Transitional metal ions such as cobalt and manganese ions catalyze the peracetic acid decomposition; however, the catalytic effect could be virtually eliminated by the addition of a suitable chelating agent (Koubek et al., 1963). In addition, peracetic acid can be hydrolyzed to fo...

A new method for the fast pyrolysis of lignin is presented. The addition of calcium formate to lignin prior to fast pyrolysis results in deoxyhydrogenation of the lignin during pyrolysis. In the inert atmosphere, the calcium formate thermally decomposes to form hydrogen, which facilitates the chemical transformation in situ. The process occurs at atmospheric pressure and without catalysts. There are several immediate benefits to this method for fast pyrolysis of lignins, including improvements in lignin feeding to the pyrolysis reactor, an increase in liquid yield, and an increase in the carbon yield in the oil phase of the liquid product. Gas chromatography–mass spectrometry analysis indicated that methoxy groups were removed from the lignin with the addition of calcium formate. Therefore, the primary products of this method are alkylated phenols.

Formic acid is demonstrated as a hydrogen source in a solid reaction system by first stabilizing the acid as a calcium salt which then decomposes at temperatures of relevance in pyrolytic reactions. High yields of deoxygenated hydrocarbons are produced by thermal decomposition of formic and levulinic acid mixtures where the optimum feed stoichiometry is consistent with that of cellulose hydrolysis and dehydration. The method promises a high-yield, robust, low-pressure, non-catalytic route for converting biomass hydrolyzates to hydrocarbon mixtures which are similar to petroleum crude oils.

Hemicelluloses derived from biomass are presently underutilized. In order to develop more profitable biorefinery processes, the mechanism responsible for hemicellulose removal by pretreatments has to be further explored. The hydrothermal dissolution profile of the wood components cellulose, hemicelluloses, and lignin of a hardwood mixture during autohydrolysis in a modified Dionex ASE-100 is described. Well-closed material balances were obtained for lignin-free yield, xylan, and glucomannan when comparing the solid and liquid phases. Xylo-oligomers were the predominant component in the extract. Xylan initially dissolved as oligosaccharides and then slowly depolymerized into monomeric xylose. The residual xylan in wood was only slightly deacetylated. A smaller amount of glucomannan was removed as oligosaccharides. Arabinose and galactose were completely removed from wood as monomers at the end of the extraction process. Initially all acetyl groups were removed while still bound to oligosaccharides. Then, acetic acid was released by deacetylation of the dissolved oligosaccharides.